Method and apparatus to control handoff between different wireless systems

Abstract

A wireless communications network includes a first base station system that performs wireless communications according to a first protocol (e.g., 1xEV-DO protocol) and a second base station system that performs wireless communications according to a second, different protocol (e.g., IS-2000). A link is provided between the first and second base station systems to enable a network-initiated handoff procedure. If a source base station system detects that a handoff of a mobile station to a target base station system is required, the source base station system exchanges messaging over the link with the target base station system to perform the handoff. In one example, the handoff is a hard handoff.

1 . A method of performing wireless communications, comprising:
 communicating bearer traffic for a packet-switched communications session from a first base station associated with a first type of wireless system to a mobile station;   determining, by the first base station, if handoff is required from the first base station to a second base station associated with a second, different type of wireless system; and   in response to determining that the handoff is required, sending a message from the first base station to the second base station over an interface between the first base station and second base station, the message indicating to the second base station that handoff is required.   
     
     
         2 . The method of  claim 1 , wherein the first base station comprises an IS-2000 base station, and wherein communicating the bearer traffic comprises communicating the bearer traffic from the IS-2000 base station to the mobile station. 
     
     
         3 . The method of  claim 2 , wherein determining if handoff is required from the first base station to the second base station comprises determining if handoff is required from the IS-2000 base station to a 1xEV access network. 
     
     
         4 . The method of  claim 2 , wherein determining if handoff is required from the first base station to the second base station comprises determining if handoff is required from the IS-2000 base station to a High Data Rate (HDR) access network. 
     
     
         5 . The method of  claim 1 , wherein the first base station comprises a High Data Rate access network, and wherein communicating the bearer traffic comprises communicating the bearer traffic from the High Data Rate access network to the mobile station. 
     
     
         6 . The method of  claim 5 , wherein determining if handoff is required from the first base station to the second base station comprises determining if handoff is required from the High Data Rate access network to an IS-2000 base station. 
     
     
         7 . The method of  claim 1 , wherein the first base station comprises a 1xEV access network, and wherein communicating the bearer traffic comprises communicating the bearer traffic from the 1xEV access network to the mobile station. 
     
     
         8 . The method of  claim 7 , wherein determining if handoff is required from the first base station to the second base station comprises determining if handoff is required from the 1xEV access network to a 1xRTT base station. 
     
     
         9 . The method of  claim 1 , further comprising receiving another message from the second base station at the first base station to initiate a handoff procedure. 
     
     
         10 . The method of  claim 9 , further comprising sending a further message from the first base station to the second base station to indicate that the mobile station has been directed to hand off to the second base station. 
     
     
         11 . The method of  claim 1 , wherein sending the message comprises sending the message over a link between the first base station and the second base station. 
     
     
         12 . The method of  claim 1 , further comprising performing a hard handoff from the first base station to the second base station. 
     
     
         13 . A first base station system that performs wireless communications with a mobile station according to a first protocol, the first base station system comprising:
 an interface to a second base station system that performs wireless communications with the mobile station according to a second, different protocol; and   a controller to communicate bearer traffic for a packet-switched communications session with the mobile station,   the controller to further determine that the handoff is required from the first base station to the second base station, and in response to determining the handoff is required, send messaging to the second base station system through the interface to perform a handoff of the packet-switched communications session from the first base station system to the second base station system.   
     
     
         14 . The first base station system of  claim 13 , wherein the controller is to perform the handoff by performing a hard handoff. 
     
     
         15 . The first base station system of  claim 13 , wherein the controller is to communicate bearer traffic according to a 1xRTT format with the mobile station. 
     
     
         16 . The first base station system of  claim 15 , wherein the second base station system comprises a 1xEV base station, and wherein the controller is to send the messaging to the 1xEV base station. 
     
     
         17 . The first base station system of  claim 13 , wherein the controller is to send the messaging by sending a message indicating that a handoff is required to the second base station system through the interface. 
     
     
         18 . The first base station system of  claim 17 , wherein the controller is to further receive a message initiating the handoff procedure. 
     
     
         19 . The first base station system of  claim 18 , wherein the controller is to send a further message from the first base station system to the second base station system to indicate that the mobile station has been directed to hand off to the second base station system. 
     
     
         20 . An article comprising at least one storage medium containing instructions that when executed cause a first base station system to:
 communicate signaling according to a first protocol with a mobile station to establish a packet-switched communications session between the mobile station and another endpoint;   determine if a handoff is required to a second base station system that performs wireless communications with the mobile station according to a second, different protocol; and   in response to determining that the handoff is required, send messaging to the second base station system through a link between the first and second base station systems to perform the handoff.   
     
     
         21 . The article of  claim 20 , wherein the first base station comprises a 1xRTT base station, and wherein the instructions when executed cause the first base station system to communicate 1xRTT signaling with the mobile station. 
     
     
         22 . The article of  claim 21 , wherein the instructions when executed cause the first base station system to determine if handoff is required by determining if handoff is required from the 1xRTT base station to one of a 1xEV access network and a High Data Rate (HDR) access network. 
     
     
         23 . The article of  claim 20 , wherein the first base station comprises one of a High Data Rate (HDR) access network and a 1xEV access network, and wherein the instructions when executed cause the first base station system to communicate one of High Data Rate (HDR) signaling and 1xEV signaling with the mobile station. 
     
     
         24 . The article of  claim 23 , wherein the instructions when executed cause the first base station system to determine if handoff is required by determining if handoff is required from the one of the High Data Rate (HDR) access network and 1xEV access network to a 1xRTT base station. 
     
     
         25 . The article of  claim 20 , wherein the instructions when executed cause the first base station system to send messaging by sending a message to the second base station system indicating that a handoff is required. 
     
     
         26 . The method of  claim 1 , wherein sending the message comprises sending the message over a link that directly connects the first base station and second base station. 
     
     
         27 . The apparatus of  claim 13 , wherein the interface allows the messaging to be sent from the first base station system directly to the second base station system. 
     
     
         28 . The article of  claim 20 , wherein sending the messaging to the second base station through the link comprises sending the messaging to the second base station through the link that directly connects the first base station system to the second base station system. 
     
     
         29 . The method of  claim 1 , wherein the mobile station comprises a hybrid mobile station that is able to support at least two different wireless communications protocols including a first wireless communications protocol and a second wireless communications protocol,
 wherein determining if the handoff is required from the first base station to the second base station comprises determining if the handoff is required from the first base station that communicates with the hybrid mobile station according to the first wireless communications protocol, to the second base station that communicates with the hybrid mobile station according to the second wireless communications protocol.   
     
     
         30 . The method of  claim 29 , wherein the first wireless communications protocol comprises a 1xEV protocol, and the second wireless communications protocol comprises a 1xRTT protocol. 
     
     
         31 . The apparatus of  claim 13 , wherein the mobile station comprises a hybrid mobile station that is able to perform wireless communications according to both the first and second protocols, the controller to communicate the bearer traffic with the hybrid mobile station. 
     
     
         32 . The apparatus of  claim 31 , wherein the first protocol comprises a 1xEV protocol, and the second protocol comprises a 1xRTT protocol. 
     
     
         33 . The article of  claim 20 , wherein exchanging the signaling with the mobile station comprises exchanging the signaling with a hybrid mobile station that is able to perform wireless communications according to both the first and second protocols. 
     
     
         34 . The article of  claim 33 , wherein the first protocol comprises a 1xEV protocol, and the second protocol comprises a 1xRTT protocol.