Communications system frequently include a plurality of network nodes which are coupled to access nodes through which end nodes, e.g., mobile devices, are coupled to the network. Network nodes may be arranged in a hierarchy. Access Authentication and Authorization (AAA) servers are nodes which are normally placed relatively high in the network hierarchy. They normally provide information used for security and access control purposes. Access nodes frequently have a secure link with an AAA server in cases where such servers are used. The secure link may be through one or more node in the hierarchy.
Operators typically manage access sessions in IP networks using the RADIUS protocol and associated RADIUS AAA servers. In the future, AAA systems may be based on new protocols such as DIAMETER. In a system using a RADIUS AAA server, when a user attempts to gain access to an operator network, for the duration of an access session, the local Access Router normally issues one or more RADIUS Access-Requests to an Authentication Server to authenticate that user based on its identity such as a Network Access Identifier (NAI). The AAA database typically has stored the identities of those users allowed to access its system along with the services features they are able to invoke. When the user is successfully authenticated, its access port on the access device is configured with policy state commensurate with the user's service Authorization. The service authorization is normally delivered via RADIUS to the Access Router by the Authorization Server. Whilst authorized, service usage during an access session is recorded by the Access Router, and sent as accounting records to an Accounting Server using Accounting-Request messages in the RADIUS protocol. The Accounting Server may be part of the AAA server or it may be an independent server using the same protocol with the authorization server. If the user is connected to multiple Access Routers during a single session then the multiple sessions need to be aggregated in the Accounting Servers.
In addition to authorization and accounting issues, communications systems which support mobile devices need to include mechanisms for conveying location information so that a mobile device can change its point of attachment to the network and still have signals, e.g., IP packets, routed to it.
Mobile IP, (versions 4 and 6) also known as MIPv4 [MIPv4] and MIPv6 [MIPv6], enables a mobile node (MN) to register its temporary location indicated by a care-of-address (CoA) to its Home Agent (HA). The HA then keeps a mapping (also called a binding) between the MN's permanent address, otherwise called Home Address (HoA), and the registered CoA so that packets for that MN can be redirected to its current location using IP encapsulation techniques (tunneling). The CoA used by a MN can be an address that belongs to a Foreign Agent (FA) in an Access Router when MIPv4 is used or it can be a temporarily allocated address to the MN itself, from the Access Router prefix, in which case it is called a collocated care-of-address (CCoA). The latter model also applies to MIPv4 while it is the only mode of operation in MIPv6. Note that for the purpose of this document the terms CCoA and CoA as well as Registration and Binding Update (BU) are interchangeable since they are the corresponding terms for MIPv4 and MIPv6. The methods and apparatus of the invention are applicable to both MIPv4 and MIPv6 unless otherwise mentioned.
AAA systems are typically used with mobile IP to manage IP address allocations (HoAs), to dynamically allocate HAs, to distribute MN profiles to the Access Router and also to distribute security keys to authenticate MIP messages and to secure the air-link. The Mobile Node, an end node which is capable of changing its point of network attachment, typically sends a MIP message to gain access to the system, which triggers an AAA request to authenticate and authorize the Mobile Node. The AAA MN profile and security state is then passed from the AAA system to the Access Router to control services consumed by the MN.
MNs may change their point of network attachment, e.g., as they move from one cell to another cell. This involves changing the MNs point of attachment from a first access node, e.g., a first router, to a second access node, e.g., a second router. This processes is commonly known as a handoff. As part of a handoff the MN's CoA/CCoA needs to be updated and then transferred into the HA using MIP signaling so that packets are redirected to the MN via the new Access Router. As part of handoff process, it is necessary to transfer at least some of the first access router's state information corresponding to the MN involved in the handoff to the new access router so that the MN service is not interrupted. This process is known as State Transfer. State transfer may include, e.g., the transfer of AAA profile state information that was previously delivered via RADIUS to the AR, at which the MN access session commenced. It also may include, e.g., the transfer of air-link security vectors, MN-NAI, MN IP Address, MN-EUI-64, remaining MIP Registration Lifetime, MN multicast group membership, admission control state, resource reservation state, diff-serv state, SIP session state, compressor state, MN scheduling history and/or many other potential items of MN specific AR state information.
In at least one known system, the transfer of state information during a handoff is accomplished by the new access node to which a mobile node is connecting sending a state transfer message through the communications network to the old access node to which the mobile node was connected. In response the old access node forwards state information to the new access node. This technique, while effective, has the disadvantage of requiring that a message be sent between the old and new access nodes to initiate the transfer of the state information. The links between access nodes used for the transmission of such messages may become congested or could be used to convey other information and/or signals if the need for messages between access nodes used to initiate the transfer of state information could be eliminated.
In view of the above discussion, it should be appreciated that there is a need for new methods of implementing the communication of state information to a new access node in the case of a mobile node handoff or in other cases where a mobile node enters a new cell. It should also be appreciated that, for the reasons discussed above, avoiding the use of messages between access nodes to trigger the transfer of state information during a handoff is desirable.
In a wireless network, mobile end users use end nodes, e.g., wireless devices, to communicate with other network entities, e.g., wireless devices used by other end users, via access nodes. The access nodes may be implemented as wireless access routers. The access nodes may be, e.g., base stations. Associated with each end node there is state, e.g., a set of information comprising various parameters relating to service(s) and/or application(s) corresponding to the end node. This state is used by an access router which serves as the end node's point of network attachment. Each time the end node changes the point of attachment to the network, the state should be re-built or transferred to the access router which serves as the new point of network attachment so that the new access node can continue to provide communication services with regard to existing communications sessions or provide new communications services, e.g., as requested by the end node. The methods and apparatus of the present invention are directed to a novel method of transferring state between access points/routers through the use of a wireless terminal, e.g., mobile node, as the conduit for the state information.
The transferred state may, and in some embodiments does, include one or more of the following: an access key to be used in obtaining at least one of secure access and authenticated access to said second access node; a master session key to be used in obtaining at least one of secure access and authenticated access to said second access node; service authorization information indicating at least one service the end node is authorized to be provided with; a communications session identifier identifying an ongoing communications session, resource allocation information indicating resources allocated to an ongoing communications session; air link resource information; communications group membership information; an IP address assigned to said end node and an address lifetime corresponding to said IP address.
In accordance with the invention, the wireless terminal is provided with a large amount of control over the handoff process and the need to transfer state through one or more core network elements or from one base station to another via a backhaul link can be avoided. This is because the mobile node receives the relevant state information from the current base station as part of a handoff and then communicates the state to a new base station as part of a handoff procedure. The communication of the state information to the mobile node and the transfer of the state information to the new base station, e.g., the target base station, can be provided over wireless connections. After the transfer a communications session which was ongoing with another node, e.g., another end node, may be continued through the target base station through the use at the target base station of transferred state.
For security reasons, the state information is encrypted in some embodiments by the first base station prior to transmission. The base stations in the system maintain a security association, e.g., by having common access to a security server in the network. Thus, in various embodiments, the target base station is able to decode the encrypted state information, using a shared secret accessible to the current base station and the target base station, while the mobile node can not. Also, while the state information is communicated from the old base station to the mobile over an airlink and then from the mobile node to the new base station over an air link, security is maintain due to the encrypted nature of the transmitted information.
After successful decryption of the state information, the target base station is able to serve as the mobile nodes new point of network attachment. The target base station may send one or more routing messages to various nodes in the network after successful decryption of the state information received from the mobile node. Such messages may be used to update network routing information so that IP packets intended for the mobile node will be directed to the target base station instead of the old base station.
The state transfer methods and apparatus of the present invention can be used in both make before break handoffs and break before make handoffs. In the case of break before make handoffs the connection with the old base station is terminated following transfer of the signed and optionally encrypted state to the mobile node and before the connection with the target base station is established. Thus, in such embodiments, the connection with the old base station may be terminated prior to the target base station receiving the state information.
In accordance with the invention, the old base station need not be informed of the target base station. If a handoff to a first target base station fails, e.g., due to communications problems or lack of communications capacity, the mobile node can complete the handoff to a second target base station. In such a case, the state information stored in the mobile node would be transmitted from the mobile node to the second target base station, e.g., instead of the first target base station. Thus, it should be appreciated that the mobile nodded based state transfer methods of the present invention provide a highly flexible system where the mobile node is allowed a great deal of flexibility and control over handoffs. In particular, depending on the implementation, the mobile node can control one or more of the following: 1) determining when to perform a handoff, 2) selecting one or more target base stations to which a handoff is completed; and 3) changing the target of a handoff operation should a handoff to an initial target base station fail or conditions change. Such decisions and operations can be performed in accordance with the invention without having to first notify a master network controller in the communications network or receiving authorization for a handoff from a master network controller located in the core of the network.
The nature of the state transported, according to this invention, may be purely under the control of the base station that controls the state. However, the mobile node may request the transfer of particular state. In some but not necessarily all embodiments of the invention, one base station serves as a primary base station for a given terminal at nay point in time, although it is possible that a terminal is connected to multiple base stations at the same time. In such embodiments, the primary base station is the one that controls and is responsible for maintaining the currency of the state required to support the terminal's communications, e.g., voice or data communications sessions. The primary base station, in one such embodiment may send state to the terminal as the state for the terminal is updated. The state can be stored in the mobile and can be transferred to another access node when needed, e.g., upon handoff. State stored in the access node may be replaced or updated using additional state received from the first access node. Thus, changed or updated state sent to the end node after some first state received from an access node has already been stored in the end node, may be used to replace or update the older stored state. As a result of updating of the stored state, current state will be provided to an access node as part of a handoff or other state update operation. It should be appreciated that the state transfer methods of the invention can be used for synchronizing state used by multiple access nodes and not simply as part of a handoff procedure.
In an alternative embodiment of the invention the primary base station sends the state to the terminal on terminal's request, e.g., at the time the terminal wants to handoff, it requests said state from its primary base station.
By distributing handoff control and state transfer functionality in such a way that a handoff can occur without the need to transmit state information through the core of the network, a great deal of resiliency can be achieved. Furthermore, in some embodiments, updates and modifications to handoff procedures can be implemented overtime without having to make changes to network elements in the core of a communications network. This is particularly desirable in systems where base stations and mobile nodes are controlled by a service provider and another entity is responsible for core network functions, e.g., the backhaul between routers or base stations.
In view of the above discussion, it should be appreciated that the present application describes methods for transfer of state to support events such as the movement of an end node (EN) between access nodes (ANs). The methods use the end nodes, e.g., mobile nodes, to store and/or forward state information between access nodes as part of a handoff or another process. In addition to the case of handoffs, the methods and apparatus can be used for updating and maintaining state in multiple access nodes, e.g., when an end node maintains connections with multiple access nodes at the same time. The methods of the invention can be used in other state update applications as well.
Additional features and benefits of the present invention are discussed in the detailed description which follows.
The methods and apparatus of the present invention for storing, manipulating, retrieving, and forwarding state, e.g., context and other information used to support communications sessions with one or more end nodes, e.g., mobile devices, can be used with a wide range of communications systems. For example the invention can be used with systems which support mobile communications devices such as notebook computers equipped with modems, PDAs, and a wide variety of other devices which support wireless interfaces in the interests of device mobility. The methods and apparatus are well suited for use in wireless communications systems, e.g., systems which use OFDM signals or other types of signals transmitted over wireless communications channels.
The
Each access node 140, 140′, 140″ is depicted as providing connectivity to a plurality of N end nodes (144, 146), (144′, 146′), (144″, 146″), respectively, via corresponding access links (145, 147), (145′, 147′), (145″, 147″), respectively. In the exemplary communication system 100, each access node 140, 140′, 140″ is depicted as using wireless technology, e.g., wireless access links, to provide access. A radio coverage area, e.g., communications cell, 148, 148′, 148″ of each access node 140, 140′, 140″, respectively, is illustrated as a circle surrounding the corresponding access node.
The exemplary communication system 100 which implements the invention, is subsequently used as a basis for the description of various embodiments of the invention. Alternative embodiments of the invention include various network topologies, where the number and type of network nodes, the number and type of access nodes, the number and type of end nodes, the number and type of links, and the interconnectivity between nodes may differ from that of the exemplary communication system 100 depicted in
In various embodiments of the present invention some of the functional entities depicted in
The wireless communication interface 230 provides a mechanism by which the internal components of the end node 200 can send and receive signals to/from external devices and network nodes, e.g., access nodes. The wireless communication interface 230 includes, e.g., a receiver module 232 with a corresponding receiving antenna 236 and a transmitter module 234 with a corresponding transmitting antenna 238 used for coupling the end node 200 to other network nodes, e.g., via wireless communications channels. The receiver and transmitter modules 232, 234 can receive and transmit OFDM signals in various embodiments of the invention and can operate under control of the handoff control module 213 to transmit and receive various handoff related signals.
The exemplary end node 200 also includes a user input device 242, e.g., keypad, and a user output device 244, e.g., display, which are coupled to bus 206 via the user input/output interface 240. Thus, user input/output devices 242, 244 can exchange information, signals and data with other components of the end node 200 via user input/output interface 240 and bus 206. The user input/output interface 240 and associated devices 242, 244 provide a mechanism by which a user can operate the end node 200 to accomplish various tasks. In particular, the user input device 242 and user output device 244 provide the functionality that allows a user to control the end node 200 and applications, e.g., modules, programs, routines and/or functions, that execute in the memory 210 of the end node 200.
The processor 204 under control of various modules, e.g., routines, included in memory 210 controls operation of the end node 200 to perform various signaling and processing as discussed below. The modules included in memory 210 are executed on startup or as called by other modules. Modules may exchange data, information, and signals when executed. Modules may also share data and information when executed. In the
The signaling/control module 212 controls processing relating to receiving and sending signals, e.g., messages, for management of state information storage, retrieval, and processing. Signaling/control data 214 includes state information, e.g., parameters, status and/or other information relating to operation of the end node. In particular, the signaling/control data 214 may include configuration information 216, e.g., end node identification information, and operational information 218, e.g., information about current processing state, status of pending responses, etc. The module 212 may access and/or modify the data 214, e.g., update the configuration information 216 and/or the operational information 218.
The network/internetwork interface 320 provides a mechanism by which the internal components of the access node 300 can send and receive signals to/from external devices and network nodes. The network/internetwork interface 320 includes, a receiver circuit 322 and a transmitter circuit 324 used for coupling the node 300 to other network nodes, e.g., via copper wires or fiber optic lines. The wireless communication interface 330 also provides a mechanism by which the internal components of the access node 300 can send and receive signals to/from external devices and network nodes, e.g., end nodes. The wireless communication interface 330 includes, e.g., a receiver circuit 332 with a corresponding receiving antenna 336 and a transmitter circuit 334 with a corresponding transmitting antenna 338. The interface 330 is used for coupling the access node 300 to other network nodes, e.g., via wireless communication channels.
The processor 304 under control of various modules, e.g., routines, included in memory 310 controls operation of the access node 300 to perform various signaling and processing. The modules included in memory 310 is executed on startup or as called by other modules that may be present in memory 310. Modules may exchange data, information, and signals when executed. Modules may also share data and information when executed. In the
The State Management Module 312 controls the processing of received signals from end nodes or other network nodes regarding state storage and retrieval, e.g., signals which may be part of a handoff operation and/or the process of supporting normally communications sessions and operating as a network attachment point. The State Management Data 313 includes, e.g., end-node related information such as the state or part of the state, or the location of the current end node state if stored in some other network node. The State Management module 312 may access and/or modify the State Management data 313.
The Signaling/Control module 314 controls the processing of signals to/from end nodes over the wireless communication interface 330, and to/from other network nodes over the network/internetwork interface 320, as necessary for other operations such as basic wireless function, network management, etc. The Signaling/Control data 315 includes, e.g., end-node related data regarding wireless channel assignment for basic operation, and other network-related data such as the address of support/management servers, configuration information for basic network communications. The Signaling/Control module 314 may access and/or modify the Signaling/Control data 315.
End node state information transferred between access nodes via an end node in accordance with the present invention is signed and optionally encrypted prior to transmission to an end node and authenticated and decrypted upon receipt from an end node. The memory 310 includes an authentication and encryption module 391 for performing the signing and encryption function and an authentication and decryption module 393 for performing the authentication and decryption function. In some embodiments authentication is used without encryption while in other embodiments encryption is used without authentication. Accordingly, modules 391, 393 are implemented to perform functions used in a given system and features which are not used or required in a particular embodiment may be omitted from the modules 391, 393. As defined in this invention, the signing function may include an integrity protection function which prevents third parties from modifying any part of a message that has been signed and integrity protected. These modules 391 and 393 may, and sometimes are, implemented as hardware modules as opposed to begin implemented as software modules. To support signing/authentication as well as encryption/decryption functions, the access node includes shared secrets 395 which are available to other access nodes and can be used for signing/authenticating and encrypting/decrypting state information transferred between access nodes. These shared secrets may be supplied by the AAA server 104 or input by a system administrator depending on the particular embodiment. The shared secret 395 provides a security association between access nodes in the system which also have access to the shared secret 395. In most but not necessarily all embodiments, the end nodes are denied access to a shared secret which would allow decryption and/or modification of the state information which is to be transferred. In this way, access nodes can trust state information received from a mobile node since it is signed, integrity protected and optionally encrypted by another trusted node (e.g., an access node).
State information 397 relating to, e.g., used to support, communication with an end node which operates as part of the system and uses the access node 302 as a point of network attachment is stored in memory, one set of state information being stored per end node. In one embodiment of this invention transferred state information will typically include static, long lived and short lived components. However, in other embodiments, the state transferred through the mobile may be a subset of these different types of state. Static components may include parameters that do not change over long periods of time and multiple communication sessions. Examples of static state are end node profile information such as general quality of service parameters (e.g.: peak rates allowed) and generic authorization state (e.g.: type of data calls allowed). Examples of long lived state are parameters that do not change during the duration of a communication session (e.g.: a dynamically assigned Internet address or some long lived security information). Examples of short lived state are parameters that are very dynamic in nature and change multiple times during a communications session (e.g.: dynamic quality of service state, multicast group membership, etc.)
In one embodiment of this invention state information (static, short and long lived) is moved together according to methods described in the present invention through the mobile node involved in a handoff from one access node to another access node, e.g., as a set of state information.
In the
Having made the decision to initiate a handoff, the first end node 144 sends a handoff initiation message 404, which may be in the form of a state transfer request message, to the first access node 140 which is serving as the end nodes current network attachment point. The first access node responds to the handoff initiation message by signing and optionally encrypting the current state available in the first access node 140 corresponding to the first end node 144 and transmitting the state information to the end node 144. Signal 406 represents the transmission of the state information to the first end node 144. In an alternative embodiment of this invention the signal 406 is sent to end node 144 independently from signal 404. In this embodiment of the invention the state held by access node 140 is updated as communications between end node 144 and nodes, e.g., end node 407 progress and change the parameters held by access node 140 to support said communications. The state is then sent to end 144 in message 406 as it gets updated so it is available to the end node 144 at the time it is needed. In the embodiment of this invention where the handoff is network controlled, signal 406, apart from the signal, it also includes an identifier identifying the access node, the end node 144 needs to handoff to (e.g., access node 140′ or 140″). The signing and optional encryption performed by the first access node 140 is done using security information, e.g., a shared secret, which is available to other access nodes due to a security association between access nodes. The shared secret may be programmed into the access nodes, e.g., by a system administrator, or supplied by a security server in the network depending on the particular embodiment.
Normally, the end node 144 does not have access to the shared secret needed to decrypt and re-sign the state information so that the first end node 144 serves as a conduit of the encrypted state information but will, in most embodiments, not alter the encrypted information. The mobile node may send additional information to a target base station along with the state information as part of a handoff but normally does not alter the state information. However, in other embodiments, the mobile node is allowed to modify the state information with the information prior to transmission to the target base station.
In the
After selection of the first target access node 140′, the end node sends a handoff request signal 410 to the first target access node 140′ indicating that the first end node 144 is seeking to complete a handoff to the access node 140′. The first target access node 140′ response with a signal 412 indicating that it will either accept the first end node 144 into the cell or declines the handoff.
If the response signal 412 indicates that the first target access node will allow the handoff of the first end node 144 to be completed to the first target access node 140′, the first end node 144 sends, in signal 414, the state information corresponding to the first end node 144 to the first access node 140′. The first target access node 140′ decrypts the state information and uses the information to establish a communication link with the end node 144 thereby making the first access node 140′ the new network attachment point for the end node 144. The first target access node 140′, after successful decryption of the state information transmits a routing update signal 417 to one or more network nodes 120 and, optionally, a signal 417′ to the old network attachment point 140 indicating that packets directed to the first end node 144 should be routed to said first target access node 140′. The signal 417′ operates as a handoff completion message indicating to the old access node that the handoff has been successful. The first access node also sends a signal 416 indicating a successful handoff to the first end node 144.
In an alternative embodiment of this invention the state information sent to access node 140′ is included in the handoff request signal 410. The first target access node 140′ decrypts the state information and uses the information to establish a communication link with the end node 144 thereby making the first access node 140′ the new network attachment point for the end node 144. The first target access node 140′, after successful decryption of the state information transmits a routing update signal 417 to one or more network nodes 120 and, optionally, a signal 417′ to the old network attachment point 140 indicating that packets directed to the first end node 144 should be routed to said first target access node 140′. The signal 417′ operates as a handoff completion message indicating to the old access node that the handoff has been successful. The first access node also sends a signal 416 indicating a successful handoff to the first end node 144. In this embodiment of the invention message 412 and 414 are not required.
Upon receiving packets with an address corresponding to the first end node 144, after the handoff has been completed, the first target access node 140′ will communicate them over the air link to the first end node 144. With the handoff having been completed, the existing communications session between the first and second end nodes 144, 407, identified by the session identifier included in the state information supplied to the first target access node 140′, is permitted to continue with the first and second access nodes 140, 140′ serving to couple the first and second end nodes 144, 407 together. The exchange of signals after the handoff which includes the communication of IP packets including, for example, voice data, relating to communications session is represented in
The above discussion assumed that the first target access node 140′ accepted the handoff of the first end node 144. If the response signal 412 indicated that the first target access node would not allow the handoff of the first end node 144 to be completed to the first target access node 140′, the first end node 144 selects a second target access node 140″ to complete the handoff to. The handoff then proceeds in the same manner as discussed above but with the second target access node 140″ rather than the first access node 140′. Such a case is shown by exemplary signals 450, 452, 454, 456, 458.
In the embodiment of the invention where the messages 412 and 414 are not required and the state in included in message 410, access node 140′ basis its decision whether to access end node 144 or not on multiple parameters included but not limited to the loading on access node 140′ and the credentials of end node 144 that are included in the state included in message 410. If the response signal 416 indicated that the first target access node would not allow the handoff of the first end node 144 to be completed to the first target access node 140′, the first end node 144 selects a second target access node 140″ to complete the handoff to. The handoff then proceeds in the same manner as discussed above but with the second target access node 140″ rather than the first access node 140′. Such a case is shown by exemplary signals 450, 452, 454, 456, 458.
After selection of the second target access node 140″, the end node 144 sends a handoff request signal 450 to the second target access node 140″ indicating that the first end node 144 is seeking to complete a handoff to the access node 140″. The second target access node 140″ responds with a signal 452 indicating that it will either accept the first end node 144 into the cell or declines the handoff.
If the response signal 452 indicates that the second target access node 140″ will allow the handoff of the first end node 144 to be completed to the second target access node 140″, the first end node 144 sends, in signal 454, the state information corresponding to the first end node 144 to the second target access node 140″. In an alternative embodiment of this invention the state information is included in handoff request signal 450. The second target access node 140″ decrypts the state information and uses the information to establish a communication link with the end node 144 thereby making the second access node 140″ the new network attachment point for the end node 144. The second target access node 140″, after successful decryption of the state information transmits a routing update signal 457 to one or more network nodes 120 and, optionally, another signal (not shown) to the old network attachment point 140 indicating that packets directed to the first end node 144 should be routed to said second target access node 140″. The signal to the first access node 140 operates as a handoff completion message indicating to the old access node that the handoff has been successful. The second access node also sends a signal 456 indicating a successful handoff to the first end node 144.
Upon receiving packets with an address corresponding to the first end node 144, after the handoff has been completed, the second target access node 140′ will communicate them over the air link to the first end node 144. With the handoff having been completed, the existing communications session between the first and second end nodes 144, 407, identified by the session identifier included in the state information supplied to the second target access node 140′, is permitted to continue with the first and third access nodes 140, 140″ serving to couple the first and second end nodes 144, 407 together. The exchange of signals after the handoff which includes the communication of IP packets including, for example, voice data, relating to communications session is represented in
In another embodiment of the invention the signaling illustrated in
In the
In
In one embodiment of this invention, the state included in message 512 of
In the
An exemplary embodiment of the invention, where the end node initiates handoff, will now be discussed further with respect to
End node 144 sends handoff request message 520 to the target access node 140′. Message 520 includes the latest version of the state received from access node 140 in message 512. In an alternative embodiment of this invention message 520 is sent as message 520′ via access node 140 which just replays the message 520″ to the target access node 140′. Access node 140′ uses, in the exemplary embodiment, at least part of the state include in message 520/520″ to establish a communication path between itself and end node 144 that can support at least some of end node's 144 communications via access node 140 (e.g., a voice call between end node 144 and node 106). Optionally, communications represented by double arrow 522 are performed between end node 144 and access node 140′. Such communication 522 may include, e.g., communication to implement mutual authentication procedures. Access node 140′ replies to the end node 144 by transmitting message 525 to end node 144 indicating the outcome of the handoff process. Message may indicate success and/or failure of the attempted handoff. In another embodiment of the invention, the reply message 525 is sent via access node 140 in the form of message 525′, which is relayed by access node 140 to end node 144 as message 525″.
Assuming that the handoff to the access node 140′ is successful, seems likely to be successful, or communication with access node 140 is not likely to remain possible, end node 144 sends message 530 requesting a routing change so that all of its communications currently flowing via access node 140 are now flowing via access node 140′. Access node sends routing change message 540 to point routing of end node 144 communications to it. In one embodiment of the invention routing change message 530 is sent immediately after handoff reply message 525 is received by end node 144. In another embodiment of the invention the process causing message 530 to be sent is independent of message 525 e.g., it is driven by downlink air interface quality measurements.
In various embodiments nodes described herein are implemented using one or more modules to perform the steps corresponding to one or more methods of the present invention, for example, signal processing, message generation and/or transmission steps. Thus, in some embodiments various features of the present invention are implemented using modules. Such modules may be implemented using software, hardware or a combination of software and hardware. Many of the above described methods or method steps can be implemented using machine executable instructions, such as software, included in a machine readable medium such as a memory device, e.g., RAM, floppy disk, etc. to control a machine, e.g., general purpose computer with or without additional hardware, to implement all or portions of the above described methods, e.g., in one or more nodes. Accordingly, among other things, the present invention is directed to a machine-readable medium including machine executable instructions for causing a machine, e.g., processor and associated hardware, to perform one or more of the steps of the above-described method(s).
Numerous additional variations on the methods and apparatus of the present invention described above will be apparent to those skilled in the art in view of the above description of the invention. Such variations are to be considered within the scope of the invention. The methods and apparatus of the present invention may be, and in various embodiments are, used with CDMA, orthogonal frequency division multiplexing (OFDM), or various other types of communications techniques which may be used to provide wireless communications links between access nodes and mobile nodes. In some embodiments the access nodes are implemented as base stations which establish communications links with mobile nodes using OFDM and/or CDMA. In various embodiments the mobile nodes are implemented as notebook computers, personal data assistants (PDAs), or other portable devices including receiver/transmitter circuits and logic and/or routines, for implementing the methods of the present invention.
The present invention claims the benefit of U.S. Provisional Patent Application Ser. No. 60/718,363, filed Sep. 19, 2005 which is hereby expressly incorporated by reference.
Number | Date | Country | |
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60718363 | Sep 2005 | US |