Introduction to Gsm Optimization

7/28/2019 Introduction to Gsm Optimization

http://slidepdf.com/reader/full/introduction-to-gsm-optimization 1/318

ADA cellworksLouder than words…..




INTRODUCTION TO GSM




INTRODUCTION

• The Global System for Mobile Communications (GSM) is a set of recommendations and specifications for a digital cellular

telephone network (known as a Public Land Mobile Network, or

PLMN).

• These recommendations ensure the compatibility of

equipment from different GSM manufacturers, andinterconnectivity between different administrations, including

operation across international boundaries.

• GSM networks are digital and can cater for high system

capacities.

• They are consistent with the world-wide digitization of the

telephone network, and are an extension of the Integrated

Services Digital Network (ISDN), using a digital radio interface

between the cellular network and the mobile subscriber

equipment.

INTRODUCTION TO GSM




CELLULAR TELEPHONY

• A cellular telephone system links mobile subscribers into thepublic telephone system or to another cellular subscriber.

• Information between the mobile unit and the cellular network

uses radio communication. Hence the subscriber is able to

move around and become fully mobile.

• The service area in which mobile communication is to beprovided is divided into regions called cells.

• Each cell has the equipment to transmit and receive calls from

any subscriber located within the borders of its radio

coverage area.

Radio

Mobile subscriber

Cell

INTRODUCTION TO GSM




GSM FREQUENCIES

• GSM systems use radio frequencies between 890-915 MHz for receive and between 935-960 MHz for transmit.

• RF carriers are spaced every 200 kHz, allowing a total of 124

carriers for use.

• An RF carrier is a pair of radio frequencies, one used in each

direction.• Transmit and receive frequencies are always separated by 45

MHz.

890 960935915

UPLINK FREQUENCIES DOWNLINK FREQUENCIES

UPLINK AND DOWNLINK FREQUENCY SEPARATED BY 45MHZ

INTRODUCTION TO GSM





890 915 935 960880 925


Extended GSM (EGSM)

• EGSM has 10MHz of bandwidth on both transmit and receive.• Receive bandwidth is from 880 MHz to 890 MHz.

• Transmit bandwidth is from 925 MHz to 935 MHz.

• Total RF carriers in EGSM is 50.

INTRODUCTION TO GSM


http://slidepdf.com/reader/full/introduction-to-gsm-optimization 7/318ADA cellworks

Louder than words…..

1710 MHz 1880 MHz1805 MHz1785 MHz



DCS1800 FREQUENCIES

• DCS1800 systems use radio frequencies between 1710-1785

MHz for receive and between 1805-1880 MHz for transmit.

• RF carriers are spaced every 200 kHz, allowing a total of 373

carriers.

• There is a 100 kHz guard band between 1710.0 MHz and 1710.1

MHz and between 1784.9 MHz and 1785.0 MHz for receive, and

between 1805.0 MHz and 1805.1 MHz and between 1879.9 MHz

and 1880.0 MHz for transmit.

• Transmit and receive frequencies are always separated by 95

MHz.

INTRODUCTION TO GSM


http://slidepdf.com/reader/full/introduction-to-gsm-optimization 8/318ADA cellworks


FEATURES OF GSM




INCREASED CAPACITY

• The GSM system provides a greater subscriber capacity than

analogue systems.

• GSM allows 25 kHz per user, that is, eight conversations per 200

kHz channel pair (a pair comprising one transmit channel and one

receive channel).

• Digital channel coding and the modulation used makes the signal

resistant to interference from cells where the same frequencies are

re-used (co-channel interference); a Carrier to Interference Ratio

(C/I) level of 12 dB is achieved, as opposed to the 18 dB typical with

analogue cellular.

• This allows increased geographic reuse by permitting a reduction

in the number of cells in the reuse pattern.

FEATURES OF GSM




AUDIO QUALITY

• Digital transmission of speech and high performance digitalsignal processors provide good quality speech transmission.

• Since GSM is a digital technology, the signals passed over a

digital air interface can be protected against errors by using

better error detection and correction techniques.

• In regions of interference or noise-limited operation the speechquality is noticeably better than analogue.

USE OF STANDARDISED OPEN INTERFACES

• Standard interfaces such as C7 and X25 are used throughout the

system. Hence different manufacturers can be selected for

different parts of the PLMN.

• There is a high flexibilty in where the Network components are

situated.

FEATURES OF GSM




IMPROVED SECURITY AND CONFIDENTIALITY

• GSM offers high speech and data confidentiality.

• Subscriber authentication can be performed by the system to

check if a subscriber is a valid subscriber or not.

• The GSM system provides for high degree of confidentiality for

the subscriber. Calls are encoded and ciphered when sent over

air.

• The mobile equipment can be identified independently from the

mobile subscriber. The mobile has a identity number hard coded

into it when it is manufactured. This number is stored in a

standard database and whenever a call is made the equipment

can be checked to see if it has been reported stolen.

FEATURES OF GSM




CLEANER HANDOVERS

• GSM uses Mobile assisted handover techique.

• The mobile itself carries out the signal strength and quality

measurement of its server and signal strength measurement

of its neighbors.

• This data is passed on the Network which then uses

sophisticated algorithms to determine the need of handover.

SUBSCRIBER IDENTIFICATION

• In a GSM system the mobile equipment and the subscriber are

identified separately.• The subscriber is identified by means of a smart card known

as a SIM.

• This enables the subscriber to use different mobile equipment

while retaining the same subscriber number.

FEATURES OF GSM




FREQUENCY REUSE

• There are total 124 carriers in GSM ( additional 50 carriers are available if EGSM band is

used).• Each carrier has 8 timeslots and if 7 can be used for traffic then a maximum of 868 ( 124 X 7 )

calls can be made. This is not enough and hence frequencies have to be reused.

• The same RF carrier can be used for many conversations in several different cells at the

same time.

6

4

3

7

2

• The radio carriers available are allocated according to a regular

pattern which repeats over the whole coverage area.

• The pattern to be used depends on traffic requirement and

spectrum availability.

• Some typical repeat patterns are 4/12, 7/21 etc.5

1

2

1

FEATURES OF GSM




WHAT IS OPTIMISATION???




Optimization Process

Start / Sign NDA

Collection of required inputs

- Drive test data

- OMC data

- Customer complaints- Others

Analysis of inputs data

- Neighbor lists

- Coverage / interference

- Database strategy

- Capacity

- Quality

- Dimensioning




Optimization Process

Framing or recommendations -Field team

Recommendationreview(internal)

No

Rework & Modify

Yes

Customer presentation / Fulldocumentation

Customer approval

Change Control process /Implementation

Yes

Verification & Documentation

No

Rework & Modify




Operator perspective

Set up time

Call drop rateCell

congestion

Cell

interference

Handover

RxLevel

Call success

rate

Call success rate 35 %

Call Drop rate 13 %

Cell congestion 13 %

Cell interference 9 %

Handover 9 %

Rx Level 9 %

Set up time 12 %




Customer perspective

Call Drops

Speech

Quality

Coverage

(Indoor)

No

connection

Coverage

(outdoor)

Call set up

time

Coverage Outdoor 42 %

Coverage Indoor 26 %

Speech Quality 7 %

No Connection 12 %

Call Drops 3 %

Call setup time 10 %

• Important to decide KPIs covering customerperspective




KPI Definitions




Indicators – Coverage

• Signal Strength -outdoors

•

In building, In-Car penetration signal levels• Uplink Voice Quality

• Downlink Voice Quality

• Call Drops

• Cell Power control




Indicators – Capacity

• Erlangs per Cell

• TCH success

• TCH assignment failures

• TCH Drop calls

•

TCH Blocking• Cell congestion

• Congestion Relief Usage

• BHCA against rated MSC limit

•

mErl/subs. against rated MSC limit• SMS/subs. Against MSC limit

• MM values(HO,LU,Paging) against limits

• Overload : Voice/Signalling/Processor




Indicators – Quality

• RxLev

• Handovers

• Call Drops

• Call Success Rate

• Call set up success rate

• Call completion rate

• Call set up time

• Voice quality(MOS)

• RxQual

• Echo

• TCH success

• TCH assignment failures

• TCH Drop calls

• SDCCH traffic blocking

• SDCCH drop calls

• SDCCH Success rates

• PSTN availability and quality

D i T




Drive Tests

• Objective

– Competitor Benchmarking

– Identification of weak areas for own

network / Competitor – Map handover boundaries (in case of

Optimization)

– Review neighbor definitions




Drive Test – Sample Signal

Level Plot

Drive Test Sample Signal




Drive Test – Sample Signal

Quality Plot




Drive Test - Guidelines

• Drive test routes chosen have a great impact on the

Performance measurement and the following are theguidelines suggested for this drive test exercise:

– A short call shall have a 90 second call duration,with 30 seconds lapse in time between each shortcall.

– A long call shall have duration of one hour, with a

one-minute lapse in time between each long call. – A minimum of 8000 calls combined, are suggested

to allow for a reasonable evaluation of the entireNetwork (Assuming a major Metro). Based on thedata gathered in short calls, Areas for Long calldrive tests should be identified & tested.




Drive Test - Guidelines

• Drive test for important areas to be

carried out during Busy Hour – Busy hour i.e. the 60 minutes span with the

maximum average traffic in Erlang over the

target area. The average traffic over the

target area is equal to the total traffic inErlang carried by all Sectors included in the

area divided by the number of Sectors in

the area




Drive Test – Guidelines

• Drive test duration for the area type will betypically equivalent to N / 3 Hours, where N isthe no. of sites in the area. The following arethe rules of thumb to be kept in mind while

choosing the Drive Test Routes: – Adequate crossings of handover boundaries

– Intensive drive of most of the roads & bylanes of theservice area

– Problem areas should be drive tested in the Busyhours




Drive Test - Report

• Executive summary consisting of: – Network Performance Metrics – Based on weightage

for KPIs decided with customer

– Network Quality comparison with main competitor

• KPIs with description

–

Call Setup performance – Network Quality performance consisting of

• Accessibility: No. of successful call starts / Number of Call attempts

• Reliability: No. of calls that did not drop / No. of successful call starts

• Voice Quality: In terms of RxQual, SQI (TEMS), FER

– Blocked call performance

– Handover performance




Drive Test – Report

Definitions:

Total Call Attempts = Blocked Calls + Access Failures+ Dropped Calls + Calls Terminating with Normal Treatment;

• A Blocked Call is a call rejected on the Air Interface or

terminated before its normal completion because of lack of resource in the BSS or the NSS Network

• An Access Failure is a situation where a call is terminatedwithout being rejected, before it has reached its normalcompletion, without being a Dropped Call; and

• A Dropped Call is a situation originating from a failed

handover without re-establishment or a radio link time out atany stage of the call.




Drive Test - Report

Plots per Drive Test basis containing (for customer network &

main competitor):

• RxLev

• RxQual

• Events

– Handover

– No service

– Access Failure

– Dropped Calls




Analysis - Typical Setup

Failure Causes - Distribution




Analysis - Typical Dropped

Call Causes Distribution




Setting Targets

Quality is not a destination, it is

an Attitude




Network Audit - Recommendations

– Recommendations on Coverage Optimization

– Recommendation on Capacity Optimization

• Traffic patterns

• Signaling network

– Recommendation on BSS parameter settings

• Neighbor lists

• Handover

• Idle Mode

• Power Control etc.




Network Audit - Recommendations

– Frequency Plan

• Efficient use of spectrum

• Requirement forecast

– Requirements for In-building solutions

– Optimization recommendations for In-

building solutions




Network Audit – Issues

• Recommendations need to be completely

documented with technical justification

• A change control & logging process needs to

be setup

• All changes need to be verified after

implementation




Important processes for Optimization

• Coverage Optimization

• Frequency Plan

• SDCCH Dimensioning

• Capacity Optimization

• Control of Handover locations• Traffic Management

– HCS

– IUO

– Network initiated Handovers

– Coverage Optimization




Important parameters for Optimization

• BSS Parameter settings

– Handover

– Neighbor List

– Power Control (U/L & D/L)

– Idle Mode behavior

• Vendor specific features

– Single BCCH

– Directed retry

– Congestion relief etc.




LET’S START OPTIMISATION




Troubleshooting

Blocked Calls

Poor Quality and Drop calls

Abnormal Handovers

InterferenceTermination Failures




Blocked Call

Troubleshooting




Blocked Calls

Blocked Calls can occur due to :

• Access Failures

•SDCCH Congestion

•SDCCH Drop

•TCH Congestion

Trouble shooting cause :

•Use Layer 3 messages to analyze the cause

•Decode System Information Type 3 messages.

•Note the parameter , “max_retransmission” ;“CCCH CONF” and “BS_AG_BLKS_RES”




The best way of analyzing blocked calls, to identify the cause, is from a Layer III protocol log.

* Paging Failure

A paging message always originates from the MSC and is sent to all the BSCs in the

Location Area of the MS to be paged. The BSC will then calculate the Paging group of the MS and

send a Paging Command to the BTSs controlling the Location Area of the MS. On the air interfacethere are two cases of Paging Failure, either the Mobile receives no Paging message or it

receives a Paging message, but is not able to respond (not able to send a RACH) which could be

due errors in the Paging message.

* Access Failure

Irrespective of the purpose, for any communication required with the network, a mobile

sends a Channel Request (for SDCCH) on a RACH and waits for some time for a response which

should come from the BTS on an AGCH. A mobile will do several retransmission of RACHs (pre-defined) and if it still does not get a response, it goes back to idle mode and preferably does a cell

reselection. At this stage we call it an Access Failure.

* SDCCH Blocked

Once a mobile has sent a Channel Request on a RACH , it expects a response from

the BTS on the AGCH. This should be an Immediate Assignment Command to an SDCCH. If an

Immediate Assignment Reject comes instead , then this is SDCCH blocking.

* TCH Blocked

After the completion of call set-up signaling, a mobile expects an Assignment

Command to a TCH so that speech can commence. If no Assignment occurs for a specific period

and the Mobile has to return to idle mode, then it is due to TCH congestion.




Blocked Call Analysis - L3 messages

1 3

Channel Request Channel Request

RACH .

: Imm Assignment

RACH

max_retrans Service Request

NO RESPONSE FROM N/WACCESS FAILURE ! Signalling

:

Signalling

2

NO TCH ASSIGNMENT

Channel Request Mobile Returns To Idle

RACH TCH BLOCKED !Imm Assign Reject

SDCCH BLOCKED !




Blocked Call - Cause troubleshooting

Access Failures

- CCCH Overload at the Base Station

- Uplink Interference at the Base Station

- Low Rxlev at the Base Station

- Base Station TRX decoder malfunctioning

- Downlink Low Rxlev ( Coverage Hole )

- Downlink Interference

- Excess Cell Range




Access Failure - Troubleshooting

Access Failure - Uplink Problem

Causes:

1. AGCH Overload at Base Station

2. RACH Collisions3. MS out of Range

4. Poor Uplink quality

5. BTS Receiver Problem





AGCH Overloading - Root Cause Analysis

•If Multiple Immediate Assignment Extended Messages are seen,

problem could be AGCH overloading OR RACH Collisions/Non-detection

•If max_retrans and Tx-Integer are set to a lower value,

problem could be more towards RACH Collisions/ Non-detection

•If set high, then possibility of overloading is high!!

•Check for CCCH_CONF and BS_AG_BLKS_RES.

•If less blocks are reserved , problem is overloading.

• Analyze the OMC data for the same period for the following stats:- No of Deletions

- No of Successful RACHs

- RACH Busy counts

- No of RACH‟s with invalid establishment cause





RACH Collisions/ Max Range - Root Cause Analysis

•Max_Retrans and Tx-Integer set low - RACH Collisions Possible

•Check for Distance from Base Station

-- Plot a map for BCH ARFCN

-- Export the Channel Request and CellID Label

-- Import the Site ID‟s Raster Images on the Map -- Calculate distance between “Channel Request” and BTS

-- Compare this distance with the “Max_Distance_Allowed”

set for thjs cell.

-- Note: Max_Dist_Allowed is a BSC paramter ( not on Air )

-- If the MS distance is more than max_distance then problem

with Max Range

•If both the above conditions don‟t meet, then problem is Non-Detection





RACH Non-Detection - Root Cause Analysis

•Downlink is fine !!! Parameters are well set for RACH control !!!

•Problem could be Uplink Quality / Base Station

• Analyze the following OMC Data

-- No of Invalid RACHs

-- Interference on Idle Channel-- SDCCH RF Loss / TCH RF Loss

•If Interference and RF Losses are above normal, problem is Uplink Interference.

•If RF Losses are high, but interference is low , problem is Uplink level

•Uplink level poor indicates Link imbalance.

•If all above conditions are satisfactory and still “No of Invalid RACH‟s” high, problem

could





Downlink

Fine

Analyze

OMC Data

No of InvalidRACH‟s

Interferenceon Idle Channels

SDCCH/TCHRF Losses

High HighUplink

Intrfer YesYes

Uplink

Imbalance

No

Link Imbalance

Test

UL-Interference

Test

No

High

Problem

Found

Identify Cause

TroubleshootYes

BTS TRX

BTS Testing

No

Abis

Monitoring

No

Yes

RACH Non-Detection

Now let us go a step further in understanding the most probable causes behind call block




Now let us go a step further in understanding the most probable causes behind call block

problems.

* Access Failures

It could simply be caused by coverage holes . Interference could however play an

important role. Uplink interference on a serving cell can result in RACH rejections and hence no

AGCH assignments. Improper channel distribution between AGCH and PCH (paging channel)

can result in RACH/AGCH overloading. Paging Failures can be impacted by BCH pollution (co-

channel and adjacent channel interference).

* SDCCH Blocked

Heavy Traffic and excessive Location Updates can result in congestion of SDCCH

resources. Interference can block the channels , so though resources are available they may

not be able to be used.

* TCH BlockedHeavy Traffic is the main cause of TCH congestion. The TCH can also be blocked

due to continuous interference in the uplink.

Solutions to access failures would be to ensure continuous coverage and optimization of CCCH

configuration parameters . For TCH and SDCCH congestion, the hot spots need to be identified

and load sharing techniques implemented. Some techniques that have been used successfully

involve adjusting cell powers to vary the coverage and therefore the location where mobiles will

handover from one cell to the next.

Interference management is essential for optimum network performance. Location updates can

be optimized by independent drive tests on the ALL BCH carriers. The delta is measured of

each BCH with the current serving BCH and the Reselect Hysteresis parameters adjusted

appropriately.

Bl k d C ll A l i




Blocked Call Analysis

SDCCH Congestion Cause

Location Updatesto be analysed with OMC statistics first.

If high, determine the source to target cell ratio

Drive around the suspected area in the Idle Mode

Configure “Delta LAC < > Constant 0” alarms

Optimize Location Updates

Interference Analyze OMC statistics on “ Idle Channel Interference”

Carry out Uplink Interference Measurements using Viper

Heavy Traffic

Verify from OMC statistics SDCCH Congestion

Carry Call Setup Time measurements

Optimize set up time if high, else modify channel configuration




Blocked Call

Solutions To Blocked Calls

Optimize coverage

Optimize Cell loadingInterference management

Channel configurations

Optimize neighbors

TCH Blocked - Causes

•Interference

-- Verify Idle Channel Interference reports from OMC

-- If suspected, carry out uplink interference measurements

•Heavy Traffic

-- Verify the TCH Holding time and no of attempts statistics from OMC

-- During low traffic hours, Activate Cell barring in the cell-- Carry out Time slot testing , by setting Ignore Cell Barring.




Blocked Call - Interference

•Base Station Measures Uplink Interference on Idle Timeslots• At regular intervals, categorizes Timeslots into Interference Bands.

•There are Five Interference Bands.

•Each Interference Band has a range of interference level.

Example : Interference Band “1” = -110 to -100 dbmInterference Band “2” = - 99 to -90 dbm

Interference Band “3” = - 89 to -75 dbm

Interference Band “4” = - 75 to -60 dbm

Interference Band “5” = -59 dbm and above

•Network will assign Timeslots starting from lower band

•Interference Band “5” Timeslots are considered as “BLOCKED”

•OMC reports Hourly average statistics for each timeslot.




Timeslot - Testing

• Activate Cell Barring from OMC.•Remove this cell from the neighbor list of

other cells.

•Get the cell configuration

•ARFCN‟s and Timeslots configured for

TCH.

•For BCH carrier select the Timeslot and

carry out the Testing

•For TCH Carriers: Block the BCH Timeslots

from OMC•Carry out Timeslot testing.

•If more than 1 TCH Carrier is activated,

block all others .




Congestion Relief - Redirection

•Most of the manufacturers now provide this feature

BSC

MSC

Channel Request

Immd Assign

MM/CC Signaling

Assignment Request

ALL TCH’s Busy

Allocates a Free TCH

Assign Command

*** Some of the systems may also do handover existing calls to strong

neighbors and assign TCH for this call from the same cell

C i R li f R di i




Congestion Relief - Redirection

Role of Drive Testing

•OMC statistics may not reveal the actual congestion in a cell.

•Drive Testing may be required in the Peak traffic hours to estimate how

many times this happens.

•Drive Testing may also be required to optimize the neighbor list for

effectiveness of this feature.




Dropped Call

Troubleshooting




Call drops are identified through SACCH messages. A Radio Link Failure Counter value is

broadcast on the BCH. The counter value may vary from network to network. At the

establishment of a dedicated channel, the counter is set to the broadcast value (which will be

the maximum allowable for the connection). The mobile decrements the counter by 1 for every

FER (unrecoverable block of data) detected on the SACCH and increases the counter by 2 for

every data block that is correctly received (up to the initial maximum value). If this counter

reaches zero, a radio link failure is declared by the mobile and it returns back to the idle mode.

If the counter reaches zero when the mobile is on a SDCCH then it is an SDCCH Drop. If it

happens on a TCH, it is a TCH drop.

Sometimes an attempted handover, which may in itself have been an attempt to prevent a

drop, can result in a dropped call.

When the quality drops, a mobile is usually commanded to perform a handover. Sometimes

however, when it attempts to handover, it finds that the target cell is not suitable. When this

happens it jumps back to the old cell and sends a Handover Failure message to the old cell. At

this stage, if the handover was attempted at the survival threshold, the call may get droppedanyway. If on the other hand the thresholds were somewhat higher, the network can attempt

another handover.

Drop Calls Analysis




Drop Calls Analysis

1 2

Channel Request Channel Request

Imm Assignment Imm Assignment

Service Request Service Request

Signalling SDCCH Signalling

: :

Signalling SpeechTCH

RLT = 0 ; DROPS RLT = 0 ; DROPS

SDCCH DROP ! TCH DROP !

3 SDCCH / TCH

Handover Command

Hand Access

Handover Failure

HANDOVER FAILURE DROP !

Dropped Call Analysis




Dropped Call Analysis

• SDCCH Drops - Causes – Coverage

– Interference & Multipath

– BTS performance

• TCH Drops - Causes

– Coverage

– Interference & Multipath

– BTS performance

– Pre-emption

• Handover Failure - Causes

– Threshold parameters

– Missing neighbors

• Solutions to Dropped Calls

– Optimize Coverage

– Interference Management

– Optimize neighbors

– Optimize handover

parameters

– Effective Frequency Hopping

– Use of DTX & Power control

We will examine the potential causes behind call drops and some solutions to combat them.




* Coverage

Poor non-contiguous coverage will reduce C/N and hence will reduce the Ec/No

and will result into call drops.

* Interference

This is one of the major causes of dropped calls. Interference could be co-channel,

adjacent channel or external. Under certain severe cell interference conditions, the call will

be dropped before a handover can be initiated.. Multipath interference can also add to the

problems. Strong signal reflections result in time dispersion issues resulting in a large

coherence bandwidth.

* Network initiated drops

Certain network features, like preemption, can kill an ordinary call to provide

connection to an emergency class subscriber.

A handover is the key to survival from dropping calls. But if there are problems in the

Handover process itself, then this will not avoid a drop.

Dropped calls can be effectively reduced by improving coverage, detecting and reducing

interference, setting appropriate Handover Margins , thresholds for handovers and the

correct selection of neighbors. Use of DTX and dynamic downlink power control will also

reduce average interference which should lead to some improvements.

Drop Call Troubleshooting




Drop Call - Troubleshooting

RLT=0

RxQual > 4

YES

YES

YES

YES

Troubleshoot

Multipath/

Co-Channel/

BSIC decode

TCH=BCH Pri/Int <= 9

C/IAa <= -9C/IAb <= -9

Co-Channel /

Multipath

Interference!! No

YES

No

No

Adjacent Channel

Interference!!

YES YES

Troubleshoot

Source Cell

Using

BCH Analyzer

L3 Message

Analysis

No

Rx_Lev < -95

No **

Coverage Hole

!!!

Uplink

Problem !!!

No

Troubleshoot

Link Imbalance

UL-Interference

TCH -Pri/Int <= 9

Optimize

Neighbors/

Coverage

YES

No

** If TCH is Hopping, then all causes needs to be verified further,

before concluding on the root cause and optimizing.

YES

DROP

CALL

Handover Attempted ?

Handover Failed ?

Area of concern

No

MultipathNo




•SDCCH Drop - Coverage

•SDCCH Drop - Co- Channel Interference

•SDCCH Drop - Adjacent Channel Interference

•SDCCH Drop - Uplink Problem

•TCH Drop - Coverage•TCH Drop - Co-Channel Interference

•TCH Drop - Adjacent Channel Interference

•TCH Drop - Uplink Problem

•Handover Failure

P Q lit




Poor Quality

•Poor Speech Quality could be due to•Patchy Coverage ( holes)

•No Target cell for Handover

•Echo , Audio holes, Voice Clipping

•Interference ---:•Co-channel

• Adjacent channel

•External

•Multipath

•Noise

Speech Q alit Parameters




Speech Quality Parameters

RxQUAL : Measured on the midamble.Indicates poor speech quality due to radio interface impairments

FER : Measured on the basis of BFI ( Ping -Pong effect on speech )

Preferred under Frequency Hopping situation

Echo and distortion : Generally caused by the Transmission and switchingsystem.

Audio holes : Blank period of speech, due to malfunctioning of Transcoder

boards or PCM circuits.

Voice Clipping : Occurs due to improper implementation of DTX.

Mean Opinion Score (MOS) : ITU standard for estimating speech quality.






Mean Opinion Score

Criteria for Voice Quality : A set value “x” at which “y” percent of customers

rate the voice quality at Circuit Merits(CM) 4 - 5.

MOS Quality Scale

5 Excellent ( speech perfectly understandable)

4 Good ( speech easily understandable, some noise)

3 Fair ( speech understandable with a slight effort ,occasional repetitions needed)

2 Poor ( speech understandable only withconsiderable effort , frequent repetitions needed)

1 Unsatisfactory ( speech not understandable)

Speech Quality Estimation




Speech Quality - Estimation

Speech RxQual FER FH DTX Reason

BAD HIGH LOW NO NO Air Interface Impairments

BAD HIGH HIGH NO NO Severe Air Interface Impairments

BAD LOW HIGH NO NO Transmission and Switching system , Transcoder

BAD LOW HIGH YES NO Air Interface Impairments

BAD GOOD HIGH YES NO Transmission and Switching system , Transcoder

GOOD HIGH LOW YES NO Hopping Implementation

CLIPPING LOW HIGH YES YES Hopping Implementation and VAD

CLIPPING LOW LOW YES YES VAD

ECHO LOW LOW Y/N Y/N Transmission and Switching system , Transcoder

MOS up to a certain extent can easily estimated by configuring an algorithm

using the Alarms in the HP E74XX systems for the following elements, an

example of subset of which is illustrated above- RxQual Full and Sub

- RxLev Full and Sub

- FER and RLT

- L3 Measurement Report

- L3 Handover specfic messages

Speech Quality Troubleshooting




Speech Quality - Troubleshooting

RxQual> 6

FER > 1%

YES

YES

YES

YES

Troubleshoot

Multipath/

Co-Channel/

BSIC decode

TCH=BCH Pri/Int <= 9

C/IAa <= -9C/IAb <= -9

Co-Channel

Interference!!

No

YES

No

NoAdjacent Channel

Interference!!

YES YES

Troubleshoot

Source Cell

Using

BCH Analyzer

No

Rx_Lev < -95

No **

Coverage

Hole !!!

Uplink

Problem !!!

Troubleshoot

Link Imbalance

UL-Interference

TCH -Pri/Int <= 9

Optimize

Neighbors/

Coverage

YES

No

** If TCH is in Hopping, then all interference causes needs to be verified further,

before concluding on the root cause and optimizing.

YES

Poor

Quality

Area of concern

Hopping ON

YES

RLT going down

DTX_DL ON

FER > 2%YES

No No

NoNo

Transmission/

Switching Systems

Transcoder

Patchy QualityMultipath

High Probability

with Hopping ON

YES

NoA

A

BB

A

MOS < 4

Troubleshooting Poor Speech Quality




Troubleshooting Poor Speech Quality

Method 1 : Post Processing

Create the Following PLAN Wizards in Export

Quality-PHONEDATA

Rx_Lev

Rx_Qual

FERRLT current Value

Timing Advance

Tx Level

ARFCN ( BCH and TCH)

Serving Cell Information

-- CellID

Quality-Cell Information

Serving Cell Information

-- CellID

-- BSICNeighbor Cell Measurements

Neighbor Meas Count()

Timeslot

ARFCN

Interference

Co-Channel Interference

-- Channel

-- Primary/Interferer -- Primary BSIC

-- Secondary BSIC

-- Textual Meas Status

-- Numeric Meas Status

-- Fading

Adjacent Channel Interf

-- AdjA Channel

-- AdjA N/N-1

-- AdjA N/N+1

-- AdjB Channel

-- AdB N/N-1

-- AdjB N/N+1

ARFCN

Filtered Spots- RxQual > 4




Filtered Spots- RxQual > 4

Bad Spot 1

Troubleshooting Bad Spot 1




Troubleshooting - Bad Spot 1

Which is this CELL ??




Which is this CELL ??

•Select QualPhoneData Layer.

•Check on Labels

•Select Labels

•Select CellID.

•Display it on the MAP

Which is the cell ? 47450 !!




Which is the cell ? 47450 !!

Did the Call Drop ???




Did the Call Drop ???

•Create RLT.tab

Query for RLT < 8

•Import as Label

Layer

RLT = 0 , DROP CALL !!

Conclusion




Conclusion

•BAD Spot 1 has poor quality and Call Drop

•This spot is covered by Cell 47450•Poor Coverage. Level below -97 dbm

•But Call should not Drop

•The other Problem is Interference.

•Mobile is Hopping on 99 and 84

•99 is also the BCH.

•Co-Channel on BCH is very high.

•50% of the time quality will be poor.

•But Poor Quality is consistent.

•Channel 84 is also suffering from Interference.

•No Adjacent Channel on 84 and 99

•This means there is Co-Channel on 84 also.•It could also be multipath issue on 84.

•WHY NO HANDOVER




Troubleshooting

Handover Problems

Troubleshooting - No Handover




Troubleshooting - No Handover

Create a Hand over PLAN

Total Attempted Calls

Total Dropped Calls

Total Blocked Calls

RxQual Full

RxLeve Full

RLT Current ValueARFCN

Neighbor Cell Measurements

RR Message

Phone State

Sequency Number

Weak Neighbors - Reported by Phone

Analyzing - No Handover




Analyzing - No Handover

No Neighbor( very weak)

Missing Neighbors




CH 40

CH 35

CH 27

CH 88

CH 29

CH 35

CH 98

CH 72 BSIC

23

BSIC 16

BSIC22

BSIC 75

BSIC 15

BSIC 21

BSIC

57

BSIC 53

CH 25 BSIC

17 PHONE REPORTS CH RxQual RxLev

27 1 -80

35 -85

40 -83

25 -95

Frequency Re-

use

'A' NET

'A' NET

'A' NET

'B' NET

'B' NET

'B' NET

'B' NET

'B' NET

'B' NET

Channel 29 is not in the neighbour list !

BCH Analyzer : TOP N = 7

Configure an Alarm for Missing Neighbor “Subset BCH TOP N not-subset Value ARFCN”

g g

Real Time




Missing Neighbor is a very critical problem in optimizing GSM neighbors.

Missing Neighbor as such doesn‟t means that there is no neighbor. We

define neighbors to a cell based on the geography, I.e which base stations

are nearby. In certain cases we may also use the Planning Tools to predict

neighbors. It is such not desirable to use excessive neighbors also, since

this reduces the samples collected per neighbor. Since Mobile has to look

for each neighbor in one TDMA frame, and we have 104 frames for

measurement. This means if we define 32 neighbors , the number of samples per neighbor will be only 3-4, which means the authenticity of

Handovers will not be there. So we need to define appropriate neighbors

only. In certain cases the neighbors we define may not be able to cope up

with traffic or at certain significant patches of the cell, these neighbors

signals would be weak and may result into no handovers or handover

failures. So in such kind of problem spots , we should be see the possibilitythat signals from any other cell is coming or not, so that we can define that

as a neighbor. So how do we find such missing neighbors.

Troubleshooting - Handover Parameter




Settings

•Decide the Target Cell for handover in the Trouble Spot

•Filter the Handover.txt file on Handover Attempts ( before AND after numbers)

•Filter again on Neighbor ARFCN = Target Cell ARFCN

•Create another column as HO_Margin , with Delta for Neighbor_Level to RxLev

•Plot this on the MAP and see wether Handover Margin can be reduced to improve

quality OR increased to avoid Ping-Pong effects•If handover margin settings are proper, and still handover is not occurring then

it could be a problem with Handover decision and processing parameters at the

BSC.




Interference Measurements

and

Troubleshooting

Types of Interference




Types of Interference

We already know ….

Co-Channel

•BCH - BCH

•TCH - BCH

•BCH - TCH

•TCH - TCH

Adjacent Channel Interference

•BCH - BCH

•TCH - BCH

•BCH - TCH•TCH - TCH

Multipath

TroubleShooting




TroubleShooting




Uplink

Problems

Locating Uplink quality Bad Spots




Locating Uplink quality Bad Spots

RX_Level is near P_Con Threshold

Ms Tx Level is max ( 5)

Locating Uplink Bad Quality Spots.




Locating Uplink Bad Quality Spots.

Trend shows:High receive level

And High Ms Tx Levels

in this area.

Locating Uplink Bad Quality Spots




Locating Uplink Bad Quality Spots

•At some areas for low signal level ( < -88), MS at full power •In another area for high signal level ( -75 to -85 ) , MS full power

•MS Tx Level is controlled by the network.

•Network will ask MS to increase power if Uplink level is poor or

Quality is poor.

•Link Imbalance will result into low uplink level even if DL Level isgood.

•Then MS will be at high power in all those spots where level is

good. BUT THIS IS NOT THE CASE !!! ( as seen from two spots)

•This means this is a problem of Uplink quality being poor at good

level.

•This can happen due to UPLINK INTERFERENCE.

•This interference seems to be burst in nature !!!!

Troubleshooting - Uplink Interference




•Uplink Interference can be due to:

• Mobiles in reuse and adjacent channel cells• Spurs and Intermods from base stations

• External sources

•Interference due to Mobiles will be bursty and intermittent.

•The behavior and its effect on quality will be time dependent.

•More interference during heavy traffic hours.

•Interference from external sources can be continous or also

time dependent if the source is not continously ON.

•Uplink Interference measurement needs long term monitoring ,

collection of data, processing the data and estimating theprobability of interference , and also estimating the source.




Termination Failures

Troubleshooting

Troubleshooting - Termination Failures




g

•Termination Failures could be due to:•Paging Problems with Network

•No response to page from MS

•Blocking of Resources

•If Paging Success Rate = 100 %, but still the caller reportstermination failures, then this Blocking.

•If Paging Success Rate < 100 % ,then this could be :

- Paging Problems with Network Or

- No response to page from MS

Troubleshooting-Termination Failures




•Verify and Isolate the problem as:

•Interference

•Excessive Cell Reselection

•Excessive Location Updates

•None of above indicates Network Problem ( no paging)

•Excessive Cell Reselection and Location Updates can occur due to

•Interference ( Downlink signaling Counter reaches 0)

•BCH Pollution

•Overlapping of Location Areas.

•Carry out protocol analysis on Abis and A Interface to isolate network

problem further




Cell Optimization

Optimization




Optimization

Cell Loading

C1

C3

•Cells C1 and C2 are reporting Blocking

•Cell C3 is added to cater for capacity

•Still C1 and C2 report blocking. Why ?????

Optimizing - Cell Loading




p g g

More Traffic could be persuaded towards C3 by :•Increasing the Power Output of C3 BTS

•Tilting Antenna‟s towards Hot spots in C1 and/or C2

• Applying Reselect Offsets to certain less loaded neighbor cells

With this approach more MS's will camp on or do cell reselection to C3, thus

reduce load in C1 & C2.

These issues are very common to fast growing networks, because new cells

when are planned , we don't know the HOT SPOTS.

In most cases , new cells investment could also be minimized by understandthe RF environment and optimizing cell loading.

Optimizing - New Cell Site Location

& Antenna Tilts




& Antenna Tilts

•New cell sites in the earlier phase of the network are implemented toenhance coverage.

•Coverage enhancements takes priority over areas of predicted traffic

•Once coverage objectives are met, cell expansion takes place purely

on the basis of traffic.

•New BTS are sited near to the cells which are generating blocking

conditions.•The objective behind new cell site investment is to take the load from

the existing congested cells and hence increase revenue.

• An existing congested cell would be covering an area of 1 sqKm.

•Traffic in this area would be concentrated in small patches known as

“HOT SPOTS”.

•Network Planner always intends to optimize the cell site location or the

antenna tilts to target on some of the Hot spots .

•But the question is do we precisely know where are the Hot spots ???

Optimizing - Cell Reselections




p g

•Mobile Monitors the Neighbor cells BCCH Carriers and decodes SCHof the neighbors in the idle mode.

•The list of the BCCH ARFCN‟s which the mobiles will monitor in the

idle mode is broadcasted in the System Information Type 2 Message .

•More the neighbors , less the samples taken by the mobile per

neighbor to the calculate the value of C1.

•More neighbors of good and near to equal power levels will result intoexcessive reselections.

•Excessive reselections can result into missing of paging messages

•Solution to this problem would be to adjust power levels of base

stations.

• Adjusting power levels most of the time either effects coverage or

enhances interference, since the terrain is not flat.•To optimize cell reselections, the best possible solutions are:

• Optimizing the BA list

•Implement C2 Reselections

Optimizing - Neighbor lists




p g g

•Maximum 32 neighbor

•Less samples, averaged reported value not authentic

•Results in Ping-Pong effect of Handovers

•Neighbor list must be optimized




Mobile in the dedicated mode measures the BCH of the neighbor cells.

The list of BCH to be measured is informed to the Mobile in the System

Information Type 5 message which can have maximum 32 neighbors BCH’s Mobile has to report the measurements of the neighbors to the network , every

480ms which corresponds to 104 TDMA frames.

Mobile will take several samples of the neighbors, average it and then send the

report as one value of Rxlev of the neighbor, with a minimum requirement of

measuring at least 1 neighbor in 1 TDMA Frame.

So , more the BCH’s in the neighbor list, less will be the number of samples.

If the Mobile just meets the minimum requirement, then for a neighbor list of 32,

only 3 - 4 samples per neighbor will be available and 12-13 samples per

neighbor with a list of 8 neighbors

If the samples collected are less, then average value reported will not be

authentic, and can result into Ping-Pong effect of handovers.

So, the Neighbor list must be optimized with the minimum best possible

neighbors

Optimizing -Handover Traffic




p g

A B

C D




As shown above, Cell B is a cell which is reporting Blocking due to heavy traffic.

Cell B on OMC analysis is found to have traffic generated due to call setups

within the cell , as well as handovers, since it covers a major highway withheavy mobility traffic coming from Cell A.

Instead of implementing an excess TRX or a new cell to resolve this issue, we

can optimize this problem, we can optimize the neigbbor lists, so as to drag the

Mobiles coming from A to handover to cells other than B, unless B is the only

candidate for handover.

We can drive through the area between Cell A and Cell B and mark the spots

where handover occurs.

Look for the continuity between BCH‟s. This will indicate to us, which are the

strong BCH‟s other than Cell B which could be potential targets for handovers

and with what handover margins, so in case we don‟t get an alternative for a

certain patch which is above the handover margin threshold, we can reduce the

handover margin .

Optimizing - Handover Margin




• Handover Margin is value set for all cells, which will allow

mobiles to handover to the cell, only when this cells power budget balance exceeds the source cells power budget

balance by this value.

• Handover Margins main objective is to avoid ping-pong effects

of handovers on cell periphery, when the power levels of two

cells are near to equal , so due to multipath and mobility, thiswill result into frequent handovers between these two cells.

• Setting this value low, will result into fast handover to the

target cell, which may result in improvement in quality.

• Setting this to high value will delay the handover to the target

cell, and ensure that when handover takes place, theprobability of the mobile going back to the source cell is very

low for some significant period.

• Two examples of use of this parameter are illustrated ( next

page)





Adjacent Channel Interference Reduction

Tight Re-use patterns can permit the use of Adjacent ARFCN in

adjacent cell.

This should not pose an problem if Handover margin is set

appropriately low.

If Handover Margin is set to 6 dB, Handover will occur from C1 to

C2 at spot B itself

C/Ia = -1 db C/Ia = -6 db C/Ia = -9 db

A B C

C1 C2

Optimizing Handover Margin




ADA cellworksLouder than words….. H

Multipath solutions

Antenna Tilts

Using Directional Antenna's

Shifting the BTS site

Handover Parameters

C1

C2

Reduce HO_margin

C3

Increase HO_margin

Reduce HO_margin

p g g





g g

• Selecting an appropriate value of

handover margin is essential to ensure

good quality communication .

• Handover margin set for a cell is

applicable to all calls going on in the cells,to which this cell is a neighbor.

Optimization for Interference




Optimization for Interference

After drive test - Co-Channel benchmarking, we know whichcells are generating severe co-channel problem

We also know by decoding BSIC , the interefering source

Following processes could be adopted to optimize

interference

---- Power Control---- Antenna Tilts

---- Frequency Reallocations

---- Transmitter Tests

---- Mobile dispatch inspection

---- Space Diversity

---- Frequency Hopping /DTX




In order to optimize interference the cells which are generating high level of

interference should be located from the OMC Performance Database. It is essential

to locate the source of interference whether it is external or internal. If it is internal

then it could be due to multipath, adjacent, co-channel, inter-modulation or spurious. This can be located by analyzing the spectrum. There are various

methods involved in optimizing interference. Appropriate Power Control of the

interfering entities could be done. For Co-channel Interference problems, Tilting of

antenna could be done with proper coverage aspects, for adjacent channel analysis

should be done to locate if any adjacent channel is allocated to the neighbors , If it

is then frequency allocation could help with this. It is very essential to carry out

Transmitter and Mobile tests for Power v/s time output spectrum and inter-

modulation products, generally a mobile should be tested for these basic tests

before being dispatched. In the Uplink Space Diversity is the worldwide adopted

method for reducing the effect of Multipath fading, where as in the downlink it is

the mobiles equalizer which has to do this job. One very relevant solution to

interference is frequency hopping where the mobile constantly changes frequency

for every burst which reduces the effect of interference. Implementation of DTX.DRX also reduces average interference.



Antenna Tilts




Antenna Tilts

x 6 km 1 km

A M N

50m

Point x is having problem of C/I from Cell M

Estimate the C/I improvement required at Point x.

Refer to the Antenna Vertical Pattern, and calculate the tilting angle required

Example : To get an improvement of 3 dB , a tilt of 10 degrees is required.

Tilting of Antenna in certain cases may reduce coverage also. Tilting of Antenna should be done after proper study.




PARAMETER OPTIMISATION




Introduction to Parameter Planning

Module Objectives



ADA Louder than words…..

At the end of the module, the participant will be able to:

Sketch a BSS Managed Object Hierarchy Look up the parameters at each level, in a parameter

dictionary

Identify parameter value ranges and default settings

Describe the use and benefits of a Background Database

Find the changes to objects, parameters, and MML

commands, that occur with each BSS software release

Outline how the progression of a call through various

phases, is influenced by the parameter settings for each

MO class

Distinguish between the signalling in Idle mode and

Dedicated mode

Managed Object Hierarchy




A BSC Level Parameter




Example of a BCF Level

Parameter




Parameter

Example of a BTS Level

Parameter




Parameter

Typical Parameter in theBSS and NSS RNW Par. Dictionary




y

Example of Summary of Changes




MOC Call Phases




MS BTS BSC

AUTHENTICATION (SDCCH) Phase 2 : MM sign al l ing

CIPHERING MODE (SDCCH)

Phase 8 : Ciphering

TMSI REALLOCATION (SDCCH)

SETUP (SDCCH)

Phase 2 : MM sign al l ing

CH. REQUEST (RACH)

IMMEDIATE ASSIGN(AGCH)

SERVICE REQUEST (SDCCH)

Phase 1 : Paging, init ial MS

CH.RELEASE

Phase 4 : Release

ALERTING & CONNECT (FACCH)

Phase 2 : MM sign al l ing

CONN. ACK. and MEASUREMENT

Phase 15 : Conv ersation

DISCONNECT & RELEASE (FACCH)

Phase 4 : Release

ASSIGNMENT (SDCCH-FACCH) Phase 3 : Basic assignment

Trade-off BetweenLocation Update & Paging Traffic




p g g

Paging LocUp

# of cells in Loc. area

signallingtraffic

optimum number of cells in Loc. area

function of user density,

cell size, call arrival rate ...function of

user mobility

Handover Types




• Intracell same cell, other carrier or timeslot

• Intercell between cells (normal case)

• Inter-BSC between BSC areas

• inter-MSC between MSC areas

• inter- PLMN (only when roaming)

intracell intercell

inter-BSC




Radio Channel Configurations

Burst Period




0 7

TDMA frame = 4.615 ms

= BURST PERIOD

0

0 0

f s

Radio Timeslots & Frames




TCH

0 1 2 24 25 0 1 2 49 50

0 7

Hyperframe = 2048 Superframes

Superframe = 26x51 or 51x26 Multiframes

26 Multiframe = 120 ms 51 Multiframe = 235 ms

TDMA frame = 4.615

ms

SIGN.

GSM Logical Channels




COMMON

CHANNELSCOMMON

CHANNELS

BROADCAST

CHANNELSBROADCAST

CHANNELS

COMMON

CONTROL

CHANNELS

COMMON

CONTROL

CHANNELS

DEDICATED

CONTROL

CHANNELS

DEDICATED

CONTROL

CHANNELS

TRAFFIC

CHANNELSTRAFFIC

CHANNELS

FCCHFCCH SCHSCH BCCHBCCH SDCCHSDCCH SACCHSACCH FACCHFACCH

PCHPCH RACHRACH AGCHAGCH TCH/FTCH/F TCH/HTCH/H TCH/EFRTCH/EFR

DEDICATED

CHANNELSDEDICATED

CHANNELS

LOGICAL

CHANNELSLOGICALCHANNELS

GSM Logical Channels




FCCH - Frequency Correction CHannel

Downlink channel used to enable MS in finding the slot alignment for demodulating SCH burst (also allows for frequency correction).

SCH - Synchronisation CHannel

Downlink channel which provides MS will all the necessary information neededfor synchronisation (always follows FCCH burst, 8 BPs later, on same frequency).

Also carries BTS identification information.

BCCH - Broadcast Control CHannel

Downlink channel used to transmit cell specific information to all MSs within a cellcoverage area, at regular intervals, e.g. frequencies used in a cell & ncells,channel combination, paging groups, etc. (must be ubiquitous coverage).

PCH - Paging CHannel

Dowlink channel used to send paging messages to MSs (MTC)

AGCH - Access Grant CHannel

Downlink channel used by network to allocate a dedicated control channel to an

MS.

GSM Logical ChannelsRACH - Random Access CHannel




Uplink Channel used by MS to request a dedicated control channel.

SDCCH - Standalone Dedicated Control CHannel

Bi-directional channel used for system signalling, e.g. call set-up, location updates,SMS.

SACCH - Slow Associated Control CHannel

Bi-directional (low rate) channel used to transport signalling data (two messages per sec ~ 1 every 480ms) such as measurement reports for handover process. RLT is

also based on decoding SACCH.

FACCH - Fast Associated Control CHannel

Bi-directional channel used to transport urgent signalling messages, e.g. commanda handover, authenticate a subscriber, etc.

TCH (F/H) - Traffic CHannel Bi-directional channel used to carry user speech or data - can be either full rate or half rate.

CBCH - Cell Broadcast CHannel

Downlink channel used only for general (non point-to-point) short message

information.

Configuration of Signalling Channels




0 7

Non-combined Configuration

Combined Configuration

0 7

ts0=bcch + pch + agch ts1=sdcch/8

ts0=bcch + sdcch/4 + pch + agch

1



BCCH/CCCH Multiframe




f s bb b b c f c f c s c c c c cc c c f c f s c c c c cc c c f f c c c c cc c c f s f c c c c cc c cs

r r r r r r r f r r r r r r r r r r r r r r f r r r r r r r r r r f r r r r r r r r r r f r r r r r r r r r

Downlink

Uplink

CHANNELS: f = FCCH b = BCCH r = RACH i=idle

s = SCH c = CCCH = PCH/AGCH

51 TDMA frames = 235 ms

r

0 50

i

SDCCH/8 Multiframe




t t tt t t t f t tt t t t t t tt t t tt f t t t t t tt t t t f s s s s ss s s s f s s s s ss

s s ss s s s f s ss s t tt t t ts f t t t t t tt t t t f t t t t tt t t tt f t t t t tt t tt

Downlink

Uplink

CHANNELS: t = SDCCH/8 s = SACCH/8 i=idle

t

t


s

1. 2. 3. 5. 6. 7. 8.4.

0 50

iii

iii

Full Rate Traffic Channel

(TCH) Multiframe




( )

t t tt t t t f t tt t t tt t t tt f t t t tt

Downlink and Uplink

CHANNELS: t = TCH s = SACCH i=idle

ts


0 25

i

Half Rate Traffic Channel

(TCH) Multiframe




( )

Downlink and Uplink

CHANNELS: t = TCH s = SACCH i=idle


0 25

Downlink and Uplink


0 25

t t t t t t t t t t tt

t t t t t t t tt t tt

s i

Paging Procedure• Paging messages sent on PCH which MS continually listens to




g g g y

(TSL0 on BCCH TRX)

• Limited to geographical sub-group of BSCs using LACs

• Paging sub-groups are used to save MS battery-life since MS only

needs to listen to its own sub-channel and not to the entire PCH

• MS can be paged using IMSI or TMSI (determines number of MSs

that can be paged per message (IMSI = 2 MSs : TMSI = 4 MSs)

• Split between PCH and AGCH determined bynumberOfBlocksForAccessGrant and the type of channel

configuration used (i.e. combined or non-combined)

Blocks for PCH &AGCH

No. Blocks Res AGCH

No. Blocks Res PCH

CombinedNon

Combined

3 9

0-2 0-7

3-1 9-2

• PCH can be used for AGCHif no paging messages are tobe sent, but AGCH can notbe used for PCH

• Three types of pagingmessages (type 1, 2 and 3)depending on no. of MSspaged

Paging CapacityC bi d BCCH / SDCCH (MBCCHC) C fi t i




Combined BCCH / SDCCH (MBCCHC) Con figurat ion

• One Block Reserved for AGCH => 2 Blocks for

PCH

• Paged MS per Paging_Request Message : From

2 to 4 (average 3)

• Average 2 Pages per MS• 3 Pages/Blocks * 2 Blocks = 6 Pages every 51-

frame Multiframe ( 235 ms. )

• 2 Pages / Paged MS => 3 Paged MS every 235

ms.

• ( ( 3600 * 1000 ) / 235 ) * 3 = 45.957 Paged MSper Hour.

• In the worst case all Transactions are Mobile

Terminating

• All Cells in Location Area get the same PCH

Load

•

BTS MS

Paging_Request

BTS 3MS

2 Paging_Request

Capacity of PCH calculated for a Location Area

Non-Combined & Combined

Multiframes




f s bb b b c f c f c s c c c c cc c c f c f s t t t t tt t t f f t t t t tt t t f s f s s s s ss s ss

1 2 3BCCH + SDCCH/4 (Combined)

f s bb b b c f c f c s c c c c cc c c f c f s c c c c cc c c f f c c c c cc c c f s f c c c c cc c cs

BCCH + CCCH (Non-Combined)


1 2 3 4 5 6 7 8 9

i

i

CHANNELS: f then s = FCCH then SCH b = BCCH r =

RACH

ssss = SACCH c = CCCH t = SDCCH

i=idle

RACH Controlling




Number of retransmissions = maxNumberRetransmission (1, 2, 4, 7)

window = numberOfSlotsSpreadTrans (3 ... 12, 14, 16, 20, 25, 32, 50)

0 0

1 RACH (Re)transmission during the window

=> Total time for RACH = maxNumberRetransmission * numberOfSLotsSpreadTrans

TDMA-frames

CCCH Configuration 1 (2) numberOfBlocksForAccessGrant Parameter




• Pages always had to have priority in CCCH blocks no matter what thenumberOfBlocksForAccessGrant setting was.

• Now, if numberOfBlocksForAccessGrant =0 then AGCH messageshave priority over PCH messages.

• If numberOfBlocksForAccessGrant <> 0 then PCH messages havepriority over AGCH messages .

Thus capacity can be dynamically shared between PCH and AGCHresulting in better throughput for PCH, especially for combined-BCCH

CCCH Configuration 2 (2)

Number of Mult i f rames Between Paging




• # of 51 TDMA frame multiframes (2..9) between transmissions of Paging_Request messages to mobiles of the same paging group

# of paging groups =

(# of CCCH blocks - numberOfBlocksForAccessGrant )*

noOMultiframesBetweenPaging

Page / group every (2 ... 9) * 235 ms = 0.47 ... 2.115 s

• Mobile Station calculates its Paging Group based on IMSI and on the

Number of Paging Groups

• Affects of the # of the Paging Groups

– Battery Consumption of the Mobile Station

– Speed of Call Setups

SDCCH Capacity




• Location updates

• Short Message Service (SMS)

• Call Establishment

SDCCH used in

• Queuing (at call set-up)

SDCCH CapacityExamp le 1 - Cal l Establ ishment & Locat ion Updates inc luded





• 2 TRXs / Cell ~ 8,11 Erl / Cell (1% Blocking probability)

• 1,5 min / Subs / BH = 25 mErl. / Subs• 8,11 Erl / Cell /25 mErl / Subs = 325 Subs / Cell

• Authentication and Ciphering = 7 sec = 1,94 mErl / Call (SDCCH

reservation time)

=> 325 Calls / Cell * 1,94 mErl / Call = 0.6305 Erl / Cell (SDCCH)

• Location Update

• Location Updates once in 60 minutes ( parameter

t imerPer iodicUpdateMS )

• 325 Subs / Cell

• SDCCH reservation time for Location Update = 7 sec = 1,94 mErl

=> 325 Calls / Cell * 1,94 mErl / Call = 0.6305 Erl / Cell (SDCCH)

• Call Establishment and Location Update together

– 0,632 Erl + 0,632 Erl = 1,261 Erl / Cell

– With 1% Blocking Probability ( Erlang B table ) => 5 SDCCH / Cell

Erlang B Table




Chs 1% 2% 3% 5% Chs 1% 2% 3% 5%

1 0 .01 0 .0 2 0 .03 0 .05 21 12 .80 14 .00 1 4 .90 16 .2 0

2 0 .15 0 .2 2 0 .28 0 .38 22 13 .70 14 .90 1 5 .80 17 .1 0

3 0 .46 0 .6 0 0 .72 0 .90 23 14 .50 15 .80 1 6 .70 18 .1 0

4 0 .87 1 .0 9 1 .26 1 .52 24 15 .30 16 .60 1 7 .60 19 .0 0

5 1 .36 1 .6 6 1 .88 2 .22 25 16 .10 17 .50 1 8 .50 20 .0 0

6 1 .91 2 .2 8 2 .54 2 .96 26 17 .00 18 .40 1 9 .40 20 .9 0

7 2 .50 2 .9 4 3 .25 3 .75 27 17 .80 19 .30 2 0 .30 21 .9 0

8 3 .13 3 .6 3 3 .99 4 .54 28 18 .60 20 .20 2 1 .20 22 .9 09 3 .78 4 .3 4 4 .75 5 .37 29 19 .50 21 .00 2 2 .10 23 .8 0

10 4 .46 5 .0 8 5 .53 6 .22 30 20 .30 21 .90 2 3 .10 24 .8 0

11 5 .16 5 .8 4 6 .33 7 .08 31 21 .20 22 .80 2 4 .00 25 .8 0

12 5 .88 6 .6 1 7 .14 7 .95 32 22 .00 23 .70 2 4 .90 26 .7 0

13 6 .61 7 .4 0 7 .97 8 .83 33 22 .90 24 .60 2 5 .80 27 .7 0

14 7 .35 8 .2 0 8 .80 9 .73 34 23 .80 25 .50 2 6 .80 28 .7 0

15 8 .11 9 .0 1 9 .65 10 .60 35 24 .60 26 .40 2 7 .70 29 .7 0

16 8 .88 9 .8 3 10 .50 11 .50 36 25 .50 27 .30 2 8 .60 30 .7 0

17 9 .65 10 .7 0 11 .40 12 .50 37 26 .40 28 .30 2 9 .60 31 .6 0

18 10 .40 11 .5 0 12 .20 13 .40 38 27 .30 29 .20 3 0 .50 32 .6 0

19 11 .20 12 .3 0 13 .10 14 .30 39 28 .10 30 .10 3 1 .50 33 .6 0

20 12 .00 13 .2 0 14 .00 15 .20 40 29 .00 31 .00 3 2 .40 34 .6 0

SD

Channels

SDCCH CapacityExamp le 2 - Call Establ ishment & Locat ion Updates inc luded





• 2 TRXs / Cell ~ 8,11 Erl / Cell (1% Blocking probability)

• 1,5 min / Subs / BH = 25 mErl. / Subs

• 8,11 Erl / Cell /25 mErl. / Subs = 325 Subs / Cell

• Authentication and Ciphering = 7 sec = 1,94 mErl / Call (SDCCHreservation time)=> 325 Calls / Cell * 1,94 mErl / Call = 0,6305 Erl / Cell (SDCCH)

• Location Update

• Location Updates once in 120 minutes ( parameter t imerPer iodicUpdateMS )

• 325 Subs / Cell• SDCCH reservation time for Location Update = 7 sec = 1,94 mErl

=> 325 Calls / Cell * 1,94 mErl / Call * 1/2 = 0,31525 Erl / Cell (SDCCH)

• Call Establishment and Location Update together

• – 0,6305 Erl/Cell + 0,31525 Erl/Cell = 0,94575 Erl/Cell (SDCCH)

– With 1% Blocking Probability (Erlang B table) => ~ 5 SDCCH / Cell


SDCCH CapacityExamp le 3 - Call Establ ishm ent, Lo cat ion Upd ates & SMS





– 2 TRXs / Cell ~ 8,11 Erl / Cell (1% Blocking probability)

– 1,5 min / Subs / BH = 25 mErl. / Subs – 8,11 Erl / Cell /25 mErl. / Subs = 325 Subs / Cell

– Authentication and Ciphering = 7 sec = 1,94 mErl / Call (SDCCHreservation time)

=> 325 Calls / Cell * 1,94 mErl / Call = 0,6305 Erl / Cell (SDCCH)

• Location Update

– Location Updates once in 120 minutes ( parameter timerPeriodicUpdateMS )

– 325 Subs / Cell

– SDCCH reservation time for Location Update = 7 sec = 1,94 mErl

=> 325 Calls / Cell * 1,94 mErl / Call * 1/2 = 0,31525 Erl / Cell (SDCCH)

• SMS

– SMS traffic estimation 1.0 mErl / subscriber

=> 325 Calls / Cell * 1 mErl / Call = 0,325 Erl / Cell (SDCCH)• Call Establishment, Location Update and SMS together •

– 0,6305 Erl/Cell + 0,31525 Erl/Cell + 0,325 Erl/Call = 1,27075Erl/Cell(SDCCH)

– With 1% Blocking Probability ( Erlang B table ) => ~ 5 SDCCH / Cell

Separated channel structure is needed in this case

Parameters Related to Signalling




numberOfBlocksForAccessGrant (AG) 0 ... 7 (if BCCH/CCCH used)(non-combined)

1 ... 7 (if CBCH used on SDCCH/8)

0 ... 2 (if combined BCCH/SDCCH used)

noOfMultiframesBetweenPaging (MFR) 2 ... 9

maxNumberRetransmission (RET) 1, 2, 4, 7

numberOfSlotsSpreadTrans (SLO) 3 ... 12, 14, 16, 20, 25, 32, 50

newEstabCausesSupport (NECI) Y/N (FACCH setup allowed)

pagingAnsOnFacch (EPF) Y/N

emerCallOnFacch (EEF) Y/NordinaryCallOnFacch (EOF) Y/N

restablishCallOnFacch (ERF) Y/N

Parameters Value




Idle Mode Operation

Module Objectives

f




At the end of the module, the participant will be

able to: List functions of the MS during idle mode

Explain the parameters used for PLMN and

cell selection State the purpose of location updates and the

associated parameters

Contents




1. IDLE Mode tasks overview2. ID‟s and ID Codes, Frequencies

3. PLMN selection

4. Cell selection and cell reselection

C1 Cell (Re)-Selection Criterion

C2 Re-Selection Criterion

5. Location Area Management

Location Updates

Timer for Periodic Location Updates

6. IMSI Attach/Detach

Idle Mode Operation




• When the MS is switched ON?

• When there is no dedicated connection?

When?

• To camp on the best suitable cell

Why?

• For MS to receive system info from the NW on DL

• For MS to be able to initiate a call whenever needed

• For the NW to be able to locate the MS when there is a MT call/SMS

Why to camp on a specific cell?

• PLMN selection

• Cell selection & re-selection

• Location updates

Idle Mode Tasks

ID's and ID Codes




LAI (locationAreaId)

• NCC (Network Colour Code) 0 … 7

• BCC (BTS Colour Code) 0 … 7

BSIC (bsIdentityCode)

CI (cell-ID) 0 … 65535

Parameter Value

TSC (trainingSequenceCode) 0 … 7

•MCC (Mobile Country Code) 0 … 999

•MNC (Mobile Network Code) 0 … 99

• LAC (Location Area Code) 0 … 65535

CGI (Cell Global Identity) MCC + MNC + LAC + CI

Base Station Identity Code (BSIC)




• BSIC is a combination of NCC and BCC

• Reported in Measurement Results to BSC

• Can be listed in Hex or Decimal

NCC (0...7) BCC (0...7)

4 2 U 4 2 U32 16 8 4 2 U Range

0 0 0 x x x 0 - 7

0 0 1 x x x 8 - 15

0 1 0 x x x 16 - 23

0 1 1 x x x 24 - 31

1 0 0 x x x 32 - 39

1 0 1 x x x 40 - 47

1 1 0 x x x 48 - 55

1 1 1 x x x 56 - 63



Base Station Colour Code



ADA cellworks

MNC = Operator

MCC = Country e.g Finland

LAC 1 = HelsinkiLAC 2

LAC 3 LAC 4

f1

f2

f3

f1

f1

bcc = 1

bcc = 2

bcc = 3

Neighbour list of f3:

f1

f2

...

Location Area Code

BSC

BTSBTSBTS1 2 n

Frequencies



ADA cellworks

Parameter Value

bCCHAllocation-ID 1 ... 255

bCCHAllocationList 1 ... 124 in GSM (max. 32 freq. for all bands)

idleStateBCCHAllocation 0 (BCCH list is taken from the adjacent cell)

1 ... 255 (number of the BCCH list used)

measurementBCCHAllocation ADJ (BCCH frequency list taken from adj. cell)IDLE (active MS uses same list as MS in IDLE mo

initialFrequency 1..124 & 975..1023, 0; 512..885 GSM900;1800 (FREQ T

Use of Cell Barring for Test Measurements

Cell Barred



ADA cellworks

Cell Barred

Existing Layer• Barred, N o

New Microcell Layer• Barred, Yes

• Easy to test new Microcells with NMS/X 5.24 with Nokia 2110

GPS-satelite

NMS/X 5.2

Cell Selection in Idle Mode



ADA cellworks

Two methods for selecting a cell:

• Normal cell selection (a) - MS has no prior knowledge of which RF

channels are BCCH

• Stored list cell selection - optional (b) - MS uses list of BCCH carriers

used by PLMN

If no suitable cell is found using method (b) then (a) is tried.

What constitutes a 'suitable' cell:

• Cell is in the selected PLMN

• Cell is not barred

• It is not in a forbidden location area for national roaming• C1 >0 (range -99..0..+99)

• If there is no normal priority cell then low priority cell

Cell (Re-)Selection in Idle ModeUsing C1 Criter ion



ADA cellworks

Averaging 3-5 s.Decision 5s.

• Radio Criteria

C1 = (A - Max(B,0))

• A = Received Level Average - p1

• B = p2 - Maximum RF Output Power of the Mobile Station

• p1 = rxLevelAccessMin (Min. received level at the MS required for

access to the system)

(RXP BTS -110..-105 … -47 dBm)

• p2 = msTxPowerMaxCCH (Max. Tx power level an MS may use

when accessing the system)

(TXP BTS GSM900 5..33..43/2 33;

GSM1800 0..30 /2 30 dBm)

rxLevelAccessMin -110 ... -47 dBm 'RXP' (BTS)

msTxPowerMaxCCH 0 … 30 dBm GSM1800 (5 … 43 dBmGSM900)

'TXP' (BTS)

Parameter Value

Cell Re-selection (C1)



ADA cellworks

A = 4 dB

B = 6 dB

C = 8 dB

• A B C •

1 2

1

2

MS Moving

A B C

LA1 LA2

cellReselectHysteresis 0 … 14 dB (HYS) (BTS) 2dB steps MML

def 4dB

Parameter Value

Cell Re-selection in Idle ModeUsin g C2 Re-Selectio n Criter io n (PH 2 MS)



ADA cellworks

Cell re-selection is needed if

• Path Loss criterion C1 < 0 for cell camped on ,for more than 5 seconds.• There is DL signalling failure

• The cell camped on has become barred.

• There is a better cell in terms of C2 criterion

• A random access attempt is still unsuccessful after

maxNumberRetransmissionrepetitions.

• MS will calculate the C1 and C2 for the serving cell, every 5 s• MS will calculate the C1 and C2 for the six best neighbour cells, every

5 s

Cell Re-selection with C2 (1/3)

C1 C2



ADA cellworks

BCCH

BCCH

fast moving mobile

slow moving mobile

C2<PT<C2

C1=C2

time

microcell

macrocell

C1,C2


Equat ion & Parameters



ADA cellworks

C1 + cellReselectOffset - temporaryOffset*H(penaltyTime-T) <= penaltyTime< 640

C2 =C1 - cellReselectOffset ………………………………………….. <= penaltyTime= 640

1 when T < = penaltyTimeH(x) =

0 when T > penaltyTime

cellReselectParamInd Y / N

cellReselectOffset 0 ... 126 dBpenaltyTime 20 ... 640 sec

temporaryOffset 0 ... 70 dB

Parameter Value


Example



ADA cellworks

C1 "A"=30C1 "B"=25

C1 "C"=5

C1 "D"=50

C2 = C1 + cellReselectOffset - temporaryOffset*H(penaltyTime-T)

C2 "A"=30 + 0 serving cell H(x) = 0

C2 "B"=25 +20-30 * H(20-T)

C2 "C"=5 + 0 - 0 * H(0-T)

C2 "D"=50+0-30*H(40-T)

Microcell

900

Macrocell 1800

Macrocell 900

cellReselectOffset 0 20 0

penaltyTime 0 20 40

temporaryOffset 0 30 30

GSM900 GSM1800GSM900micro

Time T: between 0 and 19 seconds C2 "A"=30

C2 "B"=15

C2 "C"=5

C2 "D"=20

Time T: between 20 and 39 seconds C2 "A"=30

C2 "B"=45

C2 "C"=5

C2 "D"=20

Time T: greater than 40 seconds C2 "A"=30

C2 "B"=45

C2 "C"=5

C2 "D"=50

Location Updates



ADA cellworks

Location Update Procedure

BSS MSC VLR HLRMS



ADA cellworks

BSS MSC VLR HLR

REQUEST SUBSCRIBER INFO

ALL OK - HLR UPDATE

LOCATION UPDATE REQUEST

SEND SUBSCRIBER ID

REQUEST SUBSCRIBER ID

SEND SUBSCRIBER INFO

AUTHENTICATION

AUTHENTICATION RESPONSE

Trade-off between Location Update andPaging Traffic

signalling



ADA cellworks

PagingLocUp

# of cells in Loc. area

signalling

traffic

optimum number

of cells in Loc. area

function of user density,

cell size, call arrival rate ...function of

user mobility

Location Updates

• MS => MSC / VLR



ADA cellworks

timerPeriodicUpdateMS 0.0 ... 25.5 hrs (PER)(BTS) see note in

dictionary!

allowIMSIAttachDetach Yes/No (ATT)(BTS)

Parameter Value

• MS => MSC / VLR

• Mobile Station switched ON – IMSI Attach / Detach

– Same Location Area => No Location Update

– Different Location Area => Location Update

• Change of the Location Area

– Location Area under the same MSC / VLR – Location Area under another MSC / VLR => HLR will be

updated

• Service is rejected (MS unknown in VLR)

• Time-Periodic LU (MS -> MSC/VLR)

Normal Cell SelectionSearch all the RF channels, take samples during

3-5 s and calculate averages. And put them in

ascending order with respect to signal level.

Then tune to the strongest RF channel.



ADA cellworks

Search for the frequency correction burst in that

carrier in order to verify if it is a BCCH carrier

Camp on the cell

Try to synchronize to the carrier and readthe BCCH data

Is it a BCCH

carrier?

Is it a correct

PLMN ?

Is the cell barred?

Is C1>0

Tune to the next highestRF channel which is not

tried before

No

No

NoNo

Yes

Yes

Yes

Yes



ADA cellworks

BSS Protocols & Signalling Capacity

BSSPAR S10.5

Module 04

Module Objectives



ADA cellworks

At the end of the module, the participant will be able to:• State the procedures and the phases of a basic call

• List five examples of signalling messages that are sent

between BSS and MS

• Describe the signalling phases in MOC and MTC

• Discuss the signalling exchange that takes place

during a Location Update

• Explain the differences between Network-initiated and

MS-initiated Disconnect

• Describe the Handover protocols used between BSS and MS

• Show how to determine the required signalling capacity

of each type of link in the BSS• Discuss the benefits of implementing High Capacity

Signalling Links in the A-interface

Call Phases



ADA cellworks

get

service

get

SDCCH

establish

SDCCH

connection

get

TCH

establish

TCH

connection

call

phase release

phase

Call Completion Rate Call Setup Success Rate

SDCCH

Blocking (system)

and

SDCCH

call Blocking

TCH Blocking (system)

and

TCH Call Blocking

SDCCH

Success Rate

Overall Call Success Rate

Call Phase Types

PHASE PHASE_NAME



ADA cellworks

1 Paging

2 MM signalling3 Basic assignment

4 Release

5 FACCH assignment

6 SMS establishment (TCH)

7 SMS establishment (SDCCH)8 Ciphering

9 External handover (source)

10 Internal handover intra (source)

11 Internal handover inter (source)

12 External handover (target)13 Internal handover Intra (target)

14 Internal handover inter (target)

15 Conversation (TCH)

Call Phases for MTC



ADA cellworks

MS BTS BSC

AUTHENTICATION (SDCCH)Phase 2 : MM signall ing

CIPHERING MODE (SDCCH) Phase 8 : Ciphering

TMSI REALLOCATION (SDCCH)

SETUP (SDCCH)

Phase 2 : MM signall ing

CH. REQUEST (RACH)

IMMEDIATE ASSIGN(AGCH)

SERVICE REQUEST (SDCCH)

Phase 1 : Paging, initi al MS

CH.RELEASE Phase 4 : Release

ALERTING & CONNECT (FACCH)Phase 2 : MM signall ing

CONN. ACK. and MEASUREMENT Phase 15 : Conversation

DISCONNECT & RELEASE (FACCH) Phase 4 : Release

ASSIGNMENT (SDCCH-FACCH)Phase 3 : Basic assignment

Mobile Originating Call



ADA cellworks

Authentication

Ciphering Mode Setting

Service Request

Immediate assignment

CHAN REQ (RACH)

IMM ASSIGN (AGCH)

CM SERV REQ (SDCCH)

AUTH REQ (SDCCH)

AUTH RES (SDCCH)

CIPH MOD CMD (SDCCH)

CIPH MOD COM (SDCCH)

MS NETWORK

Mobile Originating Call, cont.



ADA cellworks

Call Confirmation

Call Accepted

Assignment of Traffic Channel

Call Initiation

SETUP (FACCH)

CALL PROC (SDCCH)

ASSIGN CMD (SDCCH)

ALERT (FACCH)

CONNECT (FACCH)

CONNECT ACK (FACCH)

MS NETWORK

ASSIGN COM (FACCH)

Mobile Originating Call, cont.



ADA cellworks

Mobile Terminating Call



ADA cellworks

Authentication


Service Request


PAG REQ (PCH)

CHAN REQ (RACH)

PAG RES (SDCCH)

AUTH REQ (SDCCH)

AUTH RES (SDCCH)



MS NETWORK

IMM ASSIGN (AGCH)



Location Update



ADA cellworks

Authentication


Service Request


CHAN REQ (RACH)

IMM ASSIGN (AGCH)

LOC UPD REQ (SDCCH)

AUTH REQ (SDCCH)AUTH RES (SDCCH)



LOC UPD ACC (SDCCH)

TMSI REAL COM (SDCCH)

CHAN REL (SDCCH)

Channel Release

MS NETWORK

Disconnect - Network Initiated



ADA cellworks

Release

Call Clearing

DISCONNECT (FACCH)

REL (FACCH)

CHAN REL

MS NETWORK

REL COM (FACCH)

Disconnect - MS Initiated

Disconnect, MS Initiated



ADA cellworks

Release

Call Clearing

DISCONNECT (FACCH)

REL (FACCH)

CHAN REL

MS NETWORK

REL COM (FACCH)

Inter MSC Handover



ADA cellworks

Air A

BTS

Old Cell / BTS

New Cell / BTS

BTS

BSC TC

BSC TC

VLR MSC

VLR MSC

Handover - Synchronized



ADA cellworks

New Channel, New Cell

ACTIVE CALL

HANDO CMD

HANDO ACC

HANDO ACC

HANDO ACC

HANDO ACC

HANDO COM

ACTIVE CALL

MS NETWORK

Old Channel, Old Cell

Handover - Non Synchronized



ADA cellworks


MS NETWORK

ACTIVE CALL

HANDO CMD

HANDO ACC…….

HANDO ACC

PHYS INFO

PHYS INFO

HANDO COM

ACTIVE CALL


T 3124

Ny1

Parameter

maxNumberOfRepetition ( 5 … 35 )

Handover Failure



ADA cellworks


HANDOVER CMD

ACTIVE CALL

MS NETWORK

HANDOVER FAIL

ACTIVE CALL



Timer T3124 expiry or

Radio Link Failure

Link Capacity per BCSU



ADA cellworks

High Capacity BSC2i: 64 kbit/sCCS7 link

128 kbit/sCCS7 link

256 kbit/sCCS7 link

Maximum Number of CCS7links

4 4 4

Maximum Number of BCFSIGLapD links

32 32 32

Maximum Number of TRXSIGLapD links

64 64 64

Maximum number of LapDlinks (BCFSIG+TRXSIG+ISDN+ET-LapD)

124 112 112



ADA cellworks

Radio Resource Management

Module Objectives At the end of this module, the participant will be able to:

Explain the traffic channel allocation process during call



ADA cellworks

Explain the traffic channel allocation process during callset up and handover, and name the parameters used inthis process

Discuss the frequency hopping techniques: basebandhopping, RF hopping, and Freeform RF hopping

State the parameters associated with frequency

hopping Name the parameters associated with dynamic hotspot

algorithm

List the parameters associated with the directed retry

procedure Explain the mechanisms used for queuing of call setup

and handovers and the purpose of associatedparameters

Traffic Channel Allocation (1/3)

The request includes the type and other requirements ( or

recommendations)

for the requested resource: tells what kind of resource it needs



ADA cellworks

The channel rate

• TCH/F

• TCH/H

• Dual Rate• Multi Rate

Three types of RTSL can be configured in a TRX:

• permanent FR

• permanent HR

• dual rate

The speech codecs

• Normal Full rate

• Normal Half rate

• Enhanced Full rate

for the requested resource: tells what kind of resource it needs.

Incall set-up MS informs network of its capabilities in set-up message

In case of TCH:




ADA cellworks

When only a preferred TCH rate information comes with the request the BSC

determines the type of the TCH resource to be allocated based on the

following:

• the A interface circuit that the MSC has allocated for the call

• the given list of preferred speech codecs by MS

• the speech codecs support of the BTS

• the TCH configuration on the BTS

• the resource situation in the BTS

• efficiency of the search procedure




ADA cellworks

• efficiency of the search procedure

• cellLoadForChannelSearch (BTS level)

• BSC level using LoadRateForChannelSearch , if cellLoadForChannelSearch =0

• below threshold rotation bt TRXs and TSLs in a TRX

• above threshold speech and single slot data allocated in small gaps and at ends of

TRX in order to

keep larger TSL groups free for HSCSD multislot services

• uniform use of the available resources

• availability of different channel types.

• arrangements for multislot and single slot connections (consecutive slots needed in HSCD)

The intra-cell HO is a special case ;

• In non-Hopping case a channel from an other TRX is searched.

• In RF Hopping case , a channel from an other hopping group (MA list) is searched.

cellLoadForChannelSearch 0 ... 100%

LoadRateForChannelSearch 0 …100%

Parameters Value

Idle Channel Interference

• The BTS measures and reports on the up l ink interference of the radio channels which

have

been idle during the whole measurement period



ADA cellworks

0 7-110-105-100

-95

-90

-47

1 2 3 4 5 6

rxLevUL = -75 dBmBO5

BO0

BO4BO3

BO1BO2

been idle during the whole measurement period.

• Idle TCH‟s are classified into five interference classes

• RR Management algorithm assigns a channel from the lowest possible interference class

interference AveragingProcess 1 ... 32 SACCH

boundary 1-4 -110 ... -47 (dBm)

(boundary0/5 fixed)

Parameters Value

1 Call set-up and intra-cell HO (when OptimumRxLevUL = <not

Calculation of maximum acceptableInterference level (1/2)



ADA cellworks

1. Call set-up and intra-cell HO (when OptimumRxLevUL = <not

used>)MAX_INTF_LEV =RXLEV_UL + (MsTxPwrMax - MS_TXPWR ) - CNThreshold

CNThreshold

RxLevBalance

OptimumRXLevUL

MsPwrOptLevel

Parameters Value

0… 63 dB (0 not active)

0… 20 dB

-109…-47/N (TRX level)

-110…-47/N (cell level)

2. When OptimumRxLevUL = <used>

MAX_INTF_LEV = MAX{MIN[RXLEV_UL + (MsTxPwrMax - MS_TXPWR

),OptimumRXLevUL], RXLEV_UL-(MS_TXPWR-MsTxPwrMin)} - CNThreshold

Calculation of maximum acceptableInterference level (2/2)



ADA cellworks

1. Inter-cell Handover (when MsPwrOptLevel = < not used>)

MAX_INTF_LEV=RXLEV_DL - RxLevBalance -

CNThreshold

2. Inter-cell handover (when MsPwrOptLevel = <used>)

MAX_INTF_LEV (UL) = MAX{ MIN[AV_RXLEV_NCELL(n)-RxLevBalance ,

MsPwrOptLevel(n)],

(AV_RXLEV_NCELL(n)-RxLevBalance) - (MsTxPwrMax(n) -

MsTxPwrMin(n)) } - CNThreshold(n)

The parameter MsPwrOptLevel(n) indicates the optimum UL RF

signal level on a channel in the adjacent cell after a handover.



Traffic Channel SelectionNetwork Docto r Example - Scr ipt 213



ADA cellworks

Indicates the number of idleTSLs in each interference band

TRX Prioritisation in TCH Allocation



ADA cellworks

It is possible to set priority between the TCH

TRXs and BCCH TRX.

• The advantage of using the TCH TRX for call set up:

• The hopping gain

• The advantages of using the BCCH carrier for call set up:• It would not increase interference in the network

• BCCH channels are planned to be the least interfered

one

Parameters Value

TrxPriorityInTCHAllocation 0 … 2 where0 = no preference

1 =BCCH preferred2 =Away from BCCH

FACCH Call Set-Up (Optional)



ADA cellworks

• When an idle SDCCH is not available for the request – BSC tries to allocate a TCH for signalling instead of an SDCCH.

– After the signalling is finished the channel mode is modified as TCH and

the call continues on the same channel.

Parameters Value

pagingAnsOnFACCH Y/N

restablishOnFACCH Y/N

emerCallOnFACCH Y/N

ordinaryCallOnFACCH Y/N

Preferred BCCH TRXFault Situat ion

• Recovery system returns BCCH automatically to its original TRX after fault has beeneliminated

• Supports the usage of TRXs with different output power in the same cell



ADA cellworks

• Supports the usage of TRXs with different output power in the same cell

• Can be activated cell by cell• Before restoration Forced Handover is used to avoid cutting calls

Preferred BCCHTRX-1

TRX-2

BCCH, SDCCH/8, 6xTCHs

BCCH, SDCCH/8, 6xTCHs 8xTCHs

8xTCHs BCCH, SDCCH/8, 6xTCHs

8xTCHs

Original ConfigurationTRX-1 Faulty,

After BCCH RecoveryTRX-1 Repaired,

After BCCH Restoration

• Preferred BCCH mark can not be set to floating TRX

• BSC can automatically return BCCH to original BCCH TRX, but BSC can not

return original traffic channel configuration, if BSC has changed it earlier

• If user locks BCCH TRX, then the BSC does not perform BCCH recovery

• If BSC reconfigures E-RACH to TRX having preferred BCCH mark, that TRX is

last choice for BCCH

• E-RACH recovery is not possible in fault cancel if BSC has to move BCCH to

preferred BCCH TRX

Frequency HoppingPrinciples



ADA cellworks

Frequency

Time

F1

F2

F3

Call is transmitted through severalfrequencies in order to• average the interference (interference diversity)• minimise the impact of fading (frequency diversity)

Baseband (BB) Hopping

RTSL 0 1 2 3 4 5 6 7




B

RTSL 0 1 2 3 4 5 6 7

TRX-1

TRX-2

TRX-3

TRX-4

f1 B = BCCH timeslot. It does not hop.

f2

f3

f4

Time slot 0 of TRX-2,-3,-4 hop over f2,f3,f4.

Time slots 1...7 of all TRXs

hop over (f1,f2,f3,f4).

• TRXs are fixed-frequency - the switching is done at baseband in BBFH

• Number of frequencies = number of TRXs, highest hopping gain only inlarge configurations

Parameters

G l P t




Baseband Hopping

hoppingSequenceNumber1 (HSN1) (TS 0)

0 ... 63 (0 = cyclic, 1 ... 63 = pseudorandom)

hoppingSequenceNumber2 (HSN2) (TS 1 ... 7)

0 ... 63 (0 = cyclic, 1 ... 63 = pseudorandom)

TRX 1

TRX 2

TRX 3

0 1 72 TS

TRX 4

B f 1

f 2

f 3

f 4

btsIsHopping BB (BaseBand Hopping)

RF (Radio Frequency Hopping)

N (No Hopping)

CA = Cell Allocation

MA = Mobile Allocation

MAIO = Mobile Allocation Index Offset

HSN = Hopping Sequence Number

General Parameters

HSN1 HSN2

Synthesised (RF) Hopping




BTRX-1

Non-BCCH TRXs are hopping over

the MA-list (f1,f2,f3,...,fn) attached to the cell.

TRX-2

B = BCCH timeslot. TRX does not hop.

f1,

f2,

f3,

fn

f1,

f2,

f3,

fn

. . . .

• TRXs (except BCCH) frequency hop

• Each TRX can hop over many frequencies - improved hopping gain

Parameters

RF (Synthesized Hopping) (from Talk Family BTS onward)




RF (Synthesized Hopping) (from Talk-Family BTS onward)

mobileAllocationList (MA) (E)GSM: 1..124 and 975..1023

GSM 1800: 512..885

GSM 1900: 512..810

Note! Max. 63 Frequencies

mobileAllocationId 512 … 885

usedMobileAllocation 512 … 885

hoppingSequenceNumber1 (HSN1)

0 … 63 (0 = cyclic, 1 ... 63 = pseudorandom)

TRX 1

TRX 2

TRX 3

0 1 72 TS

TRX 4

B f 1

M A

L ( f 3 , f 4 . .

f n )

HSN1



Mobile Allocation Index OffsetBenef its o f Flexible MAIO Management




• One MA list per site

• One MA list can contain a continuous band

• No risk of co-channel nor adjacent channel being used simultaneously withina site

• Single MA/HSN possible -> only BCCH frequency planning

• More/tighter reuse possible e.g. RF-FH (1/1) and thus more capacity can beachieved

ParametersFlexib le MAIO Managemen t

• Allows More Flexible RF Hopping




• enables Frequency Sharing i.e. sharing an MA list between the sectors atsame site

• longer MA lists possible

• minimised interference

• New MAIO Step Parameter (BSS7)

• When used together with MAIO offset, no successive MAIOs will beallocated for TCHs sharing the same MA list

MaioStep 1..62

UnderlayMaioStep 1..62

Parameters Value

ParametersSingle MA /HSN per Site - w ith MA IO Step

HSN f ll tMA = f1, f2, f3, f4,.... MA list can include




BCCH

Sector HSN MAIO Offset TRXMAIO, same for allRTSLs within the TRX

1 TRX-1 BCCH, not hopping

1 N

TRX-3 2

TRX-4 4


2 N

TRX-7 8

TRX-8 10


3 N

TRX-11 14

TRX-12 16

0

6

12

HSN same for all sectors

TRX-2 0

TRX-6 6

TRX-10 12

MA f1, f2, f3, f4,....adjacent frequencies

MAIO step

2

2

2

No co-channels or adjacent channelsused simultaneouslyif number of frequencies >

2*number of TRXs

Hopping Freq's

Band allocation:

Operator can set the lowestMAIOs for the cells

Operator can also set theMAIO step size



Directed Retry (DR)

• DR used to avoid the loss of a call in call setup if the accessed cell is congested




• DR used to avoid the loss of a call in call-setup if the accessed cell is congested

• When no TCH is available in serving cell, TCH can be allocated in an adjacent cell (SDCCH TCHHO)

• Mobile Originated (MOC) and Mobile Terminated (MTC) Calls

• Target cell entry based on DR Method;

• Method 0 - RxLevAccessMin

• Method 1 - drThreshold

•Imperative Handover (only equation 1)

• Candidates ranked based on radio properties.• Steps through candidates (if congested) until MaxTimeLimitDR expires

• Queuing can take place in source cell, not in target cell.

Time

AssignmentRequest

minTimeLimitDR

maxTimeLimitDR

DR not allowed : improves the reliability of

the measurements of adjacent cells and gives thequeuing process timeDR allowed

SDCCHTCH

congested

Directed Retry parameters

Parameters Value




Parameters Value

drInUse Yes / No

MinTimeLimitDR 0 … 14 sec.

MaxTimeLimitDR 1 … 15 sec.

drMethod 0: (Improvement not in use)

1: (Threshold evaluation method)drThreshold -47 … -110 dBm



Intelligent Directed Retry

congestion

macro cell (GSMcell)

micro cellsIDR

• Based on Directed Retry : Target Cell selection

d d




congestion(MCN cells)

MCNsubscriber

GSMsubscriber

congestion

macro cell (GSM cell)

micro cells(MCN cells)

DR

NOKIA TELECOMMUNICATIONS

depends on

• Classmark of the MS or MS Priority• Adjacent Cell Type

• Subscribers Classified in GSM or MCN

• Based on Classmark ( bitmap in BSC associates

classmarks to GSM / MCN )

• Based on MS Priority ( bitmap in BSC

associates MS Priorities to GSM / MCN )

• Criterion defined in the BSC• DR and IDR enabled / disabled independently on cell

basis.

ValueParameters

IdrUsed Yes/NoCellType GSM / MCN

AdjCellType GSM / MCN

• No TCH Available on Accessed Cell

• GSM or MCN subscriber ?

• MCN => IDR in Use in the Cell ?

• Yes => Directed Retry Only to MCNCells

• No => Reject Call

• GSM => DR in Use in the Cell ?

• Yes => Directed Retry (any Cell)

• No => Reject Call

Queuing of Radio Resources

• Used to avoid rejecting call set-up or HO attempt by waiting for the release of asuitable TCH




suitable TCH

• Queuing Environment

• queuing is a BTS specific procedure (controlled by the BSC)

• each BTS has a queue of its own

• individual queue parameters and queue management for each BTS

• call attempts and handovers in the same queue

• the maximum queue length is relative to the number of traffic channels• the maximum queuing time can be set individually for both queue types

• the queuing can be de-activated by setting queuing time or queue length tozero

• different priorities according to queue type (call/HO) and/or MS priorityEntering the queue:

• The queue is entered when there is no traffic channels available of requested kind and if

– queuing is allowed in the BTS

– queuing enabled in the assignment request from MSC

– queue is not full (of higher or equal priority requests)



Leaving the Queue

Queuing of Radio Resources




g

• A queuer is removed from the queue when

– No suitable channel is released within queuing time limit => timer expires

– Higher priority subscriber (queue type and/or MS priority) replaces a lower

priority queued entry when the queue is full

– The queuing TRX/TSL is blocked (call release)

– Queue size is reduced due to removing TRX‟s



• Internal inter cell Handover

Queuing of Radio ResourcesQueuing and Handover




– Ranked list is produced by the Handover algorithm and passed to RRmanagement

– Maximum sixteen cells as alternative target cells

– The best candidate with free traffic channel is selected

– If all BTSs in the list are congested

queuing possibility is checked in the candidates according toranking

• External inter cell Handover

– The BTS identified by the MSC in a HANDOVER_REQUEST message is

used as queuing target

• Averaging and processing for HO continues during queuing

• The timers for hoPeriodPBGT or hoPeriodUmbrella are stopped

during queuing



Parameters Values

Queuing of Radio ResourcesQueuing Parameters




maxQueueLength 0 ... 100 %

timeLimitCall 0 ... 15 (s)

timeLimitHandover 0 ... 10 (s)

msPriorityUsedInQueuing Yes / NoqueuePriorityUsed Yes / No

queuingPriorityCall 1 ... 14

queuingPriorityHandover 1 ... 14

queuingPriorityNonUrgentHO 1 …14



Radio Link Timeout




Indoor Outdoor

Elevator

5. floor

1. floor

MSMS

Tunnel (short)

Call Re-establishment




Outdoor

MS

radioLinkTimeout (default) = 20 (SACCH)

Tunnel (long)BTS A

BTS B

Unsuccessful Handover=> use Call Re-Establishment

The Decision Threshold Table




TRAFFIC TYPE

IDLE

TCHS 1 2 ...

1 10 5

2 20 10

3 30 20

. . .

. . .

. . .

Q XQ1 XQ2

Xij



Contents (1 of 2)

1. Module Objectives

2. Introduction to the Handover Process

3 Handover Decisions




3. Handover Decisions

4. Handover Timers

5. Target Cell Evaluation Process

6. Radio Resource Handovers

• Power Budget (PBGT)

• Umbrella, & Combined Umbrella - PBGT

• MS Speed (FMMS & MS_SPEED_DETECTION)

• Quality & Level (RXQUAL & RXLEV)

7. Imperative Handovers

• MS-BTS Distance

• Rapid Field Drop (RFD)

• Enhanced Rapid Field Drop (ERFD)

Contents (2 of 2)

8. Traffic Reason Handovers

9. Load Control between layers: AMH




10. Direct Access to Desired Layer/Band (DADL/B)

11. Handover Parameter List

12. Adjacent Cell Parameter List

13. Practical Examples of Handovers

14. Handover Control Exercise

15. Handover & Power Control Exercise

16. Key Learning Points

17. Review Questions

Overview

Why are handovers needed?




• Call continuity - to ensure a call can be maintained as an MSmoves in

geographical location, from the coverage area

of one cell to another

• Call quality - to ensure that if an MS moves into an area of

poor quality

or poor coverage, the call can be moved from

the serving cell to a

neighbouring cell (with better quality) without

dropping the call

• Traffic Reasons - to ensure that the traffic within the network is

optimallydistributed between the different layers or

bands of a network

Handover Causes

Uplink Quality AV_RXQUAL_UL_HO

QUALITY&




Timing Advance

Adjacent Cells

Downlink Quality AV_RXQUAL_DL_HO

Downlink Level

Uplink Level AV_RXLEV_UL_HO

AV_RXLEV_DL_HO

AV_RANGE_HO

AV_RXLEV_NCELL(n)

INTERFERENCE

LEVEL

DISTANCE

PERIODICCHECKS

UMBRELLA

POWER BUDGET

IMPERATIVEHOCHANNEL ADMINISTRATION

DIRECTED RETRY

THRESHOLDCOMPARISON

RAPID FIELD DROP

MS SPEED

MS Speed AV_MS_SPEED

Others causes;- Intelligent Underlay/Overlay (IUO)

- Traffic Reason Handover (TRHO)

- Direct Access to Desired Layer/Band (DADL/B)



Threshold Comparison Process

The Handover process may be triggered by:

Averaged value obtained frommeasurement averaging process




• Threshold

comparison:

• Quality

• Level

• Distance• Load

• Periodic checks:

• Power budget

• Umbrella

IF

AV_RXQUAL_DL_HO <hoThresholdsQualDL

THEN

Downlink Quality HO is performed

IF

EnablePowerBudgetHO =Yes

THEN

PBGT comparison

performed everyhoPeriodPBGT seconds

using hoAveragingQualDL

Target Cell Evaluation Process

Threshold levelbased on nx &

px

Handover Decision Algorithm

AV_RXLEV_NCELL(n) > rxLevMinCell(n) + Max (0, A)1.

In all Handover cases




A = msTxPwrMax(n) - PP = depending on MS Classmark

AV_RXLEV_NCELL(n) > hoLevelUmbrella(n)1‟.

Except for Umbrella Handover

PBGT > hoMarginLev/Qual(n) where

PBGT = (AV_RXLEV_NCELL(n) - AV_RXLEV_DL_HO)-(btsTxPwrMax -

BTS_TXPWR)

(Note: enableHoMarginLevQual must = Yes) - for RxLev & RxQual handovers

2‟.

PBGT > hoMarginPBGT(n) where

PBGT = ((msTxPwrMax - msTxPwrMax(n))-(AV_RXLEV_DL_HO -

AV_RXLEV_NCELL(n)) - (btsTxPwrMax - BTS_TXPWR))

2.

The additional condition

For imperative handovers

only Eq. 1 has to be satisfied



Target Cell Evaluation

Lo ad Evaluat ion Example

Case 1: All cells have equal priority Case 2: One cell with higher priority




Cell a b c

Rx_Level -75 -80 -83

1. Load overl. overl. n.overl.

hoLoadFactor 1 1 1

2. Priority 3 3 3New Priority 2 2 3

3. Rx_Level -75 -80

=> cell list c , a ,b

cell a b c

Rx_Level -75 -80 -83

1. Load n./overl. n.overl. n.overl.

hoLoadFactor 2 1 1

2. Priority 4 3 3New Priority 4/2 3 3

3. Rx_Level -75 -80/-80 -83

=> cell list a,b,c (if cell a is not overloaded)

=> cell list b,c,a



• C/I is calculated for the handover

candidates

– Averaged over the reference cells

priorityAdjStepforBand1 >= LowerC/ILimit1


……. …….


C/I Calculation




lowerCIlimit (L1-L6)(HOC) L1 (Lower C/I limit for band 1) -128 ... 127 dB

L2 (Lower C/I limit for band 2) -128 ... 127 dB

……

L6 (Lower C/I limit for band 6) -128 ... 127 dB

priorityAdjStepforBand1 P1 (Priority adj. for band 1) -8 ... 7

(P1-P7)(HOC) P2 (Priority adj. for band 2) -8 ... 7

……

P6 (Priority adj. for band 6) -8 ... 7

(Average) – By taking the worst interferer

(Maximum)

• C/I is compared to 7 user-defined

bands

– Priority of the Cell is incremented bythe quantity associated with the band

Parameter Value


-8 Eliminates the Adjacent Cell from thecandidates list



Radio Resource Handovers

A handover is considered as a Radio Resource




Handover if the cause is one of the following reasons:

• Level (uplink / downlink)

• Quality (uplink / downlink)

• Interference (uplink / downlink)

•Power budget

•Umbrella

Handover Thresholds

When the BSC receives measurement results from the BTS

it l h f th d lt




it always compares each of the processed results(averages) with the relevant thresholds:

hoThresholdsLevDL/UL

hoThresholdsQualDL/UL

hoThresholdsInterferenceDL/UL

msSpeedThresholdNx/Px

(STN)/(STP)(HOC)(ZEHO)(1..32)(6)/(3)

OPTIONAL - FMMS in Macrocell, lower & upper speed

thresholds, Nx, Px



Umbrella Handover • Used in multi-layer/band networks (better for bands - no speed criterion)

• Typically used in association with PBGT (Combined PBGT/Umbrella

feature)

• Trigger

P i di Ch k (h P i dU b ll ) (HPU)(HOC)




– Periodic Check (hoPeriodUmbrella ) (HPU)(HOC)

• Candidate Selection

– Equation 1' used

– Consistency between MS classmark and target cell power constraints

– Priority and Load Considered

enableUmbrellaHandover (EUM)(HOC) Y / N

hoPeriodUmbrella (HPU)(HOC) 0 … 63 (SACCH)

hoLevelUmbrella (AUCL)(ADJC) -110 … -47 dBm

Parameter Value

dcsMicrocellThreshold (DMIC)(BSC) 0..36 & 0..33 dBm (GSM1800 &

1900)

dcsMacrocellThreshold (DMAC)(BSC) 0..36 & 0..33 dBm (GSM1800 &

1900)

Handover Comparison




Max power capability of MS >= gsmMacrocellThreshold

HO allowed only to a macrocell ( MS_TXPWR_MAX(n) >=

gsmMacrocellThreshold )gsmMicrocellThreshold < Max power capability of MS < gsmMacrocellThreshold

HO only to middle size cell ( gsmMicrocellThreshold < MS_TXPWR_MAX(n) <

gsmMacrocellThreshold )Max power capability of MS <= gsm MicrocellThreshold

HO allowed only to microcell ( MS_TXPWR_MAX(n) <= gsmMicrocellThreshold )

Umbrella Handover Algorithm



Adjacent Cell Layer Parameter

• Three layers visible to serving cell (relative to

serving cell)

Parameter

adjCellLayer

(ACL)(ADJC)




UPPER layer (e.g. 900

macro)

SAME layer (serving

layer)

LOWER layer

(micro)

serving cell)• Used in target cell evaluation for;

– Fast moving MS handling in macro cell

– HOs based on MS speed (BSS6)

– Combined umbrella and power budget

N (not in use)

(ACL)(ADJC)



Fast and Slow Moving MS

macrocell with RF hopping

Combination of Fast Moving MS Handling (BSC) and MS Speed Detection (BT




BSCBTS

BTS

microcell(s) no RF hopping

fast MSs

slow MSs

meas_res

Crossing rate algorithm

B S S 6 / M S s p e e d

B S S 5 / F a s t M S

Adjacent cell

measurements

HO&PC

algorithm

Macro cell‟s parameters Counter for each adjacent micro cell

• FMMS used in macrocell layer to 'estimate' the speed of a mobile

based on measurement reports on adjacent microcells

Fast Moving Mobile Support (FMMS)Process




Macro cell‟s parameters

for each adjacent micro cell:

• fastMovingThreshold(FMT) 0..255

• rxLevMinCell (SL)(ADJC)

• hoLevelUmbrella (AUCL)(ADJC)

Counter for each adjacent micro cell

+2 measurement and over rxLevMinCell

-1 no meas. or bad level

Target cell selection based on adjacent

cell RX_LEVEL and on hoLevelUmbrella

macrocells

microcells

FMMS HO

initiated

time „t‟

FMT Counter

HO

time „t‟

hoLevelUmbrella = -85 dBm

(AUCL)(ADJC)

FMT Threshold = 40

(FMT)(ADJC)

BSC averages speed

indications using

msSpeedAveraging

AV_MS_SPEED

BSC ignores indications if;

• UL DTx used during SACCH

• MS changing power during SACCH

3

MS Speed Detection Processing




BTS

BTS

Adjacent cellmeasurements

BSC

BTS sends MS speed

measurements to

BSC

every SACCH period(~480ms)

2

BTS 'measures' MS speed based

on zero cross rate algorithm providing

call is on non-hopping TCH (no SDCCH)

MS_SPEED_DETECTION not suitable

for use with frequency hopping networks

1

MS changing power during SACCH

4AV_MS_SPEED is compared with

thresholds;

• LowerSpeedLimit (slow MS)

• UpperSpeedLimit (fast MS)

to direct MS to appropriate layer

(cell priorities used)

Candidate Selection

• Fast-moving to

upper / Slow-

moving to lower layer adjacent

cells

• Equation 1' used

• Priority

considered

FMMS & MS Speed DetectionParameters

Parameter Value

adjCellLayer (ACL)(ADJC) N / Same / Upper / Lowerh L lU b ll (AUCL)(ADJC) 110 47 dB




msSpeedAveraging (MSA)(HOC) 1 ... 32 (SACCH frames)

adjCellLayer (ACL)(ADJC) N / Same / Upper / Lower

hoLevelUmbrella (AUCL)(ADJC) -110 ... -47 dBm

lowerSpeedLimit (LSL)(HOC) 0 … 255 (1 step

2km/h) upperSpeedLimit (USL)(HOC) 0 … 255 (1 step

2km/h) msSpeedThresholdNx (STN)(HOC) 1 … 32 msSpeedThresholdPx (STP)(HOC) 1 … 32

adjCellLayer (ACL)(ADJC) N / Same / Upper / LowerhoLevelUmbrella (AUCL)(ADJC) -110 ... -47 dBm

FastMovingThreshold (FMT)(ADJC) 0 … 255 (SACCH frames)FMMS

MS Speed

Detection

FMMS & MS_SPEED_DETECTIONFlow char t for Hando ver Algor i thm




Handover due to Quality (1/3)Process

• Trigger

– Threshold Comparison (hoThresholdsQualUL/DL with px/nx)

(QUR/QDR)(HOC)





• Candidate Selection – Equation 1 used

– Equation 2 used if enableHoMarginLevQual = N (MRGS)(ADJC)

– Equation 2' used if enableHoMarginLevQual = Y


hoThresholdQualUL/DL (QUR/QDR)(HOC) 0 … 7

px (QUP/QDP) 1 … 32

nx (QUN/QDN) 1 … 32

Parameter Value

rxLevMinCell(n) (SL)(ADJC) -110 … -47 dBmmsTxPwrMax(n) (PMAX1 & PMAX2)(ADJC) 5 … 43 & 0 … 36 dBmhoMarginQual(n) (QMRG)(ADJC) -24 … 24 dB

Handover due to Quality (2/3)Flowchar t for Hando ver Algor i thm



Handover due to Level (1/3)Process

• Trigger

– Threshold Comparison (hoThresholdsLevUL/DL with px/nx)

(LUR/LDR)(HOC)





Candidate Selection – Equation 1 used

– Equation 2 used if enableHoMarginLevQual = N

(MRGS)(ADJC)

– Equation 2' used if enableHoMarginLevQual = Y


hoThresholdLevUL/DL (LUR/LDR)(HOC) -110 … -47 dBm

px (LUP/LDP) 1 … 32

nx (LUN/LDN) 1 … 32

Parameter Value

rxLevMinCell(n) (SL)(ADJC) -110 … -47 dBmmsTxPwrMax(n) (PMAX1 & PMAX2)(ADJC) 5 … 43 & 0 … 36 dBm hoMarginLev(n) (LMRG)(ADJC) -24 … 24 dB

Handover due to Level (3/3)Example

Equations 1 and 2‟ are used if parameter enableHoMarginLevQual is set “Yes” (MRGS)(ADJ




hoMarginLev = 4dB (LMRG)(ADJC)

Cell B

Cell B is not selected as candidate for HO due to level, since 2dB < 4 dB

(RxLev) Thresholddefined by;

hoThresholdLevUL/D

L

= -92 / -95 dBm

(LUR/LDR)(HOC)

2 dB

Trigger for Handover due to Level

Cell A

Handover due to Level (2/3)Flowchar t for Hando ver Algor i thm




Handover due to Interference (1/4)Process

• Trigger: – Threshold Comparison for Quality (hoThresholdsQualUL/DL with

px/nx)

– Threshold Comparison for Level(hoThresholdsInterferenceUL/DL with px/nx)




( U / with p / )

• Candidate Selection – Priority for InterCell / Intracell HO selected at BSC independently for

UL / DL

– Priority InterCell HO

– Quality HO if any candidate

– If not IntraCell HO – Priority IntraCell HO

hoThresholdInterferenceUL/DL (IUR/IDR)(HOC) -110 … -47 dBm

px (IUP/IDP) 1 … 32

nx (IUN/IDN) 1 … 32 enableIntraHoInterfUL/DL (EIC/EIH)(HOC) Y / N

Parameter Value

hoPreferenceOrderInterfUL/DL (HUL/HDL)(BSC) INTER / INTRA

Equations 1 and 2‟ are used if parameter enableHandoverMarginLevQual is set “Yes” (MRGS)

hoThresholdQualDL = 5 (QDR)(HOC)h Th h ldI t f DL 85 dB (HOC) • Field strength higher than threshold

Handover due to Interference (4/4)Example




( )( )hoThr esholdI nterferenceDL = -85 dBm (HOC)

hoPreferenceOrderI nter fDL = intra (HDL)(BSC)

• Field strength higher than threshold

(AV_RXLEV_DL_HO >

hoThresholdsInterferenceDL

• Bad quality

(AV_RXQUAL_DL

hoThresholdsQualDL

Handover due to DL interference

intra cell handover !!Trigger for Handover due to Interference

Cell A

Cell B

Threshold (Interference Lev)

-85 dBm

5

0

RXLEV

RXQUAL

Handover due to Interference (2/4)Flowchar t for Handover Algo r i thm (1)




A

Handover due to Interference (3/4)Flowchar t for Handover Algo r i thm (2)

A




8. Imperative Handovers

• Handovers considered to be




• Handovers considered to be

imperative:

– Handover due to Distance

– Order to empty a cell (from O&M)

– Directed Retry and IDR

– Rapid Field Drop (RFD)

– Enhanced Rapid Field Drop

(ERFD)

MS-BTS Distance Handover

Distance Process ---> msDistanceBehaviour (0,1..60,255) (DISB) (in BSC)• 0 : Release immediately

Distance Process




( , , ) ( ) ( )• 0 : Release immediately

• 1 - 60 : Release after certain time 1 - 60 s, try handover during that

time

• 255 : No release, only imperative Handover attempt

enableMsDistanceProcess (EMS)(HOC) Y / N

msDistanceHoThresholdParam (MSR)(HOC) 0 … 63

px (MSP) 1 … 32

nx (MSN) 1 … 32

Parameter Value

msDistanceBehaviour (DISB)(BSC) 0, 1 … 60, 255

Chained

Rapid Field Drop Parameters• Trigger

– Threshold Comparison

(HoThresholdRapidLevUl (px)

• Rx Lev UL (Not averaged / OnlyUL)




Chained

CellServing

Cell

_ _ ( g yUL)


– Only Chained adjacent cell

– Equation 1 only / no priority

• Multi-Layered Network

hoThresholdLevUL (forRapidFieldDrop)(RPD)(HOC) -110 ... -47 dBm

[hoThresholdRapidLevU1N 0 ... 32]

chainedAdjacentCell (CHAIN)(ADJC) Y / N

Parameter Value

MS Ch i d

Rapid Field Drop Example




MS Chained

CellServing

Cell

Rapid Field Drop Handover

..

1st

2nd

-93 dBm

Serving

Cell

hoThresholdRapidLevUL(RPD) = - 93 dBm

hoThresholdRapidLevUlN (px) = 2

chainedAdjacentCell = Yes

Example

Rapid Field Drop (RFD)Flow char t for Hando ver Algor i thm




Enhanced Rapid Field Drop (ERFD)Scenar ios for Fast & Slow MSs




A MS moves away from cell site,

the signal is dropping gradually

A MS turns a corner,

the signal drops rapidly

S i g n a l L e v e l

TimeFigure 7 Signal Strength of a Fast Moving MS

MS moves away from cell site,

the signal is dropping gradually

MS turns a corner, the

signal drops faster than

moving in straight line

S i g n a l L e v e l

TimeFigure 8 Signal Strength of a Slow Moving MS

• An Enhanced Rapid Field Drop is detected when the uplink receive signal level fallsby a

defined level over a set period of time. (Note: ERFD does not use a threshold like

RFD)

ERFD Basics




p (RFD)

• On detection of an ERFD, the averaging window for neighbour cells, and the number of

zero results allowed in a measurement report, are modified in order to speed up the

monitoring of neighbour cells

• The ModifiedAveWinNcell (ERAW)(HOC) and ModifiedNOZ (ERZ)(HOC) parameters

are modified over the period ErfdOver (ERD)(HOC)

• If a Handover with cause RR is requested during ErfdOver, an ERFD Handover isinitiated

using the Handover Target Cell Candidate list for that handover causeNote: An ERFD Handover does not use 'Chained Cells' for target cell evaluation

process

• If Handover with RR cause is not detected during ErfdOver , ERFD Handover isstopped

ERFD Parameters

• In case of DDE (Deep Dropping Edge), the averaging windowsizes and

power budget period are reduced • level downlink window size




level downlink window size

• level uplink window size

• adjacent cell averaging window size

• handover period power budgetParameter Value

erfdEnabled (ERFD)(HOC) DIS, UL, DL, or UDL (OPTIONAL feature)

ddeThresholdsLev (ERT)(HOC) 0 … 63 dB

Nx (ERN) 1 … 32

Px (ERP) 1 … 32

ddeWindow (ERMW)(HOC) 1 … 32 SACCH

modifiedAveWinNcell (ERAW) 1 … 32

modifiedNOZ (ERZ)(HOC) 1 … 32

erfdOver (ERD)(HOC) 0 … 64 sec

Handover

Serving cell

25dB > 20dB

DdeThreshold

ERFD Detection

ERFD Detection




Se g ce

Ncell #1

hoThresholdLevXL

ErfdOver

ERFD HO initiated

to Ncell #1

XL = DL or UL

DdeWindow =2 n(1):p(1)

-83 -87-63-61-60-60 -89 -91 -94 -89 -89

averagingWindowSizeAdjCell = 4

modifiedAveWinNcell = 2

ERFD HO

ddeWindow (ERMW)(HOC) = 3 SACCH (n = 3)

ERFD Example




ddeThresholdsLev (ERT)(HOC) = 10, px = 2 & nx =3

• the BSC compares the most recent measurement sample 8(multiframe k) with the measurement sample 5 (multiframe k-n)

• DDE_LEVEL = RXLEV(k- ddeWindow) – RXLEV(k) = -69 dBm – (-

83 dBm) = 14 dB

Sample 1 2 3 4 5 6 7 8

Signal

level

-71

dBm

-68

dBm

-70

dBm

-71

dBm

-69dBm

-70

dBm

-75

dBm

-83dBm

Handover ERFD Flowchart




Another name for ERFD Handover

MSC Controlled Traffic Reason Handover

MSC request Traffic reason handover




Target cell evaluation:

AV_RXLEV_NCELL(n) > RxLevMinCell(n) + MAX(0, Pa)

AND

AV_RXLEV_NCELL(n) > TrhoTargetLevel(n) + MAX(0, Pa)where

Pa = MsTxPwrMaxCell(n) - P

P = maximum power of MS

Interval between handovers and handover attempts:

Power budget and umbrella handovers back to the sourcecell are not allowed during the quard time:

GUARD_TIME = 20 sec + MinIntBetweenHoReq

BSC Initiated Traffic Reason Handover

Handover




+0 dB +4dB +6 dB

1. AV_RXLEV_NCELL (n) > TRHO_TARGET_LEVEL (n)

+

Max (0, (MS_TXPWR_MAX_CELL (n) - P))

2. PBGT (n) > AmhTrhoPbgtMargin and PBGT (n) <HOMarginPBGT

Practical Example of Handover

Practical Examples

1. Adjacent Channel in Adjacent Cell




2. Cell with Very Large Coverage Area

• In practice after -6 dB -> interferencies + quality goes down to 4-5

• hoMarginLev < -6 dB -> Ping-Pong !!

• MS switched off in cell A and

transferred to area of cell X

C I - 9 dBa •

A X

20 km

• • xx

• MS switched on in new place

-> MS tries first old channel + neighbourgs

• MS camped on cell A which is not in neighbourg list of cell X

-> do not listen BCCH of cell X -> no HOs to cell X !!!

Handover Control Exercise0

1

2

Quality

No Action NeededLevel Ho




3

4

5

6

7

- 1 1 0

- 1 0 8

- 1 0 6

- 1 0 4

- 1 0 2

- 1 0 0

- 9 8

- 9 6

- 9 4

- 9 2

- 9 0

- 8 8

- 8 6

- 8 4

- 8 2

- 8 0

- 7 8

- 7 6

- 7 4

- 7 2

- 7 0

- 6 8

- 6 6

- 6 4

- 6 2

- 6 0

- 5 8

- 5 6

- 5 4

- 5 2

- 5 0

dBm

HoThresholdLevUL/DL

RxlevAccMinRxlevAccMin(n)

HoThresholdQualUL/DL

HoThresholdInterferenceUL/DL

Interference HoQuality Ho


No action needed

Interference Ho

Quality Ho

Level Ho

HoThresholdLevUL/DL


RxLevMinCell(n)

RxLevAccMin

Thresholds

Actions

Handover & Power Control Exercise0

1

2

Quality

PcUpperThresholdQualUL/DL

No Action NeededLevel Ho Decrease Power




3

4

5

6

7

- 1 1 0

- 1 0 8

- 1 0 6

- 1 0 4

- 1 0 2

- 1 0 0

- 9 8

- 9 6

- 9 4

- 9 2

- 9 0

- 8 8

- 8 6

- 8 4

- 8 2

- 8 0

- 7 8

- 7 6

- 7 4

- 7 2

- 7 0

- 6 8

- 6 6

- 6 4

- 6 2

- 6 0

- 5 8

- 5 6

- 5 4

- 5 2

- 5 0

dBm

HoThresholdLevUL/DL


PcLowerThresholdLevUL/DL

PcUpperThresholdLevUL/DL


PcLowerThresholdQualUL/DL


Interference HoQuality Ho

Increase Power



Power decrease

No action needed

Interference Ho

Quality Ho

Level Ho


HoThresholdLevUL/DL




RxLevMinCell(n)

RxLevAccMin

Power increase

Thresholds

Actions

Handover Causes

Network Doctor Example




Handover Causes




Power Control

Module Objectives

At the end of the module, the participant will be able to:•State the purpose and the important considerations for power




State the purpose and the important considerations for power

control

in GSM networks

•List the steps involved in the power control process.

•Explain the difference between fixed and variable power-change step-size

•Discuss the Power Control Algorithms that are used to increase

or decrease

the MS or BTS transmit power, based on received signal

levels and quality

•Name the parameters that are used for Power Control

Reasons and StrategyREASONS

• Optimize Uplink and Downlink QOS decrease interference

• Decrease power consumption of the Mobile

STRATEGY




• Handled by the BSC

• Enough margin against Rayleigh fading

• HO has always higher priority than POC

• Controlled by interval

• Increase and decrease act independently (can be fixed or variable step

size)

• BTS and MS apply Power Control independently

• BCCH TRX doesn't use Power Control

• DL/UL Power Control can be disabled

• Initial POC level used by MS in new cell after HO, is determined by BSC(default is max permitted level, MsTXPwrMaxCell

• Optionally POC/HOC processes can optimise the initial RF power in

case of intra BSC HO

Overview (1/2)

AveragingMeasurements

EnaFastAveCallSetupEnaFastAvePCEnaFastAveHOMS + BTS




Measurements

BtsMeasAverage

AveragingWindow SizeAdjCell AllAdjacentCellsAveragedNumberOfZeroResults

Averaging

Bookkeeping

ho/pc_Averaging_Lev/Qual_UL/DLWindowSize

WeightmsDistanceAveragingParameter

WIndowSize

DTXMode Power Control ?

MS

Overview (2/2)

Uplink Quality AV_RXQUAL_UL_PC

POWER CONTROL

UPLINK




powerControlInterval 0 … 30 sec powerIncrStepSize 2, 4, 6 dB

powerRedStepSize 2, 4 dB

powerControlEnabled Y / N

Parameter Value

Uplink Level AV_RXLEV_UL_PC

Downlink Level

Downlink Quality AV_RXQUAL_DL_PC

AV_RXLEV_DL_PC

THRESHOLDCOMPARISON

Separate Averaging Parameters

For Handover and for Power Control

POWER CONTROL

DOWNLINK

POCINTERVAL

POC Parameters

Parameter Value

pcUpper/LowerThresholdsLevUL

rxLevel

px

nx

-110 ...-47 dBm

1 ... 32

1 32




nx

pcUpper/LowerThresholdsLevDL

rxLevel

px

nx

pcUpper/LowerThresholdsQualU

L

rxQual

px

nx

pcUpper/LowerThresholdsQualD

L

rxQual

px

nx

1 ... 32

-110 ... -47 dBm

1 ... 32

1 ... 32

0 ... 7

1 ... 32

1 ... 32

0 ... 7

1 ... 32

1 ... 32

Safety Region

LowerLEV UpperLEV




UpperQUAL

LowerQUAL

Applicable in both Downlink and Uplink Directions

Ranges

30 dB System

Attenuations




bsTxPwrMax 0 … 30 dB

bsTxPwrMin 0 … 30 dB

minMsTxPower 0 … 36 dBm

msTxPwrMax 0 … 36 dBm

Parameter Value

Range DependentRange

Power Values

MS/BTS Power Increase Due toSignal Level

IF AV_RXLEV_UL/DL_PC <=PcLowerThresholdsLevUL/DL

THENMS/BTS power increase due to signal level




IF

RXLEV_UL/DL + 2 *PowIncrStepSize<= PcLowerThresholdsLevUL/DL

THEN

PWR_INCR_STEP =PcLowerThresholdsLevUL/DL

- RXLEV_UL/DLELSEPWR_INCR_STEP = PowIncrStepSize

PowerControlIinterval

MS Power Increase Due to SignalLevel

• If RXLEV_UL+ 2*PowIncrStepSize

PcLowerThresholdsLevUL

PWR INCR STEP =




PWR_INCR_STEP =

PcLowerThresholdsLevUL-

RXLEV_UL

(Variable step size)

• Else

PWR_INCR_STEP =

PowIncrStepSize

• RXLEV_UL is the current signal levelmeasured by the BTS

• RXLEV_UL <> AV_RXLEV_UL_PC (

used for threshold comparison)

PcLowerThresholdsLevUL

Power Control Triggered

BTS Power Increase Due to SignalLevel• If RXLEV_DL +

2*PowIncrStepSize <=

PcLowerThresholdsLevDL




– PWR_INCR_STEP =

PcLowerThresholdsLevDL -

RXLEV_DL

– (Variable step size)

• Else

– PWR_INCR_STEP =

PowIncrStepSize

• RXLEV_DL is the current signal

level measured by the MS• RXLEV_DL <>

AV_RXLEV_DL_PC (used for

threshold comparison)





BTS Power Increase Due to SignalQuality• Only variable step size

• Two different Algorithms

• Largest increase isconsideredB d C t Q lit




PWR_INCR_STEP =

(1+MAX(0,Qa))*PowIncrStepSize

where

Qa = RXQUAL_DL - PcLowerThresholdsQualDL

PWR_INCR_STEP = PcLowerThresholdsLevDL -

RXLEV_DL

Based on Current Level

Based on Current Quality

IF : RXLEV_DL + 2*PowIncrStepSize <=


LARGEST INCREASE

BTS Power Decrease Due to SignalLevel




• if VariableDLStepUse = N

PWR_DECR_STEP =PowRedStepSize

(no variable step size)

PcUpperThresholdsLevDL


VariableDLStepUse Y/N

Parameter Value

If VariableDLStepUse =

Y

• If RXLEV_DL - 2*PowRedStepSize >=PcUpperThresholdsLevDL

BTS Power Decrease Due to SignalLevel




PcUpperThresholdsLevDL


PWR_DECR_STEP =

MIN((RXLEV_DL -

PcUpperThresholdsLevDL),10)


• Else

PWR_DECR_STEP =

PowRedStepSize

• RXLEV_DL is the current signal levelmeasured by the MS

• RXLEV_DL <> AV_RXLEV_DL_PC ( usedfor threshold comparison )

VariableDLStepUse =Y/N (S9 new feature)

OptimumRxLevDL = -109…-47 dBm/N

BTS Power Decrease Due to SignalQuality




• If VariableDLStepUse = N

PWR_DECR_STEP = PowRedStepSize (no

variable step size)The decrease in power does not take place if there is the possibility that it wouldtrigger the threshold PcLowerThresholdsLevDL (the safety margin is 6dB)


BTS Power Decrease Due to SignalQuality




– Based on whether OptimumRxLevDL is used or not

• If the resulting RXLEV_DL would get too close to

PcLowerThresholdLevDL (as a result of the decrease) there

could be a consecutive increase due to level which will lead totriggering the decrease again. To avoid this "ping pong" effect

BSC makes sure before decreasing the power due to signal

quality, that RXLEV_DL is at least 6 dB higher than the

PcLowerThresholdLevDL.

– 6 dB Margin is in-built in BSC



Power Decrease Step Calculation

If VariableDLStepUse = Y and

If OptimumRxLevDL = defined




PWR_DECR_STEP =

MIN ((MIN{PwrDecrLimit, MAX[ MAX (0, RXLEV_DL -

OptimumRxLevDL),(PwrDecrFactor + MAX(0, Qa)) *PowRedStepSize]}),10)

where

Qa = PcUpperThresholdsQualDL - AV_RXQUAL_DL_PC

IF : optimumRxLevDL <> N

MS Power Decrease Due to SignalLevel

• If RXLEV_UL - 2*PowRedStepSize >=

PcUpperThresholdsLevUL

PWR_DECR_STEP =

RXLEV UL -




RXLEV_UL -



• Else

PWR_DECR_STEP =

PowRedStepSize

• RXLEV_UL is the current signal level

measured by the BTS

• RXLEV_UL <> AV_RXLEV_UL_PC (

used for threshold comparison )



MS Power Decrease Due to Signal

Quality


B d O i R L UL b i d t




– Based on OptimumRxLevUL being used or not

• if the resulting RXLEV_UL would get too close to

PcLowerThresholdLevUL (as a result of the decrease) there

could be a consecutive increase due to level which will lead to

triggering the decrease again. To avoid this "ping pong" effect

BSC makes sure before decreasing the power due to signal

quality that RXLEV_UL is at least 6 dB higher than the

PcLowerThresholdLevUL.

– 6 dB Margin is in-built in BSC

"Ping Pong" Effect

LowerLEV UpperLEV

UpperQUAL




pp Q

LowerQUAL

Power decrement due to qualityPower increment due to level

IF : optimumRxLevUL =

N• if RXLEV_UL - 2*PowRedStepSize >=


MS Power Decrease Due to SignalQuality





PWR_DECR_STEP = RXLEV_UL -



• else

PWR_DECR_STEP = PowRedStepSizeSame as in the MS Power decrease due

to Signal Level,

but Triggered by different condition(quality)

16

• PWR_DECR_STEP =MIN[ PwrDecrLimit, MAX( MAX (0, RXLEV_UL -

O ti R L UL)

IF : optimumRxLevUL <> N

MS Power Decrease Due to SignalQuality




PcUpperThresholdQualUL = 1

0

2

4

6

8

10

12

14

- 1 0 9

- 1 0 7

- 1 0 5

- 1 0 3

- 1 0 1

- 9 9

- 9 7

- 9 5

- 9 3

- 9 1

- 8 9

- 8 7

- 8 5

- 8 3

- 8 1

- 7 9

- 7 7

- 7 5

- 7 3

- 7 1

- 6 9

- 6 7

- 6 5

- 6 3

RxLev_UL

P w r

_ D e c r_ S t e p

B = Max ( 0 , RXLEV_UL - OptimumRxLevUL ) C = (PwrDecrFactor + Max(0,Qa)) *PwrRedStepSize Min(Max(B;C) , PwrDecrLimit)

OptimumRxLevUL),

(PwrDecrFactor + MAX(0, Qa)) *PowRedStepSize ) ]

• where Qa = PcUpperThresholdsQualUL -

AV_RXQUAL_UL_PC PwrDecrLimitBand0 : if

AV_RXQUAL_UL_PC =0

PwrDecrLimit = 10dB

PwrDecrLimitBand1 : if AV_RXQUAL_UL_PC =1

PwrDecrLimitBand2 : if AV_RXQUAL_UL_PC =2

MS Power OptimizationCall Set-up

• Normally MS accesses the TCH with the maximum Tx Power allowed

in the cell:

msTxPwrMax




• When power optimization is employed

MS_TXPWR_ OPT = MsTxPwrMax - MAX ( 0, (RXLEV_UL -OptimumRxLevUL) )

• Parameter OptimumRxLevUL must be defined for each TRX in the cell.

If there are different values defined for different TRXs then maximum

value is considered in the calculation.

• RXLEV_UL is measured during signalling phase OptimumRxLevUL -109 … -47 / N dBm

Parameter Value

MS Power OptimizationIntracel l Hando ver

• Normally MS uses the maximum Tx Power allowed in the target cell

msTxPwrMax

• When power optimization is employed




MS_TXPWR_ OPT = MsTxPwrMax - MAX( 0, (AV_RXLEV_UL_HO +

(MsTxPwrMax - MS_TXPWR) - OptimumRxLevUL)

• Parameter OptimumRxLevUL must be defined for each TRX in the cell. If different values then maximum is considered

Example: AV_RXLEV_UL_HO= -75 dBm

OptimumRxLevUL= -80 dBm MS_TXPWR_OPT = 33 dBm -MAX( 0, -75 dBm+80

dBm)

MS_TXPWR_MAX= 33 dBm = 33 dBm -5 dB = 28 dBm

MS_TXPWR = 33 dBm

• Normally MS uses the maximum Tx Power allowed in the target cell

msTxPwrMax

• When power optimization is employed;

MS Power OptimizationInternal Intercell Handover




When power optimization is employed;

MS_TXPWR_ OPT(n) = MsTxPwrMax(n) - MAX ( 0, (AV_RXLEV_NCELL(n) -

MsPwrOptLevel) )

• Parameter msPwrOptLevel is defined on a per adjacent cell basis

msPwrOptLevel -110 … -47/N dBm

Parameter Value

6 dB

Handover

Serving Cell DL

Adjacent Cell DL

Adjacent

Cell ULmsPwrOptLevel

• Affects Uplink

• Either Uplink signal equalsdownlink signal

• Or Differences in UL / DLconsidered when

defining

msOptPwrLevel

Power Control - Thresholds & ActionsUplink & Downl ink

0

1

2

3

Quality



No Action Needed Decrease Power




4

5

6

7

- 1 1 0

- 1 0 8

- 1 0 6

- 1 0 4

- 1 0 2

- 1 0 0

- 9 8

- 9 6

- 9 4

- 9 2

- 9 0

- 8 8

- 8 6

- 8 4

- 8 2

- 8 0

- 7 8

- 7 6

- 7 4

- 7 2

- 7 0

- 6 8

- 6 6

- 6 4

- 6 2

- 6 0

- 5 8

- 5 6

- 5 4

- 5 2

- 5 0

dBm




Increase Power


Power decrease

No action needed




RxLevMinCell(n)

RxLevAccMin

Power increase

Thresholds

Actions

Introduction to Gsm Optimization

Documents

Transcript of Introduction to Gsm Optimization