Relaying Strategy Based on Estimated Information for Multi-Antenna Cooperative Networks

A sphere-based list forwarding scheme for multiple-input multiple-output (MIMO) relay networks is proposed and analyzed. Firstly, an estimate forwarding (EF) method is proposed, which forwards the minimum mean squared error (MMSE) estimate of the source data to the destination. Since it performs like amplify-and-forward (AF) and decode-and-forward (DF) for the low and high signal-to-noise ratio (SNR) regions, respectively, the EF relay thus outperforms conventional AF and DF across all SNRs without the need for switching algorithms for different SNRs. Because computational complexity is however high for relays with a large number of antennas (large MIMO) and/or high order constellations, list EF for large MIMO relay networks is proposed. It computes a list sphere decoder based MMSE estimate and retains the advantages of the exact EF relay at a negligible performance loss. The proposed list EF could offer a flexible trade-off between the performance and computational complexity.