EP4706314A1

EP4706314A1 - Doppler frequency estimation for reconfigurable intelligent surface communication links

Info

Publication number: EP4706314A1
Application number: EP23935915.1A
Authority: EP
Inventors: Min Huang; Jing Dai; Hao Xu
Original assignee: Qualcomm Inc
Current assignee: Qualcomm Inc
Priority date: 2023-05-05
Filing date: 2023-05-05
Publication date: 2026-03-11
Also published as: WO2024229585A1; CN121040171A

Abstract

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may receive, from a network node, an indication of time domain rotation factors associated with respective reconfigurable intelligent surfaces (RISs) of one or more RISs. The UE may receive, during a time domain measurement occasion, respective reference signals via a direct link with the network node and via one or more indirect links associated with the one or more RISs. The UE may transmit, to the network node, a report indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with measurements of the respective reference signals, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs. Numerous other aspects are described.

Description

DOPPLER FREQUENCY ESTIMATION FOR RECONFIGURABLE INTELLIGENT SURFACE COMMUNICATION LINKS

FIELD OF THE DISCLOSURE
Aspects of the present disclosure generally relate to wireless communication and to techniques and apparatuses for Doppler frequency estimation for reconfigurable intelligent surface (RIS) communication links.

BACKGROUND

Wireless communication systems are widely deployed to provide various telecommunication services, such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, or the like) . Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, time division synchronous code division multiple access (TD-SCDMA) systems, and Long Term Evolution (LTE) . LTE/LTE-Advanced is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by the Third Generation Partnership Project (3GPP) .
A wireless network may include one or more network nodes that support communication for wireless communication devices, such as a user equipment (UE) or multiple UEs. A UE may communicate with a network node via downlink communications and uplink communications. “Downlink” (or “DL” ) refers to a communication link from the network node to the UE, and “uplink” (or “UL” ) refers to a communication link from the UE to the network node. Some wireless networks may support device-to-device communication, such as via a local link (e.g., a sidelink (SL) , a wireless local area network (WLAN) link, and/or a wireless personal area network (WPAN) link, among other examples) .
The above multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different UEs to communicate on a municipal, national, regional, and/or global level. New Radio (NR) , which may be referred to as 5G, is a set of enhancements to the LTE mobile standard promulgated by the 3GPP. NR is designed to better support mobile broadband internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP) (CP-OFDM) on the downlink, using CP-OFDM and/or single-carrier frequency division multiplexing (SC-FDM) (also known as discrete Fourier transform spread OFDM (DFT-s-OFDM) ) on the uplink, as well as supporting beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation. As the demand for mobile broadband access continues to increase, further improvements in LTE, NR, and other radio access technologies remain useful.

SUMMARY

Some aspects described herein relate to a user equipment (UE) for wireless communication. The UE may include a memory and one or more processors coupled to the memory. The one or more processors may be configured to receive, from a network node, an indication of time domain rotation factors associated with respective reconfigurable intelligent surfaces (RISs) of one or more RISs. The one or more processors may be configured to receive, during a time domain measurement occasion, respective reference signals via a direct link with the network node and via one or more indirect links associated with the one or more RISs. The one or more processors may be configured to transmit, to the network node, a report indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with measurements of the respective reference signals, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs.
Some aspects described herein relate to a network node for wireless communication. The network node may include a memory and one or more processors coupled to the memory. The one or more processors may be configured to transmit, an indication, for a UE and one or more RISs, of time domain rotation factors associated with respective RISs of the one or more RISs. The one or more processors may be configured to transmit, during a time domain measurement occasion, a reference signal via a direct link with the UE and via one or more indirect links associated with the one or more RISs. The one or more processors may be configured to receive a report, associated with the UE, indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with a measurement of the reference signal, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs.
Some aspects described herein relate to a method of wireless communication performed by a UE. The method may include receiving, from a network node, an indication of time domain rotation factors associated with respective RISs of one or more RISs. The method may include receiving, during a time domain measurement occasion, respective reference signals via a direct link with the network node and via one or more indirect links associated with the one or more RISs. The method may include transmitting, to the network node, a report indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with measurements of the respective reference signals, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs.
Some aspects described herein relate to a method of wireless communication performed by a network node. The method may include transmitting, an indication, for a UE and one or more RISs, of time domain rotation factors associated with respective RISs of the one or more RISs. The method may include transmitting, during a time domain measurement occasion, a reference signal via a direct link with the UE and via one or more indirect links associated with the one or more RISs. The method may include receiving a report, associated with the UE, indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with a measurement of the reference signal, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs.
Some aspects described herein relate to an RIS for wireless communication. The RIS may include a memory and one or more processors coupled to the memory. The one or more processors may be configured to receive, from a network node, an indication of a time domain rotation factor associated with the RIS. The one or more processors may be configured to reflect, using a reflection coefficient, a reference signal associated with the network node, the reflection coefficient being based on the time domain rotation factor.
Some aspects described herein relate to a method of wireless communication performed by an RIS. The method may include receiving, from a network node, an indication of a time domain rotation factor associated with the RIS. The method may include reflecting, using a reflection coefficient, a reference signal associated with the network node, the reflection coefficient being based on the time domain rotation factor.
Some aspects described herein relate to a non-transitory computer-readable medium that stores a set of instructions for wireless communication by a UE. The set of instructions, when executed by one or more processors of the UE, may cause the UE to receive, from a network node, an indication of time domain rotation factors associated with respective RISs of one or more RISs. The set of instructions, when executed by one or more processors of the UE, may cause the UE to receive, during a time domain measurement occasion, respective reference signals via a direct link with the network node and via one or more indirect links associated with the one or more RISs. The set of instructions, when executed by one or more processors of the UE, may cause the UE to transmit, to the network node, a report indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with measurements of the respective reference signals, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs.
Some aspects described herein relate to a non-transitory computer-readable medium that stores a set of instructions for wireless communication by a network node. The set of instructions, when executed by one or more processors of the network node, may cause the network node to transmit, an indication, for a UE and one or more RISs, of time domain rotation factors associated with respective RISs of the one or more RISs. The set of instructions, when executed by one or more processors of the network node, may cause the network node to transmit, during a time domain measurement occasion, a reference signal via a direct link with the UE and via one or more indirect links associated with the one or more RISs. The set of instructions, when executed by one or more processors of the network node, may cause the network node to receive a report, associated with the UE, indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with a measurement of the reference signal, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs.
Some aspects described herein relate to a non-transitory computer-readable medium that stores a set of instructions for wireless communication by an RIS. The set of instructions, when executed by one or more processors of the RIS, may cause the RIS to receive, from a network node, an indication of a time domain rotation factor associated with the RIS. The set of instructions, when executed by one or more processors of the RIS, may cause the RIS to reflect, using a reflection coefficient, a reference signal associated with the network node, the reflection coefficient being based on the time domain rotation factor.
Some aspects described herein relate to an apparatus for wireless communication. The apparatus may include means for receiving, from a network node, an indication of time domain rotation factors associated with respective RISs of one or more RISs. The apparatus may include means for receiving, during a time domain measurement occasion, respective reference signals via a direct link with the network node and via one or more indirect links associated with the one or more RISs. The apparatus may include means for transmitting, to the network node, a report indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with measurements of the respective reference signals, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs.
Some aspects described herein relate to an apparatus for wireless communication. The apparatus may include means for transmitting, an indication, for a UE and one or more RISs, of time domain rotation factors associated with respective RISs of the one or more RISs. The apparatus may include means for transmitting, during a time domain measurement occasion, a reference signal via a direct link with the UE and via one or more indirect links associated with the one or more RISs. The apparatus may include means for receiving a report, associated with the UE, indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with a measurement of the reference signal, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs.
Some aspects described herein relate to an apparatus for wireless communication. The apparatus may include means for receiving, from a network node, an indication of a time domain rotation factor associated with the apparatus. The apparatus may include means for reflecting, using a reflection coefficient, a reference signal associated with the network node, the reflection coefficient being based on the time domain rotation factor.
Aspects generally include a method, apparatus, system, computer program product, non-transitory computer-readable medium, user equipment, base station, network entity, network node, wireless communication device, and/or processing system as substantially described herein with reference to and as illustrated by the drawings and specification.
The foregoing has outlined rather broadly the features and technical advantages of examples according to the disclosure in order that the detailed description that follows may be better understood. Additional features and advantages will be described hereinafter. The conception and specific examples disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. Such equivalent constructions do not depart from the scope of the appended claims. Characteristics of the concepts disclosed herein, both their organization and method of operation, together with associated advantages, will be better understood from the following description when considered in connection with the accompanying figures. Each of the figures is provided for the purposes of illustration and description, and not as a definition of the limits of the claims.
While aspects are described in the present disclosure by illustration to some examples, those skilled in the art will understand that such aspects may be implemented in many different arrangements and scenarios. Techniques described herein may be implemented using different platform types, devices, systems, shapes, sizes, and/or packaging arrangements. For example, some aspects may be implemented via integrated chip embodiments or other non-module-component based devices (e.g., end-user devices, vehicles, communication devices, computing devices, industrial equipment, retail/purchasing devices, medical devices, and/or artificial intelligence devices) . Aspects may be implemented in chip-level components, modular components, non-modular components, non-chip-level components, device-level components, and/or system-level components. Devices incorporating described aspects and features may include additional components and features for implementation and practice of claimed and described aspects. For example, transmission and reception of wireless signals may include one or more components for analog and digital purposes (e.g., hardware components including antennas, radio frequency (RF) chains, power amplifiers, modulators, buffers, processors, interleavers, adders, and/or summers) . It is intended that aspects described herein may be practiced in a wide variety of devices, components, systems, distributed arrangements, and/or end-user devices of varying size, shape, and constitution.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the above-recited features of the present disclosure can be understood in detail, a more particular description, briefly summarized above, may be had by reference to aspects, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only certain typical aspects of this disclosure and are therefore not to be considered limiting of its scope, for the description may admit to other equally effective aspects. The same reference numbers in different drawings may identify the same or similar elements.
Fig. 1 is a diagram illustrating an example of a wireless network, in accordance with the present disclosure.
Fig. 2 is a diagram illustrating an example of a network node in communication with a user equipment (UE) in a wireless network, in accordance with the present disclosure.
Fig. 3 is a diagram illustrating an example disaggregated base station architecture, in accordance with the present disclosure.
Fig. 4 is a diagram illustrating an example of communications using a forwarding-capable device, in accordance with the present disclosure.
Fig. 5 is a diagram illustrating an example of communication links in a wireless network that includes a reconfigurable intelligent surface (RIS) , in accordance with the present disclosure.
Fig. 6 is a diagram of an example associated with Doppler frequency estimation for RIS communication links, in accordance with the present disclosure.
Fig. 7 is a diagram of an example associated with Doppler frequency estimation for RIS communication links, in accordance with the present disclosure.
Fig. 8 is a diagram illustrating an example process performed, for example, by a UE, in accordance with the present disclosure.
Fig. 9 is a diagram illustrating an example process performed, for example, by a network node, in accordance with the present disclosure.
Fig. 10 is a diagram illustrating an example process performed, for example, by an RIS, in accordance with the present disclosure.
Fig. 11 is a diagram of an example apparatus for wireless communication, in accordance with the present disclosure.
Fig. 12 is a diagram of an example apparatus for wireless communication, in accordance with the present disclosure.
Fig. 13 is a diagram of an example apparatus for wireless communication, in accordance with the present disclosure.

DETAILED DESCRIPTION

A transmitting device may transmit a signal that is reflected by a beam reflecting device to a receiving device. The beam reflecting device may be a reconfigurable intelligent surface (RIS) and have an array of passive and reconfigurable reflecting elements that can boost coverage and spectral efficiency at a low deployment cost. The reconfigurability of an RIS may enable a transmitting device, such as a network node (or user equipment (UE) ) , to realize multiple anomalous reflections, which are reflections that would have altered reflection angles (e.g., that violate Snell’s law) . Each reflection may be specified by a target incident direction and a reflected direction. The ability to select multiple anomalous reflections may enable the network node to have more options or more flexibility in UE selection and may enhance an end-to-end channel to the UEs.
In some cases, the UE may measure and/or estimate a Doppler frequency for direct links and/or indirect links associated with the UE. The Doppler effect is the phenomenon of a change in the frequency of a wave as the source and observer of the wave move relative to each other. In the context of wireless communications, the source is the transmitting antenna and the observer is the receiving antenna. The Doppler effect can cause a shift in the frequency of the received signal relative to a frequency of the transmitted signal, which can affect the accuracy of the signal detection and decoding process. In high-speed scenarios the relative motion between the transmitter and receiver can cause a Doppler shift in the frequency of the transmitted signal. This shift can cause the received signal to fall outside of the expected frequency band, leading to errors in signal detection and decoding. Estimating the Doppler frequency may enable the network node and/or the UE to mitigate the effects of the Doppler shift. By knowing the Doppler frequency, the network node and/or the UE can adjust the transmission frequency to compensate for the Doppler shift and keep the received signal within the expected frequency band. This allows for more reliable and accurate signal detection and decoding, which improves the performance of the wireless communication system.
In some cases, the UE may separately measure each link associated with the UE to facilitate Doppler frequency estimations. For example, the UE may measure a direct link between the UE and a network node using a first time domain occasion to facilitate Doppler frequency estimation for the direct link. In other time domain occasions, the UE may measure respective indirect links between the UE and a network node to facilitate Doppler frequency estimations for the indirect link (s) . The UE may perform the measurements and/or Doppler frequency estimations in different time domain occasions so that each link can be reliably identified and measured by the UE. The network node may receive a report of the measurements and/or Doppler frequency estimations. In some examples, the network node may estimate or determine the Doppler frequency for each link based on, or in response to, the report of the measurements and/or Doppler frequency estimations. The network node may configure each forwarding-capable device (e.g., associated with the indirect link (s) ) based on the estimated Doppler frequencies. For example, the network node may configure each forwarding-capable device (e.g., each RIS) so that there is zero or only one Doppler frequency in the signal received by the UE. This enables the UE to mitigate the Doppler frequency in the received signal (e.g., if there are multiple Doppler frequencies in the received signal the UE may be unable to mitigate all of the Doppler frequencies, resulting in degraded signal detection and decoding) .
However, measuring the different links in respective time domain occasions (e.g., to mitigate interference and/or measurement confusion between the different links) may consume radio resources (e.g., time domain resources, frequency domain resources, and/or spatial domain resources) and/or may introduce latency associated with performing the measurements of the different links. For example, to measure each link using different radio resources (e.g., for Doppler frequency estimation) , a total radio resource consumption and/or processing latency may be large (e.g., when there is a high quantity of indirect links and/or forwarding-capable devices being used by the UE and the network node for communications) . If less radio resources and/or time domain occasions were to be used to measure each link (e.g., for Doppler frequency estimation) , then fewer time domain resources may be used to measure each link, resulting in less accurate and/or reliable measurements. As a result, a performance of the Doppler frequency estimation (e.g., that is based on the measurements) may be degraded.
Various aspects relate generally to Doppler frequency estimation. Some aspects more specifically relate to Doppler frequency estimation for RIS communication links. In some aspects, the UE may perform simultaneous Doppler frequency measurements on a direct link and one or more indirect links (e.g., associated with an RIS reflection) using shared or common radio resources. For example, the UE may receive an indication of time domain rotation factors associated with respective RISs of one or more RISs. The UE may receive, during a time domain measurement occasion, respective reference signals via a direct link with the network node and via one or more indirect links associated with the one or more RISs. The UE may transmit a report indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with measurements of the respective reference signals, with the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs.
Particular aspects of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. In some examples, by using the time domain rotation factor (s) associated with Doppler frequency estimations for indirect links, the described techniques can be used to reduce a quantity of radio resources consumed and/or a latency associated with estimating Doppler frequencies for indirect links (e.g., associated with RISs) . For example, the UE may be enabled to identify a Doppler spectrum for respective indirect links based on the time domain rotation factors, thereby enabling the UE to perform measurements of the respective indirect links using shared radio resources (e.g., the Doppler spectrums of the indirect links may be separated due to the use of the time domain rotation factors, reducing a likelihood of inter-link interference and/or confusion at the UE as to which measurement corresponds to which link) . Further, because the links use the shared radio resources, a received signal-to-noise ratio (SNR) of each link may be improved.
For example, the one or more indirect links are associated with reflection coefficients applied by the respective RISs that are associated with the time domain rotation factors. At a given time domain occasion, each RIS may reflect a signal using a reflection coefficient that is based on the time domain rotation factor associated with that RIS. This enables the Doppler spectrums of the received signal at the UE to be separated. As a result, the UE may estimate the Doppler frequency of each link using the corresponding Doppler spectrum (e.g., which can be identified based on the signaled or configured time domain rotation factors) . For example, for an indirect link associated with a given RIS, the Doppler spectrum associated with the given RIS may be a shifted version of a channel Doppler spectrum associated with the channel response, where a shift associated with the Doppler spectrum is based on the time domain rotation factor associated with the RIS. This enables the UE to accurately identify the Doppler spectrum for each indirect link and/or each RIS, thereby improving the performance and/or efficiency of the Doppler frequency estimations.
Various aspects of the disclosure are described more fully hereinafter with reference to the accompanying drawings. This disclosure may, however, be embodied in many different forms and should not be construed as limited to any specific structure or function presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. One skilled in the art should appreciate that the scope of the disclosure is intended to cover any aspect of the disclosure disclosed herein, whether implemented independently of or combined with any other aspect of the disclosure. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to or other than the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of a claim.
Several aspects of telecommunication systems will now be presented with reference to various apparatuses and techniques. These apparatuses and techniques will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, or the like (collectively referred to as “elements” ) . These elements may be implemented using hardware, software, or combinations thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.
While aspects may be described herein using terminology commonly associated with a 5G or New Radio (NR) radio access technology (RAT) , aspects of the present disclosure can be applied to other RATs, such as a 3G RAT, a 4G RAT, and/or a RAT subsequent to 5G (e.g., 6G) .
Fig. 1 is a diagram illustrating an example of a wireless network 100, in accordance with the present disclosure. The wireless network 100 may be or may include elements of a 5G (e.g., NR) network and/or a 4G (e.g., Long Term Evolution (LTE) ) network, among other examples. The wireless network 100 may include one or more network nodes 110 (shown as a network node 110a, a network node 110b, a network node 110c, and a network node 110d) , a UE 120 or multiple UEs 120 (shown as a UE 120a, a UE 120b, a UE 120c, and a UE 120d) , and/or other entities. A network node 110 is a network node that communicates with UEs 120. As shown, a network node 110 may include one or more network nodes. For example, a network node 110 may be an aggregated network node, meaning that the aggregated network node is configured to utilize a radio protocol stack that is physically or logically integrated within a single radio access network (RAN) node (e.g., within a single device or unit) . As another example, a network node 110 may be a disaggregated network node (sometimes referred to as a disaggregated base station) , meaning that the network node 110 is configured to utilize a protocol stack that is physically or logically distributed among two or more nodes (such as one or more central units (CUs) , one or more distributed units (DUs) , or one or more radio units (RUs) ) .
In some examples, a network node 110 is or includes a network node that communicates with UEs 120 via a radio access link, such as an RU. In some examples, a network node 110 is or includes a network node that communicates with other network nodes 110 via a fronthaul link or a midhaul link, such as a DU. In some examples, a network node 110 is or includes a network node that communicates with other network nodes 110 via a midhaul link or a core network via a backhaul link, such as a CU. In some examples, a network node 110 (such as an aggregated network node 110 or a disaggregated network node 110) may include multiple network nodes, such as one or more RUs, one or more CUs, and/or one or more DUs. A network node 110 may include, for example, an NR base station, an LTE base station, a Node B, an eNB (e.g., in 4G) , a gNB (e.g., in 5G) , an access point, a transmission reception point (TRP) , a DU, an RU, a CU, a mobility element of a network, a core network node, a network element, a network equipment, a RAN node, or a combination thereof. In some examples, the network nodes 110 may be interconnected to one another or to one or more other network nodes 110 in the wireless network 100 through various types of fronthaul, midhaul, and/or backhaul interfaces, such as a direct physical connection, an air interface, or a virtual network, using any suitable transport network.
In some examples, a network node 110 may provide communication coverage for a particular geographic area. In the Third Generation Partnership Project (3GPP) , the term “cell” can refer to a coverage area of a network node 110 and/or a network node subsystem serving this coverage area, depending on the context in which the term is used. A network node 110 may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or another type of cell. A macro cell may cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs 120 with service subscriptions. A pico cell may cover a relatively small geographic area and may allow unrestricted access by UEs 120 with service subscriptions. A femto cell may cover a relatively small geographic area (e.g., a home) and may allow restricted access by UEs 120 having association with the femto cell (e.g., UEs 120 in a closed subscriber group (CSG) ) . A network node 110 for a macro cell may be referred to as a macro network node. A network node 110 for a pico cell may be referred to as a pico network node. A network node 110 for a femto cell may be referred to as a femto network node or an in-home network node. In the example shown in Fig. 1, the network node 110a may be a macro network node for a macro cell 102a, the network node 110b may be a pico network node for a pico cell 102b, and the network node 110c may be a femto network node for a femto cell 102c. A network node may support one or multiple (e.g., three) cells. In some examples, a cell may not necessarily be stationary, and the geographic area of the cell may move according to the location of a network node 110 that is mobile (e.g., a mobile network node) .
In some aspects, the terms “base station” or “network node” may refer to an aggregated base station, a disaggregated base station, an integrated access and backhaul (IAB) node, a relay node, or one or more components thereof. For example, in some aspects, “base station” or “network node” may refer to a CU, a DU, an RU, a Near-Real Time (Near-RT) RAN Intelligent Controller (RIC) , or a Non-Real Time (Non-RT) RIC, or a combination thereof. In some aspects, the terms “base station” or “network node” may refer to one device configured to perform one or more functions, such as those described herein in connection with the network node 110. In some aspects, the terms “base station” or “network node” may refer to a plurality of devices configured to perform the one or more functions. For example, in some distributed systems, each of a quantity of different devices (which may be located in the same geographic location or in different geographic locations) may be configured to perform at least a portion of a function, or to duplicate performance of at least a portion of the function, and the terms “base station” or “network node” may refer to any one or more of those different devices. In some aspects, the terms “base station” or “network node” may refer to one or more virtual base stations or one or more virtual base station functions. For example, in some aspects, two or more base station functions may be instantiated on a single device. In some aspects, the terms “base station” or “network node” may refer to one of the base station functions and not another. In this way, a single device may include more than one base station.
The wireless network 100 may include one or more relay stations. A relay station is a network node that can receive a transmission of data from an upstream node (e.g., a network node 110 or a UE 120) and send a transmission of the data to a downstream node (e.g., a UE 120 or a network node 110) . A relay station may be a UE 120 that can relay transmissions for other UEs 120. In the example shown in Fig. 1, the network node 110d (e.g., a relay network node) may communicate with the network node 110a (e.g., a macro network node) and the UE 120d in order to facilitate communication between the network node 110a and the UE 120d. A network node 110 that relays communications may be referred to as a relay station, a relay base station, a relay network node, a relay node, a relay, or the like.
The wireless network 100 may be a heterogeneous network that includes network nodes 110 of different types, such as macro network nodes, pico network nodes, femto network nodes, relay network nodes, or the like. These different types of network nodes 110 may have different transmit power levels, different coverage areas, and/or different impacts on interference in the wireless network 100. For example, macro network nodes may have a high transmit power level (e.g., 5 to 40 watts) whereas pico network nodes, femto network nodes, and relay network nodes may have lower transmit power levels (e.g., 0.1 to 2 watts) .
A network controller 130 may couple to or communicate with a set of network nodes 110 and may provide coordination and control for these network nodes 110. The network controller 130 may communicate with the network nodes 110 via a backhaul communication link or a midhaul communication link. The network nodes 110 may communicate with one another directly or indirectly via a wireless or wireline backhaul communication link. In some aspects, the network controller 130 may be a CU or a core network device, or may include a CU or a core network device.
The UEs 120 may be dispersed throughout the wireless network 100, and each UE 120 may be stationary or mobile. A UE 120 may include, for example, an access terminal, a terminal, a mobile station, and/or a subscriber unit. A UE 120 may be a cellular phone (e.g., a smart phone) , a personal digital assistant (PDA) , a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet, a camera, a gaming device, a netbook, a smartbook, an ultrabook, a medical device, a biometric device, a wearable device (e.g., a smart watch, smart clothing, smart glasses, a smart wristband, smart jewelry (e.g., a smart ring or a smart bracelet) ) , an entertainment device (e.g., a music device, a video device, and/or a satellite radio) , a vehicular component or sensor, a smart meter/sensor, industrial manufacturing equipment, a global positioning system device, a UE function of a network node, and/or any other suitable device that is configured to communicate via a wireless or wired medium.
Some UEs 120 may be considered machine-type communication (MTC) or evolved or enhanced machine-type communication (eMTC) UEs. An MTC UE and/or an eMTC UE may include, for example, a robot, a drone, a remote device, a sensor, a meter, a monitor, and/or a location tag, that may communicate with a network node, another device (e.g., a remote device) , or some other entity. Some UEs 120 may be considered Internet-of-Things (IoT) devices, and/or may be implemented as NB-IoT (narrowband IoT) devices. Some UEs 120 may be considered a Customer Premises Equipment. A UE 120 may be included inside a housing that houses components of the UE 120, such as processor components and/or memory components. In some examples, the processor components and the memory components may be coupled together. For example, the processor components (e.g., one or more processors) and the memory components (e.g., a memory) may be operatively coupled, communicatively coupled, electronically coupled, and/or electrically coupled.
In general, any number of wireless networks 100 may be deployed in a given geographic area. Each wireless network 100 may support a particular RAT and may operate on one or more frequencies. A RAT may be referred to as a radio technology, an air interface, or the like. A frequency may be referred to as a carrier, a frequency channel, or the like. Each frequency may support a single RAT in a given geographic area in order to avoid interference between wireless networks of different RATs. In some cases, NR or 5G RAT networks may be deployed.
In some examples, two or more UEs 120 may communicate directly using one or more sidelink channels (e.g., without using a network node 110 as an intermediary to communicate with one another) . For example, the UEs 120 may communicate using peer-to-peer (P2P) communications, device-to-device (D2D) communications, a vehicle-to-everything (V2X) protocol (e.g., which may include a vehicle-to-vehicle (V2V) protocol, a vehicle-to-infrastructure (V2I) protocol, or a vehicle-to-pedestrian (V2P) protocol) , and/or a mesh network. In such examples, a UE 120 may perform scheduling operations, resource selection operations, and/or other operations described elsewhere herein as being performed by the network node 110.
Devices of the wireless network 100 may communicate using the electromagnetic spectrum, which may be subdivided by frequency or wavelength into various classes, bands, channels, or the like. For example, devices of the wireless network 100 may communicate using one or more operating bands. In 5G NR, two initial operating bands have been identified as frequency range designations FR1 (410 MHz –7.125 GHz) and FR2 (24.25 GHz –52.6 GHz) . It should be understood that although a portion of FR1 is greater than 6 GHz, FR1 is often referred to (interchangeably) as a “Sub-6 GHz” band in various documents and articles. A similar nomenclature issue sometimes occurs with regard to FR2, which is often referred to (interchangeably) as a “millimeter wave” band in documents and articles, despite being different from the extremely high frequency (EHF) band (30 GHz –300 GHz) which is identified by the International Telecommunications Union (ITU) as a “millimeter wave” band.
The frequencies between FR1 and FR2 are often referred to as mid-band frequencies. Recent 5G NR studies have identified an operating band for these mid-band frequencies as frequency range designation FR3 (7.125 GHz –24.25 GHz) . Frequency bands falling within FR3 may inherit FR1 characteristics and/or FR2 characteristics, and thus may effectively extend features of FR1 and/or FR2 into mid-band frequencies. In addition, higher frequency bands are currently being explored to extend 5G NR operation beyond 52.6 GHz. For example, three higher operating bands have been identified as frequency range designations FR4a or FR4-1 (52.6 GHz –71 GHz) , FR4 (52.6 GHz –114.25 GHz) , and FR5 (114.25 GHz –300 GHz) . Each of these higher frequency bands falls within the EHF band.
With the above examples in mind, unless specifically stated otherwise, it should be understood that the term “sub-6 GHz” or the like, if used herein, may broadly represent frequencies that may be less than 6 GHz, may be within FR1, or may include mid-band frequencies. Further, unless specifically stated otherwise, it should be understood that the term “millimeter wave” or the like, if used herein, may broadly represent frequencies that may include mid-band frequencies, may be within FR2, FR4, FR4-a or FR4-1, and/or FR5, or may be within the EHF band. It is contemplated that the frequencies included in these operating bands (e.g., FR1, FR2, FR3, FR4, FR4-a, FR4-1, and/or FR5) may be modified, and techniques described herein are applicable to those modified frequency ranges.
As shown in Fig. 1, the wireless network 100 may include a forwarding-capable device 160. A first device (e.g., UE 120a, network node 110) may communicate with a second device (e.g., network node 110, UE 120a) directly or by reflecting signals via the forwarding-capable device 160 (e.g., an RIS or another device) . The first device may be a transmitting device (e.g., the network node 110 or the UE 120) , and the second device may be a receiving device (e.g., the UE 120 or the network node 110) , because the transmitting device is transmitting a signal to the receiving device.
In some aspects, the UE 120 may include a communication manager 140. As described in more detail elsewhere herein, the communication manager 140 may receive, from a network node, an indication of time domain rotation factors associated with respective RISs of one or more RISs; receive , during a time domain measurement occasion, respective reference signals via a direct link with the network node and via one or more indirect links associated with the one or more RISs; and transmit, to the network node, a report indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with measurements of the respective reference signals, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs. Additionally, or alternatively, the communication manager 140 may perform one or more other operations described herein.
In some aspects, the network node 110 may include a communication manager 150. As described in more detail elsewhere herein, the communication manager 150 may transmit , an indication, for a UE and one or more RISs, of time domain rotation factors associated with respective RISs of the one or more RISs; transmit, during a time domain measurement occasion, a reference signal via a direct link with the UE and via one or more indirect links associated with the one or more RISs; and receive a report, associated with the UE, indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with a measurement of the reference signal, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs. Additionally, or alternatively, the communication manager 150 may perform one or more other operations described herein.
In some aspects, the forwarding-capable device 160 may include a communication manager 170. As described in more detail elsewhere herein, the communication manager 170 may receive, from a network node, an indication of a time domain rotation factor associated with the forwarding-capable device 160; and reflect, using a reflection coefficient, a reference signal associated with the network node, the reflection coefficient being based on the time domain rotation factor. Additionally, or alternatively, the communication manager 170 may perform one or more other operations described herein.
As indicated above, Fig. 1 is provided as an example. Other examples may differ from what is described with regard to Fig. 1.
Fig. 2 is a diagram illustrating an example 200 of a network node 110 in communication with a UE 120 in a wireless network 100, in accordance with the present disclosure. The network node 110 may be equipped with a set of antennas 234a through 234t, such as T antennas (T ≥ 1) . The UE 120 may be equipped with a set of antennas 252a through 252r, such as R antennas (R ≥ 1) . The network node 110 of example 200 includes one or more radio frequency components, such as antennas 234 and a modem 232. In some examples, a network node 110 may include an interface, a communication component, or another component that facilitates communication with the UE 120 or another network node. Some network nodes 110 may not include radio frequency components that facilitate direct communication with the UE 120, such as one or more CUs, or one or more DUs.
At the network node 110, a transmit processor 220 may receive data, from a data source 212, intended for the UE 120 (or a set of UEs 120) . The transmit processor 220 may select one or more modulati on and coding schemes (MCSs) for the UE 120 based at least in part on one or more channel quality indicators (CQIs) received from that UE 120. The network node 110 may process (e.g., encode and modulate) the data for the UE 120 based at least in part on the MCS (s) selected for the UE 120 and may provide data symbols for the UE 120. The transmit processor 220 may process system information (e.g., for semi-static resource partitioning information (SRPI) ) and control information (e.g., CQI requests, grants, and/or upper layer signaling) and provide overhead symbols and control symbols. The transmit processor 220 may generate reference symbols for reference signals (e.g., a cell-specific reference signal (CRS) or a demodulation reference signal (DMRS) ) and synchronization signals (e.g., a primary synchronization signal (PSS) or a secondary synchronization signal (SSS) ) . A transmit (TX) multiple-input multiple-output (MIMO) processor 230 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, the overhead symbols, and/or the reference symbols, if applicable, and may provide a set of output symbol streams (e.g., T output symbol streams) to a corresponding set of modems 232 (e.g., T modems) , shown as modems 232a through 232t. For example, each output symbol stream may be provided to a modulator component (shown as MOD) of a modem 232. Each modem 232 may use a respective modulator component to process a respective output symbol stream (e.g., for OFDM) to obtain an output sample stream. Each modem 232 may further use a respective modulator component to process (e.g., convert to analog, amplify, filter, and/or upconvert) the output sample stream to obtain a downlink signal. The modems 232a through 232t may transmit a set of downlink signals (e.g., T downlink signals) via a corresponding set of antennas 234 (e.g., T antennas) , shown as antennas 234a through 234t.
At the UE 120, a set of antennas 252 (shown as antennas 252a through 252r) may receive the downlink signals from the network node 110 and/or other network nodes 110 and may provide a set of received signals (e.g., R received signals) to a set of modems 254 (e.g., R modems) , shown as modems 254a through 254r. For example, each received signal may be provided to a demodulator component (shown as DEMOD) of a modem 254. Each modem 254 may use a respective demodulator component to condition (e.g., filter, amplify, downconvert, and/or digitize) a received signal to obtain input samples. Each modem 254 may use a demodulator component to further process the input samples (e.g., for OFDM) to obtain received symbols. A MIMO detector 256 may obtain received symbols from the modems 254, may perform MIMO detection on the received symbols if applicable, and may provide detected symbols. A receive processor 258 may process (e.g., demodulate and decode) the detected symbols, may provide decoded data for the UE 120 to a data sink 260, and may provide decoded control information and system information to a controller/processor 280. The term “controller/processor” may refer to one or more controllers, one or more processors, or a combination thereof. A channel processor may determine a reference signal received power (RSRP) parameter, a received signal strength indicator (RSSI) parameter, a reference signal received quality (RSRQ) parameter, and/or a CQI parameter, among other examples. In some examples, one or more components of the UE 120 may be included in a housing 284.
The network controller 130 may include a communication unit 294, a controller/processor 290, and a memory 292. The network controller 130 may include, for example, one or more devices in a core network. The network controller 130 may communicate with the network node 110 via the communication unit 294.
One or more antennas (e.g., antennas 234a through 234t and/or antennas 252a through 252r) may include, or may be included within, one or more antenna panels, one or more antenna groups, one or more sets of antenna elements, and/or one or more antenna arrays, among other examples. An antenna panel, an antenna group, a set of antenna elements, and/or an antenna array may include one or more antenna elements (within a single housing or multiple housings) , a set of coplanar antenna elements, a set of non-coplanar antenna elements, and/or one or more antenna elements coupled to one or more transmission and/or reception components, such as one or more components of Fig. 2.
On the uplink, at the UE 120, a transmit processor 264 may receive and process data from a data source 262 and control information (e.g., for reports that include RSRP, RSSI, RSRQ, and/or CQI) from the controller/processor 280. The transmit processor 264 may generate reference symbols for one or more reference signals. The symbols from the transmit processor 264 may be precoded by a TX MIMO processor 266 if applicable, further processed by the modems 254 (e.g., for DFT-s-OFDM or CP-OFDM) , and transmitted to the network node 110. In some examples, the modem 254 of the UE 120 may include a modulator and a demodulator. In some examples, the UE 120 includes a transceiver. The transceiver may include any combination of the antenna (s) 252, the modem (s) 254, the MIMO detector 256, the receive processor 258, the transmit processor 264, and/or the TX MIMO processor 266. The transceiver may be used by a processor (e.g., the controller/processor 280) and the memory 282 to perform aspects of any of the methods described herein (e.g., with reference to Figs. 6-13) .
At the network node 110, the uplink signals from UE 120 and/or other UEs may be received by the antennas 234, processed by the modem 232 (e.g., a demodulator component, shown as DEMOD, of the modem 232) , detected by a MIMO detector 236 if applicable, and further processed by a receive processor 238 to obtain decoded data and control information sent by the UE 120. The receive processor 238 may provide the decoded data to a data sink 239 and provide the decoded control information to the controller/processor 240. The network node 110 may include a communication unit 244 and may communicate with the network controller 130 via the communication unit 244. The network node 110 may include a scheduler 246 to schedule one or more UEs 120 for downlink and/or uplink communications. In some examples, the modem 232 of the network node 110 may include a modulator and a demodulator. In some examples, the network node 110 includes a transceiver. The transceiver may include any combination of the antenna (s) 234, the modem (s) 232, the MIMO detector 236, the receive processor 238, the transmit processor 220, and/or the TX MIMO processor 230. The transceiver may be used by a processor (e.g., the controller/processor 240) and the memory 242 to perform aspects of any of the methods described herein (e.g., with reference to Figs. 6-13) .
The controller/processor 240 of the network node 110, the controller/processor 280 of the UE 120, and/or any other component (s) of Fig. 2 may perform one or more techniques associated with Doppler frequency estimation for RIS communication links, as described in more detail elsewhere herein. In some aspects, the forwarding-capable device 160 and/or the RIS described herein is the network node 110, is included in the network node 110, or includes one or more components of the network node 110 shown in Fig. 2.
For example, the controller/processor 240 of the network node 110, the controller/processor 280 of the UE 120, and/or any other component (s) of Fig. 2 may perform or direct operations of, for example, process 800 of Fig. 8, process 900 of Fig. 9, process 1000 of Fig. 10, and/or other processes as described herein. The memory 242 and the memory 282 may store data and program codes for the network node 110 and the UE 120, respectively. In some examples, the memory 242 and/or the memory 282 may include a non-transitory computer-readable medium storing one or more instructions (e.g., code and/or program code) for wireless communication. For example, the one or more instructions, when executed (e.g., directly, or after compiling, converting, and/or interpreting) by one or more processors of the network node 110 and/or the UE 120, may cause the one or more processors, the UE 120, and/or the network node 110 to perform or direct operations of, for example, process 800 of Fig. 8, process 900 of Fig. 9, process 1000 of Fig. 10, and/or other processes as described herein. In some examples, executing instructions may include running the instructions, converting the instructions, compiling the instructions, and/or interpreting the instructions, among other examples.
In some aspects, the UE 120 includes means for receiving, from a network node, an indication of time domain rotation factors associated with respective RISs of one or more RISs; means for receiving, during a time domain measurement occasion, respective reference signals via a direct link with the network node and via one or more indirect links associated with the one or more RISs; and/or means for transmitting, to the network node, a report indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with measurements of the respective reference signals, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs. The means for the UE 120 to perform operations described herein may include, for example, one or more of communication manager 140, antenna 252, modem 254, MIMO detector 256, receive processor 258, transmit processor 264, TX MIMO processor 266, controller/processor 280, or memory 282.
In some aspects, the network node 110 includes means for transmitting, an indication, for a UE and one or more RISs, of time domain rotation factors associated with respective RISs of the one or more RISs; means for transmitting, during a time domain measurement occasion, a reference signal via a direct link with the UE and via one or more indirect links associated with the one or more RISs; and/or means for receiving a report, associated with the UE, indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with a measurement of the reference signal, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs. The means for the network node 110 to perform operations described herein may include, for example, one or more of communication manager 150, transmit processor 220, TX MIMO processor 230, modem 232, antenna 234, MIMO detector 236, receive processor 238, controller/processor 240, memory 242, or scheduler 246.
In some aspects, the forwarding-capable device 160 (e.g., an RIS) includes means for receiving, from a network node, an indication of a time domain rotation factor associated with the RIS; and/or means for reflecting, using a reflection coefficient, a reference signal associated with the network node, the reflection coefficient being based on the time domain rotation factor. In some aspects, the means for the forwarding-capable device 160 to perform operations described herein may include, for example, one or more of communication manager 170, a processor, a controller, and/or one or more reconfigurable elements (or meta-elements) , among other examples.
While blocks in Fig. 2 are illustrated as distinct components, the functions described above with respect to the blocks may be implemented in a single hardware, software, or combination component or in various combinations of components. For example, the functions described with respect to the transmit processor 264, the receive processor 258, and/or the TX MIMO processor 266 may be performed by or under the control of the controller/processor 280.
As indicated above, Fig. 2 is provided as an example. Other examples may differ from what is described with regard to Fig. 2.
Deployment of communication systems, such as 5G NR systems, may be arranged in multiple manners with various components or constituent parts. In a 5G NR system, or network, a network node, a network entity, a mobility element of a network, a RAN node, a core network node, a network element, a base station, or a network equipment may be implemented in an aggregated or disaggregated architecture. For example, a base station (such as a Node B (NB) , an evolved NB (eNB) , an NR base station, a 5G NB, an access point (AP) , a TRP, or a cell, among other examples) , or one or more units (or one or more components) performing base station functionality, may be implemented as an aggregated base station (also known as a standalone base station or a monolithic base station) or a disaggregated base station. “Network entity” or “network node” may refer to a disaggregated base station, or to one or more units of a disaggregated base station (such as one or more CUs, one or more DUs, one or more RUs, or a combination thereof) .
An aggregated base station (e.g., an aggregated network node) may be configured to utilize a radio protocol stack that is physically or logically integrated within a single RAN node (e.g., within a single device or unit) . A disaggregated base station (e.g., a disaggregated network node) may be configured to utilize a protocol stack that is physically or logically distributed among two or more units (such as one or more CUs, one or more DUs, or one or more RUs) . In some examples, a CU may be implemented within a network node, and one or more DUs may be co-located with the CU, or alternatively, may be geographically or virtually distributed throughout one or multiple other network nodes. The DUs may be implemented to communicate with one or more RUs. Each of the CU, DU, and RU also can be implemented as virtual units, such as a virtual central unit (VCU) , a virtual distributed unit (VDU) , or a virtual radio unit (VRU) , among other examples.
Base station-type operation or network design may consider aggregation characteristics of base station functionality. For example, disaggregated base stations may be utilized in an IAB network, an open radio access network (O-RAN (such as the network configuration sponsored by the O-RAN Alliance) ) , or a virtualized radio access network (vRAN, also known as a cloud radio access network (C-RAN) ) to facilitate scaling of communication systems by separating base station functionality into one or more units that can be individually deployed. A disaggregated base station may include functionality implemented across two or more units at various physical locations, as well as functionality implemented for at least one unit virtually, which can enable flexibility in network design. The various units of the disaggregated base station can be configured for wired or wireless communication with at least one other unit of the disaggregated base station.
As used herein, the network node 110 “outputting” or “transmitting” a communication to the UE 120 may refer to a direct transmission (for example, from the network node 110 to the UE 120) or an indirect transmission via one or more other network nodes or devices. For example, if the network node 110 is a DU, an indirect transmission to the UE 120 may include the DU outputting or transmitting a communication to an RU and the RU transmitting the communication to the UE 120, or may include causing the RU to transmit the communication (e.g., triggering transmission of a physical layer reference signal) . Similarly, the UE 120 “transmitting” a communication to the network node 110 may refer to a direct transmission (e.g., from the UE 120 to the network node 110) or an indirect transmission via one or more other network nodes or devices. For example, if the network node 110 is a DU, an indirect transmission to the network node 110 may include the UE 120 transmitting a communication to an RU and the RU transmitting the communication to the DU. Similarly, the network node 110 “obtaining” a communication may refer to receiving a transmission carrying the communication directly (for example, from the UE 120 to the network node 110) or receiving the communication (or information derived from reception of the communication) via one or more other network nodes or devices.
Fig. 3 is a diagram illustrating an example disaggregated base station architecture 300, in accordance with the present disclosure. The disaggregated base station architecture 300 may include a CU 310 that can communicate directly with a core network 320 via a backhaul link, or indirectly with the core network 320 through one or more disaggregated control units (such as a Near-RT RIC 325 via an E2 link, or a Non-RT RIC 315 associated with a Service Management and Orchestration (SMO) Framework 305, or both) . A CU 310 may communicate with one or more DUs 330 via respective midhaul links, such as through F1 interfaces. Each of the DUs 330 may communicate with one or more RUs 340 via respective fronthaul links. Each of the RUs 340 may communicate with one or more UEs 120 via respective radio frequency (RF) access links. In some implementations, a UE 120 may be simultaneously served by multiple RUs 340.
Each of the units, including the CUs 310, the DUs 330, the RUs 340, as well as the Near-RT RICs 325, the Non-RT RICs 315, and the SMO Framework 305, may include one or more interfaces or be coupled with one or more interfaces configured to receive or transmit signals, data, or information (collectively, signals) via a wired or wireless transmission medium. Each of the units, or an associated processor or controller providing instructions to one or multiple communication interfaces of the respective unit, can be configured to communicate with one or more of the other units via the transmission medium. In some examples, each of the units can include a wired interface, configured to receive or transmit signals over a wired transmission medium to one or more of the other units, and a wireless interface, which may include a receiver, a transmitter or transceiver (such as an RF transceiver) , configured to receive or transmit signals, or both, over a wireless transmission medium to one or more of the other units.
In some aspects, the CU 310 may host one or more higher layer control functions. Such control functions can include radio resource control (RRC) functions, packet data convergence protocol (PDCP) functions, or service data adaptation protocol (SDAP) functions, among other examples. Each control function can be implemented with an interface configured to communicate signals with other control functions hosted by the CU 310. The CU 310 may be configured to handle user plane functionality (for example, Central Unit –User Plane (CU-UP) functionality) , control plane functionality (for example, Central Unit –Control Plane (CU-CP) functionality) , or a combination thereof. In some implementations, the CU 310 can be logically split into one or more CU-UP units and one or more CU-CP units. A CU-UP unit can communicate bidirectionally with a CU-CP unit via an interface, such as the E1 interface when implemented in an O-RAN configuration. The CU 310 can be implemented to communicate with a DU 330, as necessary, for network control and signaling.
Each DU 330 may correspond to a logical unit that includes one or more base station functions to control the operation of one or more RUs 340. In some aspects, the DU 330 may host one or more of a radio link control (RLC) layer, a medium access control (MAC) layer, and one or more high physical (PHY) layers depending, at least in part, on a functional split, such as a functional split defined by the 3GPP. In some aspects, the one or more high PHY layers may be implemented by one or more modules for forward error correction (FEC) encoding and decoding, scrambling, and modulation and demodulation, among other examples. In some aspects, the DU 330 may further host one or more low PHY layers, such as implemented by one or more modules for a fast Fourier transform (FFT) , an inverse FFT (iFFT) , digital beamforming, or physical random access channel (PRACH) extraction and filtering, among other examples. Each layer (which also may be referred to as a module) can be implemented with an interface configured to communicate signals with other layers (and modules) hosted by the DU 330, or with the control functions hosted by the CU 310.
Each RU 340 may implement lower-layer functionality. In some deployments, an RU 340, controlled by a DU 330, may correspond to a logical node that hosts RF processing functions or low-PHY layer functions, such as performing an FFT, performing an iFFT, digital beamforming, or PRACH extraction and filtering, among other examples, based on a functional split (for example, a functional split defined by the 3GPP) , such as a lower layer functional split. In such an architecture, each RU 340 can be operated to handle over the air (OTA) communication with one or more UEs 120. In some implementations, real-time and non-real-time aspects of control and user plane communication with the RU (s) 340 can be controlled by the corresponding DU 330. In some scenarios, this configuration can enable each DU 330 and the CU 310 to be implemented in a cloud-based RAN architecture, such as a vRAN architecture.
The SMO Framework 305 may be configured to support RAN deployment and provisioning of non-virtualized and virtualized network elements. For non-virtualized network elements, the SMO Framework 305 may be configured to support the deployment of dedicated physical resources for RAN coverage requirements, which may be managed via an operations and maintenance interface (such as an O1 interface) . For virtualized network elements, the SMO Framework 305 may be configured to interact with a cloud computing platform (such as an open cloud (O-Cloud) platform 390) to perform network element life cycle management (such as to instantiate virtualized network elements) via a cloud computing platform interface (such as an O2 interface) . Such virtualized network elements can include, but are not limited to, CUs 310, DUs 330, RUs 340, non-RT RICs 315, and Near-RT RICs 325. In some implementations, the SMO Framework 305 can communicate with a hardware aspect of a 4G RAN, such as an open eNB (O-eNB) 311, via an O1 interface. Additionally, in some implementations, the SMO Framework 305 can communicate directly with each of one or more RUs 340 via a respective O1 interface. The SMO Framework 305 also may include a Non-RT RIC 315 configured to support functionality of the SMO Framework 305.
The Non-RT RIC 315 may be configured to include a logical function that enables non-real-time control and optimization of RAN elements and resources, Artificial Intelligence/Machine Learning (AI/ML) workflows including model training and updates, or policy-based guidance of applications/features in the Near-RT RIC 325. The Non-RT RIC 315 may be coupled to or communicate with (such as via an A1 interface) the Near-RT RIC 325. The Near-RT RIC 325 may be configured to include a logical function that enables near-real-time control and optimization of RAN elements and resources via data collection and actions over an interface (such as via an E2 interface) connecting one or more CUs 310, one or more DUs 330, or both, as well as an O-eNB, with the Near-RT RIC 325.
In some implementations, to generate AI/ML models to be deployed in the Near-RT RIC 325, the Non-RT RIC 315 may receive parameters or external enrichment information from external servers. Such information may be utilized by the Near-RT RIC 325 and may be received at the SMO Framework 305 or the Non-RT RIC 315 from non-network data sources or from network functions. In some examples, the Non-RT RIC 315 or the Near-RT RIC 325 may be configured to tune RAN behavior or performance. For example, the Non-RT RIC 315 may monitor long-term trends and patterns for performance and employ AI/ML models to perform corrective actions through the SMO Framework 305 (such as reconfiguration via an O1 interface) or via creation of RAN management policies (such as A1 interface policies) .
As indicated above, Fig. 3 is provided as an example. Other examples may differ from what is described with regard to Fig. 3.
Fig. 4 is a diagram illustrating an example 400 of communications using a forwarding-capable device, in accordance with the present disclosure. As shown in Fig. 4, a network node 110 may communicate with a UE 120 in a wireless network, such as the wireless network 100. The network node 110 and the UE 120 may use a forwarding-capable device 160 to communicate with one another. For example, the forwarding-capable device 160 may reflect, refract, or redirect a signal to the network node 110 and/or the UE 120. The forwarding-capable device 160 may also be referred to as an intelligent reflecting surface or a software-controlled meta-surface. In some examples, the forwarding-capable device 160 may be an RIS, repeater, a relay, an amplify and forward device, a decode and forward device, or another device capable of forwarding, reflecting, and/or refracting wireless communication signals.
A network may have antennas that are grouped together at a transmitter or receiver, in order to increase throughput. The grouping of antennas may be referred to as “massive MIMO. ” Massive MIMO may use active antenna units (AAUs) to achieve high beamforming gain. An AAU may combine an antenna, a radio, a tower-mounted amplifier, a feeder, and/or jumper functionalities into a single unit. An AAU may include an individual RF chain for each antenna port. There may be barriers to massive MIMO. The transmission of signals may be blocked by buildings, natural topography, or other blocking structures. In order to resolve transmission issues due to the blockage, the network may use a forwarding-capable device 160. As another example, the network may use a forwarding-capable device 160 to improve reliability for a UE 120 that is moving at high speeds (e.g., to enable multiple links for the high-speed UE 120) .
An RIS may be a two-dimensional surface of engineered material whose properties are reconfigurable rather than static. The engineered material may contain integrated electronic circuits and software that enable the control of a wireless medium by altering an impedance of the surface or a portion of the surface. The change in impedance may alter a phase shift and/or an angle of reflection. Scattering, absorption, reflection, or diffraction properties may be changed with time and controlled by the software. An RIS may act as a reflective lens. In one example, an RIS may include large arrays of inexpensive antennas spaced half of a wavelength apart. In another example, an RIS may include metamaterial-based planar or conformal large surfaces whose elements (e.g., square elements) have sizes and inter-distances that are smaller than the wavelength. Each of the elements may have a configured impedance or other surface properties that are controlled by a voltage to the element.
The forwarding-capable device 160 may be, or may include, a planar or two-dimensional structure or surface that is designed to have properties to enable a dynamic control of signals or electromagnetic waves reflected and/or redirected by the forwarding-capable device 160. The forwarding-capable device 160 may include one or more reconfigurable elements. For example, the forwarding-capable device 160 may include an array of reconfigurable elements (e.g., an array of uniformly distributed reconfigurable elements) . The reconfigurable elements may be elements with a reconfigurable electromagnetic characteristic. For example, the electromagnetic characteristic may include a reflection characteristic (e.g., a reflection coefficient) , a scattering characteristic, an absorption characteristic, and/or a diffraction characteristic. The electromagnetic characteristic (s) of each reconfigurable element may be independently controlled and changed over time. The electromagnetic characteristic (s) of each reconfigurable element may be independently configured such that the combination of configured states of the reconfigurable elements reflects an incident signal or waveform in a controlled manner. For example, the reconfigurable elements may be configured to reflect or redirect an impinging signal in a controlled manner, such as by reflecting the impinging signal in a desired direction, with a desired beam width, with a desired phase, with a desired amplitude, and/or with a desired polarization, among other examples. In other words, the forwarding-capable device 160 may be capable of modifying one or more properties (e.g., direction, beam width, phase, amplitude, and/or polarization) of an impinging signal.
The forwarding-capable device 160, when configured to operate as an RIS, may not have antennas or RF chains, but may include a large number of small, low-cost elements on a surface to passively reflect or refract incident signals transmitted from the network node 110. A controller 410 of the forwarding-capable device 160 may control the elements on the surface, and the surface may act as a phased array. The forwarding-capable device 160 may be a smart device that is configured to use a specific angle of reflection for the signals. The network node 110 may use the controller 410 to control, as part of a reflective configuration, the angle of reflection (angle of arrival θ_i for an incident wave, angle of departure θ_r for a reflected wave) , an amplitude, a phase, and/or a width of the elements of the forwarding-capable device 160 by controlling a voltage to each of the elements. The reflective configuration may also correspond to analog beamforming weights or coefficients that are provided by the forwarding-capable device 160 when reflecting signals from one device to another. The reflective configuration may also be referred to as a “forwarding configuration, ” an “RIS reflection configuration, ” an “RIS reflection matrix, ” or a “P-MIMO configuration. ” In sum, the forwarding-capable device 160 may help to control a propagation environment with less power consumption than AAUs.
The reconfigurable elements of the forwarding-capable device 160 may be controlled and/or configured by a controller 410 (e.g., an RIS controller) . The controller 410 may be a control module (e.g., a controller and/or a processor) that is capable of configuring the electromagnetic characteristic (s) of each reconfigurable element of the forwarding-capable device 160. The controller 410 may be, or may be included in, the communication manager 170. Alternatively, the communication manager 170 may be included in the controller 410. The controller 410 may be associated with certain components similar to the components described in connection with the UE 120 in connection with Fig. 2, such as a modem 254 and/or a similar component for purposes of communicating with a network node 110. The controller 410 may receive control communications (e.g., from a network node 110 and/or a UE 120) indicating one or more properties of reflected signals (e.g., indicating a desired direction, a desired beam width, a desired phase, a desired amplitude, and/or a desired polarization) . Therefore, in some examples, the forwarding-capable device 160 may be capable of receiving communications (e.g., via the forwarding-capable device 160 and/or the controller 410) . In some examples, the forwarding-capable device 160 and/or the controller 410 may not have transmit capabilities (e.g., the forwarding-capable device 160 may be capable of reflecting and/or redirecting impinging signals via the reconfigurable elements, but may not be capable of generating and/or transmitting signals) . Alternatively, in some examples, the forwarding-capable device 160 and/or the controller 410 may have transmit capabilities (e.g., the forwarding-capable device 160 may be capable of reflecting and/or redirecting impinging signals via the reconfigurable elements and may be capable of generating and/or transmitting signals) . For example, the forwarding-capable device 160 and/or the controller 410 may include one or more antennas and/or antenna elements for receiving and/or transmitting signals.
For example, as shown in Fig. 4, the network node 110 may transmit a signal 415. The signal 415 may be transmitted in a spatial direction toward the forwarding-capable device 160. The forwarding-capable device 160 may configure the reconfigurable elements of the forwarding-capable device 160 to reflect and/or redirect the signal 415 in a desired spatial direction and/or with one or more desired signal characteristics (e.g., beam width, phase, amplitude, frequency, and/or polarization) .
In some examples, the reconfigurable elements (e.g., meta-elements) of the forwarding-capable device 160 may be configured to reflect and/or redirect the signal 415 using a reflection (or reflective) coefficient. For example, for an angle of arrival θ_i, n for an incident wave at a reconfigurable element n of the forwarding-capable device 160, angle of departure θ_r, n for a reflected wave, a reflection gain of the forwarding-capable device 160 may be represented as where N is a quantity of reconfigurable elements of the forwarding-capable device 160, d_i, n-d_i, 0 is a distance between a first reconfigurable element and a reconfigurable element n associated with the incident wave, d_r, n-d_r, 0 is a distance between a first reconfigurable element and a reconfigurable element n associated with the reflected wave, λ is the wavelength, j represents an imaginary number or imaginary number for a complex number, andis the reflection coefficient for the reconfigurable element n (e.g., where α_n is the amplitude of the reflection coefficient and φ_n is the phase of the reflection coefficient) . The equation above may be associated with a general model for reflective beamforming by the forwarding-capable device 160. For a far-field model for reflective beamforming by the forwarding-capable device 160, a reflection gain of the forwarding-capable device 160 may be represented aswhere d is the distance between reconfigurable elements of the forwarding-capable device 160.
As shown by reference number 420, the forwarding-capable device 160 may be capable of reflecting the signal 415 in one or more spatial directions. Although multiple beams are shown in Fig. 4 representing different beam states or beam directions of the forwarding-capable device 160, the forwarding-capable device 160 may be capable of reflecting a signal with one beam state or one beam direction at a time. For example, in one case, as shown by reference number 425, the forwarding-capable device 160 may be configured to reflect the signal 415 using a first beam state (e.g., beam state 1) . “Beam state” may refer to a spatial direction and/or a beam of a reflected signal (e.g., a signal reflected by the forwarding-capable device 160) . The first beam state may cause the signal 415 to be reflected in a spatial direction toward a first UE 120 (e.g., UE 1) . As shown by reference number 430, in another case, the forwarding-capable device 160 may be configured to reflect the signal 415 using a second beam state (e.g., beam state 2) . The second beam state may cause the signal 415 to be reflected in a spatial direction toward a second UE 120 (e.g., UE 2) .
The forwarding-capable device 160 may be deployed in a wireless network (such as the wireless network 100) to improve communication performance and efficiency. For example, the forwarding-capable device 160 may enable a transmitter (e.g., a network node 110 or a UE 120) to control the scattering, reflection, and refraction characteristics of signals transmitted by the transmitter, to overcome the negative effects of wireless propagation. For example, the forwarding-capable device 160 may effectively control signal characteristics (e.g., spatial direction, beam width, phase, amplitude, frequency, and/or polarization) of an impinging signal without a need for complex decoding, encoding, and radio frequency processing operations. Therefore, the forwarding-capable device 160 may provide increased channel diversity for propagation of signals in a wireless network. The increased channel diversity provides robustness to channel fading and/or blocking, such as when higher frequencies are used by the network node 110 and/or the UE 120 (e.g., millimeter wave frequencies and/or sub-terahertz frequencies) . Moreover, as the forwarding-capable device 160 does not need to perform complex decoding, encoding, and radio frequency processing operations, the forwarding-capable device 160 may provide a more cost and energy efficient manner of reflecting and/or redirecting signals in a wireless network (e.g., as compared to other mechanisms for reflecting and/or redirecting signals, such as a relay device) .
As indicated above, Fig. 4 is provided as an example. Other examples may differ from what is described with respect to Fig. 4.
Fig. 5 is a diagram illustrating an example 500 of communication links in a wireless network that includes an RIS, in accordance with the present disclosure. As shown, example 500 includes a network node 110, a UE 120, and the forwarding-capable device 160. The forwarding-capable device 160 may be controlled and/or configured by the controller 410.
As shown in Fig. 5, the UE 120 may receive a communication (e.g., data and/or control information) directly from the network node 110 as a downlink communication. Additionally, or alternatively, the UE 120 may receive a communication (e.g., data and/or control information) indirectly from the network node 110 via the forwarding-capable device 160. For example, the network node 110 may transmit the communication in a spatial direction toward the forwarding-capable device 160, and the forwarding-capable device 160 may redirect or reflect the communication to the UE 120.
In some examples, the UE 120 may communicate directly with the network node 110 via a direct link 505. For example, a communication may be transmitted via the direct link 505. A communication transmitted via the direct link 505 between the UE 120 and the network node110 does not pass through and is not reflected, refracted, or redirected by the forwarding-capable device 160. In some examples, the UE 120 may communicate indirectly with the network node 110 via an indirect link 510 (also referred to as an RIS communication link) . For example, a communication may be transmitted via different segments of the indirect link 510. A communication transmitted via the indirect link 510 between the UE 120 and the network node 110 is reflected, refracted, and/or redirected by the forwarding-capable device 160. As shown in Fig. 5 and by reference number 515, the network node 110 may communicate with the forwarding-capable device 160 (e.g., with the controller 410) via a control channel. For example, the network node 110 may indicate, in an RIS control message, spatial direction (s) and/or signal characteristics for signals reflected by the forwarding-capable device 160. The controller 410 may configure reconfigurable elements of the forwarding-capable device 160 in accordance with the RIS control message. In some examples, the RIS control message may indicate information associated with the wireless network, such as a frame structure, time synchronization information, and/or slot boundaries, among other examples. Using the communication scheme shown in Fig. 5 may improve network performance and increase reliability by providing the UE 120 with link diversity for communicating with the network node 110.
In some cases, the UE 120 may receive a communication (e.g., the same communication) from the network node 110 via both the direct link 505 and the indirect link 510. In some examples, the UE 120 may receive communication (s) via multiple indirect links associated with respective forwarding-capable devices 160 (e.g., with or without a direct link 505) . In other cases, the network node 110 may select one of the links (e.g., either the direct link 505 or the indirect link 510) , and may transmit a communication to the UE 120 using only the selected link. Alternatively, the network node 110 may receive an indication of one of the links (e.g., either the direct link 505 or the indirect link 510) , and may transmit a communication to the UE 120 using only the indicated link. The indication may be transmitted by the UE 120 and/or the forwarding-capable device 160. In some examples, such selection and/or indication may be based at least in part on channel conditions and/or link reliability.
In some cases, the UE 120 may measure and/or estimate a Doppler frequency for direct links and/or indirect links associated with the UE 120. The Doppler effect is the phenomenon of a change in the frequency of a wave as the source and observer of the wave move relative to each other. In the context of wireless communications, the source is the transmitting antenna and the observer is the receiving antenna. The Doppler effect can cause a shift in the frequency of the received signal relative to a frequency of the transmitted signal, which can affect the accuracy of the signal detection and decoding process. In high-speed scenarios the relative motion between the transmitter and receiver can cause a Doppler shift in the frequency of the transmitted signal. This shift can cause the received signal to fall outside of the expected frequency band, leading to errors in signal detection and decoding. Estimating the Doppler frequency may enable the network node 110 and/or the UE 120 to mitigate the effects of the Doppler shift. By knowing the Doppler frequency, the network node 110 and/or the UE 120 can adjust the transmission frequency to compensate for the Doppler shift and keep the received signal within the expected frequency band. This allows for more reliable and accurate signal detection and decoding, which improves the performance of the wireless communication system.
In some cases, the UE 120 may separately measure each link associated with the UE 120 to facilitate Doppler frequency estimations. For example, the UE 120 may measure a direct link between the UE 120 and a network node 110 using a first time domain occasion to facilitate Doppler frequency estimation for the direct link. In other time domain occasions, the UE 120 measure respective indirect links between the UE 120 and a network node 110 to facilitate Doppler frequency estimations for the indirect link (s) . The UE 120 may perform the measurements and/or Doppler frequency estimations in different time domain occasions so that each link can be reliably identified and measured by the UE 120. The network node 110 may receive a report of the measurements and/or Doppler frequency estimations. In some example, the network node 110 may estimate or determine the Doppler frequency for each link based on, or in response to, the report of the measurements and/or Doppler frequency estimations. The network node 110 may configure each forwarding-capable device 160 (e.g., associated with the indirect link (s) ) based on the estimated Doppler frequencies. For example, the network node 110 may configure each forwarding-capable device 160 (e.g., each RIS) so that there is zero or only one Doppler frequency in the signal received by the UE 120. This enables the UE 120 mitigate the Doppler frequency in the received signal (e.g., if there are multiple Doppler frequencies in the received signal the UE 120 may be unable to mitigate all of the Doppler frequencies, resulting in degraded signal detection and decoding) .
However, measuring the different links in respective time domain occasions (e.g., to mitigate interference and/or measurement confusion between the different links) may consume radio resources (e.g., time domain resources, frequency domain resources, and/or spatial domain resources) and/or may introduce latency associated with performing the measurements of the different links. For example, to measure each link using different radio resources (e.g., for Doppler frequency estimation) , a total radio resource consumption and/or processing latency may be large (e.g., when there is a high quantity of indirect links and/or forwarding-capable devices being used by the UE 120 and the network node 110 for communications) . If less radio resources and/or time domain occasions were to be used to measure each link (e.g., for Doppler frequency estimation) , then less time domain resources may be used to measure each link, resulting in less accurate and/or reliable measurements. As a result, a performance of the Doppler frequency estimation (e.g., that is based on the measurements) may be degraded.
Some techniques and apparatuses described herein enable Doppler frequency estimation for RIS communication links. In some aspects, the UE 120 may perform simultaneous Doppler frequency measurements on a direct link and one or more indirect links (e.g., associated with an RIS reflection) using shared or common radio resources. For example, the UE 120 may receive an indication of time domain rotation factors associated with respective RISs of one or more RISs. The UE 120 may receive, during a time domain measurement occasion, respective reference signals via a direct link with the network node and via one or more indirect links associated with the one or more RISs. The UE 120 may transmit a report indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with measurements of the respective reference signals, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs.
As a result, a quantity of radio resources consumed and/or a latency associated with estimating Doppler frequencies for indirect links (e.g., associated with RISs) may be reduced. For example, the UE 120 may be enabled to identify a Doppler spectrum for respective indirect links based on the time domain rotation factors, thereby enabling the UE 120 to perform measurements of the respective indirect links using shared radio resources (e.g., the Doppler spectrums of the indirect links may be separated due to the use of the time domain rotation factors, reducing a likelihood of inter-link interference and/or confusion at the UE 120 as to which measurement corresponds to which link) . Further, because the links use the shared radio resources, a received SNR of each link may be improved.
For example, the one or more indirect links are associated with reflection coefficients applied by the respective RISs that are associated with the time domain rotation factors. At a given time domain occasion, each RIS may reflect a signal using a reflection coefficient that is based on the time domain rotation factor associated with that RIS. This enables the Doppler spectrums of the received signal at the UE 120 to be separated. As a result, the UE 120 may estimate the Doppler frequency of each link using the corresponding Doppler spectrum (e.g., which can be identified based on the signaled or configured time domain rotation factors) . For example, for an indirect link associated with a given RIS, the Doppler spectrum associated with the given RIS may be a shifted version of a channel Doppler spectrum associated with the channel response, where a shift associated with the Doppler spectrum is based on the time domain rotation factor associated with the RIS. This enables the UE 120 to accurately identify the Doppler spectrum for each indirect link and/or each RIS, thereby improving the performance and/or efficiency of the Doppler frequency estimations.
As indicated above, Fig. 5 is provided as an example. Other examples may differ from what is described with respect to Fig. 5.
Fig. 6 is a diagram of an example 600 associated with Doppler frequency estimation for RIS communication links, in accordance with the present disclosure. As shown in Fig. 6, one or more network nodes 110 (for example, a base station, a CU, a DU, and/or an RU) may communicate with a UE 120. In some aspects, the network node 110 and the UE 120 may communicate via one or more indirect links (e.g., associated with respective RISs, shown as an RIS 605 and an RIS 610) . In some aspects, the network node 110, the UE 120, the RIS 605, and the RIS 610 may be part of a wireless network (e.g., the wireless network 100) . The UE 120 and the network node 110 may have established a wireless connection prior to operations shown in Fig. 6.
Two RISs (e.g., the RIS 605 and the RIS 610) are shown as examples. The techniques and operations described herein may be applicable to scenarios where the network node 110 and the UE 120 communicate using any number of indirect links (e.g., communicate via one RIS, three RISs, four RISs, or another number of RISs) . Additionally, an RIS is provided as an example of a forwarding-capable device 160. The techniques and operations described herein may be applicable other forwarding-capable devices 160 and/or devices with reconfigurable elements.
As shown by reference number 615, the UE 120 may transmit, and the network node 110 may receive, a capability report associated with the UE 120. The UE 120 may transmit the capability report via UE capability signaling, a UE assistance information (UAI) communication, an uplink control information communication, an RRC communication, a physical uplink shared channel (PUSCH) , and/or a physical uplink control channel (PUCCH) , among other examples. The capability report may indicate UE support for one or more operations described herein. For example, the capability report may indicate whether the UE 120 supports Doppler frequency estimation of one or more links (e.g., a direct link and one or more indirect links) using shared or common radio resources, as described herein.
In some aspects, the capability report may indicate whether the UE 120 supports communications via an RIS or another forwarding-capable device. In some aspects, the capability report may indicate whether the UE 120 is capable of estimating a Doppler spectrum associated with an RIS and/or an indirect link via a channel response and a time domain rotation factor associated with the RIS and/or the indirect link, as described herein. For example, the capability report may indicate whether the UE 120 supports and/or is capable of shifting a measured or estimated channel response based on one or more configured time domain rotation factors associated with the RISs and/or the indirect links to estimate Doppler frequencies associated with respective RISs and/or respective indirect links. In some aspects, the capability report may indicate an allowable velocity associated with the UE 120.
The network node 110 may configure the UE 120 in accordance with the capability report (s) . For example, the network node 110 may configure, or may trigger, the UE 120 to perform one or more operations based on, in response to, or otherwise associated with the capability report (s) indicating that the UE 120 supports the one or more operations.
As shown by reference number 620, the network node 110 may transmit, and the UE 120 may receive, configuration information. In some aspects, the UE 120 may receive the configuration information via one or more of system information signaling, RRC signaling, one or more MAC control elements (MAC-CEs) , and/or downlink control information (DCI) , among other examples. In some aspects, the configuration information may include an indication of one or more configuration parameters for selection by the UE 120, and/or explicit configuration information for the UE 120 to use to configure itself, among other examples.
In some aspects, the configuration information may indicate that the UE 120 is to estimate Doppler frequencies for indirect links and/or RISs using respective time domain rotation factors. In some aspects, the configuration information may indicate that the UE 120 is to estimate Doppler frequencies for a direct link and one or more indirect links using shared or common radio resources (e.g., using a common time domain occasion and/or a common channel measurement resource) . The configuration information may indicate that the UE 120 is to separate Doppler spectrums of respective indirect links and/or RISs using the respective time domain rotation factors to estimate the Doppler frequency for each indirect link and/or each RIS.
In some aspects, the configuration information may indicate one or more time domain occasions associated with Doppler frequency estimations. A time domain occasion may include one or more time domain resources. A time domain occasion may be configured to periodically repeat over time. In some aspects, the one or more time domain occasions may be associated with a downlink reference signal, such as a channel state information (CSI) reference signal (CSI-RS) or a tracking reference signal (TRS) , among other examples. For example, the configuration information may include a reference signal configuration (e.g., a CSI-RS resource configuration or as TRS resource configuration) that indicates the one or more time domain occasion. The reference signal configuration may indicate that the configured resource (e.g., a CSI-RS resource or as TRS resource) is associated with Doppler frequency measurements or estimation.
In some aspects, the configuration information may indicate time domain rotation factors associated with respective RISs of one or more RISs (e.g., of the RIS 605 and the RIS 610) . For example, the configuration information may indicate a first time domain rotation factor associated with the RIS 605 and a second time domain rotation factor associated with the RIS 610. In other words, the configuration information may indicate time domain rotation factors associated with respective indirect links between the UE 120 and the network node 110. A time domain rotation factor may be an element or variable used by a given RIS to calculate a multiplicative factor to be applied to a reflection coefficient used by the given RIS. The multiplicative factor may be based on, or otherwise associated with the time domain rotation factor, an index of a current time domain occasion, and/or a duration (e.g., an interval length or an amount of time) of the time domain occasion. The time domain rotation factor and/or the multiplicative factor may enable Doppler spectrums of different indirect links to be separated in a Doppler domain, thereby enabling the UE 120 to separate and measure or estimate the Doppler frequency for each indirect link (e.g., using a reference signal transmitted by the network node 110) .
The UE 120 may configure itself based at least in part on the configuration information. In some aspects, the UE 120 may be configured to perform one or more operations described herein based at least in part on the configuration information.
As shown by reference number 625, the network node 110 may determine one or more time domain rotation factors. For example, the network node 110 may determine a time domain rotation factor for each RIS used by the network node 110 and/or each RIS associated with the UE 120. In some aspects, the network node 110 may determine a time domain rotation factor for each indirect link (e.g., via an RIS) associated with the UE 120 and the network node 110. For example, the network node 110 may determine a first time domain rotation factor for the RIS 605 and a second time domain rotation factor for the RIS 610.
The network node 110 may determine the one or more time domain rotation factors based on, or otherwise associated with, a maximum Doppler frequency associated with the UE 120. The maximum Doppler frequency may be a maximum value of the Doppler frequencies of all of the indirect links associated with the UE 120 and the network node 110. The network node 110 may determine the maximum Doppler frequency based on, or otherwise associated with, an allowed velocity (e.g., a maximum allowed velocity) associated with the UE 120. For example, the maximum Doppler frequency may be represented aswhere v_max is the allowed velocity (e.g., a maximum allowed velocity) associated with the UE 120, c is a constant (e.g., the speed of light in vacuum) , and f_c is a center frequency or carrier frequency. In some aspects, the network node 110 may determine an allowable measurable Doppler frequency (e.g., to ensure that a Doppler spectrum of the direct link and each indirect link are non-overlapping) . The allowable measurable Doppler frequency may be based on, or otherwise associated with, a duration (T) of the time occasions to be used to measure downlink reference signals for the Doppler frequency estimations and a quantity (M) of RISs or indirect links associated with the Doppler frequency estimations. For example, the network node 110 may determine the allowable measurable Doppler frequency such that the allowable measurable Doppler frequency satisfies
The network node 110 may determine the one or more time domain rotation factors for M RISs based on, or otherwise associated with, the allowable measurable Doppler frequency f_{d, max, measure}. For example, a time domain rotation factor for a given RIS may be based on, or otherwise associated with, an index (or other identifier) of the RIS, the duration (T) of the time occasions, the quantity (M) of RISs or indirect links, and the allowable measurable Doppler frequency f_{d, max, measure}. For example, the network node 110 may determine a time domain rotation factor for an RIS m aswhere Δ_m is the time domain rotation factor for an RIS having an index m and Δ₀ is a basic time domain rotation factor. The network node 110 may determine the basic time domain rotation factor based on, or otherwise associated with, the allowable measurable Doppler frequency f_{d, max, measure}, the duration (T) of the time occasions, the quantity (M) of RISs or indirect links. For example, the basic time domain rotation factor may be represented asThe network node 110 may determine a time domain rotation factor for each RIS and/or each indirect link in a similar manner.
As shown by reference number 630, the network node 110 may transmit, and the RIS 605 may receive (or a controller of the RIS 605 may receive) , an indication of a first time domain rotation factor associated with the RIS 605 (Δ₁, assuming that the index of the RIS 605 is 1) . Similarly, as shown by reference number 635, the network node 110 may transmit, and the RIS 610 may receive (or a controller of the RIS 610 may receive) , an indication of a second time domain rotation factor associated with the RIS 610 (Δ₂, assuming that the index of the RIS 605 is 2) . In other words, the network node 110 may configure each RIS to use a different time domain rotation factor. As described elsewhere herein, a given RIS may use the configured time domain rotation factor to determine a multiplicative factor to be applied to a reflection coefficient used by the given RIS.
The configurations of the RISs may indicate the actual values of the time domain rotation factor. For example, the configuration for the RIS 605 may indicate the actual value of Δ₁, and the configuration for the RIS 605 may indicate the actual value of Δ₂. In some other aspects, the configurations of the RISs may indicate information that can be used to calculate the time domain rotation factors. For example, the configuration for the RIS 605 may indicate a value of the duration (T) of the time occasions, the quantity (M) of RISs or indirect links, and an index of the RIS 605. The RIS 605 may determine the actual value of the first time domain rotation factor based on, or otherwise associated with, the information (e.g., values for T, M, and m) indicated by the network node 110. Similarly, the configuration for the RIS 610 may indicate a value of the duration (T) of the time occasions, the quantity (M) of RISs or indirect links, and an index of the RIS 610. The RIS 610 may determine the actual value of the second time domain rotation factor based on, or otherwise associated with, the information (e.g., values for T, M, and m) indicated by the network node 110. The indication of the time domain rotation factors for the RISs may be communicated via RRC signaling, MAC-CE signaling, DCI signaling, and/or a combination of signaling, among other examples. For example, some parameters (e.g., a value of T) may be indicated via RRC signaling, and some other parameters (e.g., a value of M) may be indicated by another type of signaling (e.g., MAC-CE signaling or DCI signaling) .
As shown by reference number 640, the network node 110 may transmit, and the UE 120 may receive, an indication of time domain rotation factors associated with respective RISs of the one or more RISs associated with one or more indirect links between the UE 120 and the network node 110. In some aspects, the indication of time domain rotation factors may be included in the configuration information described above. In some aspects, the indication of the time domain rotation factors includes an indication of values (e.g., actual values) of respective time domain rotation factors of the time domain rotation factors. For example, the indication of the time domain rotation factors may include the actual values of the time domain rotation factors. In other aspects, the indication of time domain rotation factors includes information that can be used to calculate the time domain rotation factors. For example, the indication of time domain rotation factors may include an indication of a duration of the time domain measurement occasions (T) , a quantity of the one or more RISs (M) , and/or index values of the one or more RISs. The UE 120 may calculate the time domain rotation factors for the RISs and/or the indirect links based on, or otherwise associated with, the information indicated by the network node 110 (e.g., using one or more of the formulas described herein) . The indication of the time domain rotation factors for the UE 120 may be communicated via RRC signaling, MAC-CE signaling, DCI signaling, and/or a combination of signaling, among other examples. For example, some parameters (e.g., a value of T) may be indicated to the UE 120 via RRC signaling, and some other parameters (e.g., a value of M) may be indicated to the UE 120 by another type of signaling (e.g., MAC-CE signaling or DCI signaling) .
As shown by reference number 645, the network node 110 may transmit a reference signal (e.g., a CSI-RS, a TRS, or another reference signal) during a time domain occasion (e.g., a measurement time domain occasion or a channel measurement time domain occasion) . The network node 110 may transmit the reference signal to the UE 120 via a direct link and via one or more indirect links (e.g., a first indirect link associated with the RIS 605 and a second indirect link associated with the RIS 610) . As shown in Fig. 8, the reference signal may be transmitted via the direct link and via the one or more indirect links using shared or common radio resources. For example, the reference signal may be transmitted via the direct link and via the one or more indirect links during the same time domain occasion.
As shown by reference number 650, the RIS 605 may reflect, redirect, and/or refract the reference signal to the UE 120. For example, the RIS 605 may reflect, redirect, refract, and/or otherwise forward the reference signal using the first time domain rotation factor (e.g., Δ₁) . For example, the RIS 605 may calculate or determine, for the time domain occasion l (e.g., where l is an index of the time domain occasion) , a multiplicative factor to be used to calculate the reflection coefficient used by the RIS 605. For example, the RIS 605 may calculate or determine the multiplicative factor based on, or otherwise associated with, the current time domain occasion l, the first time domain rotation factor Δ₁, and/or the duration of the time domain measurement occasions T. For example, the multiplicative factor for the RIS 605 associated with the time domain occasion l may be represented asMore generally, the multiplicative factor for an RIS m associated with the time domain occasion l may be represented asThe RIS 605 may multiply or otherwise modify the reflection coefficients calculated by, or configured for the RIS 605 (e.g., reflection coefficients that are associated with an incident angle, from the network node 110 to the RIS 605, and with a reflective angle from the RIS 605 to the UE 120, using the formulas described elsewhere herein) by the multiplicative factor.
For example, the RIS 605 may modify the reflection coefficients as: whereis the modified reflection coefficient for a reconfigurable element (or meta-element) n, and C_n is the reflection coefficient for the reconfigurable element (or meta-element) n. As described elsewhere herein, the original reflection coefficients of each reconfigurable element C_n can be derived based on the incident angle and the reflective angle as described elsewhere herein. The original reflection coefficients may be kept constant during a measurement duration (e.g., LT) associated with the Doppler frequency estimations (e.g., to ensure that the reference signal is correctly reflected in a spatial direction toward the UE 120) . More generally, the modified reflection coefficients for an RIS m may be represented as
As shown by reference number 655, the RIS 610 may reflect, redirect, and/or refract the reference signal to the UE 120. For example, the RIS 610 may reflect, redirect, refract, and/or otherwise forward the reference signal using the second time domain rotation factor (e.g., Δ₂) . For example, the RIS 610 may calculate or determine, for the time domain occasion l, a multiplicative factor to be used to calculate the reflection coefficient used by the RIS 610. For example, the RIS 610 may calculate or determine the multiplicative factor based on, or otherwise associated with, the current time domain occasion l, the second time domain rotation factor Δ₂, and/or the duration of the time domain measurement occasions T. For example, the multiplicative factor for the RIS 610 associated with the time domain occasion l may be represented asThe RIS 610 may multiply or otherwise modify the reflection coefficients calculated by, or configured for the RIS 610 (e.g., reflection coefficients that are associated with an incident angle, from the network node 110 to the RIS 610, and with a reflective angle from the RIS 610 to the UE 120, using the formulas described elsewhere herein) by the multiplicative factor. For example, the RIS 610 may modify the reflection coefficients as:whereis the modified reflection coefficient for a reconfigurable element (or meta-element) n, and C_n is the reflection coefficient for the reconfigurable element (or meta-element) n. As described elsewhere herein, the original reflection coefficients of each reconfigurable element C_n can be derived based on the incident angle and the reflective angle as described elsewhere herein.
As shown by reference number 660, the UE 120 may estimate Doppler frequencies for the direct link and the one or more indirect links. The UE 120 may estimate the Doppler frequencies for the one or more indirect links based on, or otherwise associated with, respective time domain rotation factors. For example, the UE 120 may estimate a channel response associated with the respective reference signals (e.g., transmitted by the network node 110 and/or reflected by the RISs) and the respective links. For example, the UE 120 may estimate a channel response based on, or otherwise associated with, an original reference symbol, p_k, l, associated with the reference signal, where k is a subcarrier and l is the current time domain occasion. The estimated channel response may include information associated with the direct link and the one or more indirect links. For example, the resulting overall equivalent channel response (e.g., estimated by measuring the original reference symbol, p_k, l) may be represented as:whereandare the original and equivalent channel responses, respectively, at subcarrier k and time domain occasion l for RIS m. because of the rotation of the reflection coefficient (e.g., in the time domain) applied by the RISs, as described in more detail elsewhere herein. The UE 120 may estimate the channel response at all subcarriers and during the time occasion l. For example, the combined or summed channel response may be represented as where K is the quantity of subcarriers associated with the reference signal.
The UE 120 may estimate, for each RIS and/or for each indirect link, a Doppler spectrum associated with that RIS and/or that indirect link via the channel response and a time domain rotation factor, of the time domain rotation factors, associated with that RIS and/or that indirect link. For example, the UE 120 may calculates the Doppler frequency of direct link and each indirect link at respective equivalent Doppler spectrums. The UE 120 may estimate or derive the Doppler spectrums of the estimated channel responses at multiple (L) time domain occasions for each link by performing an FFT operation to the overall equivalent channel response vector (e.g., a vector including the estimated channel responses at multiple time domain occasions) . For example, the overall equivalent channel response vector may be or
For the indirect links, the UE 120 may determine that the original channel response vector at multiple time occasions L for an indirect link associated with an RIS m and a subcarrier k isThe UE 120 may determine that the original channel response vector at multiple time occasions L for an indirect link associated with an RIS m and multiple subcarriers K isThe UE 120 may determine that the equivalent channel response vector at multiple time occasions L for an indirect link associated with an RIS m and a subcarrier k is Similarly, the UE 120 may determine that the equivalent channel response vector at multiple time occasions L for an indirect link associated with an RIS m and multiple subcarriers K is
The UE 120 may determine that, for an indirect link associated with the RIS m, the Doppler spectrum oforis a shifted version of the Doppler spectrum ofor h^RIS m. In other words, the UE 120 may estimate or determine a Doppler spectrum ofor h^RIS m. The UE 120 may shift the estimated or determine Doppler spectrum (e.g., where the shift is based on, or otherwise associated with, the time domain rotation factor associated with the RIS m) to obtain the Doppler spectrum associated with the indirect link that is associated with the RIS m. For example, the Doppler spectrum ofmay be represented as The Doppler spectrum of h^RIS m may be represented as H^RIS m=FFT (h^RIS m) . The Doppler spectrum ofmay be represented asSimilarly, the Doppler spectrum ofmay be represented asThe frequency domain element l may be represented asand In other words, the Doppler spectrum of the indirect link associated with an RIS m may be shifted by a value (or length) of mL₀. The UE 120 may determine that the Doppler spectrum for the direct link is not shifted (e.g., because no time domain rotation factor is applied to the transmission of the reference signal via the direct link) .
Becauseand because different RISs apply different time domain rotation factors (e.g., have different lengths or values by which the Doppler spectrums are shifted) , the Doppler spectrums of respective links (e.g., the direct link and the one or more indirect links) may be non-overlapping. Therefore, when the RIS (s) simultaneously reflect the reference signal with different time domain rotation factors, interference in the respective Doppler spectrums may be mitigated or eliminated. Additionally, because the derived Doppler spectrum of the estimated channel response may be a concatenation of length L₀, the UE 120 may identify the Doppler spectrum for the direct link and the indirect link (s) from the derived Doppler spectrum.
The UE 120 may estimate the Doppler frequency from respective Doppler spectrums. For example, an estimated Doppler frequency associated with an RIS is based on the Doppler spectrum associated with the RIS (e.g., derived from the Doppler spectrum of the estimated channel response, as described above) . For example, the Doppler frequencies for respective indirect links may be associated with a highest received power within the respective Doppler spectrums. For example, the UE 120 may determine that a Doppler frequency associated with a given indirect link (e.g., and a given RIS associated with the given indirect link) is a frequency value with a highest power of the Doppler spectrum associated with the given indirect link. As another example, a Doppler frequency for an indirect link associated with an RIS may be based on, or otherwise associated with, an inverse discrete Fourier transform (iDFT) of a shifted version of the Doppler spectrum associated with the indirect link. A shift associated with the shifted version of the Doppler spectrum may be associated with a time domain rotation factor associated with the RIS. For example, the UE 120 may shift the Doppler spectrum of RIS m by a value of -Δ_m. The UE 120 may perform an iDFT operation associated with the shifter Doppler spectrum to obtain an interference-free time domain signal. The estimated Doppler frequency may be associated with a slope value of the phases of the time domain signal.
As shown by reference number 665, the UE 120 may transmit, and the network node 110 may receive, an indication of the estimated Doppler frequencies for the direct link and the one or more indirect links. For example, the UE 120 may transmit, and the network node 110 may receive, a report indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links. The network node 110 may configure the RISs (e.g., the RIS 605 and/or the RIS 610) based on, in response to, or otherwise associated with the estimated Doppler frequencies (e.g., such that there is zero or only one Doppler frequency in the signal as received by the UE 120) .
As indicated above, Fig. 6 is provided as an example. Other examples may differ from what is described with respect to Fig. 6.
Fig. 7 is a diagram of an example 700 associated with Doppler frequency estimation for RIS communication links, in accordance with the present disclosure. As shown in Fig. 7, different RISs may apply different multiplicative factors to reflection coefficients in a given time domain occasion to facilitate efficient Doppler frequency estimations by the UE 120.
For example, the UE 120 may perform Doppler frequency estimations in G time domain occasions. As shown in Fig. 7, the multiplicative factor applied by a given RIS during a given time domain occasion may be based on, or otherwise associated with the index of the time domain occasion and the time domain rotation factor associated with the given RIS. For example, the RIS 605 may apply the multiplicative factorduring the time occasion 1, during the time occasion 2, during the time occasion 3, during the time occasion 4, andduring the time occasion G. Similarly, the RIS 610 may apply the multiplicative factorduring the time occasion 1, during the time occasion 2,during the time occasion 3, during the time occasion 4, andduring the time occasion G.
As a result, the received signal at the UE 120 may be associated with shifted, non-overlapping Doppler spectrums for respective links (e.g., including the direct link and one or more indirect links) . For example, as shown in Fig. 7, the received signal may be associated with a Doppler spectrum 705 for the direct link, a Doppler spectrum 710 for an indirect link 1 (e.g., associated with the RIS 605) , and a Doppler spectrum 715 for an indirect link 2 (e.g., associated with the RIS 610) . The Doppler spectrum 710 may span from Doppler frequencies to (e.g., with reference to a center or reference Doppler frequency) . The Doppler spectrum 710 may span from Doppler frequenciestoThe Doppler spectrum 715 may span from Doppler frequenciestoThe UE 120 may estimate or determine that a Doppler frequency 720 is associated with the direct link (e.g., using the Doppler spectrum 705) . The UE 120 may estimate or determine that a Doppler frequency 725 is associated with the indirect link 1 (e.g., using the Doppler spectrum 710) . Similarly, the UE 120 may estimate or determine that a Doppler frequency 730 is associated with the indirect link 2 (e.g., using the Doppler spectrum 715) .
As indicated above, Fig. 7 is provided as an example. Other examples may differ from what is described with respect to Fig. 7.
Fig. 8 is a diagram illustrating an example process 800 performed, for example, by a UE, in accordance with the present disclosure. Example process 800 is an example where the UE (e.g., UE 120) performs operations associated with Doppler frequency estimation for RIS communication links.
As shown in Fig. 8, in some aspects, process 800 may include receiving, from a network node, an indication of time domain rotation factors associated with respective RISs of one or more RISs (block 810) . For example, the UE (e.g., using reception component 1102 and/or communication manager 1106, depicted in Fig. 11) may receive, from a network node, an indication of time domain rotation factors associated with respective RISs of one or more RISs, as described above.
As further shown in Fig. 8, in some aspects, process 800 may include receiving, during a time domain measurement occasion, respective reference signals via a direct link with the network node and via one or more indirect links associated with the one or more RISs (block 820) . For example, the UE (e.g., using reception component 1102 and/or communication manager 1106, depicted in Fig. 11) may receive, during a time domain measurement occasion, respective reference signals via a direct link with the network node and via one or more indirect links associated with the one or more RISs, as described above.
As further shown in Fig. 8, in some aspects, process 800 may include transmitting, to the network node, a report indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with measurements of the respective reference signals, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs (block 830) . For example, the UE (e.g., using transmission component 1104 and/or communication manager 1106, depicted in Fig. 11) may transmit, to the network node, a report indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with measurements of the respective reference signals, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs, as described above.
Process 800 may include additional aspects, such as any single aspect or any combination of aspects described below and/or in connection with one or more other processes described elsewhere herein.
In a first aspect, the one or more indirect links are associated with reflection coefficients applied by the respective RISs that are associated with the time domain rotation factors.
In a second aspect, alone or in combination with the first aspect, the time domain rotation factors are based on a quantity of the one or more RISs and a maximum Doppler frequency associated with the direct link and the one or more indirect links.
In a third aspect, alone or in combination with one or more of the first and second aspects, the time domain rotation factors are based on a quantity of the one or more RISs, a duration of the time domain measurement occasion, and index values of the respective RISs.
In a fourth aspect, alone or in combination with one or more of the first through third aspects, the indication of the time domain rotation factors includes an indication of values of respective time domain rotation factors of the time domain rotation factors.
In a fifth aspect, alone or in combination with one or more of the first through fourth aspects, the indication of the time domain rotation factors includes an indication of a duration of the time domain measurement occasion, a quantity of the one or more RISs, and index values of the one or more RISs.
In a sixth aspect, alone or in combination with one or more of the first through fifth aspects, the indication of the time domain rotation factors is included in at least one of a radio resource control communication, a MAC-CE communication, or a downlink control information communication.
In a seventh aspect, alone or in combination with one or more of the first through sixth aspects, process 800 includes estimating a channel response associated with the respective reference signals and the respective links, and estimating, for an RIS of the one or more RISs, a Doppler spectrum associated with the RIS via the channel response and a time domain rotation factor, of the time domain rotation factors, associated with the RIS, wherein an estimated Doppler frequency, of the estimated Doppler frequencies, associated with the RIS is based on the Doppler spectrum associated with the RIS.
In an eighth aspect, alone or in combination with one or more of the first through seventh aspects, the Doppler spectrum associated with the RIS is a shifted version of a channel Doppler spectrum associated with the channel response, wherein a shift associated with the Doppler spectrum is based on the time domain rotation factor associated with the RIS.
In a ninth aspect, alone or in combination with one or more of the first through eighth aspects, the one or more indirect links are associated with respective Doppler spectrums that are non-overlapping based on the one or more RISs reflecting the respective reference signals using the time domain rotation factors, and wherein Doppler frequencies, of the estimated Doppler frequencies, for respective indirect links are associated with the respective Doppler spectrums.
In a tenth aspect, alone or in combination with one or more of the first through ninth aspects, the one or more indirect links are associated with respective Doppler spectrums, and wherein Doppler frequencies, of the estimated Doppler frequencies, for respective indirect links are associated with a highest received power within the respective Doppler spectrums.
In an eleventh aspect, alone or in combination with one or more of the first through tenth aspects, the one or more indirect links are associated with respective Doppler spectrums, wherein a Doppler frequency, of the estimated Doppler frequencies, for an indirect link associated with an RIS, of the one or more RISs, is based on an inverse discrete Fourier transform of a shifted version of a Doppler spectrum, of the respective Doppler spectrums, associated with the indirect link, and wherein a shift associated with the shifted version of the Doppler spectrum is associated with a time domain rotation factor, of the time domain rotation factors, associated with the RIS.
In a twelfth aspect, alone or in combination with one or more of the first through eleventh aspects, each of the respective reference signals includes a tracking reference signal or a channel state information reference signal.
Although Fig. 8 shows example blocks of process 800, in some aspects, process 800 may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in Fig. 8. Additionally, or alternatively, two or more of the blocks of process 800 may be performed in parallel.
Fig. 9 is a diagram illustrating an example process 900 performed, for example, by a network node, in accordance with the present disclosure. Example process 900 is an example where the network node (e.g., network node 110) performs operations associated with Doppler frequency estimation for RIS communication links.
As shown in Fig. 9, in some aspects, process 900 may include transmitting, an indication, for a UE and one or more RISs, of time domain rotation factors associated with respective RISs of the one or more RISs (block 910) . For example, the network node (e.g., using transmission component 1204 and/or communication manager 1206, depicted in Fig. 12) may transmit, an indication, for a UE and one or more RISs, of time domain rotation factors associated with respective RISs of the one or more RISs, as described above.
As further shown in Fig. 9, in some aspects, process 900 may include transmitting, during a time domain measurement occasion, a reference signal via a direct link with the UE and via one or more indirect links associated with the one or more RISs (block 920) . For example, the network node (e.g., using transmission component 1204 and/or communication manager 1206, depicted in Fig. 12) may transmit, during a time domain measurement occasion, a reference signal via a direct link with the UE and via one or more indirect links associated with the one or more RISs, as described above.
As further shown in Fig. 9, in some aspects, process 900 may include receiving a report, associated with the UE, indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with a measurement of the reference signal, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs (block 930) . For example, the network node (e.g., using reception component 1202 and/or communication manager 1206, depicted in Fig. 12) may receive a report, associated with the UE, indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with a measurement of the reference signal, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs, as described above.
Process 900 may include additional aspects, such as any single aspect or any combination of aspects described below and/or in connection with one or more other processes described elsewhere herein.
In a first aspect, the one or more indirect links are associated with reflection coefficients applied by the respective RISs that are associated with the time domain rotation factors.
In a second aspect, alone or in combination with the first aspect, the time domain rotation factors are based on a quantity of the one or more RISs and a maximum Doppler frequency associated with the direct link and the one or more indirect links.
In a third aspect, alone or in combination with one or more of the first and second aspects, the maximum Doppler frequency is associated with an allowable velocity of the UE.
In a fourth aspect, alone or in combination with one or more of the first through third aspects, the time domain rotation factors are based on a quantity of the one or more RISs, a duration of the time domain measurement occasion, and index values of the respective RISs.
In a fifth aspect, alone or in combination with one or more of the first through fourth aspects, the indication of the time domain rotation factors includes an indication of values of respective time domain rotation factors of the time domain rotation factors.
In a sixth aspect, alone or in combination with one or more of the first through fifth aspects, the indication of the time domain rotation factors includes an indication of a duration of the time domain measurement occasion, a quantity of the one or more RISs, and index values of the one or more RISs.
In a seventh aspect, alone or in combination with one or more of the first through sixth aspects, the indication of the time domain rotation factors is included in at least one of a radio resource control communication, a MAC-CE communication, or a downlink control information communication.
In an eighth aspect, alone or in combination with one or more of the first through seventh aspects, the respective reference signals include a tracking reference signal or a channel state information reference signal.
Although Fig. 9 shows example blocks of process 900, in some aspects, process 900 may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in Fig. 9. Additionally, or alternatively, two or more of the blocks of process 900 may be performed in parallel.
Fig. 10 is a diagram illustrating an example process 1000 performed, for example, by an RIS, in accordance with the present disclosure. Example process 1000 is an example where the RIS (e.g., RIS 605, RIS 610, forwarding-capable device 160, or a controller of the RIS) performs operations associated with Doppler frequency estimation for RIS communication links.
As shown in Fig. 10, in some aspects, process 1000 may include receiving, from a network node, an indication of a time domain rotation factor associated with the RIS (block 1010) . For example, the RIS (e.g., using reception component 1302 and/or communication manager 1306, depicted in Fig. 13) may receive, from a network node, an indication of a time domain rotation factor associated with the RIS, as described above.
As further shown in Fig. 10, in some aspects, process 1000 may include reflecting, using a reflection coefficient, a reference signal associated with the network node, the reflection coefficient being based on the time domain rotation factor (block 1020) . For example, the RIS (e.g., using communication manager 1306, depicted in Fig. 13) may reflect, using a reflection coefficient, a reference signal associated with the network node, the reflection coefficient being based on the time domain rotation factor, as described above.
Process 1000 may include additional aspects, such as any single aspect or any combination of aspects described below and/or in connection with one or more other processes described elsewhere herein.
In a first aspect, the time domain rotation factor is based on a quantity of one or more RISs, including the RIS, and a maximum Doppler frequency associated with the network node.
In a second aspect, alone or in combination with the first aspect, the time domain rotation factor is based on a quantity of one or more RISs reflecting the reference signal including the RIS, a duration of a time domain measurement occasion, and an index value of the RIS.
In a third aspect, alone or in combination with one or more of the first and second aspects, the indication of the time domain rotation factor includes an indication of a value of the time domain rotation factor.
In a fourth aspect, alone or in combination with one or more of the first through third aspects, the indication of the time domain rotation factor includes an indication of a duration of a time domain measurement occasion, a quantity of one or more RISs reflecting the reference signal, and an index value of the RIS.
In a fifth aspect, alone or in combination with one or more of the first through fourth aspects, the indication of the time domain rotation factor is included in at least one of a radio resource control communication, a MAC control element communication, or a downlink control information communication.
In a sixth aspect, alone or in combination with one or more of the first through fifth aspects, the reference signal includes a tracking reference signal or a channel state information reference signal.
Although Fig. 10 shows example blocks of process 1000, in some aspects, process 1000 may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in Fig. 10. Additionally, or alternatively, two or more of the blocks of process 1000 may be performed in parallel.
Fig. 11 is a diagram of an example apparatus 1100 for wireless communication, in accordance with the present disclosure. The apparatus 1100 may be a UE, or a UE may include the apparatus 1100. In some aspects, the apparatus 1100 includes a reception component 1102, a transmission component 1104, and/or a communication manager 1106, which may be in communication with one another (for example, via one or more buses and/or one or more other components) . In some aspects, the communication manager 1106 is the communication manager 140 described in connection with Fig. 1. As shown, the apparatus 1100 may communicate with another apparatus 1108, such as a UE or a network node (such as a CU, a DU, an RU, or a base station) , using the reception component 1102 and the transmission component 1104.
In some aspects, the apparatus 1100 may be configured to perform one or more operations described herein in connection with Figs. 6 and 7. Additionally, or alternatively, the apparatus 1100 may be configured to perform one or more processes described herein, such as process 800 of Fig. 8, or a combination thereof. In some aspects, the apparatus 1100 and/or one or more components shown in Fig. 11 may include one or more components of the UE described in connection with Fig. 2. Additionally, or alternatively, one or more components shown in Fig. 11 may be implemented within one or more components described in connection with Fig. 2. Additionally, or alternatively, one or more components of the set of components may be implemented at least in part as software stored in a memory. For example, a component (or a portion of a component) may be implemented as instructions or code stored in a non-transitory computer-readable medium and executable by a controller or a processor to perform the functions or operations of the component.
The reception component 1102 may receive communications, such as reference signals, control information, data communications, or a combination thereof, from the apparatus 1108. The reception component 1102 may provide received communications to one or more other components of the apparatus 1100. In some aspects, the reception component 1102 may perform signal processing on the received communications (such as filtering, amplification, demodulation, analog-to-digital conversion, demultiplexing, deinterleaving, de-mapping, equalization, interference cancellation, or decoding, among other examples) , and may provide the processed signals to the one or more other components of the apparatus 1100. In some aspects, the reception component 1102 may include one or more antennas, a modem, a demodulator, a MIMO detector, a receive processor, a controller/processor, a memory, or a combination thereof, of the UE described in connection with Fig. 2.
The transmission component 1104 may transmit communications, such as reference signals, control information, data communications, or a combination thereof, to the apparatus 1108. In some aspects, one or more other components of the apparatus 1100 may generate communications and may provide the generated communications to the transmission component 1104 for transmission to the apparatus 1108. In some aspects, the transmission component 1104 may perform signal processing on the generated communications (such as filtering, amplification, modulation, digital-to-analog conversion, multiplexing, interleaving, mapping, or encoding, among other examples) , and may transmit the processed signals to the apparatus 1108. In some aspects, the transmission component 1104 may include one or more antennas, a modem, a modulator, a transmit MIMO processor, a transmit processor, a controller/processor, a memory, or a combination thereof, of the UE described in connection with Fig. 2. In some aspects, the transmission component 1104 may be co-located with the reception component 1102 in a transceiver.
The communication manager 1106 may support operations of the reception component 1102 and/or the transmission component 1104. For example, the communication manager 1106 may receive information associated with configuring reception of communications by the reception component 1102 and/or transmission of communications by the transmission component 1104. Additionally, or alternatively, the communication manager 1106 may generate and/or provide control information to the reception component 1102 and/or the transmission component 1104 to control reception and/or transmission of communications.
The reception component 1102 may receive, from a network node, an indication of time domain rotation factors associated with respective RISs of one or more RISs. The reception component 1102 may receive, during a time domain measurement occasion, respective reference signals via a direct link with the network node and via one or more indirect links associated with the one or more RISs. The transmission component 1104 may transmit, to the network node, a report indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with measurements of the respective reference signals, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs.
The communication manager 1106 may estimate a channel response associated with the respective reference signals and the respective links.
The communication manager 1106 may estimate, for an RIS of the one or more RISs, a Doppler spectrum associated with the RIS via the channel response and a time domain rotation factor, of the time domain rotation factors, associated with the RIS wherein an estimated Doppler frequency, of the estimated Doppler frequencies, associated with the RIS is based on the Doppler spectrum associated with the RIS.
The number and arrangement of components shown in Fig. 11 are provided as an example. In practice, there may be additional components, fewer components, different components, or differently arranged components than those shown in Fig. 11. Furthermore, two or more components shown in Fig. 11 may be implemented within a single component, or a single component shown in Fig. 11 may be implemented as multiple, distributed components. Additionally, or alternatively, a set of (one or more) components shown in Fig. 11 may perform one or more functions described as being performed by another set of components shown in Fig. 11.
Fig. 12 is a diagram of an example apparatus 1200 for wireless communication, in accordance with the present disclosure. The apparatus 1200 may be a network node, or a network node may include the apparatus 1200. In some aspects, the apparatus 1200 includes a reception component 1202, a transmission component 1204, and/or a communication manager 1206, which may be in communication with one another (for example, via one or more buses and/or one or more other components) . In some aspects, the communication manager 1206 is the communication manager 150 described in connection with Fig. 1. As shown, the apparatus 1200 may communicate with another apparatus 1208, such as a UE or a network node (such as a CU, a DU, an RU, or a base station) , using the reception component 1202 and the transmission component 1204.
In some aspects, the apparatus 1200 may be configured to perform one or more operations described herein in connection with Figs. 6 and 7. Additionally, or alternatively, the apparatus 1200 may be configured to perform one or more processes described herein, such as process 900 of Fig. 9, or a combination thereof. In some aspects, the apparatus 1200 and/or one or more components shown in Fig. 12 may include one or more components of the network node described in connection with Fig. 2. Additionally, or alternatively, one or more components shown in Fig. 12 may be implemented within one or more components described in connection with Fig. 2. Additionally, or alternatively, one or more components of the set of components may be implemented at least in part as software stored in a memory. For example, a component (or a portion of a component) may be implemented as instructions or code stored in a non-transitory computer-readable medium and executable by a controller or a processor to perform the functions or operations of the component.
The reception component 1202 may receive communications, such as reference signals, control information, data communications, or a combination thereof, from the apparatus 1208. The reception component 1202 may provide received communications to one or more other components of the apparatus 1200. In some aspects, the reception component 1202 may perform signal processing on the received communications (such as filtering, amplification, demodulation, analog-to-digital conversion, demultiplexing, deinterleaving, de-mapping, equalization, interference cancellation, or decoding, among other examples) , and may provide the processed signals to the one or more other components of the apparatus 1200. In some aspects, the reception component 1202 may include one or more antennas, a modem, a demodulator, a MIMO detector, a receive processor, a controller/processor, a memory, or a combination thereof, of the network node described in connection with Fig. 2. In some aspects, the reception component 1202 and/or the transmission component 1204 may include or may be included in a network interface. The network interface may be configured to obtain and/or output signals for the apparatus 1200 via one or more communications links, such as a backhaul link, a midhaul link, and/or a fronthaul link.
The transmission component 1204 may transmit communications, such as reference signals, control information, data communications, or a combination thereof, to the apparatus 1208. In some aspects, one or more other components of the apparatus 1200 may generate communications and may provide the generated communications to the transmission component 1204 for transmission to the apparatus 1208. In some aspects, the transmission component 1204 may perform signal processing on the generated communications (such as filtering, amplification, modulation, digital-to-analog conversion, multiplexing, interleaving, mapping, or encoding, among other examples) , and may transmit the processed signals to the apparatus 1208. In some aspects, the transmission component 1204 may include one or more antennas, a modem, a modulator, a transmit MIMO processor, a transmit processor, a controller/processor, a memory, or a combination thereof, of the network node described in connection with Fig. 2. In some aspects, the transmission component 1204 may be co-located with the reception component 1202 in a transceiver.
The communication manager 1206 may support operations of the reception component 1202 and/or the transmission component 1204. For example, the communication manager 1206 may receive information associated with configuring reception of communications by the reception component 1202 and/or transmission of communications by the transmission component 1204. Additionally, or alternatively, the communication manager 1206 may generate and/or provide control information to the reception component 1202 and/or the transmission component 1204 to control reception and/or transmission of communications.
The transmission component 1204 may transmit, an indication, for a UE and one or more RISs, of time domain rotation factors associated with respective RISs of the one or more RISs. The transmission component 1204 may transmit, during a time domain measurement occasion, a reference signal via a direct link with the UE and via one or more indirect links associated with the one or more RISs. The reception component 1202 may receive a report, associated with the UE, indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with a measurement of the reference signal, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs.
The number and arrangement of components shown in Fig. 12 are provided as an example. In practice, there may be additional components, fewer components, different components, or differently arranged components than those shown in Fig. 12. Furthermore, two or more components shown in Fig. 12 may be implemented within a single component, or a single component shown in Fig. 12 may be implemented as multiple, distributed components. Additionally, or alternatively, a set of (one or more) components shown in Fig. 12 may perform one or more functions described as being performed by another set of components shown in Fig. 12.
Fig. 13 is a diagram of an example apparatus 1300 for wireless communication, in accordance with the present disclosure. The apparatus 1300 may be an RIS (or another forwarding-capable device) , or an RIS (e.g., or another forwarding-capable device) may include the apparatus 1300. In some aspects, the apparatus 1300 includes a reception component 1302, a transmission component 1304, and/or a communication manager 1306, which may be in communication with one another (for example, via one or more buses and/or one or more other components) . In some aspects, the communication manager 1306 is the communication manager 170 described in connection with Fig. 1. As shown, the apparatus 1300 may communicate with another apparatus 1308, such as a UE or a network node (such as a CU, a DU, an RU, or a base station) , using the reception component 1302 and the transmission component 1304.
In some aspects, the apparatus 1300 may be configured to perform one or more operations described herein in connection with Figs. 6 and 7. Additionally, or alternatively, the apparatus 1300 may be configured to perform one or more processes described herein, such as process 1000 of Fig. 10, or a combination thereof. In some aspects, the apparatus 1300 and/or one or more components shown in Fig. 13 may include one or more components of the RIS described in connection with Fig. 2. Additionally, or alternatively, one or more components shown in Fig. 13 may be implemented within one or more components described in connection with Fig. 2. Additionally, or alternatively, one or more components of the set of components may be implemented at least in part as software stored in a memory. For example, a component (or a portion of a component) may be implemented as instructions or code stored in a non-transitory computer-readable medium and executable by a controller or a processor to perform the functions or operations of the component.
The reception component 1302 may receive communications, such as reference signals, control information, data communications, or a combination thereof, from the apparatus 1308. The reception component 1302 may provide received communications to one or more other components of the apparatus 1300. In some aspects, the reception component 1302 may perform signal processing on the received communications (such as filtering, amplification, demodulation, analog-to-digital conversion, demultiplexing, deinterleaving, de-mapping, equalization, interference cancellation, or decoding, among other examples) , and may provide the processed signals to the one or more other components of the apparatus 1300. In some aspects, the reception component 1302 may include one or more antennas, a modem, a demodulator, a MIMO detector, a receive processor, a controller/processor, a memory, or a combination thereof, of the RIS (e.g., forwarding-capable device) described in connection with Fig. 2.
The transmission component 1304 may transmit communications, such as reference signals, control information, data communications, or a combination thereof, to the apparatus 1308. In some aspects, one or more other components of the apparatus 1300 may generate communications and may provide the generated communications to the transmission component 1304 for transmission to the apparatus 1308. In some aspects, the transmission component 1304 may perform signal processing on the generated communications (such as filtering, amplification, modulation, digital-to-analog conversion, multiplexing, interleaving, mapping, or encoding, among other examples) , and may transmit the processed signals to the apparatus 1308. In some aspects, the transmission component 1304 may include one or more antennas, a modem, a modulator, a transmit MIMO processor, a transmit processor, a controller/processor, a memory, or a combination thereof, of the RIS (e.g., forwarding-capable device) described in connection with Fig. 2. In some aspects, the transmission component 1304 may be co-located with the reception component 1302 in a transceiver.
The communication manager 1306 may support operations of the reception component 1302 and/or the transmission component 1304. For example, the communication manager 1306 may receive information associated with configuring reception of communications by the reception component 1302 and/or transmission of communications by the transmission component 1304. Additionally, or alternatively, the communication manager 1306 may generate and/or provide control information to the reception component 1302 and/or the transmission component 1304 to control reception and/or transmission of communications.
The reception component 1302 may receive, from a network node, an indication of a time domain rotation factor associated with the RIS. The communication manager 1306 may reflect, using a reflection coefficient, a reference signal associated with the network node, the reflection coefficient being based on the time domain rotation factor.
The number and arrangement of components shown in Fig. 13 are provided as an example. In practice, there may be additional components, fewer components, different components, or differently arranged components than those shown in Fig. 13. Furthermore, two or more components shown in Fig. 13 may be implemented within a single component, or a single component shown in Fig. 13 may be implemented as multiple, distributed components. Additionally, or alternatively, a set of (one or more) components shown in Fig. 13 may perform one or more functions described as being performed by another set of components shown in Fig. 13.
The following provides an overview of some Aspects of the present disclosure:
Aspect 1: A method of wireless communication performed by a user equipment (UE) , comprising: receiving, from a network node, an indication of time domain rotation factors associated with respective reconfigurable intelligent surfaces (RISs) of one or more RISs; receiving, during a time domain measurement occasion, respective reference signals via a direct link with the network node and via one or more indirect links associated with the one or more RISs; and transmitting, to the network node, a report indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with measurements of the respective reference signals, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs.
Aspect 2: The method of Aspect 1, wherein the one or more indirect links are associated with reflection coefficients applied by the respective RISs that are associated with the time domain rotation factors.
Aspect 3: The method of any of Aspects 1-2, wherein the time domain rotation factors are based on a quantity of the one or more RISs and a maximum Doppler frequency associated with the direct link and the one or more indirect links.
Aspect 4: The method of any of Aspects 1-3, wherein the time domain rotation factors are based on a quantity of the one or more RISs, a duration of the time domain measurement occasion, and index values of the respective RISs.
Aspect 5: The method of any of Aspects 1-4, wherein the indication of the time domain rotation factors includes an indication of values of respective time domain rotation factors of the time domain rotation factors.
Aspect 6: The method of any of Aspects 1-5, wherein the indication of the time domain rotation factors includes an indication of a duration of the time domain measurement occasion, a quantity of the one or more RISs, and index values of the one or more RISs.
Aspect 7: The method of any of Aspects 1-6, wherein the indication of the time domain rotation factors is included in at least one of a radio resource control communication, a medium access control (MAC) control element communication, or a downlink control information communication.
Aspect 8: The method of any of Aspects 1-7, further comprising: estimating a channel response associated with the respective reference signals and the respective links; and estimating, for an RIS of the one or more RISs, a Doppler spectrum associated with the RIS via the channel response and a time domain rotation factor, of the time domain rotation factors, associated with the RIS, wherein an estimated Doppler frequency, of the estimated Doppler frequencies, associated with the RIS is based on the Doppler spectrum associated with the RIS.
Aspect 9: The method of Aspect 8, wherein the Doppler spectrum associated with the RIS is a shifted version of a channel Doppler spectrum associated with the channel response, wherein a shift associated with the Doppler spectrum is based on the time domain rotation factor associated with the RIS.
Aspect 10: The method of any of Aspects 1-9, wherein the one or more indirect links are associated with respective Doppler spectrums that are non-overlapping based on the one or more RISs reflecting the respective reference signals using the time domain rotation factors, and wherein Doppler frequencies, of the estimated Doppler frequencies, for respective indirect links are associated with the respective Doppler spectrums.
Aspect 11: The method of any of Aspects 1-10, wherein the one or more indirect links are associated with respective Doppler spectrums, and wherein Doppler frequencies, of the estimated Doppler frequencies, for respective indirect links are associated with a highest received power within the respective Doppler spectrums.
Aspect 12: The method of any of Aspects 1-11, wherein the one or more indirect links are associated with respective Doppler spectrums, wherein a Doppler frequency, of the estimated Doppler frequencies, for an indirect link associated with an RIS, of the one or more RISs, is based on an inverse discrete Fourier transform of a shifted version of a Doppler spectrum, of the respective Doppler spectrums, associated with the indirect link, and wherein a shift associated with the shifted version of the Doppler spectrum is associated with a time domain rotation factor, of the time domain rotation factors, associated with the RIS.
Aspect 13: The method of any of Aspects 1-12, wherein each of the respective reference signals comprises a tracking reference signal or a channel state information reference signal.
Aspect 14: A method of wireless communication performed by a network node, comprising: transmitting, an indication, for a user equipment (UE) and one or more reconfigurable intelligent surfaces (RISs) , of time domain rotation factors associated with respective RISs of the one or more RISs; transmitting, during a time domain measurement occasion, a reference signal via a direct link with the UE and via one or more indirect links associated with the one or more RISs; and receiving a report, associated with the UE, indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with a measurement of the reference signal, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs.
Aspect 15: The method of Aspect 14, wherein the one or more indirect links are associated with reflection coefficients applied by the respective RISs that are associated with the time domain rotation factors.
Aspect 16: The method of any of Aspects 14-15, wherein the time domain rotation factors are based on a quantity of the one or more RISs and a maximum Doppler frequency associated with the direct link and the one or more indirect links.
Aspect 17: The method of Aspect 16, wherein the maximum Doppler frequency is associated with an allowable velocity of the UE.
Aspect 18: The method of any of Aspects 14-17, wherein the time domain rotation factors are based on a quantity of the one or more RISs, a duration of the time domain measurement occasion, and index values of the respective RISs.
Aspect 19: The method of any of Aspects 14-18, wherein the indication of the time domain rotation factors includes an indication of values of respective time domain rotation factors of the time domain rotation factors.
Aspect 20: The method of any of Aspects 14-19, wherein the indication of the time domain rotation factors includes an indication of a duration of the time domain measurement occasion, a quantity of the one or more RISs, and index values of the one or more RISs.
Aspect 21: The method of any of Aspects 14-20, wherein the indication of the time domain rotation factors is included in at least one of a radio resource control communication, a medium access control (MAC) control element communication, or a downlink control information communication.
Aspect 22: The method of any of Aspects 14-21, wherein the respective reference signals comprises a tracking reference signal or a channel state information reference signal.
Aspect 23: A method of wireless communication performed by a reconfigurable intelligent surface (RIS) , comprising: receiving, from a network node, an indication of a time domain rotation factor associated with the RIS; and reflecting, using a reflection coefficient, a reference signal associated with the network node, the reflection coefficient being based on the time domain rotation factor.
Aspect 24: The method of Aspect 23, wherein the time domain rotation factor is based on a quantity of one or more RISs, including the RIS, and a maximum Doppler frequency associated with the network node.
Aspect 25: The method of any of Aspects 23-24, wherein the time domain rotation factor is based on a quantity of one or more RISs reflecting the reference signal including the RIS, a duration of a time domain measurement occasion, and an index value of the RIS.
Aspect 26: The method of any of Aspects 23-25, wherein the indication of the time domain rotation factor includes an indication of a value of the time domain rotation factor.
Aspect 27: The method of any of Aspects 23-26, wherein the indication of the time domain rotation factor includes an indication of a duration of a time domain measurement occasion, a quantity of one or more RISs reflecting the reference signal, and an index value of the RIS.
Aspect 28: The method of any of Aspects 23-27, wherein the indication of the time domain rotation factor is included in at least one of a radio resource control communication, a medium access control (MAC) control element communication, or a downlink control information communication.
Aspect 29: The method of any of Aspects 23-28, wherein the reference signal comprises a tracking reference signal or a channel state information reference signal.
Aspect 30: An apparatus for wireless communication at a device, comprising a processor; memory coupled with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform the method of one or more of Aspects 1-29.
Aspect 31: A device for wireless communication, comprising a memory and one or more processors coupled to the memory, the one or more processors configured to perform the method of one or more of Aspects 1-29.
Aspect 32: An apparatus for wireless communication, comprising at least one means for performing the method of one or more of Aspects 1-29.
Aspect 33: A non-transitory computer-readable medium storing code for wireless communication, the code comprising instructions executable by a processor to perform the method of one or more of Aspects 1-29.
Aspect 34: A non-transitory computer-readable medium storing a set of instructions for wireless communication, the set of instructions comprising one or more instructions that, when executed by one or more processors of a device, cause the device to perform the method of one or more of Aspects 1-29.
The foregoing disclosure provides illustration and description but is not intended to be exhaustive or to limit the aspects to the precise forms disclosed. Modifications and variations may be made in light of the above disclosure or may be acquired from practice of the aspects.
As used herein, the term “component” is intended to be broadly construed as hardware and/or a combination of hardware and software. “Software” shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, and/or functions, among other examples, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. As used herein, a “processor” is implemented in hardware and/or a combination of hardware and software. It will be apparent that systems and/or methods described herein may be implemented in different forms of hardware and/or a combination of hardware and software. The actual specialized control hardware or software code used to implement these systems and/or methods is not limiting of the aspects. Thus, the operation and behavior of the systems and/or methods are described herein without reference to specific software code, since those skilled in the art will understand that software and hardware can be designed to implement the systems and/or methods based, at least in part, on the description herein.
As used herein, the term “determine” or “determining” encompasses a wide variety of actions and, therefore, “determining” can include calculating, computing, processing, deriving, investigating, looking up (such as via looking up in a table, a database or another data structure) , inferring, ascertaining, and/or measuring, among other examples. Also, “determining” can include receiving (such as receiving information) , accessing (such as accessing data stored in memory) , and/or transmitting (such as transmitting information) , among other examples. Also, “determining” can include resolving, selecting, obtaining, choosing, establishing, and/or other such similar actions.
As used herein, “satisfying a threshold” may, depending on the context, refer to a value being greater than the threshold, greater than or equal to the threshold, less than the threshold, less than or equal to the threshold, equal to the threshold, not equal to the threshold, or the like.
Even though particular combinations of features are recited in the claims and/or disclosed in the specification, these combinations are not intended to limit the disclosure of various aspects. Many of these features may be combined in ways not specifically recited in the claims and/or disclosed in the specification. The disclosure of various aspects includes each dependent claim in combination with every other claim in the claim set. As used herein, a phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover a, b, c, a + b, a + c, b + c, and a + b + c, as well as any combination with multiples of the same element (e.g., a + a, a + a + a, a + a + b, a + a + c, a + b + b, a + c + c, b + b, b + b + b, b + b + c, c + c, and c + c + c, or any other ordering of a, b, and c) .
No element, act, or instruction used herein should be construed as critical or essential unless explicitly described as such. Also, as used herein, the articles “a” and “an” are intended to include one or more items and may be used interchangeably with “one or more. ” Further, as used herein, the article “the” is intended to include one or more items referenced in connection with the article “the” and may be used interchangeably with “the one or more. ” Furthermore, as used herein, the terms “set” and “group” are intended to include one or more items and may be used interchangeably with “one or more. ” Where only one item is intended, the phrase “only one” or similar language is used. Also, as used herein, the terms “has, ” “have, ” “having, ” or the like are intended to be open-ended terms that do not limit an element that they modify (e.g., an element “having” A may also have B) . Further, as used herein, “based on” is intended to be interpreted in the inclusive sense, unless otherwise explicitly indicated. For example, “based on” may be used interchangeably with “based at least in part on, ” “associated with” , or “in accordance with” unless otherwise explicitly indicated. Specifically, unless a phrase refers to “based on only ‘a, ’ ” or the equivalent in context, whatever it is that is “based on ‘a, ’ ” or “based at least in part on ‘a, ’ ” may be based on “a” alone or based on a combination of “a” and one or more other factors, conditions or information. Also, as used herein, the term “or” is intended to be inclusive when used in a series and may be used interchangeably with “and/or, ” unless explicitly stated otherwise (e.g., if used in combination with “either” or “only one of” ) .

Claims

A user equipment (UE) for wireless communication, comprising:

a memory; and

one or more processors, coupled to the memory, configured to:

receive, from a network node, an indication of time domain rotation factors associated with respective reconfigurable intelligent surfaces (RISs) of one or more RISs;

receive, during a time domain measurement occasion, respective reference signals via a direct link with the network node and via one or more indirect links associated with the one or more RISs; and

transmit, to the network node, a report indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with measurements of the respective reference signals, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs.
The UE of claim 1, wherein the one or more indirect links are associated with reflection coefficients applied by the respective RISs that are associated with the time domain rotation factors.
The UE of claim 1, wherein the time domain rotation factors are based on a quantity of the one or more RISs and a maximum Doppler frequency associated with the direct link and the one or more indirect links.
The UE of claim 1, wherein the time domain rotation factors are based on a quantity of the one or more RISs, a duration of the time domain measurement occasion, and index values of the respective RISs.
The UE of claim 1, wherein the indication of the time domain rotation factors includes an indication of values of respective time domain rotation factors of the time domain rotation factors.
The UE of claim 1, wherein the indication of the time domain rotation factors includes an indication of a duration of the time domain measurement occasion, a quantity of the one or more RISs, and index values of the one or more RISs.
The UE of claim 1, wherein the indication of the time domain rotation factors is included in at least one of a radio resource control communication, a medium access control (MAC) control element communication, or a downlink control information communication.
The UE of claim 1, wherein the one or more processors are further configured to:

estimate a channel response associated with the respective reference signals and the respective links; and

estimate, for an RIS of the one or more RISs, a Doppler spectrum associated with the RIS via the channel response and a time domain rotation factor, of the time domain rotation factors, associated with the RIS,

wherein an estimated Doppler frequency, of the estimated Doppler frequencies, associated with the RIS is based on the Doppler spectrum associated with the RIS.
The UE of claim 8, wherein the Doppler spectrum associated with the RIS is a shifted version of a channel Doppler spectrum associated with the channel response, wherein a shift associated with the Doppler spectrum is based on the time domain rotation factor associated with the RIS.
A network node for wireless communication, comprising:

a memory; and

one or more processors, coupled to the memory, configured to:

transmit, an indication, for a user equipment (UE) and one or more reconfigurable intelligent surfaces (RISs) , of time domain rotation factors associated with respective RISs of the one or more RISs;

transmit, during a time domain measurement occasion, a reference signal via a direct link with the UE and via one or more indirect links associated with the one or more RISs; and

receive a report, associated with the UE, indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with a measurement of the reference signal, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs.
The network node of claim 10, wherein the one or more indirect links are associated with reflection coefficients applied by the respective RISs that are associated with the time domain rotation factors.
The network node of claim 10, wherein the time domain rotation factors are based on a quantity of the one or more RISs and a maximum Doppler frequency associated with the direct link and the one or more indirect links.
The network node of claim 12, wherein the maximum Doppler frequency is associated with an allowable velocity of the UE.
The network node of claim 10, wherein the time domain rotation factors are based on a quantity of the one or more RISs, a duration of the time domain measurement occasion, and index values of the respective RISs.
The network node of claim 10, wherein the indication of the time domain rotation factors includes an indication of values of respective time domain rotation factors of the time domain rotation factors.
A method of wireless communication performed by a user equipment (UE) , comprising:

receiving, from a network node, an indication of time domain rotation factors associated with respective reconfigurable intelligent surfaces (RISs) of one or more RISs;

receiving, during a time domain measurement occasion, respective reference signals via a direct link with the network node and via one or more indirect links associated with the one or more RISs; and

transmitting, to the network node, a report indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with measurements of the respective reference signals, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs.
The method of claim 16, wherein the one or more indirect links are associated with reflection coefficients applied by the respective RISs that are associated with the time domain rotation factors.
The method of claim 16, wherein the time domain rotation factors are based on a quantity of the one or more RISs and a maximum Doppler frequency associated with the direct link and the one or more indirect links.
The method of claim 16, wherein the time domain rotation factors are based on a quantity of the one or more RISs, a duration of the time domain measurement occasion, and index values of the respective RISs.
The method of claim 16, wherein the indication of the time domain rotation factors includes an indication of values of respective time domain rotation factors of the time domain rotation factors.
The method of claim 16, wherein the indication of the time domain rotation factors includes an indication of a duration of the time domain measurement occasion, a quantity of the one or more RISs, and index values of the one or more RISs.
The method of claim 16, further comprising:

estimating a channel response associated with the respective reference signals and the respective links; and

estimating, for an RIS of the one or more RISs, a Doppler spectrum associated with the RIS via the channel response and a time domain rotation factor, of the time domain rotation factors, associated with the RIS,

wherein an estimated Doppler frequency, of the estimated Doppler frequencies, associated with the RIS is based on the Doppler spectrum associated with the RIS.
The method of claim 22, wherein the Doppler spectrum associated with the RIS is a shifted version of a channel Doppler spectrum associated with the channel response, wherein a shift associated with the Doppler spectrum is based on the time domain rotation factor associated with the RIS.
The method of claim 16, wherein the one or more indirect links are associated with respective Doppler spectrums that are non-overlapping based on the one or more RISs reflecting the respective reference signals using the time domain rotation factors, and

wherein Doppler frequencies, of the estimated Doppler frequencies, for respective indirect links are associated with the respective Doppler spectrums.
The method of claim 16, wherein the one or more indirect links are associated with respective Doppler spectrums, and

wherein Doppler frequencies, of the estimated Doppler frequencies, for respective indirect links are associated with a highest received power within the respective Doppler spectrums.
The method of claim 16, wherein the one or more indirect links are associated with respective Doppler spectrums,

wherein a Doppler frequency, of the estimated Doppler frequencies, for an indirect link associated with an RIS, of the one or more RISs, is based on an inverse discrete Fourier transform of a shifted version of a Doppler spectrum, of the respective Doppler spectrums, associated with the indirect link, and

wherein a shift associated with the shifted version of the Doppler spectrum is associated with a time domain rotation factor, of the time domain rotation factors, associated with the RIS.
A method of wireless communication performed by a network node, comprising:

transmitting, an indication, for a user equipment (UE) and one or more reconfigurable intelligent surfaces (RISs) , of time domain rotation factors associated with respective RISs of the one or more RISs;

transmitting, during a time domain measurement occasion, a reference signal via a direct link with the UE and via one or more indirect links associated with the one or more RISs; and

receiving a report, associated with the UE, indicating estimated Doppler frequencies for respective links including the direct link and the one or more indirect links in association with a measurement of the reference signal, the estimated Doppler frequencies being estimated using the time domain rotation factors associated with the respective RISs.
The method of claim 27, wherein the indication of the time domain rotation factors includes an indication of values of respective time domain rotation factors of the time domain rotation factors.
The method of claim 27, wherein the indication of the time domain rotation factors includes an indication of a duration of the time domain measurement occasion, a quantity of the one or more RISs, and index values of the one or more RISs.
The method of claim 27, wherein the indication of the time domain rotation factors is included in at least one of a radio resource control communication, a medium access control (MAC) control element communication, or a downlink control information communication.