How Much Feedback Is Enough for MIMO? III Codebook Design
[How Much Feedback Is Enough for MIMO? I Introduction] [How Much Feedback Is Enough for MIMO? II Channel Estimation] [How Much Feedback Is Enough for MIMO? IV Channel Quantization] [How Much Feedback Is Enough for MIMO? V Feedback Reliabilities] [How Much Feedback Is Enough for MIMO? VI Rank Deficiency] Figure 2. Voronoi cell and various bounds MIMO beamforming mismatch upper bound depends on the codebook design. The maximum MIMO beamforming mismatch can be determined by the largest radius of the codebook’s Voronoi cell { V i : 1 ≤ i ≤ 2 R }, which in general is the solution to the disk-covering problem that still is open. Instead of finding the exact boundary for the Voronoi cell V i , a heuristic approach using sphere-packing bound and sphere cap to approximate the actual polytope boundary can be used. The result is an approximate of the sphere packing solution, in which all spheres are supposed to be non-overlappedly placed. With this approach, sphere...