Fine-grained channel access in wireless networks

• US 9,445,432 B2
• Filed: 06/25/2010
• Issued: 09/13/2016
• Est. Priority Date: 06/25/2010
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Inventors: Tan, Kun, Zhang, Jiansong, Zhang, Yongguang, Fang, Ji
• Primary Examiner(s): SINKANTARAKORN, PAWARIS
• Application Number:
  US12/824,104
• Publication Number:
  US 20110317633A1
• Time in Patent Office: 2,272 Days
• Field of Search: 370276-281, 370/329, 370/338
• US Class Current: 1/1
• CPC Class Codes: H04L 27/2607 Cyclic extensions
• CPC Class Codes: H04W 72/00 Local resource management
• CPC Class Codes: H04W 72/044 based on the type of the allocated resource
• CPC Class Codes: H04W 74/08 Non-scheduled access, e.g. ALOHA hybrid access H04W74/02
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

A fine-grained channel access system and method to facilitate fine-grained channel access in a high-data rate wide-band wireless local-area network (WLAN). Embodiments of the system and method divide an entire wireless channel into proper size subchannels commensurate with the physical layer data rate and typical frame size. Once the subchannels are defined, each node on the WLAN contends independently for each of the fine-grained subchannels. A first orthogonal frequency-division multiplexing (OFDM) technique is used to signal an access point on the WLAN that the node desires one or more of the subchannels. A second OFDM technique (which is different from the first OFDM technique) is used for data transmission. Sometimes there is contention between nodes that want the same subchannel. The access point resolves any contention between the nodes using a frequency domain contention technique that includes a frequency domain backoff technique.

Claims

1. A wireless access point comprising:

at least one processing unit; and

at least one computer storage media storing computer readable instructions which, when executed by the at least one processing unit, cause the at least one processing unit to;

detect a plurality of requests from a plurality of wireless nodes in a wireless local-area network to communicate over requested subchannels of a wireless channel having multiple subchannels, wherein the requests are detected by;

comparing energy in subcarriers of the multiple subchannels to a threshold,

identifying individual subcarriers for which the energy exceeds the threshold, and

designating individual subchannels having the individual subcarriers for which the energy exceeds the threshold as the requested subchannels;

assign different requested subchannels to different wireless nodes; and

broadcast individual subchannel assignments to the different wireless nodes.

2. The wireless access point of claim 1, wherein the computer readable instructions cause the at least one processing unit to:

detect the requests as amplitude-modulated signals on the individual subcarriers of the requested subchannels.

3. The wireless access point of claim 2, wherein the amplitude-modulated signals are binary amplitude-modulated signals.

4. The wireless access point of claim 1, wherein the computer readable instructions cause the at least one processing unit to:

assign a particular subchannel of the requested subchannels to a first wireless node instead of a second wireless node, wherein the first wireless node requested the particular subchannel using a first subcarrier of the particular subchannel and the second wireless node requested the particular subchannel using a second subcarrier of the particular subchannel; and

broadcast a corresponding subchannel assignment of the particular subchannel to the first wireless node by transmitting on the first subcarrier that was used by the first wireless node to request the particular subchannel.

5. The wireless access point of claim 1, wherein the computer readable instructions cause the at least one processing unit to:

broadcast the individual channel assignments by transmitting a multi-tone clear-to-send signal to the different wireless nodes.

6. The wireless access point of claim 5, wherein the computer readable instructions cause the at least one processing unit to:

perform amplitude modulation of at least some of the subcarriers of the requested subchannels to generate the multi-tone clear-to-send signal.

7. The wireless access point of claim 6, wherein the amplitude modulation is binary amplitude modulation.

8. The wireless access point of claim 1, wherein the wireless channel is a 20 megahertz channel.

9. The wireless access point of claim 8, wherein at least two of the requested subchannels are orthogonal to one another.

10. The wireless access point of claim 1, wherein the computer readable instructions cause the at least one processing unit to:

use a first guard time and a second guard time to handle symbol time misalignment of asynchronous signaling and data transmission over the requested subchannels, where the first guard time and the second guard time are different from each other.

11. A wireless communication device comprising:

at least one processing unit; and

at least one computer storage media storing computer readable instructions which, when executed by the at least one processing unit, cause the at least one processing unit to;

detect a first request from a first contending wireless node to communicate over a wireless subchannel in a wireless local area network, the first request comprising a first amplitude-modulated signal on a first subcarrier of the wireless subchannel;

detect a second request from a second contending wireless node to communicate over the wireless subchannel in the wireless local area network, the second request comprising a second amplitude-modulated signal on a second subcarrier of the wireless subchannel; and

resolve contention between the first contending wireless node and the second contending wireless node by;

designating the first contending wireless node as a winning node and designating the second contending wireless node as a losing node; and

broadcasting a subchannel assignment granting the wireless subchannel to the first contending wireless node.

12. The wireless communication device of claim 11, wherein the computer readable instructions cause the at least one processing unit to:

assign another wireless subchannel to a third contending wireless node; and

concurrently communicate data with both the first contending wireless node and the third contending wireless node using the wireless subchannel and the another wireless subchannel, respectively,

wherein the wireless subchannel and the another wireless subchannel are part of the same wireless channel.

13. The wireless communication device of claim 11, wherein the computer readable instructions cause the at least one processing unit to:

determine that another wireless subchannel is not requested when other subcarriers of the wireless subchannel do not include other amplitude-modulated signals,

wherein the wireless subchannel and the another wireless subchannel are part of the same wireless channel.

14. The wireless communication device of claim 11, wherein the computer readable instructions cause the at least one processing unit to:

broadcast the subchannel assignment by performing amplitude modulation on the first subcarrier of the wireless subchannel.

15. The wireless communication device of claim 11, embodied as a wireless access point.

16. A method comprising:

performing frequency-domain detection of a plurality of tones indicating requests by a plurality of wireless nodes to communicate using a plurality of requested subchannels of a wireless channel, the requests being detected by identifying the tones in corresponding subcarriers of the requested subchannels;

assigning different requested subchannels to different wireless nodes of the plurality of wireless nodes, the different requested subchannels including a first requested subchannel assigned to a first wireless node for communicating in a wireless local area network and a second requested subchannel assigned to a second wireless node for communicating in the wireless local area network; and

receiving first data from the first wireless node over the first requested subchannel and second data from the second wireless node over the second requested subchannel.

17. The method of claim 16, wherein the assigning comprises selecting the first wireless node as a winning node and designating a third wireless node as a losing node for the first requested subchannel.

18. The method of claim 17, wherein the first requested subchannel comprises a set of non-contiguous subcarriers.

19. The method of claim 17, wherein the requests include a first tone transmitted by the winning node on a first subcarrier of the first requested subchannel and another tone transmitted by the losing node on a second subcarrier of the first requested subchannel.

20. The method of claim 19, further comprising:

detecting the requests by comparing energy on the first subcarrier and the second subcarrier of the first requested subchannel to a threshold.