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EDGE and GPRS CS-3/CS-4 in Release B8 Alcatel File Reference Date Edition Page EDGE and GPRS CS-3CS-4 in Release B8 v 33DC 21144 0050 TQZZA 03/05/2004 02 1 All ri hts reserve d. Passin on and co in of this document use and commu nicati on of its conte nts not ermitt ed without writte n au thoriz ation. Functional Feature Description EDGE and GPRS CS-3/CS-4 in Release B8 This document covers the following features : 30 06 14: Coding Scheme CS-3 30 06 16: Coding Scheme CS-4 30 07 00: EDGE Coding Schemes 30 07 10: Support of all EDGE Modulation and Coding schemes 30 07 20: EDGE Link adaptation 30 07 30: Incremental Redundancy 30 10 55: Combined GPRS/EDGE resource management 30 14 40: Two incoming A-bis links per BTS

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    EDGE and GPRS CS-3/CS-4 in Release B8

    Alcatel File Reference Date Edition PageEDGE and GPRS CS-3CS-4 in Release B8 v 33DC 21144 0050 TQZZA 03/05/2004 02 1

    All ri hts reserved. Passin on and co in of this document use and communication of its contents not ermitted without written authorization.

    Functional Feature Description

    EDGE and GPRS CS-3/CS-4 in Release B8

    This document covers the following features :

    30 06 14: Coding Scheme CS-3

    30 06 16: Coding Scheme CS-4

    30 07 00: EDGE Coding Schemes30 07 10: Support of all EDGE Modulation and Coding schemes

    30 07 20: EDGE Link adaptation

    30 07 30: Incremental Redundancy

    30 10 55: Combined GPRS/EDGE resource management

    30 14 40: Two incoming A-bis links per BTS

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    Contents

    1. INTRODUCTION ............................................................................................................................. 3

    2. HARDWARE SUPPORT ................................................................................................................. 3

    2.1 Radio equipment performances ............................................................................................4

    2.1.1 EVOLIUM A9100 Base Station :...........................................................................4

    2.1.2 EVOLIUM A9110 micro-BTS : .............................................................................. 6

    2.2 Support of EDGE in a first generation of EVOLIUM BTS..................................................7

    3. ARCHITECTURE PRINCIPLES : .................................................................................................... 7

    3.1 TRX classes concept............................................................................................................. 7

    3.2 2 incoming A-bis links per BTS ............................................................................................. 9

    3.3 Dimensioning rules..............................................................................................................10

    3.3.1 EDGE/GPRS Capacity in the EVOLIUM BTS ....................................................10

    3.3.2 EDGE/GPRS Capacity in the EVOLIUM BSC :.................................................. 103.3.3 EDGE/GPRS Capacity in the EVOLIUM MFS/GPU........................................... 11

    4. EDGE RADIO FEATURES............................................................................................................ 11

    4.1 Modulation and Coding schemes........................................................................................ 11

    4.2 Link adaptation (LA) ............................................................................................................12

    4.3 Incremental Redundancy (IR) ............................................................................................. 13

    4.4 The EDGE Family Concept ................................................................................................. 13

    4.5 Maximum RLC window size supported by Alcatel BSS......................................................14

    5. CS-3 / CS-4 RADIO FEATURES..................................................................................................14

    5.1 Coding schemes.................................................................................................................. 14

    5.2 Coding scheme adaptation ................................................................................................. 14

    5.3 Activation of high GPRS coding schemes........................................................................... 15

    6. RESOURCE MANAGEMENT .......................................................................................................16

    6.1 Principles of resource management.................................................................................... 16

    6.1.1 Ranking of TRX for Circuit / packet allocation........................................................16

    6.1.2 Ranking of TRX in mixed BTS configurations ........................................................16

    6.1.3 Support of EDGE on the BCCH TRX ..................................................................... 17

    6.2 Dynamic allocation of radio resource.................................................................................. 186.3 A-ter resource management ............................................................................................... 20

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    1. INTRODUCTION

    This document deals with the support of EDGE and the highest coding schemes CS-3 and CS-4 of

    GPRS in Alcatel BSS B8.

    The scope of the present document is hereafter detailed:

    Section 2 deals with the Hardware support of both features

    In section 3, architecture principles are presented .

    Section 4 describes EDGE radio features.

    Section 5 focuses on GPRS CS-3 & CS-4 radio features.

    In section 6, Radio Resource Management algorithms are described.

    2. HARDWARE SUPPORT

    The Alcatel EDGE / GPRS (all coding schemes) solution is very interesting as it minimises the initial

    investment. Indeed, its introduction in a GPRS network does not require any new network element.

    As a consequence, the existing GPRS network is widely prepared for EDGE/GPRS CS-3&CS-4 on

    the hardware part as these features are fully compatible with:

    - The A9135 MFS product (PCU function), deployed for GPRS purpose since the B6.2 release,

    - The A9120 BSC.

    - On the BTS side, EDGE is supported on all A9100 EVOLIUM BTS, shipped since 1998,

    and the A9110 micro-BTS Evolution.

    In addition all TRXs shipped since 2001 in the EVOLIUM BTS (EVOLIUM Evolution step 2

    TRX2) are EDGE compatible. No specific TRX is needed with the Alcatel solution.

    2EVOLIUM Evolution step 2 TRX are usually called TRA, while first generation EVOLIUM TRX are called

    TRE.

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    In networks equipped with first generation of EVOLIUMBTS, the support of EDGE is achieved by

    simple plug & play of the EDGE TRX in the cabinet, one TRX per sector being sufficient to provide

    EDGE service.

    GPRS Coding Schemes CS-3 & CS-4 are supported by all A9100 EVOLIUM BTSs (by all

    generations of TRX), by the A9110 micro BTS and by the A9110 micro-BTS Evolution.

    2.1 Radio equipment performances

    The GPRS/ EDGE features are supported in all GSM bands: 900, 1800, 850 and 1900 MHz.

    GSM and GPRS make use of the same GMSK modulation. EDGE makes uses of both GMSK and

    8-PSK modulation.

    Therefore the output power of EDGE TRX is expressed for both modulations.

    2.1.1 EVOLIUM A9100 Base Station :

    The radio performances of the EVOLIUM A9100 Base Station are detailed in 3DC 21083 0001

    TQZZA EVOLIUM A9100 Base Station Product Description and are recalled hereafter :

    TX power of EVOLIUM Evolution step 2 TRX :

    Frequency band TX output power, GMSK TX output power, 8-PSK (EDGE)

    GSM 850 45 W = 46.5 dBm 15 W = 41.8 dBm

    GSM 900 MP 45 W = 46.5 dBm 15 W = 41.8 dBm

    GSM 900 HP 60 W = 47.8 dBm 25 W = 44.0 dBm

    GSM 1800 MP 35 W = 45.4 dBm 12 W = 40.8 dBm

    GSM 1800 HP 60 W = 47.8 dBm 25 W = 44.0 dBm

    GSM 1900 45 W = 46.5 dBm 25 W = 44.0 dBm

    TX power of EVOLIUM Evolution TRX (first generation):

    Frequency band TX output power, GMSK

    GSM 900 35 W = 45.4 dBm

    GSM 1800 35 W = 45.4 dBm

    In GSM 900 and 1800, two types of TRX support EDGE and GPRS: the Medium Power (MP) TRX

    and High Power (HP) TRX. It is up to the Operator to select the TRX type, depending on the

    environment and required radio data throughputs.

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    Why is there a difference between GMSK and 8-PSK output power ?

    8-PSK modulation brings severe constraints on linearity because of its non-constant modulation

    envelope: Power amplifiers can not be used at their maximum power, unlike with GMSK modulation.

    This results in a difference between maximum output power for GMSK and 8-PSK modulations,

    called back-off or sometimes APD (Average Power Decrease). The impact of the back-off is

    relatively small, and only determines the extent of the 8-PSK coverage ,which depends on the radio

    environment as well . In urban areas the impact is smaller than in rural environment.

    RX sensitivity of TRX :

    The RX sensitivity of the TRX allows the delivery at antenna connector of the following values

    independently from the frequency band.

    Reference sensitivity, GMSK :

    - 111 dBm (static and dynamic)

    Reference sensitivity, 8-PSK (EDGE):

    < -111 dBm, (static, MCS-1)

    -108 dBm, (static, MCS-5)

    -99 dBm, (static, MCS-9)

    Why is there a difference in sensitivity between various MCS ?

    3GPP standard (Rec. 05.05) defines various sensitivity levels for various MCS. These different

    sensitivities simply mean that high throughputs (high MCS) require better radio conditions (higher

    signal to noise ratio) than lower data throughputs. The noise factor in the BTS is kept unchanged,

    whatever the coding scheme.

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    2.1.2 EVOLIUM A9110 micro-BTS :

    A9110 micro-BTS Evolution :

    The radio performances of the EVOLIUM A9110-E Micro-BTS are detailed in 3DC 21083 0003

    TQZZA Ed. 07 EVOLIUM A9110 Micro-BTS Product Description and are recalled hereafter :

    Frequency bandNb of antennas

    TX output power, GMSK TX output power, 8-PSK (EDGE)

    GSM 850 & 900

    1 antenna

    3.2 W = 35.1 dBm 2.3 W = 33.6 dBm

    GSM 1800 & 1900

    1 antenna

    3.2 W = 35.1 dBm 1.8 W = 32.6 dBm

    GSM 850 & 900

    2 antennas

    7.0 W = 38.5 dBm 5.0 W = 37.0 dBm

    GSM 1800 & 19002 antennas

    7.0 W = 38.5 dBm 4.0 W = 36.0 dBm

    Reference sensitivity, GMSK :

    - 110 dBm (static and dynamic)

    Reference sensitivity, 8-PSK (EDGE):

    < -110 dBm, (static, MCS-1)

    -1068 dBm, (static, MCS-5)

    -96 dBm, (static, MCS-9)

    A9110 micro-BTS :

    TX output power : GMSK : 2 W or 33 dBm

    In low Loss configuration, GMSK : 4.5 W or 36.5 dBm

    The sensitivity of A9110 BTSs (at the BTS antenna connector) is -107 dBm.

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    2.2 Support of EDGE in a first generation of EVOLIUM BTS

    The Operator simply has to plug as many EDGE TRX (TRA) as EDGE traffic requires.

    EDGE TRX (TRA) may provide with a higher GMSK output power than TRE (indeed, a TRE 900

    offers 35W while a Medium Power TRA offers 45W)

    In case of mixed TRA / TRE configuration, GMSK output power of the EDGE TRX is

    automatically aligned to the power of the TRE of the cell, while the 8-PSK output power is

    kept untouched.

    As a consequence, in a GSM 900 BTS made of a mix of TRE and TRA, the power per TRX will be:

    GMSK 8-PSK

    High Power TRA : 60 W 35 W 25W

    Medium Power TRA : 45 W 35 W 15 W

    3. ARCHITECTURE PRINCIPLES :

    With the introduction of EDGE or GPRS CS-3/CS-4, a new technical issue appears: the throughput

    on the air interface becomes too big and the data traffic corresponding to one radio timeslot cannot

    anymore be transported over one single 16kb/s nibble on the terrestrial (A-bis or A-ter) interface, as

    it was the case with voice or low data rates; it thus becomes mandatory to use higher bandwidth on

    A-bis and A-ter.

    The Alcatel solution consists in using several 16kb/s nibbles on A-bis and A-ter interfaces for the

    transport of one radio timeslot supporting EDGE or GPRS CS-3 / CS-4.

    3.1 TRX classes concept

    To support these high data throughputs, Alcatel has developed a solution, which aims at providing

    the best trade-off between offered radio throughput and impact on the telecom resource

    consumption.

    This solution is based on the concept of multiple classes of TRX, which support more or less data

    throughput. The higher the packet class, the higher the maximum data throughput, the higher the

    impact on BSS Telecom resources.

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    Five TRX classes have been defined :

    TRX class Supported packet coding

    scheme

    Class 1

    Simple TRX

    CS 1,2

    MCS 1,2Class 2

    Double TRX

    CS 1,2,3,4

    MCS 1,2,3,4,5,

    Class 3Triple TRX

    CS 1,2,3,4MCS 1,2,3,4,5,6,

    Class 4Quad TRX

    CS 1,2,3,4MCS 1,2,3,4,5,6,7,8

    Class 5

    Quintuple TRX

    CS 1,2,3,4

    MCS 1,2,3,4,5,6,7,8,9

    All TRX, whatever their class, support also voice traffic.

    The Operator defines per cell the number of TRXs of each class. A class 3 TRX offers up to 30 kb/s

    per radio timeslot, while a class 1 offers up to 11 kb/s. As a consequence, a class 3 TRX consumes

    on the A-bis interface three times more than a class 1 TRX.

    The following figures illustrate the example of a cell with one Class 3 TRX and two Simple TRX - the

    triple TRX is transported over 6 64 kbps timeslots on A-bis.

    1 PDCH = 3 terrestrial nibbles= 1 main nibble, also used for voice

    + 2 additional nibbles,only used for packet

    Radio

    TRX1

    TRX2

    TRX3

    B S

    Cell

    RSL

    TRX1

    TRX2

    TRX3

    Abis

    3 nibbles

    EDGE TRX (triple)

    Main

    nibbles:voice &packet

    additionalnibbles:packet

    only

    The distribution of the TRX classes is a choice let to the Operator according to the expected data

    traffic, the radio conditions and the requested data throughput:

    For example in a rural environment with large cells, the proportion of mobiles which could get benefit

    from the highest Modulation & Coding Schemes is quite low, and the mean data throughput with a

    class 3 TRX is almost as high as the one obtained with a class 5 TRX.

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    3.2 2 incoming A-bis links per BTS

    The EVOLIUM BTS can support up to 12 TRX. For such large configuration, and when filled with

    simple TRXs, a single PCM (2Mb/s E1 link) is already almost full. To support EDGE in such large

    BTS, The EVOLIUMBTS

    is able to transport data on a second E1 link.

    The following table provides non exhaustive examples of the supported configurations, with one or

    two E1 links:

    BTS configuration One A-bis link perBTS

    Possible

    distribution of TRX

    per cell

    Two A-bis links perBTS

    Possible distribution of

    TRX

    per cell

    BTS 12 TRX

    3 cells @ 4 TRX

    4 simple TRX 1 class 5 + 1 doubleTRX + 2 simple TRX

    or

    1 triple + 3 double TRX

    or

    1 triple TRX+ 1 quad

    TRX +2 simple TRX

    BTS 9TRX

    3 cells @ 3 TRX

    1 double + 2 simpleTRX

    2 quad TRX + 1 simpleTRX

    or

    3 triple TRXBTS 6TRX

    3 cells @ 2 TRX

    1 triple + 1 simpleTRX

    2 quad TRX

    BTS 3 TRX

    3 cells @ 1 TRX

    1 class 5 TRX

    The second incoming A-bis link of a BTS is used for packet traffic only. The first link is used for both

    packet and circuit.

    A parameter MAX_EXTRA_TS_PRIMARY defines the number of additional A-bis timeslots

    dedicated to packet on the primary link. This allows the Operator keeping some free timeslots on the

    primary link, for example in anticipation of a further TRX extension of the BTS.

    The following figure depicts examples of A-bis topology. Primary link is directly connected from BSC

    to BTS. Secondary link may terminate a daisy chain.

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    BSC

    BTS

    EVOLIUMBTS

    Primary Abis

    Secondary Abis

    Primary Abis

    Secondary Abis

    EVOLIUMBTS

    BTS

    Examples of A-bis topology

    Note: There is no constraint about the position of the primary and secondary links in the BSC. Theymay be connected to different A-Bis TSUs, and even different BSC racks.

    The support of a second incoming A-bis link requires a SUMA (EVOLIUM Evolution step 1 board).

    For the older Alcatel BTS generations, the replacement of SUMP by SUMA is necessary.

    In case of very high packet traffic, the Operator can use the cell split over two BTS feature. Thanks

    to this feature a cell can be splitted between 2 BTS which can be equipped with two A-bis links

    each, delivering in total 4 A-bis links.

    3.3 Dimensioning rules

    3.3.1 EDGE/GPRS Capacity in the EVOLIUM BTS

    All TRXs of a BTS may support GPRS/EDGE.

    3.3.2 EDGE/GPRS Capacity in the EVOLIUM BSC :

    The global BSC capacity remains unchanged with the introduction of EDGE or GPRS CS-3/CS-4.

    As an example, a BSC configuration 6, is able to handle 3584 (448 * 8) channels @ 16 kb/s,

    whatever the type of traffic conveyed: voice, GPRS or EDGE.

    In terms of number of TRX, the support of one class N TRX consumes in the BSC the equivalent of

    the connectivity consumed by N simple Full Rate TRXs.

    This is similar to the management of Dual Rate TRXs, where one DR TRX is equivalent to 2 FR

    TRX.

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    In the same way, for high data traffic, we will have :

    1 class 2 TRX ~ 2 FR TRX,

    1 class 3 TRX ~ 3 FR TRX

    1 class 4 TRX ~ 4 FR TRX

    1 class 5 TRX ~ 5 FR TRX.

    It has to be noted that Dual Rate can be also supported on a class N TRX ; the support of one dual

    rate class N TRX consumes in the BSC the equivalent of the connectivity consumed by (N+1)

    simple Full Rate TRXs.

    3.3.3 EDGE/GPRS Capacity in the EVOLIUM MFS/GPU

    The GPU is able to handle both GPRS and EDGE traffic.

    The maximum number of simultaneously active PDCH obviously depends on the type of the PDCH,

    as an EDGE MCS-9 PDCH transports much more data than a GPRS CS-2 PDCH.

    The number of GPU to address the packet traffic can be increased up to 6 GPU per BSS.

    More information about Dimensioning Rules can be obtained in Dimensioning Rules for CS and PS

    traffic with BSS Software Release B8 .

    4. EDGE RADIO FEATURES

    4.1 Modulation and Coding schemes

    Nine Modulation and Coding Schemes have been defined by the Standard for E-GPRS.

    Their modulation (either GMSK or 8-PSK) as well as their data throughput, per radio timeslot, are

    depicted in the table below.

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    System Scheme Modulation

    schemes

    Maximum data rate

    per time slot (RLC payload)

    [kbps]

    EGPRS MCS-9 8PSK 59.2MCS-8 8PSK 54.4

    MCS-7 8PSK 44.8

    MCS-6 8PSK 29.6

    MCS-5 8PSK 22.4

    MCS-4 GMSK 17.6

    MCS-3 GMSK 14.8

    MCS-2 GMSK 11.2

    MCS-1 GMSK 8.8

    All EDGE Modulation and Coding schemes (MCS) from MCS1 up to MCS 9 are supported by the

    EVOLIUMBSS in the downlink.

    Standardisation bodies have defined two classes of EDGE MS: a class 1 MS supports 8-PSK MCSs

    in downlink only, while a class 2 MS supports 8-PSK MCSs in both directions. Alcatel BSS supports

    both classes of MS, and provides them with MCS1 up to MCS-4 in uplink.

    4.2 Link adaptation (LA)

    The selection of the most suitable MCS (Link Adaptation) is based on measurements reported by

    the MS for the downlink path and performed by the BTS for the uplink path. New metrics have been

    introduced with EDGE : MEAN_BEP and CV_BEP variables, which represent respectively

    the mean quality of the channel (BEP stands for Bit Error Probability) and its variance. These

    variables are defined in 3GPP Recommendation 05.08.

    The choice of the MCS is based on these two variables. Simulations have been run in order to fill

    look-up tables which define the optimal MCS as a function of (MEAN_BEP; CV_BEP). Several

    tables have been defined, as this function depends on the activation of the feature incremental

    redundancy, on the current modulation, and on the APD (average power decrease, difference

    between 8-PSK and GMSK output power).

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    4.3 Incremental Redundancy (IR)

    In addition to Link Adaptation, the feature Incremental Redundancy3

    is introduced for EGPRS. This

    function was specified by ETSI as optional for base stations and mandatory for mobiles. The Alcatel

    BSS implementation makes use of this feature.

    If a block transmitted by the BTS is not properly decoded in the first instance, the bits are stored in

    the mobile, as soft bits. The same block is repeated with a different puncturing scheme. The

    resulting soft bits of the second (and, if necessary, third) transmission are then combined with the

    previously transmitted block(s). The decoding is then based on several transmissions and not only

    one: this is called joint decoding. This improves the likelihood of ending up with the correct data.

    Even if one block of data is found to be not good, it still can be used to improve the total bit error rate

    of the system.

    In B8 Release, Incremental Redundancy is supported in downlink.

    Thanks to Incremental Redundancy, the link adaptation procedure can be more aggressive : if the

    chosen MCS is a bit too optimistic, the general quality will not be affected, as Incremental

    Redundancy will correct it thanks to joint decoding. However it would be quite dangerous to rely on

    Incremental redundancy only since there may be memory shortage in the MS, and the TBF would

    then be lost. If the MS indicates that IR operation shall be stopped, the Alcatel BSS will switch to a

    mode where IR is not used, which is referred to as type 1 ARQ.

    For optimal radio performances, the Alcatel BSS combines both Incremental Redundancy and Link

    Adaptation.

    4.4 The EDGE Family Concept

    In EDGE the family concept allows to change the modulation and coding scheme within a given

    family during re-transmission. The re-transmission of a block may be done with the same MCS as

    used for the first transmission or with a different more robust MCS.

    The Alcatel equipment is fully compliant with this feature.

    3Incremental Redundancy is also referred to as type 2 ARQ (Automatic Repeat Request) mechanism.

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    There are 3 families of modulation and coding schemes:

    - family A: MCS-3, MCS-6, MCS-8 and MCS-9

    - family B: MCS-2, MCS-5 and MCS-7

    - family C: MCS-1 and MCS-4

    4.5 Maximum RLC window size supported by Alcatel BSS

    Contrary to GPRS, where the maximum RLC window size has a fixed value equal to 64, the EDGE

    maximum window size depends on the multislot characteristic of the TBF. The maximum window

    size implemented in Alcatel BSS is 512, which is the maximum supported by a 4 timeslots capable

    MS, as defined in 3GPP 04.60.

    5. CS-3 / CS-4 RADIO FEATURES

    5.1 Coding schemes

    Four Modulation and Coding Schemes have been defined by the Standard for GPRS.

    Their data throughput, per radio timeslot, is depicted in the table below.

    System Scheme Maximum data rate

    per time slot (RLC payload)

    [kbps]

    GPRS CS-4 20

    CS-3 14.4

    CS-2 12

    CS-1 8

    5.2 Coding scheme adaptation

    A new mechanism is introduced for coding scheme adaptation between CS-3 and CS-4 on the

    downlink path.

    Actually this new mechanism is mandatory, as RXQUAL may be not relevant in CS-4 (3GPP

    recommendations allow the MS to report systematically a value of 7).

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    A new metric is therefore used : it is an estimation of SIR (Signal to Interference Ratio), based on

    measurements reported by the Mobiles . These measurements, called I_level (level of interference),

    are defined in Rec. 05.08. It may happen that I_level is not transmitted by the MS to the BSS ( in

    case of usage of BCCH frequency). In this case, the BSS performs an estimation of the Block Error

    Rate (BLER).

    This metric (SIR or possibly BLER) is used for CS-4 to CS-3 adaptation.

    The adaptation from CS-3 to CS-4 makes usage of both RXQUAL and I_level (resp. BLER).

    RXQUAL is used for coding scheme adaptation between CS-2 and CS-3.

    In the uplink path, RXQUAL is always used for coding scheme adaptation.

    5.3 Activation of high GPRS coding schemes

    The Operator may define, for each cell, the maximum GPRS coding scheme allowed in this cell,

    through an O&M parameter MAX_GPRS_CS. This parameter can take the values CS-2, CS-3 or

    CS-4.

    Indeed, the choice of the Operator will be determined by the radio conditions in the cell and the

    maximum expected throughput.

    As CS-4 is not recommended in case of frequency hopping, the choice of CS-3 in a cell where

    EDGE and frequency hopping are activated bring high GPRS data throughput at no additional cost.

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    6. RESOURCE MANAGEMENT

    6.1 Principles of resource management

    6.1.1 Ranking of TRX for Circuit / packet allocation

    In Radio Resource Management, the first principle is to avoid conflicts between Circuit and Packet :

    TRX with the highest priority for circuit have the lowest priority for packet, and reciprocally. This

    maximizes the chance of having a contiguous set of timeslots available for packet-switched traffic

    while ensuring also that PS traffic is taking the most benefit from the high TRX classes.

    The Operator may use the parameter TPM (TRX Preference Mark) to define his preference about

    Circuit allocation.

    A TRX with a non null TPM is reserved for circuit. The higher the value of TPM, the higher the

    priority for circuit.

    TRXs with TPM equal to 0 may be used for both packet and circuit. They have the lowest priority for

    circuit.

    A specific flag concerning the BCCH TRX has been added PS_PREF_BCCH_TRX which allows to

    direct packet preferably on the BCCH TRX.

    On TRXs where packet is allowed, TRXs are ranked depending on their class : packet is preferably

    allocated on a high class TRX.

    For equivalent TPM and classes, Circuit is allocated first on TRX with high identity, while packet is

    allocated first on TRX with low identity.

    Example :

    TRX identity TPM

    O&Mparameter

    TRX class Voiceallocationranking

    Packetallocationranking

    1 3 1 1 X

    2 2 1 3 X

    3 2 1 2 X4 0 4 6 1

    5 0 1 5 2

    6 0 1 4 3

    6.1.2 Ranking of TRX in mixed BTS configurations

    It may happen that a cell is made of several TRX equipment with different 8-PSK capabilities.

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    For example, in a BTS EVOLIUM, there may be a mix of :

    - EVOLIUM TRX (usually called TRE), supporting all GPRS coding schemes but no EDGE,

    - EVOLIUM Evolution step 2 TRX (TRA) with Medium Power

    - EVOLIUM Evolution step 2 TRX (TRA) with High Power.

    There is an automatic mapping of logical TRX on TRX equipment. The highest class TRX are

    mapped on the highest EDGE capability TRX equipment.

    On the opposite, dual rate is mapped on TRX equipment with lower packet capability.

    The following figure depicts in an example the mapping between hardware and software, leading to

    the best EDGE/GPRS throughput:

    T

    R

    E

    T

    R

    E

    T

    R

    A

    MP

    T

    R

    A

    HP

    Hardware configuration

    Logical cell

    TRX1 (BCCH)

    TRX2 (1 SDCCH)

    TRX3

    TRX4

    Packet VoiceAllocation

    Example : One 4TRX cell, made of 2 TRE, one TRA Medium Power and one TRA High Power

    6.1.3 Support of EDGE on the BCCH TRX

    Support of EDGE on the BCCH TRX is possible. However the activation of EDGE on the BCCH

    TRX should be performed cautiously. 3GPP Rec. 05.08 has defined a constraint on the transmittedpower of BCCH frequency. This frequency shall usually be transmitted at a constant level. A

    tolerance has been introduced with 8-PSK modulation : a fluctuation of up to 2 dB is allowed.

    Depending on the configuration in the BTS, it may happen that the difference between GMSK and 8-

    PSK power on the BCCH TRX is greater than 2dB. In this case, the Operator is informed that the

    back-off is high, and that EDGE should not be activated on the BCCH TRX.

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    6.2 Dynamic allocation of radio resource

    The principles which are applied since the introduction of GPRS in Release B6 are kept for EDGE

    (capacity on demand). They use the allocation of dynamic pools for circuit and for packet,

    depending on the traffic conditions in the cell.

    Inside the packet pool, new mechanisms are introduced for the management of GPRS/EDGE traffic.

    The main principles are the following :

    There are no dedicated (reserved) resource for EDGE traffic: this would be difficult to be tuned by

    the Operator, as the penetration of EDGE handsets will increase progressively.

    Both GPRS and EDGE traffic are directed to the highest class TRX,

    When GPRS and EDGE MS are mixed on the same timeslots, the GPRS traffic is pushed towards

    timeslots without EDGE, to allow a maximum EDGE traffic availability.

    More details on GPRS and EDGE Resource management :

    The packet resource management algorithm aims at maximising data throughputs, both for EDGE

    and GPRS. Therefore the allocation is performed first on the highest class TRX.

    Hereafter are detailed mechanisms which are triggered, when the most suitable timeslots (on the

    highest class TRX) are already busy. They depend on the type of the new TBF (EDGE or GPRS)

    and on the type of the already allocated TBF :

    Already allocated : GPRS or EDGE TBF; new demand : GPRS TBF

    As in previous BSS Releases, this GPRS TBF is allocated on other PDCH, as long as packet

    resources are available. Otherwise the new GPRS TBF shares PDCH with previously allocated TBF,

    until the maximum number of piled TBF is reached.

    Already allocated : GPRS TBF, new demand : EDGE TBF

    The EDGE TBF is allocated in the same way as if the GPRS TBF was not present. The GPRS TBFbecomes a candidate for reallocation, and is pushed through this reallocation towards other radio

    timeslots. This is performed through a new reallocation process, which is triggered for a GPRS UL

    when it shares at least one PDCH with a downlink EDGE TBF. Before the re-allocation is performed,

    the EDGE TBF is limited to GMSK modulation (see the annex for more details about the limitations

    in multiplexing EDGE and GPRS on the same timeslot).

    Already allocated : EDGE TBF, new demand : EDGE TBF

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    In order to take into account the various throughputs offered by the different EDGE capable TRXs,

    specific conditions are defined for TRX selection in case of a new EDGE TBF establishment.

    Consequently, as long as the TRXs with the highest throughput do not support a maximum number

    of EDGE TBF, the other EDGE capable TRXs (of lower class) are not chosen for EDGE allocation.

    As a summary, it is preferred to pile several EDGE TBF on the same high class TRX, rather than

    spreading them over TRX of lower class.

    Parameters have been defined which indicate for each TRX class the number of TBFs beyond

    which it becomes more interesting to serve new EDGE MS on TRX with a lower EGPRS capability.

    As an example, in a cell with a class 5 TRX and a class 2 TRX, two EDGE TBF will be piled upon

    the class 5 TRX before allocating an EDGE TBF on the class 2 TRX.

    TBF Re-allocation

    The mechanisms for re-allocation defined in Alcatel B7 Release for GPRS MS apply also for EDGE

    and GPRS TBF in B8.

    There were three types of re-allocation :

    The immediate resource re-allocation upon packet resources decrease (due to load increase in the

    cell),

    The immediate resource re-allocation upon concurrent TBF establishment,

    The re-allocation of the TBF which is allocated less timeslots than its multislot capability.

    In addition, an EDGE TBF may be re-allocated if it is not established on the highest class TRX . This

    criteria applies for EDGE MS only.

    A GPRS TBF will be re-allocated if it shares timeslots with EDGE, as mentioned in the previous

    paragraph.

    It has to be noted that a re-allocation can not change the type of the TBF, as this has not been

    standardised : an EDGE TBF can only be re-allocated as an EDGE TBF, while a GPRS TBF is re-allocated as a GPRS TBF.

    Maximum number of timeslots allocated to an EDGE or GPRS MS :

    A mobile may have different multislot classes for EDGE and for GPRS. The Alcatel BSS makes use

    of the EDGE multislot class, for allocating an EDGE TBF.

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    There is no difference between GPRS and EDGE in the maximum number of timeslots which can be

    allocated.

    The Alcatel BSS supports the dynamic allocation MAC mode.

    The BSS always tries to allocate the maximum number of timeslots to one MS. The theoretical

    maximum number of consecutive timeslots that can be allocated to a MS by the BSS depends on

    whether the MS is half-duplex or full-duplex :

    full-duplex MS will be allocated up to 5 timeslots for uplink and 5 timeslots for downlink,

    half-duplex MS will be allocated up to 4 timeslots in the downlink path and 2 timeslots in the uplink

    path for TX.

    Maximum number of MS which can share a radio timeslot :

    There is no difference between GPRS and EDGE in number of MS which can share a PDCH.

    Up to 6 TBF on the uplink and 10 TBF on the downlink can be allocated.

    The Operator may reduce the maximum number of TBF in each direction through O&M parameters

    (MAX_UL_TBF_SPDCH & MAX_DL_TBF_SPDCH).

    6.3 A-ter resource management

    As in B7 Release, GCH are allocated dynamically on the A-ter interface. A PDCH allocated on a

    class N TRX uses N GCH on the A-ter interface. This is valid whatever the TBF allocated on this

    PDCH (EDGE or GPRS).

    It may happen that the system encounters A-ter congestion. These situations are managed through

    a new A-ter Congestion Control mechanism.

    The system enters A-ter congestion state when the number of free GCH on the A-ter interface

    becomes lower than a pre-defined threshold.

    In this situation, the number of GCH allocated to PDCH carrying only GPRS is reduced. This is validfor new GPRS establishment and also for on-going GPRS TBF.

    End of Document