Maximum Secondary Stable Throughput of a Cooperative Secondary   Transmitter-Receiver Pair: Protocol Design and Stability Analysis
  In this paper, we investigate the impact of cooperation between a secondary transmitter-receiver pair and a primary transmitter (PT) on the maximum stable throughput of the primary-secondary network. Each transmitter, primary or secondary, has a buffer for storing its own traffic. In addition to its own buffer, the secondary transmitter (ST) has a buffer for storing a fraction of the undelivered primary packets due to channel impairments. Moreover, the secondary destination has a relaying queue for storing a fraction of the undelivered primary packets. In the proposed cooperative system, the ST and the secondary destination increase the spectrum availability for the secondary packets by relaying the unsuccessfully transmitted packets of the PT. We consider two multiple access strategies to be used by the ST and the secondary destination to utilize the silence sessions of the PT. Numerical results demonstrate the gains of the proposed cooperative system over the non-cooperation case. 
Ahmed El Shafie, Tamer Khattab, Amr El-Keyi, Mohamed Nafie
cs.IT cs.NI math.IT