`Gernert et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 6,600,734 B1
`Jul. 29, 2003
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`USOO6600734B1
`
`(54)
`
`(75)
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`(73)
`
`(*)
`
`(21)
`(22)
`(51)
`(52)
`(58)
`
`APPARATUS FOR INTERFACING A
`WIRELESS LOCAL NETWORKAND A
`WIRED VOICE TELECOMMUNICATIONS
`SYSTEM
`
`Inventors: Alex Gernert, Cupertino, CA (US);
`Sarosh Vesuna, Los Altos, CA (US);
`David Goren, Smithtown, NY (US)
`Assignee: Symbol Technologies, Inc., Holtsville,
`NY (US)
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`Notice:
`
`Appl. No.: 09/213,958
`Filed:
`Dec. 17, 1998
`Int. Cl................................................. H04L 12/66
`U.S. Cl. ........................ 370/352; 370/328; 455/403
`Field of Search ................................. 370/312, 313,
`370/328, 401, 329, 349, 352-358; 455/432,
`403, 425, 550, 575
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`7/2001 Lewis ........................ 455/103
`6,259,898 B1
`6.298,062 B1 * 10/2001 Gardell et al. .............. 370/401
`6,330,244 B1 12/2001 Swartz et al. ............... 370/401
`* 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
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`200-
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`HOST
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`7-
`-
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`BASE
`STATION
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`7-
`-
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`BASE
`STATION
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`BRIDGE 60
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`400
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`115
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`CD-III
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`
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`COMPUTER
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`100-
`14
`BASEBASE
`STATION
`STATION
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`ROUTER
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`1
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`13
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`BASE
`STATION
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`tri----
`BRIDGE 50
`12
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`15
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`15
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`15
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`Ex.1019
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`Sheet 1 of 7
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`US 6,600,734 B1
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`T-60,
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`Sheet 2 of 7
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`US 6,600,734 B1
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`• • • * * * * * … • • • • •
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`Jul. 29, 2003
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`308 WHOE}}
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`Sheet 4 of 7
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`HANDSET
`166
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`KEYPAD r or
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`KEYPAD
`170
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`TRANSMITTER/
`RECEIVER
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`16
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`FIG.4
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`AUDIO CODEC:
`G.711, OR G.723.1
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`(E)
`UNRELIABLE TRANSPORT (UDP)
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`se
`E. DNS
`RELIABLE TRANSPOR
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`200
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`202
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`DETECT WHEN USER
`ACTIVATES WIRELESS
`IP PHONE
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`SEND SIGNAL TO
`WIRELESS P PHONE
`TO PRODUCEDAL TONE
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`DETECT WHEN
`NUMBERS ARE DALED
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`STORE DALED
`NUMBERS IN MEMORY
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`SEND "RING" MESSAGE
`TO PHONE NUMBER
`STORED IN MEMORY
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`PERIODICALLY SEND
`SIGNAL TO WIRELESS
`IP PHONE UNTIL CALL
`IS CONNECTED TO
`PRODUCE "RING SOUND
`
`FG.6
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`Sheet 7 of 7
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`US 6,600,734 B1
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`RECEIVE INCOMING CALL
`WITH "PHONE NUMBER"
`OF RECIPIENT WIRELESS
`IP PHONE
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`
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`COMPARE "PHONE
`NUMBER RECEIVED WITH
`DIRECTORY OF WIRELESS
`P PHONES ON THE LAN
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`250
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`252
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`256
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`IS RECIPIENT
`WIRELESS P PHONE
`ALREADY IN USE
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`254
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`YES
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`CALL WATING SIGNAL
`GENERATED AT RECIPIENT
`IP PHONE
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`SEND SIGNAL TO
`RECIPIENT WIRELESS IP
`PHONE TO ACTIVATE
`"RINCINC."
`
`CONNECT CALL WHEN A
`USER ACTIVATES THE
`RECIPIENT WIRELESS
`IP PHONE
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`258
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`260
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`FIG.7
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`1
`APPARATUS FOR INTERFACING A
`WIRELESS LOCAL NETWORK AND A
`WIRED VOICE TELECOMMUNICATIONS
`SYSTEM
`
`2
`Cable modems interface to coaxial cable lines that are
`typically used for providing cable television signals into
`homes and 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,
`Ill; 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 base Stations 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 which at 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
`CCCC.
`
`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.
`Each of 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. More specifically, the present invention relates to an
`apparatus which interfaces 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
`many years for voice communication. The typical telephone
`converts Sound waves into 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 home in 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 who require 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.
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`3
`Another such protocol is described in U.S. Pat. No.
`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 “IEEE 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 roaming in 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 communications of 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.
`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
`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). LANE relies on a LAN Emulation
`Server (LES), which performs MAC-to-ATM address reso
`lution; a Broadcast and Unknown Server (BUS), which
`
`4
`performs data broadcast; and an optional LAN Emulation
`Configuration Server (LECS), which performs initialization
`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 downloading Station 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 provide initial
`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
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`applications, modifications and embodiments in other fields,
`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 communications net
`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
`processor is located at one of the access points for detecting
`a message Sent by a first mobile unit and determining from
`the message whether it 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 docking Station 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 when the phone or 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 network Station correspond
`ing to Said destination, Said ring Signal designed to alert
`the recipient that a call is attempting to connect; and
`transmitting an acknowledgment Signal to the mobile
`handset, Said acknowledgement Signal designed to 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 address call, an intercom call, or a name call.
`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 includes the Steps of Storing a set of network
`addresses available for use by users in a Server computer on
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`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
`FIG. 1 is a diagram illustrating a wireless local area
`network in which the present invention may be imple
`mented.
`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 incoming call 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 base Stations 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 number of 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 reader or 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.
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`Ex.1019
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`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 may also 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 embodiment of
`the invention, an RF packet communications protocol is
`provided between the remote units and the base Stations, and
`includes a 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
`channel is 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 to (typically 0.3 msec.) and, if the
`RF channel is quiet, Starting a transmission at a time of its
`own selection (asynchronous to 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 embodiment this period is 4.8 milliseconds. Then at
`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 responds to receipt of the
`packet beginning in a very rigid time window t of a few
`microSeconds length, and if the packet has not started 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 embodiment of the
`invention showing an apparatus 50 which combines the
`functions of a wireleSS communication System access point
`and a telephony gateway in 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,
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`although other features Such as keyboard data entry, mag
`netic card data entry, bar code reading data entry could be
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`US 6,600,734 B1
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`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 WANs and other types of media
`access control, including FDMA, TDMA, CDMA, and
`combinations thereof 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 MAC standards 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,
`which are 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