Employing the One-Sender-Multiple-Receiver Technique in Wireless LANs

In this paper, we study the One-Sender-Multiple- Receiver (OSMR) transmission technique, which allows one sender to send to multiple receivers simultaneously by utilizing multiple antennas at the sender. We implemented a prototype OSMR transmitter/receiver with GNU Software Defined Radio, and conducted experiments in a university building to study the physical layer characteristics of OSMR. Our results are positive and show that wireless channels allow OSMR for a significant percentage of the time. Motivated by our physical layer study, we propose extensions to the 802.11 MAC protocol to support OSMR transmission, which is backward compatible with existing 802.11 devices. We also note that the AP needs a packet scheduling algorithm to efficiently exploit OSMR. We show that the scheduling problem without considering the packet transmission overhead can be formalized as a Linear Programming problem, but the scheduling problem considering the overhead is NP-hard. We then propose a greedy algorithm to schedule OSMR transmissions. We tested the proposed protocol and algorithm with simulations driven by traffic traces collected from wireless LANs and channel state traces collected from our experiments, and the results show that OSMR significantly improves the downlink performance.