Performance Analysis of Cognitive User Cooperation Using Binary Network Coding

We consider a cognitive radio network where a primary and a secondary transmitter, respectively, communicate a message to their primary and secondary receivers over a packet-based wireless link, using a joint automatic-repeat-request (ARQ) error control scheme. The secondary transmitter assists in the retransmission of the primary message, which improves the primary performance, and as a reward it is granted limited access to the transmission resources. Conventional ARQ, as well as two network-coding schemes are investigated for applications in the retransmission phase; namely the static network-coding scheme and the adaptive network-coding scheme. For each scheme we analyze the transmission process by investigating the distribution of the number of transmission attempts. We divide every frame into three transmission sessions and in each session we discover that the number of transmission attempts follows a certain negative binomial distribution, in which case can be further approximated by a normal distribution. Considering both the cases of an adaptive frame size and a truncated frame size, we derive analytical results on system performances and discuss the comparison of three schemes. Besides, the approximation method greatly reduces the complexity of transmission analysis, especially in the truncated frame-size case. Numerical results show that our analysis are valid and closely match the simulations.