Optimal Transmission for Dying Channels

In this paper, we investigate the optimal transmission schemes for dying channels, which were introduced in (M. Zeng et al., 2008). The dying channels are resulted in wireless networks subject to random fatal impacts, e.g., sensor networks under sudden physical attacks or cognitive radio networks with unpredictable primary user occupancy. Due to the non-ergodic and delay- limited nature of a dying channel, the outage capacity is adopted as the performance metric. Firstly, we show that the optimal power allocation profile is non-increasing when fading gains are independently and identically distributed (i.i.d.). Secondly, when the fading gains over the blocks are the same, we prove that the optimal number of blocks over which a codeword should be spanned is K = 1. At last, we consider the case where uniform power allocation is utilized and fading gains are i.i.d. In this case, we derive the upper and lower bounds for the outage probability. Moreover, for the high signal-to-noise ratio (SNR) case with Rayleigh fading , we derive analytical results on the optimal number of coding blocks K. For the low SNR case, we show that repetition transmissions are approximately optimal.