1. A method of managing multiple user access to a communication link comprising:
receiving user transmissions on a contention-based channel of the communication link that supports a maximum number of simultaneous user transmissions, wherein each user transmission includes a unique signature sequence;
detecting contention overloads where more than the maximum number of users simultaneously transmit on the contention-based channel;
identifying the users involved in a contention overload based on the unique signature sequences received from those users; and
scheduling retransmissions for one or more of the identified users on a scheduled channel of the communication link.
2. The method of claim 1, wherein scheduling retransmissions for one or more of the identified users on a scheduled channel of the communication link comprises determining retransmission schedule information for each of the one or more of the identified users, and sending the retransmission schedule information to the one or more of the identified users such that the one or more of the identified users operate at least temporarily as scheduled users on the scheduled channel.
3. The method of claim 1, further comprising dynamically allocating channel resources from the communication link for scheduled channel use responsive to detecting contention overloads.
4. The method of claim 1, further comprising statically allocating channel resources from the communication link for scheduled channel use.
5. The method of claim 1, further comprising defining the contention-based channel and the scheduled channel based on allocating channel resources from the communication link, said channel resources comprising at least one of frequency, time, and code channelization resources.
6. The method of claim 1, further comprising indicating whether scheduled retransmissions are to be full retransmissions or partial retransmissions that exploit incremental or redundant decoding.
7. The method of claim 1, wherein receiving user transmissions on a contention-based channel of the communication link comprises receiving user transmissions within synchronized transmission slots of the contention-based channel.
8. The method of claim 7, wherein detecting contention overloads comprises detecting contention overloads on a transmission slot basis, and wherein identifying the users involved in a contention overload comprises identifying users on a transmission slot basis.
9. The method of claim 8, wherein scheduling retransmissions comprises, for a given transmission slot in which a contention overload occurred, sending scheduling information to the users identified from the unique signature sequences that were received in the given transmission slot.
10. The method of claim 7, further comprising sending individualized acknowledgment information to the users that transmitted in a given transmission slot, if a contention overload did not occur in the given transmission slot, and otherwise sending individualized scheduling information to those users, at least to the extent that unique signature sequences were successfully received from the users that transmitted in the given transmission slot.
11. A base station for use in a wireless communication network and configured to manage multiple user access to a communication link supported by the base station, said base station comprising:
receiver circuits to receive user transmissions on a contention-based channel of the communication link that supports a maximum number of simultaneous user transmissions, wherein each user transmission includes a unique signature sequence; and
one or more processing circuits operatively associated with the receiver circuits and configured to detect contention overloads where more than the maximum number of users simultaneously transmit on the contention-based channel, identify the users involved in a contention overload based on the unique signature sequences received from those users, and schedule retransmissions for one or more of the identified users on a scheduled channel of the communication link.
12. The base station of claim 11, wherein the one or more processing circuits include a detection processor configured to detect contention overloads in cooperation with the receiver, an identification processor configured to identify the users involved in contention overloads from the unique signature sequences received during the contention overloads, and a scheduling processor configured to schedule retransmissions on the scheduled channel for the identified users.
13. The base station of claim 11, wherein the one or more processing circuits include a channel allocation processor configured to dynamically allocate channel resources from the communication link for scheduled channel use responsive to the detection of contention overloads.
14. The base station of claim 11, wherein the one or more processing circuits include a channel allocation processor that is configured to define the contention-based channel and the scheduled channel by allocating channel resources from the communication link, said channel resources comprising at least one of frequency, time, and code channelization resources.
15. The base station of claim 11, wherein the one or more processing circuits include a retransmission processor configured to control whether scheduled retransmissions are to be full retransmissions or partial retransmissions that exploit incremental or redundant decoding at the base station.
16. The base station of claim 11, wherein the base station is configured to receive the user transmissions on the contention-based channel within synchronized transmission slots.
17. The base station of claim 16, wherein the base station is configured to detect contention overloads on a transmission slot basis, and to identify the users involved in a contention overload on a transmission slot basis.
18. The base station of claim 17, wherein the base station is configured to schedule retransmissions in response to a contention overload occurring within a given transmission slot by sending scheduling information to the users identified from the unique signature sequences that were successfully received at the base station on the contention-based channel for that given transmission slot.
19. The base station of claim 16, wherein the base station is configured to send individualized acknowledgment information to the users that transmitted in a given transmission slot, if a contention overload did not occur in the given transmission slot, and otherwise send individualized scheduling information to those users for whom unique signature sequences were successfully received at the base station in the given transmission slot.
20. A method of managing multiple users sharing access to a communication link comprising:
defining a contention-based channel on the communication link;
defining a scheduled channel on the communication link;
receiving user transmissions on the contention-based channel from individual users transmitting autonomously on the contention-based channel, wherein each user transmission on the contention-based channel includes a unique signature sequence;
detecting a contention overload on the contention-based channel where too many users simultaneously transmit on the contention-based channel;
identifying the users involved in the contention overload based on successfully decoding the unique signature sequences received during the contention overload; and
sending retransmission schedule information to the identified users to control scheduled retransmissions by the identified users on the scheduled channel.
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 detection apparatus which detects a mark formed on a lower surface of a target object, the apparatus comprising:
a first detector which illuminates the mark from an upper surface side of the target object to detect an image of the illuminated mark;
a second detector which detects an upper surface position of the target object; and
a processor which obtains information indicating a focus position to focus on the mark in said first detector, based on the upper surface position detected by said second detector.
2. The apparatus according to claim 1, wherein said processor obtains the information based on the upper surface position detected by said second detector, a thickness of the target object, and a refractive index of the target object.
3. The apparatus according to claim 1, wherein said first detector illuminates the mark with infrared light.
4. The apparatus according to claim 1, wherein said second detector guides light to be obliquely incident on an upper surface of the target object, and detects the light reflected by the upper surface of the target object to detect the upper surface position of the target object.
5. The apparatus according to claim 1, wherein said second detector ejects a gas toward an upper surface of the target object, and detects a pressure of the gas rebounded by the upper surface of the target object to detect the upper surface position of the target object.
6. The apparatus according to claim 1, wherein said second detector detects an amount of charges generated when a voltage is applied onto an upper surface of the target object to detect the upper surface position of the target object.
7. An exposure apparatus which exposes a substrate to light, the apparatus comprising:
a detection apparatus which detects at least one of a mark formed on a lower surface of a substrate as a target object, and a mark arranged on a lower surface of a resist as a target object coated on the substrate;
a substrate stage which holds the substrate; and
a control unit which controls said substrate stage to set a focus state of the mark to fall within an allowable range,
said detection apparatus including:
a first detector which illuminates the mark from an upper surface side of the target object to detect an image of the illuminated mark;
a second detector which detects an upper surface position of the target object; and
a processor which obtains information indicating a focus position to focus on the mark in said first detector, based on the upper surface position detected by said second detector,
wherein the control unit controls the substrate stage based on the information obtained by said processor.
8. The apparatus according to claim 7, wherein said processor
obtains information indicating a focus position to focus on an image of a first mark, formed on a lower surface of a first substrate in a lot, in said first detector, based on an upper surface position of the first substrate in the lot detected by said second detector, and
obtains information indicating focus position to focus on images of second marks, formed on lower surfaces of a second substrate and subsequent substrates in the lot, in said first detector, based on the information indicating the focus position to focus on the image of the first mark in said first detector, and upper surface positions of the second substrate and the subsequent substrates detected by said second detector.
9. A method of manufacturing a device, the method comprising:
exposing a substrate to light using an exposure apparatus;
developing the exposed substrate; and
processing the developed substrate to manufacture the device,
the exposure apparatus including:
a detection apparatus which detects at least one of a mark formed on a lower surface of the substrate as a target object, and a mark arranged on a lower surface of a resist as a target object coated on the substrate;
a substrate stage which holds the substrate; and
a control unit which controls the substrate stage to set a focus state of the mark to fall within an allowable range,
the detection apparatus including:
a first detector which illuminates the mark from an upper surface side of the target object to detect an image of the illuminated mark;
a second detector which detects an upper surface position of the target object; and
a processor which obtains information indicating a focus position to focus on the mark in the first detector, based on the upper surface position detected by the second detector,
wherein the control unit controls the substrate stage based on the information obtained by said processor.
10. A detection apparatus which illuminates a mark, formed on a lower surface of a target object, from an upper surface side of the target object to detect an image of the illuminated mark, the apparatus comprising:
a control unit which controls to detect the mark in a first detection mode in which the mark is detected with a first detection accuracy while changing an interval between the detection apparatus and the mark at a first pitch, and a second detection mode in which the mark is detected with a second detection accuracy higher than the first detection accuracy while changing the interval at a second pitch smaller than the first pitch; and
a processor which obtains information indicating a focus position to focus on the mark in the second detection mode of the detection apparatus, based on the result of detecting the mark in the first detection mode,
wherein the control unit controls the substrate stage based on the information obtained by said processor.