US Patent 7251227 Access stratum manager

A multi-mode mobile communication device may include a processing device, a memory sub-system, a communication sub-system operable to communicate with the plurality of wireless access networks, and a protocol stack stored in the memory sub-system and executed by the processing device. The protocol stack may include a first access stratum, a second access stratum, a non-access stratum and an access stratum manager. The first access stratum may communicate with a first wireless access network via the communication sub-system. The second access stratum may communicate with a second wireless access network via the communication sub-system. The non-access stratum may communicate with a core network. The access stratum manager may interface the non-access stratum with the first and second access strata, and may be operable to activate the first access stratum to establish a communication link with the core network over the first wireless access network. The access stratum manager may be further operable to maintain the communication link between the non-access stratum and the core network while transferring the communication link from the first access stratum to the second access stratum.