19-04-2011, 03:26 PM
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1. INTRODUCTION
1.1 WHAT IS MOBILE TRACKING AND POSITIONING?
Mobile phone tracking tracks the current position of a mobile phone even on the move. To locate the phone, it must emit at least the roaming signal to contact the next nearby antenna tower, but the process does not require an active call.By measuring the power levels and antenna patterns,the position of a mobile phone can be tracked using various GSM localization techniques. The GSM mobile phone tracking system, more often referred to as GSM localization, is a cell phone tracking system which uses the hyperbolic positioning process to determine the exact location of a GSM enabled cell phone, thus indirectly tracking its user. In hyperbolic positioning, a particular object is accurately located by computing the time difference in arrival of the signals that are emitted from the object to three or more receivers. There are three methods of GSM mobile phone tracking, viz. network based mobile phone tracking system, handset based mobile phone tracking system and hybrid mobile phone tracking system
Mobile positioning, which includes location basedservice 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”.
1.2 WHY SHOULD MOBILE PHONES BE TRACKED?
One of the most powerful ways to personalize mobile services is based on location. The location based services, provides the subscribers very best of the service. Recent demands from new applications require positioning capabilities of mobile telephones or other devices.Mobile tracking also helps detectives in pbserving the movement of a suspect.This technique was once deployed by Italian and british cops to track a terrorist. The ability to obtain the geo-location of the Mobile Telephone (MT) in the cellular system allows the network operators to facilitate new services to the mobile users. The most immediate motivation for the cellular system to provide MT position is enhanced in accident emergency services. The geolocation of the mobile user could provide services like :
Emergency service for subscriber safety
Location sensitive billing
Cellular Fraud detection
Intelligent transport system services
Efficient and effective network performance and managemen
Locating stolen phone
2. INTRODUCTION TO MOBILE TECHNOLOGY
As shown in Figure 1, the mobile telecommunication network includes a several base stations (BSs) T 1 to T N for providing mobile telecommunication service to a mobile subscriber through a mobile telephone M1, a base station controller (BSC) for controlling the BSs T 1 to T N, and a mobile telephone switching office (MTSO) for connecting the BSC to another BTS or a PSTN (Public Switched Telephone Network).
In a cellular mobile telecommunication network, the whole service area is divided into a several coverage areas having respective base stations (BS). Each BS coverage area is called a "cell." Each BS is provided with a frequency of a range between 450 to900 MHz. More than one cells can use same frequency. Only condition is that no two adjacent cells must have same frequencies. An MTSO controls these BSs so that a subscriber can continue his call without interruption while moving between different cells. The MTSO can reduce the time required for calling a subscriber by locating the cell of the subscriber. Tracking the location of a mobile subscriber within the boundary of a cell in a mobile telecommunication network is known as "location based services “
Mobile technology includes mainly two functions. They are call fixing and hands-off process. All the BSs are sending a signal of power 25 to 30w to the mobile unit. When a user switches ON his mobile, it will search for the strongest signal and got connected to that BS. Then the mobile unit sends an identification signal to the BS. When he fixes a call, the BS accepts the request and sends the request to the BSC and MTSO. Then the MTSO will searches where the subscriber is and connects the call.
When a user moves to another cell the MTSO will change the frequency allotted to it and allots the frequency of the new BS.For both these processes “GEOLOCATION” of the mobile unit is essential.
3. ARCHITECTURE OF A GEOLOCATION SYSTEM
An example of geolocation system architecture [KOS00] is shown in Figure. As we said earlier, in order to fix a call the subscriber we are calling must be located accurately. A geolocation service provider provides location information and location aware services to subscribers.
Upon a request from a subscriber for location information about an MS, the service provider will contact a location control center querying it for the coordinates of the MS. This subscriber could be a commercial subscriber desiring to track a mobile device or a PSAP trying to answer an E-911 call. The location control center will gather information required to compute the MS’s location.
This information could be parameters such as received signal strength, BTS ID, TOA of signals, and so on that we discuss later. Depending on past information about the MS, a set of BS’s could be used to page the MS, and directly or indirectly obtain the location parameters. These are sometimes called Geolocation base stations (GBSs).
Once this information is collected, the location control center can determine the location of the mobile with certain accuracy and convey this information to the service provider. The service provider will then use this information to visually display the MS’s location to the subscriber. Sometimes the subscriber could be the MS itself, in which case the messaging and architecture will be simplified, especially if the application involves self-positioning.
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 if you know which base station the phone communicates with, you know that the phone is close to the respective base station.
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, usually with the intent to locate the user.
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, 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.
1. INTRODUCTION
1.1 WHAT IS MOBILE TRACKING AND POSITIONING?
Mobile phone tracking tracks the current position of a mobile phone even on the move. To locate the phone, it must emit at least the roaming signal to contact the next nearby antenna tower, but the process does not require an active call.By measuring the power levels and antenna patterns,the position of a mobile phone can be tracked using various GSM localization techniques. The GSM mobile phone tracking system, more often referred to as GSM localization, is a cell phone tracking system which uses the hyperbolic positioning process to determine the exact location of a GSM enabled cell phone, thus indirectly tracking its user. In hyperbolic positioning, a particular object is accurately located by computing the time difference in arrival of the signals that are emitted from the object to three or more receivers. There are three methods of GSM mobile phone tracking, viz. network based mobile phone tracking system, handset based mobile phone tracking system and hybrid mobile phone tracking system
Mobile positioning, which includes location basedservice 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”.
1.2 WHY SHOULD MOBILE PHONES BE TRACKED?
One of the most powerful ways to personalize mobile services is based on location. The location based services, provides the subscribers very best of the service. Recent demands from new applications require positioning capabilities of mobile telephones or other devices.Mobile tracking also helps detectives in pbserving the movement of a suspect.This technique was once deployed by Italian and british cops to track a terrorist. The ability to obtain the geo-location of the Mobile Telephone (MT) in the cellular system allows the network operators to facilitate new services to the mobile users. The most immediate motivation for the cellular system to provide MT position is enhanced in accident emergency services. The geolocation of the mobile user could provide services like :
Emergency service for subscriber safety
Location sensitive billing
Cellular Fraud detection
Intelligent transport system services
Efficient and effective network performance and managemen
Locating stolen phone
2. INTRODUCTION TO MOBILE TECHNOLOGY
As shown in Figure 1, the mobile telecommunication network includes a several base stations (BSs) T 1 to T N for providing mobile telecommunication service to a mobile subscriber through a mobile telephone M1, a base station controller (BSC) for controlling the BSs T 1 to T N, and a mobile telephone switching office (MTSO) for connecting the BSC to another BTS or a PSTN (Public Switched Telephone Network).
In a cellular mobile telecommunication network, the whole service area is divided into a several coverage areas having respective base stations (BS). Each BS coverage area is called a "cell." Each BS is provided with a frequency of a range between 450 to900 MHz. More than one cells can use same frequency. Only condition is that no two adjacent cells must have same frequencies. An MTSO controls these BSs so that a subscriber can continue his call without interruption while moving between different cells. The MTSO can reduce the time required for calling a subscriber by locating the cell of the subscriber. Tracking the location of a mobile subscriber within the boundary of a cell in a mobile telecommunication network is known as "location based services “
Mobile technology includes mainly two functions. They are call fixing and hands-off process. All the BSs are sending a signal of power 25 to 30w to the mobile unit. When a user switches ON his mobile, it will search for the strongest signal and got connected to that BS. Then the mobile unit sends an identification signal to the BS. When he fixes a call, the BS accepts the request and sends the request to the BSC and MTSO. Then the MTSO will searches where the subscriber is and connects the call.
When a user moves to another cell the MTSO will change the frequency allotted to it and allots the frequency of the new BS.For both these processes “GEOLOCATION” of the mobile unit is essential.
3. ARCHITECTURE OF A GEOLOCATION SYSTEM
An example of geolocation system architecture [KOS00] is shown in Figure. As we said earlier, in order to fix a call the subscriber we are calling must be located accurately. A geolocation service provider provides location information and location aware services to subscribers.
Upon a request from a subscriber for location information about an MS, the service provider will contact a location control center querying it for the coordinates of the MS. This subscriber could be a commercial subscriber desiring to track a mobile device or a PSAP trying to answer an E-911 call. The location control center will gather information required to compute the MS’s location.
This information could be parameters such as received signal strength, BTS ID, TOA of signals, and so on that we discuss later. Depending on past information about the MS, a set of BS’s could be used to page the MS, and directly or indirectly obtain the location parameters. These are sometimes called Geolocation base stations (GBSs).
Once this information is collected, the location control center can determine the location of the mobile with certain accuracy and convey this information to the service provider. The service provider will then use this information to visually display the MS’s location to the subscriber. Sometimes the subscriber could be the MS itself, in which case the messaging and architecture will be simplified, especially if the application involves self-positioning.
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 if you know which base station the phone communicates with, you know that the phone is close to the respective base station.
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, usually with the intent to locate the user.
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, 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.
