Partial Interference Alignment for Downlink Heterogeneous Network in the Medium SNR

Interference alignment is a common method in the analysis of interference network capacity. By dividing the signal space into two parts in the transmitter, the expected signal and interference signal are distinguished. The traditional interference alignment can obtain the optimal solution only at high signal-to-noise ratio, and its performance decreases greatly at low and medium signal-to-noise ratio. This paper proposes a partial interference alignment scheme for the downlink transmission of heterogeneous networks under medium signal-to-noise ratio. Firstly, the downlink network interference model composed of macro cells and small cells is established; Secondly, according to the power constraint of the cell transmitter, the hard part interference alignment is proposed, which can adaptively select the transmission subspace and capture the tradeoff between the transmission dimension of small cell users and macro cell users; Then, the hard part interference alignment algorithm is further improved, that is, the soft part interference alignment. The desired signal and undesired signal are balanced at each client, and the receiving matrix is solved by iterative method. The experimental results show that the proposed partial interference alignment method can achieve better capacity under moderate SNR conditions, and the convergence of the iterative method is independent of SNR.