In the high times of GSM, mobile enthusiasts equipped with mobile phones with an engineering menu had a lot of fun finding base stations by taking a closer look at the timing advance parameter. This parameter implicitly contains the distance to the base station the mobile currently communicates with. A GSM mobile requires this parameter as it has to start sending data in it’s timeslot earlier the farther it is away from the base station. This is necessary as radio waves only travel at the speed of light. If no adjustment is made, transmissions of a far away mobile tramples over transmissions in the next time slot of another mobile as they would arrive too late.
With UMTS things got a bit difficult as due to the CDMA approach of the radio interface a timing advance parameter was not necessary anymore. Unfortunately this makes finding specific UMTS base stations quite difficult. But don’t despair, LTE and WiMAX will require a timing advance parameter again since these systems are based on OFDMA and timeslots. This means that the network has to send timing advance information to the mobiles again to ensure their data always arrives at the instant it is supposed to. So network tracking should get easier again in the future!