Robust coexistence service for mitigating wireless network interference

• US 7,664,465 B2
• Filed: 11/04/2005
• Issued: 02/16/2010
• Est. Priority Date: 11/04/2005
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Poncini, Victoria, Madhavan, Poovanpilli G., Shen, Hui, Abhishek, Abhishek, Ruan, Jiandong, Duong, Francis
• Primary Examiner(s): Milord; Marceau
• Application Number:
  US11/267,458
• Publication Number:
  US 20070105501A1
• Time in Patent Office: 1,565 Days
• Field of Search: 455/67.13, 455/67.11, 455/420, 455/63.1, 455/434, 455/41.2, 455/450, 455/452.1, 455/296, 455/63.4, 455/226.1, 370/252, 370/338, 370/465, 370/331, 375/346
• US Class Current: 455/63.1
• CPC Class Codes: H04B 17/24 with feedback of measurements to the transmitter
• CPC Class Codes: H04L 1/0002 by adapting the transmission rate
• CPC Class Codes: H04L 1/0007 by modifying the frame length
• CPC Class Codes: H04L 1/0015 characterised by the adaptation strategy
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/08 by repeating transmission, e.g. Verdan system H04L1/1858 and H04L1/189 take precedence
• CPC Class Codes: H04W 52/243 taking into account interferences

Abstract

Described is a determination of whether interference in a wireless network has achieved a threshold level that adversely impacts communication bandwidth. If so, action is taken to mitigate the effects of the interference and thereby improve the bandwidth. The action that is taken may be in the form of at least one mitigation solution, including mitigating by packet fragmentation, mitigating by changing the wireless network'"'"'s current operating frequency, mitigating by changing a power level, mitigating by transmit dodging, and/or mitigating by pre-selecting at least one transmission criterion based on an observed pattern. A framework is provided to coordinate mitigation of interference-related problems, and includes an interferer decision mechanism that receives RF interference related-data and evaluates the interference data against a threshold. Mitigation is employed when the threshold is achieved on the current operating frequency.

Claims

1. At least one computer storage medium having computer-executable instructions, which when executed by a processor of a computer system perform steps for determining whether interference has achieved a threshold level in a wireless network, wherein the wireless network comprises a serving basic service set (BSS) that includes a first device for receiving wireless signals, and a second device for transmitting wireless signals, the steps comprising:

receiving classified data from one or more classifiers, the classified data describing interference that is detectable within the wireless network;

determining, by the processor, whether the interference is being generated by a non-WLAN interferer or by a WLAN interferer that is part of a different BSS operating in the same channel;

if it is determined that the interferer is a non-WLAN interferer, performing the following;

the processor generating a noise floor for the first device by subtracting a required signal to noise ratio at each data rate from a receive sensitivity of the first device at the corresponding data rate; and

comparing the interference level to the noise floor such that if the interference level is below the noise floor, the interference is ignored, otherwise the interference is addressed;

if it is determined that the interferer is a WLAN interferer that is part of a different BSS, performing the following;

the processor sending a command to each wireless node in the serving BSS, the command causing each wireless node to cease transmitting;

the processor sending a command to a sniffer to cause the sniffer to sniff the channel to detect the presence of the WLAN interferer;

the processor receiving a radio signal strength indicator (RSSI) from the different BSS that includes the WLAN interferer;

comparing the RSSI of the different BSS to the RSSI of the serving BSS such that if the RSSI of the different BSS is a threshold level below the RSSI of the serving BSS,

the interference is ignored, otherwise the interference is addressed;

addressing the interference by performing one of fragmenting packets of a signal transmitted from the second device to the first device, or by performing instantaneous frequency selection.

2. The at least one computer storage medium of claim 1 wherein prior to comparing the RSSI of the different BSS to the RSSI of the serving BSS, the RSSI of the different BSS and the RSSI of the serving BSS are averaged over a specified time to generate average values for each RSSI that are used for the comparison.

3. The at least one computer storage medium of claim 1 wherein the threshold level is 20 dB.

4. The at least one computer storage medium of claim 1 wherein the interference is addressed by performing fragmenting and wherein fragmenting comprises:

determining a minimum fragmentation size that may be used to achieve a minimum transmission rate;

determining whether the minimum fragmentation size is lower than a current fragmentation size, and if so, commencing to send packets that are fragmented at the minimum fragmentation size.

5. The at least one computer storage medium of claim 1 wherein instantaneous frequency selection is performed by:

sending a message to the first device that indicates a new channel and a switch time, the message causing the first device to commence receiving data on the new channel at the switch time.

6. The at least one computer storage medium of claim 5 wherein the message is sent as a high priority 802.11 packet through the channel.

7. The at least one computer storage medium of claim 5 wherein the message is sent at both the highest and lowest physical rates.

8. The at least one computer storage medium of claim 5 wherein the new channel is selected from a list of channels based on the potential bandwidth provided by each channel.

9. A method performed by a processor of a computing device in a wireless network for determining whether interference has achieved a threshold level in the wireless network, wherein the wireless network comprises a serving basic service set (BSS) that includes a first device for receiving wireless signals, and a second device for transmitting wireless signals, the steps comprising:

receiving classified data from one or more classifiers, the classified data describing interference that is detectable within the wireless network;

determining, by the processor, whether the interference is being generated by a non-WLAN interferer or by a WLAN interferer that is part of a different BSS operating in the same channel;

if it is determined that the interferer is a non-WLAN interferer, performing the following;

the processor generating a noise floor for the first device by subtracting a required signal to noise ratio at each data rate from a receive sensitivity of the first device at the corresponding data rate; and

comparing the interference level to the noise floor such that if the interference level is below the noise floor, the interference is ignored, otherwise the interference is addressed;

if it is determined that the interferer is a WLAN interferer that is part of a different BSS, performing the following;

the processor sending a command to each wireless node in the serving BSS, the command causing each wireless node to cease transmitting;

the processor sending a command to a sniffer to cause the sniffer to sniff the channel to detect the presence of the WLAN interferer;

the processor receiving a radio signal strength indicator (RSSI) from the different BSS that includes the WLAN interferer;

comparing the RSSI of the different BSS to the RSSI of the serving BSS such that if the RSSI of the different BSS is a threshold level below the RSSI of the serving BSS,

the interference is ignored, otherwise the interference is addressed;

addressing the interference by performing one of fragmenting packets of a signal transmitted from the second device to the first device, or by performing instantaneous frequency selection.

10. The method of claim 9 wherein prior to comparing the RSSI of the different BSS to the RSSI of the serving BSS, the RSSI of the different BSS and the RSSI of the serving BSS are averaged over a specified time to generate average values for each RSSI that are used for the comparison.

11. The method of claim 9 wherein the threshold level is 20 dB.

12. The method of claim 9 wherein the interference is addressed by performing fragmenting and wherein fragmenting comprises:

determining a minimum fragmentation size that may be used to achieve a minimum transmission rate;

determining whether the minimum fragmentation size is lower than a current fragmentation size, and if so, commencing to send packets that are fragmented at the minimum fragmentation size.

13. The method of claim 12 further comprising detecting that the interferencecomprises a periodic signal having a short period, and in response, performing the fragmentation.

14. The method of claim 12 wherein it is determined that the minimum fragmentation size is not lower than the current fragmentation size and in response, performing instantaneous frequency selection.

15. The method of claim 9 wherein instantaneous frequency selection is performed by:

sending a message to the first device that indicates a timestamp, a new channel, and a switch time, wherein the timestamp indicates the time when the message is transmitted, the message causing the first device to commence receiving data on the new channel at the switch time.

16. The method of claim 15 wherein the message is sent as a high priority 802.11 packet through the channel.

17. The method of claim 15 wherein the message is sent at both the highest and lowest physical rates.

18. The method of claim 15 wherein the new channel is selected from a list of channels based on the potential bandwidth provided by each channel.

19. The method of claim 15 wherein the first device switches to the new channel within 100 milliseconds of the message being transmitted.