Cooperative cognitive relaying under primary and secondary quality of service satisfaction

This paper proposes a new cooperative protocol which involves cooperation between primary and secondary users. We consider a cognitive setting with one primary user (PU) and multiple secondary users (SUs). The time resource is partitioned into discrete time slots. Each time slot, one of the SUs is scheduled for transmission according to time division multiple access scheme, and the remainder of the SUs, which we refer to as secondary relays, attempt to decode the primary packet. If more than one relay can decode the primary packet, the secondary relays then employ cooperative beamforming to forward the packet and to provide protection to the destination of the SU scheduled for transmission from interference. We characterize the diversity-multiplexing tradeoff of the primary source under the proposed protocol. We consider certain quality of service for each user specified by its required throughput. The optimization problem is stated under such condition. It is shown that the optimization formulation is linear and can be readily solved.