D.2 MS-Assisted GPS

03.713GPPFunctional descriptionLocation Services (LCS)Release 1999Stage 2TS

The mobile-assisted solution shifts the majority of the traditional GPS receiver functions to the network processor. This method requires an antenna, RF section, and digital processor for making measurments by generating replica codes and correlating them with the received GPS signals. The network transmits a very short assistance message to the mobile station (MS), consisting of time, visible satellite list, satellite signal Doppler, and code phase search window. These parameters help the embedded GPS sensor reduce the GPS acquisition time considerably. These assistance data are valid for a few minutes. It returns from the MS the pseudorange data processed by the GPS sensor. After receiving the pseduorange data, the corresponding network processor or location server estimates the position of the MS. The differential correction can be applied to the final result at the network side to improve the position accuracy.