Optimizing Multicast Delay with Switched Beamforming in Wireless Networks

In this paper we investigate the issue of exploiting switched beamforming antennas to improve multicast transmission in wireless networks. Under the practical assumptions that different beams may have arbitrary overlapping patterns and that each user can receive data at different rates under different beams, we formulate the problem as minimizing the total multicast delay subject to the constraint that all users need to be covered. We prove that the problem is NP-hard and propose a greedy algorithm that achieves log(J) approximation guarantee where J is the number of clients. Measurements in both indoor and outdoor experiments validate our assumptions on the beamforming model. Trace-driven simulations based on these measurements show significant improvement over previous schemes and corroborate our analytical results.