A New Approach to Layered Space-Time Code Design

The block layered space-time codes, with the intent of simultaneously achieving high coding gain and high code rate, have been suggested. These codes are based on the design principles of existing layered space-time codes and space-time block codes. The previously known concept of a layer has been modified to a block layer wherein a block layer has more than one antenna transmitting at the same instant and hence the name for this scheme. Each block layer incorporates Alamouti’s transmit diversity scheme which decreases the decoding complexity. Alamouti’s scheme is preferred as it is the simplest unique linear processing technique for achieving full diversity with two transmit antennas. The block layers are made transparent to each other by Diophantine approximation. The use of space-time codes improves the coding gain for the proposed code design scheme. This scheme has been implemented for four transmit antennas and four receive antennas but can easily be extended to any number of antennas depending on the code rate desired. The proposed codes achieve a normalized rate of 2-symbol/s. Simulation results show that the block layered space-time codes outperform threaded algebraic space-time (TAST) codes, which is the best known layering scheme that achieves full-rate and full-diversity with arbitrary number of transmit and receive antennas, in certain scenarios. Index terms Block Layered Space-Time Codes (BLST), Maximum Likelihood (ML), Diagonal Algebraic Space-Time Codes (DAST), Threaded Algebraic Space-Time Codes (TAST)