Patent ID: 7961687

Claim:
A method of effecting handoff of a mobile station from a first base station in a first cellular communications system controlled by a first mobile switching control station to a second base station in a second cellular system controlled by a second mobile switching control station, said first cellular communications system being a CDMA system, and said second cellular system being a GSM system, the method comprising: receiving a signal quality message from the mobile station via the first base station at said first mobile switching control station, when a first parameter of a first signal transmitted by the first base station and a second parameter of a second signal transmitted by said second base station, as measured by the mobile station, reach a predetermined condition; generating at the first mobile switching control station an Application Data Delivery Service (ADDS) message containing handoff data in response to the signal quality message, the ADDS message being a type of tunnelling mechanism, which transparently passes the handoff data within the CDMA system, wherein the handoff data comprises GSM parameters including timing information for effecting the handoff to the GSM system; and communicating the ADDS message from said first mobile switching control station to said mobile station.