Title :
Opportunistic Retransmission in WLANs
Author :
Lu, Mei-Hsuan ; Steenkiste, Peter ; Chen, Tsuhan
Author_Institution :
Microsoft Corp., Bellevue, WA, USA
Abstract :
This paper presents an efficient opportunistic retransmission protocol (PRO, Protocol for Retransmitting Opportunistically) to improve the performance of IEEE 802.11 WLANs. PRO is a link-layer protocol that allows overhearing nodes to function as relays that retransmit on behalf of a source after they learn about a failed transmission. Relays with better connectivity to the destination have a higher chance of delivering the packet than the source, thereby resulting in a more efficient use of the channel. PRO has four main features. First, channel reciprocity coupled with a runtime calibration process is used 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, 802.11e Enhanced Distributed Channel Access (EDCA) is leveraged to make sure high-quality relays transmit with higher probability. PRO is designed to coexist with legacy 802.11 stations. Our extensive evaluation on both a controlled testbed and in the real world shows that PRO can improve throughput in diverse wireless environments. PRO helps the most when there is significant contention for the ether, under fading, and with user mobility.
Keywords :
calibration; fading channels; filtering theory; protocols; radio links; wireless LAN; wireless channels; 802.11 enhanced distributed channel access; EDCA; IEEE 802.11 WLAN; PRO; channel reciprocity; distributed relay selection algorithm; diverse wireless environments; failed transmission; high-quality relays; instantaneous link quality; legacy 802.11 stations; link-layer protocol; local qualification process filters; opportunistic retransmission protocol; packet delivery; qualified relays; runtime calibration process; user mobility; Electronic mail; Protocols; Receivers; Relays; Wireless LAN; Wireless communication; Opportunistic retransmission; relaying; wireless LANs;
Journal_Title :
Mobile Computing, IEEE Transactions on
DOI :
10.1109/TMC.2011.227