1. A method of operating a first mobile device, comprising: determining that a level of ambiguity with regard to which one of a plurality of candidate regions includes the location of the first mobile device exceeds a threshold; generating, in response to said level of ambiguity exceeding said threshold, an ambiguity resolution request signal, wherein the ambiguity resolution request signal includes information identifying said first mobile device and multiple candidate regions; transmitting the ambiguity resolution request signal; removing at least one candidate region from the plurality of candidate regions based on a response signal which is in response to said transmitted ambiguity resolution request signal; and determining the location of the first mobile device in a candidate region remaining in the plurality of candidate regions after removing said at least one candidate region.