A channel monitoring scheme in multiple-antenna wireless communications

We consider the design of the channel monitoring scheme in flat-fading and limited feedback multiple-input multiple-output (MIMO) wireless systems. The equal gain pre-coders with scalar quantization are applied, which do not require the predefined codebook. In such precoders, bit assignment can be used for quantization to further improve the system performance. There are two conventional bit assignment schemes. One is the uniform bit assignment and the other is the optimal bit assignment obtained by using exhaustive search. The uniform bit assignment is simple but turns out to have obvious performance degradation. On the other hand, the exhaustive search method leads to the optimal performance. However, its computational complexity is extremely high and may be somewhat impractical to be realized. In this paper, we propose two bit assignment methods for the MIMO equal gain precoder with scalar quantization. The proposed methods are with low complexity and their performance are close to that of the optimal scheme. Consequently, the proposed bit assignments provide good trade-off between performance and complexity.