UWB Localization systems
By Eng.Shaima'a AL-Mathkor
Ultra-wideband technology (UWB) is considered as one of the latest innovations in wireless communication and it has many powerful applications in communications, sensors, position location (localizers), tracking and radar[1]. UWB has many features, including low transmitted power, availability of low cost transceivers, and low interference, which makes it perfect for indoor, short-range localizers (localization systems).
Localization systems make use of the fine time resolution of UWB signals to locate a specific item with low cost and small size devices within a range. Location estimation can be done based on various techniques including angle of arrival (AOA), time of arrival (TOA), time difference of arrival (TDOA) and received signal strength (RSS)[2]. However, TOA technique is more suited for UWB positing systems [2-6]. It is estimated by precisely identifying the first arrived path of multipath component (MPC).
One of the main challenges of localization systems is the impact of non-line of sight (NLOS), which can delay TOA and cause unreliable positioning. Any obstacle between transmitter and receiver will block LOS path and causes NLOS scenario that can have two effects: 1) the first travelling path is either attenuated or blocked by the obstacle therefore TOA can detect one of the MPC as the first path. 2) In case the signal is not fully attenuated by the obstacle only delayed, appositive bias will be added to TOA/distance estimation [5]. Thus, in both cases accurate positioning will be affected. That is why NLOS is significant issue in localization that can be approached by first distinguish LOS from NLOS and then tries to mitigate NLOS effects.
ultra-wideband localization systems is growing rabidly due to its great features that includes: low transmitted power, low interference and the ability to provide low cost transceiver. Such devices will have great low-cost applications that can change the way we track and organized items. UWB localization system can be used in security, rescue missions, industrial field and many other applications. We can think of it similar to GPS services but for indoor short-range locaters. IEEE 802.15.4a standard is the low data rate standard of UWB that is mainly used in the positioning location applications.
References
[1] K.Siwiak & D.McKeown,”Application and future direction” in Ultra-wideband radio technology,West Sussex,England:Wiely,2004,pp.192-201.
[2] I.Guvenc and CC Chong, “A Survey on TOA Based Wireless Localization and NLOS Mitigation Techniques”,IEEEcommun. Surveys & tutorials, vol.11, no.3, 3rd Q, 2009.
[3] H.Arslan, Z.N.Chen and M.Di Benedetto, “UWB Location and Tracking” in Ultra wideband wireless communication, New Jersey: Wiley, 2006,pp.458-459.
[4] X.Shen, M.Guizani, R.C. Qiu and T.Le-Ngoc, ”Localization” in Ultra wideband wireless communications and networks, West Sussex, England: Wiley, 2006,pp.279-301.
[5]H.SoganciS.Gezici, “Accurate positioning in ultra-wideband systems”, IEEE wirlesscommun. , April 2011, pp.19-27.
[6] X. Wang, Z. Wang, and B.O’Dea,”A TOA-based Location Algorithm Reducing the Errors due to Non-Line-of-Sight (NLOS) propagation”, IEEE Trans. on Vec.technology,vol.52, no.1, January 2003, pp.112-116.