1. A method comprising:
determining one or more factors to be applied to one or more likelihood ratio values of one or more current symbols received over one or more communication subcarriers, respectively, based on one or more sets of estimated error values, respectively, wherein said set of error values corresponds to a plurality of previous symbols received over said subcarrier.
2. The method of claim 1, wherein determining said factor comprises determining a factor to be applied to a likelihood ratio corresponding to a ratio between a probability that said current symbol represents a first transmitted symbol value, and a probability that said current symbol represents a second transmitted symbol value.
3. The method of claim 1, wherein determining said factor comprises determining said factor based on said set of estimated error values corresponding to said plurality of previous symbols received during a time period longer than a coherence time of a channel of said subcarrier.
4. The method of claim 1 comprising determining said factor based on a plurality of boost and hit values corresponding to a plurality of interferers over said subcarrier.
5. The method of claim 1, wherein determining said factor comprises determining said factor based on a channel estimation of said subcarrier.
6. The method of claim 1, wherein determining said one or more factors comprises determining a plurality of factors to be applied to a plurality of likelihood ratio values of a plurality of current symbols received over a plurality of communication subcarriers, respectively, said method comprising multiplying said plurality of likelihood ratio values by said plurality of factors, respectively, to generate a plurality of normalized ratio values.
7. The method of claim 1 comprising determining an average of two or more of said set of error values, wherein determining said factor comprises determining said factor based on said average.
8. The method of claim 1, wherein determining said factor comprises determining a factor corresponding to an estimated carrier-to-interference-and-noise-ratio of said current symbol.
9. An apparatus comprising:
one or more factor estimators to determine one or more factors to be applied to one or more likelihood ratio values of one or more current symbols received over one or more communication subcarriers, respectively, based on one or more sets of estimated error values, respectively, said set of error values corresponding to a plurality of previous symbols received over said subcarrier.
10. The apparatus of claim 9, wherein said likelihood ratio corresponds to a ratio between a probability that said current symbol represents a first transmitted symbol value, and a probability that said current symbol represents a second transmitted symbol value.
11. The apparatus of claim 9, wherein said set of estimated error values comprises error values corresponding to said plurality of previous symbols received during a time period longer than a coherence time of a channel of said subcarrier.
12. The apparatus of claim 9, wherein said factor estimator is able to determine said factor based on a plurality of boost and hit values corresponding to a plurality of interferers over said subcarrier.
13. The apparatus of claim 9, wherein said factor estimator is able to determine said factor based on a channel estimation of said subcarrier.
14. The apparatus of claim 9, wherein said one or more factor estimators comprise a plurality of factor estimators to determine a plurality of factors to be applied to a plurality of likelihood ratio values of a plurality of current symbols received over a plurality of communication subcarriers, respectively, said apparatus comprising a plurality of normalizers to generate a plurality of normalized values based on said plurality of likelihood ratio values and said plurality of factors, respectively.
15. The apparatus of claim 9, wherein said factor estimator is able to determine an average of two or more of said set of error values, and to determine said factor based on said average.
16. The apparatus of claim 9, wherein said factor corresponds to an estimated carrier-to-interference-and-noise-ratio of said current symbol.
17. A wireless transmission system comprising:
a wireless station including:
at least one dipole antenna to receive one or more current symbols over one or more communication subcarriers, respectively; and
one or more factor estimators to determine one or more factors to be applied to one or more likelihood ratio value of said one or more current symbols, respectively, based on one or more sets of estimated error values, respectively, said set of error values corresponding to a plurality of previous symbols received over said subcarrier.
18. The wireless transmission system of claim 17, wherein said set of estimated error values comprises error values corresponding to said plurality of previous symbols received during a time period longer than a coherence time of a channel of said subcarrier.
19. A method comprising:
determining a likelihood ratio value of a current symbol received by a communication device over a communication subcarrier based on a probability that said current symbol includes interference caused by one or more other communication devices transmitting over said subcarrier.
20. The method of claim 19, wherein determining said likelihood ratio value comprises determining a likelihood ratio value corresponding to a ratio between a probability that said current symbol represents a first transmitted symbol value, and a probability that said current symbol represents a second transmitted symbol value.
21. The method of claim 19, wherein determining said likelihood ratio value comprises determining said likelihood ratio value based on a combination of probabilities of a plurality of interference cases and a respective plurality of probability distribution functions corresponding to the interference over said subcarrier in said plurality of interference-cases.
22. The method of claim 21, wherein said plurality of interference cases represent a plurality of respective combinations of interference values corresponding to said one or more other stations, said interference values comprising at least one of hit indicator values and boost values.
23. The method of claim 21, wherein one or more of said distribution functions comprise one or more Gaussian distribution functions having one or more variances corresponding to carrier-to-interference-and-noise-ratio variances of one or more of said plurality of cases, respectively.
24. The method of claim 21, wherein determining said likelihood ratio value comprises determining said likelihood ratio value based on a predetermined approximation function representing said combination.
25. The method of claim 24, wherein determining said likelihood ratio value based on said approximation function comprises determining said likelihood ratio value based on a piecewise linear function including one or more linear portions.
26. An apparatus comprising:
a generator to generate a likelihood ratio value of a current symbol received by a station over a communication subcarrier based on a probability that said current symbol includes interference caused by one or more other stations transmitting over said subcarrier.
27. The apparatus of claim 26, wherein said likelihood ratio value comprises a likelihood ratio value corresponding to a ratio between a probability that said current symbol represents a first transmitted symbol value, and a probability that said current symbol represents a second transmitted symbol value.
28. The apparatus of claim 26, wherein said generator is able to determine said likelihood ratio value based on a combination of probabilities of a plurality of interference cases and a respective plurality of probability distribution functions corresponding to the interference over said subcarrier in said plurality of interference cases.
29. The apparatus of claim 28, wherein said plurality of interference cases represent a plurality of respective combinations of interference values corresponding to said one or more other stations, said interference values comprising at least one of hit indicator values and boost values.
30. The apparatus of claim 28, wherein one or more of said distribution functions comprise one or more Gaussian distribution functions having one or more variances corresponding to carrier-to-interference-and-noise-ratio variances of one or more of said plurality of cases, respectively.
31. The apparatus of claim 28, wherein said generator is able to determine said likelihood ratio value based on a predetermined approximation function representing said combination.
32. The apparatus of claim 31, wherein said approximation function comprises a piecewise linear function including one or more linear portions.
33. A wireless transmission system comprising:
a wireless station including:
at least one dipole antenna to receive a current symbol over a communication subcarrier; and
a generator to generate a likelihood ratio value of said current symbol based on a probability that said current symbol includes interference caused by one or more other stations transmitting over said subcarrier.
34. The wireless transmission system of claim 33, wherein said generator is able to determine said likelihood ratio value based on a combination of probabilities of a plurality of interference cases and a respective plurality of probability distribution functions corresponding to the interference over said subcarrier in said plurality of interference cases.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A half-tone-phase-shift type photomask comprising:
a field region which attenuates exposure light; and
a pattern region which transmits the exposure light, wherein exposure light passed through said field region and exposure light passed through said pattern region are substantially in phase, a rim region which transmits exposure light is provided outside of and provided to come in contact with said pattern region, and exposure light passed through said rim region has substantially an opposite phase relative to the phase of exposure light passed through said field region and exposure light passed through said pattern region.
2. The photomask according to claim 1, wherein
said rim region has a line width which is in the range of from 16 to \u2153 of the line width of said pattern region.
3. A photomask manufacturing method comprising the steps of:
forming, on a glass substrate, a so-called half tone film which attenuates exposure light and inverts the phase of exposure light passed therethrough with respect to the phase of exposure light which did not pass through the film;
forming a half tone pattern by forming a resist pattern on said half tone film and etching away the half tone film within a resist opening;
etching said glass substrate within said resist opening to a depth which causes exposure light passed through the etched opening portion to have substantially the same phase as that of exposure light passed through said half tone film;
widening the opening portion of said half tone pattern by isotopic etching; and
removing said resist pattern.
4. A semiconductor device manufacturing method comprising forming a semiconductor device using:
a half-tone-phase-shift type photomask including a field region which attenuates exposure light and a pattern region which transmits the exposure light wherein exposure light passed through said field region and exposure light passed through said pattern region are substantially in phase, a rim region which transmits exposure light is provided outside of and provided to come in contact with said pattern region, and exposure light passed through said rim region has substantially an opposite phase relative to the phase of exposure light passed through said field region and exposure light passed through said pattern region.
5. The semiconductor device manufacturing method according to claim 4 further comprising forming hole patterns using said half tone phase shift type photomask.
6. The semiconductor device manufacturing method according to claim 5 further comprising performing patterning of a contact hole layer for establishing connection with substrate active layer and patterning of a first via hole layer for establishing connection between a gate electrode and a wiring layer using said half-tone-phase-shift type photomask.
7. The semiconductor device manufacturing method according to claim 5 further comprising the steps of:
forming a resist hole pattern having an opening larger than a desired dimension; and
adjusting said resist hole pattern to a desired dimension by resist shrink method, wherein
said forming the resist hole pattern is performed using said half-tone-phase-shift type photomask.
8. The semiconductor device manufacturing method according to claim 7, wherein
said resist shrink method is performed by heat treatment.
9. The semiconductor device manufacturing method according to claim 7, wherein
said resist shrink method comprises the steps of forming a coated film, performing heat treatment and removing said coated film.
10. The semiconductor device manufacturing method according to claim 9, wherein
said coated film is a heat shrinkable film.
11. The semiconductor device manufacturing method according to claim 9, wherein
said coated film has a property of mixing with a resist.
12. The semiconductor device manufacturing method according to claim 9, wherein
said coated film is insolubilized when subjected to heat treatment in the presence of oxygen.
13. The semiconductor device manufacturing method according to claim 4, wherein
said exposure light is an oblique-incident light on the photomask.
14. The semiconductor device manufacturing method according to claim 4, further comprising forming a semiconductor device using:
a half tone phase shift mask in which exposure light passed through the field region and exposure light passed through the pattern region are substantially in opposite phases.