CA2272576A1 - Apparatus and method for communicating voice and data between a customer premises and a central office - Google Patents
Apparatus and method for communicating voice and data between a customer premises and a central office Download PDFInfo
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- CA2272576A1 CA2272576A1 CA002272576A CA2272576A CA2272576A1 CA 2272576 A1 CA2272576 A1 CA 2272576A1 CA 002272576 A CA002272576 A CA 002272576A CA 2272576 A CA2272576 A CA 2272576A CA 2272576 A1 CA2272576 A1 CA 2272576A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J1/00—Frequency-division multiplex systems
- H04J1/02—Details
- H04J1/12—Arrangements for reducing cross-talk between channels
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M11/00—Telephonic communication systems specially adapted for combination with other electrical systems
- H04M11/06—Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors
- H04M11/062—Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors using different frequency bands for speech and other data
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- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
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- Telephonic Communication Services (AREA)
Abstract
A method and apparatus are provided for communicating data (25) across a communication link (26), in a manner that senses and dynamically adapts to the simultaneous transmission of voice information (30, 32) across the local loop. In accordance with one aspect of the invention, a method is provided for dynamically communicating data (25) over a local loop using a modem (20) comprising the steps of transmitting data in a full-band transmission state, sensing a band-limiting condition, and adjusting the transmission of data from the full-band transmission state to a band-limited transmission state, in response to the sensing step. A significant aspect of the present invention is the dynamic allocation of the data transmission bandwidth, whereby the invention senses a condition indicative of whether voice information (30, 32) is being communicated. If so, then the system shifts and/or narrows the data transmission bandwidth to allow for voice communications without interference from or with the data transmission.
Description
Serial. No. 60/033.660, filed on December 1 T, 1996, and entitled Di~7ital Subscriber POTS Filters/Splitters or Special Premise Wiring.
> > hi~~h speed moderns offering robust communication between a central office and a Field of the Invention The present invention generally relates to modems. and more particular( to ?o ("RADSL'~) modems are able to transfer data at high rates over the local loop. because Discussion of the Related Art High speed digital modems. such as Rate Adaptive Digital Subscriber Loop DATA BETWEEN A CUSTOMER PREMISES AND A CENTRAL OFFICE
Cross-Reference to Related Applications This application claims the benefit of U.S. Provisional Patent Application Loop Data Communications Method Enabling Simultaneous Data and POTS Vl'ithout Background of the Invention customer premises.
they use frequencies which are significantly higher than the voice band frequencies used in Plain Old Telephone Service ("POTS"). By way of example. speech on a POTS system generally occurs in the frequency spectrum betty-een about 0 Hz ("DC'') and about -1 KHz. whereas RADSL modems use the frequency spectrum of between 25 about 20 KHz to about 1 MHz. High speed digital modems ;enerallv include error detection circuitrw vwhich measures the errors which occur during communications.
Bv making such measurements. they are then able to update their statistical SUBSTITUTE SHEET (PULE 26~
knowledge of the wire pair which extends between the subscriber's location and the central office. Using that statistical knowledge, the modems can select optimal operating speeds. These modems were originally proposed when it was thou~~ht that services, such as video-on-demand, would be desirable.
a As modem technology has developed, another need has arisen. in that the Internet has become a popular medium for both personal and work related use.
While the high speeds of RADSI. modems seem to be quite desirable. their use of high frequencies mean that they also need to be protected from higTh frequency noise, such as cross-talk from adjacent channels or adjacent loops in the loop cable binder, as such noise causes them to downwardly adjust their operating' speeds. In order to avoid certain types of noise, RADSI, modems typically require the use of filters, called POTS filters. together with splitters for isolating Public Switched Telephone Network ("PSTN") equipment from the IRADSL modems. Indeed, without POTS filters and POTS splitters. POTS si;~nals directly interfere with the RADSL
~ 5 spectrum below about ?0 kilohertz and the RADSL spectrum directly interferes with the POTS. POTS filters and POTS splitters reduce POTS si~~naliny transients from interferin~l with RADSL data transmission. In addition, the use of the hl~_h RADSL
bandwidth demands relatively high transmit power. w ~hich can cause distortions and dynamic range overload to POTS equipment.
?o Unfortunately. the manufacture and installation of POTS filters and splatters are expensive, and their use sometimes requires rewiring of the customer premises to ensure that all PSTN equipment is properly isolated from the RADSL modems and computing equipment. Consequently, it would be desirable to avoid the use of POTS
SUBSTITUTE SHEET (RULE 26) sputters and filters. in order to avoid the expense they impose (e.g..
purchase cost and possible rewiring of customer premises).
Accordingly. their appears to be a need for a mass market modem which has data transfer rates ;greater than the 33.6 Kbps attainable by PSTN modems. yet under the rate that requires the addition of POTS filters, splitters. etc. to address noise and deleterious transmission line effects often encountered in high speed DSL
modems.
Yet another problem which is manifest in increased Internet access and data communications is the increasin~~Iy limited availability to the customer phone line or local loop for its ori'_inal purpose. i. e.. voice communications. Of course.
one solution is for a customer to purchase an additional phone line. This.
however.
imposes an additional cost on the customer. Woreover. unless the line is dedicated by the customer for a specific purpose (which is poor utilization). the second line may not always be available when needed.
Accordingly. there is a need to provide an improved modem that accommodates data transmissions. while simultaneously allowing traditional voice operation of a telephone attached to the same line at the customer premise. It is particularly desirable to have such a modem that does not require the use of costly POTS alters and splitters.
Zo Summary of the Invention Certain objects. advantages and novel ff:atures of the invention will be set forth 1I1 part in the description that follows and in part will become apparent to those skilled in the art upon examination of the follovving or may be learned with the SUBSTITUTE SHE!-? (RULE 26) practice of the invention. The objects and advanta~Tes of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the advantages and novel features. the present invention is <~enerally directed to a method and apparatus for communicating data across a local loop. in a manner that senses and dynamically adapts to the simultaneous transmission of POTS (e.g.. voice or PSTN modem) information across the local loop. In accordance with one aspect of the invention. a method is provided for dynamically communicating data over a local loop usin~~ a modem comprising= the steps of transmittin~T data in a full-band transmission state. sensin;~ a band-limitin~l condition.
and adjusting the transmission of data from the fill-band transmission state to a band-limited transmission state. in response to the sensing step. The step of sensing a band-limiting condition includes both the detection of the onset of a condition it;dicatin~T
that the method should enter the band-limited transmission state. as welt as the i 5 detection of the cessation of that condition. indicating that the method should enter the full-band transmission state ti-om the band-limited transmission state.
In accordance with the method of the present invention. data may be transmitted by the modem across the local loop at the same time that POTS
(e.~,T..
voice or PSTN modem data) information is communicated across the same local loop.
30 _a significant aspect of the present invention is the dynamic allocation of the data transmission bandwidth. whereby the invention senses a condition indicative of whether POTS information is bein~~ communicated. If so. then the system shifts and/or narrows the data transmission bandwidth to allow for voice communications SUBSTITUTE SHEET (RULE 26) WO 98l27665 PCTlL1S97122632 without interference from or with the data transmission. However. when no POTS
information is being= communicated. the invention dynamically allocates the data transmission bandwidth to utilize at least a portion. if not all. of the frequency band otherwise used for communicatint= voice information.
In accordance with the preferred embodiment) the method senses an off hook condition of a telephone handset of a telephone electrically connected to the local loop. In use. a local loop extending between a customer premises and a central office branches. at the customer premise, to support multiple connections to the local loop.
In this regard. the various branches or connec;tions are typically routed throughout a customer premises to phone _jacks. such as RJ-I I jacks. Multiple telephones may be plugged directly into these jacks for voice communication across the local loop.
Similarly. a modem constructed in accordance with the present invention may be plugged directly into one of these jacks. The off hook condition is preferably sensed by detectin~~ either a change in impedance in the telephone line, or alternatively a drop ~ s in line voltage across the telephone line.
In accordance with one embodiment of the invention. the full-band transmission state is defined by a transmission frequency bandwidth having a lower frequency boundary of less than about 1 ~-20 kilohertz (and preferable less than ~
kilohertz). In the band-limited transmission state, the transmission frequency ?o bandwidth has a lower frequency boundary of greater than ~l kilohertz. The significance of these values. for purposes of the invention, is that when no voice information is bein<~ communicated across the local loop, the transmission frequency bandwidth invades that ti-equency band generally dedicated to the transmission of SUBSTITUTE SHEE? (RULE 26) voice information ( i. e.. the 0-4 kilohertz POTS frequency band. When.
however. the invention senses that POTS information is being communicated across the local loop.
or that there is a demand for the POTS band (e.g., telephone off hook, ring.
ctc.). then the embodiment shifts the lower boundary of the transmission frequency bandwidth s above the generally 4 kilohertz upper limit of the voice band. Preferably, the lower boundary will be shifted upwardly to approximately 20 kilohertz, to allow sufficient separation between the voice and data transmission frequency bands to that no interference between the two is realized, either by voice information corruptin~~ data.
or data transmission being heard in the voice band as noise.
For purposes of the preferred embodiment of the present invention, the precise value of upper boundary of the transmission Ii-equencv bandwidth is not so significant. as it is the dynamic adjustment of the lower boundary and/or the reduced power in POTS mode. that realizes the inventive step. However. it will be appreciated that the upper boundary will generally be greater than 40 kilohertz. in order to def ne a meanin~~ful transmission frequency bandwidth for data transmission. Indeed. in the preferred embodiment. the upper li~equency boundary is approximately 80 kilohertz.
It is believed that this frequency is low enou~~h that transmissions may be effectively implemented without the need for POTS filters or POTS splatters. and therefore significantly reducing the cost of implementing the inventive system. Signal-to-noise 2o ratio is hi~~h to permit reasonable data throughput without excessive power incident on attached P01'S devices. Also, premises wirinf,~ and subscriber loop stubs do not cause substanti~ a nulls in the frequency response. It will be further appreciated that shifting of the upper frequency boundary is not relevant to the present invention. That is. the O
SUBSTITUTE SHEET (RULE 26) upper boundary may be shifted in conjunction with the shifting of the lower frequency boundary. or alternatively the upper frequency boundary may remain substantially fixed.
It will be further appreciated that - depending upon loading, line conditions.
and other factors - the spectral shape of the band-limited xDSL transmission may be varied to minimize noise, intermodulation products. or other interference within the POTS frequency band. More particularly. it is generally understood that the power density of xDSL transmissions is generally greater than that of POTS
transmissions.
Merely shiftin~T the xDSL tral7Sm1SS1011 lIltO the band-limited transmission state with a lower cut-off frequency of approximately ?OkHz may not always provide a wide enough ward band to prevent interference wish the POTS band. Line loading.
line conditions. and other factors (which differ among local loops) factor into this determination. Intermodulation products are another source of noise that often is present within the POTS band. When such noise is present within the POTS band, the band-limited transmission state may be further configured by reducing the power-density of the xDSL transmission. Another. rel~3ted solution may be to uniquely shape the spectral curve for xDSL transmissions. This. for example. may be done by tapering the lower frequency portion of the curve (i. e., that portion near the approximately 15-20 kHz frequency).
2o In accordance with another aspect of tt~~e preferred embodiment. a modem is provided for communicating data across a local loop. The modem includes an input/output signal line that is electrically connected with the local loop (e.g.. plugged into an R.1-1 1 phone jack). The modem also includes a processor unit that is adapted SUBSTITUTE SHEET (RULE 26) WO 98l27665 PCT/US97/22632 for operation in one of two states: a full-band transmission state and a band-limited transmission state. The full-band transmission state is defined by a lower frequency boundary at a value below approximately 15-20 kilohertz and an upper frequency boundary Qenerally greater than 40 kilohertz (as discussed above). The band-limited state is defined by a lower frequency boundary greater than 4 kilohertz and an upper frequency boundary greater than 40 kilohertz (which may or may not be the same as the upper frequency boundary for the full-band transmission state). The modem further includes a sensor or other sensiny~ means for sensing that the local loop is in POTS mode (e. ~~.. transmitting POTS information. or preparing to transmit POTS
1 o information ). and the data signal power and bandwidth are adaptively altered to provide data without out interfering with the POTS transmission. Upon sensing the band-limiting condition. such as an off hook condition, the controller causes the processor unit to upwardly shift the lower frequency boundary of the transmission frequency band and operate in the band-limited. or reduced-power, state.
Likewise.
~ 5 upon sensing no band-limiting condition (or a cessation in the band-limiting condition 1. the controller causes the processor unlt to dowwvardly shift the lower frequency boundary of the transmission frequency band, and operate in the full-band transmission state, to maximize data throughput.
In accordance with yet a further aspect of the present invention. a method is ?o provided for simultaneously communicating both voice and data between a customer premises and a central office across a local loop. In accordance with this aspect of the invention. the method comprises the steps of: ( 1 ) transmitting data between the customer premises and the central office in a first frequency band. wherein the first s SUBSTITUTE SHEET (RULE 26) frequency band is defined by an upper frequc:ncv boundary and a lower frequency boundary: (?) allocatin~~ a second ti-equency band for transmitting voice information between the customer premises and the central office; (3) sensing a band-limiting condition: and (4) dynamically shifting the lower frequency boundary of the first s frequency band in response to the sensed band-:limiting condition. In accordance with the invention. the lower frequency boundary on the first frequency band shifted to at least partially overlap the second frequency band when no band-limitin~~
condition exists. The lower frequency boundary of the f rst frequency band is further shifted to avoid overlapping with any portion of the second frequency band when the band-iimitin~~ condition exists.
In accordance with yet a further aspect of the invention. a modem is provided for communicating across a communication IIIlk capable of single-use transmissions and multiple-use transmissions. The term single-use transmissions is used to generally connote that a single transmission or communication is occurrinU
across the link. For example. a single PSTN voice call. or a siny~ie data communication transmission. The term multiple-use transmissions is used to generally imply that multiple transmissions or communications are occurring simultaneously. For example. the simultaneous transmission of a daoa communication and a PSTN
voice call. The modem constructed in accordance with this aspect of the invention includes ?o an input/output signal line in communication with the communication Illlk.
It further includes a processor unit adapted for operation in one of at least two states.
a fill-band transmission state and a band-limited state. wherein the full-band transmission state occurs when sin_le-use transmissions are occurrin<~ across the transmission link. and SUBSTlTIlTE SHEET' (RULE 26) WO 98l27665 PCT/I1S97/22632 the band-limited transmission state occurs when multiple-use transmissions are occurring across the communication link.
It will be appreciated that, in accordance with a broad inventive aspect. the present invention operates by adjusting transmit power between a band-limited s transmission state and a full-band transmission state. Generally (but not necessarily always). the full-band transmission state occurs when the communication link is operating in a single-use transmission mode, while the band-limited transmission state generally occurs when the communication link is operating in a multiple-use transmission mode. In accordance with this broad concept of the invention.
1 o substantial transmission energy is transmitted by the modem in or near the POTS
frequency band. when the modem is transmitting in the full-band state.
Conversely.
very little (ideally zero) energy is transmitted by the modem in or near the POTS
frequency band, when the modem is transmitting in the band-limited state. This allows for simultaneous POTS transmissions (e.g.. voice, PSTN modem. erc. ) in the POTS fi~equencv band, and band-limited modem transmissions.
Brief Description of the Drawings The accompanvin~T drawinLgs incorporated in and forminy_ a part of the specification. illustrate several aspects of the present invention, and together with the 2o description serve to explain the principles of the invention. In the drawin~~s:
FIG. 1 is an illustration of the frequency spectrum of a dual frequency band communications system of the prior art. depicting the POTS transmission frequency band and the xDSL transmission frequency band;
io SUBSTITUTE SHEET (RULE 26) FIG. 2 is a block diagram illustrating the primary components in a system utilizing the present invention:
FIG. 3A is a frequency spectrum illustrating the full-band transmission frequency band of the present invention;
FIG. 3B is a frequency spectrum illustrating the band-limited transmission frequency band of the present invention;
FIG. 3C is a frequency spectrum illustrating a band-limited transmission frequency band of an alternative embodiment of~ the present invention. having a uniquely shaped xDSL. transmission band:
1o FIG. 3D is a frequency spectrum illustratin4_ a band-limited transmission frequency band of an alternative embodiment of the present invention. having a reduced power YDSL transmission band:
FIG. 4 is a block diagram illustrating the primary components of a modem constructed in accordance with the present invention;
l5 FIG. 5 is a circuit diagram illustrating the analog front end component of the modem block diagram of FIG. 4:
FIG. 6 is a software flowchart depicting the operation of the functional operation of the analog front end element. illustrated in FIG. ~: and FIG. 7 is a software flowchart illustrating the top-level operation of~ a system 3o constructed in accordance with the present invention.
Detailed Description of the Preferred Embodiment of the Invention SUBSTITUTE SHEE'I~ (RULE 26) Having summarized the invention. reference will now be made in detail to the description of the invention as illustrated in the drawings. While the invention will be described in connection with these drawin~~s. there is no intent to Limit it to the embodiment or embodiments disclosed therein. On the contrary. the intent is to cover all alternatives. modifications and equivalents included within the spirit and scope of the invention as defined by the appended claims.
Turnin~~ now to the drawin~~s. FIG. 1 is a diagram illustratin~~ frequency' band communications. as is knovyn in the prior art. The term frequency band communications is used to indicate communication of information within a certain IO defined. frequency band. As is known in the prior art. plain old telephone system (POTS) communications are transmitted in the frequency band 1? defined between about 0 (DC) and about ~ kHz. A second transmission frequency band 14 is defined at a higher ti-equency level than the POTS ti-equency band 1?. and is used in the transmission of digital subscriber line (DSL) communications. A ~~uard dead band 16 is typically provided to separate the two transmission frequency bands 12 and 1 ~l. 'The DSL transmission frequency band 14 is more broadly denominated as "xDSL-'.
wherein the "x" generically denominates any of a number of transmission techniques within the DSL family. For example, ADSL, - Asymmetric Digital Subscriber Line.
RADSL -- Rate Adaptive Diy=ital Subscriber Line. HDSL -- Hi~~h-Bit-Rate DSL.
etc.
?o As is known. xDSL transmission frequency bands 14 may encompass a bandwidth of greater than 1 MHz. As a result. and for the reasons described above, without the addition of extra equipment such as POTS filters, splitters. etc. xDSL
si<~nals are not n SUBSTITUTE SHEET (RULE 26) WO 98l27665 PCT/US97/22632 compatible with attached POTS type equipment. such as telephones. PSTiV
modems.
facsimile machines, etc.
As will be discussed in more detail below, the present invention provides an upper transmission band having an upper frequency boundary that is much lower than the 1 MHz frequency boundary often encountered in ;cDSL transmissions. Indeed.
the upper frequency boundary of the present invention is defined in a ran<~e that is readily supported by. or compatible with. transmission systems (and attached POTS type equipment) presently in place between a customer premises and a central office.
without the need for extraneous devices such as POTS filters and POTS
splitters. In I o this regard. reference is made to FIG. ?. ~yhich is a top level diagram illustrating the principal hardvyare components of a system utilizing the present invention. In accordance with one aspect of the invention. a modem 'ZO is provided for achieving efficient data communications between a customer premises ?2 and a central office ?4 across a local loop 26. by dynamically allocatin~~ a transmission frequency bandwidth t 5 and/or power for transmitting data. Certainly. one of the factors motivating the development of the present invention is the expanded demand for hi<~~her speed communications in recent years. This enhanced demand is primarily attributed to communications over the Internet.
'the present invention dynamically allocates a data transmission frequency ?o band and/or power spectral density (PSD) in response to POTS communications across the same line. More particularly. the present invention may utilize the frequency band otherwise allocated for POTS/voice transmission. at times when there is no present demand for transmitting voice information. When. however. there is a f3 SUBSTITUTE SHEET (RULE 26) demand for voice transmissions. then the present invention reallocates the transmission frequency band and PSD for the data communications so that there is no overlap or interference with the POTS transmission Irequencv band 12, and so that there is not significant interference to POTS type attached equipment.
In keeping within the description of FIG. 2, the customer premises ?~ may be a single-family household having a single phone line ?6 for communicating between the customer premises 22 at a central office ?4. Within the house or customer premises ??, multiple connections branch off of the local loop 26 and are terminated at phone jacks (such as RJ-I 1 ) located in various rooms of the household. In this wav.
multiple telephones 30. and 32 may be plu~~~~ed in and supported from the same phone line 26. In the same way, a personal computer may be disposed in communication with the local loop 26 by way of a modem 20.
Presently, unless a user purchases an additional phone line. or a more costly communication service. such as xDSL. simultaneous transmissions of voice and data > > to different locations are not possible. As a result. one person in a household may have the focal loop 26 tied up with data communications (such as Internet communications). while another person at the same household is awaitin~_= the use of the local loop 26 for voice communication. An accordance with the present invention.
and as will be discussed in more detail below, this shortcoming is overcome.
2o In keeping with the description of F1G. ?, a companion modem ~10. that is compatible with the modem 20. is provided at the central office 24. As is know w.
other equipment. such as wire distribution frame and standard telephone sw itching equipment ~2 may also be in communication with the local loop 26, Since the is SUBSTITUTE SHEET (RULE 26) conti~~uration and operation of such equipment is known in the prior art and does not effect or impact the present invention, it will not be discussed herein. FIG.
> > hi~~h speed moderns offering robust communication between a central office and a Field of the Invention The present invention generally relates to modems. and more particular( to ?o ("RADSL'~) modems are able to transfer data at high rates over the local loop. because Discussion of the Related Art High speed digital modems. such as Rate Adaptive Digital Subscriber Loop DATA BETWEEN A CUSTOMER PREMISES AND A CENTRAL OFFICE
Cross-Reference to Related Applications This application claims the benefit of U.S. Provisional Patent Application Loop Data Communications Method Enabling Simultaneous Data and POTS Vl'ithout Background of the Invention customer premises.
they use frequencies which are significantly higher than the voice band frequencies used in Plain Old Telephone Service ("POTS"). By way of example. speech on a POTS system generally occurs in the frequency spectrum betty-een about 0 Hz ("DC'') and about -1 KHz. whereas RADSL modems use the frequency spectrum of between 25 about 20 KHz to about 1 MHz. High speed digital modems ;enerallv include error detection circuitrw vwhich measures the errors which occur during communications.
Bv making such measurements. they are then able to update their statistical SUBSTITUTE SHEET (PULE 26~
knowledge of the wire pair which extends between the subscriber's location and the central office. Using that statistical knowledge, the modems can select optimal operating speeds. These modems were originally proposed when it was thou~~ht that services, such as video-on-demand, would be desirable.
a As modem technology has developed, another need has arisen. in that the Internet has become a popular medium for both personal and work related use.
While the high speeds of RADSI. modems seem to be quite desirable. their use of high frequencies mean that they also need to be protected from higTh frequency noise, such as cross-talk from adjacent channels or adjacent loops in the loop cable binder, as such noise causes them to downwardly adjust their operating' speeds. In order to avoid certain types of noise, RADSI, modems typically require the use of filters, called POTS filters. together with splitters for isolating Public Switched Telephone Network ("PSTN") equipment from the IRADSL modems. Indeed, without POTS filters and POTS splitters. POTS si;~nals directly interfere with the RADSL
~ 5 spectrum below about ?0 kilohertz and the RADSL spectrum directly interferes with the POTS. POTS filters and POTS splitters reduce POTS si~~naliny transients from interferin~l with RADSL data transmission. In addition, the use of the hl~_h RADSL
bandwidth demands relatively high transmit power. w ~hich can cause distortions and dynamic range overload to POTS equipment.
?o Unfortunately. the manufacture and installation of POTS filters and splatters are expensive, and their use sometimes requires rewiring of the customer premises to ensure that all PSTN equipment is properly isolated from the RADSL modems and computing equipment. Consequently, it would be desirable to avoid the use of POTS
SUBSTITUTE SHEET (RULE 26) sputters and filters. in order to avoid the expense they impose (e.g..
purchase cost and possible rewiring of customer premises).
Accordingly. their appears to be a need for a mass market modem which has data transfer rates ;greater than the 33.6 Kbps attainable by PSTN modems. yet under the rate that requires the addition of POTS filters, splitters. etc. to address noise and deleterious transmission line effects often encountered in high speed DSL
modems.
Yet another problem which is manifest in increased Internet access and data communications is the increasin~~Iy limited availability to the customer phone line or local loop for its ori'_inal purpose. i. e.. voice communications. Of course.
one solution is for a customer to purchase an additional phone line. This.
however.
imposes an additional cost on the customer. Woreover. unless the line is dedicated by the customer for a specific purpose (which is poor utilization). the second line may not always be available when needed.
Accordingly. there is a need to provide an improved modem that accommodates data transmissions. while simultaneously allowing traditional voice operation of a telephone attached to the same line at the customer premise. It is particularly desirable to have such a modem that does not require the use of costly POTS alters and splitters.
Zo Summary of the Invention Certain objects. advantages and novel ff:atures of the invention will be set forth 1I1 part in the description that follows and in part will become apparent to those skilled in the art upon examination of the follovving or may be learned with the SUBSTITUTE SHE!-? (RULE 26) practice of the invention. The objects and advanta~Tes of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the advantages and novel features. the present invention is <~enerally directed to a method and apparatus for communicating data across a local loop. in a manner that senses and dynamically adapts to the simultaneous transmission of POTS (e.g.. voice or PSTN modem) information across the local loop. In accordance with one aspect of the invention. a method is provided for dynamically communicating data over a local loop usin~~ a modem comprising= the steps of transmittin~T data in a full-band transmission state. sensin;~ a band-limitin~l condition.
and adjusting the transmission of data from the fill-band transmission state to a band-limited transmission state. in response to the sensing step. The step of sensing a band-limiting condition includes both the detection of the onset of a condition it;dicatin~T
that the method should enter the band-limited transmission state. as welt as the i 5 detection of the cessation of that condition. indicating that the method should enter the full-band transmission state ti-om the band-limited transmission state.
In accordance with the method of the present invention. data may be transmitted by the modem across the local loop at the same time that POTS
(e.~,T..
voice or PSTN modem data) information is communicated across the same local loop.
30 _a significant aspect of the present invention is the dynamic allocation of the data transmission bandwidth. whereby the invention senses a condition indicative of whether POTS information is bein~~ communicated. If so. then the system shifts and/or narrows the data transmission bandwidth to allow for voice communications SUBSTITUTE SHEET (RULE 26) WO 98l27665 PCTlL1S97122632 without interference from or with the data transmission. However. when no POTS
information is being= communicated. the invention dynamically allocates the data transmission bandwidth to utilize at least a portion. if not all. of the frequency band otherwise used for communicatint= voice information.
In accordance with the preferred embodiment) the method senses an off hook condition of a telephone handset of a telephone electrically connected to the local loop. In use. a local loop extending between a customer premises and a central office branches. at the customer premise, to support multiple connections to the local loop.
In this regard. the various branches or connec;tions are typically routed throughout a customer premises to phone _jacks. such as RJ-I I jacks. Multiple telephones may be plugged directly into these jacks for voice communication across the local loop.
Similarly. a modem constructed in accordance with the present invention may be plugged directly into one of these jacks. The off hook condition is preferably sensed by detectin~~ either a change in impedance in the telephone line, or alternatively a drop ~ s in line voltage across the telephone line.
In accordance with one embodiment of the invention. the full-band transmission state is defined by a transmission frequency bandwidth having a lower frequency boundary of less than about 1 ~-20 kilohertz (and preferable less than ~
kilohertz). In the band-limited transmission state, the transmission frequency ?o bandwidth has a lower frequency boundary of greater than ~l kilohertz. The significance of these values. for purposes of the invention, is that when no voice information is bein<~ communicated across the local loop, the transmission frequency bandwidth invades that ti-equency band generally dedicated to the transmission of SUBSTITUTE SHEE? (RULE 26) voice information ( i. e.. the 0-4 kilohertz POTS frequency band. When.
however. the invention senses that POTS information is being communicated across the local loop.
or that there is a demand for the POTS band (e.g., telephone off hook, ring.
ctc.). then the embodiment shifts the lower boundary of the transmission frequency bandwidth s above the generally 4 kilohertz upper limit of the voice band. Preferably, the lower boundary will be shifted upwardly to approximately 20 kilohertz, to allow sufficient separation between the voice and data transmission frequency bands to that no interference between the two is realized, either by voice information corruptin~~ data.
or data transmission being heard in the voice band as noise.
For purposes of the preferred embodiment of the present invention, the precise value of upper boundary of the transmission Ii-equencv bandwidth is not so significant. as it is the dynamic adjustment of the lower boundary and/or the reduced power in POTS mode. that realizes the inventive step. However. it will be appreciated that the upper boundary will generally be greater than 40 kilohertz. in order to def ne a meanin~~ful transmission frequency bandwidth for data transmission. Indeed. in the preferred embodiment. the upper li~equency boundary is approximately 80 kilohertz.
It is believed that this frequency is low enou~~h that transmissions may be effectively implemented without the need for POTS filters or POTS splatters. and therefore significantly reducing the cost of implementing the inventive system. Signal-to-noise 2o ratio is hi~~h to permit reasonable data throughput without excessive power incident on attached P01'S devices. Also, premises wirinf,~ and subscriber loop stubs do not cause substanti~ a nulls in the frequency response. It will be further appreciated that shifting of the upper frequency boundary is not relevant to the present invention. That is. the O
SUBSTITUTE SHEET (RULE 26) upper boundary may be shifted in conjunction with the shifting of the lower frequency boundary. or alternatively the upper frequency boundary may remain substantially fixed.
It will be further appreciated that - depending upon loading, line conditions.
and other factors - the spectral shape of the band-limited xDSL transmission may be varied to minimize noise, intermodulation products. or other interference within the POTS frequency band. More particularly. it is generally understood that the power density of xDSL transmissions is generally greater than that of POTS
transmissions.
Merely shiftin~T the xDSL tral7Sm1SS1011 lIltO the band-limited transmission state with a lower cut-off frequency of approximately ?OkHz may not always provide a wide enough ward band to prevent interference wish the POTS band. Line loading.
line conditions. and other factors (which differ among local loops) factor into this determination. Intermodulation products are another source of noise that often is present within the POTS band. When such noise is present within the POTS band, the band-limited transmission state may be further configured by reducing the power-density of the xDSL transmission. Another. rel~3ted solution may be to uniquely shape the spectral curve for xDSL transmissions. This. for example. may be done by tapering the lower frequency portion of the curve (i. e., that portion near the approximately 15-20 kHz frequency).
2o In accordance with another aspect of tt~~e preferred embodiment. a modem is provided for communicating data across a local loop. The modem includes an input/output signal line that is electrically connected with the local loop (e.g.. plugged into an R.1-1 1 phone jack). The modem also includes a processor unit that is adapted SUBSTITUTE SHEET (RULE 26) WO 98l27665 PCT/US97/22632 for operation in one of two states: a full-band transmission state and a band-limited transmission state. The full-band transmission state is defined by a lower frequency boundary at a value below approximately 15-20 kilohertz and an upper frequency boundary Qenerally greater than 40 kilohertz (as discussed above). The band-limited state is defined by a lower frequency boundary greater than 4 kilohertz and an upper frequency boundary greater than 40 kilohertz (which may or may not be the same as the upper frequency boundary for the full-band transmission state). The modem further includes a sensor or other sensiny~ means for sensing that the local loop is in POTS mode (e. ~~.. transmitting POTS information. or preparing to transmit POTS
1 o information ). and the data signal power and bandwidth are adaptively altered to provide data without out interfering with the POTS transmission. Upon sensing the band-limiting condition. such as an off hook condition, the controller causes the processor unit to upwardly shift the lower frequency boundary of the transmission frequency band and operate in the band-limited. or reduced-power, state.
Likewise.
~ 5 upon sensing no band-limiting condition (or a cessation in the band-limiting condition 1. the controller causes the processor unlt to dowwvardly shift the lower frequency boundary of the transmission frequency band, and operate in the full-band transmission state, to maximize data throughput.
In accordance with yet a further aspect of the present invention. a method is ?o provided for simultaneously communicating both voice and data between a customer premises and a central office across a local loop. In accordance with this aspect of the invention. the method comprises the steps of: ( 1 ) transmitting data between the customer premises and the central office in a first frequency band. wherein the first s SUBSTITUTE SHEET (RULE 26) frequency band is defined by an upper frequc:ncv boundary and a lower frequency boundary: (?) allocatin~~ a second ti-equency band for transmitting voice information between the customer premises and the central office; (3) sensing a band-limiting condition: and (4) dynamically shifting the lower frequency boundary of the first s frequency band in response to the sensed band-:limiting condition. In accordance with the invention. the lower frequency boundary on the first frequency band shifted to at least partially overlap the second frequency band when no band-limitin~~
condition exists. The lower frequency boundary of the f rst frequency band is further shifted to avoid overlapping with any portion of the second frequency band when the band-iimitin~~ condition exists.
In accordance with yet a further aspect of the invention. a modem is provided for communicating across a communication IIIlk capable of single-use transmissions and multiple-use transmissions. The term single-use transmissions is used to generally connote that a single transmission or communication is occurrinU
across the link. For example. a single PSTN voice call. or a siny~ie data communication transmission. The term multiple-use transmissions is used to generally imply that multiple transmissions or communications are occurring simultaneously. For example. the simultaneous transmission of a daoa communication and a PSTN
voice call. The modem constructed in accordance with this aspect of the invention includes ?o an input/output signal line in communication with the communication Illlk.
It further includes a processor unit adapted for operation in one of at least two states.
a fill-band transmission state and a band-limited state. wherein the full-band transmission state occurs when sin_le-use transmissions are occurrin<~ across the transmission link. and SUBSTlTIlTE SHEET' (RULE 26) WO 98l27665 PCT/I1S97/22632 the band-limited transmission state occurs when multiple-use transmissions are occurring across the communication link.
It will be appreciated that, in accordance with a broad inventive aspect. the present invention operates by adjusting transmit power between a band-limited s transmission state and a full-band transmission state. Generally (but not necessarily always). the full-band transmission state occurs when the communication link is operating in a single-use transmission mode, while the band-limited transmission state generally occurs when the communication link is operating in a multiple-use transmission mode. In accordance with this broad concept of the invention.
1 o substantial transmission energy is transmitted by the modem in or near the POTS
frequency band. when the modem is transmitting in the full-band state.
Conversely.
very little (ideally zero) energy is transmitted by the modem in or near the POTS
frequency band, when the modem is transmitting in the band-limited state. This allows for simultaneous POTS transmissions (e.g.. voice, PSTN modem. erc. ) in the POTS fi~equencv band, and band-limited modem transmissions.
Brief Description of the Drawings The accompanvin~T drawinLgs incorporated in and forminy_ a part of the specification. illustrate several aspects of the present invention, and together with the 2o description serve to explain the principles of the invention. In the drawin~~s:
FIG. 1 is an illustration of the frequency spectrum of a dual frequency band communications system of the prior art. depicting the POTS transmission frequency band and the xDSL transmission frequency band;
io SUBSTITUTE SHEET (RULE 26) FIG. 2 is a block diagram illustrating the primary components in a system utilizing the present invention:
FIG. 3A is a frequency spectrum illustrating the full-band transmission frequency band of the present invention;
FIG. 3B is a frequency spectrum illustrating the band-limited transmission frequency band of the present invention;
FIG. 3C is a frequency spectrum illustrating a band-limited transmission frequency band of an alternative embodiment of~ the present invention. having a uniquely shaped xDSL. transmission band:
1o FIG. 3D is a frequency spectrum illustratin4_ a band-limited transmission frequency band of an alternative embodiment of the present invention. having a reduced power YDSL transmission band:
FIG. 4 is a block diagram illustrating the primary components of a modem constructed in accordance with the present invention;
l5 FIG. 5 is a circuit diagram illustrating the analog front end component of the modem block diagram of FIG. 4:
FIG. 6 is a software flowchart depicting the operation of the functional operation of the analog front end element. illustrated in FIG. ~: and FIG. 7 is a software flowchart illustrating the top-level operation of~ a system 3o constructed in accordance with the present invention.
Detailed Description of the Preferred Embodiment of the Invention SUBSTITUTE SHEE'I~ (RULE 26) Having summarized the invention. reference will now be made in detail to the description of the invention as illustrated in the drawings. While the invention will be described in connection with these drawin~~s. there is no intent to Limit it to the embodiment or embodiments disclosed therein. On the contrary. the intent is to cover all alternatives. modifications and equivalents included within the spirit and scope of the invention as defined by the appended claims.
Turnin~~ now to the drawin~~s. FIG. 1 is a diagram illustratin~~ frequency' band communications. as is knovyn in the prior art. The term frequency band communications is used to indicate communication of information within a certain IO defined. frequency band. As is known in the prior art. plain old telephone system (POTS) communications are transmitted in the frequency band 1? defined between about 0 (DC) and about ~ kHz. A second transmission frequency band 14 is defined at a higher ti-equency level than the POTS ti-equency band 1?. and is used in the transmission of digital subscriber line (DSL) communications. A ~~uard dead band 16 is typically provided to separate the two transmission frequency bands 12 and 1 ~l. 'The DSL transmission frequency band 14 is more broadly denominated as "xDSL-'.
wherein the "x" generically denominates any of a number of transmission techniques within the DSL family. For example, ADSL, - Asymmetric Digital Subscriber Line.
RADSL -- Rate Adaptive Diy=ital Subscriber Line. HDSL -- Hi~~h-Bit-Rate DSL.
etc.
?o As is known. xDSL transmission frequency bands 14 may encompass a bandwidth of greater than 1 MHz. As a result. and for the reasons described above, without the addition of extra equipment such as POTS filters, splitters. etc. xDSL
si<~nals are not n SUBSTITUTE SHEET (RULE 26) WO 98l27665 PCT/US97/22632 compatible with attached POTS type equipment. such as telephones. PSTiV
modems.
facsimile machines, etc.
As will be discussed in more detail below, the present invention provides an upper transmission band having an upper frequency boundary that is much lower than the 1 MHz frequency boundary often encountered in ;cDSL transmissions. Indeed.
the upper frequency boundary of the present invention is defined in a ran<~e that is readily supported by. or compatible with. transmission systems (and attached POTS type equipment) presently in place between a customer premises and a central office.
without the need for extraneous devices such as POTS filters and POTS
splitters. In I o this regard. reference is made to FIG. ?. ~yhich is a top level diagram illustrating the principal hardvyare components of a system utilizing the present invention. In accordance with one aspect of the invention. a modem 'ZO is provided for achieving efficient data communications between a customer premises ?2 and a central office ?4 across a local loop 26. by dynamically allocatin~~ a transmission frequency bandwidth t 5 and/or power for transmitting data. Certainly. one of the factors motivating the development of the present invention is the expanded demand for hi<~~her speed communications in recent years. This enhanced demand is primarily attributed to communications over the Internet.
'the present invention dynamically allocates a data transmission frequency ?o band and/or power spectral density (PSD) in response to POTS communications across the same line. More particularly. the present invention may utilize the frequency band otherwise allocated for POTS/voice transmission. at times when there is no present demand for transmitting voice information. When. however. there is a f3 SUBSTITUTE SHEET (RULE 26) demand for voice transmissions. then the present invention reallocates the transmission frequency band and PSD for the data communications so that there is no overlap or interference with the POTS transmission Irequencv band 12, and so that there is not significant interference to POTS type attached equipment.
In keeping within the description of FIG. 2, the customer premises ?~ may be a single-family household having a single phone line ?6 for communicating between the customer premises 22 at a central office ?4. Within the house or customer premises ??, multiple connections branch off of the local loop 26 and are terminated at phone jacks (such as RJ-I 1 ) located in various rooms of the household. In this wav.
multiple telephones 30. and 32 may be plu~~~~ed in and supported from the same phone line 26. In the same way, a personal computer may be disposed in communication with the local loop 26 by way of a modem 20.
Presently, unless a user purchases an additional phone line. or a more costly communication service. such as xDSL. simultaneous transmissions of voice and data > > to different locations are not possible. As a result. one person in a household may have the focal loop 26 tied up with data communications (such as Internet communications). while another person at the same household is awaitin~_= the use of the local loop 26 for voice communication. An accordance with the present invention.
and as will be discussed in more detail below, this shortcoming is overcome.
2o In keeping with the description of F1G. ?, a companion modem ~10. that is compatible with the modem 20. is provided at the central office 24. As is know w.
other equipment. such as wire distribution frame and standard telephone sw itching equipment ~2 may also be in communication with the local loop 26, Since the is SUBSTITUTE SHEET (RULE 26) conti~~uration and operation of such equipment is known in the prior art and does not effect or impact the present invention, it will not be discussed herein. FIG.
2 also illustrates a variety of services that may be connected at the central office ?4 to the modem 40. constructed in accordance with the present invention. These services may include a hi~~h speed ISP service 44. a high speed LAN access service ~16.
etc. Ajain, since the provision and operation of such services are generally understood and are further not necessary in order to describe the operation of the present invention, they will not be described herein.
Turning now to Fi~ys. ;A and 3B. the dynamic allocation and deallocation of ~o the data transmission frequency band is illustrated. Specilicallv, FIG. 3A
illustrates the data transmission frequency band 50 in a full-band transmission frequency state.
while FIG. 3B illustrates a data transmission fi-e~quency band 52 in a band-limited (POTS compatible) transmission frequency state. :1s illustrated in FICi. 3A) the full-band transmission frequency band ~0 extends from approximately 0 Hz (DC) to 1 a approximately 100 KI-Iz. In contrast. in FIG. 3>=3 the data transmission frequency band ~? extends from approximately 20 KI-Iz to approximately 100 KHz. In accordance with an important aspect of the preferred embodiment. a modem 20 constructed in accordance with the invention senses the need to dynamically allocate or deallocate a portion of the transmission frequency band in order to accommodate voice 20 communications within the 0 to 4 KHz POTS fi~c:quency band 12. As will be described further herein, the present invention may sense this demand for voice transmissions (or band-limiting condition) by sensing an OFF-HOOK condition of a telephone 30. 32. ( see FIG. ? ) connected to the local loop 26.
Alternatively) this IS
SUBSTITUTE SHEE1' (RULE 26) band-limiting, condition may be detected by an impedance cilan!~e on the local loop 26, For phone compatibility. in addition to detecting= RING and OFF-HOOK
conditions. the system may also be configured to detect voice conversation.
Upon voice detection, the system may increase transmit power as it shifts into the band-limited transmission state. to increase data rate dynamically, so long as the voice band SNR is about 30 to ~t0 dB. When silence is once again detected (for a predetermined amount of time). the system will again reduce the transmit power for ~~ood idle channel perception.
t o Unlike typical xDSL communications_ where the data transmission frequency band is often 1 MHz in width, the data transmission frequency hand of the present Illv2nitOll 1S mLICh less than that. This permits relatively high-speed data communication without the addition of expensive equipment. such as POTS
sputters and POTS filters. Importantly. this addresses a market need from consumers that do i a not wish to incur. or cannot afford. the additional expenses normally incurred with purchasing an xDSL communication service. An important aspect of the present invention is its ability to sense when voice-band communications are not occurrin<~. or otherwise when a band-limiting condition is not present. and expand the transmission frequency band into the frequency band otherwise reserved for POTS
transmissions.
?o and/or increase transmit power to increase the data rate. As can be seen from the illustrations in Figs. ~A and 3B, expanding the transmission frequency band from a 20 kHz cutoff (FIG. 3B) to approximately DC (FIG. 3A) realizes a ?~ percent increase in Ib SUBSTfTUTE SHEET (RULE 26) WO 98l27665 PCT/US97/22632 bandwidth (i.e.. from 80 kHz to 100 kHzf. and thus realize a si~,nificant improvement in performance.
FIGS. 3C and 3D illustrate alternative embodiments of the present invention.
In short. FIGS. 3C and 3D illustrate a spectrally-shaped transmission curve and an s adaptive power transmission curve. respectively. As illustrated in FIG. 3B.
under normal operatin'r condition. the power density of tile ~DSL transmission band is greater than that of the POTS transmission band. However, there may be instances when the guard band I6 is not large enough to sufficiently separate the xDSL
transmission band 5? from the POTS frequency band 1?. As a result. sDSL
transmissions may be evident in the POTS frequency band 1 ? as noise ( audible static ).
The reasons this may occur are varied. and include factors such as telephone set sensitivity and non-linearities. Intermodulation products may also be manifest wlthln the POTS transmission band 1? as noise.
It will be appreciated that. consistent with the concepts and teachin~~s of the I s present invention. various adaptations of the band-limited transmission state may be implemented to minimize or eliminate noise in the POTS transmission band I'_'.
One solution is to further increase the size of the ~Tua.rd band 16. thereby increasing the frequency separation between the POTS transmission band 12 and the xDSL
transmission band ~?. Another solution is to adaptively reduce the transmit power of 2o the ~DSL transmission band. This solution is illustrated in FIG. 3D.
wherein the normal power spectrum ~? is illustrated in dashed Iine and the reduced power spectrum ~6 is superimposed in solid line. Reducing the transmit power in this w~av reduces the amount of noise that is manifest within the POTS frequency band.
The t7 SUBSTITUTE SHEET (RULE 26) specific amount of power reduction may vary anion g customer premises. based upon the attached equipment.
Yet another solution is to more particularly define the spectral shape of the transmission band. This solution is illustrated in FIG. 3C. As shown. the power spectrum of the xDSL transmission band ~4 may be asymmetrically shaped to provide a greater taper on the lower frequency end of the curve. This taper. ensures sufficient attenuation of the xDSI_ transmission signal above the POTS frequency band 1?.
and therefore minimizes intermodulation products and noise (resultin~~ from the YDSL
transmission) within the POTS band 1'_'. Although only one such shaped signal band ~6 is illustrated in FIG. pD. it will be appreciated that this aspect of the invention is not so limited. Instead. other shapes may be deemed desirable. dependin~~ upon the specific environment and line conditions.
Reference is now made to F'IG. -1. which shows a block diagram of a modem ?0 constructed in accordance with the present invention. As is common among modems. the modem 20 is in communication with both a local loop 26 and computin~~
equipment '?s. such as a personal computer. More specifically. the modem ?0 communicates with the computing equipment 2~ across line 60. The telephone line ?6 is typically comprised of a two wire service. which wires are often denoted as TIP
62 and RI~1G 6=I. The TIP 62 and RING 6~1 lines are input to an ana(oy front-end ?o circuit 66 tsee FIG, s) as well as a monitor circuit 68. which is confi~~ured to detect an OFF-HOOK condition of the local loop ?6.
Analog to digital and digital to analo~~ converter circuitry 70 is in communication with the analo~~ front end circuitry 66. and is in further ~s SUBSTITUTE SHEET (RULE 26) communication with digital signal processor 7 ~. Data received from the local loop 26 passes through the analog front-end G6 and is converted from analoL_ to digital form by the analo~~ to digital converter of block 70, before being passed to the digital signal processor 7?. Conversely. outgoing data output from the di;~itai signal processor 72 is converted by the digital to analog converter of block 70. before being communicated to the local loop 26. by way of the analog front--end 66. Finally, a Data Terminal Equipment (DTE interface 74) is in communication with the digital signal processor 72 and in further communication across line 60. with the data terminal equipment.
such as a computer ?~. The analog to digital and digital to analo~l converter circuitry l0 70. the di~zital signal processing 72. and the DTL interface 74 are all veil known and generally operate in accordance with the prior art. Therefore. their individual structure and operation need not be described herein.
Indeed. a si;;nificant component of the modem 20, constructed in accordance with the present invention. is a controller 80 that is in communication with the various I a other components of the modem ?0. While there are various ways to implement the controller 80. one way, as illustrated. is to further partition the controller 80 into functional units denoted as a processing unit 8?. a memory 84 (which may futrther include an executable code segment 86? and a controller 88.
For purposes of the broad concepts of the present invention. the controller 80 ?o receives a signal from the monitor circuit 68 on I:ine 90, which signal indicates whether the invention should transmit data in a band-limited transmission state or a full-band transmission state. In this regard, the monitor circuitry 68 may be confi~~ured to detect an OFF-HOOK condition or alternatively a RING condition on SUBSTITUTE SHEET (RULE 26) focal loop 26. As is 1170W11 1I1 the art, the OFF-HOOK COlldltlon InaV be detected by a drop in voltage across the local loop 26. or alternatively a sudden chance in impedance on the local loop ?6. On the other hand, a RING detect condition is identified by a low frequency oscillatory voltage on local loop ?6. For example. the voltage drops from about 48 volts (on hook) to approximately 10 volts or less (off hook), at the customer premises end of the local loop.
In short. the controller 80 evaluates the signal received on line 90 to determine whether data should be transmitted in the full-band transmission state or the band-limited transmission state. Appropriate signals may. accordingly, be transmitted to the digital signal processor 72 for formulatin<~ data transmissions (or interpretin;~
received data trarlsmISSlUns).
In accordance with an alternative embodiment of the invention. it will be appreciated that thc: monitor circuitry 68 may be incorporated within the controller 80.
whereby certain signal conditions may be evaluated to detect the band-limiting condition. In this regard. an analo~~ to digital converter would also be implemented as pan of the controller 80, to ~~enerate a si~~nal in di~ital format which may be more readily evaluated and processed by the processing unit 82. In this rey~ard.
the processing LiIllt 8? may be a microprocessor. a microcontroller. all appllcatlon specific integrated circuit (ASIC) or other digital circuitry configured to specially processed ?o information. In the illustrated embodiment, the controller 80 includes fundamental components (processor unit, controller, memory) that together operate to perform distinct computing operations. Such operations may be controlled. for example.
by eaecuiable code 8G contained within the memory 84.
SUBSTITUTE SHEET (RULE 26) Reference is now made to FIG. ~) whic:h shows a more detailed dia~~ram of the circuitry comprising the analoy~ front-end 66. The preferred embodiment includes blockin~~ capacitors 102 and 10~. which are see~ies connected with the TIP 62 and RING 6~1 signal lines. and serve to block any DC voltage otherwise carried OIl the TIP
s 62 and RING 6~ lines. A transformer I06 couples alternating current to the remainder of the circuitry. as well as provides safety and signal isolation for the remaining circuitry in the modem. A termination resistor 108 and switch I 10 are disposed for series connection with each other (depending upon whether the switch 110 is opened or closed). and together are connected in parallt~l across the secondary windin~~ of the transformer I06. The switch 1 10 is controlled by controller 80 (FIG. 4) to close and therefore switch in the terminating resistor 108 when the telephones 30 and 32 (see FIG. ? ) are all ON-HOOK (as observed by the monitor circuit 68). The switch 1 may be open to switch out the terminating resisvtor 108, upon detection of an incoming RING signal or OFF-HOOK on the local loop 26. Capacitors 102 and 10~ are chosen 1 a to pass data. block DC. and yield acceptable Rin~~er Equivalence Number per FCC
part 68. The switch 1 10 is generally opened to switch out the terminatin~T
resistor when the monitor circuit 68 determines that the local loop 26 is in the OFF-HOOK
state. The reason for this is that, when one or more telephones are taken OFF-HOOK.
then the OFF-HOOK telephone will terminate the line. and the terminatin<~
resistor 2o I08 is not needed. Optionally, the switch I 10 cm be closed in the Off NOOK
state to improve line termination provided by the OFF-HOOK telephone.
The item represented by reference numeral 1 l2 denotes circuitry that is configured in a form of a dependent current source. The current source is prompted SUBSTlTIlTE SHEEC (RIiLE 26) WO 98l27665 PCT/US97/22632 by the transmit signal Tx to create an out~~oin'1 transmission si~~nal. As a current source. the item 1 12 has a very his~h impedance (as seen across the secondary windin~~
of transformer 106) and therefore. only the termination resistor 108 operates to ternlinate the line (when switched in). Similarly. amplifier I 14 is the receive amplifier that generates the Rx signal. as is known in the art. Like the current source 1 12, the amplifier 1 1 ~ has an extremely high input impedance and thus does not effect line termination.
Reference is now made to FIG. 6. which a software flow-chart illustrating the operation of the analog front-end element of FIG. ~. Be~~innin~ at step 120.
the element determines whether the local loop 26 is ON-I-IOOK or OFF-HOOK. .-~s will be appreciated from the Ibregoing discussion. this decision is made by the controller 80 which outputs a si~~nal I 22 (see FIG. ~l) to the analob front-end 66 indicative of the ON-HOOK/OFF-HOOK status. If the resolution of step 120 is NO, the analog front-end element 66 opens switch I 12 (step l22) to remove the termination resistor from the circuit. That is. if the system detects that a telephone connected to the local loop 26 is OFF-HOOK. it will remove the termination resistor I08 from the circuit.
since the lllle e-111 then be terminated by the OFF-I-IOOK telephone.
Thereafter.
operation proceeds to step 122. wherein data is transmitted in accordance with the band-limited transmission frequency band (e. ~., 20 kHz-100 kHz). In accordance ?o with one embodiment of the present im~ention. the system may emit periodic tones within the audible frequency range to alert a user talking on an attached telephone the local loop 26 is also being used for data transmissions. Thus, a person. for example.
speakin~~ in another part of the house over a telephone hearing periodic beeps would SUBSTITUTE SHEET (RULE 26) know that someone else in the household is using a computer to communicate data.
and therefore may wish to keep his or her conversation to a minimum, in order to free up the local loop 26. so that the present invention may obtain a full utilization of the full-banded transmission frequency band, for maximum data throughput.
If the resolution of step l20 is YES. indicating that all telephones attached to the locai loop 26 are ON-HOOK. then the system ensures that switch 1 10 is closed thereby placing termination resistor l08 in the circuit. so as to achieve proper line termination (step I30). Thereafter, the system may transmit data across the local loop 1It111Z1I1~.: the entire. full-band transmission ti-equency (i.c~.. DC to approximately l00 KHz).
Reference is now made to FIG. 7. which is a software flow-chart illustrating the top-level operation of a system communicating in accordance with the present invention. Beginning at block l40. the system awaits the initiation of data transmission. This initiation may occur either upon the instruction of a user at the 1 s computer 25 (see FIG. ? ). or alternatively from a remote user that is dialing the phone number of computer ~'~ to connect up to that computer (this assumes that that computer ?~ is in auto answer mode). Once the system has been instructed to begin data communications. it first makes a check (at step l44) to determine whether the loop is in the OFF-HOOK state. If so, it begins the data communications in the band-?o limited frequency transition state (,step 146)(e.h., 20 kHz - 100 kHz).
During the data transmissions. the system will make continuous checks to determine whether the data transmission has ended (step 148. or whether thc: band-limiting condition has subsided (step 1 ~0). As previously mentioned. the band-limiting condition is ~~enerally SUBSTITUTE SHEET (RULE 26) identiCed by the OFF-HOOK detection circuitry. If the end data communications check. at step 148. resolves to YES. then the system returns to step 140.Y
not. the system proceeds to step 1 s0 where it checks for the cessation of the band-limitin~~
condition. If this step resolves to YES, then the system continues the data transmission in the fill-band transmission frequency bandwidth ( step 154).
Returning to the decision block l44. if, upon initiation of data communication.
the system determines that all telephones are presently ON-HOOK. then the system proceeds to step 1 ~4 where it transmits data in accordance with the full-band data transmission state (i. e.. utilizin~~ the full 0 to I 00 KHz transmission ti-equencv to bandwidth). Durin<~ transmission in this frequency band. the system periodically checks to see if the data communications has terminated (step 1 ~6). or whether the occurrence of a band-limitin~~ condition has occurred (step 1 ~8 ). This latter condition occurs. for erample, when a person lifts a handset of an attached telephone.
If this occurs. the system proceeds to step l46 and continues the data transmissions in accordance with the band-limited transmission frequency band c ~0 kHz - 100 kHz).
It will be appreciated from a review ofthe flow-chart of FIG. 7, that the system. during' data transmission. can dynamically shift back and forth between the full-band and band-limited transmission frequency bandwidths as users may lift or reset telephone handsets (or as RING conditions occur). It will be appreciated.
?o however. that other band-limitin~~ conditions (other than RING or OFF-HOOK) may be utilized to invoke the frequency shifting feature of the present invention, depending upon the system configuration or other pertinent system factors.
SUBSTITUT~ SHEET (RULE 26}
It will be appreciated that the invention described herein could provide a low-cost solution to Internet access for the mass consumer market. 1n this re~~ard. It could fill the ~~ap in our product offerin~~ between low-cost 33.6 kbps modems and high speed xDSL modems, which require the addition of relatively expensive equipment (such as POTS sputters and POTS filters) at the customer premise. and is labor intensive. The present invention, as described above. ~~enerally achieves transmissions rates in the range of 64 kbps to 640 kbps.
As described above, the invention utilizes the low frequency portion of the telephone subscriber loop spectrum (roughly DC to approximately 100 KHz) to transport user data. The modulation could be CAP. QAM. DMT. spread spectrum.
eic. as the invention is not limited to any particular form. Utilization of the lower frequency portion of the telephone subscriber loop has the advantage of lowest possible signal attenuation (usually the nurr~ber one siymal impairment in data communications) and !ow cross-talk. Other advantages are reduced transmission line 1 s concerns like reflections due to stubs.
In use. the invention requires a simple brid~~e (electrical parallel) connection to the subscriber loop or premise wiring. Therefore. Olle Lllllt would connect (in bridge fashion) at the central office, and one companion unit connect at the customer premises.
?U The fore~~oin~~ description has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obvious modifications or variations are possible in light of the above teachin~~s. The embodiment or embodiments discussed were chosen and ?5 SUBSTITUTE SHEEP (RULE 26) WO 98l27665 PCT/US97/22632 described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modit7cations as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly and legally entitled.
?6 SUBSTITUTE SHEET (RULE 26)
etc. Ajain, since the provision and operation of such services are generally understood and are further not necessary in order to describe the operation of the present invention, they will not be described herein.
Turning now to Fi~ys. ;A and 3B. the dynamic allocation and deallocation of ~o the data transmission frequency band is illustrated. Specilicallv, FIG. 3A
illustrates the data transmission frequency band 50 in a full-band transmission frequency state.
while FIG. 3B illustrates a data transmission fi-e~quency band 52 in a band-limited (POTS compatible) transmission frequency state. :1s illustrated in FICi. 3A) the full-band transmission frequency band ~0 extends from approximately 0 Hz (DC) to 1 a approximately 100 KI-Iz. In contrast. in FIG. 3>=3 the data transmission frequency band ~? extends from approximately 20 KI-Iz to approximately 100 KHz. In accordance with an important aspect of the preferred embodiment. a modem 20 constructed in accordance with the invention senses the need to dynamically allocate or deallocate a portion of the transmission frequency band in order to accommodate voice 20 communications within the 0 to 4 KHz POTS fi~c:quency band 12. As will be described further herein, the present invention may sense this demand for voice transmissions (or band-limiting condition) by sensing an OFF-HOOK condition of a telephone 30. 32. ( see FIG. ? ) connected to the local loop 26.
Alternatively) this IS
SUBSTITUTE SHEE1' (RULE 26) band-limiting, condition may be detected by an impedance cilan!~e on the local loop 26, For phone compatibility. in addition to detecting= RING and OFF-HOOK
conditions. the system may also be configured to detect voice conversation.
Upon voice detection, the system may increase transmit power as it shifts into the band-limited transmission state. to increase data rate dynamically, so long as the voice band SNR is about 30 to ~t0 dB. When silence is once again detected (for a predetermined amount of time). the system will again reduce the transmit power for ~~ood idle channel perception.
t o Unlike typical xDSL communications_ where the data transmission frequency band is often 1 MHz in width, the data transmission frequency hand of the present Illv2nitOll 1S mLICh less than that. This permits relatively high-speed data communication without the addition of expensive equipment. such as POTS
sputters and POTS filters. Importantly. this addresses a market need from consumers that do i a not wish to incur. or cannot afford. the additional expenses normally incurred with purchasing an xDSL communication service. An important aspect of the present invention is its ability to sense when voice-band communications are not occurrin<~. or otherwise when a band-limiting condition is not present. and expand the transmission frequency band into the frequency band otherwise reserved for POTS
transmissions.
?o and/or increase transmit power to increase the data rate. As can be seen from the illustrations in Figs. ~A and 3B, expanding the transmission frequency band from a 20 kHz cutoff (FIG. 3B) to approximately DC (FIG. 3A) realizes a ?~ percent increase in Ib SUBSTfTUTE SHEET (RULE 26) WO 98l27665 PCT/US97/22632 bandwidth (i.e.. from 80 kHz to 100 kHzf. and thus realize a si~,nificant improvement in performance.
FIGS. 3C and 3D illustrate alternative embodiments of the present invention.
In short. FIGS. 3C and 3D illustrate a spectrally-shaped transmission curve and an s adaptive power transmission curve. respectively. As illustrated in FIG. 3B.
under normal operatin'r condition. the power density of tile ~DSL transmission band is greater than that of the POTS transmission band. However, there may be instances when the guard band I6 is not large enough to sufficiently separate the xDSL
transmission band 5? from the POTS frequency band 1?. As a result. sDSL
transmissions may be evident in the POTS frequency band 1 ? as noise ( audible static ).
The reasons this may occur are varied. and include factors such as telephone set sensitivity and non-linearities. Intermodulation products may also be manifest wlthln the POTS transmission band 1? as noise.
It will be appreciated that. consistent with the concepts and teachin~~s of the I s present invention. various adaptations of the band-limited transmission state may be implemented to minimize or eliminate noise in the POTS transmission band I'_'.
One solution is to further increase the size of the ~Tua.rd band 16. thereby increasing the frequency separation between the POTS transmission band 12 and the xDSL
transmission band ~?. Another solution is to adaptively reduce the transmit power of 2o the ~DSL transmission band. This solution is illustrated in FIG. 3D.
wherein the normal power spectrum ~? is illustrated in dashed Iine and the reduced power spectrum ~6 is superimposed in solid line. Reducing the transmit power in this w~av reduces the amount of noise that is manifest within the POTS frequency band.
The t7 SUBSTITUTE SHEET (RULE 26) specific amount of power reduction may vary anion g customer premises. based upon the attached equipment.
Yet another solution is to more particularly define the spectral shape of the transmission band. This solution is illustrated in FIG. 3C. As shown. the power spectrum of the xDSL transmission band ~4 may be asymmetrically shaped to provide a greater taper on the lower frequency end of the curve. This taper. ensures sufficient attenuation of the xDSI_ transmission signal above the POTS frequency band 1?.
and therefore minimizes intermodulation products and noise (resultin~~ from the YDSL
transmission) within the POTS band 1'_'. Although only one such shaped signal band ~6 is illustrated in FIG. pD. it will be appreciated that this aspect of the invention is not so limited. Instead. other shapes may be deemed desirable. dependin~~ upon the specific environment and line conditions.
Reference is now made to F'IG. -1. which shows a block diagram of a modem ?0 constructed in accordance with the present invention. As is common among modems. the modem 20 is in communication with both a local loop 26 and computin~~
equipment '?s. such as a personal computer. More specifically. the modem ?0 communicates with the computing equipment 2~ across line 60. The telephone line ?6 is typically comprised of a two wire service. which wires are often denoted as TIP
62 and RI~1G 6=I. The TIP 62 and RING 6~1 lines are input to an ana(oy front-end ?o circuit 66 tsee FIG, s) as well as a monitor circuit 68. which is confi~~ured to detect an OFF-HOOK condition of the local loop ?6.
Analog to digital and digital to analo~~ converter circuitry 70 is in communication with the analo~~ front end circuitry 66. and is in further ~s SUBSTITUTE SHEET (RULE 26) communication with digital signal processor 7 ~. Data received from the local loop 26 passes through the analog front-end G6 and is converted from analoL_ to digital form by the analo~~ to digital converter of block 70, before being passed to the digital signal processor 7?. Conversely. outgoing data output from the di;~itai signal processor 72 is converted by the digital to analog converter of block 70. before being communicated to the local loop 26. by way of the analog front--end 66. Finally, a Data Terminal Equipment (DTE interface 74) is in communication with the digital signal processor 72 and in further communication across line 60. with the data terminal equipment.
such as a computer ?~. The analog to digital and digital to analo~l converter circuitry l0 70. the di~zital signal processing 72. and the DTL interface 74 are all veil known and generally operate in accordance with the prior art. Therefore. their individual structure and operation need not be described herein.
Indeed. a si;;nificant component of the modem 20, constructed in accordance with the present invention. is a controller 80 that is in communication with the various I a other components of the modem ?0. While there are various ways to implement the controller 80. one way, as illustrated. is to further partition the controller 80 into functional units denoted as a processing unit 8?. a memory 84 (which may futrther include an executable code segment 86? and a controller 88.
For purposes of the broad concepts of the present invention. the controller 80 ?o receives a signal from the monitor circuit 68 on I:ine 90, which signal indicates whether the invention should transmit data in a band-limited transmission state or a full-band transmission state. In this regard, the monitor circuitry 68 may be confi~~ured to detect an OFF-HOOK condition or alternatively a RING condition on SUBSTITUTE SHEET (RULE 26) focal loop 26. As is 1170W11 1I1 the art, the OFF-HOOK COlldltlon InaV be detected by a drop in voltage across the local loop 26. or alternatively a sudden chance in impedance on the local loop ?6. On the other hand, a RING detect condition is identified by a low frequency oscillatory voltage on local loop ?6. For example. the voltage drops from about 48 volts (on hook) to approximately 10 volts or less (off hook), at the customer premises end of the local loop.
In short. the controller 80 evaluates the signal received on line 90 to determine whether data should be transmitted in the full-band transmission state or the band-limited transmission state. Appropriate signals may. accordingly, be transmitted to the digital signal processor 72 for formulatin<~ data transmissions (or interpretin;~
received data trarlsmISSlUns).
In accordance with an alternative embodiment of the invention. it will be appreciated that thc: monitor circuitry 68 may be incorporated within the controller 80.
whereby certain signal conditions may be evaluated to detect the band-limiting condition. In this regard. an analo~~ to digital converter would also be implemented as pan of the controller 80, to ~~enerate a si~~nal in di~ital format which may be more readily evaluated and processed by the processing unit 82. In this rey~ard.
the processing LiIllt 8? may be a microprocessor. a microcontroller. all appllcatlon specific integrated circuit (ASIC) or other digital circuitry configured to specially processed ?o information. In the illustrated embodiment, the controller 80 includes fundamental components (processor unit, controller, memory) that together operate to perform distinct computing operations. Such operations may be controlled. for example.
by eaecuiable code 8G contained within the memory 84.
SUBSTITUTE SHEET (RULE 26) Reference is now made to FIG. ~) whic:h shows a more detailed dia~~ram of the circuitry comprising the analoy~ front-end 66. The preferred embodiment includes blockin~~ capacitors 102 and 10~. which are see~ies connected with the TIP 62 and RING 6~1 signal lines. and serve to block any DC voltage otherwise carried OIl the TIP
s 62 and RING 6~ lines. A transformer I06 couples alternating current to the remainder of the circuitry. as well as provides safety and signal isolation for the remaining circuitry in the modem. A termination resistor 108 and switch I 10 are disposed for series connection with each other (depending upon whether the switch 110 is opened or closed). and together are connected in parallt~l across the secondary windin~~ of the transformer I06. The switch 1 10 is controlled by controller 80 (FIG. 4) to close and therefore switch in the terminating resistor 108 when the telephones 30 and 32 (see FIG. ? ) are all ON-HOOK (as observed by the monitor circuit 68). The switch 1 may be open to switch out the terminating resisvtor 108, upon detection of an incoming RING signal or OFF-HOOK on the local loop 26. Capacitors 102 and 10~ are chosen 1 a to pass data. block DC. and yield acceptable Rin~~er Equivalence Number per FCC
part 68. The switch 1 10 is generally opened to switch out the terminatin~T
resistor when the monitor circuit 68 determines that the local loop 26 is in the OFF-HOOK
state. The reason for this is that, when one or more telephones are taken OFF-HOOK.
then the OFF-HOOK telephone will terminate the line. and the terminatin<~
resistor 2o I08 is not needed. Optionally, the switch I 10 cm be closed in the Off NOOK
state to improve line termination provided by the OFF-HOOK telephone.
The item represented by reference numeral 1 l2 denotes circuitry that is configured in a form of a dependent current source. The current source is prompted SUBSTlTIlTE SHEEC (RIiLE 26) WO 98l27665 PCT/US97/22632 by the transmit signal Tx to create an out~~oin'1 transmission si~~nal. As a current source. the item 1 12 has a very his~h impedance (as seen across the secondary windin~~
of transformer 106) and therefore. only the termination resistor 108 operates to ternlinate the line (when switched in). Similarly. amplifier I 14 is the receive amplifier that generates the Rx signal. as is known in the art. Like the current source 1 12, the amplifier 1 1 ~ has an extremely high input impedance and thus does not effect line termination.
Reference is now made to FIG. 6. which a software flow-chart illustrating the operation of the analog front-end element of FIG. ~. Be~~innin~ at step 120.
the element determines whether the local loop 26 is ON-I-IOOK or OFF-HOOK. .-~s will be appreciated from the Ibregoing discussion. this decision is made by the controller 80 which outputs a si~~nal I 22 (see FIG. ~l) to the analob front-end 66 indicative of the ON-HOOK/OFF-HOOK status. If the resolution of step 120 is NO, the analog front-end element 66 opens switch I 12 (step l22) to remove the termination resistor from the circuit. That is. if the system detects that a telephone connected to the local loop 26 is OFF-HOOK. it will remove the termination resistor I08 from the circuit.
since the lllle e-111 then be terminated by the OFF-I-IOOK telephone.
Thereafter.
operation proceeds to step 122. wherein data is transmitted in accordance with the band-limited transmission frequency band (e. ~., 20 kHz-100 kHz). In accordance ?o with one embodiment of the present im~ention. the system may emit periodic tones within the audible frequency range to alert a user talking on an attached telephone the local loop 26 is also being used for data transmissions. Thus, a person. for example.
speakin~~ in another part of the house over a telephone hearing periodic beeps would SUBSTITUTE SHEET (RULE 26) know that someone else in the household is using a computer to communicate data.
and therefore may wish to keep his or her conversation to a minimum, in order to free up the local loop 26. so that the present invention may obtain a full utilization of the full-banded transmission frequency band, for maximum data throughput.
If the resolution of step l20 is YES. indicating that all telephones attached to the locai loop 26 are ON-HOOK. then the system ensures that switch 1 10 is closed thereby placing termination resistor l08 in the circuit. so as to achieve proper line termination (step I30). Thereafter, the system may transmit data across the local loop 1It111Z1I1~.: the entire. full-band transmission ti-equency (i.c~.. DC to approximately l00 KHz).
Reference is now made to FIG. 7. which is a software flow-chart illustrating the top-level operation of a system communicating in accordance with the present invention. Beginning at block l40. the system awaits the initiation of data transmission. This initiation may occur either upon the instruction of a user at the 1 s computer 25 (see FIG. ? ). or alternatively from a remote user that is dialing the phone number of computer ~'~ to connect up to that computer (this assumes that that computer ?~ is in auto answer mode). Once the system has been instructed to begin data communications. it first makes a check (at step l44) to determine whether the loop is in the OFF-HOOK state. If so, it begins the data communications in the band-?o limited frequency transition state (,step 146)(e.h., 20 kHz - 100 kHz).
During the data transmissions. the system will make continuous checks to determine whether the data transmission has ended (step 148. or whether thc: band-limiting condition has subsided (step 1 ~0). As previously mentioned. the band-limiting condition is ~~enerally SUBSTITUTE SHEET (RULE 26) identiCed by the OFF-HOOK detection circuitry. If the end data communications check. at step 148. resolves to YES. then the system returns to step 140.Y
not. the system proceeds to step 1 s0 where it checks for the cessation of the band-limitin~~
condition. If this step resolves to YES, then the system continues the data transmission in the fill-band transmission frequency bandwidth ( step 154).
Returning to the decision block l44. if, upon initiation of data communication.
the system determines that all telephones are presently ON-HOOK. then the system proceeds to step 1 ~4 where it transmits data in accordance with the full-band data transmission state (i. e.. utilizin~~ the full 0 to I 00 KHz transmission ti-equencv to bandwidth). Durin<~ transmission in this frequency band. the system periodically checks to see if the data communications has terminated (step 1 ~6). or whether the occurrence of a band-limitin~~ condition has occurred (step 1 ~8 ). This latter condition occurs. for erample, when a person lifts a handset of an attached telephone.
If this occurs. the system proceeds to step l46 and continues the data transmissions in accordance with the band-limited transmission frequency band c ~0 kHz - 100 kHz).
It will be appreciated from a review ofthe flow-chart of FIG. 7, that the system. during' data transmission. can dynamically shift back and forth between the full-band and band-limited transmission frequency bandwidths as users may lift or reset telephone handsets (or as RING conditions occur). It will be appreciated.
?o however. that other band-limitin~~ conditions (other than RING or OFF-HOOK) may be utilized to invoke the frequency shifting feature of the present invention, depending upon the system configuration or other pertinent system factors.
SUBSTITUT~ SHEET (RULE 26}
It will be appreciated that the invention described herein could provide a low-cost solution to Internet access for the mass consumer market. 1n this re~~ard. It could fill the ~~ap in our product offerin~~ between low-cost 33.6 kbps modems and high speed xDSL modems, which require the addition of relatively expensive equipment (such as POTS sputters and POTS filters) at the customer premise. and is labor intensive. The present invention, as described above. ~~enerally achieves transmissions rates in the range of 64 kbps to 640 kbps.
As described above, the invention utilizes the low frequency portion of the telephone subscriber loop spectrum (roughly DC to approximately 100 KHz) to transport user data. The modulation could be CAP. QAM. DMT. spread spectrum.
eic. as the invention is not limited to any particular form. Utilization of the lower frequency portion of the telephone subscriber loop has the advantage of lowest possible signal attenuation (usually the nurr~ber one siymal impairment in data communications) and !ow cross-talk. Other advantages are reduced transmission line 1 s concerns like reflections due to stubs.
In use. the invention requires a simple brid~~e (electrical parallel) connection to the subscriber loop or premise wiring. Therefore. Olle Lllllt would connect (in bridge fashion) at the central office, and one companion unit connect at the customer premises.
?U The fore~~oin~~ description has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obvious modifications or variations are possible in light of the above teachin~~s. The embodiment or embodiments discussed were chosen and ?5 SUBSTITUTE SHEEP (RULE 26) WO 98l27665 PCT/US97/22632 described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modit7cations as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly and legally entitled.
?6 SUBSTITUTE SHEET (RULE 26)
Claims (65)
1. A modem for communicating across a communication link comprising:
an input/output signal line in communication with the communication link:
a processor unit adapted for operation in one of at least two states, a full-band transmission state and a band-limited state, wherein the full-band transmission state is defined by significant transmission energy in a frequency range below a first frequency, and a band-limited transmission state defined by a negligible amount of energy in the frequency range below the first frequency.
an input/output signal line in communication with the communication link:
a processor unit adapted for operation in one of at least two states, a full-band transmission state and a band-limited state, wherein the full-band transmission state is defined by significant transmission energy in a frequency range below a first frequency, and a band-limited transmission state defined by a negligible amount of energy in the frequency range below the first frequency.
2. The modem as defined in claim 1, wherein the first frequency is approximately 15 kilohertz.
3. The modem as defined in claim 1, wherein the communication link is a multiple-use communication link.
4. The modem as defined in claim 1, further including:
sensing means for sensing a band-limiting condition; and control means associated with the processor unit responsive to the sensing means for controlling the operating stale of the processor unit, wherein upon sensing the band-limiting condition the control means causes the processor to operate in the band-limited state, and upon sensing no band-limiting condition the control means causes the processor to operate in the full-band transmission state.
sensing means for sensing a band-limiting condition; and control means associated with the processor unit responsive to the sensing means for controlling the operating stale of the processor unit, wherein upon sensing the band-limiting condition the control means causes the processor to operate in the band-limited state, and upon sensing no band-limiting condition the control means causes the processor to operate in the full-band transmission state.
5. The modem as defined in claim 1, wherein significant energy transmissions are transmissions substantially exceeding a audible level.
6. A modem for communicating across a communication link capable of single-use transmissions and multiple-use transmissions comprising:
an input/output signal line in communication with the communication link:
a processor unit adapted for operation in one of at least two states, a full-band transmission state and a band-limited state, wherein the full-band transmission state occurs when single-use transmissions are occurring across the transmission link, and the band-limited transmission state occurs when multiple-use transmissions are occurring across the communication link.
an input/output signal line in communication with the communication link:
a processor unit adapted for operation in one of at least two states, a full-band transmission state and a band-limited state, wherein the full-band transmission state occurs when single-use transmissions are occurring across the transmission link, and the band-limited transmission state occurs when multiple-use transmissions are occurring across the communication link.
7. A modem for communicating across a communication link comprising:
an input/output signal line in communication with the communication link:
a processor unit adapted for operation in one of at least two states, a full-band transmission state and a band-limited state, wherein the full-band transmission state is defined by significant energy transmission below a first frequency and the band-limited state is defined by substantially zero energy transmission below the first frequency;
sensing means for sensing a band-limiting condition; and control means associated with the processor unit responsive to the sensing means for controlling the operating state of the processor unit, wherein upon sensing the band-limiting condition the control means causes the processor to operate in the band-limited state, and upon sensing no band-limiting condition the control means causes the processor to operate in the full-band transmission state.
an input/output signal line in communication with the communication link:
a processor unit adapted for operation in one of at least two states, a full-band transmission state and a band-limited state, wherein the full-band transmission state is defined by significant energy transmission below a first frequency and the band-limited state is defined by substantially zero energy transmission below the first frequency;
sensing means for sensing a band-limiting condition; and control means associated with the processor unit responsive to the sensing means for controlling the operating state of the processor unit, wherein upon sensing the band-limiting condition the control means causes the processor to operate in the band-limited state, and upon sensing no band-limiting condition the control means causes the processor to operate in the full-band transmission state.
8. The modem as defined in claim 7, wherein the first frequency is approximately 15 kilohertz.
9. The modem as defined in claim 7, wherein the sensing means is configured to detect a multi-position switch, the position of which defines the band-limiting condition.
10. The modem as defined in claim 7, wherein the sensing means is configured to detect an off hook condition of a telephone that is electrically connected to the input/output signal line.
11. The modem as defined in claim 10, wherein the sensing means further includes means for detecting the onset of a condition indicative of a handset of the telephone being taken off-hook.
12. The modem as defined in claim 11, wherein the means for detecting the onset of the condition is configured to detect a voltage drop on the input/output signal line.
13. The modem as defined in claim 11, wherein the means for detecting the onset of the condition is configured to detect an impedance shift in the input/output signal line.
14. The modem as defined in claim 7, wherein the full-band transmission state is defined by a transmission frequency bandwidth having a lower frequency boundary of less than 4 kilohertz.
15. The modem as defined in claim 14, wherein the full-band transmission state is defined by a transmission frequency bandwidth having a lower frequency boundary of approximately DC.
16. The modem as defined in claim 7, wherein the full-band transmission state is defined by a transmission frequency bandwidth having an upper frequency boundary of greater than 50 kilohertz.
17. The modem as defined in claim 16, wherein the full-band transmission state is defined by a transmission frequency bandwidth having an upper frequency boundary of approximately 100 kilohertz.
18. The modem as defined in claim 7, wherein the band-limited transmission state is defined by a transmission frequency bandwidth having a lower frequency boundary of greater than 4 kilohertz.
19. The modem as defined in claim 18, wherein the full-band transmission state is defined by a transmission frequency bandwidth having a lower frequency boundary of approximately 20 kilohertz.
20. The modem as defined in claim 7, wherein the full-band transmission state is defined by a first transmission frequency bandwidth and the band-limited transmission state is defined by a second transmission frequency bandwidth, wherein the first transmission frequency bandwidth has an upper frequency boundary that is substantially the same an upper frequency boundary of the second frequency bandwidth.
21. The modem as defined in claim 7, wherein the full-band transmission state is defined by a first transmission frequency bandwidth and the band-limited transmission state is defined by a second transmission frequency bandwidth, wherein the first transmission frequency bandwidth has an upper frequency boundary that is different than an upper frequency boundary of the second frequency bandwidth.
22. The modem as defined in claim 7, wherein the communication link is a two-wire telecommunications link.
23. The modem as defined in claim 7, wherein the communication link is a local loop.
24. The modem as defined in claim 7, wherein the sensing means includes a code segment containing executable code.
25. The modem as defined in claim 7, wherein the control means includes a code segment containing executable code.
26. A modem for communicating across a communication link comprising:
an input/output signal line in communication with the communication link;
a processor unit adapted for operation in one of two states, a full-band transmission state and a band-limited state, wherein the full-band transmission state is defined by a lower frequency boundary below a second frequency and an upper frequency boundary greater than a first frequency, and the band-limited state is defined by a lower frequency boundary greater than the second frequency and an upper frequency boundary greater than the first frequency;
a sensor configured to detect the presence of a band-limiting condition;
and a controller associated with the processor unit and responsive to the sensor, configured to control the operating state of the processor unit, wherein upon sensing the band-limiting condition the controller causes the processor to operate in the band-limited state, and upon sensing no band-limiting condition the controller causes the processor to operate in the full-band transmission state.
an input/output signal line in communication with the communication link;
a processor unit adapted for operation in one of two states, a full-band transmission state and a band-limited state, wherein the full-band transmission state is defined by a lower frequency boundary below a second frequency and an upper frequency boundary greater than a first frequency, and the band-limited state is defined by a lower frequency boundary greater than the second frequency and an upper frequency boundary greater than the first frequency;
a sensor configured to detect the presence of a band-limiting condition;
and a controller associated with the processor unit and responsive to the sensor, configured to control the operating state of the processor unit, wherein upon sensing the band-limiting condition the controller causes the processor to operate in the band-limited state, and upon sensing no band-limiting condition the controller causes the processor to operate in the full-band transmission state.
27. The modem as defined in claim 26, wherein the first frequency is approximately 50 kilohertz.
28. The modem as defined in claim 26, wherein the second frequency is approximately 4 kilohertz.
29. A method for dynamically communicating data over a communication link using a modem comprising the steps of:
transmitting data in a full-band transmission state;
sensing a band-limiting condition; and adjusting the transmission of data from the full-band transmission state to a band-limited transmission state, in response to the sensing step.
transmitting data in a full-band transmission state;
sensing a band-limiting condition; and adjusting the transmission of data from the full-band transmission state to a band-limited transmission state, in response to the sensing step.
30. The method as defined in claim 29, wherein the sensing step includes detecting the position of a multi-position switch.
31. The method as defined in claim 29, further including the step of adaptively varying transmit power of the transmission of data to minimize interference of data signals with a lower frequency band.
32. The method as defined in claim 29, further including the step of uniquely shaping a power spectral transmission band of the data transmission to minimize interference of data signals with a lower frequency band.
33. The method as defined in claim 29, further including the step of sensing a cessation of the band-limiting condition.
34. The method as defined in claim 33, further including the step of adjusting the transmission of data from the band-limited transmission state to the full-band transmission state, in response to the step of sensing the cessation of the band-limiting condition.
35. The method as defined in claim 29, wherein the step of sensing the band-limiting condition includes sensing an incoming ring signal on the communication link.
36. The method as defined in claim 29, wherein the step of sensing a band-limiting condition includes sensing an off-hook condition of a telephone handset of a telephone electrically connected to the communication link.
37. The method as defined in claim 36, wherein the step of sensing the off-hook condition includes sensing an impedance of the communication link.
38. The method as defined in claim 36, wherein the step of sensing the off-hook condition includes sensing a voltage on the communication link.
39. The method as defined in claim 29, wherein the full-band transmission state is defined by a transmission frequency bandwidth having a lower frequency boundary of less than 4 kilohertz.
40. The method as defined in claim 39, wherein the full-band transmission state is defined by a transmission frequency bandwidth having a lower frequency boundary of approximately DC.
41. The method as defined in claim 29, wherein the full-band transmission state is defined by a transmission frequency bandwidth having an upper frequency boundary of greater than 50 kilohertz.
42. The method as defined in claim 41, wherein the full-band transmission state is defined by a transmission frequency bandwidth having an upper frequency boundary of approximately 100 kilohertz.
43. The method as defined in claim 29, wherein the band-limited transmission state is defined by a transmission frequency bandwidth having a lower frequency boundary of greater than 4 kilohertz.
44. The method as defined in claim 43, wherein the full-band transmission state is defined by a transmission frequency bandwidth having a lower frequency boundary of approximately 20 kilohertz.
45. The method as defined in claim 29, wherein the full-band transmission state is defined by a first transmission frequency bandwidth and the band-limited transmission state is defined by a second transmission frequency bandwidth, wherein the first transmission frequency bandwidth has an upper frequency boundary that is substantially the same an upper frequency boundary of the second frequency bandwidth.
46. The method as defined in claim 29, wherein the full-band transmission state is defined by a first transmission frequency bandwidth and the band-limited transmission state is defined by a second transmission frequency bandwidth, wherein the first transmission frequency bandwidth has an upper frequency boundary that is different than an upper frequency boundary of tine second frequency bandwidth.
47. A method for dynamically communicating data across a communication link using a modem comprising the steps of:
transmitting data in a band-limited transmission state;
sensing a cessation in a band-limiting condition; and adjusting the transmission of data from the band-limited transmission state to a full-band transmission state, in response to the sensing step.
transmitting data in a band-limited transmission state;
sensing a cessation in a band-limiting condition; and adjusting the transmission of data from the band-limited transmission state to a full-band transmission state, in response to the sensing step.
48. The method as defined in claim 47, further including the step of sensing a band-limiting condition.
49. The method as defined in claim 48, further including the step of adjusting the transmission of data from the full-band transmission state to the band-limited transmission state, in response to the step of sensing the band-limiting condition.
50. A method for communicating both voice and data between a customer premises and a central office across a communication link comprising the steps of:
transmitting data between the customer premises and the central office in a first frequency band, wherein the first frequency band is defined by an upper frequency boundary and a lower frequency boundary;
allocating a second frequency band for transmitting voice information between the customer premises and the central office in the second frequency band:
sensing a band-limiting condition; and dynamically shifting the lower frequency boundary of the first frequency band in response to the sensed hand-limiting condition.
transmitting data between the customer premises and the central office in a first frequency band, wherein the first frequency band is defined by an upper frequency boundary and a lower frequency boundary;
allocating a second frequency band for transmitting voice information between the customer premises and the central office in the second frequency band:
sensing a band-limiting condition; and dynamically shifting the lower frequency boundary of the first frequency band in response to the sensed hand-limiting condition.
51. The method as defined in claim 50, wherein the step of dynamically shifting the lower frequency boundary includes shifting the lower frequency boundary of the first frequency band to at least partially overlap between the first frequency band and the second frequency band, when the band-limiting condition is not present.
52. The method as defined in claim 50, wherein the step of dynamically shifting the lower frequency boundary includes shifting the lower frequency boundary of the first frequency band so that there is no overlap between the first frequency band and the second frequency band, when the band-limiting condition is present.
53. The method as defined in claim 50, wherein the step of sensing a band-limiting condition includes sensing an off-hook condition of a telephone electrically connected to the communication link.
54. The method as defined in claim 50, further including the step of shifting the upper frequency boundary of the first frequency band in response to the sensed band-limiting condition.
55. The method as defined in claim 50, wherein the lower frequency boundary is less than 4 kilohertz.
56. The method as defined in claim 55, wherein the step of dynamically shifting the lower frequency boundary includes the step of shifting the lower frequency boundary to a frequency greater than 4 kilohertz.
57. The method as defined in claim 55, wherein the lower frequency boundary is approximately DC, and the step of dynamically shifting the lower frequency boundary includes the step of shifting the lower frequency boundary to a frequency greater than 4 kilohertz.
58. The method as defined in claim 57, wherein the step of dynamically shifting the lower frequency boundary includes the step of shifting the lower frequency boundary upwardly to a frequency of approximately 20 kilohertz.
59. The method as defined in claim 50, wherein the step of sensing the band-limiting condition includes the step of detecting the onset of a condition indicative of demand for voice communications.
60. The method as defined in claim 50, wherein the step of sensing the band-limiting condition includes the step of detecting the cessation of a condition indicative of the termination of voice communications.
61. The method as defined in claim 60, wherein the step of dynamically shifting the lower frequency boundary includes the step of shifting the lower frequency boundary from a value greater then 4 kilohertz to a value less that kilohertz.
62. A computer readable storage medium containing program code for controlling the operation of a modem used for dynamically communicating data over a phone in accordance with a method comprising the steps of:
transmitting data in a full-band transmission state;
sensing a band-limiting condition; and adjusting the transmission of data from the full-band transmission state to a band-limited transmission state, in response to the sensing step.
transmitting data in a full-band transmission state;
sensing a band-limiting condition; and adjusting the transmission of data from the full-band transmission state to a band-limited transmission state, in response to the sensing step.
63. A computer readable storage medium containing program code for controlling the operation of a modem for communicating data across a communication link comprising:
a first code segment operative to transmit and receive data across an input/output signal line in communication with the communication link:
a second code segment operative to control a processor unit for operation in one of two states, a full-band transmission state and a band-limited state, wherein the full-band transmission state is defined by a lower frequency boundary below a second frequency and an upper frequency boundary greater than or equal to a first frequency, and the band-limited state is defined by a lower frequency boundary greater than the second frequency and an upper frequency boundary greater than or equal to the first frequency;
a third code segment for sensing a band-limiting condition; and a fourth code segment for controlling the operating state of the processor unit, wherein upon sensing the band-limiting condition the control means causes the processor to operate in the band-limited state, and upon sensing no band-limiting condition the control means causes the processor to operate in the full-band transmission state.
a first code segment operative to transmit and receive data across an input/output signal line in communication with the communication link:
a second code segment operative to control a processor unit for operation in one of two states, a full-band transmission state and a band-limited state, wherein the full-band transmission state is defined by a lower frequency boundary below a second frequency and an upper frequency boundary greater than or equal to a first frequency, and the band-limited state is defined by a lower frequency boundary greater than the second frequency and an upper frequency boundary greater than or equal to the first frequency;
a third code segment for sensing a band-limiting condition; and a fourth code segment for controlling the operating state of the processor unit, wherein upon sensing the band-limiting condition the control means causes the processor to operate in the band-limited state, and upon sensing no band-limiting condition the control means causes the processor to operate in the full-band transmission state.
64. The computer readable storage medium as defined in claim 63, wherein the first frequency is approximately 50 kilohertz.
65. The computer readable storage medium as defined in claim 63, wherein the second frequency is approximately 4 kilohertz.
Applications Claiming Priority (7)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US3366096P | 1996-12-17 | 1996-12-17 | |
| US3439096P | 1996-12-30 | 1996-12-30 | |
| US08/962,796 | 1997-11-03 | ||
| US60/034,390 | 1997-11-03 | ||
| US60/033,660 | 1997-11-03 | ||
| US08/962,796 US6061392A (en) | 1996-12-17 | 1997-11-03 | Apparatus and method for communicating voice and data between a customer premises and a central office |
| PCT/US1997/022632 WO1998027665A1 (en) | 1996-12-17 | 1997-12-04 | Apparatus and method for communicating voice and data between a customer premises and a central office |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2272576A1 true CA2272576A1 (en) | 1998-06-25 |
Family
ID=27364458
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002272576A Abandoned CA2272576A1 (en) | 1996-12-17 | 1997-12-04 | Apparatus and method for communicating voice and data between a customer premises and a central office |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JP2001526849A (en) |
| CA (1) | CA2272576A1 (en) |
| WO (1) | WO1998027665A1 (en) |
Families Citing this family (19)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6798735B1 (en) | 1996-06-12 | 2004-09-28 | Aware, Inc. | Adaptive allocation for variable bandwidth multicarrier communication |
| US6101216A (en) * | 1997-10-03 | 2000-08-08 | Rockwell International Corporation | Splitterless digital subscriber line communication system |
| WO1999020027A2 (en) * | 1997-10-10 | 1999-04-22 | Aware, Inc. | Splitterless multicarrier modem |
| US20030026282A1 (en) | 1998-01-16 | 2003-02-06 | Aware, Inc. | Splitterless multicarrier modem |
| ATE521152T1 (en) | 1997-10-10 | 2011-09-15 | Daphimo Co B V Llc | MULTI CARRIER MODEM WITHOUT SPLITTER |
| US6445750B1 (en) * | 1998-04-22 | 2002-09-03 | Lucent Technologies Inc. | Technique for communicating digitally modulated signals over an amplitude-modulation frequency band |
| SE518730C2 (en) * | 1998-05-12 | 2002-11-12 | Ericsson Telefon Ab L M | Method and apparatus for securing an ADSL connection |
| WO2000001127A1 (en) | 1998-06-26 | 2000-01-06 | Aware, Inc. | Multicarrier communication with variable overhead rate |
| US6522730B1 (en) * | 1999-01-15 | 2003-02-18 | Texas Instruments Incorporated | DSL communication system with improved bandwidth |
| US6324268B1 (en) * | 1999-03-01 | 2001-11-27 | Ericsson Inc. | Splitter-less digital subscriber loop modems with improved throughput and voice and data separation |
| US20060274840A1 (en) | 2005-06-06 | 2006-12-07 | Marcos Tzannes | Method for seamlessly changing power modes in an ADSL system |
| EP1956785B1 (en) | 1999-03-12 | 2012-12-26 | Daphimo Co. B.V., LLC | Multicarrier modulation system and method |
| US6775320B1 (en) | 1999-03-12 | 2004-08-10 | Aware, Inc. | Method and a multi-carrier transceiver supporting dynamic switching between active application sets |
| US6748016B1 (en) | 1999-07-16 | 2004-06-08 | Aware, Inc. | System and method for transmitting messages between transceivers using electromagnetically coupled signals |
| US6795548B2 (en) * | 2000-01-05 | 2004-09-21 | Texas Instruments Incorporated | Method and system for data communication |
| DE10001152A1 (en) * | 2000-01-13 | 2001-07-19 | Siemens Ag | Data transmission rate matching procedure e.g. for asymmetric digital subscriber line (ADSL) transmission method - involves automatic matching of data transmission rate to predictable changes in line properties or characteristics during the duration of data transmission |
| US6934368B2 (en) | 2002-08-12 | 2005-08-23 | Smartlink Ltd. | Multi-band modem |
| US7151794B2 (en) | 2002-08-14 | 2006-12-19 | Smartlink Ltd. | Modem channel sharing based on frequency division |
| EP1626563A1 (en) * | 2004-08-10 | 2006-02-15 | Nederlandse Organisatie voor toegepast-natuurwetenschappelijk onderzoek TNO | DSL access multiplexer |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3875339A (en) * | 1972-09-05 | 1975-04-01 | I I Communications Inc | Variable bandwidth voice and data telephone communication system |
| US4442540A (en) * | 1981-06-04 | 1984-04-10 | Bell Telephone Laboratories, Incorporated | Data over voice transmission arrangement |
| US4757495A (en) * | 1986-03-05 | 1988-07-12 | Telebit Corporation | Speech and data multiplexor optimized for use over impaired and bandwidth restricted analog channels |
| US5463616A (en) * | 1993-01-07 | 1995-10-31 | Advanced Protocol Systems, Inc. | Method and apparatus for establishing a full-duplex, concurrent, voice/non-voice connection between two sites |
| US5553063A (en) * | 1994-09-12 | 1996-09-03 | Dickson; William D. | Voice over data communication system |
-
1997
- 1997-12-04 WO PCT/US1997/022632 patent/WO1998027665A1/en not_active Application Discontinuation
- 1997-12-04 JP JP52780298A patent/JP2001526849A/en active Pending
- 1997-12-04 CA CA002272576A patent/CA2272576A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| WO1998027665A1 (en) | 1998-06-25 |
| JP2001526849A (en) | 2001-12-18 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |