cellular network overview

8/19/2019 Cellular Network Overview

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Mobile Cellular Network

Overview


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Cellular Network Basics

There are many types of cellular services; before delving intodetails, focus on basics (helps navigate the “acronym soup”)

Cellular networktelephony is a radio!based technology; radiowaves are electromagnetic waves that antennas propagate

"ost signals are in the #$% "&', %% "&', #%% "&', and

%% "&' fre*uency bands

Cell phones operate in this frequency

range (note the logarithmic scale)


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Cellular Network

+ase stations transmit to and receive from mobilesat the assigned spectrum

"ultiple base stations use the same spectrum (spectral reuse)

The service area of each base station is called a cell

ach mobile terminal is typically served by the-closest. base stations

&ando/ when terminals move


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Cellular Network Generations

0t is useful to think of cellular1etworktelephony in terms of generations2

%32 +riefcase!si'e mobile radio telephones

32 Analog cellular telephony432 Digital cellular telephony

532 High-speed digital cellular telephony (includingvideo telephony )

632 07!based “anytime, anywhere” voice, data, andmultimedia telephony at faster data rates than 53(to be deployed in 4%484%$)


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Evolution of Cellular Networks

3 43 53 6349$3


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The Multiple Access Problem

The base stations need to serve manymobile terminals at the same time (bothdownlink and uplink)

:ll mobiles in the cell need to transmit tothe base station

0nterference among di/erent senders and

receiverso we need multiple access scheme


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Multiple Access Schemes

•


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re!uenc" #ivision MultipleAccess

ach mobile is assigned a separate fre*uency channel for theduration of the call

u>cient guard band is re*uired to prevent ad?acent channelinterference

@sually, mobile terminals will have one downlink fre*uency bandand one uplink fre*uency band

=i/erent cellular network protocols use di/erent fre*uencies


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Time #ivision Multiple Access

Time is divided into slots and only one mobile terminaltransmits during each slotBike during the lecture, only one can talk, but others may take the oor in turn

ach user is given a speciDc slot9 1o competition in cellularnetwork

@nlike Carrier ensing "ultiple :ccess (C":) in Ai


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Co$e #ivision Multiple Access

@se of orthogonal codes to separate di/erenttransmissions

ach symbol of bit is transmitted as a larger

number of bits using the user speciDc code 8preading

+andwidth occupied by the signal is much larger than theinformation transmission rate

+ut all users use the same fre*uency band togetherErthogonal amongusers


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GSM

:bbreviation for 3lobal ystem for "obileCommunications

Concurrent development in @: andurope in the #%.s

The uropean system was called 3"and deployed in the early %.s


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GSM Services

Foice, 59 k&'hort "essage ervice (")#$ 3" standard that allows messages of at most G%chars9 (incl9 spaces) to be sent between handsets and otherstationsEver 496 billion people use it; multi!billion H industry

3eneral 7acket Iadio ervice (37I)3" upgrade that provides 07!based packet data transmissionup to 6 kbps@sers can “simultaneously” make calls and send data

37I provides “always on” 0nternet access and the "ultimedia"essaging ervice ("") whereby users can send rich teJt,audio, video messages to each other7erformance degrades as number of users increase37I is an eJample of 49$3 telephony 8 43 service similar to53


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GSM Channels

7hysical Channel2 ach timeslot on a carrier is referred toas a physical channel

Bogical Channel2 Fariety of information is transmittedbetween the " and +T9 =i/erent types of logicalchannels2

Tra>c channel

Control Channel

#ownlink

%plink

Channels


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GSM re!uencies

Eriginally designed on %%"&' range, nowalso available on #%%"&', #%%"&' and%% "&' ranges9

eparate @plink and =ownlink fre*uenciesEne eJample channel on the #%% "&' fre*uencyband, where I< carriers are space every 4%% "&'

&'&( M)* &++( M)*&+(, M)*&'+, M)*

%P-.N/ 0E1%ENC.ES #O2N-.N/ 0E1%ENC.ES

%P-.N/ AN# #O2N-.N/ 0E1%ENC3 SEPA0ATE# B3 4,M)5


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GSM Architecture


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Mobile Station 6MS7

" is the user.s handset and has twoparts"obile *uipment

Iadio e*uipment@ser interface7rocessing capability and memory re*uired forvarious tasksCall signalling

ncryption"

*uipment 0"0 number

ubscriber 0dentity "odule


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Subscriber .$entit" Mo$ule

: small smart card

ncryption codes needed to identify the subscriber

ubscriber 0"0 number

ubscriber.s own information (telephone directory) Third party applications (banking etc9)

Can also be used in other systems besides 3",e9g9, some AB:1 access points accept 0" based

user authentication


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Base Station Subs"stem

Transcoding Iate and :daptation @nit (TI:@)7erforms coding between the G6kbps 7C" coding used inthe backbone network and the 5 kbps coding used forthe "obile tation (")

+ase tation Controller (+C)Controls the channel (time slot) allocation implementedby the +Tes"anages the handovers within + areaKnows which mobile stations are within the cell and

informs the "CFBI about this+ase Transceiver ystem (+T)Controls several transmittersach transmitter has # time slots, some used forsignaling, on a speciDc fre*uency


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Network an$ Switchin8Subs"stem

The backbone of a 3" network is a telephone networkwith additional cellular network capabilities

"obile witching Center ("C):n typical telephony eJchange (0=1 eJchange) whichsupports mobile communications

Fisitor Bocation Iegister (FBI): database, part of the "C

Contains the location of the active "obile tations

3ateway "obile witching Center (3"C)Binks the system to 7T1 and other operators

&ome Bocation Iegister (&BI)Contain subscriber information, including authenticationinformation in :uthentication Center (:uC)

*uipment 0dentity Iegister (0I)0nternational "obile tation *uipment 0dentity (0"0) codesfor e9g9, blacklisting stolen phones


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)ome -ocation 0e8ister

Ene database per operatorContains all the permanent subscriber information"0=1 ("obile ubscriber 0=1 number) is thetelephone number of the subscriber

0nternational "obile ubscriber 0dentity (0"0) is a $digit code used to identify the subscriber0t incorporates a country code and operator code

0"0 code is used to link the "0=1 number to thesubscriber.s 0" (ubscriber 0dentity "odule)

Charging informationervices available to the customer

:lso the subscriber.s present Bocation :rea Code,which refers to the "C, which can connect to the"9


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Other S"stems

Eperations upport ystem The management network for the whole 3" network@sually vendor dependentFery loosely speciDed in the 3" standards

Falue added servicesFoice mailCall forwarding3roup calls

hort "essage ervice Centertores and forwards the " messagesBike an !mail serverIe*uired to operate the " services


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-ocation %p$ates

The cells overlap and usually a mobilestation can -see. several transceivers(+Tes)

The " monitors the identiDer for the +Ccontrolling the cells

Ahen the mobile station reaches a new+C.s area, it re*uests an location update

The update is forwarded to the "C,entered into the FBI, the old +C isnotiDed and an acknowledgement ispassed back


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)an$o9 6)an$over7

Ahen a call is in process, the changes inlocation need special processing

Aithin a +, the +C, which knows the

current radio link conDguration (includingfeedbacks from the "), prepares anavailable channel in the new +T

The " is told to switch over to the new+T

This is called a hard hando/ 0n a soft hando/, the " is connected to two+Tes simultaneously


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0oamin8

Ahen a " enters another operatorsnetwork, it can be allowed to use theservices of this operator

Eperator to operator agreements and contracts&igher billing

The " is identiDed by the information inthe 0" card and the identiDcation

re*uest is forwarded to the homeoperator

The home &BI is updated to reect the ".scurrent location


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:G; :


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:G Overview

53 is created by 0T@!T and is called 0"T!4%%%


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Evolution from >G

IS-95 IS-136 & PDCGSM-

EDGE

GPRS

HSCSDIS-95B

Cdma2000-1xRTT

Cdma2000-1xEV,DV,DO

Cdma2000-3xRTT

W-CDMA

EDGE

TD-SCDMA

2G

3G

25G

3GPP3GPP2


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Service 0oa$map

Improved performance, decreasing cost of delivery

Typicalaverage bitrates(peak rateshigher)

WEB !"#$%'(C#")#"a*+ da*a a+%%

S*"+am'( ad#./d+#

V#+ & SMSP"+%+'+.#a*#'

xHTM !"#$%'(A))a*#' d#$'#ad'(E-ma

MMS )*"+ . /d+#

M**a%'(

3G-specific services takeadvantage of higher bandwidth

and/or real-time Qo

3G-specific services takeadvantage of higher bandwidth

and/or real-time Qo

! n"mber of mobileservices are bearer

independent in nat"re

! n"mber of mobileservices are bearer

independent in nat"re

#$%!&-&'bps

*$!+

bps

,G%.3kbps

G%&&kbps

G012

kbps

P%-*#-*a

B"#ad!a'd' $d+ a"+a

Vd+# %a"'(Vd+# *++)#'4R+a-*m+ IPm*m+da a'd (am+%

M*a%*'(

C D M A

2 0 0 0 -

E V D O

C D M A

2 0 0 0 -

E V D V

C D M A

2 0 0 0 1 x


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GSM Evolution to :G

GSM9Gkbps (onetimeslot)3" =ata:lso called C=

GSMGeneral Packet 0a$io Services=ata rates up to L $ kbps"aJ2 # timeslots used as any one time7acket switched; resources not tied up all thetime

Contention based9 >cient, but variabledelays

GP0S

)SCS#

)i8h Spee$ Circuit Switche$ #ata=edicate up to 6 timeslots for data connectionL $% kbps3ood for real!time applications c9w9 37I0ne>cient !M ties up resources, even whennothing sent1ot as popular as 37I (many skipping &C=)

E#GE

Enhance$ #ata 0ates for GlobalEvolution@ses #7K modulation5J improvement in data rate on shortdistancesCan fall back to 3"K for greaterdistancesCombine with 37I (37I) L 5#6 kbpsCan also be combined with &C=

2C#MA


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%MTS

@niversal "obile Telecommunicationsystem (@"T)@"T is an upgrade from 3" via 37I

or =3 The standardi'ation work for @"T iscarried out by Third 3eneration7artnership 7ro?ect (5377)

=ata rates of @"T are266 kbps for rural5#6 kbps for urban outdoor4%6# kbps for indoor and low range outdoor

Firtual &ome nvironment (F&)


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%MTS re!uenc" Spectrum

@"T +and

%%!4%4$ "&' and 4%!44%% "&' for 53transmission

0n the @, O%8O$$ "&' and 4%84$$ "&' willbe used instead, as the %% "&' band was alreadyused9


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%MTS Architectureobile tation

MSC.

VR

ase tation

"bsystem

GMSC

4etwork "bsystem

ACEIR HR

5ther 4etworks

#*+7 I'*+"8a+% a/+ !++' #m**+d 8#" a"*4 )")#%+%

GGSSGS

BTSBSC

#d+

BRC

RNS

6T!4

SIMME

SIMME

PST

PM

I'*+"'+*


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%MTS Network Architecture

P@"T network architecture consists ofthree domains8Core 1etwork (C1)2 7rovide switching, routing and

transit for user tra>c8@"T Terrestrial Iadio :ccess 1etwork (@TI:1)27rovides the air interface access method for usere*uipment9

8@ser *uipment (@)2 Terminals work as airinterface counterpart for base stations9 The variousidentities are2 0"0, T"0, 7!T"0, TBB0, "0=1,0"0, 0"0F


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%T0AN

Aide band C=": technology is selected for@TI:1 air interfaceAC=":

T=!C=":+ase stations are referred to as 1ode!+ andcontrol e*uipment for 1ode!+ is called as Iadio1etwork Controller (I1C)9


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:


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=G 6-TE7

BT stands for Bong Term volution

1eJt 3eneration mobile broadbandtechnology

7romises data transfer rates of %% "bps

+ased on @"T 53 technology

Eptimi'ed for :ll!07 tra>c


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A$vanta8es of -TE


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Comparison of -TE Spee$


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Ma?or -TE 0a$io Techno8ies

@ses Erthogonal


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-TE Architecture


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-TE vs %MTS

cellular network overview

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