Research On Mutual Interference Processing Technology For Radar--Communication Systems

Increased amounts of bandwidth are required to guarantee both high-quality/high-rate wireless services and reliable sensing capabilities.Integrating communication and radar is thus becoming a promising way to solve spectrum shortage problem as radar has occu-pied abundant spectra together with the fact that radar and wireless communication have more and more similar radio frequency(RF)front-end architectures.Various signal pro-cessing techniques,such as interference elimination,precoding or spatial separation and waveform design,allow both radar and communications to share the spectrum.Departing from the fundamental signal characteristics of mutual interferences,this thesis has system-atically investigated the critical techniques associated with radar-communications mutual interferences processing,including the ergodic interference alignment(IA),ergodic inter-ference steering(IS),mutual IA,interference ultilization(IU).The main contributions of this thesis are summarized as follows.(1)Theoretical analysis for the impact of mutual interferences on the bit error rate(BER)performance of communication functionality and detect perfromance of radar func-tionality.This thesis proposes an ergodic interference alignment(IA)method for interfer-ence elimination in multiple-input multiple-output(MIMO)radar and multiple-user(MU)MIMO communication systems together with phased array(PA)radar and MU-MIMO communication systems.This thesis compares first the performance of communication zero-forcing(ZF)signal with the ergodic IA method and communication zero-forcing beamforming(ZFBF)signal with the ergodic IA method in terms of BER.Besides,detect probability with and without ergodic IA method are derived for MIMO radar and PA radar by generalized likelihood ratio test(GLRT)together with signal to interference plus noise ratio(SINR)analysis for the radar functionality.(2)Ergodic IS method for radar-communication systems is proposed.For the big problem of high transmitter power consumption of ergodic IA algorithm,this thesis de-signs an ergodic IS method for MIMO radar and MU-MIMO communication systems together with PA radar and MU-MIMO communication systems based on the essence of complementary channels.The essence of a pair of complementary channels is that they have different channel state information(CSI)from the transmitters to their correspond-ing receivers at distinct time,while the other channel coefficients at different time are identical.Based on the radar-communication systems model,this thesis derives the detect probability of MIMO radar with the ergodic IS method and PA radar with the ergodic IS method.This thesis also derives the power consumption expressions of ergodic IS method and ergodic IA method.Both theoretical analysis and simulation results show that the ap-plication superiority of ergodic IS method in power consumption reduction.(3)Mutual IA method is proposed for radar-communication systems.For low com-munication degrees of freedom(Do Fs)with ergodic IA method and ergodic IS method,this thesis proposes a mutual IA algorithm without sending the same signal repeatly.Both the ergodic IA algorithm and the ergodic IS algorithm need to take up a lot of extra time slots to repeatedly send the same signal,which will definitely reduce the channel capacity of the communication systems.Considering the optimal freedom theory of the traditional IA algorithm,this thesis first applies the IA algorithm to the MIMO radar and MU-MIMO communication systems,then derives the detection probability of the MIMO radar with the IA algorithm.Because the IA algorithm uses the ”cake” mode,the signal space is di-vided into two parts,one space is used for interfering signals,another for desired signals.This practice will lead to the reduction of Do Fs of the radar system,thus lead to poor de-tection performance.This thesis proposes a mutual IA algorithm,the method is first aligns all the interferences of each receiver to the same signal space,then the interferences are eliminated by designing a receiving filter.Because the mutual IA method does not reduce the spatial dimension of the transmitted signal,compared to the traditional IA method,it can both guarantee the performance of communication systems and imporve the Do Fs of radar system.(4)IU method for radar-communication systems is proposed.In order to glean most benefit from the interferences inherent in the co-existence systems,this thesis proposes a data-aided interference ultilization method for the phase-shift-keying(PSK)based MIMO radar and MU-MIMO commmunication systems.By observing the symbol characteris-tics of the cross-correlation matrix according to the known information of the CSI and the transmitted signal,this thesis designs a new precoding scheme to orthogonalize ev-ery interference symbol but only to the symbols that impose destructive interferences to the useful signal.Based on this characteristics,this thesis designs three criteria and com-pares them in terms of complexity.Besides,this thesis analysis the BER performance of communication functionality and detect perfromance of radar functionality.Compared to standard interference suppression methods,the useful signal with IU method utilizes the constructive interferences existing in the system as signal power source,by doing so,the effective INR delivered to the expected receivers is enhanced without the need to invest additional transmitted signal power.