The Taub Faculty of Computer Science Events and Talks

A crucial step in the evolution of broadband wireless (cellular) networks is reducing the size of the cells and increasing their number. This target is usually obtained using cell sectorization, where the omni-directional antenna at each base station (BS) is replaced by 3 or 6 directional antennas. With respect to this evolution, the contribution of our work is two-fold. First, we propose a new protocol stack for a BS that governs multiple directional antennas. In the new stack there is a common MAC sublayer for all the antennas rather than a separate MAC layer for each. This new architecture is shown to have two major advantages over currently employed architectures: it significantly reduces the handover overhead, and it significantly increases bandwidth utilization. Our main contribution is to address the new scheduling problem encountered by the BS when the new architecture is employed. The new problem is referred to as joint scheduling, because a single entity (the BS) makes scheduling decisions for multiple transmitting antennas. The problem is proven to be NP-hard, but we propose a new algorithm with a worst-case performance guarantee for solving it. We then show that the proposed architecture and algorithms indeed substantially increase the network throughput and decrease the handover overhead.