Nokia BSC2i Overview

7/23/2019 Nokia BSC2i Overview

1/16

1. General design of the GSM/EDGE BSC

The GSM/EDGE BSC is based on a modular software and hardware structure. Because

there are exact specifications for the interfaces between different modules, new functions

can easil be added without chan!in! the architecture of the sstem. Thus, the BSC canha"e a lon! operational life span and still alwas ha"e up#to#date functionalit.

The distributed architecture of the BSC is implemented b a multiprocessor sstem. $n amultiprocessor sstem the data processin! capacit is di"ided amon! se"eral computer

units, each of which has a microcomputer of its own.

Call handlin! capacit depends on the number of call control computer units. The

capacit of the BSC can easil be increased b addin! more call control computer units.%i!ure Bloc& dia!ram of the GSM/EDGE BSC with Bit Group Switch shows the bloc&

structure of the BSC. The most important functional units of the BSC are'

Group Switch (GS)B* is used for switchin! speech and data, and connectin!

si!nallin! circuits.

Base Station Controller Si!nallin! +nit (BCS+* handles the BSC si!nallin!functions. The optional ac&et Control +nits (C+s* are included in e"er BCS+,

when the G-S/EDGE ser"ice is implemented.

Mar&er and Cellular Mana!ement +nit (MCM+* controls and super"ises the

GS)B and implements radio resource mana!ement (--M* functions, bein!

responsible for cells and radio channels. The MCM+ also acts as a BSC sstemmaintenance unit in case of M+ failure.

peration and Maintenance +nit (M+* ser"es as an interface between the user

and the BSC, but also wor&s as a sstem maintenance unit of the BSC and

automaticall super"ises the BSC.

The hi!h#speed Messa!e Bus (MB* interconnects the call control computers and

the M+. Exchan!e Terminals (ET* connect transmission sstems to the GS)B.

Cloc& and Snchronisation +nit (CS* !enerates the cloc& si!nals for the BSC.

Transcoder submultiplexer (TCSM*, althou!h a separate networ& element and

usuall installed on the MSC site, is normall "iewed as a functional unit of the

BSC.


2/16

%i!ure 0' Bloc& dia!ram of the GSM/EDGE BSC with Bit Group Switch

The functional units and cartrid!e tpes used in the GSM/EDGE BSC are described inthe followin! sections, which pro"ide the information on both the basic confi!urations of

the functional units (or cartrid!es* and the extension possibilities.

$n principle, the BSCi consists of the same functional units as the BSC1i. The onldifference is that since the ori!inal ET0C cartrid!es (that accept onl ET0E plu!#in units*

are not replaced b ET2C cartrid!es, there must be an additional 3%S plu!#in unit in the

BCS+ to control the ET0E plu!#in units.%or an o"er"iew, see "er"iew of BSC1i and BSCi 4i!h Capacit Base Station

Controller.


3/16

1.1 Bit Group Switch

The Bit Group Switch con"es the traffic passin! throu!h the BSC and switches the tones

to the subscribers of the exchan!e and to the trun& circuits. The Bit Group Switch alsoestablishes the needed connections to the si!nallin! units and the internal data

transmission channels, and is responsible for the submultiplexin! functions of the BSC.

The operation of the Bit Group Switch is controlled and super"ised b the Mar&er andCellular Mana!ement +nit (MCM+5 S)C*. The MCM+ performs all necessar

connectin! and releasin! functions.

The Bit Group Switch switches on 6, 07, 81, and 79 &bit/s le"el.The Bit Group Switch Cartrid!e, S)0C, consists of power suppl (SC0* and from two

to four S)79B plu!#in units, which all ha"e 81 pcs of 9 Mbit/s interfaces. The capacit

of the GS)B is 016, 0:1 or 127 CMs.

The Bit Group Switch of the GSM/EDGE BSC is a full di!ital, one#sta!ed, and non#bloc&in! time switch with full a"ailabilit. $ts !reat ad"anta!e is its simplicit. 3fter the

Bit Group Switch has identified the correct time slots, it can alwas connect them in a

uniform manner without usin! a special search path.

1.2 Call control computers

$n the GSM/EDGE BSC, the call control functions are executed b microcomputers,

called call control computers. The call control computers ha"e an identical Centralrocessin! +nit (C+*, which is based on the most suitable commerciall a"ailable $ntel

microprocessors. The C+ board contains a microprocessor and a local -andom 3ccess

Memor (-3M*. Each call control computer also contains the additional units that are

re;uired for performin! specific tas&s.3ll plu!#in units of each call control computer are interconnected b a DMC processor

bus. The DMC processor bus operates accordin! to the specifications of the internal

communication of the control computers. The DMC processor bus is independent ofcomponent technolo! e"olution. Conse;uentl, the DMC processor bus facilitates

further de"elopment of the plu!#in units, resultin! in an up#to#date and cost#effecti"e

BSC with hi!h capacit.

1.3 Marker and Cellular Management Unit (MCMU)

The Mar&er and Cellular Mana!ement +nit (MCM+* controls and super"ises the Bit

Group Switch and performs the huntin!, connectin! and releasin! of the switchin!networ& circuits. The ran!e of the tas&s it handles ma&es up a combination of !eneral

mar&er functions and radio resource mana!ement functions.

The MCM+ is connected to the other computer units of the exchan!e, M+ and BCS+,throu!h the messa!e bus. $t performs the control functions of a switchin! matrix and the

BSC#specific mana!ement functions of the radio resources.

The hardware of the MCM+ consists of three modules' a microcomputer, a SwitchControl $nterface, and a Messa!e Bus $nterface.


4/16

%i!ure 1' Structure of the MCM+The mar&er functions of the MCM+ control the Bit Group Switch. These controlfunctions include the connection and the release of the circuits of the switchin! matrix.

)hen the MCM+ performs the mar&er functions, it exchan!es messa!es with other Call

Control Computers "ia the Messa!e Bus (MB*.The Switch Control $nterface writes the re;uired connections into the switch control

memor and reads its contents. The switch control interface also performs "arious tests

on the switchin! networ&, defined b the microcomputer, and !enerates the re;uired

timin! si!nals.The cellular mana!ement functions of the MCM+ are responsible for cells and radio

channels that are controlled b the BSC. This responsibilit is centralised in the MCM+.

The MCM+ reser"es and &eeps trac& of the radio resources re;uested b the MSC andthe hando"er procedures of the BSC. The MCM+ also mana!es the confi!uration of the

cellular networ&.

The cellular mana!ement functions of the MCM+ do not re;uire an specific hardwarein addition to the standard microcomputer and a Messa!e Bus $nterface +nit (MB$%*.

ne GSM/EDGE BSC alwas includes two MCM+s that are permanentl connected to

the duplicated pair of the Bit Group Switches, the acti"e MCM+ to the acti"e GS)B and

the passi"e MCM+ to the passi"e GS)B.


5/16

1. BSC Signalling Unit (BCSU)

The BSC Si!nallin! +nit (BCS+* performs those BSC functions that are hi!hl

dependent on the "olume of traffic. The BCS+ is housed in a cartrid!e of its own. $tconsists of two parts, which correspond to the 3 and 3bis interfaces. The optional ac&et

Control +nits (C+s* can be housed in the BCS+s.

The 3 interface part of the BCS+ is responsible for the followin! tas&s' performin! the distributed functions of the Messa!e Transfer art (MT* and the

Si!nallin! Connection Control art (SCC* of SS@0 redundanc

principle re;uires that the BCS+s are e;ui"alent to each other.ac&et Control +nit (C+*

There are two !enerations of C+s. The first !eneration C+s are C+#Ts and thesecond !eneration C+s are C+1#+s in BSC1i. The preferred option is the second

!eneration C+1s.

The C+ unit performs all the data processin! tas&s that are related to the G-S/EDGEtraffic. $t implements both pac&et switched traffic#oriented Gb and 3bis interfaces in the

BSC.

3 C+ includes a microprocessor and di!ital si!nal processors inte!rated to the same

plu!#in#unit to handle the tas&s. The main functions are G-S traffic radio resourcemana!ement, for example connection establishment and mana!ement, resource

allocation, schedulin!, data transfer, MS uplin& power control, Gb load sharin! (uplin&*

and flow control (downlin&*. C+s must be confi!ured to e"er BCS+ installed, but onlthe acti"ated ones are to be used. 3 similar principle applies to the optional second C+

unit. This re;uirement comes from the !eneral >@0 redundanc principle of the fault

tolerant D= 1?? computin! platform.)ith C+1 poolin! it is possible to form a pac&et ser"ice entit (SE* that can contain

up to 2? C+s. 3 SE is a lo!ical concept that hides the phsical C+ plu!#in units from

the lo!ical networ& confi!uration. C+1 poolin! increases the data capacit in the >SE

and enhances operabilit on the Gb and 3bis interfaces.


7/16

1.! "peration and Maintenance Unit ("MU)

The peration and Maintenance +nit (M+* is an interface between the BSC and a

hi!her#le"el networ& mana!ement sstem (such as >et3ct* and/or the user. The M+can also be used for local operations and maintenance. The M+ recei"es fault

indications from the BSC. $t can produce local alarm printouts to the user or send the

fault indications to >et3ct. $n the e"ent of a fault, the M+ automaticall acti"atesappropriate reco"er and dia!nostics procedures within the BSC. -eco"er can also be

acti"ated b the MCM+ if the M+ is lost.

The tas&s of the peration and Maintenance +nit (M+* can be di"ided into four!roups'

traffic control functions

maintenance functions

sstem confi!uration administration functions

sstem mana!ement functions

The M+ consists of microcomputers similar to the call control computers. $n addition,

the M+ contains $/ interfaces for local operation.The peration and Maintenance +nit (M+* consists of the followin! modules'

microcomputer

alarm interface

Messa!e Bus $nterface

peripheral de"ice interface

optional analo! =.12 interface (modem to SD> or 3>*

optional di!ital =.12 interface (time#slot#based AM interface*

Ethernet interface

%i!ure 9' Structure of the M+

The alarm interface module connects internal wired alarms to the M+ from, forexample, the BSC cartrid!es, power suppl, and air conditionin! e;uipment. This module

pro"ides both input and output interfaces for external alarms to >et3ct.


8/16

The M+ communicates with the call control computers of the BSC "ia the Messa!e

Bus. The M+ is located in a cartrid!e of its own.

The C+ controls the peripheral de"ice interface module, which is used to connect dis&units, "isual displa unit, M Dis& Dri"e and printer to the M+. 3 mirrored pair of

hard ()inchester* dis& units, a D3T tape dri"e, and one 8.2 dis& unit can be controlled

b the M+. The dis& units are installed in a separate cartrid!e, which houses both harddis& and flopp dis& units.

The "isual displa unit and printer interfaces are standard asnchronous serial interfaces

complin! with the $T+#T -ecommendation .19.The analo! =.12 modem interface module pro"ides an =.12 Data Terminatin! E;uipment

(DTE* interface for the pac&et switched networ& (SD>* with a phsical laer of .19,

.19 restricted, .82, or =.10.

The di!ital =.12 CM#based AM interface module is used for the networ& mana!ementinterfaces implemented in time slots. This module pro"ides an =.12 connection "ia the 3

interface time slot.

The 3> interface pro"ides an Ethernet interface accordin! to $EEE6?1.8. 3>

interfaces are located at the C+s.S$ o"er TC/$ introduces TC/$ protocol support for all traffic that comes "ia the

Ethernet interface. This remo"es the need for usin! $S $ routers in the DC> networ&sand therefore simplifies the $ confi!uration of the BSC site.

1.# Message Bus (MB)

3 duplicated hi!h#speed Messa!e Bus (MB* is used for data transfer between the M+

and the Call Control Computers of the GSM/EDGE BSC.

The len!th of each messa!e is determined indi"iduall b a messa!e len!th parameter at

the be!innin! of the messa!e. The sender and the recei"er of the messa!e are indicated inthe address field of the messa!e. The recei"er can be a sin!le microcomputer, or it can be

a !roup of microcomputers specified b the broadcast address.

The hardware of the Messa!e Bus consists of se"eral parallel twisted pairs, which carrthe actual data and also control the information re;uired for the messa!e transfer.

$n the e"ent of a failure, the hot standb Messa!e Bus ta&es o"er the functions of the

acti"e bus without interferin! with the on!oin! calls.

%i!ure 2' Structure of the Messa!e Bus sstem

1.$ %&change 'erminal (%')

The ET performs the electrical snchronisation and adaptation of external CM lines. $tperforms the 4DB8 (ET1E*, or B6S or 3M$ (ET13* codin! and decodin!, inserts the


9/16

alarm bits in the out!oin! direction and produces CM frame structure. 3ll ET1 plu!#in

units contain two separate ETs but the ET0E plu!#in units of the first !eneration BSC

contain onl one ET.3ll 1.?96 Mbit/s (in the ETS$ en"ironment* or 0.299 Mbit/s (in the 3>S$ en"ironment*

interfaces for the MSC and the BTSs are connected to the Exchan!e Terminals. The

Exchan!e Terminals adapt the external CM circuits to the GS)B and snchronise to thesstem cloc&. Snchronisation is included in the bit frame.

The ETs are located in Exchan!e Terminal cartrid!es. The ET0 plu!#in units are housed

in the ET0C cartrid!e and the ET1 plu!#in units are housed in the ET2C cartrid!e.The ET0C cartrid!es of the first !eneration BSC house Exchan!e Terminal plu!#in units

(ET0E*. The BCBE rac& contains two ET0C cartrid!es and the BCEE rac& fi"e ET0C

cartrid!es. Each ET0C cartrid!e contains ei!ht ET0E plu!#in units and two SC8 plu!#in

units.$n the BSC1i application, the BCBE rac& can contain up to two ET2C cartrid!es and the

BCEE rac& up to se"en. The BSCi application, on the other hand, can contain onl two

ET2C cartrid!es (as an option, in addition to the se"en ori!inal ET0C cartrid!es*' one in

the BCBE rac& and the other in the BCEE rac&.Each ET is connected to the switchin! networ& and the Cloc& +nit of the GSM/EDGE

BSC "ia permanent, wired connections. The ETs are also connected to the 3Dinterface "ia a 3D lin&. Two tpes of connectors, smmetrical and coaxial (S$ en"ironment* into binar form. 3t the

same time, the ET1 is snchronised to the bit rate of the incomin! si!nal.

$n the out!oin! direction, the ET1 recei"es a binar CM si!nal from the switchin!networ& and !enerates the CM frame structure. The resultin! si!nal is con"erted into a

line code (4DB8 in the ETS$ en"ironment, B6S or 3M$ in the 3>S$ en"ironment* and

transmitted further onto the 1.?96 Mbit/s (ETS$* or 0.299 Mbit/s (3>S$* circuit.

1. Clock and Snchronisation Unit (C*S)

The Cloc& and Snchronisation +nit (CS* distributes timin! reference si!nals to the

functional units of the GSM/EDGE BSC. $t can operate plesiochronousl orsnchronousl with the timin! references it recei"es from the di!ital CM trun&s. Three

CM reference inputs with priorit order are pro"ided for the timin! reference si!nals.

The oscillator of the CS is normall snchronised to an external source, usuall anMSC, throu!h a CM line. +p to two additional CM inputs are pro"ided for

redundanc.

The Cloc& A Tone Generator (C0TG* plu!#in unit meets the re;uirements of the $T+#T.2?? Series -ecommendation with respect to the Time $nter"al Error (MT$E*, the Fitter,

the wander, and the transfer function. $n the plesiochronous operation mode, the

fre;uenc shift of the C0TG is 1 0?#6 within each 19#hour period, if the temperature

of the en"ironment does not "ar.


10/16

3n optional Cloc& A Tone Generator plu!#in unit, C8TG, with external snchronised

input is also a"ailable.

)hen the sstem consists of two rac&s, the timin! reference si!nals are buffered for theextension rac& b a duplicated Cloc& and 3larm Buffer (C3B* plu!#in unit.

2 . Configurations of the BSC2i and BSCiThere are two basic confi!urations of the BSCi/BSC1i' one#rac& and two#rac&. Both ofthem can be e;uipped flexibl with a number of T-=s and trun& circuits.

The BSCi and BSC1i can be e;uipped with'

one#rac& confi!uration'

o a maximum of 016 T-=s

o a maximum of 016 BTSs

o a maximum of 71 BC%s

two#rac& confi!uration'

o a maximum of 201 T-=so a maximum of 201 BTSs

o a maximum of 196 BC%s.

3. Capacity and connectivity of the BSC2i and BSCi)ith the reference model below, the maximum processin! capacit of a GSM/EDGEBSC1i is 8?9? Erl/:0??? B4C3, !i"in! full support to 201 %- T-=s.

-eference model of call traffic (call

mix and parameters*'

Mean holdin! time 01?s

roportion of MS ori!inated calls


11/16

Table 8' Circuit switched processin! capacit of the BSC1i

The abo"e#mentioned traffic processin! capacit of the BSC can be with the new BSC

hardware en"ironment. The maximum traffic processin! capacit of the BSC1i/BSCisupports 201 full rate T-=s or 127 half rate T-=s. Connecti"it for 201 3M- 4- T-=s

is a"ailable for BSC1i as optional Soft Channel Capacit functionalit. 4owe"er, some

new functionalities ma ha"e an influence on the capacit of the BSC. Circuit switcheddata calls are ta&en into account in the reference model of call traffic in the followin!

wa'

one data call with one radio time slot is seen as one mobile ori!inatin! or

terminatin! call

one full rate data call is seen as one mobile ori!inatin! or terminatin! call

one hi!h speed circuit switch data (4SCSD* call with two or more radio time slots

is seen as se"eral calls, based on how man time slots are reser"ed for the call.%or example, if two time slots are reser"ed (1 x 09,9 &bit/s* the call is seen as two

mobile ori!inatin! or terminatin! calls.

Different tpes of connections are pro"ided as follows' in BSC1i, a maximum of 099 CM connections, and in BSCi, 27 or a maximum

of 66 CM connections used on external interfaces

in BSC1i, a maximum of 127 CM connections, and in BSCi, a maximum of 016,

up!radable to 0:1, CM connections connected to the non#bloc&in! switchin!

matrix

a maximum of 07 SS< si!nallin! lin&s. ptionall some wider 016 or 127 &bit/s

si!nallin! lin&s can be confi!ured instead of standard 79 &bit/s lin&s.

in BSC1i, a maximum of ::1 3D protocol lin&s, and in BSCi, a maximum of

:87 3D protocol lin&s

3D si!nallin! lin&s can be confi!ured to 07, 81, or 79 &bit/s speeds.$ntroduction of 4- enables T-= confi!urations of more than 06 radio channels,

which leads to increased load in measurement reportin!. Because of this, thecapacit of a 07 &bit/s si!nallin! lin& is not sufficient in all cases.

Therefore it is recommended that also with 4-, the T-= confi!urations should be

restricted to the maximum of 06 radio channels if 07 &bit/s si!nallin! lin&s are

used. )ith T-= confi!urations of more than 06 radio channels, a 81 &bit/s 3Dlin& is hi!hl recommended for supportin! the telecom si!nallin! which half rate

re;uires. The o"erload of the si!nallin! lin& can be monitored b the telecom

3D lin& super"ision with a possibilit to set an alarm in an o"erload situation.

$n GSM/EDGE BSC the pac&et handlin! capacit is pro"ided b ac&et Control+nits (C+s*. Maximum pac&et handlin! capacit and connecti"it per each

C+0 is 79 BTSs, 016 T-=s, and 127 traffic channels (07 &bit/s, 3bis* for

G-S/EDGE use and, correspondin!l, pac&et handlin! capacit and connecti"itper each C+1 is 016 BTSs, 127 T-=s and 127 traffic channels (07 &bit/s, 3bis*

for G-S/EDGE use.


12/16

o maximum capacit with full confi!uration (6 C+s* is 127 x 6 I 1?96

traffic channels (07 &bit/s, 3bis* per BSCi for G-S/EDGE use

o maximum capacit with full confi!uration (07 C+s* is 127 x 07 I 9?:7

traffic channels (07 &bit/s, 3bis* per BSC1i for G-S/EDGE use

The abo"e#mentioned pac&et handlin! capacit can be achie"ed with the newhardware en"ironment. 4owe"er, some functionalities mi!ht ha"e extrare;uirements for the hardware. >ew functionalities ma also ha"e an influence on

the pac&et handlin! capacit of the BSC.

%or an o"er"iew, see "er"iew of BSC1i and BSCi 4i!h Capacit Base Station

Controller.

. Mechanical design and po!er supply of BSC2i and

BSCi

The GSM/EDGE BSC can be located flexibl in the GSM networ&. $t can be installed as

stand#alone, on the same site as the base transcei"er station (BTS* it controls, or at a

remote location, which can be either co#located or non#co#located with the MSC.The most common solution is to locate the BSC remotel to the MSC near the BTSs it

controls and install the transcoder submultiplexer (TCSM* at the MSC site.

Submultiplexin! can then be used between the BSC and TCSM to reduce transmission

costs.

Mechanical design

The mechanical structure of the GSM/EDGE BSC is hierarchical, based on plu!#in units,

cartrid!es and rac&s. The dimensions of different units and cartrid!es are in accordance

with the recommendations of the $EC ($nternational Electrotechnical Commission*. TheGSM/EDGE BSC is eas to install, operate, and maintain. Special attention has been paid

to thermal resistance and immunit to "arious tpes of interference.

lu!#in units

Cartrid!es

-ac&s

Cablin!

Cable Conduit and Cablin! -ac& for raised floor installations3pplicable >EBS8 compliance (optional*

. 1 /lug0in units

The BSC1i is constructed b usin! a total of 02 plu!#in unit tpes, includin! the DC/DC

con"erters. The siJe of these plu!#in units is either 188.9 mm x 07? mm, 188.9 mm x 11?mm, 0?? mm x 11? mm, or 00? mm x 11? mm.


13/16

The printed circuit boards (CBs* of plu!#in units are multilaered. The are co"ered

with a protecti"e coatin! that ma&es the CBs eas to handle and protects the foils from

scratches.Both surface#mounted and hole#mounted components are used on the CBs. The

connectors are of the Euro#connector tpe.

.2 Cartridges

Most of the functional units consist of one cartrid!e that contains a selection of CBs. 3

fixed rac& position has been assi!ned to the cartrid!e of each functional unit.The cartrid!es of the BSC1i are of the followin! tpes'

MC0C cartrid!e for MCM+, M+, and BCS+

C3C cartrid!e for the Cloc& and 3larm Buffer +nit

CC cartrid!e for the Cloc& and Snchronisation +nit

ET2C cartrid!e for Exchan!e Terminals

S)0C cartrid!e for the Bit Group Switch

SD8C#S cartrid!e for hard dis& ()inchester* units, D3T and %lopp Dis& dri"es

The cartrid!es of the BSCi are of the followin! tpes'

MC0C cartrid!e for MCM+, M+, and BCS+

C3C cartrid!e for the Cloc& and 3larm Buffer +nit

CC cartrid!e for the Cloc& and Snchronisation +nit

ET0C and ET2C cartrid!es for Exchan!e Terminals

S)0C cartrid!e for the Bit Group Switch

)DDC cartrid!e for hard dis& ()inchester* units, D3T and %lopp Dis& dri"es or

SD8C#S cartrid!e for hard dis& ()inchester* units, D3T and %lopp Dis& dri"es

>ote that the BSC1i does not include the ET0C cartrid!e.

The siJe of each cartrid!e tpe is !i"en below' SD8C#S' 171 mm x 17? mm x 0


14/16

The closed space in both one#rac& and two#rac& confi!urations is surrounded b the side

plates, the doors, the upper cable conduit, and the baseboard. The doors are perforated to

facilitate coolin!.The hei!ht, width and depth of a standard BSCi rac& are (with cablin! and doors*' 11??

mm x 7?? mm x 2?? mm.

The hei!ht, width and depth of a standard BSC1i rac& are (with cablin! and doors*' 1?1?mm x 7?? mm x 2?? mm.

Each installed BSC has side plates on its both sides. Each side plate is 9? mm wide,

which must be ta&en into account when estimatin! the total width of the rac&s.$f more than one BSC1i is located on the same site, the rac&s can be connected to each

other. $n this case, each row of rac&s constitutes a closed EMC#shielded space.

%i!ure 6' -ac& laout of the BSC1i first deli"eries


15/16

%i!ure :' -ac& laout of the BSCi, 27 CM "ersion


16/16

%i!ure 0?' -ac& laout of the BSCi, 66 CM "ersion

Documents

Nokia BSC2i Overview