EP4348875A1

EP4348875A1 - Identification of reconfigurable intelligent surface

Info

Publication number: EP4348875A1
Application number: EP21943542.7A
Authority: EP
Inventors: Huaisong Zhu; Ming Li; Zhan Zhang
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2021-06-03
Filing date: 2021-06-03
Publication date: 2024-04-10
Also published as: WO2022252176A1

Abstract

The present disclosure provides a reconfigurable intelligent surface (RIS), a wireless device, and methods for identifying radio signals therefrom. A method at a RIS for facilitating a first wireless device in identifying radio signals from the RIS comprises: receiving, from a second wireless device, a sequence of radio signals; adjusting the received sequence of radio signals in the analog domain to enable the first wireless device to determine that the adjusted sequence of radio signals comes from the RIS; and transmitting, to the first wireless device, the adjusted sequence of radio signals.

Description

IDENTIFICATION OF RECONFIGURABLE INTELLIGENT SURFACE

Technical Field

The present disclosure is related to the field of telecommunication, and in particular, to a reconfigurable intelligent surface, a wireless device, and methods for identifying radio signals therefrom.

Background

This section introduces aspects that may facilitate better understanding of the disclosure. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.
Recent years have witnessed the successful deployment of massive multiple input multiple output (Massive MIMO) in the fifth generation (5G) wireless communication systems, as a promising approach to support massive number of users at high data rate, low latency, and secure transmission simultaneously and efficiently. However, implementing a Massive-MIMO base station (BS) is challenging, as high hardware cost, constrained physical size, and increased power consumption scaling up the conventional MIMO systems by many orders of magnitude, arise when the conventional large-scale antenna array is used at base stations (BSs) .
On another hand, the reconfigurable intelligent surface (RIS) , benefited from the breakthrough on the fabrication of programmable meta-material, has been speculated as one of the key enabling technologies for the future six generation (6G) wireless communication systems scaled up beyond Massive-MIMO to achieve smart radio environment. The meta-material based RIS makes possible wideband antennas with compact size, such that large scale antennas can be easily deployed at both ends of the user equipments (UEs) and BSs, to achieve Massive-MIMO gains but with significant reduction in power consumption. With the help of varactor diode or other micro electrical mechanical systems (MEMS) technology, electromagnetic (EM) properties of the RIS are fully defined by its micro-structure, and can be programmed to vary the phase, amplitude, frequency, and even orbital angular momentum of an EM wave, effectively modulating a radio signal without a mixer and radio frequency (RF) chain.
The RIS can be deployed as reconfigurable transmitters, receivers, and passive reflecting arrays. Being reflecting arrays, the RIS is usually placed in between the BS and single-antenna receivers, and consists of a vast number of nearly passive, low-cost, and low energy consuming reflecting elements, each of which introduces a certain phase shift to the signals impinging on it. By reconfiguring the phase shifts of elements of RIS, the reflected signals can be added constructively at the desired receiver to enhance the received signal power or destructively at non-intended receivers to reduce the co-channel interference. Due to the low power consumption, the reflecting RIS can be fabricated in very compact size with light weight, leading to easy installation of RIS in building facades, ceilings, moving trains, lamp poles, road signs, etc., as well as ready integration into existing communication systems with minor modifications on hardware.
However, the use of RIS may be accompanied with problems, for example, in positioning, interference mitigation, cell selection, by introducing additional propagation paths between the BSs and the UEs.
Summary
According to some embodiments of the present disclosure, a method at a reconfigurable intelligent surface (RIS) for facilitating a first wireless device in identifying radio signals from the RIS is provided. The method comprises: receiving, from a second wireless device, a sequence of radio signals; adjusting the received sequence of radio signals in the analog domain to enable the first wireless device to determine that the adjusted sequence of radio signals comes from the RIS; and transmitting, to the first wireless device, the adjusted sequence of radio signals.
In some embodiments, the step of adjusting the received sequence of radio signals in the analog domain comprises at least one of: replacing at least one of the received radio signals with a zero-power signal; applying a phase shift to at least one of the received radio signals; and applying a frequency shift to at least one of the received radio signals. In some embodiments, before the step of adjusting the received sequence of radio signals in the analog domain, the method further comprises at least one of: pre-configuring a criterion for selecting one or more radio signals for adjustment; and receiving the criterion for selecting one or more radio signals for adjustment. In some embodiments, before the step of transmitting, to the first wireless device, the adjusted sequence of radio signals, the method further comprises: transmitting, to the first wireless device, the criterion for selecting one or more radio signals for adjustment.
In some embodiments, the step of replacing at least one of the received radio signals with a zero-power signal comprises: determining at least one of the received radio signals according to the criterion; and replacing the at least one determined radio signal with a zero-power signal. In some embodiments, the step of applying phase shift to at least one of the received radio signals comprises: determining at least one of the received radio signals according to the criterion; and applying the phase shift to the at least one determined radio signal. In some embodiments, for each of the at least one determined radio signal, a signal-specific phase shift or a common phase shift is applied.
In some embodiments, the step of applying a frequency shift to at least one of the received radio signals comprises: determining at least one of the received radio signals according to the criterion; and applying the frequency shift to the at least one determined radio signal. In some embodiments, for each of the at least one determined radio signal, a signal-specific frequency shift or a common frequency shift is applied.
In some embodiments, the step of adjusting the received sequence of radio signals in the analog domain further comprises: adjusting the received sequence of radio signals in the analog domain to enable the first wireless device to further determine one or more of: -geometry information of the RIS and/or the second wireless device; and -information about signal delay introduced by the RIS. In some embodiments, one of the first wireless device and the second wireless device is a User Equipment (UE) , and the other of the first wireless device and the second wireless device is a Radio Access Network (RAN) node. In some embodiments, the criterion is received from the RAN node.
According to a second aspect of the present disclosure, a reconfigurable intelligent surface (RIS) is provided. The RIS comprises: a processor; a memory storing instructions which, when executed by the processor, cause the processor to perform any of the methods of the first aspect.
According to a third aspect of the present disclosure, a method at a first wireless device for determining that a sequence of radio signals comes from a reconfigurable intelligent surface (RIS) is provided. The method comprises: receiving the sequence of radio signals; and determining that the sequence of radio signals comes from the RIS in response to determining that at least one of the received radio signals is adjusted at least partially based on a criterion for selecting one or more radio signals from the sequence of radio signals for adjustment.
In some embodiments, the method further comprises: receiving a second sequence of radio signals; and determining that the second sequence of radio signals comes from a second wireless device in response to determining that none of the radio signals of the second sequence of radio signals is adjusted at least partially based on the criterion. In some embodiments, the method further comprises: receiving a third sequence of radio signals; and determining that the third sequence of radio signals comes from another RIS in response to determining that at least one of the radio signals of the third sequence of radio signals is adjusted at least partially based on another criterion.
In some embodiments, the method further comprises at least one of: performing a first positioning procedure at least partially based on the sequence of radio signals and information related to the RIS; performing a second positioning procedure at least partially based on the second sequence of radio signals and information related to the second wireless device; and performing a third positioning procedure at least partially based on the third sequence of radio signals and information related to the other RIS.
In some embodiments, the criterion and/or the other criterion are pre-configured or received from the second wireless device, the RIS, and/or the other RIS. In some embodiments, the step of determining that at least one of the received radio signals is adjusted at least partially based on the criterion comprises at least one of: determining that at least one of the received radio signals is replaced with a zero-power signal at least partially based on the criterion; determining that a phase shift is applied to at least one of the received radio signals at least partially based on the criterion; and determining that a frequency shift is applied to at least one of the received radio signals at least partially based on the criterion. In some embodiments, the step of determining that at least one of the received radio signals is replaced with a zero-power signal at least partially based on the criterion comprises: determining a pattern of missing signals in the received sequence of radio signals; comparing the pattern of missing signals with the criterion; and determining that at least one of the received radio signals is replaced with a zero-power signal in response to determining that the pattern of missing signals is matched with the criterion.
In some embodiments, the step of determining that a phase shift is applied to at least one of the received radio signals at least partially based on the criterion comprises: determining a pattern of received signal power changing for the received sequence of radio signals; comparing the pattern of received signal power changing with the criterion; and determining that a phase shift is applied to at least one of the received radio signals in response to determining that the pattern of received signal power changing is matched with the criterion. In some embodiments, the step of determining that a frequency shift is applied to at least one of the received radio signals at least partially based on the criterion comprises: determining a pattern of received signal power changing at different frequencies for the received sequence of radio signals; comparing the pattern of received signal power changing at the different frequencies with the criterion; and determining that a frequency shift is applied to at least one of the received radio signals in response to determining that the pattern of received signal power changing at the different frequencies is matched with the criterion.
In some embodiments, the method further comprises: further determining, from the received sequence of radio signals one or more of geometry information of the RIS and/or the second wireless device and information about signal delay introduced by the RIS at least partially based on the criterion. In some embodiments, the RIS is a Reconfigurable Intelligent Surface (RIS) , one of the first wireless device and the second wireless device is a User Equipment (UE) , and the other of the first wireless device and the second wireless device is a Radio Access Network (RAN) node.
According to a fourth aspect of the present disclosure, a first wireless device is provided. The first wireless device comprises: a processor; a memory storing instructions which, when executed by the processor, cause the processor to perform any of the methods of the third aspect.
According to a fifth aspect of the present disclosure, a computer program comprising instructions is provided. The instructions, when executed by at least one processor, cause the at least one processor to carry out the method of any of the first and third aspects.
According to a sixth aspect of the present disclosure, a carrier containing the computer program of the fifth aspect is provided. In some embodiments, the carrier is one of an electronic signal, optical signal, radio signal, or computer readable storage medium.
According to a seventh aspect of the present disclosure, a wireless telecommunications system is provided. The wireless telecommunication system comprises: a first wireless device of the fourth aspect; a second wireless device configured to transmit radio signals; and a reconfigurable intelligent surface (RIS) of the second aspect, which is configured to adjust and forward the radio signal to the first wireless device.

Brief Description of the Drawings

The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only several embodiments in accordance with the disclosure and therefore are not to be considered limiting of its scope, the disclosure will be described with additional specificity and detail through use of the accompanying drawings.
Fig. 1 is a diagram illustrating an exemplary wireless telecommunication network in which a method for identifying radio signals from a RIS according to an embodiment of the present disclosure is applicable.
Fig. 2 is a diagram illustrating an exemplary RIS at which a method for enabling identification of the RIS according to an embodiment of the present disclosure is applicable.
Fig. 3 is a diagram illustrating another exemplary RIS at which a method for enabling identification of the RIS according to an embodiment of the present disclosure is applicable.
Fig. 4 is a diagram illustrating an exemplary positioning procedure in which a method for enabling identification of the RIS according to an embodiment of the present disclosure is applicable.
Fig. 5 is a diagram illustrating a comparison between Rayleigh fading channels with and without RIS involved.
Fig. 6 is a diagram illustrating an exemplary wireless telecommunication network in which a method for identifying radio signals from one or more RISs according to an embodiment of the present disclosure is applicable.
Fig. 7 is diagram illustrating exemplary power delay profiles (PDP) in different situations when one or more RISs are used.
Fig. 8 is a diagram illustrating exemplary PDPs when a method for identifying radio signals from RISs is applied according to an embodiment of the present disclosure.
Fig. 9 is a diagram illustrating exemplary PDPs and simulated PDPs when another method for identifying radio signals from RISs is applied according to another embodiment of the present disclosure.
Fig. 10 is a diagram illustrating exemplary PDPs when yet another method for identifying radio signals from RISs is applied according to yet another embodiment of the present disclosure.
Fig. 11 is a diagram illustrating exemplary PDPs for positioning a UE according to an embodiment of the present disclosure.
Fig. 12 is a flow chart illustrating an exemplary method at a RIS for facilitating a first wireless device in identifying radio signals from the RIS according to an embodiment of the present disclosure.
Fig. 13 is a flow chart illustrating an exemplary method at a first wireless device for determining that a sequence of radio signals comes from a RIS according to an embodiment of the present disclosure.
Fig. 14 schematically shows an embodiment of an arrangement which may be used in a RIS according to an embodiment of the present disclosure.
Fig. 15 schematically shows an embodiment of an arrangement which may be used in a first wireless device according to an embodiment of the present disclosure.
Fig. 16 is a block diagram of an exemplary RIS according to an embodiment of the present disclosure.
Fig. 17 is a block diagram of an exemplary wireless device according to an embodiment of the present disclosure.

Detailed Description

Hereinafter, the present disclosure is described with reference to embodiments shown in the attached drawings. However, it is to be understood that those descriptions are just provided for illustrative purpose, rather than limiting the present disclosure. Further, in the following, descriptions of known structures and techniques are omitted so as not to unnecessarily obscure the concept of the present disclosure.
Those skilled in the art will appreciate that the term ″exemplary″ is used herein to mean ″illustrative, ″ or ″serving as an example, ″ and is not intended to imply that a particular embodiment is preferred over another or that a particular feature is essential. Likewise, the terms ″first″ and ″second, ″ and similar terms, are used simply to distinguish one particular instance of an item or feature from another, and do not indicate a particular order or arrangement, unless the context clearly indicates otherwise. Further, the term ″step, ″ as used herein, is meant to be synonymous with ″operation″ or ″action. ″ Any description herein of a sequence of steps does not imply that these operations must be carried out in a particular order, or even that these operations are carried out in any order at all, unless the context or the details of the described operation clearly indicates otherwise.
Conditional language used herein, such as ″can, ″ ″might, ″ ″may, ″ ″e.g., ″ and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or states are included or are to be performed in any particular embodiment. Also, the term ″or″ is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term ″or″ means one, some, or all of the elements in the list. Further, the term ″each, ″ as used herein, in addition to having its ordinary meaning, can mean any subset of a set of elements to which the term ″each″ is applied.
The term ″based on″ is to be read as ″based at least in part on. ″ The term ″one embodiment″ and ″an embodiment″ are to be read as ″at least one embodiment. ″ The term ″another embodiment″ is to be read as ″at least one other embodiment. ″ Other definitions, explicit and implicit, may be included below. In addition, language such as the phrase ″at least one of X, Y and Z, ″ unless specifically stated otherwise, is to be understood with the context as used in general to convey that an item, term, etc. may be either X, Y, or Z, or a combination thereof.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limitation of example embodiments. As used herein, the singular forms ″a″ , ″an″ , and ″the″ are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms ″comprises″ , ″comprising″ , ″has″ , ″having″ , ″includes″ and/or ″including″ , when used herein, specify the presence of stated features, elements, and/or components etc., but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof. It will be also understood that the terms ″connect (s) , ″ ″connecting″ , ″connected″ , etc. when used herein, just mean that there is an electrical or communicative connection between two elements and they can be connected either directly or indirectly, unless explicitly stated to the contrary.
Of course, the present disclosure may be carried out in other specific ways than those set forth herein without departing from the scope and essential characteristics of the disclosure. One or more of the specific processes discussed below may be carried out in any electronic device comprising one or more appropriately configured processing circuits, which may in some embodiments be embodied in one or more application-specific integrated circuits (ASICs) . In some embodiments, these processing circuits may comprise one or more microprocessors, microcontrollers, and/or digital signal processors programmed with appropriate software and/or firmware to carry out one or more of the operations described above, or variants thereof. In some embodiments, these processing circuits may comprise customized hardware to carry out one or more of the functions described above. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.
Although multiple embodiments of the present disclosure will be illustrated in the accompanying Drawings and described in the following Detailed Description, it should be understood that the disclosure is not limited to the disclosed embodiments, but instead is also capable of numerous rearrangements, modifications, and substitutions without departing from the present disclosure that as will be set forth and defined within the claims.
Further, please note that although the following description of some embodiments of the present disclosure is given in the context of 5th Generation New Radio (5G NR) , the present disclosure is not limited thereto. In fact, as long as radio signal relaying is involved, the inventive concept of the present disclosure may be applicable to any appropriate communication architecture, for example, to Global System for Mobile Communications (GSM) /General Packet Radio Service (GPRS) , Enhanced Data Rates for GSM Evolution (EDGE) , Code Division Multiple Access (CDMA) , Wideband CDMA (WCDMA) , Time Division -Synchronous CDMA (TD-SCDMA) , CDMA2000, Worldwide Interoperability for Microwave Access (WiMAX) , Wireless Fidelity (Wi-Fi) , Long Term Evolution (LTE) , etc. Therefore, one skilled in the arts could readily understand that the terms used herein may also refer to their equivalents in any other infrastructure. For example, the term ″a wireless device″ used herein may refer to a user equipment (UE) , a mobile device, a mobile terminal, a mobile station, a user device, a user terminal, a wireless terminal, an IoT device, a vehicle, a base station, a base transceiver station, an access point, a hot spot, a NodeB (NB) , an evolved NodeB (eNB) , a gNB, a network element, an access network (AN) node, or any other equivalents.
Fig. 1 is a diagram illustrating an exemplary wireless telecommunication network 10 in which a method for identifying radio signals from a RIS 110 according to an embodiment of the present disclosure is applicable.
As shown in Fig. 1, the network 10 may comprise a BS 100, a RIS 110, and a UE 120, and the BS 100 may communicate with the UE 120 via the RIS 110. However, the present disclosure is not limited thereto. In some other embodiments, multiple BS, multiple RISs, and/or multiple UEs may be comprised in the network 10. Further, although it is shown in Fig. 1 that the BS 100 is indirectly communicating with the UE 120 via the RIS 110, the BS 100 may communicate with the UE 120 directly simultaneously or alternatively.
As shown in Fig. 1, the RIS 100 may be a node that receives a radio signal from a transmitter (e.g., the BS 100 or the UE 120) and then re-radiates the radio signal to a receiver (e.g., the UE 120 or the BS 100) with controllable time-delays (e.g., e ^jθn as shown in Fig. 1) . The RIS 110 may consist of many small elements or particles 111 that can be assigned different time-delays and thereby synthesize the scattering behavior of an arbitrarily shaped object of the same size. This feature can, for instance, be used to beamform the radio signal towards the receiver, with cooperation between the BS 100 and the RIS 110 (e.g., its controller 115) , as shown in Fig. 1.
The RIS 110 may be a full-duplex transparent relay since the radio signals are processed in the analog domain and its surface may receive and re-transmit waves simultaneously. A very large surface area may then capture an unusually large fraction of the signal power and use the large aperture to re-radiate narrow beams to desired UEs.
As shown in Fig. 1, assuming that a channel from the BS 100 to the RIS particle 111 is g _n and a channel from the RIS particle 111 to the UE 120 is h _n, then a received signal at the UE 120 may be given by the following equation:
where s is a signal transmitted by the BS 100, and noise is a noise term.
According to the equation (1) , the RIS 110 may change the channel between the BS 100 and the UE 120 from the channel′s perspective. In other words, the RIS 110 may change the radio environment for the BS 100 and the UE 120.
There are some researches about implementation of RIS. A typical one is based on meta materials, which are referred to as meta-surface. The architecture of an RIS is substantially different as compared with phased arrays or multiple-antenna systems. More specifically, a RIS may contain a largest number of scattering elements, but each of them may need to be formed by the fewest and least costly components. In addition, active elements, e.g., power amplifiers, are typically not necessary for operating a RIS.
A meta-surface based RIS may be very thin, and its thickness is much less than a wavelength of a radio signal. A meta-surface is a sub-wavelength array formed by sub-wavelength metallic or dielectric scattering particles. It may be described as an electromagnetic discontinuity that is sub-wavelength in thickness, with typical values ranging from 1/10 to 1/5 of the wavelength and is electrically large in transverse size. Its unique properties lie in its capability of shaping the electromagnetic waves.
Through a proper design, a radio signal incidents into the meta-surface may be reflected with a predefined phase offset, since a reflection coefficient of each scattering particle is changeable in real time. Such a change may be achieved by electronic devices, for example, PIN diodes, MEMS switches.
Fig. 2 is a diagram illustrating an exemplary RIS 200 at which a method for enabling identification of the RIS according to an embodiment of the present disclosure is applicable. As shown in Fig. 2, the RIS 200 may comprise three layers: a meta-surface 230 for receiving and transmitting radio signals, a copper backplane 220 for shielding the electromagnetic waves, and a control circuit 210 for controlling the reflection amplitude and/or phase.
As shown in Fig. 2, there are multiple reflecting elements (or meta-atoms or particles) 231 provided on the meta-surface 230 for receiving and transmitting radio signals. As also shown in Fig. 2, a typical PIN diode-based design is achieved in each of the reflecting elements 231. DC voltage control may switch the diode on or off, to realize phase offset. Each of the reflecting elements 231 may have an equivalent circuit 232 in different states (e.g. on or off) . Although only two states are shown in Fig. 2, the present disclosure is not limited thereto. In some other embodiments, a different number of states may be provided by a reflecting element 231. For example, with a different circuit design (e.g., multiple PIN diodes) , a reflecting element 231 may be operated in four states, which enable a same received radio signal to be transmitted with four different phases in different states, respectively.
Further, in some embodiments, the RIS 200 may further comprise a RIS controller 215 for communicating with a BS (e.g., the BS 100 shown in Fig. 1) to receive instructions on how to change the amplitude and/or phase of the radio signals for each particle.
Fig. 3 is a diagram illustrating another exemplary RIS 300 at which a method for enabling identification of the RIS according to an embodiment of the present disclosure is applicable. The RIS 300 may be a passive reflect array, whose elements′antenna termination may be controlled electronically to backscatter and phase-shift incident signals. Each element may individually have a very limited effect on the propagated waves, but a sufficiently large number of elements may effectively manipulate the incident wave in a controllable manner. To be effective, this implementation may require a vastly large number of antenna elements, probably thousands.
Fig. 4 is a diagram illustrating an exemplary positioning procedure in which a method for enabling identification of the RIS according to an embodiment of the present disclosure is applicable. As shown in Fig. 4, when a UE 400 is being positioned through time-of-arrival (ToA) measurements, its position may be calculated in different ways. For example, in a real telecommunication network, calculating the position of the UE may be performed though the time-difference-of-arrival (TDOA) technology.
In TDOA, the difference between the measured ToAs may be calculated which eliminates the UE signal arrival timing offset difference. The resulting hyperbolas (e.g., those indicated by ToA ₂-ToA ₁ and ToA ₃-ToA ₁ in Fig. 4) may define possible locations of the UE 400 (e.g., the dotted curves in Fig. 4) and the intersection between all calculated hyperbolas may be determined as the actual location of the UE 400 (in absence of error sources) . Fig. 4 shows a 2D scenario. At least four BSs are needed to calculate the 3D position of the UE 400 when these BSs are not located in a same plane. In this case, the position errors do not depend on the distances between the UE 400 and the BSs 410, 420, and/or 430. In TDOA, all the BSs used need to be well synchronized. This is a commonly used algorithm for range based indoor positioning.
As mentioned earlier, the use of RIS may be accompanied with problems, for example, in positioning, interference mitigation, cell selection, by introducing additional propagation paths between the BSs and the UEs. A RIS may change channels to some level briefly, and a RIS has capabilities in shaping a MIMO channel to improve performance while at the same time simplifying precoding at the transmitter and equalization at the receiver. With RIS, a MIMO channel between a transmitter and a receiver may be effectively orthogonalized and a near-unity condition number may be achieved. This greatly simplifies the processing at the transmitter and the receiver, shifting the complexity to the RIS controller optimization instead.
Fig. 5 is a diagram illustrating a comparison between Rayleigh fading channels with and without RIS involved. From the comparison, it can be clearly seen that a RIS may concentrate energy of a radio signal. The problem accompanied with the RIS is shown in Fig. 6.
Fig. 6 is a diagram illustrating an exemplary wireless telecommunication network 20 in which a method for identifying radio signals from one or more RISs 610, 615 according to an embodiment of the present disclosure is applicable.
Assuming there are two RISs 610 and 615 in a propagation channel between a BS 600 and a UE620, three paths may be defined:
- Path #1, BS 600 to RIS #1 610 to UE 620, a non-line-of-sight (NLOS) path;
- Path #2, BS 600 to UE 620, a line-of-sight (LOS) path; and
- Path #3, BS 600 to RIS #2 615 to UE 620, an NLOS path.
This situation can be treated as a traditional LOS single tap channel, if only considering the path #2. Further, the path #2 and the path #3 may be additional multi-paths introduced by the RIS #1 610 and the RIS #2 615, respectively.
For simplification, assuming that all the three paths are single tap channels, the CIR (channel impulse response) difference among the three paths only is relative delay difference. Further, assuming that path gains of the three paths are same, the ideal power delay profile (PDP) for the three paths is shown in Fig. 7. For better demonstration, the distances among PDPs for the three paths are exaggerated.
As shown in (a) of Fig. 7, the receiver (e.g., the BS 600 or the UE 620) may get three samples, and based on PDP, the receiver may identify positioning related characteristics, relying on the path #2 and skipping the path #1 and the path #3. Please note that: for data receiving, all data samples from the path #1, the path #2, and the path #3 are combined, while for positioning, data samples from the LOS path, e.g. the path #2 in this case, are preferred. A received signal at the receiver may be given by the following equation:
where, h2 is the gain of the path #2, g1 and h1 correspond to the path #1, and g3 and h3 correspond to the path #3. For other symbols, they have similar meanings to those in the equation (1) .
As shown in (a) of Fig. 7, an ideal PDP for the three paths indicate that the three data samples have a roughly same amplitude or received signal power. However, in reality, a different but practical situation may be observed, for example, as shown in (b) of Fig. 7. For example, due to the RIS beamforming effect, the gain of the path #2 may be lower than those of the path #1 and the path #3, for example, when there is an obstacle between the BS 600 and the UE 620. Stronger paths reflected by RIS may be good for data receiving from receiving combination′s point of view, and that is exactly the reason why RIS is attractive. However, it may cause a positioning solution (e.g., that shown in Fig. 4) less effective and accurate.
Please note that this is quite different from scatters, walls, glasses, or trees with which the gains of the NLOS paths is typically much lower than that of the LOS path, if there is an LOS path. However, a RIS may concentrate energy to its receiver as described above, the beamforming gain may be significantly more than that of the LOS path sometimes, especially when there is an obstacle on the LOS path between the transmitter and the receiver.
As shown in (b) of Fig. 7, to identify the LOS path #2, some algorithms are needed to find the weak signal from the path #2 and distinguish it from the stronger signals from the path #1 and the path #3. For a legacy receiver, paths with higher power will typically be more likely to be viewed as LOS paths since no loss from reflect/scatter. However, a RIS may provide additional beamforming gain on RIS reflected NLOS path, and this may ruin legacy receiver estimation on LOS delay. A serious issue is that a RIS reflected signal will be accompanied with relative high delay which in turn may render a positioning related function less effective or accurate.
In summary, a RIS may beamform an incident signal, bring a negative effect in positioning if a legacy positioning concept is used directly. Therefore, a method for identifying radio signals from RISs may be needed for use cases comprising but not limited to positioning, interference mitigation, cell selection, etc.
In some embodiments of the present disclosure, a method for identifying radio signals from a RIS may be proposed, such that no-RIS reflected signal and RIS reflected signal may be distinguished from each other. Further, radio signals reflected by different RISs may be identified as well.
With the above mentioned method, a receiver may be aware the source of radio signals that are received via different paths (for example, which radio signal is a reflected signal coming from which RIS, or which radio signal is a radio signal received over-the-air without reflection) , and treat them differently for positioning. For example, path information may be utilized with help of RIS controller and some pre-measured information, which may comprise but not limited to: RIS and base station geometry information and/or RIS introduced delay information. With this assistance information, positioning accuracy can be further improved. Further, with the method, the RIS concept can still be kept the same while it may be transparent to the BS and the UE. Next, three different methods for identifying radio signals from a RIS will be described in detail with reference to Fig. 8 to Fig. 10, respectively. Please note that these methods may be performed alone or in any combination thereof.
When a RIS reflects a radio signal, some additional information may be added to the reflected signal explicitly or implicitly, to make sure that a receiver can identify the additional information, while the signal, channel, and data themselves itself are not impacted. Please note that, in some embodiments, a UE may have a zero or low moving speed, which brings head room to utilize the proposed methods.
In general, a sequence of radio signals may be received by the RIS from the transmitter, and the received sequence of radio signals may be adjusted by the RIS in the analog domain to enable the receiver to determine that the adjusted sequence of radio signals comes from the RIS. Finally, the adjusted sequence of radio signals may be transmitted to the receiver.
There are three methods for adjusting radio signals by the RIS, which could be utilized in a same RIS structure or in different RIS structures:
- on-off pattern by RIS;
- phase shifting pattern by RIS; and
- frequency shifting pattern by RIS.
In other words, the step of adjusting the received sequence of radio signals at the RIS in the analog domain may comprise at least one of:
- replacing at least one of the received radio signals with a zero-power signal;
- applying a phase shift to at least one of the received radio signals; and
- applying a frequency shift to at least one of the received radio signals.
Fig. 8 is a diagram illustrating exemplary PDPs when a method for identifying radio signals from RISs is applied according to an embodiment of the present disclosure. To be specific, Fig. 8 shows exemplary signal adjustment based on one or more on-off patterns for one or more RISs. Such on-off patterns may be pre-configured at the receivers and the RISs, or negotiated dynamically between the receivers and the RISs. For example, during the provisioning of the RISs, a predetermined on-off pattern may be specified for each RIS and associated with a corresponding BS by the operator, such that any UE served by the BS may be aware of the patterns by a broadcasted system message or dedicated signaling received from the BS.
As shown in Fig. 8, an on-off pattern of ″on, off, on, off″ is assigned to a RIS associated with the path #1, and another on-off pattern of ″on, on, off, off″ is assigned to another RIS associated with the path #3, such that the receiver may distinguish the three samples based on these on-off patterns. For example, for samples that are always on, the receiver may determine that these samples come from the BS directly since no RIS process is involved. For another example, for samples that have a pattern of″on, off, on, off″ , the receiver may determine that these samples come from the RIS associated with the path #1, while for samples that have a pattern of″on, on, off, off″ , the receiver may determine that these samples come from the RIS associated with the path #3.
Please note that although on-off patterns with four time instances are shown in Fig. 8, the present disclosure is not limited thereto. For example, an on-off pattern with two, three, five or more time instances may be used in other embodiments. Further, the time intervals between different time instances may be varied as required. For example, the RISs may reflect radio signals in their ″on″ states (as shown in (a) of Fig. 8) for a much longer time than they reflect radio signals in their ″off″ states (as shown in (b) , (c) , and (d) of Fig. 8) , such that one or more missing samples via a certain path do not affect the signal decoding at the receiver.
From the channel′s perspective, the received signal at the receiver at the different time instances may be given by the following equations:
y = h2. s+ noise (6)
Therefore, different paths may be identified separately based on the above equations (3) to (6) .
Fig. 9 is a diagram illustrating exemplary PDPs and simulated PDPs when another method for identifying radio signals from RISs is applied according to another embodiment of the present disclosure. To be specific, Fig. 9 shows exemplary signal adjustment based on one or more phase shifting patterns for one or more RISs. Such phase shifting patterns may be pre-configured at the receivers and the RISs, or negotiated dynamically between the receivers and the RISs. For example, during the provisioning of the RISs, a predetermined phase shifting pattern may be specified for each RIS and associated with a corresponding BS by the operator, such that any UE served by the BS may be aware of the patterns by a broadcasted system message or dedicated signaling received from the BS.
As shown in the top half of Fig. 9, a phase shifting pattern is assigned to both a RIS associated with the path #1 and another RIS associated with the path #3, such that both of the RISs may apply a phase shifting to their reflected radio signals at the same time instance. In this way, the receiver will receive the reflected radio signals with a different power level at the time instance than those received at other time instances as shown in Fig. 9, because the directivity of the phase shifted, reflected signals will be changed from the original reflected signal. Therefore, the receiver may distinguish the three samples based on their phase shifting patterns. For example, for samples that always have a stable power level, the receiver may determine that these samples come from the BS directly since no RIS process is involved. For another example, for samples that have a lower power level at a certain time instance, the receiver may determine that these samples come from a RIS. Although Fig. 9 shows that the RISs associated with the path #1 and the path #3 have a same phase shifting pattern, the present disclosure is not limited thereto. For example, in some other embodiments, for samples that have a pattern of ″high, low, high, low″ , the receiver may determine that these samples come from the RIS associated with the path #1, while for samples that have a pattern of ″high, high, low, low″ , the receiver may determine that these samples come from the RIS associated with the path #3.
As shown in the bottom half of Fig. 9, a simulated result for applying a phase shifting pattern at a RIS is shown. The curve 910 indicates signals received via the LOS path while the curve 920 indicates signals received via the NLOS path (or RIS) . This can be determined from the different power levels at the same time instance (e.g., 2000 shown in the bottom half of Fig. 9) .
From the channel′s perspective, the received signal at the receiver when a phase shifting is applied at the RIS associated with the path #1 may be given by the following equation:
where θ is the phase. With phase shifting, the change may be observed.
Therefore, different paths may be identified separately based on the above equations (7) and (3) , for example.
Fig. 10 is a diagram illustrating exemplary PDPs when yet another method for identifying radio signals from RISs is applied according to yet another embodiment of the present disclosure. To be specific, Fig. 10 shows exemplary signal adjustment based on one or more frequency shifting patterns for one or more RISs. Such frequency shifting patterns may be pre-configured at the receivers and the RISs, or negotiated dynamically between the receivers and the RISs. For example, during the provisioning of the RISs, a predetermined frequency shifting pattern may be specified for each RIS and associated with a corresponding BS by the operator, such that any UE served by the BS may be aware of the patterns by a broadcasted system message or dedicated signaling received from the BS.
With PIN diodes in the RIS structure, a diode switching frequency f _d may be introduced. The harmonics (1, 2, 3, ...) of f ₁ may be added into the incident signal frequency. At the receiver, PDPs may be calculated for different frequencies, f and f + f ₁, as shown by (a) and (b) of Fig. 10, respectively. Most of energy of a radio signal received over the path #1 may be observed at the frequency f + f ₁. In other words, its frequency is shifted by diode switching of the RIS associated with the path #1.
From the channel′s perspective, the received signal at the receiver when a frequency shifting is applied at the RIS associated with the path #1 may be given by the following equation:
Similar to the on-off pattern and phase shifting pattern, with the frequency shifting pattern, the change may be observed. Therefore, different paths may be identified separately based on the above equations (8) and (3) , for example.
Please note that although certain patterns for identifying RISs are described in the above embodiments, the present disclosure is not limited thereto. In some other embodiments, a same or different on-off pattern, a same or different phase shifting pattern, and/or a same or different frequency pattern may be used for identifying one or more RISs, separately or in any combination thereof.
For example, in a modified version of the embodiment shown in Fig. 10, another frequency shifting pattern may be applied by the RIS associated with the path #3, such that most of energy of a radio signal received over the path #3 may be observed at the frequency f + f ₃ that is different from f and f + f ₁. In this way, the RIS associated with the path #3 may be distinguished from the path #2 and the path #1 as well. For another example, in a modified version of the embodiment of Fig. 9, different phase shifting patterns may be applied by the RISs associated with the path #1 and the path #3, respectively, such that the RIS associated with the path #3 may be distinguished from the path #1 as well.
For yet another example, in a simplified version of the embodiment shown in Fig. 8, the on-off patterns for the path #1 and the path #3 may be same and is ″on off″ . With this pattern, the receiver may easily identify the radio signals received via the LOS path #2, as shown in (d) of Fig. 8 and use the identified radio signals for positioning, for example, by using the LOS path based positioning.
With the above mentioned method, a receiver may be aware the source of radio signals that are received via different paths (for example, which radio signal is a reflected signal coming from which RIS, or which radio signal is a radio signal received over-the-air without reflection) , and treat them differently for positioning.
Fig. 11 is a diagram illustrating exemplary PDPs for positioning a UE according to an embodiment of the present disclosure. As shown in Fig. 11, each of the multiple samples of a radio signal observed at the receiver may be distinguished one from another. For example, based on an on-off predefined pattern, the receiver may determine that path #2 is a LOS path, and a legacy algorithm for positioning the UE may be used to identify UE signal arrival timing at the base station via air. Additionally or alternatively, based on the path #1 and the path #3, a RIS based positioning method may be used to estimate ToA of LOS path #2 between the BS and the UE.
Further, a RIS in principle may provide more reflection information and this information may further improve positioning performance. A BS may need some assistance information from a RIS controller and/or some pre-measured information, which may comprise but not limited to:
- RIS and base station geometry information; and/or
- RIS reflector introduced delay information.
In reality, an important issue is identifying paths separately before RIS positioning can work. With the methods proposed above, paths from RISs can be identified, and RIS reflection information can be utilized for positioning.
Fig. 12 is a flow chart of an exemplary method 1200 at a RIS for facilitating a first wireless device in identifying radio signals from the RIS according to an embodiment of the present disclosure. The method 1200 may be performed at a RIS (e.g., any of the RISs 110, 200, 300, 610, 615) for facilitating a receiving wireless device in identifying the RIS. The method 1200 may comprise steps S1210, S1220, and S1230. However, the present disclosure is not limited thereto. In some other embodiments, the method 1200 may comprise more steps, less steps, different steps, or any combination thereof. Further the steps of the method 1200 may be performed in a different order than that described herein. Further, in some embodiments, a step in the method 1200 may be split into multiple sub-steps and performed by different entities, and/or multiple steps in the method 1200 may be combined into a single step.
The method 1200 may begin at step S1210 where a sequence of radio signals is received from a second wireless device.
At step S1220, the received sequence of radio signals is adjusted in the analog domain to enable the first wireless device to determine that the adjusted sequence of radio signals comes from the RIS.
At step S1230, the adjusted sequence of radio signals is transmitted to the first wireless device.
In some embodiments, the step S1220 may comprise at least one of: replacing at least one of the received radio signals with a zero-power signal; applying a phase shift to at least one of the received radio signals; and applying a frequency shift to at least one of the received radio signals. In some embodiments, before the step S1220, the method 1200 may further comprise at least one of: pre-configuring a criterion for selecting one or more radio signals for adjustment; and receiving the criterion for selecting one or more radio signals for adjustment. In some embodiments, before the step S1230, the method 1200 may further comprise: transmitting, to the first wireless device, the criterion for selecting one or more radio signals for adjustment.
In some embodiments, the step of replacing at least one of the received radio signals with a zero-power signal may comprise: determining at least one of the received radio signals according to the criterion; and replacing the at least one determined radio signal with a zero-power signal. In some embodiments, the step of applying phase shift to at least one of the received radio signals may comprise: determining at least one of the received radio signals according to the criterion; and applying the phase shift to the at least one determined radio signal. In some embodiments, for each of the at least one determined radio signal, a signal-specific phase shift or a common phase shift may be applied.
In some embodiments, the step of applying a frequency shift to at least one of the received radio signals may comprise: determining at least one of the received radio signals according to the criterion; and applying the frequency shift to the at least one determined radio signal. In some embodiments, for each of the at least one determined radio signal, a signal-specific frequency shift or a common frequency shift may be applied.
In some embodiments, the step S1220 may further comprise: adjusting the received sequence of radio signals in the analog domain to enable the first wireless device to further determine one or more of: -geometry information of the RIS and/or the second wireless device; and -information about signal delay introduced by the RIS. In some embodiments, one of the first wireless device and the second wireless device may be a User Equipment (UE) , and the other of the first wireless device and the second wireless device may be a Radio Access Network (RAN) node. In some embodiments, the criterion may be received from the RAN node.
Fig. 13 is a flow chart of an exemplary method 1300 at a first wireless device for determining that a sequence of radio signals comes from a reconfigurable intelligent surface (RIS) according to an embodiment of the present disclosure. The method 1300 may be performed at a BS (e.g., any of the BSs 100, 410, 420, 430, 600) or a UE (e.g., any of the UEs 120, 400, 620) for identifying one or more RISs. The method 1300 may comprise steps S1310 and S1320. However, the present disclosure is not limited thereto. In some other embodiments, the method 1300 may comprise more steps, less steps, different steps, or any combination thereof. Further the steps of the method 1300 may be performed in a different order than that described herein. Further, in some embodiments, a step in the method 1300 may be split into multiple sub-steps and performed by different entities, and/or multiple steps in the method 1300 may be combined into a single step.
The method 1300 may begin at step S1310 where the sequence of radio signals is received.
At step S1320, it is determined that the sequence of radio signals comes from the RIS in response to determining that at least one of the received radio signals is adjusted at least partially based on a criterion for selecting one or more radio signals from the sequence of radio signals for adjustment.
In some embodiments, the method 1300 may further comprise: receiving a second sequence of radio signals; and determining that the second sequence of radio signals comes from a second wireless device in response to determining that none of the radio signals of the second sequence of radio signals is adjusted at least partially based on the criterion. In some embodiments, the method 1300 may further comprise: receiving a third sequence of radio signals; and determining that the third sequence of radio signals comes from another RIS in response to determining that at least one of the radio signals of the third sequence of radio signals is adjusted at least partially based on another criterion.
In some embodiments, the method 1300 may further comprise at least one of: performing a first positioning procedure at least partially based on the sequence of radio signals and information related to the RIS; performing a second positioning procedure at least partially based on the second sequence of radio signals and information related to the second wireless device; and performing a third positioning procedure at least partially based on the third sequence of radio signals and information related to the other RIS.
In some embodiments, the criterion and/or the other criterion may be pre-configured or received from the second wireless device, the RIS, and/or the other RIS. In some embodiments, the step of determining that at least one of the received radio signals is adjusted at least partially based on the criterion may comprise at least one of: determining that at least one of the received radio signals is replaced with a zero-power signal at least partially based on the criterion; determining that a phase shift is applied to at least one of the received radio signals at least partially based on the criterion; and determining that a frequency shift is applied to at least one of the received radio signals at least partially based on the criterion. In some embodiments, the step of determining that at least one of the received radio signals is replaced with a zero-power signal at least partially based on the criterion may comprise: determining a pattern of missing signals in the received sequence of radio signals; comparing the pattern of missing signals with the criterion; and determining that at least one of the received radio signals is replaced with a zero-power signal in response to determining that the pattern of missing signals is matched with the criterion.
In some embodiments, the step of determining that a phase shift is applied to at least one of the received radio signals at least partially based on the criterion may comprise: determining a pattern of received signal power changing for the received sequence of radio signals; comparing the pattern of received signal power changing with the criterion; and determining that a phase shift is applied to at least one of the received radio signals in response to determining that the pattern of received signal power changing is matched with the criterion. In some embodiments, the step of determining that a frequency shift is applied to at least one of the received radio signals at least partially based on the criterion may comprise: determining a pattern of received signal power changing at different frequencies for the received sequence of radio signals; comparing the pattern of received signal power changing at the different frequencies with the criterion; and determining that a frequency shift is applied to at least one of the received radio signals in response to determining that the pattern of received signal power changing at the different frequencies is matched with the criterion.
In some embodiments, the method 1300 may further comprise: further determining, from the received sequence of radio signals one or more of geometry information of the RIS and/or the second wireless device and information about signal delay introduced by the RIS at least partially based on the criterion. In some embodiments, one of the first wireless device and the second wireless device may be a User Equipment (UE) , and the other of the first wireless device and the second wireless device may be a Radio Access Network (RAN) node.
Fig. 14 schematically shows an embodiment of an arrangement which may be used in a RIS according to an embodiment of the present disclosure. Comprised in the arrangement 1400 are a processing unit 1406, e.g., with an application specific integrated circuit (ASIC) , a field programmable gate array (FPGA) , a Digital Signal Processor (DSP) , or a Central Processing Unit (CPU) . The processing unit 1406 may be a single unit or a plurality of units to perform different actions of procedures described herein. The arrangement 1400 may also comprise an input unit 1402 for receiving signals from other entities, and an output unit 1404 for providing signal (s) to other entities. The input unit 1402 and the output unit 1404 may be arranged as an integrated entity or as separate entities.
Furthermore, the arrangement 1400 may comprise at least one computer program product 1408 in the form of a non-volatile or volatile memory, e.g., an Electrically Erasable Programmable Read-Only Memory (EEPROM) , a flash memory and/or a hard drive. The computer program product 1408 comprises a computer program 1410, which comprises code/computer readable instructions, which when executed by the processing unit 1406 in the arrangement 1400 causes the arrangement 1400 and/or the remote UE and/or the relay UE in which it is comprised to perform the actions, e.g., of the procedure described earlier in conjunction with Fig. 7 through Fig. 12 or any other variant.
The computer program 1410 may be configured as a computer program code structured in computer program modules 1410A -1410C. Hence, in an exemplifying embodiment when the arrangement 1400 is used in the RIS, the code in the computer program of the arrangement 1400 includes: a module 1410A for receiving, from a second wireless device, a sequence of radio signals; a module 1410B for adjusting the received sequence of radio signals in the analog domain to enable the first wireless device to determine that the adjusted sequence of radio signals comes from the RIS; and a transmitting module 1410C for transmitting, to the first wireless device, the adjusted sequence of radio signals.
The computer program modules could essentially perform the actions of the flow illustrated in Fig. 7 through Fig. 12, to emulate the RIS. In other words, when the different computer program modules are executed in the processing unit 1406, they may correspond to different modules in the RIS.
Although the code means in the embodiments disclosed above in conjunction with Fig. 14 are implemented as computer program modules which when executed in the processing unit causes the arrangement to perform the actions described above in conjunction with the figures mentioned above, at least one of the code means may in alternative embodiments be implemented at least partly as hardware circuits.
The processor may be a single CPU (Central processing unit) , but could also comprise two or more processing units. For example, the processor may include general purpose microprocessors; instruction set processors and/or related chips sets and/or special purpose microprocessors such as Application Specific Integrated Circuit (ASICs) . The processor may also comprise board memory for caching purposes. The computer program may be carried by a computer program product connected to the processor. The computer program product may comprise a computer readable medium on which the computer program is stored. For example, the computer program product may be a flash memory, a Random-access memory (RAM) , a Read-Only Memory (ROM) , or an EEPROM, and the computer program modules described above could in alternative embodiments be distributed on different computer program products in the form of memories within the RIS.
Fig. 15 schematically shows an embodiment of an arrangement which may be used in a wireless device according to an embodiment of the present disclosure. Comprised in the arrangement 1500 are a processing unit 1506, e.g., with an application specific integrated circuit (ASIC) , a field programmable gate array (FPGA) , a Digital Signal Processor (DSP) , or a Central Processing Unit (CPU) . The processing unit 1506 may be a single unit or a plurality of units to perform different actions of procedures described herein. The arrangement 1500 may also comprise an input unit 1502 for receiving signals from other entities, and an output unit 1504 for providing signal (s) to other entities. The input unit 1502 and the output unit 1504 may be arranged as an integrated entity or as separate entities.
Furthermore, the arrangement 1500 may comprise at least one computer program product 1508 in the form of a non-volatile or volatile memory, e.g., an Electrically Erasable Programmable Read-Only Memory (EEPROM) , a flash memory and/or a hard drive. The computer program product 1508 comprises a computer program 1510, which comprises code/computer readable instructions, which when executed by the processing unit 1506 in the arrangement 1500 causes the arrangement 1500 and/or the remote UE and/or the relay UE in which it is comprised to perform the actions, e.g., of the procedure described earlier in conjunction with Fig. 7 through Fig. 11 and Fig. 13 or any other variant.
The computer program 1510 may be configured as a computer program code structured in computer program modules 1510A -1510B. Hence, in an exemplifying embodiment when the arrangement 1500 is used in the RIS, the code in the computer program of the arrangement 1500 includes: a module 1510A for receiving the sequence of radio signals; and a module 1510B for determining that the sequence of radio signals comes from the RIS in response to determining that at least one of the received radio signals is adjusted at least partially based on a criterion for selecting one or more radio signals from the sequence of radio signals for adjustment.
The computer program modules could essentially perform the actions of the flow illustrated in Fig. 7 through Fig. 11 and Fig. 13, to emulate the wireless device. In other words, when the different computer program modules are executed in the processing unit 1506, they may correspond to different modules in the wireless device.
Although the code means in the embodiments disclosed above in conjunction with Fig. 15 are implemented as computer program modules which when executed in the processing unit causes the arrangement to perform the actions described above in conjunction with the figures mentioned above, at least one of the code means may in alternative embodiments be implemented at least partly as hardware circuits.
The processor may be a single CPU (Central processing unit) , but could also comprise two or more processing units. For example, the processor may include general purpose microprocessors; instruction set processors and/or related chips sets and/or special purpose microprocessors such as Application Specific Integrated Circuit (ASICs) . The processor may also comprise board memory for caching purposes. The computer program may be carried by a computer program product connected to the processor. The computer program product may comprise a computer readable medium on which the computer program is stored. For example, the computer program product may be a flash memory, a Random-access memory (RAM) , a Read-Only Memory (ROM) , or an EEPROM, and the computer program modules described above could in alternative embodiments be distributed on different computer program products in the form of memories within the wireless device.
Correspondingly to the method 1200 as described above, an exemplary RIS is provided. Fig. 16 is a block diagram of a RIS 1600 according to an embodiment of the present disclosure. The RIS 1600 may be, e.g., any of the RISs 110, 200, 300, 610, 615 in some embodiments.
The RIS 1600 may be configured to perform the method 1200 as described above in connection with Fig. 12. As shown in Fig. 16, the RIS 1600 may comprise a receiving module 1610 for receiving, from a second wireless device, a sequence of radio signals; an adjusting module 1620 for adjusting the received sequence of radio signals in the analog domain to enable the first wireless device to determine that the adjusted sequence of radio signals comes from the RIS; and a transmitting module 1630 for transmitting, to the first wireless device, the adjusted sequence of radio signals.
The above modules 1610, 1620, and/or 1630 may be implemented as a pure hardware solution or as a combination of software and hardware, e.g., by one or more of: a processor or a micro-processor and adequate software and memory for storing of the software, a Programmable Logic Device (PLD) or other electronic component (s) or processing circuitry configured to perform the actions described above, and illustrated, e.g., in Fig. 12. Further, the RIS 1600 may comprise one or more further modules, each of which may perform any of the steps of the method 1200 described with reference to Fig. 12.
Correspondingly to the method 1300 as described above, an exemplary wireless device is provided. Fig. 17 is a block diagram of a wireless device 1700 according to an embodiment of the present disclosure. The wireless device 1700 may be, e.g., a BS (e.g., any of the BSs 100, 410, 420, 430, 600) or a UE (e.g., any of the UEs 120, 400, 620) in some embodiments.
The wireless device 1700 may be configured to perform the method 1300 as described above in connection with Fig. 13. As shown in Fig. 17, the wireless device 1700 may comprise a receiving module 1710 for receiving the sequence of radio signals; and a determining module 1720 for determining that the sequence of radio signals comes from the RIS in response to determining that at least one of the received radio signals is adjusted at least partially based on a criterion for selecting one or more radio signals from the sequence of radio signals for adjustment.
The above modules 1710 and/or 1720 may be implemented as a pure hardware solution or as a combination of software and hardware, e.g., by one or more of: a processor or a micro-processor and adequate software and memory for storing of the software, a Programmable Logic Device (PLD) or other electronic component (s) or processing circuitry configured to perform the actions described above, and illustrated, e.g., in Fig. 13. Further, the wireless device 1700 may comprise one or more further modules, each of which may perform any of the steps of the method 1300 described with reference to Fig. 13.
The disclosure has been described with reference to embodiments and drawings. It should be understood that various modifications, alternations and additions can be made by those skilled in the art without departing from the spirits and scope of the disclosure. Therefore, the scope of the disclosure is not limited to the above particular embodiments but only defined by the claims as attached and equivalents thereof.
Abbreviation Explanation
UL/DL Uplink/Downlink
LoS/NLoS Line-of-sight/non-line-of-sight
RTS Reconfigurable intelligent surface
PDP Power delay profile

Claims

A method (1200) at a reconfigurable intelligent surface (RIS) (110, 200, 300, 610, 615, 1400, 1600) for facilitating a first wireless device (100, 120, 400, 410, 420, 430, 600, 620, 1500, 1700) in identifying radio signals from the RIS (110, 200, 300, 610, 615, 1400, 1600) , the method comprising:

receiving (S1210) , from a second wireless device (120, 100, 410, 420, 430, 400, 620, 600) , a sequence of radio signals;

adjusting (S1220) the received sequence of radio signals in the analog domain to enable the first wireless device (100, 120, 400, 410, 420, 430, 600, 620, 1500, 1700) to determine that the adjusted sequence of radio signals comes from the RIS (110, 200, 300, 610, 615, 1400, 1600) ; and

transmitting (S1230) , to the first wireless device (100, 120, 400, 410, 420, 430, 600, 620, 1500, 1700) , the adjusted sequence of radio signals.
The method (1200) of claim 1, wherein the step (S1220) of adjusting the received sequence of radio signals in the analog domain comprises at least one of:

replacing at least one of the received radio signals with a zero-power signal;

applying a phase shift to at least one of the received radio signals; and

applying a frequency shift to at least one of the received radio signals.
The method (1200) of claim 2, wherein before the step (S1220) of adjusting the received sequence of radio signals in the analog domain, the method further comprises at least one of:

pre-configuring a criterion for selecting one or more radio signals for adjustment; and

receiving the criterion for selecting one or more radio signals for adjustment.
The method (1200) of claim 3, wherein before the step (S1230) of transmitting, to the first wireless device (100, 120, 400, 410, 420, 430, 600, 620, 1500, 1700) , the adjusted sequence of radio signals, the method further comprises:

transmitting, to the first wireless device (100, 120, 400, 410, 420, 430, 600, 620, 1500, 1700) , the criterion for selecting one or more radio signals for adjustment.
The method (1200) of claim 3 or 4, wherein the step of replacing at least one of the received radio signals with a zero-power signal comprises:

determining at least one of the received radio signals according to the criterion; and

replacing the at least one determined radio signal with a zero-power signal.
The method (1200) of any of claims 3 to 5, wherein the step of applying phase shift to at least one of the received radio signals comprises:

determining at least one of the received radio signals according to the criterion; and

applying the phase shift to the at least one determined radio signal.
The method (1200) of claim 6, wherein for each of the at least one determined radio signal, a signal-specific phase shift or a common phase shift is applied.
The method (1200) of any of claims 3 to 7, wherein the step of applying a frequency shift to at least one of the received radio signals comprises:

determining at least one of the received radio signals according to the criterion; and

applying the frequency shift to the at least one determined radio signal.
The method (1200) of claim 8, wherein for each of the at least one determined radio signal, a signal-specific frequency shift or a common frequency shift is applied.
The method (1200) of any of claims 1 to 9, wherein the step (S1220) of adjusting the received sequence of radio signals in the analog domain further comprises:

adjusting the received sequence of radio signals in the analog domain to enable the first wireless device (100, 120, 400, 410, 420, 430, 600, 620, 1500, 1700) to further determine one or more of:

- geometry information of the RIS (110, 200, 300, 610, 615, 1400, 1600) and/or the second wireless device (120, 100, 410, 420, 430, 400, 620, 600) ; and

- information about signal delay introduced by the RIS (110, 200, 300, 610, 615, 1400, 1600) .
The method (1200) of any of claims 1 to 10, wherein one of the first wireless device (100, 120, 400, 410, 420, 430, 600, 620, 1500, 1700) and the second wireless device (120, 100, 410, 420, 430, 400, 620, 600) is a User Equipment (UE) , and the other of the first wireless device (100, 120, 400, 410, 420, 430, 600, 620, 1500, 1700) and the second wireless device (120, 100, 410, 420, 430, 400, 620, 600) is a Radio Access Network (RAN) node.
The method (1200) of claim 11, wherein the criterion is received from the RAN node (100, 410, 420, 430, 600) .
A reconfigurable intelligent surface (RIS) (110, 200, 300, 610, 615, 1400, 1600) , comprising:

a processor (1406) ;

a memory (1408) storing instructions (1410) which, when executed by the processor (1406) , cause the processor (1406) to perform any of the methods of claims 1 to 12.
A method (1300) at a first wireless device (100, 120, 400, 410, 420, 430, 600, 620, 1500, 1700) for determining that a sequence of radio signals comes from a reconfigurable intelligent surface (RIS) (110, 200, 300, 610, 615, 1400, 1600) , the method comprising:

receiving (S1310) the sequence of radio signals; and

determining (S1320) that the sequence of radio signals comes from the RIS (110, 200, 300, 610, 615, 1400, 1600) in response to determining that at least one of the received radio signals is adjusted at least partially based on a criterion for selecting one or more radio signals from the sequence of radio signals for adjustment.
The method (1300) of claim 14, further comprising:

receiving a second sequence of radio signals; and

determining that the second sequence of radio signals comes from a second wireless device (120, 100, 410, 420, 430, 400, 620, 600) in response to determining that none of the radio signals of the second sequence of radio signals is adjusted at least partially based on the criterion.
The method (1300) of claim 14 or 15, further comprising:

receiving a third sequence of radio signals; and

determining that the third sequence of radio signals comes from another RIS (110, 200, 300, 610, 615, 1400, 1600) in response to determining that at least one of the radio signals of the third sequence of radio signals is adjusted at least partially based on another criterion.
The method (1300) of claim 15 or 16, further comprising at least one of:

performing a first positioning procedure at least partially based on the sequence of radio signals and information related to the RIS (110, 200, 300, 610, 615, 1400, 1600) ;

performing a second positioning procedure at least partially based on the second sequence of radio signals and information related to the second wireless device (120, 100, 410, 420, 430, 400, 620, 600) ; and

performing a third positioning procedure at least partially based on the third sequence of radio signals and information related to the other RIS (110, 200, 300, 610, 615, 1400, 1600) .
The method (1300) of any of claim 14 to 16, wherein the criterion and/or the other criterion are pre-configured or received from the second wireless device (120, 100, 410, 420, 430, 400, 620, 600) , the RIS (110, 200, 300, 610, 615, 1400, 1600) , and/or the other RIS (110, 200, 300, 610, 615, 1400, 1600) .
The method (1300) of any of claims 14 to 18, wherein the step (S1320) of determining that at least one of the received radio signals is adjusted at least partially based on the criterion comprises at least one of:

determining that at least one of the received radio signals is replaced with a zero-power signal at least partially based on the criterion;

determining that a phase shift is applied to at least one of the received radio signals at least partially based on the criterion; and

determining that a frequency shift is applied to at least one of the received radio signals at least partially based on the criterion.
The method (1300) of claim 19, wherein the step of determining that at least one of the received radio signals is replaced with a zero-power signal at least partially based on the criterion comprises:

determining a pattern of missing signals in the received sequence of radio signals;

comparing the pattern of missing signals with the criterion; and

determining that at least one of the received radio signals is replaced with a zero-power signal in response to determining that the pattern of missing signals is matched with the criterion.
The method (1300) of claim 19 or 20, wherein the step of determining that a phase shift is applied to at least one of the received radio signals at least partially based on the criterion comprises:

determining a pattern of received signal power changing for the received sequence of radio signals;

comparing the pattern of received signal power changing with the criterion; and

determining that a phase shift is applied to at least one of the received radio signals in response to determining that the pattern of received signal power changing is matched with the criterion.
The method (1300) of any of claims 19 to 21, wherein the step of determining that a frequency shift is applied to at least one of the received radio signals at least partially based on the criterion comprises:

determining a pattern of received signal power changing at different frequencies for the received sequence of radio signals;

comparing the pattern of received signal power changing at the different frequencies with the criterion; and

determining that a frequency shift is applied to at least one of the received radio signals in response to determining that the pattern of received signal power changing at the different frequencies is matched with the criterion.
The method (1300) of any of claims 14 to 22, further comprising:

further determining, from the received sequence of radio signals one or more of geometry information of the RIS (110, 200, 300, 610, 615, 1400, 1600) and/or the second wireless device (120, 100, 410, 420, 430, 400, 620, 600) and information about signal delay introduced by the PIS (110, 200, 300, 610, 615, 1400, 1600) at least partially based on the criterion.
The method (1300) of any of claims 14 to 23, wherein one of the first wireless device (100, 120, 400, 410, 420, 430, 600, 620, 1500, 1700) and the second wireless device (120, 100, 410, 420, 430, 400, 620, 600) is a User Equipment (UE) , and the other of the first wireless device (100, 120, 400, 410, 420, 430, 600, 620, 1500, 1700) and the second wireless device (120, 100, 410, 420, 430, 400, 620, 600) is a Radio Access Network (RAN) node.
A first wireless device (100, 120, 400, 410, 420, 430, 600, 620, 1500, 1700) , comprising:

a processor (1506) ;

a memory (1508) storing instructions which, when executed by the processor (1506) , cause the processor (1506) to perform any of the methods of claims 14 to 24.
A computer program (1410, 1510) comprising instructions which, when executed by at least one processor (1406, 1506) , cause the at least one processor (1406, 1506) to carry out the method of any of claims 1 to 12 and 14 to 24.
A carrier (1408, 1508) containing the computer program (1410, 1510) of claim 26, wherein the carrier (1408, 1508) is one of an electronic signal, optical signal, radio signal, or computer readable storage medium.
A wireless telecommunications system (10, 20) , comprising:

a first wireless device (100, 120; 600, 620) of claim 25;

a second wireless device (120, 100; 620, 600) configured to transmit radio signals; and

a reconfigurable intelligent surface (RIS) (110; 610, 615) of claim 13, which is configured to adjust and forward the radio signal to the first wireless device (100, 120; 600, 620) .