Mechanisms for adjusting atoms of an intelligent reflective surface
Mechanisms for adjusting atoms of an Intelligent Reflective Surface (IRS) are provided. A method is performed by a controller configured to control an IRS comprising an array of atoms, each having an individually adjustable phase shift and gain. At least some of the atoms are provided with a measurement sensor. The method comprises obtaining, from the measurement sensors, measurements of received power of a signal transmitted from a user equipment and received by the atoms and determining, by a gradient in received power between two of the measurement sensors is larger than a threshold value, that the user equipment is in near-field of the IRS. The method comprises, as a result thereof, adjusting the phase shift of a first subset of the atoms for reflection at the IRS of subsequent communication between a network node and the user equipment when the user equipment is in the near-field of the IRS.
1. A method for adjusting atoms of an intelligent reflective surface, IRS, the method being performed by a controller, the controller being configured to control the IRS, the IRS comprising an array of the atoms, wherein each of the atoms has an individually adjustable phase shift and gain, and wherein at least some of the atoms are provided with a measurement sensor, the method comprising:
obtaining, from the measurement sensors, measurements of received power of a signal transmitted from a user equipment and received by the atoms;
determining, by a gradient in received power between two of the measurement sensors being larger than a threshold value, that the user equipment is in near-field of the IRS; and as a result thereof:
adjusting the phase shift of a first subset of the atoms for reflection at the IRS of subsequent communication between a network node and the user equipment when the user equipment is in the near-field of the IRS.
2. The method according to claim 1 , wherein the method further comprises:
muting a second subset of the atoms for reflection at the IRS of the subsequent communication between the network node and the user equipment.
3. The method according to claim 2 , wherein each of the atoms is either a member of the first subset or the second subset but not both.
4. The method according to claim 2 , wherein none of the atoms in the second subset yield an adjustment of the phase shift within the predefined interval.
5. The method according to claim 1 , wherein the atoms in the first subset all yield an adjustment of the phase shift within a predefined interval and maximize number of members in the first subset subject to a power maximization criterion.
6. The method according to claim 5 , wherein the predefined interval is either [0, π], or [0, 4π].
7. The method according to claim 1 , wherein how much the phase shift is adjusted is proportional to the gradient in received power.
8. The method according to claim 1 , wherein the gradient in received power is obtained in terms of an angle of arrival value of the signal transmitted from the user equipment.
9. The method according to claim 8 , wherein the angle of arrival value is denoted θ and is determined according to:
θ
=
tan
-
1
P
1
-
P
2
P
2
,
where P 1 is measurement of received power obtained from one of the measurement sensors and where P 2 is the measurement of received power obtained from another one of the measurement sensors.
10. The method according to claim 9 , wherein P 1 is the highest of all the obtained measurements of received power and where P 2 is one of the obtained measurements of received power that is more than a threshold lower than P 1 but still higher than a noise floor.
11. The method according to claim 9 , wherein the signal transmitted from the user equipment has a wavelength 2 , wherein the atoms from which the measurements of received power were made by the measurement sensors are separated a distance D, and wherein the phase shift is adjusted by a compensation factor Δϕ determined according to:
Δ
ϕ
=
2
π
D
(
sin
(
θ
)
-
tan
(
θ
)
)
λ
.
12. The method according to claim 1 , wherein the threshold value is dependent on tolerated power variation among the atoms.
13. The method according to claim 1 , wherein the threshold value is dependent on how much the atoms from which the measurements of received power were made by the measurement sensors are distanced from each other and dimension of the IRS.
14. The method according to claim 1 , wherein the atoms provided with the measurement sensors are evenly distributed throughout the IRS.
15. The method according to claim 1 , wherein the atoms provided with the measurement sensors are randomly distributed throughout the IRS.
16. A controller for adjusting atoms of an intelligent reflective surface, IRS, the controller being configured to control the IRS, the IRS comprising an array of the atoms, wherein each of the atoms has an individually adjustable phase shift and gain, and wherein at least some of the atoms are provided with a measurement sensor, the controller comprising processing circuitry, the processing circuitry being configured to cause the controller to:
obtain, from the measurement sensors, measurements of received power of a signal transmitted from a user equipment and received by the atoms;
determine, by a gradient in received power between two of the measurement sensors being larger than a threshold value, that the user equipment is in near-field of the IRS;
and as a result thereof:
adjust the phase shift of a first subset of the atoms for reflection at the IRS of subsequent communication between a network node and the user equipment when the user equipment is in the near-field of the IRS.
17. A non-transitory computer readable medium comprising computer code which, when run on processing circuitry of a controller, the controller being configured to control an intelligent reflective surface, the IRS comprising an array of atoms, wherein each of the atoms has an individually adjustable phase shift and gain, and wherein at least some of the atoms are provided with a measurement sensor, causes the controller to:
obtain, from the measurement sensors, measurements of received power of a signal transmitted from a user equipment and received by the atoms;
determine, by a gradient in received power between two of the measurement sensors being larger than a threshold value, that the user equipment is in near-field of the IRS; and as a result thereof:
adjust the phase shift of a first subset of the atoms for reflection at the IRS of subsequent communication between a network node and the user equipment when the user equipment is in the near-field of the IRS.