A codebook design and feedback method based on increment for small cells

Small cell is an emerging approach to improve the throughput of cellular networks. It also brings significant changes to the wireless link. An average incremental codebook (AIC) is proposed for small cells, which makes use of the strong line of sight (LOS) channel component existed in small cells to increase system capacity. The codebook is extended to high-rank codebooks based on household transform, while the feature of average incremental is still maintained. Furthermore, we develop a feedback compression method based on incremental domain. Combined with AIC, the method reduces the search range of optimal precoding matrix from the whole codebook to the incremental domain. The feedback amount is compressed into approximate 1 bit. Moreover, by adding an adaptive indication bit, lossless feedback compression is achieved. Simulation results show that our proposed method could achieve both significant system capacity gain and great saving of feedback overhead compared with conventional methods in small cells.