Cable Modem System with Sample and Packet Synchronization
First Claim
1. An apparatus for synchronizing a first clock signal to a second clock signal, comprising:
- a downstream receiver configured to receive a downstream information flow, the downstream information flow including a timestamp message and a slot timing error message, the timestamp message indicating a frequency of the first clock signal and the slot timing error indicating a difference between the first frequency of the first clock signal and a frequency of a second clock signal;
a timebase message detector configured to provide an absolute timing reference based upon the timestamp message;
a tracking loop configured to provide a local time reference based upon the absolute timing reference; and
a first summer configured to provide the second clock signal based upon a combination of the local time reference and the slot timing error message.
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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
23 Claims
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1. An apparatus for synchronizing a first clock signal to a second clock signal, comprising:
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a downstream receiver configured to receive a downstream information flow, the downstream information flow including a timestamp message and a slot timing error message, the timestamp message indicating a frequency of the first clock signal and the slot timing error indicating a difference between the first frequency of the first clock signal and a frequency of a second clock signal; a timebase message detector configured to provide an absolute timing reference based upon the timestamp message; a tracking loop configured to provide a local time reference based upon the absolute timing reference; and a first summer configured to provide the second clock signal based upon a combination of the local time reference and the slot timing error message. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method for synchronizing a first clock signal to a second clock signal, comprising:
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(a) receiving a downstream information flow, the downstream information flow including a timestamp message and a slot timing error message, the timestamp message indicating a frequency of the first clock signal and the slot timing error indicating a difference between the first frequency of the first clock signal and a frequency of a second clock signal; (b) providing an absolute timing reference based upon the timestamp message; (c) providing a local time reference based upon the absolute timing reference; and (d) combining the providing the second clock signal based upon a combination of the local time reference and the slot timing error message. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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Specification