Non-square rate-one space-time block codes for LTE-advanced systems with optimised coding gain

Alamouti code is an excellent option for a two-transmitter and one-receiver network owing to its optimal performance and low detection complexity. Unfortunately, with the requirement of odd number of time slots in the frame structure for data transmission of long-term evolution (LTE)-advanced systems, this scheme is not applicable to such systems. In this correspondence, three new space-time block codes (STBCs) are proposed for LTE-advanced systems with two transmit antennas and a receive antenna with three-time-slots. The proposed designs achieve rate of one symbol per channel use and full transmission diversity. The main objective of designing the first and second codewords is to improve the coding gain of STBCs with three time slots. These STBCs are constructed using real rotation of quadrature amplitude modulation (QAM) information symbols in three dimensions. As will be seen later, the idea of real rotation of transmitted symbols using orthogonal matrices allows a decrease in the number of unknown parameters to be determined in order to maximise the coding gain. Using real rotation to encode the transmitted symbols, a new scheme is obtained which has the same minimum determinant (MD) as Alamouti code for 4, 16 and 64-QAM signal constellations. In designing the last codeword, the authors attempt to reduce the maximum-likelihood decoding complexity by decoupling detection of one encoded symbol from others. The simulation results confirm an improved performance of new schemes as compared to recently proposed codes.