Further results on throughput optimization using adaptive PHY/MAC/APP layer techniques

Cross-layer design breaks away from traditional wireless network design where each layer of the protocol stack is optimized independently. We develop a cross-layer design framework that judiciously combines adaptive modulation at the physical (PHY) layer, packet length adaptation strategy at the medium access control (MAC) layer, and source rate adaptation at the application (APP) layer in order to maximize the user throughput over a myriad of fading environments. Specifically, optimization equations for each of the design variables are derived in closed-form and an efficient (i.e., reduced search space) algorithm for the joint triplet-parameter optimization is also presented. The impact of restricting the design parameters (to a limited number of feasible values) on the throughput performance is also investigated. Numerical results reveal that it is sufficient to adapt the symbol rate alone in the low mean signal-to-noise ratio (SNR) regime while joint-optimization of both packet length and constellation size parameters is required in better channel conditions, to achieve the maximum throughput in a myriad of wireless fading environments.