Adaptive analog network coding strategy with variable slot numbers in two-way relay systems

Analog network coding (ANC) can effectively improve the outage performance and increase its spectrum efficiency for two-way relay systems. An adaptive analog network coding strategy (AVSN-ANC strategy) was proposed in this paper, which dynamically adjusts the number of timeslots according to the instantaneous channel information. In this manner, the outage probability can be significantly reduced. We describe the detailed realization of the strategy, derive the closed-form expression for the lower bound of the outage probability, analyze the achievable diversity order, and discuss the power allocation issue. Simulation results validate the theoretical analysis. Compared to conventional ANC protocol with fixed slot numbers, the proposed AVSN-ANC strategy offers better outage performance. In addition, it is shown from our study that, the equal power allocation scheme, despite its simplicity, can obtain the near-optimal performance in terms of the outage probability.