locator and tracker

i have read from atty. sassy’s blog site about flaws on smart’s mobile phone locator service or location based service (or lbs). gps is the first and maybe the most reliable location based service available today. but with the cellular networks explosion, gsm seems to be the right second candidate to offer this kind of service. unfortunately, from day one, gsm (cdma) and even 3g were not designed with location capability in mind. in order to provide this service, gsm operator has to invest for additional equipments in the network.

based on radio parameters, several techniques can be used to locate a mobile handset. depending on the application location precision need, different technologies can be used and location process starts from the simple “serving cell id” up to very complex radio parameters measurements and correlation taking into account path loss prediction models. in gsm location technology, radio location could be based on: (1) received radio signal strength which is the main criteria used by the mobile terminal to select the serving cell (cell site), (2) propagation time measurement on time of arrival (toa) or time difference of arrival (tdoa), (3) angle of arrival (aoa) and (4) multi-path analysis.

all this techniques can be combined to improve the location accuracy. the bad news is that all these techniques do not work well in a dense urban area where strong multi-path propagation occurs. in such a dense area, it’s very difficult to build a mathematical model linking all together distance and either radio path, or propagation time delay, or angle of arrival.

for security and emergency linked applications in rural area, a 3d precision of ten meters could be required but not so possible. that’s why smart’s location based service commercial in tv is featured in a rural area. on the opposite, for information services, like finding a hotel in the vicinity, a 2 dimensions 500 m precision is acceptable in dense urban area. globe’s location based service on the other hand, does not in fact point the exact location of their parents traversing edsa, much worse, their parents are traveling in car which passes multiple cell sites.

all gsm network provider has the capability in providing location based service, but the question is how reliable and how precise the service will be. that’s the reason why sun doesn’t provide this service. one thing, if this locator service is truly accurate, then it could help in minimizing phone theft and robbery. sad thing it’s not.

additionals:
to provide you a very short idea how cellular telephony system works, here’s a few description of the three major parts of the system. mobile phones get their network provider signals from base transceiver station (or bts), or simply cell sites, or in lay mans term, the white and orange combination towers we used to see on top of the buildings and in many areas. the base station controller (bsc) then controls one or multiple cell sites' radio signals, thus reducing the load on the central switch. performs radio signal management functions for base transceiver stations, managing functions such as frequency assignment and handoff. the central switch that controls the entire operation of a cellular system is called mobile switching center (msc). it is a sophisticated computer that monitors all cellular calls, tracks the location of all cellular-equipped vehicles traveling in the system, arranges handoffs, keeps track of billing information, etc.

united states 911 uses some of the methods refered above like time difference of arrival (tdoa) and angle of arrival (aoa).