Cross-layer resource-consumption optimization for mobile multicast in wireless networks

To save the precious wireless resources in wireless networks, we investigate cross-layer optimization schemes to reduce wireless resource consumption (WRC) for reliable mobile multicast. We characterize WRC by signal-to-noise ratio (SNR) per information bit and by power-delay product for scenarios without and with delay quality of service (QoS) constraints, respectively. Aiming at decreasing WRC, we develop a cross-layer parameter-selection (CLPS) algorithm, which dynamically adjusts the parameters of the physical layer and the medium access control (MAC) layer according to the variations of multicast group size, transport-layer error-control parameters, and delay QoS constraints. In particular, we first derive the optimal physical-layer parameters, including constellation size and transmit SNR, to minimize WRC for Threshold-0 multicast policy, where the sender transmits data regardless of channel qualities. Then, we develop a suboptimal approach for the selection of MAC-layer multicast threshold to achieve low power-delay product. In addition, we study the effects of pure automatic repeat request (ARQ) and hybrid ARQ-forward error correction (FEC) based error-control schemes on the CLPS algorithm. Also conducted is a set of numerical analyses to show the performance gain achieved through the cross-layer design and the impacts of various system parameters on the WRC optimization.