A method of handing off an ongoing wireless telecommunication session with a mobile station when the mobile station is engaging in the ongoing communication session via a first access system, and then registers in a second access system, is provided. When communicating with the first access system the mobile station communicates with a first access node according to a first protocol. When communicating with the second access system the mobile station communicates with a second access node according to a second protocol, which is a different protocol than the first protocol. After registration of the mobile station in the second access system, the ongoing communication session is carried between the mobile station and the second access node according to the second protocol over the first protocol. More specifically, the ongoing communication session is carried between the mobile station and the second access node using the first protocol encapsulated in the headers of the second protocol.