6,137,802
`[11] Patent Number:
`[19]
`United States Patent
`
`Jones et al.
`[45] Date of Patent:
`*Oct. 24, 2000
`
`U5006137802A
`
`[54] AUTOMATIC MEDIA SWITCHING
`APPARATUS AND METHOD
`
`[75]
`
`Inventors: Wesley Stuart Jones, Schaumburg;
`Louis P. Dellaverson, Barrington, both
`of 111.
`
`[73] Assignee: Motorola, Inc., Schaumburg, Ill.
`
`[*] Notice:
`
`This patent issued on a continued pros-
`ecution application filed under 37 CFR
`1.53(d), and is subject to the twenty year
`patent
`term provisions of 35 U.S.C.
`154(a)(2).
`
`[21] Appl. No.: 08/827,014
`.
`Filed:
`
`Mar. 25, 1997
`
`[22]
`
`[51]
`Int. Cl.7 .................................................... H04M 11/00
`
`[52]
`370/401; 370/445; 370/463
`[58] Field Of Search ..................................... 370/401, 402,
`370/522> 463> 445> 338; 455/556> 557
`References Cited
`U.S. PATENT DOCUMENTS
`
`[56]
`
`5,748,619
`5,790,536
`5,844,893
`5,915,002
`
`5/1998 Meier ...................................... 370/466
`......................... 370/338
`8/1998 Mahany et al.
`
`12/1998 Gollnick et al.
`.
`370/338
`6/1999 Shimosako ........................... 379/93.07
`
`Primary Examiner—Chi H. Pham
`ASSiSlam Examiner—Frank Duong
`Attorney, Agent, or Firm—Charles W. Bethards
`
`ABSTRACT
`[57]
`A media switching apparatus automatically switches a user
`.
`.
`.
`.
`.
`deVice between Wired and Wireless serVice mediums of
`communications networks. The switching apparatus
`
`includes a protocol stack having a network layer, a logical
`link control, a first set of lower layers specific to a wired
`.
`.
`.
`serVice medium and a second set of lower layers spec1fic to
`a wireless service medium. A selector is responsive to the
`availability of a wired service medium for selecting the first
`set of lower layers and is further responsive to the non—
`availability of a wired service medium and the availability of
`a wireless service medium for selecting the second set of
`lower layers.
`
`5,726,984
`
`3/1998 Kubler et al.
`
`........................... 370/338
`
`24 Claims, 6 Drawing Sheets
`
`82
`
`76
`
` RADIO SPECIFIC
`
`HARDWARE
`
`Roku EX1031
`
`US. Patent No. 9,911,325
`
`Roku EX1031
`U.S. Patent No. 9,911,325
`
`

`

`US. Patent
`
`Oct. 24,2000
`
`Sheet 1 0f6
`
`6,137,802
`
`TO ATM SWITCH
` SQ
`
`WIRED MAC WIRELESS
`LAYER
`MESH LAYER
`
`WIRELESS
`WIRED
`PHYSICAL MAC LAYER
`LAYER
`
`
`
`
`
`APPLICATION
`I
`
`NETWORK LAYER I
`
`
`
`LOGICAL LINK
`CONTROL (802.2)
`
`
`
`WIRELESS
`PHYSICAL
`LAYER
`
`
`
`
`42
`
`
`
`
`
`
`
`5O
`
`52
`
`

`

`US. Patent
`
`Oct. 24, 2000
`
`Sheet 2 0f 6
`
`6,137,802
`
`
`
`600
`
`STATE 0-
`DETERMINE
`SERVICES
`
`
`
`
`
`STATE 3—
`SERVICE
`
`
`
`
`
`
`602
`
`STATE 2-
`WIRELESS
`SERVICES
`UTILIZED
`
`
`
`
`EVALUATION
`
`
`
`601
`
`
`STATE 1—
`WIRED
`
`SERVICES
`UTILIZED
`
`
`
`11
`
`12
`
`
`
`STATE 4—
`TRANSITION
`
`604
`
`

`

`US. Patent
`
`Oct. 24, 2000
`
`Sheet 3 0f 6
`
`6,137,802
`
`600
`
`STATE 0-
`DETERMINE <—
`SERVICES
`
`
`
`
`
`
`
`
`
`
`
`IS
` NO
`
`WIRED NETWORK
`
`AVALIABLE
`
`
`?
`
`
`
`IS
`WIRELESS
`NETWORK AVAILABLE
`?
`
`
`
`NO
`
`YES
`
`YES
`
`IS
`WIRELESS NETWORK
`AVALIABLE
`?
`
`NO
`
`flfl
`
`702
`
`
`
`YES
`704
`/—\
`l' ————————————————— - _ — J- ‘l
`703
`
`
`
`
`
`CONFIGURE WIRED
`NETWORK
`INFORMATION, ag.
`ROUTING & ADDRESS
`
`
`
`CONFIGURE
`WIRELESS NETWORK
`
`
`INFORMATION. e.g.
`ROUTING & ADDRESS
`
`
`
`
`
`HARDWARE
`UTILIZED
`
`ACTIVATE WIRED
`HARDWARE
`
`ACTIVATE WIRELESS
`
`STATE 3—
`EvSAELRuVAITCIEON
`
`
`
`
`STATE 1—
`WIRED
`SERVICES
`
`
`UTILIZED
`
`
`FIG. 7
`
`
`
`
`
`
`STATE 2_
`WIRELESS
`SERVICES
`
`
`
`
`
`
`

`

`US. Patent
`
`()ct.24,2000
`
`Sheet 4 0f 6
`
`6,137,802
`
`
`
`New
`
`INmp<bm
`
`mmmgmxH;
`
`mmoH>mmm
`
`QMNHAHH:
`
`
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`RE
`
`IFmp<pm
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`
`MmoH>mmm
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`omNHAHH:
`
`xmoghmmZHmug;
`
`mm4m<H4<><
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`mmMJmmHSmH
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`mmMJmmHsmH
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`ommH;mH
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`msm
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`moH>mmm
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`
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`
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`
`
`
`

`

`US. Patent
`
`Oct. 24, 2000
`
`Sheet 5 0f 6
`
`6,137,802
`
`603
`
`STATE 3—
`SERVICE
`
`
`EVALUATION
`
`901
`
`YES
`
`
`
`FOR WIRED SERVICES
`MET?
`
` 903
`
` PREFERENCES
`
`
`
`
`YES
`PREFERENCES
`PREFERENCES
`
`NO
`FOR WIRED SERVICES
`FOR WIRELESS SERVICES
`
`
`
`MET?
`MET?
`
`
`
`
`
`
`
` USER
`
`WIRLESS
`PREFERENCE
`
`
`
`
`CURRENTLY
`
`CURRENTLY
`UTILIZING WIRED
`UTILIZING WIRELESS
`
`
`
`NETWORK?
`NETWORK?
`
`
`
`
`
`
`
`STATE 1—
`
`STATE 2-
`WIRED
`STATE 4-
`WIRELESS
`
`
`
`
`SERVICES
`TRANSITION
`SERVICES
`
`
`
`
`UTILIZED
`UTILIZED
`
`
`
`
`
`FIG. .9
`
`

`

`US. Patent
`
`Oct. 24, 2000
`
`Sheet 6 0f 6
`
`6,137,802
`
`STATE 4—
`
`TRANSITION
`
`1001
`
`YES
`
`
`
` CURRENTLY
`UTILIZING WIRED
`
`NETWORK?
`
`
`NO
`
`1002
`
`NOTIFY APPLICATIONS
`OF NETWORKING
`CHANGE AND 008
`
`CHANGE AND 003
`
`NOTIFY APPLICATIONS
`OF NETWORKING
`
`CONFIGURE WIRELESS
`NETWORK
`INFORMATION, ag.
`ROUTING & ADDRESS
`
`
`
`
`
`
`
`
`CONFIGURE WIRED
`NETWORK
`INFORMATION. e.g.
`ROUTING & ADDRESS
`
`ACTIVATE WIRELESS
`HARDWARE
`
`ACTIVATE WIRED
`
`HARDWARE
`HARDWARE
`
`DEACTIVATE WIRED
`HARDWARE
`
`1003
`
`DEACTIVATE WIRELESS
`
`
`
`
`1004
`
`12
`
`
`
`
`
`STATE 2—
`WIRELESS
`SERVICES
`UTILIZED
`
`
`
`
`
`H
`
`
`
`
`STATE 1—
`WIRED
`SERVICES
`UTILIZED
`
`FIG. 10
`
`

`

`6,137,802
`
`1
`AUTOMATIC MEDIA SWITCHING
`APPARATUS AND METHOD
`
`FIELD OF THE INVENTION
`
`This invention is directed generally to the field of com-
`munications networks, and more particularly to a novel
`method and apparatus which permits automatic switching of
`a user device between wired and wireless service mediums
`of communications networks.
`
`BACKGROUND OF THE INVENTION
`
`Multimedia communications between two stations may
`use either wired or wireless communications networks.
`
`These wired networks may be either packet based, such as
`Ethernet, or circuit based networks such as asynchronous
`transfer mode (ATM). Such networks may eXist in an office
`building or between office locations of the same company,
`for use by company employees. In the case of portable
`equipment such as a laptop computer, when the user is away
`from his own office, either within the company premises, or
`traveling, he may wish to make use of a wireless commu-
`nication network to communicate with other devices, includ-
`ing devices on the wired company network. Similarly, it may
`be desirable under some circumstances even for stationary
`equipment such as the desktop computer to communicate
`over a wireless network with other devices.
`
`In a wireless network, a high speed wired communica-
`tions network (a backbone network) may communicate with
`a number of base stations, which in turn communicate with
`users of the network services by wireless connections. These
`networks may be based on ATM technology. Thus, a number
`of subscribers may be coupled by wireless communications
`to a base station, and the base station is in turn coupled
`through an ATM switch to the high speed backbone network.
`The subscribers may be either stationary or mobile, and in
`the case of mobile subscribers, it may be necessary for the
`subscriber to communicate with a different base station from
`time to time, as a subscriber enters and leaves areas serviced
`by various base stations. In a wired network using an ATM
`backbone network, the users may be wired directly to ATM
`switches.
`
`In the case of desktop computers, wired and wireless
`communications are usually supported by an appropriate
`interface board or “bus adapter” (e.g., S-bus, Nubus, ISA,
`PCI, EISA, or the like) installed inside the casing or housing
`of the computer, with suitable connector elements, or plugs,
`for a given wired network, or a suitable antenna to commu-
`nicate with a wireless network, emerging exteriorally of the
`casing or housing. However, in order to switch from a wired
`network to a wireless network,
`it may be necessary to
`terminate a connection, if communication is currently in
`progress. That is, typically the steps would be: shut down the
`computer, remove the eXisting interface board, install a new
`interface board appropriate to the network to be used, and
`often provide new software for supporting the new interface.
`Adding to the problem, high level application software
`normally requires reconfiguration in order to utilize the
`changes in the network configuration.
`In the case of laptop computers, communications are
`often provided by a network interface card, such as a
`PCMCIA type interface card, which is a relatively small,
`approximately credit card-sized element
`that physically
`enters a slot in a side panel of the laptop housing. However,
`these various network interface cards, or PCMCIA type
`cards, are specific to either wired or wireless networks, such
`that a communication session must terminate,
`the laptop
`
`2
`shut down, and the network interface card changed to
`communicate with a new network. Again, it may also be
`necessary to provide new software to support
`the new
`interface card upon changing cards in this fashion.
`Thus, the prior art has generally required multiple inter-
`face cards that must be interchanged, or other special
`configurations of equipment to allow a user device to change
`from wired to wireless communications networks. Modular
`
`10
`
`15
`
`interface cards such as ATM boards allow for users to plug
`in different modules for different types of wired connections;
`however, the user must still remove the interface cards from
`the host computer to change the module. Multiple modules
`cannot be connected to one interface board, and all modules
`supported utilize a wired medium. Thus, automatic switch-
`ing between wired and wireless mediums is not possible
`with this approach.
`BRIEF SUMMARY OF THE INVENTION
`
`20
`
`A media switching apparatus for automatically switching
`a user device between wired and wireless service medium of
`communications networks is disclosed and described. The
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`apparatus includes a protocol stack that includes a network
`layer, a logical
`link control, a first set of lower layers
`associated with a wired service medium and a second set of
`
`lower layers associated with s wireless service medium.
`Further included is a selecting means, responsive to an
`availability of the wired service medium, for selecting the
`first set of lower layers to provide service for user device,
`and further responsive to a non-availability of the wired
`service medium and an availability of the wireless service
`medium for selecting said second set of lower layers to
`provide service for the user device.
`A corresponding method embodiment for automatically
`switching a user of a communications network device,
`which includes wired hardware and wireless hardware,
`between wired and wireless service mediums includes the
`
`following steps. Determining whether a wired service
`medium is available and determining whether a wireless
`service medium is available. Activating the wired hardware
`to provide service to the user of a communications network
`device when the wired service medium is determined to be
`available and the wireless service medium is determined to
`
`be unavailable. Activating the wireless hardware to provide
`service to the user of a communications network device
`when the wireless service medium is determined to be
`available, and the wired service medium is determined to be
`unavailable.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a functional diagram of an ATM network that
`may be accessed by both wired and wireless mediums, in
`accordance with the present invention;
`FIG. 2 is a functional diagram of a modified protocol
`stack for use with both wired and wireless communication
`
`mediums, in accordance with the present invention;
`FIG. 3 is a functional diagram illustrating selection of one
`of two sets of layers specific to wired and wireless mediums,
`respectively, in the protocol stack of FIG. 2;
`FIG. 4 is a block diagrammatic illustration of a network
`interface card showing hardware components for respective
`wired and wireless communication mediums, in accordance
`with a first embodiment of the invention;
`FIG. 5 is a simplified side elevation of a network interface
`card, wherein wired specific hardware is provided off the
`card, in accordance with another embodiment of the inven-
`tion;
`
`

`

`6,137,802
`
`3
`FIG. 6 is a diagram illustrating a plurality of operational
`states, in accordance with the invention, and the interopera-
`tion therebetween; and
`FIGS. 7—10 are flow charts depicting operation of the
`apparatus and method in accordance with the invention,
`using the operational states of FIG. 5.
`
`DETAILED DESCRIPTION OF A THE
`PREFERRED EMBODIMENT
`
`Referring to the drawings and initially to FIG. 1, an
`asynchronous transfer mode (ATM) network is illustrated as
`a backbone network 10, made up of a plurality of ATM
`switches such as ATM switch 12, which are interconnected
`by fiber, cable or other suitable wired connection medium
`14. Aplurality of user devices 16, 18, 20, 22, 24, 26 and 28
`are connected at the ATM switch 12, which forms a node of
`the ATM backbone network 10 by either wired or wireless
`communications or service mediums.
`In a preferred
`embodiment, the user device 28 is connected by a wired
`service medium 38 to the ATM switch 12.
`
`The user devices 16, 18, 20, 22, 24, and 26 are served by
`wireless service mediums so as to communicate with respec-
`tive base stations 30, 32. These base stations 30 and 32 in
`turn communicate with the ATM switch 12, preferably
`through wired facilities such as coaxial or fiber optic cables
`34, 36. Each of the base stations 30, 32 may be assigned to
`service a given area represented by the ovals shown in FIG.
`1. The arrangement is such that laptop computers or other
`mobile communication devices within the areas represented
`by the ovals in FIG. 1 may communicate with one of the
`base station 30 and the base station 32, with some overlap
`in these areas being possible, as illustrated by the area
`surrounding user devices 20 and 22.
`While the invention will be described in detail herein with
`
`reference to a preferred embodiment—wherein a user device
`comprises a laptop computer—it will be understood that the
`invention is not necessarily limited to this application. Other
`applications, for example, a desktop computer, or any other
`user device that may communicate over various types of
`wired or wireless communications or service networks may
`also make use of the present invention. The present inven-
`tion encompasses an automatic medium switching apparatus
`and method by which any of the user devices 16—28 may
`communicate with the backbone network 10 using either
`wired or wireless service mediums, and may switch between
`wired and wireless service mediums, in accordance with
`predetermined criteria for selecting and utilizing either a
`wired or a wireless service medium. While an ATM network
`
`was described above, the invention may be used with other
`networks, such as Ethernet. Both ATM and Ethernet may
`also support wireless network communications products,
`one example of which in an ATM environment is illustrated
`and described above with reference to FIG. 1. Further
`
`examples of wireless networks include Code Division Mul-
`tiple Access (CDMA) and Global System for Mobile Com-
`munications (GSM). GSM is a European cellular (wireless)
`communications system, while CDMA is a wireless com-
`munications technique presently used in parts of Asia.
`Referring to FIG. 2, a modified protocol stack for use with
`both wired and wireless communications or service
`mediums, in accordance with the invention, is illustrated. At
`the highest layer is the Application 40 to be served by the
`communication network,
`for example, voice
`communications, data communications, text, video, etc. The
`protocol stack further comprises a network layer 42 and a
`logical link control layer 44. These two layers are common
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`4
`to both wired and wireless communication service mediums.
`
`these two layers handle packetization of data,
`Briefly,
`framing, buffering of data, and similar data processing
`functions for allowing data communication between devices
`over the ATM network or any other network selected for
`communications. Further descriptions of the functions of
`network layer and logical link control layer and the above
`functions of packetization framing, buffering, etc. may be
`found in the publications Telecommunications Networks,
`Protocols, Modeling, and Analysis by Mischa Schwartz,
`Addison-Wesley Publishing Co., 1988; Data Networks by
`Dmitri Bertsekas and Robert Gallager, Prentice Hall, 1992;
`and Internetworking with TCP/IP, Vol. 1 by Douglas Comer,
`Prentice Hall, 1991.
`Below the logical link control 44, two sets of lower layers,
`which are respectively specific to wired and wireless service
`mediums, are provided, and designated in FIG. 2 generally
`by the reference numerals 46 and 48. The first set 46 of
`lower layers is specific to a wired service medium and
`comprises a wired media access (MAC) layer 50 and a wired
`physical layer 52. The wired physical layer 52 represents
`hardware specific to connection to a wired service medium,
`including a suitable physical connector or terminal that may
`project externally from the user device for connection to a
`mating connector on a cable or other wired input to the wired
`service medium.
`
`The respective network, logical link control and media
`access layers 42, 44 and 50 are primarily embodied in
`software that may be run on suitable processor components
`for performing the various functions assigned to each layer.
`In this regard, the MAC layer 50 is responsible for such
`functions as collision detection, that is, detecting two users
`transmitting simultaneously to avoid collision between the
`data from two such users as it enters the network. A further
`
`description of the makeup and function of the MAC layer
`may be found in the above referenced publications.
`they
`Referring to the second set of lower layers 48,
`comprise a wireless MAC layer 54 and wireless physical
`layer 56 specific to a wireless service medium. The structure
`and functions of the wireless MAC layer 54 are analogous
`to those of the wired MAC layer 50, as described above. The
`wireless physical layer 56 may include radio transmission
`and reception components and a suitable antenna for com-
`munication with a wireless service medium. In addition to
`
`the MAC and physical layers 54, 56 the second set of lower
`layers includes a wireless mesh layer 58 (described below),
`which may be embodied primarily in software and executed
`by suitable processor components.
`The mesh layer 58 is specific to wireless service mediums
`and controls, for example, which user device connects to
`which base station, such as in the network described with
`reference to FIG. 1. The mesh layer 58 also controls and
`handles hand-offs between base stations and routing from
`the backbone network to the correct base station to complete
`communications of data between respective user devices
`coupled with the network. Essentially, the mesh layer 58
`does everything necessary to facilitate communications
`between two user devices in a wireless environment. Further
`
`description of the structure and functions of a mesh layer of
`this type may also be found in the above-referenced publi-
`cations.
`
`Referring to FIG. 3, a functional diagram shows an
`automatic media or network switching apparatus that
`includes a selector or selecting means 60, which is respon-
`sive to the availability of a wired service medium for
`selecting the first set 46 of lower layers or “wired layers”, as
`
`

`

`6,137,802
`
`5
`they are designated in FIG. 3. Similarly, the selector 60 is
`responsive to the non-availability of a wired service medium
`and the availability of a wireless service medium for select-
`ing the second set 48 of lower layers or “wireless layers”, as
`they are designated in FIG. 3.
`The selector or selecting means 60 might comprise suit-
`able sensing hardware and software for determining the
`presence or absence of various wired or wireless service
`mediums. The sensing of a wired service medium can be
`accomplished by carrier sensing methods, as indicated at
`reference numeral 62 in FIG. 3. The selector 60 also includes
`suitable software for making a determination of which
`network (wired or wireless) is to be selected in accordance
`with predetermined criteria, and suitable processor compo-
`nents for executing the software necessary to this function.
`In this latter regard, the selector 60 may share processor
`components with other functions of the user device.
`The foregoing description of operation of the selecting
`means or selector 60 based only upon availability of wired
`or wireless mediums is in accordance with the simplest or
`most basic form of the invention. In accordance with a
`preferred form of the invention,
`the selector or selecting
`means 60 will further be responsive to the acceptability or
`suitability of various wired and wireless service mediums
`that may be available, in addition to determining the avail-
`ability of such mediums, so as to select either a wired or a
`wireless service medium for particular applications,
`in
`accordance with predetermined criteria. Thus, for applica-
`tions in which a wired service medium is preferred,
`the
`selecting means will include means responsive to a wired
`service medium becoming available, even while using a
`wireless service medium, for switching between the wireless
`layers (second set of lower layers) 48 and the wired layers
`(first set of lower layers) 46.
`With respect to the switching between the two sets of
`lower layers 46 and 48, the wireless mesh layer 58 also
`includes means for handling hand-off and routing protocols
`for switching between layers and for signaling the network
`and logical link control layers 42 and 44, respectively, as
`well as notifying the application 40 when a switch between
`media has occurred.
`
`In accordance with a preferred embodiment, the mesh
`layer 58 also includes means for notifying the user device of
`information regarding the availability of a wireless network
`(i.e., whether the user device is within the range of a
`compatible wireless network service provider, such as a base
`station 30 or 32 of the system illustrated in FIG. 1). In this
`regard, an additional human perceptible means is preferably
`employed and signaled by the mesh layer in order to so
`notify the user of such information. This human perceptible
`indication may take the form of a simple LED or other such
`light emitting element, or may take the form of producing a
`message on a screen of a laptop computer or other user
`device which utilizes a video display.
`Referring now to FIG. 4, there is illustrated in diagram-
`matic form a network interface card 70 (also known as a
`PCMCIA interface adapter) that may be provided as a
`specific embodiment of the invention for use with a laptop
`computer. Briefly, a typical laptop computer includes one or
`more externally accessible slots that receive one or more
`interface cards or adapters, which generally are about the
`size of a credit card (although usually several times as thick).
`These interface cards contain all the components necessary
`for a particular function, such as providing a fax modem, etc.
`However, prior network interface cards were specific to only
`a single type of network and did not permit switching
`between wired and wireless networks as with the present
`invention.
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`In accordance with the invention, the network interface
`card 70 includes suitable components such as a micropro-
`cessor 72 and memory in the form of both read only memory
`(ROM) 74 and random access memory (RAM) 76. These
`components may embody the hardware and software com-
`ponents of the network layer 42 and logical link control layer
`44 described above with reference to FIG. 2. These com-
`ponents may further embody the hardware and software
`associated with the two sets of lower layers 46 and 48, with
`the exception of the wired physical layer 52 and wireless
`physical layer 56.
`In this regard, the wireless, or radio, specific hardware and
`wired specific hardware, which comprise the aforemen-
`tioned layers 52 and 56, are separately provided on the card
`70 and designated by like reference numerals 52 and 56. The
`radio specific hardware may include an externally extending
`antenna component 78 and the wired specific hardware 56
`may include an externally projecting connector member 80,
`as previously discussed hereinabove. A software controlled
`switch 72 is provided to select the appropriate physical layer
`or hardware when either wired or wireless service mediums
`
`are selected, in accordance with predetermined criteria as
`will be described further hereinbelow.
`
`the network interface card 70
`As indicated above,
`includes hardware to support both wired and wireless (radio)
`connections. Software on the device will enable the card to
`switch between either wired or wireless services in a
`
`seamless, transparent manner. To provide this functionality,
`the interface card 70 includes a switch 82 implemented in
`software that controls which hardware is being utilized. The
`specific hardware utilized by the radio or wired link will
`perform all the necessary “packetization” required by the
`network protocol being utilized. The data sent across the
`switch is formatted to the higher network layers’
`specifications, but typically requires additional formatting
`for compatibility with the specific network being utilized.
`Referring briefly to FIG. 5, a somewhat simplified side
`elevation of a network interface card is shown, designated
`generally by reference numeral 70a. As indicated in FIG. 5,
`it is also within the scope of the invention to provide the
`wired specific hardware,
`that is,
`the additional hardware
`needed to make a wired connection, off the network inter-
`face card 70a. This hardware for making a wired network
`connection is designated in FIG. 5 by reference numeral
`52a. Also in FIG. 5, an additional card interface 57, which
`bypasses the radio specific hardware 56 (including antenna
`78), is used to interface with the wired specific hardware
`52a. In other respects, the embodiment of FIG. 5 is sub-
`stantially identical to what is shown and described above
`with reference to FIG. 4. Thus,
`in the description that
`follows, the apparatus, or device, is understood to include
`both the network interface card 70 as shown in FIG. 4, and
`the network interface card 70a together with the additional
`off-card wired specific hardware 52a as shown in FIG. 5.
`According to the invention, the device can detect when it
`is connected to a wired network backbone using carrier
`sensing techniques; i.e., by sensing a carrier signal of the
`network. After detecting the presence of a wired network the
`invention will determine if the network is “compatible” or
`connected to the information, servers, and/or sites that are
`desired by the user. The word “ping,” as used herein, refers
`generally to a process and program for testing the reach-
`ability of destinations by transmitting a signal that requests
`a reply, and waiting for a reply. Processes and programs of
`this type are available for various networking protocols.
`In the case where a wireless connection is in progress, the
`wired network is utilized to “ping” the base station. This will
`
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`6,137,802
`
`7
`determine if the appropriate network routing is available to
`maintain all the user’s wireless connections. The results of
`
`the ping operation and other user preferences are then used
`to determine if a switch between networking services should
`be performed.
`Similarly, the radio hardware 56 is constructed in such a
`manner that it will automatically detect a base station or
`other transmitting node to which connection can be made. In
`the case where a wired connection is in progress,
`the
`wireless connection is utilized to “ping” an appropriate
`network station with which the device is communicating via
`the wired link. This will determine if the appropriate net-
`work routing is available to maintain all the users’ wired
`connections. The device utilizes the result of the ping
`operation and other user preferences to determine if a switch
`between networking services should be performed.
`For the case when neither wired nor wireless services is
`
`being utilized, but the networks are detected, the device
`“pings” the appropriate, predetermined (based on user
`preferences) network stations to determine if either network
`service is available and compatible. Then, based on user
`preferences, the device determines the preferred connection,
`in accordance with the present invention as described below.
`
`OPERATION
`
`At a high level, the automatic media or network switching
`method (and the apparatus or device employing the method)
`has five states of operation. These states will be described
`independently in the following sections to enhance clarity,
`with reference to the diagram of FIG. 6 and to the flow charts
`that follow (FIGS. 7—10).
`
`State 0 (600)—Determine Services (Searching)
`
`When the user device is started up (i.e., first turned on, or
`when no communications services are present), the device
`enters a “search” mode. In this mode the device continually
`attempts to detect a base station via a wireless link, and
`checks for the presence of a wired connection. The device
`stays in this state until either of the services is available. If
`both of the services become available at the same time the
`
`device enters State 3 (603), the Service Evaluation state.
`FIG. 7 shows a flow chart for operation while in State 0
`(600). It should be pointed out that upon leaving State 0
`(600), the device is either connected to the wired network
`(701), connected to the wireless network (702), or both
`services are available (703) and the device enters State 3
`(603).
`In this regard,
`the transitions between states are
`labeled with reference character 1—12 in FIG. 6, and these
`same reference characters are repeated at corresponding
`transition points in FIGS. 7—10.
`When the device is utilizing a wired or a wireless
`connection, it has completed the necessary steps to perform
`a connection setup. At a minimum, this includes configuring
`the wired/wireless network information and activating the
`wired/wireless hardware (704), as shown in FIG. 7. Setup
`may further include, for example, virtual circuit assignment
`in the case of an ATM network and assigning of a network
`address to the card 70 (70a) and the host computer.
`
`State 1 (601)—Wired Services Utilized
`
`Referring to FIG. 8, State 1 (601) is entered when a
`compatible wired service medium or network connection is
`sensed and being utilized or when a wired connection is
`being utilized after determining that
`it
`is the preferred
`connection when the wireless service medium is also avail-
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`able. In this state the device has detected, via the appropriate
`carrier signal, that it is connected to a compatible wired
`backbone and has performed the necessary steps to utilize
`this networking connection.
`Accordingly, the present invention allows the user and
`supporting software to communicate to the network via the
`wired link (801), while periodically attempting (802) to
`detect a base station via a wireless link.
`
`State 2 (602)—Wireless Services Utilized
`
`Referring still to FIG. 8, State 2 (602) is entered when a
`wireless link to a base station is established with a compat-
`ible backbone network or when a wireless service medium
`
`or connection is being utilized after determining that it is the
`preferred connection when a wired service medium is also
`available. In this state the device has detected a wireless base
`
`station and has determined that it is connected to a compat-
`ible backbone network. The interface card 70 (70a) has also
`performed the necessary steps to utilize this networking
`connection.
`
`Accordingly, the present invention allows the user and
`supporting software to communicate to the network via the
`wireless service medium (803), while periodically attempt-
`ing (804) to connect to a wired service medium.
`For both States 1 and 2, the device remains in the state
`until either the network connection via this service medium
`
`is unavailable, causing a return to State 0 (600), or until the
`other service medium becomes available, causing a return to
`State 3 (603), where the two service mediums are evaluated.
`FIG. 8 shows flow charts for both States 1 and 2.
`
`It is noted that State 3 (603) is entered in the event that
`both wired and wireless service mediums become available.
`
`In this state the device determines, based on network loading
`and throughput, and user options for quality of service, i.e.,
`the desired throughput (bit rate), latency, and jitter (latency
`variance), which service medium should be selected.
`When entering State 3 (603) from either State 1 (601) or
`State 2 (602), the existing service medium network connec-
`tion is maintained while determining which of the service
`mediums is desired. In other words, the user’s services will
`not be interrupted or disconnected while monitoring for the
`connection quality of the other service medium.
`
`State 3 (603)—Service Evaluation
`
`FIG. 9 shows a flow chart for State 3 (603). Since both
`