1. QoS-guaranteed Transmission Scheme Selection for OFDMA Multi-hop Cellular Networks Jemin Lee, Sungsoo Park, Hano Wang, and Daesik Hong, ICC 2007

2. Outline   Introduction   OFDMA Multi-hop cellular model   Transmission Scheme Selection Algorithm (TSSA)   Performance   Conclusion

3. Introduction   Multi-hop cellular networks (MHCN) have been proposed to enhance throughput and extend coverage   The advantage of multi-hop networks comes from the reduction in the overall path loss Base Station -> Relay Station -> Mobile Station

4. Introduction   The penalty of transmission with multi-hop is in need for additional resources Eg. power and bandwidth   [2] IEEE Trans. on Wireless Comm. 2003 resource reuse transmission enhances the system capacity in multi-hop networks

5. Introduction   QoS guarantee of MS Supported various QoS requirements of MSs Increasing the number of QoS-guaranteed MSs BS controls the number of subcarriers allocated to the MS   Proposed a transmission scheme selection SH MH MHSR

6. Introduction   Goal Select the best performance scheme for the efficient utilization of subcarriers

7. OFDMA Multi-hop cellular model   Cellular Architecture Two-hop relaying system BS-FRS link LOS BS-MS and FRS-MS link NLOS

8. OFDMA Multi-hop cellular model SINR Channel gain of the link between x and y BS’s transmission power Noise powerTotal interferences Transmission scheme

9. OFDMA Multi-hop cellular model  Channel gain constant Distance between x and y Path loss exponent Shadowing random variable

10. OFDMA Multi-hop cellular model  Total interferences The interference from BSs of other cells The interference from FRSs of other cells The interference from spatial reuse of subcarrier

11. OFDMA Multi-hop cellular model  Example of interference

12. OFDMA Multi-hop cellular model data rate per subcarrier of the kth MS at the nth hop Satisfying the target rate of the kth MSrequired number of subcarriers

13. OFDMA Multi-hop cellular model  Example Calculating the number of subcarriers Calculating the number of subcarriers BS RS MS 3 R 2,3,1 =20 bps R 2,3,2 =5 bps R k =50 bps MS 2 R 3,2,2 =12 bps R k =60 bps BS RS R 3,2,1 =20 bps

14. OFDMA Multi-hop cellular model a k =1 If the kth MS is supported Total number of subcarriers

15. TSSA

16. Performance

19. Conclusion   This paper has verified that the best transmission scheme which requires the fewest subcarriers to guarantee QoS   The simulation results have demonstrated that subcarriers are used efficiently by the proposed algorithm.

20. Thanks

21. Simple analysis