Optimal Pilots for Maximal Capacity of Secret Key Generation

Abstract

Through a wireless channel, two users can transmit pilot signals to each other, and then utilize the received signals to agree upon a secret key through communications in a public channel without leaking any secret about this key to anyone else. This paper addresses the optimization of the two pilots to maximize the capacity of secret key generation for a MIMO channel with any given receive and transmit correlation matrices. This study shows how the globally optimal pilots can be obtained if the transmission power is either low or high. For an arbitrary transmission power, the algorithm developed is at least locally optimal. Comparison to pilots based on minimum channel estimation errors and uniform power distribution is also presented. It is also shown that the designed pilots meet the requirement for anti- eavesdropping channel estimation.