Abstract
Recently, wireless communication is a common way to transmit message. But the broadcast message has the risk to be wiretapped by the malicious third party. In this research, we focus on the physical layer security for using orthogonal frequency division multiplexing (OFDM) system in wireless communication. In this model, we consider there is an eavesdropper (Eve) trying to eavesdrop the information communicating between legitimate transmitter (Alice) and legitimate receiver (Bob). And consider it’s a multiple-input single- output (MISO) system for both side. We try to form a multiple constellation mapping diagrams set and randomly choose one constellation mapping way out of it in a digital modulation to confuse Eve when she is doing de-mapping process. The information about choice of constellation mapping for each OFDM symbol will contain in the same OFDM symbol to transmit to receiver. On the other hand, it will sacrifice a little partial accuracy of received message at Bob and overall data rate. This method is based on the situation that Eve has worse overall SNR than Bob. We use transmitting beamforming to ensure this case. The results show that it can degrade Eve more than Bob at BPSK, QPSK, and 16-QAM modulation, it ensure the signal that Bob estimate can still maintain certain accuracy compared with beamforming scheme.