An Orthogonal Resource Allocation An Orthogonal Resource Allocation Algorithm to Improve the Performance Algorithm to Improve the Performance of OFDMA-based Cellular Wireless of OFDMA-based Cellular Wireless Systems using RelaysSystems using Relays

Woonsik Lee, Minh-Viet Nguyen, Jeonghan JeWoonsik Lee, Minh-Viet Nguyen, Jeonghan Jeong, Byungjik Keum, and Hwang Soo Leeong, Byungjik Keum, and Hwang Soo Lee

Department of EECS, Division of Electrical EngineDepartment of EECS, Division of Electrical Engineering, KAIST, Koreaering, KAIST, Korea

IEEE Consumer Communications & Networking CIEEE Consumer Communications & Networking Conference (CCNC 2008)onference (CCNC 2008)

Outline

• Introduction• System model• The proposed algorithm (ORAA) • Simulation results• Conclusions

Introduction

• In OFDMA systems, the allocation scheme of radio resources among users is important and can lead to high spectral efficiency.

• Most algorithms for OFDMA resource allocation have been limited to single-cell scenarios, where the sensitivity of the algorithms cannot be estimated in the presence of inter-cell interference (ICI).

Introduction

Motivation• In a multi-cell/multi-user environment, the inter-cell interference

(ICI) at the cell edge areas becomes a critical problem.

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Introduction

Goals• To propose a new system architecture, termed the OFDMA-

based cellular wireless system architecture using relays (OCWSAR).

• To propose a orthogonal resource allocation algorithm (ORAA) to assign radio resources effectively in the OCWSAR.

System model

• To sectorize cells and put fixed relays at the cell-edges.

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System model

• Considering one sector with three relays at the cell edge.

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System model

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• Considering one sector with three relays at the cell edge.– The resource bandwidth f1, f2, and f3 are allocated to the area A

(inner sector area), while f4, f5, and f6 are allocated to the area C (sector edge area).

– To avoid the intra-cell interference, frequency bands f4, f5, and f6 are used

for the BS-inner MS communication with a much reduced signal power.

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The proposed algorithm (ORAA) - overview

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(1) The priority of sectors.(2) The resource allocation algorithm of BS. The resource allocation algorithm of RS.

The proposed algorithm (ORAA) - overview

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(1) The priority of sectors.(2) The resource allocation algorithm of BS. The resource allocation algorithm of RS.

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(1) The priority of sectors.(2) The resource allocation algorithm of BS. The resource allocation algorithm of RS.

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The proposed algorithm (ORAA) - overview

The proposed algorithm (ORAA)

Resource allocation algorithm for B-iM and B-R communications

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: Direction that BS searches for available sub-carriers

To make the distance between the sub-carriers used by the inner MSs and the edge MSs of the same sector as far as possible.

The proposed algorithm (ORAA)

Resource allocation algorithm for R-EM communications

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The proposed algorithm (ORAA)

Resource allocation algorithm

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The proposed algorithm (ORAA)

Resource allocation algorithm

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: Direction that BS searches for available sub-carriers

The proposed algorithm (ORAA)

Resource allocation algorithm

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The proposed algorithm (ORAA)

An example of resource allocation algorithm

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The proposed algorithm (ORAA)

An example of resource allocation algorithm

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: Direction that BS searches for available sub-carriers

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The proposed algorithm (ORAA)

An example of resource allocation algorithm

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: Direction that BS searches for available sub-carriers

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Simulation results

Simulation results

Simulation results

Conclusions

• The proposed system architecture (OCWSAR) and its associated ORAA are evaluated in a multi-cell/multi-user environment.

• The simulation results shows that the proposed ORAA improves system performance significantly in view point of the SINR distribution and data throughput.

Thank you!