Measurement And Modeling Research On Scattered Communication Channels

In the process of communication system design,the most basic and most important part is to understand the signal propagation characteristics of wireless communication systems,and then use the appropriate techniques.Scatter communications utilize the heterogeneity of the media in the atmosphere for out-of-sight communication,with the characteristic of long distance communication,good confidentiality and strong anti-interference,which plays an important role in military communications and dealing with extreme natural disasters.Scatter channel has the characteristic of large path loss,time-varying multipath channel and small Doppler shift,the measurement methods of which are also different from traditional wireless channel measurements.In the research and development of communication system,it is usually necessary to simulate the propagation characteristics based on the channel measurement to verify the system.Therefore,the research on the measurement and modeling of the scattering channel is of great theoretical and engineering significance.First of all,this paper designs and realizes the channel data acquisition system in FPGA based on the existing scattering communication equipment.Relevant detectors are designed to collect the channel data.Gray sequences are used as the PN sequence in this paper.After the whole system completes the synchronization acquisition,it collects the channel data and resynchronizes with 10 seconds as a period,and then transmits the data to the PC through the network port.This equipment collects data for a few days in the field with 2 hours as a period.Then,this paper refers to the multipath channel modeling model,and uses the method of correlation value calculation to analyze the propagation characteristics of the channel.We get the following conclusions:Scattering channel is a typical multipath channel,the maximum effective path number is 4?5 path,the maximum multipath delay extension will not exceed 0.4?s;scattering channel is a slow time-varying channel,the maximum Doppler frequency shift to about 5-6 Hz;Scattered channel has large path loss,which can reach about a few hundreds dB;The device also detected the system's two transmit antenna obvious power imbalance phenomenon,the difference of about 2 times.Finally,this paper implements MIMO multipath channel experiment platform.The multipath channel experiment platform is implemented in the baseband in FPGA.The noise is added to the analog part of the intermediate frequency,and the channel parameters are introduced through the network port.This platform has played an important role in the communication system performance test and channel acquisition system verification.This paper also studied the design and implementation of a simple channel simulator.All of the design and implementation of this paper have been rigorously verified,applied in the actual system,which verifying the correctness of the system.