| Along with the wireless mobile communication system moving into3G/4G era, the demand for wireless capacity is still rapidly growing. However, the wireless resources of spectrum and power have become increasingly insufficient to cope with this higher-capacity growing. So the wireless transmission techniques are urgently required to be enhanced and reformed to meet this increasingly demand for even-higher capacity.This thesis aims at constructing enhanced transmission techniques for the fu-ture wireless mobile communication system. Specially, our research focuses on the multiple-antenna transmission techniques with respect to two kinds of typical mobile communication scenario, one is multiple-antenna down-link transmission, the other is bi-directional relay networks. The main research works include closed-loop extended space-time block coding, spatial modulation and wireless network coding. As conclu-sions, several enhanced transmission techniques have been successfully developed. The main works and innovation are briefly described as follows:1. In multiple input and single output (MISO) system, one new closed-loop extended orthogonal space-time block coding (CL-EOSTBC) scheme is proposed to pro-vide full transmit diversity and higher antenna array gain. By selecting2-antenna Alamouti STBC as the group encoder, the CL-EOSTBC realizes the full space-time coding rate of1, and the low-complexity single-symbol linear decoding. The optimal scaling factors are achieved by formulating the closed-loop design as one Convex optimizing problem. Furthermore, the practical feedback code-book is de-signed. The results show that the novel CL-EOSTBC with p bits feedback achieves better performance than the traditional GCC-based EOSTBC scheme with p-1bits feedback, and the SNR gain is about1dB. With4transmit antennas as a special case, the novel scheme also achieves improved performance than the tra-ditional ones with power allocation or phase rotation only, while the feedback overhead is maintained the same. Another result is the effect of phase quantifica-tion is more sensitive than that of amplitude quantification. Notice that at each transmit symbol time slot only one half transmit antennas are activated for the novel CL-EOSTBC scheme, which is really significant for the real implementation. As a result, the novel scheme achieves better performance in term of SNR gain, implementation cost and feedback overhead.2. In multiple input multiple output (MIMO) system, the unequal error protection (UEP) performance of spatial modulation (SM) is analyzed in detail, based on which one new spatial modulation scheme is developed, and a new set of design criteria for the trellis coded spatial modulation are proposed.1) It is proved that the error performance of SM is mainly determined by the minimum difference between the adjacent antennas and the minimum distance be-tween the adjacent modulation symbols, and less depends on the cross performance between the different antennas and different modulation symbol. Thus, by only comparing the distance characteristics of antenna domain and modulation constel-lation individually, the UEP performance of SM could be easily obtained.2) Based on the UEP performance of SM, the set-partitioning rule for SM is devel-oped and a new set of design criteria for trellis coded spatial modulation (TCSM) are proposed, with help of which several TCSM schemes are constructed success-fully. The research results show that the novel TCSM schemes achieves better performance than the traditional ones, especially over Rician or correlated fading channels. Moreover, the novel TCSM schemes are robust to the channel variation.3) A novel spatial modulation scheme is proposed based on the UEP performance of SM and the set-partitioning rule of modulation constellation. Different from the traditional SM scheme, the novel SM uses one expanded modulation signal constellation to carry all bits mapping to one SM symbol, in which the bits used to select transmit antenna are also used to select one sub-set after the set-partitioning, while the other left bits are used to determine the transmit symbol from the cho-sen sub-set. By adopting Ungerboeck set-partitioning, the performance of the bits used to select the transmit symbols in one sub-set is preserved as much as possible, while the performance of the bits used to select the transmit antenna is improved by retransmitting them in the modulation symbols. The results demonstrate that the novel SM achieves better performance than the traditional one over Rician or correlated fading channels. Furthermore, the novel SM has the same decoding complexity as the traditional one. Hence, the novel SM is one appealing scheme for the large-MIMO configuration or optical communications, where the MIMO channel is difficult to be independent, or the line-of-sight parts often exist.3. In two-way (bi-directional) relay networks, the physical-layer network coding (PNC) and modulation techniques are studied in details.1) We studied the physical-layer network coding based on maximum-likelihood (ML) detection with the relay node employing multiple receiving antennas, which can directly produce the soft decision information for the XORed (bitwise exclusive or) version of two source bits in the form of logarithmic likelihood ratio (LLR), and we further provide its Max-Log approximation form from the viewpoint of practical applications. Moreover, the averaged error performance of PNC with ML detection is analyzed and the upper bound of averaged bit error rate is achieved as a closed-form. The simulation results show that the derived error upper bound could accurately evaluate the performance of PNC with ML detection. It also proves that the PNC with ML detection could achieve full diversity gain, which is better than the traditional PNC based on ZF and MMSE detection, where the di-versity order is equal to Nr-1with Nr denoting the number of receiving antennas. Furthermore, simulation results show that the Max-log approximation achieves al-most the same performance as the ML detection, so it is a prefer scheme in the practical applications.2) A novel rectangular QAM nesting method jointly with physical-layer network coding is proposed for the broadcast phase in two-way relay networks, by which the asymmetric data rate transmission is achieved with a higher-order modulation constellation carrying the higher data rate information while the lower data rate in-formation carried by a sub-constellation nested in the higher-order constellation. It firstly proved that the nesting method based on the traditional UP set-partitioning is not optimal. And hereby the new improved nesting method is developed. The results are significant for the joint design of PNC, channel coding and modulation schemes. |
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