Improving Reliability in Cognitive Radio Networks Using Multiple Description Coding

This paper looks at the problem of multimedia traffic transmission over Cognitive Radio networks in a delay sensitive context and under lossy network conditions. Secondary Users are allowed to share the vacant subchannels using the Time Division Multiple Access method based on the Opportunistic Spectrum Sharing. Each Secondary User is assigned one time slot where it habitually transmits with a certain probability. The given model allows each Secondary User to transmit opportunistically in the remaining slots. Accordingly, the reasons for packets to be discarded are threefold: primary traffic interruptions, collisions between the competing secondary users and erasures due to subchannels fading. To mitigate the collision effects, an innovative idea is to exploit the Multiple Description Coding technique. More particularly, a specific packetization framework derived from the Priority Encoding Transmission is used to deal with the packet loss pattern. Numerical simulations, in view of Message Error Probability and Spectral Efficiency, show that the system still exhibit good secondary traffic robustness despite of the presence of primary reclaims, secondary collisions and subchannel errors.