| Spatial modulation(SM) scheme can overcome the inter channel interference and synchronization problems effectively, and further reduce the implementation complexity and cost of multi-antenna system. Also, SM is able to obtain high data transmission rate by using the antenna index to transmit information invisibly. Multiple input multiple output(MIMO) scheme can improve the capacity and spectrum efficiency of wireless communication system greatly. Therefore, the combination of SM and MIMO(SM-MIMO) technology may be one of the most promising technology for the next generation of mobile communication system. Considering the rate of conventional SM-MIMO technology is fixed, the discrete rate adaptive modulation technology is introduced into the SM-MIMO system to make full use of channel state information for adaptive transmission, and the spectrum efficiency is improved effectively, which provide good theoretical basis for the practical application of SM-MIMO. The main work of this paper is as follows:1. Adaptive transmission technology in SM-MIMO systems is investigated. Firstly, the system model of adaptive SM-MIMO is introduced, and the probability density function of the received signal to noise ratio is derived. Secondly, the accurate formula of the bite error rate(BER) of the constellation symbol is used to obtain the improved switching thresholds, avoiding the inaccuracy of switching thresholds computation and performance analysis caused by using approximate formula in some work. The theoretical expressions of the spectral efficiency(SE) and BER of the system are derived. Thirdly, based on the average BER, the adaptive switching thresholds are optimized by using KKT condition and Newton method. Using the thresholds, the system can achieve the maximum spectral efficiency while satisfying the constraint of target BER.2. The adaptive spatial modulation MIMO technology over spatially correlated Rayleigh fading channels is investigated.. Considering the distance between the receive antennas of mobile terminal is very small in the wireless system downlink, strong correlation will happen. For this reason, the adaptive SM-MIMO and its performance over correlated channels are studied. The probability density function of the received signal to noise ratio, the closed form expressions of the SE and average BER are given. In order to overcome the problem of high complexity by using KKT condition, the optimized thresholds are obtained by using the one-dimensional solution while satisfying the constraint of target BER. The simulation results verify the correctness of the theoretical analysis.3. By combining the space time block code(STBC) and the SM technology, the adaptivetransmission in the STBC-SM system is studied. With this adaptive STBC-SM, high transmission rate and diversity gain may be obtained at the same time. The system model is given firstly, and the theoretical BER performance STBC-SM system is analyzed. The SE and average BER of the adaptive STBC-SM system are derived then, and the theoretical analysis are verified by simulation results.Finally, the simulation results show that STBC-SM technology can get better BER performance compared to the conventional SM-MIMO under the same transmission rate. |
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