Apparatus and method for synchronizing communication between systems with different clock rates

• US 9,674,804 B2
• Filed: 12/29/2014
• Issued: 06/06/2017
• Est. Priority Date: 12/29/2014
• Status: Active Grant

• Current Assignee: Hughes Network Systems LLC (Echostar Corporation)
• Original Assignee: Hughes Network Systems LLC (Echostar Corporation)
• Inventors: Tender, Neil H., Vasavada, Yash, Arur, Deepak, Muhammad, Tariq
• Primary Examiner(s): Sheikh, Ayaz
• Assistant Examiner(s): HAMPTON, TARELL A
• Application Number:
  US14/584,652
• Publication Number:
  US 20160192303A1
• Time in Patent Office: 890 Days
• Field of Search: None
• CPC Class Codes: H04B 7/18513 Transmission in a satellite or space-based system
• CPC Class Codes: H04W 56/001 Synchronization between nodes

Abstract

An apparatus and method for synchronizing communication between systems having different clock rates, is described. The apparatus includes a communication unit, a synchronization unit, and an interface unit. The communication unit receives upstream information and generates a first sample stream representative of the upstream information based on a first clock rate. The synchronization unit converts the first sample stream to a second sample stream based on a second clock rate and in accordance with a predetermined burst plan. The interface unit receives the second sample stream at the second clock rate and outputs it based on the predetermined burst plan.

Claims

1. An apparatus comprising:

a communication unit for receiving upstream information and generating a first sample stream based on a first clock rate, the first sample stream being representative of the upstream information;

a synchronization unit for converting the first sample stream to a second sample stream based on a second clock rate, the second sample stream being configured as a plurality of sequential bursts arranged in accordance with a predetermined burst plan; and

an interface unit for receiving the second sample stream at the second clock rate and outputting the second sample stream in accordance with the predetermined burst plan,

wherein the synchronization unit is configured to perform at least one of dropping one or more samples contained in the first sample stream and adding one or more samples to the second sample stream, during a subsequent guard period within the first sample stream,

wherein the first clock rate is different from the second clock rate, and

wherein the first sample stream is converted based, at least in part, on predetermined guard periods within the first sample stream.

2. The apparatus of claim 1, wherein the upstream information received by the communication unit includes at least packet data, voice, voice over IP (VOIP), or a combination thereof.

3. The apparatus of claim 1, wherein the first clock rate is based on timing from Global Positioning Satellites (GPS).

4. The apparatus of claim 3, wherein the second clock rate is based on a Doppler-shifted offset to the timing from the GPS.

5. The apparatus of claim 1, wherein the interface unit outputs the second sample stream to a ground based beam former in a satellite transmission system.

6. The apparatus of claim 5, wherein the second clock rate is based, at least in part, on orbital drift of a satellite which communicates with the satellite transmission system.

7. The apparatus of claim 1, wherein the synchronization unit comprises:

an output buffer; and

a depth monitor for monitoring contents of the output buffer and generating a control signal for adjusting a rate at which the first sample stream is converted.

8. The apparatus of claim 7, wherein:

the depth monitor generates the control signal to indicate an increase in contents of the output buffer; and

the synchronization unit drops the one or more samples contained in the first sample stream based, at least in part, on the control signal generated by the depth monitor.

9. The apparatus of claim 7, wherein:

the depth monitor generates the control signal to indicate a decrease in contents of the output buffer; and

the synchronization unit adds the one or more samples to the second sample stream based, at least in part, on the control signal generated by the depth monitor.

10. The apparatus of claim 1, wherein:

the interface unit comprises;

an output buffer; and

a depth monitor for monitoring contents of the output buffer and transmitting a control signal indicative of the size of the output buffer, and

the synchronization unit adjusts a rate at which the first sample stream is converted based, at least in part, on the control signal.

11. An apparatus comprising:

an interface unit for receiving a first sample stream at a first clock rate, the first sample stream being configured as a plurality of sequential bursts arranged in accordance with a predetermined burst plan;

a synchronization unit for converting the first sample stream to a second sample stream based on a second clock rate; and

a communication unit for outputting downstream information representative of the second sample stream based on the second clock rate;

wherein the synchronization unit is configured to perform at least one of dropping one or more samples contained in the first sample stream and adding one or more samples to the second sample stream, during a subsequent guard period within the first sample stream,

wherein the first clock rate is different from the second clock rate, and

wherein the first sample stream is converted based, at least in part, on predetermined guard periods within the first sample stream.

12. The apparatus of claim 11, wherein the synchronization unit comprises:

an input buffer; and

a depth monitor for monitoring contents of the input buffer and generating a control signal for adjusting a rate at which the first sample stream is converted.

13. The apparatus of claim 12, wherein:

the depth monitor generates the control signal to indicate an increase in contents of the input buffer; and

the synchronization unit drops the one or more samples contained in the first sample stream based, at least in part, on the control signal generated by the depth monitor.

14. The apparatus of claim 12, wherein:

the depth monitor generates the control signal to indicate a decrease in contents of the input buffer; and

the synchronization unit adds the one or more samples to the second sample stream based, at least in part, on the control signal generated by the depth monitor.

15. The apparatus of claim 11, wherein:

the interface unit comprises;

an input buffer, and

a depth monitor for monitoring contents of the input buffer and transmitting a control signal indicative of the size of the output buffer; and

the synchronization unit adjusts a rate at which the first sample stream is converted based, at least in part, on the control signal.

16. An apparatus comprising:

a communication unit for receiving upstream information and generating a first sample stream representative of the upstream information based on a first clock rate during a transmit process, and for outputting downstream information representative of the first sample stream based on the first clock rate during a receive process;

a synchronization unit for;

converting the first sample stream to a second sample stream based on a second clock rate during the transmit process, the second sample stream being configured as a plurality of sequential bursts arranged in accordance with a predetermined burst plan, and

converting the second sample stream to the first sample stream based on the first clock rate during the receive process; and

an interface unit for receiving the second sample stream at the second clock rate and outputting the second sample stream in accordance with the predetermined burst plan during the transmit process, and for receiving the second sample stream and supplying the second sample stream to the synchronization unit at the second clock rate and in accordance with the predetermined burst plan during the receive process,

wherein the synchronization unit is further configured to perform at least one of dropping one or more samples contained in the first sample stream and adding one or more samples to the second sample stream,

wherein the first clock rate is different from the second clock rate,

wherein, during the transmit process, the first sample stream is converted based, at least in part, on predetermined guard periods within the first sample stream, and

wherein, during the receive process, the second sample stream is converted based, at least in part, on predetermined guard periods within the second sample stream.

17. A method comprising:

generating a first sample stream representative of received upstream information, the first sample stream being based on a first clock rate;

converting the first sample stream, using a synchronization unit, to a second sample stream based on a second clock rate, the second sample stream being configured as a plurality of sequential bursts arranged in accordance with a predetermined burst plan; and

outputting the second sample stream, by an interface unit, in accordance with the predetermined burst plan,

wherein the converting includes at least one of dropping one or more samples contained in the first sample stream and adding one or more samples to the second sample stream, during a subsequent guard period within the first sample stream,

wherein the first clock rate is different from the second clock rate, and

wherein the converting is performed based, at least in part, on predetermined guard periods within the first sample stream.

18. The method of claim 17, wherein the outputting comprises outputting the second sample stream to a ground based beam former in a satellite transmission system.

19. The method of claim 18, wherein the second clock rate is based on orbital drift of a satellite which communicates with the satellite transmission system.

20. The method of claim 17, further comprising:

monitoring contents of an output buffer within the synchronization unit;

generating a control signal indicative of a size of the output buffer, and

adjusting a rate at which the first sample stream is converted based, at least in part, on the control signal.

21. The method of claim 20, wherein:

the control signal indicates an increase in contents of the output buffer; and

the one or more samples are dropped from the first sample stream based, at least in part, on the control signal.

22. The method of claim 20, wherein:

the control signal indicates a decrease in contents of the output buffer; and

the one or more samples are added to the second sample stream based, at least in part, on the control signal.

23. The method of claim 17, further comprising:

monitoring an output buffer within the interface unit; and

transmitting a control signal, to the synchronization unit, indicative of a size of the output buffer, and

adjusting a rate at which the first sample stream is converted based, at least in part, on the control signal.

24. A method comprising:

receiving, by an interface unit, a first sample stream at a first clock rate, the first sample stream being configured as a plurality of sequential bursts arranged in accordance with a predetermined burst plan;

converting the first sample stream, using a synchronization unit, to a second sample stream based on a second clock rate; and

outputting downstream information representative of the second sample stream at the second clock rate;

wherein the converting includes at least one of dropping one or more samples contained in the first sample stream and adding one or more samples to the second sample stream, during a subsequent guard period within the first sample stream,

wherein the first clock rate is different from the second clock rate, and

wherein the converting is performed based, at least in part, on predetermined guard periods within the second sample stream.

25. The method of claim 24, further comprising:

monitoring contents of an input buffer within the synchronization unit;

generating a control signal indicative of a size of the input buffer; and

adjusting a rate at which the first sample stream is converted based, at least in part, on the control signal.

26. The method of claim 24, wherein:

the control signal indicates an increase in contents of the input buffer; and

the one or more samples are dropped from the first sample stream based, at least in part, on the control signal.

27. The method of claim 24, wherein:

the control signal indicates a decrease in contents of the input buffer; and

the one or more samples are added to the second sample stream based, at least in part, on the control signal.

28. The method of claim 24, further comprising:

monitoring an input buffer within the interface unit; and

transmitting a control signal, to the synchronization unit, indicative of a size of the input buffer, and

adjusting a rate at which the first sample stream is converted based, at least in part, on the control signal.

29. The method of claim 24, wherein:

the bursts are further arranged in accordance with a TDMA protocol; and

one or more bursts extend across boundaries of TDMA frames.