1. Multimedia Transmission Over Cognitive Radio Networks using Decode-and-Forward Multi-Relays and Rateless Coding Abdelaali Chaoub, Elhassane Ibn-Elhaj National Institute of Posts and Telecommunications, Rabat, Morocco 2014 International Conference on Communications and Networking

2. Outline Introduction System Description Numerical Results Conclusion

3. Introduction The cognitive radio technology (CR) [1] has emerged as new solution which aims to increase the spectral efficiency by leveraging the spectrum holes. [1] J. Mitola III and G.Q Maguire, “Cognitive radio: making software radios more personal,” Personal Communications, IEEE, vol.6, no.4, pp.13-18, Aug 1999.

4. Introduction The Cognitive Radio for Virtual Unlicensed Spectrum (CORVUS) model is a cognitive radio based approach to create and use virtual unlicensed spectrum [2]. – Allowing the cognitive device to use different non- contiguous sub-channels (SCs) scattered over multiple primary frequency bands. [2] R. W. Broderson, A. Wolisz, D. Cabric, S. M. Mishra, and D. Willkomm, “Corvus: A cognitive radio approach for usage of virtual unlicensed spectrum,” White Paper, Univ. California Berkeley, Tech. Rep., Jul. 2004.

5. Introduction Authors in [3] have exploited the CORVUS architecture to distribute a fountain encoded multimedia stream over CR networks with a Poisson primary traffic pattern. – channel correcting codes – avoid the problem of coordination between sub- channels [3] H. Kushwaha, Y. Xing, R. Chandramouli, and H. Heffes, “Reliable multimedia transmission over cognitive radio networks using fountain codes,” Proc. IEEE, vol. 96, no. 1, pp. 155-165, Jan. 2008.

6. Introduction The basic idea of cooperative communications is to create transmit diversity via spatial diversity by transmitting and forwarding the same signals through the relay nodes. Castura and Mao introduced a relaying protocol in which a relay collaborates with the source by forming a distributed space-time coding scheme based on rateless codes [5]. [5] J. Castura and Yongyi Mao, “Rateless Coding for Wireless Relay Channels,” Information Theory, 2005. ISIT 2005. Proceedings. International Symposium on, vol., no., pp. 810-814, 4-9 Sept. 2005.

7. Introduction In [6], results have shown that the use of fountain codes helps reducing the transmission time. In this paper we will consider a generalized case of multiple sub-channels selected among different PU frequencies (CORVUS). [6] Weijia Lei, Xianzhong Xie and Guangjun Li, “Performance Analysis of Wireless Dynamic Cooperative Relay Networks Using Fountain Codes,” Journal of Communications, vol. 5, no. 4, pp. 307-316, April 2010.

8. Outline Introduction System Description – System model – From source to relays – From relays to destination Numerical Results Conclusion

9. System Description In this paper, we focus on multimedia transmissions through multi-relay dual-hop networks with information accumulation at the receiver side. Secondary data packets are encoded using fountain codes and secondary links are established according to CORVUS design.

10. System Description

11. System Description System model

13. It is a matter of fact that secondary users could be evicted from their sub-channels at any time whenever the corresponding primary user returns. To compensate for the eventual discarded packets, rateless codes are considered for use. System Description System model

14. The initial stream is fragmented into a given number of messages, each divided into the same number of packets K. The LT decoder needs at least N packets to recover the original K packets with a high probability. System Description System model

17. System Description From source to relays

20. System Description From relays to destination Assume that each relay among the arbitrary L intermediate nodes that have first finished receiving the message sent by the source has the capability to relay information the moment it achieves correct decoding of the N packets.

21. System Description From relays to destination

23. Outline Introduction System Description Numerical Results Conclusion

24. Numerical Results

25. X = 9

26. Numerical Results X = 9

27. Numerical Results

28. N = 40 and X = 3.

29. Numerical Results N = 40 and X = 3.

30. Outline Introduction System Description Numerical Results Conclusion

31. The properties of fountain codes have been exploited to mitigate the effects of packet loss and avoid the need for coordination among relaying nodes. Experiments have described the available tradeoffs between different system parameters. – Number of relaying nodes and the added redundancy must be carefully adjusted.