Research On Signal Processing Of Joint Communication And Radar System Based On 802.11AD

In more and more fields such as the Internet of vehicles and unmanned aerial vehicles,the hardware platform is required to integrate communication data transmission and radar detection to serve future emerging industry application scenarios,which drives the urgent need for joint design communication and radar system（JCRS）.Meanwhile,with the increasing number of wireless connected devices,communications systems have had to move to higher frequencies.As a result,the frequency bands of these two systems gradually overlap to each other.In addition,digital signal processing has been widely used in modern radar,and there are many similarities in system structure between radar and communication,which makes it possible to design the JCRS with the functionality of both data transmission and target detection.For the sub-6 GHz band,the performance of JCRS is limited.On the contrary,the mm Wave band has a much wider bandwidth,which could increase data rate and reduce latency for communication and improve the range resolution significantly for radar.IEEE802.11ad standard operates at 60 GHz unlicensed band,and its preamble consists of Golay complementary sequences with excellent correlation properties.Therefore,we focus on designing a radar detection method for JCRS under the framework of the IEEE 802.11ad standard.Without improving the original hardware,the strategy of this thesis is to extend the radar detection function by adding processing algorithms based on the original data transmission function.The main contributions of this thesis are as follows:Firstly,this thesis studies the key signal processing technology of the receiver,including time synchronization,frequency synchronization and channel estimation technology based on the preamble of communication,pulse compression and constant false alarm rate detection technology of pulse radar.And the integrated system preamble coding pulse radar signal is designed based on the IEEE 802.11 ad standard Single-Carrier Physical Layer（SC PHY）preamble.Then the radar performance of the signal is analyzed.This radar signal has a high main-lobe peak and narrow main-lobe width,but its main-lobe to side-lobe ratio is poor and the echo signal-to-noise ratio is low,which is the focus of the subsequent design of the signal processing strategy.Secondly,aiming at the technical problem of detecting through the preamble coded pulse radar signal,a JCRS radar detection signal processing strategy is designed in a single target scenario.To overcome the high side-lobe problem introduced by the repeated fields of the preamble,we proposed to employ partial sequences to generate matched filter coefficients during the pulse compression process.To alleviate the deterioration of the main to side ratio caused by the incomplete echo of the short-range target,we optimized the selection conditions of partial sequences,which significantly improves the main to side ratio of the matched filter output waveform.In addition,we introduce a smoothing filtering operation before constant false alarm rate（CFAR）to improve the echo SNR.And during CFAR detection,the reference window is aligned with the side-lobes,and the side-lobes are used for mutual suppression,which can further reduce the false alarm probability.The simulation results show that the range estimation accuracy is 8.5cm and the velocity estimation error could only be within 0.33m/s in a single target scenario.Compared with communication synchronization and frequency offset estimation algorithms,this strategy has better detection performance.Finally,the radar detection of the integrated system is extended to multi-target scenarios.In these scenarios,if the current target is located in other target echo sidelobes after pulse compression,it will be masked.To overcome this problem,by utilizing the complementarity correlation of the Golay complementary sequence pair[G_u512,G_v512],a JCRS radar detection signal processing strategy is designed.First,the partial sequence matched filtering processing and CFAR detection is performed on the received signal.The results of the preliminary detection contain both the target and the high side-lobes.Then,by computing the cross-correlation stack of[G_u512,G_v512]sequences,a specific location of the stack results will generate a highly peaked correlation peak with no side-lobes.Thus,the real target and side-lobes in the preliminary detection results can be distinguished by the peak coordinates.At last,the velocity of the target can be estimated from the channel response of the echoes which are from the same range unit in multiple pulses.The simulation results show that the proposed strategy has good radar detection performance.In addition,the target recognition ability of the proposed strategy is also verified by simulation.For sidelobe masking scenarios,when the ratio of the radar cross-section of the two targets is greater than 20,the proposed strategy is able to identify weak signal targets with a detection probability greater than 0.98.For target-adjacent scenarios,the proposed strategy can provide a multi-target resolution of 0.25m.We further test the performance of the proposed multi-target detection strategy for single-target scenarios.Its range estimation performance is slightly higher than that of the single-target detection strategy.However,the detection range of the multi-target detection strategy is smaller,and the velocity estimation performance is the same for both strategies.