United States Patent [19J
`Mahany
`
`I 1111111111111111 11111 111111111111111 11111 111111111111111 IIIIII Ill lllll llll
`5,960,344
`Sep.28,1999
`
`US005960344A
`[11] Patent Number:
`[45] Date of Patent:
`
`[54] LOCAL AREA NETWORK HAVING
`MULTIPLE CHANNEL WIRELESS ACCESS
`
`[75]
`
`[73]
`
`Inventor: Ronald L. Mahany, Cedar Rapids,
`Iowa
`
`Assignee: Norand Corporation, Cedar Rapids,
`Iowa
`
`[21]
`
`Appl. No.: 08/878,357
`
`[22]
`
`Filed:
`
`Jun. 27, 1997
`
`[63]
`
`[51]
`[52]
`[58]
`
`[56]
`
`Related U.S. Application Data
`
`Continuation-in-part of application No. 08/772,895, filed as
`application No. PCT/US96/09474, Jun. 3, 1996, abandoned,
`which is a continuation-in-part of application No. 08/696,
`086, Aug. 13, 1996, abandoned, which is a continuation of
`application No. 08/238,180, May 4, 1994, Pat. No. 5,546,
`397, which is a continuation-in-part of application No.
`08/197,392, Feb. 16, 1994, abandoned, which is a continu(cid:173)
`ation-in-part of application No. 08/170,121, Dec. 20, 1993,
`abandoned.
`Int. Cl.6
`....................................................... H04Q 7/00
`U.S. Cl. ........................... 455/432; 455/434; 455/435
`Field of Search ..................................... 455/432, 435,
`455/455, 450, 517, 582, 515, 553, 78, 434;
`370/310, 311, 328, 329, 330, 335
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,046,130
`5,513,184
`5,551,060
`5,561,845
`
`9/1991 Hall et al. ................................. 455/78
`4/1996 Yannucci ................................. 455/422
`8/1996 Fujii et al. .............................. 455/562
`10/1996 Bendixen et al.
`...................... 455/434
`
`5,655,219
`5,734,645
`5,768,267
`
`8/1997 Jusa et al. ............................... 455/435
`3/1998 Raith et al. ............................. 370/329
`6/1998 Raith et al. ............................. 455/434
`
`Primary Examiner-Salvatore Cangialosi
`Attorney, Agent, or Firm-Akin, Gump, Strauss, Hauer &
`Feld, L.L.P.
`[57]
`
`ABSTRACT
`
`A communication network having at least one access point
`supports wireless communication among a plurality of wire(cid:173)
`less roaming devices via a first and a second wireless
`channel. The access point comprises a first and a second
`transceiver. The first and second transceivers operate on the
`first and second wireless channels, respectively. Each of the
`plurality of wireless roaming devices are capable of com(cid:173)
`municating on the first and second wireless channel. In one
`embodiment, the first wireless channel is used to exchange
`data, while the second channel is used to manage such
`exchanges as well as access to the first channel. In an
`alternate embodiment, both channels are used to support
`communication flow, however the first channel supports a
`protocol that is more deterministic than that of the second
`channel. Allocation of ones of the plurality of wireless
`roaming devices from one channel to the next may occur per
`direction from the access point. It may also result from
`decisions made by each of the wireless roaming devices
`made independent of the access point. For example, a
`decision may be made based on the data type being trans(cid:173)
`ferred or based on the current channel load. Such factors
`may also be used by the access point for allocation deter(cid:173)
`minations. In addition, allocation may be based on the type
`of roaming device involved, such as allocating peripherals to
`a slower channel.
`
`28 Claims, 17 Drawing Sheets
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`Additional
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`
`Ex.1024
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`

`U.S. Patent
`
`Sep.28,1999
`
`Sheet 1 of 17
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`5,960,344
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`Fig. 1
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`Ex.1024
`APPLE INC. / Page 2 of 29
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`

`

`U.S. Patent
`
`Sep.28,1999
`
`Sheet 2 of 17
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`5,960,344
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`Ex.1024
`APPLE INC. / Page 3 of 29
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`Ex.1024
`APPLE INC. / Page 4 of 29
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`

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`U.S. Patent
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`Sep.28,1999
`
`Sheet 4 of 17
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`5,960,344
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`Ex.1024
`APPLE INC. / Page 5 of 29
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`Ex.1024
`APPLE INC. / Page 6 of 29
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`

`

`U.S. Patent
`
`Sep.28,1999
`
`Sheet 6 of 17
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`5,960,344
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`Ex.1024
`APPLE INC. / Page 7 of 29
`
`

`

`U.S. Patent
`
`Sep.28,1999
`
`Sheet 7 of 17
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`5,960,344
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`Ex.1024
`APPLE INC. / Page 8 of 29
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`

`

`U.S. Patent
`
`Sep.28,1999
`
`Sheet 8 of 17
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`5,960,344
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`Ex.1024
`APPLE INC. / Page 9 of 29
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`

`

`U.S. Patent
`
`Sep.28,1999
`
`Sheet 9 of 17
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`5,960,344
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`Ex.1024
`APPLE INC. / Page 10 of 29
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`

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`U.S. Patent
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`Sep.28,1999
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`Sheet 10 of 17
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`5,960,344
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`APPLE INC. / Page 11 of 29
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`U.S. Patent
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`Sep.28,1999
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`Sheet 11 of 17
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`APPLE INC. / Page 13 of 29
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`

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`U.S. Patent
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`Sep.28,1999
`
`Sheet 13 of 17
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`APPLE INC. / Page 14 of 29
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`Ex.1024
`APPLE INC. / Page 15 of 29
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`Ex.1024
`APPLE INC. / Page 16 of 29
`
`

`

`U.S. Patent
`
`Sep.28,1999
`
`Sheet 16 of 17
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`Ex.1024
`APPLE INC. / Page 17 of 29
`
`

`

`U.S. Patent
`
`Sep.28,1999
`
`Sheet 17 of 17
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`5,960,344
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`Ex.1024
`APPLE INC. / Page 18 of 29
`
`

`

`1
`LOCAL AREA NETWORK HAVING
`MULTIPLE CHANNEL WIRELESS ACCESS
`
`5,960,344
`
`2
`Some prior WLANs attempted to solve operational dif(cid:173)
`ficulties by simply increasing the transmission capacity
`available on the infrastructure. Such expansion temporarily
`decreased conflicts in operation of the WLANs. However,
`the infrastructure, which is expensive to install, typically
`became overloaded quickly resulting in the same or similar
`problems.
`
`SUMMARY OF THE INVENTION
`
`5
`
`CROSS-REFERENCE To RELATED APPLICATIONS
`The present application is a continuation-in-part of U.S.
`application Ser. No. 08/772,895 filed Dec. 24, 1996, now
`abandoned, which is a continuation-in-part of U.S. applica(cid:173)
`tion Ser. No. 08/696,086 filed Aug. 13, 1996, abandoned,
`which is a continuation of U.S. application Ser. No. 08/238,
`180 filed May 4, 1994, now issued as U.S. Pat. No. 5,546, 10
`397, which is a continuation-in-part of U.S. application Ser.
`No. 08/197,392 filed Feb. 16, 1994, now abandoned which
`is a continuation-in-part of U.S. application Ser. No. 08/170,
`121 filed Dec. 20, 1993 now abandoned.
`The U.S. application Ser. No. 08/772,895 filed Dec. 24, 15
`1996, now abandoned also claims priority to PCT Applica(cid:173)
`tion Ser. No. PCT/US96/09474, filed on Jun. 3, 1996.
`All of the aforementioned applications are hereby incor(cid:173)
`porated herein by reference in their entirety. In addition, U.S.
`Pat. No. 5,425,051 issued Jun. 13, 1995 to Ronald L. 20
`Mahany is also hereby incorporated herein by reference in
`its entirety.
`
`BACKGROUND
`1. Technical Field
`The present invention relates generally to access points
`used in wireless local area networks, and more specifically
`to an access point which includes multiple wireless adapters.
`2. Related Art
`Wireless local area networks (WLAN's) use radio fre- 30
`quency transmissions to communicate between roaming
`computer devices and access points (or base stations). The
`access points are connected to an infrastructure that elec(cid:173)
`tronically connects all of the access points to a host system.
`The wired infrastructure and the access points make up an
`information distribution network used for the transfer of
`information and for communications.
`In a wireless networking environment, various types of
`devices may need to communicate within a given area.
`When incompatibilities between device types arise, the
`wireless infrastructure must accommodate the various
`device types. Accommodating the different device types in
`a single infrastructure is generally difficult to accomplish.
`Further, devices within the wireless networking environ(cid:173)
`ment typically communicate differing types of data, each
`with its own priority and bandwidth requirements. Accom(cid:173)
`modating the various types of data with their related priori(cid:173)
`ties often could not be accomplished by prior devices due to
`bandwidth limitations, conflicting priorities and incompat(cid:173)
`ible standards within the wireless network.
`In prior WLANs, a first wireless terminal that desired to
`communicate with a base station often could not detect
`transmissions from a second wireless terminal currently
`engaged in ongoing communication with the access point.
`As a result, the wireless terminal often initiated transmis(cid:173)
`sions that collided with the ongoing communications.
`Operation of this type is referred to as a "hidden terminal"
`situation. To solve the hidden terminal situation, some prior
`base stations were configured with a second transmitter for
`delivering a carrier signal on a "busy channel" whenever the
`base station was engaged in communication on the "data
`channel." All terminals were also fitted with a second
`receiver, tuned to the busy channel, and required to check the
`busy channel before initiating communication on the data
`channel. However, the additional power required, bandwidth 65
`used, hardware needed and associated cost made the busy
`channel solution undesirable for most applications.
`
`The present invention is directed to communication net(cid:173)
`work that supports communication within a premises. The
`communication network comprises an access point, a plu(cid:173)
`rality of wireless roaming devices, a first wireless commu-
`nication channel, and a second wireless communication
`channel. The access point itself comprises a first processing
`circuit, a first radio transceiver coupled to the first process(cid:173)
`ing circuit, and a second radio transceiver coupled to the first
`processing circuit. Each of the plurality of wireless roaming
`devices comprising a second processing circuit, a third radio
`transceiver and a radio receiver. Therein, the first wireless
`communication channel that supports communication flow
`via the communication network, while the second wireless
`communication channel is used to manage the flow of
`communication through the first wireless communication
`25 channel. In addition, the first and third radio transceivers are
`operable on the first wireless communication channel, while
`the second radio transceiver and the radio receiver are
`operable on the second wireless communication channel.
`The communication network also supports various other
`aspects of the present invention. For example, the access
`point may further comprises a wired communication inter(cid:173)
`face circuit coupled to the first processing circuit. Selective
`participation on the first and second communication chan-
`35 nels may also provide further benefits. In one embodiment,
`each of the plurality of wireless roaming devices utilizes the
`radio receiver on the second wireless communication chan(cid:173)
`nel before participating with the third radio transceiver on
`the first wireless communication channel. In another, each
`40 utilizes the radio receiver on the second wireless commu(cid:173)
`nication channel to gain access with the third radio trans(cid:173)
`ceiver on the first wireless communication channel. Each
`may also or alternatively utilize the second wireless com(cid:173)
`munication channel to identify ongoing communication on
`45 the first wireless communication channel to, perhaps, pro(cid:173)
`vide an indication as to when channel capacity may become
`available.
`Other aspects may be found in an alternate communica(cid:173)
`tion network which also supports communication within a
`50 premises. This communication network comprises an access
`point, first and second wireless communication channels and
`plurality of wireless roaming devices. The first wireless
`communication channel has first communication flow
`characteristics, while the second wireless communication
`55 channel has second communication flow characteristics. The
`first and second radio transceivers participate on the first and
`second wireless communication channels, respectively.
`Therein, each of the plurality of wireless roaming devices
`comprises a second processing circuit and means for selec-
`60 tively participating on the first and second wireless commu(cid:173)
`nication channels.
`The access point may also comprise a wired communi(cid:173)
`cation interface circuit coupled to the first processing circuit
`that may itself comprise a first and a second microprocessor.
`Additionally, at least one of the plurality of wireless roaming
`devices may participate on the first wireless communication
`channel while the other of the plurality of wireless roaming
`
`Ex.1024
`APPLE INC. / Page 19 of 29
`
`

`

`5,960,344
`
`3
`devices participates on the second wireless communication
`channel. Although the at least one of the plurality of wireless
`roaming devices may participate on the first wireless com(cid:173)
`munication channel as directed by the access device, other
`variations and combinations are also possible. For example, 5
`the at least one of the plurality of wireless roaming devices
`may participate on the first wireless communication channel
`to exchange a specific type of data, and/or may participate
`based on current channel conditions. Such participation may
`be based the fact that, in some embodiments, the second 10
`wireless communication channel is more deterministic than
`the first wireless communication channel.
`In any of the aforementioned embodiment, the commu(cid:173)
`nication network may comprise at least a second access
`point. Other variations and aspects of the present invention
`will become apparent to ones of ordinary skill in the art after
`reviewing the entire specification and drawings.
`
`4
`wherein an access point uses a dedicated control/busy chan(cid:173)
`nel transmitter to manage transmissions between the access
`point and a plurality of roaming portable data terminals
`within its cell.
`FIG. 12 is a drawing illustrating advantageous operation
`of the access device and portable data terminals of FIG. 11
`when two roaming terminals encounter hidden terminal
`conditions.
`FIG. 13 is a block diagram illustrating an alternate
`embodiment of the communication system of the present
`invention wherein an access point includes a dedicated
`control/busy channel transceiver and roaming data terminals
`communicate with the access point using either frequency
`nimble multi-channel transceivers or dedicated control/busy
`15 channel transceivers.
`FIG. 14a is a block diagram illustrating a communication
`system of the present invention wherein access points and
`portable data terminals operate on a deterministic first
`channel and a non-deterministic second channel and the
`system routes communications on the channels based upon
`system conditions.
`FIG. 14b is a diagram illustrating operation of a commu(cid:173)
`nication system of the present invention having both wired
`25 and wireless communication capability that includes at least
`one access point providing communication over a
`deterministic, time bounded first channel and a non(cid:173)
`deterministic, contention access second channel.
`FIG. 15 is a diagram illustrating the use of the access
`30 points and portable data terminals of FIG. 14a wherein the
`system routes various transmissions within the network
`system according to system conditions such as channel
`activity, data type and data priority.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a schematic representation of a high reliability 20
`access point in accordance with the present invention.
`FIG. 2 is a schematic representation of another high
`reliability access point of the present invention utilizing an
`antenna diversity scheme at each wireless adapter.
`FIG. 3 is a representation of a distribution network for a
`wireless LAN system utilizing high reliability access points.
`FIG. 4 is a schematic representation of a high reliability
`access point with a backup power supply.
`FIG. 5 is a schematic representation of a remote high
`reliability access point connecting to the distribution net(cid:173)
`work.
`FIG. 6 is block diagram illustrating an embodiment of an
`access point built in accordance with the present invention
`which includes two radios and a wired network interface, a 35
`first one of the radios operable on a first channel and a
`second one of the radios is operable on a second channel.
`FIG. 7a is a block diagram illustrating an embodiment of
`a portable data terminal according to the present invention,
`the portable data terminal having a single PCMCIAcard that 40
`contains two radios, a first one of the radios operable on the
`first channel and a second one of the radios operable on the
`second channel.
`FIG. 7b is a block diagram illustrating an alternative
`embodiment of the portable data terminal of FIG. 7a, 45
`wherein the single PCMCIA card includes a single radio
`operable on the first channel and the second channel and
`controlled by the processing circuitry.
`FIG. 8 is a block diagram illustrating an alternative
`embodiment of a portable data terminal according to the
`present invention, the portable data terminal having a single
`PCM CIA card that contains a multi-channel wireless trans(cid:173)
`ceiver and a wired network interface.
`FIG. 9 is a diagram illustrating a communication system
`built and operating according to the present invention, the
`communication system including at least one access point
`having multiple radios, portable terminals having multiple
`radios and portable terminals having multi-channel radios.
`FIG. 10 is a diagram illustrating a communication system
`built and operating according to the present invention
`wherein one of the access points facilitates communication
`between portable terminal units operating on different chan(cid:173)
`nels within its cell by routing communication between two
`of its radios.
`FIG. 11 is a block diagram illustrating an embodiment of
`a communication system according to the present invention
`
`50
`
`DETAILED DESCRIPTION
`Referring now to the drawings wherein like reference
`numerals designate identical or corresponding parts
`throughout the several views, FIG. 1 shows a high reliability
`access point 10 built in accordance with the present inven-
`tion. An access point is a base station on a wireless local area
`network with which roaming portable or mobile computer
`devices can connect and communicate. The access point is
`typically part of an overall distribution network which is
`connected to a host computer or entire computer local area
`network (LAN). The access points and the infrastructure
`make up the distribution network and allow for communi(cid:173)
`cations between the roaming computer devices and the host
`computer or entire computer local area network (LAN).
`A high reliability access point 10 of the present invention
`includes a central processing unit CPU processor 13 and at
`least two wireless adapters 15 and 16. Each of the wireless
`adapters 15 and 16 include a radio 17 and 18, a media access
`control (MAC) processor 19 and 20 and an antenna 21 and
`22, respectively. The radios and antennas are used for RF
`55 transmission and reception. The MAC processor controls
`low level protocol functions including controlling the opera(cid:173)
`tion of the radio, radio channel, error control, e.g., ARQ or
`Selective Response, and communication with the CPU pro(cid:173)
`cessor 13. The CPU processor 13 controls the high level
`60 communications protocol functions and controls the inter(cid:173)
`face 25 between the high reliability access point 10 and the
`infrastructure 26. In a preferred embodiment there is a
`PCMCIA standard interface between the wireless adapters
`and the access point.
`The distribution network is comprised of all of the access
`points and the infrastructure which connects all of the access
`points. A host computer or an entire host network is con-
`
`65
`
`Ex.1024
`APPLE INC. / Page 20 of 29
`
`

`

`5,960,344
`
`5
`nected to the distribution network. The distribution network
`allows computer devices to communicate with the host
`computer or host network.
`The division between what is high level protocol, and thus
`handled by the CPU processor, and what is low level
`protocol, and thus handled by the MAC processor, can vary
`greatly depending upon the intelligence level of the MAC
`processor. In a preferred embodiment, the infrastructure
`conforms to an industry standard wired LAN such as Eth(cid:173)
`ernet. The MAC processor can be made very intelligent and 10
`therefore capable of handling a great deal of radio specific
`protocol. On the other hand, the MAC processor can be
`minimally intelligent and handle only the most basic pro(cid:173)
`tocol functions allowing the CPU processor to handle the
`majority of the protocol functions.
`Utilizing multiple wireless adapters in a single access
`point, as well as incorporating independent intelligence and
`low level protocol responsibility into each wireless adapter,
`yields several significant advantages. The examples depicted
`in FIGS. 1-4 show access points using only two wireless
`adapters per access point. Utilizing two wireless adapters in
`the manner discussed below will greatly increase the reli(cid:173)
`ability of a particular access point, as well as increase the
`reliability of the entire distribution network. Access points
`could use more than two wireless adapters and the utilization 25
`of the multiple wireless adapters would be similar to the
`implementation describes using only two wireless adapters
`with addition protocol being required to handle the increased
`redundancy and to allow for more sophisticated self moni-
`toring.
`Referring still to FIG. 1, the CPU processor 13 can
`designate the RF address to which each wireless adapter 15
`and 16 is to respond. The CPU processor 13 can, but need
`not, assign the same address to each wireless adapter.
`Therefore, in one configuration, the CPU processor 13 can
`designate that each of the wireless adapters 15 and 16
`respond to the address assigned to that access point 10.
`Designated as such, both radios 17 and 18 will be operating
`simultaneously on the same channel. In a frequency hopping
`system, both radios 17 and 18 would be operating on the
`same hopping sequence, and be mutually synchronized to
`that hopping sequence.
`Accordingly, the wireless adapters 15 and 16 are config(cid:173)
`ured to receive incoming transmission from roaming com- 45
`puter devices within range. As both wireless adapters 15 and
`16 receive the transmission, each adapter can evaluate the
`quality information to the CPU processor 13. The CPU
`processor 13 uses the quality information to determine
`which wireless adapter is receiving the higher quality signal. 50
`The CPU processor 13 will then typically choose to receive
`the incoming transmission on the wireless adapter with the
`higher signal quality and respond using the same adapter.
`The antennas 21 and 22 can be positioned to allow the
`access point 10 to implement an antenna diversity scheme 55
`which will help reduce the negative effects caused by
`multipath interference. Antenna diversity can be accom(cid:173)
`plished in various ways. For example, the antennas can be
`placed sufficiently far apart, typically greater than a quarter
`wavelength apart, or the antennas can be positioned at a 90 60
`degree angle with respect to each other to create a polar(cid:173)
`ization antenna diversity scheme.
`With an antenna diversity scheme in place, the signal from
`a wireless computer device will be received differently on
`each antenna due to multipath signal propagation. Therefore, 65
`each wireless adapter may receive a signal of a different
`quality. The CPU processor 13 can choose which wireless
`
`6
`adapter to use based upon the quality of the received signal.
`Each wireless adapter includes the capability of measuring
`signal quality and only good messages will be forwarded on
`to the CPU processor 13. The quality can be appended to the
`5 message or can be presented to the CPU in a memory
`register.
`Referring now to FIG. 2, another high reliability access
`point 20 built in accordance with the present invention is
`shown. In this embodiment, in addition to having an antenna
`diversity scheme at the access point level, there is an antenna
`diversity scheme at the wireless adapter level. Each wireless
`adapter 15 and 16 includes at least two antennas 21 and 23,
`22 and 24, respectively positioned to create an antenna
`diversity scheme. Thus for the wireless adapter 15 the
`15 antennas 21 and 23 are either positioned sufficiently far
`apart, more than a quarter wavelength, or the antennas 21
`and 23 are positioned in an asymmetrical or orthogonal
`manner to provide polarization diversity. The antennas 22
`and 24 for the wireless adapter 26 are placed in a similar
`20 manner.
`In this embodiment, an incoming signal is received on
`both antennas 21 and 23 of the wireless adapter 15. The
`MAC processor 19 then determines the quality if the signal
`coming in on each of the antennas 21 and 23 connected to
`the wireless adapter 15. Based upon the signal quality
`information, the MAC processor 19 will choose which of the
`antennas 21 and 23 to use to receive the incoming trans(cid:173)
`mission. The MAC processor will also forward the signal
`quality information regarding the selected antenna to the
`CPU processor 13. The wireless adapter 16 will perform a
`similar process and forward the signal quality information
`for its best antenna to the CPU processor 13. The CPU
`processor 13 can then determine which wireless adapter is
`receiving the highest quality signal and use that wireless
`adapter to receive the incoming transmission and respond to
`the transmitting station.
`When a high reliability access point wishes to transmit a
`message, such as an acknowledgment of a received message