A hybrid FEC-ARQ communication system for zero-error digital transmissions on the troposcatter channel

The results of a study defining an error-correcting scheme that permits very-high-reliability links for digital data transmissions over the troposcatter (Rayleigh) channel are presented. When the transmission channel is unidirectional, transmission error correction is made by means of a forward error correction (FEC). An automatic repeat request (ARQ) strategy feedback channel is used to reduce the complexity of the coding scheme and the interleaving depth. A hybrid ARQ and FEC system is proposed using a long constraint length convolutional code and sequential decoding algorithm, associated with a modified go-back-N ARQ protocol, able to cope with a two-way noisy channel. The protocol control is achieved by a modified high-level data link control (HDLC) structure. The system is tested on a simulated Rayleigh channel. The simulations have shown no transmission errors, corresponding to a binary error rate lower than 10^-9