Method and system for a low-complexity soft-output MIMO detection
View Patent ↗An approach for Soft-output K-Best MIMO detection comprises computing an estimated symbol vector and Log-Likelihood Ratio (LLR) values for transmitted bits. The approach includes a relevant discarded paths selection process, a last-stage on-demand expansion process, and a relaxed LLR computation process. The relevant discarded paths selection process includes analyzing the K-Best paths and discarded paths at each intermediate tree level and selecting only those discarded paths for further processing that will help in LLR computation for at least one of the transmitted bits. The last-stage on-demand expansion process includes expanding K paths at the tree level 2N T −1 (N T =number of transmit antennas) on-demand to only 2K−1 lowest Partial Euclidean Distance (PED) paths at last tree level 2N T . The relaxed LLR computation scheme includes approximating LLR computations by assuming that discarded path PED is greater than or equal K-Best path PED.
1. A method for soft-output K-Best MIMO detection, the method comprising:
receiving a vector associated with data bits transmitted over a multiple-input multiple output (MIMO) system, the MIMO system having N transmit antennas, N being an integer greater than unity;
processing the received vector using a plurality of processing elements, the processing elements being arranged in a plurality of levels and connected in series; and
computing Log-likelihood Ratio (LLR) values for the transmitted data bits; and
expanding K paths at a level 2N−1 to 2K−1 paths at a last level 2N, wherein K is an integer greater than one.
2. The method of claim 1 , wherein the plurality of levels comprises 2N levels.
3. The method of claim 1 further comprising:
retaining selected discarded paths from intermediate levels within the 2N levels;
computing partial Euclidean distance (PED) values in the intermediate levels utilizing the retained selected discarded paths; and
sorting the PED values.
4. The method of claim 1 further comprising a relevant discarded paths selection process, the relevant discarded paths selection process comprising:
examining paths at the intermediate levels; and
selecting discarded paths for computing the LLR values.
5. The method of claim 1 , wherein the 2K−1 paths have the lowest PED values among K*√Q paths, Q being an integer of a constellation symbol size.
6. The method of claim 1 , wherein the 2K−1 paths are sorted in the order of ascending PED values.
7. The method of claim 1 further comprising a relaxed LLR computation process, the relaxed LLR computation process comprising:
filling a PED table using K paths having the lowest LLR values in the last level; and
filling empty entries in the PED table with discarded paths in the ascending order of PED values.
8. A soft-output K-Best multiple input multiple output (MIMO) detector, the detector comprising:
an input terminal configured to receive a vector associated with transmitted bits over a multiple-input multiple output (MIMO) system, the MIMO system having N transmit antennas, N being an integer greater than unity;
a plurality of processing elements connected in series and arranged in a plurality of levels, the processing elements being configured to compute Log-likelihood Ratio (LLR) values for the transmitted bits and expand K paths at a level 2N−1 to 2K−1 paths at a last level 2N, wherein K is an integer greater than one.
9. The soft-output K-Best MIMO detector of claim 8 , wherein the plurality of levels comprises 2N levels.
10. The soft-output K-Best MIMO detector of claim 8 further comprising an output terminal having two output ports configured to output the computed LLR values of the transmitted bits in parallel.
11. The soft-output K-Best MIMO detector of claim 8 , wherein the plurality of processing elements is configured to:
retain selected discarded paths from intermediate levels within the plurality of levels;
compute partial Euclidean distance (PED) values in the intermediate levels utilizing the retained selected discarded paths; and
sort the PED values.
12. The soft-output K-Best MIMO detector of claim 8 , wherein the plurality of processing elements is configured to:
examine paths at intermediate levels within the plurality of levels; and
select discarded paths for computing LLR values.
13. The soft-output K-Best MIMO detector of claim 8 , wherein the 2K−1 paths have the lowest PED values among K*√Q paths, Q being a size of a constellation symbol.
14. The soft-output K-Best MIMO detector of claim 8 , wherein the 2K−1 paths are sorted in the order of ascending PED values.
15. The soft-output K-Best MIMO detector of claim 8 , wherein the plurality of processing elements is configured to:
fill a PED table using K best paths in a last level; and
fill empty entries in the PED table with discarded paths in the ascending order of PED values;
wherein the K best paths comprise the lowest LLR values in the last level.