APPLICATION OF TRELLIS CODED MODULATION TO TACTICAL TROPOSCATTER TRANSMISSIONS

This paper presents an optimized solution applicable to the transmission of data and radiotelephony at low data rates for troposcatter tactical transmissions. In the proposed system, diversity is obtained thanks to the association of frequency hopping, interleaving and efficient coding scheme. The latter uses an outer Reed-Solomon code concatenated with a TCM (trellis coded modulation) inner code. The presented approach is applied to the coherent demodulation of an 8-PSK modulation transmitted on a frequency and time non-selective Rayleigh channel. As a first step the most promising codes are selected based on an extensive bibliographical research. As a second step, the overall performance is evaluated using computer simulations including the effects of imperfect channel estimation and non-ideal interleaving. It is shown that the proposed solution fulfils all the requirements (particularly those relative to the maximal transmission end to end delay)