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GSM/GPRS/EDGE Principles
Curriculum Objective:
Learn GSM development history;
Learn and master network structure o GSM system and unctions !
principles o dierent portions;
Learn and be amiliar with GSM wireless channel and protocol
Learn and be amiliar with main service call process or GSM
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Content
1 GSMOverview...............................................................................................................................................1
"#" GSM $asic Concepts###########################################################################################################################"
"#"#" %istory o the mobile communication######################################################################################"
"#"#& GSM 'einition########################################################################################################################(
"#& Services Supported by GSM System###################################################################################################)
"#" *elecom Services +rovided by GSM########################################################################################)
"#& Supplementary Services o the GSM System##########################################################################,
"#- GSM Speciication###############################################################################################################################,
2 GSM Network Structure..............................................................................................................................9
" GSM .rea 'ivision Concepts####################################################################################################### ######/
& GSM composition##############################################################################################################################"0
- Mobile Switchin1 System 2MSS3######################################################################################################"-
( $ase Station Subsystem 2$SS3##########################################################################################################"(
Operation ! Maintenance Subsystem 2OMS3############################################################################## ####"(
) Mobile Station 2MS3##########################################################################################################################"4
, GSM System number#########################################################################################################################"4
,#" Mobile subscriber 5S'6 number 2MS5S'63##################################################################### ###"4
,#& 5nternational Mobile Subscriber 5dentity 25MS53###################################################################")
,#- Mobile subscriber roamin1 number 2MS763########################################################################",
,#( %andover number###################################################################################################################",
,#4 *emporary mobile subscriber identiication 2*MS53######################################################## #####"8
,#) Location area 5dentiication 2L.53#########################################################################################"8
3 GSM Radio Channel...................................................................................................................................19
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-#" GSM 9orkin1 reuency $and########################################################################################################"/
-#& Structure o GSM 7adio rame#########################################################################################################&"
-#- +hysical Channel and Lo1ical Channel#############################################################################################&-
-#-#" +hyC% +hysical Channel###################################################################################################### #&-
-#-#& Lo1ic channel############################################################################################################### ##########&-
-#-#- Channel Combination#############################################################################################################&)
4 Basic Service and Sinalin !rocess.........................................................................................................33
(#" Mobile subscriber state######################################################################################################################--
(#"#" MS starts< network does =.ttach= marks on it#######################################################################--
(#"#& MS shutdowns< separated rom network################################################################################-(
(#"#- MS $usy######################################################################################################################## #########-(
(#& Location >pdate#################################################################################################################################-(
(#" Location update at a MSC oice############################################################################################-(
(#& 5nteroice Location >pdate################################################################################################ ###-4
(#- *ypical Call and %andover +rocess###################################################################################################-)
(#-#" Call between Mobile Subscribers###########################################################################################-)
(#-#& 5nter?$SC %andover within MSC######################################################################################## ##-,
(#-#- 5nter?MSC %andover##############################################################################################################-8
(#( $asic Si1nalin1 +rocess#####################################################################################################################-/
(#(#" Location >pdate +rocess########################################################################################################-/
(#(#& 5MS5 'etach +rocess########################################################################################################## ####("
(#(#- Mobile?Ori1inated Call and Called +arty On?hook +rocess##################################################(&
(#(#( Mobile?*erminated Call and Callin1 +arty On?hook +rocess########################################### ####((
(#(#4 5nter?cell %andover low########################################################################################################()
" #oice !rocessin and $e% Radio &echnolo%...........................................................................................4'
4#" @oice +rocessin1################################################################################################################################(,
4#"#" $asic low o @oice +rocessin1######################################################################################### ####(,
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4#"#& @oice Ancodin1#######################################################################################################################(8
4#"#- Channel Ancodin1###################################################################################################################(8
4#"#( 5nterleavin1Bdeinterleavin1#####################################################################################################(/
4#"#4 AncryptionB'ecryption###########################################################################################################4&
4#"#) ModulationB'emodulation#####################################################################################################4-
4#& 'iversity 7eceivin1###########################################################################################################################4-
4#- 'iscontinuous *ransmission 2'*3##################################################################################################44
4#( +ower Control####################################################################################################################################44
4#(#" $asic Concepts o +ower Control############################################################################### ###########44
4#(#& GSM +ower Control +rocess##################################################################################################4)
4#(#- %i1h?speed power control######################################################################################################48
4#4 *imin1 .dvance#################################################################################################################################4/
4#) reuency %oppin1 *echnolo1y#################################################################################################### ###)0
( G!RS and )*G)........................................................................................................................................(3
)#" 'einition and eature#######################################################################################################################)-
)#"#" G+7S 'einition#####################################################################################################################)-
)#"#& G+7S eatures########################################################################################################################)-
)#"#- A'GA 'einition####################################################################################################################)(
)#"#( A'GA eatures#######################################################################################################################)(
)#& 5nheritance and Avolution##################################################################################################################))
)#- G+7S 7adio Channel################################################################################################################## ######),
)#-#" G+7S +hysical Channel#########################################################################################################),
)#-#& G+7S Lo1ic Channel#############################################################################################################)8
)#-#- Mappin1 o Lo1ical Channel Combination in the +hysical Channel####################################,0
)#-#( G+7S Channel Codin1###########################################################################################################,4
)#( *erminal and .pplication########################################################################################################### #######,8
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1 GSMOverview
Knowledge points
*his chapter mainly introduces some basic inormation or GSM< includin1 GSM
development history< supported service type< speciication< and system eatures#
1.1 GSM Basic Concepts
1.1.1 Histor o! t"e #o$ile co##%nication
*he mobile communication was irst used in military and some special ields in "/&0Ds#
5n "/(0Ds< it be1an to be employed or civil use# *he mobile communication really booms
in recent decade# *he development o the mobile communication comprises the
ollowin1 three phases:
*he irst 1eneration 2"G3 mobile communication system
*he second 1eneration 2&G3 mobile communications system
*he third 1eneration 2-G3 mobile communications system
"# Startin1 rom "/80Ds< the "G analo1 mobile communication system adopts cellular
networkin1 technolo1y#
%owever< the "G mobile communication system has the ollowin1 disadvanta1es:
*here is no common interace between systems#
5t cannot keep up with the ast di1itiEin1 o the iFed network and provide di1ital
bearer services#
5t cannot meet the demand or lar1e capacity due to low reuency utiliEation#
5t eatures poor security# *he inormation bein1 eFchan1ed on the radio path may
be easily eavesdropped< and the subscriber account may be easily embeEEled#
'ue to the deects o analo1 systems< the di1ital mobile communication system
characteriEed by di1ital transmission< *ime 'ivision Multiple .ccess 2*'M.3*7.
9C'M.
5M*?&000
&G G -G
A'GA
>9C?"-)
,4G
i1ure "#"?" Avolution rom &G to -G
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) G+7S and A'GA
5n +hase& and +hase&H< two hi1h?rate data service models are put orward or the GSM
system#
%i1h Speed Circuit Switched 'ata 2%SCS'3 based on hi1h?speed data bit rate and
circuit switchin1
General +acket 7adio Service 2G+7S3 based on packet switched data
*hese two services are called G services# .doptin1 hi1h?rate adaptive codin1 solutionnicom is
represented by K0"#
GSM service area contains the +LM6s o countries all over the world#
&.& GSM co#position
*he GSM communication system consists mainly o three parts: mobile switchin1 sub?
system 2MSS3< base?station sub?system 2$SS3 and mobile station 2MS3< as shown in
i1ure & ?-#
IBM
IBM
$SS MSS
MS
MS
+S*6
+LM6
>m .
i1ure &?- GSM System Composition
Moile Switchin Sus%ste /MSS
ulills messa1e eFchan1in1< user inormation mana1ement< call connection and number
mana1ement unctions#
Base Station Sus%ste /BSS
*he $SS is controlled by MSC in a certain wireless covera1e and communicates with the
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) G+7S and A'GA
MS# 5t implements channel allocation< user access and pa1in1< and inormation
transmission unctions#
Moile Station /MS
MS which is the mobile euipment o the GSM system consists o two parts: mobile
terminal and customer 5' card 2S5M card3# *he mobile terminal is nothin1 but a
Khandset< which perorms such unctions as voice codin1< channel codin1< inormation
encryption< inormation modulation and demodulation< inormation transmission and
receivin1#
Oeration 5 Maintenance Sus%ste /OMS
.lso includin1 the operation and maintenance subsystem 2OMS3< the GSM system
mana1es and monitors the entire GSM network# 5t implements the unctions like
monitorin1< status reportin1 and ault dia1nosis o all the component unctions within the
GSM network#
+osition o GSM di1ital mobile communication network in $SS is as shown in i1ure
& ?(#
$SCn
$*S
MSCB@L7
SGS6
SMC
%L7B.>C
A57
MS
+LM6
GGS6GGS6
+'6 *A
+S*6MSCB@L7
.bis
$*S
MS
>m
.bis
6
$SC"6
.
Gb
i1ure &?( +osition o the $SS in the GSM 6etwork
*he $SS provides a brid1e between the iFed part and the wireless part in the +LM6
network< connects the MS or communications directly via the wireless interace and
connects the MSC o MSS#
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G+7S A'GA +rinciples
i1ure & ?4shows the basic GSM network structure#
$SC *7.> MSCB@L7
SMC
GMSC
.>C
59: A57
%L7
+S*6
5S'6
+'6
$*S
MS
$*S
MS
i1ure &?4 GSM 6etwork Structure
*he meanin1 o each name is as ollows:
MS: Mobile Station
$*S: $ase *ransceiver Station
$SC: $ase Station Controller
*7.>: *ranscodin1 and 7ate .daptation >nit
59: 5nterworkin1 unction
A57: Auipment 5dentity 7e1ister
MSC: Mobile Switchin1 Center
@L7: @isitor Location 7e1ister
GMSC: Gateway MSC
%L7: %OMA Location 7e1ister
.>C: .uthentication Center
SMC: Short Messa1e Center
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) G+7S and A'GA
+S*6: +ublic Switched *elephone 6etwork
5S'6: 5nte1rated Services 'i1ital 6etwork
+'6: +ublic 'ata 6etworks
. GSM di1ital mobile communication system is composed o the Mobile Switchin1
System 2MSS3< $ase Station Subsystem 2$SS3< Operation Maintenance Sub?system
2OMS3 and Mobile Station 2MS3# *he ollowin1 introduces the unctions o each part#
&.( Mo$ile Switc"ing Sste# ,MSS-
6SS perorms switchin1 unction and database or mana1ement o user data < mobilityand security#
*he MSS consists o such entities as the mobile switchin1 center 2MSC3< home location
re1ister 2%L73< visitor location re1ister 2@L73< euipment identity re1ister 2A573C3 and short messa1e center 2SMC3#
MSC: .s the core o the GSM< the MSC implements the switchin1 unction< that
is< accomplishes the communication connection between the +LM6 subscribers
and the subscribers in other networks# 5t implements the unctions such as the
pa1in1 access o +LM6 subscribers< channel assi1nment< call connection< traic
control< billin1< and base station mana1ement# 5t provides interaces to other
unctional entities< interaces with other networks< and interaces or connectin1
with other MSCs#
%L7: *he central database o the system# 5t stores all subscriber?related
inormation< includin1 roamin1 authority< basic services< supplementary services
and current location inormation# 5t provides routin1 inormation or MSC or the
purpose o call setup# .n %L7 may cover multiple MSCs or even the whole
mobile network#
@L7: @L7 stores inormation o all subscribers in the covera1e< and provides
conditions or establishin1 call connections or the re1istered mobile subscribers#
.s a dynamic database< the @L7 must eFchan1e lar1e volume o data with the
%L7 to ensure data validity# 9hen a subscriber leaves the controllin1 area o a
@L7< it re1isters in another @L7# *he ori1inal @L7 deletes the temporary records
o that subscriber# *he @L7 is always inte1rated with the MSC physically#
.>C: . strictly protected database that stores subscriber authentication
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G+7S A'GA +rinciples
inormation and encryption parameters# *he .>C and %L7 are inte1rated
physically#
A57: Stores parameters related to the mobile station euipment# 5t can identiym interace#
5n addition< the $SS also comprises the *7.># Located between the $SC and the MSC perorms the conversion between ") bitBs 7+A?L*+ codes and )( bitBs .
law +CM codes#
&. Operation 0 Maintenance S%$sste# ,OMS-
*he OMS reers to the operation ! maintenance part o the GSM system# .ll unctional
units in the GSM system can be connected to the OMS via respective networks# *he
OMS perorms such unctions as monitorin1 various unctional units in the GSM
network< issuin1 status report< and dia1nosin1 aults#
*he OMS consists o two parts: Operation ! Maintenance Center System 2OMC?S3
and OMC?7adio 2OMC?73# *he OMC?S serves the 6SS< while the OMC?7 serves the
$SS#
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) G+7S and A'GA
&. Mo$ile Station ,MS-
.s the subscriber euipment in the GSM< the MS can be vehicle installed or handportable# *he MS consists o mobile terminals and Subscriber 5dentity Module 2S5M3
card#
*he mobile terminal is in char1e o voice si1nal processin1 and radio transceivin1#
*he S5M stores all inormation reuired or identiyin1 a subscriber and security
inormation< preventin1 unauthoriEed user access# . mobile terminal can not 1ain
access to the GSM network without an S5M card#
&.2 GSM S%ste nuer
&.2.1 Mo$ile s%$scri$er 3SD) n%#$er ,MS3SD)-
MS5S'6 number is the number dialed by caller while callin1 certain subscriber in
di1ital public terrain celluar mobile communication network# 5ts number
comprises o:
State 6o# %ome valid 5S'6 number
%ome Mobile 5S'6 number
China code number is 8)#
*he structure or valide 5S'6 number in China is:
6"6&6-
Mobile service number
%"%&%-
%L7 5'
.$C'
Mobile number
%ome valid 5S'6 number
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G+7S A'GA +rinciples
'omestic valid 5S'6 number is a number with "0 di1its#
"# Mobile service access number 26"6&6-3
*o identiy dierent mobile systems< mobile service access number is "-4?"-/ or
current post and telecom; "-0 or China >nicom#
%L7 identiication number 2%"%&%-3
%"%& in %L7 identiication number is allocated uniormly by state; %- is
assi1ned by dierent provinces# One %L7 can contain one or more %"%&%-numbers#
-# Mobile subscriber number 2.$C'3
.$C' is mobile suscriber number in each %L7< automatically assi1ned by
dierent %L7s#
&.2.& 3nternational Mo$ile S%$scri$er 3dentit ,3MS3-
5MS5 is the only one number to identiy a mobile subscriber in +LM6< composed o "4
di1its#
MCC M6C MS56
5nternational mobile number
%ome mobile number
MCC N mobile country code< composed o - di1its< to uniuely identiy the country or
mobile subscriber# China is ()0#
M6C N mobile network code< composed o & di1its< to uniuely identiy the mobile
network or mobile subscriber# GSM +LM6 network is 00 or post and telecom ministrynicom is 0"#
MS56Mobile subscriber identiication number< a number with "0 di1its< such as
%"%&%-/# 9here< %"%&%- is same as %"%&%- in MS5S'6; / represents
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) G+7S and A'GA
GSM/00M%; is subscriber number#
5MS5 is used to all si1nalin1 in GSM mobile communication network< saved in %L7plink and 'ownlink Oset o *C%
rom the above description< it can be concluded that on 0:
*S0: a lo1ical control channel< with repeat cycle o 4" timeslots#
*S": a lo1ical control channel< with repeat cycle o "0& timeslots#
*S&: a lo1ical service channel< with repeat cycle o &) timeslots#
*S- to *S,: lo1ical traic channels< with repeat cycle o &) timeslots#
*he *S0 to *S, o other 0 P 6 are all traic channels#
*he channel coni1uration adopted by *A or common cells is as ollows:
6umber o carrier reuencies " & - ( 4 ) ,
6umber o control channels " & & & - - -
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G+7S A'GA +rinciples
6umber o service channels , "( && -0 -, (4 4-
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Basic Service and Signaling Process
Knowledge points
*his section introduces GSM terminal start< position re1isterBupdate< service call and
handover service implementation and si1nalin1 interaction process#
.1 Mo$ile s%$scri$er state
.1.1 MS starts8 networ* does 9+ttac"9 #ar*s on it
*hat is< commonly used 5MS5 attachment< divided into the ollowin1 three cases:
"# 5 MS is started irstly: no L.5 in S5M card< MS transmits =location update
reuest= messa1e to MSC< inorm GSM system this is a new subscriber in this
location area# MSC transmits =location update reuest= to %L7 based on 5MS5
number sent by this subscriber< %L7 records MSC number that sends reuest< and
correspondin1 @L7 number< and send MSC =location update acceptance=
messa1e# >p to now< MSC considers the MS is activated< do attachement mark on
correspondin1 5MS5 or this subscriber< then send =location update validation=
messa1e to MS< and S5M card o this MS records this location area identiication#
5 MS is not irstly started< but start ater shutdown< L.5 accepted by MS is not
consistent with ori1inal L.5 in its S5M card< MS immediately sends =location
update reuest= to MSC< @L7 shall jud1e whether ori1inal L.5 is the ori1inal
location in service area#
5 jud1ement is airmative< MSC only reuires chan1e ori1inal L.5 code in userS5M card to new L.5 code#
5 it is ne1ative< MSC sends =location update reuest= to %L7 based on the
inormation in 5MS5 number or this subscriber< %L7 records the MSC number to
send reuest into database< then return =location update acceptance=# MSC does
=attachment= mark or user 5MS5< and send =location update acknowled1ement=
messa1e to MS< and MS chan1es ori1inal L.5 code in S5M card to new L.5 code#
9hen MS starts a1ain< the received L.5 is consistent with that saved in ori1inal
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S5M card: at this time< @L7 does =attachment= mark or this subscriber#
.1.& MS s"%tdowns8 separated !ro# networ*.
.ter MS powers o< MS sends separation processin1 reuest to MSC< MSC inorms
@L7 to do =separation= marks or this MS on correspondin1 5MS5 ater receivin1 the
reuest# .t this time< %L7 doesnDt 1et the notiication that this subscriber has detach rom
the network# 9hen this subscriber is pa1ed< %L7 reuests MS76 rom visitor
MSCB@L7< and then @L7 inorms %L7 this subscriberDs MS power o#
.1.( MS B%s
.t this time< assi1n a service channel to transmit voice or data or this MS< and label this
subscriber as =busy= on subscriber 5S'6#
.& 4ocation :pdate
9hen an MS moves into another location area< it will ind that the received L.5 diers
rom the ori1inal one stored in the S5M card and then re1isters the new one# *his process
is location update process that is initiated by the MS# *here are two cases or location
update:
"# Location area o MS is chan1ed< but still at same MSC oice;
MS transers rom one MSC oice to the other MSC oice#
.&.1 4ocation %pdate at a MSC o!!ice
5 location is updated at a MSC oice< %L7 doesnDt participate in location update
process# Location update at same oice is as shown in :
$SC
&
"
- (
MSCB@L7
L.5
"
L.5
&
M
S
M
S
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) G+7S and A'GA
i1ure (#&?/ Location >pdate at Same MSC Oice
Location update at same MSC oice is simple< allin1 into the ollowin1 our steps:
9hen MS roams to a new location area< it is ound received L.5 is not consistent with
that saved in S5M card throu1h analysis< then a location update reuest is sent to current
base station controller 2$SC3#
5 $SC receives location update reuest rom MS< it sends a location update reuest to
MSCB@L7#
@L7 modiies the data or this MS< chan1es the L.5 to current L.5< then sends a
response messa1e to $SC#
$SC sends a response messa1e to MS< and MS chan1es L.5 saved in its S5M card to
current L.5# So the location update process at same MSC oice is completed#
.&.& 3ntero!!ice 4ocation :pdate
9hen mobile subscriber roams rom a MSC oice to the other< you shall do interoice
location update# .t this time< %L7 shall participate in location update process< as shown
in i1ure (#& ?"0:
"# Location update between dierent MSCs is more complicated than that at same
MSC# *o more conveinient description< ori1inal MSC oice or subscriber is
MSC"< roamed MSC oice is MSC 5n the i1ure< $SC is omitted< but it also will
be mentioned durin1 description< $SC and MSC are called as $SC" and $SC&+' 7ATAS* 56'
>.
S.$M
5MM .SS5MM .SS CM'
C% .C* .C
C% .C*
C% 7T'C% 7AT
MS $*S $SC MSC
'*.+LOC >+' .CCA+*
i1ure (#(?"- Location >pdate +rocess o MS
*he MS sends a C% 7AT 2Channel 7euest3 messa1e throu1h the 7.C% to the $*S#
>pon receivin1 the C% 7T' 2Channel reuired3 messa1e< the $*S processes it and then
sends it to the $SC#
.ter receivin1 the C% 7AT messa1e< the $SC sends a C% .C* messa1e to the $*S to
activate the S'CC%# .ter activatin1 the channel< the $*S returns a C% .C* .C
messa1e#
*he $SC sends the 5MM .SS CM' to the $*S# >pon receivin1 the messa1e< the $*S
sends the 5MM .SS throu1h the .GC% to the MS# 9hen receivin1 the messa1e< the MS
sends the S.$M# *he $*S sends the >. to the MS#
.t the same time< the $*S sends a channel establishment indication 2AS* 56'3 to the
$SC< containin1 a reuest to update the mobile phone location# *he $SC orwards the
location update reuest to the MSC 2LOC >+' 7AT3 via C7# .s receivin1 the reuestp to now< the S'CC% has been established between the mobile phone and the $*S#
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) G+7S and A'GA
*he location update messa1e is transmitted to the MSC over S'CC%< and the MSC
sends a location update acceptance messa1e 2LOC >+' .CCA+*3 to the mobile phone
ater perormin1 an optional encryption#
*he MSC sends a Clear CM' messa1e to the $SC# *he $SC returns a Clear COM
messa1e to the MSC# Meanwhile< the $SC sends the $*S a C% 7AL messa1e to release
the S'CC% and a 'A.C* S.CC% messa1e to deactivate the S.CC%#
*he $*S sends a C% 7AL messa1e to the MS# *he MS reuests the $*S to release radio
link 2'5SC3# *he $*S returns the >. and reports the channel release indication to the
$SC#
*he $SC sends a 7 C%L 7AL messa1e to the $*S# *he $*S returns a 7 C%L 7AL
.C messa1e# *he radio channel is released#
..& 3MS3 Detac" Process
i1ure (#( ?"( shows the 5MS5 detach procedure#
7: C% 7AL .C
7: C% 7AL
7AL 56'>.
'5SC'A.C* S.CC%
'7C% 7ALC% 7AL
C7A:
C75MS5 'A*.C%AS* 56'
>.
S.$M
5MM .SS5MM .SS CM'
C% .C* .C
C% .C*
C% 7T'C% 7AT
MS $*S $SC MSC
i1ure (#(?"( 5MS5 'etach +rocess
*o power o a mobile phone< an S'CC% channel should be established irst# *hen a
power?o messa1e is sent to the MSC over S'CC% 25MS5 'A*.C%3# >pon receivin1
the messa1e< the MSC releases the S'CC%#
..( Mo$ile;Originated Call and Called Part On;"oo* Process
i1ure (#( ?"4 shows the mobile?ori1inated call and the called party on?hook process#
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G+7S A'GA +rinciples
9hen a mobile subscriber ori1inates a call< the S'CC% is established irst< and then a
reuest or the *C% is sent throu1h the S'CC% to the MSC#
7 C% 7AL .C
7 C% 7AL
7LC
7LS'
C% 7AL
'5SC
>.7 C% 7AL
7 C% 7AL .C
7AL 56'
'A.C* S.CC%
'7C% 7AL
AS* 56'
.SS COM'*".SS COM
'*":.SS 7AT
'*"C5+% MO'A CM'
C% .C* .C
C% .C*
+% CO6* CO6
>.
S.$M
+% CO6* 7AT
'7.SS CM'.SS CM'
'*"Clear COM
'*"Clear CM'
'*"C5+% MO'A COM'5C5+% MO'A COM
C5+% MO'A COM
C5+% MO'A CM'A6C7 CM'
CC
C7CM SA7@ 7ATAS* 56'
>.
S.$M
5MM .SS5MM .SS CM'
C% .C* .C
C% .C*
C% 7T'C% 7AT
MS $*S $SC MSC
'*.+:SA*>+
'*.+:C.LL +7OC
'5.SS COM
'*.+.lertin1
'*.+Connect
'*.+Connect .C
'*.+'isconnect
'*.+7elease
'*.+7elease COM
'*.+:CM SA7@ .CC+
i1ure (#(?"4 Mobile?Ori1inated Call and Called +arty On?hook +rocess
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) G+7S and A'GA
*he MSC sends an .ssi1nment 7euest messa1e to the $SC# .ter receivin1 the
messa1e< the $SC sends an 5MM .SS CM' messa1e to the MS# *he MS establishes a
*C% with the $*S# *he $*S sends a channel establishment indication< completes
immediate assi1nment< and release the S'CC%#
*he MSC sends a rin1?back tone to the mobile phone over the established *C%# . call
session is set up by connection establishment and connection conirmation#
9hen the called hooks on< the MSC sends a disconnection messa1e to the mobile phone#
*hen the mobile phone releases the *C% and the MSC replies with a release
acknowled1ement to complete the *C% release process#
.. Mo$ile;'er#inated Call and Calling Part On;"oo* Process
i1ure (#( ?") shows the mobile?terminated call and the callin1 party on?hook process#
*o call a mobile phone< the MSC initiates a pa1in1 messa1e to the mobile phone< which
establishes an S'CC% upon receivin1 the pa1in1 messa1e# *hen the S'CC% is released
ater a *C% has been established# *he call setup is accomplished over the *C%#
9hen the call is ended< the *C% is to be released#
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G+7S A'GA +rinciples
>'*+.G+.G CM'+.G 7AT
7 C% 7AL .C
7 C% 7AL
7LC
7LS'
C% 7AL
'5SC
>.7 C% 7AL
7 C% 7AL .C
7AL 56'
'A.C* S.CC%
'7C% 7AL
AS* 56'
.SS COM'*".SS COM
'*":.SS 7AT
'*"C5+% MO'A CM'
C% .C* .C
C% .C*
+% CO6* CO6
>.
S.$M
+% CO6* 7AT
'7.SS CM'.SS CM'
'*"Clear COM
'*"Clear CM'
'*"C5+% MO'A COM'5C5+% MO'A COM
C5+% MO'A COM
C5+% MO'A CM'A6C7 CM'
CC
C7+.G 7ASAS* 56'
>.
S.$M
5MM .SS5MM .SS CM'
C% .C* .C
C% .C*
C% 7T'C% 7AT
'*.+:SA*>+
'*.+:C.LL CO6
'5.SS COM
'*.+.lertin1
'*.+Connect
'*.+Connect .C
'*.+'isconnect
'*.+7elease
'*.+7elease COM
$SC MSC$*SMS
i1ure (#(?") Mobile?*erminated Call and Callin1 +arty On?hook +rocess
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) G+7S and A'GA
.. 3nter;cell Handover 6low
i1ure (#( ?", illustrates the inter?cell handover low#$ased on the measurement reports ori1inated rom the mobile phone continuously< the
$SC jud1es whether it is necessary to perorm handover#
9hen intra?cell handover is necessary< the mobile phone is located in the source cell
$*S"# *he $SC activates a *C% in the tar1et cell $*S&< and sends a handover command
to the mobile phone# *he mobile phone is switched to the *C% in $*S& and completes
the handover process#
.s the intra?cell handover is completed< the $SC inorms the MSC o the event and
releases the *C% in the source cell#
'*"%O +A7:
%O CM'
C% .C*
MA.S 7A+
7: C% 7AL .C
7: C% 7AL
'5%O COM
AS* 56'
%O 'A*
C% .C* .C
MS $*S" $*S& $SC MSC
MA.S 7AS
'7%O CM'
%O .CCASS
+% 56:O
S.$M
>.
%O COM
i1ure (#(?", 5nter?cell %andover +rocess
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assembled into a (4)?bit messa1e# *hen come the steps o channel decodin1< checkin1
and correctin1 errors in the transmission# inally< the bitstreams 1enerated by the decoder
are decoded< and converted to analo1 voices#
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) G+7S and A'GA
so that they are suitable or transmission in a serial port manner# $esides they also show
very little delay# *he coded n code elements are not only related to k inormation code
elements o this packet< but also to inormation code elements in the precedin1 26?"3plink and 'ownlink Oset o *C%
Supposin1 an MS occupies *S&< and call si1nals tend to shit away rom the $S< a
messa1e rom the $S will delay in reachin1 the MS# Meanwhile< the response messa1e
ori1inated rom the SM will also delay in reachin1 the $S# 5 nothin1 is done to iF the
problem< the messa1e sent rom *S& in the MS will eventually overlap with another
callin1 messa1e received in *S- in the $S# 5t is important to monitor the time when a call
reaches the $S# .s the distance between the MS and the $S chan1es< the system issues
instructions to the MS notiyin1 it o the transmission time lead# *his process is called
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G+7S A'GA +rinciples
adjustment o time lead#
.ter a speciic connection has been established< the $*S measures the time shitbetween the pulse *Ss and the received MS *Ss# 5t calculates the appropriate time lead
based on the measured time shit< and notiies the MS o it on S.CC% at certain
reuency#
. 6re7%enc Hopping 'ec"nolog
Spread spectrum techniues< includin1 direct spread 2'S3 and reuency hoppin1 2%3sually< the % number should be 1reaterthan three# 5 reuency diversity is also available or the % system and the messa1e is
decided more eectively via a lar1e number decision law ater several 1roups o %s
simultaneously transmit one messa1e< more subscribers can work at the same time with
least mutual intererence#
*he reuency hoppin1 comprises baseband hoppin1 and 7 hoppin1#
$ase band % keeps the transmittin1 and receivin1 reuencies o each carrier unit
unchan1ed< but sends the rame unit transmittin1 data to dierent carrier units at
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G+7S A'GA +rinciples
dierent 6 2rame 6umber3 moments#
%owever< radio reuency hoppin1 is to control the reuency synthesiEer o eachtransceiver< makin1 it hop in each time slot accordin1 to dierent schemes#
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GPRS and EDGE
Knowledge points
*his section describes evolution o GSM technolo1ies: basic concept< network
structure< radio channel< and basic application o G+7S and A'GA#
.1 De!inition and 6eat%re
.1.1 GPRS De!inition
G+7S: General +acket 7adio Service#
*he General +acket 7adio Service 2G+7S3 is the packet data service introduced in GSM
+hase&H# 5t provides subscribers with the end?to?end mobile data services based on
packet switchin1 and transmission technolo1ies# *he G+7S can eectively utiliEe the
radio resources and network terrestrial resources and is suitable or lon1?time small?
volume burst data services#
.1.& GPRS 6eat%res
*he G+7S has the ollowin1 eatures:
Seamless connection with 5+ network
5+ technolo1y is adopted in the core network o the G+7S< and many transmission
technolo1ies are employed in the bottom layer o the G+7S# *hus< it is easy to
implement the seamless connection with the hi1hly developed 5+ network#
%i1h rate
9ith the help o multi?slot bindin1 and hi1h?speed codin1 scheme< the G+7S
phase 5 adopts CS" and CS& codin1 schemes< and provides the access rate up to
""4 bitBs# *he G+7S phase 55 adopts CS- and CS( codin1 schemes< and provides
up the rate up to "," bitBs#
.lways online and low char1in1
*he G+7S provides the =availability or connection everywhere and the
perormance o always online=< oerin1 new means or mobile subscribers to
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access the 5nternet and 5ntranet rapidly# Once a G+7S terminal is powered on and
connected with the G+7S network< it can maintain the online status all the way#
*he subscriber can receive and send inormation at any time without the dial?up
process reuired in circuit switchin1# .s lon1 as the G+7S terminal does not
transmit data< it will not occupy network and radio resources# *hus< the mobile
subscribers can beneit rom the low char1in1# *hat is< the mobile subscribers can
stay online as lon1 as possible without botherin1 the prohibitive bill#
Mature technolo1y
*he G+7S provides solutions to implement data services in the mature GSM
technolo1ies and current networks# 5t can save investment and make uick return#
.1.( EDGE De!inition
A'GA: Anhanced 'ata 7ate or GSM Avolution#
Anhanced 'ata 7ate or GSM Avolution 2A'GA3 is a kind o technolo1y or transition o
GSM to -G# 5t mainly adopts a new modulation mode in the GSM system includin1 most
advanced multislot operation and 8+S modulation technolo1y# 8+S technolo1y makes
the si1nal space o GMS modulation technolo1y in eFistin1 GSM network eFtend rom
& to 8 so that each symbol contains ( times o previous messa1es#
*he reason why A'GA is called the solution or transition o G+7S to -G mainly lies in
such technolo1y can ully utiliEe eFistin1 GSM resources includin1 eFistin1 GSM
reuency and most o eFistin1 GSM euipment# *his technolo1y only makes small
chan1es to the network sotware and hardware part# 5n this way< operators can provide
mobile subscribers with such wireless multimedia services as 5nternet browsin1< video
teleconerence and hi1h?speed email transer< that is< individual multimedia
communication services can be oered to subscribers beore the -G mobile network is
put into commercial use# .s A'GA is the transition technolo1y between eFistin1 &G
mobile network and -G network< it is also called G 2,4 1eneration3 technolo1y#
.1. EDGE 6eat%res
5n terms o protocol< the A'GA technolo1y mainly aects the $SS 2i#e# $*S and $SC#3
o the wireless access part in the GSM system< but does not aect eFistin1 GSM core
network and network applications< and the interaces between the $SS and the MSC and
SGS6 in the eFistin1 system will be kept# *hus< network operators can utiliEe eFistin1
wireless network euipment to maFimum eFtent to provide subscribers with individual
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) G+7S and A'GA
multimedia communication services beore the -G mobile network is put into
commercial use# A'GA has the ollowin1 eatures:
A'GA neither chan1es GSM or G+7S network structure nor introduces new
network element< but only up1rades the $SS#
5n terms o wireless interaces< A'GA does not chan1e the GSM channel structure.LCOM< and
orean Samsun1 ! LG always canDt 1et more commercial opportunity#
rom evolution mode< due to GSM scale advanta1es< it enables more countries preer
9C'M. or *'?SC'M. evolution scheme# G transitional technolo1y or this
evolution scheme is G+7S< so G+7S technolo1y is outstandin1# Currently< there are over
"00 operators that open G+7S commerce system< trial commerce system< or
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) G+7S and A'GA
eFperimental system 1lobally# G+7S technolo1y has been eFtensively deployed in 1lobal
GSM network# Some amous telecom euipment manuacturers< such as 6okia< Siemensnder the packet switchin1 mode< the +'*C% bears subscriber data# 5t is
allocated temporarily to a speciic MS or a 1roup o MSs 2under the +*M?M
mode3# >nder multi?slot mode< an MS can use several +'*C%s concurrently#
$ecause dierent lo1ical channels can be multipleFed on a physical channel< a
+'*C% can bear 0 to &"#( bitBs pure data rate 2includin1 7LC header3# 'ierent
rom the CS service< all the +'*C%s are unidirectional# *he MS uses the
+'*C%B> to send packet data to the network and uses the +'*C%B' to receive
packet data rom the network#
(# +acket dedicated control channel
*he +.CC% transmits si1nalin1 inormation< such as conirmation and power
control# 5t also carries resource allocation and reallocation messa1es< which can be
used to allocate +'*C% capacity or add new +.CC% in the uture# 'urin1 packet
transmission< the MS can enter the CS mode throu1h +.CC% pa1in1# *he +.CC%
is dynamically allocated to the physical channel which carries +'*C%# 5t is a
bidirectional channel#
+*CC%B> serves to transer random access burst pulse and estimate the time lead
o an MS in packet transmission mode#
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G+7S A'GA +rinciples
+*CC%B' is used to correct the time lead o several MSs# One +*CC%B'
corresponds to several +*CC%B>#
.(.( Mapping o! 4ogical C"annel Co#$ination in t"e P"sical C"annel
.ter G+7S is added< three lo1ical channel combinations will be added:
+$CC% H +CCC% H +'*C% H +.CC% H +*CC%
+CCC% H +'*C% H +.CC% H +*CC%
+'*C% H +.CC% H +*CC%
9here< +CCC% N ++C% H +7.C% H +.GC% H +6C%#
'ierent lo1ical channels may appear on the same +'C%# *he physical channel is
shared in unit o blocks# *hat is< on a +'C%< the type o the lo1ic channel that the block
belon1s to varies rom one block to another# Channel type is the messa1e type 5'
contained in the head o a block 2eFcept or +7.C%3#
.(.(.1 Mapping o! :plin* C"annel
"# Mappin1 o the +'*C%B> and +.CC%B>
or each +'C% allocated to the MS< the MS will be allocated with an >S2>plink State la13# *he network uses the >S to control the multipleFin1 o radio
blocks o dierent MSs in the uplink +'C%# *he >S controls the timeslot use o
the MS# 5t is used in the dynamic and eFtended dynamic medium access modes#
*he three?bit >S is located on the header o each downlink radio block< and can
orm ei1ht states used or uplink transmission multipleFin1# 5n the +CCC%< one
>S value is used to mark the +7.C% 2>S N idle3< and other values are reserved
or use by seven dierent MSs 2>S N 7"B7& R 7,3# 9hen a +'C% is not the
+CCC%< the ei1ht >S values are all used to reserve uplinks or ei1ht dierent
MSs# 9hen an MS without a >S uses the uplink< a >S value can be used to
prevent conlict o the uplink channel# *he >S is directed to the neFt uplink radio
block#
9hen the MS inds its own >S on the header o a $ 2$F N $0R$""3 downlink
block o a +'C%< the MS will be able to use $H" 2]N ""3 or $0 2when N""3
uplink block on this +'C% # 5 the network permits< the MS can also use three
consecutive blocks 2there are our blocks in total3#
*he +.CC%B> correspondin1 to the +'*C%B' will be determined by the network
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) G+7S and A'GA
in the pollin1 mode#
Mappin1 o the +*CC%B>
9hen the MS obtains +'*C% allocation rom a certain +'C%< it will also obtain
+*CC%B> allocation rom the +'C%# *he cycle o the +*CC%B> is ei1ht 4&?
multirames< includin1 ") +*CC%B> sub?channels 20R"43# *he +*CC%B> sub?
channel 6o# possessed by an MS is determined by the time advance indeF 2*.53
obtained by the MS in resource allocation< 5t is as shown in i1ure )#- ?&)#
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G+7S A'GA +rinciples
$0P$""N7adio blocks
5dle rames are numbered rom " to -" ^odd numbers_
+*CC% rames are numbered rom 0 to -0 even numbers_
4&?multirame number nH,:
uplink *.5N"( *.5N"4
downlink *.?messa1e ( *.?messa1e (
$0 $" $& $- $( $4 $) $, $8 $/ $"0 $"" -"-0&/&8
$0 $" $& &( $- $( $4 &4 $) $, $8 &) $/ $"0 $"" &,
4&?multirame number nH):
uplink *.5N"& *.5N"-
downlink *.?messa1e ( *.?messa1e (
$0 $" $& &0 $- $( $4 &" $) $, $8 && $/ $"0 $"" &-
4&?multirame number nH4:
uplink *.5N"0 *.5N""
downlink *.?messa1e - *.?messa1e -
$0 $" $& ") $- $( $4 ", $) $, "8 $/ $"0 $"" "/
4&?multirame number nH(:
uplink *.5N8 *.5N/
downlink *.?messa1e - *.?messa1e -
$8
downlink *.?messa1e " *.?messa1e "
$0 $" $& 0 $- $( $4 " $) $, $8 & $/ $"0 $"" -
4&?multirame number n:
uplink *.5N0 *.5N"
$0 $" $& ( $- $( $4 4 $) $, $8 ) $/ $"0 $"" ,
4&?multirame number nH":
uplink *.5N& *.5N-
downlink *.?messa1e " *.?messa1e "
4&?multirame number nH&:
uplink *.5N( *.5N4
downlink *.?messa1e & *.?messa1e &
$"$0 $& 8 $- $( $)/$4 $, $8 "0 $/ $"0 $"" ""
$0 $" $& "& $- $( $4 "- $) $, $8 "( $/ $"0 $"" "4
4&?multirame number nH-:
uplink *.5N) *.5N,
downlink *.?messa1e & *.?messa1e &
i1ure )#-?&) Mappin1 o +*CC% on the +hysical Channel
-# >plink +CCC%: mappin1 o +7.C%
.s described above< on the +'C% with +CCC%< i the >S is marked as idle< it
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) G+7S and A'GA
indicates that the correspondin1 downlink block is the +7.C%# *he +7.C% can
be mapped in a iFed manner# *he number o +7.C% blocks iFedly allocated on
a +CCC% is determined by the system broadcastin1 parameter
K$S[+7.C%[$LS# 5ts relationship with the speciic blocks is determined by
the block occupyin1 order described above#
.(.(.& Mapping o! Downlin* C"annel
"# Mappin1 o the +'*C%B' and +.CC%B'
*he MS interprets every downlink block on the allocated +'C%< and determines i
the block is its +'*C%B' and +.CC%B' accordin1 to the *5#
*he *$ is a physical connection used by two 77 entities to transmit LLC +'>
in a unidirectional manner on the packet data wireless channel# *his parameter is
used in the LLC rame transmission seuence o the same timeslot in the same cell
to replace the MS identiication in the 7LCBM.C layer# 5t is a wireless resource
assi1ned to one or multiple +'C%s# 5t transmits some 7LCBM.C blocks carryin1
one or multiple LLC +'>s# One *$ is temporary and only kept in the data
transmission period 2that is< until there are no 7LCBM.C blocks or transmission
or< in the 7LC acknowled1ement mode< all 7LCBM.C blocks are acknowled1ed
to be received by the receiver3#
or each *$< the network allocates a *5# or concurrent *$s in each direction< other packet control channels adopt CS?"# or the packet access
pulse on +7.C% and +*CC%B>< there are 8?bit and ""?bit codin1 schemes# i1ure )#-
?&,andi1ure )#- ?&8shows the codin1 process o our dierent codin1 schemes#
>S: $CS
7adio block
rate "B& convolutional codin1
puncturin1
(4) bits
i1ure )#-?&, Codin1 +rocess o CS?" to CS?-
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G+7S A'GA +rinciples
>S: $CS
block
code
7adio block
no codin1
(4) bits
i1ure )#-?&8 Codin1 +rocess o CS?(
.s shown in the i1ure above< the irst step o the encodin1 is to append a $lock Check
Seuence 2$CS3 to the radio block< which is used or error detection# or the CS"PCS-
codin1 schemes< the second step is to pre?encode the >S 2not or CS"3< then append (
tail bits< and perorm hal?rate convolutional encodin1< which is used or error correction#
*he last step is puncturin1 to obtain desired encodin1 rate# Arror?correction codin1 is not
perormed in CS?(#
*able )#- ?(shows the speciic codin1 process o the our channel codin1 schemes#
*able )#-?( Channel Codin1 +rocess o +'*C%*ype
%andlin1 low
CS" CS& CS- CS(
Len1th o data
source
"8( bits &," bits -"4 bits ("- bits
+acket codin1 "3 ire codin1# *he
multinomial 1enerated
is:
2'&-"3 2'",'-"3S preprocessin1< as
shown in *able "?(#-3 .dd our tail bits# *he
codin1 data len1th is &/(
bits#
"3 +acket codin1#
*he multinomial
1enerated is:
'")'"&'4"S
preprocessin1 is thesame as CS
-3 .dd tail bits# *he
codin1 data len1th is
--8 bits#
"3 +acket codin1# *he
multinomial
1enerated is:
'")'"&'4"S
preprocessin1< asshown in *able "?4#
-3 .dd tail bits# *he
codin1 data len1th is
(4) bits#
Convolutional
code
"3 Convolutional codin1
with a "B& code rate# *he
multinomial 1enerated is
G0"'-'(< G"
"''-'(
&3 6o hole
"3 Convolutional codin1
with a "B& code rate# *he
multinomial 1enerated is
G0"'-'(< G""
''-'(
&3 Cut a code o "-& bits
"3 Convolutional
codin1 with a "B&
code rate# *he
multinomial
1enerated is: G0"
'-'(< G""
6one
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) G+7S and A'GA
*ype
%andlin1 low
CS" CS& CS- CS(
with the hole# *he positiono the hole:
C 2-H(Fk3< kN-< R< "()
and k/< &"< --< (4< 4,< )/