Mobile Intelligence

10.2 LBS: THE FIRST GENERATION

One of the main origins of LBSs is the E911 mandate in the United States, which was passed by the Federal Communications Commission (FCC) in 1996 and which obliges operators of cellular networks to locate the callers of emergency services with a prescribed minimum accuracy and to deliver their geographic position to a nearby Public Safety Answering Point (PSAP), the office where emergency calls arrive. According to the emergency number 911 in the United States, this mandate is known as Enhanced 911 (E911). In 1996, however, the networks were not equipped for meeting the high-accuracy demands imposed by this mandate. The location of an emergency caller could only be determined by mapping the Cell-Id of the serving base station to its geographic coordinates, which, depending on the size of radio cells, results in accuracies not better than 300 m. Also, the use of GPS was not an option, as low-cost GPS receivers for integration into mobile phones were not available at that time. In order to cope with this lack, enormous efforts were launched to extend cellular networks by advanced positioning methods, which are based on lateration between mobile phones and at least three base stations and which achieve accuracies between 50 and 150 m. An overview of these methods can be found in [1, 8]. These advanced methods are called enhanced observed time difference (E-OTD) or advanced forward link trilateration (A-FLT), and the operators had to spend huge investments ...