Performance of Satellite Communications On The Move Systems in the Presence of Antenna Pointing Errors

On the move satellite communications is a major new capability that is being sought by the Army to support new operational concepts. Because of their size and weight, small aperture terminals are very attractive in such communications on the move applications. These terminals have wide beamwidths and may increase interference to adjacent satellite systems. Also, motion induced antenna pointing errors are unavoidable in communications on the move systems and these will increase the interference level to adjacent satellites. In order to limit interference to adjacent satellite systems, the International Telecommunications Union (ITU) and the Federal Communications Commission (FCC) have established strict recommendations and rules on the off-axis emissions and antenna gain patterns. These recommendations and rules do not account for the motion induced antenna pointing errors and, in the presence of such errors, the transmit power spectral density from these terminals will be so small that only very low data rates can be realized. In order to facilitate communications on the move systems, a modification to the relevant existing ITU recommendations was proposed. In this paper we will examine the bit-error-rate (BER) performance of communications on the move systems subject to those suggested modifications. Analysis carried out in this paper shows that the motion induced antenna errors can have a significant impact on the BER performance