CellNetworksGSM

8/13/2019 CellNetworksGSM

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Sistemi Mobili e Wireless

Mobile and wireless

technologies

Stefano Burigat

Laboratorio di Interazione Uomo-Macchina

Dipartimento di Matematica e InformaticaUniversit di Udine

www.dimi.uniud.it/[email protected]

Part of the content is an excerpt of the slides made available b!

Prof. Jochen H. Schiller - Freie Universitt Berlin - Computer

Systems & Telematics
http://www.dimi.uniud.it/burigathttp://www.dimi.uniud.it/burigat


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Cellular networks#$M


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%

&verview

' ()*+s! in ,urope different analog mobile phonesstems coexisted -e.g. M 01+2 34$2 ...52 running onslightl different carrier fre6uencies

' ()*" ! #roupe $p7ciale Mobile was founded to design asstem supporting the seamless roaming within ,urope

' he ,uropean elecommunications $tandardi8ation Institutepublished the first #$M -#lobal $stem for Mobile4ommunication5 specification in ())+ -1+++ pages95

' oda man providers all over the world use #$M

-"() countries in 3sia2 3frica2 ,urope2 3ustralia2 3merica5: #$M networ;s cover more than )+< of the world=s population


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0

#$M versions

' Please note! fre6uenc ranges ma var depending on the countr9

' 4hannels at the lower/upper edge of a fre6uenc band are tpicall not used

UplinkM!z"

#ownlinkM!z"

$SM %&& *)+ > )(1 )%1 : )?+ Initiall deploed in ,urope

#CS $SM '(&&"-digital cellular sstem5

((+ > (*1 (*+1 > (**+

)CS $SM '%&&"-personal communications service5

(*1+ > ()(+ ()%+ > ())+ Developed for U$

$SM *&& 01+.0 > 01.?

0*.* > 0*?

0?+.0 > 0?.?

0**.* > 0)?

Proposal for replacinganalog sstems insparsel populated areas

$SM-+ail Introduced in several,uropean countries


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1

#$M cellular networ;

' #$M is based on segmenting an area into cells

: use of several carrier fre6uencies

: not the same fre6uenc in adAoining cells: cell si8es var from some (++ m up to %1 ;m depending on user densit2

geograph2 transceiver power2 etc.

: hexagonal shape of cells is ideali8ed -cells overlap2 shapes depend ongeograph5

: if a mobile user changes cells2 handover of the connection to the neighbor

cell

possible radio coverage of the cell

ideali8ed shape of the cell

cell


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?

#$M vs. 3nalog sstems

' 4ommunication: support for voice and data circuit>switched services

' otal mobilit

: international access2 use of access points of different providers

' Borldwide connectivit: one number2 the networ; handles locali8ation

' Cigh capacit

: better fre6uenc efficienc2 smaller cells2 more customers per cell

' Cigh transmission 6ualit: high audio 6ualit2 uninterrupted phone calls at higher speeds -e.g.2

from cars2 trains5

' $ecurit functions

: access control2 authentication via PI


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#$M services

' #$M offers several services: moile telephony! primar goal of #$M was to enable mobile

telephon offering the traditional bandwidth of %.( ;C8

: emer"ency numer! common number throughout ,urope -(("5mandator for all service providers free of charge connection with

the highest priorit -preemption of other connections possible5: Short #essa"e Service-$M$5!

' alphanumeric data transmission to/from the mobile terminal -(?+characters5

' exploits unused capacit in the signaling channel -thus2 sending andreceiving $M$ is possible during data or voice transmission5

' $M$ was in the standard from the beginning2 initiall designed forEseriousF purposes -e.g.2 displa road conditions5

' huge business for networ; operators and man content providers

' tpicall the onl wa to reach a mobile phone from within the networ;-e.g.2 used for updating mobile phone $B5


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#$M services

' #$M offers several services: $ata services! data rate up to ).? ;bit/s -original standard5 data

transmission has a constant dela and throughput if no transmissionerrors occur toda2 better data rates are possible

: "roup % fa

: voice mailo -implemented in the fixed networ; supporting themobile terminals5

: numer i$entification! forwarding of caller number2 suppression ofnumber forwarding

: call for'ar$in"

: call arrin" -incoming or outgoing calls5: call 'aitin"

: a$vice of char"e

: conferencin" -with up to participants5

: ...


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(+

#$M components! mobile phones2PD3s2 H co.

he visible but smallest

partof the networ;9


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((

#$M components! antennas

$till visible : cause man discussions


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#$M components! infrastructure

Gase $tations

4abling


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#$M components! infrastructure

$witching units

Data bases

Monitoring

ot EvisibleF2 butcomprise the maAor part

of the networ; -also

from an investment

point of view5


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(0

#$M architecture

+adio Subs,stem

covers all radio aspects

etwork and Switching Subs,stemcall forwarding2 handover2 switching

.peration Subs,stemmanagement of the networ;


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(1

Gase station subsstem

MS MS

B/S

B/S

BSC

Um

BSS

radio cell

MS

Mobile Station

Base Station Controller

manages G$s2 e.g.2 reserving radio

fre6uencies2 handling the handover

from one G$ to another within the

G$$

Base /ransceiverStation

comprises antennas2 signal processing2

amplifiers necessar for radio

transmission

radio cell

BaseStationSubsstem

Interface containing all mechanisms

necessar for wireless transmission

-DM32 JDM32 5


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(?

Mobile station

' Mobile e6uipment!

: identified via the International Mobile ,6uipment Identit -IM,I5

: transmit power! #$M )++ up to "B2 #$M (*++ (B -due to smaller cell si8e5

' $ubscriber Identit Module -$IM5

: used for charging2 authentication2 etc.

: without $IM2 onl emergenc calls are possible

: contains static information2 such as

' 4ard>tpe

' $erial number

' Kist of subscribed services

' Personal Identit umber -PI5

' PI Unbloc;ing Le -PUL5

' International Mobile $ubscriber Identit -IM$I5

' Mobile $tation I$D umber -M$I$D52 i.e.2 telephone number

: contains dnamic information2 such as

' Kocation 3rea -K35

' emporar mobile subscriber identit -M$I5


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adio interface

' #aussian Minimum $hift Leing for modulation' Jre6uenc Division Duplexing

: Downlin; and uplin; use different fre6uencies

: Kower fre6uencies for the uplin; to save batter power

' Cbrid JDM3/DM3 access scheme: Uplin; and downlin; spectrum partitioned into ("0 "++LC8 carriers-%0 carriers for #$M (*++5

: ,ach carrier partitioned into * time slots

: ,ach time slot carries one data burst

: 3 combination of carrier number and time slot number identifies aphsical channeluni6uel

: ot all phsical channels can be assigned to users to carr userpaload

' &ptional slow fre6uenc hopping mechanism


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(*

Media access

( " 0 1 ? *

)%1>)?+ MC8("0 channels -"++ ;C85

*)+>)(1 MC8

("0 channels -"++ ;C85

fre6ue

nc

time

#$M DM3 frame

#$M time>slot

0.?(1 ms

1 Ns

uplin;

downlin;

%

tail user data raining$guard

space $ user data tailguard

space

10?.1 Ns% bits 1 bits "? bits 1 bits( ( %


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()

Media access

' wo factors allow for the use of simple transmitters: slotsfor up and down lin;s are separated in fre6uenc -01 MC82

#$M )++5

: framesare shifted in time for three slots!

' i.e.2 if the G$ sends data at time t+in slot one on the downlin;2 the M$

assesses slot one on the uplin; at time t+O%1 Ns

uplin;

downlin;

t+ t+O%1

01 MC8

*)+ MC8

)%1 MC8


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"+

Gase transceiver station and Gasestation controller

' as;s of a G$$ are distributed over G$4 and G$: G$ comprises radio specific functions

: G$4 is the switching center for radio channels

MS MS

B/S

B/S

BSC

BSS

MS

0unctions B/S BSC

Management of radio channels QJre6uenc hopping -JC5 Q Q

Management of terrestrial channels QMapping of terrestrial onto radio channels Q

4hannel coding and decoding Q

ate adaptation Q

,ncrption and decrption Q Q

Paging Q Q

Uplin; signal measurements Q

/raffic measurement Q3uthentication Q

Kocation registr2 location update Q

Candover management Q


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"(

etwor; and switching subsstem

' he etwor; $witching $ubsstem -$$5 is theEheartF of the #$M sstem

: 4onnects the wireless networ; with standard public networ;s

: Performs handovers between different G$$s

: 4omprises functions for worldwide locali8ation of users

: $upports charging2 accounting and roaming of users betweendifferent providers in different countries


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etwor; and switching subsstem

SS+SS

networ;

subsstem

fixed partner

networ;s

I$D

P$

BSC

BSC

Mobile $ervices Switching Center

Cigh>performance digital switch handles all signaling

needed for connection setup2 connection release and

handover of connections to other M$4s. $everal G$4 can

connect to a M$4

MSC

MSC

!ome Location +egister

4entral master database containing user data -one

provider can have several CKs53ll these user>specific information elements onl exist once

for each user in a single CK. CK comprises!' static information -e.g.2 subscribed services2 the internationalmobile subscriber identit2 M$I$D2 5

' $ynamic information -e.g.2 current location area and M$45

3s soon as a M$ leaves the current K32 the information in

the CK is updated. his information is necessar to

locali8e a user into the worldwide #$M networ;

1isitor Location +egister

Kocal database for a subset of user data2 including data

about all users currentl in the domain of the RKIf a new M$ comes into an K3 the RK is responsible for2 it

copies all relevant information for this user from the CK

his hierarch of RK and CK avoids fre6uent CK

updatesCK

RK

RK

L2


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#estione di una chiamata nel #$M


Mobile $ervices Switching

Center

MSC

BSC

B

B/S

$upponiamo che all=interno di una rete

ci siano due utenti mobili 3 e G che voglionocomunicare tra di loro

BSC

2

B/S

MSC

CK

RK

RK



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"0




Center

MSC

BSC

B

B/S



3 compone il numero telefonico di G-e.g.2 %1*00+***5

essendo un utente mobile2 l=analisi del numerocomposto non consente di determinare la posi8ione

di G -contrariamente alle reti fisse5

BSC

2

B/S

MSC

CK

RK

RK



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"1




Center

MSC

BSC

B

B/S



3 compone il numero telefonico di G-e.g.2 %1*00+***5

essendo un utente mobile2 l=analisi del numerocomposto non consente di determinare la posi8ione

di G -contrariamente alle reti fisse5

BSC

2

B/S

M$4 anali88a il numero!

il prefisso S%1*S identifica che G T unabbonato di una certa rete #$M

le prime due cifre dopo il prefisso2 cioT S00S2identificano un determinato CK -CK>005

M$4 di 3 effettua 6uindi unopera8ioneibrida! con le prime cin6ue cifre chiama CK>00 e poi gli trasferisce le seconde cin6ue-+***5

MSC

CK

RK

RK



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Center


BSC

B

B/S

CK>002 anali88ato il numero -+***52

riconosce labbonato e ne ricava il suo codiceIM$I e il sistema RK in cui lutente T registrato

Kutente G potrebbe anche non essereregistrato in nessun RK della rete sia perch7fuori copertura radio sia perch7 non ha acceso ilsuo telefonino

BSC

2

B/S

CK

MSC RK

MSC RK

CK>00 prende contatto col RK>%1+1111?0? e gli trasferisce il codice IM$I

RK verifica se il codice IM$I ricevuto Tattualmente registrato in caso affermativorestituisce a CK>00 un numero telefonicodetto M$ -Mobile $tation oaming

umber5


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"*



Center


BSC

B

B/S

CK>002 anali88ato il numero -+***52

riconosce labbonato e ne ricava il suo codiceIM$I e il sistema RK in cui lutente T registrato

Kutente G potrebbe anche non essereregistrato in nessun RK della rete sia perch7fuori copertura radio sia perch7 non ha acceso ilsuo telefonino

BSC

2

B/S

CK>00 trasferisce il numero M$ allacentrale M$4 di origine

CK

MSC RK

MSC RK

CK>00 prende contatto col RK>%1+1111?0? e gli trasferisce il codice IM$I

RK verifica se il codice IM$I ricevuto Tattualmente registrato in caso affermativorestituisce a CK>00 un numero telefonicodetto M$ -Mobile $tation oaming

umber5


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%+

$ignaling needed for connection setup

G$M$

paging re6uest

channel re6uest

immediate assignment

paging response

authentication re6uest

authentication response

ciphering command

ciphering complete

setup

call confirmed

assignment command

assignment complete

alerting

connect

connect ac;nowledge

data/speech exchange

G$M$

channel re6uest

immediate assignment

service re6uest

authentication re6uest

authentication response

ciphering command

ciphering complete

setup

call confirmed

assignment command

assignment complete

alerting

connect

connect ac;nowledge

data/speech exchange

M/C M.C


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%(

&peration subsstem

' he &peration $ub$stem -&$$5 enables centrali8edoperation2 management2 and maintenance of all #$Msubsstems

' 4omponents

: &peration and Maintenance 4enter

' different control capabilities for the radio subsstem and the networ;subsstem

' e.g.2 management functions li;e traffic monitoring2 status reports ofnetwor; entities2 securit management2 accounting and billing

: 3uthentication 4enter

' generates user specific authentication parameters on re6uest of a RK

: ,6uipment Identit egister

' registers #$M mobile stations and user rights

' stolen or malfunctioning mobile stations can be loc;ed and sometimeseven locali8ed


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%"

#$M handover

' 4ellular sstems re6uire handover of mobile stationsbetween base stations

' here are two basic reasons for a handover!

: he mobile station moves out of the range of a G$. he receivedsignal level decreases continuousl until it falls below the minimal

re6uirements for communication. he error rate ma grow due tointerference

: he wired infrastructure -M$42 G$45 ma decide that the traffic inone cell is too high and shift some M$ to other cells with a lower load-if possible5. Candover ma be due to load balancing

' he smaller the cell si8e and the faster the movement of amobile station through the cells -up to "1+ ;m/h for #$M52the more handovers of ongoing calls are re6uired


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%%

pes of handover

M$4 M$4

G$4 G$4G$4

G$ G$ G$G$

M$ M$ M$ M$

(" % 0

intra>cell handoverinter>cell

intra>G$4 handover

inter>G$4

intra>M$4 handover inter>M$4 handover

B/S

B/S

MS

BSC

BSC

MSC


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Candover decision

' M$ and G$ both perform periodic measurements of thedownlin; and uplin; 6ualit respectivel

' Kin; 6ualit comprises signal level and bit error rate

' Measurement reports are sent b the M$ about ever half>second andcontain the 6ualit of the current lin; used for the transmission as well asthe 6ualit of certain channels in the neighbouring cells

receive level

G$

receive level

G$

M$ M$

C&WM3#I

G$old G$new


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%1

Inter>G$42 intra>M$4 handover

C& access

G$old G$4new

measurement

result

G$4old

Kin; establishment

M$4M$

measurement

report

C& decision

C& re6uired

G$new

C& re6uest

resource allocation

ch. activation

ch. activation ac;C& re6uest ac;

C& commandC& command

C& command

C& completeC& complete

clear commandclear command

clear completeclear complete

M$4

G$4newG$4old

G$old G$new

M$

i3e3 fre4uencies and time slots


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%?

Initial enhancements

' Data transmission standardi8ed with onl ).? ;bit/s: advanced coding allows (0.0 ;bit/s

: not enough for Internet and multimedia applications

' C$4$D -Cigh>$peed 4ircuit $witched Data5

: abilit to use multiple time slots -max is 05 into a single frame

: possible asmmetrical assignment -e.g.2 more slots for the downlin;5

: advantage! read to use -sw update52 constant 6ualit2 simple

: disadvantage! connection>oriented2 not suitable for burst andasmmetrical data traffic2 charging on connection time2 channelsbloc;ed for voice transmission

kbit5s *3( kbit5s %36 kbit5s '*3* kbit5s

0.* (

).? " (

(0.0 % (

()." 0 "

"*.* % "

%*.0 0

0%." %

1@.? 0


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%

4urrent enhancements

' #P$ -#eneral Pac;et adio $ervice5: extends the existing #$M architecture

: pac;et>oriented -li;e internet5 no connection has to be set up prior todata transfer


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%*


' #P$ -#eneral Pac;et adio $ervice5

: the sstem can allocate between one and eight time slots within aframe these slots can be shared -allowing broad/multi cast services5

: time slots are not allocated in a fixed2 pre>determined manner but ondemand

: uplin; and downlin; are allocated separatel: allocation of slots is based on the current load and operator

preferences

: transfer rate depends also on the M$ capabilities

: all services can be used in parallel to conventional services

: more flexible than C$4$D2 charging on volume of data

: more investment needed -re6uires new CD and $B5


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%)


' #P$ data rates

: Depend on the used coding scheme -how much error correction issupported5 and the number of assigned time slots

: 0 possible schemes! 4$>( -).+1 ;bit/s52 4$>" -(%.0 ;bit/s52 4$>% -(1.?;bit/s52 4$>0 -"(.0 ;bit/s5

' 4$>0 is the least robust but fastest coding scheme available near a G$-"1< cell coverage5

' 4$>( is the most robust scheme -)1< cell coverage5

Codingscheme

' slot 7 slots 8 slots * slots 9 slots 6 slots : slots ( slots

4$>( ).+1 (*.( ".(1 %?." 01."1 10.% ?%.%1 ".0

4$>" (%.0 "?.* 0+." 1%.? ? *+.0 )%.* (+."

4$>% (1.? %(." 0?.* ?".0 * )%.? (+)." ("0.*

4$>0 "(.0 0".* ?0." *1.? (+ ("*.0 (0).* ((."


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' ,D#, -,nhanced Data ates for #$M ,volution5

: enhances the radio interface of #P$ b using better coding andmodulation schemes -M4$5

: a rate adaptation algorithm chooses the best M4$ according to theradio channel 6ualit


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' 4omparison of possible #$M>#P$>,D#,data rates

/echnolog,#ownload

kbit5s"Upload kbit5s"

/#M2 /imeslotsallocated

4$D ).? ).? (O(

C$4$D "*.* (0.0 "O(

C$4$D 0%." (0.0 %O(

#P$ *1.? -4$>05 "(.0 -4$>05 0O(

#P$ ?".0 -4$>05 0".* -4$>05 %O"

,D#, "%?.* -M4$>)5 1)." -M4$>)5 0O(

,D#, (.? -M4$>)5 ((*.0 -M4$>)5 %O"

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