PRO: Protocol for Retransmission Opportunistically

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ABSTRACT

This paper presents an efficient link-level opportunistic retransmission protocol (PRO) to improve the performance of IEEE 802.11 WLANs. PRO has four main features. First, it leverages channel reciprocity to estimate the instantaneous link quality to the destination. Second, a local qualification process filters out poor relays early. Third, a distributed relay selection algorithm chooses the best set of eligible relays among all qualified relays and prioritizes them. Finally, it leverages 802.11e Enhanced Distributed Channel Access (EDCA) to make sure high priority relays are selected with high probability. PRO is designed to coexist with legacy 802.11 stations. We have implemented PRO in the driver of a commodity wireless card. Our evaluation both on a controlled testbed and in the real world shows that PRO boosts performance in many wireless environments.


DEMO I

A emulation based demo of a single source-destination pair and two relays is here. In the demo, you will see throughput increases as we introduce relays to (re)transmit on behalf of the source.

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DEMO II

A emulation based demo of two source-destination pairs and a single relay is here. The demo includes two sessions: a good session and a poor session from a single source. Due to the property of 802.11 protocols, the poor session results in low throughput for both  sessions. You will see, after we introduce a relay, throughput improves for both sessions.

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DEMO III

I also made a demo using real-world experiments. You may see the taped demo here.

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