Error-correcting code interleaver
Memory may be partitioned into ever-sliding FIFOs. Each of the FIFOs may be stacked end-to-end in memory with the oldest data at the base offset and the newest at the end (or vice-virsa). Each symbol, the pointer may be incremented (modulo the set size) by an appropriate amount (typically J more than for the previous symbol). After each set, the pointers may be incremented by J more than the previous increment and the process starts over, wrapping around the memory if the end of the memory is reached. After a preset number of symbols, the process may restart from an increment of J. Alternatively, the pointers may be decremented rather than incremented. Thus, the newest symbol cannibalizes the memory position vacated by the oldest symbol in the current FIFO, causing the FIFOs to “slide”, providing for a very efficient and reliable use of memory for error-correcting code interleaving.
1. A method for interleaving symbols of an error-correcting code having I symbols in a set, the method comprising:
setting a placeholder to an initial location in a memory of size
I
(
I
-
1
)
*
J
2
+
1
,
wherein J is a delay value;
for every I symbols received:
repetitively counting from a step of 0 to a step of I−1, performing the following:
a) setting a write pointer equal to said placeholder;
b) if step is 0 , setting said placeholder equal to a read pointer;
c) if step is not 0 , advancing said placeholder step*J memory locations, wrapping around if said placeholder value would be past an end of said memory;
d) setting said read pointer equal to said placeholder;
e) reading out from a location in said memory indicated by said read pointer; and
f) writing a next of said I symbols to a location in said memory indicated by said write pointer, unless step is 0 , in which case it is bypassed.
2. The method of claim 1 , wherein said advancing said placeholder involves adding step*J to said placeholder, modulo said memory size.
3. The method of claim 1 , wherein said advancing said placeholder involves subtracting step*J from said placeholder, modulo said memory size.
4. The method of claim 1 , wherein a symbol is bypassed by transmitting it without delay.
5. A method for interleaving symbols of an error-correcting code having I symbols in a set, the method comprising:
setting a write pointer to an initial location in a memory of size
I
(
I
-
1
)
*
J
2
+
I
+
1
,
wherein J is a delay value;
for every I symbols received:
repetitively counting from a step of 0 to a step of I−1, performing the following:
a) setting a read pointer equal to one memory location behind said write pointer, wrapping around if said read pointer would be past an end of said memory;
b) reading out from a location in said memory indicated by said read pointer;
c) writing a next of said I symbols to a location in said memory indicated by said write pointer; and
d) advancing said write pointer (step+1)*J memory locations, wrapping around if said write pointer would be past an end of said memory.
6. The method of claim 5 , wherein said advancing said write pointer involves adding step*J to said write pointer, modulo said memory size.
7. The method of claim 5 , wherein said advancing said write pointer involves subtracting step*J from said write pointer, modulo said memory size.
8. The method of claim 5 , wherein one memory location behind is equivalent to one memory location less than.
9. The method of claim 5 , wherein one memory location behind is equivalent to one memory location greater than.
10. A method for interleaving symbols of an error-correcting code having I symbols in a set, the method comprising:
setting a write pointer to an initial location in a memory of size
I
(
I
-
1
)
*
J
2
+
I
+
1
,
wherein J is a delay value;
for every I symbols received:
repetitively counting from a step of 0 to a step of I−1, performing the following:
a) reading out from a location in said memory one memory location behind said write pointer, wrapping around if said location would be past an end of said memory;
c) writing a next of said I symbols to a location in said memory indicated by said write pointer; and
d) advancing said write pointer (step+1)*J memory locations, wrapping around if said write pointer would be past an end of said memory.
11. The method of claim 10 , wherein said advancing said write pointer involves adding step*J to said write pointer, modulo said memory size.
12. The method of claim 10 , wherein said advancing said write pointer involves subtracting step*J from said write pointer, modulo said memory size.
13. The method of claim 10 , wherein one memory location behind is equivalent to one memory location less than.
14. The method of claim 10 , wherein one memory location behind is equivalent to one memory location greater than.
15. An apparatus for interleaving symbols of an error correcting code having I symbols in a set, the apparatus comprising:
a memory;
a memory initializer coupled to said memory;
a placeholder setter coupled to said memory;
a step repetitive counter coupled to said placeholder setter;
a write pointer setter coupled to said memory and to said step repetitive counter;
a read pointer setter coupled to said memory and to said step repetitive counter;
a memory location reader coupled to said memory and to said step repetitive counter; and
a symbol writer coupled to said memory and to said step repetitive counter.
16. An apparatus for interleaving symbols of an error-correcting code having I symbols in a set, the apparatus comprising:
a memory;
a memory initializer coupled to said memory;
a write pointer setter coupled to said memory;
a step repetitive counter coupled to said write pointer setter;
a read pointer setter coupled to said memory and to said step repetitive counter;
a memory location reader coupled to said memory and to said step repetative counter; and
a symbol writer coupled to said memory and to said step repetitive counter.
17. An apparatus for interleaving symbols of an error-correcting code having I symbols in a set, the apparatus comprising:
a memory;
a memory initializer coupled to said memory;
a write pointer setter coupled to said memory;
a step repetitive counter coupled to said write pointer setter;
a memory location reader coupled to said memory and to said step repetitive counter; and
a symbol writer coupled to said memory and to said step repetitive counter.
18. An apparatus for interleaving symbols of an error-correcting code having I symbols in a set, the apparatus comprising:
means for setting a placeholder to an initial location in a memory of size
I
(
I
-
1
)
*
J
2
+
1
,
wherein J is a delay value;
for every I symbols received:
means for repetitively counting from a step of 0 to a step of I−1, performing the following:
a) setting a write pointer equal to said placeholder;
b) if step is 0 , setting said placeholder equal to a read pointer;
c) if step is not 0 , advancing said placeholder step*J memory locations, wrapping around if said placeholder value would be past an end of said memory;
d) setting said read pointer equal to said placeholder;
e) reading out from a location in said memory indicated by said read pointer; and
f) writing a next of said I symbols to a location in said memory indicated by said write pointer, unless step is 0 , in which case it is bypassed.
19. The apparatus of claim 18 , wherein said advancing said placeholder involves adding step*J to said placeholder, modulo said memory size.
20. The apparatus of claim 18 , wherein said advancing said placeholder involves subtracting step*J from said placeholder, modulo said memory size.
21. The apparatus of claim 18 , wherein a symbol is bypassed by transmitting it without delay.
22. An apparatus for interleaving symbols of an error-correcting code having I symbols in a set, the apparatus comprising:
means for setting a write pointer to an initial location in a memory of size
I
(
I
-
1
)
*
J
2
+
I
+
1
,
wherein J is a delay value;
for every I symbols received:
means for repetitively counting from a step of 0 to a step of I−1, performing the following:
a) setting a read pointer equal to one memory location behind said write pointer, wrapping around if said read pointer would be past an end of said memory;
b) reading out from a location in said memory indicated by said read pointer;
c) writing a next of said I symbols to a location in said memory indicated by said write pointer; and
d) advancing said write pointer (step+1)*J memory locations, wrapping around if said write pointer would be past an end of said memory.
23. The apparatus of claim 22 , wherein said advancing said write pointer involves adding step*J to said write pointer, modulo said memory size.
24. The apparatus of claim 22 , wherein said advancing said write pointer involves subtracting step*J from said write pointer, modulo said memory size.
25. The apparatus of claim 22 , wherein one memory location behind is equivalent to one memory location less than.
26. The apparatus of claim 22 , wherein one memory location behind is equivalent to one memory location greater than.
27. An apparatus for interleaving symbols of an error-correcting code having I symbols in a set, the apparatus comprising:
means for setting a write pointer to an initial location in a memory of size
I
(
I
-
1
)
*
J
2
+
I
+
1
,
wherein J is a delay value;
for every I symbols received:
means for repetitively counting from a step of 0 to a step of I−1, performing the following:
a) reading out from a location in said memory one memory location behind said write pointer, wrapping around if said location would be past an end of said memory;
c) writing a next of said I symbols to a location in said memory indicated by said write pointer; and
d) advancing said write pointer (step+1)*J memory locations, wrapping around if said write pointer would be past an end of said memory.
28. The apparatus of claim 27 , wherein said advancing said write pointer involves adding step*J to said write pointer, modulo said memory size.
29. The apparatus of claim 27 , wherein said advancing said write pointer involves subtracting step*J from said write pointer, modulo said memory size.
30. The apparatus of claim 27 , wherein one memory location behind is equivalent to one memory location less than.
31. The apparatus of claim 27 , wherein one memory location behind is equivalent to one memory location greater than.
32. A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform a method for interleaving symbols of an error-correcting code having I symbols in a set, the method comprising:
setting a placeholder to an initial location in a memory of size
I
(
I
-
1
)
*
J
2
+
1
,
wherein J is a delay value;
for every I symbols received:
repetitively counting from a step of 0 to a step of I−1, performing the following:
a) setting a write pointer equal to said placeholder;
b) if step is 0 , setting said placeholder equal to a read pointer;
c) if step is not 0 , advancing said placeholder step*J memory locations, wrapping around if said placeholder value would be past an end of said memory;
d) setting said read pointer equal to said placeholder;
e) reading out from a location in said memory indicated by said read pointer; and
f) writing a next of said I symbols to a location in said memory indicated by said write pointer, unless step is 0 , in which case it is bypassed.
33. A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform a method for interleaving symbols of an error-correcting code having I symbols in a set, the method comprising:
setting a write pointer to an initial location in a memory of size
I
(
I
-
1
)
*
J
2
+
I
+
1
,
wherein J is a delay value;
for every I symbols received:
repetitive counting from a step of 0 to a step of I−1, performing the following:
a) setting a read pointer equal to one memory location behind said write pointer, wrapping around if said read pointer would be past an end of said memory;
b) reading out from a location in said memory indicated by said read pointer;
c) writing a next of said I symbols to a location in said memory indicated by said write pointer; and
d) advancing said write pointer (step+1)*J memory locations, wrapping around if said write pointer would be past an end of said memory.
34. A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform a method for interleaving symbols of an error-correcting code having I symbols in a set, the method comprising:
setting a write pointer to an initial location in a memory of size
I
(
I
-
1
)
*
J
2
+
I
+
1
,
wherein J is a delay value;
for every I symbols received:
repetitively counting from a step of 0 to a step of I−1, performing the following:
a) reading out from a location in said memory one memory location behind said write pointer, wrapping around if said location would be past an end of said memory;
c) writing a next of said I symbols to a location in said memory indicated by said write pointer; and
d) advancing said write pointer (step+1)*J memory locations, wrapping around if said write pointer would be past an end of said memory.