1. A fluid-flow machine having a main flow path, in which at least one row of blades is arranged, and a shroud embedded in a cavity of a component, with the component and the blades being in rotary movement relative to each other, wherein
the shroud, as referred to a longitudinal section of the fluid-flow machine, is at least partly embedded in the component, forming a cavity connecting to the main flow path,
the shroud, as referred to an axial direction of the fluid-flow machine is arranged between two reference points (A) and (B) at a periphery of the main flow path of the fluid-flow machine,
the reference point (A) is established by at least one of a base point of a trailing edge of a blade row located upstream of the shroud and by a peripheral point of the main flow path which is located upstream of a leading edge of the shrouded blade row by 25 percent of an axial extension of the shrouded blade row,
the reference point (B) is established by at least one of a base point of a leading edge of the blade row located downstream of the shroud and by a peripheral point of the main flow path which is located downstream of a trailing edge of the shrouded blade row by 25 percent of the axial extension of the shrouded blade row,
the shroud projects beyond a rectilinear connection of the reference points (A) and (B) into the flow path in at least one location of the circumference and in at least one of the areas of the leading or trailing edge of the appertaining blade row such that the shroud protrusion provides for a sweep of the effective confinement of the main flow path and curving of the flow lines at the periphery of the main flow path in the area of at least one of the openings by which the main flow path connects to the cavity around the shroud.
2. The fluid-flow machine of claim 1, wherein a protruding inflow edge of the shroud is radiused for improved flow control.
3. The fluid-flow machine of claim 2, wherein the protruding inflow edge of the shroud includes a nose for stagnation point formation and improved flow control.
4. The fluid-flow machine of claim 3, wherein the protruding inflow edge of the shroud is provided with an overlap for stagnation point formation and improved flow control such that, as viewed in the main flow direction, a forward confining wall of the cavity is not orientated axially, but at least locally obliquely in an upstream direction, with an oblique shape of a rear of the shroud in this area accordingly providing for a duct between the shroud and the surrounding component which is at least one of inclined against a radial direction and curved.
5. The fluid-flow machine of claim 1, wherein an outflow edge of the shroud is protruding and essentially blunted.
6. The fluid-flow machine of claim 1, wherein an outflow edge of the shroud is protruding and radiused for improved flow control.
7. The fluid-flow machine of claim 1, wherein an outflow edge of the shroud is protruding and essentially sharp-edged.
8. The fluid-flow machine of claim 1, wherein an outflow edge of the shroud is protruding and provided with a nose for improved flow control.
9. The fluid-flow machine of claim 1, wherein an outflow edge of the shroud is provided with an overlap such that, as viewed in the main flow direction, a rearward confining wall of the cavity is not orientated radially, but at least locally obliquely in a downstream direction, with an oblique shape of a rear of the shroud in this area accordingly providing for a duct between the shroud and the surrounding component which is at least one of inclined against the radial direction and curved.
10. The fluid-flow machine of claim 1, and further including a shroud protrusion in a leading-edge area and a shroud protrusion in a trailing-edge area of the blade.
11. The fluid-flow machine of claim 1, wherein a shroud contour facing the main flow path extends essentially rectilinearly in at least one partial section between an inflow and an outflow edge of the shroud.
12. The fluid-flow machine of claim 1, wherein a shroud contour facing the main flow path extends essentially in a concave manner in at least one partial section between an inflow and an outflow edge of the shroud.
13. The fluid-flow machine of claim 1, wherein a shroud contour facing the main flow path extends essentially in a convex manner in at least one partial section between an inflow and an outflow edge of the shroud.
14. The fluid-flow machine of claim 1, wherein an inflow edge of the shroud and also an outflow edge of the shroud are protruding and overlap the component to form an essentially V-shaped cavity around the shroud.
15. The fluid-flow machine of claim 1, wherein a shroud protrusion, as well as a shape of a shroud edge concerned, vary periodically in a circumferential direction of a blade row to which the shroud belongs.
16. The fluid-flow machine of claim 15, wherein a period (P) of the circumferential variation of the shroud protrusion and the shroud edge shape are in integer relation to a blade spacing (S) of the shrouded blade row and the following equation applies:
n\xb7P=S
17. The fluid-flow machine of claim 1, wherein the shroud includes a protrusion d, defined as a distance between the reference line A-B and a parallelly extending tangent to a location of maximum shroud protrusion, and related to an annulus width W at a blade edge (leading edge (VK) or trailing edge (HK)) nearest to the location of maximum shroud protrusion, is more than 1 percent and the following equations apply:
dVKWVK>0.01 resp.
dHKWHK>0.01,
with the shroud protrusion in the leading edge area dVK being established directly on the blade leading edge and the shroud protrusion in the trailing edge area dHK being established directly on the blade trailing edge, if the location of the maximum shroud protrusion within the blade row is between leading and trailing edge.
18. The fluid-flow machine of claim 17, and further including a free section (XVK) of the shroud provided upstream of the blade leading edge whose length in relation to an axial extension of the blade row at a periphery of the main flow path (leading edge (VK) to trailing edge (HK)) is at least 7 percent.
19. The fluid-flow machine of claim 17, and further including a free section (XHK) of the shroud provided downstream of the blade trailing edge whose length in relation to the axial extension of the blade row at the periphery of the main flow path (leading edge (VK) to trailing edge (HK)) is at least 7 percent.
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 for processing information in a communication system, comprising:
partitioning a control channel used for transmitting control information into a plurality of subchannels, each subchannel being operated at a specific data rate;
selecting, for each of one or more user terminals, one of the subchannels to be used for transmitting control information from an access point to the respective user terminal, based on one or more selection criteria; and
transmitting control information from the access point to a particular user terminal on a particular subchannel selected for the respective user terminal.
2. The method of claim 1 wherein the control information is transmitted in a segment of a data frame specifically allocated for the control channel.
3. The method of claim 1 wherein each subchannel is associated with a specific set of operating parameters.
4. The method of claim 3 wherein the operating parameters are selected from the group consisting of a code rate, a modulation scheme, and a signal-to-noise ratio (SNR).
5. The method of claim 1 wherein the plurality of subchannels are transmitted sequentially in an order from a subchannel with a lowest data rate to a subchannel with a highest data rate.
6. The method of claim 5 wherein a subchannel that is transmitted first in the plurality of subchannels includes a field to indicate whether other subchannels are also being transmitted.
7. The method of claim 6 wherein the field comprises a plurality of bits each of which corresponds to a particular subchannel and is used to indicate whether the corresponding subchannel is present in the segment allocated for transmitting control information.
8. The method of claim 1 wherein the one or more selection criteria are selected from the group consisting of a first criterion corresponding to a link quality associated with the respective user terminal, a second criterion corresponding to quality of service requirements associated with the respective terminal, and a third criterion corresponding to a subchannel preference indicated by the respective terminal.
9. A method for processing information in a communication system, comprising:
segregating a control channel into a plurality of subchannels each of which being operable at a specific data rate;
transmitting control information including resource allocation information from an access point to a user terminal on particular subchannel of the plurality subchannels selected for the user terminal, based on one or more selection criteria; and
decoding, at the user terminal, one or more subchannels of the plurality of subchannels to obtain control information designated for the user terminal.
10. The method of claim 9 wherein decoding comprises:
performing a decoding procedure to decode the one or more subchannels, starting with a subchannel operated at a lowest data rate, until at least one of a plurality of conditions is met.
11. The method of claim 10 further comprising:
terminating the decoding procedure if one of the plurality of conditions is met.
12. The method of claim 11 wherein the plurality of conditions includes a first condition indicating a failure to correctly decode one of the plurality of subchannels.
13. The method of claim 11 wherein the plurality of conditions includes a second condition indicating that control information designated for the user terminal has been obtained from one of the plurality of subchannels.
14. The method of claim 11 wherein the plurality of conditions includes a third condition indicating that all subchannels have been processed.
15. The method of claim 10 wherein performing a decoding procedure comprises:
determining whether information transmitted on a subchannel has been correctly received, based on a quality metric corresponding to the respective subchannel.
16. The method of claim 15 wherein the quality metric comprises a cyclic redundancy check (CRC).
17. The method of claim 10 wherein performing a decoding procedure comprises:
determining whether control information designated for the user terminal is present in the respective subchannel, based on an identifier associated with the user terminal.
18. The method of claim 17 wherein the identifier comprises a Medium Access Control (MAC) identifier.
19. The method of claim 9 wherein the one or more selection criteria are selected from the group consisting of a first criterion corresponding to operating conditions of the respective user terminal, a second criterion corresponding to quality of service requirements associated with the respective terminal, and a third criterion corresponding to a subchannel preference indicated by the respective terminal.
20. An apparatus for processing information in a communication system, comprising:
means for partitioning a control channel that is used for transmitting control information into a plurality of subchannels, each subchannel being operated at a specific data rate;
means for selecting, for each of one or more user terminals, one of the subchannels to be used for transmitting control information from an access point to the respective user terminal, based on one or more selection criteria; and
means for transmitting control information from the access point to a particular user terminal on a particular subchannel selected for the respective user terminal.
21. The apparatus of claim 20 wherein each subchannel is associated with a distinct set of operating parameters including a code rate, a modulation scheme, and an SNR.
22. The apparatus of claim 20 wherein the plurality of subchannels are transmitted sequentially in an order from a subchannel with a lowest data rate to a subchannel with a highest data rate.
23. The apparatus of claim 22 wherein a subchannel that is transmitted first in the plurality of subchannels includes a field to indicate whether other subchannels are also being transmitted.
24. The apparatus of claim 20 wherein the one or more selection criteria including a first criterion corresponding to a link quality associated with the respective user terminal, a second criterion corresponding to quality of service requirements associated with the respective terminal, and a third criterion corresponding to a subchannel preference indicated by the respective terminal.
25. An apparatus for processing information in a communication system, comprising:
means for segregating a control channel into a plurality of subchannels each of which being operable at a specific data rate;
means for transmitting control information including resource allocation information from an access point to a user terminal on particular subchannel of the plurality subchannels selected for the user terminal, based on one or more selection criteria; and
means for decoding, at the user terminal, one or more subchannels of the plurality of subchannels to obtain control information designated for the user terminal.
26. The apparatus of claim 25 wherein means for decoding comprises:
means for performing a decoding procedure to decode the one or more subchannels, starting with a subchannel operated at a lowest data rate, until at least one of a plurality of conditions is met.
27. The apparatus of claim 26 wherein the plurality of conditions includes a first condition indicating a failure to correctly decode one of the plurality of subchannels, a second condition indicating that control information designated for the user terminal has been obtained from one of the plurality of subchannels, and a third condition indicating that all subchannels have been processed.
28. The apparatus of claim 25 wherein means for performing a decoding procedure comprises:
means for determining whether information transmitted on a subchannel has been correctly received, based on a quality metric corresponding to the respective subchannel; and
means for determining whether control information designated for the user terminal is present in the respective subchannel, based on an identifier associated with the user terminal.
29. The apparatus of claim 25 wherein the one or more selection criteria including a first criterion corresponding to operating conditions of the respective user terminal, a second criterion corresponding to quality of service requirements associated with the respective terminal, and a third criterion corresponding to a subchannel preference indicated by the respective terminal.
30. An apparatus for processing information in a communication system, comprising:
a controller configured to select one of a plurality of control subchannels to send control information to a user terminal, based on one or more selection criteria, each subchannel being operable at a specific data rate; and
a transmitter to send the control information designated for the user terminal on the subchannel selected for the user terminal.
31. The apparatus of claim 30 wherein each subchannel is associated with a specific set of operating parameters, including a data rate at which control information is transmitted, a code rate, a modulation scheme, and an SNR.
32. The apparatus of claim 30 wherein the plurality of subchannels are transmitted sequentially in an order from a subchannel with a lowest data rate to a subchannel with a highest data rate.
33. The apparatus of claim 30 wherein the one or more selection criteria including a first criterion corresponding to a link quality associated with the respective user terminal, a second criterion corresponding to quality of service requirements associated with the respective terminal, and a third criterion corresponding to a subchannel preference indicated by the respective terminal.
34. An apparatus for processing information in a wireless communication system, comprising:
a receiver to receive information on one or more control subchannels each of which being operated at a specific data rate; and
a decoder to decode the one or more control subchannels to obtain control information designated for a particular user terminal, starting with a subchannel operated at a lowest data rate, until at least one of a plurality of conditions is met.
35. The apparatus of claim 34 wherein the plurality of conditions includes a first condition indicating a failure to correctly decode one of the plurality of subchannels, a second condition indicating that control information designated for the user terminal has been obtained from one of the plurality of subchannels, and a third condition indicating that all subchannels have been processed.
36. The apparatus of claim 34 wherein the decoder is configured to determine whether information transmitted on a subchannel has been correctly received, based on a quality metric corresponding to the respective subchannel and to determine whether control information designated, for the user terminal is present in the respective subchannel, based on an identifier associated with the user terminal.
37. A machine-readable medium comprising instructions which, when executed by a machine, cause the machine to perform operations including:
partitioning a control channel that is used for transmitting control information into a plurality of subchannels, each subchannel being operated at a specific data rate;
selecting, for each of one or more user terminals, one of the subchannels to be used for transmitting control information from an access point to the respective user terminal, based on one or more selection criteria; and
transmitting control information from the access point to a particular user terminal on a particular subchannel selected for the respective user terminal.
38. The machine-readable medium of claim 37 wherein each subchannel is associated with a set of operating parameters, including a data rate at which control information is transmitted, a code rate, a modulation scheme, and an SNR.
39. The machine-readable medium of claim 37 wherein the one or more selection criteria including a first criterion corresponding to a link quality associated with the respective user terminal, a second criterion corresponding to quality of service requirements associated with the respective terminal, and a third criterion corresponding to a subchannel preference indicated by the respective terminal.
40. A machine-readable medium comprising instructions which, when executed by a machine, cause the machine to perform operations including:
receiving information on one or more control subchannels each of which being operated at a specific data rate; and
decoding the one or more control subchannels to obtain control information designated for a particular user terminal, starting with a subchannel operated at a lowest data rate, until at least one of a plurality of conditions is met.
41. The machine-readable medium of claim 40 wherein the plurality of conditions includes a first condition indicating a failure to correctly decode one of the plurality of subchannels, a second condition indicating that control information designated for the user terminal has been obtained from one of the plurality of subchannels, and a third condition indicating that all subchannels have been processed.
42. The machine-readable medium of claim 40 wherein the decoder is configured to determine whether information transmitted on a subchannel has been correctly received, based on a quality metric corresponding to the respective subchannel and to determine whether control information designated for the user terminal is present in the respective subchannel, based on an identifier associated with the user terminal.
43. A method for processing information in a system, comprising:
receiving information on one or more control subchannels each of which being operated at a specific data rate; and
decoding the one or more control subchannels to obtain control information designated for a particular user terminal, starting with a subchannel operated at a lowest data rate, until at least one of a plurality of conditions is met.
44. The method of claim 43 wherein the plurality of conditions includes a first condition indicating a failure to correctly decode one of the plurality of subchannels, a second condition indicating that control information designated for the user terminal has been obtained from one of the plurality of subchannels, and a third condition indicating that all subchannels have been processed.
45. The method of claim 43 wherein decoding comprises:
determining whether information transmitted on a subchannel has been correctly received, based on a quality metric corresponding to the respective subchannel; and
determining whether control information designated for the user terminal is present in the respective subchannel, based on an identifier associated with the user terminal.