PCT
`WORLD INTELLECTUAL PROPERTY ORGANIZATION
`International Bureau
`INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`WO 95/29576
`
`(11) International Publication Number:
`
`(51) International Patent Classification 6 :
`H06M 11/06
`
`A2
`
`(43) International Publication Date:
`
`2 November 1995 (02.11.95)
`
`.....
`
`I r :1 "'
`
`(21) International Application Number:
`
`PCT/US95/05034
`
`(22) International Filing Date:
`
`18 April 1995 (18.04.95)
`
`(81) Designated States: CA, JP, European patent (AT, BE, CH, DE,
`DK, ES, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE) .
`
`Published
`Without international search report and to be republished
`upon receipt of that report.
`
`(30) Priority Data:
`08/229,958
`08/333,365
`
`19 April 1994 (19.04.94)
`2 November 1994 (02.11.94)
`
`us
`us
`
`(71) Applicant: MULTI-TECH SYSTEMS, INC. [US/US]; 2205
`Woodale Drive, Mounds View, MN 55112 (US).
`
`(72) Inventors: ARIMILLI, Harinarayana; 12185 Lily Street N.W.,
`Coon Rapids, MN 55433 (US). TRANA WALA, Ashish,
`A.; Unit 25, 20812 4th Street, Saratoga, CA 95070 (US).
`KANCHAN, Vasant, Kumar; 809 Durshire Way, Sunnyvale,
`CA 94087 (US).
`
`(74) Agent: RAASCH, Kevin, W.; Schwegman, Lundberg &
`Woessner, 3500 IDS Center, 80 South Eighth Street, Min(cid:173)
`neapolis, MN 55402 (US).
`
`(54) Title: DATA/VOICE/FAX ADVANCED PRIORITY STATISTICAL MULTIPLEXER
`
`(57) Abstract
`
`A data multiplexing network is described which multiplexes a plurality of asynchronous data channels with an asynchronous data
`stream representing compressed voice signals and/or facsimile signals onto a single synchronous data packet stream. The single synchronous
`data packet stream is then transmitted by a high speed statistical multiplexer over a composite link to a second site using a modified high-level
`synchronous data link control protocol with an overlay of an advanced priority statistical multiplexing algorithm. The asynchronous data
`channels and the compressed voice channel and/or facsimile signals are demultiplexed and reconstructed for sending to other asynchronous
`computer terminals and to a standard telephone or facsimile analog port at the second site, respectively. PBX trunk interfaces are also
`provided to allow PBX's to share the composite link between sites. Communication between the first site by voice or facsimile and the
`second site is transparent to the users. The multiplexer efficiently allocates the bandwidth of the composite link by detecting silence periods
`in the voice signals and suppressing the sending of the voice information to preserve bandwidth. An advanced priority statistical multiplexer
`is also described which dynamically allocates composite link bandwidth to both time-sensitive and non-time-sensitive data to maximize data
`throughout efficiency and quality while simultaneously reducing multiplexer processing overhead.
`
`Pet., Exh. 1006, p. 1
`
`

`
`FOR THE PURPOSES OF INFORMATION ONLY
`
`Codes used to identify States party to the PCT on the front pages of pamphlets publishing international
`applications under the PCT.
`
`AT
`AU
`BB
`BE
`BF
`BG
`BJ
`BR
`BY
`CA
`CF
`CG
`CH
`CI
`CM
`CN
`cs
`CZ
`DE
`DK
`ES
`FI
`FR
`GA
`
`Austria
`Australia
`Barbados
`Belgium
`Burkina Faso
`Bulgaria
`Benin
`Brazil
`Belarus
`Canada
`Central African Republic
`Congo
`Switzerland
`Cbte d'Ivoire
`Cameroon
`China
`Czechoslovakia
`Czech Republic
`Germany
`Denmark
`Spain
`Finland
`France
`Gabon
`
`GB
`GE
`GN
`GR
`HU
`IE
`IT
`JP
`KE
`KG
`KP
`
`KR
`KZ
`LI
`LK
`LU
`LV
`MC
`MD
`MG
`ML
`MN
`
`United Kingdom
`Georgia
`Guinea
`Greece
`Hungary
`Ireland
`Italy
`Japan
`Kenya
`Kyrgystan
`Democratic People's Republic
`of Korea
`Republic of Korea
`Kazakhstan
`Liechtenstein
`Sri Lanka
`Luxembourg
`Latvia
`Monaco
`Republic of Moldova
`Madagascar
`Mali
`Mongolia
`
`MR
`MW
`NE
`NL
`NO
`NZ
`PL
`PT
`RO
`RU
`SD
`SE
`SI
`SK
`SN
`TD
`TG
`TJ
`TT
`UA
`us
`uz
`VN
`
`Mauritania
`Malawi
`Niger
`Netherlands
`Norway
`New Zealand
`Poland
`Portugal
`Romania
`Russian Federation
`Sudan
`Sweden
`Slovenia
`Slovakia
`Senegal
`Chad
`Togo
`Tajikistan
`Trinidad and Tobago
`Ukraine
`United States of America
`Uzbekistan
`Viet Nam
`
`,.i
`
`J,'
`.,, ·'
`•
`
`Pet., Exh. 1006, p. 2
`
`

`
`WO 95/29576
`
`PCT/US95/05034
`
`DATA/VOICFJFAX ADVANCED PRIORTIY
`STATISTICAL MULTIPLEXER
`
`Field of the Invention
`The present invention relates to data communication
`multiplexers and in particular to automatic data bandwidth allocation in
`communication multiplexers which multiplex data, facsimile and compressed
`voice over a single composite link.
`
`5
`
`10
`
`15
`
`20
`
`Background of the Invention
`Data multiplexers in the telecommunications field are used to
`combine several asynchronous and synchronous data communication signals
`from individual data terminal equipment (DIB) sources such as computer
`terminals or personal computers (PC's) onto a single composite link. The
`individual asynchronous and synchronous signals from the PC's are connected
`to the multiplexer channel inputs and converted into a single signal called the
`composite signal which is then sent over a single analog or digital link called
`the composite link. Of course, the composite link may be a dedicated
`telephone line, a leased line, or a single private wire.
`The data multiplexer combines the channel signals from
`individual PC's into a composite signal by using one of a variety of
`techniques such as frequency division multiplexing, time division multiplexing
`and statistical time division multiplexing. Frequency division multiplexers
`assign separate frequencies to each signal and combine the frequencies onto
`the single composite link. Time division multiplexers assign a time slice of a
`single carrier to each of the channels being combined. Statistical time
`division multiplexers are an adaptation of time division multiplexers in which
`only those channels actually sending data get a slice of time. This results in a
`30 more efficient use of the composite link.
`Typically, a data multiplexer is used as an efficient alternative
`to traditional data communications in which a single channel uses a single
`telephone line link. By combining a plurality of ac;ynchronous channels into a
`composite link, fewer telephone lines or leased lines and less equipment is
`35 used to transfer the data. This is especially cost effective when a four wire
`
`25
`
`"'
`
`Pet., Exh. 1006, p. 3
`
`

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`WO 95/29576
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`PCT/US95/05034
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`2
`
`"leased" line is used to connect a pair of synchronous modems. This type of
`private line offers a degree of security that public dial-up telephone lines
`cannot match. In addition, the superior error correction of a synchronous
`multiplexer network is preferred over the single telephone line asynchronous
`5 connections. Better yet, the use of a digital line with a DSU (Digital Service
`Unit) connection is more reliable and error free than analog.
`Figure 1 shows a typical arrangement for a prior art connection
`of a plurality of PC's at building A 101 and a computer system at building B
`102. The computer system at building B may be personal computers (PC's)
`103 such as those shown in building A or any variety of computer equipment
`devices. Traditional dial-up telephone links 105a, 105b, 105c through 105n
`are used between the plurality of PC's in building A 101 and the plurality of
`data terminal equipment (DTE) devices of building B such as a VAX
`computer I 06. Each asynchronous link, therefore, requires its own dial-up
`link I 05a, I 05b, 105c through 105n , which is in many cases not cost
`effective. The connections may be between two sites, or multiple sites may
`be connected.
`
`10
`
`15
`
`Figure 2 shows a prior art data multiplexer scheme in which a
`plurality of PC's 203 at building "A" 201 are multiplexed using a data
`20 multiplexer and synchronous modem 207 to transmit the information over a
`single telephone link 205 to building "B" 202. The signals are then
`demultiplexed by a similar multiplexor/modem 208 and transmitted to the
`DTE of building "B" 202, which for illustrative purposes is shown as a VAX
`computer 206.
`In general, Figure 2 describes a data multiplexer 207 and, in
`particular, a device manufactured by the assignee of the present invention
`called the MultiMux (model 900, 1600 or 3200) product from Multi-Tech
`Systems, Inc. of Mounds View, Minnesota. The product allows for up to n(cid:173)
`RS232 connections to local PC's 203. dumb terminals, host computers such as
`a DEC VAX 206, or other devices which communicate via asynchronous
`connection. In one product environment, n equals eight where eight PC's or
`other asynchronous devices can be attached to eight RS232 ports. The
`
`25
`
`30
`
`Pet., Exh. 1006, p. 4
`
`

`
`..
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`W095/29576
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`PCT/US95/05034
`
`3
`
`composite link is typically handled through an proprietary protocol with data
`rates up to 64 kilobytes per second. Not shown is a command port for menu
`driven control of the operational settings of the data multiplexer .
`Connections from one site to another site over a composite link
`5 using a dedicated line is an efficient use of the line resources, however
`additional line connections are still typically needed between the two sites or
`more sites for traditional telephone voice or facsimile connections between the
`sites. There is a need in the art, therefore, to combine compressed voice
`grade telephone signals with data signals and facsimile signals and transmit all
`10 over a composite link to further increase the efficient use of a single
`telephone line connection. There is yet a further need in the art to combine
`
`voice grade telephone signals with both synchronous and asynchronous data
`signals for transmission over a composite link for enhanced efficiency of a
`single telephone line connection.
`
`15
`
`Summary of the Invention
`The present invention solves the aforementioned deficiencies of
`the prior art and solves other problems that will be understood and
`appreciated by those skilled in the art upon reading and understanding the
`20 present specification. The present invention describes a data multiplexing
`network which combines a plurality of asynchronous and synchronous data
`channels with an asynchronous data stream representing compressed voice
`signals and/or facsimile signals onto a single synchronous data packet stream.
`The single synchronous data packet stream is then transmitted by a high speed
`statistical multiplexer over a composite link to a second site using a modified
`high-level synchronous data link control protocol with an overlay of an
`advanced priority statistical multiplexing algorithm. The asynchronous/
`synchronous data channels and the compressed voice channel and/or facsimile
`signals are demultiplexed and reconstructed at the second site for sending to
`30 other asynchronous and synchronous data terminal equipment and to a
`standard telephone or facsimile analog port or PBX interface, respectively.
`
`25
`
`Pet., Exh. 1006, p. 5
`
`

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`WO 95/29576
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`4
`
`Communication between the first site by voice or facsimile and the second
`site is transparent to the users.
`The total bandwidth of the composite link communicating
`between sites may be instantaneously allocated to high priority data (time
`sensitive) and low priority data (non-time-sensitive) based on instantaneous
`system demands. In voice over data communications it is possible to greatly
`reduce bandwidth allocated to the high priority voice packet infonnation by
`eliminating transmissions of repeated silent packets. The voice detection
`algorithm tells the data processor that the packet is empty which is
`representative of silence. The data processor then does not send the packet,
`but instead sends a flag to the other side of the composite link to indicate no
`voice is being sent. In the event of silence, the maximum low priority data
`(asynchronous or synchronous data) packet size is dynamically changed based
`on the use of the voice channel. If there is a lot of silence, or the voice
`channel is not active at all, then the maximum low priority data packet size
`can grow to be quite large providing a larger asynchronous and synchronous
`data channel throughput. An advanced priority statistical multiplexer ensures
`maximum data throughput quality and efficiency while simultaneously
`reducing multiplexer processing overhead.
`
`5
`
`IO
`
`15
`
`20
`
`Description of the Drawings
`In the drawings, where like numerals describe like components
`throughout the several views,
`Figure I is a drawing of a prior art connection between
`25 building A and building B using traditional dial-up telephone links by modem;
`Figure 2 is a prior art description of the connection between
`building A and building Busing a statistical multiplexer link;
`Figure 3 is a general block diagram showing the preferred
`embodiment of the present invention which combines both telephone and
`facsimile information through a number of possible alternative interfaces with
`digital data infonnation for transmission to and demultiplexing at a remote
`site;
`
`30
`
`..
`
`..
`
`.•
`
`Pet., Exh. 1006, p. 6
`
`

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`WO 95/29576
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`
`5
`
`Figure 4A (two sheets of drawings) is a detailed block diagram
`showing the use of the multiplexor 300 of the present invention to combines
`both telephone (voice), facsimile through a variety of connections with data
`over a single composite link to a remote site;
`Figure 4B is a detailed block diagram showing the division of
`major components of the data/voice/fax multiplexor of Figure 4A including
`the FXS, FXO and E&M interfaces;
`Figure SA is a diagram showing a first one of the preferred
`connections of the present invention which multiplexes voice telephone,
`facsimile information and digital data information for transmission to and
`demultiplexing at a remote site for connection to other DIB devices and for
`connection to remote voice telephone and facsimile equipment;
`Figure SB is a diagram showing a second one of the preferred
`connections of the present invention which multiplexes voice telephone,
`facsimile information and digital data information for tra{lsmission to and
`demultiplexing at a remote site for connection to other DIB devices and to a
`remote PBX;
`
`Figure SC is a diagram showing a third one of the preferred
`connections of the present invention which multiplexes voice telephone,
`facsimile information and digital data information for transmission to and
`demultiplexing at a remote site for connection to other DIB devices and to
`remote voice telephone and facsimile equipment through a remote PBX;
`Figure SD is a diagram showing a fomth one of the preferred
`connections of the present invention which multiplexes voice telephone and
`facsimile information through a local PBX with local digital data information
`for transmission to and demultiplexing at a remote site for connection to other
`DIB devices and to remote PBX for remote voice telephone and facsimile
`equipment;
`
`S
`
`10
`
`15
`
`20
`
`2S
`
`30
`
`Figures 6A, 6B and 6C are detailed block diagrams of the
`asynchronous channel cards, the aggregate cards and the voice/ fax cards,
`respectively, of the multiplexer shown in Figure 4B;
`
`Pet., Exh. 1006, p. 7
`
`

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`WO 95/29576
`
`PCT/US95/05034
`
`6
`
`Figures 7 A-71, 8A-8I, 9A-9I and lOA-1 OI are detailed electrical
`
`schematic diagrams of the voice/fax card of Figure 6C;
`
`Figure 11 is a signal flow diagram of the speech compression
`
`algorithm;
`
`5
`
`Figure 12A is a detailed function flow diagram of the speech
`
`compression algorithm;
`
`Figure 12B is a signal flow diagram of the speech compression
`
`algorithm showing details of the code book synthesis;
`
`Figure 13 is a detailed function flow diagram of the speech
`
`10 decompression algorithm;
`
`Figure 14 is a flow chart of the modified HDLC transmission
`
`packet protocol using priority statistical multiplexing of the data/voice/fax
`
`multiplexor of Figures 6A, 6B and 6C;
`
`Figure 15 shows a Link Request Frame used to initiate and
`
`15
`
`establish a connection between multiplexers using modified HDLC with
`•
`Advanced Priority Statistical Multiplexing;
`
`Figure 16 shows a Voice/Fax Data Frame used to transmit
`
`voice/fax channel data;
`
`Figure 17 shows a Network Control Frame used in a
`
`20 networking environment;
`Figure 18 shows an Asynchronous Channel Data Frame used to
`
`transmit asynchronous channel data;
`
`Figure 19 shows an Acknowledgement Frame used to
`
`acknowledge communications between multiplexers;
`
`25
`
`Figure 20A shows one embodiment of a two priority level
`
`multiplexer;
`
`Figure 20B shows a portion of the multiplexed high priority
`
`and low priority data transmitted by one embodiment of a two priority level
`
`advanced priority statistical multiplexer;
`
`30
`
`Figure 21 is an example of multiplexing two priority levels of
`
`data in a hybrid frame;
`
`Pet., Exh. 1006, p. 8
`
`

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`WO 95/29576
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`PCT!US95/05034
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`7
`
`Figure 22 is another example of multiplexing two priority levels
`of data in a hybrid frame; and
`Figure 23 shows one embodiment of a three priority level
`
`multiplexer.
`
`Detailed Description of the Preferred Embodiments
`In the following Detailed Description of the Preferred
`Embodiment, reference is made to the accompanying drawings which form a
`part hereof and in which is shown by way of illustration specific embodiments
`in which the invention may be practiced. These embodiments are described in
`sufficient detail to enable those skilled in the art to practice and use the
`invention, and it is to be understood that other embodiments may be utilized
`and that electrical, logical, and structural changes may be made without
`departing from the spirit and the scope of the present invention. The
`following detailed description is, therefore, not to be taken in a limiting sense
`and the scope of the present invention is defined by the appended claims.
`
`5
`
`10
`
`15
`
`20
`
`System Overview
`Figure 3 is a block diagram showing a plurality of connection
`combinations for the preferred embodiment of the present invention which is a
`communication system in which a data/voice/fax multiplexer 300a is
`configured to take voice information from telephone equipment, facsimile
`information from facsimile machines and asynchronous and synchronous data
`from data terminal equipment (DIB) devices and combine this information
`and data for transmission over a single composite communications link.
`Data/voice/fax multiplexers 300a and 300b (generally referred to as
`data/voice/fax multiplexer 300) are identically configured for multiplexing and
`demultiplexing this data and information. The result of this connection allows
`telephone, facsimile and data communications between sites "A" and "B" in a
`30 method of communication which appears to users at both sites to be
`simultaneous and transparent.
`
`25
`
`,.
`
`Pet., Exh. 1006, p. 9
`
`

`
`...
`
`..
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`WO 95/29576
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`PCT!US95/05034
`
`8
`
`The present invention shown in Figure 3 connects a plurality of
`
`5
`
`10
`
`data tenninal equipment (DTE) devices such as computers, tenninals, printers,
`modems, etc., through asynchronous and synchronous channels to the
`data/voice/fax multiplexer 300 at site "A". Also, telephone equipment such as
`telephone desk sets, PBX equipment and facsimile (fax) equipment are also
`connected to data/voice/fax multiplexer 300. The data/voice/fax multiplexer
`300 is configured to take analog voice channel inputs from telephone
`equipment through specially configured voice channel interfaces to be
`digitized, compressed and encoded into a special packet protocol using a voice
`compression algorithm. Multiplexer 300 is also configured to connect to fax
`equipment to receive and demodulate the fax picture data to place the decoded
`picture data into the special packet protocol. The asynchronous/synchronous
`data received by multiplexer 300 from the DTE devices is combined with
`packetized picture data and packetized compressed voice information for
`15 multiplexing and synchronous transmission over the composite link.
`At site "B", multiplexer 300b operates identically to multiplexer
`300a at Site "A" to multiplex outgoing data, voice or fax information and to
`demultiplex incoming data from site "A". Each multiplexer 300 operates to
`compress or decompress the digitized voice data from telephone equipment
`20 using a voice compression algorithm described more fully below.
`Multiplexers 300 also operate to modulate and demodulate the fax picture data
`so that all three forms of data (DTE data, compressed voice data and facsimile
`picture data) are combined using a special packet protocol for transmission
`over the composite link, and synchronous data, such as LAN signals are
`25 modulated and demodulated as well. The composite link 313 may be an
`analog line such as a public telephone line using S)'nchronous modems, a
`private leased line using synchronous modems or a digital line using DSU
`(Digital Service Units).
`
`30
`
`Hardware Overview
`As shown in Figure 4, the present invention combines a
`plurality of asynchronous data channels 302a-302n, which in many cases are
`
`Pet., Exh. 1006, p. 10
`
`

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`W095/29576
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`PCT/US95/05034
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`9
`
`RS232 interfaces 303a through 303n, along with a data packet stream of
`compressed voice or facsimile information into a single data stream. The
`single packetized data stream is transmitted using synchronous modem 314
`
`over a single telephone line 315 to a remote site (Site "B"). As described
`
`5 more fully below, the composite link 313 may be selected to be an analog line
`
`such as a public telephone line using synchronous modems, a private leased
`
`line using synchronous modems or a digital line using DSU (Digital Service
`
`Units). Figure 4 shows only one such composite link implementation which
`
`is a public telephone line 315 using synchronous modems 314.
`
`10
`
`As shown in Figure 4, the basic elements at the local site (Site
`
`"A") connected to multiplexer 300a are terminals or PCs 301a-301n which are
`connected to channel ports 302a-302n which in turn connect to RS232
`
`interfaces 303a-303n. The channel ports 302a-302n provide access to data
`
`buffers 304a-304n controlled by microprocessor 306 which assembles the data
`
`15
`
`packets for the data processor 318. The combined data packets are connected
`
`to the phone line 315 by synchronous modem 314 for transmission at high
`
`speeds over the dedicated phone line 315.
`Asynchronous data from the individual PC's contain start and
`
`stop flags. The asynchronous data is collected from the individual PC's and is
`
`20
`
`assembled into synchronous data packets, each with a header and a trailer.
`
`Typically, 85% to 90% of an asynchronous line is not used efficiently since
`the line is not carrying any data most of the time. By using a statistical
`multiplexer 314, the sporadic data activity of several individual channels
`
`302a-302n connected to PC's 301a-301n can be combined onto a single line
`
`25
`
`315 to make more efficient use of that line. The microprocessor statistically
`
`multiplexes and collects the asynchronous data and packetizes it into
`
`synchronous data packets for transmission.
`Synchronous data transmissions also gain efficiency over
`asynchronous data transmissions by reducing framing overhead. By way of
`example of the data transmission efficiency gain, asynchronous data is by
`definition formatted by framing each character with a start and stop bit. This
`
`30
`
`process can account to up to one-third of the bits in a single transmission on
`
`Pet., Exh. 1006, p. 11
`
`

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`10
`
`an asynchronous link. In contrast to this, synchronous data is transmitted in a
`
`packet that first contains a header (which contains destination address),
`
`followed by a block of data characters and followed by trailer information
`
`(such as error checking codes, checks sums, etc.). Since the packet is
`
`5
`
`addressed, a statistical multiplexer can arrange the packet in any order with
`
`the other asynchronous data based on demand and use of the asynchronous
`
`data lines.
`
`Data from the asynchronous channels 302a-202n connected to
`
`the PC's 301a-301n is sent to the microprocessor for statistical multiplexing
`
`10
`
`after first being buffered through buffer 305 and collected by internal
`
`microprocessor 306. The microprocessor 306 assembles the data into the
`
`synchronous data stream in the form of synchronous data packets which are
`
`framed by the address and error correcting data and sent to data processor 318
`
`for multiplexing with voice and fax data packets for transmission over the
`
`15
`
`synchronous composite link.
`
`The composite link 315 may be a digital or analog network
`
`link, a simple analog leased line, a four-wire leased line or private line.
`
`Communication over the composite link is through a special synchronous
`
`modems operating typically at 300 to 19.2kbps, 38.4kbps or DSUs (Digital
`
`20 Service Units) operating at 9600 to in excess of 256Kbps. The management
`
`and control format of the data transmitted over the composite link is described
`
`more fully below. This format is similar to the high-level synchronous data
`
`link control format (HDLC) used for inter-modem or DSU communication. A
`
`proprietary modified form of the HDLC is used with the preferred
`
`25
`
`embodiment of the present invention which is called Modified HDLC or
`
`MHDLC. MHDLC is used in combination with an Advanced Priority
`
`Statistical Multiplexing (APSM) algorithm to achieve a highly efficient use of
`
`the composite link.
`
`30
`
`Multiplexer Overview
`
`Figure 4B is a block diagram of a single data/voice/fax
`
`multiplexer 300 with the circuits shown divided according to the physical
`
`Pet., Exh. 1006, p. 12
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`11
`
`implementation on multiple cards. Those skilled in the art will readily
`
`recognize that the physical implementation of the present invention need not
`
`follow the physical partitioning exemplified here. The multiplexer 300 uses
`
`statistical time division multiplexing to transmit data, voice and facsimile data
`
`5
`
`in a fashion that appears simultaneous to the user at each end. In the
`
`illustrated embodiment of the present invention, two eight-channel interface
`
`cards 401a and 401b are included to provide a total of sixteen RS232
`
`asynchronous ports for connection to PC's, mainframe computers, and other
`
`DTE devices, although as shown below, more channel cards may be added to
`
`10
`
`extend the number of asynchronous channels serviced. In the preferred
`
`implementation, 32 asynchronous channels are interfaced using four 8-channel
`
`cards. The channels are buffered and connected to the host or aggregate card
`
`400 of the multiplexer 300 for multiplexing with packetized voice or facsimile
`
`information from Voice Channel Equipment (VCE) Channel 1 circuit 308 or
`
`15 VCE Channel 2 circuit 309 (both VCE channels implemented on a single
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`card).
`
`Those skilled in the art will readily recognize that a variable
`
`number of asynchronous RS232 port cards and a variable number of voice or
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`facsimile interface cards may be combined in the preferred embodiment of the
`
`20 present invention without limiting the scope of the invention. Thus, the
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`design of the data/voice/fax multiplexor 300 is modular to allow the addition
`of cards to expand the capability of the system. In the preferred
`implementation ~hown in Figure 4B, two VCE channel circuits 308 and 309
`on a single card are used to send/receive facsimile or analog voice
`
`25
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`information connections for packetizing and transmission over the composite
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`link lines 313a and 313b. As part of the modular design, the preferred
`
`implementation of data voice/fax/multiplexor 300 is shown with two dedicated
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`lines 313a and 313b connected to ports 403a and 403b respectively. Network
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`ports 403a and 403b each interface to separate lines using dedicated
`synchronous modems 314 for analog lines or to DSUs (Data Service Units)
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`30
`
`for digital lines.
`
`Pet., Exh. 1006, p. 13
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`The facsimile infonnation from a fax machine is received as a
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`telephone connection on VCE channel 1 circuit 308 or VCE channel 2 circuit
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`309. The facsimile infonnation is taken off the analog carrier by
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`demodulating the carrier so that the picture or pixel packets are recovered.
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`5 The picture or pixel packets are then passed through dual port RAM 307 to be
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`received by the data processor 318. The data processor 318 combine the
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`facsimile or pixel packets with the synchronous data packets received from
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`the asynchronous data channels 401a-401 b for statistical multiplexing and
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`transmission over one of the composite link lines 313a or 313b through
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`10 network ports 403a or 403b, respectively.
`In addition, or alternatively, telephone equipment connected to
`either VCE channel 1 circuit 308 or VCE channel 2 circuit 309 will receive
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`analog voice information, digiti:ze the voice infonnation, compress and encode
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`the digiti:zed voice infonnation into packets and load the packets into dual
`
`15
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`port RAM (Random Access Memory) 307 for receipt by the data processor
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`318. These compressed voice packets are then statistically multiplexed with
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`the facsimile picture packets and/or the asynchronous data packets from
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`asynchronous channel cards 401a and 401b for multiplexed transmission over
`the composite link lines 313a or 313b. The packets are collected and
`transmitted over the telephone line using a proprietary synchronous data link
`
`20
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`fonnat which, for purposes of the present discussion, is described as a
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`modified high speed data link control or MHDLC using a proprietary
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`advanced priority statistical multiplexing algorithm described more fully
`
`below.
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`25
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`Qperation of the Voice/Facsimile Channel Interface
`
`The VCE channel 1 circuit 308 and VCE channel 2 circuit 309
`
`of Figure 4B are identical circuits which are capable of operating in parallel
`
`to transmit and receive signals to and from telephones and facsimile machines.
`
`30
`
`Illustrated in Figure 4B for VCE channel 1 circuit 308 and VCE channel 2
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`circuit 309 are three types of telephone line interfaces labeled FXS, FXO, and
`E&M The FXS acronym stands for Foreign Exchange Station. The FXS
`
`Pet., Exh. 1006, p. 14
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`13
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`interface mimics the subscriber-side of a standard tip and ring two-wire
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`telephone connection either as a loop or a ground start configuration. The
`
`FXO acronym stands for Foreign Exchange Office. The FXO interface
`
`mimics the central office or provider-side of a standard tip and ring two-wire
`
`S
`
`telephone connection. The E&M acronym was historically designated in
`
`telephone circuit diagrams as the "e" in "received" and the "m" in "transmit"
`
`for trunk signalling. The E&M interface mimics a typical PBX trunk
`
`interface.
`
`As shown in more detail in Figure 6C, each voice channel card
`
`10
`
`is capable of handling the three interfaces: FXS, FXO and E&M to provide a
`
`wide variety of connectivity for interfacing to different types of telephone
`
`equipment. Four of these types of connections are illustrated in Figures 5A
`
`though 5D.
`
`As shown in Figure 5A, a telephone or facsimile machine may
`be connected to the FXS interface at Site "A", which will appear to this
`
`IS
`
`equipment as though it were connected to the subscriber side of a standard tip
`
`and ring two-wire analog telephone connection. The FXS connection on VCE
`
`channel 1 circuit 308 or VCE channel 2 circuit 309 shown in Figures 4A and
`
`4B would appear to be a telephone central office (CO) to this telephone
`
`20
`
`equipment (or a PBX-mimic of a CO). Thus, if a user picked up the handset
`of a standard telephone connected to the FXS interface at Site "A" of Figure
`SA, the telephone or fax machine at site "B" would ring.
`A PBX may be connected to the FXO interface on VCE
`
`channel 1 circuit 308 or VCE channel 2 circuit 308 shown in Figures 4A and
`
`2S
`
`4B. Referring to Figure SB, the PBX at site "B" is attached to the FXO
`
`interface of the multiplexer 300b. The PBX at site "B" will see the
`
`multiplexer FXO interface as a piece of telephone equipment responding to
`
`the PBX connection. A telephone or fax machine at site "A" is connected to
`the FXS interface of multiplexer 300a but will appear to be connected to the
`
`30
`
`station connection of the PBX at site "B". The telephone or fax machine at
`
`site "A" will then be able to dial any extem;ion serviced by the PBX at site
`
`"B" or dial out to the local Public Switched Telephones Network (PS1N)
`
`Pet., Exh. 1006, p. 15
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`from the PBX The telephone or fax equipment at site "A" appears to be
`
`directly connected to the PBX at site "B".
`
`A PBX trunk interface may also