Beacon-assisted spectrum access with cooperative cognitive transmitter and receiver

We propose a novel cooperative communication protocol for multicasting a common message from one source to two destinations and based on that offer a spectrum access scheme for the cognitive radios that seek to utilizing the spectrum holes within the bands licensed to the legacy systems. The proposed cooperation model has two major traits; first, by opportunistically and dynamically assigning one of the destination nodes as relay for the other one, via a single-time relaying both destinations achieves a second order diversity gain. Secondly, it guarantees performance improvement over all SNR regimes, which is not the case in most cooperation protocols as diversity gain is a high SNR measure and yielding higher diversity orders ensures improvement only over high enough SNRs. Next, we consider cognitive users, to whom the codebook of the primary users is known as side information, and offer a beacon-assisted mechanism for spectrum access. We assume that a primary user multicasts a beacon message upon releasing a spectrum band and adopt the proposed cooperation model to strengthen a cognitive transmitter-receiver pair in decoding the beacon message. Finally, we quantify the effect of such cooperation on the capacity of the channel between the cognitive transmitter-receiver pair, as a meaningful measure to assess how the proposed cooperation model assists the secondary users in exploiting communication opportunities.