Robust techniques for optimal upstream communication between cable modem subscribers and a headend
First Claim
Patent Images
1. A cable modem termination system for a cable plant comprising:
- a burst receiver for processing data signals having physical layer parameters that control the manner in which the data signals are transmitted on an upstream channel of the cable plant;
a transmitter for sending messages on a downstream channel of the cable plant to cable modems; and
a monitoring circuit for collecting packet based statistics representative of the channel quality of the upstream channel, the monitoring circuit sending a message to the transmitter for the cable modems to change a physical layer parameter responsive to the collected statistics and to the burst receiver to process data signals based on the changed physical layer parameter, wherein channel quality is an ability of a channel to transmit data reliably thereon, such that a higher quality channel transmits data reliably at a higher data rate than a lower quality channel.
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Abstract
A number of features for enhancing the performance of a cable transmission system in which data is transmitted between a cable modem termination system at a headend and a plurality of cable modems located different distances from the headend. The power transmission level, slot timing, and equalization of the cable modems are set by a ranging process. Data is transmitted by the modems in fragmented form. Various measures are taken to make transmission from the cable modems robust. The upstream data transmission is controlled to permit multiple access from the cable modems.
166 Citations
42 Claims
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1. A cable modem termination system for a cable plant comprising:
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a burst receiver for processing data signals having physical layer parameters that control the manner in which the data signals are transmitted on an upstream channel of the cable plant; a transmitter for sending messages on a downstream channel of the cable plant to cable modems; and a monitoring circuit for collecting packet based statistics representative of the channel quality of the upstream channel, the monitoring circuit sending a message to the transmitter for the cable modems to change a physical layer parameter responsive to the collected statistics and to the burst receiver to process data signals based on the changed physical layer parameter, wherein channel quality is an ability of a channel to transmit data reliably thereon, such that a higher quality channel transmits data reliably at a higher data rate than a lower quality channel. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A headend terminal for a bidirectional asymmetric, transmission system having a downstream channel that broadcasts data from the headend terminal to a plurality of subscriber terminals and an upstream channel that unicasts data from the individual subscriber terminals to the headend terminal, the headend terminal comprising:
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a burst receiver for processing data signals having physical layer parameters that control the manner in which the data signals are transmitted on the upstream channel; a transmitter for sending messages on the downstream channel; and a monitoring circuit for collecting statistics about the data signals transmitted on the upstream channel, the statistics representative of the channel quality of the upstream channel, the monitoring circuit sending a message to the transmitter for the cable modems to change a physical layer parameter responsive to the collected statistics and to the burst receiver to process data signals based on the changed physical layer parameter, wherein channel quality is an ability of a channel to transmit data reliably thereon, such that a higher quality channel transmits data reliably at a higher data rate than a lower quality channel.
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17. A method for transmitting data over a cable system in an upstream direction to a headend from a plurality of subscriber stations located at different distances from the headend such that the transmission paths to the headend are different, the method comprising the steps of:
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establishing an upstream channel from the subscriber stations to the headend; monitoring at the headend the channel quality of the upstream channel; establishing a downstream channel from the headend to the subscriber stations; transmitting to the subscriber stations over the downstream channel a command to change the mode of transmission to the headend over the upstream channel if the monitored channel quality fails to meet a prescribed threshold level; receiving the command at the subscriber stations; and transmitting data over the upstream channel from the subscriber stations to the headend in accordance with the changed mode of transmission after receipt of the command, wherein channel quality is an ability of a channel to transmit data reliably thereon, such that a higher quality channel transmits data reliably at a higher data rate than a lower quality channel. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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- 36. A cable modem termination system having an upstream channel shared among a plurality of cable modems and a burst receiver connected to the upstream channel to process physical layer signals transmitted on the upstream channel, a monitoring circuit for collecting packet based statistics representative of the channel quality of the upstream channel, the monitoring circuit comprising an input for receiving the physical layer signals from the burst receiver, means for sensing parameters that control the manner of transmission of the physical layer signals, and a plurality of counters for collecting the sensed physical layer parameters, wherein channel quality is an ability of a channel to transmit data reliably thereon, such that a higher quality channel transmits data reliably at a higher data rate than a lower quality channel.
Specification