Research On UWB-MIMO Technology Based On Time Reversal

At present,with the widespread access of intelligence terminal devices,the new wireless applications for the mobile Internet have increased dramatically,making it difficult for current air interface transmission technologies to meet the increasing user demands,and especially the problem of scarce wireless spectrum resources has become the shackles for many applications promotion.Ultra-wideband(UWB)is a new type of carrier-free communication technology that uses narrow pulses of extremely short duration to transmit information.It is mainly applied in short-range wireless communications with the superiorities of strong anti-interference performance,high transmission rate,low power consumption,and insensitive to channel fading and therefore the problem of lack of spectrum resources would be alleviated.Time-Reversal(TR)technology,combined with UWB system can not only to effectively deal with multipath effects,but also to reduce the complexity of communication system design due to its unique space-time focusing characteristics.The TR-based UWB system introduces the multiple-input multiple-output(MIMO)technology,which can bring more significant performance gains to communication systems using spatial multiplexing and diversity gain of multiple antennas.This dissertation focuses on TR-based ultra-wideband multiple-input multiple-output(UWB-MIMO)systems,and addresses the interference and feedback calculation problems in two scenarios where the transmitter and receiver antennas are separated from each other by different distances.The reasonable pre-processing is used to suppress the interference of the communication system and reduce the system complexity.The specific content is as follows:1.A power-limited Time Reversal-Block Diagonalization-Minimum Mean Square Error(TR-BD-MMSE)precoder is raised to suppress the multi-stream interference and inter-symbol interference in ultra-wideband single-input multiple-output system(UWB-SIMO)system.The precoder is designed with a shortened equivalent channel based on the space-time focus characteristics of time reversal then the prefilter and the precoder are cascaded and placed at the transmitting end of the UWB-SIMO system.Finally,the simulation experiments is realized using standard ultra-wideband channel model,and results show that the scheme greatly suppresses multi-stream interference and inter-symbol interference in the UWB-SIMO system,reduces the complexity of the receiver,and increases the capacity of the UWB-SIMO system.2.A new feedback design scheme based on vector quantization is proposed to reduce the amount of feedback data for the problem that a large amount of feedback is needed to transmit the channel impulse response(CIR)from the receiver to the transmitter by applying time reversal pre-filtering technology to UWB-MIMO system.This scheme cluster the estimated channels into several clusters,and selects the channel-cluster-heads(CCHs)to be fed back using machine learning algorithm.The CCHs and their tags are recorded on both sides of the UWB transceiver,and they are fed back to the transmitter through similarity measure and estimating the similarity between the tags of the channel cluster heads,and eventually,the time reversal filter is applied through the feedback channel cluster head.The proposed new digital feedback system significantly reduces the dedicated bandwidth required for feedback and greatly improves the speed of the transceiver.In addition,it is robust to noise in the feedback channel,thereby improving overall communication performance.