The active badge location system
ACM Transactions on Information Systems (TOIS)
The Cricket location-support system
MobiCom '00 Proceedings of the 6th annual international conference on Mobile computing and networking
OFDM Wireless LANs: A Theoretical and Practical Guide
OFDM Wireless LANs: A Theoretical and Practical Guide
Practical robust localization over large-scale 802.11 wireless networks
Proceedings of the 10th annual international conference on Mobile computing and networking
The Horus WLAN location determination system
Proceedings of the 3rd international conference on Mobile systems, applications, and services
ARIADNE: a dynamic indoor signal map construction and localization system
Proceedings of the 4th international conference on Mobile systems, applications and services
PinPoint: An Asynchronous Time-Based Location Determination System
Proceedings of the 4th international conference on Mobile systems, applications and services
Understanding and mitigating the impact of RF interference on 802.11 networks
Proceedings of the 2007 conference on Applications, technologies, architectures, and protocols for computer communications
Sensor Measurements for Wi-Fi Location with Emphasis on Time-of-Arrival Ranging
IEEE Transactions on Mobile Computing
Experience with an implementation of the Idle Sense wireless access method
CoNEXT '07 Proceedings of the 2007 ACM CoNEXT conference
Computer Networks: The International Journal of Computer and Telecommunications Networking
Access Point Localization Using Local Signal Strength Gradient
PAM '09 Proceedings of the 10th International Conference on Passive and Active Network Measurement
SofTOA: Software Ranging for TOA-Based Positioning of WLAN Terminals
LoCA '09 Proceedings of the 4th International Symposium on Location and Context Awareness
Indoor localization without the pain
Proceedings of the sixteenth annual international conference on Mobile computing and networking
Demo: distance tracking using WLAN time of flight
MobiSys '11 Proceedings of the 9th international conference on Mobile systems, applications, and services
Measuring round trip times to determine the distance between WLAN nodes
NETWORKING'05 Proceedings of the 4th IFIP-TC6 international conference on Networking Technologies, Services, and Protocols; Performance of Computer and Communication Networks; Mobile and Wireless Communication Systems
Survey of Wireless Indoor Positioning Techniques and Systems
IEEE Transactions on Systems, Man, and Cybernetics, Part C: Applications and Reviews
From RSSI to CSI: Indoor localization via channel response
ACM Computing Surveys (CSUR)
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Wireless local area networks have been designed for wireless communication. Frames are acknowledged (ACKed) after a short and predefined MAC idle time. The MAC idle time varies with i) the physical distance between stations, caused by the delay of wireless signal propagation, and ii) the time to detect the ACK at the local station, which varies with the signal strength of the incoming ACK. We present CAESAR, CArriEr Sense-bAsed Ranging, that combines time of flight and signal-to-noise ratio measurements to calculate the distance between two stations. CAESAR measures the distance by estimating the MAC idle time in a data/ACK communication at a 44 MHz clock resolution and the ACK detection time on a per-frame basis. CAESAR is a software-based solution that is entirely implemented at the transmitter and it requires no protocol modifications and only a limited calibration in links with multi-path propagation. We implement CAESAR on commodity hardware and conduct extensive experiments both in controlled network conditions and dynamic radio environments. Our measurements confirm the accuracy of the solution and show the capability to track the distance to WLAN smartphones at pedestrian speeds.