Research On Wireless Secure Communication Technology Based On Space-hopping Scrambling

Existing wireless Physical-layer-security technology sends artificial noise or randomizesweights of antenna array using multiple antennas, so that received signal of legitimate receiver isstable, but the signal of eavesdropper is scrambled randomly, then implementing low probabilityof intercept. However, due to the artificial noise and random weighting vector is subjected tocertain constraints, existing technology still has the following problems: Artificial scramblingthat is produced by the method of artificial noise and antenna array weighted randomly, is alwayslocated in the null space of the legitimate channel, and the confidential signal which is on thedirection of the legitimate channel, is not scrambled, so that it can be separated from artificialnoise by multi-antenna eavesdropper who combine a number of the received signal.Aiming at above problems, the wireless secure communication technology based onSpace-hopping scrambling is studied from switching randomly the null space of legitimatechannel and artificially scrambling confidential signal. The Space-hopping communicationtechnology is a Physical-layer-security technology, and it randomizes the signal of every transmitantenna using spatial characteristics of wireless channel, so that the signal on the differenttransmission path of spatial channel is fast vary randomly, so as to prevent eavesdropping. Themain work in this paper is as follows:1. The Physical-layer-security Space-hopping method based on receiving antenna switchingrandomly is proposed. The sender randomly selects an antenna of legitimate receiver accordingto the Space-hopping pattern, and send confidential signal by the method of null space artificialnoise. Due to different time selected antenna by the sender is different, the null space artificialnoise located vary randomly. The legitimate receiver according to the pattern to select thecorresponding antenna to receive signals, but eavesdropper cannot be separate artificial noise andconfidential signal from received signal. Simulations show that, the receiver can normallydemodulate, guaranteeing low probability of intercept of eavesdropper, and the bit error rate ofeavesdropper is close to0.5in the BPSK modulation, and achievable confidential rate isnon-negative.2. The Physical-layer-security Space-hopping method based on signal subspace artificialnoise is proposed. The method selects randomly signal subspace to transmit confidential signal,and add artificial noise to the confidential signal generating random interference. The legitimatereceiver according to the Space-hopping pattern select correspond signal subspace to receiveconfidential signal, and remove the artificial noise added to confidential signal using the agreedartificial noise information. Without Space-hopping pattern and artificial noise information,eavesdropper cannot find the signal subspace and remove artificial noise in the confidentialsignal. Simulations show that, the SNR loss of receiver is less than3dB, and the symbol errorrate of eavesdropper close to0.75in QPSK modulation.3. The Physical-layer-security Space-hopping method based on antenna array weightedrandomly is proposed. Sender use random vector those elements are mutually independent toweight the transmitting confidential symbol, complementing that the phase and power of the received signal in different space positions is vary randomly. Receiver recover the stable signalby weighting the receiving signal according to the pattern, however, the receiving signal is fastvary randomly so it is unable to demodulate the confidential information. For the situation of thepattern leaking, the artificial noise which is orthogonal with the weighted vector is added to theweighted signal preventing eavesdropping. Simulations show that, the receiver is not affected,the bit error rate of eavesdropper close to0.5in BPSK modulation.