United States Patent
`
`[19]
`
`Bowie
`
`[11] Patent Number:
`[45] Date of Patent:
`
`5,956,323
`
`Sep. 21, 1999
`
`USUU5956323A
`
`[54] POWER CONSERVATION FOR POTS AND
`MODULATED DATA TRANSMISSION
`
`[75]
`
`Inventor: Bruce H. Bowie, Santa Rose, Calif.
`
`[73] Assignee: Nokia High Speed Access Products
`Inc., Petaluma, Calif.
`
`[21] Appl. No.: 08/903,504
`
`[22]
`
`Filed:
`
`Jul. 30, 1997
`
`Int. Cl.“ ............................. H04M 11/00; H04Q 1/00
`[51]
`[52] U.S. Cl.
`........................................... .. 370/241; 379/413
`[58] Field of Search ................................... .. 370/216, 241,
`370/242, 244, 249, 250, 251, 204, 205,
`212, 213; 379/1, 2, 5, 9, 15, 23, 26, 27,
`32, 93.06, 399, 412, 413, 377
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,484,028
`4,979,208
`5,483,574
`5,590,396
`5,742,527
`5,799,064
`
`11/1984 Kelley et al.
`12/1990 Pruden et al
`1/1996
`12/1996 Henry
`4/1998 Ryhicki et al.
`8/1998 Sridhar et al.
`
`................... .. 379/93.14
`.. 379/145
`. 379/32
`455/426
`. 364/705.05
`..................... .. 375/222
`
`Primary Examiner—Chi H. Pham
`Assistant Examiner—Kwang B. Yao
`Attorney, Agent, or Firm—Fish & Richardson P.C.
`
`[57]
`
`ABSTRACT
`
`Methods and apparatus for conserving power in terminal
`units that transmit and receive modulated data over a com-
`munications loop that is shared with voiceband telephone
`equipment are disclosed. The methods include monitoring
`the loop to detect a shut-down condition and reducing power
`consumption of certain of the electronic circuits in the
`terminal unit upon detection of a shut—doWn condition. The
`methods also include monitoring the loop with a monitoring
`circuit
`to detect a resume signal outside the voicebaud
`frequency range on the loop and restoring power to the
`clcctronic circuits when the resume signal is dctcctcd. The
`apparatuses include a modulated data transmitting and
`receiving unit having a connector for coupling the unit to a
`communications loop, circuitry to transmit and receive a
`modulated data signal
`in a
`frequency range above
`voiceband, and circuitry to detect a resume signal in the
`frequency range above voicehand and then to initiate a
`power up sequence for the transmit and receive circuitry.
`
`27 Claims, 3 Drawing Sheets
`
`300
`
`\
`
`CPE Unit
`Receives Start-up
`Signal
`l
`CPE Unit
`Restores Saved
`Parameters
`
`CPE Unit
`Transmits
`Resume Signal
`
`COT Unit Detects
`Resume Signal
`
`ow-Power a
`COT?
`
`COT and CPE
`Units Exchange
`Handshaking
`Information
`
`Restores Saved
`Parameters
`
`Exchange Data
`
`V
`CPE Sends Shut-
`Down Signal
`V
`
`Monitor Loop until
`shut—down is
`detected
`
`v
`Store Parameters
`
`V
`
`Reduce Power
`Consumption
`
`Dish
`Exhibit 1004, Page 1
`
`

`
`U.S. Patent
`
`Sep. 21, 1999
`
`Sheet 1 of 3
`
`5,956,323
`
`
`
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`
`Dish
`Exhibit 1004, Page 2
`
`

`
`U.S. Patent
`
`Sep. 21, 1999
`
`Sheet 2 of 3
`
`5,956,323
`
`
`
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`Dish
`Exhibit 1004, Page 3
`
`

`
`U.S. Patent
`
`Sep. 21, 1999
`
`Sheet 3 of 3
`
`5,956,323
`
`300
`
`\
`
`301 \
`
`CPE Unit
`
`Receives Start—up
`Signal
`:
`CPE Unit
`Restores Saved
`Parameters
`
`\
`
`302
`
`303
`
`:
`CPE Unit
`Transmits
`
`\
`
`Resume Signal
`_l___
`304 \ COT Unit Detects
`Resume Signal
`
`Exchange Data
`
`CPE Sends Shut-
`
`Down Signal
`
`Monitor Loop until
`shut-down is
`detected
`
`ow-Power a
`COT?
`
`Store Parameters
`
`COT Unit
`Restores Saved
`Parameters
`
`Reduce Power
`
`Consumption
`
`COT and CPE
`
`Units Exchange
`Handshaking
`Information
`
`Dish
`Exhibit 1004, Page 4
`
`

`
`1
`POWER CONSERVATION FOR POTS AND
`MODULATED DATA TRANSMISSION
`
`The present invention is directed to a power conservation
`system for modulated data communications, and more par-
`ticularly to a power conservation system for transmission
`systems in which data is modulated over a communications
`loop from a central office location to a customer premises.
`BACKGRO U ND
`
`Wire loops extending from a telephone company central
`office to a customer premises are a ubiquitous part of the
`existing communications infrastructure. These wire loops
`form a communications network often referred to as the
`plain old telephone service’ (POTS) network. The POTS
`network originated to support analog voice phone service.
`The POTS network currently supports a wide range of
`communications services in addition to analog voice phone
`calls. These services include digital data transmissions from
`facsimile
`machines and computer modems. Voice
`calls, FAX connections, and computer modem transmissions
`all operate within the frequency spectrum of traditional
`POTS calls, thus ensuring compatibility with the existing
`wire loop infrastructure and allowing transport of these
`services end-to-end through the POTS phone network.
`However,
`the use of POTS-compatible transmission fre-
`quencies severely limits the maximum information carrying
`capacity of the wire loop.
`Certain transmission technologies may use carrier fre-
`quencies greater than those required for POTS services to
`exceed the information capacity limits of POTS calls over
`wire loops. However, since the existing POTS loop infra-
`structure was not designed for carrying such high frequency
`signals, severe impediments to such transmission exist. In
`particular, as a result of electromagnetic coupling among
`wire loops, electromagnetic noise signals are induced on the
`loops. This electromagnetic coupling may occur among the
`large number of loops in the wire bundles that extend from
`the central ollice to various customer distribution points.
`Noise signals induced on the loops by electromagnetic
`coupling may not be perceptible on POTS voice calls.
`However, such signals may significantly interfere with wide-
`bandwidth modulated data transmissions that use high fre-
`quency signals. To reduce interference problems, sophisti-
`cated sigial processing circuitry, such as digital signal
`processors (DSPs), are used within modulated data receiver
`and transmitter units to remove noise, to encode and decode
`desired signals, and to perform error correction functions.
`To minimize the number of wire loops needed to service
`a customer’s premises, POTS signals and modulated data
`transmission signals may be combined on a single wire loop.
`To combine POTS and wide-bandwidth modulated data
`transmission signals, the wide-bandwidth modulated data is
`transported using frequencies (spectrum) greater than those
`of POTS services. This spectrum usage allows a POTS
`service connection to be supported by its traditionally allo-
`cated spectrum while simultaneously supporting high fre-
`quency modulated data transmission. Thus, current technol-
`ogy permits POTS and high bandwidth data may be carried
`between customer premise equipment (CPE) and a central
`offiee (CO) on a single wire loop. At the central office, the
`POTS signal frequencies are separated from the high fre-
`quency data signal; the POTS signal is then handled by the
`existing POTS switch and network, while the high fre-
`quency spectrum is directed to separate processing compo-
`nents.
`
`.
`
`2
`Signal processing, transmitting, and receiving circuitry
`for such high frequency modulated data signals requires a
`substantial amounts of power, typically 11p to 5 watts per
`loop served. For a large central oflice, potentially serving
`many thousands of such data connections, this power usage
`is substantial.
`
`SUMMARY
`
`In general, in one aspect, the invention features a method
`of conserving power in a terminal unit having a transmitter
`and receiver for modulated data communication over a
`communications loop that is shared with voiceband tele-
`phone equipment. The method includes monitoring the loop
`to detect a sl1ut-down condition, reducing power consump-
`tion of certain of the electronic circuits in the terminal unit
`upon detection of a shut-down condition, monitoring the
`loop with a monitoring circuit to detect a resume signal
`outside the voiceband frequency range on the loop, and
`restoring power to the electronic circuits when the resume
`signal is detected.
`Implementations of the invention may include one or
`more of the following features. The modulated data may be
`a bit stream including framing information, and a shut-down
`condition may be indicated by a loss of framing information.
`The modulated data may include a signaling channel and a
`shut down condition may be indicated by bits transmitted in
`the signaling channel. The resume signal may be an AC
`signal at a frequency above voiceband, such as a 16 kHz AC
`signal.
`in another aspect, the invention features a
`In general,
`modulated data transmitting and receiving unit. The unit
`includes a connector for coupling the unit to a communica-
`tions loop, circuitry to transmit and receive a modulated data
`signal in a frequency range above voiceband, and circuitry
`to detect a resume signal in the frequency range above
`voiceband and then to initiate a power up sequence for the
`transmit and receive circuitry.
`Implementations of the invention may include one or
`more of the following features. The connector may be a
`two-wire connector. The transmit and receive circuitry may
`include Asymmetric Digital Subscriber Line transmit and
`receive circuitry. The resume signal detection circuitry may
`be a 16 kHz frequency detector. The communications loop
`may be a wireless communications loop. The resume signal
`may be an AC signal greater than 4 kHz or may be a
`multi-tone AC signal. The unit may also include a control
`signal interface to receive a start—up signal, and circuitry to
`transmit a resume signal upon receipt of the start-up signal.
`In general,
`in another aspect, the invention features a
`modulated data transmitting and receiving unit. The unit
`includes a connector for coupling the unit to a communica-
`tions loop, a control signal interface for receiving a start-up
`signal, circuitry to transmit and receive a modulated data
`signal at frequencies above voiceband, and circuitry to
`transmit a resume signal on the loop upon receipt of a
`start-up signal on the control signal interface.
`Implementations of the invention may include one or
`more of the following features. The communications loop
`may a wireless loop. The control signal interface may be a
`data interface, such as a peripheral component interconnect
`(PCI) interface. The start-up signal may be indicated by
`receipt of data on the control signal interface. The control
`signal interface may be used for the exchange of both the
`start-up signal and of data between the modulated data
`transmitting and receiving unit and customer premise equip-
`ment.
`
`Dish
`Exhibit 1004, Page 5
`
`

`
`5,956,323
`
`3
`Among the advantages of the invention are the following.
`Modulated data signal processing, transmitting, and receiv-
`ing circuitry can be placed in a
`low power state when
`inactive, and then re—energized to resume full power opera-
`tion as needed. Central o ice terminals (COTs) and cus-
`tomer premises equipment (CPE) units can exchange shut-
`down and resume signals without interfering with POTS
`services on the wire loop. Additionally, either a CPE or a
`COT unit can initiate both a low power state and resumption
`to a full power state.
`DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a block diagram of an ADSI.unit in accordance
`with the invention.
`
`FIG. 2 is a diagram of a central office with a central olfice
`terminal (COT) ADSL unit connected by a two-wire loop to
`a customer premises equipment (CPE) ADSL unit in accor-
`dance with the invention.
`
`FIG. 3 is a flowchart of a data exchange between two
`connected ADSL units in accordance with the invention.
`
`DETAILED DESCRIPTION
`
`‘
`
`Asymmetric Digital Subscriber Line (ADSL) technology
`is used to transmit wide—bandwidth modulated data over a
`two-wire loop using high frequency carrier signals. ADSL
`allows a two-wire loop to simultaneously transport POTS
`analog voice phone services along with high speed modu-
`lated digital data over wire loops of up to 18,000 feet. This
`simultaneous support of POTS and modulated digital ser-
`vices is provided by transporting POTS services using their
`traditionally allocated spectrum wl1ile transporting n1odu-
`lated digital data using spectrum outside of the POTS ran ge.
`FIG. 1 is a block diagram of a11 ADSL unit. To send and
`receive modulated digital data, the ADSL unit 100 employs
`high speed signal processing electronics 111 that includes,
`for example, digital signal processing (DSP) circuitry. Sig-
`nal processing electronics 111 eliminate stray electronic
`noise induced on the two-wire loop 120 and, along with
`transmit circuitry 112 and receive circuitry 113, are used to
`send and receive modulated data. In addition, signal pro-
`cessing circuitry 111 may implement error correcting
`algorithms, such as the Reed-Solomon algorithm, to further
`reduce data errors that arise during transmission. The signal
`processing, transmit, and receive functions may be provided ,
`by, for example, a Motorola CopperGold chip set or a
`GlobeSpan Technologies STAR or SLADE chip set. Control
`circuitry 117 is provided to control operation of the ADSL
`11nit 100, to control power usage byADSL 11nit circuitry, and
`for storage of ADSL unit parameters.
`To provision ADSI. service, an ADSI_ unit 100 is located I
`at each end of a wire loop 120. Referring to FIG. 2, an ADSL
`unit 100 located at the subscriber premises 240 is referred to
`as a customer premises equipment (CPE) ADSI. unit 242. A
`second ADSL unit 100,
`typically located at a telephone
`company central office 230, is known as the central olfice
`terminal (COT) unit 232. The CPE unit and the COT unit are
`connected by a two-wire loop 220 of up to 18,000 feet.
`Central office and customer premises equipment connects
`to the ADSL unit through a data interface 116 (FIG. 1). At
`the central office end of the loop 230, the data interface of
`the COT unit 232 is connected to central office data switch-
`ing equipment 234. At the subscriber end of the loop 240, the
`data interface of the CPE unit 242 is connected to customer
`premise equipment such as a personal computer 244.
`Data to be transmitted by an ADSL unit is arranged in a
`structure known as a ‘frame’ prior to being transmitted. A
`
`4
`frame is an arrangement of bits including both user data and
`signaling information required by the ADSL units. When
`there is nothing to transmit between ADSL units, the user
`data portion of the frame may be filled with idle packets.
`Within the ADSL framing structure is a low bit rate signaling
`channel over which handshaking information can be
`exchanged between ADSLunits. This signaling channel may
`be used, for example, to test the wire loop transmission path
`and to send ADSI. device status information.
`
`Circuitry within each ADSL unit 232 and 242 is used to
`remove noise, to perform error correction, to multiplex data,
`and to transmit and receive data. This is done without
`interfering with POTS audio and signaling transmissions
`over the two-wire loop 220, which uses spectrum below 4
`kilohertz (kHz). Modulated data from the ADSL units 232
`and 242 is transmitted using spectrum above 4 kHz, typi-
`cally using a range of frequencies of 40 kHz and greater.
`Signal filters 233 and 243 (known as “splitters”) are used to
`join signals being transmitted from one location,
`for
`example, the central office 230, and to separate signals when
`they are received at the distant location, for example, the
`customer premises 240.
`Within the central oflice 230, a splitter 233 is used to
`combine outgoing signals from the POTS switching equip-
`ment 231 and the COT ADSI. unit 232 for transmission on
`the loop 220. The splitter 233 also provides signals received
`on the two-wire loop 220 to both the POTS switching
`equipment 231 and to the COT ADSI. unit 232. Signals to
`be sent to the POTS switching equipment 231 are filtered by
`the splitter 233 so as to remove frequencies above voice-
`band. The resulting filtered signal may be handled by the
`POTS switch 231 as if it had originated on a traditional
`analog POTS connection. The signal from the splitter 233 to
`the COT ADSL unit 232 may contain the full frequency
`spectrum as it arrives over the wire loop 220 or may be
`filtered to remove voice band frequencies.
`At the customer premises 240, a splitter 243, which may
`serve as a telephone company network interface (NI) device,
`is used to combine outgoing signals from customer premises
`POTS—compatible equipment 241 and the CPE ADSL unit
`242 for transmission on the loop 220. The splitter 243 is also
`used to direct signals received on the two-wire loop 220 to
`both customer premises POTS equipment 241, such as an
`analog telephone or a FAX machine, and to the CPE ADSL
`unit 242.
`
`Signals to be sent to the customer premises POTS equip-
`ment 241 are filtered to remove frequencies above voice
`band. The resulting filtered signal may be handled by the
`customer premises POTS equipment 241 as if it had origi-
`nated on a traditional analog POTS connection. The signal
`from the splitter 243 to the CPE ADSL unit 242 may contain
`the full frequency spectrum as it arrives over the wire loop
`220 or it may be filtered to remove voieeband frequencies.
`The CPE ADSL unit 242 may be incorporated in, for
`example, an ADSL modem connected to a personal com-
`puter 244 that is programmed to send and receive over the
`ADSL connection. Circuitry to handle POTS and ADSL data
`functions may be combined within a single physical device
`handling signal splitting and filtering, POTS call processing
`and modulated data processing, transmitting, and receiving.
`Alternatively,
`these functions may be achieved using a
`number of physically separate devices.
`Prior to initiating transport of modulated data over the
`loop 220, signals are exchanged over the loop 220 between
`the COT unit 232 and the CPE unit 242 to adapt the ADSL
`units to the electronic characteristics of the particular wire
`
`Dish
`Exhibit 1004, Page 6
`
`

`
`5,956,323
`
`5
`loop 220. For example, loop loss characteristics, which are
`a function of loop length, wire gauge, wire composition, and
`other factors, are exchanged. This exchange of information
`is often referred to as handshaking. Once handshaking is
`completed, transmission of user data may begin.
`To reduce power requirements, the ADSL units 232 and
`242 may enter low power mode when user data transmission
`is complete. Either unit may initiate the low power mode. If,
`for example, the CPE unit 242 initiates low power mode, it
`does so by sending a shut-down signal to the COT unit 232.
`This shut-down signal may be conveyed in the ADSL low bit
`rate signaling channel; alternatively, an out—of—band signal
`on the loop may be used, for example, a 16 kHz AC signal.
`Still another alternative is for the CPE unit to stop sending
`ADSL framing information (such as would happen if the
`CPE unit were powered down).
`Upon receipt of the shut-down signal, the COT unit 232
`optionally stores in memory 117 characteristics of the loop
`220 that were determined by CPE to COT handshaking.
`Likewise, upon sending the shut-down signal, the CPE unit
`242 may also optionally store the loop characteristics that it
`obtained through CPE to COT handshaking. Storing loop
`characteristics enables rapid resumption of user data trans-
`mission when the units are returned to full power mode.
`Each unit 232 and 242 may then enter low-power mode by
`shutting off the now unnecessary sections of signal process-
`ing 111, transmitting 112, and receiving 113 circuitry. The
`loop 220 will then be in an inactive state. (Circuitry 115 to
`detect
`the resume signal must remain capable of signal
`detection during low power operation. If the COT unit 232
`were to initiate low power mode, signals would be
`exchanged with the CPE unit 242 in a like fashion.
`In alternative embodiments, both CPE 242 and (COT 232
`units may be capable of reduced power operation.
`Alternatively, only the COT 232 unit may reduce its power
`consumption, or only the CPE unit 242 may reduce its power
`consumption. If only the COT unit 232 is to reduce its power
`consumption,
`the COT unit 232 will not require resume
`signal generation 114 circuitry, nor will the CPE unit 242
`require resume signal detection circuitry 115. Similarly, if
`only the CPE unit 242 is to reduce power consumption, the
`CPE unit 242 will not require resume signal generation 114
`circuitry nor will the COT unit 232 require resume signal
`detection circuitry. Thus, the particular circuit components ,
`that can be placed in a low power mode may vary among
`differing brands, models, and versions of ADSL units.
`To return a unit that is in low power mode to full power
`operation, a resume signal
`is sent
`to the unit. In one
`embodiment, a COT ADSL unit resumes full power opera-
`tion upon receipt of a 16 kHz AC signal that is sent over the
`wire loop by a CPE ADSL unit. This resume signal may be
`detected by the COT unit using a 16 kHz AC signal detector
`115 that employs conventional frequency detection tech-
`niques. This detector 115 remains operative when the unit
`232 is in low-power mode. If the CPE unit 242 is capable of
`reduced power operation, a resume signal sent from the COT
`unit 232 to the CPE unit 242 would be similarly received at
`the customer premises and detected by the CPE unit 242.
`Upon receipt of the resume signal, the receiving ADSL
`unit returns the signal processing 111, transmitting 112, and
`receiving 113 circuitry to full power mode. If loop trans-
`mission characteristics had been stored, these parameters are
`retrieved from memory 117 and used to enable data trans-
`mission to resume quickly by reducing the time needed to
`determine loop transmission characteristics. After resump-
`tion of full power mode, additional liandsliaking between
`
`_
`
`‘
`
`6
`ADSL units 232 and 242 may occur. Upon reaching a fully
`operational state, transmission of user data may resume.
`Referring to FIGS. 2 and 3, one exemplary application of
`the invention is to reduce power requirements needed to
`maintain a link between a personal computer (PC) 244 and
`a remote data source 250. The remote data source 250 may
`be, for example, an Internet service provider (ISP) or an
`online service provider
`(OSP).
`In an exemplary
`configuration, a CPE ADSL unit 242 is connected by a
`digital
`interface 247 to a personal computer 244 pro-
`grammed to send and receive data over the ADSL unit 242.
`The CPE ADSL unit 242 may be incorporated in an ADSL
`modem that is installed in, or connected to, the PC 244. The
`CPE ADSL unit 242 is connected by a wire loop 220 to a
`COT ADSL unit 232 at a central office 230 at which a link
`to the remote data source 250 exists.
`
`the wire loop 220 is
`In the exemplary configuration,
`initially inactive, thus preventing information Ilow between
`the (‘PE 242 and COT 232 ADSL units. To return the loop
`220 to an active state, a start—up signal is sent to the CPE
`ADSL unit (step 301). The start-up signal is, for example, a
`command sent over the digital interface 247 from a device
`driver or other program module running in the PC 244 or
`may be represented by power to the CPE ADSL unit being
`turned on. Upon receipt of the start-up signal,
`the CPE
`ADSL unit may restore saved loop characteristic parameters
`(step 302). The CPE ADSL unit then transmits a 16 kHz
`resume signal on the loop (step 303) The resume signal is
`subsequently detected by loop monitoring circuitry in the
`COT unit (step 304). If the COT unit is in a low power state,
`it will return to full power operation upon detection of the
`resume signal from the CPE unit, this may include restoring
`loop characteristic parameters (step 305). If the COT unit
`was not in a low power state, the resume signal may be
`ignored by the COT unit. CPE and COT ADSL units may
`then exchange liandsliaking information to establish reliable
`data communication between the units (step 306). Hand-
`shaking information may be required where, for example,
`loop characteristics have changed due, for example,
`to
`temperature-dependent changes in loop resistance.
`Handsliaking information may also be exchanged for
`other device initialization purposes.
`Once reliable data transmission from the CPE to the COT
`ADSI. units is established, information may be exchanged
`over the established data path (step 307). Referring to FIG.
`2, the personal computer 244 may use the data path between
`ADSI. units to communicate with a remote data source by
`sending information over a digital interface 247 to the CPE
`ADSL unit 242. This digital interface may be an industry
`standard computer interface such as a small computer sys-
`tems interface (SCSI), an Ethernet interface, or a peripheral
`component interconnect (PCI) interface, or other industry
`standard or vendor proprietary interfaces allowing two-way
`data exchange. Information from the PC to the CPE unit may
`include both user data and signaling information to control
`CPE ADSI. unit operation or, by relaying such signaling
`over an ADSL to ADSL unit signaling channel, to control
`COT ADSL unit operation. User data provided to the CPE
`unit by the PC is transmitted to the COT unit over the
`established CPE to COT data transmission path.
`Data received at the COT unit may be converted to a data
`signal format compatible with standard telephone company
`switching equipment, for example, a 1.544 million hits per
`second (Mbps) T1 data signal, or to asynchronous transfer
`mode (ATM) cells over an optical carrier level 3 (OC—3)
`synchronous optical network (SONET)
`interface. The
`
`Dish
`Exhibit 1004, Page 7
`
`

`
`5,956,323
`
`7
`received data, now in a central office equipment compatible
`format, may be provided over a standard telephony interface
`236 to telephone company high speed data switching equip-
`ment 234, such as a digital cross connect switch or multi-
`plexing equipment to a second interface 251 that connects to
`a remote data source 250. Alternatively, the data may flow
`from the COT ADSL unit 232 directly to the remote data
`source 250 without handling by intermediary switching
`equipment 234. Two way data transfers between the remote
`data source 250 and the PC1244 may then take place over the
`resulting path from PC 244 to CPE unit 242 to COT unit 232
`to switching equipment 234 to remote data resource 250.
`Referring again to FIG. 3, the COT unit may be returned
`to low power mode by sending a shut—down signal from the
`CPE unit to the COT unit (step 308). The shut—down signal
`may be an expressly transmitted signal or may be inferred.
`For example, the shut down signal may be expressly sent as
`a series of signaling bits transmitted between the CPE and
`COT ADSL units. Alternatively, if the PC and COT ADSL
`unit are shut olf, a shut—down signal may be inferred from
`the loss of transmitted framing information between the CPE
`unit and the COT unit. The shut—down signal is subsequently
`detected by monitoring circuitry in the COTADSL unit (step
`309). Upon detecting a shut—down signal, the COT unit may
`save loop characteristics (step 310) and enter low power
`mode by reducing power to now unnecessary circuitry (step
`311). The described procedure 300 may be repeated to
`resume data transmission. Essentially the same sequence
`may occur to reduce power at a CPE ADSL unit 242. A CPE
`ADSL unit may enter a low power mode when, for example,
`a preset or programmed period of time passes without any
`user activity on the data path or an appropriate signal is sent
`from the COT ADSL unit.
`
`Other embodiments are within the scope of the following
`claims. For example, while the invention has been described
`in the context of ADSL units providing an asymmetric data
`channel, the invention may be applied to other terminal units
`wherein voice band services share a loop with modulated
`data transmission, such as in Symmetric Digital Subscriber
`Line
`and Rate Adaptive Digital Subscriber Line
`(RADSL) terminal units. Similarly, while systems with
`two-wire loops have been described, the invention may be
`used in systems including wireless loops and loop segments.
`Wakeup signals may include multi tone signals and other
`signals outside the POTS spectrum. Terminal unit circuitry /
`may include digital circuitry, analog circuitry, software,
`firmware, or a combination of these elements. The scope of
`the invention should be limited only as set forth in the claims
`that follow.
`What is claimed is:
`1. A method of conserving power in a terminal u11it having
`a transmitter and receiver for modulated data communica-
`tion over a communications loop, comprising:
`monitoring the loop to detect a shut—down condition;
`reducing power consumption of demodulation circuitry in
`the terminal unit upon detection of a shut—down con-
`dition;
`monitoring the loop with a monitoring circuit to detect a
`resume signal that is not a modulated data signal and
`that is outside the voiceband frequency range on the
`loop; and
`activating demodulation circuitry when the resume signal
`is detected.
`2. The method of claim 1 wherein modulated data C0[11-
`prises a bit stream including framing information, and a
`shut—down condition comprises a loss of framing informa-
`tion.
`
`8
`3. The method of claim 1 wherein modulated data com-
`prises a bit frame including signaling bits and data bits and
`monitoring the loop to detect a shut—down condition com-
`prises monitoring the signaling bits in the bit frame.
`4. The method of claim 1 where the resume signal
`comprises a 16 kHz AC signal.
`5. The method of claim 1 further comprising:
`storing loop characteristic parameters in a memory circuit
`upon detection of the shut—down condition; and
`transferring loop characteristic parameters from the
`memory circuit
`to the demodulation circuitry upon
`activating the demodulation circuitry.
`6. The method of claim 5 further comprising performing
`handshaking to determine loop characteristics.
`7. A modulated data transmitting and receiving unit,
`comprising:
`a connector operatively coupling the unit to a communi-
`cations loop;
`first circuitry coupled to the connector to transmit and
`receive a modulated data signal in a frequency range
`above voiceband;
`memory circuitry operatively coupled to the first circuitry
`to store loop characteristic parameters in a low—power
`state and to transfer loop characteristic parameters to
`the first circuitry during a power up sequence; and
`second circuitry coupled to the connector to detect a
`resume signal in the frequency range above voiceband
`and then to initiate the power up sequence for the first
`circuitry.
`8. The modulated data transmitting and receiving unit of
`c aim 7 wherein the connector comprises a two-wire con-
`nector.
`
`9. The modulated data transmitting and receiving unit of
`c aim 7 wherein the irst circuitry comprises asymme ric
`digital subscriber line data transmission circuitry.
`10. The modu ated C ata transmitting and receiving uni of
`c aim 7 wherein the second circuitry comprises 16 kHz
`frequency detection circuitry.
`11. The modu ated Cata transmitting and receiving uni of
`c aim 7 wherein the communications loop comprises a
`wireless communications loop.
`12. The modu ated C ata transmitting and receiving uni of
`c aim 7 wherein the resume signal comprises an AC signal
`greater than 4 kHz.
`13. The modu ated C ata transmitting and receiving uni of
`c aim 7 wherein he resume signal comprises transmission of
`an AC signal at a first frequency followed by transmission of
`an AC signal at a second frequency.
`14. The modu ated C ata transmitting and receiving 1u1i of
`c aim 6 further comprising:
`a control signal interface for receiving a start-up signal;
`and
`
`third circuitry coupled to the connector to transmit a
`resume signal 011 the loop upon receipt of a start-up
`signal on the control signal interface.
`15. The apparatus of claim 7 wherein the first circuitry
`further comprises handshaking circuitry to determine loop
`characteristic parameters associated with the loop.
`16. A modulated data transmitting and receiving unit,
`comprising:
`a connector operatively coupling the unit to a communi-
`cations loop;
`a control signal interface for receiving a start-up signal;
`first circuitry coupled to the connector to transmit and
`receive a modulated data signal at frequencies above
`voiceband;
`
`Dish
`Exhibit 1004, Page 8
`
`

`
`5,95 6,323
`
`9
`memory circuitry operatively coupled to the first circuitry
`to store loop characteristic parameters in a low—power
`state and to transfer loop characteristic parameters to
`the first circuitry upon receipt of a start-up signal on a
`control signal interface; and
`second circuitry coupled to the connector to transmit a
`resume signal on the loop upon receipt of the start-up
`signal on the control signal interface.
`17. T16 moculatec data transmitting and receiving unit of
`claim 16 wherein the communications loop comprises a
`two-wire communications loop.
`18. T16 moculatec data transmitting and receiving unit of
`claim 16 wherein the communications loop comprises a
`wireless commiinica