Soft decision Viterbi decoding with large constraint lengths
US5802116A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 4, 1996 |
| Grant date | Sep 1, 1998 |
| Priority date | — |
| Expiry date | Apr 4, 2016 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03M13/4153
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A method and apparatus for obtaining a soft symbol decoded output of a received signal by a two pass Viterbi operation. The technique is especially advantageous where the signal is convolutionally encoded with large constraint lengths. During the first pass, the error-correction co-processor (ECCP) is programmed for hard decoded output alone. After all the received symbol sets are hard-bit decoded, a second pass Viterbi operation is performed. Using the previously decoded hard bit to identify the most likely next state at an initial time instant, and initializing the present states at that initial time instant with pre-saved accumulated costs from the first pass Viterbi operation, branch metrics are computed for those state transitions leading to the most likely next state at that time instant. The accumulated cost values of the present states leading to the most likely next state are updated, and the absolute value of their difference is coded as a reliability of the hard decoded output corresponding to that time instant. The combination of the hard decoded output and the reliability obtained from the second pass Viterbi operation results in a soft symbol decoded output. At this p…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.