Nokia BSC Enlarged Version

Base Station Controller, BSC2E/A,BSCE

dn99558557Issue 5-0 en

# Nokia CorporationNokia Proprietary and Confidential

1 (68)

2003330Nokia BSC S10.5 ED, Vers. 2, ProductDocumentation

The information in this documentation is subject to change without notice and describes only theproduct defined in the introduction of this documentation. This documentation is intended for theuse of Nokia's customers only for the purposes of the agreement under which the documentationis submitted, and no part of it may be reproduced or transmitted in any form or means without theprior written permission of Nokia. The documentation has been prepared to be used byprofessional and properly trained personnel, and the customer assumes full responsibility whenusing it. Nokia welcomes customer comments as part of the process of continuous developmentand improvement of the documentation.

The information or statements given in this documentation concerning the suitability, capacity, orperformance of the mentioned hardware or software products cannot be considered binding butshall be defined in the agreement made between Nokia and the customer. However, Nokia hasmade all reasonable efforts to ensure that the instructions contained in the documentation areadequate and free of material errors and omissions. Nokia will, if necessary, explain issueswhich may not be covered by the documentation.

Nokia's liability for any errors in the documentation is limited to the documentary correction oferrors. NOKIA WILL NOT BE RESPONSIBLE IN ANY EVENT FOR ERRORS IN THISDOCUMENTATION OR FOR ANY DAMAGES, INCIDENTAL OR CONSEQUENTIAL(INCLUDING MONETARY LOSSES), that might arise from the use of this documentation or theinformation in it.

This documentation and the product it describes are considered protected by copyrightaccording to the applicable laws.

NOKIA logo is a registered trademark of Nokia Corporation.

Other product names mentioned in this documentation may be trademarks of their respectivecompanies, and they are mentioned for identification purposes only.

Copyright © Nokia Corporation 2003. All rights reserved.

2 (68) # Nokia CorporationNokia Proprietary and Confidential


Base Station Controller, BSC2E/A, BSCE

Contents

Contents 3

List of tables 5

List of figures 6

Summary of changes 7

1 Base Station Controllers BSC2E/A and BSCE, Overview 91.1 Use of the terms BSC, BSCE, BSCi, BSC2E/A, BSC2i and BSC3i 101.2 The GSM/EDGE Product Family 111.3 The Nokia Base Station Controller product upgrades 121.4 Features of the BSC platform 12

2 Functionality of the BSC2E/A and BSCE 15

3 Architecture of the Base Station Controller, BSC2E/A, BSCE 253.1 General design of the GSM/EDGE BSC 253.2 Bit Group Switch 273.3 Call Control Computers 273.3.1 Marker and Cellular Management Unit (MCMU) 283.3.2 BSC Signalling Unit (BCSU) 293.4 Operation and Maintenance Unit (OMU) 313.5 Message Bus (MB) 333.6 Exchange Terminal (ET) 343.7 Clock and Synchronisation Unit (CLS) 353.8 Peripheral devices 363.8.1 Disk units 363.8.2 DAT (optional) 373.8.3 Printer (optional) 373.8.4 Visual display unit (optional) 373.8.5 Alarm lamp panel (optional) 373.8.6 Cable Conduit with Cabling Rack for raised floor installations 37

4 Interfaces relating to the BSC2E/A and BSCE 394.1 A interface 394.2 Abis interface 404.3 Gb interface 414.4 Q3 interface (BSC-NetAct) 424.5 CBC interface (BSC-CBC) 43

5 BSC2E/A and BSCE Software 455.1 Platform architecture 455.2 Layers 465.3 Databases 465.4 Description and programming languages 475.4.1 Programming languages 47



3 (68)

Contents

6 Configurations and capacity of the BSC2E/A and BSCE 496.1 General description of configuration 496.2 Capacity of the BSC 50

7 Mechanical design and power supply of the BSC2E/A and BSCE 537.1 Mechanical design 537.1.1 Plug-in units 537.1.2 Cartridges 537.1.3 Racks 567.1.4 Cabling 587.2 Dimensioning of the GSM/EDGE BSC 597.3 Power supply 597.3.1 Structure of power supply 597.3.2 Power consumption 59

8 Reliability of the BSC2E/A and BSCE 618.1 Fault management 618.2 Overload protection 628.3 Redundancy principles 628.4 System availability 628.5 Planned downtime 63

9 Operating environment of the BSC2E/A and BSCE 659.1 Equipment room 659.2 Environmental conditions 669.2.1 General 669.2.2 Climatogram 679.2.3 Cooling of racks 679.2.4 Electromagnetic environment 68




List of tables

Table 1. The Nokia GSM/EDGE BSC product family 10

Table 2. Circuit switched processing capacity of the BSC2E/A and BSCE 50

Table 3. Power consumption of the BSC cartridges; the BCSU includes the PCU 59

Table 4. Power consumption of the BSCE and BSC2E/A racks, PCU included 60

Table 5. Availability of the BSC2E/A in maximum configuration 62



5 (68)

List of tables

List of figures

Figure 1. Block diagram of the GSM/EDGE BSC with Bit Group Switch 26

Figure 2. Structure of the MCMU 28

Figure 3. Structure of the BCSU 30

Figure 4. Structure of the OMU 32

Figure 5. Structure of the Message Bus system 34

Figure 6. The protocol stack on the Gb interface 42

Figure 7. BSC conceptual model 46

Figure 8. Cartridges and functional units of the BSC2E/A and BSCE with GSWB,excluding BCSU 55

Figure 9. BCSU in BSC2E and BSCE including Packet Control Unit 56

Figure 10. Rack layouts of the BSC2E/A 57

Figure 11. Rack layouts of the BSCE: 56 and 88 PCM versions. 58

Figure 12. Typical layout of a BSC site 66

Figure 13. Climatogram of the GSM/EDGE BSC 67




Summary of changes

Summary of changes

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

Changes made between issues 5 and 4a

One occurrence of 'BSC2E/A' was changed to 'BSCE' in the chapter Mechanicaldesign and power supply of the BSC2E/A and BSCE .

Changes made between issues 4a and 4

Only minor structural changes have been made; no changes have been made tothe content.

Changes made between issues 4 and 3

The information has been updated to software release S10.5 level.

Chapters About the Base Station Controllers BSC2E/A and BSCE andIntroduction to the DX 200 BSC2E/A and BSCE have been combined to BaseStation Controllers BSC2E/A and BSCE, Overview.

Added references to BSC3i.

The chapter Configurations and capacity of the BSC2E/A and BSCE has beenmoved to after the chapter BSC2E/A and BSCE Software . The chapterReliability of the BSC2E/A and BSCE has been moved to after Mechanicaldesign and power supply of the BSC2E/A and BSCE .


Chapter Architecture of the High Capacity Base Station Controller, BSC2i (ETSI/ANSI), BSCi , section Peripheral devices

Added two new sections: Cable Conduit with Cabling Rack for raised floorinstallations and Applicable NEBS3 compliance (optional) .


Chapter Introduction to the DX 200 BSC2E/A and BSCE , section The NokiaBase Station Controller Product Family

Added Second PCU upgrade delivery and SMLC (Serving Mobile LocationCentre) upgrade delivery .

Chapter Functionality of the BSC2E/A and BSCE



7 (68)

Summary of changes

Added new sections Advanced Multilayer Handling , EDGE/EGPRS and MSLocation Services .

Chapter Configurations and capacity of the BSC2E/A and BSCE , sectionCapacity of the BSC

The maximum processing capacity figures have been revised.

Chapter Reliability of the BSC2E/A and BSCE

The availability figures have been updated.

Chapter Mechanical design and power supply of the BSC2E/A and BSCE ,section Power consumption

Power consumption figures have been updated.




1 Base Station Controllers BSC2E/A andBSCE, Overview

The following is an overview of the second generation GSM/EDGE Base StationController for ETSI and ANSI environment, DX 200 BSC2E/A, and the firstgeneration DX 200 Base Station Controller for ETSI environment, DX 200BSCE. Here are described, for example, functionality, architecture, interfaces,configurations and capacity, reliability, and operating environment. The softwarefeatures are described elsewhere in the GSM/EDGE BSC documentation library.

BSC is used here as the general term for the Nokia GSM/EDGE Base StationController. When the information is applicable only to the BSC2E, BSC2A orBSCE variant, the specific name BSC2E, BSC2A or BSCE is used.

There are different types of S10.5 Release deliveries:

. upgrade deliveries of the BSCE (BSCE to BSCi)

. upgrade deliveries of the BSC2E/A (BSC2E/A to BSC2i)

. upgrade deliveries of the BSC2i

. GPRS upgrade to all of the above

. SMLC upgrade

. first deliveries of the BSC2i

. first deliveries of the BSC3i

In addition to the above, extension deliveries are available for the BSC2i andBSC3i.

The Nokia GSM/EDGE BSC product family provides the operator with themeans to control terrestrial and radio channels. They also control signalling to theBTS. Another important function of the BSC is to have an operation andmaintenance interface towards NetAct.



9 (68)

Base Station Controllers BSC2E/A and BSCE, Overview

PCM lines are mentioned frequently here. There are two types of PCM lines inthe BSC2: internal or external. In the ANSI (US) BSC2A, internal PCM lines(lines which run within the BSC) are 2 Mbit/s lines of E1 ETSI hierarchy.External PCM lines (lines which go out of the BSC) are 1.5 Mbit/s lines of T1ANSI hierarchy. In the ETSI version, both internal and external lines are 2 Mbit/slines of E1 ETSI hierarchy.

1.1 Use of the terms BSC, BSCE, BSCi, BSC2E/A,BSC2i and BSC3i

The terms BSC, BSCE, BSCi, BSC2E/A, BSC2i and BSC3i are explained in thetable below.

Table 1. The Nokia GSM/EDGE BSC product family

BSC Base Station Controller, a general term for all Nokia GSM/EDGE BSC versions

General name Product name Explanation

BSCE BSCE First generation Nokia DX 200 BSC

BSCi BSCi High Capacity (upgraded andimproved) version of the first generationNokia DX 200 BSC

BSC2 BSC2A American National Standards Institute(ANSI) version of the secondgeneration Nokia DX 200 BSC2

BSC2E European TelecommunicationsStandards Institute (ETSI) version ofthe second generation Nokia DX 200BSC2

BSC2i BSC2i, ANSI version American National Standards Institute(ANSI) High Capacity version of theNokia DX 200 BSC2

BSC2i, ETSI version European TelecommunicationsStandards Institute (ETSI) HighCapacity version of the Nokia DX 200BSC2

BSC3i BSC3i, ANSI version American National Standards Institute(ANSI) High Capacity version of theNokia GSM/EDGE BSC3i




Table 1. The Nokia GSM/EDGE BSC product family (cont.)

BSC3i, ETSI version European TelecommunicationsStandards Institute (ETSI) HighCapacity version of the Nokia GSM/EDGE BSC3i

Note

When the information in the text is only applicable to one of the versions orapplications, the name of that specific version or application is used; and whenthe text is applicable to all versions and applications, the general term BSC isused.

1.2 The GSM/EDGE Product Family

The Nokia GSM/EDGE Base Station Controller is a modern fault-tolerant systemfor GSM 800/GSM 900/GSM 1800/GSM 1900 networks. The Nokia BSC isbased on modular software and hardware architecture. The distributedarchitecture of the Nokia BSC is implemented with a high-capacity and redundantmultiprocessor system - the DX 200 Computing Platform. The system enables thedistribution of processing capacity to several computer units with dedicated tasks.

The DX 200 product family covers a wide application area in GSM/EDGEmobile networks and fixed telephone networks. The DX 200 product familycontains products for digital mobile applications, such as Base Station Controller(BSC), Transcoder Submultiplexer (TCSM2), Mobile Switching Centre (MSC),Home Location Register (HLR) and 2G Serving GPRS Support Node (SGSN).

The main function of the BSC is to control and manage the Base StationSubsystem (BSS) and the radio channels. Based on Nokia's long experience incellular networks, the BSC is designed for efficient use of radio resources and iseasy to operate and maintain. The Nokia BSC is a stable, mature and highlyreliable product. One major feature of the BSC is its field-proven multivendorfunctionality.

Together with the functionally distributed modular architecture of the DX 200Computing Platform and the latest commercially available industry standardhardware components, the BSC is easily expandable and cost-efficient and hashigh capacity.



11 (68)


1.3 The Nokia Base Station Controller productupgrades

The S10.5 release consists of High Capacity upgrade deliveries, BSC to BSCiand BSC2E to BSC2i and a new BSC2i delivery. GPRS upgrade deliveries andcapacity extensions are also possible.

BSCE upgrade delivery

The existing BSCE can be upgraded to BSCi, High capacity configurations up to512 TRXs with hardware upgrade.

BSC2E/A upgrade delivery

The existing BSC2E/A can be upgraded to BSC2i, High capacity configurationsup to 512 TRXs with hardware upgrade.

(E)GPRS upgrade deliveries

All the deliveries above can include the GPRS upgrade as optional hardware. TheGPRS upgrade delivery is available for all BSC versions. The 2nd PCU upgradeis available for the BSC2E/A and BSC2i. The second PCU is upgraded to allconfigured BCSUs as GPRS/EGPRS extension.

SMLC (Serving Mobile Location Centre) upgrade delivery

The SMLC upgrade delivery is available for all BSC versions.

1.4 Features of the BSC platform

The main features of the BSC platform are:

Reliable platform:

. distributed processing

. modular structure

. fault tolerance

. upgradable processors (Intel family)

Easy operability:




. good online operability

. OSI protocol model for O & M functions

. user-friendly MML interface according to ITU-T (InternationalTelecommunication Union) recommendations

Flexible configuration:

. BSC2E/A and BSCE expandability in 16 TRX steps from 16 TRXs to upto 128 TRXs and above that to 256 TRXs in the Large Capacity BSCconfiguration. With the High Capacity BSC option the expandabilityreaches up to 512 TRXs.

. the modular architecture allows you to build economically dimensionedswitching systems according to your needs, and it also reduces the cost ofsurplus capacity and enables new facilities to be readily added.

No special room requirements:

. BSCs are small and compact and low on power consumption

. the cooling of the BSC is implemented by means of natural convection



13 (68)


2 Functionality of the BSC2E/A and BSCE

The GSM/EDGE BSC can be located flexibly in the GSM network. It can beinstalled as stand-alone, on the same site as the Base Transceiver Station (BTS) itcontrols, or at a remote location, which can be either co-located or non-co-locatedwith the MSC. The most common solution is to locate the BSC remotely to theMSC near the BTSs it controls and install the TransCoder SubMultiplexer(TCSM) at the MSC site. Submultiplexing can then be used between the BSC andTCSM to reduce transmission costs.

The BSC manages a variety of tasks ranging from channel administration to shortmessage service. The tasks are explained in brief below.

Management of terrestrial channels

. indication of blocking on the A interface channels between the BSC andthe MSC

. allocation of traffic channels between the BSC and the BTSs

. pool support for A interface circuits

. concept support for flexible channel assignments, for example, half rateand high speed circuit switched data.

Management of radio channels

. Management of channel configurations, that is, how many traffic channelsand signalling channels can be used in the BSS. This is done in connectionwith radio network configuration.

. Management of traffic channels (TCH) and stand-alone dedicated controlchannels (SDCCH). This function can be subdivided into the followingtasks:

- resource management

- channel allocation

- link supervision

- channel release

- power control



15 (68)

Functionality of the BSC2E/A and BSCE

. Management of broadcast control channels (BCCH) and common controlchannels (CCCH). This function can be subdivided into the followingtasks:

- channel management

- random access

- access grant

- paging

- management of PCCCH/PBCCH for (E)GPRS

. Management of frequency hopping:

The BSC is in charge of frequency hopping management which enableseffective use of radio resources and enhanced voice quality for a GSMsubscriber.

. Handovers

The frequency of the mobile is changed in connection with handoverswhich are executed and controlled by the BSC. Such a handover can beone of the following three types:

- intra-BSC, intra-cell (both intra-TRX and inter-TRX), which meansthat the handover takes place within the area controlled by the BSCand the mobile stays in the same cell

- intra-BSC, inter-cell, which means that the mobile stays in the areaof the BSC but moves from one cell to another

- inter-BSC, both outgoing and incoming, which means that themobile moves into the area of another BSC

Management of signalling channels between the BSC and the BTSs

The BSC supervises all 16, 32 or 64 kbit/s permanent point-to-point LAPDsignalling connections. There are 2 types of LAPD channels: TRXSIG(connection for TRX signalling per TRX) and OMUSIG (BCFSIG) (connectionfor BTS Operation and Maintenance).

Maintenance

The BSC offers the possibility for the following maintenance procedures:

. fault localisation for the BSC

. reconfiguration of the BSC

. reconfiguration support to the BTS

. updating of the software in the BSC, TCSM2 and BTS




Operation

During normal operation, the BSC offers various possibilities for the operator:

. modification of the parameters of the BSC and the BTS

. modification of the radio network parameters

. configuration of the BSC hardware

. administration of the BSC equipment

Interface for the CBC

The BSC has an X.25 and LAN connection to the Cell Broadcast Centre (CBC).The interface between the BSC and the CBC is based on the OSI layer 4 protocol.

The CBC interface offers operators a centralised means of operating CellBroadcast. In addition, the Cell Broadcast Interface offers improved tools forrequesting and reporting of CBCH-related loading and error conditions. The CBCcan also request information on the amount of transmission for each CB.

Interface for NetAct

The BSC has an X.25 and a LAN connection to NetAct. The interface betweenthese two network elements is based on the OSI protocol. This interface enablesthe following events:

. file transfer capability for downloading software and data into the BSC andthe BTSs

. file transfer capability for measurement and observation results.

User interface

The BSC has a user-friendly interface with plain-text messages and commands,which are easy to learn and use. This user interface complies with therecommendations of the International Telecommunication Union (ITU-T).

Measurements and observations

In order to run the network effectively, that is, to minimise costs and maximiseservice quality to the subscriber, you need information on the performance andservice level of the BSC and the radio network. Useful information is, forexample, how much traffic different cells carry, is there congestion on theSDCCH or TCH channels, and how many handovers are successful and howmany fail. Traffic measurements provide this information.



17 (68)


When you analyse the information, you can, for example, find out if the load isdistributed evenly or are there problems in load distribution, that is, does thenetwork have both heavily and lightly loaded parts. If the load distribution is noteven you can make changes to the dimensioning of the network in order tobalance it and to improve performance. When you observe certain trafficcharacteristics over a period of time, you are able to forecast the time when newresources or extensions must be introduced into the network.

The BSC measures traffic, observes signalling events, and traces a specific call. Itthen forwards these results to Nokia NetAct for further processing. Themeasurements are grouped together to allow better functionality and handling.This gives you an easier selection of the measurements you need at a particulartime. BSC measurements are independent of each other even though they arehandled via the same user interface.

Short Message Service (SMS)

The BSC forwards mobile originating and mobile terminating short messagestransparently.

Cell Broadcast Messages (CB)

Cell Broadcast provides the BSC with the short message service cell broadcast(SMSCB) capabilities defined by GSM recommendations. The SMSCB is a basicteleservice that is used for broadcasting short messages to mobile stations in aspecified area within the PLMN. The input is MMI, local, or remote. OptionallyCBC can be used as the input for CB messages.

Circuit Switched Data Services

The BSC supports the following bearer services, including both transparent andnon transparent data services, defined in GSM Specification ETS 300 904 withapplicable ETSI/3GPP specifications:

. Data Circuit Duplex (300-9600 kbit/s) Transparent/Non transparent

. High Speed Circuit Switched Data;

. 14.4 kbits/s Data Traffic Channel;

. Telefax Automatic Group 3, Transparent;

. Short Message Service Functionality.




Full Rate/Half Rate/EFR

The BSC supports Full Rate traffic channels, Half Rate traffic channels, andEnhanced Full Rate traffic channels. If the network includes both first generationtranscoders (TCSM) and second generation transcoders (TCSM2), the MSC mustsupport the circuit pool. If the network includes only second generationtranscoders, the circuit pool is not needed, but can be used.

Dual Band GSM/EDGE 900/1800 and GSM/EDGE 800/1900

The BSC supports the Dual Band network. The Dual Band operation supportsdual band mobiles able to perform handovers between the GSM 900 and GSM1800 bands as well as between 800 and 1900 bands during a call.

Tri-Band

The Tri-Band feature supports the use of the ETSI-specified GSM900 frequencyband extension, the area of 880-890 MHz uplink and 925-935 MHz downlinkwhere available. This means that a total of 50 radio frequency channels areincluded in this E-GSM900 band. For a GSM operator, the E-GSM900 extensionband can represent the most cost-effective way of adding capacity to his system ifthe Primary GSM spectrum is used.

Common BCCH

There is an option to allow GSM 900 and GSM 1800 TRXs to share the sameBCCH in the same cell. This functionality could be considered a progressionfrom the integrated dual band BTS and EGSM 900 frequency band support (TriBand). The Common BCCH feature is also supported for GSM/EDGE 800/1900frequency bands.

High Speed Circuit Switched Data

The optional high speed circuit switched data (HSCSD) feature providesaccelerated data rates for end-user applications. HSCSD supports both transparentand non-transparent data services. A multiple set of basic resources is reserved forone HSCSD call, and up to four time slots can be used for a HSCSD call. HSCSDcan be combined with 14.4 kbit/s data service for higher data speed rates.

Intelligent Underlay Overlay

The Intelligent Underlay-Overlay (IUO) feature allows the operator to reusefrequencies more intensively and hence achieve a higher radio network capacity.In IUO the operating spectrum of a network is divided into regular frequenciesand super-reuse frequencies. The overlay network uses regular frequencies andoffers a continuous coverage area. The underlay network uses the super-reusefrequencies which are reused very intensively to provide the extended capacity.



19 (68)


Intelligent Frequency Hopping

The Intelligent Frequency Hopping (IFH) feature provides the benefits of IUOand frequency hopping at the same time: the operator can enjoy powerful radiospectrum efficiency and the quality benefits of frequency hopping, avoidingfrequency-dependent fading in the radio path.

Advanced Multilayer Handling

The Nokia Advanced Multilayer Handling (AMH) concept is a part of the SoftCapacity features. It is used to redistribute traffic to the appropriate layer orfrequency band according to the prevailing load of the network. AMH providesthe network operator with the tools to relief load of the congested cells andsmooth out the load over the network, in other words provides the operator bothimproved quality and capacity.

General Packet Radio Service (GPRS)

Data and internet services will be the areas of future growth in the mobilecommunications. Mobile data is the key to open the door to the high revenuecorporate sector and to value-added services for consumers.

GPRS is a major step forward in mobile data. It gives customers the benefits ofinstant IP connectivity on-the-move and being continuously connected. GPRSprovides the possibility of being charged only for transferred data in addition tomore efficient use of limited air interface resources.

All Nokia BTSs support GPRS (channel coding schemes CS-1 and CS-2) withoutany hardware changes. The BSC requires new Packet Control Units (PCU) HWupgrades to be installed into each BCSU unit to support GPRS.

GPRS provides packet radio access for a GSM/GPRS mobile. The benefit ofGPRS is that it can use the same resources that circuit-switched connections doby sharing the overhead capacity. This means that one mobile uses the resourcesonly for a short period of time, that is, when there is data to send or receive. Thesharing of resources together with a very fast method of reserving radio channelsmakes the air interface usage even more efficient.

EDGE/(EGPRS)

Enhanced Data Rates for Global Evolution (EDGE) provides services such asEnhanced GPRS (EGPRS) allowing much higher data rates than current GPRSconfigurations. EDGE enhances the data capabilities of GSM networks towards3rd generation services. With new modulation, EDGE increases the Air interfacedata throughput on average three-fold compared to today's GSM and boosts bothcircuit-switched and packet-switched services. EDGE is being specified in such away that it will enhance the throughput per time slot triplefold. In EGPRS, the




maximum standardised data rate per time slot will triple and the peak throughput,with all eight time slots in the radio interface, will be up to 473 kbps. The basicconcept, therefore, is to provide a higher data rate on the 200kHz carrier. EDGEusing 8-PSK modulation enables 3 times higher gross data rate of 69.2 kbps perradio time slot by transmitting 3-bits/symbol with the existing symbol rate. Withmulti-slot reservation, EDGE offers an evolution path for GSM to supportmedium rate multimedia applications. The user can send more data per radio timeslot with the same amount of air time used and operators do not need to invest inanother frequency band and license to offer higher data rate services like mobilemultimedia.

Dynamic Abis Allocation

Dynamic Abis allocation is a solution for higher data rates of EGPRS to ensurecost efficient and flexible Abis transmission capacity addition. The Dynamic Abisfunctionality allocates Abis transmission capacity to cells when needed instead ofreserving a full fixed transmission link per TRX.

As data rates per radio time slot can vary between 8.8 and 59.2 kbps, traditionalstatic Abis allocation does not use transmission resources efficiently. TheDynamic Abis feature uses existing Abis more efficiently by splitting PCMs intopermanent time slots for signalling and voice or data, and a dynamic pool fordata. The pool can be shared by a number of transceivers. The Dynamic Abistransmission solution saves up to 70% in the Abis transmission expansion cost asit allows Abis dimensioning to be performed near to the average data rates insteadof peak rates. This also applies to the number of 2M BSC interfaces needed.

Dynamic Abis is implemented as a software feature. Quality of service isimproved by the Dynamic Abis method, which uses allocation of circuit switchedconnections under real time centralised control. The implementation of sharedtransmission channel connection pools is supported by Nokia cellulartransmission cross connection products and made easy with the Nokia NPS/10transmission network planning tool.

Support of PCCCH/PBCCH

This feature will bring dedicated CCCH capacity for (E)GPRS services.

PCCCH comprises logical channels for packet common control signalling. Thefollowing common control channels are available:



21 (68)


. PRACH is used by MS to initiate uplink transfer for sending data orsignalling information. Packet Access burst and Extended Packet Accessburst are used on PRACH.

. PPCH is used to page an MS prior to downlink packet transfer. PPCH usespaging groups in order to allow usage of DRX mode. PPCH can be usedfor paging of both circuit switched and packet data services.

. PAGCH is used in the packet transfer establishment phase to send aresource assignment to an MS prior to packet transfer.

PBCCH broadcasts packet data-specific System Information (for example C31and C32 cell selection criteria).

The new cell re-selection criteria C31 and C32 are provided as a complement tothe current GSM cell re-selection criteria. C31/C32 provide a more general tool tomake cell planning for GPRS as similar to existing planning in GSM as possible.C31 is a signal strength criterion used to decide whether prioritised cell re-selection shall be used. For cells that fulfil the C31 criterion, the cell with highestpriority class shall be selected. If more than one cell has the highest priority, theone of those with the highest C32 value shall be selected. If no cell fulfils the C31criterion, the one among all cells with the highest C32 value shall be selected.

MS Location Services

MS Location Services allows a GSM subscriber and/or valid mobile equipment tobe positioned with a certain Quality of Service. Positioning may be initiated bythe subscriber, the network, or an external party utilising the Mobile PositioningFunction. Positioning is subject to various restrictions based on capability,security, service profiles, and so on. LCS will allow the location of a GSM mobilestation (MS) to be determined at any time whilst the MS is within the radiocoverage area of the GSM HPLMN or VPLMN. Important applications ofLocation Services are, for example:

. Government Applications:

- Emergency calls (E911 requirement by FCC in US)

- location of emergency calls with the RMS accuracy 125m

- Electronic surveillance

. Operator Applications:

- Home zone calls

. Commercial Services:

- Fleet management, tracking packages

- Information on the nearest hotel, petrol station and so on

- Car Navigation




- Emergency roadside service

- Search for stolen property

Different MS Location methods have different benefits and drawbacks. No singlemethod is suitable for all applications. Nokia BSS10.5 includes the E-OTDmethod, and improved cell ID + TA method for legacy phones with Enhanced TA(E-TA). That means that TA correction will be done to improve legacy MSlocation accuracy. The method includes location calculation using radio interfacemeasurements, for example RxLev, MS speed information. Support for the stand-alone GPS method is also implemented. The signalling between SMLC and MSis similar for E-OTD and stand-alone GPS method. All methods calculate 2-dimension location estimation. A 3-dimension location calculation is for furtherdevelopment.

GSM-WCDMA Interworking

GSM-WCDMA Interworking in GSM means Inter-System handover from GSMBSS to WCDMA RAN and the same vice versa.

In order for an operator to provide seamless coverage in areas where WCDMA isnot available, for example in rural areas, inter-system handovers provide amethod of extending the radio network coverage area by making a handover fromthe WCDMA network to the GSM network.

Additionally, in situations where the WCDMA network and GSM networkoverlap, an inter-system handover from GSM to WCDMA can be made in orderto relieve the traffic load in the GSM system.

There are quite substantial benefits of having inter-system handovers in place,including:

. seamless coverage extension for 3G with existing GSM network (or viceversa);

. capacity extension for GSM with load sharing between 3G and GSM;

. 3G services to all dual-mode subscribers.

Both the circuit switched (handover and MS cell re-selection) and packetswitched (MS cell re-selection) modes will be supported.

The above-mentioned BSC functionalities consist of basic functionalities. Thesefunctionalities and options are described in more detail in BSS featuredescriptions.



23 (68)


3 Architecture of the Base StationController, BSC2E/A, BSCE

3.1 General design of the GSM/EDGE BSC

The GSM/EDGE BSC is based on a modular software (SW) and hardware (HW)structure. Because there are exact specifications for the interfaces betweendifferent modules, new functions can easily be added without changing thearchitecture of the system. Thus, the GSM/EDGE BSC can have a longoperational lifespan and still always have up-to-date features.

The distributed architecture of the GSM/EDGE BSC is implemented by amultiprocessor system. In a multiprocessor system the data processing capacity isdivided among several computer units, each of which has a microcomputer of itsown. Call handling capacity depends on the number of Call Control ComputerUnits. The capacity of the BSC can easily be increased by adding more CallControl Computer Units to the BSC.

Figure 1 shows the block structure of the GSM/EDGE BSC. The most importantfunctional units of the BSC are:

. Group Switch (GSWB), which is used for switching speech and data, andconnecting signalling circuits.

. Base Station Controller Signalling Unit (BCSU), which handles the BSCsignalling functions. The optional Packet Control Units (PCUs) areincluded in every BCSU, when the (E)GPRS service is implemented.

. Marker and Cellular Management Unit (MCMU), which controls andsupervises the GSWB and implements radio resource management (RRM)functions, being responsible for cells and radio channels. The MCMU alsoacts as a BSC SYM (system maintenance) unit in case of OMU failure.

. Operation and Maintenance Unit (OMU), which serves as an interfacebetween the user and the BSC, but also works as a SYM unit of the BSCand automatically supervises the BSC.



25 (68)

Architecture of the Base Station Controller, BSC2E/A, BSCE

. The high-speed Message Bus (MB), which interconnects the call controlcomputers and the OMU.

. Exchange Terminals (ET), which connect transmission systems to theGSWB.

. Clock and Synchronisation Unit (CLS), which generates the clock signalsfor the BSC.

. Transcoder (TCSM2) which, though a separate network element usuallyinstalled on the MSC site, is normally viewed as a functional unit of theBSC (for further information, please refer to the TCSM2 userdocumentation).

Functional units (FU) are composed of individual HW and SW modules.

Figure 1. Block diagram of the GSM/EDGE BSC with Bit Group Switch

The functional units and cartridge types used in the GSM/EDGE BSC aredescribed in the following sections, which provide the information on both thebasic configurations of the functional units (or cartridges) and the extensionpossibilities. The units and cartridges are presented in alphabetical order.

In principle, the BSCE consists of the same functional units as the BSC2E/A. Theonly difference is the following: since the original ET1C cartridges (that acceptonly ET1E plug-in units) are not replaced by ET5C cartridges, there must be anadditional AFS plug-in unit in the BCSU to control the ET1E plug-in units.

BCSU MCMUOMU

ETBTS MSC

X.25 / LAN

MB

GSWBCLS

ET

ET

SGSN

PCU Hard diskDisk driveDAT drive

A bis A ter

Gb




3.2 Bit Group Switch

The Bit Group Switch conveys the traffic passing through the BSC and switchesthe tones to the subscribers of the exchange and to the trunk circuits. The BitGroup Switch also establishes the needed connections to the signalling units andthe internal data transmission channels, and is responsible for the submultiplexingfunctions of the BSC.

The operation of the Bit Group Switch is controlled and supervised by the Markerand Cellular Management Unit (MCMU; SWCOP). The MCMU performs allnecessary connecting and releasing functions.

The Bit Group Switch switches on 8, 16, 32, and 64 kbit/s level.

The Bit Group Switch Cartridge, SW1C, consists of power supply (PSC1) andtwo or three SW64B plug-in units, which all have 32 4 Mbit/s interfaces. Thecapacity of the GSWB is 128 or 192 PCMs.

The Bit Group Switch of the GSM/EDGE BSC is a fully digital, one-staged, andnon-blocking time switch with full availability. Its great advantage is simplicity.After the Bit Group Switch has identified the correct time slots, it can alwaysconnect them in a uniform manner without using a special search path.

3.3 Call Control Computers

In the GSM/EDGE BSC, the call control functions are executed bymicrocomputers, called Call Control Computers. The Call Control Computershave an identical Central Processing Unit (CPU), which is based on the mostsuitable commercially available Intel microprocessors. The CPU board contains amicroprocessor and a local Random Access Memory (RAM). Each Call ControlComputer also contains the additional units that are required for performingspecific tasks.

All the different plug-in units of each Call Control Computer are interconnectedby a DMC processor bus. The DMC processor bus operates according to thespecifications of the internal communication of the Control Computers. TheDMC processor bus is independent of component technology evolution.Consequently, the DMC processor bus facilitates further development of theplug-in units, resulting in an up-to-date and cost-effective BSC with highcapacity.



27 (68)


3.3.1 Marker and Cellular Management Unit (MCMU)

The Marker and Cellular Management Unit (MCMU) controls and supervises theBit Group Switch and performs the hunting, connecting and releasing of theswitching network circuits. The range of the tasks it handles makes up acombination of general marker functions and radio resource managementfunctions.

The MCMU is connected to the other computer units of the exchange, OMU andBCSU, through the message bus.

The MCMU performs the control functions of a switching matrix and the BSC-specific management functions of the radio resources.

The hardware of the MCMU consists of three modules: a microcomputer, aSwitch Control Interface, and a Message Bus Interface (see Figure 2 ).

Figure 2. Structure of the MCMU

The marker functions of the MCMU control the Bit Group Switch. These controlfunctions include the connection and the release of the circuits of the switchingmatrix. When the MCMU performs the marker functions, it exchanges messageswith other Call Control Computers via the Message Bus (MB).

MCMU

DMC BUS

1

0MB

micro-computer

controlinterface

GROUPSWITCH

clock

equipment

message businterface




The Switch Control Interface writes the required connections into the switchcontrol memory and reads its contents. The switch control interface also performsvarious tests on the switching network, defined by the microcomputer, andgenerates the required timing signals.

The cellular management functions of the MCMU are responsible for cells andradio channels that are controlled by the BSC. This responsibility is centralised inthe MCMU. The MCMU reserves and keeps track of the radio resourcesrequested by the MSC and the handover procedures of the BSC. The MCMU alsomanages the configuration of the cellular network.

The cellular management functions of the MCMU do not require any specifichardware in addition to the standard microcomputer and a Message Bus InterfaceUnit (MBIF).

In case the optional MS locationing with E-OTD method is used, the SMLCcalculation algorithm is handled in the MCMU.

One GSM/EDGE BSC always includes two MCMUs that are permanentlyconnected to the duplicated pair of the Bit Group Switches, the active MCMU tothe active GSWB and the passive MCMU to the passive GSWB.

3.3.2 BSC Signalling Unit (BCSU)

The BSC Signalling Unit (BCSU) performs those BSC functions that are highlydependent on the volume of traffic. The BCSU is housed in a cartridge of its own.It consists of two parts, which correspond to the A and Abis interfaces. Thesecond optional Packet Control Unit (PCU) is included in each BCSU.

The A interface part of the BCSU is responsible for the following tasks:

. performing the distributed functions of the Message Transfer Part (MTP)and the Signalling Connection Control Part (SCCP) of SS7

. controlling the mobile and base station signalling (Base Station SubsystemApplication Part, BSSAP)

. performing all message handling and processing functions of the signallingchannels connected to it.

The Abis interface part of the BCSU controls the Radio interface channelsassociated with transceivers (TRXs) and Abis signalling channels. Every speechcircuit on the Abis interface is mapped one-to-one to a GSM-specific speech/datachannel on the Radio interface. The handover and power control algorithmsreside in this functional unit.



29 (68)


The hardware of the BCSU consists of the following modules:

. a microcomputer

. an SS7 (Signalling System No. 7) interface

. a LAPD (Link Access Protocol on the D-Channel) interface

. a LAPD interface for control of the ET

. the Message Bus interface

. the Packet Control Unit (see Figure 3 )

Figure 3. Structure of the BCSU

The interface units, that is, the SS7 and the LAPD protocols, are connected to theswitching network via PCM connections.

The SS7 interface module is for the A interface. It contains a preprocessor, whichis capable of handling a maximum of four 64 kbit/s signalling channels. Thesignalling terminal is semipermanently connected to the time slots used forsignalling.

The BCSU uses the LAPD Interface to supervise the 2 Mbit/s circuits (time slot 0handling) connected to the Bit Group Switch.

GROUP SWITCH

BCSU

DMC BUS

1

0MB

micro-computer

SS7interface

LAPDinterface

LAPDinterface

ET





The BCSU is equipped with LAPD interface terminals. The standard equipmentof the BCSU includes two terminals for LAPD interfaces for signalling towardsBTSs and towards ETs, and one for the A interface. Each LAPD signallingterminal can handle a maximum of 64 LAPD links. The bit rate of a single linkcan be either 16 kbit/s, 32 kbit/s, or 64 kbit/s. The layer 2 LAPD functions areperformed by the signalling terminal, but application-specific messages arehandled by the microcomputer of the BCSU.

One BCSU can handle traffic in a maximum of 16 transceivers (TRXs) in thebasic configuration and 32 TRXs in the optional Large Capacity BSCconfiguration.

According to the N+1 redundancy principle (see the section Redundancyprinciples ), there is one extra BCSU compared to the number set by thedimensioning rules. The additional unit is used only if one of the active unitsfails.

Packet Control Unit (PCU)

The PCU performs all the data processing tasks that are related to the (E)GPRStraffic. It implements both packet switched traffic oriented Gb and Abis interfacesin the BSC. A PCU includes a microprocessor and digital signal processorsintegrated to the same plug-in-unit to handle the tasks. The main functions areGPRS traffic radio resource management, for example connection establishmentand management, resource allocation, scheduling, data transfer, MS uplink powercontrol, Gb load sharing (uplink) and flow control (downlink). PCUs must beconfigured to every BCSU installed, but only the activated ones are to be used. Asimilar principle applies to the optional second PCU. This requirement comesfrom the general N+1 redundancy principle of the fault tolerant DX 200Computing Platform.

3.4 Operation and Maintenance Unit (OMU)

The Operation and Maintenance Unit (OMU) is an interface between the BSCand a higher-level network management system (like Nokia NetAct) and/or theuser. The OMU can also be used for local operations and maintenance. The OMUreceives fault indications from the BSC. It can produce local alarm printouts tothe user or send the fault indications to NetAct. In the event of a fault, the OMUautomatically activates appropriate recovery and diagnostics procedures withinthe BSC. Recovery can also be activated by the MCMU if the OMU is lost.

The tasks of the Operation and Maintenance Unit (OMU) can be divided into fourgroups:



31 (68)


. traffic control functions

. maintenance functions

. system configuration administration functions

. system management functions

The OMU consists of microcomputers similar to the Call Control Computers. Inaddition, the OMU contains I/O interfaces for local operation.

The Operation and Maintenance Unit (OMU) consists of the following modules(see Figure 4 ):

. microcomputer

. alarm interface

. Message Bus Interface

. peripheral device interface

. analog X.25 interface (modem to PSPDN or LAN)

. Digital X.25 interface (time-slot-based O & M interface)

. Ethernet interface

Figure 4. Structure of the OMU

GROUP SWITCH X.25, PSPDN or LAN

OMU

DMC BUS

1

0MB

peripheraldeviceinterface

micro-computer

X.25 modem orLAN interface

alarminterface

X.25, PCMinterface





The alarm interface module connects internal wired alarms to the OMU from theBSC cartridges, power supply, air conditioning equipment, etc. This moduleprovides both input and output interfaces for external alarms to NetAct.

The OMU communicates with the Call Control Computers of the BSC via theMessage Bus.

The CPU controls the peripheral device interface module, which is used toconnect disk units, visual display unit, and printer to the OMU. A mirrored pair ofWinchester disk units, a DAT tape drive, and one 3.5" disk unit can be controlledby the OMU. The disk units are installed in a separate cartridge, which housesboth hard disk and floppy disk units.

The visual display unit and printer interfaces are standard asynchronous serialinterfaces complying with the ITU-T Recommendation V.24.

The analog X.25 modem interface module provides an X.25 Data TerminatingEquipment (DTE) interface for the packet switched network (PSPDN) with aphysical layer of V.24, V.24 restricted, V.35, or X.21.

The digital X.25 PCM-based O & M interface module is used for the networkmanagement interfaces implemented in time slots. This module provides an X.25connection via the A interface time slot. It also provides an O & M interface forthe transcoders and the transmission equipment.

The LAN interface module provides an ethernet interface according toIEEE802.3.

The OMU of the GSM/EDGE BSC is located in a cartridge of its own.

3.5 Message Bus (MB)

A duplicated high-speed Message Bus (MB) is used for data transfer between theOMU and the Call Control Computers of the GSM/EDGE BSC (see Figure 5 ).

The length of each message is determined individually by a message lengthparameter at the beginning of the message. The sender and the receiver of themessage are indicated in the address field of the message. The receiver can be asingle microcomputer, or it can be a group of microcomputers specified by thebroadcast address.

The hardware of the Message Bus consists of several parallel twisted pairs, whichcarry the actual data and also control the information required for the messagetransfer.



33 (68)


In the event of a failure, the hot standby Message Bus takes over the functions ofthe active bus without interfering with the ongoing calls.

Figure 5. Structure of the Message Bus system

3.6 Exchange Terminal (ET)

The ET performs the electrical synchronisation and adaptation of external PCMlines. It performs the HDB3 (ET2E, ET1E), or B8ZS or AMI (ET2A) coding anddecoding, inserts the alarm bits in the outgoing direction and produces PCMframe structure. All ET2 plug-in units contain two separate ETs but the ET1Eplug-in units of the first generation BSC contain only one ET.

All 2,048 Mbit/s (in the ETSI environment) or 1,544 Mbit/s (in the ANSIenvironment) interfaces for the MSC and the BTSs are connected to theExchange Terminals. The Exchange Terminals adapt the external PCM circuits tothe GSWB and synchronise to the system clock. Synchronisation is included inthe bit frame.

The ETs are located in Exchange Terminal cartridges. The ET1 plug-in units arehoused in the ET1C cartridge and the ET2 plug-in units are housed in the ET5Ccartridge.

The ET1C cartridges of the first generation BSC house Exchange Terminal plug-in units (ET1E). The BCBE rack contains two ET1C cartridges and the BCEErack five ET1C cartridges. Each ET1C cartridge contains eight ET1E plug-inunits and two PSC3 plug-in units.

DMC BUS

1

MESSAGE BUS 0

micro-computer


interfaceunit 0

interfaceunit 1




In the BSC2 application, the BCBE rack can contain up to two ET5C cartridgesand the BCEE rack up to five. The BSCE application, on the other hand, cancontain only two ET5C cartridges (as an option, in addition to the seven originalET1C cartridges): one in the BCBE rack and the other in the BCEE rack.

Each ET is connected to the switching network and the Clock Unit of the GSM/EDGE BSC via permanent, wired connections. The ETs are also connected to theLAPD interface via a LAPD link. Two types of connectors, symmetrical andcoaxial (75/120 SL), are available for the ET1Es and ET2Es.

In the incoming direction, the ET2 decodes the 2,048 Mbit/s (ETSI) or 1,544Mbit/s (ANSI) signal of a circuit into data signals. The decoder decodes the linecode (HDB3 in the ETSI environment, B8ZS or AMI in the ANSI environment)into binary form. At the same time, the ET2 is synchronised to the bit rate of theincoming signal.

In the outgoing direction, the ET2 receives a binary PCM signal from theswitching network and generates the PCM frame structure. The resulting signal isconverted into a line code (HDB3 in the ETSI environment, B8ZS or AMI in theANSI environment) and transmitted further onto the 2,048 Mbit/s (ETSI) or1,544 Mbit/s (ANSI) circuit.

3.7 Clock and Synchronisation Unit (CLS)

The Clock and Synchronisation Unit (CLS) distributes timing reference signals tothe functional units of the GSM/EDGE BSC. It can operate plesiochronously orsynchronously with the timing references it receives from the digital PCM trunks.Three PCM reference inputs with priority order are provided for the timingreference signals. The oscillator of the CLS is normally synchronised to anexternal source, usually an MSC, through a PCM line. Up to two additional PCMinputs are provided for redundancy.

The Clock & Tone Generator (CL1TG) plug-in unit meets the requirements of theITU-T Q.500 Series Recommendation with respect to the Time Interval Error(TIE), the jitter, the wander, and the transfer function. In the plesiochronousoperation mode, the frequency shift of the CL1TG is 2 * 10-8 within each 24-hour period, if the temperature of the environment does not vary.

An optional Clock & Tone Generator plug-in unit, CL3TG, with externalsynchronised input is also available.

When the system consists of two racks, the timing reference signals are bufferedfor the extension rack by a duplicated Clock and Alarm Buffer (CLAB) plug-inunit.



35 (68)


3.8 Peripheral devices

The peripheral O & M devices of the GSM/EDGE BSC are:

. disk units;

. Digital Audio Tape unit (DAT) tape drive;

. printer;

. visual display unit;

. alarm lamp panel.

Other peripheral devices of the GSM/EDGE BSC are:

. Cable Conduit with Cabling Rack for raised floor installations

There are two types of Storage Device cartridges: the WDDC in the BSC2E/Aand BSCE and the optional SD3C-S in the BSCE.

The BSCE contains one SD3C-S cartridge (optional) housing the floppy and harddisk units and the CTU (DAT). The basic configuration of a SD3C-S cartridge isthe following:

. two hard disk units (WDU)

. one floppy disk unit (FDU)

. one cartridge tape unit (CTU) / (DAT)

. two power supplies for the disk units (PSC4-S).

3.8.1 Disk units

The GSM/EDGE BSC has a duplicated system disk unit (Winchester) and 3.5"disk drive. The software can be loaded locally to the BSC by using 3.5" disks orDAT tape. See the section DAT .

The system disk units contain the operative software as well as fallback softwareof the BSC and BTS software including the BTS HW database. Trafficmeasurements are also stored on the system disks. All the disk drives areconnected to the OMU, which controls the system disk units.




3.8.2 DAT (optional)

The GSM/EDGE BSC can have a Digital Audio Tape (DAT) tape drive as anoption. The DAT is a recommended solution for software backups and for otheradditional disk storage, because it has high capacity and is easy to use. In theBSC, the DAT is used for loading software locally to the BSC and also as asoftware backup medium.

3.8.3 Printer (optional)

A printer can be connected to the OMU. The interface complies with the ITU-TRecommendation V.24.

3.8.4 Visual display unit (optional)

In the BSC, a visual display unit is used as a user interface. With a VDU terminal,the user can perform normal operational functions with MML commands anddiagnostic tests on various units.

Visual display units can be connected to the OMU in the same way as printers byusing interfaces that comply with the ITU-T Recommendation V.24.

3.8.5 Alarm lamp panel (optional)

The alarm lamp panel shows BSC alarms, depending on the predefined urgencyand equipment type (SWITCH, TRANSM, POWER, O/M, EXTERNAL). It canbe installed to a place where the observations of alarms can be noticed easily.

3.8.6 Cable Conduit with Cabling Rack for raised floor installations

If there is a raised floor in the equipment room, the incoming and outgoing cablescan be placed under the floor and connected to the equipment racks through avertical cable conduit and a cable rack, which can be placed at either end of therack row, or between two equipment racks.



37 (68)


4 Interfaces relating to the BSC2E/A andBSCE

The policy of open standard interfaces has been adopted for the design of theGSM/EDGE BSC. The GSM/EDGE BSC provides interfaces for the MSC,NetAct, the Base Transceiver Stations (BTSs), the Serving GPRS Support Node(SGSN), and the Cell Broadcast Centre (CBC). The interfaces are first brieflydescribed, then the following sections explain them in more detail.

4.1 A interface

The A interface between the MSC and the GSM/EDGE BSC is implementedaccording to the GSM standards. Because the A interface is open, the NokiaGSM/EDGE BSC can be used with switching centres from other suppliers.

Layered interface structure in A interface

The interface between the DX 200 MSC and the Base Station Subsystem, BSS, isdefined in accordance with the Signalling System No.7 (SS7), which is similar tothe layered OSI protocol model. The Message Transfer Part (MTP) and theSignalling Connection Control Part (SCCP) provide the signalling networkfunctions required to carry the messages of the Base Station SubsystemApplication Part (BSSAP) layer.

OSI Layer 1 represents the physical layer. It is a digital interface at 2048 kbit/s(ETSI) or 1544 kbit/s (ANSI), based on the ITU-T Recommendation G.703. Thisinterface is normally used as an A interface between the MSC and the BSS,providing a 64 kbit/s transmission rate on each channel. Additionally, wide SS7links (128 or 256 kbit/s) can be configured, if the NSS supports them.

OSI Layer 2 is based on the MTP level 2 of SS7. The MTP level 2 provides amechanism for reliable transfer of signalling messages between the MSC and theBSS. At least two signalling links are normally provided between the BSS andthe MSC for both capacity and reliability reasons.



39 (68)

Interfaces relating to the BSC2E/A and BSCE

OSI Layer 3 of the signalling network includes the SCCP and MTP level 3.Together, the MTP and the SCCP functions provide both connectionless andconnection-oriented network services. These services are used to transfer circuit-related and non-circuit-related signalling information and other types ofinformation between the MSC and the BSS.

Functions of the application parts of the A interface

The Base Station Subsystem Application Part (BSSAP) provides procedures forthe A interface, which are in accordance with GSM standards.

4.2 Abis interface

The Abis interface telecommunication part between the GSM/EDGE BSC andthe BTS is implemented according to the 08.5X Series of GSMRecommendations. The Abis O & M part is Nokia property which supportsadditional features like the Site Test Monitoring unit, alarm consistency, remotetransmission equipment management, and BTS database management.

Layered interface structure in Abis interface

The interface between the GSM/EDGE BSC and the BTS is defined inaccordance with the OSI protocol model.

Layer 1 represents the physical layer. It is a digital interface at 2048 kbit/s (ETSI)or 1544 kbit/s (ANSI), based on the ITU-T Recommendation G.703.Submultiplexing is used on the Abis interface as a standard solution, becauseeach speech channel reserves only 16 kbit/s (FR channel or DR channel) or 8kbit/s (HR channel) in the ETSI environment, 16 kbit/s in the ANSI environment.

Layer 2 is based on the LAPD protocol. The LAPD protocol is implemented toprovide the data link functions required to carry layer 3 messages. The GSM/EDGE BSC can handle LAPD signalling links with the bit rates of 16 kbit/s, 32kbit/s and 64 kbit/s.

ISDN connections can also be used as the bearer for the Abis interface. Theinterface between the BSC and the ISDN network is based on ITU-T's DigitalSubscriber Signalling System No. 1 (DSS1) Network layer Q.931 (03/93) andData link layer Q.921. Connection between the BSC and the BTS have to beunrestricted digital 2 x 64 kbit/s.

Functions of the telecom application parts

The following procedures are provided for the Abis interface:




. radio link management procedures

. dedicated channel management procedures

. common channel management procedures

. TRX management procedures

Functions of the O & M application parts on Abis Interface

The application parts of the Abis interface contain the following O & Mfunctions:

. fault management

. fault reporting

. BTS recovery

. BTS test handling

. configuration management

. software configuration management

. radio network management including extensions and parameters

. performance management

4.3 Gb interface

The Gb interface between BSC (PCU) and Serving GPRS Support Node (SGSN)is implemented according to 08.1X Series of GSM Recommendations. It is anopen interface connecting the BSS and GPRS core network.

Layered interface structure in Gb interface

The interface between the SGSN and the Nokia Base Station Subsystem, BSS, isdefined in accordance with the OSI protocol model. The protocol stack comprisesBSSGP, Network Service layer including Frame Relay (FR), and L1. NetworkService layer further divides into two: Sub-network Service and Network ServiceControl. The Sub-network Service uses either Frame Relay or UDP/IP-basedprotocol.

Sub-network Service Layer

The physical layer is implemented as one or several PCM lines with G.703interface. On top of the physical layer in the Gb interface direct point-to-pointFrame Relay connections or intermediate Frame Relay network can be used.



41 (68)


Figure 6. The protocol stack on the Gb interface

Network Service Control is responsible for virtual circuit management andGPRS-specific addressing, which maps cells to virtual connections. BSSGP is alayer 3 protocol for delivering data packets and associated control information(TLLI, QoS profile, MS classmark, DRX parameters, IMSI).

4.4 Q3 interface (BSC-NetAct)

The GSM/EDGE BSC provides the following types of interfaces between NetActand the BSC, depending on the network operator's requirements:

. an X.25 connection via a semipermanent time slot on the A interface

. an X.25 interface, connected directly or via the Packet Switched PublicData Network, PSPDN

. a LAN interface, connected via the LAN Switch

The Nokia NetAct interface is of the Q3 type. The implementation of thisinterface is based on the O & M framework of the ITU-T and the InternationalStandards Organization (ISO).

Network interface

The X.25 protocol is used on the interface between the GSM/EDGE BSC andNokia NetAct. Either the PSPDN or the PCM-time-slot-based connection can beused. In the case of PSPDN connections, the physical interface can be V.24, V.35or X.21 and in the case of PCM time slot connections, the physical interface isG.703.

MAC

RLC

LLC

GMM/SM

GSM RF

NetworkService

BSSGP

LLC

GMM/SM

L1bis

MS SGSN

MAC

RLC

NetworkService

BSSGP

GSM RF L1bis

Relay

BSSUm Gb




The BSC also supports the LAN interface. The physical interface supported isEthernet IEEE802.3.

The connections can be made redundant as an option.

The X.25 software in the GSM/EDGE BSC can be configured to function as theDTE or the DCE.

Interface with a full OSI Stack

The upper layers of the OSI model, above the network layer, are implemented inthe GSM/EDGE BSC. The upper layers use the X.25 protocol or LAN as a sub-network.

The following protocols are implemented:

. transport protocol, X.224 (TP0, TP2 and TP4)

. session protocol, X.225

. presentation protocol, X.226

. association control service element (ACSE), X.227

. remote operations service element (ROSE), X.229

. file transfer, access and management (FTAM), ISO 8571

. common management information service element (CMISE), ISO 9596

The FTAM protocol, using ACSE, is used for transferring files between theGSM/EDGE BSC and Nokia NetAct.

The CMISE protocol, using the ACSE and the ROSE, is used for NetworkManagement.

4.5 CBC interface (BSC-CBC)

The BSC Cell Broadcast Centre Interface provides an interconnection betweenthe BSC and Cell Broadcast Centre (CBC). The implementation is according toGSM Specification 03.41 and permits the open interconnection between BSC andCBC.



43 (68)


In the BSC, the CBC connection is made through the OMU using current Q3interface plug-in units AC25-S, AS7-US (ANSI version) and AS7-VA (ANSIversion for first deliveries) or AS7-V (ETSI version). The CBC connection sharesthe same transport media as Q3, only a new logical connection is introduced. If anon-redundant Q3 connection is used, more transmit capacity can be gained byusing a dedicated plug-in unit for the CBC.

Network interface

The interface between the BSC and the CBC is similar to the interface betweenthe BSC and NetAct.

Interface with OSI layer 4

The protocol used between the BSC and the CBC is the XTI-interface. The XTI-interface uses the services of the OSI Transport Layer. The CBC Application canbe developed using the XTI Application Programming Interface (X/OpenTransport Interface) to interconnect the application to the OSI Transport Layer.




5 BSC2E/A and BSCE Software

In the BSC, each Computer Unit has common system software. The uniformsystem software provides a standard, easy-to-use operating environment for theapplication software. The uniform operating environment facilitates thedevelopment and maintenance of the application software, and helps the userunderstand the operation of the software.

5.1 Platform architecture

A fundamental part of the GSM/EDGE Switching System software is the real-time operating system kernel, DMXRTE, implemented in the OMU and each CallControl Computer. The operating system is a platform for other system levelsoftware and all the application software.

The most significant functions of the operating system are:

. scheduling of processor time

. synchronisation of processes

. exchange of messages between processes located in one computer orseparate computers

. time supervision

. creation and deletion of processes

. memory allocation and protection

. observation of message traffic and processor load

. initialisation of the operating system.



45 (68)

BSC2E/A and BSCE Software

Figure 7. BSC conceptual model

5.2 Layers

A layer is an up-level hierarchy level of the system platform. It divides themonolithic platform into smaller modules. Layers can be developed relativelyindependently.

5.3 Databases

The DX 200 Switching Systems contain different types of data. In the case of theBSC the database includes, for example, reduced routing and cellular data. Thedatabase also includes data that is needed for control and operation of the BSC.

In this context, the files are RAM memory arrays. Some files are loaded from adisk unit after restarting the control computer. Other files are updated on the diskwhen the contents are changed.

Base Station ControllerApplication

Common Switching Platform

Fault Tolerant Computing Platform

Modular and Scalable Hardware Platform




5.4 Description and programming languages

In the design and documentation of the BSC software, readability and visualquality of the programs are improved by using special description languages inaddition to the actual programming language. These description languages alsofacilitate effective software design and enable the use of automatic tools fordevelopment and testing.

5.4.1 Programming languages

More than 90% of the program code in the GSM/EDGE BSC is written in a high-level programming language, namely PL/M or C. Assembly language is usedonly in critical parts of the software, where real-time operations have to beexecuted at very high speed.



47 (68)

BSC2E/A and BSCE Software

6 Configurations and capacity of theBSC2E/A and BSCE

6.1 General description of configuration

In the BSS, the GSM/EDGE BSC is a stand-alone network element that isconnected to the surrounding network elements by means of standard PCMinterfaces.

There are two basic configurations of the BSC2E/A and BSCE: 1-rack and 2-rack. Both of them can be equipped flexibly with a number of TRXs and trunkcircuits.

The BSC2E/A and BSCE can be equipped with:

. 1-rack configuration:

- a maximum of 32 BTSs

- a maximum of 32 TRXs

. 2-rack configuration:


- a maximum of 128 TRXs

. 2-rack Large Capacity BSC configuration:


- a maximum of 200 BCFs

- a maximum of 256 TRXs.

The BSC2 and BSCE can be upgraded to High Capacity BSC with hardware andsoftware upgrades. See Base Station Controller, Engineering Descriptions for adescription of the configurations.



49 (68)

Configurations and capacity of the BSC2E/A and BSCE

6.2 Capacity of the BSC

With the reference model below, the maximum processing capacity of a GSM/EDGE BSC with optional Large Capacity is 1520 Erl/46000 BHCA, giving fullsupport to 256 FR TRXs.

Table 2. Circuit switched processing capacity of the BSC2E/Aand BSCE

Reference model of call traffic (call mix and parameters):

Mean holding time 120s

Proportion of MS originated calls 70 %

Proportion of MS terminated calls 30 %

Proportion of handovers (HOs) 1.5 HOs per call

Proportions of location updates (LUs) 2 LUs per call

Proportion of IMSI detaches 0.1 detaches per call

For terminating call attempts, the proportion of no-answercall attempts to paging requests

63 %

SMS call rate 1 req./subs./1 hour

The above-mentioned traffic processing capacity of the BSC can be achievedwith S10.5-level features activated and with the new BSC hardware environment.The maximum traffic processing capacity of the BSC2E/A/BSCE supports 256full rate TRXs in the ANSI version, 256 full rate TRXs or 128 half rate TRXs inthe ETSI version. However, some future features might have an influence on thecapacity of the BSC. Circuit switched data calls are taken into account in thereference model of call traffic in the following way:

. one data call with one radio timeslot is seen as one mobile originating orterminating call

. one full rate data call is seen as one mobile originating or terminating call

. one high speed circuit switch data (HSCSD) call with two or more radiotimeslots is seen as several calls, based on how many timeslots are reservedfor the call. For example, if two timeslots are reserved (2 x 14,4 kbit/s) thecall is seen as two mobile originating or terminating calls.

Different types of connections are provided as follows:




. in BSC2, a maximum of 80 PCM connections, expandable to 112, and inBSCE, 56 or a maximum of 88 PCM connections used on A, Abis and Gbinterfaces

. a maximum of 128, upgradable to 192 PCM connections connected to thenon-blocking switching matrix

. a maximum of 16 SS7 signalling links. Optionally wider 128 or 256 kbit/ssignalling links can be configured instead of standard 64 kbit/s links.

. in BSC2, a maximum of 256 LAPD protocol links, expandable to 512LAPD protocol links with Large Capacity BSC configuration

LAPD signalling links can be configured to 16, 32 or 64 kbit/s speeds.Introduction of HR will enable TRX configurations of more than 18 radiochannels which leads to increased load in measurement reporting. Becauseof this, the capacity of a 16 kbit/s signalling link is not sufficient in allcases.

Therefore it is recommended that also with HR the TRX configurationsshould be restricted to the maximum of 18 radio channels if 16 kbit/ssignalling links are used. With TRX configurations of more than 18 radiochannels a 32 kbit/s LAPD link is highly recommended for supporting thetelecom signalling which half rate requires. The overload of the signallinglink can be monitored by the Telecom LAPD link supervision with apossibility to set an alarm in an overload situation.

In GSM/EDGE BSC the packet handling capacity is provided by PacketControl Units (PCUs). Packet handling capacity and connectivity per eachPCU is 64 BTSs, 128 TRXs, and 256 traffic channels (16 kbit/s) for GPRS/EDGE use.

- maximum capacity with full configuration (8 PCUs) is 256 x 8 =2048 traffic channels (16 kbit/s) per BSCE for GPRS/EDGE use

- maximum capacity with full configuration (16 PCUs) is 256 x 16 =4096 traffic channels (16 kbit/s) per BSC2E/A for GPRS/EDGE use

The above-mentioned packet handling capacity can be achieved with thenew HW environment. However, some future features might have aninfluence on the packet handling capacity of the BSC.



51 (68)

Configurations and capacity of the BSC2E/A and BSCE

7 Mechanical design and power supply ofthe BSC2E/A and BSCE

7.1 Mechanical design

The mechanical structure of the GSM/EDGE BSC is hierarchical, based on plug-in units, cartridges and racks. The dimensions of different units and cartridges arein accordance with the recommendations of the IEC (InternationalElectrotechnical Commission). The GSM/EDGE BSC is easy to install, operate,and maintain. Special attention has been paid to thermal resistance and immunityto various types of interference.

7.1.1 Plug-in units

The BSC2E/A is constructed by using a total of 15 plug-in unit types, includingthe DC/DC converters. The size of these plug-in units is either 233.4 mm x 160mm, 233.4 mm x 220 mm, 100 mm x 220 mm, or 110 mm x 220 mm.

The printed circuit boards (PCBs) of plug-in units are multilayered. They arecovered with a protective coating that makes the PCBs easy to handle andprotects the foils from scratches.

Both surface-mounted and hole-mounted components are used on the PCBs. Theconnectors are of the Euro-connector type.

7.1.2 Cartridges

Most of the functional units consist of one cartridge that contains a selection ofPCBs. A fixed rack position has been assigned to the cartridge of each functionalunit.

The cartridges of the BSC2E/A are of the following types:



53 (68)

Mechanical design and power supply of the BSC2E/A and BSCE

. MC1C cartridge for MCMU, OMU, and BCSU

. CLAC cartridge for the Clock and Alarm Buffer Unit

. CLOC cartridge for the Clock and Synchronisation Unit

. ET5C cartridge for Exchange Terminals

. SW1C cartridge for the Bit Group Switch.

The cartridges of the BSCE are of the following types (see Figure 8 ):

. MC1C cartridge for MCMU, OMU, and BCSU

. CLAC cartridge for the Clock and Alarm Buffer Unit

. CLOC cartridge for the Clock and Synchronisation Unit

. ET1C and ET5C cartridges for Exchange Terminals

. SW1C cartridge for the Bit Group Switch

. WDDC cartridge for Winchester units, DAT and Floppy Disk drives or

. SD3C-S cartridge for Winchester units, DAT and Floppy Disk drives.

The size of each cartridge type is given below:

. type SD3C-S:

- 262 mm x 260 mm x 170 mm

. type MC1C:

- 262 mm x 260 mm x 170 mm

. type ET1C :

- 262 mm x 240 mm x 230 mm

. type ET5C :

- 262 mm x 120 mm x 230 mm

. type SW1C:

- 262 mm x 180 mm x 230 mm

. types CLAC, CLOC, WDDC:

- 262 mm x 120 mm x 230 mm.




Figure 8. Cartridges and functional units of the BSC2E/A and BSCE withGSWB, excluding BCSU

CPU

::::::::::::::::::::::::::::::::::

::::::::::::::::::::::::::::::::::

MBIF-T

MBIF-T

PSC3

AS7-U

AS7-U

/AC25

/COCEN

HWAT

SCSIF

AS7-U

/AC25

/COCEN

2 3 4 5 6 7 8 9 10

CLAB

CLAB

PSC4

PSC4

PSC4

FDD

WDD

WDD

DAT

ET1C

CPU

::::::::::::::::::::::::::::::::::

::::::::::::::::::::::::::::::::::

MBIF-T

MBIF-T

PSC3

SWCOP

2 3 4 9 10

MCMUCLAC CLOC

SW1C with extended GSWBET5C

CL1T

G

CL1T

G

PSC1

SW64B

SW64B

SW64B

32 64

OMU WDDC

PSC3

PSC3

ET1E

0 1 2 3 4 6 875 9

ET1E

ET1E

ET1E

ET1E

ET1E

ET1E

ET1E



55 (68)


Note

The BSC2E/A does not include the ET1C cartridge.

Figure 9. BCSU in BSC2E and BSCE including Packet Control Unit

7.1.3 Racks

All the racks are of a standard type. The frame of a rack consists of side rails,made of plated steel sheet, that support an upper shelf and a lower shelf withadjustable legs. Only two types of racks are used in the BSC2E/A: BCBE andBCEE (see Figures 10 and 11 ).

In the case of a 2-rack configuration, the two frames are connected to each otherin order to create a closed space and reduce the possibility of interference.

The closed space in both 1-rack and 2-rack configurations is surrounded by theside plates, the doors, the upper cable conduit, and the baseboard. The doors areperforated to facilitate cooling.

The height, width and depth of a standard BSCE rack are (with cabling anddoors): 2200 mm x 600 mm x 500 mm

The height, width and depth of a standard BSC2E/A rack are (with cabling anddoors): 2020 mm x 600 mm x 500 mm

::::::::::::::::::::::::::::::::::

::::::::::::::::::::::::::::::::::

AS7-U

MBIF-UA

MBIF-UA

AS7-U

AS7-U

PSC3

CPU

2 3 4 5 6 8 109

::::::::::::::::::::::::::::::::::

::::::::::::::::::::::::::::::::::

AFS-T

MBIF-UA

MBIF-UA

AS7-U

AS7-U

PSC3

CPU

02 03 04 05 06 08 100100 07 09

PCU

PCU




Each installed BSC has side plates on its both sides. Each side plate is 40 mmwide, which must be taken into account when estimating the total width of theracks.

If more than one BSC2E/A is located on the same site, the racks can be connectedto each other. In this case, each row of racks constitutes a closed EMC-shieldedspace.

Figure 10. Rack layouts of the BSC2E/A

GSWB 0SW1C0

GSWB 1SW1C1

CLSCLOC

MCMU 0MC1C

MCMU 1MC1C

BCSU 3MC1C

BCSU 4MC1C

BCSU 5MC1C

BCSU 6MC1C

BCSU 7MC1C

BCSU 8MC1C

BCSU 1MC1C

BCSU 2MC1C

CLSCLAC

ET5C2

ET5C3

ET5C4

BCSU 4MC1C

BCSU 0MC1C

ET5C0

ET5C1

OMUMC1C

SD3C-S

PSA20_0PSFP0

PSA20_1PSFP1

PSA20_2PSFP2

PSA20_3PSFP3

ET5C5

ET5C6

BCEEBCBE



57 (68)


Figure 11. Rack layouts of the BSCE: 56 and 88 PCM versions.

7.1.4 Cabling

Standard length cables are used for the internal cabling of the GSM/EDGE BSC.The internal cables of the racks are installed at the factory. In the 2-rackconfiguration the connecting cables between the racks are also factory-installedfrom the other end to ensure easy and fast installation at site.

Each rack in the row is connected to the next rack by cables. Within a rack, thecabling is installed from each cartridge to the next one.

BCBE BCEE

MCMU 0MC1C

SW1C0

SW1C1

CLACWDDC

WDDC

ET1C 0 ET1C 1

CLAC ET1C 6

ET1C 5ET1C 4

ET1C 2 ET1C 3

BCBE BCEE

SW1C0 CLAC ET1C 6

SW1C1 ET1C 4 ET1C 5

CLAC ET1C 2 ET1C 3

ET1C 0 ET1C 1

SD3C-S

ET5C

ET5C

BCSU 2MC1C

BCSU 1MC1C

OMUMC1C

MCMU 1MC1C

BCSU 0MC1C

PSA20_2PSFP2

PSA20_3PSFP3

PSA20_2PSFP2

PSA20_3PSFP3

BCSU 3MC1C

BCSU 4MC1C

BCSU 6MC1C

BCSU 5MC1C

BCSU 7MC1C

BCSU 8MC1C

BCSU 0MC1C

OMUMC1C

BCSU 1MC1C

BCSU 2MC1C

BCSU 3MC1C

BCSU 4MC1C

BCSU 5MC1C

BCSU 6MC1C

BCSU 8MC1C

BCSU 7MC1C

MCMU 1MC1C

MCMU 0MC1C

PSA20_0PSFP0

PSA20_1PSFP1

PSA20_2PSFP2

PSA20_3PSFP3




The PCM trunks and other station cables (external alarm cables, X.25 cables) ofthe GSM/EDGE BSC enter the exchange room via a cable conduit and they enterthe rack via earthing elements on top of the racks. These cables are attached to theconnectors on the front panels of plug-in units. The power supply cables areterminated to the power supply connector on top of the rack.

7.2 Dimensioning of the GSM/EDGE BSC

The dimensioning rules of the GSM/EDGE BSC equipment are described inother documents of the GSM/EDGE BSC (see for example Engineering for BSC,Plan Network ).

7.3 Power supply

7.3.1 Structure of power supply

Reliability, easy installation, and easy maintenance have been the main objectivesin the design of the power supply system of the GSM/EDGE BSC.

All the voltages required for the GSM/EDGE BSC are generated from the DCvoltage by high frequency transformers using chopper technique.

The input voltage is between 41.5 V and 72 V. Because the range is wide, themain battery voltage of the GSM/EDGE BSC can be 48 Vor 60 V. In both cases,it is possible to use a direct floating battery.

7.3.2 Power consumption

The power consumption values for the cartridge types used in the BSC are shownin the table below. The figures are for maximum equipment configurations.

Table 3. Power consumption of the BSC cartridges; theBCSU includes the PCU

Application Cartridge type Power consumption

BSCE CLAC 15 W

CLOC 20 W



59 (68)


Table 3. Power consumption of the BSC cartridges; theBCSU includes the PCU (cont.)

Application Cartridge type Power consumption

ET1C 25 W

ET5C 29 W

MCMU 43 W

OMU 60 W

BCSU 70 W

SW1C with GSWB application 75 W

SD3C-S 45 W

BSC2E/A CLAC 15 W

CLOC 20 W

ET5C 29 W

MCMU 43 W

OMU 60 W

BCSU 70 W

SW1C with GSWB application 87 W

The power consumption values for the BCBE and BCEE racks are shown in thetable below. The figures are for maximum equipment configurations.

Table 4. Power consumption of the BSCE and BSC2E/A racks, PCUincluded

Application Rack type Power consumption

BSCE BCBE 620 W

BCEE 560 W

BSC2E/A BCBE 650 W

BCEE 640 W




8 Reliability of the BSC2E/A and BSCE

The simplicity and the fast speed of the maintenance procedures are theprerequisites for the availability of the Nokia BSC. Maintenance is improved bythe modular structure of the equipment, automatic fault detection procedures, andby the elimination of downtime by using a hot standby unit in the event of afailure.

8.1 Fault management

The DX 200 system is a loosely coupled, fault-tolerant distributed system withsome centralised functions. The DX 200 System Maintenance functions conformwith the idea of loose coupling of autonomous control computers. This means, forexample, that state control mechanisms do not depend on any centralisedhardware, control computers control their own software and are able to restart ontheir own by asking for the appropriate loading services, and an individualprogram block failure or an individual hardware failure has a minor effect on theoverall operation of the whole system. The fault situation is hardly ever so bad orcomplex that the whole system has to be restarted.

In most cases, a restart in a program block, preprocessor, or a single controlcomputer is enough. The control computer states are controlled from a centralisedpoint which can be dynamically reallocated from the OMU to a pair of controlcomputers when, for example, an OMU with no redundancy fails. This meansthat this centralised function has 3N redundancy. Only the control computers areautonomous as described above. The preprocessors run under the control of amaster computer.



61 (68)

Reliability of the BSC2E/A and BSCE

8.2 Overload protection

The BSC overload protection handles excessive traffic or signalling load bylimiting the load level of the BSC's main CPUs and preprocessors, and alsoprovides information of excessive load, so that preventive actions can be taken.The main cause of this kind of load might be related to special end-user behaviourand is mainly related to radio network planning and dimensioning according tothe required level.

8.3 Redundancy principles

When the BSC was designed, great attention was paid to the reliability ofoperation. The following redundancy methods are used for various units:

. 2N principle for duplicated units, including an active unit and a spare unit

. N+1 or N+m redundancy principle for provision of one or more units,active or reserve, in addition to what is required by the correctdimensioning.

All the critical parts of the switching system have an appropriate type ofredundancy. The Exchange Terminals of the PCM trunk circuits and the terrestrialchannels are not critical, however, because the failure of a single terminal doesnot prevent service. There are usually several PCM circuits available in eachdirection. Thus, the Exchange Terminals are without redundancy.

Power supply and the distribution of the basic timing signal are arranged so thatthe units backing each other up get their supply from different or redundant DC/DC converters and their basic timing signals from different distribution lines.

8.4 System availability

The BSC2E/A is designed to meet the availability requirements of the ITU-T. Thefollowing design objectives have been adopted to ensure that the unavailability ofthe BSC is very low.

Table 5. Availability of the BSC2E/A in maximum configuration

MTBF 30,330,000h

Mean down time 0.02 min/year




The above calculations have been based on plug-in unit failure statistics with thecomplete configuration of the BSC2E/A (e.g. 256 TRXs Mean time to recoveryhas been assumed as 1.0 hours).

The following general design objectives have been established for themaintenance of the BSC:

. mean active repair time less than half an hour

. fault localisation with the accuracy of a plug-in unit for 70% of the faults

. fault localisation with the accuracy of four plug-in units for 95% of thefaults.

For more detailed information see BSC Availability Performance Prediction .

8.5 Planned downtime

The BSC is based on the DX 200 Computing Platform that makes it possible tominimise the downtime caused by, for example, software upgrades. BSC softwarecan be downloaded without any disturbance to user data traffic, but the activationof new software requires computer unit restarts. Thanks to the trial configuration,the possible downtime can be minimised. The trial configuration means that firstthe new software is loaded into spare units, then a unit switchover is performed,that is, the spare units are switched into active state and vice versa, and finally thenew software is loaded into the primary units.



63 (68)

Reliability of the BSC2E/A and BSCE

9 Operating environment of the BSC2E/Aand BSCE

9.1 Equipment room

The mechanical structure of the GSM/EDGE BSC does not place any specialrequirements on the ceiling, the walls, or the floor. No raised floor is needed.

The height of the room should be at least 2500 mm. This ensures that there isalmost 500 mm of open working space above the cable troughs on top of theracks.

The racks of the GSM/EDGE BSC can be located in many different ways in theequipment room. However, take the following points into consideration whenplanning where to locate the BSC:

. future expansion of the BSC

. standard lengths of the cables between the racks

. location of other equipment on the same site

. air-conditioning of the equipment room

. sufficient working space around the racks.

Location of the racks is discussed in more detail in Base Station Controller,Engineering Descriptions .

Figure 12 shows examples of equipment layouts of the GSM/EDGE BSC.



65 (68)

Operating environment of the BSC2E/A and BSCE

Figure 12. Typical layout of a BSC site

9.2 Environmental conditions

9.2.1 General

The internationally recognised and comprehensive description of theenvironmental conditions is covered by the following ETS standards:

. ETS 300 019-1-1, 1992: Equipment Engineering (EE); Environmentalconditions and environmental tests for telecommunications equipment Part1-1; Classification of environmental conditions, Storage

. ETS 300 019-1-2, 1992: Equipment Engineering (EE); Environmentalconditions and environmental tests for telecommunications equipment Part1-2; Classification of environmental conditions, Transportation

. ETS 300 019-1-3, 1992: Equipment Engineering (EE); Environmentalconditions and environmental tests for telecommunications equipment Part1-3; Classification of environmental conditions, Stationary use atweatherprotected locations

RACK 1 RACK 2600

300

WORKING AREA

1000

1000

500

600




9.2.2 Climatogram

Changes of temperature and relative humidity affect the reliability of theequipment. The relationship between the availability, performance and theenvironment is defined in the climatogram in Figure 13 . The functional ambienttemperature is -5 to +45 °C. No start-up below 0 °C temperature is allowed.

Figure 13. Climatogram of the GSM/EDGE BSC

9.2.3 Cooling of racks

Because the power consumption of the GSM/EDGE BSC is low, the cooling ofthe equipment can be implemented by means of natural convection. Cool air isdirected into the cartridges from the room. Inside the cartridge, the air warms upand rises.

When natural convection is used for cooling purposes, the temperature of the airin the equipment room must naturally be within the limits of therecommendations (see Figure 13 ). In this case, no special fans or other extraequipment are needed in the racks.

A

B

C

0

RELATIVE HUMIDITY

20 40 60 80 100%

0

10

20

30

40

50

60

-10

TEMPERATURE ÊC

A

B

C

Nominal conditions: The equipment meetsthe functional reliability and life cyclerequirements in accordance with the productspecifications. These conditions must bemaintained 85 % of time.

Normal conditions: The equipment meetsthe functional requirements in accordancewith the product specifications.

Exceptional conditions: The main functions ofthe equipment are not jeopardized.The duration of these conditions is limitedto 1 % of time or 48 h consecutively.



67 (68)

Operating environment of the BSC2E/A and BSCE

9.2.4 Electromagnetic environment

EN 300 386-2, 1997, Equipment Engineering (EE); Telecommunication networkequipment; Electromagnetic Compatibility (EMC) requirements; Part 2: Productfamily standard.

ANSI C63.4 (FCC Rules in Title 47, Part 15, Subpart B, 2001), Class A.




Nokia BSC Enlarged Version

Documents

Transcript of Nokia BSC Enlarged Version