Design Of Space-Time Block Code In MIMO Wireless Communication Systems

Space-time coding is an effective approach to improve the reliability of data transmission as well as the data rates over multiple-input multiple-output (MIMO) fading wireless channels. By encoding simultaneously transmitted signals in both time domain and spatial domain, space-time coding results in time-spatial correlation between transmitted signals. This correlation can effectively reduce the effect of multipath fading to data transmission in MIMO wireless communication channels. There are many space-time block codes (STBC) that were proposed to achieve full diversity full rate and single-symbol decodable for different number of transmit antennas. In designing STBC, the peak-to-average power ratio (PAPR) at each transmit antenna is also an important parameter which affects cost and difficulty in practical implementation. In this thesis, we research low PAPR low decoding complexity space-time block codes in MIMO wireless communication system over different fading channels and with different receivers. The main work includes:(1) For MIMO system with maximum likelihood receiver, Orthogonal Space-Time Block Codes (OSTBC) are the most simple codes, but have a very low code rate. Restricted Full-rank Single-symbol Maximum Likelihood Decodable Designs (RFSDD) along with Coordinate Interleaved Orthogonal Designs (CIOD) and Generalized Coordinate Interleaved Orthogonal Designs (GCIOD) contain many zeros and have high PAPR, though their code rate is higher than that of OSTBC codes. To solve this problem we propose two new single-symbol maximum likelihood decodable STBC codes. The first proposed STBC is Group precoding-based No-Zero-Entry Single-Symbol maximum likelihood Decodable STBC (G-NZESSDC). The G-NZESSDCs use coordinate interleaving and group precoding technique. In comparison to existing no zero entry single-symbol maximum likelihood STBCs, the proposed G-NZESSDCs have the same error rate with lower PAPR. The second proposed STBC is High-Rate Single-Symbol maximum likelihood Decodable STBC with Low fraction of Zero (HR-SSDC-LZ). The HR-SSDC-LZs use coordinate interleaving and constellation rotation technique. In comparison to high rate GCIODs, the proposed HR-SSDC-LZs have the same error rate with less zeros and lower PAPR.(2) For MIMO system with maximum linear receiver, Toeplitz codes, overlapped Alamouti codes (OACs) and embedded Alamouti codes (EACs) can achieve full diversity with linear receivers, such as zero-forcing (ZF) receivers and minimum mean square error (MMSE) receivers. However, these codes have a large number of zeros in their codeword matrix. To solve this problem, we propose two No-Zero-Entry Toeplitz (NZE-Toeplitz) matrices. We then use NZE-Toeplitz matrices to construct three new code classes including no-zero-entry Toeplitz codes (NZE-TCs), no-zero-entry overlapped Alamouti code (NZE-OACs) and no-zero-entry embedding Alamouti codes (NZE-EACs). These three new codes can achieve full diversity and good error rate. In addition, these codes do not contain zeros, so they have lower PAPR than the existing full-diversity STBCs.(3) For LTE-Advanced systems with the requirement of two transmit antennas imposed on the user equipment (UE, i.e. mobile station), two three-time-slot STBC schemes, Hybrid STBC (H-STBC) and Quasi-orthogonal STBC (QOSTBC) were proposed. However, the H-STBC has just partial diversity and the QOSTBC has the downside of high decoding complexity. To solve this problem, we propose a three-time-slot space-time block code (TTS-STBC). The proposed TTS-STBC uses coordinate interleaving and constellation rotation to achieve full diversity, full rate and low decoding complexity. In comparison to the QOSTBC, the proposed TTS-STBC has better error rate and lower decoding complexity.(4) We provide full-rate No-Zero-Entry Coordinate Interleaved Orthogonal Designs (NZECIOD) for time-varying fading channels. The proposed NZECIOD codes work well over time-varying fading channels with low decoding complexity. Furthermore, a new "different interference index" is introduced to investigate the effect of time-varying fading channels on STBCs, thus showing that the proposed NZECIOD codes are more robust against the time-selectivity of fading channels than other competitive STBC codes. By completely eliminating zeros and balanced power property, the proposed NZECIOD codes are more efficient than the full-rate CIOD codes in practical implementation.