Performance Analysis of Short Packet Communications with Multiple Eavesdroppers

This paper studies the performance of short packet communications in the presence of multiple eavesdroppers. We start our investigation by examining the fading wiretap channel, where the communication is overheard by multiple non-colluding single antenna eavesdroppers. A closed-form expression for the average secrecy throughput is derived, when the transmitter has a single antenna. The Monte-Carlo simulations show a close match of the analytical expression with the numerical results. Moreover, the optimal blocklength value that maximizes the secrecy throughput is determined, when the communication is observed by single and multiple eavesdroppers. We then extend our analysis for the case of a multiple-antenna transmitter and consider artificial noise (AN) to confuse the eavesdroppers. A closed-form expression for the average secrecy throughput is obtained for the scenario of a two-antenna transmitter and two eavesdroppers with a single antenna. The results demonstrate the validity of the approximation when compared with Monte-Carlo simulations. The results further reveal that an increased number of antennas at the transmitter is associated with higher average secrecy throughput and applying AN helps to eliminate the harm of the eavesdroppers.