Jointly Optimal MAC and Transport Layers in CDMA Broadband Networks

In this paper, we focus on cross-layer (MAC and transport) design for variable-rate CDMA networks. First, we formulate the cross-layer rate assignment task as a constrained convex optimization problem. Next, we develop two sets of distributed feedback algorithms to solve this problem - one which merges the rate assignments at the MAC and transport layers (one-shot), and one which coordinates them (modular). We show that both sets of algorithms converge to the same equilibrium. In particular, we show that the addition of queues between the transport and MAC layers can actually facilitate the coordination required for the modular algorithm with only minimal modification to existing protocols. Practical distributed implementation and its impact on the convergence of both algorithms is addressed.