Metric updater for maximum likelihood decoder
US4015238A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 24, 1975 |
| Grant date | Mar 29, 1977 |
| Priority date | — |
| Expiry date | Nov 24, 1995 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L1/0054
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
In a convolutional code decoder, a current received input corresponds to a last data state of a received sequence. Path metrics, respective correlations of the received sequence to each of a limited number of possible sequences, are determined to choose the "correct" possible sequence. Decoding then proceeds by known means. The current input addresses "look-up" memories, each associated with a possible input data state and providing a "branch metric address" output. "Update" memories, each associated with one of the data states, are each addressed by path metrics of prior sequences which can enter its associated state and by one "branch metric address." In functional effect, each "update" memory adds a separate branch metric to update each prior path metric leading into each state. Path metrics for the limited number of possible sequences are thus provided. An indication of which updated path metric is larger for each state and its value are output from each "update" memory. The largest of the updated path metrics provided by the memories identifies the "correct" possible sequence.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.