OBTAINING PILOT PHASE OFFSET TIME DELAY PARAMETER FOR A WIRELESS TERMINAL OF AN INTEGRATED WIRELESS-GLOBAL POSITIONING SYSTEM

摘要

An integrated wireless-global positioning system determines the location of awirelessterminal from satellite measurements and wireless network measurements. Theaccuracy of thelocation identified is dependent upon the quality of the measurement from thewireless networkwhich, unfortunately, can contain measurement errors such as biases. Biasesare caused by timedelays which occur during the processing and transmission of signals. The timedelays vary foreach sector/base station and for each type of wireless terminal model beingused. Calibration ofthese biases is important for the success of the integrated wireless globalpositioning system. Fora small network system which has only a handful of base stations/wirelessterminals, a specificsystem to calibrate the time delays for each base station and/or wirelessterminal can be set up.The approach is, however, costly, time consuming, and subject to many errors.It is not feasiblefor a large scale, commercial system where hundreds of base stations anddozens of differenttypes of wireless terminals are involved. This invention is a method of usingan integratedwireless global positioning system to obtain pilot phase offset delayparameters, to continuouslyimprove the quality of the values obtained, and to adaptively adjust theparameters for changesthat may occur. The method does not require that a particular system be set upfor the calibration,and it does not require a team of technical experts to perform fieldcalibrations. With this method,the wireless terminals that have unobstructed reception of global positioningsystem signals areused to determine an estimate of the pilot phase offset time delay parameterswhich are then usedto update previously obtained parameters in the database. The estimated pilotphase offset timedelay parameter is then used to calibrate the pilot phase offset measurementsapplied to fix theposition of a wireless terminal that does not have unobstructed GPS signalreception.