US 6,600,734 B1
`(10) Patent No.:
`a2) United States Patent
`Gernert et al.
`(45) Date of Patent:
`Jul. 29, 2003
`
`
`US006600734B1
`
`(54) APPARATUS FOR INTERFACING A
`WIRELESS LOCAL NETWORK AND A
`WIRED VOICE TELECOMMUNICATIONS
`SYSTEM
`
`(75)
`
`Inventors: Alex Gernert, Cupertino, CA (US);
`Sarosh Vesuna, Los Altos, CA (US);
`David Goren, Smithtown, NY (US)
`
`(73) Assignee: Symbol Technologies, Inc., Holtsville,
`NY (US)
`
`(*) Notice:
`
`Subject to any disclaimer, the term ofthis
`patent is extended or adjusted under 35
`US.C. 154(b) by 0 days.
`
`(21) Appl. No.: 09/213,958
`(22)
`Filed:
`Dec. 17, 1998
`°
`(SL) Ute C0 eee eecessesscsseeseesseseeneeneeneens HO4L 12/66
`
`.. 370/352; 370/328; 455/403
`(52) U.S. Cl.
`(58) Field of Search 0.00.00. 370/312, 313,
`370/328, 401, 329, 349, 352-358; 455/432,
`403, 425, 550, 575
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`6,259,898 B1 *
`7/2001 Lewis oo... eeeeeeeeeeee 455/103
`
`6,298,062 B1 * 10/2001 Gardell et al.
`6,330,244 B1 * 12/2001 Swartz et al... 370/401
`.
`eos
`cited by examiner
`Primary Examiner—Wellington Chin
`Assistant Examiner—Brenda Pham
`
`(57)
`
`ABSTRACT
`
`An apparatus for interfacing a wireless local area network
`with a wide area, cellular or public switched telephone
`network including the function of a wireless LAN base
`station or access point, and a gateway. The interface may
`contain one or more different types of gateways, including
`a PSTN voice gateway, an analog modem gateway, and
`others. The apparatus may also include a well designed to
`receive the handset or mobile computer device to recharge
`the battery as well as to automatically transfer data when the
`phone or device is secured in the well.
`
`11 Claims, 7 Drawing Sheets
`
`200
`
`HOST
`
`|I
`I
`
`
`115
`
`400
`a)
`
`oo BASE] + BASE|BRIDGE 60
`ss STATION] = STATION
`
`
`
`100 COMPUTER
`
`"
`
`ROUTER
`
`pa |IL
`'
`13
`
`
`BASE |...|BASE BASE|BRIDGE 50
`STATION
`STATION
`STATION
`
`12
`
`AN pS fe
`
`15
`
`15
`
`15
`
`1
`
`SAMSUNG 1038
`
`1
`
`SAMSUNG 1038
`
`

`

`U.S. Patent
`
`Jul. 29, 2003
`
`Sheet 1 of 7
`
`US 6,600,734 B1
`
`Gll
`
`Yalow
`
`GG
`
`Os
`
`00F
`
`1SOH
`
`Looe
`
`NOLLWLS
`
`—_s—~*~__[NOLVISsa
`
`—_,‘asaLs
`
`==
`ee
`09300INa|ASV
`OS3900INa|JSvd
`iWaLNdWODLoo)
`SlSl
`Ol1SOH
`
`NOUWIS],,,[NOLVIS
`
`asva3Sve
`
`Sl
`
`él
`
`NOLLVLS
`
`iNiNI
`
`vl
`
`2
`
`
`

`

`US 6,600,734 B1
`
`Sheet 2 of 7
`
`Jul. 29, 2003
`
`U.S. Patent
`
`3
`
`

`

`U.S. Patent
`
`Jul. 29, 2003
`
`Sheet 3 of 7
`
`US 6,600,734 B1
`
`
`
`
`
`YYOMLINAVNGIYSUGHLO
`
`
`
`NOONYS.4d1yaznynod
`
`40NWAOLSit}faomroasin}0g
`
`
`
`wnIgaNNOUVINGONOlUTTBAVENS
`
`LINY3HE
`
`JdONY
`
`JNOHAITAL
`
`ATONaNdOLW300KSO1WNY
`
`
`
`CGHOLIMSAVMALWD
`
`AaniendOL
`
`
`
`YOMIININOHAITL
`
`
`TaraQ3HOIINSIN8NdOL
`SHOUAYMGIVDdlBAOJOI0A
`
`
`
`
`YMOMLNTOMINOD
`
`TeV)01-NOISSINSNYEL
`
`
`
`WIGONNOLA3O34
`
`c)4Y3A30IY
`
`TeV)
`
`W300N
`
`TeV
`
`WIQ0N
`
`YALUASNVUL
`
`YOLVYINAD
`
`
`
`YAGOONIlad
`
`TIGNVIYd
`
`YOIVYINIO
`
`JOYVHIIY
`
`4
`
`
`
`
`
`
`
`

`

`U.S. Patent
`
`Jul. 29, 2003
`
`Sheet 4 of 7
`
`US 6,600,734 B1
`
`HANDSET
`
`TRANSMITTER/
`RECEIVER
`
`166
`
`
`CONTROL
`
`17
`
`5
`
`

`

` i=eBlo|ooce
`
`6
`
`

`

`U.S. Patent
`
`Jul. 29, 2003
`
`Sheet 6 of 7
`
`US 6,600,734 B1
`
`DETECT WHEN USER
`ACTIVATES WIRELESS
`IP PHONE
`
`SEND SIGNAL TO
`WIRELESS IP PHONE
`TO PRODUCE DIAL TONE
`
`200
`
`202
`
`204
`DETECT WHEN
`NUMBERS ARE DIALED|—
`
`206
`
`208
`
`210
`
`STORE DIALED
`NUMBERS IN MEMORY
`
`SEND "RING" MESSAGE
`TO PHONE NUMBER
`STORED IN MEMORY
`
`
`
`PERIODICALLY SEND
`SIGNAL TO WIRELESS
`IP PHONE UNTIL CALL
`IS CONNECTED TO
`PRODUCE “RING” SOUND
`
`
`
`
`
`
`
`
`
`FIG.6
`
`7
`
`

`

`U.S. Patent
`
`Jul. 29, 2003
`
`Sheet 7 of 7
`
`US 6,600,734 B1
`
`
`
`
`
`RECEIVE INCOMING CALL
`WITH "PHONE NUMBER”
`OF RECIPIENT WIRELESS
`IP PHONE
`
`
`
`COMPARE "PHONE
`
`NUMBER” RECEIVED WITH
`
`DIRECTORY OF WIRELESS
`IP PHONES ON THE LAN
`
`
`
`
`
`250
`
`252
`
`256
`
`294
`
`
`IS RECIPIENT
`Yes|CALL WAITING SIGNAL
`WIRELESS IP PHONE
`
`
`GENERATED AT RECIPIENT
`ALREADY IN USE?
`IP PHONE
`
`258
`
`260
`
`
`"RINGING"
`
`SEND SIGNAL TO
`RECIPIENT WIRELESS IP
`PHONE TO ACTIVATE
`
`
`
`
`
`CONNECT CALL WHEN A
`USER ACTIVATES THE
`RECIPIENT WIRELESS
`IP PHONE
`
`FIG.7
`
`8
`
`

`

`US 6,600,734 B1
`
`1
`APPARATUS FOR INTERFACING A
`WIRELESS LOCAL NETWORK AND A
`WIRED VOICE TELECOMMUNICATIONS
`SYSTEM
`
`RELATED APPLICATIONS
`
`This application is related to U.S. patent application Ser.
`No. 08/794,782,filed Feb. 3, 1997.
`This application is also related to U.S. patent application
`Ser. No. 08/906,722,filed Aug. 5, 1997.
`This application is also related to U.S. patent application
`Ser. No. 09/008,710,filed Jan. 16, 1998.
`This application is also related to U.S. patent application
`Ser. No. 09/047,015, filed Mar. 24, 1998.
`Eachof the above applications are expressly incorporated
`herein by reference.
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`The present invention relates to the field of voice com-
`munications over different types of communications net-
`works. Morespecifically, the present invention relates to an
`apparatus whichinterfaces a wireless IP network and a wide
`area network or public switched telephone network (PSTN)
`for voice communications.
`
`2. The Background Art
`Public switched telephone networks have been used for
`manyyears for voice communication. The typical telephone
`converts sound wavesinto analog signals, which are then
`transmitted through the public switched telephone network
`to another telephone, which converts the analog audio
`signals back into sound waves. In recent years, wireless and
`cellular telephones have been rising in popularity, due to
`their mobility. Users are no longer tied to a stationary
`telephone, but are free to carry their telephones with them.
`With the advent of computers and fax machines, there
`arose a need to transmit data in a similar fashion. Due to the
`
`fact that analog telephone lines were already in existence in
`every part of the nation, these lines were also used in the
`transmission of data. Specific protocols were designed, such
`as the V.32 protocol, which specified how digital data is
`encoded into analog signals for transmission over public
`switched telephone networks.
`The apparatus that performs conversion from digital data
`to an analog telephone signal is known as an analog modem.
`Analog modems do not require dedicated or specialized
`lines, as they use pre-existing telephone lines, which are
`already in existence in nearly every homein the country. The
`main drawback, however, is in the relatively low speed of
`transmissions. Current protocols allow only up to about 56
`Kbps to be transmitted through an analog phone line, and
`FCC regulations currently limit this number to 53 Kbps due
`to power output concerns.
`Users whorequire faster transmission speeds have turned
`to carriers which allow digital transmission, which not only
`provide much faster speeds and higher bandwidth, but also
`reduce errors that occur during transmission. Examples of
`such carriers are ISDN lines, T1 and T3 lines, and cable
`lines. ISDN lines are in actuality twisted pair telephone
`lines. While ISDN service allows a user to obtain digital
`transmission without a dedicated or specialized line,
`the
`inherent physical drawbacks of twisted pair lines limits the
`amount of bandwidth and speed of such systems. T1 and T3
`lines are specialized, dedicated lines (T1 lines can carry up
`to 1.544 Mbps while T3 lines can carry up to 44.736 Mbps.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`Cable modemsinterface to coaxial cable lines that are
`typically used for providing cable television signals into
`homesand they provide a large amount of bandwidth. While
`it is generally necessary for the cable provider to upgrade the
`overall cable network system in order to enable Internet
`access through cable modems,it is generally not necessary
`to install new lines into homes.
`Wide Area Networks (WANS) using wireless data com-
`munications techniques and systems have been generally
`available for many years.
`Implementations exist which
`employ microwave radio-frequency (RF) communication
`systems and frequency-modulated (FM) radio communica-
`tions. The data rate is generally up to 19.2 Kbps, which is
`sufficient for the intended class of applications. Frequency-
`modulated communication techniques include both conven-
`tional point-to-point radio and broadcast. These systems
`include RAM Mobile Data Service using the Mobitex pro-
`tocol;
`the Advanced Radio Data Information Service
`(ARDIS), manufactured by ARDIS Company, Lincolnshire,
`Tl; and the Cellular Digital Packet Data (CDPD)service.
`The ARDIS system, for example, uses a dedicated radio
`network which includes a number of radio base stations
`deployed throughout larger metropolitan areas in the United
`States. The remote devices in the field communicated with
`the base stations, and vice versa. The basestations are fixed
`and can cover an approximate radius of 15 to 20 miles when
`transmitting and receiving. The base stations communicate
`with a limited number of radio network controllers located
`at various points throughout the United States. Each radio
`network controller is responsible for maintaining authoriza-
`tion and registration of the remote terminals. The radio
`network controllers are further connected to one of three
`network hubs. The network hubs are connected by dedicated
`leased lines and are accessed by the customer host applica-
`tions to send and receive data to and from the remote
`devices. The customer host applications are also connected
`to the network hubs by dedicated leased line or through a
`value added network VAN).
`Wireless local area networks (LANS)are used in business
`applications such as inventory, price verification mark-
`down,portable point of sale, order entry, shipping, receiving
`and package tracking. Wireless local area networks use
`infrared or radio frequency communications channels to
`communicate between portable or mobile computer units
`and stationary access points or base stations. These access
`points are in turn connected by a wired or wireless commu-
`nication channel to a network infrastructure which connects
`groups of access points together to form a local area
`network, including, optionally, one or more host computer
`systems.
`Wireless infrared and radio frequency (RF) protocols are
`known which support the logical interconnection of portable
`roaming terminals having a variety of types of communica-
`tion capabilities to host computers. The logical interconnec-
`tions are based upon an infrastructure in whichat least some
`each of the remote terminals are capable of communicating
`with at least two of the access points when located within a
`predetermined range therefrom, each terminal unit being
`normally associated with and in communication with a
`single one of such access points. Based on the overall spatial
`layout, response time, and loading requirements of the
`network, different networking schemes and communication
`protocols have been designed so as to most efficiently
`regulate the association of the mobile unit with specific
`access points, and the availability of the communication
`channel to individual mobile units for broadcasting.
`One such protocol is described in U.S. Pat. Nos. 5,029,
`183; 5,142,550; 5,280,498; and 5,668,803 each assigned to
`Symbol Technologies, Inc. and incorporated herein by ref-
`erence.
`
`9
`
`9
`
`

`

`US 6,600,734 B1
`
`3
`is described in U.S. Pat. No.
`Another such protocol
`5,673,031. Still another protocol is set forth in the IEEE
`Standard 802.11 entitled “Wireless LAN Medium Access
`Control (MAC) and Physical Layer (PHY) Specifications”
`available from the IEEE Standards Department, Piscataway,
`N.J. (hereinafter the “TEEE 802.11 Standard”).
`The IEEE 802.11 Standard permits either infrared or RF
`communications, at 1 Mbps and 2 Mbps data rates, a
`medium access technique similar to carrier sense multiple
`access/collision avoidance (CSMA/CA), a power-save mode
`particularly important for battery-operated mobile units,
`seamless roamingin a full cellular network, high throughput
`operation, diverse antennae systems designed to eliminate
`“dead spots”, and an easy interface to existing network
`infrastructures.
`
`The basic specifications for the communicationsof audio,
`video and multimedia that are applicable to the networks
`pertaining to the present
`invention are set forth in the
`International Telecommunications Union Telecommunica-
`tion Standards Sect ITU-T) standards H.320-323.
`The H.321 recommendation relates to asynchronous
`transfer mode (ATM)channels, H.322 to guaranteed Quality
`of Service LANs, and H.323 to packet based systems. Data
`packets are created from a compressed data stream of digital
`voice samples. The data packets are formatted for transmis-
`sion over a data network. Since network latency and packet
`transmission delays can be disastrous to the intelligibility
`and quality of real-time phone conversations, a variety of
`approaches of giving priority of voice packets (or other
`real-time multimedia packets) over data packets in the
`network have been proposed, thus allowing delay-sensitive
`packets to supercede data packets across any network node
`in any traffic situation. The H.323 recommendation also
`provides for call establishment and control, including deter-
`mining the sequencing and timing of establishing and dis-
`connect procedures, as well as the control of the H.323
`session after it is established.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`To the extent the Internet Protocol or “IP”(as set forth in
`IETF RFC 791) is used as the network layer protocol, the
`recommendations of the International Multimedia Telecon-
`
`40
`
`ferencing Consortium’s Voice over IP Forum are also appli-
`cable to such a Voice over IP (“VoIP”) network. In a VoIP
`network, the voice signal is digitized, encapsulated into IP
`packets, and then routed between VoIP capable devices in an
`IP network. These packets of voice may then be delivered in
`real time as voice communications, or stored as voice mail.
`Communications between a LAN and a wide area net-
`work or public switched telephone network are generally
`performed by communications controller known as a gate-
`way. In the H.323 standard, a gateway generally refers to an
`endpoint which provides for real-time, two-way communi-
`cations between H.323 terminals on an IP network and other
`ITU terminals, telephones on a PSTN, and terminals on
`other networks. An example of a gateway is the Cisco 3600
`series of Cisco Systems, Inc. The Cisco 3600 series is a
`modular gateway that can be configured to provide gateway
`functions over a wide variety of communications mediums.
`These include, among others, analog modem access, ISDN
`access, digital modem access, and voice and fax access.
`Other types of interfaces between wired LANs and con-
`nected or switched networks such as frame relay and ATM
`networks are known. For example,
`the ATM Forum has
`developed a bridging implementation agreement called
`LAN Emulation (LANE). LANErelies on a LAN Emulation
`Server (LES), which performs MAC-to-AIM address reso-
`lution; a Broadcast and Unknown Server (BUS), which
`
`45
`
`50
`
`55
`
`60
`
`65
`
`4
`performs data broadcast; and an optional LAN Emulation
`Configuration Server (LECS), which performsinitialization
`and configuration.
`Prior to the present invention, there has not been a simple
`and user-transparent way to interface a wireless LAN with
`the diverse range of currently available public and private
`networks, including the public switched telephone network
`(PTSN), cable networks, wide area networks (WAN), cel-
`lular telephone networks, and satellite communications net-
`works.
`
`REFERENCES
`
`ITU-T Recommendation G.711 (1993) “Pulse Code Modu-
`lation (PCM) OF Voice Frequencies”
`ITU-T Recommendation G.729 (1995) “Coding of Speech
`At 8 kbit/s Using Conjugate-Structure Algebraic-Code-
`Excited Linear-Prediction (CS-ACELP)”
`ITU-T Recommendation H.323 (May, 1996): Visual Tele-
`phone Systems and Equipment for Local Area Networks
`Which Provide a Non-Guaranteed Quality of Service.
`ITU-T Recommendation Q.931 (1993): “Digital Subscriber
`Signaling System No. 1 (DSS 1)-ISDN User-Network
`Interface Layer 3 Specification for Basic Call Control
`IETF RFC 791 “Internet Protocol”. J. Postel. Sep. 1, 1981
`IETF RFC 793 “Transmission Control Protocol’, J. Postel.
`Sep. 1, 1981
`
`BRIEF DESCRIPTION OF THE INVENTION
`
`1. Objects of the Invention
`It is an object of the invention to provide an interface
`between a wireless LAN and a gateway to a voice commu-
`nications network.
`
`It is another object of the present invention to provide an
`apparatus including a base station or access point
`in a
`wireless LAN and a communications gateway to one or
`more different communications channels or networks.
`
`It is still another object of the invention to provide a
`portable wireless desk telephone which communicates with
`one or more stationary base stations using a packet com-
`munications protocol, wherein the base station interfaces to
`a gateway for connection to an IP network, a WAN,or the
`PSTN.
`
`It is a further object of the present invention to provide an
`apparatus which functions as a data downloadingstation for
`a portable computer, pen-like bar code reader, or the like,
`and also transmits the downloaded data to an IP network, a
`WAN or the PSTN.
`
`It is yet another object of the invention to provideinitial-
`ization and authorization of a communications handset in a
`wireless LAN.
`
`It is yet a further object of the present invention to provide
`an end-to-end real time voice channel through wired and
`wireless, and connected and connectionless (packet
`switched) communications channels.
`It is an even further object of the invention to provide a
`method which can be used to accomplish one or more of the
`above objectives.
`Additional objects, advantages and novel features of the
`present invention will become apparent to those skilled in
`the art from this disclosure, including the following detail
`description, as well as by practice of the invention. While the
`invention is described below with reference to preferred
`embodiments, it should be understood that the invention is
`not limited thereto. Those of ordinary skill in the art having
`access to the teachings herein will recognize additional
`10
`
`10
`
`

`

`US 6,600,734 B1
`
`5
`applications, modifications and embodiments in otherfields,
`which are within the scope of the invention as disclosed and
`claimed herein and with respect to which the invention could
`be of significant utility.
`2. Features of the Invention
`
`The present invention provides data communicationsnet-
`work including a plurality of stationary access points and a
`plurality of remote mobile units, the mobile units being
`capable of wirelessly communicating with at least two of the
`access points when located within a predetermined range
`therefrom and being normally associated with and in com-
`munications with a single one of such access points. A
`processoris located at one of the access points for detecting
`a message sent by a first mobile unit and determining from
`the message whetherit is to be routed to another mobile unit
`or over another channel to another type of communication
`station; and a gateway is connected to the access point and
`functions to provide a two-way voice channel of communi-
`cations between the first mobile unit and another commu-
`nication station.
`
`The present invention further provides an integral appa-
`ratus combining the functions of an access point and a
`gateway for interfacing a wireless local area network with a
`wide area network or the public switched telephone net-
`work. The apparatus may contain one or more gateways,
`including a PSTN voice gateway (including xDSL or ISDN
`interfaces), an analog modem gateway, and others such as a
`cable modem for connection to a cable network. The appa-
`ratus may also include an Ethernet port or serial port for
`connection to a wired local area network. The apparatus may
`also include a dockingstation or well designed to receive the
`handset or other portable computer device to recharge the
`battery of the handset or optionally transfer data or control
`information whenthe phoneor device is secured in the well.
`The present invention provides an end-to-end method for
`handling an outgoing call from a caller using a handset in a
`wireless local area network, through other communications
`networks to the called party, including the steps of
`detecting when the user activates the mobile handset to
`make an outgoing call;
`receiving in the mobile handset the identification of the
`destination of the outgoing call from the user;
`transmitting a ring signal to a networkstation correspond-
`ing to said destination, said ring signal designedto alert
`the recipient that a call is attempting to connect; and
`transmitting an acknowledgment signal
`to the mobile
`handset, said acknowledgementsignal designedto alert
`the user that the cell made by the user is attempting to
`connect. The present
`invention further includes the
`steps of receiving in the handset an indication from the
`user of the type of call the user desires to make, and
`determining in the handset whether the user is making
`a network addresscall, an intercom call, or a namecall.
`The present invention further provides a method of oper-
`ating a data communications network including a plurality
`of sets of stationary access points and a gateway connected
`to the access points, and a plurality of remote mobile units,
`the mobile units being capable of wirelessly communicating
`with at least two of the access points when located within a
`predetermined range therefrom. Each mobile unit is nor-
`mally associated with and in communications with a single
`one of such access points, and has a single network address
`that is selectable from a set of network addresses that is
`
`utilized by the mobile unit only while such mobile unit is
`active.
`The method includesthe steps of storing a set of network
`addresses available for use by users in a server computer on
`
`6
`the network; transmitting a network address request to the
`server computer from a first mobile unit; and assigning a
`network address from the set of network addresses available
`
`to said first mobile unit. The method further includes pro-
`viding identification information of the user from said first
`mobile unit to an authentication server; validating the user
`privileges by the authentication server and communicating
`such validation to said first mobile unit; and transmitting the
`network address associated with the user’s mobile unit to the
`
`telephony gateway.
`BRIEF DESCRIPTION OF THE DRAWING
`
`10
`
`FIG. 1 is a diagram illustrating a wireless local area
`network in which the present
`invention may be imple-
`mented.
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`FIG. 2 is a timing diagram showing RF transmission
`versus time for a data transmission sequence.
`FIG. 3 is a block diagram illustrating an apparatus for
`interfacing a wireless local area network and a wide area
`network or public switched telephone network in accordance
`with a first embodiment of the invention.
`
`FIG. 4 is a block diagram illustrating a wireless desk
`phone in accordance with a second embodiment of the
`invention.
`
`FIG. 5 is a block diagram of the protocol stacks that may
`be implemented in the wireless LAN in accordance with the
`invention.
`
`FIG. 6 is a flow diagram illustrating a method for handling
`an outgoing call in a wireless IP phone system according to
`the present invention.
`FIG. 7 is a flow diagram illustrating a method for handling
`an incomingcall in a wireless IP phone system according to
`the present invention.
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`Referring now to the figures, FIG. 1 shows a data com-
`munications network in which the embodiments of the
`
`present invention may be implemented. A first local area
`network 100 is illustrated, including a host processor 10 is
`connected by a wired communications link 11 to a number
`of stationery access points or basestations 12,13; other base
`stations 14 can be coupled to the host through the base
`stations or by an RF link. Each one of the base stations
`12,13,14 is coupled by an RF link to a numberof remote
`mobile units 15 In one embodiment, the remote mobile units
`15 are hand-held, battery-operated data terminals portable
`digital assistants or voice communication handsets such as
`described in U.S. Pat. No. 5,029,183; Ser. No. 08/794,782
`filed Feb. 3, 1997, and Ser. No. 09/008,710, filed Jan. 16,
`1998, all assigned to Symbol Technologies, Inc., and incor-
`porated herein by reference.
`Various other types of remote terminals may be advanta-
`geously employed in a system having features of the inven-
`tion; these remote terminals ordinarily would include data
`entry facilities such as a magnetic card readeror the like, as
`well as a display (or printer) for indicating or providing to
`a user information detected, transmitted and/or received by
`the terminal. In this embodiment used as an illustrative
`example, there may be from one up to sixty-four of the base
`stations (three stations being shown in the Figure) and up to
`several hundred of the remote units; of course, the network
`may be expanded by merely changing the size of address
`fields and the like in the digital system, as will appear, but
`a limiting factor is the RF traffic and attendant delays in
`waiting for a quiet channel.
`11
`
`11
`
`

`

`US 6,600,734 B1
`
`7
`The first LAN 100 may be coupled to additional LANs
`200, 300, 400 etc. through controllers such as bridges 50, 60,
`etc. or routers 55, 65, 75, 85, 95, 105, etc. This communi-
`cations network as seen in FIG. 1 would ordinarily be used
`in a manufacturing facility, office building complex,
`warehouse, retail establishment, or like commercial facility
`or combination of these facilities, where the data-gathering
`terminals would be used for inventory control in stockroom
`or receiving/shipping facilities, at checkout (point of sale)
`counters, for reading forms or invoices of the like, for
`personnel security checking at gates or other checkpoints, at
`time clocks, for manufacturing or process flow control, and
`many other such uses.
`Although hand-held, laser scanning bar-code reader data
`terminals are mentioned, the data terminals mayalso include
`bar-code readers of the CCD or wand type, and may be
`portable or stationery rather than hand-held. The mobile
`units 15 may also be voice communication handsets, pagers,
`still image or video cameras; or any combination of the
`foregoing. Other types of data gathering devices may be
`utilized as terminals and use the features of the invention,
`such as temperature, pressure, or other environmental mea-
`suring devices, event counters, voice or sound activated
`devices, intrusion detectors, etc.
`According to an important feature of one embodimentof
`the invention, an RF packet communications protocol is
`provided between the remote units and the base stations, and
`includesa transmit/receive exchange, referred to hereinafter
`simply as an “exchange”. This protocol
`is similar
`to
`collision-sense multiple access (CSMA)in that a unit first
`listens before transmitting, and does not transmit if the
`channelis not free. As seen in FIG. 2, this exchange always
`begins with a remote-to-base transmitted packet, represent-
`ing an RF transmission from a remote unit to be received by
`the base stations within range. The transmitted packet is
`followed after a fixed time interval by a base-to-remote unit
`of RF information transmitted by the base station servicing
`this particular remote unit. Each of these packets and is of
`fixed timing; a transceiver in a remote unit begins an
`exchange at its own initiative by first listening for other
`traffic for a brief interval ty (typically 0.3 msec.) and, if the
`RF channelis quiet, starting a transmission at a time of its
`ownselection (asynchronousto any clock period of the base
`stations or host computer). This outgoing transmission
`packet lasts for a time t, as seen in the Figure, and in an
`example embodimentthis period is 4.8 milliseconds. Thenat
`a precise time delay t, after it started transmission (e.g. 5
`msec after the beginning of t,) the transceiver begins lis-
`tening for the return packet from the base station. The
`transceiver in the remote unit only respondsto receipt of the
`packet beginning in a very rigid time windowt, of a few
`microsecondslength, and if the packet has notstarted during
`this window then anything to follow is ignored. The packet
`is an acknowledge signal, and also contains dam if the base
`station has any message waiting to be sent. The packet also
`is millisecond in length, regardless of what data is included,
`if any, so a
`remote-to-base exchange,
`including
`acknowledge, takes about 9.8 msec in the example.
`FIG. 3 is a diagram illustrating a first embodimentof the
`invention showing an apparatus 50 which combines the
`functions of a wireless communication system access point
`and a telephony gatewayin a single unit in accordance with
`the present invention. In the discussion that follows, we will
`assume that the mobile unit 15 being utilized as a voice
`communication handset or wireless portable telephone,
`although other features such as keyboard data entry, mag-
`netic card data entry, bar code reading data entry could be
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`8
`incorporated in such unit as well, and such unit utilized for
`simultaneous voice and data transfer over the wireless link.
`Since IP is the preferred network layer protocol,
`in the
`present invention, the handset may also be referred to as a
`“IP phone” in this patent specification, but
`it
`is to be
`understood that network layer protocols other than IP could
`be used as well.
`
`The apparatus 50 contains one or more transmitter/
`receivers 52 for radio communications to the mobile units.
`The transmitter/receiver 52 is coupled to an access point
`Media Access Control (MAC) processor 54, which functions
`to send and receive data frames in the appropriate format to
`and from the transmitter/receiver 52 at the appropriate times.
`The processor 54 is also coupled to a memory 58, which
`buffers data packets.
`Although in the present preferred embodiment the MAC
`processor 54 utilizes an IEEE 802.11 data link protocol,
`other wireless LANs or WANsand other types of media
`access control,
`including FDMA, TDMA, CDMA,and
`combinationsthereof are also within the scope of the present
`invention. Different MAC processors may be used to accom-
`modate two or more different access techniques, including
`those of proposed MACstandards of Home RF, Bluetooth,
`and others.
`
`The memory 58 may be coupled to a switch or processor
`and multiplexor/demultiplexor 60 which provides process-
`ing and switching functions to route the data packets
`between the MAC processor 54 and an appropriate gateway.
`The switch or multiplexor/demultiplexor 60 may for
`example be coupled to voice gateway 62, which utilizes
`signal processor and codecs to translate the voice packets
`into analog audio signals suitable for transmission over a
`public switched telephone network or PBX. The switch or
`multiplexor/demultiplexor 60 may also be coupled to an
`analog modem gateway 64, which translates the digital
`datagrams from the LAN into encoded analog signals suit-
`able for transmission over a public switched telephone
`network, such as signals complying with the V.90 transmis-
`sion protocol.
`A Voice Gateway 62 also permits audio feedback from a
`telephone network (e.g. a busy signal) to an IP phone user
`in a wireless LAN system. For example, a series of feedback
`audible tones may be provided by the telephone network,
`whichare transmitted to the gateway, packetized, and trans-
`mitted over the wireless link to the mobile IP phone. At the
`IP phone, the data packets are then converted into an analog
`signal, thereby producing an audible copy of the series of
`feedback audible tones.
`
`In addition to the voice gateway interfacing to a wired
`telephone network, interfaces to wireless voice and data
`networks may also be implemented. There are also a wide
`variety of both analog and digital cellular radio systems
`which are in use around the world for telephony and data
`network applications. The digital ones include GSM, DCS
`1800,IS 54 and others. To the extent there is available at the
`gateway a landline telecommunications system to the des-
`tination called party, the use of a cellular radio system may
`be unnecessary and redundant. However, if such landline
`system is unavailable or has its service impeded,the provi-
`sion of a cellular radio system gateway is also within the
`scope of the present invention. Similarly, in certain remote
`areas it may also be desirable to provide a satellite radio
`system capability, such as connectivity to the Irdium phone
`network. Thus, the multiplexor/demultiplexor 60 may be
`coupled to any other appropriate type of gateway 66, such as
`for xDSL, ISDN, FDDI, cellular radio telephony (such as
`GSM), RAM, ARDIS, CDPD, orsatellite radio networks.
`12
`
`12
`
`

`

`US 6,600,734 B1
`
`10
`
`20
`
`25
`
`30
`
`35
`
`40
`
`9
`The apparatus may also contain a cable modem interface
`for access to a high bandwidth cable network. A cable
`network is a network running on traditional coaxial cable
`(which in most places, wasoriginally designed to carry cable
`tel