Performances of Amplify-and-Forward based wireless relay networks with Traveling-Wave Tube Amplifiers

Due to the constraint of cost for relay nodes, nonlinear power amplifiers are employed in wireless relay networks. In this paper, we investigate the effect of Traveling-Wave Tube Amplifiers (TWTA) on the performances of Amplify-and-Forward based relay networks. Through Bussgang linearization theory, the nonlinear amplifying process can be equivalently expressed as a linear process with a random distortion term. Accordingly, the signal to noise distortion ratio (SNDR) is derived. Furthermore, we also give the instantaneous capacity and symbol error rate at the receiver. By the simulations, the validity of our analysis is verified. It is found that if the transmit power exceeds a threshold the system performances start to degrade. The analytical method in this paper can be employed to evaluate the performances for other nonlinear processes.