Cognitive Cooperative Random Access for Multicast: Stability and Throughput Analysis

In this paper, we investigate the queue stability and throughput of a two-user cognitive radio system with multicast traffic. We study the impact of network-level cooperation, in which one of the nodes can relay the packets of the other user that are not received at the destinations. Under this approach, if a packet transmitted by the primary user is not successfully received by the destination set but is captured by the secondary source, then the secondary user assumes responsibility for completing the transmission of the packet; therefore, the primary releases it from its queue, enabling it to process the next packet. We demonstrate that the stability and throughput regions of this cooperative approach is larger than that of the noncooperative approach, which translates into a benefit for both users of this multicast system. Our system model allows for the possibility of multipacket reception (MPR), and the optimal transmission strategies for different levels of MPR capability are observed in our numerical results. In addition to achieving a larger stability region, our results show that cooperation can result in reduced average delay for both primary and secondary users.