Design Of Multiple Access Methods Based On Framework Adaptation And Amplitude Adjustment Precoder

With the rapid growth of subscribers in wireless communication systems,exploring efficient medium access control（MAC）protocols to realize effective communication resource sharing among multiple users has been becoming significant.In MAC design,effective management of co-channel interference（CCI）among multiple concurrent transmissions is critical to enhancing system’s spectrum efficiency（SE）.Although existing signal processing-based MAC techniques can suppress CCI,they either consume communication resource or introduce attenuation of signal propagation,hence incurring loss of users’transmission performance.The existing signal processing（precoding）methods generally adjust the signal in space,and the modulus of precoder is constant to 1in the whole signal transmission process.In fact,in a real mobile communication system,in order to prevent adjacent channel interference and near far effect,it is usually necessary to automatically control the transmission power of the mobile station（base station）to ensure that the signal power level from each mobile station（base station）to the base station（mobile station）receiver is basically the same.Therefore,we can adjust the precoder’s modulus differently to get different communication effects.This paper designs and studies the framework adaptation and amplitude adjustment based precoder multiple access methods.The main work is as follows:Firstly,this thesis proposes a framed fidelity medium access control（F²MAC）in multiple access channels where multiple transmitters send data to a common receiver simultaneously.By introducing a virtual framework in the signal processing process,then,the pre-processed signals of multiple users are losslessly loaded into a virtual point-to-point framework.Since F²MAC can decouple the channel quality information（CQI）from channel direction information（CDI）related to the signal transmission,that is,CQI is exclusively determined by user’s communication channel while CDI is decided by the unified virtual frame channel,it can avoid transmission performance loss incurred by traditional signal processing-based MAC which adjusts both CQI and CDI simultaneously.Moreover,we propose a flexible framed fidelity MAC（F³MAC）to further improve the system’s SE.By dynamically re-constructing the virtual frame channel at each mobile user,the user’s transmission can be realized with the principal eigenmode’s gain of its communication channel.In addition,this thesis also discusses the methods of F²MAC and F³MAC with correlation-based eigenmode matching to reduce the system power overhead and present Hybrid F^2&3MAC to balance the system SE and power consumption.Our in-depth analysis and simulation results have shown that the proposed MAC methods can significantly improve the SE of a multi-user communication system.Then,this thesis proposes a relaxed orthogonal precoder based multiple access（ROPMA）method for MU-MIMO downlink transmission.By introducing an orthogonal amplitude tuning function to adjust the precoder’s amplitude in a symbol duration,and then using the adjusted precoder for signal processing and transmission,the requirement of strict orthogonality of multi-user signals in spatial domain can be relaxed to the orthogonality in the sense of correlation.Accordingly,the receiver employs correlation based desired signal detection;by exploiting the orthogonality of amplitude tuning functions,the influence of CCI can be eliminated at the decision time.Our simulation results have shown that the proposed method can significantly increase the number of users that the system can accommodate and improve the system’s SE without consuming extra spectrum resource.At the end of this paper,we summarize the main work of this paper and propose the research direction in the future.