Cable modem system with sample and packet synchronization
First Claim
1. An apparatus for synchronizing a data collection deadline time to a grant schedule, comprising:
- a receiver configured to receive a downstream information flow including a time based message and a grant slot timing message that is indicative of the grant schedule;
a time based message detector configured to provide an absolute timing reference clock utilizing the time based message;
a tracking loop configured to converge a local time reference clock to the absolute timing reference clock;
a timing offset correction module configured to provide a sampling clock based upon the local time reference clock; and
a grant time calculator module configured to analyze a time between successive grants within the grant schedule utilizing the sampling clock, to compensate for processing time of data to be transmitted to set the data collection deadline time, and to ensure the data is ready for transmission when a grant subsequent to the successive grants is received in accordance with the grant schedule.
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Accused Products
Abstract
A method and system of processing sampled voice packets from a voice packet sender for transmission over a bit-rate sampled data transmission system, such as by a cable modem over a cable modem termination system, to a voice packet recipient. Unsolicited grant arrivals in response to a request from the voice packet sender coupled to the cable modem are determined. The storing of sampled voice packets is synchronized with the unsolicited grant arrivals. Upon receipt of an unsolicited grant arrival, currently stored sampled voice packets are transmitted to the cable modem for further transmission to the voice packet recipient over the cable modem termination system.
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Citations
19 Claims
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1. An apparatus for synchronizing a data collection deadline time to a grant schedule, comprising:
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a receiver configured to receive a downstream information flow including a time based message and a grant slot timing message that is indicative of the grant schedule; a time based message detector configured to provide an absolute timing reference clock utilizing the time based message; a tracking loop configured to converge a local time reference clock to the absolute timing reference clock; a timing offset correction module configured to provide a sampling clock based upon the local time reference clock; and a grant time calculator module configured to analyze a time between successive grants within the grant schedule utilizing the sampling clock, to compensate for processing time of data to be transmitted to set the data collection deadline time, and to ensure the data is ready for transmission when a grant subsequent to the successive grants is received in accordance with the grant schedule. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An apparatus for synchronizing a data collection deadline time to a grant schedule, comprising:
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a time based message detector configured to receive a downstream information flow, which includes a time based message and the grant schedule, from a headend of a communications system, and to utilize the time based message to provide an absolute timing reference clock; a tracking loop configured to provide a sampling clock which tracks the absolute timing reference clock; and a grant time calculator module configured to analyze a time between successive grants within the grant schedule utilizing the sampling clock, to set the data collection deadline time by compensating for processing time of data to be transmitted, and to ensure the data is ready for transmission when a grant subsequent to the successive grants is received in accordance with the grant schedule. - View Dependent Claims (10)
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11. The apparatus of 9, wherein the tracking loop comprises:
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a differencing circuit configured to determine a difference between the absolute timing reference clock and a local time reference clock; a numerically controlled oscillator configured to provide an oscillator drive signal based upon the difference; and a local time reference generator configured to provide the sampling clock based upon the oscillator drive signal. - View Dependent Claims (12, 13, 14)
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15. In an apparatus for implementing synchronization between a data collection deadline time and a grant schedule, a method comprising:
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processing a downstream information flow received from a cable modem termination system (CMTS) to extract a time based message and the grant schedule; generating an absolute timing reference clock utilizing the time based message; generating a sampling clock which tracks the absolute timing reference clock; analyzing a time between successive grants within the grant schedule utilizing the sampling clock; setting the data collection deadline time based on the time between the successive grants by compensating for processing time of data to be transmitted; and storing the data to be transmitted prior to receiving a grant subsequent to the successive grants in accordance with the grant schedule. - View Dependent Claims (16, 17, 18, 19)
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Specification