Research On New Spatial Modulation Enhanced Technologies For B5G

In recent years,as the demand for wireless communication services grows,massive Multiple-Input Multiple-Output(MIMO)has become one of the core technologies of the5 th generation mobile communication systems(5G).Massive MIMO technology improves the power efficiency and spectral efficiency of the system by tapping into spatial dimensional resources without increasing the density of base stations and additional bandwidth.However,massive MIMO also poses important system design challenges due to the large number of antennas required,such as excessive radio frequency(RF)overhead,unsuitability for asymmetric transmission,difficult channel estimation and complex signal processing.Therefore,exploring transmission solutions that effectively solve the above-mentioned problems of massive MIMO technology has become an important development direction for future mobile wireless communication technology.With the in-depth study of MIMO technology,a novel efficient and low-cost MIMO transmission technique,termed as spatial modulation(SM),has emerged by using the spatial dimension as a new modulation mode.It not only simplifies the MIMO structure and effectively reduces the cost of MIMO implementation,but also better suits the diverse link configuration requirements of future communication systems.This dissertation focuses on spatial modulation and its extensions,and explores important issues such as optimized spatial diversity,low intercept transmission design,low complexity signal detection and performance analysis.The main innovations throughout the paper are summarized as follows.This dissertation investigates a new spatial diversity technique,termed as space-time line code(STLC),and verifies that STLC is suitable for achieving better diversity results in downlink scenarios with limited receiver capacity by analysing its BER under typical fading channels and optimizing the design of antenna selection criteria.The theoretical BER of STLC is derived under the non-ideal conditions of channel estimation error and channel correlation,and the accuracy of the theoretical analysis is verified by numerical simulation,providing theoretical support for the subsequent optimization design.This dissertation investigates the STLC-SM transmission scheme for downlink transmission scenarios.Based on the phase rotation precoding scheme,this dissertation investigates the phase optimization algorithm for different parameter configurations by maximising the minimum Euclidean distance criterion,and verifies that the proposed scheme can obtain higher diversity gain with low guide frequency overhead through theoretical analysis of the BER of this system.In response to the increasing demand for information security in wireless transmission,this dissertation investigates the artificial noise-assisted STLC-SM technique,which can improve the efficiency of RF resources while reducing the interception probability by introducing optimized artificial noise on the activated antenna.The theoretical BER of the system is derived and its effectiveness is verified by numerical simulations.To further reduce the switching frequency at the RF end,this dissertation proposes an STLC-assisted Offset Spatial Modulation(OSM)technique,and designs a feasible precoding scheme based on equally spaced phase rotation to extend the receiving antenna configuration of the OSM technique;Through theoretical analysis,this dissertation proposes that STLC-OSM can make use of the mean value of the normalisation factor instead of the instantaneous value,thus reducing the implementation complexity;Through the derivation and numerical simulation of the theoretical BER of the STLCOSM system,it is verified that the proposed optimized STLC-OSM system can obtain a higher diversity gain.This dissertation analyzes the impact of channel estimation error on the performance of STLC-OSM and,in line with expectations,the system is more robust to channel estimation error due to its reduced need for channel state information.To further reduce the channel information requirement at the receiver side,this dissertation investigates the STLC-GRSM technique and designs a low-complexity detection algorithm based on the receiver’s different acquisition states for channel state information.Simulation results show that,for the same spectral efficiency,STLC-GRSM can effectively reduce the guide frequency overhead required for receiver channel estimation while improving the diversity gain compared to conventional GRSM.This dissertation investigates the artificial noise-assisted GRSM technique and obtains an optimized power allocation factor by deriving the theoretical BER.The numerical simulation results verify the correctness of the theoretical analysis,and the compromise between transmission reliability and low interception capability can be achieved by configuring the power allocation factor between artificial noise and signal.Reconfigurable intelligent surface(RIS)-assisted SM enhancement techniques are investigated.For single-user scenarios,an optimized diversity design using the STLC idea is investigated,and a low-complexity detection algorithm without channel information is proposed.In order to reduce inter-user interference in RIS-SM communication systems,the paper investigates the RIS-assisted Ambient Backscatter Communication(Am BC)technique,which utilises the spreading reflection of RIS to achieve non-interference between the main transmission and the backward reflection transmission,and further designs and optimizes the symbol constellation diagram.The BER upperbound of the system is derived and simulated to prove the accuracy of the theoretical analysis and the effectiveness of interference cancellation.