| The research reported here deals with the design of the uplink flow control in a CDMA-based wireless access network. Demand from each source is assumed infinitely divisible, the control is rate-based and the service model is ATM/ABR (Available Bit Rate). The flow control problem in general is to manage—dynamically, and subject to prescribed constraints on transmitter power and signal-to-interference ratio—the instantaneous allocation of rate to individual sources. Our particular interest is in settings where the controller has access to information on downstream congestion (real or virtual) for each connection, and where quality-of-service is specified on time scales that are slow relative to the rate of channel variation. Our objective is to exploit the congestion feedback, as well as the temporal flexibility in the quality-of-service specification, to refine the match between resource allocation and need. We propose a framework in which the problem can be posed precisely, and provide a solution in the case that there is but a single base station. The solution has two components. One describes the set of rate allocations that are consistent with the power and SIR constraints. The other uses the congestion feedback, modeled by the states of certain reference buffers downstream of the base station, to select a specific rate allocation within the admissible rate region. The benefit in terms of call-carrying capacity is indicated through simulations. |
