Method for reading and writing a block interleaver and the reading circuit thereof
A method for writing a memory of a block interleaver determines in a bit-wise manner whether to write data into the memory. A method for reading a memory of a block interleaver combines two adjacent columns of the memory into a temporary column and reads data from the temporary column.
1. A method for reading a memory of a block interleaver, wherein the size of the memory is N r rows by N c columns, the effective size of the memory is M r rows by M c columns, the method reading a datum of N BPSC bits vertically from the memory with a start address of a r-th row and a c-th column of the memory, wherein N r , N c , N BPSC , r and c are all positive integers, the method comprising the steps of:
combining all bits in the c-th column and first several bits of a next column into a first combination column;
combining first M r bits of the first combination column and last several bits of the first combination column into a second combination column; and
reading N BPSC bits of the second combination column starting from a r-th bit.
2. The method of claim 1 , wherein the number of the several bits is N n −1, and N n ≦N BPSC −1.
3. The method of claim 1 , wherein the step of the combination of the first combination column comprises the steps of:
reading the first several bits of the next column if c+1 is equal to or smaller than M c ; and
reading the first several bits of the first column if c+1 is greater than M c .
4. The method of claim 1 , wherein the step of the combination of the second combination column comprises the steps of:
marking N n bits of a first temporary column with length N r +N n starting from a M r -th bit as to be written to, and marking the other bits as not to be written to;
executing AND operations for each bit of the first combination column with each bit of the first temporary column; and
executing OR operations for each bit between a (N r +N n −1)-th bit and a N r -th bit of the first combination column with each bit between a (M r +N n −1)-th bit and the M r -th bit of the first combination column.
5. The method of claim 1 , wherein the step of reading N BPSC bits of the second combination column comprises the steps of:
shifting the second combination column by r bits to the right and reading bits between a N BPSC -th bit and the first bit of second combination column as the datum.
6. The method of claim 1 , wherein the memory is realized by flip-flops.
7. A read circuit for a memory of a block interleaver, wherein the size of the memory is N r rows by N c columns, the effective size of the memory is M r rows by M c columns, the read circuit reading a datum from the memory to a specific data structure and outputting N BPSC bits vertically from the memory with a start address of a r-th row and a c-th column of the memory, wherein N r , N c , N BPSC , r and c are all positive integers, the data structure comprising:
a first combination column constructed by combining all bits in a c-th column and first several bits of a next column of the memory; and
a second combination column constructed by combining first M r bits of the first combination column and last several bits of the first combination column;
wherein the second combination column is input data of the read circuit, and bits between a r-th bit and a (r+N BPSC −1)-th bit are output data of the read circuit.
8. The read circuit of claim 7 , wherein the number of the several bits is N n , and N n ≦N BPSC −1.
9. The read circuit of claim 7 , wherein the length of the first combination column and that of the second combination column are the same.
10. The read circuit of claim 7 , wherein the data structure further comprises:
a first temporary column with length N r +N n , having N BPSC bits starting from a M r -th bit marked as zero and the other bits marked as one;
a second temporary column with length N r +N n , constructed by executing AND operations for each bit of the first combination column with each bit of the first temporary column; and
a third temporary column with length N r +N n , constructed by executing OR operations for each bit between a (N r +N n −1)-th bit and a N r -th bit of the first combination column with each bit between a (M r +N n −1)-th bit and the M r -th bit of the second temporary column.
11. The read circuit of claim 10 , wherein the second combination column is third temporary column.
12. The read circuit of claim 7 , wherein the memory is realized by flip-flops.