Fast rate adaptation for WLAN devices
A method for rate adaptation in a communication device includes, during a time interval, transmitting over a wireless channel to a peer communication device both (i) communication packets that carry user data, at a communication data rate, and (ii) channel-probing packets for probing channel conditions, at a channel-probing data rate that is derived from the communication data rate. A first statistical performance of the communication packets, and a second statistical performance of the channel-probing packets, are estimated over the time interval. The communication data rate is set for a subsequent time interval based on at least one of the first statistical performance and the second statistical performance.
1. A method for rate adaptation in a communication device, the method comprising:
during a time interval, transmitting over a wireless channel to a peer communication device both (i) communication packets that carry user data, at a communication data rate, and (ii) channel-probing packets for probing channel conditions, at a channel-probing data rate that is derived from the communication data rate;
estimating, over the time interval, a first statistical performance of the communication packets and a second statistical performance of the channel-probing packets; and
setting the communication data rate for a subsequent time interval based on at least one of the first statistical performance and the second statistical performance.
2. The method according to claim 1 , further comprising deciding, based on the first statistical performance of the communication packets, whether or not to transmit the channel-probing packets in the subsequent time interval.
3. The method according to claim 1 , further comprising deciding, based on the first statistical performance of the communication packets, whether to increase or decrease the channel-probing data rate in the subsequent time interval relative to the time interval.
4. The method according to claim 1 , further comprising:
when the first statistical performance of the communication packets is better than a first performance threshold, increasing the channel-probing data rate for the channel-probing packets in the subsequent time interval relative to the time interval;
when the first statistical performance is poorer than a second performance threshold, decreasing the channel-probing data rate in the subsequent time interval relative to the time interval; and
when the first statistical performance is between the first performance threshold and the second performance threshold, deciding not to transmit the channel-probing packets in the subsequent time interval.
5. The method according to claim 1 , wherein setting the communication data rate for the subsequent time interval comprises:
when the second statistical performance of the channel-probing packets is better than a first performance threshold, increasing the communication data rate in the subsequent time interval relative to the time interval;
when the second statistical performance is poorer than a second performance threshold, decreasing the communication data rate in the subsequent time interval relative to the time interval; and
when the second statistical performance is between the first performance threshold and the second performance threshold, retaining the communication data rate in the subsequent time interval as in the time interval.
6. The method according to claim 1 , and comprising, upon initial establishment of a link with the peer communication device or following inactivity of the link, initializing the communication data rate based on a quality of a reverse-channel signal received from the peer communication device.
7. The method according to claim 1 , wherein estimating the first statistical performance and the second statistical performance comprises estimating performance measures indicative of throughputs of the communication packets and of the channel-probing packets.
8. The method according to claim 1 , wherein estimating the first statistical performance and the second statistical performance comprises estimating performance measures indicative of error rates of the communication packets and of the channel-probing packets.
9. The method according to claim 1 , wherein estimating the first statistical performance and the second statistical performance is performed based only on first-transmissions of the communication packets and the channel-probing packets, excluding retransmissions.
10. The method according to claim 1 , comprising, at least at a given time, setting the communication data rate to be different from the channel-probing data rate.
11. A communication device comprising:
a transmitter, configured to transmit signals over a wireless channel to a peer communication device; and
a processor, configured to:
during a time interval, transmit to the peer communication device, using the transmitter, both (i) communication packets that carry user data, at a communication data rate, and (ii) channel-probing packets for probing channel conditions, at a channel-probing data rate that is derived from the communication data rate;
estimate, over the time interval, a first statistical performance of the communication packets and a second statistical performance of the channel-probing packets; and
set the communication data rate for a subsequent time interval based on at least one of the first statistical performance and the second statistical performance.
12. The communication device according to claim 11 , wherein the processor is further configured to decide, based on the first statistical performance of the communication packets, whether or not to transmit the channel-probing packets in the subsequent time interval.
13. The communication device according to claim 11 , wherein the processor is further configured to decide, based on the first statistical performance of the communication packets, whether to increase or decrease the channel-probing data rate in the subsequent time interval relative to the time interval.
14. The communication device according to claim 11 , wherein the processor is further configured to:
when the first statistical performance of the communication packets is better than a first performance threshold, increase the channel-probing data rate for the channel-probing packets in the subsequent time interval relative to the time interval;
when the first statistical performance is poorer than a second performance threshold, decrease the channel-probing data rate in the subsequent time interval relative to the time interval; and
when the first statistical performance is between the first performance threshold and the second performance threshold, decide not to transmit the channel-probing packets in the subsequent time interval.
15. The communication device according to claim 11 , wherein the processor is configured to set the communication data rate for the subsequent time interval by:
when the second statistical performance of the channel-probing packets is better than a first performance threshold, increasing the communication data rate in the subsequent time interval relative to the time interval;
when the second statistical performance is poorer than a second performance threshold, decreasing the communication data rate in the subsequent time interval relative to the time interval; and
when the second statistical performance is between the first performance threshold and the second performance threshold, retaining the communication data rate in the subsequent time interval as in the time interval.
16. The communication device according to claim 11 , wherein, upon initial establishment of a link with the peer communication device or following inactivity of the link, the processor is configured to initialize the communication data rate based on a quality of a reverse-channel signal received from the peer communication device.
17. The communication device according to claim 11 , wherein the processor is configured to estimate the first statistical performance and the second statistical performance by estimating performance measures indicative of throughputs of the communication packets and of the channel-probing packets.
18. The communication device according to claim 11 , wherein the processor is configured to estimate the first statistical performance and the second statistical performance by estimating performance measures indicative of error rates of the communication packets and of the channel-probing packets.
19. The communication device according to claim 11 , wherein the processor is configured to estimate the first statistical performance and the second statistical performance based only on first-transmissions of the communication packets and the channel-probing packets, excluding retransmissions.
20. The communication device according to claim 11 , wherein, at least at a given time, the processor is configured to set the communication data rate to be different from the channel-probing data rate.