Transmit Diversity Based Interference Cancellation

In this paper, we describe a transmit diversity technique for canceling partially-known interference. For a single interferer in a flat fading channel, the desired user transmitter transmits conjugated and time-reversed interferer symbols in two successive symbol periods (or subcarriers) along with one desired user symbol. The interferer symbols are scaled to have the same received power as that received from the interfering transmitter. This causes the received interference channel matrix (over the two symbol periods) to be singular, allowing interference cancellation by means of a linear filter. Transmit diversity based interference cancellation (TDIC) can, thus, be viewed as the opposite of the Alamouti code which maximizes the determinant of the received signal channel matrix. We derive interference canceling and minimum mean square error (MMSE) receivers for TDIC transmission and obtain their capacity expressions. Numerical results indicate large gains over spatial reuse transmission at low signal-to-interference ratios.