enhanced transmission resources management ed3

7/29/2019 Enhanced Transmission Resources Management Ed3

1/40

Enhanced transmission ressource management

Table of Contents

1 Introduction ............................................................................................. 22 Basic concepts .......................................................................................... 3

2.1 Abis resources .................................................................................... 32.2 EGCH segmentation and framing in B8 .............................................. 4

3 M-EGCH statistical multiplexing ............................................................... 53.1 M-EGCH concept ................................................................................. 53.2 M-EGCH statistical multiplexing algorithm ......................................... 7

4 Dynamic Abis allocation ........................................................................... 94.1 Pool of Abis nibbles concept ............................................................... 94.2 Abis/Ater resources manager .......................................................... 10

4.2.1 Abis resource manager .............................................................. 104.2.2 Ater resource manager .............................................................. 10

5 Enhanced transmission resources management .................................... 145.1 Management of M-EGCH link ............................................................ 14

5.1.1 Size of the M-EGCH link .............................................................. 145.1.2 Usual Procedures on the M-EGCH link ........................................ 235.1.3 Specific Procedures on the M-EGCH link ..................................... 25

5.2 Activation of GCH resources during resource allocation/ reallocation ............................................................................................................... 29

5.2.1 Allocation policy ......................................................................... 295.2.2 Radio resource allocation/reallocation algorithm ...................... 31

6 List of Open Points .................................................................................. 387 New and modified parameters ............................................................... 398 Removed parameters ............................................................................. 409 Migration rules ........................................................................................ 4010 References ........................................................................................... 40


2/40

1 Introduction

This document describes the Enhanced Transmission ResourceManagement that includes the following features developed in release B9 :

the M-EGCH Statistical Multiplexing: This feature provides a solution to share the Ater and Abis nibblesbetween the radio timeslots of a TRX so that the transmissionresources left available by a PDCH can be reused by other PDCHs aslong as those PDCHs belong to the same TRX. Thus, it allowsreducing the waste of transmission bandwidth on the Ater and Abisinterfaces.

the Dynamic Abis allocation: This feature enables to dynamically allocate Abis nibbles among thedifferent TREs used for PS traffic in a given BTS. Compared to B8, itallows a higher average Abis bandwidth per PDCH, the BSCcapacity in terms of TREs is increased, and in some BTSconfigurations it may avoid to deploy a second Abis link.

the Enhanced transmission resource management:On top of the Dynamic Abis allocation and the MEGCH statisticalmultiplexing features, a global transmission resource (Abis + Ater)management is defined.

All these features are automatically enabled in B9 release for Evolium BTS. The first two are not applied for G2 BTS as for these BTS, the B7limitations apply (as they can use only CS1/CS2). However, the enhancedtransmission resource management applies and it is adapted to G2 BTS.

The algorithms related to these features are all implemented at MFS level.

The present document described these algorithms with the followingrestrictions :

1. Only the algorithms applied to Evolium BTS are described.2. There is no description of the internal algorithms linked to the

balancing of GCHs between cells/TRXs (this is mainly related toIntra-cell GCH preemption and Inter-cell GCH preemptionmechanisms).

3. The feature QoS handling is not considered in this document.


3/40

2 Basic concepts

2.1 Abis resources

On the Abis interface between BSC and BTS, two types of 16k nibbles canbe considered: The basic Abis nibbles which are Abis nibbles used to carry CS or PS

traffic. They are always on a primary Abis PCM link of the BTS. The extra Abis nibbles which are Abis nibbles used to carry PS traffic

only. They can be on a primary or a secondary Abis PCM link of the BTS.

Similarly, the 64k basic Abis TSs (composed of 4 consecutive basic Abisnibbles) and 64k extra Abis TSs (composed of 4 consecutive extra Abis

nibbles) are defined.

There are two 64k basic Abis TSs statically associated to each TRE in theBTS. That implies that, on MFS side, each TRXs timeslot is staticallyassociated to a basic Abis nibble (the TRE-TRX mapping is done in theBSC).

As for the extra TSs, their number is fixed by the OMC. In B8 release, theextra Abis TSs are statically associated to a TRX (as the basic Abis TSs).

Moreover, in B8 release , the mapping of the basic and extra Abisnibbles to a radio timeslot is static and generalizes to all thetimeslots of one TRX , even if the timeslot is used for voice traffic (in thiscase the extra Abis nibbles are unused) or for GSM signalling (BCCHchannel, static SDCCH channels on which extra Abis nibbles are neverused and basic Abis nibbles are most of time not used) or for GPRSsignalling (Master PDCH does not apply extra Abis nibbles).

Such situation can be depicted through the following example :

X X X X X X Extra nibbles on the Abis interface(number of nibbles per RTS = TRX class-1)

X X Basic nibbles on the Abis interface

B S M M P P T T TRX configuration on the air interface

Legend:B: BCCH, S: static SDCCH, M: MPDCH, T: TCH, P: PDCH, X : Abis nibble wasted in B8, : Abis nibbleused in B8.

So, there is a noticeable waste of Abis resources that is removed in B9release through the dynamic Abis allocation feature.


4/40

2.2 EGCH segmentation and framing in B8

In B8 release, the GCH layer is adapted in order to be able to carry the

traffic of one radio timeslot on multiple 16k channels (from 1 to 5) on Abisand Ater interface. Fixed size of RLC block segments are used oneach 16k channel . Thus, for a radio timeslot supported by a class n TRX,RLC blocks will be encoded on n GCH.

The figure below describes the EGCH segmentation of an RLC block and itsframing over the GCHs allocated to the PDCH of the TRX. In B8, the TRXclass defines the number of GCH nibbles available per radio timeslot forthis TRX.

In the following example, there are 4 GCHs established for that EGCH link,but the RLC PDU is too short to generate 4 segments in the DBN=x period.

Therefore the EGCH layer adds a NODATA PDU that will be transmitted atthe same time as the useful segments.

In the periods DBN=x+1 and DBN=x+2 , the RLC PDU length hasincreased , and therefore the NODATA control PDU is no longer used butthe sub-GCH 20-ms periods are filled with padding bits.


5/40

But, here again, release B8 leads to a waste of GCH resources. Such wasteis removed in B9 release through the M-EGCH statistical multiplexing

feature

3 M-EGCH statistical multiplexing

3.1 M-EGCH concept

In order to carry PS-related data, a bi-directional link needs to beestablished between the MFS and the BTS (through the BSC).

In B9 release, that link is called M-EGCH link (M standing forMultiplexed) for Evolium BTS . Contrary to B8 release where an EGCHlink was defined per radio TS, an M-EGCH link is defined per TRX .

An M-EGCH link is composed of a set of 16k GCH channels . EachGCH channel is supported by an Ater nibble (between MFS and BSC) andan Abis nibble (between BSC and BTS), the two nibbles being crossconnected together in the BSC. Once the GCH channels of an M-EGCH linkare activated, the MFS and the BTS can exchange PS-related data, and the

BSC becomes transparent. The M-EGCH link of a given TRX is necessary:

EGCH Segmentation NO DATA

NO DATA

320 bits 320 bits 320 bits

320 bits

EGCH header (next segments)

EGCH header (first segment)

Synchronisation header CRC + Tail bits

RLC PDU for DBN=x

Padding

NO DATA

20 ms 20 ms 20 ms

sub-GCH1

sub-GCH2

sub-GCH3

sub-GCH4

DBN=x DBN=x+1 DBN=x+2

RLCheader

EGCH Framing


6/40

- to carry TBF traffic and PACCH signalling when TBFs are established onsome PDCHs of that TRX,

- to carry signalling messages when MPDCHs are defined on that TRX,- to carry UL signalling messages after one-UL-block allocation (UL two-

phase access),

- to carry some BTS-MFS signalling. The sharing (or multiplexing) of the bandwidth of a given M-EGCH betweenthe different PS-related blocks to be transmitted corresponds to the M-EGCH statistical multiplexing feature.

The way of adjusting dynamically the M-EGCH bandwidth (i.e. its numberof 16k GCH channels) corresponds to the Enhanced transmissionresources management feature. Both the Ater and Abis resources areconcerned by those dynamic adjustments.

Contrary to B8 release where the bandwidth of a given EGCH channel

could only be decreased (through Ater congestion control), the M-EGCHlink bandwidth can be either decreased or increased in B9 release.

Through the M-EGCH concept, a TRX is said to be established if there is an M-EGCH link associated to that TRX . The notion of TRXestablishment replaces the B8 notion of SPDCH or MPDCHestablishment.

Inside an M-EGCH link, a GCH channel corresponds to a 16k logical linkbetween MFS and BTS using one Abis nibble and one Ater nibble switchedtogether in the BSC. In order to carry PS traffic, a GCH channel isactivated inside the M-EGCH link. When no longer used, theGCH channel is released inside the M-EGCH link.


7/40

3.2 M-EGCH statistical multiplexing algorithm

The Statistical Multiplexing feature allows the reduction of the

consumption of GCH resources (especially on Ater) by multiplexing theblocks of all the PDCHs of a TRX on a single transmission link: the M-EGCHlink, instead of using a single EGCH link per PDCH.

Indeed, in B9 release, a GCH frame can be constituted of severalsegments belonging to different RLC blocks , as now all the RLCblocks sent on several PDCHs of a TRX are multiplexed on the same M-EGCH link. Padding bits are added to the RLC blocks segments to fill theGCH frame to 320 bits.

The following figures summarises those definitions:

As shown in this figure, a fixed 320-bit frame can have up to 2 or 3 RLCblock segments of variable size. So, a RLC block coming from one PDCHcan be spread over several 320-bit frames as in B8 release but in B9release, after its last segment, the RLC block of another PDCH can bestarted (if the remaining transmission capacity is sufficient).

Such facility increases automatically the GCH capacity :

For example, lets consider that N GCHs with a 16kbit/s capacity each areassigned to a TRX according to the algorithms in B8 and in B9.

A G4 TRE with up to 8 PDCHs and MCS9 would need N=8*5=40 GCHs inB8 whereas in B9, N would be 36 (because less than 5 GCHs are neededper MCS-9 block), through the M-EGCH whose size could vary over thetime (the criteria will be precised later in the document).

For a G3 TRE, with up to 8 PDCHs and CS-4, N would be 8*2 =16 in B8release whereas in B9, N would be 13 (because less than 2 GCHs neededper CS4 block), through the M-EGCH whose size could vary over the time(the criteria will be precised later in the document).

320 bit frame 320 bit frame

20 ms period alsocalled block period

a GCH

a segment of one RLC datablock

another segment of

another RLC data block


8/40

Moreover, the M-EGCH Statistical Multiplexing solution allows thedynamic sharing of a given number of GCHs at a TRX level . Thisimplies the following facilities :

The transmission resource left available by one TBF mapped on a

set of timeslots and being idle (in establishment or delayed releasephase) is automatically reused by another TBF mapped on the sametimeslots or on another set of timeslots (as long as those sets of timeslot are on the same TRX ). This is a first level of trunking gainthat can be obtained thanks to the statistical characteristics of packet traffic, which is often very bursty. This is very important fortraffic types like WAP, GMM signaling traffic, requiring little dataexchange.

An increase of MCS does not lead to an increase of transmissionlinks since this increase can be compensated by a decrease of MCSexperienced by another TBF. This is a second level of trunking gainthat can be obtained thanks to the statistical characteristics of theradio channel.

The GCH left while the RLC control blocks are transferred can alsobe re-used by other TBFs : Indeed control blocks are encoded withCS1 (or MCS1) and they do not use an entire GCH 320-bit frame.


9/40

4 Dynamic Abis allocation

4.1 Pool of Abis nibbles concept

In B9 release, the concept of pool of Abis nibbles is introduced :A pool of Abis nibbles is a set of basic and extra Abis nibbleswhich can be dynamically allocated among the M-EGCHs of someTREs.

So, the pool of Abis nibbles is at a higher level of sharing than the M-EGCH(whose sharing is at TRX level).

In fact, the level of sharing of the pool of Abis nibbles depends on the type

of Abis resources :

The basic Abis nibbles mapped to a PDCH currently available for PStraffic or mapped to a MPDCH can be shared at the cell (BTSsector) level . In case of cell split over 2 BTSs, the share can be doneonly for one of the two BTS sectors of the cell. This means that onlyone of the BTS sector of the cell will be PS capable (new O&Mconstraint in B9 release).

The bonus basic Abis nibbles currently used for BCCH or staticSDCCH channels can be shared at the BTS level . It means that theycan be shared between the different sectors of the same BTS cabinet.

The extra Abis nibbles can be shared at the BTS level . It meansthat they can be shared between the different sectors of the same BTScabinet.

The pool of Abis nibbles is built from : The basic Abis nibbles (bonus nibbles or not) that are still statically

mapped on each radio timeslot (i.e. there are two 64k Abis Timeslotreserved per TRE)

The extra Abis nibbles that are determined according to a number of 64k Extra Timeslots defined for each BTS through the O&M parameterN_EXTRA_ABIS_TS. This parameter replaces the transmission pooltypes and the cell parameter NB_EXTRA_ABIS_TS used in B8.

The way the basic and extra Abis nibbles are allocated within the pool of Abis nibbles is defined in the enhanced transmission resourcesmanagement.


10/40

4.2 Abis/Ater resources manager

4.2.1 Abis resource manager

The Abis resource manager manages the Abis nibble pool of a given BTS.

The main role of this Abis resource manager is to select Abisresource for each GCH to be activated within an M-EGCH link :

When activating new GCHs in the M-EGCH link of a given TRX, the freeAbis nibbles (i.e. the Abis nibbles which are currently not associated to aGCH, nor switched to an Ater nibble in the BSC) shall be selected with thefollowing priorities:

Abis nibble selection for a new GCHestablishment1. Basic Abis nibbles mapped totimeslots supporting MPDCH (case of MPDCH establishment only)2. Free Basic Abis nibbles mapped totimeslots currently available for PStraffic and within the non preemptablePS zone of the cell3. Free Extra Abis nibbles and freebonus basic Abis nibbles4. Free Basic Abis nibbles mapped to

timeslots currently available for PStraffic and out of the non preemptablePS zone of the cell

When activating some new GCHs with free (bonus or not) basic Abisnibbles, the basic Abis nibbles are selected as follows:

Priority is given to the basic Abis nibbles mapped to the timeslots of the TRXs with the highest PS priority (i.e. from the first PS-capable TRXof the cell to the last PS-capable TRX of the cell in the sorted TRX listprovided by the BSC),

On a given TRX, priority is given to the basic Abis nibbles mapped tothe RTSs having the lowest index.

Besides the Abis resource manager, there is also the Ater resourcemanager that improves the management of Ater resources. This resourcemanager is located in the GPU and it deals with the selection,maintenance and handling of the Ater resources.

4.2.2 Ater resource manager


11/40

First, the Ater resource manager sets some priority criteria for theselection of Ater resource when GCHs have to be activated. Theseselection criteria are related to the gathering of used Ater resources onthe same DSP/Atermux link.Here are the main criteria applied for selection Ater nibbles on a given

GPU :i) Select preferentially free Ater nibbles belonging to at least one

64k Ater TS already switched to the DSP (the DSP onto which the TRX, for which GCHs/PDCHs are being established, is mapped).

ii) If possible, select Ater nibbles belonging to the same Atermuxlink. This criterion tends to minimize the time to connect the Aternibble and the Abis nibble in the BSC.

iii) On the same Atermux link, select preferentially the Ater nibblesbelonging to the same 64k Ater timeslot. This criterion tends to

reduce the blocking cases where some Ater resources are free inone DSP while another DSP requires additional Ater resourcesand all the 64k Ater TSs of the GPU are currently mapped on theDSPs.

iv) On the same Atermux 64k timeslot, select preferentially the Aternibbles corresponding to the lowest nibble identity. This criterionaims at having a deterministic rule at the end of the Ater nibbleselection process.

It should be noticed that the nibbles do not have to be contiguous.

Secondly, the Ater resource manager handles the congestion situationthrough a 0&M parameter called GCH_RED_FACTOR_High_Ater_Usage.

This is done as follows :

The percentage of Ater nibbles which are currently used in the GPU isequal to:

Percentage_Of_Used_Ater_Nibbles_GPU =

100s_GPUter_NibbleTotal_Nb_A

shment_GPUor_EstabliReserved_Fivated_Or_ Nb_GCH_Act ,

with:- Nb_GCH_Activated_Or_Reserved_For_Establishment_GPU is thenumber of GCHs activated or reserved for establishment (thisconcerns the GCHs which are not yet activated in the M-EGCH linkof the TRX, but which will be activated in the future) on the TRXsmanaged by the GPU

- Total_Nb_Ater_Nibbles_GPU is the total number of Ater nibbleswhich are usable within the GPU, according to O&M configurations.

This variable is compared to the O&M parameter Ater_Usage_Thresholdand if it is higher or equal the Ater usage is seen as high.


12/40

In this case, two mechanism are modified :

1. The behaviour at the first radio resource allocation on a PDCH.

Open Point 1 : no impact of the high Ater usage state on first radio

resource allocation on a PDCH has been seen in the radio resourceallocation algorithm described in RRM-PRH whereas it is noticed in Section2.3.2.2.2.2 Normal Ater usage vs High Ater usage.

2. The computation of the variable Target_NB_GCH

The value of alpha_HiAter is used in the Target_Nb_GCH computing and inthe case of high Ater usage, it is equal toGCH_RED_FACTOR_High_Ater_Usage. This reduction factor is only appliedon PDCHs newly open.

This mechanism is described in the M-EGCH size computation.

Thirdly, the Ater resource manager allows the reservation of 64k AterTSs at the GPU level and 16K Ater nibbles at the DSP level .

This is done through the management of two margins : a GPU 64k Ater TSmargin and a DSP GCH margin. The goal of these margins is to be ableto serve, at any moment and in any cell managed by the GPU or the DSP,some prioritary requests.

Contrary to Abis resources, no equity rules are managed to fairly shareAter resources in case of Ater congestion: only prioritary requests aretargeted to be served, and with a minimum number of GCHs.

The prioritary requests are the GCH establishment requests for thefirst PS traffic in a cell , i.e. when the first One-UL-Block or TBF has tobe established in a cell. The interest of considering some prioritaryrequests is to guarantee that signaling traffic (in particular MM traffic) willbe supported at any time in any cell mapped onto the GPU.

This does not apply if there is at least one M-EGCH link alreadyestablished for a PS-capable TRX in a cell . In this case, the first One-UL-Block or best-effort TBF request in that cell are not considered asprioritary.

The O&M parameter N_ATER_TS_MARGIN_GPU indicates the number of free 64k Ater TSs that shall be kept in reserve in order to be able toserve prioritary requests. The same parameter is applied for the DSP GCHmargin but at the level of Ater nibbles for each DSP.

In the case where the number of free Ater TS at GPU level of Ater nibblesat DSP level is below this threshold, some Ater nibble/timeslots are freedaccording to specific rules. And as it can be seen in the radio resourceallocation part (at the step of Transmission resource availability), the non-prioritary request has no access to the resources in these margins.


13/40

However, this does not prevent from reaching congestion situation for theprioritary requests. Indeed such congestion can occur at lower levels thatGPU and DSP (TRX, PDCH and TBF) and it can also concern CPU congestionat DSP level.

Finally, the Ater resource manager computes the the number of free Aternibbles ( Nb_Free_Ater_Nibbles_For_Req ) according to O&Mconfigurations and with respect to the GPU Ater TS margin and the DSPGCH margin. This variable is applied when serving a request whichrequires the establishment of some GCHs (ref. to Transmission resourceavailability in the radio resource allocation part).

The exact way this variable is computed wont be described here.


14/40

5 Enhanced transmission resources management

The enhanced transmission resource management can be split in twoparts :

The first part consists in the managing of the M-EGCH link (sizedetermination, establishment, release, .)

The second consists in the activation of GCH resources duringresource allocation/reallocation (for a TBF establishment forexample).

In the descriptions below, only the case of Evolium BTS will be taken intoaccount and the case of GBR TBFs wont be tackled (it is linked to QoShandling).

5.1 Management of M-EGCH link

5.1.1 Size of the M-EGCH link

The size of the M-EGCH link of a TRX is expressed by a number of GCHsand it is determined through a set of variables.

The following variables are introduced to handle the M-EGCH link size: Established_Nb_GCH is the number of GCHs that are activated in the

M-EGCH link and that will be kept activated during a certain time.

Examples:

- On an EDGE TRX, the upper value of Established_Nb_GCH is 36.- On a non-EDGE TRX, the upper value of Established_Nb_GCH is 14.

(The explanation of these values can be found hereafter)

Current_Nb_GCH is the number of GCHs that are already activated orthat are about to be activated in the M-EGCH link.

Established_Non_CS_Preemptable_Nb_GCH corresponds to thevalue of Established_Nb_GCH by only considering the GCHs using extraAbis nibbles and bonus basic Abis nibbles and the GCHs using basicAbis nibbles mapped to timeslots within the non preemptable PSzone of the cell (ref. Autonomous Packet resource allocation).


15/40

Current_Non_CS_Preemptable_Nb_GCH corresponds to the value of Current_Nb_GCH by only considering the GCHs using extra Abis nibblesand bonus basic Abis nibbles and the GCHs using basic Abis nibblesmapped to timeslots within the non preemptable PS zone of the cell(ref. Autonomous Packet resource allocation).

Target_Nb_GCH is an estimation of the number of GCHs necessary ina given M-EGCH link to carry the signalling and data PS traffic inducedby:- The TBFs established on the TRX,- The MPDCHs established on the TRX,- The particular case of one-UL-blocks allocated to some MSs on the

TRX (in case of UL 2 phase access).

Target_Nb_GCH is only a targeted number of GCHs, which may of coursenot be reached when transmission resources (Abis and/or Ater) are incongestion.

Target_Nb_GCH is a function of:

- Nb_PDCH_EGPRS: the number of PDCHs on the TRX on which radioresources have been allocated for at least one EGPRS TBF

- Nb_PDCH_GPRS: the number of PDCHs on the TRX on which radioresources have been allocated only for GPRS TBFs

- Nb_MPDCH: the number of MPDCH(s) that the BSC has requested theMFS to establish on the TRX.

- Max_GPRS_CS and Max_EGPRS_MCS are O&M parameters.

- The values of alpha_HiAter associated to the different PDCHs of the TRX: alpha_HiAter is defined as follows :

- If the Ater usage of the GPU is normal (nominal case):

alpha_HiAter = 1,

- If the Ater usage of the GPU is high (high Ater usage situation):

alpha_HiAter = GCH_RED_FACTOR_High_Ater_Usage,where GCH_RED_FACTOR_High_Ater_Usage is an OMC changeableparameter.

Target_Nb_GCH is computed as follows :

Target_Nb_GCH = =

=

GPRS PDCH NBi

i

_ _

1

_GPRS_CS) Nb_GCH(Maxer(i)alpha_HiAt

+ =

=

EGPRS PDCH NBi

i

_ _

1

) _EGPRS_MCS Nb_GCH(Maxer(i)alpha_HiAt

+ Nb_MPDCH (*) ,Note: x means x rounded up to the next higher integer.


16/40

If Target_Nb_GCH < Min_Nb_GCH_For_Equity, then Target_Nb_GCH =Min_Nb_GCH_for_Equity

Where Min_Nb_GCH_for_Equity is defined below.

Nb_GCH(Max_GPRS_CS) and Nb_GCH(Max_EGPRS_MCS) are the number of GCHs needed to send one radio block coded with CSi or MCSi. They aredetermined according to the following tables :

CSi (i [1,4 ])

Number of requiredGCHs Nb_GCH(CSi)

UL DLCS-1 0,73 0,73 0,73CS-2 1,00 1,00 1,00

CS-3 1,25 1,22 1,25CS-4 1,64 1,60 1,64

MCSi (i [1,9 ])

Number of requiredGCHs Nb_GCH(MCSi)

UL DLMCS-1 0,89 0,86 0,89MCS-2 1,00 1,00 1,00MCS-3 1,33 1,28 1,33MCS-4 1,50 1,47 1,50MCS-5 1,86 1,81 1,86MCS-6 2,36 2,31 2,36MCS-7 3,49 3,39 3,49MCS-8 4,14 4,00 4,14MCS-9 4,49 4,39 4,49

Examples:

Assuming there is no MPDCH to establish on the considered TRX, that theFast Initial GPRS Access feature is disabled, and that the Ater usage of the GPU is normal:- Target_Nb_GCH = 1*4.49 = 5 GCHs for the MEGCH link of a

TRX supporting one 1-TS EGPRS TBF (if the Max_EGPRS_MCSparameter is set to MCS-9),- Target_Nb_GCH = 1*4.49 + 1*4.49 + 1*4.49 + 1*4.49 = 18

GCHs for the MEGCH link of a TRX supporting one 4-TS EGPRS TBF (if the Max_EGPRS_MCS parameter is set to MCS-9),

- Target_Nb_GCH = 1*1.64 = 2 GCHs for the M-EGCH link of a TRXsupporting one 1-TS GPRS TBF (if the Max_GPRS_CS parameter is setto CS-4),

- Target_Nb_GCH = 1*1.64 + 1*1.64 + 1*1.64 + 1*1.64 = 7 GCHsfor the M-EGCH link of a TRX supporting one 4-TS GPRS TBF (if theMax_GPRS_CS parameter is set to CS-4).


17/40

Assuming there is no MPDCH to establish on the considered TRX, that theFast Initial GPRS Access feature is disabled, and that the Ater usage of the GPU is high:- Target_Nb_GCH = MAX ( 0.75*4.49 , Min_Nb_GCH ) =

Min_Nb_GCH = 5 GCHs for the MEGCH link of a TRX supporting one

1-TS EGPRS TBF (if the Max_EGPRS_MCS parameter is set to MCS-9and the GCH_RED_FACTOR_High_Ater_Usage parameter is set to 0.75),


18/40

- Target_Nb_GCH = 0.75*4.49 + 0.75*4.49 + 0.75*4.49 +0.75*4.49 = 14 GCHs for the MEGCH link of a TRX supporting one4-TS EGPRS TBF (if the Max_EGPRS_MCS parameter is set to MCS-9and the GCH_RED_FACTOR_High_Ater_Usage parameter is set to 0.75).

Open Point 2 : Another Target_Nb_GCH, called TARGET_NB_GCH_UP, isalso considered in RRM-PRH in order to truncate all the other variables.It could be related to the application of GBR traffic (QoS handling).Is it a specific case or shall it be taken into account in a generaldescription ?

Min_Nb_GCH is an estimation of the minimum number of GCHsnecessary in a given M-EGCH link. It is the minimum number of GCHsnecessary to:

- Ensure that the MPDCH traffic on the TRX will not encounter anyproblem,

- Ensure that all the TBFs established on the TRX will always beable, on at least one PDCH, to send a radio block with their Maxallowed (M)CS(This is related to the variable TBF_Max_allowed_CS and

TBF_Max_allowed _MCS that are described hereafter).

The value of Min_Nb_GCH for a given TRX is defined as follows:

Min_Nb_GCH = Nb_MPDCH +Nb_GCH_For_Max_Allowed_(M)CS )

Note: x means x rounded up to the next higher integer.

Where:- Nb_MPDCH is the number of MPDCH(s) that the BSC has

requested the MFS to establish on the TRX,

- Nb_ GCH _For_Max_Allowed_(M)CS is computed as follows:

- If the TRX supports no radio resources for GPRS orEDGE TBFs :

Nb_GCH_For_Max_Allowed_(M)CS = 0,

- Else, if the TRX only supports radio resources for GPRS TBFs :

Nb_GCH_For_Max_Allowed_(M)CS =Nb_GCH(Max_GPRS_CS),

with Max_GPRS_CS the O&M parameter value, andNb_GCH(x) defined above.

- Else, if the TRX supports radio resources for at leastone EGPRS TBF :

Nb_GCH_For_Max_Allowed_(M)CS=Nb_GCH(Max_EGPRS_MCS),

with Max_EGPRS_MCS the O&M parameter value, andNb_GCH(x) defined above.


19/40

Examples:

In this example, it is assumed that there is no MPDCH allocated on the TRX.

If there is one GPRS TBF and one EGPRS TBF established on the TRX,and if Max_EGPRS_MCS = MCS-9, then:

Min_Nb_GCH= 0 + Nb_GCH(MCS-9) = 4.49= 5.

Min_Nb_GCH_Best_Effort is an estimation of the minimum number of GCHs necessary in a given M-EGCH link for the best-effort TBF trafficsupported by the TRX in both directions (UL and DL).

The exact way Min_NB_GCH_Best_Effort is computed wont bedescribed here.

Min_Nb_GCH_For_Equity is an estimation of the minimum number of GCHs necessary in a given M-EGCH link for the TBF traffic and for theMPDCH traffic supported by the TRX, by considering a stabilisedsituation where the TBF_Max_allowed_CS and TBF_Max_allowed_MCS(see next point) of the TBFs established on the TRX has reached theMAX_GPRS_CS or the MAX_EGPRS_MCS O&M parameter value.Min_Nb_GCH_For_Equity is always greater or equal to Min_Nb_GCH.

The exact way Min_NB_GCH_For_Equity is computed wont be describedhere.

Open Point 3 : The difference between Min_Nb_GCH Best_Effort and Min_Nb_GCH_For_Equity with Min_NB_GCH is not completely clear : It seems that mainly they are computed at TBF level and that they take intoaccount the T_MAX_FOR_TBF_SCHEDULING constraints coming from RLClayer.

Is it relevant to detail such issue in a general description ?

Min_Nb_GCH_GBR is an estimation of the minimum number of GCHsnecessary in a given M-EGCH link for the GBR traffic supported by the

TRX in both directions (UL and DL).

Open Point 4 : Is it necessary to take into account the variableMIN_NB_GCH_GBR even if QoS handling is not supported in the current version of B9 and not described in this document ?

TBF_Max_allowed_CS and TBF_Max_allowed_MCS correspond tothe maximum allowed CS or MCS for TBF established on a certain TRX.


20/40

For a GPRS TBF, the maximum allowed CS is determined according to thenumber of established GCHs in the M-EGCH link (Established_Nb_GCH), theGPRS capability of the TRX, the direction of the TBF (DL or UL) and theMax_GPRS_CS parameter value.

The number of established GCHs in the M-EGCH link using a basic Abis

nibble mapped onto a TS that is being deallocated by the BSC(Nb_GCH_Impacted_By_CS_Preemption ) is also taken into account toavoid TBFs to abnormally fall during the fast preemption process (refer toGCH pre-emption procedure).


21/40

Number of established GCHs in the M-EGCH link(Established_Nb_GCH

-Nb_GCH_Impacted_By_CS_Preemption)

Max allowed CS of the TBF according tothe number of GCHs of the M-EGCH link(TBF_Max_allowed_CS)

UL TBF DL TBF1 CS2 CS1 2 CS4 CS4Max allowed CS according to the number of GCHs of an M-EGCH link

TBF_Max_allowed_CS = Min (Max allowed CS according to the number of GCHs of the M-EGCHlink,GPRS capability of the TRX,Max_GPRS_CS).

For an EGPRS TBF, the maximum allowed MCS is determined accordingto the number of established GCHs in the M-EGCH link(Established_Nb_GCH), the EGPRS capability of the TRX, the direction of the TBF (DL or UL) and the Max_EGPRS_MCS parameter value.

The number of established GCHs in the M-EGCH link using a basic Abisnibble mapped onto a RTS that is being deallocated by the BSC(Nb_GCH_Impacted_By_CS_Preemption) is also taken into account toavoid TBFs to abnormally fall during the fast preemption process.

Number of established GCHs in the M-EGCH link

(Established_Nb_GCH-

Nb_GCH_Impacted_By_CS_Preemption)

Max allowed MCS of the TBF according to thenumber of GCHs of the M-EGCH link

(TBF_Max_allowed_MCS)

UL TBF DL TBF1 MCS2 MCS12 MCS5 MCS53 MCS6 MCS64 MCS7 MCS7

5 MCS9 MCS9Max allowed MCS according to the number of GCHs of an M-EGCH link

TBF_Max_allowed_MCS = Min (Max allowed MCS according to the number of GCHs of the M-EGCH

link,EGPRS capability of the TRX,Max_EGPRS_MCS)


22/40

The nominal trigger to assess the maximum allowed (M)CS of a given TBF is when that TBF is established or reallocated. In case of TBFreallocation, the maximum allowed (M)CS of the TBF can be increased ordecreased.

The maximum allowed (M)CS of a best-effort TBF already established on agiven TRX shall also be reassessed when the Established_Nb_GCH valueof the TRX is increased. In such a case (increase of theEstablished_Nb_GCH value of the TRX), all the TBFs established on the TRXshall potentially be warned of their new max allowed (M)CS value.

No maximum allowed (M)CS decrease is managed in case theEstablished_Nb_GCH value of a TRX is decreased.

Note: RRM-PCC will subsequently adapt the value of the maximum allowed(M)CS computed by RRM-PRH (for example, it will distinguish thecases where the CS adaptation is enabled or not).

Particular cases (for Target_Nb_GCH, Min_Nb_GCH,Min_Nb_GCH_Best_Effort and Min_Nb_GCH_For_Equity)

The values of Target_Nb_GCH and Min_Nb_GCH (computed as describedabove) have to be recomputed in the following cases:

Case of a TRX supporting some one-UL-block(s):

In case there is neither TBF established nor MPDCH resources onthe TRX, and in case the TRX is not currently used for the FastInitial PS Access feature : if some one-UL-blocks are established orto be established on some timeslots of the TRX, both Min_Nb_GCHand Target_Nb_GCH shall be set to 1:

Target_Nb_GCH = 1Min_Nb_GCH = 1

Min_Nb_GCH_Best_Effort = 1Min_Nb_GCH_For_Equity = 1

Case of a TRX currently used for the Fast Initial GPRSAccess

If En_Fast_Initial_GPRS_Access = enabled in the cell, and if theconsidered TRX is currently used for this feature, then the M-EGCHlink of that TRX shall contain N_GCH_FAST_PS_ACCESS GCHs (MFSinternal parameter).

Thus, on the TRX currently used for the Fast Initial PS Accessfeature, the following rules will always be respected:

Target_Nb_GCH N_GCH_FAST_PS_ACCESSMin_Nb_GCH N_GCH_FAST_PS_ACCESS


23/40

Min_Nb_GCH_Best_Effort = N_GCH_FAST_PS_ACCESSMin_Nb_GCH_For_Equity N_GCH_FAST_PS_ACCESS

Notes:- Among others, updating the variables on the TRX currently used

for the Fast PS Access feature guarantees that the GCHs of that TRX will not be preempted by some other TRXs (intra-cell orinter-cell GCH preemptions).

- When the Fast Initial PS Access feature is disabled, the O&Mparameter N_GCH_FAST_PS_ACCESS is used to determine thenumber of GCHs to keep established while the

T_GCH_Inactivity_Last timer is running. But in that case, theabove variables are not updated in a particular manner(typically, they can all be equal to 0 while the

T_GCH_Inactivity_Last timer is running).

5.1.2 Usual Procedures on the M-EGCH link

M-EGCH link establishment : An M-EGCH link is established each timethere is some new PS traffic (TBF or MPDCH establishment) on a TRXwhich has currently no established M-EGCH link. It can also be establishedthrough the Fast Initial GPRS Access feature.

A certain number of GCHs (up to Target_Nb_GCH, and in the limit of theavailable Abis and Ater transmission resources) will be attempted to beactivated, either in one or in several successive steps.

M-EGCH link capacity increase : The number of GCHs of an existingestablished M-EGCH link may have to be increased each time there issome new PS traffic (TBF establishment) on the TRX. It can also beincreased due to the Fast Initial GPRS Access feature or due to thePeriodical GCH establishment process (see below).

(Target_Nb_GCH - Established_Nb_GCH) GCHs (in the limit of the availableAbis and Ater transmission resources) will be attempted to be activated,either in one or in several successive steps. They will be activated either

through GCH establishment (see Part about resource allocation) or inter-cell or intra-cell GCH pre-emption (see below).

M-EGCH link capacity decrease and M-EGCH link release : there areseveral cases of M-ECGH link capacity decrease and release :

The nominal case corresponds to a reduction of the PS trafficon the TRX , that makes some GCHs of the M-EGCH link unused. Forthese GCHs, the timers T_GCH_Inactivity or T_GCH_Inactivity_Last areapplied, in the same way T_PDCH_Inactivity or T_PDCH_Inactivity_Lastapplied for PDCH in B8 release.Such case of M-EGCH link release or capacity decrease is subsequent tothe decrease of the Target_Nb_GCH value of the TRE. The GCHs to be


24/40

release are chosen according to the following Abis priority order (this isthe priority order inverse of the one applied for GCH establishment (seePart about resource allocation) :


25/40

Order with which the GCHs are releasedin an M-EGCH link1. Basic Abis nibbles mapped to TSs out

of the non pre-emptable PS zone of the cell2. Extra Abis nibbles and bonus basicAbis nibbles3. Basic Abis nibbles mapped to TSswithin the non pre-emptable PS zoneof the cell4. Basic Abis nibbles mapped to TSssupporting MPDCHs (case of MPDCHrelease only)

An M-EGCH link release or capacity decrease can also be due to inter-cell GCH pre-emption or intra-cell GCH pre-emption (see below).

An M-EGCH link release or capacity decrease can also be due to thefilling of the GPU Ater TS margin or of the DSP GCH margin (SeeDynamic Abis allocation, Ater resource manager part).

An M-EGCH link release or capacity decrease can also be due to someabnormal GCH releases (linked to a failure or to a desynchronisationwith the BSC or with the BTS or an O&M intervention)

An M-EGCH link release or capacity decrease can also be due to someGCH releases linked to CS pre-emption (see below).

A M-EGCH link is released when all the GCHs of the link have beenreleased (Target_Nb_GCH=0).

5.1.3 Specific Procedures on the M-EGCH link

Intra-cell or inter-cell GCH pre-emption : The inter-cell GCH pre-emption is tackled during the transmission resource availabilityprocedures. The intra-cells GCH pre-emption is tackled during the celltransmission equity procedures.

These procedures wont be detailed in this document.

Such procedures occur during the resource allocation/reallocation (seepart on resource allocation) and during periodical GCH establishmentprocess (see below).

GCH release due to CS pre-emption : The CS pre-emption mechanismin B9 release is similar as in B8 (ref to Autonomous Packet resource

allocation) but it has a specific impact on M-EGCH management :


26/40

Indeed, The basic Abis nibbles of the timeslots preempted by the BSC maybe currently used by some GCHs in the cell. Thus, the TRXs (or M-EGCHs)using these GCHs will be impacted by the pre-emption, even if thepreempted TSs are not on these TRXs.

Thats why the TRXs of the cell for which:(Nb_GCH_Impacted_By_CS_Preemption > 0) and

(Established_Nb_GCH Min_Nb_GCH_GBRNb_GCH_Impacted_By_CS_Preemption)

with:- Established_Nb_GCH and Min_Nb_GCH_GBR are defined

above.- Nb_GCH_Impacted_By_CS_Preemption is the number of

established GCHs in the M-EGCH link using a basic Abis nibblemapped onto a timeslot that is being deallocated by the BSC.

have all their PDCHs locked by the preemption process, it means thatthey cannot accept anymore traffic.

Moreover, the new incoming PS traffic (or some T2, T3, T4 TBFreallocations played) during the CS preemption process will see their Maxallowed (M)CS computation step impacted by the value of Nb_GCH_Impacted_By_CS_Preemption (ref. To TBF_Max_allowed_CS and

TBF_Max_allowed_MCS computation ).

Open Point 5 : At which level the reduction of Max allowed (M)CS in caseof GCH pre-emption should be seen ? Is it at BTS level ?

At the TBF level, two different TBF directly impacted is identified :

1. The TBFs whose PACCH is supported by a pre-empted timeslot2. The TBFs for which it will no longer be possible to serve their on-goingmax allowed (M)CS (cf. TBF_Max_allowed_(M)CS computation above)because of the subsequent reduction of the M-EGCH link size of their TRX.

For both kind of impacted TBFs, T1 reallocation is allowed.

In the case where the number of TBFs established on a TRX will becometoo high according to the remaining number of GCHs in the M-EGCH link of the TRX, then some TBFs will be released.

Open Point 6 : The conditions for the case where the number of TBFsestablished on a TRX will become too high after CS preemption are not clear : the condition described in RRM-PRH (Established_Nb_GCH Nb_GCH_Impacted_By_CS_Preemption Min_Nb_GCH_GBR gets strictly lower than Min_Nb_GCH_Best_Effort_XL, in DL direction and/or in UL direction) is not consistent (Established_Nb_GCH Nb_GCH_Impacted_By_CS_Preemption Min_Nb_GCH_GBR will be negativein this case).

The number of TBF released depend on Min_Nb_GCH_Best_Effort_XL andthe ones released are in priority the TBFs impacted by the pre-emption(ref. above) and then the youngest TBFs.


27/40

After the fast pre-emption procedure is launched to release the PDCH(considering the TBFs for which T1 reallocation failed or for which therewas only throughput reduction and it is still possible to serve their maxallowed (M)CS), the basic Abis nibbles of the pre-empted timeslots are

released and the corresponding GCHs are released from the M-EGCH link.

Periodical GCH establishment process : this process attemptsperiodically to increase the M-EGCH link size of TRXs which have not yetreached their Target_Nb_GCH (i.e. the TRXs for which Current_Nb_GCH 0 and

Current_Nb_GCH < Target_Nb_GCH (if any) are considered:

- If one of those TRXs verifies the condition: Current_Nb_GCH

enhanced transmission resources management ed3

Documents