Dynamic Topology Control for Multi-hop Relaying in a Cellular

TDD-OFDMA System

Hye J. Kang, Hyun S. Ryu, and Chung G. KangSchool of Electrical Engineering, Korea University

IEEE WCNC 2009

Outline Introduction Motivation & Goal Proposed Algorithm Simulation Conclusion

PreambleDL/UL MAP

MS

Introduction Recently, Multi-hop relay systems are considered as a

useful means for enhancing coverage and throughput. The 802.16j Relay Task group was formed to standardize

a WiMAX multi-hop relay (MMR) system.

MR-BS

RS

PreambleDL/UL MAP

MS

RS

Non-transparent RS

Introduction In an MMR system, MSs are allowed to route through inte

rmediate RSs to reach the BS, which differs from the single-hop WiMAX topology.

MR-BS

RS

PreambleDL/UL MAP

MS

MR-BS

MS

Non-transparent RS

Motivation & Goal Multi-hop relay frame structure in this paper

TDD-OFDMA

RS

MS

MS

Motivation Multi-hop relay frame structure: N=4 hops

the relay zone can be time-divided into the multiple subzones Each sub-zone is reserved for a subsequent relay link

RS 1

RS 3

RS 5

RS 2

RS 4

RS 6

RS 7

Motivation In fact, if N is too large, the N-th subzone becomes almost a null.

RS 1

RS 3

RS 5

RS 2

RS 4

RS 6

RS 7

RS 7

Motivation In fact, if N is too large, the N-th subzone becomes almost a null.

RS 1

RS 3

RS 5

RS 2

RS 4

RS 6

RS 7

RS 7

Motivation In general, we can divide the relay zone into K sub-zones a

nd then, reuse them among the different layers. In this paper we consider k = 3, because it will be the most efficient form of frequen

cy reuse.

Motivation Co-channel interference in the same branch is one serious

problem under the divide-by-K reuse strategy.

Goal Our objective is to configure a feasible tree topology subje

ct to the divideby-K reuse strategy for N-hop maximizing the bandwidth efficiency of resource available for rela

y links.

Proposed algorithm RS Layering Algorithm

The objective of RS layering is to minimize the average inter-hop interference.

RS Clustering Algorithm The objective of the RS clustering algorithm is to determine a

super-ordinate RS for each RS in the next upper layer so as to minimize the effective delay.

Assumption Given data rate between two RSs. Given the received signal strength between each RS and B

S. Given the received signal strength between two RSs. Each RS must have its own unique super-ordinate RS in th

e tree structure.

RS Layering Algorithm

RS 1 RS 2 RS 3

RS 4

BS

RS RS1 RS2 RS3 RS4 RS5 RS6 RS7 RS8

MCS 64 64 16 16 QPSK QPSK QPSK QPSK

RSS 20W 20W 15W 14W 10W 2W 3W 11W

RS 5

RS 6

RS 7RS 8

RS Layering Algorithm

RS 1 RS 2 RS 3

RS 4

BS

RS 5

RS 6

RS 7RS 8

RS RS1 RS2 RS3 RS4 RS5 RS6 RS7 RS8

MCS 64 64 16 16 QPSK QPSK QPSK QPSK

RSS 20W 20W 15W 14W 10W 2W 3W 11W

RS Layering Algorithm

RS 1 RS 2 RS 3

RS 4

BS

1bit/5Mbps1bit/10Mbps

1bit/9Mbps

RS 5

RS 6

RS 7RS 8

RS RS1 RS2 RS3 RS4 RS5 RS6 RS7 RS8

MCS 64 64 16 16 QPSK QPSK QPSK QPSK

RSS 20W 20W 15W 14W 10W 2W 3W 11W

RS Layering Algorithm

RS 1 RS 2 RS 3

RS 4

BS

RS 5

RS 6

RS 7RS 8

RS RS1 RS2 RS3 RS4 RS5 RS6 RS7 RS8

MCS 64 64 16 16 QPSK QPSK QPSK QPSK

RSS 20W 20W 15W 14W 10W 2W 3W 11W

RS Layering Algorithm

RS 1 RS 2 RS 3

RS 4

BS

RS RS4 RS5 RS6 RS7 RS8

MCS 64 64 QPSK 16 16

RSS 14W 10W 2W 3W 11W

RS 5

RS 6

RS 7RS 8

RS Layering Algorithm

RS 1 RS 2 RS 3

RS 4

BS

RS RS4 RS5 RS6 RS7 RS8

MCS 64 64 QPSK 16 16

RSS 14W 10W 2W 3W 11W

RS 5

RS 6

RS 7RS 8

RS Layering Algorithm

RS 1 RS 2 RS 3

RS 4

BS

RS RS4 RS5 RS6 RS7 RS8

MCS 64 64 QPSK 16 16

RSS 14W 10W 2W 3W 11W

RS 5

RS 6

RS 7RS 8

WRSS 25,7

WRSS 105,2

WRSS 15,6

RS Layering Algorithm

RS 1 RS 2 RS 3

RS 4

BS

RS RS4 RS5 RS6 RS7 RS8

MCS 64 64 QPSK 16 16

RSS 14W 10W 2W 3W 11W

RS 5

RS 6

RS 7RS 8

10,min5,6

5,2

5,7

5,2

thRSS

RSS

RSS

RSS

WRSS 25,7

WRSS 105,2

WRSS 15,6

RS Layering Algorithm

RS 1 RS 2 RS 3

RS 4

BS

RS RS4 RS5 RS6 RS7 RS8

MCS 64 64 QPSK 16 16

RSS 14W 10W 2W 3W 11W

RS 5

RS 6

RS 7RS 8

10,min5,6

5,2

5,7

5,2

thRSS

RSS

RSS

RSS

WRSS 104,1 WRSS 5.04,8

RS Layering Algorithm

RS 1 RS 2 RS 3

RS 4

BS

RS RS4 RS5 RS6 RS7 RS8

MCS 64 64 QPSK 16 16

RSS 14W 10W 2W 3W 11W

RS 5

RS 6

RS 7RS 8

10min4,8

4,1

thRSS

RSS

WRSS 104,1 WRSS 5.04,8

RS Layering Algorithm

RS 1 RS 2 RS 3

RS 4

BS

RS RS4 RS5 RS6 RS7 RS8

MCS 64 64 QPSK 16 16

RSS 14W 10W 2W 3W 11W

RS 5

RS 6

RS 7RS 8

1bit/5Mbps1bit/10Mbps

1bit/9Mbps

RS Layering Algorithm

RS 1 RS 2 RS 3

RS 4

BS

RS RS4 RS5 RS6 RS7 RS8

MCS 64 64 QPSK 16 16

RSS 14W 10W 2W 3W 11W

RS 5

RS 6

RS 7RS 8

10min4,8

4,1

thRSS

RSS

Proposed algorithm RS Clustering Algorithm

The objective of the RS clustering algorithm is to determine a super-ordinate RS for each RS in the next upper layer so as to minimize the effective delay.

RS Clustering Algorithm

RS 1 RS 2 RS 3

RS 4

BS

RS 5

RS 6

RS 7RS 8

RS Clustering Algorithm

RS 1 RS 2 RS 3

RS 4

BS

RS 5

RS 6

RS 7RS 8

ms12

ms20

RS Clustering Algorithm

RS 1 RS 2 RS 3

RS 4

BS

RS 5

RS 6

RS 7RS 8

ms12

RS Clustering Algorithm

RS 1 RS 2 RS 3

RS 4

BS

RS 5

RS 6

RS 7RS 8

Simulation We consider a simulation scenario in which relay stations and mobile s

tations are uniformly in a single cell of 5km radius. The transmit BS power and RS power are given by 20W and 10W, res

pectively.

Simulation Among 27 downlink OFDM symbols, 14 symbols are assi

gned to access zone while the rest of them are assigned to the relay zone.

The loading factor threshold η th for the proposed algorithm is set to 10 in the current simulation.

Simulation the proposed scheme (labeled by “Layering + Clustering”) One which employs layering only, without resort to cluster

ing (labeled by “Layering”). a layering process can be replaced by the best rate selectio

n in the proposed scheme (labeled by “Best rate + Clustering”).

Simulation Average end-to-end throughput: Divide-by-3

Simulation Average MS outage probability: Divide-by-3

Conclusion In this paper, we have proposed a dynamic topology contro

l algorithm that deals with the routing and resource allocation for the relay stations in the cellular.