Analytical survey on the design of Linear Dispersion space-time codes

Multiple antenna systems that operate at high rates require simple yet effective space-time transmission schemes to handle the large traffic volume in real time. In the last investigations, LD (Linear Dispersion) codes were proposed that can handle any configuration of transmit and receive antennas. This scheme transmits substreams of data in linear combinations over space and time and the codes are designed to optimize the mutual information between the transmitted and received signals with low complexity decoding. In this paper we try to design LD codes from two approaches. We first focus on the capacity of a multiple antenna system in the presence of LD codes and extract some conditions that LD codes must have to reach the capacity. Then we show that these conditions can be obtained from orthogonal designs exactly.