Seamless change of depth of a general convolutional interleaver during transmission without loss of data

• US 20060107174A1
• Filed: 11/15/2005
• Published: 05/18/2006
• Est. Priority Date: 11/16/2004
• Status: Active Grant

• Current Assignee: Bernd Heise
• Original Assignee: Bernd Heise
• Inventors: Heise, Bernd
• Granted Patent: US 7,529,984 B2
• Time in Patent Office: Days
• US Class Current: 714/755
• CPC Class Codes: H03M 13/2732 Convolutional interleaver; Interleavers using shift-registers or delay lines like, e.g. Ramsey type interleaver
• CPC Class Codes: H03M 13/2789 Interleaver providing variable interleaving, e.g. variable block sizes
• CPC Class Codes: H03M 13/6508 Flexibility, adaptability, parametrability and configurability of the implementation
• CPC Class Codes: H04L 1/004 by using forward error control H04L1/0618 takes precedence; coding, decoding or code conversion, for error detection or correction H03M13/00

Abstract

Methods and communication systems are presented, in which impulse noise is monitored on a communication channel, and an interleaver depth is adjusted according to the monitored impulse noise without interrupting communication service.

Claims

1. A method of adjusting a convolutional interleaver depth, comprising:

identifying a size change necessary for each of a plurality of memory queues based on a magnitude of change in the interleaver depth; and

altering the size of each of the plurality of memory queues based on the identified size change, wherein each size change is unique.

2. The method of claim 1, further comprising:

maintaining an order in which incoming data bytes are loaded into the plurality of memory queues after identifying the size change; and

altering an order in which outgoing data bytes are transferred from the plurality of memory queues based on the magnitude of change in the interleaver depth.

3. The method of claim 1, wherein altering the size of the memory queues comprises transmitting dummy data for each of the plurality of memory queues, wherein an amount of dummy data transmitted for each queue is unique and a function of the magnitude of change in the interleaver depth.

4. The method of claim 3, further comprising discarding the dummy data transferred over a transmission medium at a de-interleaver comprising a plurality of memory queues, thereby not writing the dummy data into the de-interleaver.

5. A method for adjustment of a convolutional interleaver depth in a communication system, comprising:

monitoring a transmission condition on a communication channel during communication service;

determining a change in interleaver depth of a convolutional interleaver based on the transmission condition;

modifying a virtual size of transmission FIFOs associated with convolutional interleaver, wherein the virtually modified transmission FIFOs have dummy data associated therewith according to the virtually modified size;

altering an order in which data is read from the transmission FIFOs based on the determined change in the interleaver depth;

reading data from the transmission FIFOs in accordance with the altered order; and

selectively writing the read data from the transmission FIFOs to receiver FIFOs, wherein selective portions of the data read from the transmission FIFOs are discarded based on the determined interleaver depth change, thereby discarding the dummy data.

6. The method of claim 5, wherein modifying the virtual size of the transmission FIFOs comprises altering an actual size of the transmission FIFOs, comprising:

determining the size modification according to Δ

T(z,y)=Δ

T_raw(z,y)−

Δ

Tmin(y), wherein Δ

T(z,y) comprises a change in the FIFO size of the z^th FIFO at a moment before an output of the y^th FIFO is read, wherein Δ

Tmin(y) is zero when there is an increase in interleaver depth and wherein Δ

Tmin(y)=min(Δ

T_raw(z,y)), wherein Δ

Tmin(y) is the minimum value of Δ

T_raw(z,y) for z=(0, 1, . . . I−

1) when there is a decrease in interleaver depth, and

wherein

Δ

T_raw(z,y)=T₂(z,y)−

T₁(z,y)=floor[(D₂−

1)*z/I−

Toff₂(y)]−

floor[(D₁−

1)*z/I−

Toff₁(y)],

wherein

Toff_j(y)=[(D_j−

1)*y/I−

floor((D_j−

1)*y/I)],

wherein D_j represents the interleaver depth either before the change in interleaver depth, wherein D_j is D₁, or after the change in interleaver depth, wherein D_j is D₂, and wherein floor(m) is a mathematical operator wherein the value “

m”

is rounded down to the next lowest integer value, and wherein I comprises the number of bytes associated with a data block or codeword to be transmitted; and

transmitting dummy data bytes for each transmission FIFO based on the determined size modification.

7. The method of claim 6, wherein reading data from the transmission FIFOs comprises selecting a data byte that may comprise payload data or dummy data for each transmission FIFO in accordance with the altered order.

8. The method of claim 5, wherein modifying the virtual size of the transmission FIFOs comprises not reading data from the transmission FIFOs when the altered order for a data read would otherwise dictate a data read therefrom, wherein an amount of data not read from the transmission FIFOs corresponds to an amount of dummy data associated with the transmission FIFOs.

9. The method of claim 5, wherein selectively writing the read data from the transmission FIFOs to receiver FIFOs comprises:

determining a number of dummy bytes associated with the dummy data for each transmission FIFO;

maintaining a count of transferred dummy bytes for each transmission FIFO;

discarding each of the dummy bytes based on the maintained count until all dummy bytes associated with the transmission FIFOs are transferred; and

writing data from the transmission FIFOs into the respective receiver FIFOs after the dummy bytes are discarded.

10. The method of claim 5, wherein the change in interleaver depth comprises an increase in depth or a decrease in depth.

11. The method of claim 5, wherein data written into the transmission FIFOs is not synchronous with data read from the transmission FIFOs.

12. The method of claim 5, wherein the adjustment comprises a decrease in the convolutional interleaver depth, and wherein the communication system comprises a plurality of transmission FIFOs on a transmitter side and a plurality of receiving FIFOs on a receiver side, further comprising:

identifying a present interleaver depth D₁ and a new interleaver depth D₂ after the adjustment, wherein D₂<

D₁;

simulating a change in interleaver depth from D₂ to D₁ as a hypothetical increase in interleaver depth, thereby obtaining a simulated pattern and order of data transmitted from the receiver side to the transmitter side, wherein the simulated pattern and order of transfer is based on the simulated selective transmission of data bytes or dummy bytes;

forming an inverted pattern with inverted order of data transfer based on the simulated pattern; and

employing the inverted pattern and inverted order to transmit data bytes and dummy bytes from the transmitter side to the receiver side, wherein the inverted pattern results in a decrease in interleaver depth from D₁ to D₂.

13. A convolutional interleaver, comprising:

a plurality of memory queues configures to store data bytes associated with incoming data to be transmitted over a transmission medium; and

a control circuit configured to change a size of the memory queues in accordance with a communicated change in interleaver depth by employing dummy data of differing amounts for each of the memory queues, wherein the amount of dummy data is associated with an amount of the change in the interleaver depth.

14. The convolutional interleaver of claim 13, wherein an amount of dummy data inserted into each of the memory queues by the control circuit comprises Δ

T(z,y)=Δ

T_raw(z,y)−

Δ

Tmin(y), wherein Δ

T(z,y) comprises a change in the FIFO size of the z^th FIFO at a moment before an output of the y^th FIFO is read, wherein Δ

Tmin(y) is zero when there is an increase in interleaver depth and wherein

Δ

Tmin(y)=min(Δ

T_raw(z,y)), wherein Δ

Tmin(y) is the minimum value of Δ

T_raw(z,y) for z=(0, 1, . . . I−

1) when there is a decrease in interleaver depth, and wherein

Δ

T_raw(z,y)=T₂(z,y)−

T₁(z,y)=floor[(D₂−

1)*z/I−

Toff₂(y)]−

floor[(D₁−

1)*z/I−

Toff₁(y)],

wherein

Toff_j(y)=[(D_j−

1)*y/I−

floor((D_j−

1)*y/I)],

wherein D_j represents the interleaver depth either before the change in interleaver depth, wherein D_j is D₁, or after the change in interleaver depth, wherein D_j is D₂, and wherein floor(m) is a mathematical operator wherein the value “

m”

is rounded down to the next lowest integer value, and I comprises the number of bytes associated with a data block or codeword to be transmitted.

15. The convolutional interleaver of claim 13, wherein the control circuit is further configured to alter an order in which data is read from the memory queues based on the change in interleaver depth.

16. A transmission system, comprising:

a transceiver configured to transmit data over a transmission medium; and

a forward error correction system operably coupled to the transceiver, and configured to transmit encoded data to the transceiver for transmission thereof, wherein the forward error correction system comprises a convolutional interleaver configured to receive a plurality of codewords or data blocks and interleave the plurality of codewords or data blocks based on an interleaver depth, and further configured to vary the interleaver depth by an amount other than an integer multiple of a block length of the plurality of codewords or data blocks.

17. The transmission system of claim 16, wherein the forward error correction system is configured to alter the convolutional interleaver depth based on received impulse noise data.

18. The transmission system of claim 16, wherein the interleaver comprises:

a plurality of transmission FIFOs, wherein a number of transmission FIFOs is associated with a number of data bytes in a codeword or data block; and

a control circuit configured to alter a size of each of the transmission FIFOs based on a change in interleaver depth communicated thereto.

19. The transmission system of claim 18, wherein the control circuit is configured to alter the size of the transmission FIFOs according to Δ

T(z,y)=Δ

T_raw(z,y)−

Δ

Tmin(y), wherein Δ

T(z,y) comprises a change in the FIFO size of the z^th FIFO at a moment before an output of the y^th FIFO is read, wherein Δ

Tmin(y) is zero when there is an increase in interleaver depth and wherein Δ

Tmin(y)=min(Δ

T_raw(z,y)), wherein Δ

Tmin(y) is the minimum value of Δ

T_raw(z,y) for z=(0, 1, . . . I−

1) when there is a decrease in interleaver depth, and

wherein

Δ

T_raw(z,y)=T₂(z,y)−

T₁(z,y)=floor[(D₂−

1)*z/I−

Toff₂(y)]−

floor[(D₁−

1)*z/I−

Toff₁(y)],

wherein

Toff_j(y)=[(D_j−

1)*y/I−

floor((D_j−

1)*y/I)],

wherein D_j represents the interleaver depth either before the change in interleaver depth, wherein D_j is D₁, or after the change in interleaver depth, wherein D_j is D₂, and wherein floor(m) is a mathematical operator wherein the value “

m”

is rounded down to the next lowest integer value, and I comprises the number of bytes associated with a data block or codeword to be transmitted.

20. The transmission system of claim 18, wherein the control circuit is further configured to alter an order in which data bytes are read from the transmission FIFOs based on the change in interleaver depth.

21. The transmission system of claim 18, wherein the control circuit is further configured to ascertain a decrease in the interleaver depth from an initial depth D₁ to a new depth D₂, wherein D₂<

D₁, and further configured to simulate a change in interleaver depth from D₂ to D₁ as a hypothetical increase in interleaver depth, thereby obtaining a simulated pattern and order of data transmitted from a receiver side to a transmitter side, wherein the simulated pattern is based on the simulated selective transmission of data bytes or dummy bytes, and wherein the control circuit is further configured to form an inverted pattern and inverted order of data transfer based on the simulated pattern, and employ the inverted pattern and inverted order to selectively transmit data bytes and dummy bytes from the transmitter side to the receiver side, wherein the inverted pattern results in a decrease in interleaver depth from D₁ to D₂.

22. A method for adjustment of a convolutional interleaver depth in a communication system, comprising:

determining a change in interleaver depth of a convolutional interleaver;

determining a distance in time between a data byte about to be transferred from one of a plurality of transmission FIFOs associated with the convolutional interleaver and an immediately preceding byte within an original interleaver data block; and

selectively transmitting the data byte or a dummy byte based on the determined distance in time.

23. The method of claim 22, further comprising:

comparing the determined distance in time to a predetermined threshold; and

transmitting the dummy byte if the distance in time is less than the threshold, and transmitting the data byte otherwise.

24. The method of claim 23, wherein the predetermined threshold is a distance in time between successive data bytes associated with a predetermined impulse noise protection level.

25. The method of claim 22, further comprising calculating the distance in time by accounting for both a change in transmission byte rate and the change in the interleaver depth during a time period between transmission of the data byte and the immediately preceding byte.

26. The method of claim 25, wherein calculating the distance in time further comprises calculating the distance in time when the transmission byte rate changes before the change in interleaver depth by T_DIST=A₁/L₁+(A₂+A₃)/L₂, wherein T_DIST is the distance in time, A₁ is the number of bytes transmitted at a first transmission byte rate L₁ prior to the change in interleaver depth, A₂ is the number of bytes transmitted at a second transmission byte rate L₂ prior to the change in interleaver depth, and A₃ is the number of bytes transmitted at the second transmission byte rate L₂ after the change in interleaver depth, and wherein when the transmission byte rate and interleaver depth change at the same time, A₂=0.

27. The method of claim 25, wherein calculating the distance in time further comprises calculating the distance in time when the transmission byte rate changes after the interleaver depth by T_DIST=(A₁+A₂)/L₁+A₃/L₂, wherein T_DIST is the distance in time, A₁ is the number of bytes transmitted at a first transmission byte rate L₁ prior to a change in interleaver depth, A₂ is the number of bytes transmitted at the first transmission byte rate L₁ after the change in interleaver depth, and A₃ is the number of bytes transmitted at the second transmission byte rate L₂ after the change in interleaver depth, and wherein when the transmission byte rate and interleaver depth changes at the same time, A₂=0.

28. The method of claim 22, wherein the adjustment comprises a decrease in the convolutional interleaver depth, and wherein the communication system comprises a plurality of transmission FIFOs on a transmitter side and a plurality of receiving FIFOs on a receiver side, further comprising:

identifying a present interleaver depth D₁ and a new interleaver depth D₂ after the adjustment, wherein D₂<

D₁;

simulating a change in interleaver depth from D₂ to D₁ as a hypothetical increase in interleaver depth, thereby obtaining a simulated pattern and order of data transmitted from the receiver side to the transmitter side, wherein the simulated pattern and order is based on the simulated selective transmission of data bytes or dummy bytes;

forming an inverted pattern and inverted order of data transfer based on the simulated pattern; and

employing the inverted pattern and inverted order of data transfer to transmit data bytes and dummy bytes from the transmitter side to the receiver side, wherein the inverted pattern results in a decrease in interleaver depth from D₁ to D₂.

29. A transmission system, comprising:

a transceiver configured to transmit data over a transmission medium; and

a forward error correction system operably coupled to the transceiver, and configured to transmit encoded data to the transceiver for transmission thereof, wherein the forward error correction system comprises a convolutional interleaver configured to receive a plurality of codewords or data blocks and interleave the plurality of codewords or data blocks based on an interleaver depth, and further configured to vary the interleaver depth by selectively transmitting a data byte from one of a plurality of transmission FIFOs of the interleaver or a dummy byte based on a distance in time between a data byte about to be transferred from the transmission FIFO and an immediately preceding byte within an original interleaver data block

30. The transmission system of claim 29, wherein the convolutional interleaver further comprises a control circuit configured to determine a change in the depth of the convolutional interleaver, determine the distance in time between the data byte about to be transferred from the transmission FIFO and the immediately preceding byte within the original interleaver data block, and selectively transmit the data byte or a dummy byte based on the determined distance.

31. The transmission system of claim 30, wherein the control circuit is further configured to ascertain a decrease in the interleaver depth from an initial depth D₁ to a new depth D₂, wherein D₂<

D₁, and further configured to simulate a change in interleaver depth from D₂ to D₁ as a hypothetical increase in interleaver depth, thereby obtaining a simulated pattern and order of data transmitted from a receiver side to a transmitter side, wherein the simulated pattern and order of data transfer is based on the simulated selective transmission of data bytes or dummy bytes, and wherein the control circuit is further configured to form an inverted pattern and inverted order of data transfer based on the simulated pattern, and employ the inverted pattern and inverted order to selectively transmit data bytes and dummy bytes from the transmitter side to the receiver side, wherein the inverted pattern results in a decrease in interleaver depth from D₁ to D₂.

32. The transmission system of claim 29, wherein the forward error correction system is configured to alter the convolutional interleaver depth based on received impulse noise data.

33. The transmission system of claim 29, wherein the number of transmission FIFOs in the convolutional interleaver is associated with a number of data bytes in a codeword or data block, and wherein the interleaver further comprises a control circuit and multiplexer configured to selectively transmit the data byte from one of the transmission FIFOs or the dummy byte based on the determined distance.

34. The transmission system of claim 33, wherein the control circuit is configured to compare the determined distance in time to a predetermined threshold, and transmit the dummy byte via the multiplexer if the distance in time is less than the threshold, and further configured to transmit the data byte via the multiplexer otherwise.

35. The transmission system of claim 34, wherein the predetermined threshold is a distance in time between successive data bytes associated with a predetermined impulse noise protection level.

36. The transmission system of claim 29, further comprising a control circuit configured to calculate the distance in time between successive data bytes by accounting for both a change in transmission byte rate and the change in the interleaver depth during a time period between transmission of successive data bytes.

37. The transmission system of claim 36, wherein the control circuit is configured to calculate the distance by calculating the distance in time when the transmission byte rate changes before the change in interleaver depth by T_DIST=A₁/L₁+(A₂+A₃)/L₂, wherein T_DIST is the distance in time, A₁ is the number of bytes transmitted at a first transmission byte rate L₁ prior to the change in interleaver depth, A₂ is the number of bytes transmitted at a second transmission byte rate L₂ prior to the change in interleaver depth, and A₃ is the number of bytes transmitted at the second transmission byte rate L₂ after the change in interleaver depth, and wherein when the transmission byte rate and interleaver depth changes at the same time, A₂=0.

38. The transmission system claim 36, wherein the control circuit is configured to calculate the distance by calculating the distance in time when the transmission byte rate changes after the interleaver depth by T_DIST=(A₁+A₂)/L₁+A₃/L₂, wherein T_DIST is the distance in time, A₁ is the number of bytes transmitted at a first transmission byte rate L₁ prior to a change in interleaver depth, A₂ is the number of bytes transmitted at the first transmission byte rate L₁ after the change in interleaver depth, and A₃ is the number of bytes transmitted at the second transmission byte rate L₂ after the change in interleaver depth, and wherein when the transmission byte rate and interleaver depth changes at the same time, A₂=0.