Review of Indoor Position Techniques
By Wireless Network
HASAN KHALAF ABDULWAHID #1, HAYDER SALMAN *2, BASIM ABOOD#3
# Department of Electronics and Information Engineering, Huazhong University of Science and Technology
Wuhan, China
hassan_mtech@hotmail
haydersalman1981@yahoo
bas_eng84@yahoo
Abstract—Indoor positioning systems have been designed to provide information of persons and devices in indoor environments .The position information will be used for user applications .There are various technology for the design of IPS such as infrared (IR),radio-frequency identification(RFID) , wir
eless local area network (WLAN),Bluetooth , sensor networks ,ultra-wideband (UWB).Appropriate and accurate indoor positioning in wireless networks will use to provide services and applications in different domains based on the methods to estimate location. There are four methods for indoor position estimation, namely triangulation; fingerprint, proximity and vision analysis .This paper gives a review of many types of IPS techniques by wireless networks. Performance criteria of evaluating indoor position system are proposed for assessing these systems, namely security and privacy, cost, performance, complexity.
Keywords—Wireless Networks, Personal Network PN,Indoor Positioning Systems, Radio Frequency (RF).
I.I NTRODUCTION
The popularity of wireless access infrastructure and mobile devices fulfils people desire to access the multimedia services ubiquitously. Accurate, reliable and real-time indoor positioning and position-based protocols and services are required in the future generation of communication networks [1],[2],[3] .A positioning system make a mobile device be able to determine its position and makes the position of the device available for position based services such as tracking , navigating or monitoring , etc.
position of the dayMeanwhile, providing additional context-aware services based on the existing wireless access infrastructure gets more and more interest many domains get benefits from indoor location information of mobile units to provide useful applications and services and to improve the performance of wireless networks for network planning [4] ,network adaption [5] , load balancing [6] , etc.
Some position –based tracking systems have been used in hospitals, where expensive equipment need to be tracked to avoid being stolen , and the patients can get guidance to efficiently use the limited medical resources inside complex environments of the hospitals . Indoor navigation systems are also needed in other large public area to provide position information to users. For example, museum tour-guide and location-based handoff [7] [8].
Global positioning system (GPS) [9] is the most widely used satellite-based positioning system, which offers maximum coverage .However; GPS cannot be deployed for indoor use because line-of-sight transmission between receivers and satellites is not possible in the indoor environment. Indoor environmental are more complex because there are various obstacles, for example, wall, equipment human beings influencing the propagation of electromagnetic waves, which lead to multi-path effects. Some interference and noise sources from other wired and wireless networks degrade the accuracy
of positioning. There are various available technology options for the design of indoor position system as in some articles [1] , [10] , [11] , such as infrared (IR) ,ultra sound m radio frequency identification (RFID) ,wireless local area network (WLAN) ,Bluetooth ,sensor networks ,ultra-wideband (UWB) , magnetic signals ,vision analysis and audible sound .In this paper , we will focus on the designing indoor position system by wireless network and introduce and explain various methods to estimate locations and advantages and disadvantages of this methods to determine accurate and reliable results .
The remainder of this paper will be as following. An overview of indoor position system is presented in section II. In section III, we describe 4 existing methods for measuring principles and positioning algorithms .section IV illustrates the performance criteria of evaluating indoor position system .the main search and will be in section V which discusses the indoor position techniques by wireless network.
Finally section VI summarizes our work and presents recommendations for future work.
II.AN OVERVIEW OF INDOOR POSITIONING
SYSTEM
In this section we review the concepts about indoor position system and explain some scenarios of practical applications of indoor position system and last how to classify indoor position system.
A.What is an Indoor Position System?
An indoor positioning system (IPS) is a network of devices used wirelessly locates objects or peoples inside building. Global Positioning System (GPS) is a popular positioning technology. It is very powerful outdoors, but is difficult to use in houses and buildings due to the signal attenuation caused by constriction materials where microwaves will be attenuated and scattered by roofs, walls and other objects. Instead of satellites, an IPS relies on nearby anchors (nods with a known position), which either actively locate tags or provide environmental context for devices sense as in Figure 1.
Fig. 1. Typical IPS
Dempsey [12] defines an IPS as a system that continuously and in real-time can determine the position of something or someone in a physical space such as in a hospital, a gymnasium, a school, etc. [1]. From this definition an IPS should work all the time unless the user turns off the system, offer updated position information of the target, estimate positions within a maximum time delay, and cover the expected area the users require to use an IPS.
电脑编程的工作There are different kinds of location information can IPS provide for location-based applications required by users. The absolute location information is provided by some IPSs. Before the position can be estimated, the map of the locating area such as an office, a floor, a building, etc., should be available and saved in the IPS. With respect to the map, the absolute position of a target can be measured and displayed. Usually, the absolute position information with respect to the map of a coverage area is offered by indoor positioning tracking systems and indoor navigation systems, because tracking and guiding services need the exact positions of the targets. The relative position information is another kind of outputs offered by the IPSs, which measure the motion of different parts of a target.
For example, an IPS which tracks whether the door of a car is closed or not, needs to give the relative position information of the tracked point on the door with respect to the body of the car. The third kind of position information is proximity location information, which specifies the place where a target is. Sometimes, IPSs do not need to provide absolute or relative position information. The position monitoring and tracking systems in hospitals are such examples. The IPS should provide the room where a patient is. Thus location-based applications in hospital can monitor whether the patient enters a correct room for diagnoses or operations.
Fig. 2. Location-aware Computing System Architecture
The success of IPSs is starting to enable the location aware computing systems in indoor situations. The system architecture of the location-aware computing systems [13] is illustrated in the Figure 2, which includes 3 layers, the location sensing systems, the software location abstractions and the location-based applications. At the location sensing systems layer, different location sensing technologies are used
to perform measurements of the location of the users and their devices. The software location abstractions layer converts the data reported from the location sensing systems layer into a required presentation of the locations [14]. An example of the software location abstractions layer is the Java location application programming interface (API) [15]. The Java location API can produce the location information of targets
in a standard format and provide access to a data base of land marks.
Thus the developers can use this Java location API to develop location-based applications for resource limited devices. Moreover, the location-based applications, such as navigation and geographical advertising [16],
are
implemented at the highest layer, which use the location context information measured and calculated by the lower layers.
B. Scenarios of Indoor Positioning System
In order to meet the user’s needs and offer adaptive and convenient personal services, the location information of the persons and their devices at different places such as home, office, etc., can be provided by the IPSs to any applications in PNs. Although the GPS system can provide location information for users in outdoor environments, GPS cannot give accurate positioning estimations for indoor use. Thus, IPS is required to support location-based services when the PN is located in indoor area. The need of IPS in PN is further illustrated by two typical scenarios, namely fitness center and large Meanwhile, providing additional context-aware services based on the existing wireless access infrastructure gets more and more interest many domains get benefits from indoor location information of mobile units to provide useful applications and services and to improve the performance of wireless networks.
1) Fitness Center Scenario: Many people are keen to keep a healthy lifestyle by working out in a fitness center. A person named John is in his early 20’s and would like to exercise forth purpose of losing weight. He has thus been a member of the local fitness center for the past two years. Today is one of his two weekly exercising days. As John enters the fitness room, his personal mobile device estimates his location that he is in the fitness center, which enables location based services to provid
e the information of all network enabled fitness equipment and displays this to John. Before commencing his fitness program, he needs to be weighed in order to track physical changes (i.e., weight loss) over time. He steps onto a scale capable of communicating with his mobile device. Based on the location context that he is on the scale, the personal service can communicate with the scale to get the measured weight and save it in his personal database for further comparison and exercising guidance. John can use various equipment in the fitness center. When he uses any equipment, John’s location information is required by the personal service to offer an adaptive personal training guide.
For example, John steps on the treadmill, and then the personal service automatically detects the position of John and monitors his heart rate during running. If his heart rate is too fast, which means John cannot afford the running speed, the service will inform the treadmill to decrease the speed.
2) Large Teaching Buildings: The large teaching buildings are a typical scenario, which needs location information to offer flexible services for the students and teachers. For example, a journalist named Linda is a new student in university. As she enters the large teaching building area, the local services can get her location information. Based on the location context information that she is in the service range of the local services, the services communicate with the devices carried by Linda and
offer service-related information.
Linda ’s devices receive the service -related information so that she can use various types of services provided by the large teaching building. Using IPSs, an indoor navigation service can be provided to Linda to find the right class room in teaching building. Her devices can be monitored and tracked by the positioning system to avoid them being stolen by other people. Furthermore, the temporary wireless network is self organized based on the location information of the devices of the user to offer convenient and secure personal services. For example, Linda has the right of using the printing services in the teaching building to print the lectures of her class, if her PN is formed and connected with the teaching building network so that a document in her laptop can be printed by a printer provided by the teaching building organizers. Through the use cases, the location context awareness should be implemented in PN services, which offers comfort and efficiency to the end-user. However, IPSs enable location based services and applications in PNs, which also raise significant security and privacy risks [17]. For example, in the fitness center scenario, when the user is out of the fitness center, he or she does not want the services to track him or her any more. So the location-aware services are required to ensure users’ privacy.
Fig. 3. Personal Network
What is a Personal Network?
To meet the demands of users, personal networks (PNs)[18], interconnect various users’ personal devices at different places
such as home, office, vehicle, etc., into one single network, which is transparent to the users, as shown in Figure 1. Through PNs, users can have global access to public and personal services in different types of networks with their personal devices. Personal devices may be equipped with
different cellular and wireless networking technologies including wireless personal area network (WPAN), WLAN the third-generation (3G) cellular networks. PNs connect personal devices with different networking technologies and form dynamic, private and secure networks. Thus PNs with the user-centric perspectives can facilitate personal ubiquitous communications anywhere and at anytime. The success of PNs is highly dependent on the optimal organization of the
personal devices to achieve efficient communication王者名字重复空格代码
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various types of communications networks. Using different networking technologies, personal devices in each place form a personal area network (PAN) a vehicle area network, a home area network, a company area network etc. Personal devices in the same or different places should cooperate with each other to form one single network forth user. Thus interconnecting numerous types of networks enables personal devices in these networks to communicate with each other and offer flexible personal services.
C.How to Classify Indoor Positioning System?
The IPSs can be categorized according to different criteria. One way to classify them is based on wh
ether an IPS uses an existing wireless network infrastructure to measure the position of an object. The IPSs can be grouped as network-based approach and non-network-based approach. The network based approach takes advantage of the existing network infrastructure, where no additional hardware infrastructure is needed. For cost reasons, the network-based approach is preferred. However the non-network-based approach uses dedicated infrastructure for positioning and has the freedom of physical specifications by the designers, which may offer higher accuracy.
Another way of classifying IPSs is on the system architecture. There are three kinds: self-positioning architecture, infrastructure positioning architecture and self-oriented infrastructure-assisted architecture. Self-positioning calculates the positions by the targets themselves and takes advantage of the infrastructures of positioning systems, which provide high security and privacy. The infrastructure positioning estimates the positions of the targets using the infrastructures, which can automatically track the position of devices if they are in the coverage positioning area. In the self-oriented and infrastructure-assisted architecture, a tracked target sends are quest to the positioning system to start the position measurements, and then gets its location information from the system. The key point of the third architecture is that unless the device allows a positioning system to track it, no positioning activities for the device can be carried out. In this article, we classify the IPSs based o
n the main medium used to determine location, which include six categories: IR signals, ultrasound waves, radio frequency, electromagnetic waves, vision-based analysis and audible sound.
III.MEASURING PRINCIPLES AND POSITIONING
ALGORITHMS
There are four techniques for indoor position estimations: triangulation, fingerprinting, proximity and vision analysis [10], [19]. Triangulation, fingerprinting and vision analysis positioning techniques can provide absolute, relative and proximity position information. The proximity positioning technique can only offer proximity position information. In the design of IPSs, some IPSs use one positioning technique; others combine some of these positioning techniques to compensate for the limitations of single positioning technique. positioning and has the freedom of physical specifications by the designers, which may offer higher accuracy.
Fig. 4. Triangulation Positioning Techniques
1) Triangulation
Based on the geometric properties of triangles, three methods can be used to calculate the position,
sqlite3创建数据表namely received signal strength (RSS), angle of arrival (AOA) and time of arrival (TOA) [1]. The basic principle of triangulation method for a2-D position measurement is demonstrated in Figure 4. If the geographical coordinates (x i, y i) of three reference elements A, B, C are known, the absolute position E1 can be calculated by using either the length [10] or the directions [10] of R1, R2and R3. Based on the information of the coverage area of an IPS, absolute, relative and proximity position information can be provided by the IPS using the triangulation method. Each triangulation method has advantages and limitations. TOA is the most accurate technique, which can filter out multi-path effects in the indoor situations. However, it is complex to implement [10]. RSS and TOA need to know the position of at least three reference elements, such as A, B, C in Figure 3,to estimate the position of an object. AOA only requires two position measuring elements to perform location estimation. However, when the target object to be located is far away, the AOA method may contain some errors, which will result in lower accuracy [20].
2) Fingerprinting
Fingerprinting positioning technique is proposed to improve the accuracy of indoor position measurements by using pre-measured location related data. Fingerprinting includes two phases: offline training phase and online position
determination phase [50]. In the offline phase, useful location
related data with respect to different places in the position estimation area is measured and collected for the position estimation. During the online position determination phase, the location related data of a target object is measured and compared with the pre-measured data collected in the offline phase to get a similar case in the database to make the location estimations. For example, in an IPS [21], WLAN technology is used in the position estimation. In Figure 5 (a), three access points (APs) a
re fixed in the different places in an area of 25 m x 25 m. In the offline phase, a laptop equipped with a WLAN card was moved to various sample points to measure the strength of the signals received from different APs, as shown in Figure 5 (a).These pre-measured signal strength values are used to make the fingerprinting maps of the area with respect to different APs. Figure 5 (b) shows the received signal strength fromAP1 with respect to various sample points in the IPS working area. In the online position determination phase, based on the fingerprinting maps of the area, the IPS [21] uses the k-nearest-neighbors location algorithm [22] to locate the target node.
(a) The Experiment Environment
(b) Signal Strength for AP1
Fig. 5. Fingerprinting Positioning Techniques [21]3) Proximity
The proximity location sensing technique examines the location of a target object with respect to a known position or an area. The proximity location technique needs to fix number of detectors at the known positions. When a tracked target is detected by a detector, the position of the target is considered to be in the proximity area marked by the detector.
Fig. 6. Proximity Positioning Technique
As shown in the Figure 6, E2 and E3 are the tracked targets. A proximity area of the detector D is specified and shown by the dotted square in the Figure 6. E2 and E3 are located by monitoring whether they are in the proximity area or not. Thus the target E2 is in the area of D and E3 is not. Thus the proximity location sensing technique cannot give absolute or relative position estimations as with the other three positioning techniques. The proximity location information provided is useful for various location-based services and applications. For example, a sensing area of a location measuring element is a room. Thus proximity sensing can accurately specify whether a tracked target is in the room or not.
Fig. 7. An Example of Image used in Vision Positioning Technique
4) Vision Analysis
The vision analysis estimates a location from the image received by one or multiple points [10] as shown in Figure 7.Vision positioning brings the comfort and efficiency to the users, since no extra tracked devices are needed to be carried by the tracked persons. Usually, one or multiple cameras are
fixed in the tracking area of an IPS to cover the whole place
and take real-time images. From the images, the tracked targets are identified. The observed images
of the targets are looked up in the pre-measured database to make the position estimations. In addition, vision positioning technique can provide useful location context for services based on the captured images. For example, in Figure 7, the vision positioning technique can observe that the girl is sitting on her sofa and using her laptop.有理数多重符号的化简
IV.P ERFORMANCE CRITERIA OF EVALUATING
INDOOR POSITION SYSTEM
To evaluate the IPSs for PNs, various important system performance and deployment criteria are proposed and described in this section. These criteria are proposed fully focusing on user preference and experience, and are used to evaluate if IPSs can meet the need of users in PNs.
A.Accuracy
Accuracy (or location error) is the most important requirement of positioning systems. Usually, mean distance error is adopted as the performance metric, which is the average Euclidean distance between the estimated location and the true location. Accuracy can be considered to be a potential bias, or systematic effect/offset of a positioning system. The higher the accuracy, the better the systetypescript和javascript哪个好
m; however, there is often a tradeoffs between accuracy and other characteristics. Some compromise between ―suitable‖ accuracy and other characteristics is needed.
B.Security and Privacy
Security and privacy [10] are important issues for IPSs in PNs, because PNs focus on the needs of users. Private and social activities, who want to have full control of the usability of their personal location information and history. The user cares if someone tracks him/her and gets his/her history of all past activities. Controlling access to the location information and distribution of the information [11] can improve the privacy in IPSs. The enhancements of security and privacy could be carried out from the software side and system architecture side. For example, self-localized position system architecture [11] can ensure the privacy by performing location estimations in the target device. Unless the target device gives its location information to an entity, no one can access the information. Thus IPSs with self-localized location computation architecture can offer a high degree of security and privacy for the users in PNs.
C.Cost
The cost of an IPS contains several parts: the cost of the infrastructure components, the cost of a po
sitioning device for each user and the cost of system installation and maintenance. Some positioning systems, such as GPS, have a large infrastructure to support the location measurement, which is expensive and complex. Some IPSs reuse the existing infrastructures such as WLAN, are more cost-effective, because there is no extra cost incurred by the infrastructure of IPSs. The cost of every positioning device at the user’s side contains the device and maintenance cost, which are important for an individual person. Often, the device cost is specified when a person buys the device and starts to use the service of an IPS. But the users do not consider much about the device maintenance cost such as the battery cost and life time. For example, a device with longer battery lifetime needs less frequency of changing the batteries and lower maintenance cost. Positioning devices with self-positioning calculation ability are preferred to offer privacy of the end users, which raise the price of the devices and decrease the battery life time duration, because the devices are responsible for more complex positioning calculations. In addition, the cost of a positioning system installation and maintenance needs to be addressed for the long-term use of the system. Some IPSs include extra infrastructure to be installed such as sensor-based positioning systems, which need complex and expensive installations of fixing various sensors in different places in indoor situations. And some IPSs need professional engineers to support the operation of the IPS, which brings the cost of system maintenance higher.
The cost of the system can be addressed in different ways. Time and space costs are also factors indicating the efforts for the operation of an IPS. The time cost involves the time requirements of system installation and the time length of the positioning system in case of the system fails to work because of some serious faults. Space cost contains requirements of the size and the place, where the installed infrastructure components and user devices occupy. A large positioning device is not convenient for a user to carry it in his/her daily lives.
D.Complexity
Complexity of a positioning system can be attributed to hardware, software, and operation factors. In this paper, we emphasize on software complexity, i.e., computing complexity of the positioning algorithm. If the computation of the positioning algorithm is performed on a centralized server side, the positioning could be calculated quickly due to the powerful processing capability and the sufficient power supply. If it is carried out on the mobile unit side, the effects of complexity could be evident. Most of the mobile units lack strong processing power and long battery life; so, we would prefer positioning algorithms with low complexity. Usually, it is difficult to derive the analytic complexity formula of different positioning techniques; thus, the computing time is considered. Location rate is an important indicator for complexity. The dual of location rate is location lag, which i
s the delay between a mobile target moving to a new location and reporting the new location of that target by the system.
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