Cross-layer power control and scheduling protocol
View Patent ↗A cross-layer protocol may generally provide joint control of power and schedule in a fully distributed manner without any centralized coordination for an interference-limited wireless network. Under the described protocol, each wireless device may use a detection trial to locally detect interference condition and randomly back off in a distributed manner. Based on the result of the detection trial, the wireless device may then shift between (1) a pure power control mode with power control and (2) a time sharing mode with joint power and scheduling control. The wireless device may also use the amount of backlog in its queue buffer to determine the duration of a silence period in the time sharing mode and an increment to the power level provided by the power control algorithm.
1. A method for a wireless device to jointly control transmit power and transmit time to transmit data via wireless communications to a wireless receiver in a wireless network, the wireless network including multiple wireless devices including the wireless device, the method comprising:
running a power control algorithm to determine a power used to transmit data to the wireless receiver;
determining an equilibrium transmission rate of the wireless device for transmitting data to the wireless receiver under the power control algorithm;
after determining the equilibrium transmission rate:
running a detection trial using the power control algorithm and a scheduling algorithm to transmit data to the wireless receiver;
determining an average transmission rate of the wireless device for transmitting data to the wireless receiver during the detection trial;
when the average transmission rate is greater than the equilibrium transmission rate, operating in a time sharing mode using the power control algorithm and the scheduling algorithm to transmit data to the wireless receiver; and
when the average transmission rate is not greater than the equilibrium transmission rate, operating in a pure power mode using the power control algorithm to transmit data to the wireless receiver.
2. The method of claim 1 , wherein the scheduling algorithm randomly selects a start time in a time horizon and stops data transmission to the wireless receiver for a silence period from the randomly selected start time in the time horizon.
3. The method of claim 2 , wherein the duration of the silence period depends on a backlog of a queue buffer and an interference level.
4. The method of claim 3 , wherein the duration of the silence period is defined as T=alpha*I/B, where T is the duration of the silence period, alpha is a scaling constant common to the wireless devices in the wireless network, B is the backlog of the queue buffer, and I is the interference level.
5. The method of claim 4 , wherein alpha is based on a largest queue buffer size among the wireless devices in the wireless network and a largest interference level tolerated by the wireless receiver.
6. The method of claim 1 , wherein operating in the time sharing mode comprises adjusting a contention aggressiveness of the scheduling algorithm based on a backlog of a queue buffer.
7. The method of claim 1 , wherein operating in the time sharing mode comprises adjusting a transmit duration of the scheduling algorithm based on a backlog of a queue buffer.
8. The method of claim 1 , wherein operating in the pure power mode comprises adjusting a power set by the power control algorithm based on a backlog of a queue buffer.
9. The method of claim 8 , wherein adjusting the power set by the power control algorithm comprises:
when the backlog of the queue buffer is below a first threshold, transmitting data to the wireless receiver with the power set by the power control algorithm; and
when the backlog of the queue buffer is between the first threshold and a second threshold, adding an increment to the power set by the power control algorithm, wherein the increment increases with the backlog.
10. The method of claim 9 , wherein adjusting the power set by the power control algorithm further comprises:
when the queue buffer is between the second threshold and a third threshold, adding an other increment to the power set by the power control algorithm, wherein the other increment increases with the backlog at a faster rate than the increment.
11. The method of claim 1 , further comprising:
after a timeout expires:
running the power control algorithm to determine the power used for transmitting data to the wireless receiver;
determining an other equilibrium transmission rate of the wireless device for transmitting data to the wireless receiver under the power control algorithm;
running an other detection trial using the power control algorithm and the scheduling algorithm to transmit data to the wireless receiver;
determining an other average transmission rate of the wireless device for transmitting data to the wireless receiver during the other detection trial;
when the other average transmission rate is greater than the other equilibrium transmission rate, operating in the time sharing mode; and
when the other average transmission rate is not greater than the other equilibrium transmission rate, operating in the pure power mode.
12. A non-transitory computer-readable storage medium encoded with computer-executable instructions for a wireless device to jointly control transmit power and transmit time to transmit data via wireless communications to a wireless receiver in a wireless network, the wireless network including multiple wireless devices including the wireless device, the instructions comprising:
running a power control algorithm to determine a power used to transmit data to the wireless receiver;
determining an equilibrium transmission rate of the wireless device for transmitting data to the wireless receiver under the power control algorithm;
after determining the equilibrium transmission rate:
running a detection trial using the power control algorithm and a scheduling algorithm to transmit data to the wireless receiver;
determining an average transmission rate of the wireless device for transmitting data to the wireless receiver during the detection trial;
when the average transmission rate is greater than the equilibrium transmission rate, operating in a time sharing mode using the power control algorithm and the scheduling algorithm to transmit data to the wireless receiver; and
when the average transmission rate is not greater than the equilibrium transmission rate, operating in a pure power mode using the power control algorithm to transmit data to the wireless receiver.
13. The non-transitory computer-readable storage medium of claim 12 , wherein the scheduling algorithm randomly selects a start time in a time horizon and stops data transmission to the wireless receiver for a silence period from the randomly selected start time in the time horizon.
14. The non-transitory computer-readable storage medium of claim 13 , wherein the duration of the silence period depends on a backlog of a queue buffer and an interference level.
15. The non-transitory computer-readable storage medium of claim 14 , wherein the duration of the silence period is defined as T=alpha*I/B, where T is the duration of the silence period, alpha is a scaling constant common to the wireless devices in the wireless network, B is the backlog of the queue buffer, and I is the interference level.
16. The non-transitory computer-readable storage medium of claim 15 , wherein alpha is based on a largest queue buffer size among the wireless devices in the wireless network and a largest interference level tolerated by the wireless receiver.
17. The non-transitory computer-readable storage medium of claim 12 , wherein operating in the time sharing mode comprises adjusting a contention aggressiveness of the scheduling algorithm based on a backlog of a queue buffer.
18. The non-transitory computer-readable storage medium of claim 12 , wherein operating in the time sharing mode comprises adjusting a transmit duration of the scheduling algorithm based on a backlog of a queue buffer.
19. The non-transitory computer-readable storage medium of claim 12 , wherein operating in the pure power mode comprises adjusting a power set by the power control algorithm based on a backlog of a queue buffer.
20. The non-transitory computer-readable storage medium of claim 19 , wherein adjusting the power set by the power control algorithm comprises:
when the backlog of the queue buffer is below a first threshold, transmitting data to the wireless receiver with the power set by the power control algorithm; and
when the backlog of the queue buffer is between the first threshold and a second threshold, adding an increment to the power set by the power control algorithm, wherein the increment increases with the backlog.
21. The non-transitory computer-readable storage medium of claim 20 , wherein adjusting the power set by the power control algorithm further comprises:
when the queue buffer is between the second threshold and a third threshold, adding an other increment to the power set by the power control algorithm, wherein the other increment increases with the backlog at a faster rate than the increment.
22. The non-transitory computer-readable storage medium of claim 12 , wherein the instructions further comprises:
after a timeout expires:
running the power control algorithm to determine the power used for transmitting data to the wireless receiver;
determining an other equilibrium transmission rate of the wireless device for transmitting data to the wireless receiver under the power control algorithm;
running an other detection trial using the power control algorithm and the scheduling algorithm to transmit data to the wireless receiver;
determining an other average transmission rate of the wireless device for transmitting data to the wireless receiver during the other detection trial;
when the other average transmission rate is greater than the other equilibrium transmission rate, operating in the time sharing mode; and
when the other average transmission rate is not greater than the other equilibrium transmission rate, operating in the pure power mode.
23. A wireless device configured to jointly control transmit power and transmit time to transmit data via wireless communications to a wireless receiver in a wireless network, the wireless network including multiple wireless devices including the wireless device, the wireless device comprising:
a power control algorithm module that determines a transmission power for the wireless device to transmit to the wireless receiver;
a scheduling algorithm module that determines a random time for the wireless device to stop transmitting for a silence period over a time horizon;
a first counter that determines an equilibrium transmission rate;
a second counter that determines an average transmission rate; and
a protocol module that operates the first counter and runs the power control algorithm module to determine the equilibrium transmission rate, operates the second counter and runs a detection trial using the power control algorithm module and the scheduling algorithm module to determine the average transmission rate, and operates the wireless device in one of a pure power mode using the power control algorithm module and a time sharing mode using both the power control algorithm module and the scheduling algorithm module based on a comparison of the average transmission rate and the equilibrium transmission rate.
24. The wireless device of claim 23 , wherein a duration of the silence period is based on a scaling constant common to the wireless devices in the wireless network, a backlog of a queue buffer, and an interference level detected by the wireless device.
25. The wireless device of claim 24 , wherein the scaling constant is based on a largest queue buffer size among the wireless devices and a largest interference level tolerated by the wireless receiver.
26. The wireless device of claim 23 , wherein in the time sharing mode, the protocol module adjusts a contention aggressiveness of the scheduling algorithm based on a backlog of a queue buffer.
27. The wireless device of claim 23 , wherein in the time sharing mode, the protocol module adjusts a transmit duration of the scheduling algorithm based on a backlog of a queue buffer.
28. The wireless device of claim 23 , wherein in the pure power mode, the protocol module increments the transmission power determined by the power control algorithm based on a backlog of a queue buffer.
29. The wireless device of claim 28 , wherein the transmission power is incremented by a first rate between first and second backlog thresholds, and by a second rate between the second and a third backlog thresholds.