A General Closed-Form Solution to Achieve Interference Alignment along Spatial Domain

Interference alignment along spatial dimension for the K-user constant MIMO interference channel with arbitrary antenna configuration is investigated. We show that interference alignment can be accomplished either at the transmitter or at the receiver. Based on the constraint on the total stream number L <; min[(N
²
K)/(NK-M), K/(K+1)(M+N)] with M antennas in all transmitters and N antennas in all receivers, we obtain a general closed-form solution to achieve interference alignment by nulling the constructed channel coefficients matrix. This general solution gives a simple implementation for interference alignment to replace present case-by-case solutions.