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A FILE REPAIR SCHEME FOR UMTS MBMS SERVICEIEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, 2008

Advisor: Prof. Jen-Yeu Chen

Student: Chia-Yin Wu

December 16, 2008

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AUTHORS

Yen-Cheng Lai Student Member, IEEE,

Phone Lin Senior Member, IEEE,

Yi-Bing Lin Fellow, IEEE,

Lu-Tsung Chang2

OUTLINE

INTRODUCTION EXISTING FILE REPAIR SCHEMES REUSE BEARER SERVICE (RBS) ANALYTIC MODELS NUMERICAL RESULTS CONCLUSION

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INTRODUCTION Multicasting (one-source-many-destination) is

widely utilized for multimedia content delivery in the Internet.

Multimedia Broadcast Multicast Service (MBMS) was proposed for multicasting multimedia content over the Universal Mobile Telecommunications System (UMTS).

The MBMS file blocks are delivered through a delivery tree where the root (the source) is the BM-SC, and the leaves (the destinations) are the UEs. 4

INTRODUCTION

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MBMS Bearer Context

MBMS Bearer Context

MBMS UE

Context

MBMS UE

Context

EXISTING FILE REPAIR SCHEMES

An MBMS file is divided into several file blocks. Source Block Number Encoding Symbol ID

After an MBMS file downloading, a UE determines whether the received file blocks are corrupted by cyclic redundancy check.

A UE that receives Corrupted File Blocks (CFBs) is called a Corrupted UE (C-UE). When a CFB is detected, a C-UE sends the file repair file repair

request messagerequest message to the BM-SC to indicate the Source Block Number and the Encoding Symbol ID of the CFB. 6

EXISTING FILE REPAIR SCHEMES

Upon receipt of the repair request message, the BM-SC retransmits the CFBs by executing one of the three repair schemes proposed by 3GPP 26.346:

Unicast File Repair (UFR) Re-Multicast File Repair (RMFR) New Bearer Service (NBS) File Repair

Above 3GPP file repair schemes incur extra traffic and signaling overheads for CFB retransmission.

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REUSE BEARER SERVICE (RBS)

In the Reuse Bearer Service (RBS) File Repair scheme, the concept of CFB Routing Table (CRT) is introduced, and a CFB list parameter is added in the MBMS UE Context.

The CRT is created and updated when a network node receives the repair request messages from the C-UEs, and is deleted when the CFB has been transmitted to the C-UEs requesting the CFB.

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REUSE BEARER SERVICE (RBS) The BM-SC can determine whether all repair request

messages have be received by using a timer.

The notation“{X : k}” (X = GGSN, SGSN, or RA) means that there are k C-UEs within the service area of the X node.

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REUSE BEARER SERVICE (RBS) A CFB list is maintained in a C-UE’s MBMS UE Context

to store the IDs of the CFBs requested by this C-UE.

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ANALYTIC MODELS

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ANALYTIC MODELS The output measures derived in this study are introduced as

follows.

Mg the expected number of CFBs delivered from the BM-SC to the GGSN

Ms the expected number of CFBs delivered from the GGSN to the SGSNs

MR the expected number of CFBs delivered from the SGSNs to the RAs

SR the expected number of the file repair request messages and the file

repair response messages delivered Sd

the expected number of signaling messages required to establish and delete the delivery tree for CFB delivery

Ct = b (Mg +Ms +MR) the net cost of CFB transmissions Cs = SR + Sd the cost for signaling message transmissions Cn = Ct + Cs the net repair cost

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ANALYTIC MODELS

Analysis for RBS In RBS, CRT and CFB lists are created when a network

node receives repair request messages from C-UEs. A network node only multicasts a CFB to the C-UEs listed in its CRT.

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•In RBS, the signaling messages to establish and delete the delivery tree for CFB delivery are not required.•Sd,RBS = 0•Cs,RBS = SR,RBS

NUMERICAL RESULTS

The simulation model adopts the discrete event simulation approach that has been widely used in the mobile telecommunications network studies.

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NUMERICAL RESULTS

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NUMERICAL RESULTS

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NUMERICAL RESULTS

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NUMERICAL RESULTS

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CONCLUSION

The 3GPP proposed three file repair schemes, UFR, RMFR, and RBS. These schemes introduce extra data traffic and

signaling overhead during retransmission.

This paper proposed a new scheme called Reuse Bearer Service (RBS). In this scheme, a CFB is multicasted only to the

UEs that receive the CFB erroneously, and the retransmission scoping problem is resolved.

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Thank you for your attention! !

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