Secrecy Capacity of Space Keying with Two Antennas

Spatial modulation (SM) and space shift keying (SSK) use only one out of several transmit antennas at a time to transmit data via an antenna index. In such a system, the information is encoded by exploiting channel randomness i.e. the fact that channels between different transmit and receive antennas are random. This difference is used to distinguish among the transmit antennas. While SSK uses only antenna index to transmit data, SM also uses ordinary signal modulation. In wireless secrecy systems, one of the key performance measures is secrecy capacity. It specifies the rate at which the transmitter can communicates on the main link to the desired receiver while this information cannot be decoded by the eavesdropper. We investigate SM and SSK in the context of wireless secrecy capacity when the underlying modulation and the difference between the legitimate and eavesdropper signal to noise ratios (SNRs) are varied.