NDLI: Driver layer approach to time-of-arrival ranging in IEEE 802.11g networks

Content Provider	IEEE Xplore Digital Library
Author	Ting Yang Qing Yang Lim, A.
Copyright Year	2012
Description	Author affiliation: School of Information and Software Engineering, University of Electronic Science and Technology of China, ChengDu, SiChuan, China 611731 (Ting Yang) \|\| Computer Science and Software Engineering, Auburn University, AL, USA 36849 (Qing Yang; Lim, A.)
Abstract	Round trip time (RTT) is widely used in ranging algorithms to compute the time of arrival (TOA) of a packet sent from a mobile station (STA) to an access point (AP). We propose a mechanism for measuring RTT in IEEE 802.11g using data and acknowledgement (ACK) messages at the driver layer. The scheme is implemented in the ATH9K driver in which timestamps (in nano-second) are collected when data are sent and ACK messages are received. The time differences between those two events (or interrupts) are considered the RTT for delivering these packets. However, due to noise caused by hardware, interrupt handling, and packet processing, directly using the measured RTT data to compute range of a mobile device can generate a high error of about 100ft. In fact, we discover from experiments that the standard deviation of RTT samples is 79µs. We prove that 1.7 million samples are required to achieve a ranging accuracy of 30ft. To reduce the size of samples, we use Euclidean distance (ED) to measure the difference of two sets of RTT data. With the help of ED, we only need 40k samples and achieve ranging accuracies of 10 ft and 50 ft for indoor and outdoor scenarios, respectively. Because the entire ranging system is implemented in the ATH9K driver, it can be easily installed in current STAs without modifying the existing APs.
Starting Page	240
Ending Page	244
File Size	264475
Page Count	5
File Format	PDF
ISBN	9781457720703
e-ISBN	9781457720710
DOI	10.1109/CCNC.2012.6181094
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2012-01-14
Publisher Place	USA
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	IEEE 802.11 Standards Signal to noise ratio Distance measurement Time measurement Hardware Equations Current measurement
Content Type	Text
Resource Type	Article

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