QoS-driven power and rate adaptation for multicarrier communications over mobile wireless networks

We propose a quality-of-service (QoS) driven power and rate adaptation scheme for multicarrier communications systems over mobile wireless networks. By integrating information theory with the concept of effective capacity, our proposed scheme aims at maximizing the system throughput subject to a given delay-QoS constraint. Under the framework of convex optimization, we develop the optimal adaptation algorithms. Our analytical analyses identify an important fact that when the QoS constraint becomes loose, the optimal power-control policy converges to the well-known water-filling scheme, where the Shannon capacity can be achieved. On the other hand, when the QoS constraint gets stringent, the optimal policy converges to the scheme which operates at a constant-rate, where, by using only a limited number of subchannels, the above constant-rate is close to the Shannon capacity. This observation implies that in contrast to single-channel transmission, which trades off the throughput for the QoS provisioning, the multicarrier communications can realize both the high throughput and the stringent QoS at the same time. For instance, our simulation results indicate that by using 64 independent subchannels, our proposed algorithms can achieve more than 99% of the Shannon capacity, while guaranteeing a constant-rate transmission.