Intersystem (GSM, CDMA) base station handover by simultaneously communicating with both base stations

摘要

Methods and apparatus for handing over a mobile station in the system from a CDMA base station to a GSM/TDMA base station are disclosed. A hybrid GSM/CDMA telecommunications system 20 includes base stations 32 operating according to a CDMA interface, and base stations 30 operating according to a GSM/TDMA interface. A communications link is established over the CDMA interface with a mobile station 40. Data is received at the CDMA station from the mobile station 40, in response to a signal received by the mobile station over the GSM/TDMA interface, without breaking the communications link with the CDMA station. The data includes a measurement of the signal strength. The mobile station is handed over from the CDMA to the GSM/TDMA base station in response to the data received, while a weighting factor is applied to the measurement of the signal strength. In particular, a method of conducting intersystem handover from a multicarrier system to a direct spread system is provided. Timing synchronization is also made available through the mobile station.