Scheme for operating a wireless station having directional antennas

• US 20060240780A1
• Filed: 03/27/2006
• Published: 10/26/2006
• Est. Priority Date: 04/08/2005
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Agre, Jonathan, Zhu, Chenxi, Nadeem, Tamer
• Granted Patent: US 7,630,343 B2
• Time in Patent Office: Days
• US Class Current: 455/63.400
• CPC Class Codes: H04W 16/28 using beam steering
• CPC Class Codes: H04W 74/0808 using carrier sensing, e.g. carrier sense multiple access [CSMA]
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

Disclosed is a wireless station having a receiver and a network allocation vector associated with each of a plurality of directional antennas. The receivers concurrently listen for frames from remote stations. When any receiver detects a frame from a remote station, the receiver activates its associated NAV. The station has one or more transmitters that can transmit using the antennas. While transmitting a signal using an antenna, the receivers associated with any non-transmitting antennas continue to listen for signals from remote stations. The station cancels any signals from the transmitting antenna received by the non-transmitting antennas. To perform the cancellation, the station performs a self-calibration procedure. The station can self-calibrate by either silencing neighboring stations or by inserting null tones into a transmitted calibration signal.

Claims

1. A method of operating a wireless station, comprising:

associating a first backoff timer with a first receiver associated with a first directional antenna;

associating a second backoff timer with a second receiver associated with a second directional antenna.

2. The method of claim 1, further comprising:

while operating the first receiver to monitor for transmissions from a remote wireless station, operating the second receiver to monitor for transmissions from a remote wireless station;

in response to the first receiver sensing a transmission from a remote station, activating the first backoff timer; and

in response to the second receiver sensing a transmission from a remote station, activating the second backoff timer.

3. The method of claim 1, further comprising,

in response to the first receiver sensing a transmission from a remote wireless station, storing data associating the first receiver with the sensed remote wireless station.

4. The method of claim 3, further comprising:

activating a third timer when the association is stored; and

after expiration of the timer, transmitting first search signals from the first antenna and second search signals from the second antenna.

5. The method of claim 1, further comprising:

in response to the first receiver sensing a transmission from a remote wireless station, storing data describing the quality of the signals received by the first receiver from the sensed remote wireless station.

6. The method of claim 5, further comprising:

selecting one of the antennas based on the stored data; and

transmitting signals from the selected antenna.

7. The method of claim 1, further comprising:

while operating the first receiver to detect a transmission from a remote wireless station, transmitting signals using the second antenna.

8. The method of claim 7, further comprising:

cancelling from any signals outputted by the first receiver, a cancellation amount corresponding to signals received by the first receiver from the second antenna.

9. The method of claim 8, wherein a parameter of the cancellation amount is determined by a method comprising:

transmitting training signals from the second antenna;

receiving the training signals at the first receiver; and

determining the parameter based on the value of the training signals received at the first receiver.

10. The method of claim 9, wherein the method for determining a parameter of the cancellation amount further comprises:

before transmitting the training signals, silencing any neighboring remote stations by transmitting channel reservation signals from all antennas.

11. The method of claim 9, wherein the method for determining a parameter of the cancellation amount further comprises:

including null tones in the training signals; and

determining whether the training signals received at the first receiver includes the null tones.

12. The method of claim 1, further comprising:

when a remote wireless station fails to respond to a frame transmitted from the first antenna, transmitting first search signals from the first antenna and second search signals from the second antenna.

13. An apparatus implementing any one of the methods according to claims 1-12.

14. A computer readable medium comprising a program causing a computer to implement any one of the methods according to claims 1-12.

15. A method of operating a wireless station, comprising:

associating a first receiver with a first directional antenna;

associating a second receiver with a second directional antenna.

transmitting training signals from the second antenna;

receiving the training signals at the first receiver; and

based on the training signals received at the first receiver, calculating a parameter of a value required to cancel from all signals outputted by the first receiver, a cancellation amount corresponding to signals received at the first receiver from the second antenna.

16. The method of claim 15, further comprising:

before transmitting the training signals, silencing any neighboring remote stations by transmitting a channel reservation signal from all antennas.

17. The method of claim 15, wherein:

the training signals include null tones; and

the station determines whether the training signals received at the first receiver includes the null tones.

18. A method of operating a wireless station, comprising:

receiving a symbol transmitted from a first wireless transmitter;

in response to a determination that the symbol lacks a null tone, determining that the transmission from the first wireless transmitter occurred concurrently with a transmission from a second wireless transmitter.