Studies Of Self-interference Cancellation In Full-duplex Amplify And Forward System

Spectrum is always the most scarce resource in the future communication, how to improve the utilization of the existing spectrum resources is a critical problem to study the communication technology. HDR(Half-duplex Relay) system can not meet the needs of future communication because of its transmission signal in two different time slots or frequency. FDR( Full-duplex Relay) system is being concerned with the feature of frequency reuse. However, FDR has not be widely used because of its characteristics of the same frequency transmit and receiving signal can cause serious loop self interference signal.For the core issue of SIC(Self-interference Cancellation) of the FDR system, this paper takes measures mainly in both analog and digital domains eliminate self interference to reduce interference signal power and improve the system capacity, including:(1) Based on the model of the full-duplex SISO( Single-input Single-output) relay system, compared the performance of HDR system and FD-AF relay system with different self interference cancellation capability. Simulation results show that the performance of FD-AF relay system is much better than that of HDR system.(2) Based on the model of full duplex MIMO( Multiple-input Multiple-output) Relay System, choose channel capacity as the objective function, transmission power and signal to noise as the constraint conditions, solving two optimization problems to maximize the system throughput, we can get the optimal relay transform matrix to counteract the influence of self interference signal. The simulation results show that with the same average transmission power and signal to noise ratio, after eliminating the interference a FDR system significantly improve the performance.(3) With the combination of SIC in domain of analog and digital, the model of FD-AF relay system with multiple transmit single receive antenna is being established. The spectrum efficiency of the source to the destination as the objective function, the average transmission power of relay as the constraint, establishing the optimization model. By means of calculating how to allocate the transmission power in a closed expression algorithm, then maximize improve system performance and relay system SIC. The results show that the optimal FD-AF performance is also significantly better than HD-AF, even considering the hardware limitation of the radio link.