A unified minimum-search method for resolving contentions in multiaccess networks with ternary feedback

Abstract

We propose a unified optimization method called window protocol for a class of CSMA and CSMA/CD protocols, which include the adaptive-tree-polling protocols, the urn protocols, the priority-access protocols, the arrival-time-window protocols and the virtual-window protocol. Window protocols have the following features. First, each contending station in the network generates a contention parameter and the channel will be allocated to one that generates the minimum. Second, a global window is maintained at every station to indicate the upper and lower bounds on the minimum. Lastly, a distributed window-control scheme is used to update the global window so that the minimum is uniquely isolated in the global window when the contention terminates. Based on this characterization, window protocols can be implemented by a distributed minimum-search procedure and optimized by a unique optimization method. The average overhead to resolve contentions for each transmitted packet is minimized by incorporating the channel load and the distribution of contention parameters into a dynamic programming formulation. Heuristic methods to set the windows and fast hardware implementation are also discussed.