System and method for signal demodulation
AssigneeEricsson Inc.
InventorGregory E. Bottomley
Life of this patent
Estimating the term…
Abstract
An improved system and method for reducing the computational complexity of metric updating, such as within a maximum likelihood-sequence-estimation (MLSE) detector, used in, for example, demodulating a received signal subject to intersymbol interference. Complexity is reduced by eliminating the computation of common portions of a series of path metrics and perform a full computation of the next state after the optimum path to the next state has been determined. Alternatively, a primary path metric is determined and key components of secondary path metrics are examined to determine secondary path viability. If the secondary path is viable, the full secondary path metric is formed and compared to the primary path metric, which is replaced if the secondary is better.
Claims18
A method for demodulating a symbol sequence comprising the steps of:
- receiving a portion of a transmission signal, forming a received signal, said received signal having a received signal level associated therewith and including a plurality of symbols, said plurality of symbols forming a symbol stream;
- sampling said received signal at symbol period intervals, forming a received symbol stream, said received symbol stream having a present state and a plurality of previous states associated therewith;
- calculating, from a plurality of metrics formed from at least one previous state of said received symbol stream, a multiplicity of partial candidate metrics;
- eliminating, from each of said multiplicity of partial candidate metrics, at least one common term therein;
- calculating respective current state metrics from each of said multiplicity of partial candidate metrics without a common operator;
- selecting a given one of said partial candidate metrics without said common operator, said selected given one of said partial candidate metrics without said common operator being a winning partial candidate metric;
- recalculating said given partial candidate metric with said common operator;
- and
- forming a new full path metric, wherein said full path metric includes said winning partial candidate metric.
A sequence detector for detecting a symbol sequence within a received symbol stream, said sequence detector comprising:
- first calculation means for calculating, from a plurality of metrics formed from at least one previous state of said received symbol stream, a multiplicity of partial candidate metrics;
- elimination means for eliminating, from each of said multiplicity of partial candidate metrics, at least one common term therein;
- second calculation means for calculating respective current state metrics from each of said multiplicity of partial candidate metrics without a common operator;
- selection means for selecting a given one of said partial candidate metrics without said common operator, said selected given one of said partial candidate metrics without said common operator being a winning partial candidate metric;
- recalculation means for recalculating said given partial candidate metric with said common operator;
- and
- formation means for forming a new full path metric, wherein said full path metric includes said winning partial candidate metric.
Dependencies are inferred from the claim text.