Cooperative diversity in wireless networks with stochastic and bursty traffic

This work investigates the asymptotic error performance of outage-limited communications in cooperative wireless relay networks, with fading that is quasi-static, with an information-arrival process that is stochastic and bursty, and with bits that have a strictly limited lifespan. Employing large-deviation techniques, we analyze the probability of bit error where such errors are due to both erroneous decoding as well as due to delay violation. We derive a tradeoff between, on one hand, the optimal negative SNR exponent of the total probability of error, and on the other hand, the ratio of the average bit-arrival rate to the ergodic capacity of the channel. This is for the case of the orthogonal amplify-and-forward protocol, constant system loading, many flows and asymptotically high values of SNR. The tradeoff holds for any delay limitation. As a practical consequence, the tradeoff tells us how to better balance the effects of channel a typicality (outage) and burstiness a typicality, by proper choice of transmission rate and by optimizing the cooperative cluster size, i.e., limiting the cooperation to a specific subset of the cooperative users.