| Spatial modulation is a novel multi-antenna transmission technology,which can transmit information by using the antenna index.Spatial modulation technology,as a very promising wireless physical layer transmission technology,can obtain high data transmission rate,and overcome problems of inter-antenna synchronization and inter-channel interference effectively,as well as reduce the implementation complexity.Collaborative communication technology can achieve diversity gain,enhance reliability and improve the network coverage for wireless communication systems effectively by adding relay nodes to assist with information transmission from source to destination.In this paper,a collaborative spatial modulation MIMO system is presented based on spatial modulation technology and cooperative communication technology.The system is researched in terms of power allocation schemes,adaptive modulation schemes and adaptive transmission schemes.Moreover,threshold optimization is also studied.The effectiveness of the schemes and the improvement of system performance are verified through theoretical analysis and simulation.The work of this paper provides effective methods and theoretical support for the practical application of spatial modulation and cooperative communication systems.The main work of this paper is as follows:1.Power allocation scheme in collaborative spatial modulation MIMO system is investigated.In the first place,the closed-form expression of average BER expression is derived based on the system model.Then,the asymptotic average BER formula of the system under high SNR is derived.Based on the asymptotic formula,the sub-optimal power allocation scheme is obtained.In addition,the optimal power allocation scheme is obtained by using the iteration scheme in simulation.Finally,the results show that the simulation is consistent with the theoretical analysis,and the power allocation schemes can get better performance than the equal power allocation scheme.2.Adaptive modulation scheme in collaborative spatial modulation MIMO system is investigated.Firstly,system model of adaptive modulation is given and the moment generating function of SNR is derived.The spectral efficiency and the average BER of the system are analyzed,and the fixed threshold scheme and the optimal threshold scheme are given.Then,one-dimensional solution is used to optimize the threshold scheme so that the system can obtain the maximum spectrum utilization under the constraint of the target BER.Finally,the simulation results show that the fixed threshold scheme and the optimal threshold scheme can improve the performance of the system effectively.High spectral efficiency can be obtained by optimal threshold scheme.3.Adaptive transmission scheme in collaborative spatial modulation MIMO system is investigated.System model for adaptive transmission scheme is given according to the above system models.Adaptive optimization objective function is established based on the system model and performance analysis,so that the system can achieve high spectral efficiency under the constraint of the target BER.The method of optimizing adaptive transmission coefficients is analyzed and schemes based on fixed power allocation coefficients are proposed.The suboptimal adaptive transmission scheme and the optimal adaptive transmission scheme are analyzed,respectively.Finally,the schemes are compared with adaptive modulation scheme based on equal power allocation.Performance analysis and simulation show that the performance of the system is improved effectively by the two schemes,and the low-complexity and practical values of the sub-optimal adaptive transmission scheme are also proved. |
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