Abis Ater Satellite Parameters

ED 01 RELEASED GPRS through satellite connection on Abis or Ater interface

EVOLIUMSFD_0538_01(GPRS

ABIS&ATER SATELLITE).DOC16/05/2003 3BK 10204 0538 ZZA 1/36

SiteVELIZY

EVOLIUM™ SAS

OriginatorsA. FREULOND. POULET

SFD: GPRS through satellite connection on Abis or Ater interface

System : ALCATEL 900/BSSSub-system : SYS-TLADocument Category : PRODUCT DEFINITION

ABSTRACT

This SFD describes the "GPRS through satellite connection on Abis or Ater interface” feature.

ApprovalsNameApp.

J. ACHARDSYT CCM

A. WAZANAPL

J.-P. GRUAUPM

REVIEWEd. 01 Proposal 01 <2001/04/26> Evolium/R&D/SYT/AFR/0234.2001Ed. 01 Proposal 02 <2003/04/07> Evolium/R&D/SYT/AFR/0118.2003Ed. 01 Proposal 03 <2003/May/12th> Evolium/R&D/SYT/AFR/0136.2003

HISTORYEd. 01 Proposal 01 <2001/03/26> This proposal was written in the very beginning of B8; then

work on this subject was suspended.Ed. 01 Proposal 02 <2003/03/21> Two years after proposal 1, the feature is required again,

and work is resumed, with a simpler technical solution thanthe one envisaged in proposal 1 for the tuning ofparameters. This proposal describes the feature impact forB7.2 and B8 implementation (feature implemented “on top“ of B7.2).

NO REVISION MARK IN P2 (Too many changes ).

Ed. 01 Proposal 03 <2003/04/07> Update according review report of edition 1P2

Ed. 01 Released <2003-May-15th>

Update according review report of edition 1P3 (refEvolium/R&D/SYT/AFR/0136.2003)




TABLE OF CONTENTS

1 INTRODUCTION ......................................................................................................................... 51.1 Scope ....................................................................................................................... ........... 51.2 Document Structure ........................................................................................................... 51.3 Definitions and Pre-requisite ............................................................................................. 5

1.3.1 Definitions................................................................................................................... 51.3.2 Pre-requisite: “Industrialisation of satellite feature” for CS services ............................. 71.3.3 Pre-requisite: signalling routes through Abis and Ater for PS services......................... 8

2 FEATURE DESCRIPTION........................................................................................................... 92.1 Functional Requi rements ................................................................................................... 92.2 Compliance to the M arketing Re quirements ................................................................... 102.3 Working Assumptions...................................................................................................... 102.4 Dependencies ................................................................................................................ ... 112.5 HW Coverage .................................................................................................................... 122.6 Rationale ................................................................................................................... ........ 13

3 SYSTEM IMPACTS ................................................................................................................. .. 143.1 Telecom..................................................................................................................... ........ 14

3.1.1 Functional changes................................................................................................... 143.1.2 Specification impacts ................................................................................................ 143.1.3 Interfaces.................................................................................................................. 14

3.2 Operation and maintenance ............................................................................................. 153.2.1 O&M functional level description............................................................................... 153.2.2 Parameter types and tuning policy. ........................................................................... 153.2.3 Parameter modification for B7.2................................................................................ 163.2.4 Additional tuning rules for parameters....................................................................... 173.2.5 Additional CST Parameter modification for B8.......................................................... 203.2.6 Additional CAE Parameter tuning for B8 ................................................................... 223.2.7 PM counters.............................................................................................................. 223.2.8 PM indicators............................................................................................................ 223.2.9 Migration................................................................................................................... 233.2.10 GPRS through satellite activation.............................................................................. 23

3.3 Validation .................................................................................................................. ........ 243.3.1 Validation for telecom aspects .................................................................................. 243.3.2 Validation for O&M aspects....................................................................................... 253.3.3 Testing tools ............................................................................................................. 253.3.4 Test strategy ............................................................................................................. 25

3.4 Methods..................................................................................................................... ........ 253.5 GCDs ................................................................................................................................. 253.6 Engin eering rules ............................................................................................................. 25

3.6.1 Fault Management .................................................................................................... 25

4 SUBSYSTEM IMPACTS............................................................................................................ 264.1 BTS.................................................................................................................................... 264.2 BSC.................................................................................................................................... 264.3 Transcoder.................................................................................................................. ...... 264.4 MFS.................................................................................................................................... 264.5 OMC_R .............................................................................................................................. 264.6 OEF/POLO......................................................................................................................... 26

5 PERFORMANCE & SYSTEM DIMENSIONING ......................................................................... 265.1 Traffic model ................................................................................................................ ..... 265.2 Performance ...................................................................................................................... 27

5.2.1 Maximum Data Throughput....................................................................................... 275.2.2 Service access time.................................................................................................. 27

5.3 System dimensionning..................................................................................................... 28




5.3.1 Impact of satellite delay on RSL throughput. ............................................................. 285.3.2 Impact of satellite delay on GSL throughput. ............................................................. 28

5.4 Load constraints............................................................................................................. .. 28

6 OPEN POINTS .......................................................................................................................... 29

7 IMPACTS SUMMARY................................................................................................................ 30

8 GLOSSARY...................................................................................................................... ......... 318.1 Abbreviat ions.................................................................................................................... 318.2 Terminology................................................................................................................. ..... 31

Figure 1: terrestrial and satellite round–trip delay ............................................................................... 6Figure 2: Signalling routes through the BSS ....................................................................................... 8




INTERNAL REFERENCED DOCUMENTSNot applicable

REFERENCED DOCUMENTSAlcatel references[1] 3BKA55CBR120754 RFD: GPRS on Abis & Ater Satellite Links

3GPP references

RELATED DOCUMENTSAlcatel documents[A1] 3BK 10204 0514 DTZZA: SFD Industrialisation of satellite feature.[A2] 3BKA20CBR123988 Impacts of the feature “GPRS through satellite links

on Abis/Ater interface” on BSS Telecom parameterscatalogue (B7.2 ).

[A3 RCD/MR/TD/SYT/SBO/200242_1 RLC ARQ and reassembling procedures in uplinkacknowledged mode.

[A4] ETSI SMG2, Tdoc SMG2 EDGE165/99

Evaluation of EGPRS ARQ throughput efficiency.This document was presented to SMG2 by Alcatel.

3GPP CRs3GPP TS CR nb Re

vTitle Author Accepted?

(Y/N)

PREFACEThis document is the input paper for the feature “GPRS through satellite connection on Abis or Aterinterface” inside TD. It will further on be used as reference for the development of that feature ineach subsystem.

RESTRICTIONS

This SFD is only related to PS services. For CS services, refer to document ref [A1]




1 INTRODUCTION

1.1 ScopeThe present document aims to be the basis for decision of a proposed change to be made on theBSS system. Then it provides all necessary information related to functional description, gains,description of the system impacts and subsystem impacts.

1.2 Document StructureThe section 2 of this document presents the functional requirements, the HW coverage and therationale of the feature addressed by the present SFD.The section 3 identifies the system impacts: it gives the principles and presents the functional split ofthe feature between subsystems. Impact on Step2 specifications is also given in this section.The section 4 contains the description of impacts for each subsystem.The section 5 addresses the performance and system dimensioning concerns.The section 6 identifies and describes the open points.The section 7 is a sum up of the system impacts.The section 8 contains the glossary of the present document.

1.3 Definitions and Pre-requisiteThe text in italics is informative. It typically consists of:- background information eg standardisation information.- references to future BSS enhancements to guide design choices.- references to NSS functionalities.

1.3.1 Definitions

• Satellite connection:Throughout this document the term “satellite connection” is used as a synonym of “satellite hop”. Asatellite hop between two terrestrial equipments A and B is in reality made of two connections: one“equipment A<->satellite” connection and one “satellite<->equipment B” connection.

• Round-trip-delay:The round trip delay between two equipments refers to the time taken for a message to go to thepeer equipment, plus the time taken from the response from the peer equipment to come back. Theround trip delay has three components:

- the propagation delay which depends on medium propagation speed and on the signal frequency(negligible in case of terrestrial connection)

- The transmission delay which depends on the available throughput and the message length(negligible in case of satellite connection)

- The processing time in network elements.In this document, we are interrested in the MS-to-MFS round trip delay , and on its increased valuewhen a satellite connection is introduced on the Abis or on the Ater interface.

- No satellite .connection: The MS-MFS round trip delay is a BSS system parameter, which isestimated to about 160ms, including transmission delay, MS reaction time and processing delaysin the MFS.

- Satellite connection: The additional delay induced by the satellite connection, is twice thesingle trip delay, computed as:

- propagation delay: 240ms (cf ref [A1] for detailed calculation




- delay in the earth station modems: 30ms1

- delay in the satellite: negligible (no processing, only amplification of received signal)

- delay due to additional equipment: none2.This results in a total satellite round-trip delay equal to 2x(240+30) = 540ms.

The corres ponding MS-MFS round-trip delay with a satellite connection on the Abis or onthe Ater interface is equal to 540+160ms = 700ms. To take provision for delays induced by futureadditional equipements, it is recommended to consider a maximum value of at least 900ms.

The following figure illustrates the previous definitions in case of Abis interface through satellite link.

Figure 1: t errestrial and sate llite round–trip delay

• Anticipation window:

Many protocols for data or signalling transport are acknowledged protocols, and are using the notionof anticipation window (LAPD, RLC). The anticipation window is the maximum number of protocoldata units (PDU) which can be transmitted by the transmitter, while the first of these PDU have not yetbeen acknowldeged by the receiver.

• stalled anticipation window:

When the transmitter has sent the maximum number of messages, and is waiting for acknowldgementfrom the peer, the window is stalled. This can occur when messages are lost due to tranmissionerrors, but also in case of a large round trip delay, when this round trip delay is larger than the timetaken to transmit the full antiticipation window. A stalled widow will induce a loss of throughputbetween the network elements, because the transmission is suspended while the window is stalled.

1 Information provided by Alcatel Space specialist.2 In case some compressing/decompressing equipment is introduced to diminish the bandwidthneeded from the satellite operator, the additional delay introduced by this equipment will have to betaken into account. Depending on the equipment the delay may vary to a few ms to about 100ms for asingle trip. More information can be obtained from Alcatel space.

satellite

terrestrial round-trip delay

satellite round-trip delay

MS MFS

BTS BSC

Abis




1.3.2 Pre-requisite: “Industrialisation of satellite feature” for CS services

The feature “Industrialisation of satellite feature” is supported from B7.2 onwards and it concerns CS(circuit-switched) service only. This feature only concerns the tuning of parameters needed for CScalls. A brief summary of used mechanisms is provided below, see ref [A1] for details.This feature impacts the handling of BSC parameters3 which values depend on Abis connection typeor Ater connection type in the following way.

• For a system parameter (CST):

The parameter does not become modifiable from the OMC-R. At the OMC-R, the operator onlydefines the connection type (satellite/terrestrial) of the Abis or Ater link, which is sent to the BSC.The BSC will then send to the BTSs connected to this link the value of the system parametermatching with the connection type. For such parameters, the DLS stores one value for terrestrialconnection and one value for satellite connection. The modification of transmission timers lead toa telecom outage on CS service (restart of TREs).

• For a parameter changeable from OMC-R:

Such a parameter4 is instanced on a “per cell” basis to allow the operator, in case of modificationof Abis or Ater link connection type, to tune accordingly such a parameter for all the cellssupported on this link. This tuning is neither automatic nor assisted by a tool. The operator has totune manually the parameter value for each cell supported on the link. There is no additionaldefault value for such a parameter. The default value is always the recommended value forterrestrial connection.

3These parameters were already defined before introduction of the feature (there is no new parameter exceptthe flag per Abis or Ater link indicating the connection type)4 Indeed, for CS, only two changeable parameters were potentially impacted (Max-retrans, TX-integer) for whichthe default value was suitable for satellite links. So the tuning effort of the operator was nearly null.




1.3.3 Pre-requisite: signalling routes through Abis and Ater for PS services.

The following figure shows why the impact is different in case of Abis or Ater throught satellite link

Figure 2: Signalling routes through the BSS

In both cases RLC signalling, and data transfer are delayed through the GCH interface. It should benoted that the presence of absence of a MPDCH does not modify the delay induced for the transfer ofRRM signalling information from the MFS to the MS (through the BTS).• With MPDCH: RRM signalling is delayed through the GCH interface• Without MPDCH: RMM signalling is delayed

• through the RSL for the Abis through satellite case• or through the GSL for the Ater through satellite case

But in case of Ater through satellite link, the BSCGP signalling will be delayed. This is not the case forthe Abis through satellite link. Hence the Ater through satellite link implies more perfo rmancedegradation and additional p arameter t uning related to the BSCGP protocol .

Abis interface Ater interface

BTS BSC MFS

GCH, RLC and RRM signalling through MPDCH

BSCGP signalling

+RRM signalling

through GSLRRM signalling

through RSL




2 FEATURE DESCRIPTION

No MFD is available for this feature. Only the RFD 3BKA55CBR120754 is available, the text of whichis copied below for the conveniency of the reader.

Note that this RFD has been written for B7.2. With B8, the compatibility with HSDS is also requested.

SHORT DESCRIPTION GPRS on Abis & Ater Satellite Links

The usage of satellite links growths rapidely in Business Regions like AMEI and APAC, thanks to :* Cost optimized satellite links,* Needed communications services in remote areas where long distance terrestrial links installation iseconomicaly not possible.

As it is expected that the need for data services will also growth in such areas, and considering thefact that Alcatel/MND strategy is not to develop HSCSD services, MND requires to evaluate and testGPRS services via Abis & Ater satellite links. This has been agreed by MND management andcommitted to SPD management (meeting held on 16th October 2002).

Thus it is required :* To update the TD/SYT/AFR/927.2002 analysis,* To launch detailed system analysis, in particular for the parameters adaptations/tuningcorresponding to satellite links characteristics,* To perform corresponding tests,* To support first-off if needed,* To issue methods and customer documentation to permit easy and large roll-out of the feature.

FOLLOW UP Alcatel S everity : G1 / Major

2.1 Functional Requirements

The physical path between the BTS and the MFS where are located the GPRS functions, uses theAbis and Ater interfaces, which can be routed via satellite links. The object of the present feature is tooffer GPRS and EDGE services in the cells for which the BTS-MFS physical connection uses onesatellite hop (Abis or Ater).

- Abis through satellite or Ater through satellite is possible but not both simultaneously.- If Abis or Ater interface is through satellite, then Gb through satellite is forbidden.- The case of an MS-to-MS connection where both Ms are using cell connected should be

supported, but this can be guarantied only by end-to-end tests. No specific requirement seemsneeded to cover this case.

Due to the very large round trip delay introduced by satellite connections, compared to terrestrial one,it is necessary to adapt some parameters in our BSS with specific value for the satellite connections.This adaption shall enable to provide the required services, but in the present state of the GSMstandard the loss of performances induced by the satellite connection cannot be completelycompensated by parameter tuning.

Hence this SFD is meant to:- define the best possible tuning of parameters to allow GPRS/EDGE connection,- define the O&M mechanism to set the parameters to the correct values,- estimate the limitation of the performances (throughput, service access time) which are

unavoidable, and also possible restrictions to the provided standard configurations.




2.2 Compliance to the Marketing Requirements

Feature Item Compliance Co mmentsAbis through satellite with GPRS Yes with limited performances (see 5.2)Abis through satellite with EDGE Yes with limited performances (see 5.2)

EDGE degradation not as bad as GPRS.Ater through satellite with GPRS Yes with limited performances (see 5.2), worst

than the Abis case for access time.Ater through satellite with EDGE Yes with limited performances (see 5.2), worst

than the Abis case for access time. EDGEdegradation not as bad as GPRS.

Master PDCH Yes But not recommended (one GCH allocatedfor MPDCH and not used for traffic=> highcost for little bandwidth usage)

maximum number of cells per GPU restriction In case of Ater through satellite, themaximum number of cell per GPU is limited.See 5.4 for details.

activation of feature by O&M No The feature cannot be inhibited, if the“industrialisation of satellite” is enabled.The feature GPRS through satellite has to beplanned at network level before migration tocustomise correctly CDE and BUL files.Satellite CDE p arameters shall bechangeable apart from the migrationprocess.

2.3 Working Assumptions

1. Satellite performances: Transmission of 2Mbit/s is already defined for satellite links and is out ofthe scope of this study. Error rates are assumed to be compliant with ITU-TG.826. This impliesthat the performances in term of errors due to the satellite connections do not decrease on theAter and Abis interfaces because of a satellite link, and that these performances remain far betterthan those expected on the Um interface. As a consequence the BLER between the MS and MFSis not expected to be degraded by the use of a satellite connection on the Abis or Ater interface.Other problems specific to satellite connections (jitter, wander) are assumed to be corrected byspecific equipments provided together with the satellite connection

2. Abis through satellite or Ater through satellite is possible but not both simultaneously.

3. If Abis or Ater interface is through satellite, then Gb through satellite is forbidden.

4. The case of an MS-to-MS connection where both Ms are using cell connected should besupported, but this can be guarantied only by end-to-end tests. No specific requirement seemsneeded to cover this case.

5. The maximum multislot capability implemented in the MFS is (5 TS DL +2 TS UL)




2.4 Dependencies

The Feature "GPRS through satellite links”

• requiresFeature industrialisation ofsatellite links

A cell which supports CS + PS services cannot have oneservice through satellite and not the other. This feature alsoenables to adapt parameters for BTS SW downloading.

• is enhanced byNone

• is incompatible withSee below

• will be enhanced by the following future evolutions .Se below

Compress ion/decomp ress ion.The introduction of compression/decompression equipments, in order to optimise the bandwidthusage through a satellite connection, may be used for CS services. These equipments are not part ofthe Alcatel BSS but can be proposed within the scope of an Alcatel “end-to-end” solution. Suchequipments are currently not compatible with GPRS, but compatibility may be provided in the future.

• If compatibility with GPRS is not provided : They cannot be used for CS on a cell where GPRSis enabled, since Abis and Ater nibbles are not dedicated to CS or PS services, but can do both.

• If compatibility with GPRS is provided: Such an equipment can be considered as anenhancement, because it enables to limit the bandwidth usage of the GCH interface (Abis orAter), and the corresponding high cost through a satellite connection. However, the additionaldelay introduced by such an equipment has to be taken into account into the total satellite round-trip delay, and the additional degradation of performances has to be balanced with the economicgain, to decide whether it really is an enhancement.




2.5 HW CoverageThis section defines the HW coverage of the feature. A synthetic and exhaustive table shall beprovided where the different HW generation of each subsystem is listed.The HW coverage of the feature shall be given on a per implementation step basis where needed.

System:GSM 900 YDCS 1800 / DCS1900 YGSM 850 Y

Network element:In following tables, indicate :Xsw if feature supported by the NE with software impact,Xhw if feature supported by the NE with hardware impactXsw+hw if feature supported by the NE with software and hardware impact.X : The feature is supported on the NE without hardware or software impacts.- : The feature is not supported by the NE or the NE is not concerned by the feature

BTS XBSC XswMFS XswTransmission XTranscoder XMSC -SGSN -Data IWF -HLR -OMC/SMC/NMC

Xsw(OMC)

Tools (NPA, RNO, RNP,Laser)

Xsw

MSTS

BTS Generat ion: BTS G2 with FUMO -BTS G2 with DRFU Open point 5BTS MK2 with DRFU -A9100 (Evolium standard) XA910 (micro Evolium (M4M)) XA910-E (micro Evolium M5M) XM1M, M2M -

BSC Generat ion: BSC G2 Xsw

MFS: MFS Xsw

Transmission: Alcatel TSC -

Transcoder: TRAU G2 with DT16 -TRAU G2 with MT120TRAU G2.5 (with MT120) -




O&M: OMC-R XswPOLO/OEF Xsw (POLO)NMC -Tools (NPA, RNO, RNP,Laser)

Xsw5

2.6 Rationale

• Competition: Some competitors (Erikson) have GPRS through satellite in their portfolio.• Operational gains : the NW Operator will be able to provide basic GPRS and HSDS services in

cells already connected through satellite.

See RFD text above.

5 Impact is only on RNO for B7.2. See section 4.5.




3 SYSTEM IMPACTS

3.1 Telecom

3.1.1 Functional changes

With B7.2, the implementation of this feature consists only in parameter changes, which is detailed inthe O&M section. There is no functional change in the telecom partWith release B8, six new parameters (see table Table 2) are introduced to optimise the performancesof GPRS and EGPRS by allowing more frequent polling during RLC data transfer in order to avoidwindow stalling. Those new parameters are in the MFS DLS and shall be transferred to the RLC layer,which will choose to apply either the terrestrial or the satellite values depending on the round trip delayassociated to the TRX on which the TBF is running

3.1.2 Specification impacts

3.1.2.1 Step 2 BSS Telecom parameter

See section3.2.3 and 3.2.4 for the B7.2 changes to BSS Telecom parameters.

See section 3.2.5 and 3.2.6 for the B8 changes to BSS Telecom parameters (on top of B7.2modifications).

3.1.2.2 Step 2 GPRS traffic model and performances document.

See section 5.2.

3.1.2.3 Step 2 : FBS GPRS radio interface, RLC MAC s ublayer

Impacted only for B8. See section 3.2.5.

3.1.3 Interfaces

No change on the signalling interfaces.




3.2 Operation and maintenance

3.2.1 O&M functional l evel description

3.2.1.1 Overview

In the BSS B7.2 , without the implementation of the feature, the GPRS on satellite cannot work due• To internal system timers, not changeable, which are not adapted to satellite time

constraints.• To the range of the round trip delay parameter, which is too small compared to satellite time

constraints.From an O&M point of view, the implementation of the GPRS through a satellite connection consistsof:

• The transformation of these system parameters into CDE parameters (cf 3.2.3).• The definition of two sets of values for these CDE parameters, one “compromise” adapted to

satellite and terrestrial connection and another one adapted to terrestrial connection. Thesatellite set is applied at migration time if GPRS through satellite is envisaged in thenetwork.

• The extension of the range for the parameter round trip delay adapted to the satellite timeconstraints.

From an operator point of view, the activation of the feature consists of:• Planning the usage of GPRS on satellite in the netwok, to customise the CDE table and the

BUL files with the correct set of values.• Tuning of CAE parameters to activate or deactivate the GPRS through a satellite link.

BSS B8: The same principles as B7.2 apply. Some new CST parameters are introduced in the MFSto improve the performances with satellite links.

3.2.1.2 OMC Model:

No new parameter

3.2.2 Parameter types and t uning policy.

The mechanisms described below apply to B7.2 and B8 software releases, unless otherwise stated.Four types of parameters are considered:

• OMC-changeable cell parameters (CAE/cell): When the recommended value for satellite linkdiffers from terrestrial links, the operator can enter manually6 the recommended value for thecells which are connected to MFS through a satellite link (Abis or Ater). In one case (round tripdelay) the range of the parameter must be extended, compared to what had been foreseenwithout satellite connections.

• OMC-changeable BSS parameters (CAE/BSS): When the recommended value for satellitelinks differs from terrestrial links:

- In case of satellite link on Ater: the operator can enter manually the recommended value forthe BSSs, which are connected to the MFS through a satellite link on Ater.

- In case of satellite links on Abis, a compromise value is found which should apply to any cellsof the BSS, whatever their connection type for GPRS. The possible consequences orrestrictions due to this compromise are explained.

• Constant parameters (CST):

6 Using facilities already offered by OMC-R/RNUSM (e.g. multiple cell selection).




• B7.2: A compromise value is found which should will to any cells of the network, whatever theconnection type for GPRS. But it is not acceptable to change CST parameters for allcustomers (would be too risky when the release is already at customer sites). Hence the CSTparameters, for which the compromise value differs from the default value (defined forterrestrial links), are changed into CDE parameters in order to allow their tuning on a pernetwork basis.

• B8: The same principle as B7.2 is kept, but some new CST parameters are introduced in theMFS, so as to improve the throughput at RLC layer by adapting the value to the satellite orterrestrial case. The MFS chooses to apply the terrestrial parameter or the satellite onedepending on the value of the round trip delay parameter. This is further detailed in section3.2.5.

• Virtually Changeable cell parameters (CAE/VT): These parameters may take different valuesand are computed by the OMC. The current computed values do not take into account satellitelinks. It is not possible to propose a compromise value because it would affect the QoS forcustomers who are not interested in satellite connections. Since there are only a few of theseparameters, we propose that the OMC computes two set of values, one for a cell with satelliteconnection, one for a cell with terrestrial connection. In order to simplify the OMC development,the value of the round_trip_delay parameter may be used instead of Abis connection type todetermine if a satellite link is used for a given cell (round_trip_delay > 500ms7 => satellite).

3.2.3 Parameter m odification for B7.2

The following table provides the list all the parameters, which have to be tuned for Abis or Aterthrough satellite connections for B7.2. The parameters, which are highlighted in bold , are relevant forthe Ater through satellite case only. In other words:

• For the Abis through satellite case: the parameters, which are NOT in bold, areconsidered.

• For the Ater through satellite case: the full parameter list is considered.

Other formatting conventions (MPDCH,etc.. ) are indicated below the table.

In most cases for timers, the satellite value is just an increase of the terrestrial value by about 500msso as to cope with the added round-trip-time. When the parameter is not instanciated per cell (for theAbis case) or by BSS (for the Ater case), then the satellite value is chosen as a compromise value.Consequently if a procedure fails, the BSS reaction time will be a bit increased and some resourceswill be kept busy a bit longer than necessary for terrestrial links. This may result in a small loss ofcapacity for PS services. When other consequences are expected, they are detailed as notes belowthe table (see note number in second column).

For some CAE/cell parameter, it is not easy to recommend a value for satellite links, because acompromise has to be made between resource usage and performances. In this case the influence ofsuch a parameter has to be explained to the operator who can tune the value according to his ownpriority. When needed, some comments are provided after the table to explain the reason of thechange or to provide guidelines for tuning.

When a parameter is duplicated in BSC and MFS, the duplication is indicated only if different sub-system are impacted (i.e. for CST or CDE parameters). For duplicated parameters, which areaccessible from the OMC, only one parameter is indicated, since both instances are copied from theOMC unique parameter.

7 500ms is lower than the current default value for satellite (700ms), but it is considered that the effectof a round trip delay higher than 500ms due to any reason justifies specific tuning.




parameter name protocollayer

MPDCHonly

instance category OMC Defaultvalue

satellitevalue

change ofcategory

Round_trip_delay RLC cell CAE chgbl 160ms 700ms

T_ul_assign_CCCH RRM PCC cell CAE No (VT) table newtable

T_dl_assign_CCCH RRM PCC cell CAE No (VT) table newtable

T_one_Block RRM-PRH MFS CST No 1s 2s =>CDE

Trelease GCH MFS CST No 500ms 1000ms =>CDE

T_ul_access_max RRM-PCC CST No 1.4s 1.9s =>CDE

T_ACK_WAIT RRM-PRH MFS CST No 1.2s 1.7s =>CDE

T_ack_wait_DRX_PCCCH RRM-PRH YES MFS CST No 2.5s 3s =>CDE

K_GSL(BSC) LAPD BSC CST No 7 16 =>CDE

K_GSL(MFS) LAPD MFS CST No 7 16 =>CDE

T_GPRS_resume RRM PCC BSC CST No 1 1.5 =>CDE

T_delayed_DL_TBF_rel_radio

RRM-PCC MFS CST No 1200ms 2200ms =>CDE

Tcorr GCH cell CAE chgbl 200ms 700ms

Testab GCH cell CAE chgbl 200ms 700ms

BS_CV_MAX RLC cell CAE chgbl 8 15

T3192 RRM(MS) cell CAE chgbl 0.5s see rules

T3168 RRM(MS) cell CAE chgbl 1s 1.5s

EN_MPDCH RRM_PRH cell CAE chgbl 0 see rule

N_TBF_per_SPDCH RRM_PRH cell CAE chgbl 1 see rule

EN_Delayed_DL_TBF_Rel RRM-PRH BSS CAE chgbl 0 see rule

T_ul_assign_pccch RRM PCC YES cell CAE chgbl 0.4s 0.7s

S RRM (MS) YES cell CAE chgbl 30 see rule

TX_INT RRM(MS) YES cell CAE chgbl 8 see rule

Tx_integer PAGCH cell CAE chgbl see rule

T_PDCH_inactivity RRM-PRH BSS CAE chbl 10 see rule

T_PDCH_inactivity_last RRM-PRH BSS CAE chbl 10 see rule

Table 1: parameter list for Abis or Ater sate llite connection,

Formatting meaning :Red => OMC impactBlue=> CST becomes CDEblack=> operator tuning, with (if possible) recommended value for satellite links.Bold: additional p arameters m odified if Ater is through satellite (not applicable to Abiscase).italics: parameters used for MDCH only.Method : Essential parameters to activate the feature

3.2.4 Additional tuning rules for p arameters

The parameters which are not listed below (Tcorr, Testab, BS_CV_max, T3168,T_ul_ass ign_pcch ) do not require specific additional rule or comment.

3.2.4.1 EN_MPDCH.

The Master PDCH requires the establishment of a GCH (Abis and Ater) which does notcarry traffic. In case of Abis or Ater through satellite, the usage of the MPDCH mustconsider the following criteria:• Higher cost of transmission resources through the satellite




• Limited throughput of the RSL in case of Abis through satellite to about 8 Kbitpsbecause of round trip delay effect on acknowledged protocol (see section 5.3.1 and ref [A1]for detailed explanations). In case of important CS signalling load, the RSL may not be ableto transport the additional signalling load due toTBF establishments when no MPDCH isestablished. Hence the recommendation in the GPRS through satellite case is:

• For a cell connected with Abis through satellite and with non negligible signalling load8

(CS+PS), MPDCH is recommended.

• For a cell connected with Ater through satellite, MPDCH is not recommended.

3.2.4.2 Round_trip_delay:

See section 1.3.1 for definiton and computation of round trip delay with a satellite link. The OMC andthe GPU ranges must be extended for this parameter to at least 900ms, to cope for potential increaseof the round-trip delay due to the possible future introduction of compression/decompressionequipment. The OMC-R also uses this parameter to determine whether or not GPRS traffic is carriedthrough Abis or Ater satellite links as follows:

• If round_trip_delay < 500 ms, the OMC-R considers that GPRS traffic is carried through AbisandAter terrestrial links,

• If round_trip_delay >= 500 ms, the OMC-R considers that GPRS traffic is carried either throughAbis satellite links or Ater satellite

3.2.4.3 T_ul_ass ign_CCCH, T_dl_ass ign_CCCH:

See explanation about Virtual Changeable parameters in section 3.2.2. An offset of about 500msmust be added compared to the value for terrestrial links. As the timer accuracy in the MFS is 50 ms,it is recommended to set values so that other timers derived from the above timers are a multiple of50 ms. Hence the added offset may not be exactly 500ms9.

3.2.4.4 T_ul_ access_max:

The two following rules are recommended:

i) The Time T_ul_access_max shall be longer than the duration of a radio allocation requestedtowards the BSC.

ii) A too long value of T_ul_access_max may lead to reserve unnecessarily radio resources. It isrecommended to set T_ul_access_max = T_repeat + 240 ms – Round_Trip_Delay, where theT_Repeat is the maximum time between two successive packet channel requests, 240 ms is a givenmargin. The value of T_Repeat depends on the parameters S, TX_INT, and TX_INTEGER.

It is recommended to set this parameter as follows depending whether or not GPRS traffic is carriedthrough Ater satellite links:

• IT_ul_access_max = 1400 ms if GPRS traffic is carried through Ater terrestrial links in all the cellsof the MFS,

• IT_ul_access_max = 1900 ms if GPRS traffic is carried through Ater satellite links in at least onecell of the MFS.

3.2.4.5 K_GSL

8 The Abis RSL throughput should be estimated with knowledge of the cell traffic and signallingload.For safety, if at least 4 Kbitps for CS services is needed on the downlink, then a MPDCH shall beconfigured.

9 As the SFD has been written after the B.2 CR, the exact coding can be found in CR3BKA20CBR123988




The parameter K_GSL is the anticipation window size for the LapD protocol. It conditions theavailable bandwidth per GSL link,K_GSL (BSC) for the BSC-to-MFS direction,K_GSL (MFS) for the MFS-to-BSC direction.

The value 7 is enough for GSL through terrestrial link, and the value 16 is the maximum possibleconsidered in the BSS, because of available buffer space in the BSC. The value 16 improves theGSL bandwidth but will not provide 100% of 64 Kbit/s (see Annex B for details ).

Using the satellite value with Ater through a terrestrial link will increase the number of messagerepetition in case of poor transmission quality10 on the Ater interface, which increases the risk ofcongestion on the GSL. With good transmission on the Ater interface, the change will not benoticeable.

This is important especially if the operator uses the Gs interface with no MPDCH in most cells (flow ofCS paging on the GSL from the MFS to the BSC.Depending on the K_GSL value, and on the operator choice for Gs interface, MPDCH, Location areasize, the number of cells supported by a GPU will be more or less limited (see Annex 3). The smallerthe value, the lower the number of cells which can be mapped per GPU in case of satellite link.

Note that for other non-listed GSL parameters (T200_GSL, T_GSL_ACK , etc..) default values arealready compatible with satellite links.

3.2.4.6 T_GPRS_Resume

A longer value (1.5s instead of 1s) is not a problem for terrestrial (radio resources are kept 500mslonger in case of SGSN failure to reply. It is possible that the terrestrial value (1s) may be enough tooperate with satellite links, but it may depend on SGSN performances, on which we have no data.

3.2.4.7 T _delayed_DL_TBF_rel_radio

It is advised to increase this parameter by 1s compared to terrestrial link to avoid degradation ofservice access time with satellite round trip delay.

Note that this parameter does not exist any longer with B8 software.

3.2.4.8 T3192

It is recommended to set this parameter as follows depending whether or not GPRS traffic is carriedthrough Abis or Ater satellite links:

- Case GPRS traffic is carried through Abis and Ater terrestrial links in the serving cell:i) T3192 = 1000 ms if the non-DRX mode is not activated and the delayed DL TBF release mode isnot activated in the cell (i.e. if DRX_TIMER_MAX = 0 and EN_DELAYED_DL_TBF_REL = 0)

ii) T3192 = 500 ms if the non-DRX mode is activated or the delayed DL TBF release mode isactivated in the cell (i.e. if DRX_TIMER_MAX > 0 or EN_DELAYED_DL_TBF_REL = 1)

- Case GPRS traffic is carried either through Abis satellite links or Ater satellite links in the servingcell:i) T3192 = 1500 ms if the non-DRX mode is not activated and the delayed DL TBF release mode isnot activated in the cell (i.e. if DRX_TIMER_MAX = 0 and EN_DELAYED_DL_TBF_REL = 0)

ii) T3192 = 1000 ms if the non-DRX mode is activated or the delayed DL TBF release mode isactivated in the cell (i.e. if DRX_TIMER_MAX > 0 or EN_DELAYED_DL_TBF_REL = 1)

10 It must be noted that it is quite possible to have very good quality with some satellite links and mediocre qualitywith some terrestrial links. A value of K_GSL =16 will not cause any problems with links which comply with ITU-Trecommendation G.826.




3.2.4.9 N_TBF_per_SPDCH

When GPRS traffic is carried through Abis/Ater satellite links, the repetition of (Packet) ChannelRequest messages is faster than the network response. Then, it is likely to have double and eventriple PDCH allocation for one single TBF if there is no PDCH established to serve the MS request. Inorder to avoid requesting too many PDCHs and GCHs to the BSC (which would not be used)N_TBF_PER_SPDCH can be increased to optimise the target number of TBFs to be multiplexed onone PDCH.

3.2.4.10 EN_Delayed_DL_TBF_Rel

To obtain better Telecom performance, it is recommended to set EN_DELAYED_DL_TBF_REL to 1.

3.2.4.11 S and TX_INT

The recommended value of S and TX_INT depends on the value of BS_PRACH_BLKS. Theseparameters need to be tuned only if a MPDCH is configured in the cell.

When the GPRS traffic is carried through Abis or Ater satellite links, it is recommended to set S sothat the time between two successive Packet Channel Request messages is longer than 1400 ms.

It is recommended to set TX_INT so that the corresponding spreading time is about 240 ms.

3.2.4.12 Tx_integer

When the GPRS is supported through Abis or Ater satellite links, it is recommended to set:TX_INTEGER = 32 whatever the configuration of the CCCH.

3.2.4.13 T_PDCH_inactivity

The setting of the T_PDCH_Inactivity timer comes to make a trade-off between the GCH resourceusage and the Telecom performance:

-The higher is the T_PDCH_Inactivity timer, the higher is the GCH resource usage on the Aterinterface. This may imply additional bandwidth usage on the satellite link.

-The higher is the T_PDCH_Inactivity timer, the lower is the average duration of TBF establishmentson (P)CCCH. This will improve the service access time with satellite links.

3.2.4.14 T_PDCH_inactivity_last

The setting of the T_PDCH_Inactivity_Last timer comes to make a trade-off between the GCHresource usage and the Telecom performance:

-The higher is the T_PDCH_Inactivity_Last timer, the higher is the GCH resource usage on the Aterinterface. This may imply additional bandwidth usage on the satellite link.

-The higher is the T_PDCH_Inactivity_Last timer, the lower is the average duration of TBFestablishments on (P)CCCH. This will improve the service access time with satellite links.

This parameter may also be used to ensure that the BSS reserves at least one GCH resource in theserving cell while the MS is engaged in a Web browsing session

3.2.5 Additional CST P arameter m odification for B8




Six RLC parameters have been identified as needing specific modification in the scope of B8. Four ofthem are only related to EGPRS. The two GPRS parameters were not adapted in the scope of B7.2,for budget and planning reason. These parameters shall be optimised for B8, so as to improve RLCperformance with satellite links.

These parameters are duplicated in the MFS data-base . For each parameter a one new one iscreated for satellite link, the old one is used for terrestrial link. These parameters remain CST typeparameters, which implies that they are not accessible at the OMC operator interface. The choice, ofwhich parameter (satellite or terrestrial) has to be used for a given TBF, is perfomed in the MFSdepending on the value of the round trip delay parameter in the considered cell.

• If round_trip_delay < 500 ms, the MFS considers that GPRS traffic is carried through Abis andAter terrestrial links,

• If round_trip_delay >= 500 ms, the MFS considers that GPRS traffic is carried either through Abisor Ater satellite links,

The table below provides the list of the new B8 RLC parameters.

new parameter name protocollayer

instance category OMC Default value

GPRS_DL_Ack_Period_satellite RLC MFS CST No tbd

GPRS_UL_Ack_Period_satellite RLC MFS CST No tbd

EGPRS_DL_ack_factor_satellite RLC MFS CST No tbd

E_GPRS_UL_ack_factor_satellite RLC MFS CST No tbd

N3105_limit_satellite RLC MFS CST No tbd

EGPRS_N3105_limit_satellite RLC MFS CST No tbd

Table 2: New CSTparameter (RLC) for sate llite link in B8.

The choice of the four first parameters (GPRS_DL_Ack_Period, GPRS_UL_Ack_Period,EGPRS_DL_ack_factor, E_GPRS_UL_ack_factor) is the result of a compromise bewteen twoaspects:

• With a high value of the above parameters, it will take more time for the transmiter to beinformed of an uncorrectly received block in the receiver. Consequently the risk of stalling theRLC window is increased. Hence, in case of high BLER on the radio path, the loss of throughputin the direction of the transfer will be minimised by a low value. For a satellite link, the loss ofthroughput in case of errors on the radio path will be higher than with terrestrial links because of ahigher risk of window stalling.. Applying a lower value than with a terrestrial link will enable tocompensate partly this additional loss of throughput.

• The Acknowledgments are taking some throughput on the PDCH in the direction opposite to thetransfer. It another TBF is established (for the same MS or another one) in the opposite direction,then this results in a throughput degradation for the latter TBF.

It is not simple to determine the best compromise to tune the above parameters. Some preliminarystudy with a BLER of 30% is presented in Annex A. More accurate results will be obtained fromsimulations from R&I. The default value for satellite links shall be set according to simulation results.

According to BSS telecom parameters, the N3105_limit parameter and EGPRS_N3105_limit arerelated to the four other parameters. EGPRS_N3105_limit and N3105_limit parameters shall havespecific values for satellite links, the default value shall also be set according to simulation results.




3.2.6 Additional CAE P arameter t uning for B8

The tuning of the following parameters (CAE) may be impacted by the satellite link:

parameter name protocol

layer

instance category OMC Default

value

satellite

value

EN_fast_initial_gprs_access

RRM-PRH cell CAE chgbl 0(disabled)

seecomment

below

NB_TS_MPDCH RRM-PRH cell CAE chgbl 0 seecomment

below

Table 3: Additional CAE p arameter t uning defined in B8.

The following external comments may be added to help the operator set these parametersin the satellite case.

EN_FAST_INITIAL_GPRS_ACCESS: Better performances for service access time will beobtained when this parameter is set to enabled, but one PDCH will always be established inthe cell. A compromise has to be made by the operator between performance gain and thecost of radio and terrestrial resources. This compromise becomes of higher importance incase of a cell connected through a satellite link due to the higher GPRS access time withsatellite links and also the higher cost of transmission. This parameter being set by BSS, itmay be useful to tune it in the specific case of Ater through satellite links. In the case ofAbis through satellite, the parameter should be set to the value recommended withterrestrial links, as not to degrade desired performances for the cells connected with aterrestrial link; even though the value may not be optimal for the satellite case.

NB_TS_MPDCH: The Master PDCH requires the establishment of a GCH (Abis and Ater)which does not carry traffic. In case of Abis or Ater through satellite, the usage of theMPDCH must consider the following criteria:• Higher cost of transmission resources through the satellite• Limited throughput of the RSL in case of Abis through satellite to about 8 Kbitpsbecause of round trip delay effect on acknowledged protocol (see section 5.3.1 and ref [A1]for detailed explanations). In case of important CS signalling load, the RSL may not be ableto transport the additional signalling load due toTBF establishments when no MPDCH isestablished. Hence the recommendation in the GPRS through satellite case is:

• For a cell connected with Abis through satellite and with non negligible signalling load11

(CS+PS), MPDCH is recommended.

• For a cell connected with Ater through satellite, MPDCH is not recommended.Note that this parameter corresponds to B7.2 parameter EN_MPDCH.

3.2.7 PM counters

At this stage no PM counters specific for GPRS through satellite links have been identified.

3.2.8 PM indicators

At this stage no PM counters specific for GPRS through satellite links have been identified.

11 The Abis RSL throughput should be estimated with knowledge of the cell traffic and signallingload.For safety, if at least 4 Kbitps for CS services is needed on the downlink, then a MPDCH shall beconfigured.




3.2.9 Migration

It is recommended to the operator to plan the feature GPRS through satellite at migration time.Indeed some CDE parameters have to be customized to allow the activation of the feature.As the system migration method includes the customization of CDE parameters through CDE tablefor BSC CDE parameters and CDE BUL files for MFS CDE parameters, migration is the good placeto customize these parameters.As described in chapter 3.2.3 (for B7.2) and 3.2.5 (for B8), the following parameters have to becustomized before GPRS through satellite:

GPRS through satellite on Abis:• T_one_Block (MFS CDE)• Trelease (MFS CDE)• T_ACK_WAIT (MFS CDE)• T_delayed_DL_TBF_rel_radio (MFS CDE)• T_ack_wait_DRX_PCCCH

GPRS through satellite on Ater:Same list as Abis + the following additional p arameters

• T_ul_access_max (MFS CDE)• K_GSL(BSC) (BSC CDE)• K_GSL(MFS) (MFS CDE)• T_GPRS_resume (BSC CDE)

Note: the reason why Ater requires extra parameter tuning compared to Abis is explained in section1.3.3.

Nevertheless, Satellite CDE p arameters shall be changeable apart from the migration process.

3.2.10 GPRS through satellite activation.

This chapter takes as prerequisite the customization to satellite values of needed CDE parameters.Rules and explanations about parameter tuning can be found in sections 3.2.3 (for B7.2) and section3.2.6 (for B8).

3.2.10.1.1 Activation of the feature GPRS through Abis satellite:

• BSS parameters:• EN_Delayed_DL_TBF_Rel• T_PDCH_inactivity• T_PDCH_inactivity_last• For all the BSS parameters, the feature can be activated with default values

• Cell parameters:• Round_trip_delay• Tcorr• Testab• BS_CV_MAX• T3192

The cell parameters listed above shall be set to specific values to enable the GPRS through satelliteon Abis connection.

The following parameters can remain with default values.• N_TBF_per_SPDCH• Tx_integer




• EN_MPDCH (B7.2 only)• EN_fast_initial_gprs_access (B8 only)• NB_TS_MPDCH (B8 only)

The 3 last one are relevant for Master PDCH only:• T_ul_assign_pccch• S• TX_INT

ACTION # persons /site

Leadtime

Trafficimpact

M O&MImpact

Synchroimpact

1 Set Cell parameters (using MF- SetGPRS/UMTS Common CellParameters) with edit multiple cells:

• Round_trip_delay• Tcorr• Testab• BS_CV_MAX• T3192

1/OMC-R 2’

3.2.10.1.2 Activation of the feature GPRS through Ater by satellite:

The following actions have to be done additionally to those listed for the Abis through satellite case.

BSS parameters:• none

Cell parameters:• T3168

ACTION # persons /site

Leadtime

Trafficimpact

M O&MImpact

Synchroimpact

1 Set Cell parameters (using MF- SetGPRS/UMTS Common CellParameters) with edit multiple cells:

• T3168

1/OMC-R 30”

3.3 Validation

3.3.1 Validation for telecom aspects

The validation has several goals:

• Check the possibility to establish GPRS transaction in a cell connected through satellite

• Check if the feature works with MS-to-MS transactions.

• Check that the new values of the CDE parameters, which are modified also for terrestrial links,has no detectable impact on PS performances for the cells connected through terrestrial links




• Evaluate the performances with a few typical applications (WAP, FTP, WEB-browsing, SMS…)

• For the Abis case, for which the RSL throughput may be a problem, the correct functioning ofPS+CS services, on one cell with a few TRE shall be checked. The RSL load on the TRE carryingfollowing configuration shall be estimated, and LAPD congestion assessed… with possibleconsequences (dropped calls, paging lost, etc..).

• 1CCCH combined + 4 SDCCH + 7 TCH. (TCH used for CS or as PDCH)• 1 CCCH not combined + 8 SDCCH + 6 TCH. (TCH used for CS or as PDCH)

Some calls shall be made so as to load at least such a TRE, with the Alcatel call mix (maybe witha reduced cell paging rate). The paging rate may be lowered down to one cell = one location area=> Paging rate = MT-call rate + SMS-MT rate.

3.3.2 Validation for O&M aspects

• Check the modification of CDE parameters out of the migration.• Check the activation of the feature.

3.3.3 Testing tools

Delay line needed. No other specific tool.

3.3.4 Test strategy

3.4 MethodsMethod shall be delivered to modified BUL files apart from the migrationThe impact of such a method is a GPRS outage due to GPUs reset.

Method shall be delivered to modify CDE parameters apart from migration.The method consists in a “pseudo” software replacement with the same BSS software than therunning one and with the application of CDE table. This CDE table shall be customized with correctvalues for GPRS through satellite feature.

Impact on existing method: Satellite feature activation.Add in the existing method describing the satellite feature activation, the tuning of CAE parametersessential for GPRS through satellite (CF chapter 3.2.10)

3.5 GCDs

3.6 Engineering rules

Engineering rules may be impacted by the system dimensioning constraints (see section 5.3).

3.6.1 Fault Management




4 SUBSYSTEM IMPACTS

4.1 BTS

No impact

4.2 BSC

No Software impacts. Impacts on data management.

4.3 Transcoder

No impact

4.4 MFS

B7.2 impacts: Increase of the range of round trip delay parameter.

B8 impacts: Impacts of RLC parameter choice depending on round trip delay (impact Data andsoftware). See section 3.2.5 for details. The new parameters are passed down to PTU and a specifichandling is needed in RLC layer to assess whether terrestrial or satellite parameter is to be used.

4.5 OMC_R

B7.2 impacts : Evolution of round_trip_delay parameter shall be taken into account (See section 3.2.) and virtual changeable parameter modification.RNO is impacted by Round trip delay parameter range modification.

B8 impacts: No impact

4.6 OEF/POLOThere is no impact on OEF tool.

Impact on POLO tool:The check that "if BSS.AterConnectionType = VIA_SATELLITE, there must be FULL_GSM inAterMux table” shall be removed.

5 PERFORMANCE & SYSTEM DIMENSIONING

5.1 Traffic model

We have no specific traffic model for satellite connection.




5.2 Performance

5.2.1 Maximum Data Throughput.

• GPRS case : The maximum throughput is defined by the proportion of time during which thewindow is not stalled. In the best case (no repetition due to transmission errors), it is equal to thetime taken to transmit the full window divided by the round-trip-time. For GPRS the window sizeis equal to 64 blocks. The total round-trip-time with a satellite link is equal to 700ms. So themaximum throughput expressed in RLC blocks/s is 64/0.7 = 91 RLC block/s. The normalthroughput per PDCH with terrestrial links is 50 RLC blocks/s per PDCH. So whatever the codingscheme used (i.e. CS1 to CS4), the maximum thr oughput at RLC l evel with a sate llite link isabout 90% of the maximum obtained with 2 PDCH when Abis or Ater interface are usingterrestrial link.

• EDGE case: That the large value of WS enables to reach the maximum EDGE throughput (MC8,MCS9 not taken into account) with no Error on the radio path. This however does not take intoaccount the sensitivity to radio condition in the cell.

• Sensitivity to radio conditions in the cell: In case of poor radio condition in a cell, thethroughput degradation will be more dramatic with a satellite link than with a terrestrial link, due tothe addition of satellite delay with each repeated RLC block. This can be attenuated by the tuningof some RLC parameters, as proposed in section 3.2.5. Some estimation of additional the loss ofthroughput with a BLER =30% has been performed within SYT and is reported in Annex X.However such a high BLER does not seem very realistic and more simulation results is awaited toconclude on this subject.

• cell reselect ion: The traffic interruption due to cell reselection will be increased (not quantified).

5.2.2 Service access time.

• The user applications (especially WAP and WEB browsing) are slowed down due toslower TBF establishments. This effect is diminished by the Delayed downlink TBF releasefeature and by the PDCH inactivity timer. It should be noted that the delay induced by the satellitethrough Ater is higher than with Abis through satellite, because more signalling is involved on thisinterface for resource allocation. This is illustrated with the expected “Ping” round trip delay(rough estimation), based on B7.2 expected performances. (B8 further optimisation not taken intoaccount, but the gain should be only for the Ater case).

Abis and AterTerrestrial links

Abis throughsatellite

Ater throughsatellite

Repetitive pings (less than 2s interval)with Delayed DL TBF release enabled12 800ms 1500ms 1500ms

Repetitive pings (more than 5sinterval), with radio and terrestrialresources already established.

1100ms 2000ms 2000ms

Single pings (about 15s betweenpings), with no resources established.

1600ms 3000ms 3500ms

Table 4: estimation of “ping time” through the BSS with and w/o a satellite link.

12 Except for the first ping, which behaves like a single ping




• For WAP or for other applications, which transmit a small amount of data with relativelylong interruptions (more than 10s), the degradation will be very strong in term of access time.

• For TCP based a pplications (FTP, WEB browsing), the degradation will vary dependingon the type of server used (some have specific behaviour to cope with satellite delays), anddepending on the amount of data to transfer. For small data transfer (less than 50Kbytes), theloss of throughput at user level is more significant due to the slow start mechanism.

5.3 System dimensionning

The system dimensioning must take into account the two following constraints:

If Abis through satellite, limited throughput on the RSL

If Ater through satellite, limited throughput on the GSL

5.3.1 Impact of satellite delay on RSL throughput.

This is already studied in reference [A1]. The throughput available per RSL, when considering GSMCS signalling with a window size of 15 (maximum allowed), is about 8 Kbit/s. This is already tight forthe nominal load with CS traffic. In case of important signalling load due to TBF establishments, theincreased RSL load due to PS signalling on the CCCH may not be compatible with the RSL availablethroughput. In this case configuring a MPDCH would help decreasing the RSL throughput.

5.3.2 Impact of satellite delay on GSL throughput.

The throughput available on the GSL, when considering GSM CS signalling with a window size of 16(maximum allowed), is about 12 Kbit/s. The consequence is that a lower number of cells per GPUshould be configured. See details in Annex B.

5.4 Load constraints

There is no specific load constraints in term of CPU.




6 OPEN POINTS

The following “open points” have been raised during the ellaboration of this SFD. The conclusions areprovided herebelow. When the open points are closed, the discussions have been removed from theother parts of the SFD so as not to confuse the reader.

OPEN POINT 1: Can the feature “GPRS through satellite links” be inhibited by O&M?Status: closed.The feature cannot be inhibited, if the “industrialisation of satellite” is enabled.The feature GPRS through satellite has to be planned at network level before migration to customisecorrectly CDE and BUL files. Satellite CDE parameters are not changeable apart from the migrationprocess.

OPEN POINT 2: It is not clear how to find the best compromise for the tuning of RLC parametersfrom Table 2..Some preliminary study with a BLER of 30% is presented in Annex A. More accurate results will beobtained from simulations from R&I.Status: closed.The default value for the satellite instance of the parameters will be set according to simulationresults. An update of this SFD will be provided with result summary.

OPEN POINT 3: The tuning of the RLC parameters (presented in Table 2) for satellite connections canbe envisaged in two ways…or not at all:1. either parameters instanciated at Cell level: => OMC-R and MIB impact2. or Duplication of the parameters in the MFS DLS , one value for satellite, one value for terrestrial.

The choice of the value is made in the MFS depending on the value of the round trip delayparameter.

Status: closed.The second option is the chosen one so as to limit Software impacts.

OPEN POINT 4: According to BSS telecome parameters, the N3105_limit parameter andEGPRS_N3105_limit are related to the four other RLC parameters (presented in Table 2).Status: closedRecommended values for the satellite case will be provided by simulation results.An update of this SFD will be provided with result summary.

OPEN POINT 5: Can the BTS G2 support the GPRS through satellite connection?The point is under investigation. Current status is NOT SUPPORTED.




7 IMPACTS SUMMARY

Equipments:

BTS BSC MFS TC OMC-RX x X

Interfaces:TelecomRadio Abis A Ater BTS-TC MFS-BTS MFS-BSC Gb

O&MAbis-O&M BSC-O&M TC-O&M MFS-O&M Q3

xTo be filled in by O&M experts.

List of Impacted Step2:List the Step2 documents which are impacted by the present feature.BSS telecom parameterGPRS Traffic Model and PerformancesRLC functional specificationBSS O&M parameterNetwork Modification Process and Performance (NMPP)Migration




8 GLOSSARY

8.1 Abbreviations

8.2 Terminology




A. ANNEX: EDGE THROUGHPUT IN CASE OF HIGH BLER

The calculation done for GPRS cannot be applied to EGPRS, because the much higher window sizedoes not allow to acknowledge the full ARQ window with a single Packet ACK/NACK message. Indocument ref [A3, the ACK/NACK bit-map is supposed to have an infinite length, but in reality theACK/NACK bit-map is segmented into several messages, which increases the risk of protocol stalling.

The following shows the results of simulations run with a simulator develop in SYT 13, to estimate thepossible loss of performances with satellite links (total round-trip delay is 620ms), depending on thepossible optimisation of the ARQ parameters (polling period, bit map compression). The total bit-maplength is set to be 128 bits for most cases (exceptions in bold). The simulations are run with multislotcapability 1,2, 4.14

The output of the simulator is the RLC normalized throughput with a constant BLER of 30%. Thenormalized RLC throughput is the ratio: Actual throughput/maximum throughput. With BLER =30%the maximum reachable normalized throughput is 0.7. The normalized throughput is indicated in boldwhen ≥ 0.60.

INPUTS OUTPUT

windowsize (WS)

bit-maplength

Nb Timeslots MCS ≥ 7

Ack period

Dl_Ack_factor (= WS/ Ack_period)

Bit-mapcompression

normalisedthroughput(max =0.7)

192 128 1 yes 32 0.17 No 0.36

192 128 1 yes 16 0.08 No 0.45

192 128 1 yes 8 0.04 No 0.52

192 128 1 Yes 16 0.08 yes 0.63

192 128 1 yes 8 0.04 yes 0.63

192 128 1 no 32 0.17 No 0.68

256 128 2 yes 32 0.13 No 0.46

256 128 2 yes 8 0.03 No 0.50

256 128 2 yes 16 0.06 yes 0.52

256 128 2 yes 8 0.03 yes 0.52

256 256 2 yes 32 0.03 yes 0.53

256 128 2 no 32 0.13 No 0.60

256 128 2 no 16 0.06 No 0.64

256 128 2 no 16 0.06 yes 0.67

512 128 4 yes 32 0.06 No 0.35

512 128 4 yes 32 0.06 yes 0.41

512 128 4 yes 16 0.03 yes 0.42

512 128 4 yes 8 0.02 yes 0.41

512 256 4 yes 64 0.13 yes 0.47

512 512 4 yes 64 0.13 yes 0.52

512 128 4 no 32 0.06 No 0.46

13 I have used the simulator that P.J.P. developped to make some contributions in standardisation. This simulatoris not documented, so there is some uncertainty on the way to choose the inputs, especially it seems that thesegmentation of the bit-map is not taken into account (only compression). I hope we will have simulation resultsfrom the CRC for comparison.

14 Time slot capability = 3 is not implemented in the simulator, and time slot capabilty = 4 performances arealready not very satisfactory.




512 128 4 no 16 0.03 No 0.50

512 128 4 no 16 0.03 yes 0.56

512 256 4 no 32 0.06 yes 0.63

512 512 4 no 32 0.06 yes 0.66

512 256 4 no 128 0.25 yes 0.60

Table 5: simulation of EGPRS normalized throughput with satellite round-trip-delay.

We see that we can only approach 15 the maximum normalized throughput with

• 1 time slot: all MCSs

• 2,4 time slots: only MCS-1 to 6 (1 Data block/radio block)

The throughput is improved by diminishing the polling period. It should be studied if this is in conflictwith the measurement reporting period for DL TBF.

The results of these simulations are however pessimistic, because they do not take into account thefact that the BTS may autonomously perform the repetition of previously stored data blocks, in whichcase the round-trip delay due to satellite is cancelled after the first repetition. This will improve thethroughput, but we are not able to quantify it.

These simulation were run assuming that only one TBF is using the assigned time slots. Whenseveral TBF are multiplexed, then the fact that several TBF share the resources may diminishes thewaste of radio resources, but the maximum reachable throughput per user does not improve.

15 Approach <=> Normalized throughput ≥ 0.60




B. ANNEX: GSL bandwidth and Maximum cells per GPU.

This annex is only applicable to the case of Ater c onnection through satellite links.

Parameters value unitGSL link speed 64 Kbit/s

GSL I frame average length 45 bytes

RR (Ack at Lapd level) 8 bytes

Satellite round trip delay 500 ms

process time (MFS +BSC) 10 ms

The available bandwidth on the GSL is computed as:

GSL link speed x K_val––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––I-frame transmission time + RR transmission time + Round trip delay + Processing time

K_VAL is the anticipation window for the LapD protocolThe frame transmission time is equal to the frame length (in bits) divided by the link speed (in bit/s)/

LinK speed I trans time(ms) RR transtime

K_val satellite%GSL used

GSL bandwidth(Kbit/s)

64 5.6 1.0 7 8% 4.9

64 5.6 1.0 16 18% 11.3

64 5.6 1.0 91 100% 64.0

The needed bandwidth per cell on the GSL mainly depends on the number of TBF establishment onthe CCCH, the paging load, the number of suspend /resume. (For details see document 3BK 112030077 DSZZA GPRS Traffic Model and Performances). Depending on the traffic hypothesis and thevalue of the K_GSL parameter in the MFS, the maximum number of cells, which can be mapped perGPU, will vary. Some examples are given below but a detailed dimensioning should be conducted ona per customer basis16.

Traffic HypothesisErlang/cell 20 (5 TRX cell)

CS call/s 0.4 (50s holding time)

TBF estb on CCCH per PS call 2

PS Paging/s 0.1 (low)

CS paging/s 15 (medium paging load)

Master PDCH none

suspend / resume feature yes

16 LCS traffic on the GSL has not been considered.




GSL traffic load depending on PSpenetration and Gs interface

max cells per GPU with 2 GSL

Kbit/s per cell K_VAL=7 K_VAL=16

33% PS penetration

GSL Kbit/s per cell if Gs 2.4 4 9

GSL Kbit/s per cell NO Gs 0.4 22 50

20% PS penetration



10% PS penetration






C. ANNEX : parameters to be modified for Gb.through satellite links.

The GB interface through satellite is not within the scope of this document.

Gb could be located on the Ater interface in the case where the MFS is collocated with the BSC. Thiscase is however quite rare and would rather corresponds to a large BSC in a dense urban area.Hence it is not considered in the scope of Ater interface through satellite which is expected to apply tosmall BSCs in remote area.

However, as a reminder, the following parameters need to be tuned in case of Gb through satellite

T4_BSS_GPT3_BSSGPT_delayed_PUANT_NETWORK_RESPONSE_TIME

END OF DOCUMENT

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Abis Ater Satellite Parameters