Mobile phone tracking

Mobile phone tracking refers to the attaining of the current position of a mobile phone, stationary or moving. Localization may occur either via multilateration of radio signals between (several) radio towers of the network and the phone, or simply via GPS. To locate the phone using multilateration of radio signals, it must emit at least the roaming signal to contact the next nearby antenna tower, but the process does not require an active call. GSM is based on the signal strength to nearby antenna masts.[1]

Mobile positioning, which includes location based service that discloses the actual coordinates of a mobile phone bearer, is a technology used by telecommunication companies to approximate where a mobile phone, and thereby also its user (bearer), temporarily resides. The more properly applied term locating refers to the purpose rather than a positioning process. Such service is offered as an option of the class of location-based services (LBS).[2]

Contents

Technology

The technology of locating is based on measuring power levels and antenna patterns and uses the concept that a mobile phone always communicates wirelessly with one of the closest base stations, so knowledge of the location of the base station implies the cell phone is nearby.

Advanced systems determine the sector in which the mobile phone resides and roughly estimate also the distance to the base station. Further approximation can be done by interpolating signals between adjacent antenna towers. Qualified services may achieve a precision of down to 50 meters in urban areas where mobile traffic and density of antenna towers (base stations) is sufficiently high. Rural and desolate areas may see miles between base stations and therefore determine locations less precisely.

GSM localization is the use of multilateration to determine the location of GSM mobile phones, or dedicated trackers[3][4], usually with the intent to locate the user.[2]

Localization-Based Systems can be broadly divided into:

  • Network-based
  • Handset-based
  • SIM-based
  • Hybrid

Network-based

Network-based techniques utilize the service provider's network infrastructure to identify the location of the handset. The advantage of network-based techniques (from mobile operator's point of view) is that they can be implemented non-intrusively, without affecting the handsets.

The accuracy of network-based techniques varies, with cell identification as the least accurate and triangulation as moderately accurate, and newer "Forward Link" timing methods as the most accurate. The accuracy of network-based techniques is both dependent on the concentration of base station cells, with urban environments achieving the highest possible accuracy, and the implementation of the most current timing methods.

One of the key challenges of network-based techniques is the requirement to work closely with the service provider, as it entails the installation of hardware and software within the operator's infrastructure. Often, a legislative framework, such as E911, would need to be in place to compel the cooperation of the service provider as well as to safeguard the privacy of the information.

Handset-based

Handset-based technology requires the installation of client software on the handset to determine its location. This technique determines the location of the handset by computing its location by cell identification, signal strengths of the home and neighboring cells, which is continuously sent to the carrier. In addition, if the handset is also equipped with GPS then significantly more precise location information is then sent from the handset to the carrier.

The key disadvantage of this technique (from mobile operator's point of view) is the necessity of installing software on the handset. It 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. Typically, smart phones, such as one based on Symbian, Windows Mobile, Windows Phone, BlackBerry OS, iPhone, or Android, would be able to run such software.

One proposed work-around is the installation of embedded hardware or software on the handset by the manufacturers, e.g. E-OTD. This avenue has not made significant headway, due to the difficulty of convincing different manufacturers to cooperate on a common mechanism and to address the cost issue. Another difficulty would be to address the issue of foreign handsets that are roaming in the network.

SIM-based

Using the SIM in GSM and UMTS handsets, it is possible to obtain raw radio measurements from the handset.[5][6] The measurements that are available can include the serving Cell ID, round trip time and signal strength. The type of information obtained via the SIM can differ from what is available from the handset. For example, it may not be possible to obtain any raw measurements from the handset directly, yet still obtain measurements via the SIM.

Hybrid

Hybrid positioning systems use a combination of network-based and handset-based technologies for location determination. One example would be some modes of Assisted GPS, which can both use GPS and network information to compute the location. Both types of data are thus used by the telephone to make the location more accurate (ie A-GPS). Alternatively tracking with both systems can also occur by having the phone attain his GPS-location directly from the satellites, and then having the information sent via the network to the person that is trying to locate the telephone. Services allowing such cellphone tracking are Mologogo, instaMapper, Buddyway and Google Latitude.[7][8][9]

Operational purpose

In order to route calls to a phone the cell towers listen for a signal sent from the phone and negotiate which tower is best able to communicate with the phone. As the phone changes location, the antenna towers monitor the signal and the phone is roamed to an adjacent tower as appropriate.

By comparing the relative signal strength from multiple antenna towers a general location of a phone can be roughly determined. Other means is the antenna pattern that supports angular determination and phase discrimination.

Newer phones may also allow the tracking of the phone even when turned on and not active in a telephone call-. This results from the roaming procedures that perform hand over of the phone from one base station to another.[10]

Bearer interest

A phone's location can be uploaded to a common web site where one's "friends and family" can view one's last reported position. Newer phones may have built-in GPS receivers which could be used in a similar fashion, but with much higher accuracy.

Privacy

Locating or positioning touches upon delicate privacy issues, since it enables someone to check where a person is without the person's consent. Strict ethics and security measures are strongly recommended for services that employ positioning, and the user must give an informed, explicit consent to a service provider before the service provider can compute positioning data from the user's mobile phone.

In Europe, where most countries have a constitutional guarantee on the secrecy of correspondence, location data obtained from mobile phone networks is usually given the same protection as the communication itself. The United States however has no explicit constitutional guarantee on the privacy of telecommunications, so use of location data is limited by law.

With tolling systems, as in Germany, the locating of vehicles is equally sensitive to the constitutional guarantee on the secrecy of correspondence and thus any further use of tolling information beyond deducting the road fee is prohibited. Even obviously criminal intent may not be inferred by such means, although such a use is technically possible.

Officially, the authorities (like the police) can obtain permission to position phones in emergency cases where people (including criminals) are missing. The U.S. Justice Department has argued that current laws allow them to track suspects without having probable cause to suspect a law is being violated.[11] In some instances law enforcement may even access a mobile phone's internal microphone to eavesdrop on local conversations while the phone is switched off.[12]

The Electronic Frontier Foundation is tracking some cases, including USA v. Pen Register, regarding government tracking of individuals.[13]

Some "Free" tracking services allow the cellular telephone number being tracked to be added to telemarketers' lists.

China has proposed using this technology to track commuting patterns of Beijing city residents.[14]

See also

References

  1. ^ "Tracking a suspect by any mobile phone: Tracking SIM and handset". BBC News. 2005-08-03. http://news.bbc.co.uk/1/hi/technology/4738219.stm. Retrieved 2010-01-02. 
  2. ^ a b "Location Based Services for Mobiles: Technologies and Standards“, Shu Wang, Jungwon Min and Byung K. Yi, IEEE International Conference on Communication (ICC) 2008, Beijing, China
  3. ^ Dedicated tracker example 1: KCS Beagle
  4. ^ Dedicated tracker example 2: TraceME Micro
  5. ^ ETSI TS 102 223 V9.1.0 SIM standard
  6. ^ Vodafone Local Zone PC World.
  7. ^ InstaMapper
  8. ^ Mologogo
  9. ^ Buddyway
  10. ^ "Roving Bug in Cell Phones Used By FBI to Eavesdrop on Syndicate". The Chicago Syndicate. http://www.thechicagosyndicate.com/2006/12/roving-bug-in-cell-phones-used-by-fbi.html. 
  11. ^ Ryan Singel (May 8, 2006). "Cell-Phone Tracking: Laws Needed". Wired. http://www.wired.com/politics/security/news/2006/05/70829. 
  12. ^ "FBI taps cell phone mic as eavesdropping tool". Cnet. December 1, 2006. http://news.cnet.com/2100-1029_3-6140191.html. Retrieved June 24, 2010. "Kaplan's opinion said that the eavesdropping technique "functioned whether the phone was powered on or off." Some handsets can't be fully powered down without removing the battery; for instance, some Nokia models will wake up when turned off if an alarm is set." 
  13. ^ Cell Tracking Electronic Frontier Foundation
  14. ^ Cecilia Kang (March 3, 2011). "China plans to track cellphone users, sparking human rights concerns". The Washington Post. http://voices.washingtonpost.com/posttech/2011/03/china_said_it_may_begin.html. 

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