Physical Layer Secrecy Coding Under Equivalent Channel Characteristics

Physical layer security is one of the most promising research hotspots of wireless sec uretransimission technology nowadays. The main goal of physical layer security is secrecy commu-nication among authorized nodes of networks based on the random, diverse and reciprocal cha r-acteristics of wireless channels. Secrecy coding is one of the key techniques for the implemeta-tion of physical layer security, but the study of secrecy coding has still been in phase of theoreti-cal investigation. There’re many residual problems:1) the present shemes heavily relied on thechannnel condition, once the receiving condition of authorized channel became worse the secre-cy coding was useless;2) the existing schemes almost explored time-zone coding strategy so thatthe secrecy gain is limited. Aimming at above problems, physical layer secrecy coding designunder equivalent channel characteristics is undertaken in this work with the support of the N a-tional Natural Science Fund.This paper first introduced a secrecy coding scheme based on beamformer aided with artifi-cial noise aiming at the promblem of channel condition raliability. And then two secrecy codingschemes were explored against the problem of limited time-zone secrecy gain. The one based onChannel State Information (CSI) projection is applicable for multi-antenna scene, and the otherbased on quantized Received Signal Strength Indicator (RSS) scrambling is suitable forsigle-antenna scene. The chief content of this article is as follows.1) A physical layer secrecy coding scheme based on beamformer aided with artificial noisewas proposed. At first the secure transmssion method of beamformer aided with artificial noise isexplored, so that the receiving condtion of authorized channel becomes better. And then with thehelp of punctured Low Density Parity-check Code (LDPC) based on the Maximum SurvivedCheck Node (MSCN) algorithm, secure transmission can be guarateened because the highBit-Error-Rate (BER) of wiretapping channel. Simulation results showed that, under the BERlevel of the wiretapper’s0.4and the authorized receiver’s10-6, the average system transmittingpower was5dB lower than the existing beamformer scheme under perfect CSI, while a lowersecrecy outage probability was achieved under imperfect CSI.2) A physical layer secrecy coding scheme based on CSI projection was proposed. Firstly,the method of multi-antenna CSI projection is utilized to generate a pair of projection vectorswith the CSI of authorized channel. While transmitting weighted vector is randomly selectedfrom the pair of projection vectors symbol-by-symbol, the received codewords of wiretapper’sare randomly confused so that it is hard to decode normally and secure transmission is qualified.Simulation results showed that, with the same transmitting power and small enough referenceangle, the wiretapper’s BER was approximately0.5and the authorized receiver’s BER was a lev-el lower than the existing methods of multi-antenna physical layer secure transmission.3) A physical layer secrecy coding scheme based on quantized RSS scrambling was pro-posed. First of all, an algorithm of RSS mutual quantization is introduced for the sake of highconsistent random scrambled sequences common share between the authorized transceivers. Af-ter that, the received codewords of wiretapper’s are randomly confused through the operation of scrambling-descrambling, so that it is too hard to decode rightly. Meanwhile the privacy infor-mation is coded with improved Rate Compatible Puctured LDPC (RCP-LDPC) algorithm, as thecode rate can adapt to the authorized channel SNR variation and the secrecy rate can be maxim-ized. Simulation results showed that when SNR above10dB the proposed RSS mutual quantiza-tion algorithm achieved a1dB gain in mismatch rate than the known best algorithm; comparedwith present RCP-LDPC algorithms, the improved algorithm had a better performance over awider range of code rates.