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DN9812652 © Nokia Networks Oy 1 (24)

Issue 2-0 en Nokia Proprietary and Confidential

BSC4040: Satellite Abis




2 (24) © Nokia Networks Oy DN9812652

Nokia Proprietary and Confidential Issue2-0en

The information in this document is subject to change without notice and describes only theproduct defined in the introduction of this documentation. This document is intended for theuse of Nokia Networks' customers only for the purposes of the agreement under which thedocument is submitted, and no part of it may be reproduced or transmitted in any form ormeans without the prior written permission of Nokia Networks. The document has beenprepared to be used by professional and properly trained personnel, and the customerassumes full responsibility when using it. Nokia Networks welcomes customer comments aspart of the process of continuous development and improvement of the documentation.

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Copyright © Nokia Networks Oy 2001. All rights reserved.





Contents

Contents 3

List of figures 4

Summary of changes 5

1 Introduction to Satellite Abis 7

2 Operator interface to Satellite Abis 92.1 BSC 92.2 TCSM1 92.3 TCSM2 92.4 DE21/DF12 (Nokia 2nd generation base stations) 9

2.5 DE34/DF34 and DE45/DF45 9

3 Alarm descriptions in Satellite Abis 11

4 Effects on interfaces in Satellite Abis 13

5 File descriptions in Satellite Abis 155.1 DE21/DF12 155.2 DE34/DF34 or DE45/DF45 15

6 Satellite Abis installation and testing 176.1 Configuration requirements 176.1.1 Hardware effects 17

6.1.2 Firmware effects 186.2 Remarks 186.3 Installation and activation 196.3.1 BSC 196.3.2 TCSM1 206.3.3 TCSM2 206.3.4 DE21/DF12 216.3.5 DE34/DF34 226.4 Testing 226.4.1 Test environment 226.5 Deactivation of the feature 236.5.1 Testing of deactivation 24






List of figures

Figure 1. Satellite link in the Abis interface 7





Summary of changes

Changes between document issuesare cumulative. Therefore, the latestdocumentissue contains all changes made to previous issues.

Changes made between issues 2 and 1

Chapter Satellite Abis installation and testing, section Remarks

In the ways to reduce the signalling load, Omit intra-BTS handovers has beenchanged to Disable intra-BTS handovers, and a fourth way has been added:

Disable queuing (MQL = 0%).

Chapter Satellite Abis installation and testing, section Installation and activation

The value of the parameter Number of Slots Spread Transmission (SLO) has beenchanged from 50 to 32.








Introduction to Satellite Abis



1 Introduction to Satellite Abis

Satellite circuits are useful when connecting extremely remote locations, but alsowhen no other transmission means exist. The Satellite Abis is an optional featureintended for connecting the BSC to remote BTSs. Typically, these remote BTSsare used in special low-capacity and temporary applications.

The general arrangement of the Satellite Abis connection is presented in Figure 1 .

Figure 1. Satellite link in the Abis interface

The main drawback of a (geostationary) satellite circuit is the relatively long one-way end-to-end delay of approximately 260 - 280 ms. As for bit error (BER)performance, the satellite circuits behave as radio links with a possibility of deepfades even down to the total loss of the signal. Long delay together with bit errorsdecreases signalling message throughput.

Tests using satellite circuits have shown the following:

BTS MSC

BTS

TC HLR

Satellite

Abisinterface

Aterinterface

A

interfaceMSC-HLRinterface

BSC






1. Delay slows down all signalling traffic which needs frequent handshakes. GSMsystem timers are not designed for long delays, and they must be set correctly.

2. The TRAU frame time alignment function does not tolerate long delays. The

time alignment function forms a control loop between the transcoder and theBTS, and with excessive delay this control loop becomes unstable.

The Satellite Abis feature in summary

· The feature is optional.

· The feature is introduced per BSS.

· The feature is activated by a parameter switch in the BSC and the BTS.

· Satellite Abis specific TCSM1 transcoder firmware is necessary. In TCSM2, aparameter switch is used.

· Standard mobile phones are used.

· Standard MSC is used.

The Satellite Abis feature in ETSI and ANSI networks

Mainly networks based on European ETSI standards are discussed here. Thefeature is also available in networks based on American ANSI standards. Wheredifferences arise because of ANSI standards, these are separately mentioned.



Operator interface to Satellite Abis



2 Operator interface to Satellite Abis

2.1 BSC

The Satellite Abis feature is optional. The user can control the use of the feature

with the parameter satell_abis_in_use which toggles the feature on or off asneeded.

2.2 TCSM1

No operator interface.

2.3 TCSM2

Use a remote session at the BSC to access the TCSM2.

2.4 DE21/DF12 (Nokia 2nd generation base stations)

Remote BTSs must be configured for satellite use by editing the HW database.

In the HW database, give the System defs / LAPD T200 timer the value 1000 ms.Normally T200 = 240 ms, which is the value used when T200 has been selectedas 0.

2.5 DE34/DF34 and DE45/DF45

DE34/DF34 signifies Nokia Talk-family of base stations, and DE45/DF45 isNokia PrimeSite.






Remote BTSs must be configured for satellite use by editing the HW database.

In the HW database, select the BCF / Units window . Select the Abis type asSatellite . This will further show the default satellite Abis value for LAPD T200

timer = 1000 ms. Normally, Abis type is normal and T200 = 240 ms.

After this the HW database must be saved and activated.



Alarm descriptions in Satellite Abis



3 Alarm descriptions in Satellite Abis

No alarms are involved in this feature.








Effects on interfaces in Satellite Abis



4 Effects on interfaces in Satellite Abis

Only the Abis interface is affected by this feature. The changes are caused by theincreased delay which can disturb procedures relying on handshakings or timers.

For call handling, the most important change concerns the LAPD layer L2 timerT200 (see ETSI Recommendation ETS 300 595). This timer is increased from 240ms to 1000 ms. Note that this timer affects both the telecommunications andOMU signalling channels in the whole BSS.

Timers at both ends (BSCand BTS ends) of the link are modified. Also the LAPDparameter K, Maximum number of outstanding frames, is modified from K=2 toK=7. This applies only to LAPD frames whose SAPI value is 0.

Timers supervising BTS software downloading are increased to handle theincreased delay.








File descriptions in Satellite Abis



5 File descriptions in Satellite Abis

5.1 DE21/DF12

From the version B10.0 onward a special Satellite Abis software build is needed.

For example, GSM/DCS BTS SW B10.0 contains two master files; the first isBTS_S301.101 which is intended for normal Abis, and the second isBTS_S301.033, intended for Satellite Abis.

Also FUC configuration files are different for normal and Satellite Abis; forexample, CFG_S301.101 is for normal Abis, but CFG_S301.033 is for SatelliteAbis.

The decision between the normal or the satellite build is made when the BTSbuild is set at the BSC. The BTS SW Release Note contains the file list.

5.2 DE34/DF34 or DE45/DF45

From the version DF2.1 onward a special Satellite Abis software build is needed.For example, GSM/DCS BTS SW DF3.0 contains two master files; the first isBTS_S301.180 which is intended for normal Abis, and the second isBTS_S301.19B, intended for Satellite Abis.

Also FUC configuration files are different for normal and Satellite Abis; forexample, CFG_S301.18F is for normal Abis, and CFG_S301.199 is for SatelliteAbis.

The decision between the normal or the satellite build is made when the BTSbuild is set at the BSC. The BTS SW Release Note contains the file list.








Satellite Abis installation and testing



6 Satellite Abis installation and testing

6.1 Configuration requirements

6.1.1 Hardware effects

The satellite equipment must be compatible with Nokia GSM equipment and thusfulfil the following prerequisites in the Abis satellite link:

Networks based on ETSI standards

• Interfaces operate at the bit rate 2 Mbit/s. Typically onlysome time slots of the 2 Mbit/s trunk carry traffic. The BTS - BSC connection is transparentfor these time slots, and satellite transmission capacity is reserved only forthese time slots.Theminimum transmissioncapacity requirement is two64kbit/s time slots per one TRX. The normal requirement is two and a half time slots per one TRX.

• Interface must comply with ITU-T Recommendation G.703.

• Framing must comply with ITU-T Recommendation G.704.

• HDB3 line coding must be used.

• Line impedance must be 75 or 120 ohms.

• The use of CRC-4 error detection is recommended.

• The biterror ratio (BER) must always be better than 3x10E-5 over the BTS- BSC path and typically better than 10E-6.

Networks based on ANSI standards

• Interfaces operate at the bit rate 1.5 Mbit/s. Typically only some time slotsof this trunk carry traffic. The BTS - BSC connection is transparent forthese time slots, and satellite transmission capacity is reserved only forthese time slots.Theminimum transmissioncapacity requirement is two64kbit/s time slots per one TRX. The normal requirement is two and a half time slots per one TRX.

• Interface and framing must comply with ANSI Recommendation T1.403.






• B8ZS line coding must be used.

• Line impedance must be 100 ohms.

• The use of CRC-6 error detection is recommended.

• The bit error ratio (BER) must always better than 3x10E-5 over the BTS -BSC path and typically better than 10E-6.

6.1.2 Firmware effects

Transcoder TCSM1

TCSM1 EPROM's version 1.8-5 or later must be used.

Transcoder TCSM2

No firmware requirements.

DE21/DF12

DE21/DF12 BTS OMU EPROM's version 2.3 or later must be used.

DE34/DF34 or DE45/DF45

No firmware requirements.

6.2 Remarks

When the satellite link is used in the Abis interface, the BSC has to be definedonly to the satellite use, i.e. the BSC is connected only to the BTSs that are linkedvia a satellite. You may, however, consider mixed operation, but this will be atyour own risk; all normal GSM Specifications are not met in that kind of a system(LAPD parameters and TRAU frame time alignment, for example).

Because of the cumulative speech delay, it is recommended that only one satellitehop is used at the same time in a GSM/DCS network. However, it is possible touse MSC - MSC (or MSC - HLR) satellite circuits simultaneously, but thissituation has to be taken into special consideration with the product lines. Further,

PSTN may use satellite circuits as well and this should be avoided if possible.

The GSM system delay added to satellite path delay results in a delay (of echo)of approximately 180 ms + 520 ms = 700 ms. This exceeds the values given in the

ETSI Recommendation ETS 300 903 or the ITU-T Recommendation G.114. If you(the telephone user) are aware of the delay, and (preferably) use echo control, thedelay typically causes no harm. A remote MS to remote MS call suffers a doubledelay (1400 ms) due to the double satellite hop.






It is highly recommended to use acoustic echo cancelling equipment in satelliteBSS to avoid problems with speech intelligibility due to long delay. Only theTCSM2 can support AEC with the Satellite Abis.

It is not recommended to allow handover between satellite cells and terrestrialcells due to possible frequency differences between these systems. Timingdepends on varying doppler shifts of the satellite system used. A typical doppleruncertainty is less than 2x10E-7. Using a BTS with an internal clock (MCLUclock unit) will avoid this timing problem, but regular clock unit maintenancemay be difficult.

As the BSC - BTS/TRX signalling capacity is reduced, any unnecessarysignalling should be avoided. However, some signalling cannot be avoidedbecause the network elements depend on a common MSC.

You can reduce the signalling load in the following ways:

• Periodic location updating: Disable the periodic location updatingprocedure or define it for a 24-hour interval

• Unnecessary paging: Define for satellite cells a location area of their own

• Disable intra-BTS handovers (EIC = NO, EIH = NO)

• Disable queuing (MQL = 0%)

The call processing capacity of a busy hour call attempt (BHCA) is 70% of normal GSM capacity in a satellite Abis link. This can be balanced by using moreTRXs (and SDCCH capacity) than are normally needed.

6.3 Installation and activation

It is recommended to use the default values in GSM (BSC and MSC) systemtimers. Lower values than the default ones may be inadequate for handling thedelay of the satellite connection.

Basically the procedure is the same as for normal terrestrial BSC - BTS circuits.These instructions only show actions which are needed for satellite circuits.

6.3.1 BSC

Set the parameter satell_abis_in_use = TRUE. Note also that this feature isoptional and thus the Satellite Abis feature software is not included in the standardBSC software.

To activate the feature, use the command

ZWOC:10,31,FF;






To check the feature, use the command

ZWOI:10;

To configure sufficient SDCCH capacity:

1. In TRX1, two time slots are defined for signalling: a combined BCCH andSDCCH/8 (six others are defined as TCHs). First lock the TRX1 with thecommand

ZERS:BTS=<nbr>,TRX=<trx1>:L;

and then modify time slots as follows:

ZERM:BTS=<nbr>,TRX=<trx1>:CH0=MBCCHC;

ZERM:BTS=<nbr>,TRX=<trx1>:CH1=SDCCH;

2. Inother TRXs one time slot isdefined for signalling (SDCCH/8, preferablytimeslot zero) and seven others are defined as TCHs. Use the followingcommands:

ZERS:BTS=<nbr>,TRX=<trx>:L;

ZERM:BTS=<nbr>,TRX=<trx>:CH0=SDCCH;

Unlock all locked TRXs:

ZERS:BTS=<nbr>,TRX=<trx>:U;

Other parameters (which minimise the SDCCH reservations):

Number of Slots Spread Trans (SLO) = 32

Max. Number of Retransmission (RET) = 2

Max. Number of Repetition (NY1) = 5

To set these parameters, use the command

ZEQM:BTS=<nbr>:SLO=32,RET=2,NY1=5;

where <nbr> identifies the remote BTS.

6.3.2 TCSM1

Change EPROMs in the TRC15 boards. Use the version 1.8-5 or a later version.

6.3.3 TCSM2

You can configure the TCSM2 either locally or remotely. The following textgives the commands for remote access.






First create a remote session by the following commands, where <nbr> is theaddress of the transcoder:

ZDDT:TCSM,<nbr>;

UsernameEXPERTPasswordSYSTEM

Setting time alignment OFF:

ZRS:ALL:OFF

The TCSM2 will ask:

Do you want configuration changes to bepermanent by saving them in flash memory?Please answer (Y/N) Y

Enable acoustic echo cancelling (AEC). The command depends on the type of

speech coding used. Here <codec> can be either FR, EFR or HR.

ZRU:ALL: <codec_type>=ONPlease, confirm (Y/N) Y

Do you want configuration changes to bepermanent by saving them in flash memory?Please answer (Y/N) Y

Set the AEC tail delay correctly:

ZRU:ALL:DELAY=<delay>Please, confirm (Y/N) Y

Do you want configuration changes to be

permanent by saving them in flash memory?Please answer (Y/N) Y

Normally either 520 ms, 540 ms or 560 ms are suitable values for <delay>. Youcan check this by a listening test.

To check that all selections are correct, use this command (in which<PCM_index> is the actual PCM used):

ZRC:<PCM_index>:10

Terminate the remote session:

ZX

6.3.4 DE21/DF12

Use the version 2.3 or a later version of the BTS OMU EPROM.

Remote BTSs must be configured for satellite use by editing the HW database.After that, the Satellite Abis BTS software build must be loaded in the BTS.






Give the System defs / LAPD T200 timer the value 1000 ms using the HWdatabase editor.

If there is an active BCF HW database in the BSC, a new satellite-specific HW

database must be uploaded, created, attached and activated.

ZEVU:<BCF_index>:NAME=<file_name>,EXT=<file_extension>;

ZEVC:<HW_db_name>:NAME=<file_name>,EXT=<file_extension>;

ZEVA:<BCF_index>:<HW_db_name>;

ZEVV:<BCF_index>:PAS;

6.3.5 DE34/DF34

Remote BTSs must be configured for satellite use by editing the HW database.After that, the Satellite Abis BTS software build must be loaded in the BTS.

In the HW database, select the BCF/Units window. Select the Abis type asSatellite.

If there is an active BCF HW database in the BSC, a new satellite-specific HWdatabase must be uploaded, created, attached and activated. The HW databaseactivation procedure is similar for both DE34/DF34 and DE21/DF12 BTS types.

6.4 Testing

6.4.1 Test environment

Testing requires a whole BSS dedicated for the satellite cells. Phase 1 and Phase2 mobile phones are needed. Transmission circuits to and from the operationalsatellite terminals are also required.

As regards pretesting or troubleshooting, if no real satellite circuits are available,the satellite may be simulated by suitable test equipment (adding a one-way delayof 280 ms and possibly also bit errors).

Test cases

The tests include test calls, SW downloading and (implicit) BCF reset.

Prerequisites for testing

Testing requires a whole BSS which is correctly set up for the Satellite Abisfeature. An operational MSC and mobile stations are required.






The correct BTS SW version must be created, attached and activated. Use thefollowing commands:

ZEWC:<package_name>:MF=<master_file_name>,EXT=<file_extension>,SDIR=<subdirectory>;

ZEWA:<BCF_index>:<package_status>:<package_name>;

ZEWV:<BCF_index>:<package_status>;

Test execution and expected results

Sw downloading:

The BTS software is downloaded to the remote BTS after the software buildactivation.

Satellite delay will increase the BTS software downloading time by

approximately 20 minutes.

Test calls:

Test the system by making mobile-originated (MO) and mobile-terminated (MT)test calls.

Satellite delay will increase call set-up time by approximately 7 seconds. You canhear the increased speech delay. Some UL echo may occur depending on theacoustic performance of the mobile phone. If you use AEC, no echoes should beaudible (if you hear echoes, however, changing the delay value may help).

Mobile stations typically reserve one or two extra SDCCH channels per call, andthese are automatically cleared by the BSC. Phase 2 mobile stations performbetter in this respect.

6.5 Deactivation of the feature

In the normal (terrestrial) state of operation, the long satellite delay cannot betolerated and the BTS must be connected with low delay terrestrial circuits forfeature deactivation.

You can temporarily deactivate the Satellite Abis feature by turning off the BSCswitch satell_abis_in use. Use the command

ZWOC:10,31,0;

To set the AEC delay value in the TCSM2, use the command

ZRU:ALL:DELAY=0Please, confirm (Y/N) Y

Do you want configuration changes to be



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