Mitsubishi Electric Research Laboratories

We propose a modified layered structure for multiple-input multiple-output (MIMO) systems, where the layer detection order is fixed and the data rate for each layers i allocated based on the detection order and channel statistics. With Gaussian approximation of layer capacities, we derive the optimum data rate allocation and the amount of backoff from mean layer capacity is proportional to the standard deviation of the layer capacity. The minimum overall outage probability of a layered system is uniquely determined by the normalized capacity margin. We then investigate how to select the total information rate to maximize effective throughput. Simulation results show significant performance improvement with the proposed algorithm, and the performance gap between layered structure and the channel capacity diminishes with increasing ergodicity within each codeword

Mitsubishi Electric Research Laboratories

In this paper, we incorporate the layered structure with low-density parity-check codes (LDPC) to develop a quasi-block diagonal LDPC space-time structure. The lower triangular structure of the parity check matrix introduces correlation between layers. In addition, each layer, as a part of the whole codeword, can be decoded while taking information from other undetected layers to improve the decoding performance. Belief propagation of the current layer is stopped as soon as those parity checks involving only the current layer and detected layers are satisfied. Simulation shows that the proposed system outperforms the conventional V-BLAST by 0.5 dB at WER=1%

Mitsubishi Electric Research Laboratories

Latency of available channel state information (CSI) at the transmitter in time-varying channels greatly affects the performance of multiple-input multiple-output (MIMO) systems. We have derived a simple algorithm to calculate an approximation of the expected performance loss based on the most recent channel feedback. The proposed algorithm can be used to determine the maximum tolerable channel feedback delay for each particular channel realization

Mitsubishi Electric Research Laboratories

Ultra-wideband (UWB) communication is a potential technique for future high-speed networks