Optimal Resource Allocation Technology Research Based On Energy-efficient And Spectrum-efficient In Cooperative Radio Networks

With the development of wireless communication, the wireless applications and demand have been increasing, making the spectrum more and more crowded. To improve the spectrum utilization, the cognitive radio is proposed. In the cognitive radio network, the cognitive user can found and opportunity use spectrum that are not used temporarily by primary user, improving the spectrum efficiency. To improve the rate, cooperative communication has been studied, and it can increase the user’s rate through diversity technique when the number of the antenna is limited.The spectrum utilization rate and spectrum efficiency have been studied in recent years, and the energy consumption in the base station, especially the mobile equipments are also considered because that too much energy consumption will results more waste and pollution. So the green, efficient radio has become a hot topic in future development. In view of this, the main contents are as follows:(1) Energy-efficient resource allocation is investigated for a relay-based multi-user cooperation orthogonal frequency division multiple access(OFDMA) uplink system. The objective is to maximize the total energy efficiency(EE) of the uplink system with consideration of some practical limitations, such as the individual power constraint for the users and relays and the quality of service(QoS) for every user. An energy-efficient resource allocation problem is formulated that seeks joint optimization of subcarrier pairing, relay selection, subcarrier assignment, and power allocation. Due to the complexity of the problem, the considered EE problem in fractional form is transformed into an equivalent optimal problem in subtractive form, which is solved by using dual decomposition and subgradient methods. To reduce computation costs, we propose two low-complexity suboptimal schemes. Numerical studies are conducted to evaluate the EE of the proposed algorithms and compare the impact on the circuit power and the number of relays.(2) This study investigates sensing-based spectrum sharing access(SSSA) and sensing-based spectrum opportunistic access(SSOA) schemes in cooperative OFDM-based cognitive radio networks with imperfect spectrum sensing. The optimal resource allocation strategy, including sensing time and transmit power, is designed to maximize the ergodic throughput of the secondary system. For a two-hop cooperative communication in the secondary system, the amplify-and-forward relay protocol is adopted and enables the source and relay to sense the state of the primary user(PU) jointly. To protect the PU effectively from harmful interference, the average interference power constraint in each hop is considered. Two simplified versions for the SSSA and SSOA schemes are employed because of the complexity of the problem. Then two algorithms are proposed that acquire the optimal sensing time and power allocation for both schemes. Finally, simulation results are presented to compare the performance of the two schemes.