Mobile networks has a potential for good location, infrastructure is well developed, and having an intrinsic feature location – so that a user can use mobile no tracker must be connected to a network and network connection point are fixed, and well located for the network operator.
Infrastructure of mobile networks are based on relays. Is not very dynamic positioning relay and distribution of cells in the relay and channel cell is a complicated and expensive process, which must take into account the pattern of propagation radio waves instead of the relay in question is installed.
GSM cells use a special channel called BCCH for transmitting identifiers of neighboring cells so that the mobile terminal can make easy passage between cells. Although power output is controlled both the GSM terminal level and at the level relay, for a variety of reasons, BCCH channel is always used the same power.
This enables mobile terminals to make consistent comparisons between the powers of the signal from multiple cells, and to choose the best communication. The same model can be used for localization. Because the basic pattern is the same, more algorithms presented in locating WiFi access point location applies to GSM, in particular algorithms that take into account signal strength.
Although it has better stability as regards the existence relay, mass adoption of WiFi solutions for homes and offices made the density of WiFi is considerably higher than the GSM cell. Also, positioning needs are different. If in positioning systems for exterior needed a treble which eventually can be translated then in an address where positioning systems indoor objective is to determine the position in a building at floor level, to room level or even level position in a room.
To meet these needs have developed a series of methods and systems, many of them using similar ideas to those outlined in the previous section, tailored interior. Cricket system is based on static transmitters and receivers ceiling-mounted phones. Periodically transmit ultrasonic transmitters and radio frequency messages containing an own ID and unique. Because radio signals at a rate approximately 106 times greater than ultrasound, mobile receivers use the time difference between the arrival of the radio signal to the ultrasonic to calculate the distance to each of the transmitters.
Knowing position fixed transmitters, the receiver position can be determined using trilateration or multilateration The solution uses a centralized architecture and requires a large number of ultrasonic sensors mounted precisely. The idea of the Active Badge system the same as shown in 1992, which is based signals transmitted by infrared, instead of the ultrasonic waves.
The difference between the two methods is to train the system, first using a series of empirical measurements in different locations on one floor and has two propagation model uses radio waves to avoid the need for such measurements. If empirical measurements, measurements are taken in a total of 70 locations in space measuring 3 stops to WiFi.
Article draw attention to user orientation effect on the received signal power, and proposes four measurements for each location, each with a different orientation. In the latter case, it defines a model of radio wave propagation in the space in which it is desired location, taking into account of the attenuation of the signal based on the obstacles in the space. It is considered then a grid of points over this space that approximates how much should be received signal strength.