Descrambler for memory systems and method thereof
A descrambler receives data from a memory device. The descrambler calculates a sub-syndrome weight for multiple bits in each of the plurality of descrambled sequences using a set parity check matrix to generate multiple sub-syndrome weights, one for each of the plurality of descrambled sequences. The descrambler selects a sub-syndrome weight among the multiple sub-syndrome weights. The descrambler determines, as a correct scrambler sequence for descrambling the data, a scrambler sequence corresponding to the selected sub-syndrome weight, among the plurality of scrambler sequences.
1. A memory system comprising:
a memory device; and
a controller including a descrambler, which is coupled to the memory device and suitable for:
receiving data from the memory device;
descrambling the data, using each of a plurality of scrambler sequences, to generate a corresponding plurality of descrambled sequences;
calculating a sub-syndrome weight for multiple bits in each of the corresponding plurality of descrambled sequences using a set parity check matrix to generate multiple sub-syndrome weights, one for each of the plurality of descrambled sequences;
selecting a sub-syndrome weight among the multiple sub-syndrome weights of the corresponding plurality of descrambled sequences; and
determining, as a correct scrambler sequence for descrambling the data, a scrambler sequence corresponding to the selected sub-syndrome weight, among the plurality of scrambler sequences,
wherein the descrambler calculates the sub-syndrome weight for the multiple bits in each of the plurality of descrambled sequences using a subset circulant matrix in a set parity check matrix,
and
wherein the multiple bits are the last nq bits in each of the plurality of descrambled sequences and the subset circulant matrix is a (mq×nq) matrix having a circulant size of (q×q) in the set parity check matrix, where m and n are integers greater than 1.
2. The memory system of claim 1 , wherein the parity check matrix is a parity check matrix for a low density parity check (LDPC) code.
3. The memory system of claim 1 , wherein the descrambler selects the lowest sub-syndrome weight among the multiple sub-syndrome weights.
4. The memory system of claim 1 , wherein the descrambler compares each of the multiple sub-syndrome weights with a threshold value and selects a sub-syndrome weight less than the threshold value among the sub-syndrome weights.
5. The memory system of claim 1 , wherein the data received from the memory system comprises randomized data.
6. The memory system of claim 5 , wherein the randomized data has a minimized number of sequential bits of different values.
7. A method for operating a memory system, which includes a memory device and a controller including a descrambler coupled to the memory device, the method comprising:
receiving data from the memory device;
descrambling the data, using each of a plurality of scrambler sequences, to generate a corresponding plurality of descrambled sequences;
calculating a sub-syndrome weight for multiple bits in each of the corresponding plurality of descrambled sequences using a set parity check matrix to generate multiple sub-syndrome weights, one for each of the plurality of descrambled sequences;
selecting a sub-syndrome weight among the multiple sub-syndrome weights of the corresponding plurality of descrambled sequences; and
determining, as a correct scrambler sequence for descrambling the data, a scrambler sequence corresponding to the selected sub-syndrome weight, among the plurality of scrambler sequences,
wherein the calculating of the sub-syndrome weight for multiple bits in each of the plurality of descrambled sequences comprises:
calculating the sub-syndrome weight for the multiple bits in each of the plurality of descrambled sequences using a subset circulant matrix in a set parity check matrix,
and
wherein the multiple bits are the last nq bits in each of the plurality of descrambled sequences and the subset circulant matrix is a (mq×nq) matrix having a circulant size of (q×q) in the set parity check matrix, where m and n are integers greater than 1.
8. The method of claim 7 , wherein the parity check matrix is a parity check matrix for a low density parity check (LDPC) code.
9. The method of claim 7 , wherein the selecting of the sub-syndrome weight among the multiple sub-syndrome weights comprises:
selecting the lowest sub-syndrome weight among the multiple sub-syndrome weights.
10. The method of claim 7 , wherein the selecting of the sub-syndrome weight among the multiple sub-syndrome weights comprises:
comparing each of the multiple sub-syndrome weights with a threshold value; and
selecting a sub-syndrome weight less than the threshold value among the sub-syndrome weights.
11. The method of claim 7 , wherein the data received from the memory system comprises randomized data.
12. The method of claim 11 , wherein the randomized data has a minimized number of sequential bits of different values.