Buffering user data in a core network interface for delivery over a wireless access network

A method of operating a communication system comprising:

• in a core network interface, receiving first user data from a core network for delivery to a wireless communication device and transferring the first user data to a first access network that wirelessly transfers the first user data to the wireless communication device;
• in a second access network, wirelessly receiving a service request from the wireless communication device, and in response, transferring a buffer initiation signal to the core network interface for the wireless communication device, establishing a wireless service link to the wireless communication device, and transferring a packet connection request to the core network interface for the wireless communication device;
• in the core network interface:
• a) receiving second user data for delivery to the wireless communication device and transferring the second user data to the first access network,
• b) buffering the second user data in response to the buffer initiation signal,
• c) establishing a packet connection to the wireless communication device in response to the packet connection request, and
• d) transferring the buffered second user data to the second access network over the packet connection;
• in the second access network, wirelessly transferring the second user data to the wireless communication device over the wireless service link and packet connection;
• and
• wherein transferring the buffer initiation signal comprises transferring an A11 initial packet connection request with a lifetime of zero as a dummy request.