Research On Synchronization And Multi-user Collision Pulse Detection Technique For Virtual Full-duplex System

The modern tactical data link has been increasingly developed towards a centerless dynamic Ad Hoc network,with high channel throughput,high transmission rate,low transmission delay and strong anti-interference capability.The centerless Ad Hoc network consists of multiple users in the RODD virtual full-duplex system,where one frame of data is pseudo-randomly distributed and sent in some time-slot pulses,thus each user can transmit and receive whole frame of data at the same time.Hence,the virtual full duplex technique has great significance in data link research.In the dissertation,the synchronization and multi-user collision pulse detection techniques of the virtual full-duplex system are studied.The main contents are as follows:(1)The virtual full-duplex technique based on the RODD and the time-hopping sequence design are studied.The virtual full-duplex communication system model and its transceiver structure are given.And then collision and interference problems in the sending signal pulses between multiple users for the virtual full-duplex system are analyzed.(2)The synchronization scheme for the virtual full-duplex system receiver is designed,including the frame header pulse detection,frequency coarse synchronization,and pulse timing synchronization algorithm.The data and preamble are adopted to combine the frame structure.In the frame header pulse detection and frequency coarse synchronization algorithms,the auto-correlation properties of multiple pseudo-random sequences in the training sequence are used to detect the starting pulse of the training sequence of the received signal,and the coarse frequency offsets are estimated and compensated within the starting pulse.In the pulse timing synchronization algorithm,the training sequence autocorrelation characteristics and training sequence hopping pattern distribution of each user are explored to distinguish users and the end positions of training sequences for different users.Three synchronization algorithms are simulated and analyzed,and the simulation results show that the designed frame header pulse detection algorithm can accurately locate the start pulse of the training sequence for the received signal.The frequency coarse synchronization can accurately estimate and compensate the signal frequency offset.The pulse timing synchronization can distinguish different users and locate the training sequence pulse for each user.(3)Aiming at the problem of the multi-user signal pulse collision and interference in the virtual full-duplex system receiver,the partial parallel interference cancellation algorithm suitable for multi-user collision pulse detection is proposed,where the signals are simply divided into several groups according to their preamble power strength.Parallel interference cancellation algorithm is used to detect each group signals.Before detecting each group of signals,the interference of the stronger power group signals at the previous stage needs to be subtracted.The signals of all user groups are detected in the sequence using serial interference cancellation between groups.The simulation results show that the proposed parallel interference cancellation algorithm is superior to the existing serial or parallel interference cancellation algorithms,especially for detecting weak power user signals.(4)The FPGA implementation scheme of the receiver synchronization algorithm for the virtual full-duplex system is given.The diagrams and specific steps of the three synchronization algorithms are designed in detail.The synchronization algorithm is implemented on the FPGA by using Verilog HDL,and each algorithm module is tested for the functional simulation.The simulation results show that the designed synchronization algorithm can roughly estimate the signal frequency offset,and each user's preamble training sequence and its time hopping pattern distribution are timed.