Adapative MIMO Mobile Communications With Channel Analysis,Perception And Reconstruction

In the past few years,vehicular technologies have undergone an enormous development.The number of mobile terminals,such as high speed trains,low-altitude drones and self-driving ve-hicles,as well as their velocities have increased conspicuously.Undoubtedly,this brings about tremendous challenges to current multiple-input multiple output(MIMO)communication systems.As such,it becomes quite meaningful to re-examine the impact of mobility and design new adaptive transmission schemes.Although adaptive transmission involves numbers of techniques,this paper focuses on two important methodologies,i.e.,channel analysis and channel perception.Invoking channel analysis,analytical interference model and channel spatial-temporal correlation model are exploited.On this basis,transmitter and receiver intelligently adjust the system parameters accord-ing to speeds,aiming to compensate for the underlying penalty and achieve better performance.In addition,another promising method is to use channel perception.In conventional communica-tions,mobility is bound to result in ultra-high channel estimation overhead.Nevertheless,if radar is utilized to percept the local environment,the propagation channel can be reconstructed with high accuracy and low spectrum overhead.To summarize,this dissertation uses channel analysis,per-ception and reconstruction to design adaptive MIMO communication schemes for mobile scenarios.The main contributions are listed as below:1.The interference and sum rate in mobile cellular systems are analyzed,and a MIMO adaptive transmission scheme is proposed.The uplink sum rate of a MIMO orthogonal frequency-division multiple access(OFDMA)cellular system with nodes moving randomly at different speeds is studied.In such a multi-user en-vironment,mobility not only causes inter sub-carrier interferences(ICI)among different users,but also brings the so-called channel aging which together with the above interferences incur outdated and inaccurate channel estimation and thus entail additional pilot overhead.Here we first derive the relationship between the users' mobility and the ICI power,characterize the channel aging,and de-rive the overall multi-user interference(MUI)caused by the outdated and inaccurate channel state information(CSI)as a function of mobility.Then by capitalizing on the above results,the sum rate of the MIMO-OFDMA uplink is theoretically analyzed.Moreover,an adaptive transmission scheme in which the users adjust the pilot percentage according to mobility statistics is proposed to maximize the sum rate.Finally,numerical results are provided to validate our analyses.2.The spatial-temporal channel correlation for high speed vehicles is analyzed,and a MIMO adaptive transmission scheme is proposed.Exploiting the linear mobility inherent to the HST communication scenario,we discover a new type of spatial-temporal correlation between the base station and moving antenna array on the roof top of the train.Capitalizing on the new spatial-temporal correlation information,an improved dif-ferential space-time modulation(DSTM)scheme is proposed.Analytical expressions are obtained for the pairwise error probability of the system.It is demonstrated that,the proposed approach achieves superior error performance compared with the conventional DSTM scheme.In addition,an adaptive method which dynamically adjusts the transmission block length is proposed to further enhance the system performance.Numerical results are provided to verify the performance of the proposed schemes.3.Channel perception and reconstruction in millimeter-wave(mmWave)systems are investi-gated,and an adaptive beamfonning scheme is proposed.It is believed that mm Wave plays a hugely important role in future 5G and beyond.It not only unlocks an enormous amount of spectrum resources but provides ultra-high beamfonning gains.Nonetheless,there still exist many challenges lying head of its mobile broadband appli-cations.One of them consists in channel estimation.To address this issue,we proposes a joint radar and communication system with mm Wave antenna array.Invoking mm Wave radar technolo-gies,the propagation environment is first perceived.Then,based on the environment information,high-accuracy reconstructed channels are obtained,which further helps in designing more accurate precoders and combiners.Compared with the conventional mm Wave transceiving methods,the proposed scheme reduces the spectrum overhead incurred by channel re-estimations and increases the transmission rate,especially when massive antennas and multiple users are considered.