Sum rate of two-way MIMO AF relay networks with transmit/receive zero-forcing

The sum rate of multiple-input multiple-output (MIMO) amplify-and-forward (AF) two-way relay networks (TWRNs) with transmit/receive zero-forcing (ZF) is analytically studied. Specifically, the exact sum rate expressions are derived for uncorrelated and semi-correlated Rayleigh fading cases in closed-form. Moreover, the closed-form upper and lower bounds of the sum rate are derived for doubly-correlated Rayleigh fading. In particular, these sum rate bounds are tight, and consequently, serve as benchmarks providing valuable insights into practical MIMO AF TWRN system-design. All the analyses are verified by using Monte-Carlo simulations.