PATENT DOCUMENT

Publication Number: US-11956059-B2
Application Number: US-202217944935-A
Country: US
Kind Code: B2

Title: Communication via multiple reconfigurable intelligent surfaces

Abstract:
A communication system may include an access point (AP), a user equipment (UE), and a communication path between the AP and the UE having a series of reconfigurable intelligent surfaces (RIS&#39;s). Each RIS may have a first beam pointing to a previous node and a second beam pointing to a next node in the communication path. Beams of routing RIS&#39;s and a beam from an end user RIS towards a last routing RIS may be set during calibration. The UE may perform beam discovery with the end user RIS. The UE and the AP may convey wireless data via reflections off each of the RIS&#39;s in the communication path. The beam of the end user RIS may be updated to track the UE device while the other the beams remain fixed. The beams may be calibrated using retroreflection and beam variation for each pair of RIS&#39;s up the communication path.

Claims:
What is claimed is: 
     
       1. A method of operating a first electronic device to communicate with a second electronic device, the method comprising:
 instructing a first reconfigurable intelligent surface (RIS) to form a first signal beam oriented towards the first electronic device; and 
 while the first RIS forms the first signal beam, transmitting wireless data via a first reflection, off the first RIS and towards a second RIS, and via a second reflection, off the second RIS and towards the second electronic device. 
 
     
     
       2. The method of  claim 1 , wherein instructing the first RIS to form the first signal beam comprises transmitting, using a first radio access technology (RAT), a control signal to the first RIS. 
     
     
       3. The method of  claim 2 , wherein transmitting the wireless data comprises transmitting the wireless data using a second RAT that is different from the first RAT. 
     
     
       4. The method of  claim 3 , wherein the first RAT comprises a wireless local area network (WLAN) RAT or a wireless personal area network (WPAN) RAT and the second RAT involves the transmission of radio-frequency signals at a frequency greater than 10 GHz. 
     
     
       5. The method of  claim 1  wherein, while the first electronic device transmits the wireless data, the first RIS forms a second signal beam oriented towards the second RIS and the second RIS forms a third signal beam oriented toward the first RIS. 
     
     
       6. The method of  claim 5 , further comprising:
 while the first RIS forms the first signal beam and the second signal beam, receiving additional wireless data transmitted by the second electronic device via a third reflection, off the second RIS and towards the first RIS, and via a fourth reflection, off the first RIS and towards the first electronic device. 
 
     
     
       7. The method of  claim 5 , further comprising:
 while the first RIS forms the second signal beam, controlling the first RIS to adjust the first signal beam but not the second signal beam. 
 
     
     
       8. The method of  claim 7 , further comprising:
 gathering, using one or more sensors, sensor data indicative of motion of the first electronic device, wherein controlling the first RIS to adjust the first signal beam comprises controlling the RIS to adjust the first signal beam based on the sensor data. 
 
     
     
       9. The method of  claim 8 , wherein the first electronic device comprises a user equipment device and the second electronic device comprises a wireless access point. 
     
     
       10. A method of operating a communication system to route wireless data between a wireless access point and a user equipment device, the method comprising:
 reflecting, using a first reconfigurable intelligent surface (RIS), the wireless data from a first signal beam onto a second signal beam, the second signal beam oriented towards a second RIS; and 
 reflecting, using the second RIS, the wireless data from a third signal beam onto a fourth signal beam, the third signal beam oriented towards the first RIS. 
 
     
     
       11. The method of  claim 10 , further comprising:
 adjusting, using the second RIS, the fourth signal beam to point towards the user equipment device. 
 
     
     
       12. The method of  claim 11 , wherein the first, second, and third signal beams remain fixed while the second RIS adjusts the fourth signal beam. 
     
     
       13. The method of  claim 12 , wherein the first, second, and third signal beams are pre-calibrated prior to the communication system routing the wireless data. 
     
     
       14. The method of  claim 12 , wherein the first signal beam and the second signal beam are narrower than the third signal beam and the fourth signal beam. 
     
     
       15. The method of  claim 10 , wherein the fourth signal beam is oriented towards the wireless access point. 
     
     
       16. The method of  claim 15 , wherein the first, second, third, and fourth signal beams are pre-calibrated prior to the communication system routing the wireless data. 
     
     
       17. A method of operating an electronic device, the method comprising:
 transmitting a first control signal that configures a first reconfigurable intelligent surface (RIS) to concurrently form a first signal beam pointed towards the electronic device and a second signal beam pointed in a first direction; 
 transmitting a second control signal that configures a second RIS to concurrently form a third signal beam pointed in a second direction and a fourth signal beam pointed in the second direction, the second direction being different from the first direction; 
 transmitting, using a fifth signal beam pointed towards the first RIS, a radio-frequency signal; and 
 receiving, using the fifth signal beam pointed towards the first RIS, a reflected signal associated with the radio-frequency signal. 
 
     
     
       18. The method of  claim 17 , further comprising:
 while the electronic device transmits the radio-frequency signal, transmitting a third control signal that configures the second RIS to sweep over different orientations of the third and fourth signal beams. 
 
     
     
       19. The method of  claim 18 , further comprising:
 gathering wireless performance metric data from the reflected signals received using the fifth signal beam; 
 identifying, based on the wireless performance metric data, an orientation of the third signal beam that points towards the first RIS; and 
 transmitting a fourth control signal to the second RIS that configures the second RIS to point the third signal beam in the identified orientation. 
 
     
     
       20. The method of  claim 17 , further comprising
 while the electronic device transmits the radio-frequency signal, transmitting a third control signal that configures the first RIS to sweep over different orientations of the second signal beam; 
 gathering wireless performance metric data from the reflected signals received using the fifth signal beam; 
 identifying, based on the wireless performance metric data, an orientation of the second signal beam that points towards the second RIS; and 
 transmitting a fourth control signal to the first RIS that configures the first RIS to point the second signal beam in the identified orientation.

Description:
FIELD 
     This disclosure relates generally to electronic devices and, more particularly, to electronic devices with wireless circuitry. 
     BACKGROUND 
     Electronic devices are often provided with wireless capabilities. An electronic device with wireless capabilities has wireless circuitry that includes one or more antennas. The wireless circuitry is used to perform communications using radio-frequency signals conveyed by the antennas. 
     As software applications on electronic devices become more data-intensive over time, demand has grown for electronic devices that support wireless communications at higher data rates. However, the maximum data rate supported by electronic devices is limited by the frequency of the radio-frequency signals. As the frequency of the radio-frequency signals increases, it can become increasingly difficult to perform satisfactory wireless communications because the signals become subject to significant over-the-air attenuation and typically require line-of-sight. 
     SUMMARY 
     A communication system may include a wireless access point (AP), a user equipment (UE) device, and a communication path between the AP and the UE device. The communication path may include a series of reconfigurable intelligent surfaces (RIS&#39;s) arranged in a relay or chained pattern. The RIS&#39;s and the AP may be installed in an environment. The RIS&#39;s may include an end user RIS that is closes to the UE device and routing RIS&#39;s between the end user RIS and the AP. 
     Each RIS may have a first signal beam that points to a previous node in the communication path and a second signal beam that points to a next node in the communication path. The signal beams of the routing RIS&#39;s and the signal beam of the end user RIS that points towards the last routing RIS may be identified and set during calibration. When the UE device enters the system, the UE device performs a beam discovery with the end user RIS. The beam discovery may discover a signal beam of the UE pointed towards the end user RIS and a second signal beam of the end user RIS pointed towards the UE. The UE device and the AP may convey wireless data via reflections off each of the RIS&#39;s in the communication path in series. The signal beam of the end user RIS may be updated to track the UE device as it moves and/or the end user RIS may be updated. The signal beams of the routing RIS and the signal beam from the end user RIS to the routing RIS may remain fixed in place after initial set up and calibration. 
     The calibration may involve mapping the environment and identifying optimal locations for the RIS&#39;s in the mapped environment. The placement of the RIS&#39;s may deviate from optimal locations. To mitigate this, a calibration device may perform an initial calibration to identify and set each of the signal beams of the communication path to point towards the next and previous nodes in the communication path. The calibration device may control a first RIS to point one signal beam towards the calibration device and another signal beam towards the optimal location of the previous RIS in the communication path. The calibration device may control the previous RIS to point both its signal beams towards the optimal location of the first RIS. The UE device may transmit to the first RIS and may measure reflected signal power while instructing the first RIS and the previous RIS to vary their beams. The UE device may identify the beams that produced peak reflected signal power as calibrated beams and may configure the first RIS and the previous RIS to use those calibrated beams during subsequent data transfer. The UE device may repeat this calibration with every pair of RIS&#39;s in the communication path up to the AP. 
     An aspect of the disclosure provides a method of operating a first electronic device to communicate with a second electronic device. The method can include instructing a first reconfigurable intelligent surface (RIS) to form a first signal beam oriented towards the first electronic device. The method can include while the first RIS forms the first signal beam, transmitting wireless data via a first reflection, off the first RIS and towards a second RIS, and via a second reflection, off the second RIS and towards the second electronic device. 
     An aspect of the disclosure provides a method of operating a communication system to route wireless data between a wireless access point and a user equipment device. The method can include with a first reconfigurable intelligent surface (RIS), reflecting the wireless data from a first signal beam onto a second signal beam, the second signal beam oriented towards a second RIS. The method can include with the second RIS, reflecting the wireless data from a third signal beam onto a fourth signal beam, the third signal beam oriented towards the first RIS. 
     An aspect of the disclosure provides a method of operating an electronic device. The method can include transmitting a first control signal that configures a first reconfigurable intelligent surface (RIS) to concurrently form a first signal beam pointed towards the electronic device and a second signal beam pointed in a first direction. The method can include transmitting a second control signal that configures a second RIS to concurrently form a third signal beam pointed in a second direction and a fourth signal beam pointed in the second direction, the second direction being different from the first direction. The method can include transmitting, using a fifth signal beam pointed towards the first RIS, a radio-frequency signal. The method can include receiving, using the fifth signal beam pointed towards the first RIS, a reflected signal associated with the radio-frequency signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic block diagram of an illustrative communications system having a user equipment (UE) device, external communications equipment, and a reconfigurable intelligent surface (RIS) in accordance with some embodiments. 
         FIG.  2    is a diagram showing how an illustrative wireless access point, RIS, and user equipment device may communicate using both a data transfer radio access technology (RAT) and a control RAT in accordance with some embodiments. 
         FIG.  3    is a diagram showing how a wireless access point may communicate with a user equipment device via an illustrative communication path having multiple RIS&#39;s that relay signals in accordance with some embodiments. 
         FIG.  4    is a top view of an illustrative environment having multiple RIS&#39;s mounted in different areas of the environment for providing communication paths from each of areas to a wireless access point via multiple RIS&#39;s in accordance with some embodiments. 
         FIG.  5    is a flow chart of illustrative operations involved in establishing and operating a system having a wireless access point and multiple RIS&#39;s mounted in different areas for providing communication paths from each of areas to a wireless access point in accordance with some embodiments. 
         FIG.  6    is a flow chart of illustrative operations involved in calibrating the RIS&#39;s in a system having a wireless access point and multiple RIS&#39;s mounted in different areas for providing communication paths from each of areas to a wireless access point in accordance with some embodiments. 
         FIG.  7    is a diagram showing how different pairs of RIS&#39;s in a communication path may be sequentially calibrated in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    is a schematic diagram of an illustrative communications system  8  (sometimes referred to herein as communications network  8 ) for conveying wireless data between communications terminals. Communications system  8  may include network nodes (e.g., communications terminals). The network nodes may include user equipment (UE) such as one or more UE devices  10 . The network nodes may also include external communications equipment (e.g., communications equipment other than UE devices  10 ) such as external communications equipment  34 . External communications equipment  34  (sometimes referred to herein simply as external equipment  34 ) may include one or more electronic devices and may be a wireless base station, wireless access point, or other wireless equipment for example. An implementation in which external communications equipment  34  forms a wireless access point (AP) is described herein as an example. External communications equipment  34  may therefore sometimes be referred to herein as AP  34 . UE device  10  and AP  34  may communicate with each other using one or more wireless communications links. If desired, UE devices  10  may wirelessly communicate with AP  34  without passing communications through any other intervening network nodes in communications system  8  (e.g., UE devices  10  may communicate directly with AP  34  over-the-air). 
     AP  34  may be communicably coupled to one or more other network nodes  6  in a larger communications network  4  via wired and/or wireless links. Network  4  may include one or more wired communications links (e.g., communications links formed using cabling such as ethernet cables, radio-frequency cables such as coaxial cables or other transmission lines, optical fibers or other optical cables, etc.), one or more wireless communications links (e.g., short range wireless communications links that operate over a range of inches, feet, or tens of feet, medium range wireless communications links that operate over a range of hundreds of feet, thousands of feet, miles, or tens of miles, and/or long range wireless communications links that operate over a range of hundreds or thousands of miles, etc.), communications gateways, wireless access points, base stations, switches, routers, servers, modems, repeaters, telephone lines, network cards, line cards, portals, user equipment (e.g., computing devices, mobile devices, etc.), etc. Network  4  may include communications (network) nodes or terminals coupled together using these components or other components (e.g., some or all of a mesh network, relay network, ring network, local area network, wireless local area network, personal area network, cloud network, star network, tree network, or networks of communications nodes having other network topologies), the Internet, combinations of these, etc. UE devices  10  may send data to and/or may receive data from other nodes or terminals in network  4  via AP  34  (e.g., AP  34  may serve as an interface between user equipment devices  10  and the rest of the larger communications network). Network  4  may be managed, operated, controlled, or run by a corresponding network service provider (e.g., a cellular network carrier). 
     User equipment (UE) device  10  of  FIG.  1    is an electronic device (sometimes referred to herein as electronic device  10  or device  10 ) and may be a computing device such as a laptop computer, a desktop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wristwatch device, a pendant device, a headphone or earpiece device, a device embedded in eyeglasses, goggles, or other equipment worn on a user&#39;s head, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, a wireless internet-connected voice-controlled speaker, a home entertainment device, a remote control device, a gaming controller, a peripheral user input device, equipment that implements the functionality of two or more of these devices, or other electronic equipment. 
     As shown in the functional block diagram of  FIG.  1   , UE device  10  may include components located on or within an electronic device housing such as housing  12 . Housing  12 , which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, metal alloys, etc.), other suitable materials, or a combination of these materials. In some situations, part or all of housing  12  may be formed from dielectric or other low-conductivity material (e.g., glass, ceramic, plastic, sapphire, etc.). In other situations, housing  12  or at least some of the structures that make up housing  12  may be formed from metal elements. 
     UE device  10  may include control circuitry  14 . Control circuitry  14  may include storage such as storage circuitry  16 . Storage circuitry  16  may include hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid-state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Storage circuitry  16  may include storage that is integrated within device  10  and/or removable storage media. 
     Control circuitry  14  may include processing circuitry such as processing circuitry  18 . Processing circuitry  18  may be used to control the operation of device  10 . Processing circuitry  18  may include on one or more processors such as microprocessors, microcontrollers, digital signal processors, host processors, baseband processor integrated circuits, application specific integrated circuits, central processing units (CPUs), graphics processing units (GPUs), etc. Control circuitry  14  may be configured to perform operations in device  10  using hardware (e.g., dedicated hardware or circuitry), firmware, and/or software. Software code for performing operations in device  10  may be stored on storage circuitry  16  (e.g., storage circuitry  16  may include non-transitory (tangible) computer readable storage media that stores the software code). The software code may sometimes be referred to as program instructions, software, data, instructions, or code. Software code stored on storage circuitry  16  may be executed by processing circuitry  18 . 
     Control circuitry  14  may be used to run software on device  10  such as satellite navigation applications, internet browsing applications, voice-over-internet-protocol (VOIP) telephone call applications, email applications, media playback applications, operating system functions, etc. To support interactions with external equipment, control circuitry  14  may be used in implementing communications protocols. Communications protocols that may be implemented using control circuitry  14  include internet protocols, wireless local area network (WLAN) protocols (e.g., IEEE 802.11 protocols—sometimes referred to as Wi-Fi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol or other wireless personal area network (WPAN) protocols, IEEE 802.11ad protocols (e.g., ultra-wideband protocols), cellular telephone protocols (e.g., 3G protocols, 4G (LTE) protocols, 3GPP Fifth Generation (5G) New Radio (NR) protocols, Sixth Generation (6G) protocols, sub-THz protocols, THz protocols, etc.), antenna diversity protocols, satellite navigation system protocols (e.g., global positioning system (GPS) protocols, global navigation satellite system (GLONASS) protocols, etc.), antenna-based spatial ranging protocols, optical communications protocols, or any other desired communications protocols. Each communications protocol may be associated with a corresponding radio access technology (RAT) that specifies the physical connection methodology used in implementing the protocol. 
     UE device  10  may include input-output circuitry  20 . Input-output circuitry  20  may include input-output devices  22 . Input-output devices  22  may be used to allow data to be supplied to UE device  10  and to allow data to be provided from UE device  10  to external devices. Input-output devices  22  may include user interface devices, data port devices, and other input-output components. For example, input-output devices  22  may include touch sensors, displays (e.g., touch-sensitive and/or force-sensitive displays), light-emitting components such as displays without touch sensor capabilities, buttons (mechanical, capacitive, optical, etc.), scrolling wheels, touch pads, key pads, keyboards, microphones, cameras, buttons, speakers, status indicators, audio jacks and other audio port components, digital data port devices, motion sensors (accelerometers, gyroscopes, and/or compasses that detect motion), capacitance sensors, proximity sensors, magnetic sensors, force sensors (e.g., force sensors coupled to a display to detect pressure applied to the display), temperature sensors, etc. In some configurations, keyboards, headphones, displays, pointing devices such as trackpads, mice, and joysticks, and other input-output devices may be coupled to UE device  10  using wired or wireless connections (e.g., some of input-output devices  22  may be peripherals that are coupled to a main processing unit or other portion of UE device  10  via a wired or wireless link). 
     Input-output circuitry  20  may include wireless circuitry  24  to support wireless communications. Wireless circuitry  24  (sometimes referred to herein as wireless communications circuitry  24 ) may include baseband circuitry such as baseband circuitry  26  (e.g., one or more baseband processors and/or other circuitry that operates at baseband), radio-frequency (RF) transceiver circuitry such as transceiver  28 , and one or more antennas  30 . If desired, wireless circuitry  24  may include multiple antennas  30  that are arranged into a phased antenna array (sometimes referred to as a phased array antenna) that conveys radio-frequency signals within a corresponding signal beam that can be steered in different directions. Baseband circuitry  26  may be coupled to transceiver  28  over one or more baseband data paths. Transceiver  28  may be coupled to antennas  30  over one or more radio-frequency transmission line paths  32 . If desired, radio-frequency front end circuitry may be disposed on radio-frequency transmission line path(s)  32  between transceiver  28  and antennas  30 . 
     In the example of  FIG.  1   , wireless circuitry  24  is illustrated as including only a single transceiver  28  and a single radio-frequency transmission line path  32  for the sake of clarity. In general, wireless circuitry  24  may include any desired number of transceivers  28 , any desired number of radio-frequency transmission line paths  32 , and any desired number of antennas  30 . Each transceiver  28  may be coupled to one or more antennas  30  over respective radio-frequency transmission line paths  32 . Radio-frequency transmission line path  32  may be coupled to antenna feeds on one or more antenna  30 . Each antenna feed may, for example, include a positive antenna feed terminal and a ground antenna feed terminal. Radio-frequency transmission line path  32  may have a positive transmission line signal path that is coupled to the positive antenna feed terminal and may have a ground transmission line signal path that is coupled to the ground antenna feed terminal. This example is merely illustrative and, in general, antennas  30  may be fed using any desired antenna feeding scheme. 
     Radio-frequency transmission line path  32  may include transmission lines that are used to route radio-frequency antenna signals within device  10 . Transmission lines in device  10  may include coaxial cables, microstrip transmission lines, stripline transmission lines, edge-coupled microstrip transmission lines, edge-coupled stripline transmission lines, transmission lines formed from combinations of transmission lines of these types, etc. Transmission lines in device  10  such as transmission lines in radio-frequency transmission line path  32  may be integrated into rigid and/or flexible printed circuit boards. In one embodiment, radio-frequency transmission line paths such as radio-frequency transmission line path  32  may also include transmission line conductors integrated within multilayer laminated structures (e.g., layers of a conductive material such as copper and a dielectric material such as a resin that are laminated together without intervening adhesive). The multilayer laminated structures may, if desired, be folded or bent in multiple dimensions (e.g., two or three dimensions) and may maintain a bent or folded shape after bending (e.g., the multilayer laminated structures may be folded into a particular three-dimensional shape to route around other device components and may be rigid enough to hold its shape after folding without being held in place by stiffeners or other structures). All of the multiple layers of the laminated structures may be batch laminated together (e.g., in a single pressing process) without adhesive (e.g., as opposed to performing multiple pressing processes to laminate multiple layers together with adhesive). 
     In performing wireless transmission, baseband circuitry  26  may provide baseband signals to transceiver  28  (e.g., baseband signals that include wireless data for transmission). Transceiver  28  may include circuitry for converting the baseband signals received from baseband circuitry  26  into corresponding radio-frequency signals (e.g., for modulating the wireless data onto one or more carriers for transmission, synthesizing a transmit signal, etc.). For example, transceiver  28  may include mixer circuitry for up-converting the baseband signals to radio frequencies prior to transmission over antennas  30 . Transceiver  28  may also include digital to analog converter (DAC) and/or analog to digital converter (ADC) circuitry for converting signals between digital and analog domains. Transceiver  28  may transmit the radio-frequency signals over antennas  30  via radio-frequency transmission line path  32 . Antennas  30  may transmit the radio-frequency signals to external wireless equipment by radiating the radio-frequency signals into free space. 
     In performing wireless reception, antennas  30  may receive radio-frequency signals from AP  34 . The received radio-frequency signals may be conveyed to transceiver  28  via radio-frequency transmission line path  32 . Transceiver  28  may include circuitry for converting the received radio-frequency signals into corresponding baseband signals. For example, transceiver  28  may include mixer circuitry for down-converting the received radio-frequency signals to baseband frequencies prior to conveying the baseband signals to baseband circuitry  26  and may include demodulation circuitry for demodulating wireless data from the received signals. 
     Front end circuitry disposed on radio-frequency transmission line path  32  may include radio-frequency front end components that operate on radio-frequency signals conveyed over radio-frequency transmission line path  32 . If desired, the radio-frequency front end components may be formed within one or more radio-frequency front end modules (FEMs). Each FEM may include a common substrate such as a printed circuit board substrate for each of the radio-frequency front end components in the FEM. The radio-frequency front end components in the front end circuitry may include switching circuitry (e.g., one or more radio-frequency switches), radio-frequency filter circuitry (e.g., low pass filters, high pass filters, notch filters, band pass filters, multiplexing circuitry, duplexer circuitry, diplexer circuitry, triplexer circuitry, etc.), impedance matching circuitry (e.g., circuitry that helps to match the impedance of antennas  30  to the impedance of radio-frequency transmission line path  32 ), antenna tuning circuitry (e.g., networks of capacitors, resistors, inductors, and/or switches that adjust the frequency response of antennas  30 ), radio-frequency amplifier circuitry (e.g., power amplifier circuitry and/or low-noise amplifier circuitry), radio-frequency coupler circuitry, charge pump circuitry, power management circuitry, digital control and interface circuitry, and/or any other desired circuitry that operates on the radio-frequency signals transmitted and/or received by antennas  30 . 
     While control circuitry  14  is shown separately from wireless circuitry  24  in the example of  FIG.  1    for the sake of clarity, wireless circuitry  24  may include processing circuitry that forms a part of processing circuitry  18  and/or storage circuitry that forms a part of storage circuitry  16  of control circuitry  14  (e.g., portions of control circuitry  14  may be implemented on wireless circuitry  24 ). As an example, baseband circuitry  26  and/or portions of transceiver  28  (e.g., a host processor on transceiver  28 ) may form a part of control circuitry  14 . Baseband circuitry  26  may, for example, access a communication protocol stack on control circuitry  14  (e.g., storage circuitry  16 ) to: perform user plane functions at a PHY layer, MAC layer, RLC layer, PDCP layer, SDAP layer, and/or PDU layer, and/or to perform control plane functions at the PHY layer, MAC layer, RLC layer, PDCP layer, RRC, layer, and/or non-access stratum layer. 
     The term “convey wireless signals” as used herein means the transmission and/or reception of the wireless signals (e.g., for performing unidirectional and/or bidirectional wireless communications with external wireless communications equipment). Antennas  30  may transmit the wireless signals by radiating the signals into free space (or to free space through intervening device structures such as a dielectric cover layer). Antennas  30  may additionally or alternatively receive the wireless signals from free space (e.g., through intervening devices structures such as a dielectric cover layer). The transmission and reception of wireless signals by antennas  30  each involve the excitation or resonance of antenna currents on an antenna resonating (radiating) element in the antenna by the wireless signals within the frequency band(s) of operation of the antenna. 
     Transceiver circuitry  26  may use antenna(s)  30  to transmit and/or receive wireless signals that convey wireless communications data between device  10  and AP  34  (e.g., one or more other devices such as device  10 , a wireless access point or base station, etc.). The wireless communications data may be conveyed bidirectionally or unidirectionally. The wireless communications data may, for example, include data that has been encoded into corresponding data packets such as wireless data associated with a telephone call, streaming media content, internet browsing, wireless data associated with software applications running on device  10 , email messages, etc. 
     Additionally or alternatively, wireless circuitry  24  may use antenna(s)  30  to perform wireless (radio-frequency) sensing operations. The sensing operations may allow device  10  to detect (e.g., sense or identify) the presence, location, orientation, and/or velocity (motion) of objects external to device  10 . Control circuitry  14  may use the detected presence, location, orientation, and/or velocity of the external objects to perform any desired device operations. As examples, control circuitry  14  may use the detected presence, location, orientation, and/or velocity of the external objects to identify a corresponding user input for one or more software applications running on device  10  such as a gesture input performed by the user&#39;s hand(s) or other body parts or performed by an external stylus, gaming controller, head-mounted device, or other peripheral devices or accessories, to determine when one or more antennas  30  needs to be disabled or provided with a reduced maximum transmit power level (e.g., for satisfying regulatory limits on radio-frequency exposure), to determine how to steer (form) a radio-frequency signal beam produced by antennas  30  for wireless circuitry  24  (e.g., in scenarios where antennas  30  include a phased array of antennas  30 ), to map or model the environment around device  10  (e.g., to produce a software model of the room where device  10  is located for use by an augmented reality application, gaming application, map application, home design application, engineering application, etc.), to detect the presence of obstacles in the vicinity of (e.g., around) device  10  or in the direction of motion of the user of device  10 , etc. The sensing operations may, for example, involve the transmission of sensing signals (e.g., radar waveforms), the receipt of corresponding reflected signals (e.g., the transmitted waveforms that have reflected off of external objects), and the processing of the transmitted signals and the received reflected signals (e.g., using a radar scheme). 
     Wireless circuitry  24  may transmit and/or receive wireless signals within corresponding frequency bands of the electromagnetic spectrum (sometimes referred to herein as communications bands or simply as “bands”). The frequency bands handled by wireless circuitry  24  may include wireless local area network (WLAN) frequency bands (e.g., Wi-Fi® (IEEE 802.11) or other WLAN communications bands) such as a 2.4 GHz WLAN band (e.g., from 2400 to 2480 MHz), a 5 GHz WLAN band (e.g., from 5180 to 5825 MHz), a Wi-Fi® 6E band (e.g., from 5925-7125 MHz), and/or other Wi-Fi® bands (e.g., from 1875-5160 MHz), wireless personal area network (WPAN) frequency bands such as the 2.4 GHz Bluetooth® band or other WPAN communications bands, cellular telephone frequency bands (e.g., bands from about 600 MHz to about 5 GHz, 3G bands, 4G LTE bands, 5G New Radio Frequency Range 1 (FR1) bands below 10 GHz, 5G New Radio Frequency Range 2 (FR2) bands between 20 and 60 GHz, 6G bands at sub-THz or THz frequencies greater than about 100 GHz, etc.), other centimeter or millimeter wave frequency bands between 10-100 GHz, near-field communications frequency bands (e.g., at 13.56 MHz), satellite navigation frequency bands (e.g., a GPS band from 1565 to 1610 MHz, a Global Navigation Satellite System (GLONASS) band, a BeiDou Navigation Satellite System (BDS) band, etc.), ultra-wideband (UWB) frequency bands that operate under the IEEE 802.15.4 protocol and/or other ultra-wideband communications protocols, communications bands under the family of 3GPP wireless communications standards, communications bands under the IEEE 802.XX family of standards, and/or any other desired frequency bands of interest. 
     Over time, software applications on electronic devices such as device  10  have become more and more data intensive. Wireless circuitry on the electronic devices therefore needs to support data transfer at higher and higher data rates. In general, the data rates supported by the wireless circuitry are proportional to the frequency of the wireless signals conveyed by the wireless circuitry (e.g., higher frequencies can support higher data rates than lower frequencies). Wireless circuitry  24  may convey centimeter and millimeter wave signals to support relatively high data rates (e.g., because centimeter and millimeter wave signals are at relatively high frequencies between around 10 GHz and 100 GHz). However, the data rates supported by centimeter and millimeter wave signals may still be insufficient to meet all the data transfer needs of device  10 . To support even higher data rates such as data rates up to 5-100 Gbps or higher, wireless circuitry  24  may convey wireless signals at frequencies greater than about 100 GHz. 
     As shown in  FIG.  1   , wireless circuitry  24  may transmit wireless signals  46  to AP  34  and/or may receive wireless signals  46  from AP  34 . Wireless signals  46  may be tremendously high frequency (THF) signals (e.g., sub-THz or THz signals) at frequencies greater than around 100 GHz (e.g., between 100 GHz and 1 THz, between 80 GHz and 10 THz, between 100 GHz and 10 THz, between 100 GHz and 2 THz, between 200 GHz and 1 THz, between 300 GHz and 1 THz, between 300 GHz and 2 THz, between 70 GHz and 2 THz, between 300 GHz and 10 THz, between 100 GHz and 800 GHz, between 200 GHz and 1.5 THz, or within any desired sub-THz, THz, TI- 1 F, or sub-millimeter frequency band such as a 6G frequency band), may be millimeter (mm) or centimeter (cm) wave signals between 10 GHz and around 70 GHz (e.g., 5G NR FR2 signals), or may be signals at frequencies less than 10 GHz (e.g., 5G NR FR1 signals, LTE signals, 3G signals, 2G signals, WLAN signals, Bluetooth signals, UWB signals, etc.). If desired, the high data rates supported by THF signals may be leveraged by device  10  to perform cellular telephone voice and/or data communications (e.g., while supporting spatial multiplexing to provide further data bandwidth), to perform spatial ranging operations such as radar operations to detect the presence, location, and/or velocity of objects external to device  10 , to perform automotive sensing (e.g., with enhanced security), to perform health/body monitoring on a user of device  10  or another person, to perform gas or chemical detection, to form a high data rate wireless connection between device  10  and another device or peripheral device (e.g., to form a high data rate connection between a display driver on device  10  and a display that displays ultra-high resolution video), to form a remote radio head (e.g., a flexible high data rate connection), to form a THF chip-to-chip connection within device  10  that supports high data rates (e.g., where one antenna  30  on a first chip in device  10  transmits THF signals  32  to another antenna  30  on a second chip in device  10 ), and/or to perform any other desired high data rate operations. 
     In implementations where wireless circuitry  24  conveys THF signals, wireless circuitry may include electro-optical circuitry if desired. The electro-optical circuitry may include light sources that generate first and second optical local oscillator (LO) signals. The first and second optical LO signals may be separated in frequency by the intended frequency of wireless signals  46 . Wireless data may be modulated onto the first optical LO signal and one of the optical LO signals may be provided with an optical phase shift (e.g., to perform beamforming). The first and second optical LO signals may illuminate a photodiode that produces current at the frequency of wireless signals  46  when illuminated by the first and second optical LO signals. An antenna resonating element of a corresponding antenna  30  may convey the current produced by the photodiode and may radiate corresponding wireless signals  46 . This is merely illustrative and, in general, wireless circuitry  24  may generate wireless signals  46  using any desired techniques. 
     Antennas  30  may be formed using any desired antenna structures. For example, antennas  30  may include antennas with resonating elements that are formed from loop antenna structures, patch antenna structures, inverted-F antenna structures, slot antenna structures, planar inverted-F antenna structures, helical antenna structures, monopole antennas, dipoles (e.g., planar dipole antennas such as bowtie antennas), hybrids of these designs, etc. Parasitic elements may be included in antennas  30  to adjust antenna performance. 
     If desired, two or more of antennas  30  may be integrated into a phased antenna array (sometimes referred to herein as a phased array antenna or an array of antenna elements). Each antenna  30  in the phased antenna array forms a respective antenna element of the phased antenna array. Each antenna  30  in the phased antenna array has a respective phase and magnitude controller that imparts the radio-frequency signals conveyed by that antenna with a respective phase and magnitude. The respective phases and magnitudes may be selected (e.g., by control circuitry  14 ) to configure the radio-frequency signals conveyed by the antennas  30  in the phased antenna array to constructively and destructively interfere in such a way that the radio-frequency signals collectively form a signal beam (e.g., a signal beam of wireless signals  46 ) oriented in a corresponding beam pointing direction (e.g., a direction of peak gain). 
     The control circuitry may adjust the phases and magnitudes to change (steer) the orientation of the signal beam (e.g., the beam pointing direction) to point in other directions over time. This process may sometimes also be referred to herein as beamforming. Beamforming may boost the gain of wireless signals  46  to help overcome over-the-air attenuation and the signal beam may be steered over time to point towards AP  34  even as the position and orientation of UE device  10  changes. The signal beams formed by antennas  30  of UE device  10  may sometimes be referred to herein as UE beams or UE signal beams. Each UE beam may be oriented in a different respective direction (e.g., a beam pointing direction of peak signal gain). Each UE beam may be labeled by a corresponding UE beam index. UE device  10  may include or store a codebook (sometimes referred to herein as a UE codebook) that maps each of its UE beam indices to the corresponding phase and magnitude settings for each antenna  30  in a phased antenna array that configure the phased antenna array to form the UE beam associated with that UE beam index. 
     As shown in  FIG.  1   , AP  34  may also include control circuitry  36  (e.g., control circuitry having similar components and/or functionality as control circuitry  14  in UE device  10 ) and wireless circuitry  38  (e.g., wireless circuitry having similar components and/or functionality as wireless circuitry  24  in UE device  10 ). Wireless circuitry  38  may include baseband circuitry  40  and transceiver  42  (e.g., transceiver circuitry having similar components and/or functionality as transceiver circuitry  28  in UE device  10 ) coupled to two or more antennas  44  (e.g., antennas having similar components and/or functionality as antennas  30  in UE device  10 ). Antennas  44  may be arranged in one or more phased antenna arrays (e.g., phased antenna arrays that perform beamforming similar to phased antenna arrays of antennas  30  on UE device  10 ). 
     AP  34  may use wireless circuitry  38  to transmit a signal beam of wireless signals  46  to UE device  10  (e.g., as downlink (DL) signals transmitted in a downlink direction) and/or to receive a signal beam of wireless signals  46  transmitted by UE device  10  (e.g., as uplink (UL) signals transmitted in an uplink direction). The signal beams formed by antennas  44  of UE device  10  may sometimes be referred to herein as AP beams or AP signal beams. Each AP beam may be oriented in a different respective direction (e.g., a beam pointing direction of peak signal gain). Each AP beam may be labeled by a corresponding AP beam index. AP  34  may include or store a codebook (sometimes referred to herein as an AP codebook) that maps each of its AP beam indices to the corresponding phase and magnitude settings for each antenna  44  in a phased antenna array that configure the phased antenna array to form the AP beam associated with that AP beam index. 
     While communications at high frequencies allow for extremely high data rates (e.g., greater than 100 Gbps), wireless signals  46  at such high frequencies are subject to significant attenuation during propagation over-the-air. Integrating antennas  30  and  44  into phased antenna arrays helps to counteract this attenuation by boosting the gain of the signals within a signal beam. However, signal beams are highly directive and may require a line-of-sight (LOS) between UE device  10  and AP  34 . If an external object is present between AP  34  and UE device  10 , the external object may block the LOS between UE device  10  and AP  34 , which can disrupt wireless communications using wireless signals  46 . If desired, an reconfigurable intelligent surface (RIS) may be used to allow UE device  10  and AP  34  to continue to communicate using wireless signals  46  even when an external object blocks the LOS between UE device  10  and AP  34  (or whenever direct over-the-air communications between AP  34  and UE device  10  otherwise exhibits less than optimal performance). 
     As shown in  FIG.  1   , system  8  may include one or more reconfigurable intelligent surfaces (RIS&#39;s) such as RIS  50 . RIS  50  may sometimes also be referred to as an intelligent reconfigurable surface, an intelligent reflective/reflecting surface, a reflective intelligent surface, a reflective surface, a reflective device, a reconfigurable reflective device, a reconfigurable reflective surface, or a reconfigurable surface. AP  34  may be separated from UE device  10  by a line-of-sight (LOS) path. In some circumstances, an external object such as object  51  may block the LOS path. Object  51  may be, for example, part of a building such as a wall, window, floor, or ceiling (e.g., when UE device  10  is located inside), furniture, a body or body part, an animal, a cubicle wall, a vehicle, a landscape feature, or other obstacles or objects that may block the LOS path between AP  34  and UE device  10 . 
     In the absence of external object  51 , AP  34  may form a corresponding AP beam of wireless signals  46  oriented in the direction of UE device  10  and UE device  10  may form a corresponding UE beam of wireless signals  46  oriented in the direction of AP  34 . UE device  10  and AP  34  can then convey wireless signals  46  over their respective signal beams and the LOS path. However, the presence of external object  51  prevents wireless signals  46  from being conveyed over the LOS path. 
     RIS  50  may be placed or disposed within system  8  in such a way so as to allow RIS  50  to reflect wireless signals  46  between UE device  10  and AP  34  despite the presence of external object  51  within the LOS path. More generally, RIS  50  may be used to reflect wireless signals  46  between UE device  10  and AP  34  when reflection via RIS  50  offers superior radio-frequency propagation conditions relative to the LOS path regardless of the presence of external object  51  (e.g., when the LOS path between AP  34  and RIS  50  and the LOS path between RIS  50  and UE device  10  exhibit superior propagation/channel conditions than the direct LOS path between UE device  10  and AP  34 ). 
     When RIS  50  is placed within system  8 , AP  34  may transmit wireless signals  46  towards RIS  50  (e.g., within an AP beam oriented towards RIS  50  rather than towards UE device  10 ) and RIS  50  may reflect the wireless signals towards UE device  10 , as shown by arrow  54 . Conversely, UE device  10  may transmit wireless signals  46  towards RIS  50  (e.g., within a UE beam oriented towards RIS  50  rather than towards AP  34 ) and RIS  50  may reflect the wireless signals towards AP  34 , as shown by arrow  56 . 
     RIS  50  is an electronic device that includes a two-dimensional surface of engineered material having reconfigurable properties for performing (e.g., reflecting) communications between AP  34  and UE device  10 . RIS  50  may include an array of reflective elements such as antenna elements  48  on an underlying substrate. Antenna elements  48  may also sometimes be referred to herein as reflective elements  48 , reconfigurable antenna elements  48 , reconfigurable reflective elements  48 , reflectors  48 , or reconfigurable reflectors  48 . 
     The substrate may be a rigid or flexible printed circuit board, a package, a plastic substrate, meta-material, or any other desired substrate. The substrate may be planar or may be curved in one or more dimensions. If desired, the substrate and antenna elements  48  may be enclosed within a housing. The housing may be formed from materials that are transparent to wireless signals  46 . If desired, RIS  50  may be disposed (e.g., layered) onto an underlying electronic device. RIS  50  may also be provided with mounting structures (e.g., adhesive, brackets, a frame, screws, pins, clips, etc.) that can be used to affix or attach RIS  50  to an underlying structure such as another electronic device, a wall, the ceiling, the floor, furniture, etc. Disposing RIS  50  on a ceiling, wall, window, column, pillar, or at or adjacent to the corner of a room (e.g., a corner where two walls intersect, where a wall intersects with the floor or ceiling, where two walls and the floor intersect, or where two walls and the ceiling intersect), as examples, may be particularly helpful in allowing RIS  50  to reflect wireless signals between AP  34  and UE device  10  around various objects  51  that may be present (e.g., when AP  34  is located outside and UE device  10  is located inside, when AP  34  and UE device  10  are both located inside or outside, etc.). 
     RIS  50  may be a passive adaptively controlled reflecting surface and a powered device that includes control circuitry  52  that helps to control the operation of antenna elements  48  (e.g., one or more processors in control circuitry such as control circuitry  14 ). When electro-magnetic (EM) energy waves (e.g., waves of wireless signals  46 ) are incident on RIS  50 , the wave is reflected by each antenna element  48  via re-radiation by each antenna element  48  with a respective phase and amplitude response. Antenna elements  48  may include passive reflectors (e.g., antenna resonating elements or other radio-frequency reflective elements). Each antenna element  48  may include an adjustable device that is programmed, set, and/or controlled by control circuitry  52  (e.g., using a control signal that includes a respective beamforming coefficient) to configure that antenna element  48  to reflect incident EM energy with the respective phase and amplitude response. The adjustable device may be a programmable photodiode, an adjustable impedance matching circuit, an adjustable phase shifter, an adjustable amplifier, a varactor diode, an antenna tuning circuit, etc. 
     Control circuitry  52  on RIS  50  may configure the reflective response of antenna elements  48  on a per-element or per-group-of-elements basis (e.g., where each antenna element has a respective programmed phase and amplitude response or the antenna elements in different sets/groups of antenna elements are each programmed to share the same respective phase and amplitude response across the set/group but with different phase and amplitude responses between sets/groups). The scattering, absorption, reflection, and diffraction properties of the entire RIS can therefore be changed over time and controlled (e.g., by software running on the RIS or other devices communicably coupled to the RIS such as external equipment  34  or UE device  10 ). 
     One way of achieving the per-element phase and amplitude response of antenna elements  48  is by adjusting the impedance of antenna elements  48 , thereby controlling the complex reflection coefficient that determines the change in amplitude and phase of the re-radiated signal. The control circuitry  52  on RIS  50  may configure antenna elements  48  to exhibit impedances that serve to reflect wireless signals  46  incident from particular incident angles onto particular output angles. The antenna elements  48  (e.g., the antenna impedances) may be adjusted to change the angle with which incident wireless signals  46  are reflected off of RIS  50 . 
     For example, the control circuitry on RIS  50  may configure antenna elements  48  to reflect wireless signals  46  transmitted by AP  34  towards UE device  10  (as shown by arrow  54 ) and to reflect wireless signals  46  transmitted by UE device  10  towards AP  34  (as shown by arrow  56 ). In such an example, control circuitry  36  may configure (e.g., program) a phased antenna array of antennas  44  on AP  34  to form an AP beam oriented towards RIS  50 , control circuitry  14  may configure (e.g., program) a phased antenna array of antennas  30  on UE device  10  to form a UE beam oriented towards RIS  50 , control circuitry  52  may configure (e.g., program) antenna elements  48  to receive and re-radiate (e.g., effectively reflect) wireless signals incident from the direction of AP  34  towards/onto the direction of UE device  10  (as shown by arrow  54 ), and control circuitry  52  may configure (e.g., program) antenna elements  48  to receive and re-radiate (e.g., effectively reflect) wireless signals incident from the direction of UE device  10  towards-onto the direction of external equipment  34  (as shown by arrow  56 ). The antenna elements may be configured using respective beamforming coefficients. Control circuitry  52  on RIS  50  may set and adjust the adjustable devices coupled to antenna elements  48  (e.g., may set and adjust the impedances of antenna elements  48 ) over time to reflect wireless signals  46  incident from different selected incident angles onto different selected output angles. 
     To minimize the cost, complexity, and power consumption of RIS  50 , RIS  50  may include only the components and control circuitry required to control and operate antenna elements  48  to reflect wireless signals  46 . Such components and control circuitry may include, for example, the adjustable devices of antenna elements  48  as required to change the phase and magnitude responses of antenna elements  48  (based on corresponding beamforming coefficients) and thus the direction with which RIS  50  reflects wireless signals  46 . The components may include, for example, components that adjust the impedances of antenna elements  48  so that each antenna element exhibits a respective complex reflection coefficient, which determines the phase and amplitude of the reflected (re-radiated) signal produced by each antenna element (e.g., such that the signals reflected across the array constructively and destructively interfere to form a reflected signal beam in a corresponding beam pointing direction). 
     All other components that would otherwise be present in UE device  10  or AP  34  may be omitted from RIS  50 . For example, RIS  50  does not include baseband circuitry (e.g., baseband circuitry  26  or  40 ) and does not include transceiver circuitry (e.g., transceiver  42  or  28 ) coupled to antenna elements  48 . Antenna elements  48  and RIS  50  therefore do not generate wireless data for transmission, do not synthesize radio-frequency signals for transmission, and do not receive and demodulate radio-frequency signals. RIS  50  may also be implemented without a display or user input device. In other words, the control circuitry on RIS  50  may adjust antenna elements  48  to direct and steer reflected wireless signals  46  without using antenna elements  48  to perform any data transmission or reception operations and without using antenna elements  48  to perform radio-frequency sensing operations. 
     This may serve to minimize the hardware cost and power consumption of RIS  50 . If desired, RIS  50  may also include one or more antennas (e.g., antennas separate from the antenna elements  48  used to reflect wireless signals  46 ) and corresponding transceiver/baseband circuitry that uses the one or more antennas to convey control signals with AP  34  or UE device  10  (e.g., using a control channel plane and control RAT). Such control signals may be used to coordinate the operation of RIS  50  in conjunction with AP  34  and/or UE device  10  but requires much lower data rates and thus much fewer processing resources and much less power than transmitting or receiving wireless signals  46 . These control signals may, for example, be transmitted by UE device  10  and/or AP  34  to configure the phase and magnitude responses of antenna elements  48  (e.g., the control signals may convey beamforming coefficients). This may allow the calculation of phase and magnitude responses for antenna elements  48  to be offloaded from RIS  50 , further reducing the processing resources and power required by RIS  50 . In other implementations, RIS  50  may be a self-controlled RIS that includes processing circuitry for generating its own phase and magnitude responses and/or for coordinating communications among multiple UE devices (e.g., in an RIS-as-a-service configuration). 
     In this way, RIS  50  may help to relay wireless signals  46  between AP  34  and UE device  10  when object  51  blocks the LOS path between AP  34  and UE device  10  and/or when the propagation conditions from AP  34  to RIS  50  and from RIS  50  to UE device  10  are otherwise superior to the propagation conditions from AP  34  to UE device  10 . Just a single RIS  50  may, for example, increase signal-to-interference-plus-noise ratio (SINR) for UE device  10  by as much as +20 dB and may increase effective channel rank relative to environments without an RIS. At the same time, RIS  50  only includes processing resources and consumes power required to perform control procedures, minimizing the cost of RIS  50  and maximizing the flexibility with which RIS  50  can be placed within the environment. 
     RIS  50  may include or store a codebook (sometimes referred to herein as a RIS codebook) that maps settings for antenna elements  48  to different reflected signal beams formable by antenna elements  48  (sometimes referred to herein as RIS beams). RIS  50  may configure its own antenna elements  48  to perform beamforming with respective beamforming coefficients (e.g., as given by the RIS codebook). The beamforming performed at RIS  50  may include two concurrently active RIS beams (e.g., where each RIS beam is generated using a corresponding set of beamforming coefficients). 
     In general, RIS  50  may relay (reflect) signals between two different devices. RIS  50  may form a first active RIS beam that has a beam pointing direction oriented towards the first device (sometimes referred to here as a RIS-AP beam when the first device is AP  34 ) and may concurrently form a second active RIS beam that has a beam pointing direction oriented towards the second device (sometimes referred to herein as a RIS-UE beam when the second device is UE device  10 ). In this way, when wireless signals  46  are incident from the first device (e.g., AP  34 ) within the first RIS beam, the antenna elements  48  on RIS  50  may receive the wireless signals incident from the direction the first device (e.g., AP  34 ) and may re-radiate (e.g., effectively reflect) the incident wireless signals within the second RIS beam and towards the direction of the second device (e.g., UE device  10 ). Conversely, when wireless signals  46  are incident from the second device (e.g., UE device  10 ) within the second RIS beam, the antenna elements  48  on RIS  50  may receive the wireless signals incident from the direction the second device (e.g., UE device  10 ) and may re-radiate (e.g., effectively reflect) the incident wireless signals within the first RIS beam and towards the direction of the first device (e.g., AP  34 ). 
     While referred to herein as “beams,” the first RIS beam and the second RIS beams formed by RIS  50  do not include signals/data that are actively transmitted by RIS  50  but instead correspond to the impedance, phase, and/or magnitude response settings (e.g., reflection coefficients) for antenna elements  48  that shape the reflected signal beam of wireless signals  46  from a corresponding incident direction/angle onto a corresponding output direction/angle (e.g., the first RIS beam may be effectively formed using a first set of beamforming coefficients and the second RIS beam may be effectively formed using a second set of beamforming coefficients but are not associated with the active transmission of wireless signals by RIS  50 ). 
       FIG.  2    is a diagram showing how AP  34 , RIS  50 , and UE device  10  may communicate using both a control RAT and a data transfer RAT for establishing and maintaining communications between AP  34  and UE device  10  via RIS  50 . As shown in  FIG.  2   , AP  34 , RIS  50 , and UE device  10  may each include wireless circuitry that operates according to a data transfer RAT  62  (sometimes referred to herein as data RAT  62 ) and a control RAT  60 . Data RAT  62  may be a sub-THz communications RAT such as a 6G RAT that performs wireless communications at the frequencies of wireless signals  46 . Control RAT  60  may be associated with wireless communications that consume much fewer resources and are less expensive to implement than the communications of data RAT  62 . For example, control RAT  60  may be Wi-Fi, Bluetooth, a cellular telephone RAT such as a 3G, 4G, or 5G NR FR1 RAT, etc. As another example control RAT  60  may be an infrared communications RAT (e.g., where an infrared remote control or infrared emitters and sensors use infrared light to convey signals for the control RAT between UE device  10 , AP  34 , and/or RIS  50 ). 
     AP  34  and RIS  50  may use control RAT  60  to convey radio-frequency signals  68  (e.g., control signals) between AP  34  and RIS  50 . UE device  10  and RIS  50  may use control RAT  60  to convey radio-frequency signals  70  (e.g., control signals) between UE device  10  and RIS  50 . UE device  10 , AP  34 , and RIS  50  may use data RAT  62  to convey wireless signals  46  via reflection off antenna elements  48  of RIS  50 . The wireless signals may be reflected, via the first RIS beam and the second RIS beam formed by RIS  50 , between AP  34  and UE device  10 . AP  34  may use radio-frequency signals  68  and control RAT  116  and/or UE device  10  may use radio-frequency signals  70  and control RAT  116  to discover RIS  50  and to configure antenna elements  48  to establish and maintain the relay of wireless signals  32  performed by antenna elements  48  using data RAT  62 . 
     If desired, AP  34  and UE device  10  may also use control RAT  60  to convey radio-frequency signals  72  directly with each other (e.g., since the control RAT operates at lower frequencies that do not require line-of-sight). UE device  10  and AP  34  may use radio-frequency signals  72  to help establish and maintain THF communications (communications using data RAT  62 ) between UE device  10  and AP  34  via RIS  50 . AP  34  and UE device  10  may also use data RAT  62  to convey wireless signals  46  directly (e.g., without reflection off RIS  50 ) when a LOS path is available. 
     If desired, the same control RAT  60  may be used to convey radio-frequency signals  68  between AP  34  and RIS  50  and to convey radio-frequency signals  70  between RIS  50  and UE device  10 . If desired, AP  34 , RIS  50 , and/or UE device  10  may support multiple control RATs  60 . In these scenarios, a first control RAT  60  (e.g., Bluetooth) may be used to convey radio-frequency signals  68  between AP  34  and RIS  50 , a second control RAT  60  (e.g., Wi-Fi) may be used to convey radio-frequency signals  70  between RIS  50  and UE device  10 , and/or a third control RAT  60  may be used to convey radio-frequency signals  72  between AP  34  and UE device  10 . Processing procedures (e.g., work responsibilities) may be divided between data RAT  62  one or more control RAT  60  during discovery, initial configuration, data RAT communication between UE device  10  and AP  34  via RIS  50 , and beam tracking of UE device  10 . 
     AP  34  may require internet access, a power connection, implementation of a full WLAN protocol and, in the case of a relay or mesh configuration, transfers may require handling of two links (base station and user links). In many environments, obstacles such as walls or furniture may block a LOS path to the AP. Disposing many AP&#39;s within the environment to cover all areas of the environment despite the obstacles can be unnecessarily expensive, can consume an excessive amount of resources, and may not be possible given the power outlets or connectivity available for access points in each of the areas. Further, a single RIS  50  may not be able to provide a single AP with coverage for all areas of the environment. As such, AP  34  may need to use multiple RIS&#39;s  50  to be able to communicate with UE devices located in all areas of the environment. The AP may not have a LOS path to all of the multiple RIS&#39;s. As such, multiple RIS&#39;s may be arranged in a relay configuration in which a chain of multiple RIS&#39;s serve as a communication link to route (reflect) wireless data between the AP and a UE device. 
       FIG.  3    is a diagram showing one example of how multiple RIS&#39;s may be arranged in a relay configuration to form a communication link that routes wireless data between AP  34  and UE device  10 . As shown in  FIG.  3   , AP  34  and UE device  10  may communicate, using data RAT  62 , over communication path  74 . Communication path  74  may include a set of N RIS&#39;s  50 , from a first RIS  50 - 1  with LOS to AP  34  to an Nth RIS  50 -N with LOS to UE device  10 . N may be an integer greater than or equal to two. System  8  may have other RIS&#39;s  50  that do not form part of communication path  74  but which may form part of one or more other communication paths to other potential locations for UE devices in system  8 . 
     The N RIS&#39;s  50  in communication path  74  may be arranged in a relay or chain configuration. Each RIS  50  may reflect signals to or from at least one other RIS  50  in communication path  74  (e.g., between AP  34  and a next RIS  50  in the path, between a previous RIS  50  and a next RIS  50  in the path, or between a previous RIS  50  in the path and UE device  10 ). Each RIS  50  may form a respective first RIS beam  66 A pointed towards the previous node (device) in communication path  74  and may concurrently form a respective second RIS beam  66 B pointed towards the next node (device) in communication path  74 . 
     For example, as shown in  FIG.  3   , RIS  50 - 1  may have a first RIS beam  66 A that points towards AP  34 . AP  34  may have an AP beam  73  that points towards RIS  50 - 1  (e.g., overlapping the first RIS beam  66 A of RIS  50 - 1 ). RIS  50 - 1  may also have a second RIS beam  66 B that points towards the next RIS  50  in communication path  50 , RIS  50 - 2 . RIS  50 - 2  may have a first RIS beam  66 A that points towards the previous RIS  50  in communication path  50 , RIS  50 - 1  (e.g., overlapping the second RIS beam  66 B of RIS  50 - 1 ). RIS  50 - 2  may also have a second RIS beam  66 B that points towards the next RIS  50  in communication path  50 . This relay configuration may continue until RIS  50 -N. RIS  50 -N may have a first RIS beam  66 A pointed towards the previous RIS  50  in communication path  50  (e.g., RIS  50 -(N−1)). RIS  50 -N may have a second RIS beam  66 B pointed towards UE device  10 . UE device  10  may have a UE beam  75  that points towards RIS  50 -N. 
     The first RIS  50  in communication path  74 , which is the RIS closest to AP  34  (e.g., RIS  50 - 1 ), may sometimes be referred to herein as the AP RIS of communication path  74 . The Nth RIS  50  in communication path  74 , which is the RIS closest to UE device  10  (e.g., RIS  50 -N), may sometimes be referred to herein as the end user RIS of communication path  74 . If desired, some of the RIS&#39;s in system  8  may be configured to operate as end user RIS&#39;s for one or more communication paths  74  whereas other RIS&#39;s in system  8  are configured to operate as routing RIS&#39;s. Routing RIS&#39;s are used to relay wireless signals  46  to/from other RIS&#39;s but not to end user  50  (e.g., RIS&#39;s  50 - 1  through  50 -(N−1) may be routing RIS&#39;s). 
     End user RIS&#39;s are used to relay wireless signals between a routing RIS and a UE device  10 . UE device  10  may move and rotate over time (e.g., as the UE device is operated by an end user). End user RIS&#39;s therefore also need to perform tracking on the UE device to update the second beam  66 B of the end user RIS as the UE device  10  moves relative to the end user RIS over time. The tracking may also involve updating the UE beam of UE device  10  so the UE beam continues to point towards the end user RIS as the UE device moves/rotates over time. As such, the end user RIS&#39;s may have wider RIS beams than routing RIS&#39;s, if desired. This may configure the end user RIS&#39;s to allow for more movement of UE device  10  before losing a beam (e.g., because the distance between end user RIS&#39;s and the UE device is generally smaller than the distance between the UE device and the AP). On the other hand, using narrower RIS beams for the routing RIS&#39;s may help to mitigate path loss and can easily bridge several rooms. Since RIS beams of the routing RIS&#39;s only need to reflect signals between other RIS&#39;s (or a RIS and AP  34 ), and the RIS&#39;s and the AP are fixed in place after installation within system  8 , the routing RIS&#39;s do not need to update their RIS beams after being installed and set up (calibrated). 
       FIG.  4    is a top view of an exemplary environment in which system  8  may be deployed for providing communication paths such as communication path  74  between AP  34  and UE devices. As shown in  FIG.  4   , system  8  may include a building having different areas  80  (e.g., rooms) joined by a common area  82  (e.g., a hallway). Areas  80  and  82  may be bounded and divided by obstacles  86 . Obstacles  86  may include walls, the floor, the ceiling, doors, windows, cubicle walls, furniture, etc. 
     AP  34  may be disposed within a first area  80 . UE device  10  may be located in a second area  80  that is separated from the first area  80  by at least area  82 . If desired, radio-frequency transparent windows  84  may be present between each area  80  and area  82  to allow for the passage of radio-frequency signals. Radio-frequency transparent windows  84  may include doorways, entranceways, or openings in obstacles  86  through which a user can pass while moving through the environment, may include radio-frequency transparent paneling or windows in obstacle  86 , etc. In some implementations, radio-frequency transparent windows  84  may be formed in the top of walls of the building where the walls meet the ceiling. This may allow signals to be routed through the windows with minimal risk of being blocked by people or other objects on the floor in the building, and can simplify routing for communication path  74  (e.g., to within a two-dimensional plane instead of a three-dimensional space). 
     Each area  80  and area  82  may include at least one RIS  50  disposed therein. If desired, RIS&#39;s  50  may be mounted to obstacles  86  (e.g., walls, a portion of the walls that meet the ceiling, etc.). The RIS&#39;s in areas  80  may, if desired, be configured as end user RIS&#39;s whereas the RIS&#39;s in area  82  may be configured as routing RIS&#39;s. If desired, dedicated routing RIS&#39;s may be provided for each area  80  and/or for each end user RIS that is placed. This may, for example, help to ensure that the routing RIS can be pre-configured without any further control overhead required to change its active RIS beams. If desired, several end user RIS&#39;s may be placed in each area  80  to ensure optimum connection to a UE device while the UE device is in motion. If desired, a routing RIS may concurrently serve several areas  80 , although an additional connection to the AP via an additional long range power interface may be needed. When located in the second area  80 , as shown in  FIG.  4   , UE device  10  does not have a LOS to AP  34 . As such, N RIS&#39;s  50  may be used to relay wireless signals  46  between UE device  10  and AP  34  (e.g., through windows  84  and around obstacles  86 ). 
     In the example of  FIG.  4   , N is equal to 4. UE device  10  may have a LOS to  50 - 4  (e.g., the end user RIS for UE device  10 ), which has a LOS to RIS  50 - 3  in the second area  80 , which has a LOS to RIS  50 - 2  in common area  82 , which has a LOS to RIS  50 - 1  in common area  50 - 1 , which has a LOS to AP  34  in the first area  80 . RIS&#39;s  50 - 1 ,  50 - 2 ,  50 - 3 , and  50 - 4  may thereby be used to form communication path  74  ( FIG.  3   ) between AP  34  and UE device  10  while UE device  10  is at the location shown in  FIG.  4   . 
     In general, all of the RIS&#39;s  50  in the environment may be calibrated (e.g., after or upon installation) to have knowledge of which RIS beams to use to direct wireless signals to each other visible RIS in the system. As such, RIS  50 - 4  has knowledge of which of its RIS beams points towards RIS  50 - 3  (as well as all other RIS&#39;s  50  with a LOS to RIS  50 - 4 ). Similarly, RIS  50 - 3  is calibrated to have knowledge of which of its RIS beams point towards RIS  50 - 2  and which of its RIS beams points towards RIS  50 - 4  (as well as all other RIS&#39;s  50  with a LOS to RIS  50 - 4 ), RIS  50 - 2  is calibrated to have knowledge of which of its RIS beams point towards RIS  50 - 1  and which of its RIS beams points towards RIS  50 - 3  (as well as all other RIS&#39;s  50  with a LOS to RIS  50 - 4 ), and RIS  50 - 1  is calibrated to have knowledge of which of its RIS beams points towards RIS  50 - 2  and which of its RIS beams points towards AP  34 . 
     To perform wireless communication over the communication path  74  from AP  34  to UE device  10  of  FIG.  4   , UE device  10  first needs to connect to the end user RIS. This may involve a discovery procedure in which UE device  10  sweeps over different UE beams until a UE beam pointing towards a satisfactory end user RIS such as RIS  50 - 4  is found and in which the end user RIS such as RIS  50 - 4  sweeps over different RIS beams until a RIS beam pointing towards UE device  10  is found. UE device  10  may, for example, have M UE  different formable UE beams  75  (e.g., from UE beam  75 - 1  to UE beam  75 -M UE , as given by the UE codebook). Each UE beam  75  points in a different direction. Similarly, RIS  50 - 4  may have a set of different formable RIS beams  66  (only the RIS beams used to form the second beam  66 B for pointing towards UE device  10  are shown in  FIG.  4    for the sake of clarity). The discovery operation may allow UE device  10  to discover its UE beam  75 -X pointing towards RIS  50 - 4  and may allow RIS  50 - 4  to discover its RIS beam  66 B-X pointed towards UE device  10 . 
     If desired, once UE device  10  has connected to the end user RIS (e.g., RIS  50 - 4 ), UE device  10 , AP  34 , and/or RIS  50 - 4  may control each of the other RIS&#39;s in communication path  74  to form the appropriate RIS beams that are used to form communication path  74 . In other implementations (e.g., when each routing RIS is used to serve only a single area  80  or a single set of end user RIS&#39;s such as end user RIS&#39;s of a single area  80 ), the other RIS&#39;s in the communication path need not be controlled to form the required RIS beams after initial calibration is completed, since those RIS&#39;s may always form the same RIS (static) beams that serve their corresponding area(s). 
     During wireless communication over communication path  74 , UE device  10  may use the data RAT to transmit wireless signals  46  ( FIG.  1   ) within UE beam  75 -X towards RIS  50 - 4 . RIS  50 - 4  may receive the wireless signals over its second RIS beam  66 B pointed towards UE device  10  (e.g., RIS beam  66 B-X). RIS  50 - 4  concurrently forms its first RIS beam  66 A oriented towards RIS  50 - 3  (e.g., where the angle of the first RIS beam  66 A oriented towards RIS  50 - 3  is known from the calibration of the system). As such, RIS  50 - 4  reflects the wireless signals from its second RIS beam  66 B-X and onto its first RIS beam  66 A and towards RIS  50 - 3 , as shown by arrow  94 . 
     RIS  50 - 3  may receive the wireless signals over its second RIS beam  66 B pointed towards RIS  50 - 4  (e.g., in the direction of arrow  94 , where the angle of the second RIS beam  66 B oriented towards RIS  50 - 4  is known from calibration of the system). RIS  50 - 3  concurrently forms its first RIS beam  66 A oriented towards RIS  50 - 2  (e.g., where the angle of the first RIS beam  66 A oriented towards RIS  50 - 2  is known from the calibration of the system). As such, RIS  50 - 3  reflects the wireless signals from its second RIS beam  66 B and onto its first RIS beam  66 A and towards RIS  50 - 2 , as shown by arrow  92 . 
     RIS  50 - 2  may receive the wireless signals over its second RIS beam  66 B pointed towards RIS  50 - 3  (e.g., in the direction of arrow  92 , where the angle of the second RIS beam  66 B oriented towards RIS  50 - 3  is known from calibration of the system). RIS  50 - 2  concurrently forms its first RIS beam  66 A oriented towards RIS  50 - 1  (e.g., where the angle of the first RIS beam  66 A oriented towards RIS  50 - 1  is known from the calibration of the system). As such, RIS  50 - 2  reflects the wireless signals from its second RIS beam  66 B and onto its first RIS beam  66 A and towards RIS  50 - 1 , as shown by arrow  90 . 
     RIS  50 - 1  may receive the wireless signals over its second RIS beam  66 B pointed towards RIS  50 - 2  (e.g., in the direction of arrow  90 , where the angle of the second RIS beam  66 B oriented towards RIS  50 - 2  is known from calibration of the system). RIS  50 - 1  concurrently forms its first RIS beam  66 A oriented towards AP  34  (e.g., where the angle of the first RIS beam  66 A oriented towards AP  34  is known from the calibration of the system). As such, RIS  50 - 1  reflects the wireless signals from its second RIS beam  66 B and onto its first RIS beam  66 A and towards AP  34 , as shown by arrow  90 . AP  34  receives the wireless signals in its AP beam, which is oriented in the direction of arrow  88  (e.g., where the angle of the AP beam oriented towards RIS  50 - 1  is known from the calibration of the system). Arrows  88 ,  90 ,  92 , and  94  and the link from UE device  10  to RIS  50 - 4  may collectively characterize/support communication path  74  ( FIG.  3   ) for UE device  10  at this location. 
     Conversely, AP  34  may use the data RAT to transmit wireless signals  46  within its AP beam towards RIS  50 - 1 . RIS  50 - 1  may receive the wireless signals from AP  34  in its first RIS beam  66 A (oriented in the direction of arrow  88 ) and may reflect the wireless signals towards RIS  50 - 2  in its second RIS beam  66 B (oriented in the direction of arrow  90 ). RIS  50 - 2  may receive the wireless signals from RIS  50 - 1  in its first RIS beam  66 A (oriented in the direction of arrow  90 ) and may reflect the wireless signals towards RIS  50 - 3  in its second RIS beam  66 B (oriented in the direction of arrow  92 ). RIS  50 - 3  may receive the wireless signals from RIS  50 - 2  in its first RIS beam  66 A (oriented in the direction of arrow  92 ) and may reflect the wireless signals towards RIS  50 - 3  in its second RIS beam  66 B (oriented in the direction of arrow  92 ). RIS  50 - 4  may receive the wireless signals from RIS  50 - 3  in its first RIS beam  66 A (oriented in the direction of arrow  94 ) and may reflect the wireless signals towards UE device  10  in its second RIS beam  66 B-X. 
     In this way, multiple RIS&#39;s  50  in system  8  may be used to reflect and relay wireless signals  46  between AP  34  and UE device  10 . UE device  10  may also move or rotate over time, as shown by arrow  96 . As such, the end user RIS (e.g., RIS  50 - 4 ) and UE device  10  need to perform UE tracking over time to update the UE beam and the second RIS beam  66 B of RIS  50 - 4 , and/or to switch a different end user RIS into use over time. However, since the configuration (e.g., RIS beams) of the routing RIS&#39;s are already set on calibration and the RIS&#39;s  50  and AP  34  do not move after installation, only the active end user RIS, the second RIS beam of the active end user RIS, and/or the UE beam need to be updated to track movement of UE device  10  over time. The example of  FIG.  4    is illustrative and non-limiting and, in general, the environment may have any number of areas of any sizes or shapes and any number of RIS&#39;s arranged in any desired manner. The AP may concurrently communicate with multiple UE devices in the environment using different respective communication paths  74 , which may include different RIS&#39;s  50  or may include one or more of the same RIS&#39;s  50 . 
       FIG.  5    is a flow chart of illustrative operations involved with setting up and operating system  8  of  FIG.  4   . At operation  100 , a calibration device may generate a three-dimensional or two-dimensional map of the environment of system  8 . The calibration device may be a UE device such as UE device  10  or a different mapping device. The calibration device may be operated by an administrator of the system. 
     The calibration device may, for example, include an optical sensor such as a light detection and ranging (lidar) sensor that transmits light and receives the light after reflection off different points in an area to map the distance between the calibration device and each point, thereby generating a spatial map of the area. In other examples, the calibration device may include ultra-wideband (UWB) antennas that maps the areas using UWB signals transmitted to UWB tags distributed throughout the environment. The calibration device may generate such a map for all areas  80  and  82  of the environment. If desired, the calibration device may be omitted and a pre-drawn map or floor plan (file) of the environment may be used for subsequent processing. 
     At operation  102 , a software application running on the calibration device, AP  34 , or elsewhere (e.g., as executed by one or more processors) may generate (output) a list of optimal locations for RIS  50  in the environment based on the maps generated while processing operation  100 , information about the environment (e.g., a floor plan or room plan), the location of AP  34 , and/or information about the RIS&#39;s (e.g., the number and capability of each of the available RIS&#39;s  50  to be deployed in the environment). If desired, the application may treat walls in the environment as perfect reflectors (e.g., where the incident angle of a radio-frequency wave is equal to the output angle of the radio-frequency wave as reflected off the wall) plus some angular variation x. The amount of angular variation x should be kept as small as possible to keep the effects of beam damping low. 
     The optimal locations output by the application algorithm may, for example, be locations such that AP  34  is able to cover, via the available RIS&#39;s, each part of every area in the environment using a minimal number of RIS&#39;s and a minimal deviation x from perfect reflection. The algorithm may also account for obstacles and other RIS elements. The application may, for example, use ray-tracing algorithms creating a large set of solutions for the locations, which may be weighted according to the above set of parameters. If desired, the optimal positions may be located at or close to the ceiling of the environment, to help avoid obstacles in the LOS paths, to ease passage of the signals through windows  84  of  FIG.  4    (e.g., doorways, glass openings transparent to wireless signals  46 , false ceilings, etc.). Selecting optimal positions at or close to the ceiling may, for example, simplify the placement optimization to a two-dimensional routing problem instead of a three-dimensional routing problem (e.g., only the UE device and the end user RIS may need to incorporate the third dimension), reducing the amount of time required to install and calibrate the system. 
     At operation  104 , the application may output the list of optimal RIS locations to the administrator of the system (e.g., using a display, printer, speaker, or other output device, as a plan or map file to be viewed by the administrator of the system, etc.). The application may also output the optimal beams between each of the routing RIS&#39;s used to form communication path  74 . The administrator may then place RIS&#39;s  50  at or as close as possible to the optimal RIS locations output by the application. 
     At operation  106 , the administrator may use a UE device or other calibration device to calibrate the AP and each of the RIS&#39;s installed in the system (e.g., in an initial calibration procedure). The calibration may involve discovering, within a relatively small angular variation around the pre-calibrated optimal beams output by the application, the first RIS beam  66 A and the second RIS beam  66 B for each RIS  50  in the system to support each of the communication links  74  formable by the system (e.g., to support communication links  74  for UE devices  10  located in each of the areas  80  of the environment). In other words, the calibration, which is described in further detail below, may involve discovering RIS beams for each of the RIS&#39;s that point towards each of the other RIS&#39;s that are visible to each RIS, each of the RIS beams that point towards AP  34  (e.g., for RIS&#39;s with LOS to AP  34 ), as well as the AP beam(s) pointing to one or more RIS&#39;s  50  in the system. 
     The calibration may be performed using both the control RAT and the data RAT if desired. The calibration may also involve using the control RAT to instruct each of the routing RIS&#39;s of their RIS beams to be used, each of the end user RIS&#39;s of their RIS beams to be used that point towards one or more routing RIS&#39;s, and/or to instruct AP  34  of the AP beam(s) to be used. The control RAT may also be used to actively configure the routing RIS&#39;s to form their corresponding discovered first RIS beam  66 A and second RIS beam  66 B, as well as to configure the end user RIS&#39;s to form their first RIS beam  66 A in a suitable direction oriented towards a corresponding routing RIS. The RIS&#39;s are then pre-configured (calibrated) to relay wireless signals from each area  80  upon connection of a UE device  10  to an end user RIS  50  during a subsequent transfer mode. No further active (control) communication between the AP and routing RIS&#39;s is required (e.g., for configuring beams of the routing RIS&#39;s) after the initial setup and calibration, thus minimizing power consumption for the AP and the routing RIS&#39;s. 
     At operation  108 , UE device  10  may enter an area  80  and may wish to communicate with AP  34 . The UE device may discover and connect to an end user RIS in its area. For example, the UE device may use the control RAT to connect to its closest end user RIS. The discovery may involve discovering the UE beam pointed towards the end user RIS and may involve discovering the second RIS beam of the end user RIS pointed towards the UE device. For example, in the deployment of  FIG.  4   , UE device  10  may discover that UE beam  75 -X points towards end user RIS  50 - 4  and end user RIS  50 - 4  may discover that second RIS beam  66 B-X points towards UE device  10 . 
     UE device  10  and the end user RIS may perform this discovery while splitting procedures (e.g., processing responsibilities) between the control RAT and the data RAT if desired. For example, the UE device and the end user RIS may use the control RAT to coordinate sweeping over UE beams and/or second RIS beams of the end user RIS while UE device  10  and/or AP  34  transmits wireless signals  46  (using the data RAT) that are reflected off RIS  50 - 4 . UE device  10  and/or AP  34  may gather wireless performance metric data associated with the reflected signals and may select the UE beam and the second RIS beam of the end user RIS that produced optimal wireless performance data (e.g., peak wireless performance metric data, wireless performance metric data that exceeded a threshold, etc.) as the discovered UE beam pointed towards the end user RIS (e.g., UE beam  75 -X of  FIG.  4   ) and the discovered second RIS beam for the end user RIS (e.g., RIS beam  66 B-X of  FIG.  4   ). The wireless performance metric data may include received power level values, signal-to-noise ratio (SNR) values, noise floor values, error rate values, or any other desired values characterizing wireless performance. This procedure may also be performed across multiple candidate end user RIS&#39;s to select the end user RIS to use. 
     The control RAT may be used to instruct UE device  10  and/or AP  34  of the discovered (optimal) UE beam and the discovered (optimal) second RIS beam. The control RAT may also be used to inform the end user RIS (e.g., RIS  50 - 4  of  FIG.  4   ) of the discovered second RIS beam and/or to actively configure the end user RIS to form the discovered second RIS beam as its second RIS beam  66 B ( FIG.  3   ). Once the UE beam and the second RIS beam of the end user RIS have been established, the UE device may use the control RAT to place the end user RIS into a transfer mode (e.g., from an initialization mode, calibration mode, or back-reflection mode). In the transfer mode, the end user RIS may concurrently form its first RIS beam pointed towards the previous RIS  50  in communication path  74 . AP  34  may continuously listen for incoming signals via the routing RIS(s) to detect the presence of the new UE device  10  and to begin data transfer. 
     At operation  110 , UE device  10  and AP  34  may then convey wireless data via reflection (hops or bounces) of wireless signals  46  off each of the N RIS&#39;s  50  in communication path  74  (e.g., using the pre-calibrated and configured first and second RIS beams for each of the routing RIS&#39;s in the communication path, using the pre-calibrated and configured first RIS beam for the end user RIS in the communication path, using the pre-calibrated AP beam for AP  34 , using the discovered second RIS beam for the end user RIS, and using the discovered UE beam pointed towards the end user RIS). 
     At the same time, UE device  10 , AP  34 , and/or the end user RIS may track the location of UE device  10  as the UE device moves over time. This may involve updating the UE beam, the second RIS beam of the end user RIS, and/or the active end user RIS over time based on the orientation/position of UE device  10 . As one example, UE device  10  and/or the end user RIS may periodically attempt to communicate using different UE beams and/or different second RIS beams to see if any of the beams exhibit superior performance to the current beams. This may involve, for example, periodically sweeping UE device  10  over a set of UE beams (e.g., all UE beams or a subset of the UE beams around the current UE beam) and/or periodically sweeping the end user RIS and/or other end user RIS&#39;s over second RIS beams (e.g., all second RIS beams or a subset of the second RIS beams around the current second RIS beam). 
     If desired, sensor data gathered by UE device  10  and/or other sensors in the system may be used to perform or supplement UE tracking. For example, UE device  10  (or a sensor elsewhere) may gather sensor data indicative of the movement of UE device  10  (e.g., accelerometer data, motion sensor data, compass data, satellite navigation data, light sensor data, gyroscope data, etc.). UE device  10  may use information about its current location or movement to preemptively update its UE beam (e.g., to a UE beam that points towards the end user RIS given its movement or new location or to perform a sweep of UE beams around a UE beam expected to be optimal given its movement or new location) and/or may use the control RAT to instruct the end user RIS to update the second RIS beam of the end user RIS based on this information (e.g., to a second RIS beam that points towards the UE device given its movement or new location or to perform a sweep of second RIS beams around the expected location of the UE device). Augmenting tracking using sensor data may help to reduce the amount of time required to update the UE beam and second RIS beam of the end user RIS, thereby minimizing disruptions in communication as the UE device moves. Since all steps in communication path  74  except for the final link between the end user RIS and UE device  10  (e.g., over UE beam  75  and the second RIS beam  66 B of the end user RIS) are pre-calibrated and configured during operation  106 , the other RIS&#39;s in the system need not be controlled further while the system tracks UE device  10 . 
       FIG.  6    is a flow chart of illustrative operations involved in calibrating the RIS&#39;s  50  and AP  34  after (upon) installation in the environment. These calibration operations may help to mitigate any deviation in the actual placement of RIS&#39;s  50  from the optimal RIS locations identified while processing operation  104  of  FIG.  5    (e.g., to ensure that each RIS has RIS beams pointing in the correct directions for forming communication paths  74  and/or to overcome angular variation x). The operations of  FIG.  6    are, for example, performed while processing operation  106  of  FIG.  4    and may, if desired, be re-performed when a geometry of the environment changes, obstacles are added or removed from the environment, etc. 
     At operation  120 , the administrator may bring a calibration device into the vicinity of a first deployed RIS  50  (e.g., an end user RIS). An implementation in which the calibration device is UE device  10  is described herein as an example. The RIS&#39;s  50  in the communication path  74  from AP  34  to the end user RIS may be labeled with an index n, from n=1 to n+1=N. Index n may, for example, label the hop distance to AP  34  along the communication path, as well as the order the different RIS&#39;s are connected in the communication path. The first deployed RIS  50  may be labeled by index n+1 and may therefore sometimes referred to herein as RIS n+1. During a first iteration of the operations of  FIG.  6   , RIS n+1 may be the end user RIS  50 -N for the corresponding communication path ( FIG.  4   ). RIS n+1 may have a LOS to the previous RIS in communication path  74  (e.g., RIS n). This example is illustrative and conversely, if desired, calibration may equivalently be performed in the opposite order, from the AP to the end user RIS (e.g., during a first iteration of the operations of  FIG.  6   , RIS n+1 may be the AP RIS  50 - 1  for the corresponding communication path, where the index order for n is reversed). 
     At operation  122 , UE device  10  may use the control RAT to connect to RIS n+1 and RIS n. 
     At operation  124 , UE device  10  may use the control and the data RAT to identify a UE beam that points from the current location of UE device  10  towards RIS n+1 and to identify the second RIS beam of RIS n+1 that points toward UE device  10 . UE device  10  may, for example, identify the UE beam and the second RIS beam using similar beam sweeping and data RAT transmission/measurement procedures as performed at operation  108  of  FIG.  5   . 
     At operation  126 , UE device  10  may use the control RAT to place RIS n into a back-reflection mode. Prior to calibration, each RIS may have knowledge of the optimal (ideal) locations of each of the other RIS&#39;s in the system (e.g., as given by the map/list output at operation  104  of  FIG.  5   ). However, each RIS does not have knowledge of the actual locations of each of the RIS&#39;s, which may differ from the optimal locations. 
     In the transfer mode, prior to calibration, RIS n may have a first RIS beam pointed towards the optimal location of RIS n−1 (e.g., the previous RIS in communication path  74 ) and may have a second RIS beam pointed towards the optimal location of RIS n+1. On the other hand, in the back-reflection mode, prior to calibration, both the first RIS beam and the second RIS beam are pointed towards the optimal location of RIS n+1. 
     At operation  128 , UE device  10  may use the control RAT to configure RIS n+1 to orient its first RIS beam  66 A towards the optimal location of RIS n (e.g., as given by the map/list output at operation  104  of  FIG.  5   ). UE device  10  may also use the control RAT to configure RIS n+1 to form its second RIS beam  66 B towards the location of UE device  10  (e.g., as identified at operation  124 ). 
     At operation  130 , UE device  10  may use the data RAT to transmit signals (e.g., calibration or test signals) over the UE beam oriented towards RIS n+1. RIS n+1 may receive the signals over its second RIS beam  66 B and may reflect the signals over its first RIS beam  66 A oriented towards the optimal location of RIS n. Since RIS n is configured in the back-reflection mode, any of the signals that are incident within the second RIS beam  66 B of RIS n will be reflected back in in the same direction (e.g., towards RIS n+1) via its first RIS beam  66 A. RIS n+1 may then reflect these reflected signals from its first RIS beam  66 A onto its second RIS beam  66 B and towards UE device  10 . UE device  10  may gather wireless performance metric data from the received reflected signals while transmitting the signals. The wireless performance metric data may include measured (received) power levels, for example. 
     At operation  132 , while transmitting signals and measuring reflected signals, UE device  10  may use the control RAT to control RIS n to vary (e.g., sweep) its first RIS beam  66 A and its second RIS beam  66 B (pointed towards RIS n+1) and/or to control RIS n+1 to vary (sweep) its first RIS beam  66 A (pointed towards RIS n). Since the optimal positions of RIS n and/or RIS n+1 might vary from the actual positions of the RIS&#39;s, this variation may help to mitigate any misalignment between actual and optimal positions until RIS beams are found that produce peak reflection back towards UE device  10 . 
     UE device  10  may continue this process until the measured power levels of the reflected signals are maximized or exceed a threshold value, which is indicative of the first RIS beam  66 A of RIS n+1 pointing towards the actual location of RIS n, and the first and second RIS beams of RIS n pointing towards RIS n+1. UE device  10  may identify the first RIS beam  66 A of RIS n+1 that produced the maximum reflected power level as the calibrated first RIS beam  66 A for RIS n+1 (e.g., for use during subsequent transfer mode operations via the data RAT). UE device  10  may identify the second RIS beam of RIS n that produced the maximum reflected power level as the calibrated second RIS beam  66 B for RIS n (e.g., for use during subsequent transfer mode operations via the data RAT). 
     At operation  134 , UE device  10  may use the control RAT to configure RIS n+1 to use its calibrated first RIS beam  66 A during transfer mode. UE device  10  may also use the control RAT to configure RIS n to use its calibrated second RIS beam  66 B during transfer mode. These calibrated beams may be oriented towards the actual positions of the RIS&#39;s even if the actual positions deviate from the optimal positions as initially mapped. 
     If RIS&#39;s remain in communication path  74  to calibrate, processing may proceed to operation  136 . At operation  138 , UE device  10  may move one RIS closer to AP  34  up the chain of RIS&#39;s in communication path  74  device. As such, UE device  10  may set the current RIS n−1 as the RIS n for the next iteration of operations  120 - 136  and may set the current RIS n as the RIS n+1 for the next iteration of operations  120 - 136 . Processing may then loop back to operation  120  via path  140 . This may continue sequentially up each pair of RIS&#39;s  50  in communication path  74  until each RIS  50  in communication path  74  has been calibrated. This example is illustrative and non-limiting and, if desired, the RIS&#39;s may be calibrated in the reverse order (e.g., where the indices are reversed and decrease from the AP towards the end user RIS). For example, AP RIS  50 - 1  may form the RIS n+1 during the first iteration of  FIG.  6   , RIS  50 - 2  may form the RIS n during the first iteration of  FIG.  6   , UE device  10  may set RIS  50 - 2  as the RIS n+1 and RIS  50 - 3  as the RIS n during the second iteration of  FIG.  6   , and calibration may continue sequentially up each pair of RIS&#39;s  50  in communication path  74  from the AP to the end user RIS until communication path  74  has been calibrated. Performing calibration in this direction may, for example, be particularly convenient with the mounting process with which a user deploys the system (e.g., beginning at the AP and walking outward along different potential communication paths mounting RIS&#39;s in the environment), as the user may calibrate each new RIS as the user places the RIS in the environment before placing the next RIS. When no RIS&#39;s remain in the communication path, calibration is complete (path  142 ) and processing may proceed to operation  108  of  FIG.  5   . The operations of  FIG.  6    may be performed (e.g., repeated) for each deployed end user RIS in the environment (e.g., for each possible communication path  74  or at least once for each area  80 ) until the entire system has been calibrated. 
       FIG.  7    is a diagram showing how the RIS&#39;s  50  in communication path  74  may be calibrated in sequential pairs beginning from a first RIS with a LOS to a first device  156  (e.g., UE device  10  or AP  34 ) to an Nth RIS with a LOS to a second device  158  (e.g., AP  34  or UE device  10 ). As shown in  FIG.  7   , during a first iteration of  FIG.  6   , UE device  10  may first calibrate a first pair  150  of RIS&#39;s such as RIS  50 -N and RIS  50 -(N−1). In other words, RIS  50 -N may form RIS n+1 and RIS  50 -(N−1) may form RIS n. Once RIS  50 -N and RIS  50 -(N−1) have been calibrated, RIS  50 -(N−1) is configured to form a second RIS beam  66 B pointed towards the actual location of RIS  50 -N and RIS  50 -N is configured to form a first RIS beam  66 A pointed towards the actual location of RIS  50 -(N−1). 
     During a second iteration of  FIG.  6   , UE device  10  may then calibrate a second pair  152  of RIS&#39;s such as RIS  50 -(N−1) and RIS  50 -(N−2). In other words, RIS  50 -(N−1) may form RIS n+1 and RIS  50 -(N−2) may form RIS n. Once RIS  50 -(N−1) and RIS  50 -(N−2) have been calibrated, RIS  50 -(N−2) is configured to form a second RIS beam  66 B pointed towards the actual location of RIS  50 -(N−1) and RIS  50 -(N−1) is configured to form a first RIS beam  66 A pointed towards the actual location of RIS  50 -(N−2). This process may be continued as UE device  10  calibrates communication path  74 , two RIS&#39;s at a time, up the chain of relayed RIS&#39;s (in the direction of arrow  154 ) until all RIS&#39;s in communication path  74  have been calibrated. The connection between AP  34  and the AP RIS in communication path  74  may be established in a similar way. This calibration procedure may only need to be performed once and the short range communication between UE device  10  and the RIS&#39;s may be switched off afterwards, thereby conserving battery and power during the subsequent transfer mode operations. If desired, this calibration procedure may be combined with mounting of the routing RIS&#39;s, where the user must already move from room-to-room. 
     During transfer mode operations (e.g., operation  110  of  FIG.  5   ), UE device  10  may move outside of the coverage area of its end user RIS (e.g., RIS  50 - 4  of  FIG.  4   ). In these situations, a new RIS selection procedure may begin (e.g., using the procedure of operation  108  of  FIG.  5   ). During the new selection of the end-user RIS and establishment of the communication path, no data connection to the AP is available. To keep the service outage as short as possible, UE device  10  may measure the strength of surrounding end-user RIS&#39;s while communicating with a given end user RIS, thereby speeding up the search procedure when the UE device moves outside of the coverage area of the given end user RIS. Additionally or alternatively, the UE device may measure its movement as well as selected beams to deduce when the connection will break ahead of time. The UE device may then attempt to select and establish a connection to a new end user RIS (e.g., operation  108  of  FIG.  5   ) prior to the connection breaking, thereby minimizing the service outage. 
     If desired, the systems and methods described above in connection with  FIGS.  1 - 7    may be extended to situations where one or more AP&#39;s  34  in the environment concurrently communicate with multiple UE devices  10  in the same area  80  or in different areas  80  of the environment. In these situations, AP  34  may use time division duplexing (TDD) mechanisms to handle communications with multiple UE devices  10  (e.g., selecting different routes/communication paths that serve different UE devices in different time slots). Additionally or alternatively, AP  34  may use parallel beam forming (e.g., to concurrently form two or more AP beams for two or more routes/communication paths  74  serving two or more different UE devices). If desired, a single end user RIS may use frequency division duplexing (FDD) and/or TDD to serve multiple UE devices located in its area. 
     UE device  10  may gather and/or use personally identifiable information. It is well understood that the use of personally identifiable information should follow privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining the privacy of users. In particular, personally identifiable information data should be managed and handled so as to minimize risks of unintentional or unauthorized access or use, and the nature of authorized use should be clearly indicated to users. 
     The methods and operations described above in connection with  FIGS.  1 - 7    may be performed by the components of UE device  10 , RIS  50 , and/or AP  34  using software, firmware, and/or hardware (e.g., dedicated circuitry or hardware). Software code for performing these operations may be stored on non-transitory computer readable storage media (e.g., tangible computer readable storage media) stored on one or more of the components of UE device  10 , RIS  50 , and/or AP  34 . The software code may sometimes be referred to as software, data, instructions, program instructions, or code. The non-transitory computer readable storage media may include drives, non-volatile memory such as non-volatile random-access memory (NVRAM), removable flash drives or other removable media, other types of random-access memory, etc. Software stored on the non-transitory computer readable storage media may be executed by processing circuitry on one or more of the components of UE device  10 , RIS  50 , and/or AP  34 . The processing circuitry may include microprocessors, central processing units (CPUs), application-specific integrated circuits with processing circuitry, or other processing circuitry. 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20220914
Publication Date: 20240409
Grant Date: 20240409
Priority Date: 20220914
Inventors: MEYER, STEFAN
ELLENBECK, JAN K
GUNZELMANN, Bertram R
Assignee: APPLE INC
CPC Classifications: [{"code": "H04B7/145", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B7/043", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B7/0617", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B7/043", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B7/145", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B7/0617", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B7/04013", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B7/0617", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B7/043", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B7/15528", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 90140687