gsm_principles_com_4.pps

7/27/2019 GSM_principles_com_4.pps

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Wireless technology is accelerating veryfast.It is quickly moving into 1G,2G,2.5G,3G,4G and NGN


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1 st Generation

The first generation of mobile cellular telecommunications systems appeared in the

1980s.The first generation used analog transmissiontechniques for traffic, which was almost entirelyvoice.There was no dominant standard but severalcompeting ones.


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Such as Nordic M obile Telephone (NMT) used inScandinavia,southern Europe etc

It comes in two variations:

o NMT-450o NMT-900

Total Access Communications System(TACS) used in UK,and middle Easterncountries.It uses 900MHz band. Advanced M obile Phone Service (AMPS ).- used in US,Australia,New Zealand.Ituses 800MHz band


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2 nd Generation

It has been introduced from the year 1992.It uses digital radio transmis-sion for traffic.The 2G networks have much higher capacity than the

first-generation systems.

GSM is by far the most successful and widely used 2Gsystem.Data rate supported : 9.6kbps to 14.4 kbpsIt uses Circuit switching


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There are several standards for 2G systems.such as-

#Global System for Mobile (GSM) communications -Designed and developed by a number of differentorganization working together.

# code-division multiple access (CDMA) IS-95 -Designed and developed by a single company,Qualcomm.

v CDMA uses different codes to separatetransmissions on the same frequency.

v IS-95 is the only 2G CDMA standard so far to beoperated commercially.v It is used in the United States, South Korea, HongKong, Japan, Singapore etc.


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Generation 2.5It has been introduced in the year 2000-2001

Generation 2.5 is a designation that broadly includes all advancedupgrades for the 2G networks

2.5G GSM system includes General Packet Radio Services(GPRS), and Enhanced Data Rates for Global Evolution (EDGE) inaddition to the 2G systems .

Data rate supported: depending on the coding scheme(CS) and theno. of time slots used( 1 up to 8)

It uses circuit switching and packet switching both

It supports the data rate up to 384 kbps


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3 rd Generation It has been introduced in the year 2001 as trialversion

It supports the data rate up to 2 mbps

Evolution of GSM and CDMA has taken them asW-CDMA(UMTS) and CDMA-2000 in thirdgeneration.

It supports both circuit switching and packet

switching


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4 th generation and NGN

This technology is expected to arrive not before the year 2010 .

It will support the data rate up to 100 mbps.

Multimedia, mobile TV,mobile broadband

wireless access etc will be possible becauseof its high band width.

It will support both circuit switching and packet switching


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GSM Overview>GSM stands for Global System for Mobile communication

>GSM Technology is one of the different types of the wirelesscommunication available in the world.

Frequency range-*Uplink Frequency: 890 Mhz 915Mhz*Downlink Frequency: 935Mhz- 960Mhz.

Modulation Technique- GMSK


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Speech is divided into 20 msec sample.Each20ms sample is encoded using 260 bits.(Thatrequires 13 kbps.)

Band width:each radio channel in the GSM systemhas a frequency bandwidth of 200khz.

Number of Channels:124 radio channel.


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GSM Network


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BSS

BSS - Controls radio link with mobile station.It consists of

BTS (Base transreceiver Station)-It defines acell and is responsible to establish the radiolink control protocol with MS.

BSC (Base Station Controller)-Controls multiple

BTSs and manages radio channel set up andhandovers.BSC is the connection betweenBTS and the MSCs.


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NSS

Network & Switching Subsystem(NSS) -Mobility management and Switching of callsbetween mobile users and between mobileand fixed network users.It consists of :MSC - is the central component of the NSS.

Operates all switching functions formobiles within its jurisdiction.Interfaces withmobile and other (Including fixed) networks.Manages the location of mobile


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Continued

Switches callsManages security features.

Controls hand over between BSCsResources managementInterworks with and manages network database.Collect call billing data and sends to Billingcenter.Collects traffic statistics for performancemonitoring.


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Continued..HLR -Contains all subscriber information for the

purposes of call control and location determination.

VLR - is only a temporary storage while theparticular subscriber is located in the geographicalarea controlled by the MSC/VLR.

AUC - Is a protected database that stores thesecurity information for each subscriber.(A copy of the secret key is stored in the SIM)


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Continued

EIR -It contains three list of IMEI number.

White list .-Valid mobile equipment in thenetwork

Grey list .- Suspected numbers

Black list -Totally barred.


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Logical ChannelsFive types of logical channels:1.Traffic Channels

* TCH - Used to carry traffic.

2.Broadcast channels.*BCCH- used to carry signaling and control info* FCCH- used to correct the frequency of Mobile* SCH- used for synchronization of the base station

3.common control channels*PCH- used to page the mobile*AGCH- used to access the signaling channel*RACH- used by MS to request for signaling channel

4.Dedicated Control Channels*SDCCH- used as signaling channel*SACCH- used to carry measurement reports*FACCH- used during handover

5.CellBroad cast channel*CBCH- used to broadcast short messages in cells


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MSISDNThe only important number for a user of GSM is thephone number i.e.MSISDN.

The MSISDN follows the ITU-T standard E.164 foraddresses as it is also used in fixed ISDN networks.

This number consists of the country code(cc) ( 91for India),the national destination code (NDC) (theaddress of the network provider ; e.,g., 9434 forBSNL WB) and the subscriber number (SN) .


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IMSI

GSM uses the IMSI for internal unique identificationof a subscriber.

The IMSI follows the ITU-T standard E.212 Numberseries.

IMSI consists of mobile country code (MCC) (e.g.,404 for India),the mobile network code (MNC) (i.e.,code of the HLR; e.g.,74 of BSNL WB),and finallythe mobile subscriber identification number (MSIN).


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Location Updating (LU)When the LU request is received by the new

VLR,authentication is performed.

If authentication is successful,the VLR checks its database todetermine whether it has a record for this MS-subscription.

When VLR finds no record for the MS,it sends a request tothe subscribers HLR for a copy of the MS -subscription.

The HLR passes the information to the VLR and updates itslocation information for the subs.The HLR instructs the old VLR to delete the information it has about the MS-subscription.


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Inbound Roamer registration -Location Update-Diagram

1. UpLoc

1. UpLoc1. UpLoc

WB BSNL

NLDHLR

UKSubscriber

GMSC

VMSC/VLR

3. ISD_resp

UK

HLRGMSC

SCCPCdPA: 44-181-123456(MGT derived fromIMSIS analysis)CgPA: 919434099995(VLR)

MAPIMSI: 234-15-123456MSC/VLR: 919434099995

SCCPCdPA: 44-181-HLRUK

CgPA: 919434099995(VLR1 )

3. ISD_resp

2. ISD

4. UPL_resp

SCCPCdPA: 919434099995(VLR) CgPA: 44-181-HLRofUK1

MAPIMSI: 234-15-123456MSISDN: 44-181-654321

2.ISD

2.ISD

4. UPL_resp


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Call from an MS(MO Calls)

The MS uses RACH to ask for a signaling channel.

The BSC/TRC allocates a signaling channel,using AGCH.

The MS sends a call set-up request via SDCCH to the

MSC/VLR.Over SDCCH all signaling preceding a calltakes place (e.g.,authentication, ciphering,sending B-subscribers number,checking of o/g barringparameter etc.).


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MO CALL Continued..

The MSC/VLR instructs the BSC/TRC to allocate anidle TCH.The RBS and MS are told to tune to theTCH.

The MSC/VLR forwards the B-number to an exchangein the PSTN,which establishes a connection to thesubscriber.

If the B-subscriber answers,the connection isestablished.


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Call to an MS (MT Calls)The PSTN subscriber dials in the MSs telephone number(MSISDN).The MSISDN is analyzed in the PSTN,whichidentifies that this is a call to a mobile network subscriber.A connection is established to the MSs homeGMSC.

The GMSC analyzes the MSISDN to find out which HLR the MS is registered in,and queries the HLR forinformation about how to route the call to the servingMSC/VLR.

The HLR translates MSISDN into IMSI,and determineswhich MSC/VLR is currently serving the MS.


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MT Calls continued..The HLR requests an MSRN from the serving

MSC/VLR.The MSC/VLR returns an MSRN via HLR tothe GMSC.

The GMSC analyses the MSRN and routes the call tothe MSC/VLR.

The MSC/VLR knows which LA the MS is located in.A paging message is sent to the BSCs controlling theLA.

The BSCs distribute the paging message to the RBSsin the desired LA.

MT C ll i d


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MT Calls continued..The RBSs transmit the message over the air interfaceusing PCH with IMSI/TMSI.

When the MS detects the paging message,it sends arequests on RACH for a SDCCH.

The BSC provides a SDCCH,using AGCH.

SDCCH is used for the call set-up procedures.Over theSDCCH all signaling preceding takes place.

The MSC/VLR instructs the BSC/TRC to allocate an idleTCH.The RBS and MS are told to tune to the TCH.Themobile phone rings.If subscriber answers,the connectionis established.


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Call to an MS(MT Calls) in Roaming-Diagram

WB BSNL

NLDHLR

UKSubscriber

GMSC

VMSC/VLR

UK

HLR

GMSC

44-181-123456

PSTN

DIALS

IAM

1.SRI2.PRN

2.PRN2.PRN

MSISDN

IMSI

2.PRN3.PRNACK

3.PRNACK

3.PRNACK

3.PRNACK

MSRN MSRN

4.SRIACK

MSRN

5.ISUPIAM

5.ISUPIAM

5.ISUPIAM

6.PAGING

6.ACM

6.ACM

6.ACM

7.ANM

7.ANM

7.ANM

8.Disconnect

8.REL

8.REL

9.RELACK

9.RELACK

9.RELACK


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MO SMS -DiagramWB BSNL

NLDHLR

UKSubscriber

GMSC

VMSC/VLR

UK

HLRGMSC

SCCPCdPA: 44-181-123456(MGT derived fromIMSIS analysis)CgPA: 919434099995(VLR)

MAPIMSI: 234-15-123456

SCCPCdPA: 919434099995(VLR) CgPA: 44-181-HLRofUK1

MO -FSM MO -FSM

SMSC

MO-FSM-RSP MO -FSM

MO-FSM-RSPMO-FSM-RSP

An MS establishes a connection to the network,

as in the normal call set- up.The MS sends the short message using SDCCH to the

SMSC via MSC/VLR.The SMSC in turn forwards the shomessage to its destination.


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MT SMS A user sends a message to a SMSC.

The SMSC sends the message to the SMS-GMSC.

The SMS-GMSC queries the HLR for routinginformation.

The HLR returns routing information to the SMS-GMSC.

The SMS-GMSC reroutes the message to theMSC/VLR.

The MS is paged and a connection is set up between

the MS and the network,as in the normal call set-upcase.


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MT SMS Continued

The MSC/VLR delivers the message to the MS.Shortmessages are transmitted on SDCCH.

If the delivery was successful,a report is sent fromthe MSC/VLR to the SMSC,if not,the HLR is informedby the MSC/VLR, and a failure report is sent to SMSC.

The HLR then informs the SMSC when the MS

becomes available.


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PREPAID SYSTEMPrepaid system adds few other nodes than the

existing GSM network.

It is the IN system which handles the prepaidsubscriber.

IN system consist of Mainly1.SCF2.SDP3.PPAS4.IVR

In MSC SSF module handles the prepaid call Scenarioin MSC side.


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GPRS

GPRS Core network consists of

SGSN :Serving GPRS Support Node; the gatewaybetween the RNC and the core network in aGPRS/UMTS network

GGSN :Gateway GPRS Support Node; the gatewaybetween a cellular network and a IP network.


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GPRS ATTACH

SGSN

EIR

HLR

1.GPRS ATTACHREQUEST

2.Authenticationrequest

3.Athentication

res

4.Equipmentidentity check

5.Equipment idemtitycheck response

6.update location

7.ISD

8.ISDACK

9.GPRS attachaccepted


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PDP Context activation

SGSN

DNSSERVER

GGSN

RadiusServer

DHCPSERVER

1.Activate PDP contest

2.DNSquery(APN)

3.DNSResp(GGSN

IP ADR

4.CreatePDP

Contest

req.

5.Radiusauthentication

request

6.Res7.DHCP

ADDR.REQ

8.DHCP

ADDR.RES

9. Create PDP ContextResponse

10. ActivatePDP Context

Accept

( )


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CDMA (IS-95) TECHNOLOGY Code-Division Multiple Access, a digital cellular

technology that uses spread-spectrum techniques

IS-95 CDMA system operates in 800 Mhz

CdmaOne is the brand name of IS-95 technology from1997.CdmaOne is basically an air-interface standard.

IS-95 uses Frequency division duplex.Forward link andreverse link transmission occur in different frequency

band.


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Duplex separation used in IS-95 is 45Mhz

Carrier spacing is 1.25 Mhz

Forward link frequency: 824-849Mhz

Reverse Link frequency: 869Mhz-894Mhz

The forward link consists of Base station(BS)transmitter,radio channel and the MS receiver.

CDMA Continues


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CDMA Continues CdmaOne system supports four different types of forwardchannels

# Pilot channel -is continuously transmitted by each CDMAcarrier and is used by MS to identify the BS and to asses thesuitability of the cell hand over.In this respect it may belikened to the BCCH carrier in GSM system.

#Synchronous channel -It allows MS to achieve timesynchronization with BS and the network .

# Paging channel -is used to page MSs to alert them to anincoming call.

#Traffic channel -are assigned to the users as required and theyma carr s eech or user data at bit rates of u to 9.6 kb s.


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CDMA Continues

Access channel data are presented in the form of one 96- bit frame every 20 ms.Of this 96 bits,88 are used tocarry information and remaing eight are encoder tail

bits.

# Traffic channel -are assigned to the individual user asrequired.A reverse link traffic channel may carry

speech and data at bit rates up to 9.6 kbps.


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The cdmaOne MS does not transmit a pilot signalas this would significantly decrease reverse link capacity.

BS receiver uses RAKE receiver to demodulatethe reverse link signal from a particular MS.

MS handover process occur by measuring thestrength of the pilot channels signal from a BSother than its current BS.

CdmaOne system supports three main types of handover


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CDMA Continues # Idle mode handover -It occurs when an MSmoves from the coverage area of one BS into thecoverage area of a second BS while an MS is anidle mode.

# Soft handover - is used between BSs havingCDMA carriers with identical frequencyassignments.

# Hard handover - occur when a mobile isswitched between two BSs using different carriers.


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Simplified data flow for the access procedure of a mobile terminated call.


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Basic cdmaOne diagram

CDMA 2000


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CDMA 2000 This is the evaluated 3G version of IS-95/cdmaOne

technology.

CDMA2000 is an ITU-approved standard that was the first 3Gtechnologies (October,2000).

provides advanced voice communications and high-speed dataconnectivity, including access to the Internet, mobile dataapplications and multimedia content.

Supports data services at minimum transmission rates of 144kbps in mobile (outdoor) and 2 Mbps in fixed (indoor)environments.

The world's first 3G commercial system was launched by SK Telecom (South Korea) in October 2000 using CDMA2000


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CDMA2000 represents a family of standardsand includes

>CDMA2000 1X>CDMA2000 1xEV-DO Technologies>CDMA2000 1xEV-DO Rev A>CDMA2000 1xEV-DO Rev B>Ultra Mobile Broadband - UMB(CDMA2000 1xEV-DO Rev C)

CDMA 2000 ti


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CDMA 2000 continues

CDMA2000 builds on the inherent advantages of CDMAtechnologies,such as

>introduction of Orthogonal Frequency Division

Multiplexing (OFDM and OFDMA)

>advanced control and signaling mechanisms

>improved interference management techniques end-to-endQuality of Service (QoS)


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>new antenna techniques such as MultipleInputs Multiple Outputs (MIMO) and Space

Division Multiple Access (SDMA) toincrease data throughput rates and quality of service

>improving network capacity and reducingdelivery cost.

CDMA2000 Advantages:


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CDMA2000 Advantages: >Superior Voice quality

>High-Speed Broadband Data connectivity

>Increased Voice and Data Throughput capacity

>Long-Term, Robust and Evolutionary Migration Path withForward and Backward Compatibility

>Differentiated Value-Added Services such as VoIP, PTT,Multicasting, Position Location, etc.


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>Flexible Network Architecture with connectivity to ANSI-41,GSM-MAP and IP-based Networks and flexible Backhaul

Connectivity

>Flexible Spectrum Allocations with Excellent PropagationCharacteristics

>Robust Link Budget for Extended Coverage and Increased DataThroughputs at the Cell Edge

>Improved Security and Privacy


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CDMA 2000 NETWORK DIAGRAM

UMTS/WCDMA


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UMTS/WCDMA UMTS (WCDMA)is a 3G evolution of GSM and GPRS

UMTS is one of the Third Generation (3G) mobile systems being developed within the ITU's IMT-2000 framework

The coverage will be provided by a combination of cellsizes ranging from 'in building' Pico Cells to Global Cells

provided by satellite, giving service to the remote regionsof the world

created a platform to converge the worlds of speech, dataservices and the Internet to create a global market for mobile multimedia.

UMTS is designed to increase a subscribers data rates andsystem capacity.


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Technical Features:

Modulation Techniques used QPSK

Multiple access technology used as CDMA

Frequency reuse pattern : 1*1 (cell*sector)

Maximum data rates supported: 384kbps to 2mbps

Both packect switch and circuit switch aresupported


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Radio channels are 5MHz wide

Chip(fundamental unit of transmission in a CDMAsystem) rate of 3.84 Mcps

Supports two basic modes of duplex, frequency divisionand time division. Current systems use frequencydivision, one frequency for uplink and one for downlink.For time division, UMTS uses 15 slots per radio frame.


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Technical Features continues .>Employs coherent detection on uplink and downlink basedon the use of pilot symbols

> Supports inter-cell asynchronous operation

>Variable mission on a 10 ms frame basis

>Adaptive power control

> Multiuser detection and smart antennas can be used toincrease capacity and coverage.


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>initially poor coverage due to the time it takes to build a network

>for fully fledged UMTS incorporating Video onDemand features, one base station needs to be set

up every 1 1.5 km (0.62 0.93 mi). While this iseconomically feasible in urban areas, it isinfeasible in less populated suburban and ruralareas.

>Requires huge frequency spectrum

UMTS Network Architechture


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UMTS Network Architechture UMTS core network architechturally a GSM phase 2+

Core network that is power up so that it can also handle thehigher volume,higher bit rate,UMTS traffic.

RNS(Radio network subsystem) is the additional part for UMTS network than GSM Phase 2 + network.

RNS consists of RNC (Radio network Controller) and NodeB(part of User Equipment and Base station)

The UMTS terrestrial Radio interface(UTRA) frequencyduplex(FDD) mode is the W-CDMA radio interface of theUMTS.

Carrier frequency is defined by the UTRA absolute radiofrequency channel number(UARFCN).


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Physical Channels there are two basic types of physical channels.

# Dedicated Channels -These are used by UEs for theduration of the call.There are two Dedicated channels-

>PCCH -Dedicated physical control channel carries physical layer control information

>DPDCH -Dedicated physical data channeltransports the user traffic.

#Common channels -these are used to carry information to theUEs within a cell and are used by the UEs to access thenetwork. Common channels are of two types: Commonchannels are of two types:

1. Down link common channels

2. Uplink common channels


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Down link common channels

CPICH -Common Pilot Channel provides a commondemodulation reference over all or part of a cell.

P-CCPCH -Primary common control physical channelcaries general network information.

S-CCPCH -Secondary common control physical channel isused for paging and packet data

SCH -Synchronisation channel is used by UE for its initialcell search

AICH -Acquisition indication channel controls the use of

common uplink channels.

UP Li k h i l


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UP Link common physicalchannels

PRACH -Physical Random Access Channels used byUEs initially to access the network

PC-PCH -Physical Common Packet Channel allows bursts of data to be transferred from UEs to thenetwork.CPCH is typically used for short,infrequent

burst of data where as dedicated channels are moresuited to long burst.

UMTS Frame structure


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UMTS Frame structureThe duration of a frame is 10ms

One frame contains 15 slots

Each slot duration =0.667 ms

Each slot contains 2560 chips

Chip rate=3.838Mchips/s

One super frame =72 frame= 720ms duration

Difference between CDMA2000 and


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UMTS technology>Cdma2000 and UMTS were developed separately

and are 2 separate ITU approved 3G standards

>cdma2000 were developed to be backward

compatible with cdmaOne but UMTS phones arenot meant to be backward compatible with GSMsystems.

>Cdma2000 is easy to implement because operatorsdo not need new frequencies but implementationof UMTS is very difficult because of its newrequirement of wide range of frequency and new

implementation of the radio access network.


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