Research on Improved Quasi-orthogonal Space-time Block Code
|School||Nanjing University of Posts and Telecommunications|
|Course||Communication and Information System|
|Keywords||MIMO Space-Time System Quasi-orthogonal space -time block codes Givens matrix Differential Unitary Space- Time Coding Differential quasi- orthogonal space-time block codes|
Space-time block coding (STBC) multi-input multi-output (MIMO) system is an important one channel coding technology. STBC coding structure and channel estimation is relatively simple, relatively low decoding complexity and able to provide full spatial diversity gain other advantages, in recent years it has been a wide range of research and application. When the number of transmit antennas is greater than 2, to reach the full diversity of complex OSTBC not be able to achieve full rate transmission, the proposed concept and method of construction of full-rate quasi-orthogonal space-time block codes (QOSTBC) to solve this problem, Jafarkhani et al. Such space-time block code decoding requires the receiving end must be known channel state information (CSI), channel estimation is necessary at the receiving end. But the channel estimates will increase the system cost and complexity of sexual and when at the receiving end of high-speed moving, the channel state of rapid change of the environment, the fast fading so that the receiving end can not accurately letter channel estimation, sometimes even simply not be able to conduct estimation. Thereby generating an unwanted CSI differential space-time coding, which utilizes two adjacent received signal matrix at the differential decoding. But to achieve the encoding and decoding of DSTC, the encoding matrix you need to meet certain constraints (such as differential unitary space-time coding requirements of the transmission matrix is ??a unitary matrix). Orthogonal space-time block codes (OSTBC) will be able to achieve differential encoding constraints in recent years, the study of differential OSTBC is accounted for a significant portion of the DSTC. However, the design in accordance with the Jafarkhani thinking QOSTBC generally not unitary matrix, and therefore can not be implemented directly QOSTBC differential encoding. How to design a full-rate and high-performance the differential QOSTBC become a hot and difficult in recent years, research. Similarly, we also in-depth research differential coding QOSTBC. First, according to the the rank criteria principle of the design of space-time coding, in order to get the full diversity gain QOSTBC the Jafarkhani code the Givens matrix rotation and the constellation rotation combination, to design a full-rate full diversity QOSTBC encoding and decoding. The simulation results show the system performance of the coding scheme is a significant improvement over traditional QOSTBC. Secondly, based on the M-PSK modulated differential QOSTBC of the program, such programs by introducing a rotation factor QOSTBC constructed unitary matrix, so that we can conduct QOSTBC differential encoding. This new program has a large Euclidean distance and multi-receiver antenna system can improve the transmission performance of the system, but can not achieve full diversity, compared with other differential QOSTBC program, the single receiving antenna system transmission performance slightly have declined. Finally, the paper proposes another differential QOSTBC, this encoding scheme is not only able to achieve full diversity, achieved better than twiddle factor-based differential QOSTBC error performance and decoding complexity than the the Jafarkhani code of joint decoding complexity is much lower.