Information network access apparatus and methods for communicating information packets via telephone lines
DC CAFCFirst Claim
1. A method of providing communications with a CSMA/CD (Carrier Sense Multiple Access with Collision Detection) network via a bidirectional communications path, comprising the steps of:
- at a first end of the communications path, providing a CSMA/CD interface to the network, buffering information packets received from the network via the interface in a first buffer, supplying information packets from the first buffer to the communications path, and supplying control information to the communications path;
at a second end of the communications path, buffering information packets received via the communications path in a second buffer, receiving the control information from the communications path, buffering information packets to be supplied via the communications path to the network in a third buffer, and supplying information packets from the third buffer to the communications path in dependence upon the control information; and
at the first end of the communications path, supplying information packets received via the communications path to a fourth buffer, and supplying the information packets from the fourth buffer to the network via the interface;
wherein the control information and the dependence on the control information for supplying information packets from the third buffer to the communications path are arranged to avoid collisions on the communications path between information packets communicated from the first buffer to the second buffer and information packets communicated from the third buffer to the fourth buffer.
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Abstract
Access to a CSMA/CD (Carrier Sense Multiple Access with Collision Detection) network is provided via a telephone line by providing a master modem at the head end and a slave modem at the subscriber end of the line. The master modem provides a CSMA/CD interface to the network and controls half duplex communications with the slave modem via the line to avoid collisions of information packets on the line. The information packets are enveloped in frames on the line with error checking information; control information between the modems is contained in the same and/or in separate frames. The modulation method and signal bandwidth can be varied depending on errors to provide optimum communications capacity via any particular line, and a ratio of upstream to downstream information packets can be varied depending on buffer fills at the modems. The master modem can be multiplexed for multiple lines. The modulated signal frequencies are above telephone signal frequencies so that each line can be frequency diplexed for simultaneous telephone communications.
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Citations
71 Claims
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1. A method of providing communications with a CSMA/CD (Carrier Sense Multiple Access with Collision Detection) network via a bidirectional communications path, comprising the steps of:
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at a first end of the communications path, providing a CSMA/CD interface to the network, buffering information packets received from the network via the interface in a first buffer, supplying information packets from the first buffer to the communications path, and supplying control information to the communications path; at a second end of the communications path, buffering information packets received via the communications path in a second buffer, receiving the control information from the communications path, buffering information packets to be supplied via the communications path to the network in a third buffer, and supplying information packets from the third buffer to the communications path in dependence upon the control information; and at the first end of the communications path, supplying information packets received via the communications path to a fourth buffer, and supplying the information packets from the fourth buffer to the network via the interface; wherein the control information and the dependence on the control information for supplying information packets from the third buffer to the communications path are arranged to avoid collisions on the communications path between information packets communicated from the first buffer to the second buffer and information packets communicated from the third buffer to the fourth buffer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41)
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42. A method of coupling a terminal device to a CSMA/CD (Carrier Sense Multiple Access with Collision Detection) network via a two-wire telephone subscriber line, comprising the steps of:
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coupling a first end of the line to the network via a first modem including a CSMA/CD interface to the network; coupling a second end of the line to the terminal device via a second modem including an interface to the terminal device; communicating information packets downstream from the network to the terminal device via the CSMA/CD interface, first modem, line, second modem, and terminal device interface; communicating control information downstream from the first modem to the second modem; and communicating information packets upstream from the terminal device to the network via the terminal device interface, second modem, line, first modem, and CSMA/CD interface under control of the control information at times to avoid interference with the information packets and control information communicated downstream. - View Dependent Claims (43, 44, 45, 46, 47, 66, 67, 68, 69)
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48. A network access arrangement for providing communications with a CSMA/CD (Carrier Sense Multiple Access with Collision Detection) path via a communications path, comprising:
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a first unit for coupling a first end of the communications path to the CSMA/CD path, the first unit comprising a CSMA/CD interface for connection to the CSMA/CD path, a buffer for buffering information packets supplied from the CSMA/CD path via the CSMA/CD interface for supply to the communications path, a buffer for buffering information packets received from the communications path for supply to the CSMA/CD path via the CSMA/CD interface, and a control unit; and a second unit for connection to a second end of the communications path, the second unit comprising a buffer for buffering information packets received via the communications path, a buffer for buffering information packets to be supplied to the communications path, and a control unit; wherein the control units of the first and second units are arranged to exchange control information via the communications path for communicating information packets bidirectionally via the communications path between the buffers of the first and second units in a half duplex manner. - View Dependent Claims (49, 50, 51, 52, 53, 54, 55)
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56. A modem for communicating information packets of Ethernet frames via a two-wire line, comprising:
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a control unit; an interface for supplying and receiving information packets of Ethernet frames; a first buffer for receiving and buffering information packets from the interface; a modulator responsive to the control unit for supplying modulated signals comprising information packets from the first buffer to a two-wire line; a demodulator for demodulating modulated signals received via the two-wire line to produce demodulated signals; and a second buffer for receiving and buffering information packets contained in the demodulated signals for-supply to the interface; wherein the control unit is arranged to produce or respond to control information in the modulated signals on the two-wire line to control the modulator to supply modulated signals to the two-wire line only at times when modulated signals are not being received via the two-wire line. - View Dependent Claims (57, 58, 59, 60, 61, 62, 63, 64, 65, 70)
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71. A modem for coupling a device to a two-wire line for providing packetized communications for the device via the line, the modem comprising:
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an interface for coupling to the device; a controller; a demodulator for receiving, from the line and for demodulating downstream modulated signals comprising control signals for the controller and information packets for supply via the interface to the device; a buffer for buffering information packets received from the device via the interface; and a modulator for receiving information packets from the buffer for producing and supplying upstream modulated signals to the line, the controller being responsive to the demodulated control signals for controlling the modulator so that the upstream modulated signals are timed to avoid interference with the downstream modulated signals.
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Specification