1. Adaptive Multiple Relay Selection Scheme for Cooperative Wireless Networks WCNC 2010 Gayan Amarasuriya, Masoud Ardakani and Chintha Tellambura {amarasur, ardakani, chintha}@ece.ualberta.ca 6/1/2015 University of Alberta, Canada 1

2. Outline: introduction – single relay selection, multiple relay selection motivation proposed scheme analysis numerical results conclusion 6/1/20152

3. All participate relaying (APR): 6/1/2015 APR [Laneman, 2003]  needs L +1 orthogonal time-slots  low spectral-efficiency  all L relays cooperate  simple and efficient  optimal in the sense of diversity and coding gains  low spectral efficiency can be overcome by  selection a subset of available relays 3

4. - only one relay cooperates  spectral-efficiency increases 6/1/2015 Single relay selection (SRS): SRS - SRS schemes  best SRS [Zhao, 2007]   best–worst SRS [Bletsas, 2006]   best–harmonic mean SRS [Bletsas, 2006]   partial SRS [Sadek, 2006]  4

5. 6/1/2015 Multiple relay selection (MRS): MRS - more than one relay cooperates  better trade-off between spectral- efficiency and available degree of freedom of the wireless channel - MRS schemes  Optimal MRS for orthogonal channels - [Michalopoulos, 2006]  Optimal/suboptimal MRS for shared channels - [Jing, 2009]  GSC-based MRS - [Ikki, 2009] 5

6. Motivation:  best SRS  does not use available degree of freedom  SNR outage and BER are lower  optimal MRS  high search complexity  complexity increases exponential with number of relays  GSC-based MRS  may select more relays unnecessary  end-to-end SNR may far exceed the system requirements  above schemes require CSI of all relayed paths  We would like a MRS scheme which offers better trade-offs between the error/outage performance and spectral-efficiency! 6/1/20156

7. Proposed MRS scheme: 6/1/2015  Key idea  Adaptive threshold checking at D [Chen, 2004], [Yang, 2005]  proposed scheme selects the first relays such that the combined SNR of the first relayed paths and the direct path exceeds a preset threshold. 7

8. Analysis:  The end-to-end SNR can be written as  The CDF of is given by  to make the analysis tractable, we use the well-known upper bound:   the CDF, PDF and the MFG of are derived in closed-forms.  lower bounds are derived for (i) outage probability, (ii) average SER, and (iii) the average number of selected relays.  upper bounds are derived for (i) average SNR and (ii) ergodic capacity. 6/1/20158

9. Analysis (ctd):  the CDF of can be derived as where and  The PDF of is given by 6/1/20159

10. Analysis (ctd):  the average SER is derived as  the average number of selected relays is given by 6/1/201510

11. Numerical results: 6/1/2015  Average BER of BPSK 11

12. Numerical results (ctd): 6/1/2015  Average number of selected relays 12

13. 6/1/2015 Numerical results (ctd):  Outage probability comparison 13

14. 6/1/2015 Numerical results (ctd):  Average BER of BPSK comparison 14

15. Conclusion: Our MRS scheme – outperforms optimal SRS, GSC-based MRS and fixed L c out of L relays in low-to-moderate SNRs. – utilizes the wireless resources adaptively in fading environments. Future directions – performance in high SNRs can be improved by  first ordering the relays  then applying the proposed algorithm 6/1/201515

16. References: 1.[Laneman, 2003] J. N. Laneman and G. W. Wornell, “Distributed space-time-coded protocols for exploiting cooperative diversity in wireless networks,” IEEE Trans. Inf. Theory, vol. 49, no. 10, pp. 2415–2425, Oct. 2003. 2.[Bletsas, 2006] A. Bletsas, A. Khisti, D. P. Reed, and A. Lippman, “A simple cooperative diversity method based on network path selection,” IEEE J. Sel. Areas Commun., vol. 24, no. 3, pp. 659–672, Mar. 2006. 3.[Zhao, 2007] Y. Zhao, R. Adve, and T. J. Lim, “Improving amplify-and-forward relay networks: optimal power allocation versus selection,” IEEE Trans. Wireless Commun., vol. 6, no. 8, pp. 3114–3123, Aug. 2007. 4.[Sadek, 2006] A. K. Sadek, Z. Han, and K. J. R. Liu, “A distributed relay-assignment algorithm for cooperative communications in wireless networks,” in IEEE International Conf. on Commun. ICC., vol. 4, Jun. 2006, pp. 1592–1597. 5.[Michalopoulos, 2006] D. S. Michalopoulos, G. K. Karagiannidis, T. A. Tsiftsis, and R. K. Mallild, “An optimized user selection method for cooperative diversity systems,” in IEEE Global Telecommun. Conf., Nov./Dec. 2006. 6.[Jing, 2009] Y. Jing and H. Jafarkhani, “Single and multiple relay selection schemes and their achievable diversity orders,” IEEE Trans. Wireless Commun., vol. 8, no. 3, pp. 1414–1423, Mar. 2009. 7.[Ikki, 2009] S. S. Ikki and M. H. Ahmed, “Performance analysis of generalized selection combining for amplify-and-forward cooperative-diversity networks,” in IEEE International Conf. on Commun., ICC., Dresden, Germany, Jun. 2009. 8.[Chen, 2004] Y. Chen and C. Tellambura, “An adaptive maximal ratio combining scheme and its performance analysis,” in 16-th international conf. on wireless commun., Wireless 2004, Calgary, Alberta, Canada, vol. 2, Jul. 2004, pp. 325–337. 9.[Yang, 2005] H.-C. Yang and M. S. Alouini, “MRC and GSC diversity combining with an output threshold,” IEEE Trans. Veh. Technol., vol. 54, no. 3, pp. 1081–1090, May 2005. 6/1/201516

17. 6/1/2015 Thank You! 17