This paper presents a ranging receiver architecture able to timestamp IEEE 802.11b Wireless LAN signals with sub-100 picosecond precision enabling time-based range measurements. Starting from the signal model, the performance of the proposed architecture is assessed in terms of statistical bounds when perturbed by zero-mean additive white Gaussian noise (AWGN) as well as in case of multipath propagation. Results of the proposed architecture, implemented in a Field Programmable Gate Array-(FPGA-) based prototype, are presented for different environments. For AWGN channels, the prototype system is able to attain an accuracy of 1.2？cm while the ranging accuracy degrades in dynamic multipath scenarios to about 0.6？m for 80% of the measurements due to the limited bandwidth of the signal. 1. Introduction Despite the fact that Global Navigation Satellite Systems (GNSSes) cover nearly 100% of the planet, satellite-based localization is not available within buildings as the roofing and walls deteriorate the signal to a degree where an errorless decoding is no longer possible. Mounting pseudolites, devices transmitting the navigation signals, under the roofs are certainly not a valid solution, not only due to legal restrictions. The differences between indoor and outdoor localization are more substantial than just the received power. Radio propagation within complex environments, typical for indoor scenarios, are challenging for high-speed wireless communication, but even tougher for any form of localization service. Many localization concepts (e.g., based on ultrasonic, electromagnetic waves, inertial sensors) have been proposed to bridge the gap between GNSSes and the lack of indoor locating systems. Nevertheless, for indoor environments, there is still no general satisfactory solution available as different key factors, such as low power consumption and high refreshment rate are incompatible. One major reason why indoor radio localization systems are way behind satellite navigation solutions is that the majority of all current wireless communication standards have not been designed with position determination in mind. These signals are often referred to as Signals of Opportunity (SoO). In theory, adding a localization service upon an existing standard is always possible. However, the key parameters like accuracy, reliability, or cost depend on the restrictions of the wireless standard. As a result, retrofitting a localization service to an existing technology might turn out to be highly complex as, for example, the integration of the Enhanced 911 service into
References
[1]
O. Bar-Shalom and A. J. Weiss, “Direct position determination using MIMO radar,” in Proceedings of the IEEE 25th Convention of Electrical and Electronics Engineers in Israel (IEEEI '08), pp. 575–579, December 2008.
[2]
O. Bar-Shalom and A. J. Weiss, “Efficient direct position determination of orthogonal frequency division multiplexing signals,” IET Radar, Sonar and Navigation, vol. 3, no. 2, pp. 101–111, 2009.
[3]
P. Closas, C. Fernández-Prades, and J. A. Fernández-Rubio, “Cramer—Rao bound analysis of positioning approaches in GNSS receivers,” IEEE Transactions on Signal Processing, vol. 57, no. 10, pp. 3775–3786, 2009.
[4]
M. Ibrahim and M. Youssef, “CellSense: a probabilistic RSSI-based GSM positioning system,” in Proceedings of the 53rd IEEE Global Communications Conference (GLOBECOM '10), December 2010.
[5]
A. Kushki, K. N. Plataniotis, and A. N. Venetsanopoulos, “Intelligent dynamic radio tracking in indoor wireless local area networks,” IEEE Transactions on Mobile Computing, vol. 9, no. 3, pp. 405–419, 2010.
[6]
K. Derr and M. Manic, “Wireless based object tracking based on neural networks,” in Proceedings of the 3rd IEEE Conference on Industrial Electronics and Applications (ICIEA '08), pp. 308–313, June 2008.
[7]
P. Bahl and V. N. Padmanabhan, “RADAR: an in-building RF-based user location and tracking system,” in Proceedings of the 19th Annual Joint Conference of the IEEE Computer and Communications Societies (IEEE-INFOCOM '00), pp. 775–784, March 2000.
[8]
M. Emery and M. K. Denko, “IEEE 802.11 WLAN based real-time location tracking in indoor and outdoor environments,” in Proceedings of the Canadian Conference on Electrical and Computer Engineering (CCECD '07), pp. 1062–1065, April 2007.
[9]
S. Ivanov, E. Nett, and S. Schemmer, “Automatic WLAN localization for industrial automation,” in Proceedings of the 7th IEEE International Workshop on Factory Communication Systems (WFCS '08), pp. 93–96, May 2008.
[10]
S. Mazuelas, A. Bahillo, and R. Lorenzo, “Robust indoor positioning provided by Real-Time RSSI values in unmodified WLAN networks,” IEEE Journal of Selected Topics in Signal Processing, vol. 3, no. 5, pp. 821–831, 2009.
[11]
H. Lepp？koski, S. Tikkinen, and J. Takala, “Optimizing radio map for WLAN fingerprinting,” in Proceedings of the Ubiquitous Positioning Indoor Navigation and Location Based Service (UPINLBS '10), pp. 1–8, October 2010.
[12]
M. Ciurana, D. Giustiniano, A. Neira, F. Barcelo-Arroyo, and I. Martin-Escalona, “Performance stability of software ToA-based ranging in WLAN,” in Proceedings of the International Conference on Indoor Positioning and Indoor Navigation (IPIN '10), pp. 1–8, September 2010.
[13]
A. Bahillo, S. Mazuelas, R. M. Lorenzo et al., “Accurate and integrated localization system for indoor environments based on IEEE 802.11 round-trip time measurements,” Eurasip Journal on Wireless Communications and Networking, vol. 2010, Article ID 102095, 2010.
[14]
H. Reddy, M. G. Chandra, S. G. Harihara, P. Balamuralidhar, J. Sen, and D. Arora, “WLAN-based local positioning using distorted template,” in Proceedings of the International Symposium on Communications and Information Technologies (ISCIT '07), pp. 1043–1048, October 2007.
[15]
H. Reddy, M. G. Chandra, P. Balamuralidhar, S. G. Harihara, K. Bhattacharya, and E. Joseph, “An improved time-of-arrival estimation for WLAN-based local positioning,” in Proceedings of the 2nd International Conference on Communication System Software and Middleware and Workshops (COMSWARE '07), pp. 1–8, January 2007.
[16]
S. K？nig, M. Schmidt, and C. Hoene, “Precise time of flight measurements in IEEE 802.11 networks by cross-correlating the sampled signal with a continuous barker code,” in Proceedings of the IEEE 7th International Conference on Mobile Adhoc and Sensor Systems (MASS '10), pp. 642–649, November 2010.
[17]
J. Benesty, J. Chen, and Y. Huang, “Time-delay estimation via linear interpolation and cross correlation,” IEEE Transactions on Speech and Audio Processing, vol. 12, no. 5, pp. 509–519, 2004.
[18]
T. J. S. Khanzada, A. R. Ali, and A. S. Omar, “Time difference of arrival estimation using super resolution algorithms to minimize distance measurement error for indoor positioning systems,” in Proceedings of the 12th IEEE International Multitopic Conference (IEEE INMIC '08), pp. 443–447, December 2008.
[19]
I. A. Ibraheem and J. Schoebel, “Time of arrival prediction for WLAN systems using prony algorithm,” in Proceedings of the 4th Workshop on Positioning, Navigation and Communication (WPNC '07), pp. 29–32, March 2007.
[20]
E. Kaplan and C. Hegarty, Understanding GPS: Principles and Applications, Artech House, London, UK, 2005.
[21]
P. Loschmidt, G. Gaderer, and T. Sauter, “Location based services for IEEE 802.11a/b/g Nodes,” in Proceedings of the IEEE International Workshop Real-Time Networks (RTN '07), pp. 64–70, Pisa, Italy, July 2007.
[22]
R. Exel, J. Mad, G. Gaderer, and P. Loschmidt, “A novel, high-precision timestamping platform for wireless networks,” in Proceedings of the IEEE Conference on Emerging Technologies and Factory Automation (ETFA '09), pp. 1–8, September 2009.
[23]
R. Exel, G. Gaderer, and P. Loschmidt, “Localisation of wireless LAN nodes using accurate TDoA measurements,” in Proceedings of the IEEE Wireless Communications and Networking Conference (WCNC '10), pp. 1–6, April 2010.
[24]
A. Nagy, R. Exel, P. Loschmidt, and G. Gaderer, “Time-based localisation in unsynchronized wireless LAN for industrial automation systems,” in Proceedings of the IEEE Conference on Emerging Technologies and Factory Automation (ETFA '09), September 2011.
[25]
IEEE, Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications, IEEE Std., 2003.
[26]
F. Van Graas and M. Braasch, “GPS interferometric attitude and heading determination: initial flight test results,” Navigation, Journal of the Institute of Navigation, vol. 38, no. 4, pp. 297–316, 1991.
[27]
A. Brutti, M. Omologo, and P. Svaizer, “Comparison between different sound source localization techniques based on a real data collection,” in Proceedings of the Hands-free Speech Communication and Microphone Arrays (HSCMA '08), pp. 69–72, May 2008.
[28]
B. Kwon, Y. Park, and Y. S. Park, “Multiple sound sources localization using the spatially mapped GCC functions,” in Proceedings of the ICROS-SICE International Joint Conference (ICCAS-SICE '09), pp. 1773–1776, August 2009.
[29]
W. A. Gardner and C. M. Spooner, “Comparison of autocorrelation and cross-correlation methods for signal-selective TDOA estimation,” IEEE Transactions on Signal Processing, vol. 40, no. 10, pp. 2606–2608, 1992.
[30]
W. A. Gardner and C. K. Chen, “Signal-selective time-difference-of-arrival estimation for passive location of man-made signal sources in highly corruptive environments—I: theory and method,” IEEE Transactions on Signal Processing, vol. 40, no. 5, pp. 1168–1184, 1992.
[31]
M. D. E. Gisselquist, “A comparison of stationary and cyclostationary TDOA estimators,” in Proceedings of the Military Communications Conference (MILCOM '06), pp. 1–7, October 2006.
[32]
M. Teplitsky and A. Yeredor, “TDOA estimation for cyclostationary sources: new correlations-based bounds and estimators,” in Proceedings of the IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP '09), pp. 3309–3312, April 2009.
[33]
B. Cheng, C. Chen, Z. Xu, H. Li, and X. Guan, “Wireless sensor networks based localization for audio-source: a GCC-GA method,” in Proceedings of the IEEE International Symposium on “A World of Wireless, Mobile and Multimedia Networks” (WoWMoM '10), pp. 1–6, June 2010.
[34]
U. Mengali and A. D’Andrea, Synchronization Techniques for Digital Receivers, Plenum Press, 1997.
[35]
F. Classen and H. Meyr, “Two frequency estimation schemes operating independently of timing information,” in Proceedings of the IEEE Global Telecommunications Conference, vol. 3, pp. 1996–2000, Houston, Tex, USA, Nov 1993.
[36]
H. Meyr, M. Moeneclaey, and S. Fechtel, Digital Communication Receivers, John Wiley & Sons, 1998.
[37]
I. Lita, D. A. Visan, and H. Popa, “Localization system based on enhanced software GPS receiver,” in Proceedings of the 29th International Spring Seminar on Electronics Technology: Nano Technologies for Electronics Packaging (ISSE '06), pp. 350–354, May 2006.
[38]
H. Van Trees, Detection, Estimation, and Modulation Theory, Part I, vol. 1, John Wiley & Sons, 2001.
[39]
J. Proakis and D. Manolakis, Digital Communications, Prentice Hall, 4th edition, 2006.
[40]
A. Bensky, Wireless Positioning Technologies and Applications, Artech House, 2007.
[41]
I. Guvenc, S. Gezici, and Z. Sahinoglu, “Ultra-wideband range estimation: theoretical limits and practical algorithms,” in Proceedings of the IEEE International Conference on Ultra-Wideband (ICUWB '08), pp. 93–96, September 2008.
[42]
S. Parichha and M. Molle, “Localization and clock synchronization need similar hardware support in wireless LANs,” in Proceedings of the IEEE International Symposium on Precision Clock Synchronization for Measurement, Control and Communication (ISPCS '08), pp. 131–136, September 2008.
[43]
F. Viola and W. F. Walker, “A spline-based algorithm for continuous time-delay estimation using sampled data,” IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, vol. 52, no. 1, pp. 80–93, 2005.
[44]
C. E. Cook and M. Bernfeld, Radar Signals: An Introduction to Theory and Application, Artech House, 1993.
[45]
A.-F. Molisch, Wireless Communications, John Wiley & Sons, West Sussex, UK, 1st edition, 2006.
[46]
J.-M. Sleewaegen and F. Boon, “Mitigating short-delay multipath: a promising new technique,” in Proceedings of the ION GPS, September 2001, http://www.septentrio.com/content/mitigating-short-delay-multipath-promising-new-technique.
[47]
W. A. Gardner, A. Napolitano, and L. Paura, “Cyclostationarity: half a century of research,” Signal Processing, vol. 86, no. 4, pp. 639–697, 2006.
[48]
X. Li and K. Pahlavan, “Super-resolution TOA estimation with diversity for indoor geolocation,” IEEE Transactions on Wireless Communications, vol. 3, no. 1, pp. 224–234, 2004.
[49]
M. S. Braasch, “Performance comparison of multipath mitigating receiver architectures,” in Proceedings of the IEEE Aerospace Conference, pp. 31309–31315, March 2001.
[50]
S. Kay, Fundamentals of Statistical Signal Processing, Volume I: Estimation Theory, Prentice Hall, 1993.
[51]
A. Masmoudi, F. Bellili, S. Affes, and A. Stéphenne, “Closed-form expressions for the exact cramér-Rao bounds of timing recovery estimators from BPSK, MSK and square-QAM transmissions,” IEEE Transactions on Signal Processing, vol. 59, no. 6, pp. 2474–2484, 2011.
[52]
IEEE, IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems, IEEE Std, 2008.
