Portable terminals have become necessities of modern life for people of all ages. Thus, service providers and terminal manufacturers are competitively developing differentiated products and services.
For example, the portable terminal has developed into a multimedia device capable of providing various services such as phonebooks, games, Short Message Service (SMS), Electronic mail (E)-mail, morning calls, MPEG-1 Audio Layer 3 (MP3) player, scheduling, digital cameras, Multimedia Message Service (MMS), and wireless Internet.
Additionally, the aforementioned portable terminal provides a location information service which measures a location of the portable terminal, i.e., a location of a user, to inform the location. By using the location information service, the user can determine a user's current location, a bus stop around the current location, a path to a destination from the current location, and so forth. The location information service is one service frequently used by the user.
The location information service uses a Global Positioning System (GPS) in general. The GPS can obtain correct information in an outdoor zone where a satellite signal can be readily received, but cannot be used in an indoor zone where the satellite signal cannot be received.
In order to use the location information service in the indoor zone where the satellite signal cannot be received, a Wi-Fi Positioning System (WPS) technique that utilizes a Wi-Fi signal can be used. The WPS technique can be classified into a triangulation technique and a fingerprint technique. However, since Wireless Local Area Network (WLAN) signal strength is measured and used in both of the two techniques, at least 3 or more Access Points (APs) may be required to provide the location information service with high accuracy. Further, there is a problem in that AP information (e.g., Service Set IDentifier (SSID), Media Access Control (MAC) address, location, and the like) has to be managed in advance in a form of a database.
Instead of the aforementioned method, a sensor may be installed in a lattice form in an indoor zone (floor, ceiling, and the like), and thereafter a user location may be recognized by using a difference in a signal transfer rate between an ultrasonic signal and a signal generated from the sensor, or the user location can be recognized by utilizing a plurality of cameras, a pressure sensor, an infrared ray, and a Radio Frequency IDentification (RFID). However, this method may result in great expenses to install the sensor.
In addition, when using a method in which a magnetic field sensor is utilized to recognize the user location, a magnetic field generator is used to implement the method. Therefore, this method also has a problem in that the installation cost increases similarly to the case of using the sensor.