Directive antennas diversity reception for an adaptive modulation system in land mobile communications

This paper proposes a directive antennas diversity reception scheme for adaptive modulation/time-division multiple access (TDMA)/time division duplex (TDD) systems to achieve high quality, high bit rate and high spectral efficient data transmission in high mobility land mobile communication environments. In mobile stations, a directive antennas diversity is applied to equivalently reduce the Doppler spread in each branch. At each branch, the offset frequency (f_off) and f_off-canceled fading variation are estimated to achieve precise propagation path characteristics estimation and to decide the most appropriate modulation level even in high maximum Doppler frequency (f_d) environments. Computer simulation confirms that the proposed scheme can achieve successful adaptive modulation transmission in fast fading environments