1076 IEEE TRANSACTIONS ON SYSTEMS.MAN.AND CYBERNETICS-PART C:APPLICATIONS AND REVIEWS,VOL.37.NO.6.NOVEMBER 2007 The Topaz local positioning solution 3is based on Tadlys' that MPS position location information,accurate to within 10 m. Bluetooth infrastructure and accessory products.This modu- is generated in less than I s at mobility speeds of up to 200 mi/h lar positioning solution is made up of three types of elements: 2)Positioning Using Multiple Media:Designing a location positioning server(s),wireless access points,and wireless tags. system for a single environment presents difficulties when the The system's performance makes it suitable for tracking hu- system is applied to other environments.To successfully bridge mans and assets.This system provides roomwise accuracy (or, the differences among different types of sensors and overcome alternatively,2-m spatial accuracy),with 95%reliability.The the limitations of a single type of positioning sensor,hybrid positioning delay is 15-30 s.The performance is further en- systems attempt to compensate for the shortcomings of a single hanced in their new generation Topaz system that integrates technology by using multiple sensor types.HP Labs Smart- infrared and other transducers,with the Bluetooth positioning LOCUS [58]uses synchronized RF and ultrasound differential and communication capabilities. time-of-flight measurements to determine the internodal range Antti et al.present the design and implementation of a Blue- between any two nodes.HP Labs researchers developed sev- tooth Local Positioning Application (BLPA)[55].First,they eral techniques to create relative coordinate geometries with convert the received signal power levels to distance estimates little user intervention.To create an absolute frame of reference according to a simple propagation model,and then,they use the and tie internodal topology to building geometry,a minimum extended kalman filter(EKF)to compute 3-D position estimate of three or four nodes (for 2-D or 3-D localizations)must be on the basis of distance estimates.The accuracy of BLPA is re- preassigned to suitable fixed locations.All the remaining nodes ported to be 3.76 m.A similar work has been done by Hallberg are free to move,and locations are continuously updated and et al.[56]. known to the rest of the system.The well-known cricket indoor location system also uses RF and ultrasound media [59]. G.Others Infrared Radiation (IR)wireless is the use of wireless tech- 1)Proprietary Solutions Using Ultra High Frequency nology in devices or systems that convey data through infrared (UHF):The UHF location systems operate,typically either at radiation.IR is used in wireless personal area network (WPAN) the 433-MHz band (medical telemetry)or at the 868-MHz and since it is a short-range narrow-transmission-angle beam suit- 2.4-GHz ISM band.At such frequency ranges,walls have a able for aiming and selective reception of signals.Most of the moderate attenuation. Infrared Data Association (IrDA)wireless system is based on Some proprietary solutions such as the 3-D-ID system from the LOS mode.Considering the high room accuracy of the IR PinPoint [57]or the TDOA system from WhereNet14 have sim- location [60],and the high availability of the UHF location,it ilar performance as the WLAN systems mentioned later.How- makes sense to combine the two methods into a hybrid location ever,the specially designed hardware and a protocol with longer system.Several other companies like Radiansel6 and Versus17 power down periods allows for minimal power consumption in use a combination of RF and IR signals to perform location po- the mobile.For example,WhereNet,a real-time locating sys- sitioning.Their tags emit IR and RF signals containing a unique tem (RTLS),uses the same 2.4 GHz band as the IEEE 802.11 identifier for each person or asset being tracked.The use of RF and Bluetooth systems,but it uses a dedicated standard pro- allows coarse-grain positioning (e.g.,floor)while the IR signals tocol (ANSI 371.1)optimized for low-power spread-spectrum provide additional resolution(e.g.,room).The EIRIS local posi- location.It works by timing the signals transmitted from tags tioning system uses an IRFID triple technology that combines to a network of receivers.3D-ID is a commercial location sys- IR,RF(UHF),and LF(RF low-frequency transponder)signals. tem produced by PinPoint.Pinpoint uses RTOF to do ranging.It It combines the advantages of each technology,i.e.,the room uses an installed array of antennas at known positions to perform location of IR,the wide range of RF,and the tailored range sen- multilateration.When a mobile tag receives a broadcast,the tag sitivity of LF.However,comparing to RF and IR hybrid system, immediately rebroadcasts it on a different frequency,modulated it could be more costly. with the tag's identifier.A cell controller cycles through the an- 3)Positioning Using Cordless Phone System:Cordless tennas,collecting a set of ranges to the tag.Using a 40 MHz phone system is a modern wireless communication infrastruc- signal,this system achieves a 30-m range,1-m precision,and ture.Schwaighofer et al.[61]used digital enhanced cordless 5-s location update rate. telecommunications (DECT)cellular network to solve the in- Commercial indoor positioning systems using mesh network door positioning problem.They used Gaussian process (GP) techniques such as MeshNetwork positioning system(MPS)15 algorithm to calculate the phone location based on the RSS of are also worth to mention.The MPS technology leverages the phones in the DECT network.They showed that their Gaussian patented position location and determination methods built into process positioning system(GPPS)can provide sufficient ac- MeshNetwork Quadrature Division Multiple Access (QDMA) curacy of 7.5 m when used within a DECT network.They radio technology,which uses direct sequence spread spectrum also used kNN to compare with the GP method,and showed (DSSS)and operates in the ISM 2.4-GHz bands.It is reported that kNN can reach an accuracy of 7 m for DECT cellular network. 13 Topaz local positioning solution.http://www.tadlys.com 16Radianse.Inc.Radianse Indoor Positioning.http://www.radianse.com 14WhereNet Company.http://www.wherenet.com/ 17Versus Technology.http://www.versustech.com 15MPS.http://mesh.nowwireless.com/index.htm 18EIRIS System.http://www.elcomel.com.ar/english/eiris.htm Authorized licensed use limited to:University of Pittsburgh.Downloaded on January 27.2009 at 17:04 from IEEE Xplore.Restrictions apply.1076 IEEE TRANSACTIONS ON SYSTEMS, MAN, AND CYBERNETICS—PART C: APPLICATIONS AND REVIEWS, VOL. 37, NO. 6, NOVEMBER 2007 The Topaz local positioning solution13is based on Tadlys’ Bluetooth infrastructure and accessory products. This modu￾lar positioning solution is made up of three types of elements: positioning server(s), wireless access points, and wireless tags. The system’s performance makes it suitable for tracking hu￾mans and assets. This system provides roomwise accuracy (or, alternatively, 2-m spatial accuracy), with 95% reliability. The positioning delay is 15–30 s. The performance is further en￾hanced in their new generation Topaz system that integrates infrared and other transducers, with the Bluetooth positioning and communication capabilities. Antti et al. present the design and implementation of a Blue￾tooth Local Positioning Application (BLPA) [55]. First, they convert the received signal power levels to distance estimates according to a simple propagation model, and then, they use the extended kalman filter (EKF) to compute 3-D position estimate on the basis of distance estimates. The accuracy of BLPA is re￾ported to be 3.76 m. A similar work has been done by Hallberg et al. [56]. G. Others 1) Proprietary Solutions Using Ultra High Frequency (UHF): The UHF location systems operate, typically either at the 433-MHz band (medical telemetry) or at the 868-MHz and 2.4-GHz ISM band. At such frequency ranges, walls have a moderate attenuation. Some proprietary solutions such as the 3-D-ID system from PinPoint [57] or the TDOA system from WhereNet14 have sim￾ilar performance as the WLAN systems mentioned later. How￾ever, the specially designed hardware and a protocol with longer power down periods allows for minimal power consumption in the mobile. For example, WhereNet, a real-time locating sys￾tem (RTLS), uses the same 2.4 GHz band as the IEEE 802.11 and Bluetooth systems, but it uses a dedicated standard pro￾tocol (ANSI 371.1) optimized for low-power spread-spectrum location. It works by timing the signals transmitted from tags to a network of receivers. 3D-ID is a commercial location sys￾tem produced by PinPoint. Pinpoint uses RTOF to do ranging. It uses an installed array of antennas at known positions to perform multilateration. When a mobile tag receives a broadcast, the tag immediately rebroadcasts it on a different frequency, modulated with the tag’s identifier. A cell controller cycles through the an￾tennas, collecting a set of ranges to the tag. Using a 40 MHz signal, this system achieves a 30-m range, 1-m precision, and 5-s location update rate. Commercial indoor positioning systems using mesh network techniques such as MeshNetwork positioning system (MPS)15 are also worth to mention. The MPS technology leverages the patented position location and determination methods built into MeshNetwork Quadrature Division Multiple Access (QDMA) radio technology, which uses direct sequence spread spectrum (DSSS) and operates in the ISM 2.4-GHz bands. It is reported 13Topaz local positioning solution. http://www.tadlys.com 14WhereNet Company. http://www.wherenet.com/ 15MPS. http://mesh.nowwireless.com/index.htm that MPS position location information, accurate to within 10 m, is generated in less than 1 s at mobility speeds of up to 200 mi/h. 2) Positioning Using Multiple Media: Designing a location system for a single environment presents difficulties when the system is applied to other environments. To successfully bridge the differences among different types of sensors and overcome the limitations of a single type of positioning sensor, hybrid systems attempt to compensate for the shortcomings of a single technology by using multiple sensor types. HP Labs Smart￾LOCUS [58] uses synchronized RF and ultrasound differential time-of-flight measurements to determine the internodal range between any two nodes. HP Labs researchers developed sev￾eral techniques to create relative coordinate geometries with little user intervention. To create an absolute frame of reference and tie internodal topology to building geometry, a minimum of three or four nodes (for 2-D or 3-D localizations) must be preassigned to suitable fixed locations. All the remaining nodes are free to move, and locations are continuously updated and known to the rest of the system. The well-known cricket indoor location system also uses RF and ultrasound media [59]. Infrared Radiation (IR) wireless is the use of wireless tech￾nology in devices or systems that convey data through infrared radiation. IR is used in wireless personal area network (WPAN) since it is a short-range narrow-transmission-angle beam suit￾able for aiming and selective reception of signals. Most of the Infrared Data Association (IrDA) wireless system is based on the LOS mode. Considering the high room accuracy of the IR location [60], and the high availability of the UHF location, it makes sense to combine the two methods into a hybrid location system. Several other companies like Radianse16 and Versus17 use a combination of RF and IR signals to perform location po￾sitioning. Their tags emit IR and RF signals containing a unique identifier for each person or asset being tracked. The use of RF allows coarse-grain positioning (e.g., floor) while the IR signals provide additional resolution (e.g., room). The EIRIS local posi￾tioning system18 uses an IRFID triple technology that combines IR, RF (UHF), and LF (RF low-frequency transponder) signals. It combines the advantages of each technology, i.e., the room location of IR, the wide range of RF, and the tailored range sen￾sitivity of LF. However, comparing to RF and IR hybrid system, it could be more costly. 3) Positioning Using Cordless Phone System: Cordless phone system is a modern wireless communication infrastruc￾ture. Schwaighofer et al. [61] used digital enhanced cordless telecommunications (DECT) cellular network to solve the in￾door positioning problem. They used Gaussian process (GP) algorithm to calculate the phone location based on the RSS of phones in the DECT network. They showed that their Gaussian process positioning system (GPPS) can provide sufficient ac￾curacy of 7.5 m when used within a DECT network. They also used kNN to compare with the GP method, and showed that kNN can reach an accuracy of 7 m for DECT cellular network. 16Radianse, Inc. Radianse Indoor Positioning. http://www.radianse.com 17Versus Technology. http://www.versustech.com 18EIRIS System. http://www.elcomel.com.ar/english/eiris.htm Authorized licensed use limited to: University of Pittsburgh. Downloaded on January 27, 2009 at 17:04 from IEEE Xplore. Restrictions apply