There are many terms used to determine the location of mobile station such as position, location, geo location, radio location etc. This includes the information about latitude and longitude. Geo location technology is widely used in military and commercial applications. Here location based service means providing service to remote mobile user based on their geographical position. Positioning systems are used in many applications such as mapping service, information services, reservation, booking service etc. in such system, accuracy is very important. It is similar to Bit error rate in telecommunication systems. Voice packets tolerate only one percentage of bit error rate. Location based system accuracy is defined as the area of uncertainty around the exact location where the % of repeated location measurement are reported. The physical characteristic such as radio propagation environment, noise and interference characteristics and receiver design affects the system. The GOS in telecommunication system is the call blocking rate during the peak hour. In these systems the coverage corresponds to the availability of measurements to perform a location computation.
Indoor Geo location applications:
Some examples are given below
Locating person within the building
Finding mentally impaired patients in hospitals
PLS (personal locator service) – It has the locator device which is available with a person.
Telematics- It combines GP with wireless communications
Intelligent transport systems- It includes automatic steering of vehicles, navigation of vehicles according to current traffic information.
E-911 services- wireless enhanced -911 services. It is suitable to cellular communication.
Types of positioning systems:
1. Self-positioning systems- Mobile station can locate own position by measuring its distance from known locations.
2. Remote positioning systems- Mobile stations can be small size and consume low power. Receiver which is in known location on the network together compute the location of mobile transmitter by measuring the distance of this mobile from each receiver.
Architecture of wireless GEO location system:
Location estimation of the mobile is used find the position location. This location information is shared with the network. Initially subscriber requests the location information from the service provider. Then service provider sends the location information to subscriber. After receiving the request from the subscriber the service provider contact the location control center which can gather the information to calculate the location of the mobile station. With the past information about mobile station location, a set of base is used to page the mobile station. After collecting this information the location control center find out the location of the mobile while can be given to the service provider.