27-06-2013, 04:54 PM
TRACKING AND POSITIONING OF MOBILE SYSTEMS IN TELECOMMUNICATION NETWORKS
TRACKING AND POSITIONING.docx (Size: 241.42 KB / Downloads: 35)
ABSTRACT
Mobile positioning technology has become an important area of research, for emergency as well as for commercial services. Mobile positioning in cellular networks will provide several services such as, locating stolen mobiles, emergency calls, different billing tariffs depending on where the call is originated, and methods to predict the user movement inside a region. The evolution to location-dependent services and applications in wireless systems continues to require the development of more accurate and reliable mobile positioning technologies. The major challenge to accurate location estimation is in creating techniques that yield acceptable performance when the direct path from the transmitter to the receiver is intermittently blocked. This is the Non-Line-Of-Sight (NLOS) problem, and it is known to be a major source of error since it systematically causes mobile to appear farther away from the base station (BS) than it actually is, thereby increasing the positioning error.
NEED FOR GEOLOCATION
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. 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.
DIRECTION BASED GEOLOCATION
ANGLE OF ARRIVAL METHOD
As said earlier there will be transmission and reception of signals between the mobile unit and BSs. This method calculates the angle of arrival of signal receiving at the BS. When a mobile user switches the system ON it receives the signal from different base stations, may be 3 or 4 or more. The angle of arrival method two or more base station for the determination. It measures the direction of signal falling on the base station and measures the angle of incidence with respect to a normal and determines the position of the system. Angle of arrival method is not an accurate method used for the mobile positioning because of its some disadvantages such as:
• The determination of the system will be in error if the angle of incidence is changed due to any obstacle like atmospheric particles or due to scattering etc.
• The accurate location cannot be determined if the mobile user is in between the BSs, that is in a straight line.
• It cannot be used for the indoor environments.
DISTANCE BASED POSITIONING
TIME OF ARRIVAL (TOA)
The TOA method calculates the distance of a mobile telephone and a BS based on the TOA of a signal transmitted from the mobile telephone at the BS. It is assumed that the mobile telephone is located at the intersection point of three circles having the radius of the distances between the BSs and the mobile telephone.
CONCLUSION
Our proposal is advantageous in that the location of a mobile telephone can be accurately tracked even in the multi-path fading and the NLOS environment, by using more accurate tracking curves connecting the intersection points among circles with the radii being the distances between corresponding BSs and the mobile telephone in a cellular mobile communication system. We have described about accurate positioning of mobile telephones, which can be used for several applications. The important considerations to be undertaken while selecting a location based technology are location accuracy, implementation cost, reliability, increasing functionality.