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Ed.01 Released 2007/04/23 No remark received. Released.


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TABLE OF CONTENTS

1 SCOPE ..........................................................................................................................................................6

2 FUNCTIONAL DESCRIPTION .....................................................................................................................7

2.1 Overview...............................................................................................................................................7

2.2 Functional entities ...............................................................................................................................7

2.3 BSS entities ..........................................................................................................................................8

2.3.1 GSM requirements ......................................................................................................................8

2.3.2 BSC .............................................................................................................................................9

2.3.3 BTS..............................................................................................................................................9

2.4 Radio link supervision and command...............................................................................................9

2.5 Power control.......................................................................................................................................9

2.6 Functional diagrams..........................................................................................................................10

3 DYNAMIC BEHAVIOUR .............................................................................................................................14

3.1 General behaviour .............................................................................................................................14

3.1.1 Algorithms configuration............................................................................................................14

3.1.2 Algorithms enabling and disabling.............................................................................................14

3.1.3 Algorithms operation..................................................................................................................16

3.1.4 Support of concentric cells ........................................................................................................17

3.1.5 Support of multiband cells .........................................................................................................18

3.1.6 Support of microcellular environment........................................................................................19

3.2 Detailed behaviour.............................................................................................................................20

3.2.1 Radio link supervision and command .......................................................................................20

3.2.2 Power control.............................................................................................................................23

4 INTERFACES DESCRIPTION....................................................................................................................46

4.1 GSM interfaces/Physical interfaces.................................................................................................46

4.2 Internal interfaces..............................................................................................................................46

4.3 Timers list ...........................................................................................................................................46

4.4 Parameters and variables list ...........................................................................................................47

4.4.1 Power control.............................................................................................................................47

4.4.2 Radiolink Supervision................................................................................................................50

4.4.3 MS classmark and power levels in GSM-850, GSM-900, DCS-1800 and DCS-1900..............52

4.4.4 Relationships between parameters...........................................................................................55

5 RELEASE CHANGES.................................................................................................................................57

6 FEATURES .................................................................................................................................................58

7 GLOSSARY ................................................................................................................................................59

8 APPENDIX A...............................................................................................................................................61

9 APPENDIX B...............................................................................................................................................64


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INTERNAL REFERENCED DOCUMENTS

[i1] 3BK 10204 0367 DTZZA - Enhanced power control

REFERENCED DOCUMENTS

3GPP references

[1] 3GPP TS 44.006 MS-BS Interface data link layer specifications

[2] 3GPP TS 45.008 Radio Subsystem Link Control

[3] 3GPP TS 48.058 BSC-BTS Layer 3 specification

Version numbers of the 3GPP Technical Specifications are given in ref [13].

Doctree references

[4] 3BK 11202 0286 DSZZA Normal Assignment

[5] 3BK 11202 0310 DSZZA Classmark handling

[6] 3BK 11202 0293 DSZZA Radio measurements & codec adaptation

[7] 3BK 11202 0296 DSZZA DTX functional specification

[8] 3BK 11202 0289 DSZZA Internal channel change

[9] 3BK 11202 0290 DSZZA External channel change

[10] 3BK 11202 01291 DSZZA Call release

[11] 3BK 11202 0305 DSZZA BSS initialisation of the telecom part

[12] 3BK 11202 0062 DSZZA BSS Telecom parameters

[13] 3BK 11203 0043 DSZZA Alcatel BSS Application document to GSM - General Overview

[14] 3BK 11202 0297 DSZZA Handover Preparation

[15] 3BK 11202 0298 DSZZA System Information management

[16] 3BK 11202 0294 DSZZA Radio measurements data processing

[17] 3BK 11203 0060 DSZZA Radio link and radio resources management

RELATED DOCUMENTS


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Not applicable.

PREFACE

OPEN POINTS / RESTRICTIONS


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1 SCOPE

This document specifies the algorithms to be implemented in this release of the Alcatel BSS for : - MS power control on the uplink path, - BS power control on the downlink path, - Radio link supervision and command.

Note : Within this document, DCS 1900 is assimilated to DCS 1800 operation except where explicitly

specified. Mobiles which operate within DCS1900 are referred as PCS1900 MS.


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2 FUNCTIONAL DESCRIPTION

2.1 Overview

The main objective of the power control, in connection with handover algorithms (see [14]), is to allow a maximum number of MS to operate in the network while maintaining a minimum interference level. The algorithms shall ensure that any mobile is connected with the cell in which the output powers from the MS and the BS are as low as possible (to reduce MS power consumption and interference in the network) while keeping a satisfactory link quality.

When on a sufficient duration the propagation conditions keep worsening, then action must be taken. The first action is to increase the output power levels at the MS or the BS. When the maximum allowed value has been reached, a handover may become necessary.

To reflect this philosophy in macrocells (not in microcellular environment), the algorithm allows for handover on quality and strength reasons only when the last step of power control has been reached (for further details, see [14]). If propagation conditions worsen rapidly when the MS is at low power, the power control algorithm allows to reach quickly the maximum power.

Nevertheless great care must be taken in choosing the relative values of the thresholds for power control and handover as well as the averaging window sizes (smaller window size and higher threshold for power control than for handover). It must be remembered that, although it is desired that the MS transmits with the lowest possible power, it is more important not to lose a call. Thus early triggering for the power control are possible, by choosing, small values for the averaging window sizes and higher comparison thresholds.

For further description about the power control refer to [17].

2.2 Functional entities

The two main functions specified in this document and implemented in the ALCATEL BSS are :

- Radio link supervision and radio link command.

These functions handle the detection of the radio link failure so that calls which fail either from loss of radio

coverage or unacceptable interference are satisfactorily handled by the network. The radio link supervision is

responsible for detection of the loss of the radio link, based on incorrectly received SACCH frames. The

radio link command is responsible for commanding to set the power at maximum level for radio link recovery

or to clear the call when the radio link has failed.

The radio link recovery can be activated or not, depending on a configuration flag. The radio link failure

procedure is always running and clears the call when the radio link has failed.

- Power control.

This function handles the adaptive control of the RF transmit power from the MS and the BS. The RF power

control aims at minimising the co-channel interference and also at reducing the DC power consumption of

the MS. This function is in charge of detecting a need for a power command and then of applying this power

command. Therefore it can be divided into two processes : PC threshold comparison and PC command.

MS and BS power control are operating independently, they can be activated or not, depending on

configuration flags.


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All these functions require directly or indirectly (see below) input parameters provided by the function in

charge of the radio link measurements. This function is described in [6].

Most of the input data required by the power control functions are provided by a function called : Active

channel pre-processing. This function is described in [16]. It processes raw data given by the radio link

measurements (quality and level) through the A-bis interface in compression mode or non compression

mode. The compression mode uses two functions: Radio measurements data compression in the BTS

and Radio measurements data decompression in the BSC. They are described in [16].

Figure 1 depicts in a general way :

- the interconnections between all these functions,

- the implementation of these functions in the ALCATEL BSS. The functions which are specified in this

document are represented in bold type.

Figure 1: Assignment of PC functions in the ALCATEL BSS.

2.3 BSS entities

2.3.1 GSM requirements

Power control According to the 3GPP TS 45.008 ([2]), the implementation of the power control is optional in the BSS. In the ALCATEL BSS, the choice was made to implement power control as stated in [2], the exact strategy of the power control must be determined by the network operator and [2] gives in appendix "an RF power control that may be implemented in the GSM system". The ALCATEL algorithm is described in Section 3.2.2 of this document.

Radio link supervision


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The determination of the radio link failure is based on a counter. According to the 3GPP TS 45.008 ([2]) for the BSS, the criterion for incrementing/decrementing this counter should be based : - either on the error rate on the uplink SACCH, - or on RXLEV/RXQUAL measurements of the MS.

In the ALCATEL BSS, it is based on the number of SACCH frames which cannot be decoded.

It must be stressed that this criterion is related to the first one recommended above but it is not exactly the same. The ALCATEL criterion is in fact the one recommended by the 3GPP TS 45.008 for the MS.

The complete ALCATEL algorithm is described in Section 3.2.1 of this document.

2.3.2 BSC

The BSC supports the following set of functions : - radio link command, - power control : PC threshold comparison and PC command.

2.3.3 BTS

The BTS supports the radio link supervision function.

2.4 Radio link supervision and command

The objective of the radio link supervision is twofold :

- detection of a need of radio link recovery when there is loss of communication with the MS,

- detection of a radio link failure (the radio link recovery has failed).

The detection is based on the counting of decoded and not decoded frames received by the BTS from the

MS on the SACCH (see also Section 2.3.1 for the GSM requirements).

The radio link command handles the radio link recovery and the radio link failure according to the information

provided by the radio link supervision.

This functional split is due to the fact that the BTS and the BSC performs respectively the radio link

supervision and the radio link command.

The radio link recovery consists in increasing the power of the MS and of the BS to their maximum values.

This procedure is not defined by the GSM and is specific to the ALCATEL BSS. The radio link recovery can

be inhibited on a per cell basis by the use of the flag EN_RL_RECOV.

The radio link command function gives an indication to the MS power control function (see Section 2.5) when

a radio link recovery occurs. It is specified in detail in Section 3.2.1

2.5 Power control

As stated in Section 2.2, the power control function is divided into two processes :


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- PC threshold comparison : it handles the detection of a need for a PC command, - PC command : it handles the execution of the power command according to the information sent by the

previous function.

PC threshold comparison

This process detects the need to change the MS or the BS power level. This detection is done by comparison of the averaged values produced by the 'active channel preprocessing' function to thresholds.

When a threshold is reached, the process gives information to the PC command function.

PC command

This process handles independently the MS and BS power commands.

The power commands are sent by the BSC to the BTS in the messages MS POWER CONTROL and BS POWER CONTROL.

The MS power command is forwarded to the MS in the L1 header of the SACCH frame (see [1]).

Power Control inhibition

The MS and BS power commands may be inhibited by the use of two flags: respectively EN_MS_PC and EN_BS_PC. This inhibition is done on a per cell basis.

In addition, the BS power control is inhibited on channels using the BCCH frequency. This inhibition is mandatory for non-hopping channel using the BCCH frequency (for further details see Section 3.2.2.2).

Interaction with radio link recovery mechanism

In case of radio link recovery, the MS power control function is informed by the radio link command function of the ordered power values and the MS PC threshold comparison is resumed immediately (see details in Section 3.2.2).

Interaction with handover preparation

Power control, for both BTS and MS, runs independently in parallel with the handover algorithm. The BSS will automatically maintain call quality with power control. A sufficient margin between power control target (desired received level and quality) and HO thresholds will prevent call termination due to strong shadowing effects.

2.6 Functional diagrams

Figure 2 and Figure 3 are the SADT diagrams of the power control respectively in the BTS and in the BSC.

These diagrams are just a functional description. It does not constraint the implementation.

At the BTS side, only the functional block 'Radio link supervision' is specified in this document. That is why, it is represented in bold type.

At the BSC side, the functional blocks represented in the diagram differ from the ones specified in this document : Power control function and Radio link command function have been replaced by 'Power level tuning' (which stands for Power control threshold comparison) and 'Power level command' (which stands for


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Radio link command and Power control command). This has been done in order to separate in the power control functions, the protocol entity ('Power level command') from the algorithm entity ('Power level tuning').

Radio link

m easurem ents

Radio link

supervis ion

Channel& SACCH

status

BFI SACCH

N_BSTXPWR_MRADIO_LINK_TIMEOUT_BS

EN_RL_RECOV

CONNECTION_FAILURE_INDICATION('radio link failure/recovery')

timing advance parameters

Abis interface

RACH load measurements

RF_RESOURCE_IND

Figure 2: SADT diagram of power control functions in the BTS

Note: in the figure above, RADIO_LINK_TIMEOUT_BS stands for RADIOLINK_TIMEOUT_BS(_AMR)

Active channel

preprocessing

Pow er Level

command

MS pow er level

BS pow er level

averagedmeasurements

for pow er control

P

MS & BSparameters

* PC configuration

parameters* PC thresholds

Pow er Controlparameters (*)

MS/BS_TXPWR_CONF

CONNECTION_FAILURE_INDICATION

MS_POWER_CONTROL

'call release'

BS_POWER_CONTROL

Abis interface

EN_MS_PCEN_BS_PC (*)

BCCH_FREQ

Channel identification

Initial MS & BS pow ers

'radio link recovery'

cellconfigurationparameters

Tuning

Pow er level

Figure 3: SADT diagram of power control functions in the BSC

Flows description

a. BTS (See Figure 2)


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The flows are described at BTS level. Most of the variables in capital letters are defined in Sections 4.3 and 4.4.

Input flows

- BFI_SACCH : bad frame indicator of the SACCH block produced every SACCH multiframe (≈ 480ms).

0 = SACCH frame successfully decoded,

1 = SACCH frame not successfully decoded,

Control flows

- Channel and SACCH status : Two flags indicating whether the TCH and its associated SACCH are active or idle. Note that if the SACCH is not active, the radio link supervision and command is not operating,

- EN_RL_RECOV, N_BSTXPWR_M, RADIOLINK_TIMEOUT_BS, RADIOLINK_TIMEOUT_BS_AMR : see Sections 4.3 and 4.4,

Output flows

- CONNECTION FAILURE INDICATION : refer to [3] for message contents.

- 'radio link failure/recovery' : indicator of the radio link failure or recovery (implementation dependent, see Section 3.2.1),

Mechanisms

- Air and Abis interfaces.

b. BSC (See Figure 3)

The flows are described at BSC level. Most of the variables in capital letters are defined Sections 4.3 and 4.4.

Input flows

- Averaged measurements for power control :

* AV_RXQUAL_UL_PC : MS power control/threshold comparison,

* AV_RXLEV_UL_PC : MS power control/threshold comparison,

* AV_RXQUAL_DL_PC : BS power control/threshold comparison,

* AV_RXLEV_DL_PC : BS power control/threshold comparison.

- MS/BS_TXPWR_CONF : last power level reported by the MS and transmit power currently used by the BS

- CONNECTION FAILURE INDICATION : refer to [3] for message contents.

with indication 'radio link failure/recovery' : indicator of the radio link failure or recovery (implementation dependent, see Section 3.2.1),

Control flows

- Cell configuration parameters : CELL_DIMENSION_TYPE, CELL_COVERAGE_TYPE, CELL_RANGE, CELL_PARTITION_TYPE, ZONE_TYPE, FREQUENCY_RANGE.


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- Initial MS & BS powers

- EN_MS_PC : flag enabling/disabling MS power control,

- EN_BS_PC : flag enabling/disabling BS power control,

- PC thresholds :

For MS power control : L_RXQUAL_UL_P, U_RXQUAL_UL_P,

L_RXLEV_UL_P, U_RXLEV_UL_P,

For BS power control : L_RXQUAL_DL_P, U_RXQUAL_DL_P,

L_RXLEV_DL_P, U_RXLEV_DL_P,

- BCCH_FREQ, channel identification :

BCCH_FREQ : ARFCN of the BCCH frequency in the cell,

Channel identification : channel description and mobile allocation (see definition of CHANNEL_ACTIVATION message in [3]),

- MS and BS parameters :

MS_TXPWR_MAX, BS_TXPWR_MAX, MS_TXPWR_MIN, BS_TXPWR_MIN,

Maximum and minimum MS/BS powers allowed in the cell,

MS_TXPWR_MAX_INNER, Maximum MS power in the inner zone of a concentric or multiband cell.

BS_TXPWR_MAX_INNER, Maximum BS power in the inner zone of a concentric or multiband cell.

- P : MS classmark (maximum MS power) for the concerned frequency band (GSM850, GSM900, DCS1800, DCS1900),

- PC configuration parameters : BS_P_CON_ACK, BS_P_CON_INT,

MS_P_CON_ACK, MS_P_CON_INT,

POW_RED_STEP_SIZE, POW_INC_STEP_SIZE,

MAX_POW_INC : maximum power increase,

MAX_POW_RED : maximum power decrease,

POW_INC_FACTOR : weighting factor for power increase,

POW_RED_FACTOR : weighting factor for power decrease,

Output flows

- MS_POWER_COMMAND : MS power command to be sent on SACCH downlink,

- BS_POWER_COMMAND : BS power command to be sent to the appropriate CUs,

- 'call release' : indication of radio link failure : the call must be released.

Mechanisms

- Air and Abis interfaces.

Internal flows

- MS power level : power level to be applied by the MS,

- BS power level : power command to be applied by the BS,

- 'radio link recovery' : indication of radio link recovery provided by the radio link command function.


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3 DYNAMIC BEHAVIOUR

3.1 General behaviour

3.1.1 Algorithms configuration

At BSS initialisation, the parameters of power control (see control flows of SADT diagrams in Section 2.6) are contained in the BSC database (for further details on BSS initialisation, see [11]).

Concerning the BSS reconfiguration, all the power control parameters can be modified at OMC side and then provided to the concerned BSS (see messages description in]).

For both initialisation and reconfiguration, the algorithms are configured in the BTS by the BSC with the two consecutive messages BS POWER CONTROL and MS POWER CONTROL (see messages description in Section 4). These messages are sent on the Abis radio signalling link (see [3]) on an TRX basis.

Note : In case of TCU restart, the two above messages and the PREPROCESS CONFIGURE message (refer to [16]) are sent to the BTS (i.e. to the TRX(s) connected to the corresponding TCU).

3.1.2 Algorithms enabling and disabling

Enabling

The enabling may result from : - a radio link establishment procedure, - an intracell handover, - an interzone handover, - an intercell handover, - an intrazone handover.

- the BTS enables the algorithms upon receipt of the SABM frame sent by the MS (RR ESTABLISH INDICATION on LapDm),

- the SC enables the algorithms upon receipt of the ESTABLISH INDICATION message from the BTS.

For further details on the call establishment and handover protocol and algorithms, refer respectively to [4], [8], [9] and [14].

The power control is initialised with the following values of MS and BS powers : - radio link establishment procedure (channel activation),

� MS power : MS_TXPWR_MAX, � BS power : BS_TXPWR_MAX,

Note : the reception of the ESTABLISH INDICATION message with the MS classmark triggers the same procedure as for the classmark change (See Section 3.2.2.1.2, parameter set e.).

- normal assignment in the inner zone of a concentric cell


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� MS power : min(Current MS Power, MS_TXPWR_MAX_INNER, P) with P classmark of the MS for the concerned frequency band (GSM850, GSM900, DCS1800 or DCS1900),

� BS power : min(Current BS Power, BS_TXPWR_MAX_INNER),

- normal assignment in the inner zone of a multiband cell, � MS power : min(P , MS_TXPWR_MAX_INNER) with P classmark of the MS for the concerned

frequency band (GSM900 or DCS1800) in the inner zone, � BS power : BS_TXPWR_MAX_INNER,

- intercell handover to the inner zone of a concentric cell � MS power : min(P, MS_TXPWR_MAX_INNER) with P classmark of the MS for the concerned

frequency band (GSM850, GSM900, DCS1800 or DCS1900), � BS power : BS_TXPWR_MAX_INNER,

- intercell handover towards the inner zone of a multiband cell, � MS power : min(P , MS_TXPWR_MAX_INNER) with P classmark of the MS for the concerned


- intercell handover and directed retry, � MS power : min(P , MS_TXPWR_MAX) with P classmark of the MS for the concerned

frequency band (GSM850, GSM900, DCS1800 or DCS1900), � BS power : BS_TXPWR_MAX,

- intracell handover and change over from SDCCH to TCH and TCH to SDCCH (e.g. for SMS continuation after call release),

� MS power : last value used on the previous channel, � BS power : last value used on the previous channel.

In case these values cannot be obtained, the default values are those defined above for the intercell handover.

- interzone handover (from outer zone to inner zone in concentric cells): � MS power : min(Current MS Power, MS_TXPWR_MAX_INNER), � BS power : min(Current BS Power, BS_TXPWR_MAX_INNER),

(see [14] and Appendix A)

- interzone handover (from outer zone to inner zone in multiband cells): � MS power : min(P , MS_TXPWR_MAX_INNER) with P classmark of the MS for the concerned



- interzone handover (from inner zone to outer zone in concentric cells): � MS power : last value used on the previous channel if EN_MS_PC is set to ENABLE

min(P; MS_TXPWR_MAX) if EN_MS_PC is set to DISABLE, � BS power : last value used on the previous channel if EN_BS_PC is set to ENABLE

BS_TXPWR_MAX if EN_BS_PC is set to DISABLE,


- interzone handover (from inner zone to outer zone in multiband cells):


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� MS power : min(P , MS_TXPWR_MAX) with P classmark of the MS for the concerned frequency band (GSM900 or DCS1800) in the outer zone,

� BS power : BS_TXPWR_MAX,


- intrazone handover : same behaviour as for intracell handover (interference).

The MS and BS powers are sent on a channel basis in messages which are defined in Table 4 to Table 9 of appendix A.

Disabling

- the BTS disables the algorithms upon receipt of one of the three following messages : � DEACTIVATE SACCH, � RF CHANNEL RELEASE, � DISC (layer 2 message sent by the MS).

- the BSC disables the algorithms whenever it initiates a channel release on the radio interface.

For further details on the call release procedure, refer to [10].

3.1.3 Algorithms operation

Power Control

The power control is completely handled by the BSC

Every time a new BS (resp. MS) power command is computed, the BSC sends it in the BS POWER

CONTROL (resp. MS POWER CONTROL) message.

The MS and the BS power commands are computed independently every time a need for a BS or a MS

power command is detected by the PC threshold comparison process (see Section 3.2.2).


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GSM Layer 3 message

MS pow er Command(Pn-1)in the L1 SACCH header

MEASUREMENT REPORT

MS BTS BSC

MEASUREMENT RESULT

GSM Layer 3 message (Pn)

1 SACCH multiframe(480 ms)

MS POWER CONTROLNew PC command Pn+1

(1)

MEASUREMENT REPORT

MEASUREMENT RESULT

(2)

BS POWER CONTROL

MEASUREMENT REPORT

MEASUREMENT RESULT

GSM Layer 3 message (Pn+1)

(3)

(1) : a need for MS power command is detected by the BSC.

(2) : a need for BS power command is detected by the BSC.

(3) : the BTS applies the new BS power command.

Note 1 : this figure is only an example which does not constrain the occurrence of transmission of MS/BS POWER CONTROL messages.

Note 2 : GSM layer 3 message on the SACCH is either SYSTEM INFORMATION TYPE 5 or 5bis or 5 ter or SYSTEM INFORMATION TYPE 6 or SAPI 3 message.

Figure 4: Message flows between BTS, BSC and MS for power control.

Radio link supervision and command

The BTS handles the radio link supervision and the BSC the radio link command. See Section 3.2.1.

3.1.4 Support of concentric cells

3.1.4.1 General

A cell is considered to be a concentric cell, if two concentrically arranged zones are realised with different maximum transmission powers. Disjunctive groups of frequency channels are associated to the radio zones. Each radio zone has a set of carrier frequencies (called "zone allocation"). A carrier frequency cannot belong to both radio zones. The cell allocation (list of carrier frequencies used in the cell) is the sum of the two zone allocations : inner and outer.

Frequency channels with lower maximum transmission power are used exclusively to connect those mobile stations which are within the inner zone of the cell according to the measurement values existing in the BSC. Frequency channels with higher maximum transmission power are used to connect those mobile stations which stay within the outer zone of the concentric cell.


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Inner and outer zones are served by a cell with a single BCCH frequency, a cell identity and a BSIC. All control channels (BCCH, CCCH and SDCCH) are associated to the frequency group of the outer zone of the concentric cell.

The BCCH carrier is always transmitted with the maximum transmission power BS_TXPWR_MAX, determined for the outer zone.

A concentric cell is identified in the BSS by setting its attached flag CELL_PARTITION_TYPE to CONCENTRIC .

Each frequency carrier of the cell is allocated to either the inner zone or the outer zone. This allocation is indicated by the flag ZONE_TYPE (OUTER ZONE OR INNER ZONE) on a per frequency carrier basis.

Any SDCCH connection is always allocated to the outer zone (ZONE_TYPE = OUTER ZONE).

3.1.4.2 Power Control in concentric cell

BS Power Control

A concentric cell handles only one class of TRX(s) for both inner zone and outer zone.

Parameters BS_TXPWR_MAX_INNER and BS_TXPWR_MAX determine the maximum BS permissible transmission power levels in the inner and outer zones respectively (with BS_TXPWR_MAX > BS_TXPWR_MAX_INNER ) ).

BS_TXPWR_MIN which determines the minimum permissible BS transmission power level in the cell is the same for the inner and outer zones.

MS Power Control

Parameters MS_TXPWR_MAX_INNER and MS_TXPWR_MAX determines the maximum MS permissible transmission power levels in the inner and outer zones respectively (with MS_TXPWR_MAX > MS_TXPWR_MAX_INNER ).

MS_TXPWR_MIN which determines the minimum permissible transmission power level in the cell is the same for the inner and outer zones.

See Section 3.2.2.1.

3.1.5 Support of multiband cells

3.1.5.1 General

A cell is considered to be a multiband cell, if it is a concentric cell in which the outer zone uses frequencies from the original band and the inner zone uses frequencies from the new band.

Inner zone and outer zone are served by a cell with a single BCCH frequency, cell identity and BSIC. All control channels (BCCH, CCCH and SDCCH) are associated to the frequency group of the multiband cell outer zone. The inner zone includes only TCH channels.

The BCCH carrier is always transmitted with the maximum transmission power BS_TXPWR_MAX, determined for the outer zone.


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A multiband cell is identified in the BSS by setting its FREQUENCY_RANGE to “PGSM-DCS1800” or “EGSM-DCS1800” (CELL_PARTITION_TYPE is forced to CONCENTRIC). In this release, a multiband cell never involves DCS1900 nor GSM850 frequencies.

Each frequency carrier of the cell is allocated to either the inner zone or the outer zone. This allocation is indicated by the flag ZONE_TYPE (OUTER ZONE OR INNER ZONE) on a per frequency carrier basis.

Any SDCCH connection is always allocated to the outer zone (ZONE_TYPE = OUTER ZONE).

3.1.5.2 Power Control in multiband cell

BS Power Control

A multiband cell handles only one class of TRX(s) for both inner zone and outer zone.

Parameters BS_TXPWR_MAX_INNER and BS_TXPWR_MAX determine the maximum BS permissible transmission power levels in the inner zone in the new band and in the outer zone in the original band respectively.

BS_TXPWR_MIN which determines the minimum permissible BS transmission power level in the cell is the same for the inner and outer zones.

MS Power Control

Parameters MS_TXPWR_MAX_INNER and MS_TXPWR_MAX determines the maximum MS permissible transmission power levels in the inner zone in the new band and in the outer zone in the original band respectively.

MS_TXPWR_MIN which determines the minimum permissible transmission power level in the cell is the same for the inner and outer zones.

3.1.6 Support of microcellular environment

Interaction between radio link supervision and handover algorithms

In microcellular environment, new causes for emergency handovers have been defined in order to take into account the fast variation of radio conditions. One of these causes is based on consecutive bad SACCH frames not correctly received (cause 7, for further details, see [14]).

This cause therefore interacts with the radio link supervision which also counts the bad SACCH frames (see Section 3.2.1.1). The parameters of both processes should be set so that a radio link recovery is triggered just before the validation of handover cause 7. This would enable to perform the emergency handover with the maximum power on the BS side, increasing the probability for this handover to be successful.

So, it is proposed to apply the following recommendation to the parameters :

Where : - N_BAD_SACCH : Number of consecutive bad frames not correctly received after which an emergency handover is triggered (see [14])

N_BAD_SACCH = RADIOLINK_TIMEOUT_BS(_AMR) - N_BSTXPWR_M + 1


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- RADIOLINK_TIMEOUT_BS, RADIOLINK_TIMEOUT_BS_AMR and N_BSTXPWR_M : Parameters of radio link supervision (see Section 3.2.1.1).

The parameters are represented in SACCH multiframe units (480 ms on TCH, 471 ms on SDCCH). So, the unit added to the right hand side member of the equation corresponds to 480 ms or 471 ms according to the case..

Since the handover cause 7 must be triggered very quickly as from the degradation of the signal quality, it is also proposed to set the difference between RADIOLINK_TIMEOUT_BS(_AMR) and N_BSTXPWR_M to less than 2 seconds (4 SACCH multitrames) in order to perform the handover early enough.

Figure 5 shows how this recommendation applies.

Radio link recovery Radio link recovery

S

RADIOLINK_

N_BSTXPWR_M

0

(Radio link failure)

N_BAD_SACCH

handover

+ 1

handover

First example : Abrupt loss of signal

The emergency handover is triggered just

after the radio link recovery

Second example : Discontinuous loss of signal

The emergency handover is triggered a longer

time after the radio link recovery but soon

enough towards radio link failure

(counter which is decremented every bad SACCH)

TIMEOUT_BS(_AMR)

(initial value of S)

Time

< 2 seconds

N_BAD_SACCH

1

Figure 5: Examples of the application of the recommendation

3.2 Detailed behaviour

3.2.1 Radio link supervision and command

3.2.1.1 Radio link supervision

The radio link supervision function is performed in the BTS and it uses three parameters given to the BTS in

the TRX configuration data message :

- EN_RL_RECOV : flag enabling/disabling the sending of CONNECTION FAILURE INDICATION by the

BTS when the need for radio link recovery is detected,

- N_BSTXPWR_M : threshold for the radio link recovery,

- RADIOLINK_TIMEOUT_BS : threshold (number of SACCH messages) for the radio link failure of calls

not using an AMR codec.

- RADIOLINK_TIMEOUT_BS_AMR: threshold (number of SACCH messages) for the radio link failure of

calls using an AMR codec


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In addition, the function handles a counter named S.

RADIOLINK_TIMEOUT_BS(_AMR) is the initial and maximum value of S.

For each SACCH not decoded, S is decremented by 1 while for each SACCH decoded, it is incremented by

2. The incrementation or decrementation is performed if the following condition is met:

RADIOLINK_TIMEOUT_BS(_AMR) ≥ counter S ≥ 0.

As soon as the counter S is equal to the threshold N_BSTXPWR_M, the radio link recovery is triggered if

EN_RL_RECOV = ENABLE (see below). Therefore, in the case where the shadowing is so strong that all

SACCH frames are lost, the radio link recovery will be triggered after (RADIOLINK_TIMEOUT_BS(_AMR) -

N_BSTXPWR_M) SACCH periods.

The parameter N_BSTXPWR_M shall be set according this simple behaviour.

If the radio link recovery is not successful, as soon as S reaches 0, the radio link failure procedure is applied

(see below).

As soon as a radiolink failure is detected, the radio link supervision must be started again in the BTS.

Figure 6 is the SDL diagram of the function 'radio link supervision'.

Received events

- Activate supervision : activation of the radiolink supervision from the BTS telecom layer 3,

- SACCH, BFI = 1 : not decoded SACCH frame,

- SACCH, BFI = 0 : decoded SACCH frame,

Note : the BFI flag is internal to the BTS and does not deal with the BFI flag defined by the GSM (see [7]).

- Deactivate supervision : deactivation of the radiolink supervision by the BTS telecom layer 3.

Transmitted events

- Radio link recovery : indication sent to the radio link command function in order to set the BS and MS

powers at maximum. See next section for the different actions achieved.

- Radio link failure : indication sent to the radio link command function in order to release the call.

These events are sent to the BSC in the CONNECTION FAILURE INDICATION message :

- In case of Radio link recovery, the BTS sends only once (to avoid overload of the Abis interface) the

CONNECTION FAILURE INDICATION message to the BSC with cause "set MS/BS-TXPWR-M" (value :

'001 1111', reserved for National use). This action (message formatting) is performed by the GSM layer 3.

- In case of Radio link failure, the BTS sends CONNECTION FAILURE INDICATION message with cause

'Radio link Failure' (value : ‘000 0001’) to the BSC.

3.2.1.2 Radio link command

The radio link command is internal to the BSC and it performs two different actions depending of the

received event : radio link recovery or radio link failure.

Radio link recovery


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The action consists in increasing the power of the MS and of the BTS to its maximum, in a single step, if the

link is failing, i.e. the BTS is not able to decode the SACCH any more for some period of time.

This functionality is performed upon reception of the message CONNECTION FAILURE INDICATION

(cause “set MS/BS-TXPWR-M”) from the BTS. This message can be sent by the BTS only if

EN_RL_RECOV = ENABLE. Upon reception of this message, the radio link command function :

1. sends to the BTS a power increase command up to BS_TXPWR_MAX (BS_TXPWR_MAX_INNER if

the MS is on the inner zone of a concentric or multiband cell) in the message BS POWER

CONTROL.

2. sends to the MS a power increase command up to min(MS_TXPWR_MAX,P) (min

(MS_TXPWR_MAX_INNER,P) if the MS is in the inner zone of a concentric or multiband cell) in the

message MS POWER CONTROL.

When a radio link recovery occurs, the radio link command function gives an indication to the power control

function once the power increase has been commanded.

Note : the BS Power Control process does not interfere with the recovery procedure since the former comes

to a halt when no SACCH multiframe is received. Thus, the BS power control process does not take into

account the radio link recovery event (see SDL diagrams, Section 3.2.2.1.2).

Radio link failure

The task of the radio link command consists in informing the call control function to release the call.

Concentric cell or multiband cell

The power value BS_TXPWR_MAX_INNER is applied in case of radio link recovery for an MS in the inner

zone. The power value BS_TXPWR_MAX is applied in case of radio link recovery for an MS on an outer

zone channel.

The table below summarises the functions performed by the radio link supervision and command

Procedure Counter S value Action taken

Radio Link Recovery

with EN_RL_RECOV = enable

N_BSTXPWR_M The Power control entity orders maximum

allowed MS and BS transmit power (Note 1)

Radio Link Recovery

With EN_RL_RECOV = disable

N_BSTXPWR_M No Action (Note 2)

Radio Link Failure 0 The BTS alerts the BSC that the radio link

has failed (Note 3)

Note : the radio link supervision procedure will function also if SACCH frames are not lost continuously, but

with a longer reaction time.

Note 1: Emergency handovers on level or quality which require maximum power can be triggered as soon as the corresponding power command is confirmed (MS power command for uplink causes, BS power command for downlink causes). If the corresponding power is already at maximum, there is no need to wait for the power command confirmation (see causes 2,3,4,5 in ref [16]).


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Note 2: Radio link failure is triggered if radio conditions remain the same. Emergency handovers on level or quality which require maximum power can not be triggered unless corresponding power (MS power command for uplink causes, BS power command for downlink causes) is already at maximum.

Note 3: The call is cleared by the BSC (See call release scenario N0700 in [10]).

active channel

idle channel

active channel

active channel active channel

active channel

RLF1

RLF1

active channel

Yes

No

Yes

No

idle channel

deactivate

supervisionsupervision

activate

Radio link

Recovery

Radio link

failure

S=N_BSTXPWR_M

S:=Max(S,0)

S:=RADIOLINK_

TIMEOUT_BS

S=0?

S:=S-1

SACCH, BFI=1SACCH, BFI=0

S:=RADIO_LINK

TIMEOUT_BSS:= S+2

S:=min(S,RADIOLINK

TIMEOUT_BS EN_RL_RECOV FALSE

TRUE

Figure 6: SDL diagram - radio link supervision

Note : in the figure above, RADIO_LINK_TIMEOUT_BS stands for RADIOLINK_TIMEOUT_BS(_AMR).

3.2.2 Power control

3.2.2.1 MS power control

3.2.2.1.1 MS PC threshold comparison

This process detects the need to change the MS power level. This detection is done by comparison between the averaged values produced by the active channel pre-processing function and thresholds.

The activation of this process is described in the next section.

A need for a PC command is detected when one of the following conditions is true. Then, the information for

the execution of the PC command is given to the ‘PC command’ process (see next section for the definition

of PC_COMMAND).

The MS power control function can be disabled with a flag EN_MS_PC. This flag is changeable from the

OMC-R.


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The timer T_SDCCH_PC allows to inhibit the MS and BS power control on SDCCH.

This timer is changeable at the OMC-R on a per cell basis.

It is triggered upon receipt of the message ESTABLISH INDICATION after SDCCH activation for immediate

assignment procedure.

As long as the timer runs, the power control is inhibited on SDCCH.

If the timer expires, the power control will be enabled again on SDCCH.

If the timer is running at the sending of the message RF CHANNEL RELEASE, the timer is stopped.

The following conditions are checked only if EN_MS_PC = ENABLE.

Note : The GSM coding of quality is contra-intuitive, since the value 0 codes for the best quality and 7 for

the worst. Thus, the comparison between two quality values must be understood in the opposite way in

terms of quality.

Note : POW_RED_STEP_SIZE is used in two ways : for PC_COMMAND (increase or decrease of MS

power), power control levels are used (see Section 4.4.3); whereas for comparisons, dBm values are

considered.

When MS power control level is 30 during DCS 1900 operation, this will lead to an error of 1dB in the

decrease of the MS power (see equation PC-2).

In order to take into account the frequency hopping in the RXQUAL evaluation the variable

OFFSET_RXQUAL_FH is introduced (for more information refer to [17]).

If on the corresponding channel,

Frequency hopping is applied then OFFSET_RXQUAL_FH = Offset_Hopping_PC

otherwise OFFSET_RXQUAL_FH = 0

Offset_Hopping_PC is a parameter defined on a per cell basis.

Too bad uplink quality cause :

If AV_RXQUAL_UL_PC > L_RXQUAL_UL_P + OFFSET_RXQUAL_FH

(PC-1)

then PC_COMMAND(MS, INC, MS_P_INC dB, <min(MS_TXPWR_MAX, P))

Too good uplink quality cause :

If AV_RXQUAL_UL_PC < U_RXQUAL_UL_P (PC-2)

and AV_RXLEV_UL_PC >= L_RXLEV_UL_P + POW_RED_STEP_SIZE

then PC_COMMAND(MS, RED, MS_P_RED dB, >MS_TXPWR_MIN)


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Too low uplink level cause :

If AV_RXQUAL_UL_PC <= L_RXQUAL_UL_P + OFFSET_RXQUAL_FH

(PC-3)

and AV_RXLEV_UL_PC < L_RXLEV_UL_P

then PC_COMMAND(MS, INC, MS_P_INC dB, <min(MS_TXPWR_MAX, P))

Too high uplink level cause :

If AV_RXQUAL_UL_PC <= L_RXQUAL_UL_P + OFFSET_RXQUAL_FH

(PC-4)

and AV_RXQUAL_UL_PC >= U_RXQUAL_UL_P

and AV_RXLEV_UL_PC > U_RXLEV_UL_P

then PC_COMMAND(MS, RED, MS_P_RED dB, >MS_TXPWR_MIN)

Note : The case where L_RXQUAL_UL_P + OFFSET_RXQUAL_FH > 7 corresponds in the equations to L_RXQUAL_UL_P + OFFSET_RXQUAL_FH = 7.

Note : For GSM phase 1 DCS-1800 mobiles, P_min, the lowest power control level of the MS, depends on

the MS classmark. Thus, P_min value may be higher than MS_TXPWR_MIN (see Section 4.4.3). Therefore,

in DCS 1800, the power decrease commands are performed with clipping at max(P_min,

MS_TXPWR_MIN).

Note : For GSM-900 mobiles, Pmin depends on the phase of the mobile.


In the case of a concentric cell or a multiband cell (CELL_PARTITION_TYPE = CONCENTRIC), the MS

maximum transmission powers in the inner and outer zones are different :

- outer zone : MS_TXPWR_MAX. This value corresponds also to the maximum permissible power in the cell,

- inner zone : MS_TXPWR_MAX_INNER.

For a connection in the inner zone (ZONE_TYPE = INNER ZONE), MS_TXPWR_MAX must be replaced by

MS_TXPWR_MAX_INNER.

For a connection in the inner zone of a multiband cell MS_TXPWR_MIN for GSM Phase 1 mobile must be

replaced by Max(13 dBm; (MS_TXPWR_MIN + 1 dB)) in (PC-2) and (PC-4) to take the difference between

the GSM power (which are odd) and the DCS power (which are even) into account.

For a connection in the inner zone of a multiband cell MS_TXPWR_MIN for GSM Phase 2 GSM-900 and

GSM Phase 2 DCS-1800 mobiles must be replaced by Max(5 dBm; (MS_TXPWR_MIN + 1 dB)) in (PC-2)

and (PC-4) to take the difference between the GSM power (which are odd) and the DCS power (which are

even) into account


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All the increasing (respectively decreasing) step sizes for the MS as well as the BS are referred to as

MS_P_INC (respectively MS_P_RED).

MS_P_INC and MS_P_RED are defined in the next section.

The SDL diagram in Figure 8 gives another view of the PC threshold comparison process.

Note : the SDL diagram applies to both MS and BS PC threshold comparison processes (for BS, see

Section 3.2.2.2.1).

Figure 7 is the state diagram of the MS power control.

The threshold values are not indicative.

RXLEV

RXQUAL

605040302010

0

0

1

2

3

4

5

6

7

PC-1

PC-2

PC-3

PC-4

Power increase

Power decrease

Power decrease

Power increase

No

PC

r

e

q

u

i

r

e

d

U_RXLEV_UL_PL_RXLEV_UL_P

L_RXQUAL_UL_P

U_RXQUAL_UL_P

L_RXLEV_UL_P + POW_RED_STEP_SIZE

Figure 7: State diagram for power control (signal level - signal quality)


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Yes

YesNo

No

No

Power

IncreaseMS/BS_TXPWR

Yes

PowerDecreaseMS/BS_TXPWR

(PC-2/PC-6)

(PC-1/PC-5)

AV_RXQUAL_ UL/DL_PC

< U_RXQUAL _UL/DL_P

AV_RXLEV_UL/DL_PC

< L_RXLEV_UL/DL_P+ POW_RED_STEP_SIZE

AV_RXQUAL_UL/DL_PC

> L_RXQUAL_UL/DL_P +

OFFSET_RXQUAL_FH

(PC-4/PC-8)

Yes

Power

DecreaseMS/BS_TXPWR

Yes

No

No

PowerIncrease

MS/BS_TXPWR

(PC-3/PC-7)

AV_RXLEV_UL/DL_PC

< L_RXLEV_UL/DL_P

AV_RXLEV_UL/DL_PC> U_RXLEV_UL/DL_P

Figure 8: SDL diagram - PC threshold comparison

3.2.2.1.2 MS PC command


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Whenever any of the threshold condition (PC 1) to (PC 4) occurs, a PC command must be sent to the MS

over the air interface.

In order to compute the adaptive power step size, the middle threshold between the upper threshold

U_RXLEV_UL_P and the lower threshold L_RXLEV_UL_P is considered.

This threshold is regarded as the target received level around which the MS should always stay. The

following algorithm tries to maintain and bring the MS power closer to this target threshold. The size of the

power step is limited to MAX_POW_INC for an increase of the MS power and MAX_POW_RED for a

decrease of the MS power (See Figure 10).

When the received level is between the two thresholds U_RXLEV_UL_P and L_RXLEV_UL_P (ie no need to

change the level) and a power control on quality cause is triggered, fixed power step sizes are applied:

POW_INC_STEP_SIZE for power increase and POW_RED_STEP_SIZE for power decrease (See Figure

9).

Two weighting factors POW_INC_FACTOR (for power increase) and POW_RED_FACTOR (for power

decrease) allow to modify the reactivity of the algorithm (the more POW_INC_FACTOR is nearby 1, the

more the reactivity of the algorithm is great and the more power step size is large).

The target received level is TARGET_RXLEV_UL for the uplink path.

TARGET_RXLEV_UL corresponds to the next higher multiple of 1 dB from (U_RXLEV_UL_P +

L_RXLEV_UL_P)/2.

∆ Power applied to MS (dB)

POW_INC_FACTOR <= 1

POW_RED_FACTOR <= 1

L_RXLEV_UL_P TARGET_RXLEV_UL U_RXLEV_UL_PAverage received

level (dBm)

0

Power step size computed according to the average received level

POW_INC_STEP_SIZE

POW_RED_STEP_SIZE

abs(Slope)=

abs(Slope)=

Fixed step size

POW_INC_STEP_SIZE for pow er increase

POW_RED_STEP_SIZE for pow er decrease

MAX_POW_INC

MAX_POW_RED

Problem of quality and too high levelOnly problem of qualityProblem of quality and too low level

abs(Slope) corresponds to the absolute value of the straight line slope

Figure 9: Calculation of the power step size according to the average received level when there is a problem of quality.


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Figure 10: Calculation of the power step size according to the average received level when there is only a problem of level.

The notation which is used in Section 3.2.2.1.1:

PC_COMMAND(MS, INC, MS_P_INC dB, <powermax)

means if MS_TXPWR < powermax

then increase MS_TXPWR by min(MS_P_INC, MAX_POW_INC, powermax-MS_TXPWR)

where MS_P_INC is evaluated by the following algorithm.

if (AV_RXLEV_UL_PC < L_RXLEV_UL_P) (problem of level)

if (AV_RXQUAL_UL_PC ≤ L_RXQUAL_UL_P + OFFSET_RXQUAL_FH) (sufficient quality)


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then MS_P_INC = roundup[ POW_INC_FACTOR* (TARGET_RXLEV_UL - AV_RXLEV_UL_PC)]

else MS_P_INC = roundup[ MAX ( POW_INC_FACTOR * ( TARGET_RXLEV_UL - AV_RXLEV_UL_PC ), POW_INC_STEP_SIZE )]

else (problem of quality)

MS_P_INC = POW_INC_STEP_SIZE

Similarly:

PC_COMMAND(MS, RED, MS_P_RED dB, >powermin)

means if MS_TXPWR > powermin

then decrease MS_TXPWR by min(MS_P_RED, MAX_POW_RED, MS_TXPWR - powermin)

where MS_P_RED is evaluated by the following algorithm.

if (AV_RXLEV_UL_PC > U_RXLEV_UL_P)

if (AV_RXQUAL_UL_PC ≥ U_RXQUAL_UL_P) (sufficient quality)

then MS_P_RED = rounddown[ MAX ( POW_RED_FACTOR * ( AV_RXLEV_UL_PC - TARGET_RXLEV_UL ), 2dB)]

else MS_P_RED = rounddown[ MAX ( POW_RED_FACTOR * ( AV_RXLEV_UL_PC - TARGET_RXLEV_UL ), POW_RED_STEP_SIZE )]

else (good quality)

MS_P_RED = POW_RED_STEP_SIZE

Note: In the equations, MS_TXPWR is the last MS_TXPWR_CONF value reported by the BTS.

Note: ‘roundup’ means ‘round to its next higher multiple of 2 dB’.

‘rounddown’ means ‘round to its next lower multiple of 2 dB’.

Note: In ref[2], the rate of change of MS power is required to be one nominal 2 dB step every 60 msec. Thus

a 30 dB step change should be accomplished in 900 msec. The operator should be warned of this as it may

impact on the choice of settings for MS_P_CON_ACK and MS_P_CON_INT.

Then the ordered value of the MS transmit power, called MS_TXPWR, is sent to the MS as follows:

The BSC sends the message MS POWER CONTROL to the BTS (i.e. to the TRX handling the relevant

channel) which then forwards the PC command to the MS in the Layer 1 header.

The MS applies the PC command and confirms this action by transmitting the applied power value

(MS_TXPWR_CONF) on the uplink SACCH in the layer 1 header.

On SACCH channel, the MS may not send the MEASUREMENT REPORT message (e.g. in case of

transmission of Short Message).


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In this case, the BSC receives a MEASUREMENT RESULT message which does not contain the

MEASUREMENT REPORT. The BSC takes into account the MS_TXPWR_CONF variable.

After any PC command is sent to the MS, some time must be expected before MS_TXPWR_CONF (power

confirmation sent by the MS on the uplink SACCH) can reach the desired value. The timer

MS_P_CON_ACK is triggered after any power modification command to monitor that the desired

transmission power MS_TXPWR is reached. If MS_P_CON_ACK elapses before the expected value of

MS_TXPWR_CONF is received, the power control decision process is resumed immediately with the last

MS_TXPWR_CONF received.

If the expected value of MS_TXPWR_CONF is received before the timer MS_P_CON_ACK is elapsed, the

timer MS_P_CON_ACK is stopped and the timer MS_P_CON_INT is triggered. Then the MS PC threshold

comparison process is resumed with MS_TXPWR_CONF for the same MS as soon as MS_P_CON_INT

expires.

Interaction with radio link command

The MS power control function is informed of a radio link recovery by the radio link command function. Once

the indication is received, the PC command process is resumed immediately:

- timer MS_P_CON_ACK is started (or reset and started if running),

If MS_P_CON_ACK elapses before the expected value of MS_TXPWR_CONF is received, the power

control decision process is resumed immediately with MS_TXPWR_CONF = min(MS_TXPWR_MAX , P).

See details in Figure 11.

Modification of MS PC parameters

1) MS Power control is enabled

The following parameters used by the PC function may change on-line (i.e. when the function is enabled) :

a. RXLEV and RXQUAL thresholds, changeable by the network operator,

b. POW_RED_STEP_SIZE, POW_INC_STEP_SIZE, MAX_POW_INC, MAX_POW_RED,

POW_INC_FACTOR and POW_RED_FACTOR, changeable by the network operator,

c. Timers MS_P_CON_INT and MS_P_CON_ACK, changeable by the network operator,

d. MS_TXPWR_MAX, MS_TXPWR_MIN and MS_TXPWR_MAX_INNER (only in case of concentric cell or

multiband cell configurations), changeable by the network operator,

e. P : MS classmark at the concerned frequency band. This happens each time a new MS RF Power

capability is received and stored by the BSC. Storage cases are described in [5] under the section on MS

Classmark 1,2,3 IE processing.

The on-line change of parameters in sets a., b. and c. shall be taken into account by the PC function when a

new PC command has to be sent to the MS (i.e. after MS_P_CON_INT or MS_P_CON_ACK expiry).


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In this case, the PC threshold comparison does not need to be resumed immediately. The need for a new

PC command will be checked after a maximum time interval of MS_P_CON_INT + MS_P_CON_ACK.

Namely between 0 sec and 60 sec (with timers default values : 4.5 sec).

The on-line change of parameters in sets d. and e. shall be immediately taken into account by the PC

function : the PC command process shall be resumed with the new control parameters without waiting for an

indication from the PC threshold comparison process.

The value of Powermax = min (P, MS_TXPWR_MAX) and , for GSM Phase 1 DCS-1800 and GSM Phase 1

GSM-900 Powermin = max ( P_min, MS_TXPWR_MIN) are recalculated.

The value of MS_TXPWR is then recalculated using the rules :

MS_TXPWR < Powermax and , for DCS 1800 only, MS_TXPWR > Powermin.

If the value of MS_TXPWR changes, then MS_POWER_CONTROL is sent immediately to the BTS. The

timers MS_P_CON_INT and MS_P_CON_ACK are not started in this case, except if they are already

running (see SDL diagrams).

If the MS_TXPWR needs no change, no action is taken.

The behaviour of the MS PC command process is illustrated in Table 1.

This behaviour is required to avoid the case where after the parameters change none of the five PC

conditions is met for a long period of time while the MS is transmitted at a power higher than the new

thresholds.

Condition after

parameters change ->

Parameter change

MS_TXPWR<Powermin Powermin<MS_TXPWR

<Powermax

Powermax<MS_TXPWR

P Power increase

(Ph1 DCS1800 MS only)

No action Power decrease

MS_TXPWR_MIN Power increase No action Not applicable

MS_TXPWR_MAX Not applicable No action Power decrease

Table 1: PC command reaction in case of power parameters change.

with :

- Powermin = either MS_TXPWR_MIN or max(P_min, MS_TXPWR_MIN) for phase 1 DCS1800 MS.

- Powermax = min(MS_TXPWR_MAX, P).

- For a connection in the inner zone of a concentric cell or multiband cell, MS_TXPWR_MAX must be

replaced by MS_TXPWR_MAX_INNER.


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2) MS Power control is disabled

In this case, the MS_TXPWR should always be equal to Powermax = min(P,MS_TXPWR_MAX)

(min(P,MS_TXPWR_MAX_INNER) if the MS is in the inner zone of a concentric cell or multiband cell).

The change of the parameter P (see conditions in ref [5]) or MS_TXPWR_MAX (MS_TXPWR_MAX_INNER

in an inner zone of a concentric cell or multiband cell) shall trigger the recalculation of Powermax. If this

value has changed after recalculation, then MS_TXPWR shall be set to the new value, and

MS_POWER_CONTROL sent to the BTS.

If this value has not changed, no action is done.

The change of other parameters does not trigger a specific action.

On-line disabling of MS Power Control

When the MS Power Control is disabled on-line, MS_POWER_CONTROL is sent with MS_TXPWR_MAX

(MS_TXPWR_MAX_INNER for the inner zone of a concentric cell or multiband cell) for all active

connections.

Figure 11 is the SDL diagram which details the dynamic behaviour of the MS Power Control function.

Note 1 : the radio measurements function introduces a delay of one multiframe between the reception of the

MS_TXPWR_CONF on the air interface and its transmission to the power control function. This delay is due

to the synchronisation of uplink and downlink measurements. For further details, refer to [6].

Note 2 : for the definition of 'powermax' and 'powermin' used in the SDL diagram of the PC command

process, refer to the previous section.

Note 3 : In the SDL diagram 'YY' refers to either 'MS' or 'BS'.

Note 4 : the event "thresholds change" corresponds to the sets a., b., c. described above.

the event "power parameters change" corresponds to the sets d. and e. described above.


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Document produced by GEODE <VERILOG (C)>

Partition 1/4

1.5

DESCRIPTION: PCHO

PROCESS PCHO/Power_Control/PC_command

Page: 1

02-Apr-1996

PC thresholdcomparison

PC command

idle channel

Activate

Channel

active channel

active channel

Thresholdschange

'Store PCparameters'

active channel

Deactivate

Channel

idle channel

Powerparameters

change

'Store powerparameters'

PCmeasurements

radio link

recovery *

Radio link

recovery := TRUE

'Trigger YY P CON

ACK'

wait YY P CON ACK

PC thresholdcomparison

'PC conditionoccurs?'

(Yes)

PC command

'Trigger YY P CON

ACK'

wait YY P CON ACK

(No)

active channel

Recalculate

PowerMax &

YY_TXPWR

YY_TXPWRchanged ?

(Yes)

PC command

(No)

active channel

active channel

EN_YY_PCenabled ?

(No)(Yes)

(Yes)

YY_TXPWR =

Powermax

PC command

EN_YY_PCenabled ?

* Warning : the event 'radio link recovery' does not apply to BS power control (see note Section 3.2.1.2).

Figure 11: SDL diagram - MS and BS PC function Partition 1/4


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Partition 2/4

1.5

DESCRIPTION: PCHO


Page: 1

02-Apr-1996

wait YY P CON ACK

Thresholdschange

wait YY P CON ACK

PC

measurements

wait YY P CON ACK

deactivate

channel

idle channel

Powerparameters

change


radio link

recovery *

radio link recovery

:= TRUE

'reset YY P CONACK'

'Trigger YY P CONACK'

wait YY P CON ACK

(Yes)

PC command

'resetYY P CON

ACK'

(No)

Recalculate

Powermax &

YY_TXPWR

YY_TXPWRchanged ?

wait YY P CON ACK

YY_TXPWR =

Powermax

PC command


wait YY P CON ACK





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Partition 3/4

1.5

DESCRIPTION: PCHO


Page: 1

02-Apr-1996

Wait YY P CON ACK

YY P CON ACKexpiry

'Radio link

recovery=TRUE?'

(Yes)

YY TXPWR CONF :=Powermax

(No)

YY TXPWR :=

YYTXPWR CONF

active channel

YY TXPWR CONF

'YY TXPWR CONF=YYTXPWR?'

(Yes)

Reset YY P CON ACK

Wait YY P CON INT

(No)

Wait YY P CON ACK

Radio link recovery

:= FALSE

Radio link recovery

:= FALSE

Trigger YY P CON INT



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Partition 4/4

1.5

DESCRIPTION: PCHO


Page: 1

02-Apr-1996

Wait YY P CON INT

Deactivatechannel

idle channel

YY P CON INTexpiry

active channel

PC measurements

Wait YY P CON INT

radio linkrecovery *

radio link recovery

:= TRUE

'reset YY P CON INT'


wait YY P CON ACK

Powerparameters

changeThresholds

change

Wait YY P CON INT

(Yes)

PC command


wait YY P CON ACK

(No)

YY_TXPWR =

Powermax

PC command

Recalculate

Powermax &

YY_TXPWR

YY_TXPWRchanged ?

Wait YY P CON INT

'reset YY P CON INT'





3.2.2.2 BS power control

3.2.2.2.1 BS PC threshold comparison

This process detects the need to change the BS power level. This detection is done by comparison of the averaged values produced by the 'active channel preprocessing' function to thresholds.

The activation of this process is described in the next section.

A need for a PC command is detected when one of the following conditions is true. Then, the information for

the execution of the PC command are given to the ‘PC command’ function (see next section for the definition

of PC_COMMAND).

The BS power control process can be disabled with a flag EN_BS_PC. This flag is changeable from the

OMC-R.

The timer T_SDCCH_PC allows to inhibit the MS and BS power control on SDCCH.

This timer is changeable at the OMC-R on a per cell basis.


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It is triggered upon receipt of the message ESTABLISH INDICATION after SDCCH activation for immediate

assignment procedure.

As long as the timer runs, the power control is inhibited on SDCCH.

If the timer expires, the power control will be enabled again on SDCCH.

If the timer is running at the sending of the message RF CHANNEL RELEASE, the timer is stopped.

The following conditions are checked only if EN_BS_PC = ENABLE.

If on the corresponding channel,

Frequency hopping is applied then OFFSET_RXQUAL_FH = Offset_Hopping_PC

otherwise OFFSET_RXQUAL_FH = 0

Offset_Hopping_PC is a parameter defined on a per cell basis.

Too bad downlink quality cause :

If AV_RXQUAL_DL_PC > L_RXQUAL_DL_P + OFFSET_RXQUAL_FH

(PC-5)

then PC_COMMAND(BS, INC, BS_P_INC dB, < BS_TXPWR_MAX)

Too good downlink quality cause :

If AV_RXQUAL_DL_PC < U_RXQUAL_DL_P (PC-6)

and AV_RXLEV_DL_PC >= L_RXLEV_DL_P + POW_RED_STEP_SIZE

then PC_COMMAND(BS, RED, BS_P_RED dB, >BS_TXPWR_MIN)

Too low downlink level cause :

If AV_RXQUAL_DL_PC <= L_RXQUAL_DL_P + OFFSET_RXQUAL_FH

(PC-7)

and AV_RXLEV_DL_PC < L_RXLEV_DL_P

then PC_COMMAND(BS, INC, BS_P_INC dB, < BS_TXPWR_MAX)


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Too high downlink level cause :

If AV_RXQUAL_DL_PC <= L_RXQUAL_DL_P + OFFSET_RXQUAL_FH

(PC-8)

and AV_RXQUAL_DL_PC >= U_RXQUAL_DL_P

and AV_RXLEV_DL_PC > U_RXLEV_DL_P

then PC_COMMAND(BS, RED, BS_P_RED dB, >BS_TXPWR_MIN)

Note : The case where L_RXQUAL_DL_P + OFFSET_RXQUAL_FH > 7 corresponds in the equations to L_RXQUAL_DL_P + OFFSET_RXQUAL_FH = 7.


In the case of a concentric cell or multiband cell (CELL_PARTITION_TYPE = CONCENTRIC), the BS

maximum transmission powers in the inner and outer zones are different :

- outer zone : BS_TXPWR_MAX. This value corresponds also to the maximum permissible power in the cell,

- inner zone : BS_TXPWR_MAX_INNER.

For a connection in the inner zone (ZONE_TYPE = INNER ZONE), BS_TXPWR_MAX must be replaced by

BS_TXPWR_MAX_INNER.

All the increasing (respectively decreasing) step sizes for the BS are referred to as BS_P_INC (respectively

BS_P_RED).

BS_P_INC and BS_P_RED are defined in the next section.

Figure 8 gives another view of the BS PC threshold comparison.

Figure 7 applies also to BS power control with the following correspondences :

- "DL" instead of "UL",

- "PC-5" instead of "PC-1",




3.2.2.2.2 BS PC command


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Whenever any of the threshold condition (PC 5) to (PC 8) occurs, a PC command must be sent to the

responsible equipment (which is called the transmitter) within the BTS.

In order to compute the adaptive power step size, the middle threshold between the upper threshold

U_RXLEV_DL_P and the lower threshold L_RXLEV_DL_P is considered.

This threshold is regarded as the target received level around which the BS should always stay. The

following algorithm tries to maintain and bring the BS power closer to this target threshold. The size of the

power step is limited to MAX_POW_INC for an increase of the BS power and MAX_POW_RED for a

decrease of the BS power (See Figure 16).

When the received level is between the two thresholds U_RXLEV_DL_P and L_RXLEV_DL_P (ie no need to

change the level) and a power control on quality cause is triggered, fixed power step sizes are applied:

POW_INC_STEP_SIZE for power increase and POW_RED_STEP_SIZE for power decrease (See Figure

15).

Two weighting factors POW_INC_FACTOR (for power increase) and POW_RED_FACTOR (for power

decrease) allow to modify the reactivity of the algorithm (the more POW_INC_FACTOR is nearby 1, the

more the reactivity of the algorithm is great and the more power step size is large).

The target received level is TARGET_RXLEV_DL for the downlink path.

TARGET_RXLEV_DL corresponds to the next higher multiple of 1 dB from (U_RXLEV_DL_P +

L_RXLEV_DL_P)/2.

∆ Power applied to BS (dB)

POW_INC_FACTOR <= 1

POW_RED_FACTOR <= 1

L_RXLEV_DL_P TARGET_RXLEV_DL U_RXLEV_DL_PAverage received

level (dBm)

0

Power step size computed according to the average received level

POW_INC_STEP_SIZE

POW_RED_STEP_SIZE

abs(Slope)=

abs(Slope)=

Fixed step size

POW_INC_STEP_SIZE for pow er increase

POW_RED_STEP_SIZE for pow er decrease

MAX_POW_INC

MAX_POW_RED

Problem of quality and too high levelOnly problem of qualityProblem of quality and too low level

abs(Slope) corresponds to the absolute value of the straight line slope


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Figure 15: Calculation of the power step size according to the average received level when there is a problem of quality and level.

Figure 16: Calculation of the power step size according to the average received level when there is a problem of level.

The notation which is used in Section 3.2.2.2.1:

PC_COMMAND(BS, INC, BS_P_INC dB, <powermax)

means if BS_TXPWR < powermax

then increase BS_TXPWR by min(BS_P_INC, MAX_POW_INC, powermax-BS_TXPWR)

where BS_P_INC is evaluated by the following algorithm.

if (AV_RXLEV_DL_PC < L_RXLEV_DL_P) (problem of level)

if (AV_RXQUAL_DL_PC ≤ L_RXQUAL_DL_P + OFFSET_RXQUAL_FH) (good quality)

then BS_P_INC = roundup[ POW_INC_FACTOR* (TARGET_RXLEV_DL - AV_RXLEV_DL_PC) ]


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else BS_P_INC = roundup[ MAX ( POW_INC_FACTOR * ( TARGET_RXLEV_DL - AV_RXLEV_DL_PC ), POW_INC_STEP_SIZE ) ]

else (problem of quality)

BS_P_INC = POW_INC_STEP_SIZE

Similarly:

PC_COMMAND(BS, RED, BS_P_RED dB, >powermin)

means if BS_TXPWR > powermin

then decrease BS_TXPWR by min(BS_P_RED, MAX_POW_RED, BS_TXPWR - powermin)

where BS_P_RED is evaluated by the following algorithm.

if (AV_RXLEV_DL_PC > U_RXLEV_DL_P)

if (AV_RXQUAL_DL_PC ≥ U_RXQUAL_DL_P) (sufficient quality)

then BS_P_RED = rounddown[ MAX ( POW_RED_FACTOR * ( AV_RXLEV_DL_PC - TARGET_RXLEV_DL ), 2dB) ]

else BS_P_RED = rounddown[ MAX ( POW_RED_FACTOR * ( AV_RXLEV_DL_PC - TARGET_RXLEV_DL ), POW_RED_STEP_SIZE ) ]

else (good quality)

BS_P_RED = POW_RED_STEP_SIZE

Note: ‘roundup’ means ‘round to its next higher multiple of 2 dB’.

‘rounddown’ means ‘round to its next lower multiple of 2 dB’.

Note: GSM does not define the rate of change of the BTS power. However, the operators should be warned

of the potentially large step change in the micro-BTS power as it may impact on the choice of settings for

BS_P_CON_ACK and BS_P_CON_INT.

Then, this PC command is sent to the transmitter as follows : The BSC sends the PC command in the

message BS POWER CONTROL to the TRX handling the relevant channel which then forwards it to the

transmitter as described above.

The BSC applies a filtering mechanism of the PC commands similar to the one implemented for the MS (see

Section 3.2.2.1.2). The two timers used are named BS_P_CON_INT and BS_P_CON_ACK.

On-line change of BS PC parameters

The following parameters used by the PC function may change on-line (i.e. when the function is enabled) :


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a. RXLEV and RXQUAL thresholds, changeable by the network operator,

b. POW_RED_STEP_SIZE, POW_INC_STEP_SIZE, MAX_POW_INC, MAX_POW_RED,

POW_INC_FACTOR and POW_RED_FACTOR, changeable by the network operator,

c. Timers BS_P_CON_INT and BS_P_CON_ACK, changeable by the network operator.

d. BS_TXPWR_MAX, BS_TXPWR_MIN and BS_TXPWR_MAX_INNER (only in case of concentric cell or

multiband cell configurations), changeable by the network operator,

The on-line change of parameters in sets a., b. and c. shall be taken into account by the PC function when a

new PC command has to be applied by the BS (i.e. after BS_P_CON_INT or BS_P_CON_ACK expiry).

In this case, the PC threshold comparison does not need to be resumed immediately. The need for a new

PC command will be checked after a maximum time interval of BS_P_CON_INT + BS_P_CON_ACK.

The on-line change of parameters in set d. shall be immediately taken into account by the PC function : the

PC command process shall be resumed with the new control parameters, without waiting for an indication

from the PC threshold comparison process.

This behaviour is required to avoid the case where after the parameters change none of the five PC

conditions is met for a long period of time while the BS is transmitted at a power higher than the new

thresholds.

Note : The PC commands sent in this case are never filtered, neither by the BSC nor the BTS :

- In the BTS, the transmitter which carries the BCCH ignores normally all the BS power commands (see

Section 3.2.2.2.3). However, in this case, the transmitter takes into account the PC commands so that the

change of BS_TXPWR_MAX can be repeated for the power of the BCCH frequency (which is always set to

BS_TXPWR_MAX).

- In the BSC, no filtering shall be applied to these commands : the flag EN_BS_PC shall not be considered in

this case.

On-line disabling of BS Power Control

When the BS Power Control is disabled on-line, BS_TXPWR is set automatically to BS_TXPWR_MAX

(BS_TXPWR_MAX_INNER for the inner zone of a concentric cell or multiband cell) for all active

connections.

The SDL diagrams of Figure 11 depict the dynamic behaviour of respectively the BS Power Control function.

In Figure 11, 'powermin' and 'powermax' must be replaced respectively by 'BS_TXPWR_MIN' and

'BS_TXPWR_MAX'. MS/BS_TXPWR_CONF corresponds to BS_POWER (in the message MEASUREMENT

RESULT, see Section 4.1). MS/BS_P_CON_ACK and MS/BS_P_CON_INT must be replaced respectively

by BS_P_CON_ACK and BS_P_CON_INT.

Figure 8 is the SDL diagram of the threshold comparison process.

Note 1 : It is possible to have a power command followed by a handover command, since both procedures

run independently.


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Note 2 : the event "thresholds change" corresponds to the sets a., b., c. described above.

the event "power parameters change" corresponds to the set d. described above.

3.2.2.2.3 PC inhibition on downlink BCCH

According to 3GPP TS 45.008 Section 7.1 ([2]), the BCCH carrier must be broadcast with a constant power

in the cell. In this release of the ALCATEL BSS, this constant value is set to the maximum power allowed in

the cell that is defined by the parameter BS_TXPWR_MAX. This means that all dedicated channels (TCH,

SDCCH) which are on the BCCH frequency must always be transmitted with the maximum power, i.e. the

BCCH power must not be changed by the BS power control function.

3.2.2.2.3.1 Frequency hopping case

For any channel which has the BCCH frequency in its hopping sequence (MA) the MS is measuring a very

good downlink level each time it hops on the BCCH. To avoid that this results in a too optimistic average, it

is possible to require from the MS not to include the BCCH measurement in the averages. This is achieved

by setting the PWRC flag to 1 in the SYSTEM INFORMATION TYPE 6 messages sent by the BSS on the

SACCH (for further details, refer to [15]). Note that the PWRC O&M parameter is also sent to the MS in the

SYSTEM INFORMATION TYPE 3 messages on the BCCH.

If the channel is hopping only on the BCCH frequency (after a transmitter failure), it is considered as a non-

hopping channel and it is concerned by the non frequency hopping case.

3.2.2.2.3.2 Non frequency hopping case

In this case, the BSC inhibits the BS power control on all the channels which use the BCCH carrier.

The entity performing the BS power control in the BSC gets all the information concerning a new channel

and decides whether to activate the BS power control for this channel. The power control must be inhibited

when the frequency used by the new channel is the same as the frequency used for the BCCH in the BTS

(cell) in which the channel is activated.

Note : if the BCCH transmitter gets a BS power command, this power command is ignored. This however is

not sufficient due to the following effect : as the BTS and BSC does not receive acknowledgement from the

transmitter of the discarding of the power command, the power used by the transmitter and the power the

BTS and BSC "believe" is used may be different. This would cause problems with the power budget

calculation and the channel activation in an intracell channel change. That's why the power commands must

be filtered at the BS power function level.

When the BSC sends a CHANNEL_ACTIVATION message to the BTS for an intracell channel change

(intracell handover, SDCCH->TCH assignment or TCH->SDCCH), the BS power value to be included must

be the following (refer also to annex A) :

- if the new channel is not on the BCCH frequency, the BS power value is the actual value the BSC gets from

the BTS in the PHYSICAL CONTEXT CONFIRM message, except for the inter zone handover in the case of

concentric cell where the BS power value must be set to min (Current Power, BS_TXPWR_MAX_INNER),

for the inter zone handover (outer->inner) in a multiband cell where the BS power value must be set to

BS_TXPWR_MAX_INNER and for the inter zone handover (inner -> outer) in a multiband cell where the BS

power value must be set to BS_TXPWR_MAX.


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- if the new channel is on the BCCH frequency, the BS power value must be set to BS_TXPWR_MAX.

3.2.2.3 Support of power control with fixed power step sizes

The algorithm described in the previous sections can be tuned so as to apply fixed power step sizes for power increase or power decrease whatever the cause.

The size chosen for the fixed power steps is set with the parameters POW_INC_STEP_SIZE and POW_RED_STEP_SIZE.

All the increasing (respectively decreasing) step sizes for the MS as well as the BS will be the same. They will be referred to as POW_INC_STEP_SIZE (respectively POW_RED_STEP_SIZE).

The parameters are set in the following way:

POW_INC_FACTOR=1

POW_RED_FACTOR=1

MAX_POW_INC=POW_INC_STEP_SIZE

MAX_POW_RED=POW_RED_STEP_SIZE

There are some limitations to this tuning: - The computation of fixed power step size is ensured only if the gap between U_RXLEV_UL_P and

L_RXLEV_UL_P (and between U_RXLEV_DL_P and L_RXLEV_DL_P for the downlink path) is at least of 10 dB.

- In GSM900/GSM850 or DCS1800/DCS1900, if POW_INC_STEP_SIZE is set to a higher value than 6 dB, this tuning will not ensure the computation of fixed power step size anymore.


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4 INTERFACES DESCRIPTION

4.1 GSM interfaces/Physical interfaces

The messages used by the power control are carried on the Abis interface only.

In the following, the description of the messages is done on an operation mode basis.

Note : Below are given the general structure of the Abis messages required by the power control algorithms. In particular, the fields for which it is stated in the 3GPP TS 48.058 ([3]) "the coding of this field requires further elaboration" are described. For the coding of the others information elements, refer to [3].

From BSC to BTS :

* MS POWER CONTROL

MSG_DISC

MSG_TYPE

CHAN_NUMBER_IEID

CHANNEL_NUMBER

Element Identifier

R{3} / MS_TXPWR

* BS POWER CONTROL

MSG_DISC

MSG_TYPE

CHAN_NUMBER_IEID

CHANNEL_NUMBER

Element Identifier

R{3} / BS_TXPWR

4.2 Internal interfaces

The information exchanged between power control functions is described in Sections 2 and 4.4.

4.3 Timers list

NAME RANGE BIN.RANGE BITS

BS_P_CON_ACK (0 to 31)x960 ms 0:31 8

Timer for acknowledgement of 0=0 ms


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Change on BS Transmit Power 31=31x960ms

BS_P_CON_INT (0 to 31)x960 ms 0:31 8

Timer to allow for time 0=0 ms

after a BS PC command 31=31x960ms

MS_P_CON_ACK (0 to 31)x960 ms 0:31 8

Timer for acknowledgement of 0=0 ms

Change on MS Transmit Power 31=31x960ms

MS_P_CON_INT (0 to 31)x960 ms 0:31 8

Timer to allow for time 0=0 ms

after a MS PC command 31=31x960ms

T_SDCCH_PC (0 to 31)x960 ms 0:31 8

Timer to inhibit power control on SDCCH 0=0 ms

31=31x960ms

4.4 Parameters and variables list

This section provides a list of all the variables and parameters used in the algorithms and thus encountered

in the text. For each entry will be found :

- its name,

- its meaning,

- its physical range,

- its binary range,

- the number of bits into which it is encoded.

The variables and parameters are ranked in the alphabetical order.

4.4.1 Power control

NAME RANGE BIN. RANGE BITS

AV_RXLEV_DL_PC -110 to -47 dBm 0:63 8

Average Receive Downlink level of step size 1 dBm 0=-110

Serving cell (Power Control) 63=-47

AV_RXLEV_UL_PC -110 to -47 dBm 0:63 8


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Average Receive Uplink step size 1 dBm 0=-110

of serving cell (Power Control) 63=-47

AV_RXQUAL_DL_PC 0 to 7 0:7 coded with 8

Average Receive Downlink Quality of step size 0.1 a step size of 0.1

serving cell (Power Control)

AV_RXQUAL_UL_PC 0 to 7 0:7 coded with a 8

Average Receive Uplink Quality of step size 0.1 step size of 0.1

serving cell (Power Control)

BA_IND_SACCH 0 or 1 0 : no change 1

Indicator of the change of the BA allocation (toggle indicator)

1 : change

BS_P_INC 0 to 16 dB 0:8 8

Power step size in case of BS power increase step size 2 dB 0=0

8=16

BS_P_RED 0 to 16 dB 0:8 8

Power step size in case of BS power decrease step size 2 dB 0=0

8=16

BS_TXPWR max - 30 dB 0:15 8

Transmit Power at BS to min 0 dB 0=0 dB

step size 2 dB

(relative value)

15= -30 dB

BS_TXPWR_MAX max - 30 dB 0:15 8

Maximum Transmit Power to min 0 dB 0=0 dB

at BS step size 2 dB

(relative value)

15= -30 dB

BS_TXPWR_MAX_INNER max - 30 dB 0:15 8

Maximum BS Transmit Power to min 0 dB 0=0 dB

Permissible in the inner zone of the concentric or

multiband cell.

step size 2 dB

(relative value)

15= -30 dB

BS_TXPWR_MIN max - 30 dB 0:15 8

Minimum Transmit Power to min dB 0=0 dB

at BS step size 2 dB

(relative value)

15= -30 dB

EN_BS_PC enable or disable 0 : disable 1

Flag enabling/disabling BS PC 1 : enable

EN_MS_PC enable or disable 0 : disable 1

Flag enabling/disabling MS PC 1 : enable

L_RXLEV_DL_P -110 to -47 dBm 0:63 8

Minimum Receive Level step size 1 dBm 0=-110

for Downlink (Power Control) 63=-47


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L_RXLEV_UL_P -110 to -47 dBm 0:63 8

Minimum Receive Level step size 1 dBm 0=-110

for Uplink (Power Control) 63=-47

L_RXQUAL_DL_P 0 to 7 0:7 coded with a 8

Minimum Receive Quality step size 0.1 step size of 0.1

for Downlink (Power Control)

L_RXQUAL_UL_P 0 to 7 0:7 coded with a 8

Minimum Receive Quality step size 0.1 step size of 0.1

for Uplink (Power Control)

MAX_POW_INC 0 to 16 dB 1:8 8

Maximum power increase step size 2 dBm 1=2

8=16

MAX_POW_RED 0 to 16 dB 1:8 8

Maximum power decrease step size 2 dBm 1=2

8=16

MS_P_INC 0 to 16 dB 0:8 8

Power step size in case of MS power increase step size 2 dB 0=0

8=16

MS_P_RED 0 to 16 dB 0:8 8

Power step size in case of MS power decrease step size 2 dB 0=0

8=16

MS_TXPWR See Table 3 of See Table 3 8

Transmit Power at MS Section 4.4.3 of Section 4.4.3

MS_TXPWR_MAX

Maximum Transmit Power at MS

See Table 3 of

Section 4.4.3

See Table 3

of Section 4.4.3

8

MS_TXPWR_MAX_INNER

Maximum MS transmit power permissible in the inner

zone of the concentric or multiband cell

See Table 3 of

Section 4.4.3

See Table 3

of Section 4.4.3

8

MS_TXPWR_MIN

Minimum Transmit Power at MS

See Table 3 of

Section 4.4.3

See Table 3

of Section 4.4.3

8

OFFSET_RXQUAL_FH 0 to 7 stepsize 0.1 0:70 8

Offset added to quality thresholds 0=0

70=7

Offset_Hopping_PC 0 to 7 stepsize 0.1 0:70 8

Offset which considers frequency hopping in power

control quality causes

0=0

70=7

P

Maximum Transmit Power for class of MS

for the concerned frequency band

See Table 2 in

Section 4.4.3

See Table 2 in

Section 4.4.3

8


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POW_INC_FACTOR 0 to 1 step 0.1 8

Weighting factor for power increase

POW_RED_FACTOR 0 to 1 step 0.1 8

Weighting factor for power decrease

POW_RED_STEP_SIZE 2 , 4 dB 1:2 8

Decrease Step Size for 1=2 dB

Quality Level Control at MS and BS 2=4 dB

POW_INC_STEP_SIZE 8

Increase Step Size for 2.,4,...14 dB 1:7

Quality Level Control at 1=2 dB

MS and BS 2=4 dB...7 14 dB

TARGET_RXLEV_DL -110 to -47 dBm 0:63 8

Target threshold for BS power control step size 1 dBm 0=-110

63=-47

TARGET_RXLEV_UL -110 to -47 dBm 0:63 8

Target threshold for MS power control step size 1 dBm 0=-110

63=-47

U_RXLEV_DL_P -110 to -47 dBm 0:63 8

Maximum Receive Level step size 1 dBm 0=-110

for Downlink (Power Control) 63=-47

U_RXLEV_UL_P -110 to -47 dBm 0:63 8

Maximum Receive Level step size 1 dBm 0=-110

for Uplink (Power Control) 63=-47

U_RXQUAL_DL_P 0 to 7 0:7 coded with a 8

Maximum Receive Quality step size 0.1 step size of 0.1

for Downlink (Power Control)

U_RXQUAL_UL_P 0 to 7 0:7 coded with a 8

Maximum Receive Quality step size 0.1 step size of 0.1

for Uplink (Power Control)

4.4.2 Radiolink Supervision

NAME RANGE BIN. RANGE BITS


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EN_RL_RECOV

flag enabling/disabling radio link recovery controlling

the emission of CONNECTION FAILURE

INDICATION by the BTS in case of radiolink recovery

0 or 1 0 : disable

1 : enable

1

N_BSTXPWR_M 0 to 127 0:127 8

Threshold for the counter S

to trigger an increase of

SACCH multiframes 0=0 SACCH

multiframe

BS and MS at the maximum power

127=127 SACCH

multiframes

RADIOLINK_TIMEOUT_BS 1 to 128 1:128 8

Threshold for the counter S to declare a radiolink

failure at the BTS for non AMR calls


multiframe

128=128 SACCH

multiframes

RADIOLINK_TIMEOUT_BS_AMR 1 to 128 1:128 8

Threshold for the counter S to declare a radiolink

failure at the BTS for AMR calls


multiframe

128=128 SACCH

multiframes

Note : These 4 parameters are given through the OMU (e.g. at initialisation time).

S 0 to 128 0:128 8

counter decremented for each bad SACCH blocks

(messages) at the BTS, used to trigger either radiolink

recovery or radiolink timeout


multiframe

128=128 SACCH

multiframes


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4.4.3 MS classmark and power levels in GSM-850, GSM-900, DCS-1800 and DCS-1900

There are differences between the GSM-900 and the DCS-1800 concerning the MS power class and the number of power control level values : GSM phase 1

Power

Class

P

GSM-900

DCS-1800

Maximum peak

power

Binary value Maximum peak

power

Binary value

1 20W (43 dBm) 0 1 W (30 dBm) 0

2 8 W (39 dBm) 2 0.25 W (24 dBm) 3

3 5 W (37 dBm) 3

4 2 W (33 dBm) 5

5 0.8 W (29 dBm) 7

GSM phase 2

Power

Class

P

GSM-850 and GSM-900

DCS-1800

Maximum peak

power

Binary value Maximum peak

power

Binary value

1 -- -- 1 W (30 dBm) 0

2 8 W (39 dBm) 2 0.25 W (24 dBm) 3

3 5 W (37 dBm) 3 4 W (36 dBm) Not supported

4 2 W (33 dBm) 5 (note 2)

5 0.8 W (29 dBm) 7

DCS-1900

Power

Class

P

DCS 1900

Maximum peak

power

Binary value

1 1 W (30dBm) 0

2 0.25 W (24dBm) 3

3 2 W (33dBm) 30

Table 2: MS classmark in GSM-850, GSM-900, DCS-1800 and DCS 1900


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GSM phase 1

Power Control

level

GSM-900

DCS-1800

Peak power Binary value Peak power Binary value

0 43 dBm 0 30 dBm 0

1 41 dBm 1 28 dBm 1

2 39 dBm 2 26 dBm 2

3 37 dBm 3 24 dBm 3

4 35 dBm 4 22 dBm 4

5 33 dBm 5 20 dBm 5

6 31 dBm 6 18 dBm 6

7 29 dBm 7 16 dBm 7

8 27 dBm 8 14 dBm 8

9 25 dBm 9 12 dBm 9

10 23 dBm 10 10 dBm 10

11 21 dBm 11 8 dBm 11 (note 1)

12 19 dBm 12 6 dBm 12 (note 1)

13 17 dBm 13 4 dBm 13 (note 1)

14 15 dBm 14

15 13 dBm 15


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GSM phase 2

Power Control

level

GSM-850 and GSM-900

DCS-1800

Peak power Binary value Peak power Binary value

0 - - 30 dBm 0

1 - - 28 dBm 1

2 39 dBm 2 26 dBm 2

3 37 dBm 3 24 dBm 3

4 35 dBm 4 22 dBm 4

5 33 dBm 5 20 dBm 5

6 31 dBm 6 18 dBm 6

7 29 dBm 7 16 dBm 7

8 27 dBm 8 14 dBm 8

9 25 dBm 9 12 dBm 9

10 23 dBm 10 10 dBm 10

11 21 dBm 11 8 dBm 11

12 19 dBm 12 6 dBm 12

13 17 dBm 13 4 dBm 13

14 15 dBm 14 2 dBm 14

15 13 dBm 15 0 dBm 15

16 11 dBm 16

17 9 dBm 17

18 7 dBm 18

19 5 dBm 19

DCS-1900

Power Control

level

DCS-1900

Peak power

30 33 dBm

31 32 dBm

0 30 dBm

1 28 dBm

2 26 dBm

3 24 dBm

4 22 dBm

5 20 dBm

6 18 dBm

7 16 dBm

8 14 dBm

9 12 dBm

10 10 dBm

11 8 dBm

12 6 dBm

13 4 dBm

14 2 dBm

15 0 dBm

Table 3: MS power control levels in GSM-850, GSM-900, DCS-1800 and DCS 1900.


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Note 1 : These power control levels are not authorised for MS DCS-1800 class 1. They are only used by the MS class 2. Note 2: For DCS-1800 GSM phase 1, Pmin(class1) = 10 dBm and Pmin(class2) = 4 dBm.

For DCS-1800 GSM phase 2, Pmin(all classes) = 0 dBm. For DCS-1800 GSM phase 2, maximum value of P is 30 dBm. Thus, the MS class 3 are handled like MS class 1 (for further details, refer to [5]).

For GSM-900 GSM phase 1, Pmin(all classes) = 13 dBm.

For GSM-850 and GSM-900 GSM phase 2, Pmin(all classes) = 5 dBm.

For DCS-1900 GSM phase 2, Pmin(all classes) = 0 dBm.

4.4.4 Relationships between parameters

The document "BSS telecom parameters" ([12]) specifies also the rules to be fulfilled by the PC & HO

parameters. The present specification is the reference document in case of discrepancy.

The default values for parameters are indicated in the document [12].

Each relationship is either mandatory or recommended.

The recommended relationships are not checked by an automatic procedure.

Remarks : - For thresholds relative to quality measurements, the GSM coding is assumed, as already stated, it is contra-intuitive.

- The relationships between power control parameters and handover preparation parameters can be found in [14].

Mandatory relationships

� L_RXQUAL_DL_P > U_RXQUAL_DL_P. � L_RXQUAL_UL_P > U_RXQUAL_UL_P. � U_RXLEV_DL_P > L_RXLEV_DL_P. � U_RXLEV_UL_P > L_RXLEV_UL_P. � BS_TXPWR_MAX >= BS_TXPWR_MIN � MS_TXPWR_MAX >= MS_TXPWR_MIN

� N_BSTXPWR_M < RADIOLINK_TIMEOUT_BS

� N_BSTXPWR_M < RADIOLINK_TIMEOUT_BS_AMR

� MS_TXPWR_MAX_INNER >= MS_TXPWR_MIN

This relationship is only used for concentric or multiband cell (CELL_PARTITION_TYPE = CONCENTRIC).

� BS_TXPWR_MAX_INNER >= BS_TXPWR_MIN

This relationship is only used for concentric or multiband cell (CELL_PARTITION_TYPE = CONCENTRIC).

Recommended relationships � U_RXLEV_UL_P >= L_RXLEV_UL_P + 10 dB � U_RXLEV_DL_P >= L_RXLEV_DL_P + 10 dB


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� POW_INC_STEP_SIZE > POW_RED_STEP_SIZE

� POW_RED_FACTOR ≤ POW_INC_FACTOR

� SDCCH_COUNTER ≤ T_SDCCH_PC


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5 RELEASE CHANGES Release 5 to 6

The changes from Release 5 to Release 6 are based on the following documents :

TFD 3.19 : HSCSD

TFD : 11.33 Enhanced Power Control

Approved Release 5 CRQ 10617

Release 6 to 7

The changes from release 6 to release 7 are based on the following document: - SFD 4.81 “Indoor Layer Support” - SFD: Support of the GSM-850 band Release 9 to 10

− RFD 55/202100 Dedicated radio link timer for AMR


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6 FEATURES Release 6 : Feature list

11.33: Enhanced power control Release 7 : Feature list

SFD: Indoor Layer Support

SFD: Support of the GSM-850 band Release 10 : Feature list

RFD 55/202100 Dedicated radio link timer for AMR


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7 GLOSSARY

ARFCN Absolute Radio Frequency Channel Number

BA BCCH-allocation

BFI Bad Frame Indication

BS Base Station

BSC Base Station Controller

BSIC Base Station Identity Code

BSS Base Station Subsystem

BTS Base Transceiver Station

dB deciBel

DC Direct Current

DR Directed Retry

DTX Discontinuous transmission

DCS-1800 Digital Cellular system using the uplink frequency band [1710,...,1785] MHz and the downlink frequency band [1805,...,1880] MHz

DCS-1900 Digital Cellular system using the uplink frequency band [1850,...,1910] MHz and the downlink frequency band [1930,...,1990] MHz

FH Frequency Hopping

GSM-850 Global System for Mobile communications using the uplink frequency band [824,...,849] MHz and the downlink frequency band [869,...,894] MHz

GSM-900 Global System for Mobile communications using the uplink frequency band [880,...,915] MHz and the downlink frequency band [925,...,960] MHz (including the G1 band)

HO Handover

LOS Line Of Sight

MSC Mobile Switching Centre

MS Mobile Station

O&M Operation and Maintenance

OMC Operation and Maintenance Centre

PBGT Power Budget


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PC Power Control

SACCH Slow associated control channel

SADT Structured Analysis and Design Technics

SDCCH Slow dedicated control channel

SDL Structured Definition Language

TCH Traffic channel

TCH/FS Traffic channel Full Speech

TCU Terminal Control Unit

TOA Time Of Arrival

TRX Transmitter Receiver

TS Technical Specification

Note : all the parameters and variables used in the algorithms are thoroughly described in the dedicated

sections and in Section 4.


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8 APPENDIX A

Transfer of MS and BS power level on Abis interface

1) MS_POWER

GSM has defined a number of parameters dealing with the power of the Mobile Station. They are :

- MS_TXPWR_MAX_CCH : maximum at access.

- MS_TXPWR_MAX : maximum authorised in the cell.

- MS_TXPWR_MAX_INNER : maximum authorised in the inner zone of a cell. It is an ALCATEL BSS

parameter not defined by GSM.

- MS_TXPWR : current or ordered level.

- MS_TXPWR_CONF : last reported power level.

- P : maximum level for the mobile class.

In some messages appear the word Power Level, which has several possible meaning, depending on the

context. This appendix is meant to clarify all this, as far as Power Control is concerned.

The tables below summarise the various situations in which the power information is initially transferred to

the BTS and MS. The tables do not take into account the case where the physical context procedure failed.

For more information about the initial values of MS power and BS power, ref. to [8] and [4].

Message Immediate

Assignment

Normal assignment &Change

over

Intracell HO & intrazon

HO

Intercell HO

CHANNEL_

ACTIVATION

MS_TXPWR_MAX min(P,Current power)

Current power min(P,

MS_TXPWR_MA

X)

ASSIGNMENT_

COMMAND

message not

used

min(P,Current power)

Current power message not

used

HANDOVER_

COMMAND

message not

used

message not

used

message not used min(P,

MS_TXPWR_MAX

Table 4: Initial values of the MS power level.


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Message Handover from

inner zone to

outer zone, MS

power control

enabled

Handover from

inner zone to outer

zone, MS power

control disabled

Handover from outer

zone to inner zone, MS

power control enabled

or disabled

Normal

Assignment in

inner zone

Intercell

handover to

the inner zone

of a

concentric cell

CHANNEL_

ACTIVATIO

N

Current Power min(P,MS_TXPWR

_MAX)

min(Current Power,

MS_TXPWR_MAX_IN

NER)

min(Current

Power,

MS_TXPWR_M

AX_INNER,P)

min(P,MS_T

XPWR_MAX

_INNER)

ASSIGNME

NT_

COMMAND

Current Power min(P,MS_TXPWR

_MAX)

min(Current Power,

MS_TXPWR_MAX_IN

NER)

min(Current

Power,

MS_TXPWR_M

AX_INNER,P)

min(P,MS_T

XPWR_MAX

_INNER)

Table 5: Initial values of the MS power level in concentric cell environments.

Message Handover from inner

zone to outer zone, MS


or disabled

Handover from outer

zone to inner zone, MS


or disabled

Normal Assignment

in inner zone

Intercell handover to

the inner zone of a

multiband cell

CHANNEL_

ACTIVATION

min(P,MS_TXPWR_M

AX)

min(P,

MS_TXPWR_MAX_IN

NER)

min(MS_TXPWR_M

AX_INNER,P)

min(P,MS_TXPWR_

MAX_INNER)

ASSIGNMENT_

COMMAND

min(P,MS_TXPWR_M

AX)

min(P,

MS_TXPWR_MAX_IN

NER)

min(MS_TXPWR_M

AX_INNER,P)

min(P,MS_TXPWR_

MAX_INNER)

Table 6: Initial values of the MS power level in multiband cell environments.

For external handover, the classmark information is received in HANDOVER REQUEST. For internal

handover, the classmark information is stored in the BSC from the value received in the ESTABLISH

INDICATION from the BTS (however the value is transparent to the BTS).

2) BS POWER

The table below summarises the various situations in which the BS power information is initially transferred

to the BTS and MS.

Message Immediate

Assignment

Intracell HO & Normal

assignment & intrazone HO

& Change over

Intercell HO

CHANNEL_

ACTIVATION

BS_TXPWR_MAX Current power (1) BS_TXPWR_MAX

Table 7: Initial values of BS power level.


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Message Handover from

inner zone to outer

zone, BS power

control enabled

Handover from

inner zone to outer

zone, BS power

control disabled

Handover from outer

zone to inner zone,

BS power control

enabled or disabled

Normal

Assignment in

inner zone

Intercell

handover in

the inner zone

of a

concentric cell

CHANNEL_

ACTIVATION

Current Power (1) BS_TXPWR_MAX min(Current Power,

BS_TXPWR_MAX_I

NNER)

min(Current

Power,

BS_TXPWR_MA

X_INNER)

BS_TXPWR_

MAX_INNER

Table 8: Initial values of BS power level in concentric cell environments

Message Handover from inner

zone to outer zone, BS

power control enabled or

disabled

Handover from outer

zone to inner zone, BS


or disabled

Normal Assignment

in inner zone

Intercell handover in the

inner zone of a multiband

cell

CHANNEL_

ACTIVATION

BS_TXPWR_MAX BS_TXPWR_MAX_IN

NER

BS_TXPWR_MAX_I

NNER

BS_TXPWR_MAX_INNE

R

Table 9: Initial values of BS power level in multiband cell environments

(1) If in the non-hopping case a channel using the BCCH-frequency is activated, the power value contained

in the CHANNEL_ACTIVATION message must be BS_TXPWR_MAX.


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9 APPENDIX B

Mapping of the adaptive step size computation to the power causes

Another way of considering the computation of adaptive step sizes is to make a link between the power causes which trigger the power command and the formula used in this case to compute the adaptive step size.

This mapping allows the simplification of the formula because there is a priority between power causes on quality and on level : for example, if a power command is raised on “Too low level”, it means that there is no problem of quality, otherwise the power command would be raised on “Too bad quality”.

This mapping gives the following tables:

Power Cause Formula to compute adaptive step sizes for the MS

Too bad quality IF (AV_RXLEV_UL_PC < L_RXLEV_UL_P)

MS_P_INC = roundup[MAX(POW_INC_FACTOR*(TARGET_RXLEV_UL -AV_RXLEV_UL_PC), POW_INC_STEP_SIZE)]

ELSE MS_P_INC = POW_INC_STEP_SIZE

Too good quality IF (AV_RXLEV_UL_PC > U_RXLEV_UL_P)

MS_P_RED = rounddown[MAX( POW_RED_FACTOR*(AV_RXLEV_UL_PC - TARGET_RXLEV_UL),POW_RED_STEP_SIZE)]

ELSE MS_P_RED = POW_RED_STEP_SIZE

Too low level MS_P_INC = roundup[POW_INC_FACTOR*(TARGET_RXLEV_UL - AV_RXLEV_UL_PC)]

Too high level MS_P_RED = rounddown[MAX(POW_RED_FACTOR* (AV_RXLEV_UL_PC - TARGET_RXLEV_UL), 2dB)]

Power Cause Formula to compute adaptive step sizes for the BS

Too bad quality IF (AV_RXLEV_DL_PC < L_RXLEV_DL_P)

BS_P_INC = roundup[MAX(POW_INC_FACTOR*(TARGET_RXLEV_DL -AV_RXLEV_DL_PC), POW_INC_STEP_SIZE)]

ELSE BS_P_INC = POW_INC_STEP_SIZE

Too good quality IF (AV_RXLEV_DL_PC > U_RXLEV_DL_P)

BS_P_RED = rounddown[MAX( POW_RED_FACTOR*(AV_RXLEV_DL_PC -


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TARGET_RXLEV_DL),POW_RED_STEP_SIZE)]

ELSE BS_P_RED = POW_RED_STEP_SIZE

Too low level BS_P_INC = roundup[POW_INC_FACTOR*(TARGET_RXLEV_DL - AV_RXLEV_DL_PC)]

Too high level BS_P_RED = rounddown[MAX(POW_RED_FACTOR* (AV_RXLEV_DL_PC - TARGET_RXLEV_DL), 2dB)]

END OF DOCUMENT

Power Control and Radio Link Supervision

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