I IIIII IIIIIIII Ill lllll lllll lllll lllll lllll lllll lllll lllll 111111111111111111
`US007039358Bl
`
`c12) United States Patent
`Shellhammer et al.
`
`(IO) Patent No.:
`(45) Date of Patent:
`
`US 7,039,358 Bl
`May 2, 2006
`
`(75)
`
`(54) COEXISTENCE TECHNIQUES IN WIRELESS
`NETWORKS
`Inventors: Stephen J. Shellhammer, Lake Grove,
`NY (US); Jacob Sharony, Dix Hills,
`NY (US); Anthony D. Binso, South
`Setauket, NY (US); Sean A. Connolly,
`Stony Brook, NY (US); William
`Sackett, Rocky Point, NY (US); Joseph
`Cabana, Centereach, NY (US); Patrick
`Tilley, Coram, NY (US); Robert
`Beach, Los Altos, CA (US)
`(73) Assignee: Symbol Technologies, Inc., Holtsville,
`NY (US)
`
`( *) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 499 days.
`
`(21) Appl. No.: 09/714,803
`
`(22) Filed:
`
`Nov. 16, 2000
`
`Related U.S. Application Data
`
`(60) Provisional application No. 60/175,262, filed on Jan.
`10, 2000, provisional application No. 60/196,979,
`filed on Apr. 13, 2000.
`
`(51)
`
`Int. Cl.
`H04B 7100
`(2006.01)
`(52) U.S. Cl. ................................... 455/41.2; 455/426.1
`(58) Field of Classification Search ...... 455/41.1-41.3,
`455/561, 414.1, 414.4, 454, 462, 463, 554.1,
`455/554.2, 552.1, 426.1, 426.2, 435.1-435.3,
`455/448, 450,466,560,556.1, 90.1; 343/701,
`343/702
`See application file for complete search history.
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`5,610,386 A * 3/1997 Ball et al ............... 235/462.44
`
`6,023,241 A *
`6,047,165 A *
`6,326,926 Bl *
`6,377,608 Bl*
`6,414,643 Bl*
`6,452,910 Bl *
`6,477,378 Bl*
`6,526,264 Bl *
`6,529,584 Bl *
`6,531,985 Bl*
`6,560,443 Bl *
`
`2/2000 Clapper ................. 342/357.13
`4/2000 Wright et al. .............. 455/66.1
`12/2001 Shoobridge et al.
`........ 343/702
`4/2002 Zyren ......................... 375/132
`7 /2002 Cheng et al.
`............... 343/702
`9/2002 Vij et al ..................... 370/310
`11/2002 Halminen ................... 455/450
`2/2003 Sugar et al ................... 455/84
`3/2003 Ravago et al .............. 379/67.1
`3/2003 Jones et al. ................. 343/702
`5/2003 Vaisanen et al. .............. 455/73
`
`EP
`
`FOREIGN PATENT DOCUMENTS
`* 7/2001
`
`1119137
`
`* cited by examiner
`
`Primary Examiner---Charles Craver
`(74) Attorney, Agent, or Firm-Baker Botts LLP
`
`(57)
`
`ABSTRACT
`
`Techniques are provided for frequency coordination among
`two different wireless network protocols, such as the IEEE
`802.11 and Bluetooth protocols, operating in proximity with
`one another. Coordination is accomplished by the use of a
`first radio transceiver operating in accordance with a first
`communication protocol ( which may be the 802 .11 protocol)
`and using a frequency band (which may be the 2.4 GHz
`band), a base station connected to a wired network and
`operating in accordance with the first communication pro(cid:173)
`tocol, a second radio transceiver operating in accordance
`with a second communication protocol (which may be the
`Bluetooth protocol) and using the frequency band, and a
`coordinator associated with the base station for, in tum,
`activating the first radio transceiver, deactivating the first
`radio transceiver, activating the second radio transceiver,
`and deactivating the second radio transceiver.
`
`31 Claims, 4 Drawing Sheets
`
`CPU
`
`12
`
`20
`80
`
`120
`
`280 7 ::- ~ ) 6 0
`......... _...., _---'>-~y",10
`230 reil
`-
`MU1
`1 - - - -1 · - ~ - - ~
`--- ~)
`190
`.,,,--~ 290
`I /
`290
`--..,,,,,
`/ 250 ~ BT
`' (
`
`60
`
`70
`
`t
`100
`
`140
`I
`
`~ o ? - - ~ 1 0 0
`
`---- -----
`
`10
`
`50
`
`9 0 ~ - - -- ~S2A 200
`- -7
`BT
`S28
`_ 260
`
`/
`
`150
`
`t
`110
`
`\21~-... ~T
`"" ---- -----
`
`S2C
`
`210
`
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`
`

`

`U.S. Patent
`
`May 2, 2006
`
`Sheet 1 of 4
`
`US 7,039,358 Bl
`
`1
`100
`
`~o ,,>- -~ , e o
`'--.. _____.-,
`190
`,,,,,-- -------
`
`290
`
`2807' :0 ~;o
`,20
`...-.-.....r _ ~ _,,. '>- ~ '\ \
`_,,.,110
`230 IBTl~
`_,,.
`t - - - - f f - _L_ - ~
`---
`f!TI)
`~ _ _....
`.,,- --
`..,.....__
`
`/ 250~
`
`200
`
`BT
`t-----a-- - - - 7
`BTM2 , __
`..... 260
`S2B
`)
`150 1
`\ 210?'- --. ~T
`210
`S2C
`110
`"' '--.. _____.
`
`12
`
`CPU
`
`10
`
`40
`
`AP
`
`AP
`
`60
`
`30
`
`70
`
`90
`
`FIG. 1
`
`50
`
`90
`
`FIG. 2
`
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`
`

`

`U.S. Patent
`
`May 2, 2006
`
`Sheet 2 of 4
`
`US 7,039,358 Bl
`
`300
`
`T
`
`320\
`
`t nav
`
`<1111
`
`~ 340
`
`330
`\
`
`_..
`
`t 802.11cam
`
`350
`
`120--........__
`
`MU J~
`140 "'-. MU 2 '
`--:,:
`20 -
`--.. AP 1
`130 - --.,,BTM 1
`280 160-....._ BTS
`1A
`170 "'-. BTS
`1B
`150 -
`--.,, BT M2
`190 "'-. BTS
`2A
`200-....._BTS 28
`
`290
`
`....
`r I ., ~
`CS r-
`lr-:::1"" 360)...,
`f
`..J. ~
`., n
`
`380\
`
`\
`1 r
`
`n
`,,
`
`.~
`
`I r-::r' 370 ~
`
`t
`,, r,
`
`FIG. 3
`
`,....,.. __ .... ___ .,._.
`
`/470
`
`.,.. __ __,_ _____ _.,._.
`
`/480
`
`...
`
`t 802.11
`
`400
`
`t BT
`410
`
`/490
`
`t 802.11
`
`460
`
`20
`"'-. AP1
`120-....... - - - - -~ ........ -,.._.,.......,...."""" _ _ _ _ _ _ _ _ ....,.,........,.,.._,.__
`130
`MU .... 1 _ _._."""'""' _ _ ...._ _ _ _ .__ _ _ _ _ _ _ _ ......, ..... _ _ _
`~ BTM1
`--~------+-..._.._..~ ..... -+"1 ...... """*"---+Z------
`160
`170 "'-. BTS_1_A_-+-------+----"-......,..,....--i--+----+------
`150 '-- BTS~1!!_B_-1------+:.:::...::::::::::==:1::::t.....J. _ __J. _ _ _ _
`"'-. BTM2
`190 - - - - - - - - - - - - - -~ - - . , - -..... ~ - - - - - - - -
`200
`BTS_2_A _ _ _ _ _ _ _ _ _ _._.......,""""""...._~....,.__._ _ _ _ _ _ __
`-....._ BTS2B
`
`280
`
`290
`
`FIG. 4
`
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`

`

`U.S. Patent
`
`May 2, 2006
`
`Sheet 3 of 4
`
`US 7,039,358 Bl
`
`T(f(n-2))
`
`R(f(n-1))
`
`T(f(n))
`
`R(f(n+1)) T(f(n+2))
`
`tuning
`
`80 usec
`
`60 usec
`
`80 usec
`
`Clear Channel
`Assessment using RSSI
`
`tune to f(n+1)
`
`FIG. 5
`
`502
`
`------------
`
`504
`
`506
`
`508
`
`510
`
`FIG. 6
`
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`

`U.S. Patent
`
`May 2, 2006
`
`Sheet 4 of 4
`
`US 7,039,358 Bl
`
`210
`
`MU
`
`110
`
`FIG. 7
`
`524
`
`522
`
`526
`
`530
`
`528
`
`t - - - - - a COMP/
`PACKET
`
`RF
`
`532
`
`FIG. 8
`
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`

`US 7,039,358 Bl
`
`1
`COEXISTENCE TECHNIQUES IN WIRELESS
`NETWORKS
`
`BACKGROUND OF THE INVENTION
`
`This application claims the benefit of provisional appli(cid:173)
`cation Ser. No. 60/175,262, filed Jan. 10, 2000 and Ser. No.
`60/196,979, filed Apr. 13, 2000. This invention relates to
`wireless data communications networks, and in particular to
`arrangements for ensuring coexistence between wireless
`networks that share the same frequency band with different
`operating protocols.
`Wireless devices communicate with one another using
`agreed-upon protocols that are transmitted in predefined
`frequency bands. Often, devices using one or more wireless
`protocols may operate by transmission within the same
`frequency band. lt is therefore necessary to develop coor(cid:173)
`dination techniques in order for devices using one or more
`wireless protocols to efficiently operate in the same band of
`frequencies at the same time.
`For example, the assignee of the present invention sup(cid:173)
`plies wireless data communications systems known as the
`Spectrum 24® System that follows the communications
`protocol oflEEE 802.11 Standard (802.11), which is hereby
`incorporated by reference. ln the system as implemented,
`mobile units (MUs) are in data communication with a
`central computer through one or more access points (APs).
`The APs may communicate with a computer directly or over
`an Ethernet wired network. Each of the MU s associates itself
`with one of the APs. As defined in 802.11, this communi(cid:173)
`cations protocol uses the 2.4 GHz ISM frequency band.
`As currently designed, 802.11 devices may use several
`predefined methods for transmission within the 2.4 GHz
`band to perform as a wireless local area network. One
`method is to use a frequency hopping spread spectrum
`(FHSS) mechanism wherein data is transmitted for a certain
`period of time in a particular channel and, following a
`pseudorandom sequence, continues transmission at a differ(cid:173)
`ent channel for the same predetermined length of time. As
`currently designed, 802.11 devices operate at a frequency
`hopping rate of 10 hops/second. Another method is to use a
`direct sequence spread spectrum (DSSS) mechanism
`wherein the data is transmitted in a predetermined frequency
`channel and is multiplied by a pseudorandom chipping
`sequence during transmission.
`As all 802.11 devices use the same ISM frequency band,
`interference among these devices is minimized by use of a
`Carrier Sense MultipleAccess/CollisionAvoidance (CSMA/
`CA) protocol. Under CSMA/CA, an 8021.11 device listens
`for another's devices transmission prior to initiating its own 50
`transmission. lf no other transmission is detected, the device
`transmits its information and waits for an acknowledgment
`(ACK) from the receiving device. lf no acknowledgment of
`receipt is received after a pre-determined time interval, the
`device will retransmit after waiting for a randomly chosen 55
`interval of time. Thus, if two or more devices began trans(cid:173)
`mitting coincidentally at the same time and the resulting
`interference blocks all of the transmissions, each device will
`wait a random amount of time to attempt a retransmission.
`This allows the devices to transmit at different times.
`Another example of a wireless specification that also uses
`the 2.4 GHz ISM frequency band is Bluetooth™, which is
`designed for communication among devices within a short
`range transmitting at a lower power level. The Bluetooth
`specification, version 1.1, which would be known to one of 65
`ordinary skill in the art, is fully incorporated herein by
`reference. As currently designed, Bluetooth operates using a
`
`2
`frequency hopping spread spectrum mechanism at a rate of
`1600 hops/second. Bluetooth uses a master/slave system of
`communication. One example of a Bluetooth network may
`be a mobile device attached to the user's belt that commu-
`5 nicates with a cordless scanner for reading bar codes and
`worn by the user as a ring. ln this case, the mobile device
`would operate as the master and the cordless ring scanner
`would operate as the slave. ln this system for data trans(cid:173)
`mission, the master and slave only communicate at pre-
`10 defined intervals. At the first interval, the master may
`communicate to a first slave device, which may only respond
`during the second interval. At the third interval, a master
`may communicate to a second slave device, which may only
`respond during a fourth interval. By using this system, it is
`15 ensured that only one device within a particular Bluetooth
`"piconet" is transmitting at any particular time. Thus, inter(cid:173)
`ference is minimized.
`Additionally, it is desirable for one Bluetooth piconet to
`operate in close proximity with another, separate Bluetooth
`20 piconet. Because there are 79 different frequency channels
`used by Bluetooth, different Bluetooth networks are unlikely
`to be operating on the same frequency at the same time.
`Interference between the separate Bluetooth piconets is thus
`minimized. This allows, for example, multiple individuals
`25 working in close proximity with one another to each have his
`or her own mobile unit along with a cordless ring scanner.
`Along with the need to operate multiple networks of the
`same protocol in close proximity, there is also a recognized
`need in the art to coordinate the transmissions of devices
`30 operating under different protocols that use the same fre(cid:173)
`quency band. For example, it may be desirable to use a
`cordless ring scanner that communicates with belt-mounted
`terminal using the Bluetooth protocol while the same belt
`mounted terminal communicates with an access point using
`35 the 802.11 protocol. For example, once the user scans a bar
`code using the cordless ring scanner, the bar code informa(cid:173)
`tion may be sent to the belt-mounted terminal. That bar code
`information may then be transmitted to the 802.11 AP. Then
`an acknowledgment, and possibly a message, may need to
`40 be sent from the AP back to the belt-mounted terminal. The
`terminal may also need to communicate with other Blue(cid:173)
`tooth enabled peripherals like a printer or a headset.
`Although communication protocols such as 802.11 and
`Bluetooth are designed to ensure that devices using the same
`45 protocol may operate in the same frequency band with a
`minimum of interference, there has heretofore been no
`method of coordination for the use of these wireless devices
`in the same frequency operating under different communi-
`cation protocols.
`lt is additionally desirable to provide voice service using
`the Bluetooth communications protocol, for example,
`between a belt-mounted terminal and a headset worn by the
`user. Bluetooth supports voice communications using Syn(cid:173)
`chronous Connection Oriented (SCO) voice packets which
`are transmitted every 3.75 ms. The requirement for such
`frequent Bluetooth packet transmission makes it difficult to
`coordinate voice transmission using the Bluetooth SCO
`packets with 802.11 communications.
`lt is therefore an object of this invention to utilize coor-
`60 dination techniques to ensure that, for example, both Blue(cid:173)
`tooth and 802.11 enabled devices, may operate robustly in
`the same frequency band at the same time.
`
`SUMMARY OF THE INVENTION
`
`An embodiment of the present invention includes a first
`radio transceiver operating in accordance with a first com-
`
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`

`US 7,039,358 Bl
`
`25
`
`4
`3
`munication protocol (which may be the 802.11 protocol) and
`access point according to the first wireless protocol. Global
`using a frequency band (which may be the 2.4 GHz ISM
`clear to send signals are transmitted from the access point
`according to the first wireless protocol, whereby the global
`band), a base station operating in accordance with the first
`clear to send signals prevent mobile units from transmitting
`communication protocol, a second radio transceiver operat(cid:173)
`signals using the first data communications protocol during
`ing in accordance with a second communication protocol 5
`(which may be the Bluetooth protocol) and using the fre(cid:173)
`an allocated time interval within the beacon signal period.
`quency band, and a coordinator associated with the base
`The access point is controlled to avoid transmissions during
`station for, in tum, activating the first radio transceiver,
`the allocated time interval, and the mobile unit is operated
`deactivating the first radio transceiver, activating the second
`in response to the global clear to send signal to conduct
`radio transceiver, and deactivating the second radio trans- 10
`wireless communications acting as a master unit using the
`ce1ver.
`second wireless protocol during the allocated time interval.
`The first radio transceiver and the second radio trans(cid:173)
`In one embodiment, the beacon signal period is divided
`ceiver may be mounted together in a housing, which may be
`into three time intervals, wherein the access point conducts
`suitable for wearing on a belt or a laptop computer or a PDA.
`power saving mode data communications during a first time
`15 interval, wherein the access point conducts data communi(cid:173)
`One or more slave devices may be associated with the
`cations using the second communications protocol during
`second transceiver and operate in accordance with the
`the second time interval and wherein the access point
`second communication protocol. The slave devices may
`conducts data communications using the first wireless pro(cid:173)
`include a scanner, worn on a user's finger and capable of
`tocol during a third time interval. The first time interval may
`transmitting bar code information to the second transceiver,
`the beacon signal. In another
`20 immediately following
`a printer, or a personal data managing device.
`embodiment, the first time interval may not be utilized.
`In one arrangement wherein the first and second trans(cid:173)
`In accordance with another aspect of the invention, there
`ceivers are mounted together in a housing, they may include
`is provided a method of operating a data communications
`orthogonally polarized antennas. In another arrangement a
`system using a master-slave protocol (such a Bluetooth),
`Bluetooth protocol transceiver transmits at power level of
`wherein a master transceiver transmits to slave units during
`about O dBm. In still another arrangement, two or more sub
`first even time slots and wherein slave units transmit to the
`bands within the frequency band are provided and the 802.11
`master unit during odd time slots, and wherein the trans(cid:173)
`protocol transceiver uses one of the two or more sub-bands
`missions follow a predetermined frequency hop pattern at a
`and the Bluetooth protocol transceiver uses another of the
`hop rate corresponding to the time slots. The master unit is
`two or more sub-bands. In still another arrangement in the
`operated during a first time period of each time slot to detect
`second radio transceiver is equipped with a look-ahead
`30 interfering signals at a frequency corresponding to the
`function for determining whether two or more sub-bands are
`following time slot. Transmission by the master transceiver
`being used by the first radio transceiver that will also be used
`is inhibited during even time slots if interfering signals have
`by the second transceiver. In still another arrangement, a
`been detected during either of the current or previous time
`coordinator is associated with the first radio transceiver for
`slots.
`deactivating the second radio transceiver while the first radio 35
`In a preferred practice, the operating step includes tuning
`transceiver is in use.
`the master unit to receive signals corresponding to the
`According to the invention, there is provided a method for
`frequency allocated to the next following time slot; detecting
`operating a portable data communications device using first
`the strength of signals received and retuning the master unit
`and second wireless data communications protocol. The data
`to send or receive signals corresponding to the frequency
`communications device is operated in a power saving mode 40 allocated to the current time slot.
`of the first communication protocol, whereby the device has
`In another aspect of the invention, there is provided a
`method for providing voice communications in a wireless
`active time periods for transmitting and receiving data
`data communications system having a mobile unit arranged
`communications signals using the first communications pro(cid:173)
`to communicate with an access point using a first data
`tocol and dormant time periods during which the device
`communications protocol (such as 802.11) and arranged to
`neither transmits nor receives data communications signals 45
`communicate with other devices using a second data com(cid:173)
`using the first protocol. The data communications device is
`munications protocol (such as Bluetooth). Data correspond(cid:173)
`operated as a master device according to the second com(cid:173)
`ing to the voice communication is communicated between
`munications protocol whereby the data communication
`the access point and the mobile unit using the first data
`device controls operation of slave devices communicating
`communications protocol. The data corresponding to the
`therewith. The operation according to the second data com- 50
`voice communications is communicated between the mobile
`munications protocol is controlled to operate only during the
`unit and a portable device using the second data communi(cid:173)
`dormant time periods of the first protocols.
`cation protocol. The communication is arranged at time
`In one embodiment, a signal indicating that the active
`intervals which avoid interference with the communicating
`time period will commence following a predetermined time
`using the first data communications protocol. Voice signals
`interval is provided to terminate operation according to the 55
`are converted to data corresponding to the voice signals and
`second data communication protocol during the predeter(cid:173)
`data signals corresponding to voice signal are converted into
`mined time interval. The first wireless data communications
`voice signals in the portable device.
`protocol may be the 802.11 protocol. The second wireless
`In a preferred arrangement, the data corresponding to
`communication protocol may be Bluetooth.
`voice signals comprises compressed voice signal data. The
`In another aspect of the invention, there is provided a 60
`communication between the mobile unit and the portable
`method for operating a wireless data communications sys(cid:173)
`device preferably uses a Bluetooth ACL link.
`tem having an access point and at least one mobile unit
`According to a further aspect of the invention, there is
`associated with said access point using a first wireless
`provided a method for operating a mobile unit arranged to
`protocol (which may be 802.11), wherein said mobile unit is
`communicate using first and second data communication
`arranged to conduct wireless data communications with 65
`protocols operating in the same frequency band (such as
`other units using a second wireless protocol (which may be
`802.11 and Bluetooth) wherein the mobile unit associates
`Bluetooth). Periodic beacon signals are transmitted from the
`with an access point and receives therefrom beacon signals
`
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`

`US 7,039,358 Bl
`
`5
`demarcating time intervals according to the first communi(cid:173)
`cations protocol. Signals are received from the access point
`(such as CTS signals) designating a portion of one of the
`time intervals during which mobile units associated with the
`access point refrain from transmissions using said first data
`communications protocol. The mobile unit is operated as a
`master unit using the second data communications protocol
`to communicate with slave units during the designated
`portion of the time interval.
`According to a further aspect of the invention, there is
`provided a method for operating a wireless data communi(cid:173)
`cations network having at least one access point and at least
`one mobile unit, including a mobile unit arranged to com(cid:173)
`municate with the access point using a first wireless data
`communication protocol (such as 802.11) in a first frequency
`band and to communicate with other devices using a second
`wireless data communication protocol (such as Bluetooth) in
`the first frequency band. Signals (such as CTS) as sent from
`the access point in the first communications protocol, which
`designate a time period wherein mobile units associated with
`the access point refrain from transmitting using the first data
`communications protocol. The mobile units operate as a
`master unit to conduct wireless data communications with
`the other devices operating as slave units using the second
`data communications protocol during the designated time
`period.
`According to still another aspect of the invention, a
`method is provided for operating a mobile unit arranged to
`communicate using first and second data communications
`protocols operating in the same frequency band (such as 30
`802.11 and Bluetooth), wherein the mobile unit associates
`with an access point. The mobile unit receives first and
`second control signals using the first data communications
`protocol. The mobile units are operated in response to the
`first control signals to act as a master unit and conduct data 35
`communications with slave units using the second data
`communications protocol. Communications by the mobile
`unit using the second data communications protocol 1s
`discontinued in response to the second control signal.
`
`20
`
`25
`
`6
`multiple access points connected to a CPU 12 is a typical
`installation, the system may use a single computer and single
`AP. Each AP contains apparatus 60, 70 for the transmission
`and reception of radio frequency (RF) signals under the
`5 802.11 protocol. Also using the 802.11 protocol, a plurality
`of radio transceivers or mobile units (MUs) 120, 140 com(cid:173)
`municate using apparatus 80, 90 for the transmission and
`reception of RF signals. Each MU 120, 140 may also be
`associated with a radio transceiver which is a Bluetooth
`10 Master (BTM) device 130, 150, which together make up a
`dual mode devices 100, 110. The association between the
`MU and BTM may be, for example, by way of being
`physically housed in the same unit. An example of a dual
`mode device 100, 110 may be portable terminal worn on a
`15 belt.
`Each BTM 130, 150 communicates with one or more
`Bluetooth Slave (BTS) devices 160, 170, 180, 190, 200, 210
`via the Bluetooth protocol. The Bluetooth protocol is estab(cid:173)
`lished such that each BTS is uniquely associated with a
`BTM. Thus, as illustrated, BTSlA 160, BTSlB 170, and
`BTSlC 180 communicate using RF signals 220, 230, 240
`only with BTMl 130. This forms a piconet 280. Corre(cid:173)
`spondingly, BTS2A 190, BTS2B 200, and BTS2C 210
`communicate using RF signals 250, 260, 270 with BTM2
`150. This forms a piconet 290. An example of a BTS may
`be a cordless ring scanner, a printer, or personal data
`managing device.
`With no coordination, there will be times when the BTM
`130, 150 and the associated MU 120, 140 attempt to operate
`at the exact same time. Since the two devices operate in the
`same 2.4 GHz ISM frequency band the BTM 130, 150 and
`the MU 120, 140 may severely interfere with one another,
`especially if they are housed in a dual mode device 100, 110.
`Therefore, there is a need for coordination between the two
`devices. One such coordination scheme is primarily based
`on time multiplexing of the 802.11 and BT radios, which is
`especially suitable for a controlled environment ( e.g., the
`802.11 and BT radios are housed in the same terminal or
`40 dual mode device). ln one embodiment, the Bluetooth
`systems are enabled or disabled according to a global/central
`signal from the 802.11 AP as described herein. The central
`signal may also be coordinated among the two devices
`without coordinating with the AP.
`ln a further embodiment, the dual mode devices 100, 110
`may be designed such that the 802.11 antennas 80, 90 have
`orthogonal polarization with respect to the Bluetooth anten(cid:173)
`nas used to generate RF signals 220, 230, 240, 250, 260,
`270. This technique may provide additional protection from
`802.11 Bluetooth interference and does not require the need
`for centralized control.
`FIG. 6 shows one example of orthogonally polarized
`antennas that can be used to reduce interference. The
`antenna structure of FIG. 6 includes a vertically polarized
`monopole antenna 502, which is connected to a transmitter/
`receiver by an unbalanced transmission line 510. The struc-
`ture also includes a horizontally polarized dipole antenna
`having dipole arms 504, 506 which are connected to a
`transmitter/receiver by balanced transmission line 508.
`60 Those skilled in the art will recognize that many other
`orthogonal-polarized antenna configurations may be used. ln
`a further embodiment, the BTMs 130, 150 may be designed
`to transmit at a relatively low power level such as lower than
`0 dBm. This technique may provide additional protection
`65 from 802.11 Bluetooth interference and may be used with
`other antenna or frequency coordination methods discussed
`herein.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a block diagram of a wireless communications
`system using 802.11 and Bluetooth devices.
`FIG. 2 is a block diagram of a wireless communications 45
`system using 802.11 and Bluetooth devices at the same time
`along with a connect button switch and connected indica(cid:173)
`tors.
`FIG. 3 is a schematic diagram of an embodiment of the
`present invention illustrating a coordinated time line 50
`between the operation of 802.11 and Bluetooth devices.
`FIG. 4 is a schematic diagram of an embodiment of the
`present invention illustrating another coordinated time line
`between the operation of 802.11 and Bluetooth devices.
`FIG. 5 is a diagram showing a modified Bluetooth aper- 55
`ating method for avoiding interference.
`FIG. 6 is a drawing showing one example of orthogonally
`polarized antennas.
`FIG. 7 is a drawing of a wireless headset arranged for
`voice communications.
`FIG. 8 is a block diagram of the headset of FIG. 7.
`
`DESCRIPTION OF THE INVENTION
`
`Turning to FIG. 1, shown are a plurality of base stations
`or Access Points (APs) 20, 30 that are physically connected
`40, 50 to a wired network 10. While a wired network with
`
`Marvell Semiconductor, Inc. - Ex. 1005, Page 0008
`IPR2019-01349 (Marvell Semiconductor, Inc. v. Uniloc 2017 LLC)
`
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`US 7,039,358 Bl
`
`7
`ln a further embodiment, the 802.11 APs 20, 30 and MUs
`120, 140 may be designed to operate in one portion of the
`2.4 GHz spectrum, while the BTMs 130, 150 and BTSs 160,
`170, 180, 190, 200, 210 may be designed to operate in
`another portion of the 2.4 GHz spectrum.
`ln a further embodiment, the BTMs 130, 150 may be
`equipped with a look-ahead function to determine which
`frequencies within the 2.4 GHz band will be used for two or
`more future Bluetooth frequency hops to occur. lf the BTM
`130, 150 determines that one of the next two or more
`frequency hops will use the same frequency that the 802.11
`system is using, the BTMs 130, 150 will blank their output,
`thus reducing the effect of the interference on the 802.11
`transmissions. By using this method, interference between
`Bluetooth and 802.11 could be reduced or eliminated at the 15
`expense of dropping a couple of packets when channel
`overlap occurs. This approach may also be expanded to
`include the blanking of adjacent channels that may also
`interfere with the 802.11 transmissions.
`Bluetooth uses a Frequency Hopping Spread Spectrum
`(FHSS) radio, which hops much faster than most IEEE
`802.11 radios. Bluetooth sends a short packet as it dwells on
`a given frequency. Most IEEE 802.11 radios hop much
`slower and send much longer packets. Also there are ver(cid:173)
`sions of IEEE 802.11 WLANs that use Direct Sequence
`Spread Spectrum (DSSS) which do not hop and occupy a
`wide band.
`As a result, during the transmission of an IEEE 802.11
`packet the Bluetooth radio hops across many frequencies
`and potentially sends a packet on each frequency. These
`Bluetooth packets can interfere with the IEEE 802.11 pack(cid:173)
`ets and cause the IEEE 802.11 packet to be in error. The
`IEEE 802.11 packet needs to be retransmitted, and once
`again may be destroyed by the signal from the Bluetooth
`radio.
`This technique shown in FIG. 5 can be used in any
`Bluetooth radio and in any device that will operate in an
`IEEE 802.11 WLAN environment. Since it detects devices
`radiating in the 2.4 GHz ISM band it could also be used to
`prevent interference with other devices in that band.
`A Bluetooth network consists of up to eight Bluetooth
`devices operating in a piconet. The piconet has one master
`and up to seven slaves. All the Bluetooth devices in the
`piconet hop in unison, at a rate of 1600 hops/second. The
`time that the frequency hopper dwells on a given frequency
`is called the slot time. At this hop rate the slot time is 625
`microseconds. Typically packets are completed within one
`slot time, however, it is also possible to have 3 and 5 slot
`packets. The master and the slaves take turns transmitting,
`with the master transmitting on even slots and the slaves
`transmitting on odd slots. See also Bluetooth Specification,
`version 1.0, Dec. 1, 1999, which is hereby incorporated by
`reference in full.
`There are two types of links between the master and each
`of the slave devices in a Bluetooth piconet. There is an
`asynchronous connection-less link (ACL) which is used to
`transfer data. There is also a synchronous connection ori(cid:173)
`ented link (SCO) that is used to transfer voice data. The
`master in the picolink determines when data on an ACL link
`is transferred. Data is transferred when the master has data
`to send to a slave or the master wants to receive data from