Effective Capacity for Mobile Multicast Over Fading Channels in Wireless Networks

Effective capacity is an effective technique in devising and evaluating the capability of a time-varying wireless channel to support delay-sensitive services with statistical quality of service (QoS) guarantees. In this paper, we propose the efficient framework of effective capacity analyses and optimization for mobile multicast over broadcast fading channels. Due to the heterogeneous channel fading across multicast receivers at the same time instant, perfect reliability, low delay, and high service rate cannot be fulfilled simultaneously. Our analyses identify the fundamental tradeoffs among the system throughput, delay statistical QoS guarantees, and reliability in terms of the effective capacity, QoS exponent, and average loss-rate threshold, respectively. The QoS exponent specifies the exponentially decaying speed of the violation probability against the queue-length bound, playing a key role in statistical QoS guarantees, while the average loss-rate threshold upper-bounds the tolerable loss-level for all multicast receivers. The tradeoff is achieved by optimizing the effective capacity via channel-aware rate adaptation subject to the specified QoS exponent and average loss-rate threshold. For rate adaptation, we employ the time-sharing technique to handle the heterogeneous qualities over channels across multicast receivers, and develop a novel pre-drop scheme to implement the more flexible rate control. Simulation evaluations demonstrate the tradeoff between the effective capacity and QoS metrics, and show the superiority of our derived optimal schemes as compared to the other suboptimal schemes.