What is claimed is:
1. A method comprising:
listening for a registration message from a mobile node at an external interface of a gateway node of a wireless packet service, the registration message containing a care-of address for the mobile node that is outside of the wireless packet service;
accepting a registration message from the mobile node at the external interface;
registering the mobile node to the care-of address contained in the registration message;
sending a registration reply message to the mobile node via the care-of address, the registration reply message indicating successful registration;
creating a binding for the mobile node;
tunneling packets addressed to the mobile node to the care-of address; and
receiving tunneled packets from the mobile node, decapsulating the tunneled packets and sending them to the appropriate address.
2. The method of claim 1, wherein listening, accepting, registering sending, encapsulating and receiving are performed by a home agent collocated with the gateway node.
3. The method of claim 1, further comprising intercepting, from the gateway node, packets addressed to the mobile node, and tunneling the intercepted packets to the care-of address of the mobile node.
4. The method of claim 1, wherein the care-of address is an address of an access router.
5. The method of claim 4, wherein sending a registration reply message comprises sending a Mobile IP registration reply message via a foreign agent collocated with the access server.
6. The method of claim 1, wherein the mobile node is assigned to a serving node before accepting the registration message, and wherein creating a binding comprises creating a Mobile IP binding, the method further comprising assigning the mobile node from the assigned serving node to a virtual serving node in association with creating a Mobile IP binding for the mobile node to the care-of address.
7. The method of claim 6, wherein the virtual serving node maintains a PDP context for the mobile node without serving any packets to the mobile node.
8. The method of claim 7, wherein assigning the mobile node comprises making an API call to the virtual serving node to indicate a routing area update request.
9. The method of claim 1, further comprising intercepting release messages from the gateway node in association with registering the mobile node to the care-of address.
10. The method of claim 9, wherein the mobile node is assigned to a serving node before accepting the registration message, and the release messages are to cancel the mobile node’s assignment to the serving node.
11. The method of claim 9, wherein the release messages are Dynamic Host Configuration Protocol release messages generated by the gateway node to cancel a PDP context for the mobile node.
12. A machine-readable medium having stored thereon data representing instructions which, when executed by a machine, cause the machine to perform operations comprising:
listening for a registration message from a mobile node at an external interface of a gateway node of a wireless packet service, the registration message containing a care-of address for the mobile node that is outside of the wireless packet service;
accepting a registration message from the mobile node at the external interface;
registering the mobile node to the care-of address contained in the registration message;
sending a registration reply message to the mobile node via the care-of address, the registration reply message indicating successful registration;
creating a binding for the mobile node;
tunneling packets addressed to the mobile node to the care-of address; and
receiving tunneled packets from the mobile node, decapsulating the tunneled packets and sending them to the appropriate address.
13. The medium of claim 12, further comprising instructions which, when executed by the machine, cause the machine to perform further operations comprising intercepting, from the gateway node, packets addressed to the mobile node, tunneling the intercepted packets to the care-of address.
14. The medium of claim 12, wherein the mobile node is assigned to a serving node before accepting the registration message, the instruction further comprising instructions which, when executed by the machine, cause the machine to perform further operations comprising assigning the mobile node from the assigned serving node to a virtual serving node in association with registering the mobile node to the care-of address.
15. An apparatus comprising:
a gateway node of a wireless packet service;
an external interface of the gateway node; and
a home agent to listen for a registration message from a mobile node at the external interface, the registration message containing a care-of address for the mobile node that is outside of the wireless packet service, to accept a registration message from the mobile node at the external interface, to register the mobile node to the care-of address contained in the registration message, to send a registration reply message to the mobile node via the care-of address, the registration reply message indicating successful registration, to create a binding for the mobile node, to tunnel packets addressed to the mobile node to the care-of address, and to receive tunneled packets from the mobile node, decapsulate the tunneled packets and send them to the appropriate address.
16. The apparatus of claim 15, wherein the care-of address is an address of an external access router.
17. The apparatus of claim 15, further comprising a virtual serving node and wherein the mobile node is assigned to a serving node before accepting the registration message, the home agent further enabling the assignment of the mobile node from the assigned serving node to the virtual serving node in association with creating a binding for the mobile node to the care-of address.
18. The apparatus of claim 17, wherein the virtual serving node maintains a PDP context for the mobile node without serving any packets to the mobile node.
19. A method comprising:
registering a mobile node at a server node of a first wireless packet service;
registering the mobile node at an access router of a second wireless packet service;
obtaining a care-of address from the access router;
sending a registration message to a home agent associated with the first wireless packet service, the registration message including the care-of address;
receiving a registration reply message from the home agent,
tunneling to the home agent, packets for transmission from the mobile node;
receiving tunneled packets from the home agent at the mobile node.
20. The method of claim 19, wherein the home agent is permanently assigned to the mobile node.
21. The method of claim 19, wherein the home agent is collocated with a gateway server node of the first wireless packet service.
22. The method of claim 19, further comprising maintaining the registration with the first wireless packet service by sending packets in accordance with protocols of the first wireless packet service.
23. The method of claim 22, wherein maintaining the registration comprises maintaining a PDP context of the first wireless packet service.
24. The method of claim 19, wherein tunneling the packets comprises encapsulating the packets destined to the last PDP-context related IP address from the first wireless packet service within an IP packet destined to the care-of address.
25. The method of claim 24, wherein the last PDP-context related IP address comprises a permanent address field of the mobile node.
26. The method of claim 19, wherein obtaining a care-of address comprises obtaining a public IP routable public address from the access router and using the IP routable public address as the care-of address.
27. The method of claim 19, wherein registering at an access router of a second wireless packet service comprises discovering a foreign agent associated with the access router and registering with the discovered foreign agent and wherein sending a registration message to a home agent comprises using foreign-agent-assisted mobile IP registration.
28. The method of claim 27, wherein the foreign agent is collocated with the access router.
29. The method of claim 19, wherein the tunneled packets are structured in accordance with a Mobile Internet Protocol.
30. The method of claim 19, further comprising moving from the service area of the first wireless packet service after registering at the server node and moving into the service area of the second wireless packet service after registering at the access router.
31. A machine-readable medium having stored thereon data representing instructions which, when executed by a machine, cause the machine to perform operations comprising:
registering a mobile node at a server node of a first wireless packet service;
registering the mobile node at an access router of a second wireless packet service;
obtaining a care-of address from the access router;
sending a registration message to a home agent associated with the first wireless packet service, the registration message including the care-of address;
receiving a registration reply message from the home agent, tunneling packets from the mobile node to the home agent;
receiving tunneled packets from the home agent at the mobile node.
32. The medium of claim 31, further comprising instructions which, when executed by the machine, cause the machine to perform further operations comprising maintaining the registration with the first wireless packet service by sending packets in accordance with protocols of the first wireless packet service.
33. The medium of claim 32, wherein maintaining the registration comprises maintaining a PDP context of the first wireless packet service.
34. The medium of claim 31, wherein the instructions for tunneling the packets comprise instructions which, when executed by the machine, cause the machine to perform further operations comprising tunneling the packets destined to the last PDP-context related IP address from the first wireless packet service to the care-of address.
35. The medium of claim 31, wherein the instructions for registering at an access router of a second wireless packet service comprise instructions which, when executed by the machine, cause the machine to perform further operations comprising discovering a foreign agent associated with the access router and performing mobile IP registration through the discovered foreign agent and wherein instructions for sending a registration message to a home agent comprise instructions which, when executed by the machine, cause the machine to perform further operations comprising using foreign-agent-assisted mobile IP registration.
36. An apparatus comprising:
a communications device to register at a server node of a first wireless packet service;
a communications device to register at an access router of a second wireless packet service;
a memory containing instruction containing instructions for registration and communication with the wireless packet services; and
a processor coupled to the communications device and the memory to obtain a care-of address from the access router, to send a registration message to a home agent associated with the first wireless packet service, the registration message including the care-of address, to receive a registration reply message from the home agent, to tunnel packets for transmission to the home agent, and to receive tunneled packets from the home agent.
37. The apparatus of claim 36, wherein the processor further maintains the registration with the first wireless packet service by sending packets through the communications device in accordance with protocols of the first wireless packet service.
38. The apparatus of claim 37, wherein maintaining the registration maintains a PDP context of the first wireless packet service.
39. The apparatus of claim 36, wherein the processor tunnels the packets by encapsulating the packets destined to the last PDP-context related IP address from the first wireless packet service within an IP packet destined to the care-of address.
40. The apparatus of claim 39, wherein the last PDP-context related IP address comprises a permanent address field of the apparatus.
41. A wireless packet service system comprising:
a gateway node;
an external interface of the gateway node;
a plurality of serving nodes, each coupled to the gateway node and to which mobile nodes are assigned;
a home agent to listen for a registration message from a mobile node at the external interface, the registration message containing a care-of address for the mobile node that is outside of the wireless packet service, to accept a registration message from the mobile node at the external interface, to register the mobile node to the care-of address contained in the registration message, to send a registration reply message to the mobile node via the care-of address, the registration reply message indicating successful registration, to create a binding for the mobile node, to tunnel packets addressed to the mobile node to the care-of address, and to receive tunneled packets from the mobile node, decapsulate the tunneled packets and send them to the appropriate address; and
a virtual serving node of the wireless packet service coupled to the gateway node to accept an assignment of a mobile node from a serving node in association with creating a binding for the mobile node to the care-of address.
42. The apparatus of claim 41, wherein the care-of address is an address of an external access router.
43. The apparatus of claim 41, wherein the virtual serving node maintains a PDP context for the mobile node without serving any packets to the mobile node.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method for manufacturing a semiconductor device, comprising the steps of:
forming a source electrode layer and a drain electrode layer over a substrate;
forming a buffer layer having n-type conductivity over the source electrode layer and the drain electrode layer;
forming a semiconductor layer over the buffer layer;
forming a gate insulating layer over the semiconductor layer; and
forming a gate electrode layer over the gate insulating layer,
wherein the semiconductor layer and the buffer layer are formed using oxide semiconductor layers,
wherein a carrier concentration of the buffer layer is higher than a carrier concentration of the semiconductor layer, and
wherein each of the source electrode layer and the drain electrode layer is electrically connected to the semiconductor layer with the buffer layer interposed between the source electrode layer or the drain electrode layer and the semiconductor layer.
2. The method for manufacturing a semiconductor device, according to claim 1, wherein the source electrode layer, the drain electrode layer, the buffer layer, the semiconductor layer, the gate insulating layer, and the gate electrode layer are formed by a sputtering method.
3. The method for manufacturing a semiconductor device, according to claim 1, wherein the semiconductor layer and the gate insulating layer are formed in an oxygen atmosphere.
4. The method for manufacturing a semiconductor device, according to claim 1, wherein the buffer layer is formed in a rare gas atmosphere.
5. The method for manufacturing a semiconductor device, according to claim 1, wherein the carrier concentration of the semiconductor layer is lower than 1\xd71017 atomscm3, and the carrier concentration of the buffer layer is 1\xd71018 atomscm3 or higher.
6. The method for manufacturing a semiconductor device, according to claim 1, wherein the buffer layer contains a metal selected from magnesium, aluminum, or titanium.
7. The method for manufacturing a semiconductor device, according to claim 1, wherein the oxide semiconductor layers contain indium, gallium, and zinc.
8. A method for manufacturing a semiconductor device, comprising the steps of:
forming a source electrode layer and a drain electrode layer over a substrate;
forming a buffer layer having n-type conductivity over the source electrode layer and the drain electrode layer;
forming a semiconductor layer over the buffer layer;
forming a gate insulating layer over the semiconductor layer; and
forming a gate electrode layer over the gate insulating layer,
wherein the semiconductor layer and the buffer layer are formed using oxide semiconductor layers,
wherein a carrier concentration of the buffer layer is higher than a carrier concentration of the semiconductor layer,
wherein each of the source electrode layer and the drain electrode layer is electrically connected to the semiconductor layer with the buffer layer interposed between the source electrode layer or the drain electrode layer and the semiconductor layer; and
wherein the semiconductor layer, the gate insulating layer, and the gate electrode layer are successively formed without exposure to air.
9. The method for manufacturing a semiconductor device, according to claim 8, wherein the source electrode layer, the drain electrode layer, the buffer layer, the semiconductor layer, the gate insulating layer, and the gate electrode layer are formed by a sputtering method.
10. The method for manufacturing a semiconductor device, according to claim 8, wherein the semiconductor layer and the gate insulating layer are formed in an oxygen atmosphere.
11. The method for manufacturing a semiconductor device, according to claim 8, wherein the buffer layer is formed in a rare gas atmosphere.
12. The method for manufacturing a semiconductor device, according to claim 8, wherein the carrier concentration of the semiconductor layer is lower than 1\xd71017 atomscm3, and the carrier concentration of the buffer layer is 1\xd71018 atomscm3 or higher.
13. The method for manufacturing a semiconductor device, according to claim 8, wherein the buffer layer contains a metal selected from magnesium, aluminum, or titanium.
14. The method for manufacturing a semiconductor device, according to claim 8, wherein the oxide semiconductor layers contain indium, gallium, and zinc.