Resource Allocation in Correlated and Non-Correlated MIMO Systems

The multiple-input multiple-output (MIMO) transmission concept targets at increasing the throughput of communication links by employing multiple transmit and receive antennas. As regularly in digital transmission, for such systems the bit-error probability is the crucial quality criterion - also known as the bit-error ratio (BER). If simple MIMO transmission channel and data source models are assumed, the BER can be computed analytically and the system under consideration can be optimized with the respect to a minimum BER. In this contribution, we consider BER minimization for MIMO links with uncertainty in their channel parameters under good and poor scattering conditions. Optimal solutions such as the Lagrange multiplier method regarding bit and power allocation in the transmitter are designed to achieve the best link performance. However, suboptimum solutions are able to achieve a similar performance with a significantly lower complexity. The obtained analytical results show that the achievable performance strongly depends on the number of active MIMO layers as well as the assigned transmit power per layer and the number of bits per transmitted symbol. Furthermore it turns out that the natural choice of creating MIMO layers with identical BER's does not guarantee the best performance.