Regenerative hierarchical codebooks for limited channel feedback in MIMO systems

It has been well known that channel-adaptive systems (closed-loop) have better performance than the systems without channel knowledge (open-loop). For closed-loop systems, the receiver need to feed back its own channel information to the transmitter through the reverse channel. As the codebook size gets larger, the system performance improves, but the computational (search) complexity grows exponentially with respect to the size in conventional codebook structure. In this letter, we propose 2 codebook design schemes with hierarchical structure to overcome the complexity problem, which maintains near-optimal performance.