interface over satellite

User Description, Interfaces over Satellite

USER DESCRIPTION

Copyright

© Ericsson AB 2004-2009 - All Rights Reserved

Disclaimer

No part of this document may be reproduced in any form without the writtenpermission of the copyright owner.

The contents of this document are subject to revision without notice due tocontinued progress in methodology, design, and manufacturing. Ericsson shallhave no liability for any error or damage of any kind resulting from the useof this document.

Trademark List

Ericsson is a trademark owned by Telefonaktiebolaget LMEricsson.

All other product or service names mentioned in this User Description aretrademarks of their respective companies.

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Contents

Contents

1 Introduction 1

2 Capabilities 3

2.1 General Capabilities 3

2.2 General Limitations 3

2.3 A-Interface over Satellite 3

2.4 Abis-Interface over Satellite 4

2.5 Ater-Interface over Satellite 5

3 Technical Description 7

3.1 Transmission Requirements on Interfaces Using theSatellite Connection 7

3.2 A-Interface over Satellite 7

3.3 Abis-Interface over Satellite 9

3.4 Ater-Interface over Satellite 12

3.5 Speech Quality 14

3.6 GPRS and EGPRS 14

3.7 Main Changes 14

4 Engineering Guidelines 15

4.1 SDCCH Dimensioning 15

4.2 RACH Control Parameters 15

4.3 PCH Control Parameters 15

4.4 LAPD Signalling Dimensioning 15

4.5 Bandwidth 16

4.6 GPRS and EGPRS 17

5 Parameters 19

5.1 Main Controlling Parameters 19

5.2 Parameters for Special Adjustments 21

5.3 Value Ranges and Defaults Values 21

6 Concepts 25

Glossary 27

Reference List 29

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Introduction

1 Introduction

Interface (A, Ater, Gb or Abis) over satellite is used when satellite transmissionis the only or the most cost effective transmission media.

Typical areas of use are:

Countries where the distance between populated areas are long or where thegeography will hamper extending the normal transmission network.

Interface over satellite is suitable for remotely located islands, populated areasin the desert, industrial areas like mines, exhibitions, catastrophe areas, luxurycruise liners, forest industry and many other areas where coverage wouldotherwise be impractical due to transmission costs.

The transmission delay when using a geo stationary satellite is around 250 msin each direction from node A to node B (e.g. MSC to BSC). The long delay isdue to the long distance (36000 km) from earth to the geo stationary satellite.

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Capabilities

2 Capabilities

2.1 General Capabilities

This document describes how the system MSC, BSC, BTS can handle the longdelay introduced by the satellite connection. Satellite transmission can be usedon the following interfaces: A-interface, Abis, Ater or Gb.

The main issue to take care of is that a satellite transmission link causes anextra delay of about 250 ms in each direction, while the GSM specification,to which the networks are built , specifies shorter delays. To overcome theproblem with the long delay, various flexible adaptations have been introducedto optimize the performance of the system when using satellite links.

A BSC can handle both satellite BTS’s and non satellite BTS’s.

The system can handle up to two satellite interfaces at the same time e.g. Abisand Ater over satellite, but this is not recommended due to the long speechdelay.

GPRS and EGPRS is supported with Gb over satellite .

EGPRS is supported with Abis over satellite. GPRS may work, but performanceis not guaranteed due to limitations in the 3GPP standard.

The satellite feature can be used with or without network elements such asa DXX or a DXC.

2.2 General Limitations

This document does not cover external equipment such as satellite modems etc.

Call setup and allocation times are prolonged due to the satellite connection.

Call set up success rates could decrease for fax calls. It is not possible to senda fax between two mobile stations using a satellite hop.

2.3 A-Interface over Satellite

2.3.1 Capabilities

• Adaptation of signalling system no. 7 and data communication parameters.

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2.3.2 Limitations

• The MCC feature will work in TRA but not in EC pool due to the long roundtrip delay.

2.4 Abis-Interface over Satellite

2.4.1 Capabilities

• Adaptation of Time Alignment timers.

• Adaptation of data communication parameters.

• Flexible adaptation of LAPD link parameters on both BSC and BTS sides

• Avid Immediate Assignment shortens the system response to mobileaccess, see Reference [1] for more information.

• EGPRS is supported.

2.4.2 Limitations

• The MCC feature in either TRA or EC pool will not work due to the longround trip delay.

• The capacity of the LAPD signalling link is reduced for acknowledgedframes due to the increased round trip delay, the maximum capacity issome 28 I-frames per second per RSL link with window size 15. SeeSection 4 on page 15.

• GPRS is generally not supported.

GPRS may work, but performance is not guaranteed due to limitations inthe 3GPP standard.

• It takes more than one hour to load a base station over the satellite link.

• Cannot be used together with Flexible Abis.

• Overload handling is not activated.

• Immediate Assignment will always be on SDCCH, see Reference [1].

Note: It is possible to make calls during the SW loading.

2.4.3 HW Dependencies

• Not supported by RBS 200 .

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Capabilities

2.5 Ater-Interface over Satellite

2.5.1 Capabilities

• Adaptation of signalling system no. 7 and data communication parameters.

• Adaptation of Time Alignment timers.

2.5.2 Limitations

• The MCC feature in either TRA or EC pool will not work due to the longround trip delay.

2.5.3 HW Dependencies

—

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Technical Description

3 Technical Description

3.1 Transmission Requirements on Interfaces Using theSatellite Connection

These are the transmission requirements on interfaces using the satelliteconnection:

• The system needs a 2.048 Mbit/s, 1.544 Mbit/s interface or Ethernet, ifAbis over IP is used, at the points of interconnection, MSC, BSC, SGSN orBTS (ITU-T G.703, G.704).

• Clear Channel Capability (see Section 6 on page 25) e.g. no ADPCM orecho cancelling.

• Synctransparency If the synchronization of the remote node shall beprovided by the transmission interface, the satellite transmission must besynctransparent:

The synchronization provided by the transmission interface at the BTS sideshall be traceable to a clock complying with the G.812 Class II or ANSIT.101 Stratum II specification (better than +/- 0,016 ppm)

The synchronization provided by the transmission interface at the BSCside shall be traceable to a clock complying with the G.812 PRC or ANSIT.101 Stratum I PRS.

(The synctransparency requirement is not applicable if the remote nodesare locally synchronized, e.g. through a local GPS receiver.)

• BER better than 1*10–6

• Jitter according to ITU-T G.823 and G.824.

• Idle Pattern on not used time slots in the point of interconnection [MSC,BSC and BTS].

3.2 A-Interface over Satellite

3.2.1 MSC

Signalling

Long delays such as satellite delays and link disturbances are not goodcombinations since they hamper throughput of messages over the link.

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The signalling system no 7 has a method called Preventive CyclicRetransmission (PCR) which is specially designed to cope with the abovesituation. The idea is to retransmit frames cyclically and not wait a long time(time-out) before retransmitting (see Section 6 on page 25).

PCR can be activated by using the parameter PARMG and the size of theretransmission buffer can be set with parameter ERC .

Note: The parameters have to be changed in both the MSC and in the BSC

Data Services

The Radio Link Protocol works between an MS and the DTI or GIWU fornon-transparent data services. The protocol uses a retransmission timer T1which is located in the DTI or GIWU. The timer value of this timer has to beincreased to avoid cyclic retransmissions. It is recommended to increase thetimer with 500 ms.

The names of the parameters controlling the T1 timer are in the DTI:

T1FR1458 for 14.5kbit/s full rate

T1FR1211 for 12kbit/s full rate


T1HR1609 for 6kbit/s half rate

The names of the parameters controlling the T1 timer are in the GIWU:

T1FR12 for 12kbit/s full rate.



3.2.2 BSC

Signalling


The signalling system no 7 has a method called Preventive CyclicRetransmission PCR which is specially designed to cope with the abovesituation. The idea is to retransmit frames cyclically and not wait a long time(time-out) before retransmitting (see Section 6 on page 25).

PCR can be activated by using the parameter PARMG and the size of theretransmission buffer can be set with parameter ERC .

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Note: The parameters have to be changed in both the MSC and in the BSC.

3.3 Abis-Interface over Satellite

The figure below shows a typical Abis-interface over satellite configuration.

Figure 1 Typical Abis-interface over satellite configuration

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3.3.1 MSC

Signalling

It is not recommended to have the satellite cells within the same location areaas the non satellite cells, if the satellite cells are remotely located. This willreduce the paging load on the Abis-interface.

Data Services

The Radio Link Protocol works between an MS and the DTI or GIWU fornon-transparent data services. The protocol uses a retransmission timer T1which is located in the DTI or GIWU. The value of this timer has to be increasedto avoid cyclic retransmissions. It is recommended to increase the timer with500 ms.









T1HR6 for 6kbit/s half rate.

3.3.2 BSC

Four different adaptations have been designed to cope with the long delay:

• Flexible changes of LAPD parameters to handle satellite hops

• Avid Immediate Assign (see Section 6 on page 25)

• Flexible changes of TTA parameters

• Flexible changes of GPRS/EGPRS parameters

All four are activated by the parameter SIGDEL which can be set at TG level.

SIGDEL has the default value NORMAL. The value LONG is used for TGs withlong Abis delays such as satellite links.

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Flexible Change of LAPD Parameters to Handle Satellite Hops

The parameter SIGDEL set to LONG will change the working LAPD parametersto values that are suitable for the satellite link.

The parameters will be changed locally in the BSC and the new setting will besent to the BTS (in an XID-frame) before the link is taken into service. Thereason for the change is to accommodate the satellite round trip delay.

The adapted parameters are:

Table 1

Parameter/Timer SIGDEL =NORMAL

SIGDEL = LONG

Retransmission timer T200 240 ms 1400 ms

Window size for OML 1 11

Window size for RSL 4 in BSC, 2 in BTS 15

Flexible Change of TTA Parameters

This adaptation is for setting a time-alignment timer in the BTS.

Time Alignment is a mechanism used between the BTSs and the transcodersto minimize the time speech and data frames are stored in the BTS beforebeing sent out on the radio interface.

The time-alignment timer TTA is located in the BTS and it starts when the BTSsends time-alignment change information to the transcoder and it stops afterreceiving a response from the transcoder.

The parameters TTASHORT and TTALONG in the BSC controls the valueof the time-alignment timer.

TTALONG will be used for TGs where SIGDEL is set to LONG

TTASHORT will be used for TGs where SIGDEL is set to NORMAL.

TTASHORT and TTALONG are BSC changeable exchange properties, whichby default are set to 1 and 1.5 s respectively.

The timer value is sent down to the BTS at cell configuration.

Flexible Changes of GPRS/EGPRS Parameters

For cells with long round trip delays timers controlling the MS and the GPHneed to be changed. The MS timers are included in System InformationMessages distributed to the MS. GPH parameters described in the table below

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are set to accommodate for satellite round trip delays on the Abis path whenSIGDEL is set to LONG:

Table 2

Parameter/Timer SIGDEL = NORMAL SIGDEL = LONG

T3101 1500 ms 3000 ms

T3168Wait for Packet UplinkAssignment message.MS side timer.

500 ms 1500 ms

T3192Wait for release of theTBF after reception offinal block. MS sidetimer.

200 ms 1000 ms

BS_CV_MAX 6 15

DLDELAY Offset(1) Offset + 2s(1)

ULDELAY Offset(1) Offset + 2s(1)

(1) Max 5s

3.4 Ater-Interface over Satellite

3.4.1 MSC

Data Services

The Radio Link Protocol works between an MS and the DTI or GIWU fornon-transparent data services. The protocol uses a retransmission timer T1which is located in the DTI or GIWU. The timer value of this timer has to beincreased to avoid cyclic retransmissions. It is recommended to increase thetimer with 500 ms.








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T1HR6 for 6kbit/s half rate.

3.4.2 Stand Alone BSC

Signalling


The signalling system no 7 has a method called Preventive CyclicRetransmission PCR which is specially designed to cope with the abovesituation. The idea is to retransmit frames cyclically and not wait a long time(time-out) before retransmitting (see Section 6 on page 25).

PCR can be activated by using the parameter PARAMG and the size of theretransmission buffer can be set with parameter ERC .

Note: The parameters have to be changed in both the BSC/TRC and in theStand-Alone BSC.

Ater Flow Control

The parameters ATERFCWINMIN and ATERFCWINMAX are used to controlthe number of outstanding transmission requests towards the TRC node.ATERFCWINMAX is the maximum number used at the startup. This windowvalue can later on be decreased at e.g. overload situations in the TRC node.The parameters are changeable exchange properties in the BSC. The defaultparameter values have to be increased to compensate for the long round tripdelay.

3.4.3 BSC/TRC

Signalling


The signalling system no 7 has a method called Preventive CyclicRetransmission PCR which is specially designed to cope with the abovesituation. The idea is to retransmit frames cyclically and not wait a long time(time-out) before retransmitting (see Section 6 on page 25.)

PCR can be activated by using the parameter PARAMG and the size of theretransmission buffer can be set with parameter ERC.

Note: The parameters have to be changed in both the BSC/TRC and in theStand-Alone BSC.

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3.5 Speech Quality

It should be taken into consideration that the extra delay can be perceivedas a speech quality degrading factor.

It is important to know that the quality of a conversation will decrease when thespeech path delay is extended. It will be more difficult to interrupt one andother if there are long delays and the chance of both speaking at the sametime will increase.

It is not, however, possible to say at what level of delay the quality will beunacceptable. Standardization institutes have performed a lot of tests inorder to try and find a correlation between the quality and the delay. One testshows that the correlation is very different depending on the task that is tobe performed over the delayed telephone line and also depending on who isperforming the task, trained or untrained people. Yet another test shows thatpeople tend to experience the difficulty to interrupt without considering it to be adecrease in quality (see Reference [7]).

The only thing that can be said with certainty is that, for highly interactive tasksthe user will experience a degradation of quality as the delay increases.

3.6 GPRS and EGPRS

3.6.1 Gb Interface

The Gb interface over satellite is supported. The additional delays introducedimpacts end user performance and especially interactive applications sufferfrom the increased round trip time. No specific parameter settings is requiredwhen using Gb over satellite.

3.6.2 Abis Interface

GPRS may work, but performance is not guaranteed due to limitations in the3GPP standard.

EGPRS is supported.

3.7 Main Changes

Added support for EGPRS on Abis over Satellite. This also includes support forAbis over IP and Abis Optimization when EGPRS on Abis over Satellite is used.

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Engineering Guidelines

4 Engineering Guidelines

4.1 SDCCH Dimensioning

It is recommended to use 2 times more SDCCHs than usual, to compensate forlonger allocation time on SDCCH and mobile repetition of channel requests.A ph1 MS will occupy 2 SDCCH subchannels per call connection setup, thisis since the MS will repeat the channel request, the first allocated, not usedSDCCH will be allocated in accordance with the timer T3101. A GSM ph2 MSwill only require one SDCCH subchannel per call or location update attempt ifthe TX integer is set to 32 (see below).

Typical value for 1 TRX cell Use 8 SDCCH subchannels.

Typical value for 2-4 TRX cell Use 16 SDCCH subchannels.

Note: It is not recommended to use more than 8 SDCCH subchannels/TRX inorder not to overload the LAPD signalling link.

4.2 RACH Control Parameters

TX integer should be set to 32. This parameter controls how long time the MSshould wait before repeating the channel request. This parameter can affectthe call setup success rate. The recommended value is the best possible valueconsidering that the operator have both GSM ph1 and ph2 mobiles in theirnetwork.

MAXRET should be set 4. This will limit the number of retransmissions froman MS

4.3 PCH Control Parameters

MFRMS should be set to 2. This parameter controls how many paging groupsthat are used. By using a low value the call setup delay will be reduced forthe traffic case call to MS. This will also minimize the page response time tothe MSC.

4.4 LAPD Signalling Dimensioning

The following is valid when using Abis over satellite. The capacity of theLAPD signalling link is reduced for acknowledged frames due to the increasedround trip delay, the maximum capacity is some 28 I-frames per secondper RSL link with window size 15. In uplink direction most of the signallingis unacknowledged since the Measurement Result messages are sent inunacknowledged mode. In downlink direction most signalling is acknowledged

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and for reasonably small cells most of the downlink load consists of Pagingmessages.

The rules in Reference [2]are applicable with the addition that the load perLAPD link shall not be more than 25 I-frames per second in any direction. Aslong as the traffic in the cell is not high this is fulfilled as long as the pagingintensity is slightly below 25 paging per second in the cells. Note that themeasurement result messages, which constitutes most of the uplink signallingload, is sent unacknowledged and not as I-frames. Formulas for calculatingthe number of I-frames can be found in Reference [2]. The features LAPDconcentration and LAPD Multiplexing can be used with Abis over satellite withthe same dimensioning rule: the load per LAPD link shall be below 25 I-framesper second in any direction.

4.5 Bandwidth

4.5.1 General

The bandwidth on the satellite interface should be sufficient to cope with SYNCTRANSPARENCY (See Section 6 on page 25) and ITU-T G.704 in the pointsof interconnection (MSC, BSC, BTS). The bandwidth should also cover DXCmanagement signalling when it is used.

Note: The requested bandwidth mentioned above is dependent on thesatellite modem type and the DXC type.

Note: There is no impact on the Gb interface.

4.5.2 A-Interface

One 64 kbit/s channel per allocated traffic channel (MALT/RALT device)

Speech compression should not be used since it will not work together with faxand data services (V.110 data frames).

One 64 kbit/s channel per C7 link.

4.5.3 Abis-Interface

Two to three 64 kbit/s channels per used TRX depending on whetherconcentration or multiplexing is used.

When the Abis Optimization and Abis over IP features are used thedimensioning guideline shall be used. See Reference [3], Reference [4] andReference [5].

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Engineering Guidelines

4.5.4 Ater-Interface

Each allocated full rate TCH occupies 16 kbit/s and each allocated half rateTCH occupies 8 kb/s on the Ater-Interface (a 64 kbit/s channel can carry e.g. 4full rate TCHs or 8 half rate TCHs).

One 64 kbit/s channel per C7 link.

4.6 GPRS and EGPRS

It is recommended to use the feature EGPRS Prioritized Over GPRS, seeReference [6], since there are limitations in the 3GPP standard regardingGPRS performance.

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Parameters

5 Parameters

5.1 Main Controlling Parameters

5.1.1 Satellite over A-Interface.

MSC PARAMETERS

PARMG Used in combination with ERC to set Preventive Cyclic RetransmissionPCR as error correction method.

ERC Used in combination with the PARMG to set the buffer size for the PCRmode.

T1FR1458 Used in DTI to set the value of RLP timer T1 for Full Rate channels(14,5kbits/s).

T1FR1211 Used in DTI to set the value of RLP timer T1 for Full Rate channels(12kbits/s)


T1HR610 Used in DTI to set the value of RLP timer T1 for Half Rate channels

T1FR12 Used in GIWU to set the value of RLP timer T1 for Full Rate channels(12 kbits/s)

T1FR6 Used in GIWU to set the value of RLP timer T1 for Full Rate channels(6kbits/s).

T1HR6 Used in GIWU to set the value of RLP timer T1 for Half Rate channels

BSC PARAMETERS



5.1.2 Satellite over Abis-Interface.

MSC PARAMETERS

T1FR1458 Used in DTI to set the value of RLP timer T1 for Full Rate channels(14,5 kbits/s).

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T1FR1211 Used in DTI to set the value of RLP timer T1 for Full Rate channels(12kbits/s).






BSC PARAMETERS

SIGDEL Used to adapt the TG to cope with satellite links. Parameter set onTG level.

TTALONG Used to set the time-alignment timer for satellite TGs. Theparameter is a changeable BSC exchange property.

TTASHORT Used to set the time-alignment timer for non-satellite TGs. Theparameter is a changeable BSC exchange property.

TX is the parameter controlling how long time the MS waits before repeatingthe channel request (it can effect the call setup success rate). Set at cell level.

MFRMS is the parameter controlling how many paging groups are used. Setat cell level.

MAXRET is the parameter limiting the number of retransmissions from an MS.Set at cell level.

5.1.3 Satellite over Ater-Interface

MSC PARAMETERS



T1FR1458 Used in DTI to set the value of RLP timer T1 for Full Rate channels(14,5kbits/s).

T1FR1211 Used in DTI to set the value of RLP timer T1 for Full Rate channels(12kbits/s).

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Parameters






BSC/TRC PARAMETERS



Stand Alone BSC PARAMETERS



ATERFCWINMAX ATER flow control parameter, maximum number ofoutstanding transmission requests to TRC. The parameter is a changeableBSC exchange property.

ATERFCWINMIN ATER flow control parameter, minimum number ofoutstanding transmission requests to TRC. The parameter is a changeableBSC exchange property.

5.2 Parameters for Special Adjustments

—

5.3 Value Ranges and Defaults ValuesTable 3 A- Interface Parameters for Satellite Interfaces.

Parametername

Defaultvalue

Recommendedvalue

Valuerange

Unit

PARMG 3

ERC PCR-127

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Parametername

Defaultvalue

Recommendedvalue

Valuerange

Unit

T1FR1458 52 102 42-255 centisecs

T1FR1211 48 98 38-255 centisecs

T1FR609 54 104 44-255 centisecs

T1HR610 78 128 60-255 centisecs

T1FR12 5 10 4-10 centisecs


T1FHR6 8 10 6-10 centisecs

Table 4 Abis- Interface Parameters for Satellite Interfaces.

Parametername

Defaultvalue

Recommendedvalue

Valuerange

Unit

TTA NORMAL

10 10 2-50 decisecs

TTA LONG 15 15 2-50 decisecs

MFRMS 4 2 2 to 9 Integer

TX 50 32 3-12,14,16,

32,50

Integer

MAXRET 4 4 1,2,4,7 Integer

SIGDEL NORMAL LONG NORMAL,LONG

Integer

T1FR1458 52 102 42-255 centisecs

T1FR1211 48 98 38-255 centisecs

T1FR609 54 104 44-255 centisecs

T1HR610 78 128 60-255 centisecs




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Parameters

Table 5 Ater- Interface Parameters for Satellite Interfaces.

Parametername

Defaultvalue

Recommendedvalue

Valuerange

Unit

ATERFCWINMIN

1 7 0-32 Integer

ATERFCWINMAX

12 32 0-64 Integer

T1FR1458 52 102 42-255 centisecs

T1FR1211 48 98 38-255 centisecs

T1FR609 54 104 44-255 centisecs

T1HR610 78 128 60-255 centisecs




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Concepts

6 Concepts

Synctransparent

The timing received at the remote side is traceable through thetransport network to a clock at the local side.

Clear Channel Capability

Contents of the 64 kbit channel shall be exactly the same on thelocal and remote sides of the satellite hop.

Preventive Cyclic Retransmission

A signal unit which has been transmitted is retained atthe transmitting signalling link terminal until a positiveacknowledgement for that signal unit is received. During theperiod when there are no new signal units to be transmitted allthe signal units which have not yet been positively acknowledgedare retransmitted cyclically. This method of retransmission isused by signalling system no. 7 when using interfaces with longpropagation delay such as satellite interfaces.

Avid Immediate Assign

One of the most time critical procedures in a GSM system startswith the mobile sending a Channel Request message to theBSS and stops when receiving an Immediate Assign messagefrom the BSS. A slow response from the BSS could jeopardizeand decrease the success rate of the mobiles trying to get incontact with the system. A new signalling scheme has beendesigned where activation of the channels in the BTS andsending of Immediate Assign message is done in parallel. Thisnew signalling scheme is called Avid Immediate Assign andit is activated in cells with TGs having the parameter SIGDELset to LONG

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Glossary

Glossary

ADPCMAdaptive Differential Pulse Code Modulation

BSCBase Station Controller

BERBit Error Rate

BTSBase Transceiver Station

DTIData Transmission Interface

DXCDigital Cross Connect

DXXAcronym for Ericsson DXC Product

ECEcho Canceller

EGPRSEnhanced GPRS

GEOGeographical

GIWUGSM Inter Working Unit

GPHGPRS Protocol Handler

GPRSGeneral Packet Radio Services

LAPDLink Access Procedure On D-Channel

MCCMobile Crosstalk Control

MFRMSMultiframes

MSCMobile Services Switching Centre

PCHPaging Channel

PCMPulse Code Modulation

RACHRandom Access Channel

RLPRadio Link Protocol

SDCCHStand Alone Dedicated Control Channel

TRATranscoder and Rate Adaptation

TRXTransceiver

TTATimer for Time Alignment

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Reference List

Reference List

Ericsson Documents

[1] BSS Circuit Switched System Description

[2] BSC/TRC and BSC Hardware Dimensioning Handbook, 1555-AXE 10507 Uen

[3] User Description, Abis over IP

[4] Packet Abis Dimensioning Guideline

[5] User Description, Abis Optimization

[6] User Description, GPRS/EGPRS Channel Administration

Standards

[7] ITU-T G.114, One-way transmission time

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urn:x-ericsson:r2:reg-doc:*1551-*:*:*?title=BSS Circuit Switched System Description

urn:x-ericsson:r2:reg-doc:*1553-*:*:*?title=User Description, Abis over IP

urn:x-ericsson:r2:reg-doc:*10056-*:*:*?title=Packet Abis Dimensioning Guideline

urn:x-ericsson:r2:reg-doc:*1553-*:*:*?title=User Description, Abis Optimization

urn:x-ericsson:r2:reg-doc:*1553-*:*:*?title=User Description, GPRS/EGPRS Channel Administration

interface over satellite

Documents

satellite transmissionis

geo stationary satellite

transmission delay

transmission requirements

transmission costs

user description aretrademarks

main controlling parameters

catastrophe areas