Indoor Human Navigation Systems: A Survey <s> Direct Sensing <s> The performance of wireless infrared transmission systems for indoor use is severely impaired by the noise and interference induced by natural and artificial ambient light. In order to combat the effects of ambient light on the system performance, both optical filtering and electrical filtering is usually adopted. However, even when resorting to these techniques, the optical power penalty imposed by the interference may be very large. In particular, the interference produced by fluorescent lamps driven by electronic ballasts imposes very large optical power penalties on systems operating at data rates up to a few tens of Mbps. In this paper, a different technique to overcome the penalty induced by artificial light interference is analysed. This technique explores the different optical spectra of the transmitted signal and the artificial light and the characteristics of optical filtering to cancel the interfering signal. Some aspects of its implementation are also discussed. The results obtained with this approach are shown to be much better than those obtained through electrical high-pass filtering. (10 pages) <s> BIB001 </s> Indoor Human Navigation Systems: A Survey <s> Direct Sensing <s> Metronaut is a novel wearable computer which captures information, senses position, provides wide range communications, consumes less than one watt of power, and weighs less than one pound. Metronaut employs a bar code reader for information input and position location, a two-way pager for communications, and an ARM processor for computation. Metronaut's application is schedule negotiation and guidance instructions for a visitor to the CMU campus. The visitor's position is determined from reading bar codes at information signs around campus. Modifications to the schedule are negotiated using the two-way pager for communications with the campus computing infrastructure. Metronaut is alternatively powered by a mechanical flywheel converting kinetic energy to electrical energy. <s> BIB002 </s> Indoor Human Navigation Systems: A Survey <s> Direct Sensing <s> This paper describes a wearable navigation system based on a haptic directional display embedded in the back of a vest. The system consists of a 4-by-4 array of micromotors for delivering haptic navigational signals to the user's back, an infrared-based input system for locating the user in an environment, and a wearable computer for route planning. User testing was conducted to evaluate the effectiveness of this system as a navigation guide for sighted users in an unfamiliar lab area. It is hoped that such a system can be a useful navigation guide for individuals with severe visual impairments in an unfamiliar environment. Future work will address the specific issues concerning blind navigation. <s> BIB003 </s> Indoor Human Navigation Systems: A Survey <s> Direct Sensing <s> Instrumenting the physical world through large networks of wireless sensor nodes, particularly for applications like environmental monitoring of water and soil, requires that these nodes be very small, lightweight, untethered, and unobtrusive. The problem of localization, that is, determining where a given node is physically located in a network, is a challenging one, and yet extremely crucial for many of these applications. Practical considerations such as the small size, form factor, cost and power constraints of nodes preclude the reliance on GPS of all nodes in these networks. We review localization techniques and evaluate the effectiveness of a very simple connectivity metric method for localization in outdoor environments that makes use of the inherent RF communications capabilities of these devices. A fixed number of reference points in the network with overlapping regions of coverage transmit periodic beacon signals. Nodes use a simple connectivity metric, which is more robust to environmental vagaries, to infer proximity to a given subset of these reference points. Nodes localize themselves to the centroid of their proximate reference points. The accuracy of localization is then dependent on the separation distance between two-adjacent reference points and the transmission range of these reference points. Initial experimental results show that the accuracy for 90 percent of our data points is within one-third of the separation distance. However, future work is needed to extend the technique to more cluttered environments. <s> BIB004 </s> Indoor Human Navigation Systems: A Survey <s> Direct Sensing <s> This paper presents the design, implementation, and evaluation of Cricket , a location-support system for in-building, mobile, location-dependent applications. It allows applications running on mobile and static nodes to learn their physical location by using listeners that hear and analyze information from beacons spread throughout the building. Cricket is the result of several design goals, including user privacy, decentralized administration, network heterogeneity, and low cost. Rather than explicitly tracking user location, Cricket helps devices learn where they are and lets them decide whom to advertise this information to; it does not rely on any centralized management or control and there is no explicit coordination between beacons; it provides information to devices regardless of their type of network connectivity; and each Cricket device is made from off-the-shelf components and costs less than U.S. $10. We describe the randomized algorithm used by beacons to transmit information, the use of concurrent radio and ultrasonic signals to infer distance, the listener inference algorithms to overcome multipath and interference, and practical beacon configuration and positioning techniques that improve accuracy. Our experience with Cricket shows that several location-dependent applications such as in-building active maps and device control can be developed with little effort or manual configuration. <s> BIB005 </s> Indoor Human Navigation Systems: A Survey <s> Direct Sensing <s> This survey and taxonomy of location systems for mobile-computing applications describes a spectrum of current products and explores the latest in the field. To make sense of this domain, we have developed a taxonomy to help developers of location-aware applications better evaluate their options when choosing a location-sensing system. The taxonomy may also aid researchers in identifying opportunities for new location-sensing techniques. <s> BIB006 </s> Indoor Human Navigation Systems: A Survey <s> Direct Sensing <s> People with severe visual impairment need a means of remaining oriented to their environment as they move through it. A series of indoor and outdoor trials using a variety of technologies and interfaces led to the development and evaluation of three promising wearable orientation interfaces: a virtual sonic beacon, speech output, and a shoulder-tapping system. Street crossing was used as a critical test situation in which to evaluate these interfaces. The shoulder-tapping system was found most universally usable. Results indicated that, given the great variety of co-morbidities within this population, which is comprised of mostly older persons, optimal performance and flexibility may best be obtained in a design that combines the best elements of both the speech and shoulder-tapping interfaces. <s> BIB007 </s> Indoor Human Navigation Systems: A Survey <s> Direct Sensing <s> The design of mobile navigation systems adapting to limited resources will be an important future challenge. Since typically several different means of transportation have to be combined in order to reach a destination, the user interface of such a system has to adapt to the user's changing situation. This applies especially to the alternating use of different technologies to detect the user's position, which should be as seamless as possible. This article presents a hybrid navigation system that relies on different technologies to determine the user's location and that adapts the presentation of route directions to the limited technical resources of the output device and the limited cognitive resources of the user. <s> BIB008 </s> Indoor Human Navigation Systems: A Survey <s> Direct Sensing <s> Growing convergence among mobile computing devices and embedded technology sparks the development and deployment of “context-aware” applications, where location is the most essential context. In this paper we present LANDMARC, a location sensing prototype system that uses Radio Frequency Identification (RFID) technology for locating objects inside buildings. The major advantage of LANDMARC is that it improves the overall accuracy of locating objects by utilizing the concept of reference tags. Based on experimental analysis, we demonstrate that active RFID is a viable and cost-effective candidate for indoor location sensing. Although RFID is not designed for indoor location sensing, we point out three major features that should be added to make RFID technologies competitive in this new and growing market. <s> BIB009 </s> Indoor Human Navigation Systems: A Survey <s> Direct Sensing <s> In this paper, we discuss application possibilities of augmented reality technologies in the field of mobility support for the deaf blind. We propose the navigation system called virtual leading blocks for the deaf-blind, which consists of a wearable interface for Finger-Braille, one of the commonly used communication methods among deaf-blind people in Japan, and a ubiquitous environment for barrier-free application, which consists of floor-embedded active radio-frequency identification (RFID) tags. The wearable Finger-Braille interface using two Linux-based wristwatch computers has been developed as a hybrid interface of verbal and nonverbal communication in order to inform users of their direction and position through the tactile sensation. We propose the metaphor of "watermelon splitting" for navigation by this system and verify the feasibility of the proposed system through experiments. <s> BIB010 </s> Indoor Human Navigation Systems: A Survey <s> Direct Sensing <s> We present a robot-assisted wayfinding system for the visually impaired in structured indoor environments. The system consists of a mobile robotic guide and small passive RFID sensors embedded in the environment. The system is intended for use in indoor environments, such as office buildings, supermarkets and airports. We describe how the system was deployed in two indoor environments and evaluated by visually impaired participants in a series of pilot experiments. We analyze the system's successes and failures and outline our plans for future research and development. <s> BIB011 </s> Indoor Human Navigation Systems: A Survey <s> Direct Sensing <s> Because of its promise to revolutionize global supply chain management (SCM) systems, Ultra High Frequency (UHF) Radio Frequency Identification (RFID) was recently the cause of much optimism. Wal-Mart mandated its top 100 suppliers to begin using RFID on January 1st, 2005; this day was viewed as a watershed day in the industry. However, that date has come and gone, and the expected rapid industry adoption of RFID has not taken place. This paper explores the existing challenges and obstacles to RFID's quick adoption, the potential resolutions and approaches to the challenges, and the migration strategies to expand the RFID industry. <s> BIB012 </s> Indoor Human Navigation Systems: A Survey <s> Direct Sensing <s> Location-based mobile services have been in use, and studied, for a long time. With the proliferation of wireless networking technologies, users are mostly interested in advanced services that render the surrounding environment (i.e., the building) highly intelligent and significantly facilitate their activities. In this paper our focus is on indoor navigation, one of the most important location services. Existing approaches for indoor navigation are driven by geometric information and neglect important aspects, such as the semantics of space and user capabilities and context. The derived applications are not intelligent enough to catalytically contribute to the pervasive computing vision. In this paper, a novel navigation mechanism is introduced. Such navigation scheme is enriched with user profiles and the adoption of an ontological framework. These enhancements introduce a series of technical challenges that are extensively discussed throughout the paper. <s> BIB013 </s> Indoor Human Navigation Systems: A Survey <s> Direct Sensing <s> Wireless indoor positioning systems have become very popular in recent years. These systems have been successfully used in many applications such as asset tracking and inventory management. This paper provides an overview of the existing wireless indoor positioning solutions and attempts to classify different techniques and systems. Three typical location estimation schemes of triangulation, scene analysis, and proximity are analyzed. We also discuss location fingerprinting in detail since it is used in most current system or solutions. We then examine a set of properties by which location systems are evaluated, and apply this evaluation method to survey a number of existing systems. Comprehensive performance comparisons including accuracy, precision, complexity, scalability, robustness, and cost are presented. <s> BIB014 </s> Indoor Human Navigation Systems: A Survey <s> Direct Sensing <s> A location and tracking system becomes very important to our future world of pervasive computing, where information is all around us. Location is one of the most needed information for emerging and future applications. Since the public use of GPS satellite is allowed, several state-of-the-art devices become part of our life, e.g. a car navigator and a mobile phone with a built-in GPS receiver. However, location information for indoor environments is still very limited. Several techniques are proposed to get location information in buildings such as using a radio signal triangulation, a radio signal (beacon) emitter, or signal fingerprinting. Using radio frequency identification (RFID) tags is a new way of giving location information to users. Due to its passive communication circuit, RFID tags can be embedded almost anywhere without an energy source. The tags stores location information and gives it to any reader that is within a proximity range which can be up to 10-15 meters for UHF RFID systems. We propose an RFID-based system for navigation in a building for blind people or visually impaired. The system relies on the location information on the tag, a userpsilas destination, and a routing server where the shortest route from the userpsilas current location to the destination. The navigation device communicates with the routing server using GPRS networks. We build a prototype based on our design and show some results. We found that there are some delay problems in the devices which are the communication delay due to the cold start cycle of a GPRS modem and the voice delay due to the file transfer delay from a MMC module. <s> BIB015 </s> Indoor Human Navigation Systems: A Survey <s> Direct Sensing <s> A challenge to individuals with cognitive impairments in wayfinding is how to remain oriented, recall routines, and travel in unfamiliar areas in a way relying on limited cognitive capacity. According to psychological model of spatial navigation and the requirements of rehabilitation professionals, a novel wayfinding system is presented with an aim to increase workplace and life independence for people suffering from diseases such as traumatic brain injury, cerebral palsy, mental retardation, schizophrenia, Down syndromes, and Alzheimer's disease. This paper describes an approach to providing distributed cognition support of travel guidance for persons with cognitive disabilities. The unique strength of the system is the ability to provide unique-to-the-user prompts that are triggered by context. As this population is very sensitive to issues of abstraction (e.g. icons) and presents the designer with the need to tailor prompts to a 'universe-of-one' the use of images specific to each user and context is implemented. The key to the approach is to spread the context awareness across the system, with the context being flagged by the QR-code tags and the appropriate response being evoked by displaying the appropriate path guidance images indexed by the intersection of specific end-user and context ID embedded in the tags. By separating the context trigger from the pictorial response, responses can be updated independently of the rest of the installed system, and a single QR-code tag can trigger multiple responses in the PDA depending on the end-user and their specific path. A prototype is built and tested in field experiments with real patients. The experimental results show the human-computer interface is friendly and the capabilities of wayfinding are reliable. <s> BIB016 </s> Indoor Human Navigation Systems: A Survey <s> Direct Sensing <s> In this paper, a novel tour-guiding system is introduced, based on our space-identifying ubiquitous infrastructure, where positioning devices are deployed ubiquitously to identify the place of users. In this infrastructure, we can flexibly construct information service related to the places of interest in the city by modeling the space of the real world as a set of relations among the discrete places, and attaching space-identifying devices to them. Our developed tour-guiding system introduces many art works in a large commercial complex in Japan. Based on the benefit of the infrastructure, this system can provide detailed navigation service as well as art introduction service in both indoor and outdoor environments, and can guide the users to reach their interested art works. Currently, this system is already used in practice for a commercial service. In this paper, the design of this system is described and its navigation capability is verified through a user test in the real environment to discuss the effectiveness of our approach. <s> BIB017 </s> Indoor Human Navigation Systems: A Survey <s> Direct Sensing <s> Mobile navigation service is one of the most important Location Based Services. With the rapid advances in enabling technologies for ubiquitous computing, more and more active or passive devices/sensors are augmented in the indoor environment, indoor environment has become smarter. This paper proposes that by introducing the notions of Smart Environment and Ambient Intelligent, a ubiquitous indoor navigation service can be built to provide an adaptive smart wayfinding support and enhance users with a new experience during indoor navigation. In this paper, we set up a smart environment with a positioning module and a wireless module. Based on this smart environment, we design a ubiquitous indoor navigation system with interaction and annotation module (for user generated content), user tracking module (for collaborative filtering) and context-aware adaptation to illustrate some potential benefits of combining indoor navigation and Smart Environment. <s> BIB018 </s> Indoor Human Navigation Systems: A Survey <s> Direct Sensing <s> Indoor localization refers to the task of determining the location of a traveler in spaces (such as large building complexes or airport terminals) using coordinates appropriate to those spaces (such as floor and room number or airport terminal and gate). Indoor localization using Bluetooth beacons is attractive because of the low cost and high spatial selectivity of Bluetooth devices. However, a significant drawback of the Bluetooth protocol for this application is the large delay incurred in the discovery phase of the protocol, which is the phase used for detecting beacons. These delays, of approximately 20 seconds, hamper the use of this localization method because typical walking speeds are likely to change the set of potentially visible beacons part-way through the discovery phase. We study the causes of these delays and propose methods for alleviating them for indoor localization applications. We formalize the key problem of finding a minimum-cost complete beacon-probing plan and present an algorithm for generating such plans. <s> BIB019 </s> Indoor Human Navigation Systems: A Survey <s> Direct Sensing <s> Indoor navigation systems for users who are visually impaired typically rely upon expensive physical augmentation of the environment or expensive sensing equipment; consequently few systems have been implemented. We present an indoor navigation system called Navatar that allows for localization and navigation by exploiting the physical characteristics of indoor environments, taking advantage of the unique sensing abilities of users with visual impairments, and minimalistic sensing achievable with low cost accelerometers available in smartphones. Particle filters are used to estimate the user's location based on the accelerometer data as well as the user confirming the presence of anticipated tactile landmarks along the provided path. Navatar has a high possibility of large-scale deployment, as it only requires an annotated virtual representation of an indoor environment. A user study with six blind users determines the accuracy of the approach, collects qualitative experiences and identifies areas for improvement. <s> BIB020
Direct sensing based localization methods determine the location of the user through the sensing of identifiers or tags, which have been installed in the environment. Two different approaches exist with regard to determining the user's location: (1) location information and information on the user's environment is stored in the tag itself; or (2) this information is retrieved from a database using the tags' unique identifier. Sensing one tag is sufficient for determining the location of the user and tag reader can be easily embedded in hand held devices or in a shoe or a cane BIB015  . The user's orientation can be determined from relative changes in location from subsequent reads of tags  . Five different technologies have been identified that are being used for the tags: • Radio Frequency Identifier Description (RFID) tags are used in most current navigation systems where RFID's can either be passive  BIB011  or active  . Some systems use both active and passive tags BIB015 . Active RFID tags contain a battery and transmit signals automatically. The tags have a larger range, which reduces the number of required tags that need to be installed. The drawback of active tags is the required maintenance, as batteries need to be replaced. Passive tags do not require a battery and are powered to transmit signals by the RFID reader. While passive tags are much less expensive, they have much shorter range and can store much less data BIB009 , which increases their installation cost. RFID tags can be used to store an identifier or location information may be embedded in the tag itself. Active tags can store up to 128kb and passive tags typically store less than 128 bytes  . RFID tags themselves are relatively inexpensive  , but installing them in large environments may be costly, since such tags need to be embedded in floors or walls for users to sense them. For example, if an indoor environment has a carpet floor, installation costs may be low but in the case of concrete or marble floors this may be prohibitively expensive BIB012 . Another disadvantage of this technique is that the human body can block RF signals BIB010 . Once installed, tags may be difficult to update, some tags are only readable and they need to be replaced, while others can be updated, but this cannot be done remotely and one has to be within a short distance from the tag. Cheap RFID tags have relative short ranges, which require installing them in an environment with a larger granularity, or else the risk increases that the user will be unable to detect a tag BIB007 . Active RFID tags have a larger range but they require a power source, such as a battery. • Infrared (IR) localization uses IR transmitters that are installed in known positions where each transmitter broadcasts a unique ID in a cone shaped region BIB008 BIB013 . The user carries an IR receiver that picks up data from IR transmitters in range. In some systems, transmitters not only broadcast the position of the user but also provide information about the environment and graphical walking directions BIB003 . Locating identifiers may be hard, as IR requires line of sight due to their narrow transmission angle BIB014 . A drawback of IR is that natural and artificial light can interfere with IR BIB001 . IR systems are costly to install due to the large number of tags that need to be installed BIB004 . • Ultrasound identification (USID) uses emitters that broadcast ultrasound waves with a short wavelength  . Emitters are installed in the infrastructure and the user carries a receiver on each shoulder. The flight time difference of the ultrasound signals received from the two closest emitters to each receiver is used to locate the user. By placing a receiver on each shoulder the user's orientation  can also be calculated. Other systems have the user carry the ultrasound emitter and receivers are installed in the environment BIB005 where the users' location is determined centrally. A disadvantage of ultrasound is that walls may reflect or block ultrasound signals  , which result in less accurate localization. The other drawback of using ultrasound for localization is required line of sight between the receiver and beacons  . • Bluetooth beacons have been used for localization BIB018 . For localization, the user has to walk slower than with other techniques because of the device delay BIB019 . Bluetooth beacons require a power source and henceforth they need to be maintained. Similar to RFID localization, the change in infrastructure is one of the disadvantages of these technique since the receivers or emitters need to be installed throughout the ceiling BIB006 . • Barcodes can also be used as identifiers to localize a user, where users carry a barcode reader. While users are navigating the path, they have to scan the barcodes along the way and they are located based on their unique ID. The system can then provide the user with information about their location, surroundings, and whether they are moving in the right direction BIB016 BIB002 . This method is low cost and easy to install and maintain. The problem with this method is that the user has to find each barcode and scan that barcode, which may be cumbersome and will slow down navigation. Users with visual impairments may be unable to use the system as detecting the barcodes relies upon being able to see. Though most systems use only one type of technique for the identifiers, there exists a navigation system BIB017 that uses a combination of identifiers, e.g., active and passive RFID tags, or infrared beacons. While using multiple localization techniques might improve the accuracy, the main drawback is the additional equipment that the user has to carry. Particle filters have been used successfully  BIB020 to locate and track users in an indoor environment by combing direct sensing (user as a sensor) and low cost sensors, such as compass.