1. An iterative frequency and phase compensation apparatus for an OFDM communication system including a OFDM demodulator and an iterative decoder, comprising:
a first classifying means for classifying OFDM demodulated symbol sequences by each subcarrier wave according to a location in a frame of a corresponding data symbol;
a soft-decision calculating means for calculating a soft-decision value of a data symbol using a soft-decision reliability obtained from iterative decoding performed by the iterative decoder;
a second classifying means for receiving the soft-decision values from the soft-decision calculating means and classifying the received soft-decision values by a carrier wave;
a frequency estimating means for estimating a residual frequency error of each carrier wave for symbols of each carrier wave inputted from the first classifying unit using the soft-decision value of each carrier wave inputted from the second classifying unit;
a phase estimating means for estimating an average residual phase error of carrier waves for symbols of each carrier wave inputted from the first classifying unit using the soft-decision value of each carrier wave inputted from the second classifying unit;
a frequency and phase compensating means for compensating frequencies and phases for input symbols of each carrier wave using the estimated frequency error and the estimated phase error; and
a buffering means for temporally storing frequency and phase compensated symbols from the frequency and phase compensating means to provide the frequency and phase compensated symbols to the first classifying means.
2. The iterative frequency and phase compensation apparatus as recited in claim 1, further comprising a symbol sorting means for rearranging the frequency and phase compensated symbols according to the order of original code symbol sequence.
3. The iterative frequency and phase compensation apparatus as recited in claim 1, further comprising:
a parallelserial converting means for serializing symbols demodulated by the OFDM demodulator; and
a symbol sequence switching means for providing symbols outputted from the parallelserial converting means to the first classifying means for a first decoding stage, and providing symbols stored in the buffering means to the first classifying means from a second decoding stage.
4. The iterative frequency and phase compensation apparatus as recited in claim 3, wherein the soft-decision calculating means calculates a soft-decision value of a symbol based on soft-decision reliability obtained from a predetermined decoding stage using an equation as:
BPSK
\ue89e
:
\ue89e
\ue89e
a
l
\ue8a0
(
m
)
=
tanh
\ue8a0
(
L
l
\ue8a0
(
m
)
2
)
QPSK
\ue89e
:
\ue89e
\ue89e
a
l
\ue8a0
(
m
)
=
tanh
\ue8a0
(
L
l
,
in
\ue8a0
(
m
)
2
)
+
tanh
\ue8a0
(
L
l
,
qudri
\ue8a0
(
m
)
2
)
where Ll(m) denotes a log likelihood ratio of a mth data symbol when a subcarrier wave is BPSK modulation, and Ll,in(m) and Ll,quadri(m) and denote soft-decision values of a real part and an imaginary part when a subcarrier wave is a QPSK modulation.
5. The iterative frequency and phase compensation apparatus as recited in claim 3, wherein the frequency estimating means calculates an average of estimated frequency errors of each subcarrier wave and uses the calculated average as a final estimated frequency error.
6. The iterative frequency and phase compensation apparatus as recited in claim 5, wherein the frequency estimating means estimates a residual frequency error of a subcarrier wave by calculating an average of phase variation of symbols of each carrier wave.
7. The iterative frequency and phase compensation apparatus as recited in claim 5, wherein the frequency estimating means estimates a residual frequency error of a subcarrier wave by obtaining a phase after adding the results of conjugate multiplication between symbols.
8. The iterative frequency and phase compensation apparatus as recited in claim 5, wherein the frequency estimating means estimates a residual frequency error of a subcarrier wave by obtaining a phase difference after adding all front symbol and rear symbols separated at a predetermined distance.
9. An iterative frequency and phase compensation method for an OFDM communication system including an OFDM demodulator and an iterative decoder, the method comprising the steps of:
a) calculating a soft-decision value using soft-decision reliability obtained at a lth decoding stage;
b) arranging symbols of each subcarrier wave according to a location in an OFDM frame of a corresponding data symbol;
c) estimating a frequency error and a phase error for the arranged symbol of each subcarrier wave using the calculated soft-decision value;
d) compensating frequencies and phases of all code symbols in a corresponding carrier wave using the estimated frequency error and the estimated phase error;
e) rearranging updated sample values of each frequency and phase compensated code symbol according to an order of original code symbol sequence and inputting the rearranged sample values to the iterative decoder; and
f) performing the steps a) to e) until the number of decoding stage reaches at a predetermined iterative number.
10. The iterative frequency and phase compensation method recited in claim 9, wherein in the step a), a soft-decision value of a symbol is calculated based on soft-decision reliability obtained from a predetermined decoding stage using an equation as:
BPSK
\ue89e
:
\ue89e
\ue89e
a
l
\ue8a0
(
m
)
=
tanh
\ue8a0
(
L
l
\ue8a0
(
m
)
2
)
QPSK
\ue89e
:
\ue89e
\ue89e
a
l
\ue8a0
(
m
)
=
tanh
\ue8a0
(
L
l
,
in
\ue8a0
(
m
)
2
)
+
tanh
\ue8a0
(
L
l
,
qudri
\ue8a0
(
m
)
2
)
where Ll(m) denotes a log likelihood ratio of a mth data symbol when a subcarrier wave is BPSK modulation, and Ll,in(m) and Ll,quadri(m) denote soft-decision values of a real part and an imaginary part when a subcarrier wave is a QPSK modulation.
11. The iterative frequency and phase compensation method recited in claim 9, wherein in the step c), a residual frequency error of a subcarrier wave is estimated by calculating an average of phase variation of symbols of each carrier wave, and an average value of the estimated frequency errors of each subcarrier waves are used as a final estimated frequency error.
12. The iterative frequency and phase compensation method recited in claim 9, wherein in the step c), a residual frequency error of a subcarrier wave is estimated by obtaining a phase after adding the results of conjugate multiplication between symbols, and an average value of the estimated frequency errors of each subcarrier waves are used as a final estimated frequency error.
13. The iterative frequency and phase compensation method recited in claim 9, wherein in the step c), a residual frequency error of a subcarrier wave is estimated by obtaining a phase difference after adding all front symbol and rear symbols separated at a predetermined distance, and an average value of the estimated frequency errors of each subcarrier waves are used as a final estimated frequency error.
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 method of controlling an actuator for actuating a variable compression ratio mechanism that causes a compression ratio of an engine to vary, the method comprising:
setting a compression ratio corresponding to a state of the engine;
actuating the actuator so that the compression ratio is set;
determining an amount of mechanical work necessary for a unit actuation of the actuator;
determining that the engine is in a state limiting actuation of the actuator when the mechanical work necessary for a unit actuation of the actuator exceeds a predetermined non-zero value; and
limiting actuation of the actuator when the engine is in the state limiting actuation of the actuator.
2. The method according to claim 1, wherein the engine state limiting actuation of the actuator is a combustion state of the engine.
3. The method according to claim 2, further comprising inhibiting combustion in the engine during actuation of the actuator.
4. The method according to claim 2, further comprising actuating the actuator before combustion in an engine starting event.
5. The method according to claim 1, wherein the variable compression ratio mechanism includes:
a first link pivotably coupled to a piston;
a second link pivotably coupled to the first link and pivotably fitted to a crankshaft;
a control shaft, rotatably supported by a cylinder block, and parallel to the crankshaft, that includes an eccentric axis portion eccentric relative to a rotational axial center of the control shaft; and
a third link that is rotatably coupled to the second link by a coupling pin and that is pivotable about a pivotal axis center coincident with the eccentric axis portion of the control shaft,
wherein the engine state limiting actuation of the actuator is a combustion state of the engine under a condition where an action line of a load acting between the third link and the eccentric axis portion is spaced apart from a rotation center of the control shaft at a predetermined distance or larger.
6. The method according to claim 5, wherein the condition where the action line of the load acting between the third link and the eccentric axis portion is spaced apart from a rotation center of the control shaft at a predetermined distance or larger, is satisfied when the compression ratio of the engine is within a range of an intermediate compression ratio between a low compression ratio and a high compression ratio.
7. The method according to claim 5, further comprising inhibiting combustion of the engine during actuation of the actuator under the condition where the action line of the load acting between the third link and the eccentric axis portion is spaced apart from a rotation center of the control shaft at a predetermined distance or larger.
8. The method according to claim 5, further comprising actuating the actuator before combustion in an engine starting event.
9. The method according to claim 8, further comprising:
determining whether or not to vary a compression ratio in the engine starting event; and
when varying the compression ratio, setting a cranking time period in the engine starting event to be longer than a cranking time period in a case where the compression ratio is maintained.
10. The method according to claim 8, further comprising:
determining whether or not to vary a compression ratio in the engine starting event; and
when varying the compression ratio, setting a combustion starting timing in the engine starting event to be delayed relative to a combustion starting timing in a case where the compression ratio is maintained.
11. The method according to claim 1, further comprising reducing an amount of intake air during varying of the compression ratio of the engine.
12. The method according to claim 1, further comprising:
detecting an alcohol content of gasoline being used in the engine; and
setting the compression ratio of the engine to be higher as the alcohol content is higher.
13. The method according to claim 1, further comprising stopping the engine by setting the compression ratio to a high compression ratio when stopping the engine.
14. The method according to claim 1, further comprising stopping the engine by setting the compression ratio to an intermediate compression ratio between a high compression ratio and a low compression ratio when stopping the engine.
15. The method according to claim 13, wherein the engine state limiting the actuation of the actuator is a state other than one of accelerator-off and throttle-off states.
16. The method according to claim 13, wherein the engine state limiting the actuation of the actuator is either a state other than one of accelerator-off and throttle-off states or a pre-warmup state of the engine.
17. The method according to claim 15, further comprising:
determining whether or not an acceleration demand is present; and
reducing an amount of intake air when the acceleration demand is present during varying of the compression ratio.
18. The method according to claim 14, wherein the engine state limiting the actuation of the actuator is a state other than one of accelerator-off and throttle-off states, the method further comprising:
fixing a compression ratio being adapted during combustion of the engine to the intermediate compression ratio; and
varying the compression ratio by actuating the actuator in one of accelerator-off and throttle-off states after combustion of the engine is effected in the state where the compression ratio is fixed to the intermediate compression ratio.
19. The method according to claim 14, wherein the engine state limiting the actuation of the actuator is either a state other than one of accelerator-off and throttle-off states or a pre-warmup state of the engine, the method further comprising:
fixing a compression ratio being adapted during combustion of the engine to the intermediate compression ratio; and
varying the compression ratio by actuating the actuator in one of accelerator-off and throttle-off states after combustion of the engine is effected in the state where the compression ratio is fixed to the intermediate compression ratio.
20. The method according to claim 18, further comprising:
determining whether an acceleration demand is present or not; and
reducing an amount of intake air when the acceleration demand is present during varying of the compression ratio.
21. The method according to claim 12, further comprising:
determining whether or not an abnormality has occurred in the detection of the alcohol content; and
detecting the presence or absence of knocking occurring in a combustion chamber of the engine,
wherein, when an abnormality has occurred in the detection of the alcohol content, the compression ratio is varied in accordance with the detected presence or absence of knocking.
22. A variable compression ratio engine, comprising:
means for setting a compression ratio corresponding to a state of the engine;
means for actuating an actuator connected to a variable compression ratio mechanism so that the compression ratio is set;
means for determining an amount of mechanical work necessary for a unit actuation of the actuator;
means for determining that the engine is in a state limiting actuation of the actuator when the mechanical work necessary for a unit actuation of the actuator exceeds a predetermined non-zero value; and
means for limiting the actuation of the actuator when the engine is in the state limiting actuation of the actuator.
23. A variable compression ratio engine, comprising:
a piston disposed in a cylinder bore and constituting a combustion chamber;
a variable compression ratio mechanism connected to the piston and causing a top dead center position of the piston to vary;
an actuator connected to the variable compression ratio mechanism to actuate the variable compression ratio mechanism; and
a controller connected to the actuator to control an engine state and the actuator,
wherein the controller performs operations including:
setting a compression ratio corresponding to a state of the engine;
actuating the actuator so that the compression ratio is set;
determining an amount of mechanical work necessary for a unit actuation of the actuator;
determining that the engine is in a state limiting actuation of the actuator when the mechanical work necessary for a unit actuation of the actuator exceeds a predetermined non-zero value; and
limiting actuation of the actuator when the engine is in the state limiting actuation of the actuator.
24. The variable compression ratio engine according to claim 23, wherein the variable compression ratio mechanism includes:
a first link pivotably coupled to the piston;
a second link pivotably coupled to the first link and pivotably fitted to a crankshaft;
a control shaft, rotatably supported by a cylinder block, and parallel to the crankshaft, that includes an eccentric axis portion eccentric relative to a rotational axial center of the control shaft; and
a third link that is rotatably coupled to the second link by a coupling pin and that is pivotable about a pivotal axis center coincident with the eccentric axis portion of the control shaft.
25. The variable compression ratio engine according to claim 24, wherein the engine state limiting actuation of the actuator is a combustion state of the engine.
26. The variable compression ratio engine according to claim 24, wherein the engine state limiting actuation of the actuator is a combustion state of the engine under a condition where an action line of a load acting between the third link and the eccentric axis portion is spaced apart from a rotation center of the control shaft at a predetermined distance or larger.
27. The variable compression ratio engine according to claim 26, wherein the condition where the action line of the load acting between the third link and the eccentric axis portion is spaced apart from a rotation center of the control shaft at a predetermined distance or larger, is satisfied when the compression ratio of the engine is within a range of an intermediate compression ratio between a low compression ratio and a high compression ratio.
28. The variable compression ratio engine according to claim 23, the controller further performs an operation of reducing an amount of intake air during varying of the compression ratio of the engine.
29. The variable compression ratio engine according to claim 23, wherein the controller further performs an operation of stopping the engine by setting the compression ratio to a high compression ratio when stopping the engine.
30. The variable compression ratio engine according to claim 23, wherein the controller further performs an operation of stopping the engine by setting the compression ratio to an intermediate compression ratio between a high compression ratio and a low compression ratio when stopping the engine.
31. The variable compression ratio engine according to claim 29, wherein the engine state limiting actuation of the actuator is a state other than one of accelerator-off and throttle-off states.
32. The variable compression ratio engine according to claim 29, wherein the engine state limiting actuation of the actuator is either a state other than one of accelerator-off and throttle-off states or a pre-warmup state of the engine.
33. The variable compression ratio engine according to claim 31, wherein the controller further performs operations of:
determining whether or not an acceleration demand is present; and
reducing an amount of intake air when the acceleration demand is present during varying of the compression ratio.
34. The variable compression ratio engine according to claim 30, wherein
the engine state limiting actuation of the actuator is a state other than one of accelerator-off and throttle-off states,
the engine further comprises means for maintaining the compression ratio at the intermediate compression ratio, and
the controller further performs operations of:
fixing a compression ratio being adapted during combustion of the engine to the intermediate compression ratio; and
varying the compression ratio by actuating the actuator in one of accelerator-off and throttle-off states after combustion of the engine is effected in the state where the compression ratio is fixed to the intermediate compression ratio.
35. The variable compression ratio engine according to claim 30, wherein
the engine state limiting actuation of the actuator is a state other than one of accelerator-off and throttle-off states,
the engine further comprises a lock mechanism for maintaining the compression ratio at the intermediate compression ratio, and
the controller further performs operations of:
fixing a compression ratio being adapted during combustion of the engine to the intermediate compression ratio; and
varying the compression ratio by actuating the actuator in one of accelerator-off and throttle-off states after combustion of the engine is effected in the state where the compression ratio is fixed to the intermediate compression ratio.
36. The variable compression ratio engine according to claim 34, wherein the controller further performs operations of:
determining whether or not an acceleration demand is present; and
reducing an amount of intake air when the acceleration demand is present during varying of the compression ratio.