Provision of ephemeris from base stations to a mobile station

A method comprising: receiving (410) in a mobile station (150) one or more signals representative of hierarchical ephemeris of base stations (300), containing inputs referred to a plurality of base stations, from an ephemeris server of base stations (180), by means of a wireless communication network (120), the hierarchical ephemeris of base stations comprising a plurality of levels, configured in a hierarchical manner, which include a higher level and a lower level, wherein the upper level comprises information common to a plurality of entries corresponding to said plurality of base stations listed at the lower level, wherein said common information is recorded as a single entry at the upper level; storing (420) information of the hierarchical ephemeris of base stations in a memory of the mobile station (150); and estimate (430) a location of the mobile station based, at least in part, on the information of the hierarchical ephemeris of base stations (300).