Dynamic Topology Control for Multi-hop Relaying in a Cellular TDD-OFDMA System Hye J. Kang, Hyun S. Ryu, and Chung G. Kang School of Electrical Engineering, Korea University IEEE WCNC 2009

Outline Introduction Motivation & Goal Proposed Algorithm Simulation Conclusion

Preamble DL/UL MAP MS Introduction Recently, Multi-hop relay systems are considered as a useful means for enhancing coverage and throughput. The j Relay Task group was formed to standardize a WiMAX multi-hop relay (MMR) system. MR-BS RS Preamble DL/UL MAP MS RS Non-transparent RS

Introduction In an MMR system, MSs are allowed to route through intermediate RSs to reach the BS, which differs from the single-hop WiMAX topology. MR-BS RS Preamble DL/UL MAP MS MR-BS MS Non-transparent RS

Motivation & Goal Multi-hop relay frame structure in this paper TDD-OFDMA RS 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 1RS 3RS 5RS 2RS 4RS 6RS 7

Motivation In fact, if N is too large, the N-th subzone becomes almost a null. RS 1RS 3RS 5RS 2RS 4RS 6RS 7

Motivation In fact, if N is too large, the N-th subzone becomes almost a null. RS 1RS 3RS 5RS 2RS 4RS 6RS 7

Motivation In general, we can divide the relay zone into K sub-zones and then, reuse them among the different layers. In this paper we consider k = 3, because it will be the most efficient form of frequency reuse.

Motivation Co-channel interference in the same branch is one serious problem under the divide-by-K reuse strategy.

Motivation Co-channel interference in inter-branch is another serious problem under the divide-by-K reuse strategy.

Goal Our objective is to configure a feasible tree topology subject to the divideby-K reuse strategy for N-hop maximizing the bandwidth efficiency of resource available for relay 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 BS. Given the received signal strength between two RSs. Each RS must have its own unique super-ordinate RS in the tree structure.

RS Layering Algorithm RS 1RS 2RS 3RS 4 BS RSRS1RS2RS3RS4RS5RS6RS7RS8 MCS64 16 QPSK RSS20W 15W14W10W2W3W11W RS 5RS 6RS 7RS 8

RS Layering Algorithm RS 1RS 2RS 3RS 4 BS RS 5RS 6RS 7RS 8 RSRS1RS2RS3RS4RS5RS6RS7RS8 MCS64 16 QPSK RSS20W 15W14W10W2W3W11W

RS Layering Algorithm RS 1RS 2RS 3RS 4 BS 1bit/5Mbps 1bit/10Mbps 1bit/9Mbps RS 5RS 6RS 7RS 8 RSRS1RS2RS3RS4RS5RS6RS7RS8 MCS64 16 QPSK RSS20W 15W14W10W2W3W11W

RS Layering Algorithm RS 1RS 2RS 3RS 4 BS RS 5RS 6RS 7RS 8 RSRS1RS2RS3RS4RS5RS6RS7RS8 MCS64 16 QPSK RSS20W 15W14W10W2W3W11W

RS Layering Algorithm RS 1RS 2RS 3RS 4 BS RSRS4RS5RS6RS7RS8 MCS64 QPSK16 RSS14W10W2W3W11W RS 5RS 6RS 7RS 8

RS Layering Algorithm RS 1RS 2RS 3RS 4 BS RSRS4RS5RS6RS7RS8 MCS64 QPSK16 RSS14W10W2W3W11W RS 5RS 6RS 7RS 8

RS Layering Algorithm RS 1RS 2RS 3RS 4 BS RSRS4RS5RS6RS7RS8 MCS64 QPSK16 RSS14W10W2W3W11W RS 5RS 6RS 7RS 8

RS Layering Algorithm RS 1RS 2RS 3RS 4 BS RSRS4RS5RS6RS7RS8 MCS64 QPSK16 RSS14W10W2W3W11W RS 5RS 6RS 7RS 8

RS Layering Algorithm RS 1RS 2RS 3RS 4 BS RSRS4RS5RS6RS7RS8 MCS64 QPSK16 RSS14W10W2W3W11W RS 5RS 6RS 7RS 8

RS Layering Algorithm RS 1RS 2RS 3RS 4 BS RSRS4RS5RS6RS7RS8 MCS64 QPSK16 RSS14W10W2W3W11W RS 5RS 6RS 7RS 8

RS Layering Algorithm RS 1RS 2RS 3RS 4 BS RSRS4RS5RS6RS7RS8 MCS64 QPSK16 RSS14W10W2W3W11W RS 5RS 6RS 7RS 8 1bit/5Mbps 1bit/10Mbps 1bit/9Mbps

RS Layering Algorithm RS 1RS 2RS 3RS 4 BS RSRS4RS5RS6RS7RS8 MCS64 QPSK16 RSS14W10W2W3W11W RS 5RS 6RS 7RS 8

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 1RS 2RS 3RS 4 BS RS 5RS 6RS 7RS 8

RS Clustering Algorithm RS 1RS 2RS 3RS 4 BS RS 5RS 6RS 7RS 8

RS Clustering Algorithm RS 1RS 2RS 3RS 4 BS RS 5RS 6RS 7RS 8

RS Clustering Algorithm RS 1RS 2RS 3RS 4 BS RS 5RS 6RS 7RS 8

Simulation We consider a simulation scenario in which relay stations and mobile stations are uniformly in a single cell of 5km radius. The transmit BS power and RS power are given by 20W and 10W, respectively.

Simulation Among 27 downlink OFDM symbols, 14 symbols are assigned 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 clustering (labeled by “Layering”). a layering process can be replaced by the best rate selection 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 control algorithm that deals with the routing and resource allocation for the relay stations in the cellular.