Time-multiplexed transmission on digital-subscriber lines synchronized to existing TCM-ISDN for reduced cross-talk
First Claim
1. A Digital-Subscriber-Line (DSL) system for high-speed data transmission using passband modulation over a copper-pair telephone line, for reducing an effect of crosstalk interference with Integrated Services Digital Network (ISDN) on closely-located copper pairs, wherein ISDN devices are Time Compression Multiplexing (TCM) systems that transmit data from a central office side but not from remote sites during a downstream time-window, and wherein the ISDN devices receive but not transmit at the central office side during an upstream time-window, the DSL system comprising a central-office-side device comprising:
- a data network interface for connecting to a data network;
a burst-clock input for receiving a burst clock indicating the downstream time-window when the ISDN devices at the central office side are transmitting from the central office side to the remote sites, and for indicating the upstream time-window when the ISDN devices at the central office side are receiving remotely-transmitted data from the remote sites;
a telephone-line interface for connecting to a copper-pair telephone line connected to customer-premises DSL equipment at a remote customer site, the copper-pair telephone line being a DSL line sharing a cable bundle with TCM-ISDN lines driven by the ISDN devices; and
a DSL processor, coupled to the telephone-line interface, to the data-network interface, and to the burst clock input, for receiving the burst clock synchronized to the TCM-ISDN lines, the burst clock for controlling the DSL processor to transmit during the downstream time-window and receive during the upstream time-window, the DSL processor for receiving a data stream from the data network and for generating a downstream passband signal to represent the data stream, the DSL processor for transmitting the downstream passband signal to the customer-premises DSL equipment at the remote customer site over the DSL line, the DSL processor for receiving an upstream passband signal from the customer-premises DSL equipment and for extracting from the upstream passband signal a represented data signal for transmission to the data network,wherein the DSL system provides a higher data rate than the ISDN devices but the DSL system is synchronized to the IDSN devices to reduce the effect of the crosstalk interference.
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Accused Products
Abstract
Pulp-insulated telephone cables common in Japan and other countries have higher cross-talk interference than plastic-insulated cables common in the United States. Deployment of newer xDSL systems in Japan has been limited by the high cross-talk interference in those pulp cables, especially the near-end cross-talk (NEXT) from ISDN services using time-compression multiplexing (TCM). A TCM-DSL that can share pulp-cable bundles with TCM ISDN lines eliminates the NEXT interference by synchronizing transmission and reception with the TCM ISDN equipment for the same cable bundle. The TCM-DSL line uses TCM that is synchronized with the ISDN transmit and receive windows so that the TCM-DSL is transmitting but not receiving when the ISDN modems at the same side are transmitting. When ISDN at the same side are receiving and not transmitting, NEXT interference does not exist. Thus higher-speed TCM-DSL data can be received during the ISDN receive windows with reduced interference. A passband modulation technique such as Carrierless-amplitude/phase modulation (CAP) with advanced signal processing techniques such as trellis encoding and pre-coding achieve higher data rates for TCM-DSL. The TCM-DSL transmitted signal occupies a pass-band that is separate from a low-frequency POTS band for voice-band services. The voice calls use full-duplex continuously without regard to the TCM-DSL data transmitted simultaneously with the POTS voice calls over the same phone line. TCM-DSL is synchronized to an ISDN clock that is routed to the TCM-DSL line card, or a burst-timing extractor that detects burst timing from either the ISDN line signal or cross-talk from the ISDN line signals.
174 Citations
19 Claims
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1. A Digital-Subscriber-Line (DSL) system for high-speed data transmission using passband modulation over a copper-pair telephone line, for reducing an effect of crosstalk interference with Integrated Services Digital Network (ISDN) on closely-located copper pairs, wherein ISDN devices are Time Compression Multiplexing (TCM) systems that transmit data from a central office side but not from remote sites during a downstream time-window, and wherein the ISDN devices receive but not transmit at the central office side during an upstream time-window, the DSL system comprising a central-office-side device comprising:
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a data network interface for connecting to a data network; a burst-clock input for receiving a burst clock indicating the downstream time-window when the ISDN devices at the central office side are transmitting from the central office side to the remote sites, and for indicating the upstream time-window when the ISDN devices at the central office side are receiving remotely-transmitted data from the remote sites; a telephone-line interface for connecting to a copper-pair telephone line connected to customer-premises DSL equipment at a remote customer site, the copper-pair telephone line being a DSL line sharing a cable bundle with TCM-ISDN lines driven by the ISDN devices; and a DSL processor, coupled to the telephone-line interface, to the data-network interface, and to the burst clock input, for receiving the burst clock synchronized to the TCM-ISDN lines, the burst clock for controlling the DSL processor to transmit during the downstream time-window and receive during the upstream time-window, the DSL processor for receiving a data stream from the data network and for generating a downstream passband signal to represent the data stream, the DSL processor for transmitting the downstream passband signal to the customer-premises DSL equipment at the remote customer site over the DSL line, the DSL processor for receiving an upstream passband signal from the customer-premises DSL equipment and for extracting from the upstream passband signal a represented data signal for transmission to the data network, wherein the DSL system provides a higher data rate than the ISDN devices but the DSL system is synchronized to the IDSN devices to reduce the effect of the crosstalk interference. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A central office receiving digital-data and voice calls comprising:
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plain-old-telephone-system (POTS) line cards for terminating telephone lines carrying low-frequency voice calls; Integrated Services Digital Network (ISDN) line cards for terminating telephone lines carrying medium-rate digital-data calls, the ISDN line cards transmitting data to remote ISDN terminals at customer premises during a downstream time-window, but the ISDN line cards receiving but not transmitting during a upstream time-window; Digital-Subscriber-Loop (DSL) line cards for terminating telephone lines carrying high-rate digital-data calls, the DSL line cards transmitting data to remote DSL modems at customer premises during the downstream time-window, but the DSL line cards receiving but not transmitting during the upstream time-window; wherein the DSL line cards transmit and receive data at a higher rate than the ISDN line cards, wherein an effect of crosstalk interference among the ISDN line cards and the DSL line cards is reduced by the DSL line cards using the downstream and upstream time windows synchronized to the downstream and upstream time windows of the ISDN line cards for the same cable bundle; a high-speed data pathway for data transmission to other central offices and to international data networks, the high-speed data pathway connected to the ISDN line cards and to the DSL line cards; and a voice network for voice-call transmission to other central offices and to international voice networks, the voice network connected to the POTS line cards and to the DSL line cards; wherein telephone lines connected to the DSL line cards are bundled together at the central office with telephone lines connected to the ISDN line cards; wherein cross-talk interference among DSL telephone lines and ISDN telephone lines occurs in a shared cable bundle outgoing from the central office; wherein the DSL line cards each further comprise a frequency splitter, coupled to the telephone line, for passing low-frequency signal components to the voice network, but for passing high-frequency signal components to the high-speed data pathway; wherein the low-frequency signal components comprise a low-frequency voiceband having a frequency range down to zero hertz, but the high-frequency signal components comprise a pass band having a lower frequency limit above the low-frequency voiceband; wherein the higher rate of the DSL line cards is at least two times the medium rate of the ISDN line cards, whereby the DSL line cards are connected to both the high-speed data pathway and to the voice network, the DSL line cards each terminating a telephone line carrying both voice calls and data transmission and whereby signal components from the telephone line are split by frequency into voice calls and high-speed data transmissions and whereby the low-frequency voiceband for voice calls does not overlap the high-frequency band for data transmission of the DSL line cards. - View Dependent Claims (11)
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12. A central office receiving digital-data and voice calls comprising:
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plain-old-telephone-system (POTS) line cards for terminating telephone lines carrying low-frequency voice calls; Integrated Services Digital Network (ISDN) line cards for terminating telephone lines carrying medium-rate digital-data calls, the ISDN line cards transmitting data to remote ISDN terminals at customer premises during a downstream time-window, but the ISDN line cards receiving but not transmitting during a upstream time-window; Digital-Subscriber-Loop (DSL) line cards for terminating telephone lines carrying high-rate digital-data calls, the DSL line cards transmitting data to remote DSL modems at customer premises during the downstream time-window, but the DSL line cards receiving but not transmitting during the upstream time-window; wherein the DSL line cards transmit and receive data at a higher rate than the ISDN line cards; wherein an effect of crosstalk interference among the ISDN line cards and the DSL line cards is reduced by the DSL line cards using the downstream and upstream time windows synchronized to the downstream and upstream time windows of the ISDN line cards for the same cable bundle; a high-speed data pathway for data transmission to other central offices and to international data networks, the high-speed data pathway connected to the ISDN line cards and to the DSL line cards; and a voice network for voice-call transmission to other central offices and to international voice networks, the voice network connected to the POTS line cards and to the DSL line cards; wherein telephone lines connected to the DSL line cards are bundled together at the central office with telephone lines connected to the ISDN line cards; wherein cross-talk interference among DSL telephone lines and ISDN telephone lines occurs in a shared cable bundle outgoing from the central office; wherein the DSL line cards each further comprise a frequency splitter, coupled to the telephone line, for passing low-frequency signal components to the voice network, but for passing high-frequency signal components to the high-speed data pathway; wherein the low-frequency signal components comprise a low-frequency voiceband having a frequency range down to zero hertz, but the high-frequency signal components comprise a pass band having a lower frequency limit above the low-frequency voiceband; wherein the DSL line cards each further comprise; symbol encoding means for combining a sequence of binary bits into a symbol representing multiple binary bits for transmission over the telephone line; a carrierless amplitude/phase modulator (CAP) filter for generating a transmitted signal representing transmitted data bits within a frequency passband; a trellis encoder, coupled to the symbol encoding means, for trellis-code modulation of the data for transmission; and a viterbi decoder, coupled to receive data from the telephone line, for decoding symbols encoded by a trellis encoder at the customer premises, whereby the DSL line cards are connected to both the high-speed data pathway and to the voice network, the DSL line cards each terminating a telephone line carrying both voice calls and data transmission and whereby signal components from the telephone line are split by frequency into voice calls and high-speed data transmissions and whereby the low-frequency voiceband for voice calls does not overlap the high-frequency band for data transmission of the DSL line cards and whereby data is compressed for transmission by the DSL line cards. - View Dependent Claims (13, 14)
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15. A Time-Compression-Multiplexing Digital-Subscriber-Line (TCM-DSL) modem for use with pulp-insulated cables, the TCM-DSL modem comprising:
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a telephone-line input for terminating a telephone line; a frequency splitter for separating low-frequency voice signals from high-frequency data signals, the low-frequency voice signals sent to voice-telephone equipment; a receiver receiving the high-frequency data signals in a passband from the frequency splitter, the receiver including a symbol decoder for converting symbols into sequences of bits; a transmitter for transmitting high-frequency data signals in the passband to the telephone line input, the transmitter including a symbol encoder for converting sequences of bits into symbols, wherein each symbol represents multiple bits using one of the points in a constellation carrying a phase and an amplitude component; a carrierless-amplitude/phase (CAP) filter, coupled to the symbol encoder in the transmitter, for generating the high-frequency data signals in the passband representing transmitted data bits within a desired frequency band; a burst-clock input for receiving a burst clock, the burst clock indicating a downstream time-window when ISDN lines at the central office are transmitting during an upstream time-window when the ISDN lines are receiving remotely-transmitted data at the central office; timing control means, responsive to the burst clock, for transmitting a frame of data in response to the burst clock during the downstream time-window when the TCM-DSL modem is at a central office, but for transmitting the frame during the upstream time-window when the TCM-DSL modem is at a remote customer site, whereby TCM-DSL transmission is synchronized to ISDN transmission to reduce an effect of cross-talk interference. - View Dependent Claims (16, 17, 18, 19)
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Specification