Research On Key Technologies For Multi-antenna Reception System Under Wireless Fading Channels

Multi-antenna receiving technology has outstanding advantages in improving the stability,robustness and flexibility of communication systems and it has been widely applied in the fields such as mobile communications,deep space exploration and remote sensing survey,etc.Since channel fading is known to be the main constraint for high-speed and reliable transmission in wireless communications,it is of great theoretical and engineering significance to research on multi-antenna receiving and processing technologies under wireless fading channels.In this paper,based on the framework of multi-antenna receiving system,our research is mainly focused on the key technologies such as multi-antenna signal waveform combining,spatial diversity equalization algorithm and multi-target signal joint processing.The main work and innovations of the paper are as follows:1.A novel two-stage multi-antenna frequency domain combining algorithm based on waveform reconstruction is proposed over frequency selective fading channel,which effectively compensates channel fading characteristics and improves the signal-to-noise ratio?SNR?simultaneously to guarantee an enhanced signal quality.A frequency domain SUMPLE algorithm based on phase smoothing is propsed in the first combining stage to improve the receiving SNR.To solve the spectral distortion remained in the first stage output,soft symbol information is fed back via waveform reconstruction and functioned as a reference signal in the second combining stage to compensate the channel fading characteristic.Compared with the fixed or quasi-synthetic references based traditional combining algorithms which focus on SNR enhancement and thus unable to optimize signal waveform,the proposed algorithm will have outstanding application advantages over frequency selective fading channels.Moreover,the algorithm does not require the training sequence and timing synchronization.The simulation results show that the proposed algorithm can effectively improve combining performance and compensate the channel fading characteristics simultaneously.2.A blind spatial diversity equalization algorithm based on iterative waveform processing is proposed for the joint reception of multi-antenna systems under frequency selective fading channels.The algorithm is provided with an iterative structure of"waveform combining+equalization+reconstructed waveform feedback",which can realize the joint optimization of signal enhancement and channel equalization without the requirements on timing synchronization and training sequence.Compared with the structure of"symbol combining+equalization+signal feedback"utilized by the traditional spatial diversity equalizers,the proposed algorithm reconstructs the reference waveform with soft symbol information and then realizes the joint optimization of the signal enhancement and channel equalization by iterative waveform combining.The weight analyses based on the modulation constellation characteristics show that the weight of iterative waveform combining is proportional to the channel response under an initial bit error rate?BER?level lower than10^-1.Therefore,it can be regarded as an estimation of unknown channel characteristics.Further analyses on the combining gain and the deep fading probability show that the spectral characteristic of the equivalent combined channel tends to be flat with the increasing of diversity order,confirming the channel compensation effect of the proposed algorithm.The simulation results illustrate that the proposed algorithm has better BER performance than the traditional spatial diversity equalization algorithm under the same equalizer parameter settings.3.A multi-target signal combining algorithm based on joint parameter estimation is designed for the reception of multiple signals with frequency aliasing over flat fading channels.Based on the multi-antenna reception model analysis,the algorithm decomposes the unknown parameters into two parts:the transmission path delays between receiving antennas and the inherent phase difference between the target signals.The joint estimation of multi-signal parameters under multi-antenna reception condition is realized by the design of joint phase difference estimation based on modulus detection and joint time difference estimation based on generalized cross correlation,respectively.Symbol detection is finally achieved by maximum likelihood symbol co-demodulation.Compared with the traditional methods,the proposed algorithm has higher computational efficiency while ensuring the signal receiving performance at the same time.The simulation results of mean square error performance and bit error rate performance show the feasibility and effectiveness of the algorithm.4.We design a general multi-antenna parallel processing platform based on the general multi-core processor and the calculation software,which can realize the integrated processing of the broadband receiving system under fading channels.Based the theoretical research in this paper,a general multi-antenna parallel processing platform is designed for supporting different signals types,different array sizes and conditions by using the general multi-core processors and the calculation software.The parallelization realization of key modules such as channel processing,time-frequency conversion and synthetic weight estimation is given for different signal processing procedures,and the entire design of the combining system is given on the basis of modularization.By setting up the 8-antenna test platform,the system property is then verified from the real-time processing and the synthetic performance test.