Date Added: Oct 2012
Closed-loop MIMO technique standardized in LTE can support different layer transmissions through pre-coding operation to match the channel multiplexing capability. However, the performance of the limited size codebook still needs to be evaluated in real channel environment for further insights. Based on the wideband MIMO channel measurement in a typical indoor scenario, Capacity Loss (CL) of the limited size codebook relative to perfect pre-coding is studied first in two extreme channel conditions. The results show that current codebook design for single layer transmission is nearly capacity lossless, and the CL will increase with the number of transmitted layers. Furthermore, the capacity improvement of better codebook selection criterions is very limited compared to CL.