A joint routing-MAC model for cellular-relaying networks

We present an iterative joint scheduling-routing algorithm for characterizing the long-term performance of a cellular-relaying network. The physical layer model is based on ideal rate adaptation, fixed transmission power, and average interference. At the MAC layer, time-shares of a common channel are allocated to links in a CSMA/CA-like fashion. At the transport layer, one or more parallel routes can transfer the data flow from a source to the destination, and the average end-user rates are adjusted so as to maximize a global utility function. The general problem of allocating time-shares and selecting link rates is nonconvex. We propose an iterative algorithm and a novel approximation for the physical layer so as to obtain a convex formulation at each iteration step. If only one route is available per source, the problem admits a convex equivalent formulation and the iterative algorithm converges to the global optimum. If more routes per source are available, the problem remains nonconvex. However we show in a simple tractable example that the joint formulation yields sum-log-utility values comparable to the results obtained through exhaustive search of all possible route combinations.