(12) United States Patent
`J enness
`
`US006324212B1
`(10) Patent N0.:
`US 6,324,212 B1
`(45) Date 0f Patent:
`Nov. 27, 2001
`
`(54) APPARATUS USING LOW SPECTRUM
`SELECTIVELY FOR PROVIDING BOTH
`ADSL AND POTS SERVICE
`
`(75) Inventor: Robert Jenness, Boca Raton, FL (US)
`
`(73) Assignee: Siemens Information and
`Communication Networks, Inc., Boca
`Raton, FL (Us)
`
`*
`
`Notice:
`
`Sub'ect to an disclaimer, the term of this
`J
`y
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`_
`(21) Appl' NO" 09/249’924
`(22) Filed:
`Feb- 12, 1999
`
`(21) U S C]
`( 2)
`‘
`‘
`‘ """
`
`/
`
`’
`
`_
`1238’ H0414 5/1;
`072/94 57307 4/9251_9é7397g/34(6) 1f
`/
`’
`/
`’ 379/ 9 09’
`/
`'
`_
`(58) Fleld 0f Search ................................... .. 375/222, 220,
`375/221’ 232’ 219; 370/487’ 480’ 203’
`210> 465> 468> 484> 494> 495; 379/93'01>
`9308’ 9309’ 9328’ 9331
`References Cited
`
`(56)
`
`Us‘ PATENT DOCUMENTS
`6,061,392 * 5/2000 Bremer et a1. ..................... .. 370/487
`6,151,335 * 11/2000 K0 et a1_ _________ __
`370/487
`6,167,095 * 12/2000 Furukawa et a1.
`375/285
`6,192,109 * 2/2001 Amrany et a1. ...................... .. 379/30
`* cited by examiner
`
`Primary Examiner—Chi Pham
`Assistant Examiner—Dung X. Nguyen
`
`(57)
`
`ABSTRACT
`_
`_
`_
`_
`_
`_
`Asymmetric Digital Subscriber Line (ADSL) data service
`and Plain Old Telephone Service (POTS) are provided over
`a subscriber loop by an ADSL transceiver and a control
`processor located in a local communication center, and a
`subscriber ADSL modem at the subscriber location. The
`control processor is responsive to a detection of an origina
`tion of a POTS call for generating a ?rst control signal that
`causes the ADSL transceiver to load ADSL data into tone
`bins Which are only in a frequency band above a predeter
`mined frequency band used for a POTS call for data trans
`missions over the subscriber loop. The control processor is
`also responsive to a detection of a termination of a POTS
`call for generating a second control signal that causes the
`ADSL transceiver to load ADSL data into tone bins Which
`are in both the predetermined frequency band used for a
`POTS call and the frequency band thereabove for ADSL
`data transmissions Over the subscriber loop' The Subscriber
`ADSL modem is responsive to third and fourth control
`signals received from the control processor and multiplexed
`into the ADSL data transmissions, to load ADSL data into
`tone bins Which are only in a frequency band above a
`predetermined frequency band used for a POTS call, and
`load ADSL data into tone bins Which are in both the
`predetermined frequency band used for a POTS Call and the
`frequency band thereabove for ADSL data transmissions
`over the subscriber loop, respectively.
`
`20 Claims, 4 Drawing Sheets
`
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`U.S. Patent
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`Nov. 27, 2001
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`Nov. 27, 2001
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`Sheet 4 0f 4
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`US 6,324,212 B1
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`ATU-C
`HANDSHAKE MOOULATION
`300
`HANOSHAKE MOOULATION
`BASED PROTOCOL EXCHANGE / \ BASED PHOTOCOL EXCHANGE
`OF INITIALIZATION OATA
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`MEASUREMENT AND
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`

`
`US 6,324,212 B1
`
`1
`APPARATUS USING LOW SPECTRUM
`SELECTIVELY FOR PROVIDING BOTH
`ADSL AND POTS SERVICE
`
`CROSS REFERENCE TO RELATED
`APPLICATIONS
`
`10
`
`This application expressly claims the bene?t of earlier
`?ling date and right of priority from the following
`co-pending patent applications, all of Which are assigned to
`the assignee of the present invention and have the same
`inventor: US. Provisional Application Serial No. 60/081,
`116, ?led on Apr. 8, 1998, entitled “Use of LoW Spectrum
`Selectively for both ADSL and POTS”, and US. Provisional
`Application Serial No. 60/084,566, ?led on May 7, 1998,
`15
`entitled “Use of LoW Spectrum Selectively for both ADSL
`and POTS in G.Lite”, and to an application entitled “Method
`Using LoW Spectrum Selectively For Providing Both ADSL
`And POTS Service” Which is being ?led concurrently With
`the present application. Each cited patent application is
`expressly incorporated in its entirety by reference.
`
`20
`
`FIELD OF THE INVENTION
`
`The present invention relates to apparatus using loW
`spectrum selectively for both Asymmetric Digital Sub
`scriber Line (ADSL) and Plain Old Telephone Service
`(POTS) service over a single loop by adding predetermined
`control messages to alloW rapid mode sWitching betWeen
`just ADSL service and combined ADSL and POTS service
`based on central of?ce or subscriber events indicating voice
`call initiation.
`
`25
`
`30
`
`BACKGROUND OF THE INVENTION
`Asymmetric Digital Subscriber Line (ADSL) is de?ned,
`and pertinent standards information thereto is provided, in
`the Standards Document T1E1.4/98-007R1 entitled “Stan
`dards Project for Interfaces Relating to Carrier to Customer
`Connection of Asymmetrical Digital Subscriber Line
`(ADSL) Equipment”, Sept. 26, 1997, and subsequent revi
`sions edited by Bingham and Van der Putten. More
`particularly, Asymmetric Digital Subscriber Line (ADSL)
`has been de?ned as consisting of a pair of Discrete Multitone
`(DMT) modems, one at each end of a tWisted pair subscriber
`loop, With band splitters at each end to provide isolation
`betWeen a high frequency spectrum (above 24 KHZ) used for
`data transmission and loWer frequencies (0—4 KHZ) used for
`Plain Old Telephone Service (POTS) or Integrated Services
`Digital NetWork (ISDN) used in some applications. These
`modems use DMT technology to provide high data band
`Width and the ability to adapt the data rate at startup to match
`the transmission and noise characteristics of each individual
`subscriber loop. Each 4.3125 KHZ band of the frequency
`spectrum (referred to as a Tone Bin), With center frequencies
`from 25.875 KHZ (Tone Bin #6) to 1.04 MHZ, is populated
`With a signal Which may be considered to be a tone Whose
`amplitude and phase are modulated to encode data bits. Tone
`Bins beloW 24 KHZ (e.g., Tone Bins #1—#5) are not used for
`data transmissions.
`Proposals have been made by various companies to de?ne
`an alternate spectral assignment for Asymmetric Digital
`Subscriber Line (ADSL) Discrete Multitone (DMT)
`modems that alloW for the use of loW frequencies (beloW 24
`KHZ) for additional data throughput. In existing classical
`ADSL systems, the loWer frequencies including the 0—4
`KHZ voice band and approximately 20 KHZ of guard band
`thereabove, are reserved for Plain Old Telephone Service
`(POTS) telephony voice and signaling transmissions in
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`some applications. In these classical ADSL systems, the
`ADSL data transmissions are transmitted in frequency bands
`above 24 KHZ (Tone Bin #6 and above) With the different
`transmissions separated by ?lters in central of?ce and Cus
`tomer Premises Equipment (CPE) splitters.
`Recent interest in “splitterless” ADSL has generated an
`activity in trying to provide a dual modality for transmis
`sions Wherein a subscriber’s line could be used either in the
`classical ADSL mode as described above, or in a data only
`mode. In the data only mode, the loWer frequencies (0—24
`KHZ) Would be used to carry additional DMT “tones” (Tone
`Bins #1—#5) modulated With additional data. Since the loWer
`frequencies are transmitted preferentially by most telephone
`loops, these loWer frequencies can add substantial through
`put capability to the subscriber’s line.
`The recent focus has been on eliminating the band splitter,
`at least at the subscriber premises. This necessitates some
`reduction in data throughput, since data carrier amplitudes
`must be reduced to avoid interference to POTS voice
`generated by nonlinearities. Since the POTS phone imped
`ance loads the subscriber loop, it reduces input amplitude
`and available spectral bandWidth to the data receivers.
`Alternatively, POTS ?lters may be installed on each POTS
`telephone to prevent the ADSL signal from reaching, or
`being adversely affected by, the telephone, Whether on-hook
`or off-hook. Unfortunately, While these POTS ?lters Will
`reduce, or substantially eliminate, the POTS signal interfer
`ence and the need to reduce the ADSL signal amplitude, the
`?lters may render one or tWo of the tones beloW Tone #6
`unusable. This reduction in data bandWidth is vieWed as an
`acceptable tradeoff to reduce the complexity of installation
`of the service by eliminating equipment reWiring to accom
`modate the splitters. Coincidentally, complexity of the
`modem is reduced due to the narroWer bandWidth and the
`attendant reduced signal processing bandWidth.
`It is desirable to provide dual modality for transmissions
`Wherein a subscriber’s line can be used either in the classical
`ADSL mode as described above, or in a data only mode
`While providing rapid mode sWitching betWeen just ADSL
`service and combined ADSL and POTS service based on
`central of?ce or subscriber events indicating voice call
`initiation.
`
`SUMMARY OF THE INVENTION
`
`The present invention is directed to apparatus using loW
`spectrum selectively for both Asymmetric Digital Sub
`scriber Line (ADSL) and Plain Old Telephone Service
`(POTS) service over a single subscriber loop by adding
`predetermined control messages to alloW rapid mode sWitch
`ing betWeen just ADSL service and combined ADSL and
`POTS service based on central office or subscriber events
`indicating voice call initiation.
`VieWed from one aspect, the present invention is directed
`to apparatus for providing both Plain Old Telephone Service
`(POTS) and Asymmetric Digital Subscriber Line (ADSL)
`data service over a common subscriber loop providing a
`predetermined frequency spectrum for transmission pur
`poses. The ADSL data service makes use of a multiplicity of
`quadrature modulated tones separated in frequency from one
`another across the predetermined frequency spectrum, and
`POTS makes use of only a portion of said predetermined
`frequency spectrum. The apparatus comprises means for
`using said portion of the predetermined frequency spectrum
`for POTS While a POTS call is in progress, and means for
`excluding ADSL data service from at least said portion of
`the predetermined frequency spectrum and reducing the
`
`

`
`US 6,324,212 B1
`
`10
`
`15
`
`3
`number of tones While a POTS call is in progress, and
`expanding ADSL data service into said portion of the
`predetermined frequency spectrum and increasing the num
`ber of tones While a POTS call is not in progress.
`VieWed from another aspect, the present invention is
`directed to apparatus for providing bidirectional Asymmet
`ric Digital Subscriber Line (ADSL) data service and Plain
`Old Telephone Service (POTS) over a subscriber loop. The
`apparatus comprises an ADSL transceiver and a control
`processor located in a local communication center. The
`ADSL transceiver receives ADSL data in a ?rst direction
`from a remote source and loads the received ADSL data into
`predetermined tone bins for transmission over the subscriber
`loop to subscriber data equipment. The ADSL transceiver
`receives also ADSL data in a second direction in the
`predetermined tone bins from the subscriber loop for pro
`cessing the ADSL data for transmission to the remote source.
`The control processor is responsive to a detection of an
`origination of a POTS call for generating a ?rst control
`signal that causes the ADSL transceiver to load ADSL data
`into tone bins Which are only in a frequency band above a
`predetermined frequency band used for a POTS call for data
`transmissions over the subscriber loop. The control proces
`sor is responsive to a detection of a termination of a POTS
`call for generating a second control signal that causes the
`ADSL transceiver to load ADSL data into tone bins Which
`are in both the predetermined frequency band used for a
`POTS call and the frequency band thereabove for data
`transmissions over the subscriber loop.
`VieWed from still another aspect, the present invention is
`directed to apparatus for implementing bidirectional Asym
`metric Digital Subscriber Line (ADSL) data service and
`Plain Old Telephone Service (POTS) over a subscriber loop.
`The apparatus comprises an integrated line circuit Which
`comprises detecting and processing circuitry, an ADSL
`35
`transceiver, and a control processor. The detecting and
`processing circuitry detects an origination or termination of
`a POTS call directed to or from a subscriber coupled to the
`subscriber loop, and bidirectionally processes the POTS call
`for transmission betWeen a remote source and the subscriber
`loop. The ADSL transceiver receives ADSL data from a
`remote source and loads the received ADSL data into
`predetermined tone bins for ADSL data transmissions over
`the subscriber loop to subscriber data equipment. The ADSL
`transceiver also receives ADSL data from the subscriber
`loop in the predetermined tone bins for processing the ADSL
`45
`data for data retransmissions to the remote source. The
`control processor is responsive to a detection of an origina
`tion of a POTS call by the detecting and processing circuitry
`for generating a ?rst control signal that causes the ADSL
`transceiver to load ADSL data into tone bins Which are only
`in a frequency band above a predetermined frequency band
`used for a POTS call for ADSL data transmissions over the
`subscriber loop. The control processor is also responsive to
`a detection of a termination of a POTS call by the detecting
`and processing circuitry for generating a second control
`signal that causes the ADSL transceiver to load ADSL data
`into tone bins Which are in both the predetermined frequency
`band used for a POTS call and the frequency band there
`above for ADSL data transmissions over the subscriber loop.
`The invention Will be better understood from the folloW
`ing more detailed description taken With the accompanying
`draWings and claims.
`
`25
`
`55
`
`BRIEF DESCRIPTION OF THE DRAWING
`FIG. 1 shoWs a block diagram of an integrated line card
`for use in a central office in accordance With the present
`invention;
`
`65
`
`4
`FIG. 2 shoWs a block diagram of a subscriber modem in
`accordance With the present invention;
`FIG. 3 is a timing diagram illustrating dual mode sWitch
`ing betWeen a classical ADSL mode of transmission and a
`data only mode of transmission in a subscriber loop as
`provided by the integrated line card of FIG. 1 in accordance
`With the present invention; and
`FIG. 4 is a How diagram of an exemplary Voiceband
`InitialiZation sequence designated in a standards document
`for ADSL modems.
`
`DETAILED DESCRIPTION
`
`The present invention is directed apparatus for imple
`menting “Splitterless” Asymmetric Digital Subscriber Line
`(ADSL) service (elimination of band splitters in modems)
`Wherein integrated central of?ce line circuits (ILCs) perform
`both Plain Old Telephone Service (POTS) and ADSL data
`service interfaces over a subscriber’s loop. In accordance
`With the present invention, a single control entity located in
`the ILC, hereinafter also referred to as an ADSL Termination
`Unit-Central Of?ce (AT U-C) modem, has full access to both
`of the POTS signaling state and the ADSL data interface.
`Similarly, an ADSL Termination Unit-Residential (AT U-R)
`modem is located at the subscriber end of the loop Which is
`a Customer Premises Equipment (CPE) ADSL modem that
`has full visibility to analog parameters of the subscriber’s
`loop. The analog parameters can be used to sense the
`presence of either a POTS telephone in an off-hook state or
`a reception of a POTS call at the central of?ce destined for
`that POTS telephone.
`The present invention takes advantage of the available
`information (e.g., telephone on-hook or off-hook state, or
`ringing) to dynamically and rapidly modify the ADSL data
`modem con?gurations at the central of?ce and the subscriber
`premises to populate ?ve loW tone bins (Tones #1—#5 found
`in separate frequency bands beloW 24 KHZ) With ADSL data
`only When POTS service is inactive (i.e., telephone is
`on-hook or no call is received for termination at that
`telephone at the central of?ce). The actual tone center
`frequencies, as de?ned by T1E1.4/98-007R1 are: Tone Bin
`1=4.3125 KHZ, Tone Bin 2=8.625 KHZ, Tone Bin
`3=12.9375 KHZ, Tone Bin 4=17.25 KHZ, and Tone Bin
`5=21.5625 KHZ. More particularly, the present invention
`provides the sensing, control logic, and ADSL inter-modem
`communication functions necessary to alloW dynamic
`recon?guration of both the ADSL Termination Unit-Central
`Of?ce (ATU-C) modem and the ADSL Termination Unit
`Residential (ATU-R) modem in response to a POTS call that
`is either initiated by the subscriber coupled to the ATU-R, or
`received at the central of?ce ATU-C for that subscriber from
`a connected communication system.
`Referring noW to FIG. 1, there is shoWn a block diagram
`of an integrated line card (ILC) 10 (shoWn Within a dashed
`line rectangle) that is located, for example, in a central office
`or local communication center (e.g., a Private Branch
`Exchange) in accordance With the present invention. The
`ILC 10 generally terminates multiple subscriber loops (of
`Which only subscriber loop 52 is shoWn), each of Which may
`independently require either POTS or ADSL service, or
`both. The integrated line card 10 comprises a plurality of
`ADSL transceivers 12a—12n (shoWn Within separate dashed
`line rectangles With only 12a and 1211 expressly shoWn), a
`Control Processor 14, a Signaling Sense and Control circuits
`16, a plurality of Digital Signal Processing for Voice and
`Signaling circuits 18a—18n (shoWn Within separate rect
`angles With only 18a and 1811 expressly shoWn), a Time
`
`

`
`US 6,324,212 B1
`
`10
`
`15
`
`25
`
`5
`Division Multiplex Multiplexer/Dernultiplexer (TDM
`MUX/DEMUX) circuit 20, a plurality of adders 22a—22n
`(shown within separate rectangles with only 22a and 2211
`expressly shown), a plurality of Digital to Analog Conver
`sion (DAC) circuits 24a—24n (shown within separate rect
`angles with only 24a and 2411 expressly shown), a plurality
`of Analog to Digital Conversion (ADC) circuits 26a—26n
`(shown within separate rectangles with only 26a and 2611
`expressly shown), a plurality of analog front end circuits
`28a—28n (shown within separate rectangles with only 28a
`and 2811 expressly shown) including a corresponding plu
`rality of High Voltage (HV) circuits 29a—29n (with only 29a
`and 2911 expressly shown), a ringing source 30, a test access
`circuit 32, and a loop power feed circuit 34. It is to be
`understood that interconnections between elements of the
`integrated line card 10 are only shown for the associated ?rst
`elernents (e.g., 12a, 18a, 22a, 24a, 26a, 28a, and 29a) of
`each of the indicated plurality of n elements for simplicity
`purposes only, and that each of the other corresponding
`associated n-1 elements are interconnected and function in
`a same manner as is described hereinafter for the associated
`?rst elernents.
`Each of the plurality of ADSL transceivers 12a—12n
`comprises a serial coupling of a Multiplexer/Dernultiplexer
`(MUX/DEMUX) 40, a Forward Error Correction (FEC)
`circuit 42, and a Fast Fourier Transforrn/Inverse Fast Fourier
`Transform (FFT/IFFT) circuit 44. The combination of these
`three elements 40, 42, and 44 operates on ADSL data
`bidirectionally propagating between a data line 57 and an
`associated subscriber loop (e.g., loop 52). In the ADSL
`transceiver 12a, a ?rst (upstream) side of the MUX/
`DEMUX 40 is coupled to bidirectionally communicate
`ADSL data over data line 57, and Network Tirning Refer
`ence signals (NTR) over lead 58 with an upstream rernote
`source (not shown) of a communication system. The MUX/
`35
`DEMUX 40 also selectively transrnits and receives both a
`set of function speci?c control bits [hereinafter referred to
`indicator bits (ib)] over lead 54, and control signals indi
`cating an embedded operation channel (eoc) and an ADSL
`operations channel (aoc) over lead 56 to and from the
`Control Processor 14. The eoc and aoc channels are trans
`ported across the subscriber loop 52 as overhead in the
`multiplex with user data and indicator bits, and provide a
`bidirectional communication channel between the Control
`Processors 14 and 114 at the local exchange and the sub
`scriber prernises, respectively. A second (downstream) side
`of the MUX/DEMUX 40 is coupled for bidirectional trans
`missions to a ?rst side of the FEC 42. A second side of the
`FEC 42 is coupled for bidirectional transrnissions to a ?rst
`side of the FFT/IFFT 44. A second side of the FFT/IFFT 44
`is coupled to transmit resulting ADSL data signals to the
`adder 22a, and to receive signals from the subscriber loop 52
`via the analog front end circuit 28a and the ADC circuit 26a.
`The ADSL transceiver 12a also receives control signals from
`the Control Processor 14 via a control bus 59 for selectively
`controlling all aspects of the ADSL transceiver 12a such as,
`for example, populating and depopulating tone bins with
`ADSL data.
`The ADSL service is realiZed by a modern which is a
`combination of the transceivers 12a—12n and control func
`tions provided by the Control Processor 14. For data signals
`received via lead 57, the transceiver (e.g., 12a), in addition
`to its rnodulation functions performed in the MUX/DEMUX
`40 on the Data signals on lead 57, combines (a) the rnodu
`lated user data stream on lead 57 with (b) two ernbedded
`operations channel (eoc) and ADSL operations channel
`(aoc) rnessages provided by the control processor 14 over
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`lead 56, (c) Network tirning reference signal (NTR) on lead
`58, and (d) a set of function speci?c control bits referred to
`hereinafter as indicator bit 18 (ib 18) on lead 54 which is the
`bit number in an ADSL data signal transmitted over the
`subscriber loop (e.g., 52). These cornbined signals are used
`subsequently to create the analog signal for the high
`frequency spectrum used for ADSL transmission on the loop
`52. It is to be understood that in future irnplernentations, a
`single Digital Signal Processor (DSP) (not shown) may
`perform the modern function (shown as performed by the
`ADSL Transceivers 12a—12n and the Control Processor 14)
`for multiple subscriber loops.
`In operation, the MUX portion of the MUX/DEMUX 40
`in the ADSL Transceiver 12a combines the various compo
`nents of a single cornposite ADSL line signal received on
`leads 54, 56, 57 and 58 for transmission in the downstream
`direction to the subscriber loop 52, while the DEMUX
`portion separates the dernodulated ADSL line signal to form
`the various components for transmission on leads 54, 56, 57,
`and 58 in the upstream direction from the subscriber loop 52.
`The FEC 42 performs the encoding and decoding forward
`acting error correcting of the data bit strearns received from
`the MUX 40 in the downstream direction and from the
`associated ADC 26a in the upstream direction. In the FFT/
`IFFT 44, the ADSL data signals are constructed by Inverse
`Fourier Transform techniques based on control signals from
`the Control Processor 14 via the control bus 59. Therefore,
`the composite digital ADSL data signals received by the
`transceiver 12a from the upstream rernote source (not
`shown) via lead 57 are forward error corrected, then
`decornposed, and the bits are assigned to tone bins and
`encoded to a discrete rnultitone symbol by the IFFT portion
`of the FFT/IFFT 44 under control signals from the Control
`Processor 14 via the control bus 59. In the reverse direction,
`the ADSL data signals from the subscriber loop 52 are
`converted into a digital data signal by the FFT portion of the
`FFT/IFFT 44 before being forward error corrected in the
`FEC 42 and then dernultiplexed in the MUX/DEMUX 40 to
`separate the user and control data streams onto their proper
`leads 54, 56, 57, and 58.
`In the ILC 10, POTS service is provided between a Pulse
`Code Modulation (PCM) Link 50 and each of the associated
`subscriber loops (e.g., loop 52). For POTS service to rnul
`tiple subscriber loops, the ILC 10 uses the Time Division
`Multiplex Multiplexer/Dernultiplexer (TDM MUX/
`DEMUX) circuit 20, the plurality of Digital Signal Process
`ing for Voice and Signaling circuits 18a—18n, and the
`Signaling Sense and Control circuit 16. The PCM Link 50 is
`coupled to the TDM MUX/DEMUX circuit 20, and the
`TDM MUX/DEMUX circuit 20 is coupled to the plurality of
`Digital Signal Processing for Voice and Signaling Circuits
`18a—18n, and to the Signaling Sense and Control circuit 16.
`Each of the plurality of Digital Signal Processing for Voice
`and Signaling Circuits 18a—18n is coupled to the Control
`Processor 14, the Signaling Sense and Control circuits 16, a
`corresponding one of the plurality of adders 22a—22n for
`transmitting POTS calls to the associated subscriber loop
`(e.g. loop 52), and a corresponding one of the plurality of
`ADC circuits 26a—26n for receiving POTS calls and signal
`ing messages from the associated subscriber loop.
`For POTS operation, the TDM MUX/DEMUX circuit 20
`receives PCM channel signals and channel associated sig
`naling bits from the PCM link 50, and dernultiplexes the
`PCM channel signals for an associated subscriber loop (e.g.,
`loop 52). The dernultiplexed PCM channel signals are
`transmitted to the associated one of the Digital Signal
`Processing for Voice and Signaling circuits 18a—18n. The
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`associated signaling bits are transmitted to the Signaling
`Sense and Control circuit 16 via lead 61 Where they are
`stored for use by the Control Processor 14 to initiate
`subscriber loop events such as ringing, etc. In the reverse
`direction, the TDM MUX/DEMUX circuit 20 receives the
`PCM channel signals from the plurality of the Digital Signal
`Processing for Voice and Signaling circuits 18a—18n pro
`vided by the associated subscriber loop (e.g., loop 52), and
`time division multiplexes the PCM channel signals into their
`proper time slots for transmission on the PCM link 50 to the
`upstream remote source (not shoWn). The Digital Signal
`Processing for Voice and Signaling circuits 18a—18n pro
`vides anti-alias ?ltering, code laW computation, gain
`adjustment, hybrid impedance match, ringing generation,
`loop state detection, and other analog-loop related functions
`by performing computations on the digital representation of
`the subscriber loop signals ?oWing in both directions.
`Detected subscriber loop signaling state information is
`passed to the Signaling Sense and Control circuit 16, and in
`the reverse direction transmitted loop state information is
`received from the Signaling Sense and Control circuit 16. In
`some implementations, Where necessary, the Digital Signal
`Processing for Voice and Signaling circuits 18a—18n may
`also perform additional digital ?ltering functions. In a fully
`integrated implementation, the digital ?ltering functions Will
`be performed by the same Digital Signal Processing for
`Voice and Signaling circuit (e.g., 18a) that performs the
`ADSL transceiver functions, and Will include POTS/ADSL
`band separation ?lters (not shoWn).
`The Control Processor 14 controls all aspects of both the
`ADSL and POTS operations for multiple subscriber loops
`(e.g., loop 52). The Control Processor 14 receives status
`signals from, and transmits control signals to, both of the
`ADSL transceivers 12a—12n and the POTS Digital Signal
`Processing for Voice and Signaling circuits 18a—18n via the
`Signaling Sense and Control circuit 16. The Control Pro
`cessor 14 also monitors ADSL transmissions and adjusts bit
`loading via control signals on lead 59, and transmits levels
`in response to detected variations in the ADSL line transport
`capacity via control signals on lead 59. Still further, the
`Control Processor maintains the status of ADSL line main
`tenance information blocks (MIBs) and communicates With
`the associated AT U-R at opposite end of the associated
`subscriber’s loop via the eoc, aoc, and ib signals sent to the
`ADSL transceiver (e. g., 12a) associated With that AT U-R via
`lines 54 and 56. The Control Processor 14 further bidirec
`tionally communicates With data netWork management enti
`ties at the upstream remote source (not shoWn) via a sig
`naling message channel 55. The Control Processor 14 also
`interprets received POTS subscriber loop signaling states
`(on-hook, off-hook), sets POTS loop states (ringing, current
`feed, etc.), and controls loop test access via control messages
`sent over lead 53. These control messages are based on
`communications had With a POTS sWitch (not shoWn) at the
`upstream remote source via the signaling message channel
`55 or via channel associated (CAS) signaling bits carried in
`the PCM time slots for each channel as received via PCM
`link 50 and directed to the Signaling Sense and Control
`circuit 16 via lead 61. The above described functioning of
`the Control Processor 14, With respect to ADSL, comprises
`standard functions as suggested in the ADSL Standards
`Document T1E1.4/98-007R1 entitled “Standards Project for
`Interfaces Relating to Carrier to Customer Connection of
`Asymmetrical Digital Subscriber Line (ADSL)
`Equipment”—T1.413 Issue 2, Sep. 26, 1997, and subse
`quent revisions edited by Bingham and Van der Putten. The
`above-described functioning of the Control Processor 14
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`With respect to POTS is considered prior art as Would be
`found in eXisting line controllers of TDM digital sWitching
`equipment as found in, for example, Siemens EWSD and
`DCO line controllers.
`The present invention adds a neW function to the Control
`Processor 14 to couple the detection of POTS subscriber
`loop on-hook and off-hook state changes to accordingly
`populate (for the on-hook state) and depopulate (for the
`off-hook state) the tones #1—#5 in the 0—24 KHZ frequency
`band betWeen the subscriber’s ATU-R modem (shoWn in
`FIG. 2) and the associated ADSL transceiver (e.g., 12a). In
`operation, the Control Processor 14 receives a control signal
`via the Digital Signal Processing for Voice and Signaling
`circuits 18a—18n and the Signaling Sense and Control circuit
`16 indicating any change in the hook state of the associated
`subscriber loop, and in response to a change in hook state to
`send an appropriate hook state control signal (logical 0 or 1)
`in indicator bit 18 (ib 18) to the associated ATU-R at the
`subscriber’s end. Concurrent thereWith, the Control Proces
`sor 14 adjusts both the bit loading and the transmit amplitude
`of the tones #1—#5, and the resulting data mapping to
`transport additional data bits in the additional 0—24 KHZ
`bandWidth, via control signals on the control bus 59.
`Each of the plurality of Adders 22a—22n receives (a) the
`processed ADSL data signals (t