Practical Analysis of Codebook Design and Frequency Offset Estimation for Virtual-MIMO Systems

摘要

A virtual multiple-input multiple-output (MIMO) wireless system using thereceiver-side cooperation with the compress-and-forward (CF) protocol, is analternative to a point-to-point MIMO system, when a single receiver is notequipped with multiple antennas. It is evident that the practicality of CFcooperation will be greatly enhanced if an efficient source coding techniquecan be used at the relay. It is even more desirable that CF cooperation shouldnot be unduly sensitive to carrier frequency offsets (CFOs). This paperpresents a practical study of these two issues. Firstly, codebook designs ofthe Voronoi vector quantization (VQ) and the tree-structure vector quantization(TSVQ) to enable CF cooperation at the relay are described. A comparison interms of the codebook design and encoding complexity is analyzed. It is shownthat the TSVQ is much simpler to design and operate, and can achieve afavorable performance-complexity tradeoff. Furthermore, this paper demonstratesthat CFO can lead to significant performance degradation for the virtual MIMOsystem. To overcome this, it is proposed to maintain clock synchronization andjointly estimate the CFO between the relay and the destination. This approachis shown to provide a significant performance improvement.