Research On Pattern Hiding Based Space Hopping For Physical Layer Security

Physical layer security which can provide secure transmission performance from the mos t fundamental layer has become an advanced and effective wireless security technology. Space hopping technology can increase difficulty for Eve to obtain information through rapid and random switching of spatial channels and has become an ideal physical la yer security method. Currently, there are mainly two problems in space hopping research: 1) in existing space hopping systems, switching of spatial channels between transmitter and receiver is mainly guided by space hopping pattern, which has the risk of being stolen and may cause hidden danger for the system; 2) in space hopping systems, signal is transmitted t hrough different spatial channe ls whose gain may be large or small, thus the transmission rate is decreased. Aiming at the above problems, the paper launch a special study on the pattern hiding based space hopping for physical layer security, which is supported by the National Natural Science Foundation of China.Firstly, a space hopping model based on pattern hiding is built. Under the guidance of the model, a time domain differential space hopping mechanism is proposed to solve the pattern leakage problem in MIMO systems, and the implementation in MIMO scene and multi- user MIMO scene is provided; a sub-carrier reference space hopping method is proposed to solve the pattern leakage problem in SIMO-OFDM systems; an information guided space hopping method is proposed to increase the transmission rate of systems using space hopping technology. The content of this paper includes:1. A physical layer security mechanism based on time domain differential space hopping for MIMO systems. Randomize the receiving spatial signal of the legitimate user through adding artificial interference in transmitting signal. Using previous receiving spatial signal as the receiving weight, which can be combined with the main channel to get an equivalent transmit-receive channel, thus realize random space hopping. Because of the difference between the main channel and the wiretap channel, the eavesdropper cannot track the space hopping process, thus cannot eavesdrop through interference suppression. To the MIMO scene, artificial interference is implemented through adding artificial noise in the null space of the equivalent channel. To the multi- user MIMO scene, artificial interference is implemented through multi-user interference.2. A physical layer secure transmission method based on sub-carrier reference space hopping for SIMO-OFDM systems. Each symbol period, the transmitter selects antenna of the legitimate user randomly, uses multiple reference sub-carriers for transmitting random reference value to this antenna, and nulls the remaining antennas. The selected antenna and the reference value form the space hopping pattern. Then, the symbols on each data sub-carrier are weighted randomly according to the pattern, the legitimate user estimates the pattern from the reference sub-carriers and uses it to demodulate. The eavesdroppers cannot get the pattern and cannot build a stable channel for eavesdropping. Simulation results show that the eavesdropper cannot get message through blind equalization, the bit error rate is about 0.5 when using BPSK.3. A physical layer security method based on information guided space hopping for MIMO systems. The confidential information is divided into two parts: the radiated modulation symbol(RMS) and the channel modulation symbol(CMS). CMS is modulated using the difference of the equivalent channels in the space hopping set, use CMS to select the equivalent channel and use the selected channel to send RMS. In this method, CMS act as both confidential information and space hopping pattern. Theoretical analysis and simulation results show that the eavesdropper cannot track the space hopping process, thus cannot eavesdrop through interference suppression; because more confidential information is transmitted when using space hopping, the transmission rate is improved.