In GSM and other cellular networks already use a localization alternative to GPS called Triangulation. Since I am not in to localization techniques I cannot tell you what type of research work is going on in this area. But studying about Triangulation might provide you a starting point.

Another similar active research area is location obfuscation which deals with techniques of hiding user precise location but still enables him to use location based services. This area might be a good one to investigate too.

sir,

you are right triangulation algorithm can be used for localization but in India and many other countries location of base station is not available publicly, therefore we can't use this algorithm efficiently. fingerprinting is alternative but it requires a lot of learning for precise location.

I would approach this from a sort of Bayesian perspective. your device can observe some signal strength associated with sources of known/fixed position. any number of such sources can contribute to a statistical map of your probable location. triangulation is a simple example: one source constrains your location to a circle; a second source to two points of intersection between two circles, and a third source removes this ambiguity. viewing it statistically, though, lets you incorporate more knowlege if you have it: model each source as a *field*, which is not necessarily radially symmetric, and intersect these probability distributions in a Bayesian way. no matter how many sources, or how nuanced/naive your signal knowlege is, you'll always have some map of prediction. I guess the main appeal of this approach is that you can easily incorporate your locational history - for instance, even with two sources, you may be able to choose a single location with high probability if you know you are approaching from a particular direction. (obviously, if you're travelling directly on the line between two sources, this may not help!)

As many others have answered, triangulation due to the GSM network is possible, but in determinate areas where the density of antennas is low, you should have a backup system to give you a better idea of your going course, for example IMUs or just accelerometers.