Orthogonal frequency division multiple access with carrier sense

• US 8,374,130 B2
• Filed: 01/25/2008
• Issued: 02/12/2013
• Est. Priority Date: 01/25/2008
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Hassan, Amer A., Sapek, Adam, Shen, Hui, Kuehnel, Thomas W., Wu, Deyun, Huitema, Christian
• Primary Examiner(s): Juntima, Nittaya
• Assistant Examiner(s): DUONG, CHRISTINE T
• Application Number:
  US12/020,212
• Publication Number:
  US 20090190535A1
• Time in Patent Office: 1,845 Days
• Field of Search: None
• US Class Current: 370/329
• CPC Class Codes: H04L 27/0006 Assessment of spectral gaps suitable for allocating digitally modulated signals, e.g. for carrier allocation in cognitive radio for spectrum sharing between different networks H04W16/14
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0037 Inter-user or inter-terminal allocation
• CPC Class Codes: H04L 5/0064 Rate requirement of the data, e.g. scalable bandwidth, data priority
• CPC Class Codes: H04L 5/0094 Indication of how sub-channels of the path are allocated
• CPC Class Codes: H04W 72/04 Wireless resource allocation
• CPC Class Codes: H04W 74/0808 using carrier sensing, e.g. carrier sense multiple access [CSMA]

Abstract

A communication system in which an access point and one or more devices communicating through the access point adaptively apply Orthogonal Frequency Division Multiple Access (OFDMA). The access point may assign orthogonal subcarriers to devices as in conventional OFDMA, but the access point senses activity on the subcarriers and selects subcarriers without activity for assignment. In an alternative approach, a device that is configured for OFDMA communication may receive a channel assignment from a device that does not support OFDMA. The OFDMA-capable device may use only a portion of the subcarriers in the assigned channel, which may be communicated to the non-OFDMA device. During the non-OFDMA device may then ignore unused subcarriers in error detection and correction to avoid incorrectly classifying communications as erroneous. Information about OFDMA capabilities, subcarrier assignments and subcarriers in use may be communicated as information elements in network control communications, such as beacons and probe messages.

Claims

1. A method of operating a wireless access point to exchange data with a plurality of devices, the data being exchanged wirelessly over a frequency range having a plurality of subcarriers, the method comprising:

sensing activity in at least a portion of a plurality of subcarriers, the sensing comprising, for each subcarrier in the portion;

at a first time, detecting whether a signal is being transmitted over the subcarrier; and

when a signal is detected at the first time, waiting a random interval and detecting whether a signal is being transmitted over the subcarrier;

generating a plurality of subcarrier assignments, each subcarrier assignment indicating a plurality of subcarriers and each of the subcarrier assignments being associated with a device of the plurality of devices, and each of the subcarrier assignments being selected based at least in part on whether a signal being transmitted was detected in a subcarrier of the plurality of subcarriers, and the subcarrier assignments of the plurality of subcarrier assignments being selected to distinguish communications with each of the plurality of devices from communications with others of the plurality of devices;

sending each of the plurality of subcarrier assignments to the associated device of the plurality of devices that is configured for selecting a portion of the sent subcarrier assignment; and

communicating with the associated device using the portion of the sent subcarrier assignment where correction error processing of further communications is modified at the wireless access point so that lack of information in subcarriers that are not in the portion of the sent subcarrier assignment will not be interpreted as an error.

2. The method of claim 1, wherein:

sending each of the subcarrier assignments comprises sending the subcarrier assignment in an information element embedded in a control communication from the access point.

3. The method of claim 2, further comprising, prior to generating a subcarrier assignment associated with a device, receiving from the device a request indicating a number of subcarriers.

4. The method of claim 3, wherein:

the subcarrier assignment associated with the device assigns a number of subcarriers; and

generating the subcarrier assignment comprises selecting the number of subcarriers based at least in part on the number of subcarriers indicated in the request received from the device.

5. The method of claim 4, wherein:

the device is a first device of the plurality of devices and the subcarrier assignment is a first subcarrier assignment, and the first device executes a first application;

the method further comprises;

receiving from a second device of the plurality of devices a second request indicating a second number of subcarriers prior to generating a second subcarrier assignment, the second subcarrier assignment being associated with the second device, and the second device executing a second application;

transmitting data from the first application in datagrams transmitted in subcarriers in the first subcarrier assignment; and

transmitting data from a second application in datagrams transmitted in subcarriers in the second subcarrier assignment, the datagrams containing data from the second application containing fewer bits than the datagrams containing data from the first application.

6. The method of claim 5, wherein the second application comprises a voice over IP application.

7. The method of claim 5, further comprising, prior to sending the second subcarrier assignment, receiving a control message comprising an information element indicating a request for a subcarrier assignment based on a type of the second application.

8. The method of claim 1, wherein generating a plurality of subcarrier assignments comprises:

dynamically selecting a subset of the subcarriers for use by each device of the plurality of devices to implement Orthogonal Frequency Division Multiple Access (OFDMA) by the plurality of devices, each selected subcarrier having sensed activity below a threshold.

9. The method of claim 1, wherein generating a plurality of subcarrier assignments comprises:

assigning, for each device of the plurality of devices, a predefined subset of the plurality of channels, each selected predefined group consisting essentially of subcarriers having sensed activity below a threshold.

19. The method of claim 1, wherein:

sending each of the plurality of subcarrier assignments to the associated device of the plurality of devices comprises sending the assignment in a control communication formatted in accordance with a Wi-Fi or WiMax protocol.

10. A computer storage device storing computer-executable instructions that, when executed by a computer adapted to communicate over a wireless network through an access point, cause the computer to perform a method comprising:

identifying a subcarrier requirement based on at least one application program installed on the computer;

negotiating a subcarrier assignment with the access point, the subcarrier assignment comprising an identification of a subset of a plurality of subcarriers of a wireless communication frequency range used by the wireless network, the negotiating comprising;

formatting an information element representing the subcarrier requirement;

communicating, to the access point, the information element in a first control communication, the first control communication being in a format of a protocol of the wireless network; and

receiving, from the access point, information defining the subcarrier assignment in at least a second control communication in the format of the protocol of the wireless network;

selecting a subset of the subcarrier assignment; and

wirelessly transmitting a communication over the wireless network using the subset of the subcarrier assignment, where the communication is configured for causing modified error correction processing of further communications received at the access point so that lack of information in subcarriers that are not in the subset of the subcarrier assignment will not be interpreted as an error.

11. The computer storage device of claim 10, wherein:

the computer storage medium further comprises computer-executable instructions for, when executed, performing steps, comprising receiving from the application program an indication of a bandwidth requirement, and

identifying a subcarrier requirement comprises identifying a subcarrier requirement based at least in part on the indication of the bandwidth requirement.

12. A method of operating a device to communicate wirelessly through an access point, the method comprising:

receiving a control communication from the access point;

determining whether an information element contained in the control communication indicates that the access point is capable of performing OFDMA; and

when the access point is not indicated to be capable of performing OFDMA;

selecting a portion of a plurality of subcarriers assigned to the device;

wirelessly communicating the selected portion to the access point; and

sending a second communication to the access point using the selected portion of the subcarriers where the sent second communication is configured for causing modified error correction processing at the access point so that lack of information in subcarriers that are not in the portion will not be interpreted as an error.

13. The method of claim 12, further comprising:

when the access point is indicated to be capable of performing OFDMA;

receiving an identification of a plurality of subcarriers in a control communication from the access point; and

sending communications through the access point using the plurality of the subcarriers.

14. The method of claim 13, wherein receiving the control communication comprises receiving a beacon formatted in accordance with a Wi-Fi protocol or WiMAX protocol.

15. The method of claim 14, wherein receiving the identification of the plurality of subcarriers comprises receiving the identification in the beacon.

16. The method of claim 15, wherein selecting the portion of the plurality of subcarriers comprises selecting a number of subcarriers based on an available power level of the device.

17. The method of claim 16, wherein communicating the selected portion to the access point comprises communicating the selected portion in an information element in a control communication.

18. The method of claim 12, wherein modifying error correction processing comprises altering operation of software that performs a cyclic redundancy check.