Using one or more past channel estimates for adjusting parameters, sensing object presence, or allowing association

1. A method of obtaining channel estimation responses, comprising:

sending, by a transmitter, a first sounding sequence and a second sounding sequence to a receiver;

receiving, by the transmitter, a first channel estimation response from a receiver responsive to the first sounding sequence, and a second channel estimation response from the receiver responsive to the second sounding sequence;

detecting, by the transmitter, based at least on the first channel estimation response and the second channel estimation response, responsive to determining that a change in at least one characteristic of a channel between the transmitter and the receiver occurred; and

determining, by the transmitter, whether to update a configuration of the transmitter based on the detection.

2. The method of claim 1 , wherein one or both of the first sounding sequence or the second sounding sequence comprises a null data packet announcement (NDPA) frame followed by a null data packet (NDP).

3. The method of claim 1 , further comprising identifying a time difference associated with the first channel estimation response and the second channel estimation response.

4. The method of claim 3 , further comprising determining an estimated velocity of the receiver.

5. The method of claim 3 , further comprising determining a rate of change in the at least one characteristic of the channel based at least on the identified time difference.

6. The method of claim 1 , wherein determining whether to update the configuration of the transmitter based on the detection comprises determining, by the transmitter, a next time instant for sending a third sounding sequence based on the detection.

7. The method of claim 1 , wherein determining whether to update the configuration of the transmitter based on the detection comprises determining, by the transmitter, a next time instant for sending a third sounding sequence based on an extent of change in the at least one characteristic of the channel.

8. The method of claim 1 , further comprising updating the configuration of the transmitter, the updated configuration pertaining to modulation and coding scheme support for the receiver.

9. The method of claim 1 , wherein determining whether to update the configuration of the transmitter based on the detection comprises determining, by the transmitter, whether to operate in a mode for supporting a single receiver or a single spatial stream, or a mode for supporting multiple receivers or multiple spatial streams.

10. The method of claim 1 , further comprising determining a characteristic of the receiver's motion.

11. The method of claim 1 , further comprising detecting a presence of a new device using the at least one characteristic of the channel.

12. The method of claim 1 , further comprising correlating or comparing, by the transmitter, data in at least one of the first channel estimation response and the second channel estimation response, with one or more electromagnetic patterns in the transmitter, to identify one or more of: a type of motion and a location of the receiver.

13. The method of claim 1 , further comprising sending, by the transmitter, the first sounding sequence and the second sounding sequence to the receiver as part of a training phase for acquiring channel estimation feedback based on at least one of: the receiver occupying a plurality of locations and performing certain types of motion.

14. The method of claim 1 , further comprising determining, by the transmitter, an electromagnetic pattern of the transmitter by measurement or modeling based on one or more of: a receiver location and receiver motion.

15. The method of claim 1 , further comprising determining a location of the receiver.

16. The method of claim 1 , further comprising determining at least one of the following: whether to establish a multi-input multi-output (MIMO) association with the receiver, and a quality of service to accord to the receiver, based at least on the location of the receiver.

17. A method of detecting a person or object, the method comprising:

comparing a first channel estimation response to a first sounding sequence provided at a first time and a second channel estimation response to a second sounding sequence provided at a second time, the first channel estimation response and the second channel estimation response received from a stationary device;

determining, according to the comparison, that a degree of change to a channel exceeds a predefined Doppler threshold; and

determining, responsive to the determination that the degree of change to the channel exceeds the predefined Doppler threshold, that movement of at least one person or object has occurred in a predetermined area.

18. The method of claim 17 wherein a transmitter provides the first sounding sequence and the second sounding sequence and receives the first channel estimation response and the second channel estimation response from a receiver of the stationary device, and the transmitter performs the detecting.

19. A method of communication, the method comprising:

receiving a first channel feedback from a wireless device; and

correlating the first channel feedback to electro-magnetic patterns of an access point; and

determining, according to the correlation, whether the wireless device is in an allowed location or has been moved according to a particular path of motion for granting association.

20. The method of claim 19 , wherein the wireless device is allowed to associate or is provided a particular quality of service depending upon being in the allowed location.