Low Complexity Linear Precoding Scheme for Interference Management in Femtocell Networks

Unrelenting demand of mobile data can be met by intensive spectrum and spatial reuse which can be achieved by femtocells and multi-stream MIMO transmission. However, random deployment of femtocells may cause severe co-channel interference (CCI). In this paper we propose an algorithm, where femto base stations form a cluster and cooperatively generate precoding matrix for interference mitigation to nearby macro user (MUE) and other femto users (FUEs). We propose a modified version of conventional block diagonalization (cBD) linear precoding, where some antennas in femto cluster are de-activated for interference alignment in the null space of MUE. The cBD involves two singular-value- decomposition (SVD) operations which introduces high computational complexity. Therefore we propose a low complexity precoding algorithm which involves generalized zero forcing channel inversion (ZF-CI), QR decomposition and lattice reduction (LR) transformation. Simulation and analytical results show the superior performance of our proposed scheme in terms of sum-rate and computational complexity.