Interference decoding in cellular wireless relay networks with space-time coding

In this paper we propose a cooperative protocol and a symbol decoding algorithm that target improved performance in the presence of inter-cell interference (ICI) in wireless cellular networks. Our scheme uses the wireless signals that interfere at relay nodes located at the cell edge instead of discarding them. The relays are non-regenerative and apply a space-time code (STC) to the interfered signal. Subsequently, the relays broadcast the coded signals. At the destinations the interfered and ST-coded signals are decoded in two stages. First by decoding the STC, and then by applying successive interference cancellation (SIC). Simulation results for Rayleigh fading channel reveal significant throughput benefits even in the low SNR regime. We also present results for a small-scale LTE-based cellular scenario and we compare our scheme against the Coordinated MultiPoint (CoMP) transmission mode of LTE-A that is based on beamforming.

I. Introduction

Interference coordination has been recently proposed as an efficient mechanism to combat interference in advanced wireless cellular standards like the 3GPP UTRAN Long Term Evolution (LTE) [1]. LTE adopts a flat frequency reuse approach which means that all base stations (BS) can use the same frequency band. Thus, when two neighboring BSs schedule transmissions in the same frequency band interference is naturally present at the user equipment (UE). In advanced cellular standards like LTE this inter-cell interference (ICI) is handled with the mechanism of ICI coordination (ICIC) [1]. With ICIC when two neighboring BSs use the same orthogonal frequency-division multiple access (OFDMA) subcarrier during the same time slot (this is a single resource block in LTE terminology), then the BSs coordinate through the backhaul network in order to minimize the allocated power to these subcarriers leading thus to reduced interference. At the same time they can independently increase the allocated power to the remaining OFDMA subcarriers. This means that resource allocation between BSs is exercised in a cooperative fashion for UEs that are located at the cell edge.