| As the rapid development of wireless products, frequency spectrum has been a kind of rare resources. The usage of massive MIMO technology are capable of raising the spectrum effectiveness as well as energy efficiency, which makes it the key to the future 5G technology.As the increase of antenna on base station in Massive MIMO system, it is especially significant to eliminate the interference between users, for which we chose beam forming technology. In practice, the distortion in beam forming caused by the inconsistency of channels requires correction to meet the needs. Under this circumstance, problems of time synchronization for channels calibration are studied in this thesis. The precision of capture could have great influence on channel calibration and beam forming. In face of these challenges, the following work have been done:Firstly, the current situation of time synchronization technology in Massive MIMO are studied in depth, as well as the background of time synchronization for channels calibration, including frame structure design and channel correction algorithms, process,structure design and choice of correction sequence. Thus,structure division, synchronization process design as well as choice of algorithms for the time synchronization module are realized and simulated .(1) Considering the limit of realization in engineering and combined with the process of channel calibration and frame structure, the synchronization process is simplified: time synchronization has been done between the reference antenna and the first antenna. Refer to this, we can get the head of the calibration sequence in receipt signal from the other antennaes, so that, the resources can be saved and the power can be reduced.(2) According to the principle of selecting the calibration sequence, Zadoff-Chu sequence has been selected, and its first 256 point is selected as synchronous sequences.Aiming at the generation of Zadoff-Chu sequence, schemes has been presented. The satisfaction of the generated ZadofF-Chu sequence has been proved.(3) After the algorithm and the synchronous sequence have been comfirmed,proving the algorithm's advantage by simulation can be done. The condition of simulation is Gauss Channel, Rician Channel and the configuration of receive and transmit antenna is 8×1 When the SNR is 0 dB, capture probability and false alarm probability have been counted under the circumstance of choosing different threshold values. By selecting a suitable threshold value, capture probability can be 100% and the false alarm probability can be 0. The advantage of synchronization algorithm has been proved.Secondly, the algorithm is realized on FPGA and the port definition, inner function and processing procedure are given detailed introduction. In the realization procedure, according to the position of the calibration sequence in the frame, reduce the scope of synchronous processing, by counting the sending sequence, which can reduce power consumption.Finally, time synchronization module has been tested in the Massive MIMO.The peak value, which is the only one much higher than the other value, can be observed. Comparing the calibration coefficients before calibration and after calibration. The synchronization can satisfy the demands of Massive MIMO system,because all of the above.Through all the research and verification mentioned above, this thesis could be used as a reference for the theoretical research and engineering realization of Massive MIMO time synchronization of calibration technology. |
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