1. Semi-Parallel Reconfigurable Architecture for Real-time LDPC decoding Karkooti, M.; Cavallaro, J.R.; Information Technology: Coding and Computing, 2004. Proceedings. ITCC 2004. International Conference on, Volume: 1, April 5-7, 2004 Pages:579 - 585

2. Outline  Introduction  Algorithms Comparison  Scaling factor  BFU (Bit function unit)  CFU (Check function unit)  Quantization  Conclusion

3. Introduction  (3,6) LDPC codes  Min-sum algorithm  Parity check matrix is generated by shifting

4. Algorithms Comparison AlgorithmAdditionFunctionShift Log-Sum-Product24(N-K)+7N12(N-K)-- Min-Sum24(N-K)+7N-- Mod. Min-sum24(N-K)+10N--6N

5. Comparison  N is codeword length  K is message bits  W c is column weight  W r is row weight  b is the number of the bits per message  S is the folding factor

6. Modified (Scaling)  Scaling factor of 0.8 is optimal for (3,6) LDPC code.  Scaling the soft info. not only compensates for loss of performance, but also results in superior performance.

7. Architecture  Channel value are stored in MEMInit n  Iteration result are stored in MEMCode mn  Message are stored in MEM mn

8. BFU  Scaling Factor: 0.5+0.25=0.75~=0.8  Can be modified for irregular LDPC code

9. BFU to Memories  S/M: split and merge unit  ADGB: Address generator for BFU

10. CFU  Out i =min{abs(in i ’ )|i ’ !=i}  Min: Output will be minimum input  SM->2 ’ s:Sign- magnitude to 2 ’ s complement presentation

11. CFU to Memories  S/M: split and merge unit.  ADGC: Address generator for CFU

12. Quantization  Sign + integral + fraction=1+2+2= 5 bits

13. Cost ResourceUsedUtilization Rate Slices1135279% 4-input LUTs2037471% Bonded IOBs10014% Block RAMs6668%

14. Throughput  N=1536 K=768, S=16, μ=20  1536/16=96BFUs768/16=48CFUs  For a LDPC code with the block length of 1536 bits, the decoder achieves a data rate of up to 127Mbps.

15. Conclusion  Overflow issue  Scaling factor & LLR  Simultaneously multiple access  Pack message  Reduce interconnection complexity  Partition parity check matrix