Patent Application
20070115885
When an electronic device such as a mobile node (MN) using packet data connection moves from a first wireless network to a second wireless network, it may be handed over from the first wireless network to the second wireless network. This is known as IP handoff or Mobile/IP handoff. When IP handoff is performed in such a way that the end user does not notice the impact on quality of real time traffic during the critical path of handoff, the handoff is referred to as fast handoff of the MN. To support this handoff, each wireless network has an access router (AR) associated with it. For example, the first wireless network is associated with a first access router, and the second wireless network is associated with a second access router. The access router performs the function of a mobility agent, to support the mobility of the MN from the first wireless network to the second wireless network, which is known as network layer mobility. In the case of a fast IP handoff between the ARs, also called an inter-AR handoff, the mobility agent for the MN changes from a first AR to a second AR.
The inter-AR handoff of an MN requires the establishment of a wireless link layer connection between an MN and the second access router and the subsequent establishment of a bi directional edge tunnel between the second access router and the first access router over an existing wired link. The tunnel is established to avoid performing Mobile/IP registration during the critical path of handoff. The tunnel enables the transfer of data packets between the first wireless network and second wireless network. The first network receives data packets from the CN and forwards the packets to the second wireless access router that in turn are delivered to the MN over the newly established link layer connection of the second network, and vice versa.
The establishment of the bidirectional tunnel between access routers reduces packet loss as well as packet delay during IP layer handoff. However, the establishment of the tunnel also results in a non-optimal routing and poor utilization of the resources of the access router. The problem of non-optimal routing is introduced due to the addition of the routing segment between the first AR and the second AR. This requires the first AR and the second AR to process data packets originating at the MN and the CN.
Known methods for solving these problems are mentioned in a standard published by the 3rd Generation Partnership Project 2 entitled “CDMA2000 Wireless IP Network Standard: Simple IP and Mobile IP Services”, and in a memo published by the Network Working Group entitled “Low Latency Handoffs in Mobile IPv4”. These methods state ways of tearing down a tunnel after a period and renewing the tunnel prior to that period. However these methods do not specify any criteria for fast handoff tunnel teardown.
Various embodiments of the invention will hereinafter be described in conjunction with the appended drawings, provided to illustrate and not to limit the invention, wherein like designations denote like elements, and in which:
Before describing in detail the particular fast mobile IP handoff method and system in accordance with the present invention, it should be observed that the present invention resides primarily in combinations of method steps and system components related to fast mobile IP handoff technique. Accordingly, the system components and method steps have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.
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However, if the first AR 204 is reachable from the second AR 206, the second AR 206 establishes a tunnel with the first AR 204, at step 512. The tunnel allows the transfer of data traffic between the first AR 204 and the second AR 206. At step 514, the tunnel between the first AR 204 and the second AR 206 is released based on predefined criteria. Thereafter, the first AR 204 signals the second AR 206 to initiate the setting up of a mobile IP session with the MN 102, at step 416. At step 418, the second AR 206 initiates a mobile IP session with the MN 102. At step 520, the second AR 206 signals the first AR 204 to release the tunnel between the first AR 204 to the second AR 206.
In some embodiments of the present invention, the predefined criterion is based on the traffic profile of data traffic exchanged between the first AR 204 and the second AR 206. The first AR 204 and the second AR 206 are configured in these embodiments to identify real-time data traffic, based on the traffic profile. The pattern of the traffic is compared with the traffic profile of the real-time data traffic. If the pattern of the traffic does not match the traffic profile of the real-time data traffic, the tunnel between the first AR 204 and the second AR 206 is released.
In yet another embodiment of the present invention, the predefined criterion is based on CPU utilization at the first AR 204. The CPU utilization at the first AR 204 is determined. If CPU utilization exceeds a configurable CPU utilization threshold value, the tunnel between the first AR 204 and the second AR 206 is released. In an embodiment of the present invention, the tunnel release is associated with lower-priority users.
In yet another embodiment of the present invention, the tunnel between the first AR 204 and the second AR 206 is released if the time for which the MN 102 has been registered with one of the first AR 204 and the second AR 206 exceeds a tunnel lifetime of the MN 102. In an embodiment of the present invention, the tunnel lifetime is referred to as a visitor list lifetime. In another embodiment of the present invention, the tunnel lifetime is referred to as a binding cache lifetime.
In a case in which multiple IP sessions or flows associated with a mobile node MN 102 are anchored at the first AR 204, an IP flow/session associated with non-real time traffic can also be selectively transferred from AR 204 to AR 206 without impacting remaining flows associated with the same mobile, in accordance with yet another embodiment of the present invention. The selective transfer of an IP flow associated with MN 102 from first AR 204 to second AR 206 requires support of flow based mobility management by the underlying mobility protocol.
In still another embodiment of the present invention, a tunnel associated with a lower-priority user is released, when buffer utilization at the first AR 204 exceeds a buffer utilization threshold value. The buffering delay is compared to a preconfigured time. Tunnel teardown may be initiated when the data packets are buffered beyond the preconfigured time.
When the tunnel between the first AR 204 and the second AR 206 is released, based on at least one of the predefined criteria discussed above, a mobile IP registration procedure is initialized with the second AR 206, at step 404. In an embodiment of the present invention, the initialization module 306 initializes the mobile IP registration procedure with the second AR 206.
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It will be appreciated that the fast IP handoff described herein may be comprised of one or more conventional processors and unique stored program instructions that control the one or more processors to implement some, most, or all of the functions described herein; such as, releasing the tunnel between the first access router and the second access router. Alternatively, the same functions could be implemented by a state machine that has no stored program instructions, in which each function or some combinations of certain portions of the functions are implemented as custom logic. A combination of the two approaches could be used. Thus, methods and means for performing these functions have been described herein.
The method for fast IP handoff of a MN, described herein, can be applied to IEEE 802.16, IEEE 802.20, CDMA, HSDPA and other technologies using Mobile/IP Fast Handoff protocol.
In the foregoing specification, the present invention and its benefits and advantages have been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present invention. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims.
As used herein, the terms “comprises”, “comprising”, “includes”, “including” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
The term “another”, as used herein, is defined as at least a second or more. The term “having”, as used herein, is defined as comprising. The term “coupled”, as used herein with reference to electro-optical technology, is defined as connected, although not necessarily directly, and not necessarily mechanically. The term “program”, as used herein, is defined as a sequence of instructions designed for execution on a computer system. A “program”, or “computer program”, may include a subroutine, a function, a procedure, an object method, an object implementation, an executable application, an applet, a servlet, a source code, an object code, a shared library/dynamic load library and/or other sequence of instructions designed for execution on a computer system. It is further understood that the use of relational terms, if any, such as first and second, top and bottom, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions.
