Research On Dynamic Channelization Technique For Broadband Wireless Signal Reconnaissance

Cyberspace,a new international battlefield following land,ocean,air and universe,includes situation sensing,maintenance and recovery,attack and sustain.Information reconnaissance is one of the usual means to realize cyberspace situation sensing.Wireless signal reconnaissance is a main component of the information reconnaissance.Nowadays,the electromagnetism environment becomes more and more complicated.The received signal of the broadband digital receiver usually covers many sub-channels whose status,such as center frequency,band width and number of sub-channels,are dynamically changeable.It makes a great challenge to the broadband digital receiver.Channelization,a key technology of software defined radio(SDR)system,is employed to extract the individual sub-channels from the digitized wideband input signal.The broadband digital receiver which is designed based on the channelization technique possesses of many advantages,such as big dynamic range,broad instantaneous frequency bandwidth,simultaneous process more than one signals arriving at the same time,and a high probability of interception.It can receive the wireless signal with a wide bandwidth and process it in a narrow bandwidth.The channelization technique used in the wireless signal reconnaissance is researched.The main contribution and novelty are list as follow:(1)A structure of dynamic digital channelizer based on sub-band spectrum sensing is proposed.Most of the existing channelizer structures are designed for the signal with prior-knowledge or cooperation communication.Aiming at realizing channelization of wireless signal reconnaissance,A analyses filterbank(AFB)is designed to divide the received signal into many sub-bands.With sub-band spectrum sensing,the frequency distribution of received signal can be confirmed.Then a syntheses filterbank(SFB)is designed to reconstruct the sub-channel signal from relevant sub-bands.(2)A structure of dynamic digital channelizer based on source number estimation is proposed.To achieve channelization under the condition that the minimum guard band of the sub-channel signals is unknown,the number of sub-channel is estimated by the source number estimation algorithm.Meanwhile,an experimental value of sub-band number is used to design the AFB.According to the sub-band spectrum sensing result,another value of sub-channel signal number can be obtained.The rationality of the designed AFB can be evaluated by comparing these two value.The complexity of this structure is relatively high.But it does not need any prior-knowledge of received signal.It can realize blind channelization for the wireless signal reconnaissance.(3)A novel hybrid structure of dynamic channelization is proposed.The channelizer structures can be summarized as two kinds,the direct kind and the indirect kind.The indirect kind implements channelization by merging certain sub-bands of the AFB.The direct method designs the filter for each sub-channel signal according to the location and bandwidth of each sub-channel.The indirect structure processes the advantages of low complexity.But its reconstruction error and the passband flatness can not be guaranteed.The direct structure can achieve a good performance.But it needs the information of spectrum distribution of sub-channels.To overcome the shortcomings of these two structures,the received signal is firstly divided into many frequency sub-bands by a AFB which is implemented by a cosine modulated filterbank(CMFB).Then an eigenvalue-based spectrum sensing method is used to detect the existence of signal in each sub-band.Now that the frequency location of each subchannel signal has been estimated by spectrum sensing of each sub-band,the required nonuniform filterbank(NUFB)is designed by coefficient decimation method(CDM).When the status of sub-channels contained within the received changes,the NUFB is redesigned according to the sub-band spectrum sensing results.(4)The source number estimation methods,which are based on information theory criteria and based on GDE(Gerschgorin's disk estimation),are improved.Source number estimation is the foundation of the channelization structure based on source number estimation.Assuming that each sub-channel contains an independent source signal,the minimum description length(MDL)criteria,Akaike information criteria(AIC)and Gerschgorin's disk estimation(GDE)are employed to realize the sub-channel number estimation.The MDL and AIC methods,which are information theory criteria,can not obtain the source number accurately when the received signals contained with colored noise.The diagonal loading technique is introduced to solve this problem.The GDE method holds a poor performance at low SNR condition.Then jackknife technique is used to optimized the GDE method.(5)The eigenvalue-based spectrum sensing method is improved and a sub-band spectrum sensing method based on eigenvalue sub-space partition is proposed.Sub-band spectrum sensing of the AFB is the vital issue to realize dynamic channelization.To confirm the spectrum distribution of the received signal,a eigenvalue based spectrum sensing method is introduced.To overcome the disadvantage that detection threshold keeps unchanged under different condition,a new sub-band spectrum sensing method based on eigenvalue sub-space partition is proposed.After obtaining the mean eigenvalues of all sub-bands,MDL criteria is used to estimate the eigenvalue number which represents signal.Then mean eigenvalue of all sub-bands can be divided in to noise space and signal space to achieve sub-band spectrum sensing.