Link adaptation in a communication network

1. A method for link adaptation in a network, the method comprising:

generating, at a first network interface device, a first control field to include a first subfield indicating a request for link quality information, wherein generating the first control field comprises setting a second subfield of the first control field to a value indicating that the first control field is to be interpreted according to a first communication protocol and not according to a second communication protocol, wherein the second communication protocol does not permit a request for link quality information in a communication frame i) that is not a sounding frame, and ii) that is not a frame that announces a null data packet is to follow the communication frame;

generating, at the first network interface device, a first communication frame having a first header, wherein

the first header includes the first control field,

the first communication frame i) is not a sounding frame, and ii) is not a frame that announces a null data packet is to follow the communication frame; and

causing, with the first network interface device, the first communication frame to be transmitted in order to prompt a communication device that conforms to the first communication protocol to send link quality information.

2. A method according to claim 1 , wherein generating the first control field further comprises setting a third subfield to indicate whether the first communication frame is a single user frame or a multi user frame, and

wherein generating the first communication frame comprises i) generating the first communication frame as a single user frame when the third subfield is set to indicate a single user frame, and ii) generating the first communication frame as a multi user frame when the third subfield is set to indicate a multi user frame.

3. A method according to claim 1 , wherein the header is a media access control (MAC) header of a MAC protocol data unit.

4. A system comprising:

a first network interface device configured to

generate a first control field to include a first subfield indicating a request for link quality information;

set a second subfield of the first control field to a value indicating that the first control field is to be interpreted according to a first communication protocol and not according to a second communication protocol, wherein the second communication protocol does not permit a request for link quality information in a communication frame i) that is not a sounding frame, and ii) that is not a frame that announces a null data packet is to follow the communication frame; and

generate a first communication frame having a first header, wherein

the first header includes the first control field, and

the first communication frame i) is not a sounding frame, and ii) is not a frame that announces a null data packet is to follow the communication frame,

wherein the first network interface device is further configured to cause the first communication frame to be transmitted in order to prompt a communication device that conforms to the first communication protocol to send link quality information.

5. A system according to claim 4 , wherein the first network interface device is configured to set a third subfield to indicate whether the first communication frame is a single user frame or a multi user frame, and

wherein the first network interface device is configured to i) generate the first communication frame as a single user frame when the third subfield is set to indicate a single user frame, and ii) generate the first communication frame as a multi user frame when the third subfield is set to indicate a multi user frame.

6. A system according to claim 4 , wherein the first header is a media access control (MAC) header of a MAC protocol data unit.

7. A system according to claim 6 , wherein

the first network interface device includes a media access control (MAC) processing unit,

the MAC processing unit is configured to generate the first control field,

the MAC processing unit is configured to generate the MAC header, and

the MAC processing unit is configured to generate the MAC protocol data unit.

8. A system according to claim 6 , wherein

the first network interface device includes a physical layer (PHY) processing unit, and

the PHY processing unit is configured to generate the first communication frame to include the MAC protocol data unit.

9. A method according to claim 1 , further comprising:

determining, at a second network interface device, a link quality metric corresponding to a wireless communications link between a first communication device and a second communication device;

generating, at the second network interface device, a second communication frame having a second header, wherein the second header includes

i) a fourth subfield of a second control field to specify a modulation and coding scheme for use via the wireless communications link,

ii) a fifth subfield of the second control field that includes the link quality metric; and

causing, with the second network interface device, the second communication frame to be transmitted.

10. A method according to claim 9 , wherein the link quality metric comprises at least one of i) a signal to noise ratio (SNR), ii) a received signal strength indicator (RSSI), and iii) a link margin metric.

11. A method according to claim 9 , further comprising:

determining, at the second network interface device, the modulation and coding scheme; and

including, at the second network interface device, an indication of the determined modulation and coding scheme in the fourth subfield.

12. A method according to claim 9 , further comprising setting, at the second network interface device, the fourth subfield to a value indicating modulation and coding scheme feedback is not available.

13. A system according to claim 4 , comprising:

a second network interface device configured to

determine a link quality metric corresponding to a wireless communications link between the second network interface and another communication device, and

generate a second communication frame having a second header, wherein the second header includes

i) a fourth subfield of a second control field to specify a modulation and coding scheme for use via the wireless communications link, and

ii) a fifth subfield of the second control field that includes the link quality metric;

wherein the second network interface device is further configured to cause the second communication frame to be transmitted.

14. A system according to claim 13 , wherein the link quality metric comprises at least one of i) a signal to noise ratio (SNR), ii) a received signal strength indicator (RSSI), and iii) a link margin metric.

15. A system according to claim 13 , wherein the second network interface device is further configured to:

determine the modulation and coding scheme; and

include an indication of the determined modulation and coding scheme in the fourth subfield.

16. A system according to claim 13 , wherein the second network interface device is further configured to set the fourth subfield to a value indicating modulation and coding scheme feedback is not available.