On the design of linear precoders for orthogonal space-time block codes with limited feedback

Orthogonal space-time block codes (OSTBCs) are one of the most practical space-time codes due to their simplicity and optimal decoding. When information about the channel is available at the transmitter, the performance of OSTBCs can he significantly improved by exploiting the array gain. However, providing full knowledge of channel state at the transmitter may not be affordable in many practical cases. Thus exploiting partial channel knowledge to improve the performance of OSTBCs seems to be attractive. In this work we investigate the design of linear precoders with partial channel knowledge at the transmitter combined with an orthogonal space time code. We derive the condition for optimal precoder subject to a power constraint on the whole transmission block. We also propose a technique for precoder codebook design with limited feedback.