Orthogonal transmit diversity for self-interference suppression in multi-antenna telemetry links

One problem encountered in aeronautical telemetry is that during aircraft maneuvering, the transmission path is often obstructed by the air vehicle. Therefore, a second antenna is commonly placed on the aircraft to ensure a clear transmission path for all attitudes. However, when both antennas are in view of the receiver, this leads to an array interference pattern generally characterized by a large number of transmission s. Orthogonal transmit diversity schemes (space-time codes) can be used to overcome this interference without requiring additional bandwidth and with relatively straightforward implementation. In this paper, we illustrate how the Alamouti [see IEEE J. selected areas in communications, vol 16, p 1451-58, Oct 1998] and unitary differential space-time codes [see B. Hughes, IEEE Trans. information theory, vol 46, p 2567-78, Nov 2000] can be used for this application. Our transfer functions are equal to the SNR of a single antenna transmission system. Therefore this Alamouti scheme can completely remove the detrimental effects of the coherent interference created by the introduction of multiple antennas.