Study On Spatial Modulation Based Wireless Transmssion System

In a multiple-input multiple-output(MIMO) transmission link, multiple antennas are employed at both transmitter and receiver. MIMO is capable of exploiting the space resources to effectively improve the spectral and power efficiency of the communication system. However, the existing MIMO transmission techniques, more or less, have complex transceiver structures and/or high hardware costs. In the diverse family of MIMO techniques, the recently proposed spatial modulation(SM),which attracts much attention and extensive research in both academic society, is particularly promising, since it has a low-cost transceiver and capable of efficiently operating in diverse MIMO configurations. As a further advance, SM also allows us to use MIMO channel resources for achieving reliable high speed data transmission.Transmit signal optimization and signal detection are key techniques of digital communication systems. This dissertation focuses on the signal detection and the transmit signal design issues for the SM based MIMO systems. The performance analysis methods and the corresponding signal detection algorithms, the discrete-domain transmit-bit allocation aided SM as well as the continuous-domain transmit-vector optimization aided SM are investigated. Finally, the SM technique is extended to cooperative-assisted virtual MIMO systems and the corresponding signal detection and performance analysis methods are also involved. The main researches of this dissertation are summarized as follows.Based on the advantage of SM system that only a single transmit antenna is activated at any time instant, an ordered sphere decoder(SD) algorithm and a multi-stage match filtering(MF) algorithm, based on the statistical probability, are proposed for SM systems. The computational complexity of the proposed algorithms is also analyzed. Then, considering that SM systems typically rely on powerful channel codes, the proposed hard MF detector is extended to provide soft-decision-based information. Simulation results show that the proposed algorithms are capable of striking a flexible tradeoff between the bit error ratio(BER) performance attained and the complexity imposed.For optimizing the bits transmission in limited-feedback channel, an adaptive modulation(AM) algorithm, an adaptive transmit mode switching(TMS) algorithm and a joint AM-TMS scheme which combines both AM and TMS techniques are proposed for SM-based systems, and three adaptive SM transmission schemes are conceived, which adjust the modulation orders and the number of transmit antennas according to the channel conditions. Moreover, their associated computational complexity and feedback load are analyzed. The transmit parameter selection criterions of the proposed adaptive schemes are also derived. In particular, for the AM-aided limited-feedback SM schemes, we proposed two simplified versions based on their candidate occurrence probabilities. Our simulation results confirm that the proposed adaptive SM schemes provide considerable BER performance improvement compared to non-adaptive SM schemes.To increase the system’s robustness under time-varying channel conditions, the potential benefits of the non-codebook-based precoding SM schemes are investigated. By exploiting the SM’s special information conveying mode, a precoding matrix design criterion is achieved and a power allocation based precoding scheme and a phase rotation based precoding scheme are proposed. To avoid the high complexity of the power allocation based schemes, two low-complexity algorithms are presented. Moreover, it is plausible that the power allocation and AM techniques exploit different degrees of freedom offered by the MIMO channels. As a result, the power allocation aided SM and the ASM may result in different performances depending on the transmission configuration. As a result, it is possible to achieve a further performance benefit by efficiently combining AM and power allocation techniques in SM. In this paper, we proposed a reduced-complexity hybrid adaptive SM scheme. Simulation results show that the proposed precoding aided SM schemes provide considerable BER improvements over the conventional SM systemsMoreover, cooperative transmission is one of the most promising techniques in wireless communication. For achieving the spatial diversity provided by the cooperative technique, three detect-and-forward(DeF) relaying protocols are invoked for SM-aided cooperative systems. More specifically, upper bound expressions of the BER of the antenna indices bits and of the amplitude and phase modulation(APM) bits are derived for the non-cooperative SM system. Based on the achieved theoretical results, it is found that these two types of bits can not match different unequal error protection(UEP) requirements. Based on these observations, a hierarchical modulation technique is applied to the DeF-based SM for striking a flexible tradeoff in terms of the average BER and the UEP capability. Moreover, an upper-bound of the DeF-based SM scheme’s BER is derived. Our numerical results show that the bound is asymptotically tight in the high-SNR region. In order to further reduce the detection complexity imposed on the DeF-based SM system, a low-complexity ML detector is conceived. Simulation results verify that the proposed DeF-based SM system can achieve better BER performance compared to the classic cooperative MIMO systems.