Nokia Bss Transmission

Nokia BSS TransmissionConfiguration

DN9812391Issue 12-0 en

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BSC3119Nokia BSC/TCSM, Rel. S12, ProductDocumentation, v.1

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2 (92) # Nokia Corporation DN9812391Issue 12-0 en

Nokia BSS Transmission Configuration

Contents

Contents 3

List of tables 5

List of figures 6

Summary of changes 9

1 BSS transmission 13

2 BSC configuration 192.1 BSC location 192.2 BSC capacity limits 192.3 A and Ater BSC interface 222.4 Interface to the OMC direction 222.5 LAN interfaces 22

3 TC configuration 253.1 Installations with TCSM 253.2 TCSM3i versus TCSM2 283.3 TCSM3i versus TCSM3i for combined BSC3i/TCSM3i installation 293.4 TCSM versus transcoder in MGW 29

4 BTS configuration 314.1 TRU transmission unit descriptions 334.1.1 O & M arrangement of transmission 344.1.2 Options for transmission 354.2 FC and FXC units 364.3 FIEA, FIPA and FIFA units 38

5 GPRS and the Gb interface 415.1 Gb over Frame Relay 415.2 Gb over IP 445.3 GPRS capacity 44

6 BSS redundancy configurations 47

7 Operation and maintenance of transmission equipment 497.1 Supervisory channels 497.2 Local O & M 507.3 Remote O & M 52

8 Requirements on transmission network 538.1 2 Mbit/s transmission paths 538.2 Synchronisation of BSS network 558.3 Transmission delay of BSS network 578.4 Error rate performance of BSS network 578.5 Slips in transmission 58



Contents

8.6 Echo control in BSS 598.7 Jitter and wander prevention in BSS 59

9 Digital cross-connect nodes 619.1 Digital node equipment DN2 629.2 MetroHub transmission node 63

10 BSC-BTS transmission examples 6710.1 Overview of transmission network 6710.2 Point-to-point transmission 6810.3 Multidrop chain transmission 6810.4 Loop transmission 6910.5 Radio transmission 7010.6 DN2 in the MSC-BSC path 7010.7 Nokia UltraSite network example 71

11 Time slot allocations in BSS 7311.1 Time slot allocation in combined BSC3i/TCSM3i installation (ANSI) 8011.2 Compressed Abis time slot allocation 8211.3 Allocation of Abis time slots 8611.4 TRU TSL allocation, FR, 16 kbit/s signalling 8711.5 TRU TSL allocation, FR/HR, 64 kbit/s signalling 9011.6 TRU TSL allocation, FR/HR, 32 kbit/s signalling 90



List of tables

Table 1. BSC configurations 20

Table 2. Number of BCSUs in combined BSC3i/TCSM3i installation 20

Table 3. Circuit types of TCSM2 and TCSM3i 25

Table 4. Matching of circuit type and circuit pools 26

Table 5. The transmission units in the Nokia Talk-family and Nokia PrimeSiteBTSs 33

Table 6. SAPI values and priorities 38

Table 7. Connectivity of logical PCUs 45

Table 8. Compressed Abis time slot allocation 83

Table 9. Compressed Abis time slot allocation in the case of multi-TRX basestations 83

Table 10. Compressed Abis time slot allocation that supports five 3 x 1 TRXsites 83

Table 11. Compressed Abis time slot allocation with the TRX signalling speed 32kbit/s 84

Table 12. 16 kbit/s signalling rate 86

Table 13. 64 kbit/s signalling rate 87



List of tables

List of figures

Figure 1. General BSS/RAN topology: access through multiservice network 13

Figure 2. Through-connected channels configured in the transcoders and in theMSC switching matrix 42

Figure 3. GPRS traffic multiplexed on the same physical connection as used for theGSM traffic on the Ater interface 42

Figure 4. GPRS traffic concentrated and carried over the Gb interface in a packetdata network 43

Figure 5. GPRS traffic carried over dedicated 2 Mbit/s PCM links 43

Figure 6. GPRS traffic carried over the Gb interface with IP 44

Figure 7. Radio link hop protection 48

Figure 8. Interconnection of different networks 61

Figure 9. Multiplexing of the BSS and external channels with the DN2 63

Figure 10. Network principle 64

Figure 11. BSS network using leased lines 67

Figure 12. Point-to-point connection between BSC and BTS 68

Figure 13. Multidrop chain 69

Figure 14. Duplicated point-to-point and multidrop loop 69

Figure 15. Loop, radio relay transmission network 70

Figure 16. Example use of the DN2 71

Figure 17. Example of a Nokia UltraSite network 72

Figure 18. Time slot allocation for 16 kbit/s bit rate channels (typically full rate,enhanced full rate or AMR) on the Ater 2 Mbit/s interface with theTCSM2/TCSM3i 75

Figure 19. Time slot allocation for half rate traffic with 8 kbit/s TRAU frames on theAter 2 Mbit/s interface with the TCSM2 76

Figure 20. Ater time slot allocation example for the HSCSD application: acombination of 2 x 16 kbit/s channels (HS2) and 4 x 16 kbit/s channels(HS4) 78

Figure 21. Time slot allocation of 2 x 16 kbit/s channels of Figure A-PCM1 on Ainterface 79

Figure 22. Time slot allocation of 4 x 16 kbit/s channels of Figure A-PCM2 on Ainterface 79



Figure 23. Submultiplexing on Ater PCM in ANSI environment (16 kbit/s) 80



Figure 26. Submultiplexing on Ater PCM in ANSI environment (mixed 32 and 64 kbit/s) 82

Figure 27. Compressed allocation enabling up to 15 TRXs per 2 Mbit/s circuit 85

Figure 28. Allocation example for a three-TRX BTS 86

Figure 29. TRU chain allocation in the case of 16 kbit/s LAPD 89

Figure 30. An example of four-BTS TRU chain (highway) allocation when 32 kbit/sTRX signalling is used 91



List of figures



Summary of changes

Changes between document issues are cumulative. Therefore, the latest documentissue contains all changes made to previous issues.

Changes made between issues 12 and 11–1

Chapter BSS transmission

Information on SDH/SONET optical interface and TCSM3i for combined BSC3i/TCSM3i installation added.

Chapter BSC configuration

Sections BSC capacity limits and A and Abis BSC interface have been updatedwith information on new BSC3i variants and TCSM3i.

Chapter TC configuration

Information on TCSM3i added.

Chapter BTS configuration

Information on Nokia Flexi EDGE base station added.

Information on ISDN Abis and TRUC/D transmission units has been removed.

Chapter BSS redundancy configurations

Information on Abis chain protection has been removed.

Chapter Operation and maintenance of transmission equipment

The number of Q1 supervisory channels supported by the BSC has been changedfrom 28 to 56.

Information on V.11 has been removed.



Summary of changes

Chapter Requirements on transmission network

Section Error rate performance of BSS network has been updated.

Chapter Digital cross-connect nodes

Hardware details in section Digital node equipment DN2 have been updated.

Information on SXC T has been removed.

Chapter BSC-BTS transmission examples

Sections Radio transmission and DN2 in the MSC-BSC path have been updated.

Information on SXC T has been removed.

Chapter Time slot allocations in BSS

Section Time slot allocation in combined BSC3i/TCSM3i installation (ANSI) hasbeen added.

Changes made between issues 11–1 and 11


Information on Multimedia Gateway added.

Changes made between issues 11 and 10

Chapter BSC configuration

Table BSC capacity limits replaced with new table BSC configurations.

Sections AMR Half Rate, A and Abis BSC interface and LAN interfaces updated.

Section 2 Mbit/s Abis PCM maximum capacity moved from chapter BTSconfiguration.


Section Installations with TCSM removed.

Chapter BTS configuration

Sections Nokia MetroSite, Nokia 2nd generation, Nokia Talk-Family, BIE/BIU2M module, BIE/BIUMD module removed.



Chapter GPRS and the Gb interface

Section Gb over IP added. Section GPRS capacity updated.

Chapter BSS redundancy configurations

Contents of the chapter reorganised. Sections Abis redundancy with Nokia 2ndgeneration BTS, Abis loop with Nokia Talk-family base stations and Abis point-to-point redundancy with Nokia Talk-family base stations removed.

Chapter Operation and maintenance of transmission equipment

Contents updated.

Chapter Requirements on transmission network

Sections 2 Mbit/s transmission paths,2Mbit/s requirements with EDGE and 2Mbit/s interfaces combined as 2 Mbit/s transmission paths. Minor updates.

Chapter Digital cross-connect nodes

Chapters Service Cross-Connect SXC T and Digital node equipment DN2combined as Digital cross-connect nodes.

Chapter BSC-BTS transmission examples

Sections BIU2M point-to-point, BIUMD chain, TRU line repeater function,Extending Talk-Family Network with MetroSite and Abis spur routes removed.

Figure 19 updated.

Chapter Time slot allocations in BSS

Sections BIUMD time slot allocations and Special BIUMD configurationsremoved. Section Compressed allocation combined with section CompressedAbis time slot allocation.

Changes made between issues 10 and 9–1

The chapters BSS transmission configuration overview and BSS transmissionconfiguration approach have been combined with the chapter BSS transmission,the new name for the chapter BSS transmission generic guidelines.

Chapter BSC configuration: added a new section, LAN interfaces.

Chapter Requirements on transmission network, section Synchronisation of BSSnetwork: the section has been renewed.



Summary of changes

Changes made between issues 9–1 and 9

Information on Nokia ConnectSite 10 and Nokia ConnectSite 100 base stationshas been added.

Chapter BTS configurations, section FC and FXC units: added new subsectionsFibre optic transmission and MetroHub transmission node. Subsection FC unitswithout cross-connection: reference to FC RRI has been replaced by FC STM-1.

Chapter Requirements on transmission network: new section 2Mbit/srequirements with EDGE added.



1 BSS transmission

Usually the BSC-BTS Abis transmission configuration is a mixture of point-to-point, multidrop chain, or multidrop ring subnetworks.

Figure 1. General BSS/RAN topology: access through multiservice network

The BSC sees BTSs through 2 Mbit/s PDH ET ports which carry data to and fromthe BTSs. The transport network in between can be whatever technology when itprovides transparent PDH termination points.

BS

BS BS

BS

BS

BS BS

BS

BS

BSBS

BS

BS

BS

BS

BS

BS

BS BS

BS

BS BS

BSC / RNC

Multi ServiceSDH or ATM or IP

Network

Access network compatiblestandard high capacity IF

Access network compatiblestandard low capacity IF

BTS access medium capacity IF

BTS access low capacity IF

Access network element

Base station siteBS

BS



BSS transmission

. Transport network topology

The transport network topology can be a star, chain or loop. The starnetwork benefit is that it is very simple to manage but the disadvantagesare that the connections are typically only partially filled with payload(extra transmission cost) and any failure in the network causes traffic cut.Use of grooming at star network hub sites will optimise the use ofnorthbound transport capacity. The chain network improves the efficiencyof the use of transmission capacity but is still sensitive to failures in thenetwork. From the efficiency and reliability point of view the topology isthe loop. The disadvantage in the loop is that the related equipment settingsrequire transmission competence but that can be overcome with trainingand following the available instructions. Note that all these topologies aretransparent for the Abis traffic.

. Grooming principle

Grooming in the network means the cross-connection functions whichallow combination of partially filled transmission containers, for example 2Mbit/s G.704 frame into a single container. Nokia BTS integratedtransmission units support this function. The benefit is naturally betterefficiency in the transport layer.

. Synchronisation

In the BSS area the BSC is the synchronisation master to the BTSs.Normally the transport layer is also synchronised to the BSC by taking thefirst transmission equipment synchronisation reference from the masterBSC ET port and then delivering this synchronisation in the transmissionnetwork downwards. When using other technologies to carry the ETsignals, such as SDH, and when the non-PDH network is synchronised to asynchronisation reference on its own, then the ET port synchronisationmust be transparently transmitted into the first PDH element through theSDH layer.

. Network management principles

Nokia BTS integrated transmission elements are managed by using the Q1protocol. The essential parts of that protocol are the location of the pollingdevice (Q1 master), the Q1 data communication channel and the Q1addressing. The most typical set-up is that the local BTS operates as Q1master and forwards the Q1 messages to/from the NMS using a BTSmanagement channel in the NMS direction and Q1 channel in thetransmission direction. The Q1 data communication channel is a bus whereall elements hear all the messages along the bus. The devices are accessedby using a unique address for each element on the bus. Often there are alsonon-integrated Q1 elements in the BSS network. Those devices are polled



either by the BTS or BSC depending on the Q1 plan. Normally the Q1 planis such that the polling device is closer to the BSC than the polled device tohave management access as deep into the network as possible in case ofany failures.

BSS transmission configuration approach

The focus here is mainly on BSC-BTS transmission.

The start of the whole BSS design procedure relies on BSS traffic handlingrequirements.

The specific information needed in planning and dimensioning the networkincludes the following items:

. BTS locations and sizes

. BSC location

. MSC location

. Transcoder equipment location

. Available transmission methods

The support of half rate speech coding is introduced with BSS5. Thisapproximately doubles the voice traffic carrying capacity of the GSM network.The introduction of EDGE air interface enables a four-fold data rate per call andthe raw implementation of EDGE would require four-fold transmission capacity.Dynamic Abis is introduced to optimise the use of Abis for EGPRS purposes.

The design starts from the BTS information, followed by the BSC, the TCSM,and the MSC.

For the transmission part of the network, the following input data is needed fordimensioning:

1. The number of traffic channels on the A interface per BSS, full rate (FR/EFR), half rate (HR), AMR, High Speed Circuit Switched Data (HSCSD),General Packet Radio Service (GPRS) and the number of EDGE TRXs. The number of transcoder units (either TCSM2 or TCSM3i), their

capacities and BSC A interface connections can be deduced fromthis number.

. HSCSD will set special requirements for Ater capacity depending onhow many HSCSD circuits are used and how many parallel timeslots are supported by the transcoder. A given transcoder pool maysupport both FR/EFR/HR and multislot HSCSD.



BSS transmission

. Each HSCSD channel occupies an entity of 64 kbit/s (one time slot)at the A interface. However, the data stream itself may be carried byless than 8 bits of the time slot.

. GPRS service is implemented by a plug-in unit (PCU) in the BSC.For more information, see GPRS and the GB interface..

. Optical STM-1/OC-3 (SDH/SONET) interface can be used toincrease the external connectivity of the BSC3i and reduce thetransmission costs. One STM-1 interface consists of 63 ETs (ETSI)and one OC-3 interface of 84 ETs (ANSI).

. As a standard up to 6 BSCs (optionally up to 12 BSCs) can beconnected to one TCSM3i in stand-alone installation. In combinedBSC3i/TCSM3i installation, the transcoding capacity of a TCSM3ican be shared by up to 96 BSCs (ETSI) or 24 BSCs (ANSI).

2. The total number of TRXs controlled by the BSC. If Dual Band is in use, the TRXs operate in different frequency

bands.. The capability of the BSC processing can be deduced from this

number.

3. The total number of 2 Mbit/s links on the BSC Abis interface

The number of BSC Abis 2 Mbit/s connections can be deduced from thisnumber. EDGE TRX can be connected using a shared Dynamic Abis poolwhich allows dynamic allocation of capacity wherever it is needed. Thedimensioning of Dynamic Abis is explained in Abis EDGE Dimensioningin GSM/EDGE BSS System Documentation Set.

Once the required transmission capacity has been calculated, the transmissionnetwork planning may start.

The BSS transmission network planning is based on:

. Required BSC BTS Abis capacity

. Required Ater capacity

. Required Gb capacity

. Required IP connectivity

. Existing and/or available transmission network and its tariffing

. Decision on traffic protection

. Network management solution

The details of transmission network planning include:



. Allocating required capacities into usable conduits (such as leased linesand radio links)

. 2M time slot allocation plan for each BSC BTS Abis link, taking intoaccount the Dynamic Abis for EDGE

. Transmission capacity optimisation by grooming cross-connections

. Loop network protection planning

. Network management channel planning

. Synchronisation hierarchy planning

When the transmission network high level planning is done, the relatedtransmission settings can be entered to the equipment to make the networkoperate.

Related topics

. BSC configuration

. TC configuration

. BTS configuration

. GPRS and the Gb interface

. BSS redundancy configurations

. Operation and maintenance of transmission equipment

. Requirements on transmission network

. Digital cross-connect nodes

. BSC - BTS transmission examples

. Time slot allocations in BSS



BSS transmission



2 BSC configuration

The BSC configuration process includes two steps:

1. To determine the BSC location in the BSS network

2. To determine the configuration of each BSC

The switching field GSWB of the BSC meets both full rate and half rate speechrequirements.

Note

The dimensioning principles for enhanced full rate (EFR) channels are thesame as for FR channels.

2.1 BSC location

Locating BSCs in the BSS network is flexible. BSCs can be co-located or non-co-located with the MSC and the transcoder.

The best location depends mainly on tariff structure on transmission lines. Forexample, if the tariff correlates strongly with the distance of the transmission line,the best location for a BSC is normally non-co-located with the MSC and the TC.Transmission lines can be saved on the A interface by submultiplexing andconcentrating the traffic on fewer lines. Concentration can save a lot of expensesbecause the number of lines can be dimensioned according to the expectedvolume of traffic. For more information, see Engineering for BSC3i.

2.2 BSC capacity limits

There are certain limits to the capacity, especially to the number of TRXs and thenumber of PCM lines. These limits are presented in the table below.



BSC configuration

Table 1. BSC configurations

BSC configurations BSC2i BSC3i 660 / BSC3i 1000 /BSC3i 2000

Maximum radio networkconfiguration

248 BCF

248 / 512 BTS

512 TRX

504/1000/2000 BCF

660/1000/2000 BTS

660/1000/2000 TRX

Maximum number of externalPCMs

80 / 112 / 144 256/384/800

SS7 signalling links 16 16

Minimum number of WO-EXBCSUs

1-8 1-6/1-5/1-10

Number of BCFSIG LAPDlinks per BCSU

32 84/200/200

Number of TRXSIG LAPDlinks per BCSU

64 110/200/200

Maximum number of LAPDlinks per BCSU

(BCFSIG + TRXSIG + ET-LAPD)

124 206/412/412/

Maximum number of TCHsper BCSU

512 880/1600/1600

To ensure full LAPD signalling capacity for combined BSC3i/TCSM3iinstallation, there must be a certain number of working BCSUs in the masterBSC. The exact number depends on the radio network configuration as follows:

Table 2. Number of BCSUs in combined BSC3i/TCSM3i installation

RNW configuration Number of BCSUs

1 TRX under BTS 5

6 TRXs (2+2+2) under BTS 1

For more information, see the following BSC product descriptions:

. Product Description of Nokia Base Station Controller BSC3i

. Product Description of Nokia Base Station Controller BSC2i, BSCi

2 Mbit/s Abis PCM maximum capacity

The capacity depends on the signalling rate:



. 16 kbit/s LAPD signalling links (mainly for FR but also HR) can handle upto 12 TRXs and up to 12 Operation and Maintenance Units (OMUs) on asingle 2 Mbit/s line.

. 32 kbit/s LAPD signalling links (optimised for HR) can handle up to 12TRXs and up to 4 OMUs on a single 2 Mbit/s line.

. 64 kbit/s LAPD signalling links can handle up to 8 TRXs and up to 7OMUs, or up to 9 TRXs and up to 4 OMUs, or up to 10 TRXs and 1 OMUon a single 2 Mbit/s line; in new installations, 64 kbit/s TRX or OMUsignalling data rate is not normally used because it results in a highrequirement of capacity

For the best transmission economy, the PCM lines should be packed as full aspossible. The methods of doing this are explained later.

AMR Half Rate

Introduction of Adaptive Multi-Rate codec (AMR) Half Rate (HR) causesincreased load in measurement reporting; therefore it can happen that a capacityof 16 kbit/s LAPD signalling link is not sufficient in all cases. When the TRXcontains merely HR or dual rate (DR) traffic channel (TCH) resources, thesituation becomes even worse if the stand-alone dedicated control channels(SDCCH) have also been configured on the TRX. Therefore a 32 kbit/s LAPDlink has been introduced to support the telecom signalling.

AMR codecs support in Nokia BSC and TCSM2/TCSM3i:

. All Nokia BSCs have full AMR support, except 7.95 kbit/s on HR channel.

. Nokia TCSM2 and TCSM3i have full AMR support.

. A TC PCM pool type is needed for transcoder configuration on the Ainterface. The AMR pool type, which supports AMR FR and AMR HR(pool 23 in TCSM2 and pools 23, 28 and 32 in TCSM3i), is implemented.

. Submultiplexing on highway PCM is 8/16 kbit/s, for example if AMR FR(16 kbit/s) is used on the Abis interface, the Ater interface rate is also 16kbit/s.

. Correspondingly if AMR HR (8 kbit/s) is used on the Abis interface, theAter interface rate is 2 x 8 kbit/s (the BSC transmits ones (= bit value 1) onthe unused 8 kbit/s sub-timeslot).

With the AMR HR implementation, the BSC's maximum channel capacity of4096 must be taken into account in dimensioning the number of TRXs in theBSC. For example the traffic processing capacity of the BSC2i supports 512 fullrate TRXs or 256 half rate TRXs. Connectivity for 512 half rate TRXs isavailable with Soft Channel Capacity application software.



BSC configuration

BSC TRX capacity can be maintained by using FR to HR load thresholdparameters.

The maximum channel capacity of the BSC3i is 5280. BSC3i supports up to 2000full rate TRXs or up to 1000 half rate TRXs. Connectivity for 2000 half rateTRXs is available with Soft Channel Capacity application software.

2.3 A and Ater BSC interface

In TCSM2, the A and Ater interfaces are supplied by ET2E/ET2A plug-in unitswith two PCM connections per board). Connector line impedance on 2 Mbit/strunk lines is either 75 ohm (coaxial, asymmetric) or 120 ohm (pair, symmetric).

In TCSM3i, the A and Ater interfaces are supplied by ET16 plug-in units. InTCSM3i for combined BSC3i/TCSM3i, it is also possible to use STM-1/OC-3(SDH/SONET) optical interface, in which case the A interface is supplied byETS2 plug-in units.

The transmission performance of the interfaces is supervised by the BSCaccording to ITU-T recommendations.

2.4 Interface to the OMC direction

The OMC connection of the BSC can be one of the following:

. one 2 Mbit/s A interface time slot

. one ethernet interface according to IEEE 802.3, either 10Base5 (AIU),10Base2 (COAX) or 10BaseT (TPI); the data rate is 10 Mbit/s

. an X.25 data terminal equipment (DTE) interface with the alternativesV.24, V.35, V.36 and X.21.

Redundant OMC connections can be achieved by using, for example, X.25 ontwo separate trunk lines.

2.5 LAN interfaces

Various types of IP traffic are transported between network elements with IPconnections. The three main types that are relevant to transmission planning are:



. NetAct™ link (O&M traffic)

There is O&M traffic in every network element.

. Signalling traffic with other network elements

The Lb interface towards a stand-alone Serving Mobile Location Center(SMLC) and BSC-BSC interface with Dynamic Frequency and ChannelAllocation (DFCA) or other LAN connections can be used in the future.

. Packet traffic

IP connectivity can be used for Gb interface with packet traffic. Some otherfunctionalities will also use IP connectivity for packet traffic in the future.

Before starting to build the IP network, see BSC site architecture and IP networktopology in BSC Site IP Connectivity Guidelines. See also Nokia PacketBackbone for Mobile Networks, available in 3G Core Network SystemInformation Set.

For an overview, see BSS transmission.



BSC configuration



3 TC configuration

3.1 Installations with TCSM

TCSM refers to the second and third generation BSS transcoder-submultiplexerequipment, which provides transcoding for traffic channels in the GSM/EDGEnetworks.

The TCSM is located between the MSC and the BSC. Normally, to savetransmission capacity, the equipment is located at the MSC site. It can, however,also be situated at the BSC site.

With reference to the 3GPP TS 08.08, the circuit types listed in table Circuit typesof TCSM2 and TCSM3i are available for use in connection with the TCSMs.

Table 3. Circuit types of TCSM2 and TCSM3i

Circuit type Supported channels and speech coding inTCSM2

Supported channels and speech coding inTCSM3i

A FR speech, EFR speech, FR data (14.5,12, 6 or 3.6 kbit/s)

B HR speech, HR data (6 or 3.6 kbit/s)

C FR speech, EFR speech, HR speech, FRdata (14.5, 12, 6 or 3.6 kbit/s), HR data (6or 3.6 kbit/s)

D FR speech, EFR speech, HR speech, FRdata (14.5, 12, 6 or 3.6 kbit/s), HR data (6or 3.6 kbit/s), HSCSD max 2 x FR data(14.5, 12 or 6 kbit/s)

E FR speech, EFR speech, HR speech, FRdata (14.5, 12, 6 or 3.6 kbit/s), HR data (6or 3.6 kbit/s), HSCSD max 4 x FR data(14.5, 12 or 6 kbit/s)

F AMR speech



TC configuration

Table 3. Circuit types of TCSM2 and TCSM3i (cont.)

G 1 (FR) / 16 kbit/s

3 (DR) / 16 kbit/s

5 (EFR&FR) / 16 kbit/s

7 (EFR&DR) / 16 kbit/s

20 (EFR&DR&D144) / 16 kbit/s

23 (AMR) / 16 kbit/s

28 (EFR&DR&AMR&D144) / 16 kbit/s

H 10 (HS2) 2 x 16 kbit/s

21 (HS2&D144) / 2 x 16 kbit/s

I 13 (HS4) 4 x 16 kbit/s

22 (HS4&D144) / 4 x 16 kbit/s

32 (EFR&DR&AMR&HS4&D144) 4 x 16kbit/s

Table Matching of circuit type and circuit pools shows the matching of poolsfrom the point of view of the TCSM2/TCSM3i and BSC. For the numbering ofthe pools, see 3GPP TS 48.008.

Table 4. Matching of circuit type and circuit pools

TCSM type BSC circuit pool numberTranscoder circuit typeTCSM2/TCSM3i

TCSM2, TCSM3i 1 A/G

2 B/-

3 C/G

5 A/G

7 C/G

10 D/H

13 E/I

20 C/G

21 D/H

22 E/I

23 F/G

TCSM3i 28 -/G

32 -/I



AMR implementation with TCSM2

A TC PCM type is needed in transcoder configuration of the A interface. Thebasic AMR type, which supports AMR FR and AMR half rate (HR, pool 23), isimplemented for TCSM2.

Submultiplexing on highway PCM is 8/16 kbit/s. For example if AMR FR (16kbit/s) is used in the Abis interface, then the Ater interface rate is also 16 kbit/s.

Correspondingly if AMR HR (8 kbit/s) is used in the Abis interface, the Aterinterface rate is 2 x 8 kbit/s (BSC transmits ones (= bit value 1) on the unused 8kbit/s sub-timeslot).

Note

The circuit pools 4, 6, 8, 9, 11, 12, 15, 16, 17, 18, and 19 are not supported,but they are all included in at least one of the supported pools (18 in 21, forexample). The circuit pools 14 and 24-32 are not supported at all.

AMR implementation with TCSM3i

The AMR type supporting AMR FR, AMR HR, and EFR is implemented forTCSM3i. Pools 28 and 32 are supported in TCSM3i. The 8 kbit submultiplexing(pool 2, HR only) is not supported in TCSM3i.

Pool configuration with Multimedia Gateway (MGW)

The BSC can be directly connected to the transcoder in the MGW using the Aterin MGW feature. As a rule, MGW supports the same pool configuration as theBSC except 8 kbit/s submultiplexing on the Ater interface.

Check the detailed pool list in Multimedia Gateway (MGW) FunctionalDescription in MGW documentation.

O & M arrangement with TCSM

A LAPD-type 16 kbit/s data channel is dedicated for TCSM fault monitoring andcontrol between the BSC and the TCSM. This channel uses capacity from theTSL1 (bits 1 and 2). Each TCSM has its own LAPD channel towards the BSC.All maintenance operations are carried out over the LAPD channel (supervisionand configuration commands). A local user has access to the transcoder site viaan interface on the TCSM.



TC configuration

O & M arrangement with MGW

There is no O & M LAPD link between the BSC and MGW so the BSC does notcontrol the MGW at all. The operator is responsible for creating identicaltranscoder configurations in both BSC and MGW.

TCSM2 capacity

One rack houses 8 pre-installed Transcoder cartridges (TC1C) and 4 ExchangeTerminal cartridges (ET1TC). The maximum capacity of a rack is 8 x 120= 960TCHs in the case of 16 kbit/s submultiplexing, and 8 x 210 = 1680 TCHs in thecase of 8 kbit/s submultiplexing.

If signalling time slots (TSL16) are not used for speech channels, the maximumcapacity is 116 TCHs (16 kbit/s submultiplexing).

TCSM3i capacity

One rack in the TCSM3i cabinet consists of six Transcoder cartridges (TC2C). 16TR3E/A plug-in units are housed in each cartridge.

The maximum capacity of a cabinet is 6 x 1920 = 11520 TCHs (ETSI) or 6 x1520 = 9120 TCHs (ANSI).

3.2 TCSM3i versus TCSM2

The major differences between the TCSM3i and TCSM2 are:

. TCSM3i has 12 times more capacity compared to current TCSM2implementation.

. Redesigned hardware makes TCSM3i more compact.

. Instead of several plug-in units, one transcoder based on TCSM3ihardware technology consists of one plug-in unit.

. TCSM3i allows more flexible pool usage in A-interface.

. TCSM3i does not support 8 kbits/s submultiplexing on the Ater interface.

When the traffic capacity of a TCSM2 is dimensioned to a low value,transmission capacity may be saved. This requires that unused time slots ofexisting BSC-TCSM highways are multiplexed by an external cross-connectdevice. One option is to use DN2 equipment, as illustrated in section Digital nodeequipment DN2.




3.3 TCSM3i versus TCSM3i for combined BSC3i/TCSM3i installation

The major differences between the TCSM3i and TCSM3i for combined BSC3i/TCSM3i installation are:

. it is possible to use optical STM-1/OC-3 interface in combined BSC3i/TCSM3i installation

. in combined installation the transcoding capacity of a TCSM3i can beshared by up to 96 BSCs (ETSI) or 24 BSCs (ANSI)

3.4 TCSM versus transcoder in MGW

The major differences between using the TCSM and the transcoder in the MGWare:

. MGW and TCSM3i do not support 8 kbit/s submultiplexing on the Aterinterface, but TCSM2 does.

. MGW does not support the same pool set as the BSC.

. Since there is no O & M link between the BSC and MGW, the transcodingalarms have to be monitored and software changes performed in the MGW.Furthermore, BSC-originated routine testing and diagnostics cannot beused with MGW.

. Exactly the same pool configuration is created to the BSC and MGWseparately.

. No transcoding related hardware has to be created in the BSC.



TC configuration



4 BTS configuration

The BTS transmission subsystem is used in the BTS as an interface to the Abislinks towards the BSC. FC and FXC units are used in the Nokia UltraSite andMetroSite BTSs, and FIEA, FIPA and FIFA plug-in units in Nokia Flexi EDGEBTS.

Nokia MetroSite, Nokia Flexi EDGE and UltraSite support both full rate (FR)and half rate (HR) speech coding. As the TRX supports both FR and HR framingat the same time, call by call (dual mode operation), a given bit pair in the Abistrunk can either form two HR speech channels or a single FR speech channel.

AMR codecs are supported by different Nokia base station generations asfollows:

. Nokia MetroSite, Nokia Flexi EDGE and UltraSite base stations have fullAMR support.

. Nokia Talk-family BTS has AMR support for FR modes 4.75, 5.9, 7.4 and12.2 as well as for HR modes 4.75, 5.9 and 7.4; with this approach, the linkadaptation between full scale of FR modes and almost full scale of HR canbe achieved.

. Nokia 2nd generation DE21 BTS does not support AMR.

. Nokia InSite BTS does not support AMR.

For a description of the Nokia MetroSite, Nokia UltraSite, and Nokia FlexiEDGE base station, see the following product descriptions:

. Nokia MetroSite EDGE BTS, in Nokia MetroSite EDGE BTS ProductDocumentation.

. UltraSite EDGE BTS Product Description in Nokia UltraSite EDGE BTSProduct Documentation.

. Flexi EDGE BTS Product Description in Nokia Flexi EDGE BTS ProductDocumentation



BTS configuration

Logical BTS configurations

There is no limitation for sector configurations in the Nokia MetroSite basestation, because each transceiver has an antenna of its own. For diversity,however, more than one TRX is needed per sector.

Dual band BTS configuration

This configuration allows you to use GSM/EDGE 900/1800, 800/1800 and, 800/1900 TRX combinations in the same cabinet. The BCF function is common toboth bands. The site architecture allows separate or combined TRXconfigurations. The limitations concerning different logical BTSs under the sameBCF are also valid for dual band operation.

Combined BCF and TRX functions

The TRX can be configured as a master or as a slave. The master TRX handlesboth O & M functions and Abis interface functions.

Chained BTSs

The Nokia MetroSite can be concatenated by an extension kit, which contains D-bus and synchronising the frame clock between BTSs. Each extension cabinetsaves you the cost of one FC or FXC unit. The O & M functionality is centralisedto the master cabinet.

You need only one extension cable between cabinets. The maximum number ofcombined Nokia MetroSite BTSs is 3, and the total length of bus cable is limitedto five metres. The TRX addresses are sequentially numbered and configuredautomatically via an extension cable.

The cells can be shared between cabinets to allow flexible upgrading from, forexample, 2 + 2 TRXs to 4 + 4 TRXs.

Only the FXC transmission card can be used with chained MetroSite EDGE BTSconfiguration.

Dynamic Abis

Dynamic Abis allocation is a solution for higher data rates of EGPRS to ensurecost-efficient and flexible Abis transmission capacity addition. The DynamicAbis functionality allocates Abis transmission capacity to cells when neededinstead of reserving a full fixed transmission link per TRX.



As data rates can vary between 8.8 and 59.2 kbps per radio time slot, traditionalstatic Abis allocation does not use transmission resources efficiently. DynamicAbis uses the existing Abis more efficiently by splitting PCMs into permanenttime slots for signalling and a dynamic pool for data. The pool can be shared by anumber of transceivers. The Dynamic Abis transmission solution saves a lot inthe Abis transmission expansion cost as it allows Abis dimensioning to beperformed near the average data rates instead of peak rates. This also applies tothe number of 2M BSC interfaces needed.

Dynamic Abis interworking

. (E)GPRS

(E)GPRS territory method and EGPRS use the Dynamic Abis.

. Compatibility with base stations

Dynamic Abis is compatible with Nokia MetroSite, UltraSite EDGE, andNokia Flexi EDGE base station EDGE TRXs.

4.1 TRU transmission unit descriptions

The Transmission Unit (TRU) is a group of different units making it possible tobuild various kinds of network topologies with different types of electricalinterfaces and transmission media. These boards are located in the Common Unitsubrack of the Nokia Talk-family BTSs or in Nokia PrimeSite BTS cabinets.

Either one or two slots for TRU units are reserved in the Common Unit subrackof the Nokia Talk-family BTS, and one in the Nokia PrimeSite BTS.

Table 5. The transmission units in the Nokia Talk-family and Nokia PrimeSiteBTSs

ETSI

PCM (E1)

ANSI

PCM (T1)

Talk-family TRUA TRUE

PrimeSite TRUB TRUF

Generally, the Nokia PrimeSite BTS transmission unit differs from thecorresponding Nokia Talk-family device in that it does not include the frontpanel, LEDs, and measurement points. Any other differences in the features willbe mentioned in the text below.



BTS configuration

TRUA/B

The TRUA/B is intended for all kinds of BTS E1 PCM networks (2 Mbit/s).

The TRUA/B has three 2 Mbit/s interfaces which can be installed for both typesof line impedance (75 ohm or 120 ohm) by jumper settings individually. Thedrop/insert function where selected time slots are branched to the BTS can beexecuted at the 8 kbit/s level. Other time slots are connected automaticallystraight through between interfaces one and two.

Repeater function in the BTS

The Nokia Talk-family BTS can be a part of a line repeater chain without anyexternal line repeater. Two of the BTS Abis interfaces can tolerate 20 dBattenuation. The maximum distance between these Abis interfaces and the nextline repeater depends on the cable type used. A usual distance with symmetricalcables is about one kilometre. Distances greater than that can be achieved byplacing a line repeater in line within one kilometre from the BTS site.

If only one unit is installed, the third Abis connection in the BTS can tolerate 6dB attenuation and it has a maximum range of 300 metres. If two transmissionunits are installed, the BTS has four external 20 dB Abis interfaces.

Signal bypass repeater functions in the BTS

When a sustained power failure takes place in a Nokia Talk-family BTS, it isnecessary to maintain transmission to other pieces of BTS equipment in themultidrop configuration. This is possible if a terminal repeater, for example,DL2E, is fitted in front of the first BTS in the network. The terminal repeatergenerates the current needed in the BTS for the signal regeneration. The need foradditional line repeaters depends on the distance between the BTS and theterminal repeater.

The bypass function is possible for two 2 Mbit/s interfaces (IF1 and IF2) withtwisted pair connections of 120 ohm in the transmission unit. During the bypassfunction, time slots are connected straight through the BTS from the first interfaceto the second without any cross-connections.

4.1.1 O & M arrangement of transmission

The standard control functions of the Nokia equipment are supported.Transmission equipment can be controlled remotely from the network via theAbis interface. The BTS provides a transparent two-way path for remotecommands of transmission control and responses.



When the transmission equipment is operated locally with a service terminal, thepolling of the transmission equipment will automatically be disabled. Thisoperation prevents the generation of unnecessary alarms that would otherwise besent to the BSC from the Base Control Function Unit (OMU).

Transmission equipment can be configured to be polled, that is, managed by BSCor BTS. In BTS polling, the BTS polls its local network elements and nearbysites, for example the microwave radio (repeater). The BTS sends a status inquiryto the polled equipment. The BTS then transmits the collected Q1 information tothe BSC through a LAPD link using the OMUSIG channel, usually at a bit rate of16 kbit/s. The BSC forwards the data to NetAct. In BSC polling, the BSC is themaster which collects data from all the Q1 transmission equipment connected to itand then transmits the data to NetAct.

The local BTS transmission equipment is configured and controlled via theservice terminal or the man-machine interface (MMI).

All cabinets have a Nokia-specific external control port (Q1) for the operationand maintenance of the external transmission equipment. Nokia Flexi EDGE BTSoffers a Local Management Port (LMP) for the local connection of ElementManager via Ethernet.

4.1.2 Options for transmission

Duplicated transmission board (option)

It is possible to use a second, optional transmission board (TRUx) to expand thenumber of possible transmission links. This option is not available for the MiniBTSs and the Nokia PrimeSite BTS.

Integrated radio relay equipment (option)

The BTS is compatible with the Nokia Digital Radio Relay Equipment (DMR18-38I). The Nokia Talk-family large-capacity BTSs can be equipped with up to twointegrated radio relay equipment models that replace a part of the equipmentinside the BTS cabinet and need only the compact microwave heads to beinstalled externally.

The incorporation of the two links makes it possible to build a drop-and-insertmicrowave relay network for the BTS units when they communicate with theBSC.



BTS configuration

A single piece of radio relay equipment carries up to four 2 Mbit/s Abis links. It iseffectively transparent because it offers the same capacity and configurationpossibilities as the cabled Abis connections. Any of the 2 Mbit/s signals, or a partof the 2 Mbit/s signals at 8 kbit/s level, can be dropped to the BTS, and the rest ofthe capacity is available for other BTSs. The frequency range of the radio relay is18/23/38 GHz.

The integrated radio relay equipment is connected to the BTS and the microwavehead with two cables.

The option is not available for the Mini BTSs.

External radio relay equipment (option)

All BTSs are compatible with most of the standard 2 Mbit/s radio relayequipment supplied by different manufacturers. When the external radio relayequipment is used, all the equipment must be fitted externally to the BTS cabinetand cabled to the Abis ports. The BTS cabinets are equipped with terminals tosupply external power for the radio transmission equipment. The control isprovided through a 9-pin D-connector.

4.2 FC and FXC units

The FC and FXC are transmission units for Nokia MetroSite and Nokia UltraSiteBTSs.

In the Nokia MetroSite BTS, you can house a single FXC unit that providescross-connection, or a single low-cost FC unit without cross-connection. NokiaUltraSite BTS has slots for up to four FXC units, or one FC unit. In NokiaUltraSite BTS, you should always use an FXC unit for flexible capacity growth.

FXC units with cross-connection

The FXC units include a very powerful cross-connection system with agranularity of 8 kbit/s.

. FXC E1/T1 (4 x 2M/1.5M), symmetric wire line transmission, 120/100Ohm

. FXC E1 (4 x 2M), asymmetric wire line transmission, 75 Ohm

. FXC RRI (16 x 2M), radio link transmission (Flexbus connection for 2outdoor units)



. FXC STM-1: Unit with 2 STM-1 interfaces for fibre optic cable (L-1.1laser interface), SDH standard compliant, add/drop and cross-connection atVC-12 layer, synchronisation functions.

. FXC Bridge: Bridge for the signals between the SDH part of the BTS andthe PDH cross-connect of the FXC equipment. Includes Q1 managementand cross-connection on 8 kbit/s, 16 kbit/s, 32 kbit/s and 64 kbit/sgranularity.

This unit is always used with the FXC STM-1 card.

FC units

The FC units were designed to be used with Nokia MetroSite BTS. With NokiaUltraSite BTS, the use of a FXC unit is recommended because of EDGEevolution.

Two FC units are available:

. FC E1/T1 (1 x 2M/1.5M), wire line transmission (can be used with theNokia MetroSite BTS and Nokia UltraSite BTS)

. FC STM-1: a unit with 2 STM-1 interfaces for fibre optic cable (L-1.1 laserinterface), SDH standard compliant, add/drop and cross-connection at VC-12 layer, synchronisation functions (only to be used with Nokia MetroSiteBTS. CXM 4.1 SW or later is required.).

Microwave radio relays

The Nokia UltraSite and Nokia MetroSite base stations can include a radio relay-specific indoor interface unit FXC RRI that can connect one or two radio relayoutdoor units to the BTS. All signal connections (n x 2M, Q1) between the BTSand the FXC RRI go through the BTS mother board. Up to two radio outdoorunits can be connected to the Nokia MetroSite BTS, and up to eight to the NokiaUltraSite BTS. The power supply of the Nokia MetroSite BTS can support twoNokia MetroHopper or Nokia FlexiHopper radio relay units.

The Nokia FlexiHopper radio relay unit supports the capacities 2 x 2, 4 x 2, 8 x 2and 16 x 2 Mbit/s. The hop lengths can vary between approximately three and 60kilometres, with the radio frequencies 38 to 13 GHz, respectively.

The Nokia MetroHopper radio relay unit's capacity is 4 x 2 Mbit/s and its hoplength is up to 1 km.

Stand-alone radio relays are interfaced via standard n x 2M and Q1. Power issupplied directly to the radio, not from the BTS.



BTS configuration

Combined O & M and Telecom signalling

With combined O & M and Telecom signalling, you can use the transmissioncapacity more efficiently. Nokia MetroSite BTS can be configured either as amaster or a slave of a BTS. The master TRX handles both the Telecom and O &M functions, which facilitates the combination.

The logical links are identified by the Service Access Point Identifier (SAPI). TheSAPI values and priorities have been defined in the GSM specification 08.56. Inaddition, an access channel is defined for the establishment of the O & M link.

Table 6. SAPI values and priorities

SAPI 0 Radio signalling procedures Priority 1

SAPI 62 Operation and maintenance Priority 2

SAPI 63 L2 management (Access channel)

4.3 FIEA, FIPA and FIFA units

Flexi EDGE BTS is the future macrocellular EDGE BTS of Nokia BTS portfolio.Flexi EDGE BTS is built from two different modules: the System Module,housing all baseband and transport processing functions as well as BTS O&M,and the Radio Frequency Modules, housing the transceivers and poweramplifiers. A transport plug in unit is part of the System Module. The followingvariants are or will be available:

. FIPA: 8 x E1, T1 balanced 120/100 Ohms

. FIEA: 8 x E1 coaxial 75 Ohms

. FIFA: 2 x Nokia Flexbus Interfaces (16x 2 Mbit/s)

To keep the initial roll-out costs low and on the other hand to offer possibilitiesfor future growth, transmission interface units start with basic functionality withtwo E1/ T1 interface or one Flexbus interface. Further functionality can be easilyadded later on by additional software licence. The protection of thesefunctionalities will be integrated with the next software releases. The followinggrowth path with advanced features are available by software licence:

. additional blocks of two E1/T1s

. second Flexbus



. loop protection (slave)

. cross-connection and grooming

Nokia Flexi EDGE BTS and the transmission interfaces are managed by the sameElement Manager. However, Nokia Flexbus for Nokia Flexihopper andMetrohopper requires an own Element Manager.




BTS configuration



5 GPRS and the Gb interface

The BSC provides Gb interface towards the General Packet Radio Service(GPRS) core network (Serving GPRS Support Node, SGSN). Nokia offers GPRSsupport in the BSS with powerful radio resource management algorithms,optimised BSS network topology and transmission solutions to ensure optimalinvestment for operators and high capacity and quality of service for users. TheGPRS core network is accessed from the host GSM network via the BSC. This isaccomplished by using Packet Control Units (PCU) in the BSC. The Nokia PCUhas full support for extensive GPRS radio resource control transactions. Thisembedded PCU solution provides the most cost-effective solution for theoperator. Gb interface is implemented using Frame Relay (FR) or IP connectivity.

5.1 Gb over Frame Relay

Frame Relay can be either point-to-point (BSC-SGSN) or there can be a framerelay network located between the BSC and SGSN. The protocol stack comprisesBSSGB, NS and L1. Frame Relay as stated in standards will be part of theNetwork Service (NS) layer. On top of the physical layer in the Gb-interface thedirect point-to-point Frame Relay connections or intermediate Frame Relaynetwork can be used. The physical layer is implemented as one or several E1PCM lines with G.703 interface in ETSI environment or with T1 PCM lines inANSI environment. The FR network will be comprised of third-party off-the-shelf products. The following figures show examples of Gb interfacetransmission solutions.



GPRS and the Gb interface

Figure 2. Through-connected channels configured in the transcoders and inthe MSC switching matrix

Spare capacity of the Ater and A interfaces is used for the Gb. The Gb timeslotsare transparently through-connected in the TCSM and in the MSC. If freecapacity exists, it is best to multiplex all Gb traffic to the same physical link toachieve possible transmission savings. In many cases the SGSN will be located inthe MSC site and thus this multiplexing has to take place there as well. Normalcross-connect equipment like for example Nokia DN2 can be used for thatpurpose. The following figure shows how the same can be achieved in a differentway, by using additional equipment between the transcoder and the BSC.

Figure 3. GPRS traffic multiplexed on the same physical connection as usedfor the GSM traffic on the Ater interface

Gb Interface

Ethernet Switch

GGSN #1GGSN #2

MSC

SGSN

Transcoders

MSC/SGSN site

PCMFrameRelay

BSC

BSC

BSCAbis

Gb Interface

Ethernet Switch

GGSN #1GGSN #2

MSC

SGSN

Transcoders

MSC/SGSN site

BSC

BSC

BSCAbis

FrameRelay

2 Mbit/s PCMAter + Frame Relay

MUX



Another solution is to concentrate GPRS traffic via one network over the Gbinterface, with the transmission network providing a point-to-point connectionbetween the BSC and the SGSN.

Figure 4. GPRS traffic concentrated and carried over the Gb interface in apacket data network

Similarly, a Frame Relay network can be used. The Gb interface allows theexchange of signalling information and user data. It also allows many users to bemultiplexed over the same physical resources.

Figure 5. GPRS traffic carried over dedicated 2 Mbit/s PCM links

Gb Interface

Ethernet Switch

GGSN #1GGSN #2

MSC

SGSN

Transcoders

BSC

BSC

BSC

MSC/SGSN siteAbis

FR Switch

FR Switch

Packet DataNetwork

(FR, ATM, etc.)

Gb Interface

Ethernet Switch

GGSN #1GGSN #2

MSC

SGSN

Transcoders

BSC

BSC

BSC

MSC/SGSN siteAbis

PCM links

Frame Relay




5.2 Gb over IP

The increased demand for packet switched traffic transmission cost efficiency canbe met by the deployment of IP in the transmission network. IP can replace FrameRelay networks as the transport medium in the sub-network service layer.Network Service Control Protocol Data Units (PDU) are incapsulated within theUDP datagrams when the IP transport medium is in use. When IP is taken intouse, packet-based traffic does not go through the circuit-based Pulse CodeModulation (PCM) network, but IP network instead. The introduction of IPenables to build an efficient transport network for the future IP-based multimediaservices, and helps to reduce the transmission costs.

The IP transport can be used in parallel with FR under the same BSC and BaseStation Controller Signalling Unit (BCSU). One Network Service Entity (NSE)and each PCU always uses either one, IP or FR. Inside one BCSU, separate PCUscan use different transmission media. In the BSC, there is always one local IPendpoint per PCU. Gb over IP supports both dynamic and static configuration. Indynamic configuration, only one IP address and UDP port pair of remote endSGSN is needed to establish NS-VC configuration on Gb. Static configurationcan be used, if it is seen feasible to have fixed configuration between BSCs andSGSNs. This might be feasible when the operator has a direct cable connectionbetween the BSC and the SGSN.

Figure 6. GPRS traffic carried over the Gb interface with IP

5.3 GPRS capacity

There are two generations of Nokia PCUs:

Gb Interface

Ethernet Switch

GGSN #1GGSN #2

MSC

SGSN

Transcoders

BSC

BSC

BSC

MSC/SGSN siteAbis

Router

RouterGb over IP



. The first generation PCUs are PCU-B in BSC3i and PCU, PCU-S andPCU-T in older BSCs.

. The second generation PCUs are PCU2-D in BSC3i, and PCU2-U in olderBSCs.

The second generation PCU2s are the preferred option and mandatory GPRS CS3& CS4 application software product.

Nokia Packet Control Units are state-of-the-art plug-in units with high capacityand reliability. They control the GPRS radio resources, receive and transmitTRAU frames to the BTSs and Frame Relay packets to the SGSN. High capacityis provided through a state-of-the-art PCU design and with the possibility offuture extension. N + 1 redundant PCUs achieve high reliability.

The Nokia solution provides full TRX capacity with very high reliability andperformance. One PCU is installed into every BCSU for redundancy reasons (N +1). Additionally there is a possibility to add a second PCU per each BCSU toincrease the packet switched capacity in the BSC. In BSC3i, one physical plug-inunit consists of two logical PCUs.

The PCU removes the unnecessary TRAU overheads coming from the Abisinterface and assembles the data into frame relay for the Gb interface.

Table 7. Connectivity of logical PCUs

16kbit/s Abis TSL TRX Cell/ Segments BTS

Logical PCU2

(PCU2-D/PCU2-U)

256 256 64 128

Logical PCU1

(PCU-B/PCU-T)

256 128 64 64

Logical PCU1

(PCU/PCU-S)

256

(128 RTSL)

128 64 64

Considering the transmission protection it also needs to be decided whether twoFrame Relay bearers are needed for each logical PCU using different ETs or if thetransmission is protected with cross-connection equipment.

It is possible to multiplex more than one Gb interface directly to the SGSN, ormultiplex them on the A interface towards the MSC and from there cross-connectthem to the SGSN. The PCM carrying the Gb timeslots can be one of the BSC'sexisting ETs or an ET can be dedicated to the Gb interface.







6 BSS redundancy configurations

Depending on availability targets, BSS networks can be designed with redundanttransmission paths or equipment.

Redundancy switchover is triggered by pilot bits or directly by equipment alarmconditions.

As a consequence of availability objectives, it is recommended that at least twoTCSM units are equipped per BSS even if the required traffic capacity could behandled by one unit. Yet, in some cases also external redundancy arrangementscan be considered as described below.

Abis loop with Nokia MetroSite, Nokia UltraSite and Nokia Flexi EDGE basestations

The Abis loop protection is a very effective way to avoid a single faultytransmission link or weather (rain) affecting the cellular network performance.The use of pilot signals for protection switching and MCB & LCB forsynchronisation control are applied similarly. For more information, see Radiotransmission.

The UltraSite integrated transmission node of the FXC units can operate as a loopmaster station or a slave station. The single FXC unit in a MetroSite can operateas a loop slave. The Flexi EDGE BTS can operate as a loop slave.

Radio link hop protection

The hot standby mechanism is a commonly applied system to protect against HWfailures of radio outdoor units whenever a chain of BTSs is connected togetherusing radio transmission.



BSS redundancy configurations

Figure 7. Radio link hop protection


BSC

BTS

FIU19E

1+1 HSB

FXC RRI



7 Operation and maintenance oftransmission equipment

The ability to monitor and control the whole network is one of the most importantfeatures for the GSM operator. To facilitate this, all elements of the GSMnetwork, the BSS, the MSC, the HLR and the VLR, are connected to the NokiaNetAct for network monitoring and control.

The connection to the Nokia NetAct is made via Q3 interface. For transmissionequipment in general, typically fault management and performance managementare supported. For TRU, DN2 and DMR, basic G.821 signal quality counters aresupported. For Nokia FXC and FC transmission equipment as well as Nokia FlexiEDGE transmission units, the full or partial set of G.826 signal quality countersare supported. Configuration management for FXC and FC transmissionequipment is supported by launching an element manager integrated from theNokia NetAct.

The Nokia NetAct management functions include fault management (FM),performance management (PM) and configuration management (CM) of networkelements.

The BSC can support up to 56 Q1 supervisory channels. Also, a maximum of1024 separate transmission equipment with Q1 interface can be supervised,including the transmission equipment supervised by the BSC and the BTS. TheDN2, TRU, Nokia FXC equipment and Nokia Flexi EDGE transmission units areable to transfer Q1 data between TSL0 and some other time slot within E1 (inmany cases TSL31 is used), or to the Q1 overhead channel of a Flexbus signal.

7.1 Supervisory channels

BSC

The BSC is connected to the Nokia NetAct with a dedicated X.25 connection,using a trunk time slot for the BSC-MSC-Nokia NetAct path, or a LANconnection using Ethernet. The Nokia NetAct connection can also be duplicatedfor protection. Direct access to packet network is also available.



Operation and maintenance of transmission equipment

The supervisory channel for BSC-supervised transmission equipment is carried ina PCM time slot. Remote maintenance or control of a piece of transmissionequipment can be done with BSC MML commands, or by launching theequipment element managers integrated from the Nokia NetAct.

BTS

A BTS is connected via the BSC to the Nokia NetAct. The BTS-BSC path isrealised through a LAPD channel and the path BSC-MSC-Nokia NetAct by usingan X.25 channel or LAN.

The transmission equipment can be connected to BTS supervision in differentways. The connection is an internal Q1 bus connection if the equipment isintegrated in the BTS.

Remote maintenance or control of a piece of transmission equipment can be donewith BSC MML commands or by launching the equipment element managersintegrated from the Nokia NetAct.

TCSM

For the transcoder's remote supervision and control, one LAPD-type data channelper TCSM is used between the BSC and the TCSM. This channel uses the 16kbit/s capacity from trunk time slot 1. BSC MML commands are used forsupervision and control. The TCSM can be brought into test state and diagnostictests can be run via the BSC.

MGW

Supervisory channels are not supported.

Nokia Q1 managed transmission equipment

Nokia Q1 managed transmission equipment, not integrated to a Nokia BTS, ismanaged remotely via a Q1 management channel. DN2 and MetroHub can pickup the Q1 management channel from the PCM time slot. In some Nokia Q1managed equipment such as FIU 19 and FIFA, the Q1 management channel mustbe connected to the equipment via a Flexbus overhead.

7.2 Local O & M

BSC

The BSC has two V.24 local user interfaces.



BTS

The BTS has a V.24 local user interface. The interface is used for the BTS's ownO & M and for the transmission equipment that is under BTS supervision.

TCSM2/TCSM3i

AV.24 local user interface is available for each TCSM unit in a TCSM2/TCSM3i.

Transmission equipment

Most Nokia transmission equipment has a Q1 interface connector. The interfaceis compatible with Nokia's Transmission Management System (TMS) protocol.The Nokia FXC/FC transmission equipment used with Nokia MetroSite, NokiaUltraSite or Nokia MetroHub, and the FIU 19 support the Nokia Q1 protocol thatis an enhancement to the transmission management system (TMS) protocol. TheTMS comprises equipment ranging from a hand-held service terminal to a TMS-OS work station.

In Nokia Flexi EDGE, the Q1 interface is provided by the System Module. It alsooffers the LMP for the local management of the BTS and integrated transmission.

The Nokia Service Terminal is a tool for local configuration and maintenance ofthe TRU (and any other piece of Nokia transmission equipment). It is normallyneeded in the installation phase. The Service Terminal emulator is also availableas PC software.

The DN2 manager is a special package of software for the DN2's localconfiguration management. It requires a standard PC with Windows. The DN2manager allows easy and user-friendly configuration of transmission equipment(such as the DN2). It also includes software for service terminal emulation. AlsoTRU Manager, analogous to the DN2 Manager, is available.

For configuration management of the FXC/FC transmission equipment, a suite ofelement managers is provided. With UltraSite BTS, the element manager isUltraSite BTS Hub Manager. With MetroSite BTS, the transmission cardmanagers are integrated in the BTS manager. With MetroHub, the elementmanager is MetroHub Manager.

For Nokia Flexi EDGE, there is a common Element Manager for the BTS andtransmission. However, the FIFA Flexbus unit requires Nokia Hopper Manager.



Operation and maintenance of transmission equipment

7.3 Remote O & M

The Nokia NetAct remotely monitors and controls all GSM network elementsincluding the TCSM and transmission equipment. To enable remote configurationand interrogation of the transmission elements involved, NetAct provides theremote use of node managers, remote access via Service Terminal Emulatorsession, and remote access via MML session. The Transmission NodeManagement feature in NetAct offers the users access to node managers througha Node Manager Server.

As for the GSM OMC, the Nokia NMS is designed for full GSM networkmonitoring and control including transmission equipment.

Note

Note that some network capacity must be reserved for O & M channels.




8 Requirements on transmission network

There are different scenarios for the realisation of the network:

1. The network is owned by a GSM operator and built along with the GSMBSS.

It is possible to tailor the transmission of the network and O & M featuresexactly for GSM BSS.

2. The GSM BSS network is built by using the existing transmission networkowned by the GSM operator.

Old transmission equipment may set restrictions on the network use.

3. Transmission network capacity is only leased to the GSM operator.

The GSM operator may not be allowed to supervise the transmissionnetwork directly. The actual network realisation may be unknown.

8.1 2 Mbit/s transmission paths

The basic functional requirements on the 2 Mbit/s transmission paths are thefollowing:

1. Time slot sequence must be maintained between the TCSM and the BSCand also between the BSC and the BTS.

2. It is recommended that the entire 2 Mbit/s stream is transparent betweenthe TCSM and the BSC. If n x 64 kbit/s cross-connect devices are used(that is, fractional 2 Mbit/s), individual time slots may go out of servicebecause of faults in certain transmission sections without the BSC, TCSM,or MSC directly detecting it. This fault condition will eventually bedetected by failing calls in certain circuits.



Requirements on transmission network

3. DN2 loop protection prefers TSL0 to be transparent through the wholeloop. Loop synchronisation control bits (master clock bit, MCB, and loopcontrol bit, LCB) are normally transmitted using TSL0 bits. The TRUA,FXC/FC and FIxAunits have no restrictions; MCB and LCB can betransmitted in any time slot.

4. The EGPRS dynamic Abis pool (EDAP) size at the BSC and BTS, the timeslot order in the BSC and BTS EDAPs and the EDAP starting time slot inthe UltraSite BTS Traffic Manager and the incoming PCM to the BTSmust be the same. Because of maintenance reasons, using the sametimeslot allocation at the BSC and BTS is recommended.

If required, the EDAP starting timeslot at the BSC and the incoming PCMto the BTS can be different. Cross-connections are allowed, but the PCMframe or the n x 64 cross-connection must comply with the G.796 standardto maintain the octet sequence integrity of signals being cross-connected.EDAP and the TRXs tied to it (including traffic/EGPRS master andsignalling channels) have to share the same monolithic Abis connectionand PCM frames should have octet sequence integrity which can beachieved in two ways:

a. Using 1-3 PCM lines that function according to the G.796 standard.

If the BTS capacity requires several PCM lines, a normal networkdelay variance between the PCM lines does not impact EDGEperformance. The EDAP pool and the TRXs tied to it have to belocated on a single PCM.

b. Using fractional E1, n x 64 k connection that complies with theG.796 standard.

This means that this n x 64 k cross-connection block is handled witha single cross-connection command at every transmission node. Thismeans that the EDAP pool and the TRXs tied to it must have aconnection made with a single monolithic PCM or a singlemonolithic n x 64 k connection which comply to the octet sequenceintegrity of the G.796 standard. This structure needs to bemaintained throughout the network. In case the PCM line does notfulfil the octet sequence integrity requirement as specified in ITU-TG.796, a maximum of +/- three PCM frame delay between time slotsis tolerated when the BSC SW S10.5 ED CD1.2 or newer release isbeing used.

For more information on Dynamic Abis dimensioning, see AbisEDGE Dimensioning in GSM/EDGE BSS System DocumentationSet.

5. All E1 type interfaces conform to the ITU-T Recommendations G.703 andG.704 and the T1 interfaces conform to T1.403. All PCM interfaces are ofrepeater type, with no power feeding from the interface.



8.2 Synchronisation of BSS network

The accuracy requirement for the primary reference clock (PRC), which is themaster clock source of the whole network, is given in the ITU-T recommendationG.811. PRC equals the so-called Stratum 1 level clock and the requirement for themaximum long-term frequency departure of PRC is 1 x 10-11. In live networks,the network timing is affected by jitter/wander, but when the synchronisation ofthe network is correct, the same basic accuracy exists all over the network whenmetered over a long period.

The synchronisation of the entire network should be constructed so that thesynchronisation delivery to all over the network is hierarchical (leveling). Thisreduces the possibility for the synchronisation to be corrupted. Even though mostof the jitter is filtered when passing through transmission nodes (because of jittertransfer function), wander accumulates in synchronisation distribution chains; thelimits for network jitter/wander are set in G.823.

The BSC clock system (CL3TG) is a Stratum level 3 synchronisation source,which works slaved to the traffic trunks or from external synchronisation source.Its control range is +/- 15 x 10 exp -6 and pull-in range +/- 2 x 10 exp -6.Accuracy of automatic control is 5 x 10 exp -10. If traffic trunks/external sourcesare deemed invalid, the clock enters plesiochronous operation. CL1TG has thesame characteristics, but external synchronisation sources are not possible.

The BTS clock system can be divided into two independent parts, transmissionnode part and BTS internal. The clock of the transmission part is in Phase LockedLoop (PLL) to the incoming 2M signal (selectable to be synchronised to one ofthe 2 Mbit/s Abis signal(s) or 2MHz synchronisation input, according to thepriority list). This transmission part clock is used for timing the outgoing data ofall the 2Mbit/s interfaces, including the one towards the other units of BTS.

The principle is that in the mobile network the synchronisation goes from MSC toBSC to BTS. However, in reality that synchronisation chain might be brokensomewhere and, for example when using leased lines, the BTS may take thereference synchronisation from the transmission network of another operator.This does not harm the system if also that transmission synchronisation isoriginated from PRC and it is accurate enough; if occasional data slips occur, themobile network system can tolerate it.

The same 1 x 10-11 long-term accuracy should exist all over the network if thenetwork synchronisation is correct, only jitter/wander instability should exist. Thelong-term Abis interface accuracy requirement for Nokia BTSs is ± 0.015 ppm orbetter (1.5 x 10-8), which is 1500 times more loose than the PRC requirement.The GSM specification for the BTS Air interface accuracy is ± 0.05 ppm, whichcan be attained easily even with the worst case situation inside the BTS (RF partinaccuracy), if the Abis accuracy is ± 0.015 ppm.




Because the Abis reference signal contains jitter/wander, it cannot be useddirectly for timing the BTS air interface. The jitter/wander instability must befiltered away before that. Therefore the BTS master clock (OCXO) is not in aphase-locked loop (PLL) to the incoming Abis signal coming from thetransmission part, but it is using the Abis signal as a reference for 'calibrating' theBTS master clock periodically. There is a several-layer averaging algorithmwhich takes care of controlling the OCXO frequency and also of filtering awaythe effects of transmission jitter/wander.

Therefore, in practise the BTS runs fully under its own OCXO. The OCXOfrequency is only adjusted automatically towards the 2M reference. This does notmean it is moved sharply to the point the adjustment calculations show, but thereis a limit in the algorithm for the maximum frequency step in order to improvestability, that is, to reduce wander effects.

In case of synchronisation fault there are two cases for BTS operation:

. If BTS O & M signalling is cut, BTS OCXO starts an independentoperation (free run) and takes no reference from the Abis interface. Thenthe mistuning towards the faulty reference is avoided and the air interfacefrequency is in most cases correct immediately after the O & M recovery.

. O & M signalling exists but the synchronisation reference is not correct. Inthis case the OCXO frequency will slowly start to drift towards the faultysynchronisation. Because the maximum adjustment step is limited, it maytake several hours for the BTS to exceed the GSM specifications in the airinterface

Note

An alarm ('Difference in frequencies between the PCM and BTS masterclock') is raised when the BTS clock unit notices a difference between theincoming 2M reference and the internal OCXO frequency - the differencelimit for the alarm activation is 0.1 ppm. This means the synchronisationdisruption is noticed at the BSC.

Then, if the BSC does not get a proper synchronisation reference, it leads in thelong run to the situation that the BSC cannot feed BTSs with a reference which isaccurate enough (0.015 ppm). The effect on BTSs is explained above.



8.3 Transmission delay of BSS network

Round trip delay refers to the amount of the time it takes for an electrical signal totravel from one end of a transmission medium to the other end and back.

The 3GPP TR 03.05 defines a maximum of 188.5 ms for a round trip delay fromthe A interface to the mobile station and back. The transcoder (TC) encoder/decoder loop alone requires about 30 ms. Taking all delay contributions intoaccount leaves approximately 6 ms for pure BSS transmission delay. Thiscorresponds to about 1000 km of cable transmission equipment.

The TC and the BTS framing unit together form a control loop for adjusting thetranscoding and rate adaptation unit (TRAU) frame phase for a minimum delay.The stable operation of this controller requires that the transmission delaybetween the TC and the BTS is less than 40 ms. This forms the upper limit to thedelay.

A satellite circuit will nominally cause a delay of 260 ms. Therefore satellitecircuits cannot be directly tolerated in a BSS network between the TC and theBTS. On the other hand, satellite circuits between the TC (for example a TClocated at the BSC site) and the MSC are acceptable despite the added delay.

Satellite Abis or Ater circuits can be used as options. This requires certain systemlevel changes and the whole BSS has to be reserved for satellite use.

According to the ITU-T Recommendation G.114, the delay should be kept under400 ms and echo cancellers should be used. When using satellite circuits, thisvalue is exceeded.

Other GSM network-related traffic, such as signalling, accounting and O & M,can be transmitted through satellite circuits with due case by case consideration ofdelay. Channel throughput may suffer because of the protocol used.

In the case that acoustic echo cancellation (to cancel echo in the loop BSS - MS -BSS) is activated in the TCSM, its performance will degrade if the one-way delaybetween TCSM and BTS is more than 5 ms.

8.4 Error rate performance of BSS network

In the BSS network the speech signal is transmitted at a speed of 16 kbit/s usingFR transcoding, and at 8 kbit/s using half rate (HR). The transcoded signal hasless bit redundancy than a normal PCM but still its robustness againsttransmission bit errors is good.




Speech quality is good if the ITU-T Recommendation G.821 performanceobjectives are met. If this is the case, fewer than 10% of one-minute intervalshave a BER value higher than 10E-6, fewer than 0.2% of one-second intervalshave a BER value higher than 10E-3, and fewer than 8% of one-second intervalshave any errors.

For digital transmission links with a data rate of 1.5 Mbit/s and higherperformance statistics and objectives according to ITU-T RecommendationG.826 are applicable. The G.826 performance objectives are more stringent thanG.821, which means meeting those will result in good speech quality, too. Theperformance measurement is block error based with G.826, in difference to the biterror based measurement with G.821. The ESR and SESR values gained byperformance measurement from both standards can be approximated to eachother, but are as result not the same.

Note

At BER=10E-3 most transmission equipment starts sending 2M AIS (alarmindication signals). EDGE applications are more sensitive to degraded BERthan GSM voice.

GSM signalling channels are robust to errors because of the protocol used.

8.5 Slips in transmission

Slips in the transmission equipment are caused by synchronisation problems. A2M trunk signal frame (controlled) slip will affect two consecutive FR TRAUframe bits in roughly the same way as bit errors. Even modest slip raterequirements, 30 slips/hour, will result in rare background clicks only. Trunkcircuits conforming to the ITU-T Recommendation G.822 perform well.

Usually there are practically no slips as BSS network synchronisation ishierarchic. If faults occur, PCM signal frequencies in stand-by trunks may differby up to 50 ppm, resulting in a slip in two seconds.

GSM signalling channels are robust to slips because of the protocol used.



8.6 Echo control in BSS

As internal delays are noticeable in the GSM system, echo cancelling devices areincluded at the MSC-PSTN interface to cancel any echoes resulting from PSTNnetwork 4/2 wire hybrids. Problems may arise if additional echo controllers(satellite circuit echo controllers, acoustic echo controllers and so on) are tandemconnected with GSM echo cancellers.

Besides slips, also clock frequency differences cause convergence problems toecho cancellers.

The TCSM includes an acoustic echo cancellation function that removes theacoustic echo generated in the MS.

8.7 Jitter and wander prevention in BSS

Excessive jitter and wander will stress equipment clock recovery and buffercircuitry, causing errors and slips. It is also possible that jitter and wanderaccumulate in long transmission chains.

The GSM equipment is designed to meet the requirements of the ITU-TRecommendation G.823 as regards the maximum input jitter from the PCM line.In network nodes (such as the BSC), the jitter transfer function is designed toprevent jitter accumulation.

If a 2 Mbit/s signal from the BSC used for BTS synchronisation is carriedtransparent via a SDH network where the SDH network is not synchronised to theBSC, the 2 Mbit/s line may have abrupt frequency deviations (pointer jitter) evenif data is transmitted without problems on the line. The BSC and BTS aredesigned to tolerate these deviations. If a line used for synchronisation extractionfor the BSC experiences these deviations, the BSC frequency may start tofluctuate. However, this fluctuation will not typically mistune the frequency ofthe BTSs considerably, since the BTS has a long averaging time. Otherwise if thefluctuation frequency is low, the amplitude of fluctuation is also low.







9 Digital cross-connect nodes

Figure 8. Interconnection of different networks

MSCBSC

MetroHubDN2/MetroHub

Tellabsor 3rd party

DXX

BTS integratedcross-connection function

BTS integrated transmissionterminal function



Digital cross-connect nodes

9.1 Digital node equipment DN2

The Digital Node equipment DN2 is a general-purpose transmission cross-connect and multiplexing device. For details of the DN2, see the appropriatehandbooks, such as DN2 Operating Handbook.

Applications in GSM BSS

The DN2 equipment is normally used to save transmission costs by packing the 2Mbit/s channels more effectively. Application examples are shown in Figure 9Multiplexing of the BSS and external channels with the DN2. It is possible tomultiplex other services on a transmission link (to use the otherwise unusedcapacity).

Another important application area is redundancy. Some examples are given inthe sections discussing redundancy.

The DN2 is normally supervised by the BSC.

Mechanically the DN2 comprises one (or two, if expanded) 19-inch subrack. Afully equipped NDM 19 in Subrack has 16 board slots (+ one for the power unit):

. A bus power unit BPU (or EBPU if expanded DN2) requires one slot.

. A control unit CU requires one slot.

. Dual 2M interface units IU2 require one slot. The number of IU2s is 1 - 13(or the number of 2M interfaces 2 - 26).

. A power supply unit NDU (NDM DC Unit), NAU (NDM AC/DC Unit) orNDA (NDM DC Adapter); the right-hand board slot is wide and reservedfor power supply units

When the DN2 is supervised by the BSC, the maximum number of usable 2 Mbit/s interfaces in a DN2 subrack is 24. With two subracks, the maximum is 38interfaces.

The Q1 supervision bus from the BSC to the DN2 uses a loop-back cross-connection set-up in the DN2 (to change Q1 from TSL31 over to TSL0, requiringone IU2 board). It is also possible to form the TSL31/0 loop between the CU andone of the IU2 interfaces. This will save one IU2 interface.



Figure 9. Multiplexing of the BSS and external channels with the DN2

Note

By-pass traffic may also flow through the BSC to the MSC.


9.2 MetroHub transmission node

Nokia MetroHub transmission node is an outdoor capable stand-alone cross-connect, which is developed especially to support radio link based BSS transportnetworks. Its main traffic protection feature is the loop protection. MetroHubprovides a flexible, expandable and cost-effective solution for the purposesrequired by a GSM/EDGE operator. The maximum cross-connection capacity ofthe MetroHub is 56 x 2 Mbit/s with a switching granularity of 8 kbit/s. WithMetroHub, the same FXC units can be used as with integrated UltraSite BTStransmission. Therefore E1, T1, Flexbus and STM-1 interfaces can be integratedto MetroHub.

BSC2 Mbit/s

G.703DN2 DN2

by-pass traffic

by-pass traffic

BTS1

BTS2




Figure 10. Network principle

BSC

n x E1

BTS

Protected loop

Nokia MetroHub



Nokia MetroHub grooms the traffic from several base stations. Partially filledconnections are thus combined and trunk efficiency increased. To ensuretransmission availability, the Nokia PDH loop protection concept and SDH ringprotection are supported. For more information on PDH loop protection, seeNokia PDH loop protection in GSM networks (the document can be obtainedupon request from your Nokia representative).






10 BSC-BTS transmission examples

The following examples are intended to give you a more practical view ofnetwork design.

10.1 Overview of transmission network

Figure 11 BSS network using leased lines presents a BSS network that is mainlybased on using leased lines. Even in a case such as this, some lines (BTS2-BTS3)are directly owned and controlled by the GSM operator. The GSM operator hasonly a limited supervision and control access to the main transmission network.

Figure 11. BSS network using leased lines

PSTN

by-pass traffic

Transmission network fromwhere capacity can be leased(e.g. PSTN)

MSC TC

NokiaNetAct

BTS4

BTS2

BTS chainBTS1

BTS3

BSC DN2



BSC-BTS transmission examples

10.2 Point-to-point transmission

The most common and straightforward transmission configuration is the point-to-point connection between the BSC and all the BTSs. Figure 12 Point-to-pointconnection between BSC and BTS presents an example of this type ofconnection. Only one TRU unit is required.

Figure 12. Point-to-point connection between BSC and BTS

10.3 Multidrop chain transmission

The multidrop chain (see Figure 13 Multidrop chain) is an important networkconfiguration, especially when new services are covered. The advantage of thechain is that many low-capacity stations can be tied to a single 2M PCM line.GSM service area often suggests this kind of approach.

As with point-to-point connections, the transmission media selection isunrestricted.

3 21

FC/FXC/FIxA

BTS

3 21

FC/FXC/FIxA

BTS

BSC



Figure 13. Multidrop chain

10.4 Loop transmission

A point-to-point connection can be duplicated to look like a loop and a multidropchain can be looped back to increase circuit availability, as shown in Figure 14Duplicated point-to-point and multidrop loop.

Figure 14. Duplicated point-to-point and multidrop loop

3 21

FC/FXC/FIxA

BTS

3 21

FC/FXC/FIxA

BTS

3 21

FC/FXC/FIxA

BTS

BSC

3 21

FC/FXC/FIxA

BTS

BSC

3 21

FC/FXC/FIxA

BTS

DN2

3 21

FC/FXC/FIxA

BTS




10.5 Radio transmission

The radio relays provide a fast method of building networks, as Figure 15 Loop,radio relay transmission network indicates. If needed, radio relays can be replacedby fibre, especially when the station capacity later grows.

Figure 15. Loop, radio relay transmission network

10.6 DN2 in the MSC-BSC path

The DN2 is usually located in the MSC site. The DN2 is required at both ends ofthe MSC - BSC path as the time slot allocation is not standard.

In this application the SM2M multiplexing function can be replaced by the DN2,and at the same time the DN2 can multiplex some by-pass traffic.

Note

Since the DN2 makes connections at the timeslot or sub-timeslot level, it isnot able to pass trunk fault situations end-to-end, and the MSC and BSC maybe unaware of unavailable time slots. Because of this, this configuration canbe recommended for temporary use only. This restriction applies toconfigurations presented in Figures Example use of the DN2 and Introductionof the TCSM2 without a dedicated transmission link.

BSCMetroHub

FXCRRI

BTS

FXC RRI

BTS

FXC RRI

BTS

FXC RRI

FXC RRI FXC RRI FXC RRI

BTS BTS BTS



1 + 1 protection can be used in the transmission path between the DN2s.

Figure 16 Example use of the DN2 presents an example use of the DN2.

Figure 16. Example use of the DN2

10.7 Nokia UltraSite network example

The UltraSite network can implement the Abis loop protection or simpler star orchain network topology. Figure 17 Example of a Nokia UltraSite network showsa HSB protected link.

With UltraSite BTS and FXC/FC units as well as Flexi EDGE BTS and FIFA, thesame transmission topologies as with Talk BTS/TRUA units are supported. WithUltraSite BTS, the maximum possible number of transmission interfaces andcapacity is enhanced.

MSCN xTC

DN2

BSC4

BSC2 DN2

BSC1

BSC3

by-pass traffic




Figure 17. Example of a Nokia UltraSite network


BSC

ETMetro-Hub

E1

IF1

Dir 2

Dir 1

FB1FIU19

FB2 FB1

FB2FB3

Ultra-Site orFlexiEDGE

Flexi-Hopper

Flexi-Hopper

Flexi-Hopper

Flexi-Hopper



11 Time slot allocations in BSS

The TCSM has the capability to support different time slot allocations on the Aterinterface. Figure 18 Time slot allocation for 16 kbit/s bit rate channels (typicallyfull rate, enhanced full rate or AMR) on the Ater 2 Mbit/s interface with theTCSM2/TCSM3i shows the 16 kbit/s allocation and Figure 19 Time slotallocation for half rate traffic with 8 kbit/s TRAU frames on the Ater 2 Mbit/sinterface with the TCSM2 shows the 8 kbit/s allocation. In addition to these, it ispossible to configure a combination of 16 kbit/s and 8 kbit/s portions of timeslots. For the HSCSD service capacity, units of 16 kbit/s, 32 kbit/s and 64 kbit/sare allocated. It is also possible to combine HSCSD channels with FR/EFR andHR channels (as well as AMR with TCSM3i) on a common Ater interface.

Signalling channels between the BSC and the MSC, and sometimes OMCchannels, are carried by entire 64 kbit/s time slots. They lower the maximumnumber of traffic channels, especially in the case of 16 kbit/s allocation.

TSL0 carries normal ITU-T type framing overhead information (synchronisation,alarms and trunk line performance).

Figure 18 Time slot allocation for 16 kbit/s bit rate channels (typically full rate,enhanced full rate or AMR ) on the Ater 2 Mbit/s interface with the TCSM2/TCSM3i illustrates the Ater time slot allocation for 16 kbit/s bit rate channels(typically full rate, enhanced full rate or AMR) on the Ater 2 Mbit/s interface withthe TCSM2/TCSM3i. 64 kbit/s channels that must be through-connected betweenthe BSC and MSC are not shown explicitly in this figure; the TCSM2/TCSM3iallows any time slot to be through-connected. Typically, for example, time slot 31could be used for that purpose, in which case the traffic channels 24 - 27 wouldbe left out.

Figure 20 Ater time slot allocation example for the HSCSD application: acombination of 2 x 16 kbit/s channels (HS2) and 4 x 16 kbit/s channels (HS4)shows an example of Ater allocation for HSCSD. Channels of different capacitiescan be combined at the Ater interface. Each A-PCM may be allocated a certain(single) type of channels. In TCSM2, the channels are A, B, C, D, E, or F,whereas in TCSM3i they are G, H, or I (see Table 3 Circuit types of TCSM2 andTCSM3i). Thus it is also possible to share a common Ater line between HSCSD



Time slot allocations in BSS

channels and 16 kbit/s submultiplexed channels (FR/EFR speech, FR data, non-HSCSD data, and, with TCSM3i, also AMR). Figure 21 Time slot allocation of 2x 16 kbit/s channels of Figure A-PCM1 on A interface shows how the channelsappear at the A interface.

Unused bits are marked with x in the figures.



Figure 18. Time slot allocation for 16 kbit/s bit rate channels (typically full rate,enhanced full rate or AMR) on the Ater 2 Mbit/s interface with theTCSM2/TCSM3i

1 2 3 4 5 6 7 8

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

LAPD TCH.1 TCH.2 TCH.3 TC_PCM 1

TCH.4 TCH.5 TCH.6 TCH.7







x TCH.1 TCH.2 TCH.3 TC_PCM 2























LINK MANAGEMENT

BIT

TSL




Figure 19. Time slot allocation for half rate traffic with 8 kbit/s TRAU frames onthe Ater 2 Mbit/s interface with the TCSM2

#7 signalling / Nokia NetAct connection

2 3 4 5 6 7 81

0 LINK MANAGEMENT

1 LAPD 1 2 3 4 5 6 TC_PCM 1

8 9 10 11 12 13 1472

17 18 19 20 21 22 23153

25 26 27 28 29 30 31244

x5 TC_PCM 21 2 3 4 5 6

8 9 10 11 12 13 1476

17 18 19 20 21 22 23157

25 26 27 28 29 30 31248

x9 TC_PCM 31 2 3 4 5 6

8 9 10 11 12 13 14710

17 18 19 20 21 22 231511

25 26 27 28 29 30 312412

x13 TC_PCM 41 2 3 4 5 6

8 9 10 11 12 13 14714

17 18 19 20 21 22 231515

25 26 27 28 29 30 312416

x17 TC_PCM 51 2 3 4 5 6

8 9 10 11 12 13 14718

17 18 19 20 21 22 231519

25 26 27 28 29 30 312420

x21 TC_PCM 61 2 3 4 5 6

8 9 10 11 12 13 14722

17 18 19 20 21 22 231523

25 26 27 28 29 30 312424

x25 TC_PCM 71 2 3 4 5 6

8 9 10 11 12 13 14726

17 18 19 20 21 22 231527

25 26 27 28 29 30 312428

29

30

31



BIT

TSL



Note

The numbers in the cells refer to the number of traffic channels within a PCMtrunk.




Figure 20. Ater time slot allocation example for the HSCSD application: acombination of 2 x 16 kbit/s channels (HS2) and 4 x 16 kbit/schannels (HS4)

TC_PCM 1(HS2)

TC_PCM 2(HS4)

0 LINK MANAGEMENT

LAPD X HS2.11

2

3

4

5

6

HS2.2 HS2.3

HS2.4 HS2.5

HS2.6 HS2.7

HS2.8 HS2.9

HS2.10 HS2.11

7 HS2.12 HS2.13

8 HS2.14 HS2.15

9 HS2.16 HS2.17

10 HS2.18 HS2.19

11 HS2.20 HS2.21

12 HS2.22 HS2.23

13 HS2.24 HS2.25

14 HS2.26 HS2.27

15 HS2.28 HS2.29

16 HS2.30 HS2.31

17 HS4.1

18 HS4.2

19 HS4.3

20 HS4.4

21 HS4.5

22 HS4.6

23 HS4.7

24 HS4.8

25 HS4.9

26 HS4.10

27 HS4.11

28 HS4.12

29 HS4.13

30 HS4.14

31 HS4.15

1 2 3 4 5 6 7 8BIT

TSL



Figure 21. Time slot allocation of 2 x 16 kbit/s channels of Figure 20 A-PCM1 onA interface

Figure 22. Time slot allocation of 4 x 16 kbit/s channels of Figure 20 A-PCM2 onA interface

xHS2.1

HS2.2

HS2.3

0

1

2

3

1 2 3 4 5 6 7 8

LINK MANAGEMENT

4

5...28

29

30

31

HS2.4

...

HS.29

HS.30

HS.31

x

x

x

x

x

x

BIT

TSL

HS4.1

HS4.2

HS4.3

0

1

2

3

1 2 3 4 5 6 7 8

LINK MANAGEMENT

4

5...13

14

15

16

HS4.4

...

HS4.14

HS4.15

X

17 X

18

...

31

X

BIT

TSL




11.1 Time slot allocation in combined BSC3i/TCSM3iinstallation (ANSI)

In combined BSC3i/TCSM3i installation, the transcoding capacity of a TCSM3ican be shared by the master BSC, installed together with the TCSM3i, and one ormore remote BSCs that are connected to the master BSC. The Ater interfacebetween the master BSC and TCSM3i is internal and always based on ETSI PCMwith 32 timeslots and it is therefore able to carry five ANSI T1 TC-PCMs.

Since the external PCMs carry only 24 timeslots in ANSI environment, the groupswitch capacity of the master BSC is therefore not effectively used, unless a fifthTC-PCM is connected to a TR3E plug-in unit and submultiplexed into the freespace on the Ater PCM. This extra PCM cable is called BRANCH PCM.

The following figures describe how the MAIN PCM and BRANCH PCM aresubmultiplexed into the Ater PCM between the master BSC and TCSM3i withdifferent data rates. Note that timeslot 31 on the Ater PCM cannot be used forthrough-connection.

Figure 23. Submultiplexing on Ater PCM in ANSI environment (16 kbit/s)

TC_PCM 1

Main PCM Branch PCM Ater PCM

1..6

7..12

13..18

19..24

1..6

7..12

13..18

19..24

1..6

7..12

13..18

19..24

TCH 1-24

TC_PCM 2

TCH 1-24

TC_PCM 3

TCH 1-24

TC_PCM 4

TCH 1-24

TC_PCM 5

TCH 1-24

25..30

LAPD

TC_PCM 1

TCH 1-24

TC_PCM 2

TCH 1-24

TC_PCM 3

TCH 1-24

TC_PCM 4

TCH 1-24

TC_PCM 5

TCH 1-24

LAPD






1..12

13..24

1..6

7..12

13..18

19..24

1..12

13..24

TC_PCM 1

TCH 1-24

TC_PCM 2

TCH 1-24

TC_PCM 3

TCH 1-12

25..30

LAPD

TC_PCM 1

TCH 1-24

TC_PCM 2

TCH 1-24

TC_PCM 3

TCH 1-12

LAPD


1..24 1..6

7..12

13..18

19..24

1..24TC_PCM 1

TCH 1-24

TC_PCM 2

TCH 1-6

25..30

LAPD

TC_PCM 1

TCH 1-24

TC_PCM 2

TCH 1-6

LAPD




Figure 26. Submultiplexing on Ater PCM in ANSI environment (mixed 32 and64 kbit/s)

11.2 Compressed Abis time slot allocation

Compressed time slot allocation is rarely used and limitations apply (not all BTSfamilies support this feature).

In traditional transmission solutions some capacity is left unused, especially in thecase of BTSs with one TRX, because one radio interface time slot is always usedfor the BCCH. The compressed Abis time slot allocation makes it possible to usethis capacity for TRX signalling. It is also possible to use another 16 kbit/s slot tocarry the O & M signalling required for the site. This slot can 'steal' the TCHtransmission slot thus leaving capacity for six full rate TCHs or twelve half rateTCHs for that TRX.

In environments where it is not necessary to use the full traffic capacity of a TRX,compressed Abis time slot allocation offers an ideal solution for using thetransmission medium more efficiently. With this configuration, it is possible to fit15 TRXs to one 2 Mbit/s PCM. The following table illustrates this solution.

TC_PCM 1


1..12

13..24

1..6

7..12

13..18

19..24

1..12

13..30

TCH 1-24

TC_PCM 2

TCH 1-12

TC_PCM 2 cont.

TCH 13-18

LAPD

TC_PCM 1

TCH 1-24

TC_PCM 2

TCH 1-18

LAPD



Table 8. Compressed Abis time slot allocation

TRXSIG/OMUSIG TCH, TSL1 TCH, TSL2 TCH, TSL3

TCH, TSL4 TCH, TSL5 TCH, TSL6 TCH, TSL7

The solution is particularly advisable in low traffic areas where it is essential tohave coverage.

Note

The time slot allocation of both BSC and BTS is of semipermanent type andcannot be dynamically altered. In a multi-TRX sector, radio network recoverymay swap the positions of BCCH-TRXs and TCH-TRXs and so make itimpossible to predict the branching requirements of the transmission.

Another option for making the use of Abis interface more efficient is bettersuitable for multi-TRX BTSs. The following table illustrates the time slotallocation in this case.

Table 9. Compressed Abis time slot allocation in the case of multi-TRX basestations

TRXSIG TCH, TSL1 TCH, TSL2 TCH, TSL3


Here the first time slot of every TRX must be disabled at the BSC to leave spacefor the signalling. Possible reconfigurations may influence the time slotallocation. An additional 16 kbit/s subslot must be allocated for O & Msignalling.

By combining the above solutions it is possible to support five 3 x 1 TRX siteswith a single 2 Mbit/s PCM link. The time slot allocation of one site in this case isillustrated in the following table.

Table 10. Compressed Abis time slot allocation that supports five 3 x 1 TRXsites

OMU/TRXSIG_1 TCH, TSL1 TCH, TSL2 TCH, TSL3


TRXSIG_2 TCH, TSL1 TCH, TSL2 TCH, TSL3




Table 10. Compressed Abis time slot allocation that supports five 3 x 1 TRXsites (cont.)


TRXSIG_3 TCH, TSL1 TCH, TSL2 TCH, TSL3


If the TRX signalling speed is 32 kbit/s, the following allocation is also possible.

Table 11. Compressed Abis time slot allocation with the TRX signalling speed32 kbit/s

TRXSIG/OMU TCH, TSL2 TCH, TSL3




Figure 27. Compressed allocation enabling up to 15 TRXs per 2 Mbit/s circuit

Note

This is achieved at the cost of speech capacity.

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

TRXSIG1

TCH5/9-10

TRXSIG2

TCH5/9-10

TRXSIG3

TCH5/9-10

TRXSIG4

TCH5/9-10

TRXSIG5

TCH5/9-10

TRXSIG6

TCH5/9-10

TRXSIG7

TCH5/9-10

TRXSIG8

TCH5/9-10

TRXSIG9

TCH5/9-10

TRXSIG10

TCH5/9-10

TRXSIG11

TCH5/9-10

TRXSIG12

TCH5/9-10

TRXSIG13

TCH5/9-10

TRXSIG14

TCH5/9-10

TRXSIG15

TCH5/9-10

x/OMUSIG

OMUSIG1

TCH6/11-12

OMUSIG2

TCH6/11-12

OMUSIG3

TCH6/11-12

OMUSIG4

TCH6/11-12

OMUSIG5

TCH6/11-12

OMUSIG6

TCH6/11-12

OMUSIG7

TCH6/11-12

OMUSIG8

TCH6/11-12

OMUSIG9

TCH6/11-12

OMUSIG10

TCH6/11-12

OMUSIG11

TCH6/11-12

OMUSIG12

TCH6/11-12

OMUSIG13

TCH6/11-12

OMUSIG14

TCH6/11-12

OMUSIG15

TCH6/11-12

x/OMUSIG

TCH3/5-6

TCH7/13-14

TCH3/5-6

TCH7/13-14

TCH3/5-6

TCH7/13-14

TCH3/5-6

TCH7/13-14

TCH3/5-6

TCH7/13-14

TCH3/5-6

TCH7/13-14

TCH3/5-6

TCH7/13-14

TCH3/5-6

TCH7/13-14

TCH3/5-6

TCH7/13-14

TCH3/5-6

TCH7/13-14

TCH3/5-6

TCH7/13-14

TCH3/5-6

TCH7/13-14

TCH3/5-6

TCH7/13-14

TCH3/5-6

TCH7/13-14

TCH3/5-6

TCH7/13-14

x/OMUSIG

TCH4/7-8

TCH8/15-16

TCH4/7-8

TCH8/15-16

TCH4/7-8

TCH8/15-16

TCH4/7-8

TCH8/15-16

TCH4/7-8

TCH8/15-16

TCH4/7-8

TCH8/15-16

TCH4/7-8

TCH8/15-16

TCH4/7-8

TCH8/15-16

TCH4/7-8

TCH8/15-16

TCH4/7-8

TCH8/15-16

TCH4/7-8

TCH8/15-16

TCH4/7-8

TCH8/15-16

TCH4/7-8

TCH8/15-16

TCH4/7-8

TCH8/15-16

TCH4/7-8

TCH8/15-16

x/OMUSIG

TRX1

TRX2

TRX3

TRX4

TRX5

TRX6

TRX7

TRX8

TRX9

TRX10

TRX11

TRX12

TRX13

TRX14

TRX15




As presented in Figure Compressed allocation enabling up to 15 TRXs per 2Mbit/s circuit above, some speech capacity is lost for signalling. FR or HR speechcan be used. HR can in this case be used with 16 kbit/s TRX signalling; 32 kbit/sis also possible but it may waste capacity. Further speech TCH capacity is gainedby filling TSL31 with up to four OMUSIG channels.

Figure 28. Allocation example for a three-TRX BTS

11.3 Allocation of Abis time slots

The allocation of time slots is based on the following principles:

. One 2 Mbit/s time slot 0 is reserved for ITU-T-type frame alignment andsupervision of the link.

. One 16 kbit/s (or 64 kbit/s) channel is required between the BTS and theBSC for BTS O & M (marked as OMUSIG).

. Each TRX at the BTS processes up to 8 TCH/F traffic channels of 16 kbit/sor up to 16 TCH/H traffic channels, and a 16 kbit/s, 32 kbit/s (or 64 kbit/s)signalling link to the BSC (marked as TRXSIG). The FR and HR channelscan be used at the same time call by call in the TRX.

The following tables present the different maximum numbers of TRXs per 2Mbit/s PCM with 16 kbit/s and 64 kbit/s BCFSIG channel rates.

Table 12. 16 kbit/s signalling rate

Signalling rate Point-to-point Chain Loop

16 13* 12 11

32 12 11 10

64 10 9 9

1

2

3

4

5

6

TRX1

TRX2

TRX3

TRXSIG1

TCH5/9-10

TRXSIG2

TCH5/9-10

TRXSIG3

TCH5/9-10

OMUSIG1

TCH6/11-12

TCH2/3-4

TCH6/11-12

TCH2/3-4

TCH6/11-12

TCH3/5-6

TCH7/13-14

TCH3/5-6

TCH7/13-14

TCH3/5-6

TCH7/13-14

TCH4/7-8

TCH8/15-16

TCH4/7-8

TCH8/15-16

TCH4/7-8

TCH8/15-16



Table 12. 16 kbit/s signalling rate (cont.)

Compressed 15 *) 15 14

*) The maximum capacity is not possible because the number of TRXs that canbe installed per BTS cabinet is 12.

Table 13. 64 kbit/s signalling rate

Signalling rate Point-to-point Chain Loop

16 13 *) 9 9

32 12 8 8

64 10 7 7

*) The maximum capacity is not possible because the number of TRXs that canbe installed per BTS cabinet is 12.

The required time slot allocation is selected from the TRU menu from amongcertain time slot allocations.

The TRU is able to drop and insert full time slots (for 64 kbit/s signalling) or partsof a time slot (for 16 kbit/s signalling) without restrictions. This means that theallocation on the 2 Mbit/s highway between the BSC and the BTS (or betweenthe BTSn and BTSn + 1) can be freely selected.

11.4 TRU TSL allocation, FR, 16 kbit/s signalling

The time slot allocation principle is the following:

. Eight 16 kbit/s TCH/Fs per each TRX

. One 16 kbit/s TRXSIG (LAPD TRX - BSC) per each TRX

. One 16 kbit/s OMUSIG (LAPD OMU - BSC) per each BTS

Space is allocated for these so that the 8 TCHs occupy two entire time slots. TheTRXSIG uses one quarter of a time slot and the OMUSIG uses another quarter.




The TRU multidrop chain time slot allocation is presented in Figure 29 TRUchain allocation in the case of 16 kbit/s LAPD. This allocation can be used on the2M highway. Note that the TRU drop/insert function must be used to build acorrect internal D-bus allocation. This can be done by conforming to the rulesgiven in the figure mentioned. It is possible to use any other allocation on the 2Mhighway.

Along the BTS chain, time slots will be dropped or inserted and vacant time slotswill be formed. These vacant time slots can be used for other purposes withsuitable equipment.

This allocation is flexible enough to cover typical applications where the numberof TRXs per BTS is not greater than 12.

Unused bits, marked with x, are set to one.



Figure 29. TRU chain allocation in the case of 16 kbit/s LAPD

1 2 3 4 5 6 7 8

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

LINK MANAGEMENT

TRX12

TRX11

TRX10

TRX9

TRX8

TRX7

TRX6

TRX5

TRX4

TRX3

TRX2

TRX1TCH.1

TCH.5

TCH.1

TCH.5

TCH.1

TCH.5

TCH.1

TCH.5

TCH.1

TCH.5

TCH.1

TCH.5

TCH.1

TCH.5

TCH.1

TCH.5

TCH.1

TCH.5

TCH.1

TCH.5

TCH.1

TCH.5

TCH.1

TCH.5

TRXSIG1

TRXSIG3

TRXSIG5

TRXSIG7

TRXSIG9

TRXSIG11

X

TCH.2

TCH.6

TCH.2

TCH.6

TCH.2

TCH.6

TCH.2

TCH.6

TCH.2

TCH.6

TCH.2

TCH.6

TCH.2

TCH.6

TCH.2

TCH.6

TCH.2

TCH.6

TCH.2

TCH.6

TCH.2

TCH.6

TCH.2

TCH.6

OMUSIG1

OMUSIG3

OMUSIG5

OMUSIG7

OMUSIG9

OMUSIG11

X

TCH.3

TCH.7

TCH.3

TCH.7

TCH.3

TCH.7

TCH.3

TCH.7

TCH.3

TCH.7

TCH.3

TCH.7

TCH.3

TCH.7

TCH.3

TCH.7

TCH.3

TCH.7

TCH.3

TCH.7

TCH.3

TCH.7

TCH.3

TCH.7

TRXSIG2

TRXSIG4

TRXSIG6

TRXSIG8

TRXSIG10

TRXSIG12

x

TCH.4

TCH.8

TCH.4

TCH.8

TCH.4

TCH.8

TCH.4

TCH.8

TCH.4

TCH.8

TCH.4

TCH.8

TCH.4

TCH.8

TCH.4

TCH.8

TCH.4

TCH.8

TCH.4

TCH.8

TCH.4

TCH.8

TCH.4

TCH.8

OMUSIG2

OMUSIG4

OMUSIG6

OMUSIG8

OMUSIG10

OMUSIG12

x

BIT

TSL




Note

The number of BTSs served may be anything up to 12, with the TRXs sharedbetween them; TSL31 is unused or reserved for redundancy purposes, such asloop control bits.

11.5 TRU TSL allocation, FR/HR, 64 kbit/s signalling

This allocation is not normally used because of its high requirement of capacity.

11.6 TRU TSL allocation, FR/HR, 32 kbit/s signalling

The allocation principle is the following:

. Eight 16 kbit/s TCH/Fs or sixteen 8 kbit/s TCH/Hs

. One 32 kbit/s TRXSIG (LAPD TRX - BSC) per TRX

. One 16 kbit/s OMUSIG (LAPD OMU - BSC) per BTS

These are arranged so that one TRX TCH occupies two entire time slots. TheTRXSIG uses half of one time slot and the OMUSIG uses one quarter of time slot31.

It is possible to use 16 kbit/s TRX signalling with HR, but for the best results, 32kbit/s is recommended. During the network transition phase, 16 kbit/s may beadvantageous.

In the allocation example given in Figure An example of four-BTS TRU chain(highway) allocation when 32 kbit/s TRX signalling is used presented below, thenumber of BTSs served can be up to four with the 12 TRXs shared between them.The number of OMUSIGs can be increased by decreasing the number ofTRXSIGs— a trade-off between the number of BTSs and the number of TRXs inthe BTSs.

In the following figure, for example T1/1-2 denotes either the first full ratechannel TCH/F.1 or the first two half rate channels TCH/H.1 and TCH/H.2 of anAbis trunk. The BTS/TRX will dynamically support any combination of full rateand half rate channels call by call.



Figure 30. An example of four-BTS TRU chain (highway) allocation when 32kbit/s TRX signalling is used

1 2 3 4 5 6 7 8

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

LINK MANAGEMENT

TRX12

TRX11

TRX10

TRX9

TRX8

TRX7

TRX6

TRX5

TRX4

TRX3

TRX2

TRX1T1/1-2

T5/9-10

T1/1-2

T5/9-10

T1/1-2

T5/9-10

T1/1-2

T5/9-10

T1/1-2

T5/9-10

T1/1-2

T5/9-10

T1/1-2

T5/9-10

T1/1-2

T5/9-10

T1/1-2

T5/9-10

T1/1-2

T5/9-10

T1/1-2

T5/9-10

T1/1-2

T5/9-10

TRXSIG1

TRXSIG3

TRXSIG5

TRXSIG7

TRXSIG9

TRXSIG11

OMUSIG1

T2/3-4

T611-12

T2/3-4

T611-12

T2/3-4

T611-12

T2/3-4

T611-12

T2/3-4

T611-12

T2/3-4

T611-12

T2/3-4

T611-12

T2/3-4

T611-12

T2/3-4

T611-12

T2/3-4

T611-12

T2/3-4

T611-12

T2/3-4

T611-12

OMUSIG2

T3/5-6

T7/13-14

T3/5-6

T7/13-14

T3/5-6

T7/13-14

T3/5-6

T7/13-14

T3/5-6

T7/13-14

T3/5-6

T7/13-14

T3/5-6

T7/13-14

T3/5-6

T7/13-14

T3/5-6

T7/13-14

T3/5-6

T7/13-14

T3/5-6

T7/13-14

T3/5-6

T7/13-14

TRXSIG2

TRXSIG4

TRXSIG6

TRXSIG8

TRXSIG10

TRXSIG12

OMUSIG3

T4/7-8

T8/15-16

T4/7-8

T8/15-16

T4/7-8

T8/15-16

T4/7-8

T8/15-16

T4/7-8

T8/15-16

T4/7-8

T8/15-16

T4/7-8

T8/15-16

T4/7-8

T8/15-16

T4/7-8

T8/15-16

T4/7-8

T8/15-16

T4/7-8

T8/15-16

T4/7-8

T8/15-16

OMUSIG4

BIT

TSL




Note

The number of OMUSIG channels can be increased at the cost of reducing thetotal number of TRXs.




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Nokia Bss Transmission