1. An Orthogonal Resource Allocation Algorithm to Improve the Performance of OFDMA-based Cellular Wireless Systems using Relays Woonsik Lee, Minh-Viet Nguyen, Jeonghan Jeong, Byungjik Keum, and Hwang Soo Lee Department of EECS, Division of Electrical Engineering, KAIST, Korea IEEE Consumer Communications & Networking Conference (CCNC 2008)

2. Outline Introduction System model The proposed algorithm (ORAA) Simulation results Conclusions

3. 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).

4. Introduction Motivation In a multi-cell/multi-user environment, the inter-cell interference (ICI) at the cell edge areas becomes a critical problem. BS 1 MS BS 2

5. 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.

6. System model To sectorize cells and put fixed relays at the cell-edges. BS x y z RS

7. System model Considering one sector with three relays at the cell edge. BS RS 1 RS 2 RS 3 BS RS MS BS-inner MS Relay-edge MS

8. System model BS RS 1 RS 2 RS 3 Considering one sector with three relays at the cell edge. –The resource bandwidth f 1, f 2, and f 3 are allocated to the area A (inner sector area), while f 4, f 5, and f 6 are allocated to the area C (sector edge area). –To avoid the intra-cell interference, frequency bands f 4, f 5, and f 6 are used for the BS-inner MS communication with a much reduced signal power. A C f1f1 f2f2 f3f3 f4f4 f5f5 f6f6

9. The proposed algorithm (ORAA) - overview BS 1 x y z RS (1)The priority of sectors. (2)The resource allocation algorithm of BS. The resource allocation algorithm of RS.

10. The proposed algorithm (ORAA) - overview BS 1 x y z RS x y z BS 2 x y z RS BS 3 (1)The priority of sectors. (2)The resource allocation algorithm of BS. The resource allocation algorithm of RS.

11. x y z RS BS 2 x y z RS BS 3 (1)The priority of sectors. (2)The resource allocation algorithm of BS. The resource allocation algorithm of RS. BS 1 x y z RS The proposed algorithm (ORAA) - overview

12. The proposed algorithm (ORAA) Resource allocation algorithm for B-iM and B-R communications RGB X Y Z x y z RS BS 2 : 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.

13. The proposed algorithm (ORAA) Resource allocation algorithm for R- E M communications RGB X Y Z x y z RS BS 2 : Direction that RS searches for available sub-carriers

14. The proposed algorithm (ORAA) Resource allocation algorithm RGB X Y Z x y z RS BS 2 : Direction that RS searches for available sub-carriers : Direction that BS searches for available sub-carriers

15. The proposed algorithm (ORAA) Resource allocation algorithm RGB X Y Z x y z RS BS 2 : Direction that RS searches for available sub-carriers : Direction that BS searches for available sub-carriers

16. The proposed algorithm (ORAA) Resource allocation algorithm RGB X Y Z x y z RS BS 2 : Direction that RS searches for available sub-carriers : Direction that BS searches for available sub-carriers

17. The proposed algorithm (ORAA) An example of resource allocation algorithm RGB X Y Z : Direction that RS searches for available sub-carriers : Direction that BS searches for available sub-carriers RS BS 2 RS BS 3 BS 1 xy z RS

18. The proposed algorithm (ORAA) An example of resource allocation algorithm RGB X Y Z : Direction that RS searches for available sub-carriers : Direction that BS searches for available sub-carriers RS BS 2 RS BS 3 BS 1 RS xy z

19. The proposed algorithm (ORAA) An example of resource allocation algorithm RGB X Y Z : Direction that RS searches for available sub-carriers : Direction that BS searches for available sub-carriers RS BS 2 RS BS 3 BS 1 RS xy z

20. Simulation results

23. 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.

24. Thank you!