Concatenated coding for packet transmission over the collision channel

We consider a collision channel (Massey and Mathys 1985) with additive white Gaussian noise (AWGN) and slow fading. We assume that data on a collided slot are completely lost. Caire et al. (1998) proposed a combination of signal-space coding and slow time-frequency hopping for this channel. Code vectors (or equivalently, signals) are points in a D-dimensional real Euclidean space. The main idea is that, under certain conditions on the signal-space code and provided that signal points are transmitted so that their D components belong to different time-frequency slots, even if k