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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/burigat8/13/2019 CellNetworksGSM
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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
!ome Location +egister
Mobile $ervices Switching
Center
MSC
BSC
B
B/S
$upponiamo che all=interno di una rete
ci siano due utenti mobili 3 e G che voglionocomunicare tra di loro
BSC
2
B/S
MSC
CK
RK
RK
1isitor Location +egister
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"0
#estione di una chiamata nel #$M
!ome Location +egister
Mobile $ervices Switching
Center
MSC
BSC
B
B/S
$upponiamo che all=interno di una rete
ci siano due utenti mobili 3 e G che voglionocomunicare tra di loro
3 compone il numero telefonico di G-e.g.2 %1*00+***5
essendo un utente mobile2 l=analisi del numerocomposto non consente di determinare la posi8ione
di G -contrariamente alle reti fisse5
BSC
2
B/S
MSC
CK
RK
RK
1isitor Location +egister
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"1
#estione di una chiamata nel #$M
!ome Location +egister
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
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$4 di 3 effettua 6uindi unopera8ioneibrida! con le prime cin6ue cifre chiama CK>00 e poi gli trasferisce le seconde cin6ue-+***5
MSC
CK
RK
RK
1isitor Location +egister
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#estione di una chiamata nel #$M
Mobile $ervices Switching
Center
!ome Location +egister
BSC
B
B/S
CK>002 anali88ato il numero -+***52
riconosce labbonato e ne ricava il suo codiceIM$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 $tation oaming
umber5
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"*
#estione di una chiamata nel #$M
Mobile $ervices Switching
Center
!ome Location +egister
BSC
B
B/S
CK>002 anali88ato il numero -+***52
riconosce labbonato e ne ricava il suo codiceIM$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$4 handover
B/S
B/S
MS
BSC
BSC
MSC
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%0
Candover decision
' M$ 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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%*
4urrent enhancements
' #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 $B5
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%)
4urrent enhancements
' #P$ 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$>0 "(.0 0".* ?0." *1.? (+ ("*.0 (0).* ((."
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0+
4urrent enhancements
' ,D#, -,nhanced Data ates for #$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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0(
4urrent enhancements
' 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"