Apparatus, and associated method, for selecting and negotiating frame size of communication data communicated in a radio communication system

1. Apparatus for a wireless device operable to communicate data, in a radio communication system having a PLMN “Public Land Mobile Network) and a GAN (Generic Access Network) said apparatus comprising:

a communication transferor configured to determine a need for rove-in from the PLMN to the GAN;

a frame size calculator embodied at the wireless device and configured to calculate an optimum Logical Link Control (LLC) frame size of a frame into which the data to be communicated is to be formatted, upon a determination that a rove-in by the wireless device is needed;

a frame size negotiation initiator embodied at the wireless device, configured to initiate a frame size negotiation of the frame into which the data to be communicated is to be formatted, and configured to initiate the negotiation of the frame size upon a determination that a rove-in by the wireless device to the GAN is needed, the frame-size negotiation utilizing the optimum LLC frame size calculated by said frame size calculator;

a receiver that receives a response message returned to the wireless device from the PLMN identifying one of the optimum LLC frame size and an alternate LLC frame size to be used;

a calculator that calculates a user data MTU size based on the identified one of the optimum LLC frame size and the alternate LLC frame size; and

a packet former that forms user data into packets of sizes within the calculated MTU size.

2. The apparatus of claim 1 wherein the data to be communicated by the wireless device comprise application level data and wherein the frame, the desired frame size of which is calculated by said frame size calculator, includes a payload part populatable with the application level data.

3. The apparatus of claim 1 wherein the negotiation of the frame size initiated by said frame size negotiation initiator comprises a Third Generation Partnership Project-compliant (3GPP-compliant) network negotiation.

4. The apparatus of claim 1 wherein the MTU comprises a 1464 byte size.

5. The apparatus of claim 1 wherein the optimum LLC frame size calculated by said frame size calculator comprises a Wireless Fidelity (WiFi) Network MTU.

6. The apparatus of claim 1 wherein the optimum LLC frame size calculated by said frame size calculator is a value of the MTU less a logical layer header size.

7. The apparatus of claim 6 wherein the logical layer header size further comprises a Sub Network Dependent Convergence Protocol (SNDCP) header size.

8. A method for facilitating communication of data by a wireless device in a radio communication system having a PLMN (Public Land Mobile Network) and a GAN (Generic Access Network), said method comprising the operations of:

determining, at the wireless device, a need for rove-in from the PLMN to the GAN;

calculating in response to a determined need to rove-in, at the wireless device, an optimum Logical Link Control (LLC) frame size of a frame into which the data to be communicated is to be formatted; and

initiating, at the wireless device, upon a determination that a rove-in by the wireless device to the GAN is needed, a frame-size negotiation of the frame size of a frame into which data to be communicated is to be formatted, the frame-size negotiation utilizing the optimum LLC frame size calculated during said calculating;

receiving a response message returned to the wireless device from the PLMN identifying one of the optimum LLC frame size and an alternate LLC frame size to be used;

calculating a user data MTU size based on the identified one of the optimum LLC frame size and the alternate LLC frame size; and

forming user data into packets of sizes within the calculated MTU size.

9. The method of claim 8 wherein the optimum LLC frame size calculated during said operation of calculating an optimum LLC is a function of a Generic Access Network MTU.

10. The method of claim 8 wherein the optimum LLC frame size calculated during said operation of calculating an optimum LLC is of a size permitting the data to be communicated to be assigned to a single frame.

11. A method for Logic Link Control (LLC) layer negotiation by a multi-mode wireless device, said method comprising the operations of:

deciding a roving-in procedure from a PLMN (Public Land Mobile Network) to a GAN (Generic Access Network) is to commence;

calculating an optimal value at the LLC layer;

upon said rove-in decision, transmitting a negotiation message to the PLMN comprising the calculated optimal value at the LLC layer, wherein the LLC layer optimal value comprises an Internet Protocol (IP) bearer Maximum Transmission Unit (MTU) of the second network minus a plurality of header sizes and minus an IP Security (IPSec) expansion size;

receiving a negotiation message response message from the PLMN that identifies one of the optimum value at the LLC layer and an alternate value at the LLC layer; and

calculating a user data MTU size based on the identified one of the optimum value at the LLC layer and an alternate value at the LLC layer reduced by at least a maximum LLC header size.

12. The method of claim 11 , wherein the PLMN is a Third Generation Partnership Project (3GPP) network.

13. The method of claim 11 , wherein the GAN is a Wireless Fidelity (WiFi) network.

14. The method of claim 11 , wherein the optimal value is an N201-U value.

15. The method of claim 14 , wherein the plurality of header sizes comprises a max IP header size, a max UDP header size, and a max GAN header size, and a max LLC header size.