NTN uplink power control
Systems and methods for controlling uplink power in a non-terrestrial network (NTN). An NTN station transmits a reference signal at a first time having a defined transmission power and the reference signal is received by non-terrestrial user equipment. The user equipment evaluates the reference signal and determines a first downlink loss of the reference signal by calculating a difference between a measured power level of the received reference signal and the defined transmission power. The NTN station transmits a communication signal at a second time and is received by the user equipment, which estimates a second downlink loss of the communication signal based on the first downlink loss and a power level of the communication signal. A first uplink loss is estimated based on the second downlink loss, and the user equipment adjusts a transmission power of its transmitter based on the first uplink loss.
1. A method, comprising:
receiving, by a non-terrestrial user equipment at a first time, a reference signal transmitted by a non-terrestrial network (NTN) station, the reference signal having a defined transmission power by the NTN station;
determining a first downlink loss of the reference signal by at least determining a difference between a measured power level of the received reference signal and the defined transmission power;
receiving, by the non-terrestrial user equipment at a second time, a first communications signal transmitted by the NTN station;
estimating a second downlink loss of the first communications signal based on the first downlink loss and a power level of one or more data frames of the first communications signal;
estimating a first uplink loss for signal transmission based on the second downlink loss; and
adjusting a transmission power of a transmitter of the non-terrestrial user equipment based on the first uplink loss.
2. The method of claim 1 , wherein estimating the second downlink loss of the first communications signal involves application of an exponential filter having parameters that include the first downlink loss, the measured power level, and a filter time constant as a weight.
3. The method of claim 2 , wherein the exponential filter is defined according to the Equation:
DL
Loss
(
t
)
=
(
P
(
t
)
T
)
+
(
T
-
1
T
)
DL
Loss
(
t
prev
)
wherein DL Loss is the second downlink loss, t is a time, P(t) is the measured power of the reference signal, T is the filter time constant, and t prev is a time previous to the time t.
4. The method of claim 1 , wherein the first uplink loss is estimated based on the second downlink loss, a downlink frequency of the first communications signal, and an uplink frequency of a signal to be transmitted by the non-terrestrial user equipment.
5. The method of claim 4 , wherein the first uplink loss is defined according to the Equation:
UL
Loss
(
t
)
=
DL
Loss
(
t
)
+
α
*
log
(
f
UL
f
DL
)
wherein UL Loss is the first uplink loss, DL Loss is the second downlink loss, f UL is the uplink frequency, t is a time, f DL is the downlink frequency, and α is a constant.
6. The method of claim 1 , wherein the transmission power is determined based on the first uplink loss, the defined transmission power, and a defined uplink loss.
7. The method of claim 1 , wherein the method comprises:
receiving, by the non-terrestrial user equipment at a second time, a second communications signal transmitted by the NTN station; and
determining a third downlink loss of the second communications signal based on the second downlink loss and a power level of the second communications signal, wherein the first uplink loss is estimated based on the third downlink loss.
8. The method of claim 1 , comprising:
obtaining ephemeris information of the NTN station;
determining a distance between the non-terrestrial user equipment and the NTN station based on the ephemeris information; and
estimating a second uplink loss based on the distance and an uplink frequency of a signal to be transmitted by the non-terrestrial user equipment to the NTN station.
9. The method of claim 8 , comprising:
determining a correction factor based on differences between the first uplink loss and the second uplink loss; and
determining the transmission power using the correction factor.
10. A terminal for communicating with a non-terrestrial network (NTN) station, comprising:
a receiver configured to receive signals from the NTN station;
a transmitter configured to transmit signals to the NTN station;
one or more processors; and
memory storing a set of instructions that, as a result of execution by the one or more processors, cause the terminal to:
receive, by the receiver at a first time, a reference signal transmitted by the NTN station, the reference signal having a defined transmission power by the NTN station;
determine a first downlink loss of the reference signal by at least determining a difference between a measured power level of the received reference signal and the defined transmission power;
receive, by the receiver at a second time, a first communications signal transmitted by the NTN station;
estimate a second downlink loss of the first communications signal based on the first downlink loss and a power level of one or more data frames of the first communications signal;
estimate an uplink loss for signal transmission based on the second downlink loss; and
transmit, from the transmitter to the NTN station, a signal using a transmission power determined based on the first uplink loss.
11. The terminal of claim 10 , wherein execution of the set of instructions causes the terminal to:
estimate the second downlink loss of the first communications signal using an exponential filter that includes the first downlink loss, the measured power level, and a filter time constant as a weight of the exponential filter; and
estimate the first uplink loss based on the second downlink loss, a downlink frequency of the first communications signal, and an uplink frequency of a signal to be transmitted by the terminal.
12. The terminal of claim 10 , wherein execution of the set of instructions causes the terminal to:
obtain ephemeris information of the NTN station;
determine a distance between the terminal and the NTN station based on the ephemeris information; and
estimate a second uplink loss based on the distance and an uplink frequency of a signal to be transmitted to the NTN station by the terminal, the transmission power determined based on the second uplink loss.
13. The terminal of claim 10 , wherein execution of the set of instructions causes the terminal to:
receive, by the receiver at a second time, a second communications signal transmitted by the NTN station; and
determine a third downlink loss of the second communications signal based on the second downlink loss and a power level of the second communications signal, wherein the first uplink loss is estimated based on the third downlink loss.
14. A method, comprising:
estimating a first downlink loss estimate based on a power level of a reference signal and a second downlink loss estimate based on the first downlink loss estimate and a power level of one or more data frames of a first communications signal;
setting a transmission power of a transmitter of non-terrestrial user equipment to a first level based on the first downlink loss estimate and the second downlink loss estimate;
transmitting a second communications signal from the transmitter to a non-terrestrial network (NTN) station using the transmission power;
receiving, in response to transmitting the second communications signal, a first power control signal from a terrestrial base station directing the non-terrestrial user equipment to change the transmission power in a first direction; and
adjusting the transmission power of the transmitter by a predetermined amount in the first direction in response to the first power control signal.
15. The method of claim 14 , comprising:
receiving a second power control signal from the terrestrial base station directing the non-terrestrial user equipment to change the transmission power in a second direction opposite to the first direction; and
adjusting the transmission power of the transmitter by the predetermined amount in the second direction in response to the second power control signal.
16. The method of claim 15 , wherein the first direction represents an increase in the transmission power, and the second direction represents a decrease in the transmission power.
17. The method of claim 14 , wherein the predetermined amount is specified in memory of the non-terrestrial user equipment.
18. The method of claim 14 , comprising:
consecutively receiving a plurality of first power control signals from the terrestrial base station;
determining that a number of the plurality of first power control signals exceeds a defined threshold; and
resetting, as a result of determining that the number exceeds to defined threshold, the transmission power based on a third downlink loss estimate and a fourth downlink loss estimate.
19. The method of claim 14 , wherein the transmission power is set at a first time, the method comprising:
determining whether a defined time period has elapsed since the first time; and
resetting, as a result of determining that the power has elapsed, the transmission power based on a third downlink loss estimate and a fourth downlink loss estimate.
20. The method of claim 14 , wherein setting the transmission power includes:
obtaining ephemeris information of the NTN station;
determining a distance between the non-terrestrial user equipment and the NTN station based on the ephemeris information;
estimating a second uplink loss based on the distance and an uplink frequency of a signal to be transmitted by the non-terrestrial user equipment to the NTN station;
determining a correction factor based on differences between the first uplink loss and the second uplink loss; and
determining the transmission power using the correction factor.