A Low Complexity Quantization Technique for Virtual MIMO Systems

By means of wireless cooperation, Virtual Multiple- Input Multiple-Output (V-MIMO) systems provide significant enhancements in terms of spectral efficiency and performance. A large V-MIMO system that implements bit-interleaved coded modulation (BICM) transmission and compress-and-forward (CF) cooperation is considered. Since, constructing a reliable codebook is the most computationally complex task performed by the relay nodes, in this paper, we evaluate two low complexity quantization techniques. A comparison in terms of the codebook design and overhead complexity is presented. Error performance results show that the Lloyd - Max algorithm (LM-SQ) is simpler to design and can achieve a performance comparable to optimal Voronoi Vector Quantization (V-VQ). Further, Uniform Scalar Quantization (U-SQ) is also considered, as its low complexity makes it particularly suitable for the upcoming large wireless systems.