Lower Bound on the Shannon Capacity of MIMO Space-Time Communications Systems Based on the Leakage Level.

In MIMO space-time communications systems, the effect of a discrepancy in the channel knowledge is to give rise to a loss in the orthogonality of the eigenmodes. In the context of this work, this loss in orthogonality will be quantified in terms of a leakage level and will be due to a random error in the estimation or measurement of the communications channel. The result will be a drop in the Shannon potential capacity of MIMO communications systems. The calculations of potential capacity and leakage level will clearly be stochastic nature. This is highlighted by plotting the ensemble average as well as the minimum value of these respective quantities. Further to this, a conservative lower bound on the Shannon potential capacity is derived. It is therefore argued that the minimum value of Shannon potential capacity in the case of this lower bound would put an ultimate limit on the performance of the MIMO communications system defined here. The entire discussion is supported by relevant physical measurements.