Interference Alignment Based Transceiver Design in OSG mode of HetNets

Abstract

This paper focuses on solving co-channel interference (CCI) issues arising in the open subscriber group (OSG) mode of heterogeneous networks (HetNets). Considering a general framework consisting of arbitrary number of picocells within a macro cell, where the inter-user interference (IUI) is the main CCI to macro user equipments (UEs), while the the inter-cell interference (ICI) is the major CCI to pico UEs. In this paper, three IA based transceiver design schemes are proposed. For macro cell, we uniformly use block diagonalization (BD) scheme to eliminate the IUI. And for picocells, three IA schemes are proposed to mitigate the ICI. The first scheme, named as zero forcing IA (ZF-IA) scheme, aligns the inter picocell interference onto an arbitrary sub-space of the cross-tier interference using ZF scheme. Considering the channel state information (CSI) of the desired channel of pico UEs, the second scheme, named as optimal desired sub-channel selected IA (ODC-IA) scheme, aligns the inter picocell interference onto a certain sub-space of the cross-tier interference, which guarantees the largest channel gain of the desired signal of pico UEs. The third IA scheme, named as maximum cross-tier interference selected IA (MI-IA) scheme, is designed for the system with less receive antennas. The inter picocell interference is aligned onto the space of the strongest cross-tier interference and only the interference on this space is nullified. The complexity analysis and simulations show that the proposed transceiver design schemes outperform the existing IA schemes in the OSG mode of HetNets, and the MI-IA scheme reduces the requirement of the receive antennas number with lower complexity.

Low-Overhead Feedback Topology Design for the K-User MIMO Interference Alignment

“…Interference alignment (IA) is an advanced technique for multi-node coordination as it is optimal in terms of degrees of freedom (DoF) at high signal-to-noise ratio regime, and thus IA can be exploited in interference channel [1], relay based wireless networks [2][3], heterogeneous networks [4], etc. In fact, the DoF gains of IA are obtained by designing IA precoders whose computations require sufficient channel state information (CSI) at the transmitters (Txs).…”

“…Because the interfering links from Txs 1 and 2 to Rx 4 are aligned with each other, Rx 4 is able to consider two different interferers as one interferer which spans d dimensional subspace. Therefore, the auxiliary receive filter4 u can be constructed as 2d linearly independent vectors of the null space of 1 41…”