WO2001067734A2 - Systeme a gain de paires a capacites de debit de v.90 - Google Patents

Systeme a gain de paires a capacites de debit de v.90 Download PDF

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Publication number
WO2001067734A2
WO2001067734A2 PCT/IL2001/000193 IL0100193W WO0167734A2 WO 2001067734 A2 WO2001067734 A2 WO 2001067734A2 IL 0100193 W IL0100193 W IL 0100193W WO 0167734 A2 WO0167734 A2 WO 0167734A2
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WO
WIPO (PCT)
Prior art keywords
information
voice
digital
signal representation
pair
Prior art date
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PCT/IL2001/000193
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English (en)
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WO2001067734A3 (fr
Inventor
Doron Shani
Eitan Tsur
Avi Rapaport
Original Assignee
Inovia Telecoms Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Inovia Telecoms Ltd. filed Critical Inovia Telecoms Ltd.
Priority to MXPA02008727A priority Critical patent/MXPA02008727A/es
Priority to AU2001237692A priority patent/AU2001237692A1/en
Priority to BR0109080-1A priority patent/BR0109080A/pt
Priority to EP01910110A priority patent/EP1262056A2/fr
Publication of WO2001067734A2 publication Critical patent/WO2001067734A2/fr
Publication of WO2001067734A3 publication Critical patent/WO2001067734A3/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/38—Synchronous or start-stop systems, e.g. for Baudot code
    • H04L25/40—Transmitting circuits; Receiving circuits
    • H04L25/49—Transmitting circuits; Receiving circuits using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels ; Baseband coding techniques specific to data transmission systems
    • H04L25/4917—Transmitting circuits; Receiving circuits using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels ; Baseband coding techniques specific to data transmission systems using multilevel codes
    • H04L25/4927—Transmitting circuits; Receiving circuits using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels ; Baseband coding techniques specific to data transmission systems using multilevel codes using levels matched to the quantisation levels of the channel

Definitions

  • the present invention generally relates to telephony, and more particularly to modems in telephony.
  • V.90 standard and communicating at 56 kbps created a demand for new interfaces for existing telephone systems such as pair-gain systems.
  • Interfaces of V.90 modems and other conventional modems such as V.34 modems to existing telephone systems are described in the following publications: Published PCT application WO 99/38351 which describes a telecommunication system including an at least partially digital telephone link having an analog end portion, first and second modems disposed along the link, and analog/digital devices disposed along the link intermediate the modems which are operative to support communications between the first and second modems substantially at bit rates in excess of 28.8 kbps;
  • US Patent 5,394,437 to Ayanoglu et al which describes a modem that operates reliably at a symbol rate that corresponds to twice its bandwidth even when it is coupled to a receiving A/D converter that operates under control of a clock by synchronizing the modem's operation to the A/D's clock
  • US Patent 5,684,825 to Ko which describes a central office of a public switched telephone network that has a modem pool that includes both simultaneous voice and data (SVD) capable modems and standard, e.g., CCITT V.32 compatible modems:
  • US Patent 5,793,809 to Holmquist which describes a transmitting Mu-Law modem that creates a probe signal by the modifying the 7th bit of each of a number of PCM samples during the "hand-shaking" phase of a data connection;
  • European Patent EP 0535581 which describes a circuit arrangement which is to be specified by means of which it is possible to use TEMEX transmission techniques for analog connecting lines on transmission links which are equipped with a digital system for dedicated connections (PCM2A); and
  • the present invention seeks to provide novel system and improved methods for communicating information over communication networks that employ equipment such as multiplexers and pair-gain type systems.
  • a pair-gain system is inserted in a communication system for communicating information between a service provider unit and a subscriber unit.
  • the information is communicated at a rate that exceeds rates defined in the V.34 communication standard, and preferably at a V.90 rate as defined in the V.90 communication standard.
  • the V.34 communication standard referred to herein is the ITU-T Recommendation V.34 "A modem operating at data signalling rates of up to 33,600 bit/s for use on the general switched telephone network and on leased point-to-point 2-wire telephone-type circuits", published 02/98 and is hereby incorporated herein by reference.
  • the pair-gain system includes an exchange unit (EU) operatively associated with a central office that receives the information from the service provider unit, and a remote unit (RU) operatively associated with the EU and with a V.90 compatible modem at the subscriber unit.
  • the EU is operative to convert an analog signal representation of the information that is received from the central office to a digital-subscriber-line (DSL) signal representation of the information.
  • the RU receives the DSL signal representation of the information from the EU, converts the DSL signal representation of the information to voice-band information at the rate that exceeds rates defined in the V.34 communication standard, and transmits the voice-band information to the V.90 compatible modem.
  • a first noise-reduction mechanism includes an echo canceller in the pair-gain system that is operative to substantially cancel a far-echo signal generated at the pair-gain system and experienced by the V.90 compatible modem.
  • a first impairment-reduction mechanism includes a switch that bypasses, in non-voice communication, a high-pass-filter (HPF) which is typically used in voice communication for reduction of impairment due to electromagnetic interference generated by conventional electric networks but poses an impairment in non-voice communication.
  • a second impairment-reduction mechanism includes a compander that compresses digital samples representing the information by a first non-linear compression algorithm if the information includes voice, and by a second non-linear compression algorithm if the information does not include voice.
  • a pair-gain system in a communication system that communicates information between a service provider unit and a subscriber unit via the pair-gain system at a rate exceeding rates defined in the V.34 communication standard
  • the pair-gain system including an exchange unit (EU) operatively associated with a central office that receives the information from the service provider unit, the EU being operative to convert an analog signal representation of the information received from the central office to a digital-subscriber-line (DSL) signal representation of the information, a remote unit (RU) operatively associated with the EU and with a V.90 compatible modem, the RU being operative to receive the DSL signal representation of the information from the EU, to convert the DSL signal representation of the information to voice-band information at the rate exceeding rates defined in the V.34 communication standard and to transmit the voice-band information to the V.90 compatible modem, and an echo canceller operatively associated with one of the EU and the RU, the echo canceller being implemented as a near-
  • EU exchange unit
  • DSL digital-subscriber
  • noise-echo and “far-echo” as will be used hereinafter refer to reflections at near-end and far-end hybrid circuits, respectively. Accordingly, an echo canceller that cancels a signal of a near echo is referred to as a “near-echo canceller”, and an echo canceller that cancels a signal of a far-echo is referred to as a “far-echo canceller”.
  • far-echo canceller an echo canceller that cancels a signal of a far-echo canceller
  • hybrid is used herein to denote a circuit that separates the two directions of transmission in a communication system.
  • the information includes at least one of the following: voice, voice-band data, and facsimile information.
  • the EU may preferably include an analog-to-digital converter (ADC) operative to convert the analog signal representation of the information received from the central office to digital samples, a compander operatively associated with the ADC and operative to compress the digital samples so as to generate compressed digital samples, the digital samples being compressed by a first non-linear compression algorithm if the information includes voice, and by a second non-linear compression algorithm if the information does not include voice, and a line interface operatively associated with the compander and the RU, wherein the line interface is operative to receive the compressed digital samples from the compander, to convert the compressed digital samples to the DSL signal representation of the information, and to transmit the DSL signal representation of the information to the RU.
  • ADC analog-to-digital converter
  • the EU may include a switch which is operative, in non-voice communication, to bypass a high-pass-filter (HPF) that is used in voice communication for reducing impairment due to electromagnetic interference generated by electric networks.
  • HPF high-pass-filter
  • the EU may also include a bandwidth allocation unit that is operative to determine a bandwidth allocated to V.90 communication.
  • each of the EU and the RU includes a DSL interface unit for enabling communication of the DSL signal representation of the information between the EU and the RU.
  • the DSL interface unit preferably includes one of the following: an xDSL interface unit, and a 2B1Q interface unit.
  • a communication system for communicating information between a service provider unit and a subscriber unit at a rate exceeding rates defined in the V.34 communication standard, the system including a digital modem at the service provider unit, the digital modem being operative to transmit digital data representing the information, a central office operatively associated with the digital modem and operative to receive the digital data from the digital modem and to convert the digital data to a series of analog signals, a pair-gain system operatively associated with the central office and operative to receive the series of analog signals from the central office and to convert the series of analog signals to voice-band information at the rate exceeding the rates defined in the V.34 communication standard, and a V.90 compatible modem at the subscriber unit, the V.90 compatible modem being operatively associated with the pair-gain system and being operative to receive the voice-band information at the rate exceeding the rates defined in the V.34 communication standard from the pair-gain system, wherein the pair-gain system includes an echo canceller that is implemented
  • a pair-gain system in a communication system that communicates information between a service provider unit and a subscriber unit via the pair-gain system at a rate exceeding rates defined in the V.34 communication standard
  • the pair-gain system including a remote unit (RU) operatively associated with a V.90 compatible modem, the RU being operative to convert a digital-subscriber-line (DSL) signal representation of the information to voice-band information at the rate exceeding rates defined in the V.34 communication standard, and to transmit the voice-band information at the rate exceeding rates defined in the V.34 communication standard to the V.90 compatible modem, and an exchange unit (EU) operatively associated with the RU and a central office, the EU being operative to receive an analog signal representation of the information from the central office, and the EU includes an analog-to-digital converter (ADC) operative to convert the analog signal representation of the information received from the central office to digital samples, a compander operatively associated with the ADC and
  • ADC analog-to-digital converter
  • the first non-linear compression algorithm and the second non-linear compression algorithm are identical, and the first non-linear compression algorithm provides, at a peak-to-average ratio characterizing the V.90 compatible modem, a signal-to-noise ratio (SNR) that is higher than the SNR provided by a
  • the EU includes a switch that is operative, in non-voice communication, to bypass a high-pass-filter (HPF) which is used in voice communication for reducing impairment due to electromagnetic interference generated by electric networks.
  • HPF high-pass-filter
  • the EU may also include a bandwidth allocation unit 0 operative to determine a bandwidth allocated to V.90 communication.
  • the RU includes a first DSL interface unit
  • the line interface includes a second DSL interface unit
  • the first DSL interface unit and the second DSL interface unit are operative to communicate the DSL signal representation of the information between the EU and the RU.
  • a pair-gain system in a communication system that communicates information between a service provider unit and a subscriber unit via the pair-gain system at a rate exceeding rates defined in the V.34 communication standard
  • the pair-gain system including a remote unit (RU) operatively associated with a V.90 compatible modem and operative to convert a digital-subscriber-line (DSL) signal representation of the information to voice-band information at the rate exceeding rates defined in the V.34 communication standard, and to transmit the voice-band information at the rate exceeding rates defined in the V.34 communication standard to the V.90 compatible modem, and an exchange unit (EU) operatively associated with the RU and with a central office that receives the information from the service provider unit, the EU being operative to receive from the central office an analog signal representation of the information, to convert the analog signal representation of the information to the DSL signal representation of the information, and to transmit the DSL signal representation of the information to the RU, wherein the EU includes an echo canceller
  • a pair-gain system in a communication system that communicates information between a service provider unit and a subscriber unit via the pair-gain system at a rate exceeding rates defined in the V.34 communication standard
  • the pair-gain system including an exchange unit (EU) operatively associated with a central office that receives the information from the service provider unit, the EU being operative to convert an analog signal representation of the information received from the central office to a digital-subscriber-line (DSL) signal representation of the information, a remote unit (RU) operatively associated with the EU and with a V.90 compatible modem, the RU being operative to receive the DSL signal representation of the information from the EU, to convert the DSL signal representation of the information to voice-band information at the rate exceeding rates defined in the V.34 communication standard, and to transmit the voice-band information to the V.90 compatible modem, and a bandwidth allocation unit operatively associated with the EU and operative to determine a bandwidth allocated to V.90 compatible communication.
  • EU exchange unit
  • DSL digital-subscriber
  • each of the EU and the RU includes a DSL interface unit for enabling communication of the DSL signal representation of the information between the EU and the RU.
  • a pair-gain system in a communication system that communicates information between a service provider unit and a subscriber unit via the pair-gain system at a rate exceeding rates defined in the V.34 communication standard
  • the pair-gain system including an exchange unit (EU) operatively associated with a central office that receives the information from the service provider unit, the EU being operative to convert an analog signal representation of the information received from the central office to a digital-subscriber-line (DSL) signal representation of the information, a remote unit (RU) operatively associated with the EU and with a V.90 compatible modem, the RU being operative to receive the DSL signal representation of the information from the EU, to convert the DSL signal representation of the information to voice-band information at the rate exceeding rates defined in the V.34 communication standard, and to transmit the voice-band information to the V.90 compatible modem, and a switch operatively associated with one of the EU and the RU and operative, in non-voice communication, to bypass
  • EU exchange unit
  • DSL digital-subscriber
  • a pair-gain system in a communication system that communicates information between a digital modem in a service provider unit and a V.90 compatible modem in a subscriber unit via the pair-gain system at a rate exceeding rates defined in the V.34 communication standard, the pair-gain system including a remote unit (RU) operatively associated with the V.90 compatible modem, and an exchange unit (EU) operatively associated with the RU and a central office, where the central office is in operative association with the digital modem.
  • RU remote unit
  • EU exchange unit
  • the EU being operative to respond, after a predetermined time period, to a V.8 ANsam signal generated in a communication initialization procedure between the digital modem and the V.90 modem thereby determining a delay in an echo canceller in the digital modem.
  • a pair-gain system in a communication system that communicates information between a digital modem in a service provider unit and a V.90 compatible modem in a subscriber unit via the pair-gain system at a rate exceeding rates defined in the V.34 communication standard, the pair-gain system including a remote unit (RU) operatively associated with the V.90 compatible modem, and an exchange unit (EU) operatively associated with the RU and a central office which is in operative association with the digital modem, the EU being operative to determine that the information includes voice information, and to enable, in response to a determination that the information includes voice information, at least one of the following: operation in downstream communication of high-pas-filters (HPFs) in the EU; and filtering operations of LPFs in the EU.
  • HPFs high-pas-filters
  • the EU upon determination that the information does not include voice information, characterizes a non-voice channel between the digital modem and the V.90 compatible modem, reduces the filtering operations of LPFs in the EU so as to broaden channel response of the non- voice channel, and enables operation of the echo cancellers in the EU. Further preferably, the determination that the information does not include voice information is performed by employing communication in accordance with the protocol as set in International Standard V.8.
  • a method for communicating information between a service provider unit and a subscriber unit at a rate exceeding rates defined in the V.34 communication standard including the steps of operatively associating a pair-gain system including an exchange unit (EU) and a remote unit (RU) with a central office and a V.90 compatible modem, transmitting digital data representing the information from the service provider unit to the central office, converting, at the central office, the digital data to an analog signal representation of the information, transmitting the analog signal representation of the information from the central office to the EU, receiving, at the EU, the analog signal representation of the information, converting, at the EU, the analog signal representation of the information to digital samples, canceling, at the EU, a representation of a far-echo signal experienced by the V.90 compatible modem from the digital samples thereby to generate echo canceled digital samples, converting the echo canceled digital samples to a digital-subscriber-line (DSL) signal representation of the information, transmitting the steps of operatively associating a pair-gain system including an exchange unit
  • the canceling step includes the steps of adjusting taps of an echo canceller in the EU by training the echo canceller with periodic digital impulses, using the taps of the echo canceller to obtain an approximation of the representation of the far-echo signal experienced by the V.90 compatible modem, and subtracting the approximation of the representation of the far-echo signal experienced by the V.90 compatible modem from the digital samples to obtain the echo canceled digital samples.
  • the adjusting step preferably includes the steps of causing the central office to transmit a tone signal, dialing at least one digit to stop the tone signal, transmitting the periodic digital impulses, and using an echo of the periodic digital impulses to obtain the taps of the echo canceller.
  • a method for communicating information between a service provider unit and a subscriber unit at a rate exceeding rates defined in the V.34 communication standard including the steps of operatively associating a pair-gain system including an exchange unit (EU) and a remote unit (RU) with a central office and a V.90 compatible modem, transmitting digital data representing the information from the service provider unit to the central office, converting, at the central office, the digital data to an analog signal representation of the information, transmitting the analog signal representation of the information from the central office to the EU, receiving, at the EU, the analog signal representation of the information, converting, at the EU, the analog signal representation of the information to digital samples, compressing the digital samples so as to generate compressed digital samples, the digital samples being compressed by a first non-linear compression algorithm if the information includes voice, and by a second non-linear compression algorithm if the information does not include voice, converting the compressed digital samples to a digital-subscriber-line (
  • the compressing step includes the step of allocating a bandwidth for V.90 compatible communication based on at least one of a number and type of communication sessions simultaneously supported by the pair-gain system by determining at least one of the following: a number of bits per sample to be transmitted, and a sampling clock frequency.
  • a method for communicating information between a service provider unit and a subscriber unit at a rate exceeding rates defined in the V.34 communication standard including the steps of operatively associating a pair-gain system including an exchange unit (EU) and a remote unit (RU) with a central office and a V.90 compatible modem, transmitting digital data representing the information from the service provider unit to the central office, converting, at the central office, the digital data to an analog signal representation of the information, transmitting the analog signal representation of the information from the central office to the EU, receiving, at the EU, the analog signal representation of the information, converting, at the EU, the analog signal representation of the information to digital samples, determining whether the information is non-voice information, if the information is non-voice information, bypassing a HPF which is used in voice communication for reducing impairment due to electromagnetic interference generated by electric networks, converting the digital samples provided after the bypassing step to a digital-subscriber-line (DSL)
  • DSL digital-subscriber-line
  • a method for communicating information between a subscriber unit and a service provider unit at a rate exceeding rates defined in the V.34 communication standard including the steps of operatively associating a pair-gain system including an exchange unit (EU) and a remote unit (RU) with a central office and a V.90 compatible modem, transmitting voice-band information at the rate exceeding rates defined in the V.34 communication standard from the V.90 compatible modem to the RU, converting, at the RU, the voice-band information at the rate exceeding rates defined in the V.34 communication standard to a digital-subscriber-line (DSL) signal representation of the information, transmitting the DSL signal representation of the information from the RU to the EU, receiving the DSL signal representation of the information at the EU, canceling, at the EU, a representation of a far-echo signal generated at the RU and experienced by a digital V.34 receiver at the service provider unit from the DSL signal representation of the information
  • a method for communicating information between a digital modem in a service provider unit and a V.90 compatible modem in a subscriber unit at a rate exceeding rates defined in the V.34 communication standard including operatively associating a pair-gain system including a remote unit (RU) and an exchange unit (EU) with the V.90 compatible modem and a central office which is in operative association with the digital modem, and programming the EU to respond, after a predetermined time period, to a V.8 ANsam signal generated in a communication initialization procedure between the digital modem and the V.90 compatible modem thereby determining a delay in an echo canceller in the digital modem.
  • RU remote unit
  • EU exchange unit
  • a method for communicating information between a digital modem in a service provider unit and a V.90 compatible modem in a subscriber unit at a rate exceeding rates defined in the V.34 communication standard including operatively associating a pair-gain system including a remote unit (RU) and an exchange unit (EU) with the V.90 compatible modem and a central office which is in operative association with the digital modem, determining, at the EU, that the information includes voice information, and enabling, in response to a determination that the information includes voice information, at least one of the following: operation in downstream communication of high-pass-filters (HPFs) in the EU; and filtering operations of LPFs in the EU.
  • HPFs high-pass-filters
  • Figs. 1A and IB together constitute a simplified pictorial illustration of a pair-gain system in a communication system, the pair-gain system being constructed and operative in accordance with a preferred embodiment of the present invention
  • Figs. 2A and 2B together constitute a simplified flow chart illustration of a method of operation of the system of Figs. 1A and IB.
  • Figs. 1 A and IB which together constitute a simplified pictorial illustration of a pair-gain system 10 in a communication system 15, the pair-gain system 10 being constructed and operative in accordance with a preferred embodiment of the present invention.
  • pair-gain is used throughout the specification and claims in a broad sense to include systems that are used in conjunction with communication systems and are employed to enable transmission in a digital form of more than one communication session, either data or voice, simultaneously over a transmission medium. Such systems are also known as PCM systems or digital added main line (DAML) systems. Typically, pair-gain systems are used in telephony communication systems that typically communicate over copper wire twisted pair infrastructure.
  • the communication system 15 preferably enables communication of information between a service provider unit 20 and a subscriber unit 25 at a rate exceeding rates defined in the V.34 communication standard.
  • the communication system 15 also preferably supports communication at data rates defined in lower rate communication standards, such as V.32. It is appreciated that the communication system 15 may be a telephone system that communicates over copper wire twisted pair infrastructure and provides telephony services to the subscriber unit 25 including data transmission services that are typically provided by a service provider, such as an Internet service provider (ISP).
  • ISP Internet service provider
  • the information supplied by the ISP is communicated between the service provider unit 20 and the subscriber unit 25 via a central office 30 and the pair-gain system 10. It is appreciated that the service provider unit 20 is typically placed at premises of the ISP.
  • the digital modem 35 at the service provider unit 20 preferably transmits digital data representing the information to the central office 30 over a digital channel 32.
  • the digital modem 35 preferably includes a conventional V.90 digital transmitter (not shown) and a digital V.34 receiver (not shown). It is appreciated that the information may preferably include at least one of the following: voice; voice-band data; and facsimile information.
  • the central office 30 preferably receives the digital data provided by the digital modem 35 and converts the digital data to a series of analog signals that are transmitted over an analog channel 37 to the pair-gain system 10. It is appreciated that the series of analog signals form an analog signal representation of the information.
  • conversion of the digital data to the series of analog signals is performed by employing conventional elements such as a conventional telephony digital-to-analog converter (DAC or D/A) (not shown).
  • DAC or D/A digital-to-analog converter
  • the pair-gain system 10 typically includes an exchange unit (EU) 45 and a remote unit (RU) 50.
  • the EU 45 is typically operatively associated with the central office 30, and the RU 50 is typically preferably operatively associated with the EU 45 and the V.90 compatible modem 40 in the subscriber unit 25.
  • the EU 45 is typically located at the central office 30 or at a location near the central office 30.
  • the RU 50 is typically located near the subscriber unit 25.
  • a typical distance between the EU 45 and the RU 50 is of the order of a few kilometers, such as 3 kilometers. However, it is appreciated that the distance between the EU 45 and the RU 50 may be longer or shorter.
  • the analog signal representation of the information provided by the central office 30 to the pair-gain system 10 is received at a hybrid 55 in the EU 45.
  • the hybrid 55 may be a conventional hybrid that separates incoming signals from outgoing signals.
  • the hybrid 55 may also include additional conventional functionality, such as impedance matching, clocking control for controlling a sampling clock frequency, and echo canceling for canceling a near-echo signal generated at the hybrid 55 and experienced by the EU 45.
  • the hybrid 55 preferably provides the analog signal representation of the information to a low-pass filter (LPF) 60 that is operative to attenuate high frequency signals thereby to provide filtered analog signals.
  • LPF low-pass filter
  • the filtered analog signals are then converted to digital samples in an analog-to-digital converter 65 (also referred to as A/D or ADC).
  • ADC 65 may preferably use linear conversion with samples of length between 10-bit and 16-bit. It is appreciated that the LPF 60 is also operative to prevent aliasing in the sampling process of the ADC 65.
  • the various noise-reduction and impairment-reduction mechanisms may be implemented in the EU 45.
  • Each of the noise-reduction and impairment-reduction mechanisms is preferably independent and therefore may be implemented separately or in combination with other noise-reduction and impairment-reduction mechanisms in the EU 45.
  • a first noise-reduction mechanism preferably includes an echo canceller (EC) 70.
  • the echo canceller 70 is preferably implemented as a near-echo canceller in the pair-gain system 10 and is operative to substantially cancel a far-echo signal generated at the hybrid 55 and experienced by the V.90 compatible modem 40.
  • the echo canceller 70 may be implemented with a conventional finite impulse response (FIR) filter (not shown). It is appreciated that although the hybrid 55 includes echo-canceling functionality as mentioned above, an echo canceller in the hybrid 55 differs from the echo canceller 70.
  • FIR finite impulse response
  • the difference between the echo canceller in the hybrid 55 and the echo canceller 70 is that the echo canceller in the hybrid 55 is operative to cancel an echo signal experienced at the EU 45 and is intended to prevent overloading of the components in the EU 45, whereas the echo canceller 70 cancels a far-echo signal experienced at the V.90 compatible modem 40 in order to achieve the required overall SNR of the communication system 15 for adequate operation of the communication system 15 at the V.90 rate.
  • each of the echo canceller in the hybrid 55 and the echo canceller 70 may be implemented with a FIR filter
  • the number of taps and the values of the taps of the FIR filter of the echo canceller in the hybrid 55 may be different than the number of taps and the values of the taps of the FIR filter of the echo canceller 70.
  • the echo canceller in the hybrid 55 and the echo canceller 70 may be separately implemented.
  • the echo canceller 70 obtains an approximation of a representation of the far-echo signal experienced by the V.90 compatible modem and subtracts the approximation of the representation of the far-echo signal experienced by the V.90 compatible modem from the digital samples generated by the ADC 65 thereby to provide echo canceled digital samples. It is appreciated that the approximation of the representation of the far-echo signal experienced by the V.90 compatible modem is preferably subtracted from the digital samples in a combiner 75.
  • the echo canceled digital samples may preferably be provided to a switch 80 that is operative to enable operation of a high-pass-filter (HPF) 85 in voice communication, and to bypass the HPF 85 in non- voice V.90 communication.
  • HPF high-pass-filter
  • the HPF 85 is used in voice communication to reduce impairment due to electromagnetic interference generated by conventional electric networks, typically at 50/60 Hz.
  • the HPF 85 poses impairment in non-voice V.90 communication and therefore the HPF 85 is bypassed in non-voice communication.
  • the switch 80 that controls the operation of the HPF 85 therefore provides a first impairment-reduction mechanism.
  • all HPFs in the pair-gain system 10 that are used in downstream transmission are preferably bypassed by the switch 80 or other switches (not shown).
  • the echo canceled digital samples in non-voice communication, or echo canceled digital samples filtered by the HPF 85 in voice-communication are preferably provided to a compander 90 via a bandwidth allocation unit 95.
  • the bandwidth allocation unit 95 is preferably operative to determine a bandwidth allocated to V.90 communication based on at least one of a number and a type of communication sessions simultaneously supported by the pair-gain system 10. Preferably, the bandwidth allocation unit 95 allocates bandwidth by determining a number of bits per sample to be transmitted by the compander 90 and/or the sampling clock frequency to be used in the hybrid 55. It is appreciated that the compander 90 may preferably transmit between 10 and 16 bits per sample.
  • the bandwidth allocation unit 95 may preferably provide a determination of the number of bits per sample by performing an optimization process on all lines served by the pair-gain system 10.
  • a data rate of all voice sessions served by the pair-gain system 10 is deducted from an overall available data rate of the pair-gain system 10 and the remaining data rate is allotted to the non- voice sessions.
  • the compression ratio i.e., the number of bits per sample transmitted by the compander 90, and the sampling clock frequency are preferably determined according to the remaining data rate that is allotted to the non- voice sessions.
  • sampling clock frequency may preferably be higher than the conventional 8 kHz that is used in conventional telephony applications, such as 9.6 kHz.
  • the compander 90 is preferably operative to compress the digital samples provided thereto so as to generate compressed digital samples in accordance with a determination of the compression ratio provided by the bandwidth allocation unit 95.
  • the optimization process that controls the combination of compression ratio and sampling clock frequency provides a second impairment-reduction mechanism that reduces quantization noise with respect to conventional pair-gain systems that employ 8 bit conventional ⁇ -Law compression algorithms and 8 kHz sampling clock frequency.
  • the digital samples are compressed by a first non-linear compression algorithm if the information includes voice, and by a second non-linear compression algorithm if the information does not include voice.
  • the first non-linear compression algorithm and the second non-linear compression algorithm may be different, and the second non-linear compression algorithm may be operative to provide, at a peak-to-average ratio characterizing the V.90 compatible modem, an SNR that is higher than the SNR provided by the conventional ⁇ -Law compression algorithm that is performed in the ADC 65.
  • the first non-linear compression algorithm and the second non-linear compression algorithm may be identical.
  • SNR signal-to-noise ratio
  • the first non-linear compression algorithm may include a ⁇ -Law compression algorithm in which ⁇ ? has a value which is greater than or equal to 8 and is less than or equal to 128.
  • non ⁇ -Law compression algorithms may be used in each one of the first and second non-linear compression algorithms.
  • the compander 90 preferably provides the compressed digital samples to a line interface, preferably a digital line interface such as a digital-subscriber-line (DSL) interface unit 100.
  • the DSL interface unit 100 is preferably operative to convert the compressed digital samples to a DSL signal representation of the information, and to transmit the DSL signal representation of the information to a corresponding DSL interface unit 105 in the RU 50 over a digital channel 107 by using a conventional DSL format.
  • each of the DSL interface unit 100 and DSL interface unit 105 may include a DSL framer and modem.
  • the DSL format may include one of the following: an xDSL format; and the 2B1Q format. Accordingly, the DSL interface unit 100 and the corresponding DSL interface unit 105 may each include one of the following: an xDSL interface unit; and a 2B1Q interface unit.
  • xDSL refers to any of the well-known family of DSL standards, such as ADSL, HDSL, VDSL and SDSL.
  • the DSL interface unit 105 receives the DSL signal representation of the information from the EU 45 and converts the DSL signal representation of the information to a representation of the compressed digital samples compressed in the compander 90.
  • the representation of the compressed digital samples is preferably provided to a compander 110 in the RU 50.
  • the compander 110 is preferably operative to expand the representation of the compressed digital samples thereby to generate decompressed digital samples. It is appreciated that the compander 110 may be similar in structure and functionality to the compander 90 in the EU 45.
  • the compander 110 preferably provides the decompressed digital samples to a D/A 115 that converts the decompressed digital samples to analog signals that are filtered in a LPF 120.
  • the analog signals at the output of the LPF 120 are preferably provided to a hybrid 125 that transmits the analog signals at the output of the LPF 120 as voice-band information at a rate that exceeds rates defined in the V.34 communication standard from the RU 50 to the V.90 compatible modem 40 over a voice-band analog channel 127.
  • a hybrid 130 receives the voice-band information at the rate that exceeds rates defined in the V.34 communication standard and provides analog signals representing the information to a LPF 135 that is operative to attenuate high frequency signals thereby to provide filtered analog signals. The filtered analog signals are then converted to digital samples in an A/D 140. It is appreciated that the LPF 135 is also operative to prevent aliasing in the sampling process of the A/D 140.
  • a conventional echo canceller 145 operating as a near-echo canceller to cancel a near-echo signal generated at the hybrid 130, subtracts, in a combiner 150, a representation of the near-echo signal generated at the hybrid 130 from the digital samples at the output of the A/D 140 thereby canceling the near-echo signal.
  • the digital samples at the output of the combiner 150 are then provided to a V.90 receiver 155 which detects the digital samples and provides the digital samples to processing elements in the subscriber unit 25 (not shown) that are associated with the V.90 receiver 155.
  • the rate that exceeds the rates defined in the V.34 communication standard may preferably be a rate defined in the V.90 communication standard, i.e., a rate of 56 kbps or at least a rate exceeding 28.8 kbps.
  • the V.90 compatible modem 40 may reliably receive information at a rate of 56 kbps, or at least at a rate higher than 28.8 kbps, even in the presence of the pair-gain system 10 which is placed between the subscriber unit 25 and the central office 30.
  • a V.34 transmitter 160 at the V.90 compatible modem 40 is preferably operative to transmit upstream digital data generated by the processing elements in the subscriber unit 25.
  • the upstream digital data is preferably converted to analog signals representing the upstream digital data in a D/A 165.
  • the analog signals are filtered in a LPF 170 and provided to the hybrid 130.
  • the hybrid 130 preferably transmits the analog signals at the output of the LPF 170 to the RU 50 as voice-band information at a V.34 rate over the voice-band analog channel 127.
  • the hybrid 125 receives the voice-band information at the V.34 rate and provides analog signals representing the voice-band information to a LPF 175.
  • the LPF 175 attenuates high frequency signals and provides filtered analog signals to an A/D 180.
  • the A/D 180 is preferably operative to convert the filtered analog signals to digital samples. It is appreciated that the LPF 175 is also operative to prevent aliasing in the sampling process of the A/D 180.
  • the A/D 180 provides the digital samples to a HPF 185 which is operative to attenuate 50/60 Hz signals and to shorten the impulse response of a far-echo signal generated at the RU 50 and experienced by the digital V.34 receiver at the service provider unit 20.
  • the digital samples at the output of the HPF 185 are provided to the compander 110 which compresses the digital samples to provide compressed digital samples. It is appreciated that the compander 110 may compress the digital samples by a first non-linear compression algorithm if the information transmitted from the subscriber unit 25 includes voice, and by a second non-linear compression algorithm if the information does not include voice.
  • the compander 110 provides the compressed digital samples to the DSL interface unit 105.
  • the DSL interface unit 105 is preferably operative to convert the compressed digital samples to a DSL signal representation of the information, and to transmit the DSL signal representation of the information to the DSL interface unit 100 in the EU 45 over the digital channel 107 by using the same DSL format that is used in the downstream transmission.
  • the DSL interface unit 100 receives the DSL signal representation of the information from the RU 50 and converts the DSL signal representation of the information to a representation of the compressed digital samples compressed in the compander 110.
  • the representation of the compressed digital samples in the compander 110 is preferably provided to the compander 90 that is operative to expand the representation of the compressed digital samples in the compander 110 thereby to generate decompressed digital samples.
  • the EU 45 includes an additional echo canceller 190 that is operative to substantially cancel the far-echo signal generated at the RU 50 and experienced by the digital V.34 receiver at the service provider unit 20.
  • the echo canceller 190 may be implemented with a FIR filter. It is appreciated that the echo canceller 190 may be implemented in parallel to echo canceller 70 and independent therefrom.
  • the echo canceller 190 is preferably operative to obtain an approximation of a representation of the far-echo signal generated at the hybrid 125 and experienced by the digital V.34 receiver at the service provider unit 20.
  • the approximation of the representation of the far-echo signal experienced by the digital V.34 receiver at the service provider unit 20 is preferably subtracted, at a combiner 195, from the decompressed digital samples.
  • the digital samples at the output of the combiner 195 are preferably provided to a HPF 200 which is operative to shorten the impulse response of the far-echo signal generated at the EU 45 and experienced by the V.90 compatible modem 40 and to filter electric network interference signals at 50/60 Hz frequencies.
  • the digital samples at the output of the HPF 200 are preferably converted in a D/A 205 to analog signals that are filtered in a LPF 210.
  • the analog signals at the output of the LPF 210 are preferably provided to the hybrid 55 that transmits the analog signals at the output of the LPF 210 to the central office 30 over the analog channel 37.
  • the central office 30 preferably converts the analog signals received thereat to digital data, and transmits the digital data to the digital modem 35 at the service provider unit 20 over the digital channel 32.
  • the following EU 45 units the echo cancellers 70 and 190; the combiners 75 and 195; the switch 80; the HPFs 85 and 200; the bandwidth allocation unit 95; and the compander 90 may be all implemented in hardware or in software.
  • the echo cancellers 70 and 190, the combiners 75 and 195, the switch 80, the bandwidth allocation unit 95, and the compander 90 are implemented in a digital-signal-processor (DSP) such as TM5320C5402 by Texas Instruments Inc. or DSP 56307 by Motorola Inc.
  • DSP digital-signal-processor
  • the compander 110 and the HPF 185 in the RU 50 may also be implemented in hardware or in software.
  • the echo canceller 70 in the EU 45 may be adjusted to determine taps by training the echo canceller 70 with a training sequence including periodic digital impulses or by other suitable training sequences that fit an LMS algorithm.
  • the taps may then preferably be used to obtain the approximation of the representation of the far-echo signal experienced by the V.90 compatible modem. Determination of the taps is preferably performed when the central office 30 does not transmit any signal. This is achieved, for example, when the EU 45 causes the central office 30 to transmit a tone signal, and dials one or more digits to stop the tone signal.
  • the training sequence may be transmitted and the echo canceller 70 may be activated to obtain an approximation of a representation of an echo of the training sequence and to calculate the taps of the echo canceller 70 based on the approximation of the representation of the echo of the training sequence.
  • the echo canceller 190 may be trained by a training sequence that is similar to the training sequence used for the echo canceller 70, or by a different training sequence. Typically, the echo canceller 190 may be trained when a user picks up a telephone thereby stopping the tone signal.
  • the EU 45 may also participate in training of an echo canceller (not shown) in the digital modem 35. In such a case, when communication between the digital modem 35 and the V.90 compatible modem 40 is initialized, the EU 45 preferably identifies an ANsam signal which is typically transmitted by the modem 35 to the modem 40 during a communication initialization procedure performed in accordance with the protocol as set in International Standard V.8.
  • the EU 45 instead of the V.90 compatible modem 40 responding to the ANsam signal as is usually the case when the modems 35 and 40 communicate directly and not through the pair-gain system 10, the EU 45, for example through programming of its DSP, preferably responds to the ANsam signal after a predetermined time period of, preferably, 40 milliseconds (mSec). By responding to the ANsam signal, the EU 45 preferably determines a delay in the echo canceller in the digital modem 35 thereby enabling connection between the V.90 compatible modem 40 and the modem 35 at a rate that exceeds rates defined in the V.34 communication standard.
  • mSec milliseconds
  • the switch 80 which enables operation of the HPF 85 in voice communication and bypass of the HPF 85 in non- voice V.90 communication, is preferably controlled by the DSP of the EU 45.
  • determination of a communication session as a non-voice communication session is performed by the DSP of the EU 45 identifying predetermined V.8 signals. If the DSP of the EU 45 does not identify the predetermined V.8 signals in a session, then the session is determined as a voice communication session.
  • the switch 80 is preferably switched to a position that enables operation of the HPF 85 and all other HPFs in the pair-gain system 10 that are used in downstream communication. Additionally, the filtering operations of the LPFs in the EU 45 are enabled.
  • the EU 45 preferably characterizes the channel between the modem 35 and the modem 40 as a non- voice channel, reduces the filtering operations of the LPFs in the EU 45 so as to broaden channel response of the non- voice channel, and enables operation of the echo cancellers in the EU 45.
  • FIG. 2A and 2B together constitute a simplified flow chart illustration of a preferred method of operation of the system of Figs. 1A and IB.
  • a communication link is established between an ISP and a subscriber.
  • the ISP uses a digital modem in a service provider unit to communicate information with a subscriber unit at subscriber premises.
  • the subscriber unit includes a V.90 compatible modem that is capable of communicating at a rate that exceeds rates defined in the V.34 communication standard.
  • the service provider unit communicates with the subscriber unit via a central office and a pair-gain system that includes an exchange unit (EU) and a remote unit (RU).
  • EU exchange unit
  • RU remote unit
  • the EU is preferably associated with the central office and the RU is preferably associated with the V.90 compatible modem.
  • the ISP transmits digital data representing the information from the digital modem in the service provider unit via the central office.
  • the digital data is converted to an analog signal representation of the information.
  • the analog signal representation of the information is preferably transmitted from the central office to the EU.
  • noise-reduction and impairment-reduction mechanisms may be applied to increase communication performance and to enable communication at the rate that exceeds the rates defined in the V.34 communication standard, and preferably at a V.90 rate.
  • each of the noise-reduction and impairment-reduction mechanisms being applied is preferably independent of the others, and therefore at least one noise-reduction mechanism or at least one impairment-reduction mechanism may be implemented.
  • each noise-reduction mechanism and each impairment-reduction mechanism may be implemented separately or in combination with other noise-reduction and impairment-reduction mechanisms.
  • a far-echo signal experienced by the V.90 compatible modem may be canceled by subtracting a representation of the far-echo signal experienced by the V.90 compatible modem from the digital samples.
  • a HPF that is typically used in voice communication for reduction of impairment due to electromagnetic interference generated by conventional electric networks but poses an impairment in non-voice communication, is preferably bypassed when the digital samples do not include voice in order to reduce impairment.
  • the digital samples may be compressed in a compander by a first non- linear compression algorithm if the information includes voice information, and by a second non-linear compression algorithm if the information does not include voice information.
  • a bandwidth allocation unit in the EU allocates a bandwidth for V.90 compatible communication based on at least one of a number and type of communication sessions simultaneously supported by the pair-gain system.
  • the bandwidth allocation unit may determine at least one of the following: a number of bits per sample to be transmitted by the compander; and a sampling clock frequency to be used by a sampling mechanism, such as an ADC and a DAC.
  • the bandwidth allocation unit may preferably provide a determination of the number of bits per sample by performing an optimization process on all lines served by the pair-gain system.
  • a data rate of all voice sessions served by the pair-gain system is deducted from an overall available data rate of the pair-gain system and the remaining data rate is allotted to the non- voice sessions.
  • the compression ratio i.e., the number of bits per sample transmitted by the compander, and the sampling clock frequency are determined according to the remaining data rate that is allotted to the non- voice sessions.
  • compression in the compander may preferably be performed after cancellation of the far-echo signal experienced by the V.90 compatible modem, and after impairment-reduction is performed.
  • the EU may be programmed to respond, after a predetermined time period, to a V.8 ANsam signal generated in a communication initialization procedure between the digital modem and the V.90 compatible modem thereby determining a delay in an echo canceller in the digital modem for enabling connection between the V.90 compatible modem and the digital modem at a rate that exceeds rates defined in the V.34 communication standard.
  • the EU determines that a communication session includes voice information
  • the EU enables at least one of the following: operation in downstream communication of high-pass-filters (HPFs) in the EU; and filtering operations of LPFs in the EU.
  • HPFs high-pass-filters
  • the resulting digital samples are preferably converted to a DSL signal representation of the information.
  • the DSL signal representation of the information is preferably transmitted from the EU to the RU.
  • the DSL signal representation of the information is received and converted to voice-band information at the rate that exceeds rates defined in the V.34 communication standard.
  • the RU then transmits the voice-band information at the rate that exceeds rates defined in the V.34 communication standard to the V.90 compatible modem.
  • the voice-band information at the rate that exceeds rates defined in the V.34 communication standard is preferably received and provided to processing elements in the subscriber unit.
  • the EU may also employ an additional echo canceller in communication in an upstream direction from the subscriber to the ISP as an additional noise-reduction mechanism for substantially canceling a far-echo signal generated at the RU and experienced by a digital V.34 receiver in the digital modem in the service provider unit.
  • the far-echo signal generated at the RU and experienced by the digital V.34 receiver in the digital modem in the service provider unit may be canceled by subtracting a representation of the far-echo signal generated at the RU and experienced by the digital V.34 receiver at the service provider unit from a DSL signal representation of information transmitted in the upstream.

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  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Telephonic Communication Services (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)

Abstract

L'invention concerne un système à gain de paires dans un système de communication qui communique les informations entre une unité de fournisseur de services et une unité d'abonné à travers un système à gain de paires avec un débit qui est supérieur à ceux définis dans la norme de communication V.34. Le système à gain de paires comprend une unité d'échanges (EU) associée de manière fonctionnelle à un modem numérique via un office central et une unité distante (RU) associée de manière fonctionnelle à EU ainsi qu'un modem compatible V.90 dans l'unité d'abonné. Le système à gain de paires applique, de préférence dans l'EU, des mécanismes de réduction de bruit et de réduction de dégradation de manière à améliorer les performances de communication et permettre la communication avec un débit qui est supérieur à ceux définis dans la norme de communication V.34. Chacun des mécanismes de réduction de bruit et de réduction de dégradation est appliqué indépendamment des autres; de ce fait, chaque mécanisme de réduction de bruit et de réduction de dégradation peut être mis en oeuvre séparément ou en combinaison avec d'autres mécanismes de réduction de bruit et de réduction de dégradation.
PCT/IL2001/000193 2000-03-08 2001-03-01 Systeme a gain de paires a capacites de debit de v.90 WO2001067734A2 (fr)

Priority Applications (4)

Application Number Priority Date Filing Date Title
MXPA02008727A MXPA02008727A (es) 2000-03-08 2001-03-01 Sistema de ganancia de par con capacidades de velocidad v.90.
AU2001237692A AU2001237692A1 (en) 2000-03-08 2001-03-01 Pair-gain system with v.90 rate capabilities
BR0109080-1A BR0109080A (pt) 2000-03-08 2001-03-01 Sistema de ganho em par em um sistema de comunicação, sistema de comunicação para comunicar informação entre uma unidade de provedor de serviço e uma unidade de assinante, método para comunicar informação entre uma unidade de provedor de serviço e uma unidade de assinante, e, método para comunicar informação entre um modem digital em uma unidade de provedor de serviço e um modem v. 90 compatìvel em uma unidade de assinante
EP01910110A EP1262056A2 (fr) 2000-03-08 2001-03-01 Systeme a gain de paires a capacites de debit de v.90

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IL13494000A IL134940A (en) 2000-03-08 2000-03-08 Telecommunication system having v.90 capabilities
IL134940 2000-03-08

Publications (2)

Publication Number Publication Date
WO2001067734A2 true WO2001067734A2 (fr) 2001-09-13
WO2001067734A3 WO2001067734A3 (fr) 2002-01-17

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IL2001/000193 WO2001067734A2 (fr) 2000-03-08 2001-03-01 Systeme a gain de paires a capacites de debit de v.90

Country Status (6)

Country Link
EP (1) EP1262056A2 (fr)
AU (1) AU2001237692A1 (fr)
BR (1) BR0109080A (fr)
IL (1) IL134940A (fr)
MX (1) MXPA02008727A (fr)
WO (1) WO2001067734A2 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999038351A1 (fr) * 1998-01-25 1999-07-29 Eci Telecom Ltd. Appareil et procede de telephonie numerique
US5982768A (en) * 1997-05-13 1999-11-09 3Com Corporation Dual band modem for high bandwidth communications
WO1999065179A2 (fr) * 1998-06-08 1999-12-16 Jetstream Communications, Inc. Systeme et procede de communication vocale et de donnees sur un reseau local a commutation par paquets

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5982768A (en) * 1997-05-13 1999-11-09 3Com Corporation Dual band modem for high bandwidth communications
WO1999038351A1 (fr) * 1998-01-25 1999-07-29 Eci Telecom Ltd. Appareil et procede de telephonie numerique
WO1999065179A2 (fr) * 1998-06-08 1999-12-16 Jetstream Communications, Inc. Systeme et procede de communication vocale et de donnees sur un reseau local a commutation par paquets

Also Published As

Publication number Publication date
EP1262056A2 (fr) 2002-12-04
AU2001237692A1 (en) 2001-09-17
WO2001067734A3 (fr) 2002-01-17
IL134940A (en) 2003-10-31
IL134940A0 (en) 2001-05-20
MXPA02008727A (es) 2004-09-06
BR0109080A (pt) 2003-06-03

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