Performance-throughput For Spectrum Sensing Based On Relay Cooperation

Recently, as an effective way to solve the problem of spectrum scarcity and spectrum underutilization, Cognitive Radio (CR) has got more and more attention. CR technology can sense the around wireless environment accurately and rapidly. Spectrum sensing is the important precondition and key technology to improve CR users'spectrum utilization and protect primary users from interruption. Also, spectrum sensing is the key to improve spectrum utilization. There are two important parameters associated with spectrum sensing: probability of detection and probability of false alarm. The higher the probability of detection is, the better the primary users are protected. However, the lower the probability of false alarm is, the more chances the channel can be reused when it is available, thus the higher the achievable throughput for the second user. In this paper, we study the sensing-throughput tradeoff based on relay cooperation spectrum sensing.The thesis begins with the introduction to the development of cognitive radio system. Analyze several algorithms for spectrum sensing in the receiver's opinion. The thesis's study background, development status and importance of sensing-throughput tradeoff are pointed. The basic theory and fusion rules of cooperative spectrum sensing and spectrum sensing based on relay cooperation is summarized briefly.Then, the thesis introduces the sensing-throughput tradeoff for the single cognitive user and also studies the sensing-throughput tradeoff based on relay cooperation for two user cognitive radio system. Through relay retransmit of primary user's signal between two cognitive users, the maximum throughput of cognitive system under the constraint that the primary users are sufficiently protected is studied. Simulation results show that the relay method reduces the probability of false alarm, shorts the optimal sensing time to maximize the throughput efficiently, and also improves the maximum throughput of the worse secondary and the secondary network under the constrain that primary users are protected sufficiently.Lastly, the thesis study the sensing-throughput tradeoff based on relay cooperation for multi-user cognitive radio system. Grouping the users into pairs, and if one user acts a relay for the other in each pair, can improve the performance and throughput of the multi-user cognitive radio system. Spectrum sensing based on relay cooperation is available when the number of cognitive users is more than two. Simulations confirm the point that relay cooperation can improve the throughput of the worse cognitive user under the constraint that the primary users are protected sufficiently.