Reformulating reconfigurable intelligent surface (RIS) elements based on operation frequency
Aspects of the present disclosure provide apparatus, methods, processing systems, and computer readable mediums for determining a beamformer to apply to groups of two or more elements of a reconfigurable intelligent surface (RIS). The beamformer is applied to the groups of elements of the RIS to facilitate communications at the operating frequency by re-radiating radio signals via the elements of the RIS. For example, by grouping RIS elements in different manners and applying a beamformer (e.g., precoding weights) to the group as if the group were a single RIS element, the RIS can be reconfigured to behave differently to suit various operating frequencies of the radio signals.
1. A method for wireless communications, comprising:
determining, based on an operating frequency, a beamformer to apply to groups of two or more of elements of a reconfigurable intelligent surface (RIS); and
applying the beamformer to the groups of elements of the RIS to facilitate communications at the operating frequency by re-radiating radio signals via the elements of the RIS,
wherein at least one of the groups of elements of the RIS has a total area A′ inversely proportional to the operation frequency squared.
2. The method of claim 1 , wherein applying the beamformer to the groups of elements of the RIS causes at least one of a phase shift or an amplitude change to radio signals re-radiated by each of the groups of elements of the RIS.
3. The method of claim 1 , wherein the RIS is configured to facilitate communications at an original frequency by re-radiating radio signals via the elements of the RIS, wherein each of the elements of the RIS has an area A inversely proportional to the original frequency squared.
4. The method of claim 3 , wherein the original frequency is a highest frequency used by a base station.
5. The method of claim 3 , wherein the area A of at least one of the elements of the RIS is a fraction of a wavelength λ of the original frequency squared, wherein A=r 2 λ 2 , r 2 being the fraction.
6. The method of claim 3 , wherein the area A of at least one of the elements of the RIS is a product of a first wavelength corresponding to the original frequency and a second wavelength corresponding to the operating frequency.
7. The method of claim 6 , wherein the at least one of the elements of the RIS is in a rectangular shape.
8. The method of claim 3 , wherein the area A of at least one of the elements of the RIS is a product of a circular area and a wavelength λ of the original frequency squared, wherein A=π(r c λ) 2 , r c , re being a fraction.
9. The method of claim 8 , wherein the at least one of the elements of the RIS is in a circular shape.
10. The method of claim 3 , further comprising signaling to a transmitter one or more parameters associated with the area A.
11. The method of claim 3 , wherein at least one of the groups of two or more of the elements of the RIS is determined based on a ceiling function of a ratio between a wavelength corresponding to the operating frequency squared and the area A, the ceiling function being ceil(λ operating frequency 2 /A).
12. The method of claim 3 , wherein at least one of the groups of two or more of the elements of the RIS is determined based on a floor function of a ratio between a wavelength corresponding to the operating frequency squared and the area A, the floor function being floor(λ operating frequency 2 /A).
13. The method of claim 3 , wherein at least one of the groups of two or more of the elements of the RIS is determined based on a product of a first group wavelength and a second group wavelength, wherein the first and the second group wavelengths are respectively a function of a wavelength λ corresponding to the original frequency.
14. The method of claim 3 , wherein at least one of the groups of two or more of the elements of the RIS is determined based on a ceiling function or a floor function of a ratio between a wavelength of the operating frequency and a wavelength of the original frequency.
15. The method of claim 14 , wherein the at least one of the groups of two or more of the elements of the RIS comprises a row or a column of a number of the ceiling function or the floor function of the elements of the RIS.
16. The method of claim 1 , wherein at least one of the groups of two or more of the elements of the RIS is determined based on a general function configured to output at least one of:
an area of at least one of the groups of two or more of the elements of the RIS, or
a number of horizontal elements of the RIS and a number vertical elements of the RIS.
17. The method of claim 16 , wherein the general function is configured by radio resource control (RRC), medium access control control element (MAC CE), or downlink control information (DCI).
18. The method of claim 1 , further comprising training the beamformer to the groups of elements of the RIS to identify a set of beamformer weights based on an area or shape of the groups of elements of the RIS.
19. The method of claim 1 , further comprising:
transmitting, to a base station, an indication on a minimum element size of the elements of the RIS corresponding to a highest re-radiation frequency native to the RIS; and
receiving, from the base station, a request to participate in communications at the highest re-radiation frequency.
20. An apparatus for wireless communication, comprising:
at least one processor; and
memory coupled to the at least one processor, the memory including code or instructions executable by the at least one processor to cause the apparatus to:
determine, based on an operating frequency, a beamformer to apply to groups of two or more of elements of a reconfigurable intelligent surface (RIS); and
apply the beamformer to the groups of elements of the RIS to facilitate communications at the operating frequency by re-radiating radio signals via the elements of the RIS,
wherein the RIS is configured to facilitate communications at an original frequency by re-radiating radio signals via the elements of the RIS, wherein each of the elements of the RIS has an area A inversely proportional to the original frequency squared.
21. The apparatus of claim 20 , wherein the area A of at least one of the elements of the RIS is a fraction of a wavelength λ of the original frequency squared, wherein A=r 2 λ 2 , r 2 being the fraction.
22. The apparatus of claim 20 , wherein the area A of at least one of the elements of the RIS is a product of a first wavelength corresponding to the original frequency and a second wavelength corresponding to the operating frequency.
23. The apparatus of claim 20 , wherein the area A of at least one of the elements of the RIS is a product of a circular area and a wavelength λ of the original frequency squared, wherein A=π(r c λ) 2 , r c being a fraction.
24. The apparatus of claim 20 , further comprising signaling to a transmitter one or more parameters associated with the area A.
25. The apparatus of claim 20 , wherein at least one of the groups of elements of the RIS has a total area A′ inversely proportional to the operation frequency squared.
26. The apparatus of claim 20 , wherein at least one of the groups of two or more of the elements of the RIS is determined based on a ceiling function of a ratio between a wavelength corresponding to the operating frequency squared and the area A, the ceiling function being ceil(λ operating frequency 2 /A).
27. The apparatus of claim 20 , wherein at least one of the groups of two or more of the elements of the RIS is determined based on a floor function of a ratio between a wavelength corresponding to the operating frequency squared and the area A, the floor function being floor(λ operating frequency 2 /A).
28. An apparatus for wireless communication, comprising:
at least one processor; and
memory coupled to the at least one processor, the memory including code or instructions executable by the at least one processor to cause the apparatus to:
determine, based on an operating frequency, a beamformer to apply to groups of two or more of elements of a reconfigurable intelligent surface (RIS);
apply the beamformer to the groups of elements of the RIS to facilitate communications at the operating frequency by re-radiating radio signals via the elements of the RIS; and
train the beamformer to the groups of elements of the RIS to identify a set of beamformer weights based on an area or shape of the groups of elements of the RIS.