Two-Way AF Wireless Relay Networks under Channel Uncertainty

Two different two-way amplify-and-forward (AF) wireless relay systems with transmit power constraints at the relay(s) are studied: one- relay system with multiple N antennas between two sources, and multiple N-relay system with one antenna per relay between two sources. The iterative and explicit relay amplifying matrices (or vectors) with perfect cancelation of self- interference under channel uncertainty are determined based on the minimum mean square error (MMSE) criterion. Both iterative and explicit relay amplifying matrices are numerically investigated through the simulation. Simulation results show that the gain of diversity order with channel uncertainty can occur as N increases, while the loss of diversity order can occur as channel estimation error powers increase.