Thank you Pix for your kind answer, @Jack: the aims of the project is to develop application using Java environment, the location of MS in the GSM network using only the TA gived by the serving BTS (we can get the distance from TA) and the RxLEV measured by the MS of the neighbor Cells, but the problem here how to know the distance between the MS and the others neighbor cells basing on the RxLEV only?