Study Of Quaternion Space Time Block Codes And Their Performance

With the increasing development of mobile technology, people request more at the transmission rate and stability. MIMO (Multiple Input Multiple Output) system is considered as the new generation of wireless communication revolution. MIMO technology has become one of the key technologies in wireless communication. Through the continued development of the past few years, MIMO technology will be increasingly used in various wireless communication systems. And STBC (Space Time Block Code) is a code technology based on MIMO system. Because of its simple structure and low decoding complexity, a further research is conducted in honeycomb mobile communication and wireless local area network.In this paper, three aspects are researched as follows:(1) A new kind of space time block code based on quaternion orthogonal designs is introduced in this paper. The new code can be transmitted and received through dual polarized antennas, with rate 1. This kind of space time block code of 3 transmit antennas is designed, then modulated by BPSK,QPSK and 8PSK respectively. In the case of same condition, compared with the space time block code of 4 transmit antennas from complex orthogonal design. When BER=10^-3, the code of design outperforms compared code by about 6dB, 5.5dB and 5.3dB respectively; when BER=10^-5, the code of design gains about 8dB, 8dB and 7dB relative to the compared code, respectively. Simulation results show that the new code can decrease the bit error rate and improve the system performance with same transmit and receive antennas.(2) A new kind of space time block code based on quaternion quasi orthogonal designs is introduced in this paper. The new code can be transmitted and received through dual polarized antennas. The channel model is formulated firstly, then this kind of space time block code of six transmit antennas is designed, and fast maximum likelihood sequence decoding method is adopted and finally modulated by BPSK. The new code is compared with the quasi orthogonal space time block code of 4 transmit antennas. The transmission rate is 1bit/(s·Hz). When BER=10-3, the code of design is about 5dB better than compared code; When BER=10-5, the code of design is about 8dB better than compared code. The simulation results show that the new code can decrease the bit error rate and improve the system performance with same transmit and receive antennas.(3)A new kind of space time block code from coordinate interleaved quaternion orthogonal designs is introduced in this paper and the pairwise decoding algorithm is used at the receiver. This kind of space time block code of 8 transmit antennas with a speed of 3/4 is discussed and modulated by BPSK and QPSK, respectively. When BER=10^-3, the design code is superior by about 5dB and 5.2dB to the compared code, respectively. When BER=10^-5, the design code is superior by about 6.8dB and 6.5dB to the compared code, respectively. The simulation results show that this kind of space time block code from coordinate interleaved quaternion orthogonal designs can remarkably improve the system performance with a lower bit error probability, compared with that of the space time block code based on quaternion orthogonal design.