Research On Waveform Design Of Multi-band Transform Domain Communication And Its Efficient Sampling Technique

In order to realize the special covert communication in sensitive environment,it is urgent for reliable communication technology to reduce the probability of signal detection.However,the traditional narrow-band anti-jamming covert communication technology is difficult to transmit a large amount of detection data,optical and Synthetic Aperture Radar images.Therefore,the wide-band anti-jamming covert communication within 3.1 GHz?10.6 GHz is the development tendency in the future.As a cognitive anti-interference multi-carrier system,transform domain communication system(TDC)provides potential possibilities for wide-band convergent communication with the unoccupied frequency bins.However,in 3.1 GHz?10.6 GHz,there are three main technical bottlenecks in wideband adaptive covert communication based on TDC: First,the multi carrier TDC owns high peak to average power ratio(PAPR),which reduces the efficiency of the front-end power amplifier,yielding limited communication transmission distance.Second,it is difficult to implement direct multi carrier spectrum aggregation,which leads to a sharp deterioration in bit error rate(BER).Third,fast identification of the burst frame synchronization sequences for multi-band TDC within 3.1 GHz?10.6GHz requires high sampling rate,which increases hardware complexity and difficulty of data processing.To solve these problems in TDC,supported by the National Natural Science Foundation and other related funds,we propose the multi-band TDC(MB-TDC)system in 3.1GHz?10.6GHz to achieve wideband adaptive communication with low detection,low intercept and anti-interference by combining multi-band orthogonal frequency division multiplexing(MB-OFDM)system.In proposed system,the design of TDC waveform with low PAPR,multi-band joint design technology,adaptive rate transmission technology and efficient sampling technique are studied in this paper.The main contributions of this work are summarized as follows:(1)A novel TDC waveform based on constant envelope sequence is proposed.First,since the PAPR of TDC will reduce the efficiency of the front-end amplifier,we proposes a new waveform design of TDC based on constant envelope(CE)sequence to deal with its high PAPR.Then,the performance of TDC based on PN and chirp sequence is given.Furthermore,the chirp noise sequence is selected as the suitable CE sequence to realize the tradeoff between PAPR reduction in time domain and power reallocation in the frequency domain.Compared with the original TDC signal,the proposed TDC based on chirp noise sequence has the PAPR reduction of 4d B without extra BER loss.Besides,it will not produce interference to the existed narrow-band communication.Furthermore,in a given band,the optimal chirp noise sequence is obtained by the selection mapping(SLM)to improve the PAPR reduction with low complexity,which can reduce the PAPR8 d B without additional cost.(2)A multi-band TDC is proposed in 3.1GHz?10.6GHz.First,since direct multi carrier aggregation of wideband spectrum is difficult to implement within3.1GHz?10.6GHz and distorted in transmission,we propose the multi-band TDC by combining the proposed TDC and MB-OFDM system.Then,based on the sub-band division of multi-band OFDM,the weak and strong associated sub-bands are proposed to realize the tradeoff between transmission efficiency and low probability of detection-low probability of intercept.Furthermore,the frame structure of transmitter is constructed by synchronization sequence,polit signal and useful signal.The chirp noise sequence is designed as the same synchronization sequence for different sub-bands.The proposed TDC waveforms based on chirp noise sequence are designed as the block-type pilot sequences,which are inserted into the transmitted symbols at equal interval to realize the channel estimation.Finally,based on dection of sub-band and cyclic code shift keying(CCSK),different transmission rates from 256 Kbps to 12.8Mbps are achieved.(3)The single-channel sampling and multi-channel reconstruction AIC for multi-band TDC signal is proposed.First,to deal with high efficiency sampling for the fast identification of burst frame synchronization sequences within 3.1 GHz?10.6 GHz,an efficient sampling technique based on analogy to information converter(AIC)is proposed.Then,the single-channel sampling and multi-channel reconstruction(SCS-MCR)is introduced to the AIC scheme to overcome the signal noise folding with low hardware consumption.The multiple chirp noise sequences are introduced to SCS-MCR AIC to further improve its recovery performance.Finally,an efficient sampling hardware platform for multi-band TDC is built.The multi-band TDC synchronization sequence designed by proposed chirp noise sequence is used to realize the fast synchronization for multi-band TDC signals,followed by the subsequent signal demodulation and other related performance analysis.