11

BSS Parameters Day3

22

Course Outline

Day 3

1. Power Control

2. Capacity Enhancement Features

3. Coverage Enhancement features

33

Power Control - MS Power Optimization

Power Control Parameters

Power Control

Power Control Strategy

44

Why Power Control

Reduction in MS average power consumption

Longer service time of battery

Reduced interference on Downlink/Uplink

Activation of DL power control

Power CTRL Enabled (PENA) Y,N

Power control independent

for Downlink/Uplink for each call

Methods Include:

Adaptive Power Control

Discontinuous Transmission (DTX)

Discontinuous Reception (RTX)

55

General Power Control Parameters Power Change Step Sizes

Power control is not applied to: downlink burst using the BCCH frequency

Power CTRL Enabled PENA Y

Power Control Interval INT 2s

Power Incr Step Size INC 4dB

Power Red Step Size RED 2dB

66

Power Control Strategy

Keep current transmission power when received level is normal.

Lower the transmission power when received level is high.

Increase the transmission power when received level is low.

Keep current transmission power when BER is normal.

Increase the transmission power when BER is high.

Lower the transmission power when BER is low.

77

Lower Level Upper Level

Upper Quality

Lower Quality

Power Control Summary

No actionPower decrease

due to level

Power increase

due to quality

Power increase

due to level

or quality

Power increase

due to quality

Power decrease

due to level

or quality

Power increase

due to level

Power decrease

due to quality

Power increase

due to level

88

Power Control Priority

PC Priority:

PC due to Lower quality thresholds (UL and DL)

PC due to Lower level thresholds (UL and DL)

PC due to Upper quality thresholds (UL and DL)

PC due to Upper level thresholds (UL and DL)

99

Power Control and Handover Control

Rule of thumb:

POC should happen before HOC

RxLev Thresholds for POC > RxLev Thresholds for HOC

Example

pc lower thresholds lev dl Rx level (LDR) (Def -85dBm) > threshold level downlink Rx level (LDR)

(Def -95 dBm)

RxQual Thresholds for POC >= RxQual Thresholds for HOC

Window size (POC) =< window size (HOC)

1010

Power Control Threshold Parameters

1111

HO Thresholds parameters and values

HO Thresholds parameters and values

Default

-95

1

1

-85

3

4

4

4

6

4

4

6

-85

1

1

-85

1

1

63

1

1

Threshold Level Downlink Rx Level

Threshold Level Downlink Px

Threshold Level Downlink Nx

Threshold Level Uplink Rx Level

Threshold Level Uplink Px

Threshold Level Uplink Nx

Threshold Qual Downlink Rx Qual

Threshold Qual Downlink Px

Threshold Qual Downlink Nx

Threshold Qual Uplink Rx Qual

Threshold Qual Uplink Px

Threshold Qual Uplink Nx

Threshold Interference Downlink Rx Level

Threshold Interference Downlink Px

Threshold Interference Downlink Nx

Threshold Interference Uplink Rx Level

Threshold Interference Uplink Px

Threshold Interference Uplink Nx

MS Distance Threshold Param MS Max Range

MS Distance Threshold Param Px

MS Distance Threshold Param Nx

1212

Averaging Window size and Weighing

The Averaging parameter includes the window size in SACCH periods.

This parameter indicates the weighting factor for measurements

that have not used Discontinuous Transmission (DTX).

Value 1 indicates the DTX measurements weighting factor.

Value 3 indicates the highest weighting factor.

1313

Power Control - MS Power Optimization

MS Power Optimization

2 scenario:

During call setup

During handover

Use the optimized MS output power to reduce the uplink interference

1414

Power Control - MS Power Optimization

Without MS Power Optimisation, MS access the cell with maximum Tx power as

specified by msTxPwrMaxCCH

During Call Setup:

Related Parameters: per TRX

Optimum RX level uplink (LEV): Range -109...-47 dBm

Maximum transmission power of the MS for each : Range 5..39

Example:

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

When RXLEV_UL = -80dBm

MS-TXPWR_OPT = 33 max(0, (-80 + 85) = 28dBm

compare to maximum power 33 dBm

1515

Power Control - MS Power Optimization

During Handover:

Related Parameters: per Adjacency

Indicates the optimum UL RF signal level in adjacent cell after Handover

Range is -110...-47 dBm

Only for intra-BSC HO

Example:

If AV_RXLEV_NCELL(n) = -80dBm, and Set msPwrOptLevel = -85dBm

MS_TXPWR_ OPT(n) = msTxPwrMax(n) - MAX ( 0, (AV_RXLEV_NCELL(n) - msPwrOptLevel) )

MS_TXPWR_ OPT(n) = 33 max ( 0, (-80 + 85) = 28 dBm

Thus MS uses 28 dBm output power instead of 33 dBm

1616

Adaptive Power Control Process

Compulsory in MS, optional in BTS

32 power levels separated by 2dBm

Power changes are commanded using:

Reduction: POW_RED_STEP_SIZE (2, 4 dB steps)

Increase: POW_INC_STEP_SIZE (2, 4, 6 dB steps)

Commands issued on SACCH

One 2dB step change every 60mS

Source: ETSI GSM 05.08 (Version 4.22.1)

1717

Discontinuous Transmission (DTX)

In a conversation, a person generally only speaks for about 30% to 40% of the

time

DTX makes use of this by reducing transmission when no voice signal is detected

Uses a Voice Activity Detection (VAD) unit

Advantages:

Reduces interference

Prolongs battery life of mobile

Parameter DTX Mode (DTX) : MS may use DTX (0), MS shall use DTX (1), MS

shall not use DTX (2)

1818

Course Outline

Day 3

1. Power Control

2. Capacity Enhancement Features

3. Coverage Enhancement features

1919

Extended region (frequency f2 except timeslot 0)E-TRX (Parameter eTrxInd (ETRX) = E)

Normal region (frequency f1)N-TRX (Parameter eTrxInd (ETRX) = N)

Extended cell sizeParameter radiusExtension (EXT)

Value = 1..67km radius extension of extended cell

Value = 0 ordinary cell

One BCCH, Two TRX solution Normal and Extended area served with different TRX

Receiver timing delayed onETRX

Transmitter timing same onNTRX and ETRX

f1 f1 f1 f1 f1 f1 f1 f1

N-TRX

0 1 2 3 4 5 6 7

f1 f2 f2 f2 f2 f2 f2 f2

BB Hopping cannot be used

RF hopping cannot be usedon E-TRXs

E-TRX(Delayed receiver)

0 1 2 3 4 5 6 7

E-RACH SDCCH TCH TCH TCH TCH TCH TCH

BCCH/

SDCCH

NotUsed

TCH TCH TCH TCH TCH TCH

Extended Cell Range

2020

Cell Selection

MS can camp on BCCH (NTRX) independent of the distance to the BTSRACH from MS detected on RACH or E-RACH depending on the distance to the BTS

Handover to due Distance (Normal area Extended area)

MS Distance HO Threshold Ext Cell (MAX) 0..63 (Default 63) TA => MAX; handover triggered to extended cell

With this parameter you define the threshold level for the maximum value of timing advance. If this threshold is reached,

the call is handed over to an extended area of an extended cell

MS Distance HO Threshold Ext Cell (MIN) 0..63 (Default 2) TA => MIN; handover triggered to normal cell

Extended Cell

2121

SRC consists of :

Downlink link enhancing feature

Intelligent Downlink Diversity (IDD)

Uplink enhancing features

4-way UL Diversity (4UD)

Interference Rejection Combining (IRC)

High gain MHA

Up and downlink features can also be implemented

separately (except for 4UD, which is used with IDD)

SRC Concept

2222

Improves the mobiles receiver performance by modifying the radio channel

BTS downlink performance is boosted up to 3-5 dB

All timeslots are transmitted through 2 transceivers and 2 antennas

2nd TRX transmission is delayed and phase turned

IDD Concept

Dual TRX usage (DTRX) : Disabled (0), DTRX with 2UD diversity

(1), DTRX with 4UD diversity (2), IDD TRX with 2UD

diversity (3), IDD TRX with 4UD diversity (4)

2323

Configuring IDD in the BSC

TRX is created/added to IDD configuration during TRX commissioning

4UD is defined in the BSC with the diversity Used (RDIV) parameter:

RDIV=Y (4-way RX diversity is used).

If IDD is used only for boosting the BCCH carrier, the IDD TRX has to be Define in

the BSC as preferred BCCH TRX

2424

Very efficient Interference Rejection Combining is processed for received signals giving ultimate gain for diversity reception. IRC minimizes the effect of interfering signals in the BTS receiver.

MHAMHA

BasebandDDU

UnitsRX + TX Downlink

ignalMasthead Amplifier compensates feeder loss and matches front end of the BTS receiver optimizing sensitivity

RX div.

RX div.

TX auxCombined

Uplink

signal

EDGE

Transceiver

sEDGE

Transceiver

RX div.+

4 - Way UL Diversity

2525

2-Way/4-Way UL Receiver Diversity (IRC/MRC)

The signals from four antennas are fed into two separate

TRX. Two pair-wise signals are combined by IRC in

respective TRX and then the signal from the auxiliary TRX is

fed into the main TRX where signals are combined using

Maximum Ratio Combining

4-way uplink diversity using IRC

followed by MRC.

2626

Course Outline

Day 3

1. Power Control

2. Capacity Enhancement Features

3. Coverage Enhancement features

2727

Capacity Expansion Dual Band

890-915 MHz 935-960 MHz

1710-1785 MHz 1805-1880 MHz

GSM 900 + GSM 1800 (India) or GSM 800 + GSM 1900 (Americas)

Usually lower signal level for GSM 1800 cell

-> MS camps on GSM 900 cell

-> must be set less attractive

-> or MS must be handed over to GSM 1800 cell

GSM 900

GSM 1800

Parameter

dualBandCell Y/N Y Indicates cell as dual band cell

Multiband Cell Reporting 0..3 1 Number of adjacent dual band cells taken

into account for measurement report

900 1800

Dual band MS

900

BTS

MSC

other BSS

900

2828

900 Macro

900 Micro

1800

TCH allocation during call set up

Highest

Priority

2nd priority 2nd priority

3rd priority

MS camped on

900 microcell

MS camped on

900 macrocell

900 Micro

1800

Highest

Priority

Direct Access to Desired Layer / Band - DADL/B

2929

Cell load = 100 %

Btsloadthreshold <

cell load < 100 %

Cell load <

btsloadthreshold

Specific parameter

dadlbTargetCell Y/N indicates adjacent cell as potential target

btsLoadThreshold 0..100 % cell load triggering SDCCH handover

DR initiated

with / without

queuing

DADL/Binitiated

TCH allocatedfrom servingcell

Direct Access to Desired Layer / Band - DADL/B

3030

Common BCCH

Dual Band Operation

every BTS has its BCCH and SDCCH channels

Common BCCH Control

Improved spectral efficiency (Single

BCCH)

Optimised use of signalling channels

Better quality (decreased number of

HOs)

Improved trunking gain

Non BCCH freq. BTS

BCCH/SDCCH

BCCH freq. BTS

Cell 2BCCH/SDCCH

Cell 1BCCH/SDCCH

3131

GSM 1800

GSM 900

BCCHBTS1

BTS2

GSM 1800

GSM 900

BCCHBTS1

BTS2

bsTxPwrMax = peak power - 0 dB

bsTxPwrMax1800 = peak power - 0 dB

GSM 900 signal tends to be stronger than GSM 1800

-> wider coverage for GSM than for GSM 1800

-> useless if BCCH is taken from GSM 1800

Band specific maximum output power of BTS

bsTxPwrMax used for GSM 900

bsTxPwrMax1x00 used for GSM 1800

bsTxPwrMax = peak power - 6 dB

bsTxPwrMax1800 = peak power - 0 dB

Common BCCH - Power Control

3232

Dynamic Frequency and Channel Assignment

Effect => capacity and/or quality gain

Simulations:

~70 % capacity gain over random FH with EFR users

~40 % capacity gain over random FH with AMR users

A new channel assignment scheme that will abolish frequency planning for

non BCCH TRXs

BSC will dynamically assign the most suitable time slot and frequency for

each connection

3333

DFCA System Architecture & BSS Synchronization

BSC 1

DFCA

BSC 2

DFCA

IP network

LMU

1 LMU/site required for synchronization

DFCA RRM algorithm located in BSC

BSCs connected via inter BSC signaling link (IP based connection)

LMU fixes the air interface synchronization to GPS clock

TS1 TS8

TS1 TS8

TS1 TS8

TS1 TS8

TS1 TS8

Non Synchronised System

Cell 1

Cell 2

Cell 3

Cell 4

Cell 5

TS1 TS8

TS1 TS8

TS1 TS8

TS1 TS8

TS1 TS8

Cell 1

Cell 2

Cell 3

Cell 4

Cell 5

Synchronised System

Random relation between time

slots

Time slot level DL interference

considerations

impossible

Time slots constantly aligned

Interference can be considered on time slot level

3434

DFCA principle

Random

FH

over a

fixed

frequency

list

Random FH

TRX 1

TRX 2

TRX 3

TRX 4

Cyclic FH

and MAIOs for

each

connection

DFCA

TRX 1

TRX 2

TRX 3

TRX 4

Each connection is assigned with the most suitable radio frequency and time slot

combination (MA list, MAIO, TSL)

Accurate interference control (C/I estimations)

DFCA algorithm in BSC selects the most suitable radio channel for each user based on mobile

measurement reports

DFCA automatically provides a radio channel with sufficient C/I that depends on the type of the

connection

The connection level C/I control provides significant quality and/or capacity gains

C1

C2I1

I2

EFR User

C1/ I1 > C/I Target

(14 dB)

AMR FR User

C1/ I1 > C/I Target

(8 dB)

3535

DFCA is given a dedicated frequency pool that is divided into MA lists

1, 0

1, 1

1, 2

1, 3

2, 0

2, 1

2, 2

2, 3

0 1 2 3 4 5 6 7

Time Slot

5 14 13 13 21

10 8 16 14 9

11 6 8 8 13

10 13 12 6 9

5 3 16 13 17

13 10 11 18 7

9 7 4 11 12

7 9 11 15 10

Not

availa

ble

Not

availa

ble

Not

availa

ble

C/I matrix

MA, MAIO

50 52 54 56

51 53 55 57MA 2:

MA 1:

DFCA frequency pool

DL

meas

report

Statistical

C/I data

(BIM)

CI

A C/I matrix is calculated based on:

DL measurement report

Statistical C/I data

Active connections in interfering

cells

DFCA chooses the MA, MAIO and

time slot combination that is suitable

for the new connection and minimizes

the impact on all the existing DFCA

connections in the network

Network level C/I is always maximized

DFCA - How Does it Work?

3636

DFCA RRM

Background Interference Matrix

MS measurement reports

UL/DL PC power reductions

Radio channel usage information

Real time information

Radio channel selection

CI estimations

Information used by the DFCA algorithm

3737

BCCH

Regular TRX

DFCA TRX

DFCA TRX

DFCA TRX

DFCA TRX

BTS

No FH or RF FH

No FH

TSL level MA list, MAIO,

TSC settings. HSN=0

SDCCH

SDCCH SDCCH

BCCH GPRS territory

GPRS territory

DFCA hopping mode

3838

0 (off)

1 (standby)

2 (DFCA hopping)

Off

- DFCA not used

Standby

- DFCA not used

- C/I statistics collected, BIMs

created,

interference relations established

DFCA hopping

- DFCA used- Full channel selection freedom =>

maximum performance

STANDBY

DFCA hopping

Switching DFCA on in a BTS

Switch the DFCA mode to "Standby"

- This caused BIMs to be created and interference relations to be established

- Normal non-DFCA operation continues

uninterrupted

- To ensure this the standby more must

last at least 1 BIM update period

Switch the DFCA mode to "DFCA"

- DFCA operation starts on DFCA TRXs- This operation requires BTS locking

Possible Transitions between DFCA modes