Multiband GSM Network Radio Optimization

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EVOLIUM Base Station SubsystemMultiband GSM Network Radio Optimization / B8

TRAINING MANUAL8AS902001407VHZZA ed 4 – January 2006

© Alcatel 2

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© 2004 Alcatel. All rights reserved.

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Product Line EVOLIUM Base Station Subsystem

Course Title Multiband GSM Network Radio Optimization / B8

Course Reference 3FL 12034 AAAA - AUE

Audience

Radio Network Engineers (operator or Alcatel staff) in charge of optimizing a multi-band network.

Objectives

During the course, the trainee will be able to describe the specific radio algorithms in multi-band networks in order to enhance the offered QoS.

By the end of the course, the participant will be able to:

- Describe the concepts and strategy of multi-band networks.

- Describe the specific type of cells implemented in multi-band networks.

- Describe the specific radio algorithms used in the Alcatel BSS in a multi-band network.

- Propose default parameter values for the cells of a multi-band network using these algorithms.

- Propose a list of specific indicators to monitor QoS and traffic in a multi-band network.

Note: Radio Network Planning issues like micro site detection, site planning, frequency planning are not included.

Prerequisites

Training module “Introduction to GSM QoS and Traffic Load Monitoring” (3FL 10491 ABAA–AUE) and “Introduction to Radio Fine Tuning” (3FL 10493 ABAA–AUE) or equivalent level.

Training Methods

Theory / Practice.

Language

English, French

Duration

3 Days

Location

Alcatel University or Customer Premises.

Number of participants

Maximum 8

Course content

1 Multi-band Network Architecture

1.1 Concepts and strategies

1.2 Cellular network architecture

1.3 Choosing a relevant architecture

1.4 Requirements

2 Algorithms and Associated Parameters

2.1 Introduction

2.2 Neighboring cells list

2.3 Idle mode selection and reselection

2.4 Call setup

2.5 Handover strategies

2.6 Main standard handover algorithms

2.7 HO algorithms for multi-band networks

2.8 HO algorithms for concentric cells

2.9 Candidate cell evaluation

3 Creating a Multi-band Network

3.1 Introduction

3.2 Adding a 1800 band in an existing 900 network


3.4 Adding a 1800 band in an existing 900 (macro+micro) network

3.5 The multi-band cells solution

3.6 Monitoring QoS in a multi-band network

3.7 Case study: Quadrilayer network (Macro 900 + 1800 / Micro 900 + 1800)

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Note : Please print this document with comments pages

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All rights reserved © 2004, Alcatel

1 MULTI-BAND NETWORK ARCHITECTURE

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6Multi-band GSM Network Radio Optimization

1 MULTI-BAND NETWORK ARCHITECTURE Session presentation

> Objective: to be able to define relevant architectures for multi-band networks design

> Program:




1.4 Requirements

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> Multi-band network: a powerful solution for:

• Network capacity enhancement

– extra capacity provided by new cells / new TRXs

– specific radio algorithms send MSs to these new cells

• While keeping a good QoS

– less tight frequency plan if introducing a new band

– less congestion

1.1 Concepts and strategies Introduction to multi-band networks

> Since B7:

• new HW capabilities with “Cell split” support

• enhancement of QoS monitoring capabilities with counters split per TRX

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>Alcatel is providing multi-band solution

• Since B5.1: multi-band BSC

• From B6.2: multi-band cells

• Improvements in B7

1.1 Concepts and strategies Support of multi-band features

> B7 improvements:

• new HW capabilities with “Cell split” support

• enhancement of QoS monitoring capabilities with counters split per TRX

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> Early adopters of multi-band technology had to deal with a low proportion of multi-band MSs

– Network parameters were set to send systematically all multi-band MSstowards new band TRXs

– A new band is called the “Preferred band”

> Since year 2000, quite all new MSs include the multi-band feature– Q4 2002: the multi-band MS penetration rate is 80%

– Parameters settings have to be changed to avoid new band congestion!

– Operators introducing newly the multi-band technology use this new set of parameters

1.1 Concepts and strategies Network strategy

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> The new band introduction can be done

• In a mono-layer network

– In the same layer

– In a new layer

• In a Multi-layer network

– In the upper layer

– In the lower layer

• As part of an existing cell design: multi-band cells

>Depending on the architecture chosen:

• Different parameters settings

• Different ways of QoS and traffic monitoring

– Each architecture has drawbacks and advantages

1.1 Concepts and strategies Mono and multi-layers solutions

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> Conventional

• single cell

• concentric cell

• extended cell

• multi-band cell

> Hierarchical: introducing Upper and Lower cell layers

• indoor cell

• microcell

• mini cell

• umbrella cell

> Multi-band: Classical and Preferred frequency bands

1.2 Cellular network architectureCell environment

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>One unique combination of the five parameters

• CELL_DIMENSION_TYPE: macro, micro

• CELL _LAYER_ TYPE: single, upper, lower, indoor

• CELL _PARTITION_ TYPE: normal, concentric

• CELL _RANGE: normal, extended inner, extended outer

• FREQUENCY_RANGE: PGSM(GSM900); DCS1800; EGSM; DCS1900; PGSM-DCS1800; EGSM-DCS1800 and GSM 850

– based on BCCH frequency

>A multi-band cell is defined by:

• FREQUENCY_RANGE = “PGSM-DCS1800” or “EGSM-DCS1800”

• CELL _PARTITION_ TYPE of the cell is then forced to concentric

1.2 Cellular network architectureCell profile

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1.2 Cellular network architectureMono-band Cell profiles

DCS1800 or DCS1900DCSNormalNormalIndoorMicroDCS indoor micro cell

PGSM or EGSMGSMNormalNormalIndoorMicroGSM indoor micro cell

DCS1800 or DCS1900DCSNormalConcentricUpperMacroDCS concentric umbrella

PGSM or EGSMGSMNormalConcentricUpperMacroGSM concentric umbrella

DCS1800 or DCS1900DCSNormalConcentricSingleMacroDCS concentric cell

PGSM or EGSMGSMNormalConcentricSingleMacroGSM concentric cell

DCS1800 or DCS1900DCSExtended-outerNormalSingleMacroDCS extended outer cell

PGSM or EGSMGSMExtended-outerNormalSingleMacroGSM extended outer cell

DCS1800 or DCS1900DCSExtended-innerNormalSingleMacroDCS extended inner cell

PGSM or EGSMGSMExtended-innerNormalSingleMacroGSM extended inner cell

DCS1800 or DCS1900DCSNormalNormalUpperMacroDCS umbrella cell

PGSM or EGSMGSMNormalNormalUpperMacroGSM umbrella cell

DCS1800 or DCS1900DCSNormalNormalLowerMacroDCS mini cell

PGSM or EGSMGSMNormalNormalLowerMacroGSM mini cell

DCS1800 or DCS1900DCSNormalNormalLowerMicroDCS micro cell

PGSM or EGSMGSMNormalNormalLowerMicroGSM micro cell

DCS1800 or DCS1900DCSNormalNormalSingleMacroDCS single cell

PGSM or EGSMGSMNormalNormalSingleMacroGSM single cell

Frequency rangeCell band typeCell rangeCell partition typeCell layer typeCell dimension typeCell Profile

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1.2 Cellular network architectureMulti-band Cell profiles

PGSM-DCS1800 or EGSM-DCS1800

DCSNormalConcentricIndoorMicroDCS multiband indoor micro cell


GSMNormalConcentricIndoorMicroGSM multiband indoor micro cell


DCSNormalConcentricUpperMacroDCS multiband umbrella cell


GSMNormalConcentricUpperMacroGSM multiband umbrella cell


DCSNormalConcentricLowerMacroDCS multiband mini cell


GSMNormalConcentricLowerMacroGSM multiband mini cell


DCSNormalConcentricLowerMicroDCS multiband micro cell


GSMNormalConcentricLowerMicroGSM multiband micro cell


DCSNormalConcentricSingleMacroDCS multiband single cell


GSMNormalConcentricSingleMacroGSM multiband single cell

Frequency rangeCell band type

Cell range

Cell partition type

Cell layer type

Cell dimension type

Cell Profile

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1.2 Cellular network architectureCell profiles: example

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> In a mono-layer network, a new band may be introduced:

• In the same layer

– Macro 900 (single)

– Macro 1800 (single)

– 900-1800 interworking managed by priority set by the operator

• In a separate layer

– Macro 900 (umbrella)

– Macro 1800 = mini

– 900-1800 interworking driven by a dual layer architecture (easier to introduce but less flexible)

1.3 Choosing a relevant architectureMono-layer architecture

900 900 1800 1800

900 900

mini1800 mini1800

> All examples in this document will be using 900 as an “historical” band and 1800 as a “new” band (thus preferred band).

> All other network configurations are anyway possible.

> The dual layer configuration is interesting in case the dual band implementation strategy is traffic driven due to a low penetration rate of multi-band MSs.

> A dual layer allows for example, for a multi-band MS located in a 900 cell, to discriminate its behavior between a Forced Directed Retry and an emergency HO. 1800 neighboring cells can be favored for a FDR whereas 900 neighboring cells will be preferred on an emergency HO.

> A dual layer also allows to decide the MS transfer from 900 to 1800 band on speed criterion instead of on traffic criterion if needed (macro 1800 hot spot for instance).

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> In a multi-layer network, a new band may be introduced:

• In the upper layer



– Micro 900

• In the lower layer


– Macro 1800 = mini

– Micro 900

1.3 Choosing a relevant architectureMulti-layer architecture (1/3)

900 900 1800 1800

900 900

mini1800

µ900 µ900

µ900 µ900

> In the first configuration, the major difficulty is to manage 900-1800 interworking in the upper layer.

> In the second configuration, the operator has to deal with priority between the preferred cells: mini or micro? For both selections in idle mode and capture from the upper layer.

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> Higher Priority to 1800 macrocell– GSM 900 macrocell as a pool of traffic resources when the preferred cell is

congested


2

1

Initial access

3

Traffic

based

handover21

Directed retry

Emergency

Handover

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> Higher Priority to 900 microcell– GSM 900 & 1800 macrocell as a pool of traffic resources when the

preferred cell is congested


Traffic

based

handover

Directed retry

Emergency handover

Initial access

3

1

2

12

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> A functionality introduced in B6.2

• Also called “single BCCH”

• Based on the concentric cell feature

– New band is introduced in existing cells

– In the INNER zone (contains only TCH)

– The OUTER zone contains BCCH, SDCCH and TCH

1.3 Choosing a relevant architectureMulti-band cell solution

9001800 9001800

µ900

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1.4 Requirements

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> The multi-band BSC has been introduced in B5.1

• One single G2 BSC can manage 900 & 1800 cells

• 1800 TRXs are handled by G2 & Evolium BTSs

> The multi-band cell solution has been introduced in B6.2

• 1800 & 900 TRXs in a single cell

• 1800 & 900 TRX need to be part of the same Evolium BTS HW

> The multi-band support has been improved in B7

• With the “Cell split” feature: 1 cell over 2 BTS HW

• BTSs need to be synchronized (Master / Slave configuration)

1.4 RequirementsSoftware & Hardware requirements

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> Improvements in B7 with “cell split”

• 1 cell can be split over 2 BTS HW

• As soon as these BTSs share the same clock– Master / Slave configuration needed

– G2 & G3 BTSs can be mixed

> Example of site configurations:

• 3 * G2 BTS 4 TRX 900 + 1 Evolium BTS 3*4 TRX 1800

– 3 multi-band cells 4(900)+4(1800) TRX

• Evolium BTS 6+6 TRX 900 + Evolium BTS 6 TRX 900+ Evolium BTS 3*4 TRX 1800

– 3 multi-band cells 6(900)+4(1800) TRX

1.4 RequirementsHW solutions for multi-band cells since B7

> Master / Slave configuration:

• in B6.2: max. 1 Master + 2 Slaves

• in B7: max. 1 Master + 3 Slaves

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1.4 RequirementsExercise

Time allowed:

15 minutes

> Give the major advantages and drawbacks of the multi-band cells solution

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2 ALGORITHMS AND ASSOCIATED PARAMETERS

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2 ALGORITHMS AND ASSOCIATED PARAMETERS Session presentation

> Objective: to be able to describe algorithms dedicated to multi-band networks management

> Program:

2.1 Introduction



2.4 Call setup



2.7 Handover algorithms for multi-band networks

2.8 Handover algorithms for concentric cells


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2.1 Introduction

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> With the introduction of new features and algorithms:

– Concentric cells

– Multi-band BSC

– Multi-band cells

• Designing, managing and monitoring complex networks is more difficult,

as all these features will interact

– An in-depth knowledge of all available algorithms is necessary to

understand all possibilities and difficulties. A relevant choice of architecture

and parameters settings will precede the introduction of new frequency

band in the existing network.

2.1 Introduction Justification

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> In all this document

• System parameters (can be set at the OMC-R level) will always be written

in BLUE BOLD FONT

• Variables (averages, internal system variables, etc.) will be typed in

NORMAL FONT

> Light blue font highlights important points

2.1 Introduction Typing conventions

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> Sending a neighboring cell list in each frequency band is mandatory for multi-band networks to allow:

• Monitoring

• Selection & reselection in idle mode

• Handover in dedicated mode

2.2 Neighboring cells listPurpose

798798

2020

4545

800800

805805

22

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> Idle mode: SYSINFO 2, 2bis & 2ter

• Sent on BCCH

2.2 Neighboring cells list Idle mode

805805 BCCH 1800

SI 2 and 2bis: 1800 neighboring cells

SI 2ter: 900 neighboring cells

2020

BCCH 900

SI 2: 900 neighboring cells

SI 2ter and 2bis: 1800 neighboring cells

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> Dedicated mode: SYSINFO 5, 5bis & 5ter

• Sent on SACCH

2.2 Neighboring cells list Dedicated mode

805805 SACCH 1800

SI 5 and 5bis: 1800 neighboring cells

SI 5ter: 900 neighboring cells

2020

SACCH 900

SI 5: 900 neighboring cells

SI 5ter and 5bis: 1800 neighboring cells

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> One BSS parameter enables to send SYSINFO 2bis/2ter and 5bis/5ter

– EN_INTERBAND_NEIGH

– Default value:

– Enabled in multi-band networks

– disabled in mono-band networks

2.2 Neighboring cells list SYSINFO Parameters

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> Inform a multi-band MS of how it should report neighboring cells in dedicated mode

• The MS sends 6 neighboring cells in each MEAS REPORT

• Behavior in a standard mono-band layer: the MS reports the 6 best cells

• The expected behavior is different in a multi-band network

– Information is needed on both frequency bands

– To allow interband handovers

2.2 Neighboring cells list neighboring cells monitoring (1/2)

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> One parameter to be sent on a per cell basis

• MULTIBAND_REPORTING

• 4 possible values

– 0: 6 strongest cells irrespective of the frequency band

– 1: 1 strongest cell (non-serving cell frequency band) + 5 strongest cells (serving cell frequency band)

– 2: 2 strongest cells (non-serving cell frequency band) + 4 strongest cells (serving cell frequency band)

– 3: 3 strongest cells (non-serving cell frequency band) + 3 strongest cells (serving cell frequency band)

– Default value:

– 0 for mono-band network

– 3 for multi-band network

2.2 Neighboring cells list neighboring cells monitoring (2/2)

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> MULTIBAND_REPORTING has to be tuned carefully in multi-band network, since no handover can be done to a cell which is not reported

• The parameter value is depending on network strategy and may be tuned differently in each band

• Example: priority to 1800 cells

– In 900 layer cells

MULTIBAND_REPORTING = 1 is most of the time sufficient to make a handover towards the preferred band

– In 1800 layer cells

1800 neighboring cells have to be reported to keep the MS in the same band when possible, but 900 cells should be reliably reported as they are rescue cells. Thus, MULTIBAND_REPORTING = 3

2.2 Neighboring cells list Parameters optimization

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> Neighboring cells

• Neighboring cells list limited to 32 BCCHs

– Limit easily reached in a network with 3 or 4 layers, and several bands

– A special care must be taken when defining the list of neighboring cells

– The multi-band cells solution dramatically reduces this problem when introducing new frequency band

2.2 Neighboring cells list Number of neighboring cells

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> Adding a new band is a powerful way of increasing network capacity ifthe MS can be sent to the preferred cell

• In dedicated mode: see next sections

• But also in idle mode, so that the call is established directly in the preferred cell

– Really increase capacity

– Maintain high QoS level, without creating extra HO

2.3 Idle mode selection and reselection Strategy

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> At startup (IMSI Attach), the MS is selecting cell with

• Define priorities with CELL_BAR_QUALIFY

• best C1 amongst highest priority cells (using CBQ)

> once “camped on” one cell (in idle mode)…

> … The MS can decide to reselect on another one if:

• C1 criterion is too low

• The MS cannot decode downlink messages

• The current cell is becoming forbidden (e.g. barred)

• The MS cannot access the cell

• there is a better cell, regarding C2 criterion

2.3 Idle mode selection and reselection Selection and reselection principles

> Note:

> Cell selection (first selection) is performed using C1 criterion only (the chosen cell is the one with the best C1)

> Reselection is done using the mechanisms referenced above.

> e.g., the MS cannot access the cell.

> It can be linked to SDCCH congestion, filtering of CHARQD due to TA greater than RACH_TA_FILTER, radio access problem during the Radio Link Establishment phase.

• If SDCCH is to be seized for LU purpose, the MS will reselect on another cell.

• If SDCCH is seized for something else (e.g., MOC), the MS « may » reselect (this is up to the MS vendor choice!!!). Some MSs do nothing. Call will never be possible. Some others do reselect. In that case, the user has to reattempt his call (after the reselection, but before the MS is back to the original cell due to better C2, etc. (done after 5 s, etc.)).

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> Cell selection, use of CELL_BAR_QUALIFY:

• set on a per cell basis

• broadcast on the BCCH

• 2 possible values:

– 0 = normal priority (default value)

– 1 = lower priority

• The MS selects the suitable (C1 > 0) cell with the highest C1 belonging to the list of highest priority

2.3 Idle mode selection and reselection Cell Selection with CBQ (1/3)

> The CELL_BAR_QUALIFY parameter is not understood by phase 1 MS.

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> Example: highest priority set on Macro 1800

– The MS will select the 1800 cell (if available, C1>0), whatever the level of the 900 cell


805805BCCH 1800

CELL_BAR_QUALIFY = 0

2020

BCCH 900


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> WARNING: usage of CELL_BAR_QUALIFY:

• interacts with CELL_BAR_ACCESS

– A cell with low priority (CELL_BAR_QUALIFY = 1) cannot be barred

– Some MSs will be able to access it, whatever the value of CELL_BAR_ACCESS


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> C1

• ensures that, if a call was attempted, it would be done with a sufficient downlink and uplink received level

• based on 2 parameters, broadcast on the BCCH

– RXLEV_ACCESS_MIN [dBm]

– Minimum level to access the cell

– Default value (for Evolium): -103 dBm

– MS_TXPWR_MAX_CCH [dBm]

– Maximum level for MS emitting

– Default value: 33 dBm

2.3 Idle mode selection and reselection C1 criterion (1/2)

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> C1

• evaluated every 5 s (minimum)

• C1 = A - MAX(0,B) > 0

• A = RxLev - RXLEV_ACCESS_MIN

– assess that the MS received level is sufficient

• B = MS_TXPWR_MAX_CCH - P

– P maximum power of MS

– assess that the BTS received level will be sufficient

– if MS_TXPWR_MAX_CCH < P

2.3 Idle mode selection and reselection C1 criterion (2/2)

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> C2• If CELL_RESELECT_PARAM_IND= not present THEN C2=C1 else

– C2 = C1 + CELL_RESELECT_OFFSET - TEMPORARY_OFFSET (T) (if PENALTY_TIME ≠ 31)

– if T > PENALTY_TIME, TEMPORARY_OFFSET(T) = 0

– used to avoid locating on “transient cell”

– CELL_RESELECT_OFFSET used to favor a cell among others (e.g. microcell vs. umbrella, once T > PENALTY_TIME)

– Or C2 = C1 - CELL_RESELECT_OFFSET(if PENALTY_TIME = 31)

– CELL_RESELECT_OFFSET used to handicap some cells among others

• One reselection criterion is comparison with C2– C2neighboring cell > C2current if cells belong to the same LA

– C2neighboring cell > C2current+CELL_RESELECT_HYSTERESIS if cells from different LAs

2.3 Idle mode selection and reselection C2 criterion

> The use of a second formula (Penalty_time = 31) is restricted to very special cases, as we do not like to penalize a cell. If a cell is set with PT=31, it will be penalized compared to ALL its neighboring cells. To penalize a cell compared to one neighboring cell, one should better boost the neighboring cell (using first formula).

> The first formula is very useful to favor an indoor cell or a microcell.

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> CELL_RESELECT_PARAM_IND– C2 parameters are broadcast if = 1 (default)

– otherwise C2 = C1

> PENALTY_TIME– 0 to 31, =20s + 20s step, default value = 0

– From 0=20s to 30=620 s, plus 31: infinite penalty

> CELL_RESELECT_OFFSET– 0 to 63, 2 dB step, default value = 0

– From 0 dB to 126 dB

> TEMPORARY_OFFSET– 0 to 7, 10 dB step, default value = 0

– From 0 dB to 60 dB, plus 7: infinite dB

2.3 Idle mode selection and reselection C2 parameters

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2.3 Idle mode selection and reselection Application (1/2)

805805

BCCH 1800

CELL_RESELECT_OFFSET = 16 dB

TEMPORARY_OFFSET = 0 dB

PENALTY_TIME = 0 (20 s) 2020

BCCH 900



PENALTY_TIME = 0 (20 s)

C2(1800) = C1(1800) + 16

C2(900) = C1(900)

=> the reselection of the 1800 cell is favored

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> WARNING: CELL_RESELECT_OFFSET in a multi-band network

• Shall take into account the propagation difference between 900 and 1800

– Rough value is 10 dB

– Thus, if CELL_RESELECT_OFFSET = 16 dB on a 1800 cell compared to 0 dB in a 900 co-located cell

– Real advantage is limited to 6 dB

2.3 Idle mode selection and reselection Application (2/2)

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2.4 Call setup

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> Call setup is to be made on cell selected in idle mode

• Priorities have been defined with idle mode parameters

• MSs are sent to the preferred cell

– new band capacity

> What is the risk??

2.4 Call setup Principles

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> The risk is to have congestion in the preferred cell!

• Old cells (old band capacity) are unloaded…

• … as all MSs are sent to new cells

> This phenomenon is amplified by handovers behavior

• Dual band algorithms are based on CAPTURE mechanisms

– Send the MS in the preferred cell as soon as it is OK…

– … Without comparing serving and preferred cells...

– ... to reach maximum capacity increase

– See handover parts for details

2.4 Call setup Congestion in the preferred cell

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2.4 Call setup Algorithms principles (1/3)

new

capacity

Traffic

increase

old

capacity

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new

capacity

Water Valve with filter:

Dual band algorithms

Traffic

increase

old

capacity

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new

capacity

Water Pump:

Forced

Directed Retry

Traffic

increase

old

capacity

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> A Directed Retry:

• Is an SDCCH to TCH intercell handover

• Is triggered during a call setup procedure

> If the serving cell is completely congested, the MS is allocated an SDCCH

> If no TCH is available, the MS is queued

• Under certain conditions, the MS obtains a TCH in another cell

> SDCCH-TCH handover on:

• better condition or emergency causes = Directed Retry

• cause 20 = Forced Directed Retry

> Internal and External Directed Retries are possible (since B6.2)

2.4 Call setup Directed Retry principles

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> Directed Retry

• Set on a per cell basis with parameter EN_DR

• Same behavior as for TCH HO

• Intercell handover causes are checked (i.e. all HO causes except 10, 11 and 13 (concentric cells) and causes 15 and 16 (intracell HO))

• candidate cell evaluation process: same as for TCH HO

2.4 Call setup Directed Retry

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> CAUSE 20: Forced Directed Retry

AV_RXLEV_NCELL_DR(n) > L_RXLEV_NCELL_DR(n)

And EN_FORCED_DR = ENABLED

• EN_FORCED_DR value is only relevant if EN_DR = true

• AV_RXLEV_NCELL_DR(n) is calculated with the A_PBGT_DR window

• if less than A_PBGT_DR samples are available, the average value is calculated with the available samples and the average window is filled in with -110 dBm

2.4 Call setup Forced Directed Retry: cause 20

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> Pre-ranking• using PREF_LAYER, PRIORITY(0,n), frequency band

> Filtering process• AV_RXLEV_NCELL_DR(n) > RXLEVmin(n)

+max(0,MS_TXPWR_MAX(n) - P)

• Number of free TCHs t(n) > FREElevel_DR(n)

> The remaining cells are sorted according to their PBGT_DR(n) (average window A_PBGT_DR)

• PBGT_DR(n) = AV_RXLEV_NCELL_DR(n) - AV_RXLEV_PBGT_DR

- (BS_TXPWR_MAX - BS_TXPWR)

- (MS_TXPWR_MAX(n) - MS_TXPWR_MAX)

2.4 Call setup FDR: Candidate cell evaluation

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> L_RXLEV_NCELL_DR(n): level required in the neighboring cell n– The parameter considered is the one set in the neighboring cell

– The default value depends on the network architecture

– See the next slide

> Freelevel_DR(n): number of free TCH channels required in the neighboring cell n

– The parameter considered is the one set in the neighboring cell

– Default value = 0 to 4 TCHs (linked to the nb of TRXs)

> A_PBGT_DR: average window– Default value = 4 SACCHs

2.4 Call setupFDR: parameters

© Alcatel 65



> Thanks to idle mode parameters,

• Access to one « preferred cell »...

– Preferred band: as the 1800 band presents more capacity

• ... For better capacity increase and to avoid QoS degradation that may be induced by an increase in HO attempts

> Prevention of congestion in the “preferred cell”– Forced Directed Retry to the “old” cells

> Prevention of congestion in the “old” cells– MSs are sent in idle mode to the “preferred cell”

– HO strategy favoring the “preferred cell” in dedicated mode

2.4 Call setupAccess strategy

© Alcatel 66



> In a concentric cell,

• idle mode measurements are based on BCCH (outer zone)

• The MS is allocated an SDCCH in the outer zone

• In which zone will the TCH be allocated?

• It will be:

– either in the INNER zone

– OR in the OUTER zone

– depending on radio conditions

– If the cell is a multi-band cell, and the MS is not multi-band, the target zone is always OUTER

2.4 Call setupSpecific case of concentric cells (1/3)

INNEROUTER ??

> When Concentric cells have been introduced in R3, on call setup, the TCH was ALWAYS allocated in the OUTER zone.

> And then cause 13 was checked to send the MS in the INNER zone if radio conditions were OK.

> This was of course reducing the efficiency of CC feature, by decreasing the capacity of concentric cells.

> Since B4.1, the TCH can be allocated immediately in the INNER zone if radio conditions are OK.

© Alcatel 67



> Use part of the HO cause 13 algorithm (see session 2.8 for details)

• IF (average windows: A_LEV_HO and A_PBGT_HO (for n))

AV_RXLEV_UL_HO > RXLEV_UL_ZONE + ZONE_HO_HYST_UL ++ (MS_TXPWR - MS_TXPWR_MAX_INNER) +

and AV_RXLEV_DL_HO > RXLEV_DL_ZONE + ZONE_HO_HYST_DL ++ (BS_TXPWR - BS_TXPWR_MAX_INNER) +

and AV_RXLEV_NCELL_BIS(n) <= NEIGHBOUR_RXLEV(0,n)

and EN_CAUSE_13 = ENABLED– The TCH is allocated in the INNER zone

• ELSE– The TCH is allocated in the OUTER zone


© Alcatel 68



> This algorithm and the related parameters are detailed in session 2.8

> Compared to HO CAUSE 13 equation, parameter EN_BETTER_ZONE_HO is not used at call setup

> If less than A_LEV_HO (A_PBGT_HO for neighboring cells measurements) have been received, averages are calculated on theavailable number of measurements


© Alcatel 70



> Maximizing capacity

• Intelligent MS sharing between available resources

– Avoid congestion of historical band (for old MS)

– Use full capacity of new resources: the1800 band is offering more channels

– Consider traffic conditions of all bands

• Keep mobiles in the same band as long as possible

2.5 Handover strategiesObjectives (1/2)

© Alcatel 71



> Assuring good quality communications and avoiding call drops

• Send MSs towards the band that will provide the best QoS

• Minimize the number of HOs between cells for good speech Quality

• Identify a best target for emergency handovers cases

� The tuning of the parameters will result in trade-offs

2.5 Handover strategiesObjectives (2/2)

© Alcatel 72



> Next parts will detail available HO causes for multi-band network management

• Mainly, HO performed between cells of the same band are the same as for standard networks

• New handover causes are mandatory to manage HO between cells of

– Different frequency bands

• The management of multi-band cells will be based on concentric cells algorithms

2.5 Handover strategiesHandover algorithms

© Alcatel 73



2.5 Handover strategiesFunctional Entities

Radio

Link

Measurements

Active

Channel

Pre-processing

Assignment of HO functions in the ALCATEL BSSAssignment of HO functions in the ALCATEL BSSAssignment of HO functions in the ALCATEL BSSAssignment of HO functions in the ALCATEL BSS

BTS BSC

HO DetectionHO Candidate

Cell Evaluation

HO

management

MSC

HO

protocol

© Alcatel 74



2.5 Handover strategiesHandover causes (1/2)

> HO causes for standard networks

• cause 2 : too low quality on the uplink • cause 3 : too low level on the uplink

• cause 4 : too low quality on the downlink

• cause 5 : too low level on the downlink

• cause 6 : too large distance between the MS and the BTS

• cause 15 : high interference on the uplink (intra-cell HO)

• cause 16 : high interference on the downlink (intra-cell HO)

• cause 26 : AMR channel adaptation HO (HR to FR)

• cause 12 : power budget evaluation

• cause 23 : traffic

• cause 27 : AMR channel adaptation HO (FR to HR)

• cause 28 : Fast traffic HO

• cause 29 : TFO HO

• cause 20 : FDR

© Alcatel 75



> HO causes for multi-band networks

• cause 21 : high level in the neighboring cell in the preferred band

> HO causes for concentric cells

• cause 10 : too low level on the uplink in the inner zone

• cause 11 : too low level on the downlink in the inner zone

• cause 13 : too high level on the uplink and the downlink in the outer zone

• These causes will be used within multi-band cells

2.5 Handover strategiesHandover causes (2/2)

© Alcatel 76



2.5 Handover strategiesHandover causes priority

• cause 7 : consecutive bad SACCH frames received in a microcell• cause 17 : too low level on the uplink in a µcell compared to a high threshold• cause 18 : too low level on the downlink in a µcell compared to a high threshold• cause 2 : too low quality on the uplink • cause 3 : too low level on the uplink • cause 4 : too low quality on the downlink • cause 5 : too low level on the downlink • cause 6 : too large distance between the MS and the BTS• cause 10 : too low level on the uplink in the inner zone• cause 11 : too low level on the downlink the in inner zone• cause 26 : AMR channel adaptation HO (HR to FR)• cause 15 : high interference on the uplink (intra-cell HO)• cause 16 : high interference on the downlink (intra-cell HO)• cause 21 : high level in the neighboring cell in the preferred band

cause 14 : high level in neighboring cell of a lower or an indoor layer cell for slow mobile

cause 24 : general capturecause 12 : power budget evaluationcause 23 : traffic

• cause 13 : too high level on the uplink and downlink in the outer zone• cause 27 : AMR channel adaptation HO (FR to HR)• cause 20 : Forced Directed Retry DR• cause 28 : Fast traffic HO

© Alcatel 78



> Emergency intercell handovers

• cause 2 : too low quality on the uplink

• cause 3 : too low level on the uplink

• cause 4 : too low quality on the downlink

• cause 5 : too low level on the downlink

• cause 6 : too large distance between the MS and the BTS

> May be triggered

– From any cell type / band / layer / zone

– Towards any cell except the serving one

– If the MS is connected to the inner zone of a multi-band cell, the serving cell is a candidate

2.6 Main standard handover algorithms Emergency Intercell Handovers

© Alcatel 79



> CAUSE 2: too low quality on the uplink

AV_RXQUAL_UL_HO > L_RXQUAL_UL_H + OFFSET_RXQUAL_FH

and AV_RXLEV_UL_HO <= RXLEV_UL_IH

and MS_TXPWR = min (P, MS_TXPWR_MAX)

and EN_RXQUAL_UL= ENABLED

• Size of window for average quality: A_QUAL_HO

• Size of window for average level: A_LEV_HO

2.6 Main standard handover algorithmsHandover Cause 2: UL Quality

QUAL

LEV

> Quality and Level causes (2, 3, 4, 5, 15, 16)

> The aim of these causes is to keep the call going when the radio link is degrading otherwise the radio link failure might be detected and the call released. These causes wait generally for the power control process to increase the BTS and MS power to their maximum values, except for the causes specific to microcellular environment.

> Handover on "too low level" is used to avoid situations where the interference level is low, while the attenuation is quite high. These conditions may appear for example in big city streets which enabled a line of sight propagation from the BTS antenna. There is in this case a risk of abrupt quality degradation, if the MS moves away from the line of sight street.

> In case of simultaneous low-level and low-quality signals, an intercell handover is requested.

Level

Quality

-110 -47

7

0

PC

L_RXQUALxx_H

L_RXLEV_xx_H RXLEV_xx_IH

xx = UL or DL

Qual pb (2 / 4)

Levpb

(3 /5)

Int pb (15 / 16)

© Alcatel 80



> CAUSE 3: too low level on the uplink

AV_RXQUAL_UL_HO <= L_RXQUAL_UL_H + OFFSET_RXQUAL_FH

and AV_RXLEV_UL_HO < L_RXLEV_UL_H

and MS_TXPWR = min (P, MS_TXPWR_MAX)

and EN_RXLEV_UL= ENABLED



2.6 Main standard handover algorithms Handover Cause 3: UL Level

QUAL

LEV

© Alcatel 81



> CAUSE 4: too low quality on the downlink

AV_RXQUAL_DL_HO > L_RXQUAL_DL_H + OFFSET_RXQUAL_FH

and AV_RXLEV_DL_HO <= RXLEV_DL_IH

and BS_TXPWR = BS_TXPWR_MAX

and EN_RXQUAL_DL = ENABLED



2.6 Main standard handover algorithms Handover Cause 4: DL Quality

QUAL

LEV

© Alcatel 82



2.6 Main standard handover algorithms Handover Cause 5: DL Level

QUAL

LEV

> CAUSE 5: too low level on the downlink

AV_RXQUAL_UL_HO <= L_RXQUAL_DL_H + OFFSET_RXQUAL_FH

and AV_RXLEV_UL_HO < L_RXLEV_DL_H

and BS_TXPWR = BS_TXPWR_MAX

and EN_RXLEV_DL= ENABLED

• Size of window for averaging quality: A_QUAL_HO

• Size of window for averaging level: A_LEV_HO

© Alcatel 83



> CAUSE 6 : Too long distance

AV_RANGE_HO > U_TIME_ADVANCE

and EN_DIST_HO = ENABLED

• Size of window for distance average: A_RANGE_HO

2.6 Main standard handover algorithms Handover Cause 6: Distance

> This cause is used when a dominant cell provides a lot of scattered coverages inside other cells, due to propagation conditions of the operational network. These spurious coverages is the probable production of a high level of co-channel interference.

> This cause is different from the others as it is more preventive. It does not make use of the propagation conditions of a call. It just does not allow an MS to talk to a BTS if it is too far away.

> It may happen for example that some peculiar propagation conditions exist at one point in time that provide exceptional quality and level although the serving BTS is far and another is closer and should be the one the mobile should be connected to if the conditions were normal.

> It may then happen that these exceptional conditions suddenly drop and the link is lost, which would not have happened if the mobile had been connected to the closest cell. For these reasons also, this cause does not wait for the power control to react.

© Alcatel 84



> Emergency intracell handovers

• cause 15 : high interference on the uplink (intra-cell HO)

• cause 16 : high interference on the downlink (intra-cell HO)

> May be triggered– From any cell type / band / layer / zone

– Towards the same cell

2.6 Main standard handover algorithms Emergency Intracell Handovers

© Alcatel 85



2.6 Main standard handover algorithms Handover Cause 15: UL Interference

> CAUSE 15: High interference on the uplink

• Intra-cell HO

AV_RXQUAL_UL_HO > THR_RXQUAL_CAUSE_15 +OFFSET_RXQUAL_FH

and AV_RXLEV_UL_HO > RXLEV_UL_IH

and EN_CAUSE_15 = ENABLED

and [ no previous intracell handover for this connection failed

or EN_INTRACELL_REPEATED = ENABLED ]



> THR_RXQUAL_CAUSE_15 and EN_CAUSE_15 are not parameters but variables defined just after.

© Alcatel 86



2.6 Main standard handover algorithms Handover Cause 16: DL Interference

> CAUSE 16: High interference on the downlink

• Intra-cell HO

AV_RXQUAL_DL_HO > THR_RXQUAL_CAUSE_16 + OFFSET_RXQUAL_FH

and AV_RXLEV_DL_HO > RXLEV_DL_IH


and [ no previous intracell handover for this connection failed

or EN_INTRACELL_REPEATED = ENABLED ]



> THR_RXQUAL_CAUSE_16 and EN_CAUSE_16 are not parameters but variables defined after.

© Alcatel 87



2.6 Main standard handover algorithms New parameters for causes 15 & 16

> CAUSE 15 and CAUSE 16:

• THR_RXQUAL_CAUSE_15 (or 16) and EN_CAUSE_15 (or 16) are specific to HOP

• THR_RXQUAL_CAUSE_15 (or 16) =

– L_RXQUAL_XX_H for a non-AMR call (same threshold as CAUSE 2 or CAUSE 4)

– L_RXQUAL_XX_H_AMR for an AMR call

• EN_ CAUSE _15 (or 16) =

– EN_INTRA_XX for a non-AMR call

– EN_INTRA_XX_AMR for an AMR call

> XX = UL or DL

> For a non-AMR call, the thresholds used are identical to the ones used for CAUSE 2 and CAUSE 4.

> In this case and if EN_INTRACELL_REPEATED = DISABLED, when an HO CAUSE 15 (or 16) fails, it can be modified as UPLINK (or DOWLINK) QUALITY, HO CAUSE 2 (respectively HO CAUSE 4).

© Alcatel 88



2.6 Main standard handover algorithms Causes 15 & 16: specific case of concentric cells

> CAUSES 15 & 16: Case of concentric cells

• for an MS in the INNER zone, if cause 15 or 16 is triggered:

– a TCH may be allocated in the outer zone or in the inner zone

• for an MS in the OUTER zone, if cause 15 or 16 is triggered:

– a TCH is always allocated in the outer zone

© Alcatel 89



> CAUSE 12: Power budget

• “Normal” handover type, no matter of emergency

• Checked between

– Cells of the same layer only

– Cells may be of different cell_band_type, depending on parameter EN_MULTIBAND_PBGT_HO

– if EN_MULTIBAND_PBGT_HO = disabled and if the MS is located in the inner zone of a multi-band cell, it can only go to another multi-band cell

2.6 Main standard handover algorithms Handover Cause 12: Power Budget (1/7)

© Alcatel 90




• If EN_MULTIBAND_PBGT_HO = disabled


Single 900

Upper 900

µ900

900 1800

indoor900

Upper 1800

µ900

mini1800

Upper 900

Single 1800

900 1800

indoor900

mini900

fastfast

fastfast

fast

Upper

Upper

> This scheme highlights well the difficulty of introducing multi-band cells if EN_MULTIBAND_PBGT_HO is disabled (this was the only configuration in the first B6.2 networks): Multi-band cells interoperate only with, etc. multi-band cells.

© Alcatel 91




• If EN_MULTIBAND_PBGT_HO = enabled


Single 900

Upper 900

µ900

900 1800

Upper 1800

µ900

mini1800

Upper 900

Single 1800

900 1800

indoor900

mini900

fastfast

fastfast

fast

Upper

Upper

indoor900

> This problem is solved with EN_MULTIBAND_PBGT_HO = ENABLED.

© Alcatel 92



> CAUSE 12:

• Based on Power budget equation

PBGT(n) = AV_RXLEV_NCELL(n) - AV_RXLEV_PBGT_HO - (BS_TXPWR_MAX – AV_BS_TXPWR_HO)

- (MS_TXPWR_MAX(n) – MS_TXPWR_MAX)

- PING_PONG_MARGIN(n, call_ref)

• Size of window for level average: A_PBGT_HO


> The value of PBGT(n) is calculated every SACCH period for each neighboring cell n whose measures are kept in the book-keeping list.

© Alcatel 93




if EN_TRAFFIC_HO(0,n)=ENABLED

then PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNER

+ max(0, DELTA_HO_MARGIN(0,n))

else PBGT(n) > HO _MARGIN(0,n) + OFFSET_HO_MARGIN_INNER

and AV_RXLEV_PBGT_HO ≤ RXLEV_LIMIT_PBGT_HO

and EN_PBGT_HO = ENABLED

� Size of window for level average: A_PBGT_HO


> Cause 12 HO is correlated with cause 23 HO. This is why there are two equations according to the activation of cause 23 HO (EN_TRAFFIC_HO).

© Alcatel 94




DELTA_HO_MARGIN(0,n): evaluated according to the traffic situation of the serving cell and the neighboring cell cell n (Traffic_load(n)) in the following way:

If Traffic_load(0) = high and Traffic_load(n) = low,DELTA_HO_MARGIN(0,n) = - DELTA_DEC_HO_MARGIN

If Traffic_load(0) = low and Traffic_load(n) = high,DELTA_HO_MARGIN(0,n) = + DELTA_INC_HO_MARGIN

Else DELTA_HO_MARGIN(0,n) = 0

Philosophy

This mechanism aims at penalizing cause 12 detection when the traffic in the serving cell is low and is high in the cell n.


HIGH LOW

© Alcatel 95




• Traffic_load() is managed for every cell of a BSC

• Traffic_load() can have three values:

– HIGH: cell is loaded

– LOW: cell is unloaded

– INDEFINITE: cell load is neither loaded nor unloaded, or unknown

� The traffic_load() value is modified according to the long term traffic evaluation algorithm using the following parameters:

– A_TRAFFIC_LOAD, N_TRAFFIC_LOAD, HIGH_TRAFFIC_LOAD, IND_TRAFFIC_LOAD, LOW_TRAFFIC_LOAD: can be modified per cell

– TCH_INFO_PERIOD: cannot be modified (5 s)


Appendix 1

> TCH_INFO_PERIOD = 5s period used by the BSC to count the number of free TCHs.

© Alcatel 96



> Cause 12 handover can be used to send traffic between bands by setting EN_MULTIBAND_PBGT_HO = ENABLED

• Separated 900 - 1800 coverages

2.6 Main standard handover algorithms Cause 12: interband PBGT (1/2)

1800 cells

EN_MULTIBAND_PBGT_HO = Disabled

HO_MARGIN(0,n) =5 dB HO_MARGIN(0,n) = 5 dB

HO_MARGIN(0,n) =15 dB

EN_MULTIBAND_PBGT_HO = Enabled

HO_MARGIN(0,n) = 0 dB


900 cells

© Alcatel 97



• Common 900 - 1800 coverage:

– 1800 zone exit

2.6 Main standard handover algorithms Cause 12: interband PBGT (2/2)

macro 900

macro 1800



Exit of the macro 1800 area

EN_MULTIBAND_PBGT_HO = Enabled EN_MULTIBAND_PBGT_HO = Disabled



© Alcatel 98



> The MS is in the INNER zone of a concentric cell, the PBGT equation is:

PBGT(n) = AV_RXLEV_NCELL(n) - AV_RXLEV_PBGT_HO

- (BS_TXPWR_MAX_INNER – AV_BS_TXPWR_HO)

- (MS_TXPWR_MAX(n) –MS_TXPWR_MAX_INNER)

- PING_PONG_MARGIN(n, call_ref)

> For example, in a multi-band cells network

2.6 Main standard handover algorithms Cause 12: parameters for concentric cells (1/2)

9001800 900 1800Cell 1Serving

Cell 2Target

RxLev on TCH = -80dBm RxLev of BCCH = -72dBm

PBGT = +5 dB

> If RxLev(n) = -72 dBm, PBGT(n) = +5 dB > HO_MARGIN = 4 dB

> If cause 12 was triggered at this moment, the MS will be for example in the outer zone of cell 2. Its received level will be about -71 dBm.

> It will then check possible cause 12 HO towards cell 1. The received level of cell 1 is NOT -80 dBm (this was the level of the 1800 TCH).

> Field results show that a 900 BCCH will be received roughly at -80+10=-70 dBm. The risk of ping pong handover is then very high! In fact, cause 12 HO should NOT have been triggered.

> A solution is to be found in tuning OFFSET_HO_MARGIN_INNER used in cause 12 equation. See next slide.

© Alcatel 99



> OFFSET_HO_MARGIN_INNER

• The MS is located in a concentric cell inner zone, the main cause 12 equation is

– PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNER

• OFFSET_HO_MARGIN_INNER is used to compensate the difference of propagation between inner and outer zones (carrying BCCH)

– In a mono-band concentric cell, it is most of the time compensated by MS_TXPWR_MAX_INNER

– If BS_TXPWR_MAX_INNER is reduced compared to BS_TXPWR_MAX, MS_TXPWR_MAX_INNER may be reduced in the same manner

2.6 Main standard handover algorithms Cause 12: parameters for concentric cells (2/2)

© Alcatel 100



> OFFSET_HO_MARGIN_INNER– In a multi-band cell, the MS is using a 1800 inner zone TCH

– AV_RXLEV_PBGT_HO + OFFSET_HO_MARGIN_INNERis the DL received level as if the MS was using a 900 outer zone TCH

– OFFSET_HO_MARGIN_INNER compensates the 900-1800 propagation difference

– Default value: between 7 and 12 dB

– WARNING: OFFSET_HO_MARGIN_INNER is used regardless of the frequency band of the target cell

2.6 Main standard handover algorithms Cause 12: parameters for multi-band cells

9001800 900 1800Serving Target

RxLev on TCH = -80dBm RxLev of BCCH = -72dBmPBGT = +5 dB to be compared to HO_MARGIN+10 (14 dB)

© Alcatel 101



2.6 Main standard handover algorithms Handover Cause 23: Traffic (1/2)

> CAUSE 23: Traffic Handover

• The aim of this cause is to speed HO detection when

– The serving cell is loaded

– The target cell is unloaded

• When traffic distribution is taken into account for handover detection,

this cause reacts in the opposite way of cause 12, to maintain an

equivalent ping-pong static hysteresis

> Checked between– Cells of the same layer only

– If EN_MULTIBAND_PBGT_HO = disabled

– Cells of the same cell_band_type only

– if the MS is located in the inner zone of a multi-band cell, it can only go to another multi-band cell

– Else any other cells whatever their cell_band_type

HIGH LOW

Modified B8

B8

> In some multi-band networks, the radio coverage is ensured by DCS cells in one geographical area and by GSM cells in another geographical area. As these cells form a multi-band and mono-layer network, the capture handovers between cells of different bands will be inefficient to regulate the CS traffic load in the serving cell neighboring cellhood.

> The solution consists in allowing intra-layer traffic handovers (Cause 23) based on a power budget evaluation between cells of different bands.

© Alcatel 102



2.6 Main standard handover algorithms Handover Cause 23: Traffic (2/2)

> CAUSE 23: Traffic Handover

DELTA_HO_MARGIN(0,n) < 0 dB

and PBGT(n) >HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNER

+ DELTA_HO_MARGIN(0,n)

and EN_TRAFFIC_HO(0,n) = ENABLED

� Size of window for level average: A_PBGT_HO

B8(See comments)

> The principle of this handover is to reduce the size of the serving cell when it is high loaded relatively to a low loaded cell.

> When the mobile moves away from the BTS, the power budget will increase and a better cell handover will be triggered earlier.

> It is recommended to inhibit Traffic handover towards 1 TRX cells. These cells do not have enough resources to receive incoming handovers due to congestion of neighboring cells. Moreover because of the great variation of traffic in the 1 TRX cells, traffic load is never considered as low.

> This cause is inhibited for handover from SDCCH to SDCCH.

> Cause 23 is checked over all the neighboring cells belonging to the same layer. It means that it is checked between cells whose CELL_LAYER_TYPE is single or upper, between cells whose CELL_LAYER_TYPE is lower, and between cells whose CELL_LAYER_TYPE is indoor.

> In addition to the condition on the cell layer type, the cell frequency band condition for checking Cause 23 is as follows whether or not the MS is in the inner zone of a multi-band cell:

• a) The MS is not in the inner zone of a multi-band cell

– If the flag EN_MULTIBAND_PBGT_HO is set to “disabled”, Cause 23 must not be checked between cells which use different frequency bands (i.e cells having different CELL_BAND_TYPE).

– If the flag EN_MULTIBAND_PBGT_HO is set to “enabled”, Cause 23 will be checked over all the neighboring cells without any cell frequency band restriction.

• b) The MS is in the inner zone of a multi-band cell

– If the flag EN_MULTIBAND_PBGT_HO is set to “disabled”, Cause 23 is checked over all theneighboring cell multi-band cells (FREQUENCY_RANGE= PGSM-DCS1800 or EGSM-DCS1800) which belong to the same BSC as the serving cell.

– If the flag EN_MULTIBAND_PBGT_HO is set to “enabled”, Cause 23 will be checked over all theneighboring cells without any cell frequency band restriction.

© Alcatel 103



2.6 Main standard handover algorithms Handover Cause 28: Fast Traffic HO (1/3)

> CAUSE 28: Fast Traffic Handover• Push out of a cell a mobile in dedicated mode to allow a queued request

to be served in the serving cell

> May be triggered– From any non concentric cell OR concentric outer zone

– Towards any cell except the serving one

HO

New call attempt Most appropriate MS to be pushed out

Congested cell

New call attempt

HO

Most appropriate MS to be pushed out

Upper Layer Cell

© Alcatel 104




> CAUSE 28: Fast Traffic Handover

• Cause 28 is only checked if the channel of the candidate MS can support the channel rate (HR or FR) required by the queued request:

• HO is triggered when a request is queued at the top of the queue

QUEUED REQUEST CANDIDATE MS

HR HR or

FR on dual rate TRX

FR FR (whatever the TRX type)

© Alcatel 105




> CAUSE 28: Fast Traffic Handover equation

AV_RXLEV_NCELL(n) > L_RXLEV_NCELL_DR(n) + max (0, [MS_TXPWR_MAX(n) - P])

and t(n) > FREELEVEL_DR(n)


and EN_FAST_TRAFFIC_HO = ENABLED

� Size of window for average level: A_PBGT_DR

� Same thresholds and window as Cause 20 (FDR)

� EN_CAUSE_28 is an internal HOP process variable, enabled when a request is queued

> HO cause 28 process:

• If EN_FAST_TRAFFIC_HO = enabled, when an assignment request (or external emergency HO request) is queued, the RAM process sends to the HOP process a Fast Traffic HO request which contains the queued request reference and its channel rate.

• Then, HO cause 28 becomes checkable (EN_CAUSE_28=enabled).

• Once an HO alarm for cause 28 is triggered, the flag EN_CAUSE_28 is set to “disabled” so as not to perform more than one handover. In the same time, the HOP process gets back to the RAM process a Fast Traffic HO Acknowledge which contains the queued request reference and the reference of the MS that can perform HO.

• If several answers are sent to the RAM process, only the first one corresponding to the queued request is taken into account.

• The RAM process checks if the request is still queued. If it is so, RAM asks HOP to start HO for this mobile; otherwise the process is stopped.

• Once the HOP process receives this message, the first two conditions of Cause 28 (good enough level, enough free resources in the target cell) are checked one more time. If the conditions are fulfilled, the HOP process sends an alarm to the HOM entity and the timer T_FILTER is started; otherwise the process is stopped.

> Note: the first two conditions of cause 28 are tested twice in order to be sure that the candidate cells are still valid when the « cause 28 start HO » message is received from the RAM process.

© Alcatel 106



2.6 Main standard handover algorithms Training exercises (1/4)

> Detection of cause 12

• Parameters settings

– No Power Control DL, no anti ping-pong

– BS_TXPWR_MAX_INNER = 0 dB

– EN_PBGT_HO = enabled

– EN_TRAFFIC_HO(0,n) = disabled

– HO_MARGIN(0,n) = 5 dB

– HO_MARGIN_INNER = 0 dB

– RXLEV_LIMIT_PBGT_HO = -47 dBm

• In each case, determine if cause 12 is detected or not

Time allowed:

15 minutes

© Alcatel 107



> Is cause 12 triggered?

• With EN_MULTIBAND_PBGT_HO = DISABLED


Cause 12 ?

PBGT ?

-65 dBm-65 dBm-65 dBm-70 dBm-80 dBmRx_Lev(n)

900+18009009001800900Band

Multiband

UpperSingleSingleSingleSingleType

Target

-90 dBm-90 dBm-90 dBm-85 dBm-85 dBmRx_Lev(0)

InnerOuterInner------Zone

900+1800900+1800900+1800900900Band

Multiband

Upper

Multiband

Upper

Multiband

UpperSingleSingleType

Source

Case 5Case 4Case 3Case 2Case 1Inputs

© Alcatel 108



> Same exercise: is cause 12 triggered?

• With EN_MULTIBAND_PBGT_HO = ENABLED


Cause 12 ?

PBGT ?


900+18009009001800900Band

Multiband

UpperSingleSingleSingleSingleType

Target


InnerOuterInner------Zone

900+1800900+1800900+1800900900Band

Multiband

Upper

Multiband

Upper

Multiband

UpperSingleSingleType

Source


© Alcatel 109




> Multi-band cells parameters tuning

• The main parameter to be tuned in a multi-band cell is OFFSET_HO_MARGIN_INNER

– Propagation difference between 900 and 1800

• Propose a method for tuning accurately this parameter

Time allowed:

10 minutes

9001800

© Alcatel 110



2.7 Handover algorithms for multi-band networks

© Alcatel 111



> CAUSE 21: high level in the neighboring cell in the preferred band

• Capture towards the preferred band

• “Historical” handover to capture dual-band MS– Introduced in B5.1

– Improved in B6.2 (to avoid preferred band congestion)

– Improved in B7 (with anti ping-pong mechanism)

• May be triggered

– From any cell with cell_band_type ≠≠≠≠ preferred_band

– Towards any cell with cell_band_type = preferred_band

– Can be triggered between cells of different layers

2.7 Handover algorithms for multi-band networksCause 21: high level in the neighboring cell in the preferred band (1/4)

900

1800

© Alcatel 112



> CAUSE 21: high level in the neighboring cell in the preferred band

AV_RXLEV_NCELL(n) > L_RXLEV_CPT_HO(0,n) + max (0, [MS_TXPWR_MAX(n) - P])

and Traffic_load(0) = MULTIBAND_TRAFFIC_CONDITION

and Traffic_load(n) ≠≠≠≠ HIGH

and EN_PREFERRED_BAND_HO = ENABLED

• Size of window for average level: A_PBGT_HO

• MULTIBAND_TRAFFIC_CONDITION can take 3 values: ANY_LOAD (default), HIGH, NOT_LOW

• Anti ping-pong: not checked if T_INHIBIT_CPT is running


© Alcatel 113



> L_RXLEV_CPT_HO(0,n)

• the lower this threshold is, the more MSs are captured by the preferred band

– High capacity enhancement: full usage of the new band

– but risks of ping-pong HO between macro and micro layers when the threshold value is close to the value of emergency thresholds

– Anti ping-pong mechanism introduced in B7 for quality HO

• if hotspot 1800 cell or border of a 1800 zone– Increase the threshold value to minimize ping-pong HO

• if continuous good coverage of a 1800 layer– example: center of a 1800 zone

– Decrease the threshold value to allow more mobiles to be captured by the preferred layer

• Default value: -85 to -92 dBm


© Alcatel 114



> Traffic discrimination

• Introduced in B6.2, with:

– Traffic_load(0) = MULTIBAND_TRAFFIC_CONDITION

– Traffic_load(n) ≠≠≠≠ HIGH

• To avoid preferred band congestion

– By avoiding capture if the target traffic condition is HIGH

– By regulating sending based on the source traffic condition(HIGH or NOT_LOW or ANY_LOAD)


Appendix 1

© Alcatel 115



> Capture alarms filtering based on T_INHIBIT_CPT

• Reduce ping-pong effect for causes 21, 14, 24

• By forbidding capture for a while (T_INHIBIT_CPT) when an emergency quality handover has just been triggered

– Cause 2, 4 or 7: ULQ, DLQ or Bad SACCH

– OR external HO with A interface cause ULQ or DLQ

• In B8, the feature has been extended to the SINGLE cells

2.7 Handover algorithms for multi-band networksCapture alarms filtering (1/2)

Cell(0)

Cell(n-1) Cell(n)

1. Emergencyquality HO

2. Inhibit cause 21during T_INHIBIT_CPT

B8

> The role of the timer T_INHIBIT_CPT is to inhibit the capture handover Causes 14, 21, and 24 for a while so as to reduce the ping-pong effect. The immediately preceding cell on which the MS has been is here denoted n-1.

© Alcatel 116



> Capture alarms filtering based on T_INHIBIT_CPT

• If the serving cell is in the upper or single layercell_layer_type(0) = upper or single

– IF [ Cell_layer_type(n-1) = lower OR indoor ]

OR [ cell_band_type(n-1) ≠≠≠≠ cell_band_type(0) ]

– AND an emergency quality HO has just been performed

– THEN, T_INHIBIT_CPT is started

• If the serving cell is in a lower layer cell_layer_type(0) = lower

– IF [ Cell_layer_type(n-1) = indoor ]

OR [ cell_band_type(n-1) ≠≠≠≠ cell_band_type(0) ]

– AND an emergency quality HO has just been performed

– THEN, T_INHIBIT_CPT is started

2.7 Handover algorithms for multi-band networksCapture alarms filtering (2/2)

Modified B8

B8

> According to the layer of the serving cell the following conditions must be checked for starting the timer T_INHIBIT_CPT:

• Case of a serving cell in the upper or single layer (CELL_LAYER_TYPE(n0) = upper or single)

– Condition 1: The immediately preceding cell n-1 is in the indoor or lower layer, i.e. CELL_LAYER_TYPE(n–1) = lower or indoor, or the frequency band of the immediately preceding cell n-1 is different from the frequency band of the serving cell n0, i.e. CELL_BAND_TYPE(n–1) <> CELL_BAND_TYPE(n0).

– Condition 2: The call has previously performed i) an emergency internal handover on quality (Cause 2, 4, and 7) towards the serving cell or ii) an external handover with the A interface GSM cause “uplink quality or downlink quality” and there is a bi-directional adjacency link between the preceding external cell n-1 and the serving cell n0.

– If Conditions 1 and 2 are fulfilled, the timer T_INHIBIT_CPT is started.

• Case of a serving cell in the lower layer (CELL_LAYER_TYPE(n0) = lower)

– Condition 3: The immediately preceding cell is in the indoor layer, i.e. CELL_LAYER_TYPE(n–1) = indoor, or the frequency band of the immediately preceding cell n-1 is different from the frequency band of the serving cell n0, i.e. CELL_BAND_TYPE(n–1) <> CELL_BAND_TYPE(n0).

– Condition 4: The call has previously performed i) an emergency internal handover on quality (Cause 2, 4, and 7) towards the serving cell or ii) an external handover with the A interface GSM cause “uplink quality or down link quality” and there is a bi-directional adjacency link between the precedent external cell n-1and the serving cell n0.

– If Conditions 3 and 4 are fulfilled, the timer T_INHIBIT_CPT is started.

> If these conditions are not fulfilled, the timer T_INHIBIT_CPT is not started.

© Alcatel 117



2.7 Handover algorithms for multi-band networksTraining exercises (1/3)


• EN_PREFERRED_BAND_HO(0) = ENABLED

• L_RXLEV_CPT_HO(0,n) = -85 dBm

• MULTIBAND_TRAFFIC_CONDITION = NOT_LOW

• Check if cause 21 is triggered in each of the following cases

Time allowed:

10 minutes

© Alcatel 118



2.7 Handover algorithms for multi-band networksTraining exercises (2/3)

HIGHINDLOWINDINDLOWINDINDTraffic(n)

HIGHLOWHIGHINDINDHIGHINDINDTraffic(0)

-80 dBm

1800

Single

-84 dBm

Inner

900+1800

Multiband

Upper

Case 5

-80 dBm

900+1800

Multiband

Upper

-90 dBm

Outer

900+1800

Multiband

Upper

Case 6

-70 dBm

1800

Single

-80 dBm

---

900

Single

Case 7

Cause 21 ?


18001800180018001800Band

SingleSingleMiniSingleSingleType

Target


---Outer---------Zone

900900+1800900900900Band

SingleMultiband

SingleSingleMicroSingleType

Source



© Alcatel 119



2.8 Handover algorithms for concentric cells

© Alcatel 120



> Emergency handovers specific to concentric cells

• Intracell handovers from an inner to an outer zone

• cause 10 : too low level on the uplink in the inner zone

• cause 11 : too low level on the downlink in the inner zone

> May be triggered– From the inner zone of a concentric cell

– Towards the outer zone, same cell

2.8 Handover algorithms for concentric cells Emergency handovers

INNEROUTER

© Alcatel 121



> CAUSE 10: too low level on the uplink in inner zone

AV_RXLEV_UL_HO < RXLEV_UL_ZONE

and MS_TXPWR = min (P, MS_TXPWR_MAX_INNER)

• average window: A_LEV_HO

2.8 Handover algorithms for concentric cellsCause 10: too low level on the uplink in the inner zone

© Alcatel 122



> CAUSE 11: too low level on the downlink in the inner zone

AV_RXLEV_DL_HO < RXLEV_DL_ZONE

and BS_TXPWR = BS_TXPWR_MAX_INNER

• average window: A_LEV_HO

2.8 Handover algorithms for concentric cellsCause 11: too low level on the downlink in the inner zone

© Alcatel 123



> CAUSE 13: too high level on the UL and the DL in the outer zone

• Introduced in R3

• Improved in B6.2

• Improved in B7 (load balance)

• Better condition intracell handover

• If the cell is a multi-band cell, cause 13 is checked only for multi-band MSs

> May be triggered– From the outer zone of a concentric cell

– Towards the inner zone, same cell

2.8 Handover algorithms for concentric cells Cause 13: too high level on the UL and the DL in the outer zone (1/6)

INNEROUTER

© Alcatel 124



> CAUSE 13: too high level on the UL and the DL in the outer zone

AV_RXLEV_UL_HO > RXLEV_UL_ZONE ++ ZONE_HO_HYST_UL ++ (MS_TXPWR - MS_TXPWR_MAX_INNER) ++ PING_PONG_MARGIN(0,call_ref)

and AV_RXLEV_DL_HO > RXLEV_DL_ZONE ++ ZONE_HO_HYST_DL ++ (BS_TXPWR - BS_TXPWR_MAX_INNER) ++ PING_PONG_MARGIN(0,call_ref)

and AV_RXLEV_NCELL_BIS(n) <= NEIGHBOUR_RXLEV(0,n)


and EN_BETTER_ZONE_HO = ENABLED

• average windows: A_LEV_HO and A_PBGT_HO (for n)

2.8 Handover algorithms for concentric cellsCause 13: too high level on the UL and the DL in the outer zone (2/6)

© Alcatel 125



> ZONE_HO_HYST_UL

• UL static hysteresis for interzone HO from the outer to the inner

– In case of multi-band cells, it should take into account the difference of propagation between GSM and DCS

• Added to cause 10 threshold RXLEV_UL_ZONE

> ZONE_HO_HYST_DL

• DL static hysteresis for interzone HO from the outer to the inner

– In case of multi-band cells, it should take into account the difference of propagation between GSM and DCS and the difference of BTS transmission power in the two bands

• Added to cause 11 threshold RXLEV_DL_ZONE


© Alcatel 126



> PING_PONG_MARGIN(0,call_ref)

• Penalty PING_PONG_HCP put on cause 13 if

– The immediately preceding zone in which the call has been is the inner zone of the serving cell

– And The last handover was not external intracell

– And T_HCP is still running

• PING_PONG_MARGIN(0,call_ref) = 0

– If the call was not previously in the inner zone of the serving cell

– Or T_HCP has expired


INNEROUTER

© Alcatel 127



> NEIGHBOUR_RXLEV(0,n)

• Concentric cells are designed to create an INNER zone

– protected from external interferers

– and creating no interferences on other cells

– … to be able to face a more aggressive frequency reuse in INNER zone TRXs

• NEIGHBOUR_RXLEV(0,n) tuning enables to avoid handovers if the MS position leads to interferences

• The condition is checked towards all neighboring cells belonging to the same layer and band as the serving cell


INNEROUTER

INNER zoneinterferer 1

INNER zoneinterferer 2

?

© Alcatel 128



> EN_CAUSE_13

• Load balance between the inner and the outer zone may be allowed by setting EN_LOAD_BALANCE = ENABLED

• If EN_LOAD_BALANCE = ENABLED

– If the INNER zone is less loaded than the OUTER one,EN_CAUSE_13 = ENABLED

– If the INNER zone is more loaded than the OUTER one,EN_CAUSE_13 = DISABLED

• If EN_LOAD_BALANCE = DISABLED

– EN_CAUSE_13 = ENABLED


© Alcatel 129



> Outgoing intercell handovers from concentric cells

• As explained before, an MS located in a concentric cell can make intercell, emergency or better condition HO regardless their current zone

– For example, an MS located in the INNER zone of a concentric cell can make directly a cause 12 HO towards another cell, WITHOUT having to trigger any cause 10 or 11 to the OUTER zone before

– The only restrictions have been already presented: they are linked to EN_MULTIBAND_PBGT_HO and EN_BI-BAND_MS parameters

2.8 Handover algorithms for concentric cellsOutgoing intercell handovers from Concentric Cells

© Alcatel 130



> Incoming intercell handovers towards a concentric cell

• In case an MS is making an incoming handover towards a concentric cell (due to outer PBGT measurements, etc.), a TCH may be allocated

– either in the INNER zone

– or in the OUTER zone, as for call setup

– depending on radio conditions

– In case of a multi-band cell, if the MS is not multi-band, it will always be sent to the OUTER zone

2.8 Handover algorithms for concentric cellsIncoming intercell handovers towards a Concentric Cell (1/3)

INNEROUTER ??

© Alcatel 131



> Use part of the Handover cause 13 algorithm on each potential target

> IF Cell(n) is external– The MS is directed to the OUTER zone of (n)

> ELSE (cell(n) is internal)

• IF

AV_RXLEV_NCELL(n) > RXLEV_DL_ZONE + ZONE_HO_HYST_DL+

+ (BS_TXPWR - BS_TXPWR_MAX_INNER)

and EN_BETTER_ZONE_HO = ENABLED– The MS is directed towards the INNER zone

• ELSE

– The MS is directed towards the OUTER zone


© Alcatel 132



> The A_LEV_HO average window is used

> If less than A_LEV_HO have been received, averages are calculated on the available number of measurements

> RXLEV_DL_ZONE, ZONE_HO_HYST_DL, BS_TXPWR, BS_TXPWR_MAX_INNER and EN_BETTER_ZONE_HO correspond to the target concentric cell


© Alcatel 133



> EN_BETTER_ZONE_HO = ENABLED

> BS_TXPWR_MAX_INNER = to be tuned

> MS_TXPWR_MAX_INNER = to be tuned

> NEIGHBOUR_RXLEV(0,n) = -47 dBm (inhibited)

> EN_LOAD_BALANCE = DISABLED

> RXLEV_DL_ZONE and RXLEV_UL_ZONE: to be tuned

• Default value: RXLEV_DL_ZONE = -71 dBm (mono-band cell)

• Default value: RXLEV_DL_ZONE = -82 dBm (multi-band cell)

• Default value: RXLEV_UL_ZONE = -110 dBm (inhibited)

> ZONE_HO_HYST_DL and ZONE_HO_HYST_UL• +16 dB if 900 outer zone and 1800 inner zone

• - 4 dB if 1800 outer zone and 900 inner zone

• assumption: the propagation difference between 900 and 1800 is 10 dB

2.8 Handover algorithms for concentric cellsParameter settings for multi-band cells

© Alcatel 134



2.8 Handover algorithms for concentric cells Training exercise

> Tuning of RXLEV_DL_ZONE

• What is the impact of a modification of its value?

• Propose

– A method for a first tuning of this parameter

– A Follow-up method to adapt the parameter value to traffic evolution

Time allowed:

10 minutes

© Alcatel 136



> As soon as an intercell HO alarm has been detected

> HO Detection sends to Candidate Cell Evaluation

– the HO cause value

– the preferred layer for the target cell indicated by the variable PREF_LAYER (it depends on the cell network architecture and on the operator strategy)

– the list of potential candidates (it depends on type of handover cause)

2.9 Candidate cell evaluationFrom HO Detection to Candidate Cell Evaluation

Candidate

Cell

Evaluation

Handover

Detection

Raw cell list

cell 1: cause C1

cell 2: cause C2

cell 3: cause C3

…

Max 32 cells

PREF_LAYER

© Alcatel 137



2.9 Candidate cell evaluation Evaluation process

MEASUREMENT PREPROCESSING

according

• A_LEV_HO

• A_QUAL_HO

• A_PBGT_HO

• A_RANGE_HO

Performed every SACCH

Measurement re

sult

HO_DETECTION

cause 2: uplink quality

cause 3: uplink level

cause 4: downlink quality

cause 5: downlink level

cause 6: distance

cause 12: power budget

Performed every SACCH

Preprocess measurement

Raw cell list

cell 1: cause C2

cell 2: cause C2

cell 3: cause C2

cell 4: cause C2

cell 5: cause C2

cell 6: cause C2

cell 7: cause C2

cell 8: cause C2

…

Max 32 cells

max EverySACCH

HO CANDIDATE CELLS EVALUATION

Priority (0,n) = 0

cell 2: cause C2

cell 3: cause C3

cell 4: cause C4

Priority (0,n) = 1

cell 1: cause C1

Priority (0,n) = 2

Priority (0,n) = 3

cell 5: cause C5

cell 6: cause C6

cell 7: cause C7

cell 8: cause C8

PRE-RANKING

PBGT_FILTERING

HO_MARGIN_XX(0,n)

Priority (0,n) = 0

cell 2: cause C2

cell 3: cause C3

cell 4: cause C4

Priority (0,n) = 1

-----------------------

Priority (0,n) = 2

Priority (0,n) = 3

----------------------

cell 6: cause C6

-----------------------

cell 8: cause C8

CELLS EVALUATION PROCESS

Order or Grade

Grade

Priority (0,n) = 0

cell 4

cell 2

Priority (0,n) = 1

Priority (0,n) = 2

Priority (0,n) = 3

cell 8

Order

Priority (0,n) = 0

cell 4

cell 3

cell 2

Priority (0,n) = 1

Priority (0,n) = 2

Priority (0,n) = 3

cell 8

> The HO candidate cell evaluation process is run after all intercell handover alarms.

> In case of intra-cell handover alarm (HO causes 10, 11, 13, 15, 16), the candidate cell evaluation process is skipped: the target cell is the serving cell.

> The handover detection gives as indication the raw cell list (built from the book-keeping list) and the preferred layer for the handover.In case of emergency handover alarms or cause 20 alarm, the cell evaluation will order the cells given in the raw list, putting in the first position the cells belonging to the preferred layer, having the highest priority (if EN_PRIORITY_ORDERING=ENABLED) and/or having the same frequency band type as the serving cell. In case of an intercell handover alarm, if the serving cell belongs to the raw cell list (emergency handover from the DCS 1800 inner zone of a multi-band cell), this cell is put at the end of the candidate cell list with the MS zone indication OUTER.

> In case of better condition handover alarms (except cause 20), the cell evaluation will order the cells given in the raw list, putting in the first position the cells belonging to the preferred layer and having the highest priority (if EN_PRIORITY_ORDERING=ENABLED).

© Alcatel 138



2.9 Candidate cell evaluation Pre-ranking in standard networks

> with PRIORITY(0,n) settings, the operator can

• for each couple of cells

• tag the target cell with a defined priority (from 0 = max to 5 = min)

• this definition has a higher priority than usual order/grade ranking

> especially useful for multi band/hierarchical architectures

• a simple way to force a target cell whatever its RxLev and PBGT

• nevertheless it can be skipped over by filtering processes

• low interest for standard networks

Serving cell

Candidate cell 1: RxLev: - 70 dBm, pbgt: + 10 dB

Candidate cell 2: Rxlev: - 90 dBm, PBGT: + 5dB

P0

P1

> PRIORITY(0,n) can take 6 different values in B7, to take into account new indoor layers.

© Alcatel 139



> In hierarchical or multi-band networks, pre-ranking is used:

• For emergency handovers + Forced Directed Retry + Fast Traffic HO

– Cell_layer_type: single, upper, lower, indoor

– PRIORITY(0,n): 0 to 5

– Cell_band_type: GSM or DCS

• For better condition handovers

– Cell_layer_type: single, upper, lower, indoor

– PRIORITY(0,n): 0 to 5

• PRIORITY(0,n) are taken into account only if EN_PRIORITY_ORDERING is set to enabled on the serving cell

2.9 Candidate cell evaluation Pre-ranking in complex networks (1/3)

© Alcatel 140



> Pre-ranking in case of emergency HO, plus cause 20 and 28:


Cell_layer_type = Pref_layer

Cell_layer_type ≠ Pref_layer

List of candidate cells n

Cell_band_type = serving cell

Cell_band_type ≠ serving cell

Priority(0,n) = 0

Priority(0,n) = 1

Priority(0,n) = 5

Priority(0,n) = 0

Priority(0,n) = 1

Priority(0,n) = 5

© Alcatel 141



> Pre-ranking in case of better condition HO:


Cell_layer_type = Pref_layer

Cell_layer_type ≠ Pref_layer

List of candidate cells n

Priority(0,n) = 0

Priority(0,n) = 1

Priority(0,n) = 5

Priority(0,n) = 0

Priority(0,n) = 1

Priority(0,n) = 5

© Alcatel 142



2.9 Candidate cell evaluation PBGT Filtering

> PBGT filtering: process introduced since B5

• optional, activated through the flag EN_PBGT_FILTERING

• filter out cells from the target list

• inhibited for better conditions handovers

• based on power budget

• Mandatory for multi-band networks

PBGT(n) > HO_MARGIN_XX (0,n) + OFFSET_HO_MARGIN_INNER

– HO_MARGIN_XX (0,n) = HO_MARGIN_QUAL (0,n) for causes 2, 4, 7

– HO_MARGIN_XX (0,n) = HO_MARGIN_LEV (0,n) for causes 3, 5, 17, 18, 28

– HO_MARGIN_XX (0,n) = HO_MARGIN_DIST (0,n) for cause 6

– OFFSET_HO_MARGIN_INNER is only applied when the MS is in the inner zone of a concentric or multi band cell

– The average window is A_PBGT_HO

> The filtering process allows to filter out cells from the target list before sending them to the ORDER or GRADE evaluation process.

> It can be enabled/disabled on-line on a per cell basis from the OMC-R with the flag EN_PBGT_FILTERING.

> The candidate cells are filtered on their power budget in relation to a handover margin threshold based on the handover cause.

> Note: the average window used for this process is A_PBGT_HO (even for emergency handovers, where handover alarm could have been raised through A_LEV_HO or A_QUAL_HO samples).

> Warning: HO_MARGIN_xx (LEV, DIST or QUAL) has nothing to do with a handover margin value, specific for certain handover causes (anyway, these handovers cause only tackle source cell and are not looking at level of targets for handover detection).

> HO_MARGIN is used for handover detection (cause 12 or 23).

> HO_MARGIN_xx are used for candidate cell evaluation.

> Thus, there is no having HO_MARGIN = HO_MARGIN_xx! Let us see three examples:

1) If HO_MARGIN_xx = HO_MARGIN = 5 dB

In that case, when an emergency handover is triggered (level, quality, distance, etc.), all neighboring cells are filtered regarding their PBGT compared to 5 dB! By the way, if a cell that is not greater than the serving one + 5 dB will be filtered out: this handover, detected as an emergency case, is in fact a better cell one.

2) If HO_MARGIN_xx is very small (for example, -30 dB), risk of ping-pong handovers.

For example, all cells have L_RXLEV_DL_H = -97dBm. If Lev(cell1)=-98dBm, HO can be triggered to cell2 with level -99dBm (-99>-98-30), and then, as -99<-97, HO is triggered back to cell1: ping-pong of emergency HO.

3) HO_MARGIN_xx can be used to simulate PBGT HO (for example, usage of distance HO to simulate 900-1800 PBGT HO before it was existing). HO_MARGIN_DIST is very small (e.g., 2 on 1800). Thus, a Distance HO alarm is raised very early. If HO_MARGIN_DIST (1800,900)= 8 dB, no HO will be in fact triggered before the level of the 900 neighboring cell is greater than the one of 1800 + 8 dB: this distance HO is in fact a PBGT HO between bands.

© Alcatel 143



> ORDER cell evaluation process, if CELL_EV = ORDER

Cell "n" is ranked among other according to the best ORDER:

If EN_LOAD_ORDER = ENABLED and cell n is internal to the BSC

ORDER (n) = PBGT(n) + LINK_FACTOR(0,n) + FREEfactor(n) - FREEfactor(0) - HO_MARGIN_XX(0,n)

• LINK_FACTOR(0,n) is an operator parameter to give a bonus/penalty to a cell

• FREEfactor are TCH traffic based bonus/penalty to rank cells

If EN_LOAD_ORDER = DISABLED or cell n is external to the BSC

ORDER (n) = PBGT(n) + LINK_FACTOR(0,n) - HO_MARGIN_XX(0,n)

Cell "n" is kept if:

• AV_RXLEV_NCELL (n) > RXLEVmin (n) + max [0;(MS_TXPWR_MAX(n)-P)]

2.9 Candidate cell evaluation ORDER evaluation

> Two types of cell evaluation algorithms can be used: ORDER and GRADE.

> ORDER and GRADE are two different methods of cell ranking. They both consist in giving a mark or ’figure of merit’ to each candidate cell.

> The basic differences between ORDER and GRADE are that:

• with ORDER:

– The candidate cell evaluation process interacts with the handover detection by use of cause dependent handover margins.

– The candidate cell evaluation process takes into account the number of free TCH in the candidate cells.

• with GRADE,:

– The candidate cell evaluation process does not interact with the handover detection.

– The candidate cell evaluation process takes into account the relative load of traffic channels in the candidate cells.

> The type of cell evaluation is chosen by the operator on a (serving) cell basis and is provided to the BSC with the parameter CELL_EV

> For any handover cause, the first cell in the list is taken as the target cell, i.e. the cell with the highest value of ORDER(n). The cells do not need to fulfil any other condition.

> If no cell fulfils the condition and the serving cell does not belong to the target cell list, the target cell list is empty andno further action is carried out.

> Note: the A_PBGT_HO average window is used for this process.

© Alcatel 144



> GRADE cell evaluation process, if CELL_EV = GRADE

Cell "n" is ranked among other according to the best GRADE:

If EN_LOAD_ORDER = ENABLED and cell n is internal to the BSC

GRADE (n) = PBGT(n) + LINK_FACTOR(0,n) + LOADfactor(n)

• LINK_FACTOR(0,n) is an operator parameter to give a bonus/penalty to a cell

• LOADfactor(n) is a weighting factor that takes into account the relative load of traffic channels in a cell

If EN_LOAD_ORDER = DISABLED or cell n is external to the BSC

GRADE (n) = PBGT(n) + LINK_FACTOR(0,n)

Cell "n" is kept if:

� AV_RXLEV_NCELL (n) > RXLEVmin(n) + max [0;(MS_TXPWR_MAX(n)-P)]

2.9 Candidate cell evaluation GRADE Evaluation

> LINKfactor(0,n) is a parameter set by OMC command for each cell(n).

> LINKfactor(n1,n2) allows the operator to handicap or to favor the cell n1 with respect to its neighboring cell n2. In particular, it can be used to disadvantage an external cell when an internal cell is also a possible candidate.

> For any handover cause the first cell in the list is taken as the target cell, i.e. the cell with the highest value of GRADE(n). If no cell fulfils the condition and the serving cell does not belong to the target cell list, the target cell list isempty and no further action is carried out.

> Note: the A_PBGT_HO average window is used for this process.

> Note: an example summarizing all steps of candidate cell evaluation, in case of a multi-band network, can be given here: MS on a 1800 cell, 3 possible neighboring cells (1*900 + 2*1800). P(1800,900)=1 and P(1800,1800)=0. All HO_MARGIN_xx = 0 dB. PBGT:

• PBGT (900) = +5 (second cell seen in the book-keeping list)

• PBGT (1800_1) = -2 (first cell seen in the book-keeping list)

• PBGT (1800_2) = +2 (third cell seen in the book-keeping list)

> Cell (1800_2) is chosen.

© Alcatel 145



2.9 Candidate cell evaluation Training exercise (1/4)

> Which is the best target cell?

• Emergency qual ho triggered in serving cell

• EN_PBGT_FILTERING=Enabled

• HO_MARGIN_QUAL(0,n)=-2dB

• CELL_EV=GRADE EN_LOAD_ORDER=Disabled

• LINK_FACTOR(0,n)=0dB RXLEVmin=-100 dBm

-84 dBm

0

1800

Single

-101 dBm

0

1800

Single

1800900900Band

Best Target ?

-81 dBm-80 dBm-74 dBmRx_Lev(n)

000PRIORITY

SingleUmbrellaSingleType

Possible Target

-82 dBmRx_Lev(0)

1800Band

SingleType

Source

Time allowed:

10 minutes

© Alcatel 146




-84 dBm

1

1800

Single

-101 dBm

1

1800

Single

1800900900Band

Best Target ?


100PRIORITY


Possible Target

-82 dBmRx_Lev(0)

1800Band

SingleType

Source

> Which is the best target cell?






Time allowed:

10 minutes

© Alcatel 147




900-1800Band

-84 dBm

0

1800

Single

-101 dBm

0

1800

Single

1800900900Band

Best Target ?


000PRIORITY


Possible Target

-82 dBmRx_Lev(0)

InnerZone

Single MultibandType

Source

> Which is the best target cell ?






• OFFSET_HO_MARGIN_INNER = 10 dB

Time allowed:

10 minutes

© Alcatel 148



> What is the problem ?


PBGT=0dB

- 57 dBm- 62 dBm BCCH

BCCH

Concentric cell

EN_BS_PC = disable

BS_TXPWR_MAX = 0dB

BS_TXPWR_MAX_INNER = - 10dB

RXLEV_DL_ZONE = - 80dBm

ZONE_HO_HYST_DL = 6dB

RXLEV_UL_ZONE = - 110dBm

HO_MARGIN(concentric,single) = 4dB

Single cell

HO_MARGIN(single,concentric) = 4dB

© Alcatel 149


3 CREATING A MULTI-BAND NETWORK

© Alcatel 150



3 CREATING A MULTI-BAND NETWORKSession presentation

> Objective: to be able to define relevant parameters settings to introduce a new frequency band in an existing network

> Program:

3.1 Introduction



3.4 Adding a 1800 band in an existing 900 (macro+micro) network

3.5 The multi-band cells solution


3.7 Case study: Quadrilayer network (Macro 900+1800 / Micro 900+1800)

© Alcatel 151



3.1 Introduction

© Alcatel 152



> The introduction of a new band in an existing network will be considered through the following examples:

• adding a 1800 band in an existing 900 network

• adding a 900 band in an existing 1800 network

• adding a 1800 band in an existing 900 (macro+micro) network

• the multi-band cells solution

– The aim is to show the use of parameters and algorithms

– Values are only given as examples

3.1 Introduction

© Alcatel 154



> Cell selection: higher priority for macro 1800 cells

3.2 Adding a 1800 band in an existing 900 network Idle mode parameters (1/2)

18001800CELL_BAR_QUALIFY = 0

900900


=> a dual band MS tries to select first a macro 1800 cell

© Alcatel 155



> Cell reselection: higher priority for macro 1800 cells

3.2 Adding a 1800 band in an existing 900 network Idle mode parameters (2/2)

18001800CELL_RESELECT_OFFSET = 16 dB

900900


C2(1800) = C1(1800) + 16

C2(900) = C1(900)

=> a dual band MS re-selects a macro 1800 cell

=> The real advantage is more close to 6 dB due to the propagation

difference

© Alcatel 156



> Two network architectures are possible:

• One layer

– macro 900 = umbrella or single

– macro 1800 = umbrella or single

– More complex parameters setting but more flexible solution

• Two layers

– macro 900 = umbrella

– macro 1800 = mini

– Easy parameters setting but more difficulties to introduce a new micro or indoor layer afterwards

3.2 Adding a 1800 band in an existing 900 network Cell Administration

© Alcatel 157



> Umbrella or single 900 + 1800

• Emergency alarm or Forced DR: the traffic distribution is driven by the parameter PRIORITY(0,n) because PREF_LAYER = upper + single is the layer to which both 900 and 1800 cells belong

> Umbrella 900 + mini 1800

• Emergency alarm: the traffic distribution is first driven by the layer because PREF_LAYER = upper + single for umbrella 900 cells and lower for mini 1800 cells (according to parameter EN_RESCUE_UM)

• Forced DR: the traffic distribution is first driven by the parameter PRIORITY(0,n)because PREF_LAYER = none, then the same band is preferred

– In case of a dual layer solution, almost no parameter is to be tuned to obtain an expected emergency handovers behavior

– Easy and fast introduction of the new band

3.2 Adding a 1800 band in an existing 900 network Single 1800 versus Mini 1800 (1/2)

> The strategy of parameter setting for a dualband 900/1800 configuration will depend on the coverage of the 1800 layer on the one hand and on the capacity of the 1800 cells on the other hand:

• if 1800 coverage is good and 1800 capacity is good:

– it is better to stay on the 1800 band for both FDR and Emergency alarm:

– mono-layer case (umbrella+single 900 & 1800): use the Priority(0,n) parameter to favor1800 cells or keep the same Priority to 900 and 1800 neighboring cells knowing that cells of the same band are preferred in the candidate cell evaluation process

– bi-layer case (umbrella 900 + mini 1800): set EN_RESCUE_UM to disabled to have "lower" as Preferred layer for Emergency HO and use the Priority(0,n) parameter to favor 1800 cells for FDR or keep the same Priority to 900 and 1800 neighboring cells knowing that cells of the same band are preferred in the candidate cell evaluation process.

– it is better to favor the 1800 band in case of congestion on the 900 band (especially the 1800 cells co-site of the congested 900 cell): use Priority(0,n) since the Preferred layer is "none" in both mono-layer or bi-layer configurations

– it is better to stay on the 900 band for an Emergency alarm: no specific parameter setting is needed since Preferred Layer = "upper+single" and cells of the same band are preferred in both mono-layer or bi-layer configurations.

• if 1800 coverage is not good and 1800 capacity is good:

– it is better to leave the 1800 band for the 900 band for both FDR and Emergency alarm:

– mono-layer case (umbrella+single 900 & 1800): use the Priority(0,n) parameter to favor 900 cells

– bi-layer case (umbrella 900 + mini 1800): set EN_RESCUE_UM to “enabled” to have "upper+single" as Preferred layer for Emergency HO and use the Priority(0,n) parameter to favor 900 cells for FDR.

– it is better to stay on the 900 band for Emergency HO and FDR (except for co-sector 1800 cell): no specific parameter setting is needed since (even if Preferred Layer = "none" for FDR) cells of the same band are preferred in both mono-layer or bi-layer configurations. Use Priority(0,n) to eventually favorthe co-sector 1800 cell but only in case of a bi-layer configuration.

• if 1800 capacity is not good:

– it is better to leave the 1800 band for the 900 band for FDR: use Priority(0,n) to favor the 900 neighboring cells since the Preferred layer is "none" in both mono-layer or bi-layer configurations.

– it is better to stay on the 900 band for FDR: no specific parameter setting is needed since cells of the same band are preferred in both mono-layer or bi-layer configurations.

© Alcatel 158



> BUT, in case of future microcell introduction

• If 1800 = mini

– Capture towards 1800 will be done even if Traffic(1800) = HIGH

– Traffic regulation of cause 21 cannot be used...

– … since cause 14 will be triggered anyway

3.2 Adding a 1800 band in an existing 900 network Single 1800 versus Mini 1800 (2/2)

mini 1800

Umb 900

µ 900

Cause 21Cause 14

Cause 21

Umb 1800

Umb 900

µ 900

Cause 21

14

14

Cause 21

© Alcatel 159



> DR and FDR are enabled

– FDR (cause 20) is triggered when the average level of a neighboring cell is higher than L_RXLEV_NCELL_DR(n)

3.2 Adding a 1800 band in an existing 900 network Mini 1800: Call Setup

umbrella 900

EN_DR = Enabled

EN_FORCED_DR = Enabled

L_RXLEV_NCELL_DR(n) = -85 dBm

FREElevel_DR(n) = 0

mini 1800

EN_RESCUE_UM = Disabled

EN_DR = Enabled



FREElevel_DR(n) = 0

DR & FDR

PRIORITY(1800, 900) = 1

DR & FDR

PRIORITY(900, 900) = 2

DR & FDR

PRIORITY(900, 1800) = 1

Priority is not favoring FDR

towards 1800 neighboring cells

but frequency band criterion is

DR & FDR

PRIORITY(1800, 1800) = 1

DR only

PRIORITY(900, 1800) = 2

Priority is favoring FDR

towards co-site 1800

neighboring cells

> This example corresponds to a network design where the 1800 band has a good coverage and sufficient capacity.

> EN_RESCUE_UM is set to “Disabled” for an emergency handovers behavior (keep multi-band MS in the 1800 layer).

> Setting PRIORITY(0,n) is very important for FDR also for the Mini 1800 configuration since network behavior will not be driven by PREF_LAYER which is equal to "none" in case of FDR.

• Priority(0,n) will be used to favor co-site 1800 neighboring cells in case of FDR from a 900 cell.

• Priority(0,n) may not be used to favor 1800 neighboring cells from a 1800 cell since neighboring cells with the same frequency band are preferred in the candidate cell evaluation process.

© Alcatel 160



> Causes 12, 14 and 21

3.2 Adding a 1800 band in an existing 900 network Mini 1800: Better condition handovers (1/2)

umbrella 900

MULTI_BAND_TRAFFIC_CONDITION

= ANY_LOAD

EN_SPEED_DISC = Disabled

EN_PBGT_HO = Enabled

EN_PREFERRED_BAND_HO = Enabled

EN_MCHO_NCELL =?

mini 1800



HIGH_TRAFFIC_LOAD = 70%

Cause 21 or Cause 14

PRIORITY(900, 1800) = 1

L_RXLEV_CPT_HO(900, 1800)

= -85 dBm

Cause 12 / 23

PRIORITY(900, 900) = 2

HO_MARGIN(900, 900) = 5 dB

DELTA_INC_HO_MARGIN = 2 dB

DELTA_DEC_HO_MARGIN = 2 dB

Cause 12 / 23

PRIORITY(1800, 1800) = 1

HO_MARGIN(1800, 1800) = 5 dB



No better condition HO from 1800 to 900

(different layers)

Only Emergency HO

> This example corresponds to a network design where the 1800 band has a good coverage and a sufficient capacity.

> Use Priority(0,n) to favor 1800 neighboring cells when cause 12 and cause 21 (or 14) HO alarms are triggered at the same time in a 900 cell.

> To make sure that cause 21 is triggered whatever the load of the 1800 cell, one may choose HIGH_TRAFFIC_LOAD = 100% on a Mini 1800 cell.In case HIGH_TRAFFIC_LOAD = 100% in a 1800 layer, Cause 23 is unusable (Traffic(1800) is never HIGH).

> As the proportion of multi-band MSs in the network is increasing (about 80% by the end of year 2002, compared to 15% in summer 2000), MULTIBAND_TRAFFIC_CONDITION can be tuned to avoid sending MS to the 1800 cell when the traffic in the 900 cell is low.Consequently the 900 band could then be preferred to the 1800 band on Emergency alarm on a 1800 layer.

© Alcatel 161



> cause 21 is triggered:– When a 1800 cell is received with an average level higher than -85 dBm

– When traffic condition in 1800 cell is not HIGH

– whatever the load of the macro 900 serving cell if MULTIBAND_TRAFFIC_CONDITION= ANY_LOAD (can be tuned)

> cause 14 is triggered:– When a 1800 cell is received with an average level higher than -85 dBm

– during L_MIN_DWELL_TIME seconds as EN_SPEED_DISC = DISABLED (speed discrimination to avoid capture of fast MS)

> it is necessary to choose between causes 21 and 14– cause 14 only in case of a new of speed discrimination

– In case a microcell 900 is added in the network: no more choice!

> cause 12 is used to make intra-layer handovers (PBGT > 5dB)

3.2 Adding a 1800 band in an existing 900 network Mini 1800: Better condition handovers (2/2)

> To make sure that cause 21 is triggered whatever the load of the 1800 cell, one may choose HIGH_TRAFFIC_LOAD = 100% on a Mini 1800 cell.

> As the proportion of multi-band MSs in the network is increasing (about 80% by the end of year 2002, compared to 15% in summer 2000), MULTIBAND_TRAFFIC_CONDITION can be tuned to avoid sending MSs to the 1800 cell when the traffic in the 900 cell is low.

© Alcatel 162



> Use Level, Quality, Distance Causes

3.2 Adding a 1800 band in an existing 900 network Mini 1800: Emergency handovers

umbrella 900

PREF_LAYER = upper + single

mini 1800


PREF_LAYER = lower

PRIORITY(900, 1800) = 1

PRIORITY(900, 900) = 2

PRIORITY(1800, 1800) = 1

PRIORITY(900, 1800) = 1

PRIORITY(900, 1800) = 2


> EN_RESCUE_UM is set to “Disabled” for an emergency handovers behavior (keep multi-band MSs in the 1800 layer).

> Setting PRIORITY(0,n) is not very important for an Emergency alarm in case of a Mini 1800 configuration as the network behavior will be mainly driven by PREF_LAYER.Indeed, in case of an Emergency alarm in a 900 cell, MS will be kept on the 900 band thanks to the Preferred Layer which will be equal to "upper+single" in this case. Even if Priority(0,n) settings favor the 1800 neighboring cells, 900 cells will be preferred since they belong to the "upper+single" layer whereas 1800 cells belong to the "lower" layer as being declared as mini.

© Alcatel 163



> if 1800 minicells

3.2 Adding a 1800 band in an existing 900 network Mini 1800: Candidate cells evaluation process

umbrella 900

EN_PRIORITY_ORDERING = Enabled

EN_PBGT_FILTERING = Enabled

CELL_EV = GRADE

mini 1800



CELL_EV = GRADE


PRIORITY(900, 900) = 2

HO_MARGIN_LEV(900, 900)= 0 dB

HO_MARGIN_QUAL(900, 900)= -1 dB

HO_MARGIN_DIST(900, 900)= 0 dB

PRIORITY(1800, 900) = 1

HO_MARGIN_LEV(1800, 900)= -127 dB


HO_MARGIN_DIST(1800, 900)= -127 dB

PRIORITY(900, 1800) = 1




PRIORITY(1800, 1800) = 1




PRIORITY(900, 1800) = 2


> 900 is a rescue layer for 1800: thus, all HO_MARGIN_XX(1800, 900) are set to -127 dB. In case no good 1800 neighboring cell is found (all of them are filtered through the PBGT filtering process) then the MS will be sent to the 900 neighboring cell having the best GRADE value.

© Alcatel 164



> Several ways to exit a 1800 cell

• If continuous coverage and cell at the center of the 1800 area

– cause 12 (PBGT)

• If discontinuous coverage or cell at the 1800 zone border

– Emergency alarm on level or quality or distance

– The risk is to stay too much time on the 1800 cell and to be unable to find

a macro 900 neighboring cell

– Anticipate 1800 zone exit

– If 1800 coverage is very discontinuous

– Change parameter settings:

» EN_RESCUE_UM= NONE

» PRIORITY(1800, 900) = 0

» PRIORITY(1800, 1800) = 1

3.2 Adding a 1800 band in an existing 900 network Mini 1800: exiting a 1800 cell

© Alcatel 165



> 1800 zone exit solution

• anticipate the zone exit:

– on distance U_TIMING_ADVANCE (to be tuned per cell)

– on level L_RXLEV_DL_H = normal value + 10 dB

3.2 Adding a 1800 band in an existing 900 network Mini 1800: exiting the 1800 zone

umbrella 900

mini 1800

HO_MARGIN_DIST(1800 border, 1800 inside) = 5 dB

HO_MARGIN_LEV(1800 border, 1800 inside) = 5 dB

HO_MARGIN_DIST(1800 border, 900 inside) = 12 dB

HO_MARGIN_LEV(1800 border, 900 inside) = 12 dB

HO_MARGIN_DIST(1800 border, 900 outside) = 2 dB

HO_MARGIN_LEV(1800 border, 900 outside) = 2 dB

Exit of the 1800 area

HO_MARGIN_DIST(900 outside, 1800 border) = 8 dB

HO_MARGIN_LEV(900 outside, 1800 border) = 8 dB

HO_MARGIN_DIST(1800 border, 900 colocated) = 5 dB

HO_MARGIN_LEV(1800 border, 900 colocated) = 5 dB

© Alcatel 166



> DR and FDR are enabled

– FDR (cause 20) is triggered when the average level of a neighboring cell is higher than L_RXLEV_NCELL_DR(n)

3.2 Adding a 1800 band in an existing 900 network Single/Umbrella 1800: Call Setup

Umbrella or single 900

EN_DR = Enabled



FREElevel_DR(n) = 0


EN_DR = Enabled



FREElevel_DR(n) = 0

DR & FDR

PRIORITY(900, 900) = 1

DR & FDR

PRIORITY(900, 1800) = 1

DR & FDR

PRIORITY(1800, 1800) = 1

DR only

PRIORITY(900, 1800) = 2Priority is favoring FDR

towards co-site 1800

neighboring cells and 900

ones

DR & FDR

PRIORITY(1800, 900) = 1

Priority is not favoring FDR

towards 1800 neighboring cells

but frequency band criterion is


> EN_RESCUE_UM is set to “Disabled” for an emergency handovers behavior (keep multi-band MSs in the 1800 layer).

> In case of dual band and mono-layer configuration, there is no way to favor the 1800 band for traffic catching during an FDR occurring in a 900 cell since setting of PRIORITY(0,n) parameters interacts with the MS behavior during an Emergency alarm. Therefore Priority(0,n) settings shall be chosen in order to favor 900 neighboring cells in case of Emergency alarm in a 900 cell (see the next slides).

> Priority(0,n) may not be used to favor 1800 neighboring cells from 1800 cell since neighboring cells with same frequency band are preferred in the candidate cell evaluation process. It is the same for an Emergency alarm where 1800 neighboring cells are preferred.

© Alcatel 167



> 2 possible strategies for better conditions handover between 900 and 1800:

• Usage of capture Cause 21

– Adapted to every network design

– Traffic regulation between bands by simple parameters tuning

• Usage of cause 12 (with EN_MULTIBAND_PBGT_HO = ENABLED)

– Coverage of 1800 should be identical to 900 (TWIN configuration)

– Co-located 900 & 1800 cells

– Same transmission power and same tilt for 900 & 1800 cells

– Favors the “best” cell for better speech quality

– But risk of numerous handovers (creating bad speech quality)

– And difficult traffic sharing between bands

• Cause 14 cannot be used (same layer)

3.2 Adding a 1800 band in an existing 900 network Single/Umbrella 1800: Better condition handovers

© Alcatel 168



> Causes 12 and 21

3.2 Adding a 1800 band in an existing 900 network Single/Umbrella 1800: Better condition handovers



= ANY_LOAD






Cause 21

PRIORITY(900, 1800) = 1

L_RXLEV_CPT_HO(900, 1800)

= -85 dBm

HO_MARGIN(900, 1800) = 0 dB

Cause 12 / 23

PRIORITY(900, 900) = 1

HO_MARGIN(900, 900) = 5 dB



Cause 12 / 23

PRIORITY(1800, 1800) = 1

HO_MARGIN(1800, 1800) = 5 dB



PRIORITY(1800, 900) = 1

HO_MARGIN(1800, 900) = +127 dB


> PBGT HO has to be avoided from 1800 to 900 cells as it will create ping-pong handover with capture. This is done by setting HO_MARGIN(1800, 900) to +127 dB.

> Warning: setting EN_MULTIBAND_PBGT_HO to “disabled” is not the good solution, as it has to be used for 1800 zone exit.

> To make sure that cause 21 is triggered whatever the load of the 1800 cell, one may choose HIGH_TRAFFIC_LOAD = 100% on a Mini 1800 cell.

> As the proportion of multi-band MSs in the network is increasing (about 80% by the end of year 2002, compared to 15% in summer 2000), MULTIBAND_TRAFFIC_CONDITION can be tuned to avoid sending MSs to the 1800 cell when the traffic in the 900 cell is low.

> In case HIGH_TRAFFIC_LOAD = 100% in the 1800 layer, Cause 23 is unusable (Traffic(1800) is never HIGH).

© Alcatel 169




3.2 Adding a 1800 band in an existing 900 network Single/Umbrella 1800: Emergency handovers



PRIORITY(900, 1800) = 1

PRIORITY(900, 900) = 1

PRIORITY(1800, 1800) = 1

PRIORITY(1800, 900) = 1

PRIORITY(900, 1800) = 2


> From a 900 cell, HO towards a 900 cell is favored (same frequency band).


© Alcatel 170



> 1800 Single / Umbrella

3.2 Adding a 1800 band in an existing 900 network Single/Umbrella 1800: Candidate cells evaluation process




CELL_EV = GRADE




CELL_EV = GRADE

PRIORITY(900, 900) = 1




PRIORITY(1800, 900) = 1

HO_MARGIN_LEV(1800, 900)= -127 dB


HO_MARGIN_DIST(1800, 900)= -127 dB

PRIORITY(900, 1800) = 1




PRIORITY(1800, 1800) = 1






© Alcatel 171



> Best solution: enabled PBGT HO between 900 and 1800

3.2 Adding a 1800 band in an existing 900 network Single/Umbrella 1800: 1800 zone exit

macro 900

macro 1800

HO_MARGIN(1800,1800) = 5 dB

HO_MARGIN(900,1800) = 8 dB

HO_MARGIN_LEV(900,1800) = 5 dB

HO_MARGIN_QUAL(900,1800) = 6 dB

EN_MULTIBAND_PBGT_HO = EnabledEN_MULTIBAND_PBGT_HO = Disabled

HO_MARGIN(1800,900) = 127 dB

HO_MARGIN_LEV(1800,900) = 12 dB

HO_MARGIN_QUAL(1800,900) = 11dBHO_MARGIN(1800,900) = 2 dB

HO_MARGIN_LEV(1800,900) = -1 dB

HO_MARGIN_QUAL(1800,900) = -2 dB

HO_MARGIN(900,900) = 5 dB

Exit of the 1800 area

© Alcatel 172



> Twin 1800: use Cause 12

3.2 Adding a 1800 band in an existing 900 network Twin 1800: Better condition handovers




EN_PREFERRED_BAND_HO = Disabled




Cause 12

PRIORITY(900, Twin) = 1

HO_MARGIN(900, Twin) = 0 dB

Cause 12 / 23

PRIORITY(900, 900) = 1

HO_MARGIN(900, 900) = 5 dB



Cause 12 / 23

PRIORITY(Twin, Twin) = 1

HO_MARGIN(Twin, Twin) = 5 dB



Cause 12

PRIORITY(Twin, 900) = 1

HO_MARGIN(Twin, 900) = +15 dB


> Remark: cause 23 is not possible between different bands.

> An HO_MARGIN of 0 - 15 dB is taken between 900 and 1800 cells to avoid a ping-pong HO (levels of colocatedcells are correlated with a propagation difference around 10 dB).

> Due to PRIORITY(0,n) settings, if alarms towards cells of both bands are triggered at the same time:

• From a 900 cell, the best cell is chosen (same priority towards 900 and 1800 cells).

• From a 1800 cell, the best cell is chosen (same priority towards 900 and 1800 cells).

© Alcatel 173



> Use Level, Quality Causes

3.2 Adding a 1800 band in an existing 900 network Twin 1800: Emergency handovers




PRIORITY(900, 900) = 1






© Alcatel 174



> if 1800 Twin

3.2 Adding a 1800 band in an existing 900 network Twin 1800: Candidate cells evaluation process



EN_PBGT_FILTERING = Disabled

CELL_EV = GRADE



EN_PBGT_FILTERING = Disabled

CELL_EV = GRADE

PRIORITY(900, 900) = 1





HO_MARGIN_LEV(Twin, 900)= -127 dB

HO_MARGIN_QUAL(Twin, 900)= -127 dB

HO_MARGIN_DIST(Twin, 900)= -127 dB


HO_MARGIN_LEV(900, Twin)= 0 dB

HO_MARGIN_QUAL(900, Twin)= -1 dB

HO_MARGIN_DIST(900, Twin)= 0 dB


HO_MARGIN_LEV(Twin, Twin)= 0 dB

HO_MARGIN_QUAL(Twin, Twin)= -1 dB

HO_MARGIN_DIST(Twin, Twin)= 0 dB



© Alcatel 175



> Advantages of Twin 1800 configuration– The best cell is chosen

– May lead to better speech quality

– Simple configuration (no specific parameter settings for 1800 zone exit)

> Drawbacks of Twin 1800 configuration– Coverages 1800 & 900 have to be identical

– If not, creation of a lot of HOs

– That will of course deteriorate speech quality and call drop

– Regulation of traffic is done through HO_MARGIN(0,n) tuning!

– Difficult to get the best capacity enhancement

3.2 Adding a 1800 band in an existing 900 network Twin 1800 / Umbrella 1800 comparison

© Alcatel 177



> Cell selection: same priority for macro 1800 and macro 900 cells

3.3 adding a 900 band in an existing 1800 network Idle mode parameters (1/2)

18001800CELL_BAR_QUALIFY = 0

900900


=> a dual band MS tries to select the best cell

> This type of configuration will for example happen in a network where the historical band was 1800, dedicated to urban coverage. A network coverage extension is done in a rural area by using 900 frequency (less sites required). We examine this case in this chapter. 900 cells introduction together with 1800 cells in a urban area may be extrapolated from the previous chapter.

© Alcatel 178



> Cell reselection: same priority for macro 1800 and macro 900 cells

3.3 adding a 900 band in an existing 1800 network Idle mode parameters (2/2)


900900


C2(1800) = C1(1800)

C2(900) = C1(900)

=> a dual band MS re-selects the best cell

© Alcatel 179



> Call Setup

• DR and FDR may be enabled

– Cause 20 is triggered when the average level from a neighboring cell is higher than L_RXLEV_NCELL_DR(n)

– To be checked according to the frequency plan within 1800 and 900 area

– No interference problem between 900 and 1800 cells but risk anyway of bad speech quality

3.3 adding a 900 band in an existing 1800 network Call Setup

macro 900

EN_DR = Enabled



FREElevel_DR(n) = 0

macro 1800

EN_DR = Enabled



FREElevel_DR(n) = 0

Cause 20

© Alcatel 180



> Better conditions handovers

3.3 adding a 900 band in an existing 1800 network Better conditions handovers

Macro 900

Cell_dimension_type = macro

Cell_layer_type = single

A_PBGT_HO = 12

Macro 1800

Cell_dimension_type = macro

Cell_layer_type = upper

A_PBGT_HO = 10

Cause 12?Cause 12

HO_MARGIN(900, 900) = 5dB

Urban area = 1800 area

HO_MARGIN(1800, 1800) = 5dB

Cause 12

Rural area = 900 area

© Alcatel 181



> Enabled PBGT handovers at the border of 900/1800 zones

3.3 adding a 900 band in an existing 1800 network Better conditions handovers

1800 cells 900 cells

EN_MULTIBAND_PBGT_HO = Disabled

HO_MARGIN(1800,1800)=5 dB HO_MARGIN(900,900) = 5 dB

HO_MARGIN(1800,900) =15 dB


HO_MARGIN(900,1800) = 0 dB


© Alcatel 183



> Cell selection: highest priority for macro 1800 cells

18001800


900900


=> a dual band MS tries to select first a macro 1800 cell

µ 900µ 900CELL_BAR_QUALIFY = 1

3.4 adding a 1800 band in an existing 900 (macro+micro) networkIdle mode parameters (1/4)

© Alcatel 184



> Cell reselection:

• 2 strategies depending on the network configuration

– higher priority for a macro 1800 or micro 900 cell

– higher priority for a corporate micro 900 cell


© Alcatel 185



> Cell reselection:

• micro 900 (slow mobiles) > macro 1800 > macro 900

C2(1800) = C1(1800) + 14

C2(900) = C1(900)

C2(µ 900) = C1(µ 900) + 18 dB µ 900 serving cell or after 20 s of monitoring

= C1 - 42 dB otherwise



PENALTY_TIME = 20 s

900900



PENALTY_TIME = 20 s

µ 900µ 900



PENALTY_TIME = 20 s


© Alcatel 186



> Cell reselection:

• macro 1800 > micro 900 > macro 900



PENALTY_TIME = 20 s

900900



PENALTY_TIME = 20 s

µ 900µ 900



PENALTY_TIME = 20 sC2(1800) = C1(1800) + 18

C2(900) = C1(900)

C2(µ 900) = C1(µ 900) + 14 dB µ 900 serving cell or after 20 s of monitoring

= C1 - 46 dB otherwise


© Alcatel 187



> 2 solutions:

• 3 layers network

– macro 900 = umbrella

– macro 1800 = mini

– micro 900 = micro

– Causes 21 and 14 are to be used for capture

– Easy to implement: behavior driven by the layer algorithm

– BUT very difficult to manage traffic discrimination

• 2 layers network (detailed hereafter)

– macro 900 and 1800 cells = umbrella

– micro 900 = micro

– Cause 14 is used for capture towards micro cells

– More parameters settings to be done, but more powerful

– traffic discrimination is possible

3.4 adding a 1800 band in an existing 900 (macro+micro) network Cell administration (1/2)

© Alcatel 188



> 2 solutions: 3-layers network or 2-layers network

mini 1800

Umb 900

µ 900

Cause 21

12

Cause 14

Cause 21

Umb 1800

Umb 900

µ 900

Cause 21

14

14

Cause 21

12

3.4 adding a 1800 band in an existing 900 (macro+micro) network Cell administration (2/2)

© Alcatel 189



> DR and FDRumbrella 900

EN_DR = Enabled

EN_FORCED_DR = Disabled


FREElevel_DR(n) = 0

umbrella 1800

EN_DR = Enabled



FREElevel_DR(n) = 0

DR & FDR

PRIORITY(micro, 900) = 2 or 1

DR & FDR

PRIORITY(micro, 1800) = 1 or 0

DR & FDR

PRIORITY(1800, 900) = 1

DR & FDR

PRIORITY(1800, 1800) = 1

micro 900

EN_RESCUE_UM = Enabled

EN_DR = Enabled



FREElevel_DR(n) = 0

3.4 adding a 1800 band in an existing 900 (macro+micro) network Call Setup


> L_RXLEV_NCELL_DR(n) is set at -47 dBm in a microcell layer to avoid creating interferences in the microcell layer.

> Priority(0,n) values are driven by the expected network behavior on Better cell and Emergency alarm occurrences (see the next pages).

© Alcatel 190



> corporate micro 900 > macro 1800 > macro 900

umbrella 1800




EN_MCHO_NCELL = Enabled

Cause 14

PRIORITY(900,micro) = 0

L_RXLEV_CPT_HO(900,micro)

= -85 dBm

Cause 14



= -85 dBm

Cause 12


PRIORITY(900,900) = 1

Cause 12

HO_MARGIN(1800,1800) = 5 dB

PRIORITY(1800,1800) = 1

micro 900



EN_PREFERRED_BAND_HO = Disabled

umbrella 900


= ANY_LOAD





Cause 12

HO_MARGIN(micro,micro) = 5 dB

PRIORITY(micro,micro) = 1

PBGT is disabled towards

Upper layer

No capture is activated

HO_MARGIN(1800,900) =127dB

PRIORITY(1800,900) = 1

Cause 21

PRIORITY(900,1800) = 1

L_RXLEV_CPT_HO(900,1800)

= -85 dBm

PRIORITY(micro,900) = 2


3.4 adding a 1800 band in an existing 900 (macro+micro) network Better condition handovers (1/2)


> In 900 macrocells:

• Priority is given to lower corporate microcells since we want MSs to be preferably transferred to them. This will have no drawback in case of Emergency HO in 900 macrocells since MSs will stay on the upper layer (900 or 1800 cells) thanks to Pref Layer = "upper+single".

• Priority can not be given to 1800 macrocells over 900 macros cells because multi-band MSs should stay on the 900 band on Emergency alarm.

• However giving the same Priority(0,n) to 900 and 1800 neighboring cells allow to choose the best Graded cell if cause 12 and cause 21 are triggered at the same time.


• Priority is given to lower corporate microcells since we want MSs to be preferably transferred to them. This will have no drawback in case of Emergency HO in 900 macrocells since MSs will stay on the upper layer (900 or 1800 cells) thanks to Pref Layer = "upper+single".

• The PBGT HO is disabled towards upper 900 macrocells by choosing HO_Margin(0,n) to +127 dB.

> In corporate 900 microcells:

• The PBGT HO will only occur towards neighboring microcells except for Fast MSs when Speed discrimination is enabled.

• In this latter case, Priority(0,n) will be used to favor umbrella 1800 macrocells compared to umbrella 900 macrocells.

© Alcatel 191



> macro 1800 > micro 900 > macro 900

umbrella 1800




EN_MCHO_NCELL = Disabled

Cause 14



= -85 dBm

Cause 21


L_RXLEV_CPT_HO(micro,1800)

= -85 dBm

Cause 12


PRIORITY(900,900) = 1

Cause 12

HO_MARGIN(1800,1800) = 5 dB

PRIORITY(1800,1800) = 1

micro 900




umbrella 900


= ANY_LOAD





Cause 12

HO_MARGIN(micro,micro) = 5 dB


PBGT is disabled towards

Upper layer

No capture is activated

HO_MARGIN(1800,900) =127dB

PRIORITY(1800,900) = 1

Cause 21

PRIORITY(900,1800) = 1

L_RXLEV_CPT_HO(900,1800)

= -85 dBm



3.4 adding a 1800 band in an existing 900 (macro+micro) network Better condition handovers (2/2)



• Priority is given to 1800 macrocells over 900 microcells since we want MS to be preferably transferred to them.

• Priority can not be given to 1800 macrocells over 900 macrocells because multi-band MS should stay on the 900 band on Emergency alarm.

• However giving the same Priority(0,n) to 900 and 1800 neighboring cells allow to choose the best Graded cell if cause 12 and cause 21 are triggered at the same time.


• The Better cell (capture cause 14) has to be disabled towards 900 microcells since 1800 band is preferred. This can be done by:

– disabling cause 14 in 1800 macrocells: EN_MCHO_NCELL=disabled in 1800 cells

– disabling cause 14 towards any 900 microcells:

– either L_RXLEV_CPT_HO(1800,micro)=-47dBm

– or EN_BI-BAND_MS=disabled in 1800 cells

• PBGT HO is disabled towards upper 900 macrocells by choosing HO_Margin(0,n) to +127 dB.

> In 900 microcells:

• PBGT HO will only occur towards neighboring microcells except for Fast MSs when Speed discrimination is enabled.

• In this latter case, Priority(0,n) will be used to favor umbrella 1800 macrocells compared to umbrella 900 macrocells.

© Alcatel 192




umbrella 1800


PRIORITY(900,micro) = 0 or 2

PRIORITY(micro,1800) = 1 or 0

PRIORITY(900,900) = 1

PRIORITY(1800,1800) = 1

micro 900



umbrella 900



PRIORITY(1800,900) = 1PRIORITY(900,1800) = 1



3.4 adding a 1800 band in an existing 900 (macro+micro) network Emergency handovers


> Priority(0,n) is the same between cells of the same band and cells from the other band since neighboring cells from the same band will be anyway preferred during the HO Candidate Cell Evaluation process.

© Alcatel 193




umbrella 1800



CELL_EV = GRADE



PRIORITY(900,900) = 1

PRIORITY(1800,1800) = 1

micro 900




CELL_EV = ORDER

umbrella 900



CELL_EV = GRADE


PRIORITY(1800,900) = 1

HO_MARGIN_XX = -127 dBPRIORITY(900,1800) = 1


HO_MARGIN_XX = -127 dB


3.4 adding a 1800 band in an existing 900 (macro+micro) network Candidate Cell Evaluation



> All other HO_MARGIN_XX(0,n) are set to their default values:

• HO_MARGIN_LEV(0,n) = 0 dB

• HO_MARGIN_QUAL(0,n) = -1 dB

• HO_MARGIN_DIST(0,n) = 0 dB

© Alcatel 195



> Mix of frequency bands within a cell

> Based on concentric cell feature– The OUTER zone contains BCCH, SDCCH and TCH

– The INNER zone contains only TCH, new band

> Possible cell profiles: all (Single, Umbrella, Mini, Micro, Indoor)

3.5 Multi-band cells solution Principles

900 MHz BCCH, SDCCH and TCH

Single band

Dual band

Dual band

1800 MHz TCH

FREQUENCY_RANGE = GSM-DCS

CELL_PARTITION_TYPE = concentric

© Alcatel 196



> Less cells to operate

> Less neighboring cells / handovers– No more problem with limit of 32 BCCHs

– Dual band MSs have less cells to monitor -> more reliable measurements

– Reduced number of intercell HOs -> improved voice quality

> More efficient frequency planning– Only one BCCH frequency plan

– Higher traffic efficiency of the second frequency band not limited by a BCCH frequency plan

> More traffic capacity– 1800 BCCH TSs freed for TCH

3.5 Multi-band cells solution Advantages

> Merging 2 mono-band cells into 1 multi-band cell may lead to less SDCCH needed. Therefore some SDCCH TSmight be freed for TCH.

© Alcatel 197



> Only 900 BCCH– A pure 1800 roaming MS will not be capable to access the network

> Concentric cells algorithms tuning– The separation level between Inner and Outer zone may be complex

(optimization may have to be done on a per cell basis)

– Traffic sharing between 1800 and 900 is fully based on this tuning

> Multi-band capacity– The solution is not optimal if nb(TRX inner) > nb(TRX outer)

3.5 Multi-band cells solution Drawbacks

> QoS monitoring difficulties (see session 3.6)

– In B6.2, impossible to get QoS information per band

– Solved in B7 (counters per TRX)

> Hardware requirements

– In B6.2: 900 and 1800 TRXs to be located in the same Evolium BTS

– Since B7, the « cell split » feature solves this problem

© Alcatel 199



> QoS indicators in each band

• To identify specific problems (interference, coverage, etc.)– CDR, CSSR, SDCCH congestion, etc.

– Split of HO causes

– HO incoming / outgoing efficiency

– # of HOs per call (for speech quality)

– FDR success rate

> Traffic in each band– Distribution 900 / 1800

– Average RTCH duration

– Congestion (and queuing efficiency)

– FDR usage (internal / external)

– Proportion of multi-band MS

> Traffic flows– HO per couple of cells (PMC type 180)

– In case of problem, use ODMC type 26 and 27 for detailed incoming and outgoing behaviors

3.6 Monitoring QoS in a multi-band networkIndicators monitoring

© Alcatel 200



> It is possible to obtain:

• Erlang traffic for 900 TRX and 1800 TRX. It is interesting to calculate the

ratio Traffic inner zone / Traffic cell,

• Erlang traffic for 900 TRX and 1800 TRX due to dual band mobiles,

• TCH mean holding time for 900 TRX and 1800 TRX,

• number of HO attempts (assignment command sent to the MS) on cause

13 (outer zone to inner zone HO),

3.6 Monitoring QoS in a multi-band networkSpecific case of multi-band cells (1/3)

© Alcatel 201



> It is possible to obtain:

• number of HO attempts (assignment command sent to the MS) on

causes 10 and 11 (inner zone to outer zone HO),

• classical intracell HO statistics: efficiency, failure with drop cause radio,

failure with drop cause BSS, failure with reversion to old channel, failure

cause congestion,

• rate of inter zone handovers per call


© Alcatel 202



> Conclusion:

• All useful indicators are available

• Indicators per TRX are available (radio CDR, radio TCH assign failure

rate)

• Indicators can be computed in RNO to obtain statistics per zone, per

band, etc.

• Monitoring of multi-band cells is as powerful as standard cells


© Alcatel 204



> A network is composed of:

• Macro cells 900 + 1800

• Micro cells 900 + 1800

– So called « quadrilayer »

• Propose an architecture andparameter settings for:

– idle mode

– call setup

– better condition handovers

– emergency handovers


© Alcatel 207



Appendix

> Content:

4.1 Load & Traffic evaluation

4.2 Extended cell overview

4.3 Exercises & Case Studies Solutions

© Alcatel 209



4.1 Load & Traffic evaluation Cell TCH radio resource evaluation usage

Load evaluation Period Usage

short term TCH_INFO_PERIOD FREEfactors

LOADfactors

medium term LOAD_EV_PERIOD x TCH_INFO_PERIOD Speed discrimination for hierarchical network

Full Rate / Half Rate channel allocation

long term N_TRAFFIC_LOAD x A_TRAFFIC_LOAD x TCH_INFO_PERIOD Power budget Handover

Traffic Handover

Multiband capture Handover

General capture Handover

© Alcatel 210



4.1 Load & Traffic evaluation Short term evaluation (1/4)

> LOADfactors and FREEfactors are determined from Nb free TCH samples every TCH_INFO_PERIOD seconds (short term evaluation)

> LOADlevels are boundaries of load intervals associating a LOADfactor (db) to a Nb free TCH sample

> FREElevels are boundaries of Nb free TCH intervals associating a FREEfactor (db) to a Nb free TCH sample

© Alcatel 211




> FREEfactor determination:

• FREElevel in absolute number of TCHs

• FREEfactor in dB

Nb free TCH FREEfactor

t <= FREElevel_1 FREEfactor_1

FREELevel_1< t <= FREElevel_2 FREEfactor_2



FREELevel_4< t FREEfactor_5

© Alcatel 212




> LOADfactor determination:

• LOADlevel in %

• LOADfactor in dB

t = (1 - Nb free TCH/Total Nb TCH) x 100 LOADfactor

t <= LOADlevel_1 LOADfactor_1

LOADLevel_1< t <= LOADlevel_2 LOADfactor_2



LOADLevel_4< t LOADfactor_5

© Alcatel 213



> example: cells with 4 TRXs (28 TCHs)

Nb free TCH FREEfactor

t <= 3 - 16 dB

3 < t <= 8 - 8 dB

8 < t <= 15 0 dB

15 < t <= 21 +7 dB

21 < t +10 dB


Load = (1-Nb free TCH/Total TCH)x 100 LOADfactor

t <= 10% +10 dB

10% < t <= 25% +5 dB

25% < t <= 50% 0 dB

50% < t <= 80% -10 dB

80% < t -15 dB

Nb free TCH = 4

Load = 85,7%

Cell 0�

FREEfactor(0) = -8 dBm

LOADfactor(0) = -15 dBm

Nb free TCH = 20

Load = 28,6%

Cell n

FREEfactor(n) = +7 dBm

LOADfactor(n) = 0 dBm

�

• in ORDER(n): + FREEfactor(n) - FREEfactor(0) = +7 - (-8) = +15 dB

• in GRADE(n): + LOADfactor(n) = +0 = 0 dB

in evaluation of cell n for outgoing HO from cell 0 :

HO?

© Alcatel 214



4.1 Load & Traffic evaluation Medium term evaluation (1/2)

> medium term measurement of the load of a cell

• corresponds to function AV_LOAD(cell)

• a new sample of the “Nb free TCHs” in the cell is available every TCH_INFO_PERIOD seconds

• AV_LOAD() is a non-sliding window load average from Nb free TCH samples updated every LOAD_EV_PERIOD x TCH_INFO_PERIOD s

© Alcatel 215



4.1 Load & Traffic evaluation Medium term evaluation (2/2)

> AV_LOAD(cell n) calculated from N Nb free TCH samples available during LOAD_EV_PERIOD x TCH_INFO_PERIOD s

100*)(n) TCHTot Nb

(n) TCH free Nb1(

Nsamples

1 = AV_LOAD(n)

Nsamples

1 = i

∑ −

© Alcatel 216



4.1 Load & Traffic evaluation Long term evaluation (1/4)

> Long term measurement of the load of a cell

• corresponds to function Traffic_load(cell)

• Traffic_load() value is determined from a number N_TRAFFIC_LOAD of consecutive non-sliding window load averages AV_TRAFFIC_LOADcalculated from Nb free TCH samples updated every A_TRAFFIC_LOAD x TCH_INFO_PERIOD s

© Alcatel 217




• 3 possible values for Traffic_load(): high, low, indefinite

• initialization: Traffic_load() = indefinite

• Traffic_load() becomes :

– high if the last N_TRAFFIC_LOAD consecutive AV_TRAFFIC_LOAD load averages are all greater than the HIGH_TRAFFIC_LOADthreshold

– low if the last N_TRAFFIC_LOAD consecutive AV_TRAFFIC_LOAD load averages are all lower than the LOW_TRAFFIC_LOAD threshold

© Alcatel 218




• Traffic_load() becomes indefinite if:

– Traffic_load() was high and the last AV_TRAFFIC_LOAD load average is lower than LOW_TRAFFIC_LOAD (or IND_TRAFFIC_LOAD if not 0%)

– Traffic_load() was low and the last AV_TRAFFIC_LOAD load average is greater than HIGH_TRAFFIC_LOAD (or IND_TRAFFIC_LOAD if not 0%)

• Traffic_load(n) is always equal to indefinite if cell n is external to the BSC

• HIGH_TRAFFIC_LOAD ≥ IND_TRAFFIC_LOAD ≥ LOW_TRAFFIC_LOAD

© Alcatel 221



4.2 Extended cell overview Session presentation

> Program:

4.2.1 Presentation

4.2.2 Radio Link Establishment

4.2.3 Handover

4.2.4 Parameters setting

© Alcatel 222



> One BTS (G3 or G4): 2 cells

• INNER cell: range from 0 to 35 km

• OUTER cell: range from 33 to 70 km

4.2 Extended cell overview 4.2.1 Presentation - General

> The extended cell has up to 4 TRX in the inner cell and up to 4 TRX in the outer cell.

© Alcatel 223



4.2 Extended cell overview 4.2.1 Presentation - Synchronisation

OUTER cellINNER cell

> Freq BCCH OUTER <> Freq BCCH INNER

• MS reports measurements on both cells for the handover algorithms

> BSICINNER = BSICOUTER

• INNER cell can decode the RACH received on OUTER BCCH frequency

> INNER cell always BARRED

• MS always camps on OUTER cell

> At the border of the two cells, an overlapping area allows to provide a continuous coverage. When the MS moves from one cell to the other, a handover is triggered in the overlap zone. Two BCCH channels are needed (one for the inner cell, one for the outer cell), so that the MS reports measurements on both cells for the handover algorithms.

> The TRXs of the inner cell and of the outer cell are synchronised, but the reception of the outer cell is delayed by 60bits period to account for the propagation delay.

> In the inner cell, the MS can receive the BCCH inner frequency as wells as the outer BCCH frequency. To avoid to manage RACH reception on two different frequencies in the inner cell, the MS is forced to access the inner cell on the outer BCCH frequency. For this purpose, the RACH reception (BCCH TRX) of the inner cell is tuned to the outer BCCH frequency, and the inner cell is barred1. So on time slot 0 of the inner cell, transmission is done on the inner cell BCCH frequency, and reception is done on outer BCCH frequency.

> The chosen implementation allows to make use of all timeslots2 of the TDMA frame and to use the combined configuration for the CCCH channel.

© Alcatel 224



> UL interference on TS0 of the INNER cell if

• Access burst received in the INNER cell (on frequency BCCH OUTER)

AND

• Call on TS7 of the OUTER cell

> Then, TS7 of the OUTER cell is always set to IDLE (never used)

4.2 Extended cell overview 4.2.1 Presentation - RF Interference

© Alcatel 225



4.2 Extended cell overview 4.2.2 Radio Link Establishment - MS located in the outer cell area

> The inner cell is always barred, so the MS cannot camp on the inner cell, even if located in the inner cell range. In the whole extended cell coverage, the MS has a good reception of the outer cell BCCH, so the MS will always be camping in the outer cell, whether in the inner cell or outer cell range.

> For this reason, a special radio and link establishment procedure is used to cope with this behaviour .

> It consists of receiving the CHANNEL REQUEST messages on outer BCCH frequency, and allocating the SDCCH channel according to the MS estimated position. The IMMEDIATE ASSIGNMENT COMMAND for an SDCCH is sent on the outer cell BCCH frequencies, but the SDCCH may be allocated in either inner or outer cell, depending on the MS position.

> (1) The MS camping on the outer cell sends an access burst on the RACH on outer cell BCCH frequency. These bursts will be received successfully in the inner cell by the BCCH TRE. In the outer cell, the access burst arrives too early and cannot be decoded.

> (2) The inner cell BCCH TRE sends a CHANNEL REQUIRED message to the BSC containing the random reference sent by the mobile, the TDMA frame number when the message was sent over the air and the measured TOA.

> (3) The TCU controlling this TRE allocates an SDCCH subchannel to the transaction in the inner cell and asks the BTS to activate this subchannel.

> (4) The BTS activates the requested channel and sends back and acknowledgement, once this is done.

> (5) The TCU sends the IMMEDIATE ASSIGNMENT COMMAND (which provides the description of the allocated SDCCH) to the BCCH TRE of the inner cell.

The TCU controlling the inner cell BCCH sends a copy of the message to the TCU handling the BCCH of the outer cell. This is done if and only if the timing advance IE included in the CHANNEL REQUIRED is smaller than 60, thus indicating that the MS is strictly in the inner cell (in order to avoid that the MS receives two Immediate Assignment messages when located in the overlap zone).

The TCU controlling the outer cell BCCH forwards the IMMEDIATE ASSIGNMENT COMMAND to the outer cell BCCH TRE.

> (6) The IMMEDIATE ASSIGNMENT message is sent over the air to the MS on the AGCH of the outer cell.

> (6') The IMMEDIATE ASSIGNMENT message sent by the inner cell is lost, because the MS listens to the outer cell frequency.

> (7) The mobile switches its transceiver to the SDCCH allocated in the inner cell and sends repeatedly an SABM frame to establish the layer 2 connection with the BTS.

> (8) The BTS acknowledges the establishment of the LapDm link to the MS with a UA frame sent on the SDCCH allocated to the MS.

© Alcatel 226



If TA < 60

4.2 Extended cell overview 4.2.2 Radio Link Establishment - MS located in the inner cell area

> The TCU sends the IMMEDIATE ASSIGNMENT COMMAND (which provides the description of the allocated SDCCH ) to the BCCH TRE of the inner cell.

> The TCU controlling the inner cell BCCH sends a copy of the message to the TCU handling the BCCH of the outer cell. This is done if and only if the timing advance IE included in the CHANNEL REQUIRED is smaller than 60, thus indicating that the MS is strictly in the inner cell (in order to avoid that the MS receives two Immediate Assignment messages when located in the overlap zone).

> The TCU controlling the outer cell BCCH forwards the IMMEDIATE ASSIGNMENT COMMAND to the outer cell BCCH TRE.

> (1) The MS in the outer cell sends an access burst on the RACH of the outer cell. This burst is successfully received by the outer cell BCCH TRE. In the inner cell, the access burst arrives too late to be successfully decoded.

> (2) The outer cell BCCH TRE sends a CHANNEL REQUIRED message to the BSC containing the random reference sent by the mobile, the TDMA frame number when the message was sent over the air and the measured TOA.

> (3) The TCU controlling this TRE allocates an SDCCH subchannel in the outer cell to the transaction and asks the BTS to activate this subchannel.

> (4) The BTS activates the requested channel and sends back an acknowledgement, once this is done.

> (5) The TCU then sends the description of the channel in the IMMEDIATE ASSIGNMENT COMMAND to the outer cell BCCH TRE.

> (6) The IMMEDIATE ASSIGNMENT message is sent over the air to the MS on the AGCH of the outer cell.

> (7) The mobile switches its transceiver to the required channel and sends repeatedly an SABM frame to establish the layer 2 connection with the BTS.

> (8) The BTS acknowledges the establishment of the LAPDm link to the MS with a UA frame sent on the SDCCH allocated to the MS.

© Alcatel 228



>

4.2 Extended cell overview 4.2.2 Radio Link Establishment - MS located in the overlap zone (2/2)

> (1a&b) The MS camping on the outer cell sends an access burst on the RACH. This burst is correctly received by the inner cell BCCH TRE and outer cell BCCH TRE.

> (2a&b) The inner cell and outer cell BCCH TRE send a CHANNEL REQUIRED message to the BSC containing the random reference sent by the mobile, the TDMA frame number when the message was sent over the air and the measured TOA.

> (3a&b) Both TCUs controlling the TREs having BCCH allocate an SDCCH subchannel to the transaction and ask the BTS to activate this subchannel.

> (4a&b) The BTS activates the requested channels and sends back an acknowledgement for each, once this is done.

> (5b) The TCU controlling the outer cell, sends the IMMEDIATE ASSIGNMENT COMMAND with SDCCH description in the outer cell to the outer cell BCCH TRE.

> (5a&c)The TCU controlling the inner cell sends in the IMMEDIATE ASSIGNMENT COMMAND with SDCCH description in the inner cell. Two cases are possible:

• Access Delay IE > 59 the inner cell TCU will not send a copy of the IMMEDIATE ASSIGNMENT command to the outer cell TCU. This is the desired behaviour.

• Access Delay in [58,59] range, the inner cell TCU sends a copy of the IMMEDIATE ASSIGNMENT command to the outer cell TCU. This is not the desired behaviour (corresponds to inner cell scenario). This is due to the fact that the BSC definition of the overlap zone does not match the exact BTS overlap area (negative values of TOA in the outer cell up to –2, are clipped to 0).

> (6b) The IMMEDIATE ASSIGNMENT message describing the SDCCH allocation in outer cell, is sent to the MS on the outer cell BCCH frequency. In most cases this message should be received by the MS (except if 6c is received first)

> (6a) The IMMEDIATE ASSIGNMENT message describing the SDCCH allocation in inner cell is lost on the inner cell air interface, because the MS does not listen to that frequency. The unused SDCCH will be released by the BSC when the supervising timer expires6.

> (6c) Access Delay in [58,59] range: The IMMEDIATE ASSIGNMENT message describing the SDCCH allocation in inner cell is sent on the BCCH frequency of the outer cell. In most cases, the MS should have received message (6b) before and has already switched to the SDCCH in the outer cell, and so this message is lost. It is however possible, in case the message (6b) is delayed in the inner cell, that the message (6c) is received earlier by the MS. In this case establishment will occur on the SDCCH allocated in the inner cell (not drawn).

> (7b) The mobile receives the IMMEDIATE ASSIGNEMENT describing the SDCCH allocation in outer cell on the BCCH outer cell frequency. It then switches to the designated channel and sends repeatedly an SABM frame to establish the layer 2 connection with the BTS in the outer cell. If the message (6c) is received before (6b), then the establishment will occur in the inner cell.

> (8b) The BTS acknowledges the establishment of the LapDm link to the MS with a UA frame sent on the SDCCH allocated to the MS.

> (9) The unused SDCCH is released in the inner cell (double SDCCH allocation). If message 6c arrives first, then the unused SDCCH release will occur in the outer cell.

© Alcatel 229



> CAUSE 6 : Too long distance

AV_RANGE_HO > U_TIME_ADVANCE

and EN_DIST_HO = ENABLE

> U_TIME_ADVANCE = 62

> EN_PBGT_FILTERING = Disable

4.2 Extended cell overview 4.2.3 Handover - from the INNER cell to the OUTER cell

> In the extended cell , the handover procedure is purely controlled by settings of the handover detection parameters. Two special causes allow handover from the inner cell to the outer cell and handover from the outer cell to the inner cell. There is no change in the BSC handover algorithm either for handover preparation or execution.

> From the inner cell to the outer cell , the handover alarm is only triggered by the handover cause “too long MS-BS distance”. When this cause is triggered the extended outer cell is always a candidate cell.

> However the operator setting of the handover parameters must insure that this cause is only triggered when the distance from the serving inner cell BTS is greater than the limit of the overlap zone (TA > 62) by setting U_TIME_ADVANCE to 62.

> In order to avoid the extended outer cell to be filtered by the filtering process the flag EN_PBGT_FILTERING must be set to DISABLE.

> The candidate cell evaluation process is recommended to be the GRADE mode.

© Alcatel 230



> CAUSE 22 : Too short distance

AV_RANGE_HO < L_TIME_ADVANCE

> L_TIME_ADVANCE = 0

> EN_PBGT_FILTERING = Disable

> Cause 22 is only checked if

• Cell_range(serving) = extended_outer

4.2 Extended cell overview 4.2.3 Handover - from the OUTER cell to the INNER cell

> In the same way, from the outer cell to the inner cell , the handover alarm is only triggered by the handover cause “too short MS-BS distance”. When this cause is triggered the extended inner cell is always a candidate cell.

> However the operator setting of the handover parameters must insure that this cause is only triggered when the timing advance applied by the mobile reaches 0, this is achieved by setting L_TIME_ADVANCE to 0.

> In order to avoid the extended inner cell to be filtered by the filtering process the flag EN_PBGT_FILTERING must be set to DISABLE.

> The candidate cell evaluation process is recommended to be the GRADE mode.

© Alcatel 231



> All the standard HO causes can be used

• Emergency HO causes 2, 3, 4, 5

• Better condition HO causes 12, 23, 24

> The OUTER or INNER cell is always present in the Candidate CellEvaluation

4.2 Extended cell overview 4.2.3 Handover - from the OUTER or INNER cell towards an other cell

> The setting of the handover parameter does not prevent any handover cause to trigger an alarm for a handover towards a third cell.

> It is possible to use exactly the same rules and parameters for handover towards a third cell as in the macro cellular normal cases.

> The synchronous handover does not work between the inner and the outer cell.

> In order to avoid call terminations due to directed retry into the inner or outer cell with an incorrect distance range it is recommended to disable the forced directed retry towards the inner and the outer cell. For this purpose, the parameter FREELEVEL_DR(n) is set to the maximum value (255) for the inner and the outer cell.

• But the Normal DR can be activated.

© Alcatel 232



> The Inner Cell shall always be BARRED

> If combined CCCH/SDCCH is used in the inner extended cell, then the same configuration is required in outer extended cell, and vice-versa (ie same in both cells)

> BSICINNER = BSICOUTER

> The TS 7 of BCCH TRX of outer cell must be set to IDLE

> The INNER cell and OUTER cell must belong to the same location area

> Synchronous handover must be disabled.

> U_TIME_ADVANCE = 62

> L_TIME_ADVANCE = 0

> EN_PBGT_FILTERING = DISABLE.

> CELL_EV = “Grade”

> FREELEVEL_DR(n) = 255 (this is done automatically, at configuration time)

> INNER cell and OUTER cell must be neighbour, handover relationship must exist in both directions

4.2 Extended cell overview 4.2.4 Parameters Setting

Multiband GSM Network Radio Optimization

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