Ergodic interference alignment for the K user multiple input multiple output interference channel

This study mainly focuses on the K user multiple input multiple output (MIMO) Gaussian interference channel with M antennas at each transmitter and N antennas at each receiver, in which min(M, N)/max(M, N) ≥ (K − 1)/[K(K − 2)] and K > 3. The channel coefficients are time varying/frequency selective and drawn from a continuous distribution. Based on ergodic interference alignment (IA), an achievable scheme is proposed to achieve the KMN/(M + N) total degrees of freedom (DoF). Benefited from ergodic IA, the scheme can reach the goal with simply linear beamforming and finite symbols. Nevertheless, the limitation of ergodic IA is the long delay waiting for the desired channels. Hence, the actual delay is derived. Then, by multiplying factors on channel coefficients and adjusting orders of symbols, the authors optimise the delay. The formula shows that the new delay can be effectively reduced. In addition, the simplicity of coding scheme allows us to derive the closed form of achievable rate expression at any signal-to-noise ratio. And the optimisation of latency does not affect the data rate at all. The simulation shows that the achievable rate is close to the rate upper bound.