Covert Communication with a Purely Random Spreading Function

This paper describes a method of communicating with a low probability of intercept by using a purely random spreading function. Binary message modulation is achieved by introducing appropriate delays and the message is recovered with a correlation operation. The performance of both binary and M-ary systems is analyzed and the bit error probability obtained as function of the system bandwidth and the receiver input signal-to-noise ratio. The analysis reveals that with adequate bandwidth it is possible to achieve acceptable bit error probabilities with receiver input signal-to-noise ratios on the order of ¿30 to ¿40 dB.