Cable modem system with sample and packet synchronization

• US 7,801,176 B2
• Filed: 10/21/2005
• Issued: 09/21/2010
• Est. Priority Date: 02/12/1999
• Status: Expired due to Fees

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Horton, John D. Jr., Rabenko, Theodore F., Thi, James C. H.
• Primary Examiner(s): Ton; Dang T
• Assistant Examiner(s): Kavleski; Ryan C
• Application Number:
  US11/256,330
• Publication Number:
  US 20060050689A1
• Time in Patent Office: 1,796 Days
• Field of Search: 370/468, 370/503, 370/507, 370/508, 725/111
• US Class Current: 370/468
• CPC Class Codes: H04L 12/2801 Broadband local area networks
• CPC Class Codes: H04L 12/66 Arrangements for connecting between networks having differing types of switching systems, e.g. gateways

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.

Claims

1. A method for transmitting voice packets over a transmission system, comprising:

determining a difference between a clock of a cable modem termination system and a clock of a cable modem to provide a frequency error value;

adjusting the clock of the cable modem by the frequency error value to synchronize the clock of the cable modem termination system and the clock of the cable modem to provide a synchronized clock;

sampling voice packets using a voice sample clock derived from and synchronized with the synchronized clock;

determining time needed between adjacent unsolicited grant arrivals for storing the sampled voice packets;

storing the sampled voice packets in the determined time to provide stored voice packets; and

transmitting the stored voice packets over the transmission system, system upon receipt of an unsolicited grant arrival.

2. The method of claim 1, further comprising:

determining a transmission window based on grant arrival intervals; and

transmitting the stored voice packets over the transmission system during the determined transmission window.

3. The method of claim 1, further comprising:

scheduling processing of the stored sample packets to be ready for transmission at a next unsolicited grant arrival.

4. The method of claim 1, wherein the cable modem is coupled to a cable modem termination system and the step of transmitting the stored voice packets comprises:

transmitting the stored voice packets to a Public Switched Telephone Network (PSTN) gateway by synchronizing a clock of the cable modem termination system with a clock of the PSTN.

5. The method of claim 1, further comprising:

processing the sampled voice packets for voice compression.

6. The method of claim 1, further comprising:

compressing the stored voice packets using a compression algorithm before transmission over the transmission system.

7. The method of claim 6, wherein the step of compressing the stored voice packets comprises:

compressing the stored voice packets in the determined time.

8. The method of claim 1, wherein the step of determining the difference comprises:

determining an absolute time reference based upon the clock of the cable modem termination system;

determining a difference between the absolute time reference and a local time reference to provide the frequency error value;

filtering the frequency error value to provide a filtered error value; and

adjusting the local time reference by the filtered error value.

9. A system for transmitting voice packets over a transmission system, comprising:

means for determining a difference between a clock of a cable modem termination system and a clock of a cable modem to provide a frequency error value;

means for adjusting the clock of the cable modem by the frequency error value to synchronize the clock of the cable modem termination system and the clock of the cable modem to provide synchronized clock;

means for sampling voice packets using a voice sample clock derived from and synchronized with the synchronized clock;

means for determining time needed between adjacent unsolicited grant arrivals for storing the sampled voice packets;

means for storing the sampled voice packets in the determined time to provide stored voice packets; and

means for transmitting the stored voice packets over the transmission system, upon receipt of an unsolicited grant arrival.

10. The system of claim 9, further comprising:

means for determining a transmission window based on grant arrivals intervals; and

means for transmitting the stored voice packets over the transmission system during the determined transmission window.

11. The system of claim 9, further comprising:

means for scheduling processing of the stored sample packets to be ready for transmission at a next unsolicited grant arrival.

12. The system of claim 9, wherein the cable modem is coupled to a cable modem termination system and the stored voice packets are transmitted to a Public Switched Telephone Network (PSTN) gateway by synchronizing a clock of the cable modem termination system with a clock of the PSTN.

13. The system of claim 9, further comprising:

means for processing the sampled voice packets for voice compression.

14. The system of claim 9, further comprising:

means for compressing the stored voice packets using a compression algorithm before transmission over the transmission system.

15. The system of claim 14, wherein the means for compressing comprises:

means for compressing the stored voice packets in the determined time.

16. The system of claim 9, wherein the means for determining the difference comprises:

means for determining an absolute time reference based upon the clock of the cable modem termination system;

means for determining a difference between the absolute time reference and a local time reference to provide the frequency error value;

means for filtering the frequency error value to provide a filtered error value; and

means for adjusting the local time reference by the filtered error value.