Capacity optimization for short-range LoS 3×2 MIMO channels

Capacity optimization of line-of-sight (LoS) 3×2 multiple-input-multiple-output (MIMO) channels in indoor environments is investigated in this paper. First, the capacity fluctuation number (CFN) which reflects the change of capacity is proposed. Next, the expression of capacity against the CFN is derived. The CFN is used as a criterion for optimization of capacity by changing inter-element spacings of transmit and receive antenna arrays. The capacity sensitivity to the orientation is studied and compared with that of 2×2 MIMO channel. A small sensitivity of 3 × 2 MIMO channel is achieved and verified by both simulation and measurement results. Furthermore, the CFN can also be used as a criterion for optimization of average capacity and the proposed optimization method is validated through numerical results.