Localization

1. Localization Radu Poenaru Cosmin Catanoaie

2. Location-based services • Safety: identify a location of a person or object • Entertainment: discovering the nearest restaurant • Business: whereabouts of a logistic fleet

3. Safety first! • Emergency medical services (EMS) In 1487, the first recorded use of ambulance was by the Spanish army • Yellow Pages First produced in 1886 by Reuben Donnely • Local weather and traffic broadcast Since 1960s, radio traffic report has been very popular in US and on May 2nd 1982 the weather channel (TWC) went on the air. • Emergency phone services • In 1968, AT&T and FCC came up with this nation-wide emergency phone number - 911 (112 across EU and 999 in UK

4. Concepts • Position :spatial coordinates, single point in the Cartesian coordinate. • Location is associated with a certain place in the real world. • LoCation Service (LCS) - exclusively deals with the localization of target, and also makes the resulting location data available to external actors. • Location Based Service (LBS) is the service that ads value to target locations provided by LCS. It uses knowledge of a mobile device's location to offer value to the mobile subscriber or to a third party.

5. Wireless Location Technologies • Satellite positioning systems • GPS • aGPS • Positioning in mobile networks • Mobile based solutions • Network based solutions • Mobile-assisted solutions

6. GPS • Oldest one from the frameworks presented • It isn't the first positioning system, • But the one with the most success and longevity, started as a military project in 1957. Needs for its functioning: • you need three satellites to get your precise position in the device line of sight, unobstructed for entire period of measurement, • four if you want also the elevation.

7. Types of devices • Data loggers – log data as it arrives and here we can include almost all devices with user interface • Data pushers – the kind of devices using for tracking logistic fleet in real-time • Data pullers – almost the same as the pushers, but instead of sending by their own at specific intervals data to the central location, these ones can be queried as needed

8. aGPS • aGPS, the short form of Assisted Global Positioning System • uses triangulation to augment traditional GPS location tracking. • when GPS receivers power on, they can take minutes to acquire the proper satellites for triangulation. • aGPS speeds up the process by using another method of triangulation, typically cell phone towers or WiFi hotspots, to cut down the time from two or three minutes to 10-20 seconds maximum.

9. Advantages over GPS • GPS system has difficulty providing reliable positions in poor signal conditions - tall buildings (resulting in multipath), indoors or under trees • In addition, when first turned on in these conditions, some non-assisted GPS units may not be able to download the almanac and ephemeris information from the GPS satellites, rendering them unable to function until a clear signal can be received continuously for up to 40 seconds.

10. Advantages over GPS (cntd.) aGPS receiver can address these problems in several ways: • The assistance server can locate the phone roughly by which cell site it is connected to on the cellular network. • The assistance server has a good satellite signal, and lots of computation power, so it can compare fragmentary signals relayed to it by cell phones, with the satellite signal it receives directly, and then inform the cell phone or emergency services of the cell phone's position. • It can supply orbital data and/or almanac for the GPS satellites to the cell phone, enabling the cell phone to lock to the satellites faster in some cases. • The network can provide atomic time (Accurate Time Assistance) • Simply capturing a brief snapshot of the GPS signal, with approximate time, for the server to later process into a position. • By having accurate, surveyed coordinates for the cell site towers, it has better knowledge of ionosphere conditions and other errors affecting the GPS signal than the cell phone alone, enabling more precise calculation of position.

11. Mobile based solutions • Positioning is carried out in mobile device and sent back to the network • Requires the installation of client software on the handset to determine its location. • Requires the active cooperation of the mobile subscriber as well as software that must be able to handle the different operating systems of the handsets • Difficulty of convincing different manufacturers to cooperate on a common mechanism • Issue of foreign handsets that are roaming in the network

12. Network solutions - GSM • Uses network infrastructure to identify the location of the handset • Accuracy varies, with cell identification as the least accurate • Requirement to work closely with the service provider

13. GSM Positioning methods • Cell identity and timing advance • Uplink time of arrival (TOA) • Enhanced observed time difference (E-OTD) • Assisted GPS

14. WiFi positioning • Estimating position using WLAN access point radio propagation • Requires a plurality of Wi-Fi access points in a target area. • The Wi-Fi access points are positioned at geographic locations and have signal coverage areas. • Geographically known location of the Wi-Fi access point, dividing the signal coverage area of the Wi-Fi access point into at least one section • Requires the determination of radio propagation characteristics for each section.

15. WiFi techniques • Nearest sensor • Triangulation/trilateration • RF fingerprinting • Supplier approaches

16. Comparison • First of all: each method presented has its strengths and weaknesses. • None of these is the perfect positioning system • yet they all can collaborate in order to give • the estimated but not the precise position of a user

17. GPS • Has a plethora of satellites at its disposal, • offering almost anywhere in the world a precision in meters. • Devices are small enough to be inserted even in phones; • smart enough to do their job or even more by tracking many satellites in the same time and eating less power, affording the usage of this service for hours in a row. • But it needs clear sight to the sky in order to see at least 3 satellites and needs quite a long time in this busy era to get a clear position and be able to pinpoint the location on a map.

18. aGPS • helps by relying not only on satellites but also on GSM towers, locating and triangulating them too. • Knowing their location, the power of the emitted signal, the user can be easily triangulated. • Especially useful in crowded cities, where many GSM antennas are installed removes the need for a clear sky. • Thus, it allows even in places surrounded by tall buildings to have a good enough precision while locating the position on the map.

19. GSM • Continues the movement from the sky to ground bases by replacing completely the satellites from the picture. • In developed countries there are a lot of GSM towers in urban areas • doesn’t eat more power in phones- knows by default how to measure and get the tower’s id, • there is just a software issue to get the associated geographical positions • Triangulate the user’s position based on the strength of signal. • But if you’re in a remote area, like in mountains, where there are few emitters the quality of location falls dramatically.

20. WiFi • Newborn technology created out of the people need to communicate. • For some business a nice feature to offer, especially for the large fast foods • Ithe big cities these hotspots are countless, thus some smart guys invented a positioning system based on tracking these hotspots location • It offers sometimes a comparable precision in comparison with the classic – the GPS system.

21. Conclusion • No method is perfect • GPS needs clear sky, • aGPS improves this but still needs some satellites to be seen, • GSM works like a charm if you have lots of antennas but falls dramatically if you’re in a remote place • WiFi positioning is good in cities, but absolutely lacks in remote zones. Only the composition of all can cover all the situations encountered in a normal life – crowded city when going to work and big, empty spaces when going to mountains to relax.

22. Thank you • Questions ?