User positioning system for mobile devices

In the recent years, the Global Positioning System (GPS) has become a standard for the location and navigation for a huge number of people all over the world. This system is unquestionably one of the most significant developments of the twentieth century. GPS employs a great variety of applications from car navigation and cellular phone emergency positioning even to aeronautic positioning. Despite the fact that it plays an essential role in today´s world, GPS has some limitations. The main disadvantage is the inability to operate inside the buildings because of the loss of signal from the satellites. During the last decade, the interest in location based services has significantly increased. It is related to the existence of ubiquitous computers and context awareness of mobile devices. Information about the position plays the great role in the field of security, logistics and convenience nowadays. Thus, it is necessary to fill the gap at the point where Global Positioning System does not perform satisfactorily.