Radio Resource Management

MobileComm Professionals, Inc.

Your Partner for Wireless Engineering Solutions

•MobileComm Professionals, Inc.

RRM Introduction Power Control Handover 3G Parameters HSDPA Parameters

Agenda

Radio Resource

Management

•MobileComm Professionals, Inc. Radio Resource Management

RRM is responsible for optimal utilisation of the radio resources:

Transmission power and interference

Logical codes

The trade-off between capacity, coverage and quality is done all the time

Minimum required quality for each user (nothing less and nothing more) Maximum number of users Service Quality

Coverage Capacity

Optimization and Tailoring

The radio resources are continuously monitored and optimised by several RRM functionalities

•MobileComm Professionals, Inc. RRM Functionalities

LC Load Control

AC Admission Control

PS Packet Scheduler

RM Resource Manager

PC Power Control

HC HO Control PC

HC

For each connection/user

LC

AC

For each cell

PS

RM

•MobileComm Professionals, Inc. Load Control (LC)

LC performs the function of load control in association with AC & PS

LC updates load status using measurements & estimations provided by AC and PS

Continuously feeds cell load information to PS and AC;

Interference levels (UL)

BTS power level (DL)

LC AC

PS NRT load

Load change info

Load status


Overload threshold x

Load Target threshold y

Po

we

r

Time

Load Margin

Overload

Normal load

Measured load Free capacity

Load Control – Load Status

Load thresholds set by radio network planning parameters

•MobileComm Professionals, Inc. Admission Control (AC)

Checks that admitting a new user will not sacrifice planned coverage or quality of existing connections

Admission control handles three main tasks

1) Admission decision of new connections

Take into account current load conditions (from LC) and load increase by the new connection

Real-time higher priority than non-real time

In overload conditions new connections may be rejected

2) Connection QoS definition

Bit rate, BER target etc.

3) Connection specific power allocation:

Initial, maximum and minimum power

•MobileComm Professionals, Inc. Admission Control

Decides whether new Radio Access Bearer (RAB) is admitted or not. Real-Time traffic admission to the network is decided. Non-Real-Time traffic after RAB has been admitted the

optimum scheduling is determined. Used when the bearer is

Set up. Modified During the handover.

Estimates the load and fills the system up to the limit. Used to guarantee the stability of the network and to achieve high network capacity.

•MobileComm Professionals, Inc. Packet Scheduler (PS)

PS allocates available capacity after real-time (RT) connections to non-real time (NRT) connections

Each cell separately

Based on QoS priority level of the connection

In overload conditions bit rates of NRT connections decreased

PS selects allocated channel type (common, dedicated or HSPA)

PS relies on up-to-date information from AC and LC

Capacity allocated on a needs basis using ‘best effort’ approach

RT higher priority


Load

time

Free capacity, which can be

allowed for controllable load

on best effort basis

Non controllable load

Planned Target Load

•11

The Packet Scheduling controls the UMTS packet access and is located in the RNC.

The functions of the PS are:

To determine the available radio interface resources for Non Real Time radio bearers.

To share the available radio interface resources between Non Real Time radio bearers.

To monitor the allocation for Non Real Time.

To monitor the system loading.

To perform LC actions for Non Real

Time radio bearers when necessary.

Packet Scheduler (PS)

•MobileComm Professionals, Inc. Resource Manager (RM)

Responsible for managing the logical radio resources of the RNC in co-operation with AC and PS

On request for resources, from either AC(RT) or PS(NRT),

RM allocates:

DL Spreading code

UL Scrambling code

Code Type Uplink Downlink

Scrambling codes

Spreading codes

User separation Cell separation

Data & control channels from same UE Users within one cell

Features

•MobileComm Professionals, Inc. Power Control (PC)

Fast, accurate power control is of utmost importance – particularly in UL;

UEs transmit continuously on same frequency Always interference between users

Poor PC leads to increased interference reduced capacity

Every UE accessing network increases interference

PC target to minimise the interference Minimize transmit power of each link while still maintaining the link quality (BER)

Power control has to be fast enough to follow changes in propagation conditions (fading)

• Step up/down 1500 times/second

•MobileComm Professionals, Inc. Power Control (PC)

Minimise required UL received power minimised UL transmit power and interference

UE1 UE2

Ptx1

Ptx1

•MobileComm Professionals, Inc. Power Control Types

Power control functionality can be divided to three main types

Open loop power control

• Initial power calculation based on DL pilot level/ Pathloss measurement by UE

Outer (closed) loop power control

• Connection quality measurement (BER, BLER) and comparison to QoS target

• RF quality target (SIR target) setting for fast closed loop PC based on connection quality

Fast closed loop power control

• Radio link RF quality (SIR) measurement and comparison to RF quality target (SIR target)

• Power control command transmission based on RF quality evaluation


UL Outer Loop Power Control

Open Loop Power Control (Initial Access)

Closed Loop Power Control

RNC BS

MS

DL Outer Loop Power Control BLER Target

Power Control Types

•MobileComm Professionals, Inc. Power control in HSPA

In HSDPA (DL) the transmit power from base station is kept constant and the signal modulation and coding is adapted according to the channel conditions

• 2 ms interval 500 Hz

In HSUPA (UL)

• The power control of HSUPA channels in UL utilises both

Fast closed loop power control

Outer loop power control

• Both work according to similar principles as the R99 power control

•MobileComm Professionals, Inc. Handover Control (HC)

HC is responsible for: Managing the mobility aspects of an RRC connection as UE

moves around the network coverage area Maintaining high capacity by ensuring UE is always served by

strongest cell Soft Handover

MS handover between different base stations Softer Handover

MS handover within one base station but between different sectors

Hard Handover MS handover between different frequencies or between WCDMA and GSM


UE is simultaneously connected to 2 to 3 cells during soft handover

Soft handover is performed based on UE cell pilot power measurements and handover thresholds set by radio network planning parameters

•BS1

•BS2

•BS3 •Rec

eived

sig

na

l st

ren

gth

•BS3

•Distance from BS1

•Threshold

•Soft handover

•BS2

•BS1

Handover Control (HC)

•MobileComm Professionals, Inc. Types of 3G Handovers

Softer Handover A MS is in the overlapping coverage of

2 sectors of a NodeB.

Concurrent communication via 2 air interface channels

2 channels are maximally combined with rake receiver

Soft Handover A MS is in the overlapping coverage of 2

different NodeB.

Concurrent communication via 2 air interface channels

Downlink: Maximal combining with rake receiver

Uplink: Routed to RNC for selection

combining

•21

•MobileComm Professionals, Inc. Hard Handover

Hard handovers are typically performed between WCDMA frequencies and between WCDMA and GSM cells

GSM/GPRS GSM/GPRS

f1

f2

f1

f2 f2 f2

Inter-System handovers (ISHO)

Inter-Frequency handovers (IFHO)

Parameters

•MobileComm Professionals, Inc. Eb/No

In order to meet the defined quality requirements (BLER) a certain average bit-energy divided by total noise + interference spectral density (Eb/No) is needed

Eb/No is defined at bit detection in the receiver baseband

Eb/No depends on

• Service and bearer

Bit rate, BER requirement, channel coding

• Radio channel

Doppler spread (Mobile speed, frequency)

Multipath, delay spread

•MobileComm Professionals, Inc. Eb/No

• Receiver/connection configuration

Handover situation

Diversity configuration

Fast power control usage

• Typically given Eb/N0 includes also overhead due to physical layer control signalling

– Higher bit rates Less overhead Lower Eb/N0

•MobileComm Professionals, Inc. Required Eb/No

PGI

C

R

W

I

C

N

Eb 0

NothownDL PIII )1( NothownUL PIII

Where: C = received power R = bit rate (typically service bit rate) W = bandwidth PG = processing gain Iown = total power received from the serving cell (excluding own signal) Ioth = total power received from other cells PN = noise power = orthogonality factor

Energy per chip

Total power spectral density


Required Ec/Io is the required RF C/I needed in order to meet the baseband Eb/No criteria

Ec/No used often instead of Ec/Io in same context

NOTE: Pilot Ec/No different measure

Ec/Io depends on the bit rate and Eb/No

I

C

W

R

N

E

I

E bc 00

Energy per chip

Total power spectral density

Ec/Io

•MobileComm Professionals, Inc. Parameters Understanding

CPICH RSCP:- Received Signal Code Power (RSCP) is the received power on one code measured on the Primary CPICH.

RSSI:- UTRA carrier RSSI is the received wide band power, including

thermal noise and noise generated in the receiver, within the downlink bandwidth defined by the receiver pulse shaping filter.

Ec/Io :- This measurement is the received energy per chip of the primary CPICH divided by the power spectral density in the band.

Ec/Io = RSCP/RSSI

BLER:- This measurement is the estimation of the transport channel block error rate (BLER).


SIR:- Signal to Interference Ratio (SIR) is defined as,

SIR = (RSCP/ISCP) * SF

Where,

RSCP = Received Signal Code Power, the unbiased measurement of the received power on one code;

ISCP = Interference Signal Code Power, the interference on the received signal;

SF = The spreading factor used on the DPCCH.

Parameters Understanding

•MobileComm Professionals, Inc. WCDMA Sensitivity

Base station sensitivity depends on base station reception RF and base band performance Base station reception RF performance is measured by receiver chain noise figure (NF) Base station NF is typically measured at the base station

input NF describes how much the signal quality (C/I) is degraded in

the receiver chain NF is affected by all noise figures, gains and losses in the

receiver chain Base station reception base band performance in measured by required signal quality (Eb/No) for a given connection quality (BER, BLER)

•MobileComm Professionals, Inc. WCDMA Sensitivity

The required received signal power can be calculated when the external noise and interference power IEXT is known

NFIPGN

EI

I

CP EXT

bTOTRX

1

0

min

)(0

min dBNFIPGIP EXTNE

TOTIC

RXb

•MobileComm Professionals, Inc. HSDPA

SINR is used instead of Eb/No in HSDPA performance evaluation

Modulation and coding Bit rate can be changed every 10 ms

Definition of HS-DSCH SINR:

Narrowband signal-to-interference-plus-noise-ratio after

despreading of the HS-PDSCH

SINR includes the SF16 processing gain for the HS-PDSCH

and the effect of using orthogonal codes

Average HS-DSCH SINR:

This is the experienced HS-DSCH SINR by a user average over

fast fading.

•MobileComm Professionals, Inc. Required SINR

PDSCHHSSFI

CSINR

NothownDL PIII )1(

Where: C = received power Iown = total power received from the serving cell (excluding own signal) Ioth = total power received from other cells PN = noise power = orthogonality factor SFHS-PDSCH = Spreading factor on HSDPA (= 16)

•MobileComm Professionals, Inc. Cell Search Scenario

(P-SCH) Primary SCH

(S-SCH) Secondary SCH

CPICH

P-CCPCH P-CCPCH

Slot synchronisation

10 ms

The Primary CCPCH is detected using the identified primary scrambling code After the cell search, system and cell specific BCH information can be read.

Frame synchronisation and identification of the cell code

group

Determination of the exact primary scrambling code

used by the found cell

Phase 1 Phase 2

Phase 3

•MobileComm Professionals, Inc. Cell Search Scenario


Cp = Primary Synchronisation Code

Cs = Secondary Synchronisation Code

10 ms Frame

CP CP

2560 Chips 256 Chips

Cs1 Cs2 Cs15

Slot 0 Slot 1 Slot 14

CP CP CP

Cs1

Primary Synchronisation Channel (P-SCH)

Secondary Synchronisation Channel (S-SCH)

Slot 0

Synchronisation Channel (SCH)


15

15

Scrambling code group

Group 00

Group 01

Group 02

Group 03

Group 05

Group 04

Group 62

Group 63

1 1 2 8 9 10 15 8 10 16 2 7 15 7 16

1 1 5 16 7 3 14 16 3 10 5 12 14 12 10

1 2 1 15 5 5 12 16 6 11 2 16 11 12

1 2 3 1 8 6 5 2 5 8 4 4 6 3 7

1 2 16 6 6 11 5 12 1 15 12 16 11 2

1 3 4 7 4 1 5 5 3 6 2 8 7 6 8

9 11 12 15 12 9 13 13 11 14 10 16 15 14 16

9 12 10 15 13 14 9 14 15 11 11 13 12 16 10

Slot number

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

11

11 11

11 11

11 11

11 11

15

15

15

15 15

15

15

15 15

15 15

5

5

SSC Allocation for S-SCH

I monitor the S-SCH


With the help of the SCH, the UE was capable to perform chip, TS, and frame synchronisation.

Even the cell‘s scrambling code group is known to the UE.

But in the initial cell selection process, it does not yet know the cell‘s primary scrambling code. There is one primary scrambling code in use over the entire cell, and in neighbouring cells, different scrambling codes are in use.

There exists a total of 512 primary scrambling codes.

The CPICH is used to transmit in every TS a pre-defined bit sequence with a spreading factor 256.

The CPICH divides up into a mandatory Primary Common Pilot Channel (P-CPICH) and optional Secondary CPICHs (S-CPICH).

Understanding


The P-CPICH is in use over the entire cell and it is the first physical channel, where a spreading code is in use.

A spreading code is the product of the cell‘s scrambling code and the channelization code.

The channelization code is fixed: Cch,256,0. i.e., the UE knows the P-CPICH‘s channelization code, and it uses the P-CPICH to determine the cell‘s primary scrambling code by trial and error.

The P-CPICH is not only used to determine the primary scrambling code. It also acts as:-

phase reference for most of the physical channels, measurement reference in the FDD mode

Understanding


CP

2560 Chips 256 Chips

Synchronisation Channel (SCH)

P-CPICH

10 ms Frame

applied speading code = cell‘s primary scrambling code

Cch,256,0

Phase reference

Measurement reference

P-CPICH Cell scrambling

code? I get it with trial & error!

Primary Common Pilot Channel


The UE has to perform a set of L1 measurements, some of them refer to the CPICH channel: CPICH RSCP

RSCP stands for Received Signal Code Power. The UE measures the RSCP on the Primary-CPICH. The reference point for the measurement is the antenna connector

of the UE. The CPICH RSCP is a power measurement of the CPICH. The received code power may be high, but it does not yet indicate

the quality of the received signal, which depends on the overall noise level.

UTRA carrier RSSI. RSSI stands for Received Signal Strength Indicator. The UE measures the received wide band power, which includes

thermal noise and receiver generated noise. The reference point for the measurements is the antenna connector

of the UE. .

CPICH as Measurement Reference


CPICH Ec/No

The CPICH Ec/No is used to determine the “quality“ of the received signal.

It gives the received energy per received chip divided by the band‘s power density.

The “quality“ is the primary CPICH‘s signal strength in relation to the cell noise. (Please note, that channel quality is determined by BLER, BER, etc. )

If the UE supports GSM, then it must be capable to make measurements in the GSM bands, too.

CPICH as Measurement Reference

•MobileComm Professionals, Inc. Sample Report

Cluster Report:

Sample Report:

•MobileComm Professionals, Inc. Summary

RRM Introduction Power Control Handover 3G Parameters HSDPA Parameters


“HAPPY LEARNING”

MobileComm Professionals, Inc. www.mcpsinc.com

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Radio Resource Management

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