Method and apparatus for replacing lost PSTN data in a packet network

• US 6,208,618 B1
• Filed: 12/04/1998
• Issued: 03/27/2001
• Est. Priority Date: 12/04/1998
• Status: Expired due to Term

• Current Assignee: Tellabs Operations Incorporated (Infinera Corp.)
• Original Assignee: Tellabs Operations Incorporated (Infinera Corp.)
• Inventors: Kenney, John B., Magill, Robert B., Schafer, R. Michael
• Primary Examiner(s): HSU, ALPUS
• Application Number:
  US09/206,191
• Time in Patent Office: 844 Days
• Field of Search: 370/216, 370/242, 370/244, 370/249, 370/250, 370/352, 370/389, 370/392, 370/428, 370/514, 370/515, 370/516, 331/78, 364/717.01, 364/717.03, 364/717.04, 364/717.07, 375/140, 375/354, 375/365, 375/367, 704/201, 704/211, 704/214, 704/215, 704/226, 704/229
• US Class Current: 370/216
• CPC Class Codes: G10L 19/005 Correction of errors induced by the transmission channel, if related to the coding algorithm
• CPC Class Codes: G10L 19/012 Comfort noise or silence coding
• CPC Class Codes: H03K 3/84 Generating pulses having a predetermined statistical distribution of a parameter, e.g. random pulse generators
• CPC Class Codes: H04M 11/066 Telephone sets adapted for data transmision

Abstract

A method and apparatus for replacing lost PSTN data in a packet network and for generating variable power white noise are disclosed. In one embodiment, the method for replacing data includes the steps of receiving data packets, detecting lost data packets, and producing in response a lost data output indicating when replacement data needs to be provided. The method preferably generates the replacement data by re-using data stored in an extended playback buffer (with the re-used replacement data starting with the oldest output data byte stored in the extended playback buffer), and placing the re-used replacement data on an external network. Another aspect of the invention is a variable power white noise generator for providing replacement data. The variable power white noise generator may use, for example, a multi-bit register that stores a magnitude, and a pseudo-random sign bit generator to change the positive and negative sense of the magnitude. In one preferred embodiment, a linear feedback shift register (LFSR) is used in conjunction with a feedback network corresponding to a polynomial generating function. The pseudo-random output sequence of the LFSR then produces a pseudo-random output bit to control the positive and negative sense of the magnitude bits.

Claims

1. A method for generating variable power white noise for data replacement in a packet network, the method comprising:

storing a selected magnitude in a multi-bit register;

generating a pseudo-random sign bit using a linear feedback shift register; and

providing the sign bit in conjunction with the magnitude as a pseudo-random variable power white noise output output value.

2. The method of claim 1, wherein the step of generating comprises evaluating register contents of the linear feed back shift register in a feedback network and shifting the contents of the linear feedback shift register.

3. The method of claim 2, wherein the step of evaluating register contents of the linear feed back shift register in a feedback network comprises evaluating register contents of the linear feed back shift register in a primitive polynomial feedback network.

4. The method of claim 1, wherein the step of storing a selected magnitude comprises storing a selected magnitude corresponding to an absolute energy level above a predetermined threshold for a data call.

5. The method of claim 4, further comprising the step of outputting the output value onto a destination network.

6. The method of claim 1, wherein the step of storing a selected magnitude comprises storing a selected magnitude corresponding to an absolute energy level within a predetermined range for a data call.

7. The method of claim 1, wherein the step of storing a selected magnitude comprises storing a selected magnitude corresponding to an absolute energy level within a predetermined range for a voice call.

8. The method of claim 7, further comprising the step of outputting the output value onto a destination network.

9. The method of claim 1, further comprising the step of outputting the output value onto a destination network.

10. A variable power white noise generator comprising:

a multi-bit register storing a signed quantity in a predetermined format representing a magnitude with a sign;

a linear feedback shift register connected to a sign bit in the multi-bit register, the linear feedback shift register including an output bit determining the sign of the magnitude;

a feedback network connected to the linear feedback shift register, the feedback network implementing a generator function; and

a register control coupled to the multi-bit register that stores the magnitude in the multi-bit register.

11. The variable power white noise generator of claim 10, further comprising a lost packet detection unit including a lost data output.

12. The variable power white noise generator of claim 10, further comprising at least one additional multi-bit register storing a signed quantity in a predetermined format representing a magnitude with a sign, and wherein the linear feedback shift register is further connected to the sign bit of the additional multi-bit register to control the sign of the magnitude stored in the additional multi-bit register.

13. The variable power white noise generator of claim 12, further comprising a multiplexer for sequentially providing as output the signed quantity of each of the multi-bit registers.

14. The variable power white noise generator of claim 12, wherein the register control is coupled to each of the multi-bit registers for independently storing magnitudes therein.

15. The variable power white noise generator of claim 10, wherein the magnitude is greater than a predetermined data call threshold.

16. The variable power white noise generator of claim 15, wherein the data call threshold is approximately −

42 dBm0.

17. The variable power white noise generator of claim 10, wherein the magnitude is greater than a predetermined voice call threshold.

18. The variable power white noise generator of claim 17, wherein the voice call threshold is greater than −

69 dBm0 and the magnitude corresponds to less than −

40 dBm0.

19. A method for replacing lost PSTN data in a packet network, the method comprising the steps of:

receiving data packets from the packet network;

detecting lost data packets and producing in response a lost data output indicating when replacement data needs to be provided;

removing overhead information from the data packets to produce output data;

storing a plurality of output data in an extended playback buffer;

generating duplicate replacement data using the extended playback buffer, the duplicate replacement data starting with the oldest output data stored in the extended playback buffer;

placing the duplicate replacement data on an external network when the lost data output indicates replacement data needs to be provided and placing the output data on the external network otherwise.

20. The method of claim 19, further comprising the steps of generating white noise replacement data using at least one variable power white noise generator, each variable power white noise generator producing the white noise replacement data by the steps of:

using a linear feedback shift register to control a sign bit of a multi-bit register;

storing a magnitude in the multi-bit register

outputting the sign bit and magnitude as the white noise replacement data; and

shifting contents of the linear feedback shift register; and

wherein placing comprises placing on the external network one of the white noise replacement data and duplicate replacement data according to a replacement data selection signal.

21. The method of claim 20, further comprising the step of generating silence replacement data and wherein the placing step responds to the replacement data selection signal by placing white noise replacement data, duplicate replacement data, or silence replacement data on the external network.

22. The method of claim 20, wherein the magnitude is greater than a predetermined data call threshold.

23. The method of claim 22, wherein the data call threshold is approximately −

42 dBm0.

24. The method of claim 20, wherein the magnitude is greater than a predetermined voice call threshold.

25. The method of claim 24, wherein the voice call threshold is greater than −

69 dBm0 and the magnitude corresponds to less than −

40 dBm0.

26. A method for replacing lost PSTN packet data in a packet network, the method comprising the steps of:

receiving data packets from the packet network;

detecting lost data packets and producing in response a lost data output indicating when replacement data needs to be provided;

removing overhead information from the data packets to produce output data;

generating white noise replacement data using a variable power white noise generator producing the white noise replacement data by the steps of;

using a linear feedback shift register to control a sign bit of a multi-bit register;

storing a magnitude in the multi-bit register;

outputting the sign bit and magnitude as the white noise replacement data; and

shifting the contents of the linear feedback shift register; and

placing the white noise replacement data on an external network when the lost data output indicates replacement data need to be provided and placing the output data on the external network otherwise.

27. The method of claim 26, further comprising the step of generating silence replacement data and wherein placing comprises placing one of the silence replacement data and the white noise replacement data on the external network in accordance with the replacement data selection signal.

28. The method of claim 26, wherein the magnitude is greater than a predetermined data call threshold.

29. The method of claim 26, wherein the magnitude is greater than a predetermined voice call threshold.

30. The method of claim 26, further comprising the step of multiplexing white noise replacement data from a plurality of variable power white noise generators onto the external network.

31. The method of claim 30, further comprising the step of using the linear feedback shift register to control a sign bit in each of the plurality of variable power white noise generators.

32. The method of claim 30, further comprising the step of independently storing magnitudes in each of the plurality of variable power white noise generators according to a call type for which each of the plurality of variable power white noise generators provides replacement data.