Distributed beamforming with relay-aided interference alignment in fully connected interference network

This paper investigates the interference alignment solution for a fully connected (1 × 1, 1/2)^K K-user symmetric interference network with K single-antenna relays. The criterion of minimum total interference plus noise leakage (Min-INL) is considered with a set of lower and upper bound power constraints at each relay. And an iterative algorithm is proposed to alternatively optimize the precoders at transmitters, decoders at receivers and relay beamforming weights. There have closed-form solutions for subproblems to solve precoders and decoders. Subproblem with variables of relay beamforming weights is formulated as nonconvex quadratically constrained quadratic programs (QCQP) and efficiently solved by semi-definite relaxation (SDR). Simulation results demonstrate that the criterion of Min-INL with proposed algorithm obtains higher throughputs than that of minimum total interference leakage (Min-IL) and the conventional orthogonal transmission scheme.