Support for handoffs in high rate packet data systems
View Patent ↗A first handoff is for an inter-AN cell selection where a source AN allows the AT to add a cell under the control of a different AN to its active set and then allows the AT to switch to the target AN. A bearer path is established between the source and target AN to transfer the data traffic using an exchange of messages to register the AT's movement from one BTS to another BTS. The A8/A10 connections remain anchored at the source AN so a bearer path is needed between the source and target AN to transfer the data traffic. The second handoff occurs when the source AN specifies a move of the AT to a new AN proactively. New connections are established at the target AN to support the AT, and the AT is subsequently moved to the target AN via the relevant air-interface messaging.
1. A method for handoff of an access terminal from a source access network, the method at the source access network comprising:
sending, through a packet air interface, a handoff initiation message to a target access network;
establishing a bearer path connection between the source access network and a target access network, wherein the bearer path is configured to transfer, from the source access network to the target access network, packet data traffic that was received from a packet core network; and
receiving a handoff initiation acknowledgement from the target access network.
2. The method of claim 1 , the method further comprising determining that handoff of the access terminal is desirable, wherein determining that handoff of the access terminal is desirable comprises analyzing a signal strength indication for a cell under control of the target access network.
3. The method of claim 1 , the method further comprising determining that handoff of the access terminal is desirable, wherein determining that handoff of the access terminal is desirable comprises receiving from the access terminal a cell switch indication.
4. The method of claim 1 , the method further comprising determining that handoff of the access terminal is desirable, wherein determining that handoff of the access terminal is desirable comprises receiving an indication indicating that proactive session transfer of the access terminal to the target access network is desirable.
5. The method of claim 4 , the method further comprising receiving a route update message from the access terminal.
6. The method of claim 4 , wherein sending a handoff initiation message comprises sending a session transfer message to the target access network; and receiving a handoff initiation acknowledgement comprises receiving a session transfer acknowledgement from the target access network.
7. The method of claim 1 , wherein the handoff initiation message comprises the session state information record and cell identifiers for cells under control of the target access network, the session state information record comprising air interface protocol attributes and configuration attributes of the access terminal.
8. The method of claim 1 , wherein establishing a bearer path connection comprises:
receiving a connect message from the target access network, the connect message including cells for which radio resources are available on the target access network; and
sending a connect acknowledgement message to the target access network.
9. The method of claim 1 , wherein the handoff initiation acknowledgement comprises a list of cells at which radio resources for both forward and reverse links have been successfully committed and for which a bearer path has been established.
10. The method of claim 1 , the method further comprising sending a traffic channel assignment message to the access terminal with radio resources.
11. The method of claim 1 , wherein at least one of the target access network or the source access network includes packet-switching equipment.
12. The method of claim 1 , wherein the packet air interface is a data-only air interface.
13. A source access network comprising a processor for handoff of an access terminal to a target access network, the processor is configured to:
send, through a packet air interface, a handoff initiation message to the target access network;
establish a bearer path connection between the source access network and the target access network, wherein the bearer path is configured to transfer, from the source access network to the target access network, packet data traffic that was received from a packet core network; and
receive a handoff initiation acknowledgement from the target access network.
14. The source access network of claim 13 , further comprising determining that handoff of the access terminal is desirable, wherein determining that handoff of the access terminal is desirable comprises the processor configured to receive from the access terminal a signal strength indication for a cell under control of the target access network.
15. The source access network of claim 13 , further comprising determining that handoff of the access terminal is desirable, wherein determining that handoff of the access terminal is desirable comprises the processor configured to receive from the access terminal a cell switch indication.
16. The source access network of claim 13 , further comprising determining that handoff of the access terminal is desirable, wherein determining that handoff of the access terminal is desirable comprises the processor configured to receive an indication indicating that proactive session transfer of the access terminal to the target access network is desirable.
17. The source access network of claim 16 , wherein the processor is further configured to receive a route update message from the access terminal.
18. The source access network of claim 16 , wherein sending a handoff initiation message comprises the processor being configured to send a session transfer message to the target access network; and receiving a handoff initiation acknowledgement comprises the processor being configured to receive a session transfer acknowledgement from the target access network.
19. The source access network of claim 13 , wherein the handoff initiation message comprises the session state information record and cell identifiers for cells under control of the target access network, the session state information record comprising air interface protocol attributes and configuration attributes of the access terminal.
20. The source access network of claim 13 , wherein establishing a bearer path connection comprises the processor configured to:
receive a connect message from the target access network, the connect message including cells for which radio resources are available on the target access network; and
send a connect acknowledgement message to the target access network.
21. The source access network of claim 13 , wherein the handoff initiation acknowledgement comprises a list of cells at which radio resources for both forward and reverse links have been successfully committed on the target access network and for which a bearer path has been established.
22. The source access network of claim 13 , wherein at least one of the target access network or the source access network includes packet-switching equipment.
23. The source access network of claim 13 , wherein the packet air interface is a data-only air interface.
24. A method for handoff of an access terminal from a source access network, the method at the source access network comprising:
receiving, through a packet air interface, an indication that handoff of the access terminal is desirable;
sending a handoff initiation message to a target access network;
establishing a bearer path connection between the source access network and the target access network;
receiving a handoff initiation acknowledgement from the target access network; and
sending a traffic channel assignment message to the access terminal with radio resources.
25. The method of claim 24 , wherein at least one of the target access network or the source access network includes packet-switching equipment.
26. The method of claim 24 , wherein the packet air interface is a data-only air interface.