(12)
`
`United States Patent
`Roberts et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7,072,323 B2
`Jul. 4, 2006
`
`US007072323B2
`
`(54) SYSTEM AND METHOD FOR PERFORMING
`SOFT HANDOFF IN A WIRELESS DATA
`NETWORK
`
`9
`
`es
`
`s
`
`75
`(75) Inventors: R.E. "S.R., ().
`(US)
`(73) Assignee: MeshNetworks, Inc., Maitlands, FL
`(US)
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 1019 days.
`
`(*) Notice:
`
`(21) Appl. No.: 09/929,031
`(22) Filed:
`Aug. 15, 2001
`(65)
`Prior Publication Data
`US 2003/009 1011 A1
`May 15, 2003
`s
`
`(51) Int. Cl.
`(2006.01)
`H04Q 7/24
`(52) U.S. Cl. ....................................... 370/338; 370/331
`(58) Field of Classification Search ................ 370/310,
`370/3.10.2, 328,338,349,331; 455/436,
`455/432.1, 435.1
`See application file for complete search history.
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
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`(Continued)
`FOREIGN PATENT DOCUMENTS
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`(Continued)
`OTHER PUBLICATIONS
`Wong et al., “Soft Handoffs in CDMA Mobile Systems”,
`Dec. 1997, IEEE Personal Communications.
`(Continued)
`Primary Examiner Wellington Chin
`Assistant Examiner Brenda Pham
`(74) Attorney, Agent, or Firm—Randi L. Karpinia; Joseph J.
`Euczynski
`(57)
`
`ABSTRACT
`
`A communications network which is capable of effectively
`and efficiently handling mobility of wireless user terminals
`between access point nodes of a packet-switched network
`with minimal overhead and packet loss, and a method for
`using the same. The communications network employs a
`packet-switched core network and a plurality of access
`points coupled to the core network. Each access point is
`adapted to provide any user terminal with wireless commu
`nications access to the core network when that user terminal
`becomes affiliated with that access point. The system and
`method further employ ad-hoc routing techniques during
`handoff of a wireless user terminal between access point
`nodes of the core network to enable the network to maintain
`multiple paths via which data packets are provided to the
`user terminal during handoff to Substantially eliminate
`packet loss during handoff.
`
`33 Claims, 9 Drawing Sheets
`
`
`
`NTALAFFIATION OF
`MOBILENOd to Ap
`
`000
`
`APADDSNODE IF ADSs
`to its routine TABLE
`
`APISSUES (ATUCJSARP
`AND OFERATES ASOS Roxy
`
`0.
`
`1020
`
`
`
`IAPS AND CHER cotWORK
`DEWICESUPDATE THEIRARP CACHES
`
`1030
`
`APRECEWESPACKETAN
`COMSTSRTING ABL
`
`APDELWERS PACKT TO
`AFFLIATED MOBILE NX
`
`1040
`
`1050
`
`Cloudflare - Exhibit 1080, page 1
`
`

`

`US 7,072,323 B2
`Page 2
`
`U.S. PATENT DOCUMENTS
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`6,132,306 A 10/2000 Trompower .......
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`6,163,699 A 12/2000 Naor et al. ................. 455,453
`sion-Efficient Routing in Wireless Networks. Using Link
`6,178,337 B1
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`... 455,561
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`“Th
`L. Mad
`d Ewert
`6, 192,053 B1
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`6, 192.230 B1
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`
`EP
`EP
`EP
`EP
`FR
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`
`
`
`Cloudflare - Exhibit 1080, page 2
`
`

`

`US 7,072,323 B2
`Page 3
`
`J.R. McChesney and R.J. Saulitis, “Optimization of an
`Adaptive Link Control Protocol for Multimedia Packet
`Radio Networks’’.
`Ram Ramanathan and Regina Rosales-Hain, “Topology
`Control of Multihop Wireless Networks using Transmit
`Power Adjustment'.
`Ram Ramanathan and Martha E. Steenstrup, “Hierarchi
`cally-Organized, Multihop Mobile Wireless Networks for
`Quality-of-Service Support'.
`
`Martha E. Steenstrup, "Dynamic Multipoint Virtual Circuits
`for Multimedia Traffic in Multihop Mobile Wireless Net
`works'.
`Zhenyu Tang and J.J. Garcia-Luna-Aceves, "Collision
`Avoidance Transmission Scheduling for Ad-Hoc Networks'.
`George Vardakas and Wendell Kishaba, “QoS Networking
`With Adaptive Link Control and Tactical Multi-Channel
`Software Radios.
`* cited by examiner
`
`Cloudflare - Exhibit 1080, page 3
`
`

`

`U.S. Patent
`
`Jul. 4, 2006
`
`Sheet 1 of 9
`
`US 7,072,323 B2
`
`Octcol
`vel8c}
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`Cloudflare - Exhibit 1080, page 4
`
`Cloudflare - Exhibit 1080, page 4
`
`
`
`
`

`

`U.S. Patent
`
`Jul. 4, 2006
`
`Sheet 2 of 9
`
`US 7,072,323 B2
`
`120
`
`PACKETS
`102
`
`PACKETS
`104
`
`122
`
`
`
`
`
`FIG. 2
`
`Cloudflare - Exhibit 1080, page 5
`
`

`

`U.S. Patent
`
`Jul. 4, 2006
`
`Sheet 3 of 9
`
`US 7,072,323 B2
`
`START
`
`
`
`NITIALAFFLIATION OF
`MOBILE NODE TO AP
`
`1000
`
`IAP ADDS NODE PADDRESS
`TO TS ROUTING TABLE
`
`IAP ISSUES GRATUTOUSARP
`AND OPERATES AS NODES PROXY
`
`1010
`
`1020
`
`APS AND OTHER CORE NETWORK
`DEVICES UPDATE THER ARP CACHES
`
`1030
`
`AP RECEIVES PACKET AND
`CONSULTS ROUTING TABLE
`
`1040
`
`AP DELIVERS PACKET TO
`AFFILATED MOBILE NODE
`
`1050
`
`END
`
`FIG. 3
`
`Cloudflare - Exhibit 1080, page 6
`
`

`

`U.S. Patent
`
`Jul. 4, 2006
`
`Sheet 4 of 9
`
`US 7,072,323 B2
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`
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`Cloudflare - Exhibit 1080, page 7
`
`Cloudflare - Exhibit 1080, page 7
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`
`
`

`

`U.S. Patent
`
`Jul. 4, 2006
`
`Sheet 5 of 9
`
`US 7,072,323 B2
`
`
`
`
`
`
`
`
`
`PACKETS
`102
`
`PACKETS
`104
`
`122
`
`PACKETS
`
`FIG. 5
`
`Cloudflare - Exhibit 1080, page 8
`
`

`

`U.S. Patent
`
`Jul. 4, 2006
`
`Sheet 6 of 9
`
`US 7,072,323 B2
`
`START
`
`MOBILE NODE AFFILATESTONEWIAP
`
`OO
`
`1110
`
`NETWORKNODES CONTINUE TO SEND PACKETS TO OLDAP OF MOBILE NODE
`
`NEW AP SSUES GRATUTOUSARP
`
`1120
`
`APS AND OTHER CORE NETWORK DEVICES UPDATE
`ARP CACHES BASED ON GRATUTOUSARP
`
`NEW AP NEGOTATES WITH OLD AP
`
`1130
`
`140
`1150
`
`APS AND OTHER CORE NETWORK DEVICES CONTINUE TO SEND
`PACKETS TO OLD AP UNTILTHEY PROCESS GRATUTOUSARP
`
`
`
`
`
`
`
`
`
`CONFIGURABLE
`PERIOD WITH NO
`MISROUTED PACKETS
`RECEIVED
`
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`
`
`
`
`OLD AP ISSUES
`ADDRESS RESOLUTION
`TO APS AND/OR CORE
`NETWORK DEVICES IN
`OUESTION
`
`1180
`
`PACKETS SENT TO NEW AP FROMALL OTHER
`IAPS AND CORE NETWORK DEVICES
`
`-
`
`END
`
`FIG. 6
`
`Cloudflare - Exhibit 1080, page 9
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`

`

`U.S. Patent
`
`Jul. 4, 2006
`
`Sheet 7 Of 9
`
`US 7,072,323 B2
`
`120
`
`ADDRESS
`RESOLUTION
`REQUEST
`
`22
`
`22
`
`
`
`FIG. 8
`
`Cloudflare - Exhibit 1080, page 10
`
`

`

`U.S. Patent
`
`Jul. 4, 2006
`
`Sheet 8 of 9
`
`US 7,072,323 B2
`
`120
`
`122
`
`122
`
`PACKETS
`FROM R1
`
`18
`
`
`
`PACKETS
`FROMR1
`
`118
`
`
`
`PACKETS
`FROMR2
`
`FIG. 9
`
`120
`
`PACKETS
`FROM R2
`
`FIG. O
`
`Cloudflare - Exhibit 1080, page 11
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`

`

`U.S. Patent
`
`Jul. 4, 2006
`
`Sheet 9 of 9
`
`US 7,072,323 B2
`
`
`
`PACKETS
`FROMR1 ANDR2
`
`
`
`18
`
`122
`
`PACKETS
`
`104
`
`FIG 11
`
`Cloudflare - Exhibit 1080, page 12
`
`

`

`US 7,072,323 B2
`
`1.
`SYSTEMAND METHOD FOR PERFORMING
`SOFT HANDOFF IN A WIRELESS DATA
`NETWORK
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`Related subject matter is disclosed in a U.S. patent
`application of Charles R. Barker, Jr. and Robin U. Roberts
`entitled “A System and Method for Providing an Addressing
`and Proxy Scheme for Facilitating Mobility of Wireless
`Nodes Between Wired Access Points on a Core Network of
`a Communications Network”, application Ser. No. 09/929,
`032 filed on even date herewith, the entire contents of which
`is incorporated herein by reference.
`
`10
`
`15
`
`BACKGROUND OF THE INVENTION
`
`2
`Each base station is also connected to one or more
`gateways that enable communication between the base sta
`tion and other networks, such as the Internet and the public
`switched telephone network (PSTN). Accordingly, the base
`stations in the network enable the user terminals to com
`municate with each other, as well as with other destinations,
`such as telephony devices, in the PSTN.
`Since wireless user terminals are typically mobile, it is
`common for a user terminal to travel between different base
`station coverage areas during use. When this occurs, the base
`station whose coverage area the user terminal is leaving
`must transfer or “handoff the user terminal to the base
`station whose coverage area the user terminal is entering, so
`that the latter base station can become the base station via
`which the user terminal and network continue to commu
`nicate. In densely populated areas having many base stations
`with Small coverage areas, this handoff process may need to
`occur several times during a short period of time as the user
`terminal travels between the different coverage areas.
`Many techniques have been developed using the circuit
`Switched cellular infrastructure to minimize data packet loss
`during handoff while also minimizing overhead necessary to
`Successfully perform the handoff. For example, a technique
`known as "hard handoff refers to a break-before-make
`technique where the original connection is dropped before
`the new connection is established. On the other hand, “soft
`handoff is a make-before-break technique that maintains
`multiple simultaneous connections to the user terminal dur
`ing handoff, and only drops the original connection after the
`new connection is established. Examples of soft handoff
`techniques are described in a publication by Wong et al.
`entitled “Soft Handoffs in CDMA Mobile Systems”, IEEE
`Personal Communications, December 1997, pp. 6–17, in a
`publication by Wong et al. entitled “A Pattern Recognition
`System for Handoff Algorithms, IEEE Journal on Selected
`Areas in Communications, Vol. 18, No. 7, July 2000, pp.
`1301-1312, and in TIA document TIA/EIA-95-B entitled
`“Mobile Station-Base Station Compatibility Standard for
`Wideband Spread Spectrum Cellular Systems”. Feb. 1,
`1999, the entire contents of each of these documents being
`incorporated herein by reference.
`With the arrival of the Internet in recent years, some
`wireless communications networks have moved away from
`the use of conventional cellular networks and their associ
`ated circuit Switched routing techniques to improve voice
`communications services. Each mobile user terminal, tele
`phony device, and any other device capable of communi
`cating with the communications network, has a unique
`Internet Protocol (IP) address that uniquely identifies it from
`all other devices. A communications network employing IP
`sends data between destination points in digital form in
`discrete packets, rather than in the traditional circuit-com
`mitted protocols of the PSTN. Each of the data packets
`includes the sender's IP address as well as the intended
`receiver's IP address.
`When a wireless user terminal, for example, transmits
`Voice data to a base station of the communications network
`acting as the access point for the user terminal, a router
`associated with the base station reads the receiver IP address
`in the data packet. Each router includes a table of routing
`information, such as IP addresses of the devices local to the
`router, available routes, and so on. If the router recognizes
`from the receiver IP address that the data packet is intended
`for a telephony device in its immediate neighborhood or
`domain, the router forwards the data packet to that telephony
`device. However, if the router does not recognize the IP
`address as belonging to Such a telephony device, the router
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`1. Field of the Invention
`The present invention relates to an improved system and
`method for performing soft handoff between access points of
`a wireless communications network. More particularly, the
`present invention relates to a system and method for per
`forming soft handoff using ad-hoc routing and multiple
`access points of a packet-switched communications net
`work.
`2. Description of the Related Art:
`Wireless communications networks, such as mobile wire
`less telephone networks, have become increasingly preva
`lent over the past decade. These wireless communications
`networks are commonly referred to as “cellular networks,
`because the network infrastructure is arranged to divide the
`service area into a plurality of regions called “cells'.
`Specifically, a terrestrial cellular network includes a plu
`rality of interconnected base stations that are distributed
`geographically at designated locations throughout the Ser
`Vice area. Each base station includes one or more transceiv
`ers that are capable of transmitting and receiving electro
`magnetic signals, such as radio frequency (RF)
`communications signals, to and from user terminals, such as
`wireless telephones, located in its coverage area. The com
`munications signals include, for example, voice data that has
`been modulated according to a desired modulation technique
`and transmitted as data packets. As can be appreciated by
`one skilled in the art, the transceiver and user terminals
`transmit and receive the data packets in multiplexed format,
`such as time-division multiple access (TDMA) format,
`code-division multiple access (CDMA) format, or fre
`quency-division multiple access (FDMA) format, which
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`enables a single transceiver at the base station to commu
`nicate simultaneously with several user terminals in its
`coverage area.
`Because each base station can only handle a limited
`amount of communications signal traffic from the user
`terminals at any given time, the coverage area of a base
`station can vary depending on the amount of traffic that the
`base station is expected to experience. For example, the
`coverage area of a base station can be set to several miles in
`diameter in sparsely populated regions, such as rural regions
`having light wireless traffic, and can be set to less than a mile
`in diameter in densely populated regions, such as major
`metropolitan areas having heavy wireless traffic. The wire
`less communications network therefore must employ many
`base stations in heavily populated metropolitan areas in
`order for the network to adequately service the user termi
`nals in those regions.
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`forwards the data packet to an appropriate adjacent gateway
`in, for example, the Internet. The router of that gateway then
`reads the receiver IP address in the data packet, and either
`delivers the data packet to the appropriate telephony device
`in its domain, or forwards the data packet to another
`gateway. Once a router in a gateway recognizes the receiver
`IP address as belonging to a telephony device in its domain,
`the router in that gateway delivers the data packet to that
`telephony device.
`It can be also noted that the use of IP to route data packets
`in a communications network enables the network to handle
`data other than Voice data. For example, such IP techniques
`can be used to expand the versatility of the network to
`communicate audio, video or multimedia data between user
`terminals.
`As in traditional cellular communications networks, wire
`less user terminals in a wireless communications network
`employing IP can be mobile, and can thus periodically
`change their access point to the network. Also, wireless user
`terminals can move outside their “home' network and
`become temporarily affiliated with a foreign network, and
`thus communicate via an access point on that foreign
`network.
`Existing mobile data communications networks using IP
`techniques are based around conventional circuit-switched
`cellular infrastructures as discussed above, and therefore
`mask packet routing issues internal to their own networks.
`That is, when a user terminal moves its affiliation from one
`access point or base station to another within the network,
`the network can perform handoff techniques similar to those
`performed by a conventional wireless cellular network.
`However, when a user terminal moves away from its
`home network and becomes affiliated with an access point
`on a foreign network, Such topology changes must be
`communicated between routers in the home and foreign
`networks, so that the routers can update their respective
`routing tables as necessary, which results in Substantial
`bandwidth-consuming overhead. Accordingly, it is generally
`agreed that this solution is too slow to handle user terminals
`that may be constantly mobile between networks, because
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`routing changes must be propagated across the entirety of
`the connected network.
`Another technique to handle the mobility of user termi
`nals between networks without performing router updates is
`referred to as Mobile IP. A detailed description of Mobile IP
`is set forth in IETF document RFC 2002 entitled “IP
`Mobility Support”, October 1996, the entire content of
`which is incorporated herein by reference. In accordance
`with the Mobile IP technique, a fixed access point on the
`mobile user terminals home network, which can be referred
`to as a fixed network node, functions as a proxy agent (MIP
`home agent) for the mobile user terminal (mobile node)
`when the mobile node moves out of the home network and
`becomes affiliated with an access point (foreign node) on a
`foreign network. As understood in the Mobile IP art, the
`home network is the network at which the mobile node
`seems reachable to the rest of the Internet or to other
`networks by virtue of the mobile nodes assigned IP address
`(home address), and a foreign network is the network to
`which the mobile node is attached when it is not attached to
`its home network.
`Accordingly, when data packets are transmitted from
`another device to the mobile node, the Mobile IP home agent
`receives those data packets on the core home network behalf
`of the mobile node, and encapsulates those data packets.
`That is, the Mobile IP home agent incorporates each
`received IP data packet, less any preceding fields Such as a
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`media access control (MAC) header, inside another IP data
`packet, thereby making the fields within the original IP
`header of the IP data packet temporarily lose their effect. The
`Mobile IP home agent then tunnels those encapsulated data
`packet to an agent (Mobile IP foreign agent) on the foreign
`network to which the mobile node is currently attached. The
`Mobile IP foreign agent decomposes the capsule and sends
`the packet to the mobile node, which is currently local to the
`foreign agent.
`Although the Mobile IP technique is reasonably capable
`of handling the mobility of user terminals between net
`works, the Mobile IP technique does increase overhead in
`the networks, since each data packet must be routed to the
`home network, encapsulated, and then rerouted to the for
`eign network. Also, the problems solved by Mobile IP can
`be viewed as those associated with a macro case of mobility
`in which nodes (user terminals) are mobile between core
`networks. Mobile IP is unsuitable for handling a micro case
`of mobility in which user terminals are mobile between
`wired access points in a single core network.
`One solution for managing mobility within a circuit
`switched cellular network has been proposed and is referred
`to as Cellular IP. A description of Cellular IP is set forth in
`a publication by Andras G. Valko entitled “Cellular IP: A
`New Approach to Internet Host Mobility”, ACM Computer
`Communication Review, January 1999, the entire content of
`which is incorporated herein by reference. Although this
`solution is somewhat suitable for handling mobility in
`circuit-switched cellular networks, the technique is specific
`to the circuit-switched infrastructure of the network.
`As can further be appreciated by one skilled in the art,
`while Mobile IP is suitable for handling cases of user
`terminal mobility between networks, Mobile IP is deficient
`in handling problems with packet routing that may occur
`within a packet-switched core network when a mobile node
`moves and is handed off from one base station to another. A
`communications network employing a packet-switched core
`network is described, for example, in U.S. patent application
`Ser. No. 09/897,790 entitled “Ad Hoc Peer-to-Peer Mobile
`Radio Access System Interfaced to the PSTN and Cellular
`Networks', filed on Jun. 29, 2001, the entire content of
`which is incorporated herein by reference. An example of a
`wireless local area network (LAN) having mobility is set
`forth in IEEE Standard 802.11, Aug. 20, 1999, the entire
`content of which is incorporated herein by reference. Spe
`cifically, Mobile IP is incapable of effectively operating
`under the additional constraints imposed by a packet
`Switched core network having wired access point nodes that
`are typically connected using bandwidth-constrained leased
`lines and which cannot tolerate the additional overhead of
`twice-routed Mobile IP packets. Furthermore, the low-cost
`access point nodes also typically cannot tolerate the proces
`sor-intensive decomposition of encapsulated packets that is
`performed during Mobile IP.
`In addition to the above deficiencies, other problems
`involving the manner in which handoff is performed can
`arise. As explained above, when a user terminal is handed off
`from one access point to another, the wired network must
`dynamically reconfigure itself to route packets through the
`new attachment point. It is often difficult for the wired
`network to reconfigure itself without the loss of packets sent
`to the user terminal, because the wired network reconfigu
`ration is not instantaneous. Accordingly, during the recon
`figuration period, packets can be sent via both the old and
`new attachment points. Hence, in existing wireless data
`networks, one set of these packets will typically be lost.
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`US 7,072,323 B2
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`Furthermore, as the speed of mobility increases, the
`frequency in which handoff occurs also increases. With this
`increase in occurrence of handoff any loss of packets during
`handoff becomes more noticeable to the user because it
`occurs more often. Thus, minimizing packet loss during
`handoff becomes more important as the speed of mobility
`increases.
`Accordingly, a need exists for a system and method
`capable of effectively and efficiently handling mobility of
`wireless user terminals between access point nodes of a
`packet-switched network with minimal overhead and packet
`loss.
`
`SUMMARY OF THE INVENTION
`
`6
`resolution protocol (ARP) request, for an address, Such as an
`IP protocol address, of the user terminal which has changed
`its affiliation thereto.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`These and other objects, advantages and novel features of
`the invention will be more readily appreciated from the
`following detailed description when read in conjunction
`with the accompanying drawings, in which:
`FIG. 1 is a block diagram of an example of a wireless
`communications network employing a system and method
`for handling user terminal mobility within the network
`according to an embodiment of the present invention;
`FIG. 2 is a conceptual block diagram illustrating affilia
`tion of a mobile user terminal with an access point of the
`network shown in FIG. 1;
`FIG. 3 is a flowchart illustrating an example of operations
`performed by the network shown in FIG. 1 when a mobile
`user terminal affiliates with an access point as shown in
`FIGS. 1 and 2:
`FIG. 4 is a block diagram of the network shown in FIG.
`1 in which a mobile user terminal changes its affiliation from
`one access point to another;
`FIG. 5 is a conceptual block diagram illustrating the
`manner in which a user terminal changes its affiliation with
`an access point of the network as shown in FIG. 4;
`FIG. 6 is a flowchart illustrating an example of operations
`performed by the network as shown in FIGS. 1 and 4 when
`the mobile user terminal changes its access point affiliation
`as shown in FIGS. 4 and 5:
`FIG. 7 is a conceptual block diagram illustrating an
`example of the manner in which the access point to which
`the user terminal is affiliating communicates this affiliation
`to the network;
`FIG. 8 is a conceptual block diagram illustrating an
`example of the manner in which packets are routed during
`handoff and an exemplary manner in which the access points
`involved in the handoff negotiate with each other;
`FIG. 9 is a conceptual block diagram illustrating an
`example of the manner in which routers in the network
`operate to forward packets to the reaffiliated user while they
`are processing the reaffiliation communication from the
`access point with which the user terminal has become
`affiliated;
`FIG. 10 is a conceptual block diagram illustrating the
`manner in which the access point from which the user
`terminal is changing its affiliation communicates this change
`to the network; and
`FIG. 11 is a conceptual block diagram illustrating an
`example of the manner in which routers forward packets to
`the access point with which the user terminal has become
`affiliated after they have processed the reaffiliation commu
`nication.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`FIG. 1 is a block diagram illustrating an example of a
`wireless communications network 100 employing a system
`and method for handling user terminal mobility within the
`network according to an embodiment of the present inven
`tion. As shown, network 100, which can be referred to as a
`“core network', includes a core local access network (LAN)
`102 which provides the wired infrastructure for the network
`100. A plurality of intelligent access points (IAP) 104, 106
`and 108 are coupled to and communicate with the core LAN
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`An object of the present invention is to provide a system
`and method capable of effectively and efficiently handling
`mobi