Multiplexed input / output transmission using adaptive phase change devices

Abstract

Techniques and apparatus for multiple-input multiple-output (MIMO) transmission using adaptive phase change devices are described. In an aspect, a base station (120) selects (1010) one or more adaptive phase change devices (APDs) (180) for use in at least one communication path for multiple-input multiple-output (MIMO) transmission. The base station (120) can perform a channel characterization process (1105) for the at least one communication path using the at least one APD (180) and at least one UE (110). Based on the results of the channel characterization process, the base station (120) configures the at least one APD (180) for performing single-user-MIMO transmission with one UE or multi-user-MIMO transmission with multiple UEs (1045). By doing so, the base station (120) can perform MIMO transmission using the APD to communicate with one or more UEs (110) using the same time and frequency resources, thereby improving the spectral efficiency of the wireless network.

Description

[Background technology]

[0001] Evolving wireless communication systems, such as fifth-generation (5G) and sixth-generation (6G) technologies, use various techniques to increase data capacity over previous wireless networks. As one example, 5G technology transmits data using higher frequency ranges, such as bands above 6 gigahertz (GHz), sometimes referred to as the millimeter wave (mm wave) range. As another example, 5G technology increases the data capacity of wireless networks by using multiple-input multiple-output (MIMO) transmission.

[0002] While these techniques can increase data rates, transmitting and recovering information using higher frequency regions poses additional challenges: higher frequency signals are more susceptible to obstructions, atmospheric conditions, multipath fading, and other types of path loss, which can lead to recovery errors at the receiver, reduced throughput, or degradation of the wireless link. Summary of the Invention

[0003] This specification describes techniques and apparatus for enabling multiple-input multiple-output (MIMO) transmission using adaptive phase-changing devices (APDs). In an aspect, a base station selects one or more APDs to use in at least one communication path for MIMO transmission. The base station can perform a channel characterization process for the at least one communication path using the one or more APDs and one or more user equipments (UEs). Based on results of the channel characterization process (e.g., uplink or downlink channel measurements), the base station configures one or more APDs to perform single-user-MIMO (SU-MIMO) transmission with one UE or multi-user-MIMO (MU-MIMO) transmission with multiple UEs. By doing so, the base station can use the APDs to perform MIMO transmission to communicate with one or more UEs using the same time and frequency resources in different spatial resources, thereby improving the spectral efficiency of the wireless network.

[0004] The details of one or more embodiments of MIMO transmission using APDs are set forth in the accompanying drawings and the following description. Other features and advantages will be apparent from the description and drawings, and from the appended claims. This Summary introduces the subject matter, which is further described in the Detailed Description and Figures. Thus, this Summary should not be considered to describe essential features, nor should it be used to limit the scope of the claimed subject matter.

[0005] The details of one or more aspects of multiple-input multiple-output (MIMO) transmission using adaptive phase change devices (APDs) are described with reference to the following drawings, in which like numbers are used throughout to denote like features and components. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 illustrates an example of an operating environment in which various aspects of MIMO transmission using APDs can be implemented. [Figure 2] 1 illustrates an exemplary apparatus diagram of an entity capable of implementing various aspects of MIMO transmission using APDs. [Figure 3] 1 shows an exemplary apparatus diagram of an APD that can be used to implement various aspects of MIMO transmission using APDs. [Figure 4] 1A and 1B are diagrams illustrating examples of base stations that configure APDs in accordance with various aspects of MIMO transmission using APDs. [Figure 5A] FIG. 1 illustrates an example of a channel characterization process that can be used to implement various aspects of MIMO transmission using APDs. [Figure 5B] FIG. 1 illustrates an example of a channel characterization process that can be used to implement various aspects of MIMO transmission using APDs. [Figure 6] FIG. 1 illustrates an example of using multiple APDs for MIMO transmission with multiple user devices in accordance with one or more aspects. [Figure 7] FIG. 1 illustrates an example of using multiple APDs for MIMO transmission with a user device in accordance with one or more aspects. [Figure 8] 1 illustrates an example of using multiple APD surface partitions for MIMO transmission with multiple user devices in accordance with one or more aspects. [Figure 9] 1 illustrates an example of using multiple APD surface partitions for MIMO transmission with a user device in accordance with one or more aspects. [Figure 10] 1 illustrates exemplary details of signaling and control transactions that can be used to implement various aspects of MIMO transmission using APD. [Figure 11] 1 illustrates exemplary details of signaling and control transactions that can be used to perform channel characterization in accordance with one or more aspects. [Figure 12] 1 illustrates an example method that can be used to implement various aspects of MIMO transmission using APD. DETAILED DESCRIPTION OF THE INVENTION

[0007] While higher frequencies and MIMO transmissions offer higher data throughput, channel conditions can adversely affect these technologies. As an example, millimeter wave signals have high throughput under line-of-sight (LoS) conditions, but reflections cause multipath and frequency-selective fading, which can increase recovery errors at the receiver. Various environments, such as dense urban areas, contain multiple obstacles that further degrade signal quality, making the deployment of high-frequency communications in these environments more difficult.

[0008] An adaptive phase change device (APD) includes a reconfigurable intelligent surface (RIS). When properly configured, the RIS modifies a propagating signal to correct or reduce errors caused by communication path(s) (e.g., various obstacles), small-scale fading, and a fading MIMO channel. Typically, the RIS includes a configurable surface material. The configurable surface material determines how an incident signal impinging on the surface of the material is transformed and reflected. For example, the configuration of the surface material can affect the phase, amplitude, direction, spatial coverage area, and / or polarization of the transformed signal. Therefore, changing the surface configuration of the RIS changes how an incident signal is transformed when it reflects off the RIS. This can be useful for providing additional, modified, or alternative communication paths for downlink and / or uplink communications between a base station and one or more UEs. However, using an APD in a communication path typically requires that the RIS of the APD be configured specifically for the communication path, which may change over time due to dynamic channel conditions, UE movement, air interface resource allocation, etc. For example, adding an APD to a channel changes the propagation delay through the channel, particularly the round-trip propagation delay for uplink and downlink communications. Thus, specific configuration of the APD and UE by a base station to support MIMO transmission over a communication path can be challenging due to these time-varying channel conditions and communication constraints.

[0009] In aspects of MIMO transmissions using APD, a base station may use APD to route and / or transform MIMO transmissions to improve the signal quality of MIMO transmissions exchanged between the base station and UE(s). This results in performance benefits (e.g., improved signal quality, increased data capacity) without requiring LoS between the base station and the UE. For example, a transmitting device (e.g., a base station or user equipment) may use APD to route a wireless signal toward a second (receiving) wireless device (e.g., a user equipment or base station) by routing the wireless signal around obstacles that may cause recovery errors at the receiver and / or prevent the wireless signal from reaching the receiver. In some aspects, a base station may adjust timing calculations (e.g., timing advance calculations) for one or more communication paths (e.g., to account for propagation delays), in which case the base station may adjust APD and / or UE operation for the MIMO transmissions so that the MIMO transmissions (e.g., APD-reflected UE or BS transmissions) arrive at the receiving device at approximately the same time (e.g., within the cyclic prefix). Alternatively or additionally, the base station selects a surface configuration of the APD that transforms the characteristics of the wireless signal to improve signal quality (e.g., a surface configuration selected to mitigate destructive interference). Also, by using the APD to route and / or transform MIMO transmissions, the base station can reuse air interface resources (e.g., time and frequency resources) for different MIMO transmissions and use spatial resources to improve the spectral efficiency and data throughput of the wireless network.

[0010] In some aspects, a base station selects one or more APDs to include in at least one communication path for MIMO transmission with one or more UEs. As an example, the base station may select candidate APDs in response to detecting deteriorating channel conditions for communication with one or more UEs. Typically, the base station can initiate or perform a channel characterization process to aid in selecting an APD, selecting UEs, and / or configuring each surface of the APD for MIMO transmission. This may include the base station directing each APD to change between multiple surface configurations, transmitting a channel state information reference signal (CSI-RS) toward each surface of the APD, and receiving feedback (e.g., downlink signal quality measurements) from the UEs, which provide data on which surface configuration results in the best observed signal quality at the UE compared to other surface configurations. For the uplink, the channel characterization process may include the base station having each UE transmit a sounding reference signal (SRS) while the APD is changing between multiple surface configurations, and the base station generating metrics (e.g., uplink signal quality measurements) for the received SRS. The base station then selects the surface configuration of the APD based on the signal quality measurements (and / or link quality measurements), as further described with reference to Figures 5A and 5B. Alternatively or additionally, the base station can use measurements from a channel characterization process to select which UE and / or which APD to use for MIMO transmission. In some aspects, the base station may apply the reciprocity principle to use uplink or downlink channel measurements to configure the APD and / or UE for communications on the reverse link (e.g., downlink channel characterization to configure uplink communications). This may be used in time division duplex (TDD) or frequency division duplex (FDD) systems that use nearby or adjacent uplink and downlink frequency bands.

[0011] As an example, a base station selects two UEs to pair for MU-MIMO transmissions using the same frequency and time slot but different beam directions. The base station selects a first APD to include in a first communication path for MIMO transmission with a first UE of the pair and a second APD to include in a second communication path for MIMO transmission with a second UE of the pair. Alternatively or additionally, the base station determines to include two APDs in two communication paths to a single UE for SU-MIMO transmissions. In some aspects, the base station determines to utilize a single APD in the communication paths for MU-MIMO and / or SU-MIMO transmissions using panel division or sub-panels of the APD, such that, for one or more respective UEs, a first set of panels on the single APD reflects the first MIMO transmission and a second set of panels on the single APD reflects the second MIMO transmission. By doing so, the base station can route and / or convert MU-MIMO or SU-MIMO transmissions using APD, which allows the base station to reuse air interface resources (e.g., time and frequency resources) with different spatial resources for different MIMO transmissions, thereby improving the spectral efficiency and data throughput of the wireless network.

[0012] Although the features and concepts of the present systems and methods for MIMO transmission using APDs may be implemented in any number of different environments, systems, devices, and / or various configurations, various aspects of MIMO transmission using APDs will be described with reference to the following exemplary environments, devices, systems, and configurations.

[0013] Example Environment 1 illustrates an exemplary environment 100 including multiple user equipments 110 (UEs 110), shown as UEs 111 and 112. Each UE can communicate with one or more base stations 120 (shown as base station 121 and base station 122) via one or more wireless communication links 130 (shown as wireless links 130), shown as wireless links 131 and 132. The wireless links also include wireless link 133 and / or wireless link 134, which base station 120 uses to communicate with one or more adaptive phase change devices 180 (APDs 180), shown as APDs 181 and 182. In some aspects, base station 120 communicates with APD 180 to control surface configuration, position, and / or APD timing adjustments for applying the surface configuration and / or positioning APD 180. In other embodiments, base station 120 includes a wired interface for communicating APD control information (e.g., surface configuration, timing adjustments, position information) to APD 180. For simplicity, the UE 110 is embodied as a smartphone, but may be embodied as any suitable computing or electronic device, such as a mobile communication device, a modem, a mobile phone, a gaming device, a navigation device, a media device, a laptop computer, a desktop computer, a tablet computer, a smart appliance, an in-vehicle communication system, or an Internet of Things (IoT) device, such as a sensor, a relay, or an actuator. The base station 120 (e.g., an Evolved Universal Terrestrial Radio Access Network Node B, E-UTRAN Node B, evolved Node B, eNodeB, eNB, next generation Node B, gNodeB, gNB, ng-eNB, etc.) may be embodied in the form of a macro cell, a micro cell, a small cell, a pico cell, a distributed base station, etc., or any combination thereof.

[0014] One or more base stations 120 communicate with UE 110 using wireless links 131 and 132, which may be implemented as any suitable type of wireless link. In one example, base station 121 communicates with UE 111 using wireless link 131 and the surface of APD 181 to route and / or convert wireless signals along communication path 161 (e.g., a non-LoS path). Wireless link 131 or other wireless links described herein may include wireless signals corresponding to MIMO transmissions with UE 111, which may include SU-MIMO or MU-MIMO transmissions that enable reuse of the same time and frequency resources. In environment 100, base station 121 communicates with UE 112 using wireless link 132 and the surface of APD 182 to route and / or convert wireless signals along communication path 162 in a manner similar to that described further below for UE 111 and APD 181. This may include wireless signals corresponding to MIMO transmissions with UE 112, which may include MU-MIMO or SU-MIMO transmissions on the downlink or uplink of a wireless connection. Environment 100 illustrates base station 120 performing MU-MIMO with UE 111 and UE 112 and multiple APDs in a manner similar to that described with reference to FIG. 6. However, various aspects described with respect to environment 100 may alternatively or additionally be utilized to perform SU-MIMO with a single UE using multiple APDs (e.g., as described with reference to FIG. 7), to perform MU-MIMO with multiple UEs by panel-splitting a single APD (e.g., FIG. 8), and / or to perform SU-MIMO with a single UE by panel-splitting a single APD (e.g., FIG. 9).

[0015] Radio links 131 and 132 include control plane information and / or user plane data (e.g., downlink user plane data and control plane information communicated from base station 120 to UE 110, uplink and control plane information for other user plane data communicated from UE 110 to base station 120, or both). Radio link 130 may include one or more radio links (e.g., radio links) or bearers implemented using any suitable communications protocol or standard or combination of communications protocols or standards (e.g., 3rd Generation Partnership Project Long Term Evolution (3GPP®) LTE), 5th Generation New Radio (5GNR), 6th Generation (6G), etc.). In various aspects, base station 120 and UE 110 may be implemented for operation in sub-gigahertz bands, sub-6 GHz bands (e.g., Frequency Band 1), and / or above 6 GHz bands (e.g., Frequency Band 2, millimeter wave (mm wave) bands) defined by one or more of the 3GPP LTE, 5G NR, or 6G communications standards. As an example, the multiple wireless links may include a first sub-6 gigahertz (GHz) anchor link and a second above-6 GHz auxiliary link. For example, referring to FIG. 6, wireless link 131 may include a first wireless anchor link (e.g., low-bandwidth connection 521) using a sub-6 GHz radio signal and a second wireless link (e.g., wireless link 621) using an above-6 GHz radio signal. The multiple wireless links 130 may be aggregated using carrier aggregation or multi-connectivity techniques to provide higher data rates to the UE 110. The multiple wireless links 130 from the multiple base stations 120 may be configured for coordinated multipoint (CoMP) communication with the UE 110.

[0016] In some embodiments, wireless links (e.g., wireless links 131 and 132) utilize radio signals that are reflected or transformed (e.g., reflected to route the radio signals around obstacles 170 (illustrated as obstacles 171 and 172) by one or more intermediate devices (e.g., APD 180). While obstacles 171 and 172 are depicted as buildings and foliage, the obstacles may range from more temporary obstacles such as water vapor or moving vehicles, to seasonal obstacles such as the depicted deciduous trees, to more permanent obstacles such as the depicted buildings. For example, base station 121 uses APD 181 to propagate light rays 190, shown as signal ray 191, signal ray 192, and signal ray 193, toward (and / or receive from) UE 111. In environment 100, signal ray 190 corresponds to the individual rays of a narrow-beam or wide-beam (including up to omnidirectional) radio signal used to implement wireless link 131. The wireless signal may be, for example, a downlink wireless signal from base station 121 to UE 111 (shown in FIG. 1) and / or an uplink wireless signal from UE 111 to base station 121 (not shown in FIG. 1).

[0017] As part of communicating with UE 111 over wireless link 131, base station 121 transmits a first downlink wireless signal intended for UE 111, corresponding to a MIMO transmission. A first ray (e.g., signal ray 191) of the first downlink wireless signal propagates toward UE 111 in a line-of-sight (LoS) manner, where obstacle 171 dynamically blocks and / or attenuates LoS signal ray 191. A second ray (e.g., signal ray 192) of the first downlink wireless signal propagates toward APD 181. Second signal ray 192 strikes a surface of APD 181 and transforms into third signal ray 193 that propagates along communication path 161 toward UE 111. Similarly, base station 121 transmits the second downlink signal to UE 112 using the surface of APD 182, which routes and / or transforms the wireless signal along communication path 162.

[0018] Base station 120 can configure the RIS of APD 180 to control the manner in which the RIS changes signal characteristics (e.g., direction, phase, amplitude, and / or polarization) of an incident radio signal. In an aspect, base station 120 performs a channel characterization process to determine the surface configuration of APD(s) 180, as further described with reference to FIGS. 5A and 5B . In an aspect, base station 120 communicates respective RIS surface configuration information to APD 181 and APD 182 using wireless link 133 and / or wireless link 134 (e.g., an APD control channel). This may include an adaptive phase-change device physical downlink shared channel (APD-PDSCH), an adaptive phase-change device physical uplink shared channel (APD-PUSCH), an adaptive phase-change device physical downlink control channel (APD-PDCCH), and / or an adaptive phase-change device physical uplink control channel (APD-PUCCH). Alternatively or additionally, base station 120 determines the surface configuration(s) of APD 180 based on location information, downlink signal quality measurements / parameters received from UE 110, uplink signal quality measurements / parameters generated by base station 120, historical records of previous successful and unsuccessful uplink and / or downlink wireless communications (with and / or without APDs in the communication path), APD location, UE location, downlink / uplink (DL / UL) signal strength / quality measurement reports, APD surface configurations (e.g., indices), APD surface configuration codebooks, etc. In some cases, base station 120 determines and communicates timing adjustments (e.g., timing advance, timing delay) for the APD to APD(s) 180 using wireless link 133 and / or wireless link 134.

[0019] Collectively, the base stations 120 form at least part of a radio access network 140 (RAN 140, e.g., RAN, Evolved Universal Terrestrial Radio Access Network, E-UTRAN, 5G NR RAN, or NR RAN). The base stations 121 and 122 connect to a core network 150 at 102 and 104, respectively, via an NG2 interface for control plane signaling and an NG3 interface for user plane data communication. In this case, the base stations 121 and 122 use an S1 interface for control plane signaling and user plane data communication when connecting to a 5G core network or an Evolved Packet Core (EPC) network. The UE 110 can connect to a public network, such as the Internet, and interact with remote services (not shown in FIG. 1 ) via the RAN 140 and the core network 150.

[0020] Base station 121 and base station 122 can communicate at 106 using the Xn Application Protocol (XnAP) over the Xn interface or the X2 Application Protocol (X2AP) over the X2 interface to exchange user plane data and control plane data. Alternatively or additionally, base station 121 and base station 122 communicate with each other using a wireless Integrated Access Backhaul (IAB) link (not shown in FIG. 1 ), where one of the base stations functions as a donor base station and the other functions as a node base station. In some aspects, base station 121 and base station 122 include one or more APDs 180 surface in the communication path for the IAB link, and thus the APDs route and / or convert wireless signals associated with the IAB link communication.

[0021] Exemplary Apparatus FIG. 2 illustrates an example apparatus diagram 200 of a user equipment 110 and a base station 120. Generally, the apparatus diagram 200 illustrates network entities capable of implementing various aspects of MIMO transmission using APD. FIG. 2 illustrates an example of a UE 110 and a base station 120, respectively. The UE 110 or the base station 120 may include additional functionality and interfaces, which are omitted from FIG. 2 for clarity. The UE 110 includes an antenna 202, a radio frequency front end 204 (RF front end 204), and one or more radio transceivers 206 (e.g., radio frequency transceivers), such as any combination of LTE transceivers, 5G NR transceivers, and / or 6G transceivers, for communicating with the base station 120 in the RAN 140. In an aspect, the antenna 202 (e.g., an antenna array), the radio frequency (RF) front end 204, and the radio transceiver 206 may be implemented as radio modules of the UE 110. For example, the UE 110 may include one or more radio modules (e.g., 5G NR or mmWave modules) capable of performing respective transmit and / or receive functions. The RF front end 204 of the UE 110 may couple or connect a radio transceiver 206 to an antenna 202 to facilitate various types of wireless communication.

[0022] The antenna 202 of the UE 110 may include an array of multiple antennas configured similarly or differently from one another. The antenna 202 and RF front end 204 may be tuned and / or tunable to one or more frequency bands defined by various communication standards (e.g., 3GPP LTE, 5G NR, 6G) and implemented by the radio transceiver 206. Furthermore, the antenna 202, the RF front end 204, and / or the radio transceiver(s) 206 may be configured to support beam sweeping for transmission and reception of communication signals to and from the base station 120. By way of example and not limitation, the antenna 202 and the RF front end 204 may be implemented for operation in sub-gigahertz bands, sub-6 GHz bands, and / or above 6 GHz bands (e.g., bands described with reference to FIG. 1 ) defined by the 3GPP LTE, 5G NR, or 6G communication standards.

[0023] The UE 110 also includes a processor(s) 208 and a computer-readable storage medium 210 (CRM 210). The processor 208 may be a single-core processor or a multi-core processor implemented with a homogeneous or heterogeneous core architecture. The computer-readable storage medium described herein does not include a propagating signal. The CRM 210 may include any suitable memory or storage device usable for storing device data 212 of the UE 110, such as random access memory (RAM), static RAM (SRAM), dynamic RAM (DRAM), non-volatile RAM (NVRAM), read-only memory (ROM), or flash. The device data 212 includes any combination of user data, multimedia data, applications, and / or an operating system of the UE 110. In one embodiment, the device data 212 stores processor-executable instructions executable by the processor(s) 208 to enable the UE 110 to communicate user plane data and / or control plane information as well as enable various user interactions (e.g., applications or user interfaces).

[0024] In this example, the CRM 210 of the UE 110 also includes a user equipment adaptive phase change device manager 214 (UE APD manager 214) for managing APD usage on an access link with the base station 120. The UE APD manager 214 may be implemented in whole or in part as hardware logic or circuitry integrated with or separate from other components of the UE 110 (e.g., the radio transceiver 206). In an aspect, the UE APD manager 214 receives APD access information for using APD surfaces. Such APD access information may be, for example, reflection access information indicating timing adjustments for when to apply the APD surface and / or configurable surface element information indicating portions of the APD surface available to the UE 110. In an aspect, the UE APD manager 214 of the UE 110 decodes reflection identifiers or beam identifiers (e.g., CSI-RS resource indexes or synchronization signal block (SSB) indexes), analyzes link quality parameters, and generates feedback messages for various APDs or channels to the base station 120. The UE APD manager 214 may also maintain a low-band connection (e.g., an anchor connection) with the base station 120 via a low-frequency band (e.g., sub-6 GHz) to provide signal reflection information or beam information for high-frequency signals (e.g., above 6 GHz). This information is used to implement aspects of MIMO transmission using APD. The UE 110 may also receive beam sweeping information or phase steering configurations from the base station 120 via the low-band connection. Thus, the UE 110 may implement carrier aggregation (CA) to communicate on two frequency bands when communicating with the base station 120 to implement aspects of MIMO transmission using APD. Alternatively or additionally, the UE APD manager 214 may cause the UE 110 to send communication signals (e.g., uplink sounding signals) to the base station 120 via an APD-enabled communication channel (e.g., based on APD access information) or via a non-APD communication path (e.g., direct UE-to-base station communication).

[0025] The equipment diagram of the base station 120 shown in FIG. 2 includes a single network node (e.g., a gNode B). The functionality of the base station 120 may be distributed across multiple network nodes or devices, or in any manner suitable for performing the functions described herein. Nomenclature for this distributed base station functionality varies and includes terms such as central unit (CU), distributed unit (DU), baseband unit (BBU), remote radio head (RRH), and / or remote radio unit (RRU). The base station 120 includes an antenna 252, a radio frequency front end 254 (RF front end 254), and one or more radio transceiver(s) 256 (e.g., an LTE transceiver, a 5G NR transceiver, and / or a 6G transceiver) for communicating with the UE 110, other UEs (not shown), and / or other base stations 120.

[0026] The RF front end 254 of the base station 120 may couple or connect a radio transceiver 256 (e.g., a radio frequency transceiver) to the antenna 252 to facilitate various types of wireless communication. The antenna 252 of the base station 120 may include an array of multiple antennas (e.g., antenna panels or antenna elements) configured similarly or differently to one another. The antenna 252 and the RF front end 254 may be tuned and / or tunable to one or more frequency bands defined by various communication standards (e.g., 3GPP LTE, 5G NR, and / or 6G) and implemented by the radio transceiver 256. Furthermore, the antenna 252, the RF front end 254, and / or the radio transceiver 256 may be configured to support beamforming, such as MU-MIMO, SU-MIMO, and / or massive-MIMO, for transmission and reception of communication signals with the UE 110, other UEs, and / or another base station 120.

[0027] The base station 120 also includes a processor(s) 258 and a computer-readable storage medium 260 (CRM 260). The processor 258 may be a single-core processor or a multi-core processor constructed from various materials, such as silicon, polysilicon, high-K dielectrics, copper, etc. The CRM 260 may include any suitable memory or storage device, such as RAM, SRAM, DRAM, NVRAM, ROM, or flash memory, that can be used to store device data 262 of the base station 120. The device data 262 includes network scheduling data, radio resource management data, applications, and / or operating systems of the base station 120, which are executable by the processor(s) 258 to enable communication with other base stations 120, core network entities, and / or UEs 110. The device data 262 also includes a codebook 264 and APD information 266 for the APD 180 associated with the base station 120. The codebook 264 may include any suitable type or combination of codebooks. Such codebooks include a surface configuration codebook that stores surface configuration information for the RIS of the APD, and a beam-sweeping codebook that stores pattern, sequence, or timing information (e.g., propagation delay or timing advance) for realizing multiple surface configurations useful for causing the APD to perform various reflective beamforming (e.g., APD-enabled MIMO transmission). In some aspects, the surface configuration codebook and the beam-sweeping codebook include phase vector information, angle information (e.g., calibrated to each phase vector), and / or beam configuration information. The APD information 266 may include the identifier, capabilities, command and control information, location, orientation (e.g., fixed or last known), range, and propagation delay for each APD 180 with which the base station 120 communicates. The base station 120 may generate or modify the APD information 266 to add new APDs 180 that are detected, update information for known APDs 180, or remove existing APDs 180 that are not preferred.

[0028] In some aspects, the CRM 260 includes an APD-enabled MIMO function 268 (MIMO function 268) that manages or implements aspects of MIMO transmission using APDs. Alternatively or additionally, the MIMO function 268 may be implemented in whole or in part as hardware logic or circuitry integrated with or separate from other components of the base station 120. Typically, the MIMO function 268 may select one or more APDs to use for at least one communication path for MIMO transmission. For example, the base station 120 may select candidate APDs that can provide respective non-LoS communication paths to one or more UEs 110 (e.g., UEs experiencing degraded link quality, LoS impairments, increased throughput demands, etc.) for communication using MIMO transmission. The base station may then perform a channel characterization process for at least one communication path using one or more APDs and one or more UEs, as described with reference to FIGS. 5A, 5B, and / or 11. Based on the results of the channel characterization process (e.g., uplink or downlink channel measurements), the base station can select a UE and APD combination for conducting multi-user-MIMO (MU-MIMO) communications utilizing MIMO transmission (e.g., as described with reference to FIGS. 6, 8, and / or 10) or for conducting single-user-MIMO (SU-MIMO) communications (e.g., as described with reference to FIGS. 7, 9, and / or 10). By doing so, the base station can communicate with multiple UEs or communicate additional data with a single UE using the same time and frequency resources, thereby improving the spectral efficiency of the wireless network.

[0029] The CRM 260 also includes a base station manager 270 for managing various functions and communication interfaces of the base station 120. Alternatively or additionally, the base station manager 270 may be implemented in whole or in part as hardware logic or circuitry integrated with or separate from other components of the base station 120. In at least some aspects, the base station manager 270 configures the antenna 252, the RF front end 254, and the radio transceiver(s) 256 for communication with the UE 110, the APD 180, and / or for communication with a core network. The base station 120 includes an inter-base station interface 272, such as an Xn interface and / or an X2 interface. The base station manager 270 configures the inter-base station interface 272 to exchange user plane data and control plane information with other base stations 120 and manages communication between the base station 120 and the UE 110. The base station 120 also includes a core network interface (not shown) through which the base station manager 270 configures the core network interface (not shown) to exchange user plane data and control plane information with core network functions and / or entities.

[0030] 3 shows an example device diagram 300 of an APD 180. While the device diagram 300 generally illustrates example entities capable of implementing various aspects of MIMO transmission using an APD, additional functionality and interfaces may be included, which are omitted from FIG. 3 for clarity. The APD 180 includes one or more antenna(s) 302, a radio frequency front end 304 (RF front end 304), and one or more radio frequency transceivers 306 (e.g., a radio frequency transceiver, an LTE transceiver, a 5G NR transceiver, or a 6G transceiver) for wireless communication with the base station 120 and / or the UE 110. The APD 180 may also include a position sensor, such as a Global Navigation Satellite System (GNSS) module, that provides location information based on the location of the APD 180.

[0031] The antenna(s) 302 of the APD 180 may include an array of multiple antennas configured in a similar or different manner to one another. Additionally, the antenna 302, RF front end 304, and transceiver(s) 306 may be configured to support beamforming for transmitting and receiving communication signals to and from the base station 120 and / or the UE 110. By way of example and not limitation, the antenna 302 and RF front end 304 may be implemented for operation in sub-gigahertz, sub-6 GHz, and / or above-6 GHz bands, which may include the various frequencies described with reference to FIG. 1 . Thus, the antenna 302, RF front end 304, and transceiver(s) 306 provide the APD 180 with the capability to receive and / or transmit communication signals to and from the base station 120 and / or the UE 110 (e.g., transmitting information using an APD control channel (e.g., an APD slow control channel or an APD fast control channel), as further described).

[0032] The APD 180 includes a processor(s) 310 and a computer-readable storage medium 312 (CRM 312). The processor 310 may be a single-core processor or a multi-core processor implemented with homogeneous or heterogeneous core architectures. The computer-readable storage medium described herein does not include a propagated signal. The CRM 312 of the APD 180 may include any suitable memory or storage device, such as RAM, SRAM, DRAM, NVRAM, ROM, or flash memory, that can be used to store device data 314 of the APD 180. The device data 314 includes configuration data, RIS information, applications, and / or operating systems of the APD 180, which are executable by the processor(s) 310 to enable dynamic configuration of the APD 180, as further described. The device data 314 also includes one or more codebooks 316 of any suitable type or combination, and location information 318 of the APD 180. The location information 318 may be obtained or configured using the location sensor 308, or may be programmed into the APD 180, such as during installation. The location information 318 indicates the location of the APD 180 and may include location, geographic coordinates, orientation, elevation information, etc. The base station 120, the MIMO function 268, and / or the UE 110 may use the location information 318 in calculating angle or distance information, such as for a communication path between the base station 120 and the APD 180 and / or between the APD 180 and a target UE 110. The codebook 316 may include a surface configuration codebook that stores surface configuration information for the APD's RIS and a beam sweeping codebook that stores pattern, sequence, or timing information (e.g., phase vectors and reflection identifiers) for implementing multiple surface configurations useful for causing the APD to perform various reflection beamforming. In some aspects, the surface configuration codebook and the beam sweeping codebook include phase vector information, angle information (eg, calibrated to the respective phase vector), identifier information, and / or beam configuration information.

[0033] In one aspect of MIMO transmission using an APD, the CRM 312 of the APD 180 includes an adaptive phase-change device manager 320 (APD manager 320). Alternatively or additionally, the APD manager 320 may be implemented in whole or in part as hardware logic or circuitry integrated with or separate from other components of the APD 180. Typically, the APD manager 320 manages the surface configuration of the APD 180, such as by processing information exchanged with a base station over wireless link(s) 133 and then using that information to configure the reconfigurable intelligent surface 322 (RIS 322) of the APD 180. For example, the APD manager 320 receives an indication of the surface configuration over the wireless link 133 (APD control channel), uses the indication to extract the surface configuration from the codebook 316, and applies the surface configuration to the RIS 322. Alternatively or additionally, APD manager 320 initiates the transmission of uplink messages to the base station over wireless link 133, such as acknowledgements / negative acknowledgements (ACK / NACK) for various APD configuration or management commands. In some aspects, APD manager 320 receives indications of beam sweeping patterns (e.g., beam sweeping pattern indexes) over wireless links 133 and / or 134 and applies a sequence of various surface configurations to the RIS based on the beam sweeping pattern and / or according to synchronization or pattern timing indicated by or received with the indication. In some cases, the beam sweeping pattern may include reflection identifier information, which causes APD 180 to modulate or apply one or more reflection identifiers to downlink reference signals or uplink sounding signals reflected by APD 180 (e.g., using the RIS).

[0034] In some aspects, the APD manager 320 receives timing information in the surface configuration communication, where the timing information indicates when to apply the surface configuration to the RIS 322 (e.g., start time, duration, timing advance, periodic time information, dynamic time information). Alternatively or additionally, the APD manager 320 receives direction information along with the surface configuration, which indicates configuring the surface to reflect signals from the RIS 322 based on the direction information. For example, if the direction information indicates a communication direction from the BS to the UE, the APD manager 320 selects a first surface configuration having a first inter-reflection angle that reflects wireless signals from the base station 120 to the UE 110. If the direction information indicates a communication direction from the UE to the BS, the APD manager 320 selects a second surface configuration having a second inter-reflection angle that reflects wireless signals from the UE 110 to the base station 120.

[0035] The RIS 322 of the APD 180 includes one or more configurable surface element(s) 324, such as a configurable electromagnetic element, a configurable resonator element, or a configurable reflectarray antenna element. Typically, the configurable surface element(s) 324 can be selectively or programmatically configured to control how the RIS 322 reflects (e.g., directivity) and / or transforms an incident waveform. By way of example and not limitation, the configurable electromagnetic element includes scattering particles that are electronically connected (e.g., via PIN diodes). Some embodiments use electronic connections to position the scattering particles, such as based on principles of reflection, to control the directivity, phase, amplitude, and / or polarization of the transformed waveform (from the incident waveform). The RIS 322 can include an array(s) of independently configurable surface element(s) 324, and the array can include any number of elements having any size.

[0036] In some embodiments, the position and / or orientation of the APD 180 is configurable, and the APD 180 includes a motor controller 326 that communicates with one or more motor(s) 328 operably coupled to the physical chassis of the APD 180. Based on command and control information, such as that received from the base station 120, the motor controller 326 can send commands to the motors 328 to alter one or more kinematic behaviors of the motors 328, which may include any suitable type of stepper motor or servo. For example, the motor controller 326 can issue commands or control signals that specify the shaft rotation speed (degrees) of a stepper motor, the shaft rotation speed of the stepper motor in revolutions per minute (RPM), the linear motion (millimeters) of a linear motor, or the linear velocity of the linear motor in meters per second (m / s). The one or more motors 328 may then be coupled to mechanisms that mechanically position the physical chassis or platform that supports the APD 180 (e.g., avionics in a drone, a drive for a linear rail system, a gimbal in a base station, a linear bearing in a base station). The physical position, location, or orientation of the APD 180 (and / or the platform supporting the APD 180) may be changed via commands and signals generated by the motor controller 326 and sent to the motor 328. In response to receiving a position configuration from the base station, the APD manager 320 communicates movement commands to the motor controller 326 based on the position configuration, such as via a software interface and / or a hardware address. In an aspect of MIMO transmission using APDs, the base station 120 can reposition or reorient one or more APDs 180 to improve or enable reflection of wireless signals (e.g., uplink and / or downlink signals) between the base station 120 and the UE 110.

[0037] Typically, the APD 180 can include multiple motors, each corresponding to a different rotational or linear motion. Examples of motor(s) 328 that can be used to control the orientation and position of the APD include (i) linear servo motors that may be part of a rail system mount for the APD, (ii) motors that control the direction and pitch, yaw, and roll of a drone carrying the APD, and (iii) radial servo or stepper motors that rotate axes when the APD is in a fixed position or on a gimbal. For clarity, the motor controller 326 and motors 328 are shown as part of the APD 180; however, in alternative or additional embodiments, the APD 180 communicates with motor controllers and / or motors external to the APD. For example, the APD manager 320 communicates position configurations to motor controllers that mechanically position the platform or chassis supporting the APD 180. In one aspect, the APD manager 320 communicates the position configuration to a motor controller using a local wireless link, such as Bluetooth, Zigbee, IEEE 802.15.4, or a hardwired link. The motor controller then adjusts the platform based on the position configuration using one or more motors. The platform may correspond to or be attached to any suitable mechanism supporting rotatable and / or linear adjustment devices, such as a drone, an aircraft, a non-stationary ground station (e.g., a vehicle-towable APD tower / module), a rail propulsion system, a hydraulic lift system, etc.

[0038] As shown in FIG. 3 , the position of the APD 180 may be defined relative to a three-dimensional coordinate system. In the three-dimensional coordinate system, an X-axis 330, a Y-axis 332, and a Z-axis 334 define a spatial area and provide a framework for indicating positional configurations through rotational and / or linear adjustments. These axes are typically designated X-axis, Y-axis, and Z-axis, although other frameworks may be used to indicate positional configurations (e.g., azimuth and elevation). For example, a flight framework may reference a vertical axis (yaw), a horizontal axis (pitch), and a longitudinal axis (roll), while other motion frameworks may reference a vertical axis, a sagittal axis, and a frontal axis. As an example, position 336 refers to the center position of the APD 180, which typically corresponds to a baseline position (e.g., position (0,0,0) using XYZ coordinates).

[0039] In one aspect, the APD manager 320 communicates rotational adjustments (e.g., rotational adjustments 338) about the X-axis 330 to the motor controller 326, where the rotational adjustments include the direction of rotation (e.g., clockwise or counterclockwise), the amount of rotation (e.g., degrees), and / or the speed of rotation. Alternatively or additionally, the APD manager 320 communicates linear adjustments 340 along the X-axis, where the linear adjustments include any combination of the direction, speed, and / or distance of the adjustment. In some cases, the APD manager 320 similarly communicates adjustments about other axes, e.g., any combination of rotational adjustments 342 about the Y-axis 332, linear adjustments 344 along the Y-axis 332, rotational adjustments 346 about the Z-axis 334, and / or linear adjustments 348 along the Z-axis 334. Thus, the position configuration may include a combination of rotational and / or linear adjustments in all three spatial degrees of freedom in addition to the movement supported by the frame or platform (e.g., avionics drone or vehicle) on which the APD is mounted, thereby enabling the APD manager 320 to communicate physical adjustments to the APD 180. Alternatively or additionally, the APD manager communicates RIS surface configuration, beam sweeping index, and / or timing information, as further described.

[0040] 4 illustrates an example base station 400 that implements an adaptive phase change device in accordance with various aspects. Example 400 includes example base station 120 and APD 180, which may be implemented similarly to those described with reference to FIGS. 1-3. The RIS implemented by APD 180 includes an array of "N" independently selectable and configurable surface elements, such as configurable surface element 402, configurable surface element 404, configurable surface element 406, surface partitions, sub-panels, etc., where "N" represents the number of configurable surface elements of the RIS.

[0041] In some embodiments, the base station 120 or the MIMO function 268 manages the configuration of the RIS of the APD 180 using a surface configuration codebook 408. The surface configuration codebook 408 may be pre-configured and / or known by both the base station 120 and the APD 180. Alternatively or additionally, the base station 120 may also manage the time-dependent configuration of the RIS of the APD 180 by using a beam-sweeping codebook or beam-sweeping index as described with reference to FIGS. 5A and 5B. In some cases, the base station 120 transmits the surface configuration codebook 408 and / or the beam-sweeping codebook using the wireless link 133, such as over the APD slow control channel using one or more messages. In some aspects, the base station 120 uses the APD slow control channel to communicate large amounts of data, to communicate data without low latency requirements, and / or to communicate data without timing requirements. In some cases, the base station 120 transmits multiple surface configuration codebooks to the APD 180. The multiple surface configuration codebooks may include, for example, a first surface configuration codebook for downlink communications, a second surface configuration codebook for uplink communications, a phase vector codebook, a beam sweeping codebook, timing advance information, etc. In contrast, the APD 180 stores the surface configuration codebook(s) 408 and / or other codebooks in a CRM. This represents the codebook(s) 316 of the CRM 312, as described with reference to FIG. 3 . Alternatively or additionally, the APD 180 acquires the surface configuration codebook(s) and other codebooks through a manufacturing (e.g., programming), calibration, or installation process. Such processes store the surface configuration codebook(s) 408 and other codebooks in the CRM 312 of the APD 180 during assembly, installation, calibration, verification, network association, or by an operator manually adding or updating the codebook(s).

[0042] The surface configuration codebook 408 includes configuration information specifying surface configurations for some or all of the configurable surface elements (e.g., elements 324) that form the RIS of the APD 180. For example, in some embodiments, a phase vector defines a set of waveform transformation characteristics (e.g., phase delay, reflection angle / direction, polarization, amplitude). The configurable surface elements apply such waveform transformation characteristics to an incident signal (e.g., incident waveform, incident signal light) and transform the incident signal into a reflected signal (e.g., reflected waveform, reflected signal light) characterized by one or more transformation characteristics. With respect to the surface configuration codebook 408, when configured by phase vectors or surface configurations, each configuration entry may correspond to a phase vector and / or surface configuration associated with a set of waveform transformation characteristics provided by a respective configurable surface element of the APD.

[0043] The surface configuration may include (or indicate) a surface element hardware configuration (e.g., for one or more PIN diodes) for each configurable surface element of the APD. In some embodiments, each surface element hardware configuration of the surface configuration may correspond to a respective entry in the phase vector. That is, each surface element hardware configuration arranges the surface of each configurable surface element such that each configurable surface element transforms an incident waveform into a reflected waveform having waveform characteristics indicated by the corresponding entry in the phase vector. This may include absolute transformation based on the phase vector (e.g., generating a reflected waveform to within a threshold / standard deviation of the waveform characteristic indicated by the phase vector) or relative transformation to within a threshold / standard deviation of the waveform characteristic (e.g., generating a reflected waveform based on altering the incident waveform with the waveform characteristic indicated by the phase vector).

[0044] As an example, each index of the codebook corresponds to a phase vector and configuration information for each configurable surface element of APD 180. For example, index 0 maps phase configuration 0 to configurable surface element 402, phase configuration 1 to configurable surface element 404, phase configuration 2 to configurable surface element 406, etc. Similarly, index 1 maps phase configuration 3 to configurable surface element 402, phase configuration 4 to configurable surface element 404, phase configuration 5 to configurable surface element 406, etc. Surface configuration codebook 408 may include any number of phase vectors specifying configurations of any number of configurable surface elements; thus, a first phase vector corresponds to a first surface configuration of APD 180 (via each configurable surface element in the RIS), a second phase vector corresponds to a second surface configuration of APD 180, etc. Alternatively or additionally, the phase vectors or surface configurations of surface configuration codebook 408 may be mapped or calibrated to specific angle information of incident and / or reflected radio signals (e.g., reference signals), signal rays, beamformed transmit signals of base station 120, beamformed transmit signals of UE 110, etc. In various embodiments, base station 120 can use this angle information corresponding to the surface configurations or phase vectors to calculate angle information used to determine the phase vector of APD 180, the phase steering vector of base station 120, or the phase steering vector of UE 110 to implement MIMO transmission using APDs.

[0045] While the surface configuration codebook 408 of FIG. 4 includes phase vector information, alternative or additional codebooks can store beam configuration information (e.g., a first surface configuration specifying a first beam having a first (propagation) direction, a second surface configuration specifying a second beam having a second direction, etc.). For example, similar to the phase vector surface configuration codebook, the beam codebook includes surface element hardware configurations corresponding to each beam configuration. That is, each surface element hardware configuration arranges the surface of each configurable surface element such that the respective configurable surface element transforms an incident waveform into a reflected waveform having beam characteristics (e.g., direction) indicated in the beam codebook. Thus, in various embodiments, the surface configuration codebook 408 corresponds to a beam codebook. Similarly, to configure the surface of the APD 180, the base station determines the desired beam configuration for the transformed signal and identifies a beam codebook entry corresponding to the desired beam configuration (e.g., by identifying a beam codebook index that maps to the corresponding beam configuration or phase vector entry).

[0046] In some aspects, the phase-sweeping codebook indicates a pattern of surface configurations and / or beam configurations, such as the surface configurations and / or beam configurations indicated by the surface configuration codebook 408 and the beam configurations specified by the beam codebook. For example, the phase-sweeping codebook indicates the order of repeated surface configurations. Alternatively or additionally, the phase-sweeping codebook indicates the duration for applying each surface configuration. The surface configuration information stored in the codebook may correspond to a complete configuration, specifying an exact configuration (e.g., configure with this value), or a delta configuration, specifying a relative configuration (e.g., modify the current state with this value). In one or more embodiments, the phase configuration information specifies a phase shift and / or phase adjustment between the incident signal and the transformed signal. For example, phase configuration 0 may specify a phase shift configuration of the configurable surface element 404, such that the element 404 transforms the incident waveform with a relative phase shift of "phase configuration 0."

[0047] In environment 400, base station 120 communicates an indication 410 specifying a surface configuration to APD 180. For example, the indication 410 specifies an index (e.g., index 410) that maps to a corresponding surface configuration, phase vector, or beam sweeping pattern according to one or more aspects. In response to receiving the indication, APD manager 320 uses the index to retrieve the surface configuration, phase vector, or beam sweeping pattern from a corresponding codebook (e.g., surface configuration codebook 408) and applies the surface configuration(s) to the RIS (e.g., configures each configurable surface element according to the configuration and / or timing specified by the codebook).

[0048] In various embodiments, the base station 120 communicates timing information (not shown) to the APD 180, which may be included with the surface configuration or beam sweeping index. For example, a start time for application of the indicated surface configuration or beam sweeping pattern. In some aspects, the base station 120 communicates a stop time indicating when to remove and / or change the surface configuration or beam sweeping pattern. Alternatively or additionally, the base station 120 communicates an APD timing adjustment (e.g., timing advance, timing delay) indicating the relative adjustment to make. In some cases, the timing information for the surface configuration or beam sweeping pattern includes a period at which one or more different surface configurations are applied to one of the configurable surface elements of the APD 180. When changing the surface configuration, the APD 180, via the APD manager 320, may apply a default surface configuration, revert to a previous surface configuration (e.g., a surface configuration used before the indicated surface configuration), and / or apply a new surface configuration to control the direction in which the APD 180 reflects wireless signals. To maintain synchronized timing between the base station 120, the APD 180, and / or the UE 110 (e.g., with respect to incident radio signals for beam sweeping and / or MIMO transmission), the APD 180 may receive and / or process synchronization signals from the base station or the network (e.g., primary synchronization signals (PSS) or secondary synchronization signals (SSS) for SSB).

[0049] By specifying the timing information, the base station 120 can synchronize and / or configure the APD 180 for use in a channel sounding process, a channel state information (CSI) process, and / or a MIMO transmission (e.g., a coordinated uplink or downlink transmission) with one or more UEs 110 in accordance with various aspects of MIMO transmission using the APD. In some embodiments, the base station 120 configures one or more APDs 180 with respective surface configurations and timing information (e.g., start times, stop times, and / or timing advance / delay for time slots assigned to particular UE(s)) corresponding to MIMO transmissions to or from the UEs. In some aspects, the base station 120 transmits the surface configuration indication and / or timing information using the APD fast control channel, which allows the base station 120 to dynamically configure the APD 180 on a slot-by-slot basis. For example, the base station 120 transmits a surface configuration schedule to the APD indicating when to apply different surface configurations to the RIS / configurable surface elements to support scheduled MIMO transmissions. Alternatively or additionally, base station 120 communicates surface configuration changes on a slot-by-slot basis using signaling on the APD fast control channel. These timing and control aspects allow the base station to configure the APD to support MIMO transmissions for one or more UEs, for example, in scenarios where different UEs are assigned the same time slot or frequency resources, or to configure the APD to enable SU-MIMO transmissions for one UE, or to configure the APD to enable MU-MIMO transmissions for multiple UEs. This can improve the data rate, spectral efficiency, data throughput, or reliability of multiple UEs and the corresponding wireless network.

[0050] MIMO Transmission Using Adaptive Phase-Change Devices To facilitate MIMO transmission at higher frequencies (e.g., 6 GHz or higher), the base station 120 may use one or more APDs 180 to mitigate LoS conditions or obstructions that impair communication between the base station 120 and one or more UEs 110. Before communicating over APD-enabled communication paths, the base station 120 or the MIMO function 268 may characterize the communication channel for at least one APD-enabled communication path and configure phase vectors and timing adjustments for each of the APD(s) 180 based on the results of this channel characterization. Alternatively or additionally, the base station 120 (or the MIMO function 268) may select one or more of the APDs 180 and / or one or more of the UEs 110 for MIMO transmission based on the results of the channel characterization (e.g., measurement reports). To do so, the base station 120 may perform a downlink channel state information (CSI) process or may have the UEs 110 perform an uplink sounding reference signal (SRS) process over the channel or communication path that includes each APD 180. Typically, base station 120 can associate (e.g., synchronize) each resource of an uplink SRS process or downlink CSI process with a phase vector implementation by APD(s) to direct reflections of the uplink sounding signal or downlink CSI signal to the receiving entity. By doing so, base station 120 can select a phase vector and / or timing adjustment for APD 180 to use when reflecting subsequent MIMO transmissions between the base station and one or more UEs based on signal quality parameters of the reflections received by the base station or UE. Alternatively or additionally, base station 120 can use information from the channel characterization process to select or group combinations of APDs and / or UEs for various downlink or uplink SU-MIMO or MU-MIMO transmissions.

[0051] 5A-9 illustrate various examples of a base station communicating with one or more UEs using respective APDs in accordance with one or more aspects of MIMO transmission using APDs. The examples illustrated in FIGS. 5A and 5B include using the APDs to reflect downlink reference signals toward each UE as part of a downlink channel characterization process (e.g., a CSI procedure) or to reflect respective uplink reference signals toward the base station as part of an uplink channel characterization process (e.g., an SRS procedure). Based on the results of the channel characterization process, the base station may select and configure different combinations of APDs and UEs to implement various scenarios of MIMO transmission using APDs in accordance with one or more aspects. As described with reference to FIG. 6, a base station may implement MU-MIMO transmission with multiple UEs using multiple respective APDs. Alternatively, a base station may implement SU-MIMO transmission with a single UE using multiple APDs as described with reference to FIG. 7. Other examples include a base station using respective panel partitions of a single APD to perform MU-MIMO transmission with multiple UEs, as described with reference to FIG. 8, or a base station using multiple panel partitions of an APD to perform SU-MIMO transmission with a single UE, as described with reference to FIG. 9.

[0052] The aspects described with respect to one example may be combined with other examples, the transactions of FIGS. 10 and 11, or the method of FIG. 12 to operate MIMO transmissions using APDs in various ways or scenarios. For example, the base station or MIMO function 268 may configure the UE and APD to perform beam sweeping of respective patterns of beams and reflections of uplink reference signals and generate channel measurements that enable selection of a combination of UE beam / steering vectors, APD phase vectors, or respective timing adjustments to use for uplink MIMO transmissions. Alternatively, the base station may configure the APD to perform beam sweeping of respective patterns of reflections of downlink reference signals and generate channel measurements that enable selection of a combination of BS beam / steering vectors, APD phase vectors, or respective timing adjustments to use for downlink MIMO transmissions. In an aspect, the base station may apply the reciprocity principle to use results from downlink channel characterization or MIMO transmissions to select APD and UE configurations to operate MIMO transmissions and vice versa. Therefore, if the reciprocity principle can be applied to previously obtained channel measurements or communication path data for the reverse link direction, a two-way channel characterization process may be performed for each downlink or uplink MIMO transmission as needed.

[0053] 5A and 5B illustrate example channel characterization processes that a base station or MIMO function 268 can implement in accordance with one or more aspects of MIMO transmission using APDs. In some aspects, a base station may perform various operations, configurations, or channel measurements described with respect to the examples of FIG. 5A or 5B to perform a channel characterization process (e.g., an APD-enabled CSI or SRS procedure) useful for enabling MIMO transmission using APDs. While illustrated in the context of two APDs 180 and two UEs 110, the described embodiments may apply to any suitable communication scenario, which may include multiple UEs and a single APD, a single UE and multiple APDs, multiple UEs and multiple APDs, and / or involve transitions between the described configurations or scenarios based on the results of the process or measurements. That is, the base station may implement MIMO transmissions adaptively to dynamic channel conditions or UE movement by reselecting or regrouping APDs and / or UEs.

[0054] FIG. 5A illustrates, at 500, an example of a base station performing a downlink channel characterization process that can be used to implement various aspects of MIMO transmission using APDs. The downlink (DL) channel characterization process may include a CSI-RS process. The CSI-RS process provides the base station with information useful for calculating DL MIMO transmission configurations (e.g., phase vectors and timing adjustments) or for calculating mutual information and / or timing information for uplink (UL) MIMO transmissions. Generally, example 500 involves base station 120 using APDs 181 and 182 to steer, steer, or sweep a reflected beam of each DL wireless reference signal transmitted by base station 120 toward UEs 111 and / or 112. The described DL channel characterization process may be performed simultaneously with each APD and reference signal-receiving UE, or sequentially with the APD and one or more reference signal-receiving UEs. In an aspect, the base station may perform the DL channel characterization process to enable MU-MIMO transmission with multiple UEs or SU-MIMO transmission with a single UE.

[0055] 5A , base station 120 can use APDs 181 and 182 to reflect beams of downlink wireless signals (e.g., signals above 6 GHz) around obstacles 171 or 172 that obstruct the LoS communication path between the base station and UEs 111 and 112. Note that UEs 111 and 112 may be located at different distances from base station 120, with UE 111 being located further away than UE 112. In this example, UE 112 is located closer to the base station than UE 111 (e.g., three-quarters the distance of UE 111), but does not have an LoS communication path. In this manner, the lengths of the respective LoS and non-LoS communication paths between the base station and each UE are different, resulting in different propagation delays (e.g., one-way or round-trip) through the channel for each communication path. In an aspect, the base station 120 or the MIMO function 268 may calculate respective timing adjustments (e.g., in addition to the timing advance (TA)) for the base station originating downlink (e.g., DL MIMO transmission), the phase vector of the APD 180 (e.g., reflection of a DL or UL MIMO transmission), and / or the UE originating uplink 110 (e.g., UL MIMO transmission) to account for these different or varying propagation delays so that the MIMO transmission reaches the receiving device (e.g., a base station or a UE in SU-MIMO mode) within a sufficient amount of time (e.g., cyclic prefix) to allow decoding of the received MIMO transmission signal.

[0056] In some aspects, the base station 120 may determine to use an APD or establish an APD-enabled communication path to communicate with a respective UE in response to detecting an obstacle or deteriorating channel conditions in a communication path (e.g., a LoS or non-LoS path). For example, the base station may detect an obstacle or impaired channel condition when the link signal quality or signal strength of a received UE-originated transmission signal is below a threshold. These conditions may result from UE movement, APD movement, movement of temporary obstacles (e.g., foliage or vehicles), atmospheric changes (e.g., fog, rain, or water vapor), etc. In some cases, the base station may determine to add an APD-enabled communication path in response to a data rate or throughput with the UE dropping below a threshold. In doing so, the base station can alleviate such communication issues by enabling MIMO transmission utilizing the APD-enabled communication path to improve communication performance.

[0057] As part of the downlink or uplink channel characterization process, the base station 120 may select one or more APDs 180 (e.g., candidate APDs) to evaluate for use in a communication path or to establish an APD-enabled communication path with the UE 110. Typically, the base station 120 (e.g., a terrestrial or non-terrestrial base station or radio head) is in a known location from which the base station 120 manages or coordinates the respective channel characterization processes or MIMO transmissions of various entities. In many cases, the APD 180 is also in a known location, which may include the location of the APD 180 (e.g., relative to the base station 120) and the orientation of the APD 180's face. For example, the APD 180 may be in a fixed location, which is set at installation or determined by the APD 180's position sensor 308 (GNSS receiver). In some aspects, the base station 120 or the MIMO function 268 obtains location and / or orientation information from the APD 180 via an APD control channel (e.g., APD control channel 511, APD control channel 512). The APD control channel may include an APD slow control channel or an APD fast control channel implemented over wireless link 133 or wireless link 134. In this example, the APD control channel is implemented as separate APD control channels 511 and 512 between base station 120 and APDs 181 and 182. Although shown as separate APD control channels, base station 120 may communicate with both APDs 181 and 182 using the same wide beam communication or different narrow beam communication. Alternatively or additionally, base station 120 may query a server for location information and / or capabilities of APDs 180 proximate base station 120 or UE 110, such as by contacting a server included in core network 150 of FIG. 1 .

[0058] Based on the location information of one or more APDs 180, the base station 120 can select an APD 180 to use for MIMO transmission with the UE 110. For example, the base station 120 can select an APD 180 that is near the UE 110 (e.g., the estimated location of the UE), select an APD 180 that is located near a LoS communication path between the base station and the UE, or select an APD 180 that is likely to provide an APD-compatible communication path between the base station and the UE (e.g., based on historical records or recent APD activity). Alternatively or additionally, the base station 120 can estimate or receive the location of the UE 110 via a low-bandwidth connection 521 or a low-bandwidth connection 522 (e.g., GNSS UE location signaling or base station-UE low-bandwidth signaling), etc. In an aspect, the base station 120 can select and / or configure an APD 180 to participate in the channel characterization process and / or MIMO transmission based on the location (e.g., location and orientation) of the APD 180 and / or the estimated location of the UE.

[0059] In example 500, base station 120 selects APDs 181 and 182 to use for communications with UEs 111 and 112 based on the APDs' respective proximity to the UEs. To perform downlink channel characterization of a communication path including APDs 181 and 182, base station 120 can associate or bind resources of a downlink CSI process or synchronization process (e.g., a particular beam) with one or more corresponding phase vectors and downlink reference signal identifiers of APD 180. These identifiers (IDs) may include a BS modulation signal ID or an APD modulation reflection ID, which result in an indexed CSI downlink reference signal and / or its reflection. For example, base station 120 can determine the CSI process of a particular APD by associating parameters of a CSI-RS with the corresponding configuration settings of the APD. In an aspect, the CSI process determined by the base station may include the antenna port, the precoding matrix, the beam identifier (beam ID), the BS modulated signal ID of the CSI-RS bound or associated with the APD index (APD ID), and the phase vector of the APD (e.g., of the beam sweeping pattern) on which the CSI process is performed. In some cases, the base station can associate, assign, or map the surface configuration of the APD to the surface configuration or respective APD phase vector of the beam sweeping pattern performed by the APD during the channel characterization process.

[0060] Alternatively or additionally, the APD may modulate the reference signal reflection with an identifier associated with the reference signal index, the air interface resource of the reference signal, or the APD phase vector to enable analysis of the reflection by the receiving device. In such a case, the phase vector of the beam-sweeping pattern may be associated with or mapped to the APD-modulated reflection identifier. In this manner, the UE 110 can identify and measure signal quality parameters for the LoS downlink reference signal or reflection (e.g., reflection 552 or reflection 554) arriving at the UE, which ultimately provides information (e.g., CSI) to the base station via a downlink (DL) signal report (e.g., DL signal report 561 or 562) for analysis of the downlink beam (e.g., downlink beam 541 or 542) and APD vector. Based on analysis of the signal report, the base station can determine which combination of downlink beam(s), timing information, and / or APD vector(s) enables a communication path for MIMO transmission between the base station and one or more UEs.

[0061] In example 500, base station 120 determines each CSI process for APDs 181 and 182 by associating a respective identifier, resource, or parameter of the CSI-RS with a phase vector or respective surface configuration of a beam-sweeping pattern selected for each of the APDs. The base station may select a surface configuration, phase vector, or beam-sweeping pattern based on the location of the APD relative to the base station and an estimated location of UE 110 (e.g., UE 111 or UE 112). Base station 120 then transmits respective beam-sweeping indexes 531 and 532 to APDs 181 and 182 via APD control channel 511 and APD control channel 512 (e.g., separate low-bandwidth control channels). Base station 120 may also transmit timing information to APDs 181 and / or 182 to implement the phase vector of the beam-sweeping pattern in synchronization with a downlink reference signal. To implement the CSI process, with respect to APD 181, base station 120 causes the APD to apply a phase vector of a beam sweeping pattern while the base station transmits downlink beam 541 of the CSI-RS toward RIS 322 of APD 181. This causes reflected beams 551, 552, and 553 from APD 181 toward UE 111 to sweep, and some of the beams may reach UE 112. Base station 120 may perform a similar operation for APD 182. Such an operation includes transmitting downlink beam 542 toward RIS 322 of APD 182, while the APD implements the phase vector of its beam sweeping pattern to direct reflected beams 554, 555, and 556 toward UE 112, and some of the beams may reach UE 111. Thus, in some cases, UE 111 may receive APD reflected signals from multiple APDs. In the context of FIG. 5A, such signals may include reflected beams 554 or 555 from APD 182, as well as reflected beams 552 and 551.

[0062] Based on various combinations of downlink beams 541, 542 and phase vectors implemented by the respective APDs during the CSI process, UEs 111 and 112 may receive one or more reflections of the downlink reference signal from either or both APDs. For example, UE 111 may receive reflections from APD 181 as part of a first CSI process and reflections from APD 182 as part of a second CSI process. The second CSI process may be performed simultaneously or sequentially with respect to the first process. Typically, UE 110 can generate a downlink signal report (e.g., DL signal report 561 or 562) based on received reflections of the reference signal from one or more APDs. The received reflections of the reference signal enable base station 120 to identify and / or analyze channel state information corresponding to each combination of downlink beam and APD phase vector that results in a reflection reaching the UE. The downlink signal report may include signal or link quality measurements for signals received by the UE. Such signals may include directly received downlink signals or reflections of downlink signals. For example, the UE may decode an identifier of a received reflection or collect information (e.g., antenna port, precoding matrix, air interface resource) useful to the base station to identify the CSI index (e.g., DL beam and / or APD phase vector) of the reflection reaching the UE. Furthermore, the downlink signal report may include timing information (e.g., arrival time) useful for determining the propagation delay between the base station and the UE or the respective intervals of the propagation delay between the base station and the APD (BS-APD propagation delay) and the propagation delay between the APD and the UE (APD-UE propagation delay).

[0063] In an aspect, one or more of UEs 110 provide DL signal reports to the base station via low-band connection 521 or low-band connection 522. The DL signal reports indicate at least one CSI-RS index (e.g., highest Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), Signal-to-Noise Ratio (SNR), Signal-to-Interference-Plus-Noise Ratio (SINR), or CSI-RS index prioritized by signal strength / quality). Based on the DL signal reports, the base station can determine the respective APD IDs and phase vectors for reflections reaching the UEs. As a result of this embodiment, UE 111 and UE 112 generate DL signal reports 561 and 562 for reflections of downlink reference signals received from APD 181 and / or APD 182 as part of their respective CSI processes. UE 111 then transmits DL signal report 561 to the base station via low-band connection 521, and UE 112 transmits DL signal report 562 to the base station via low-band connection 522. In some embodiments, DL signal report 561 and / or 562 includes a respective CSI-RS index and signal quality measurement for one or more reflections received by one of UEs 110 from APD 181 and / or APD 182. Based on the results of the downlink channel characterization or CSI process, base station 120 can analyze the signal report to determine respective MIMO transmission configurations for the base station, one or more APDs, and / or one or more UEs, examples of which are described with respect to the transactions of FIGS. 6-9, 10 and 11, or the method of FIG. 12.

[0064] FIG. 5B shows, at 501, an example of a base station performing an uplink channel characterization process that can be used to implement various aspects of MIMO transmission using APDs. The uplink (UL) channel characterization process may include an SRS process. The SRS process provides the base station with information useful for calculating UL MIMO transmission configurations (e.g., phase vectors and timing adjustments) or for calculating reciprocal configurations for downlink (DL) MIMO transmissions. Generally, example 501 involves base station 120 using APDs 181 and 182 to steer, steer, or sweep the beam of each UL wireless reference signal transmitted by UE 111 and / or 112. Note that because the spatial orientation of UE 110 relative to the APD or base station is unknown, the UE may perform multiple iterations from wide uplink beam sweeping to narrow uplink beam sweeping to refine transmissions directed to the APD. The described UL channel characterization process may be performed simultaneously with each APD and reference signal transmitting UE, or sequentially with the APD and one or more reference signal transmitting UEs. The base station may perform an UL channel characterization process to enable MU-MIMO transmission with multiple UEs or SU-MIMO transmission with a single UE. For simplicity of explanation, the entities in Figure 5B may perform aspects of positioning, communication, and uplink channel characterization similar to or interrelated with the aspects of positioning (e.g., distance, propagation delay, obstacles, APD selection, etc.), communication, and downlink channel characterization described with reference to Figure 5A.

[0065] In some aspects, uplink operation may utilize downlink characterization or performance measurements, or may perform an uplink channel characterization process to use directional SRS to find feasible uplink APDs and respective APD configurations (e.g., phase vectors) for MIMO transmissions. Furthermore, base station 120 may determine uplink timing advance information. The uplink timing advance information includes timing advance commands or parameters that may account for different propagation distances via different APD-enabled communication paths. In some cases, the timing information determined by the base station includes a first timing advance (TA) value for the UE to apply to an initial UL transmission, and a second timing advance value for the APD to apply when applying a phase vector to reflect the UL transmission so that respective reflections of UL signals from different UEs (or the same UE in SU mode) arrive at the base station simultaneously (e.g., within one cyclic prefix) for proper MU-MIMO reception by the base station.

[0066] In the context of example 501, base station 120 selects APDs 181 and 182 as candidate APDs to use for communications with UEs 111 and 112 based on historical records indicating the APDs' respective proximity to the UEs or viable APD-enabled communication paths provided by APDs 181 and 182. To enable uplink channel characterization of a communication path including APDs 181 and 182, base station 120 can associate or bind resources of an uplink SRS process performed by the UE (e.g., SRS parameters 571, 572) to corresponding one or more phase vectors and uplink reference signal identifiers (e.g., signal identifiers or reflection identifiers) of one or more APDs 180. This can result in indexed SRS uplink reference signals and / or their reflections that are useful for selecting or configuring an APD for MIMO transmission. For example, base station 120 determines an SRS process for a particular APD by associating the SRS parameters with the APD's configuration settings (e.g., phase vectors and beam sweeping timing parameters). In some aspects, the SRS process determined by the base station may include the antenna port, precoding matrix, beam identifier (beam ID), UE modulation signal ID of the SRS bound or associated with the APD index (APD ID), and / or phase vector of the APD (e.g., of the beam sweeping index) by which the SRS process is performed. In some cases, the base station may associate, assign, or map the surface configuration of the APD to each APD phase vector or surface configuration implemented by the APD during the channel characterization process. By doing so, the base station can select a surface configuration for MIMO transmission based on the APD phase vector surface configuration that results in the highest uplink signal metric (e.g., RSRP, SNR) during the channel characterization process.

[0067] Alternatively or additionally, the APD may modulate the reflection of the reference signal with an identifier associated with the reference signal or APD phase vector to enable analysis of the reflection by the receiving device. In such a case, the phase vector of the beam-sweeping pattern may be associated with or mapped to the APD-modulated reflection identifier. By doing so, the BS 120 can identify and measure signal quality parameters for the reflection or LoS uplink reference signal reaching the base station to provide uplink signal metrics (e.g., uplink signal reports) for the uplink channel characterization process. Based on analysis of the uplink signal metrics or reports, the base station can determine which combination of uplink beam(s) 580, timing information, and / or APD vectors enables a communication path for MIMO transmission between the base station and one or more UEs.

[0068] In example 501, base station 120 determines respective SRS processes for APDs 181 and 182 by associating respective identifiers, resources, or parameters of the SRS with the phase vector of a beam-sweeping pattern selected for the APD or respective surface configurations. To configure UEs 111 and 112 for the SRS processes, base station 120 transmits SRS parameters 571 to UE 111 using low-bandwidth connection 521 and SRS parameters 572 to UE 112 using low-bandwidth connection 522. The base station may select the surface configuration, phase vector, or beam-sweeping pattern based on the location of the APD relative to the base station and the estimated location of each one of UE 111 or UE 112. Base station 120 then transmits respective beam-sweeping indexes 533 and 534 to APDs 181 and 182 via APD control channels 511 and 512 (e.g., separate low-bandwidth control channels). Base station 120 may also transmit timing information to APDs 181 and / or 182 to implement the phase vectors of the beam sweeping pattern in synchronization with the transmission of SRS by UEs 111 and 112.

[0069] To perform the SRS process, with respect to APD 181, base station 120 applies a phase vector of a beam sweeping pattern to the APD, while UE 111 transmits uplink beams 581, 582, 583, and 584 of the SRS according to SRS parameters 571. Uplink beam 584 reaches RIS 322 of APD 181. This sweeps reflected beams 591, 592, and 593 from APD 181 toward the base station. Note that uplink beam 583 may also reach APD 182, which may further achieve a simultaneous beam sweeping pattern, with similarly swept reflected beams shown as beams 594, 595, and 596. Thus, reflections of the SRS transmitted by UE 111 may reach the base station from one or both of APDs 181 and 182, allowing the base station to configure multiple APD-enabled communication paths to the UE. Base station 120 may perform a similar operation for APD 182. A similar operation involves having UE 112 transmit uplink beams 585, 586, 587, and 588, with uplink beam 587 reaching RIS 322 of APD 182. Meanwhile, the APD implements the phase vector of its beam-sweeping pattern, which directs reflected beams 594, 595, and 596 toward the base station for reception and subsequent measurement, which can provide uplink signal metrics. Similar to the SRS process of UE 111, the uplink beam of UE 112 can reach APD 181, resulting in another reflection of the uplink beam (e.g., UL from UE 112 to APD 181 for base station 120) that can reach the base station, allowing the base station to configure multiple APD-enabled communication paths to UE 112.

[0070] In some aspects, a base station may associate SRSs from different UEs (e.g., 111, 112) with corresponding APD indices (or APD identifiers). For example, base station 120 may instruct UEs 111 and 112 to sweep their respective SRS signals to detect which APD (having the corresponding index) results in the highest SNR or RSRP upon reception by the base station. The base station may then associate the received SRSs with the respective particular APD index or identifier that results in the highest SNR or RSRP (e.g., UE 111's SRS has the highest SNR reflected from APD 181). Based on the association of SRS measurements with APD indices, the base station can schedule the two UEs with different APDs having associated indices for MU-MIMO.

[0071] Typically, base station 120 may receive one or more reflections of an uplink reference signal from either or both APDs based on various combinations of phase vectors and uplink beams (e.g., 583, 584, 587, and 588) implemented by each APD during an SRS process. For example, the base station may receive a reflection (e.g., uplink beam 583) from APD 181 as part of a first SRS process with UE 111 and a reflection (e.g., uplink beam 588) from APD 182 as part of a second SRS process with UE 112. The second SRS process may be performed simultaneously or sequentially with respect to the first process. Typically, base station 120 may generate an uplink signal report (not shown) based on received reflections of the reference signal from one or more APDs. The received reflections of the reference signal enable base station 120 to identify and / or analyze channel state information for the APD phase vector and uplink beam combination that results in the reflection reaching the base station. The uplink signal report may include signal or link quality measurements for signals received by the base station, which may include directly received uplink signals or reflections of uplink signals. For example, the base station may decode an identifier for the received reflection or may have access to information (e.g., antenna port, precoding matrix, air interface resource) useful to the base station to identify the SRS index (e.g., UL beam and / or APD phase vector) of the reflection reaching the base station. Additionally, the uplink signal report may include timing information (e.g., time of arrival). The timing information may be useful for determining the propagation delay between the UE and the base station, or for determining the respective intervals of the propagation delay between the UE and the APD and between the APD and the base station.

[0072] In some aspects, the base station determines an UL signal report indicating at least one SRS index (e.g., highest RSRP, prioritized by signal strength). This allows the base station to determine the APD ID and phase vector for each reflection arriving at the base station. As a result of this embodiment, the base station 120 generates an UL signal report (not shown) for reflections of uplink reference signals received from the APD 181 and / or the APD 182 as part of the respective SRS processes performed by the UE 111 and the UE 112. In some embodiments, the UL signal report includes a respective SRS index and signal quality measurements for one or more reflections received by the base station from the APD 181 and / or the APD 182. Based on the results of the uplink channel characterization, the base station 120 can analyze the signal report to determine respective MIMO transmission configurations for the base station, one or more APDs, and / or one or more UEs. Examples of this are described with respect to the transactions of FIGS. 6-9, 10 and 11, or the method of FIG. 12.

[0073] 6-9 illustrate various examples of base stations communicating with one or more UEs using respective APDs in accordance with various aspects of MIMO transmission using APDs. Base station 120 may implement aspects of the described examples based on the results of one or more channel characterization processes, or may apply reciprocity principles to use results from a channel characterization process to communicate in the reverse link direction (e.g., using uplink results to implement downlink aspects in a TDD scheme or in a nearby or adjacent FDD band). Generally, the examples of FIGS. 6-9 may include selecting and grouping APD and UE combinations for MIMO transmission, determining respective MIMO configurations for the APDs and UEs, transmitting various parameters of the MIMO configurations to the APDs and UEs, and implementing MIMO transmission via communication paths enabled by the configured APDs and UEs. These non-limiting examples include implementing MU-MIMO transmission with multiple UEs using respective APDs (FIG. 6), implementing SU-MIMO transmission with a single UE and multiple APDs (FIG. 7), implementing MIMO transmission with multiple UEs using respective panel partitions of a single APD (e.g., FIG. 8), and implementing SU-MIMO transmission with a single UE using multiple panel partitions of an APD (e.g., FIG. 9). Aspects described with respect to one example may be combined with other examples, the transactions of FIGS. 10 and 11, or the method of FIG. 12 to implement MIMO transmission operations using APDs in various ways or scenarios.

[0074] In various aspects, the base station 120 uses results from the channel characterization process to select, group, and / or schedule one or more UEs and one or more APDs for MU-MIMO or SU-MIMO transmissions. With reference to FIGS. 5A, 5B, or 6-9, a UE (e.g., UE 111, UE 112) may feedback at least one CSI-RS index (e.g., highest signal strength or prioritized by signal strength) to the base station 120, which indicates an APD index (or identifier) ​​and phase vector. Alternatively, the base station may receive each SRS from the UE along with an indication useful for identifying the APD index and phase vector that cause a reflection of the SRS to reach the base station. In an aspect, the base station may use the CSI feedback (or SRS measurements) to determine the APD and phase vector that enable a communication path for MIMO transmission with the APD. For example, UE 111 may feed back its top three CSI-RS indices as APD 181 of phase vector 1, APD 181 of phase vector 2, and APD 182 of phase vector 3. Similarly, UE 112 may feed back its top CSI-RS indices as APD 182 of phase vector 4. Based on these channel characterization results (or similar SRS measurements), base station 120 may select APD 181 of phase vector 1 for UE 111 and APD 182 of phase vector 4 for UE 112 and implement MU-MIMO accordingly (e.g., FIG. 6). Otherwise, if only one UE is present or the base station fails to receive feedback from a second UE (or receives SRS from one UE), the base station may select to implement SU-MIMO with UE 111 using APD 181 of phase vector 1 and APD 182 of phase vector 3 (e.g., FIG. 7).

[0075] Alternatively or additionally, the base station can associate a UE in MU-MIMO scheduling where the CSI process selected by the UE corresponds to a specific APD index. For example, UE 111 may receive CSI-RS signals reflected from both APDs 181 and 182 and report back to the base station the CSI-RS index (e.g., the index of the CSI-RS and associated APD) corresponding to the APD where the CSI-RS signal is received with better signal strength. Base station 120 may then pair or group UEs together for MU-MIMO scheduling based on the respective CSI feedback provided by the UEs corresponding to different APD indexes. If a UE receives CSI-RS signals from the base station via multiple APDs, the base station may schedule the UE for SU-MIMO. To facilitate MIMO transmission, the base station may determine the APD and / or a MIMO transmission configuration for the UE. The base station may transmit parameters of the MIMO transmission configuration to the APD or UE via the APD control channel and low-bandwidth connection, respectively. When configured according to the determined MIMO transmission configuration, the base station may then perform downlink or uplink MIMO transmission as described herein. These and other examples of APD-enabled MIMO transmission are described with respect to the examples of FIGS. 6-9, the transactions of FIGS. 10 and 11, and the method of FIG. 12.

[0076] FIG. 6 illustrates, at 600, an example of using multiple APDs for MU-MIMO transmission with multiple UEs in accordance with one or more aspects. The environment of example 600 includes base station 120, APD 181, APD 182, UE 111, and UE 112 of FIG. 1, which may communicate as described with reference to FIGS. 1-5B. As shown in FIG. 6, in a manner similar to that described with respect to wireless link 130 of FIG. 1, base station 120 may communicate with UE 111 using a high-band connection 621 (e.g., above 6 GHz) including RIS 322 of APD 181 and / or a low-band connection 521 (e.g., below 6 GHz, sub-6 GHz). The base station may also communicate with UE 112 using a high-band connection 622 and / or a low-band connection 522 including RIS 322 of APD 182. In this example, base station 120 may conduct downlink and / or uplink MU-MIMO transmission with UE 111 and UE 112 via the high-band connections 621 and 622. In an aspect, the base station may determine to use an APD-enabled communication path or implement MIMO transmission using APDs in response to a failed attempt to establish high-bandwidth communication over the LoS communication path, or may analyze signal and / or link quality measurements to detect channel impairments or detect that the signal and / or link quality measurements are trending below an acceptable performance level. To configure and operate the application of downlink or uplink phase vectors, the base station may communicate with multiple APDs 180 using a wide-beam, low-band APD control channel or with multiple APDs 180 using respective narrow-beam or wired APD control channels 511 and 512.

[0077] To enable the MU-MIMO transmission shown in FIG. 6, base station 120 may select a group of candidate APDs 180 including APDs 181 and 182 and perform a channel characterization process, such as described with reference to FIGs. 5A, 5B, 10, 11, and / or 12, to obtain uplink or downlink signal reports (e.g., signaling metrics). Based on the uplink and / or downlink signal reports, base station 120 selects multiple UEs for performing MIMO transmission. Here, assume that the CSI-RS index provided by UE 111 indicates that phase vector 7 of APD 181 provided the highest RSRP value, and the CSI-RS index provided by UE 112 indicates that phase vector 24 of APD 182 provided the highest SNR value. Therefore, base station 120 pairs UE 111 with APD 181 and UE 112 with APD 182 to schedule MU-MIMO transmission over the respective communication paths shown in FIG. 6.

[0078] In an aspect, the base station 120 or the MIMO function 268 determines a selected APD and / or MIMO transmission configuration for the UE based on a channel characterization process. The base station may determine or generate a MIMO transmission configuration including one or more of a transmit beam configuration (e.g., beam ID or precoding matrix), an APD surface configuration, an APD timing advance, a UE timing advance, etc. For example, the base station may analyze signal or link quality measurements in uplink or downlink signal reports generated by the channel characterization process. Based on the analysis, the base station may select a respective surface configuration of the APD, which may include an APD phase vector that results in the highest signal power or highest signal quality value at the base station (e.g., SRS) or UE (e.g., CSI-RS). The base station may generate separate MIMO transmission configurations for downlink and uplink transmissions, or may generate a composite MIMO transmission configuration including parameters that enable MIMO transmission in either link direction.

[0079] In some implementations, as part of the channel characterization process, the base station may assign a respective MIMO transmission configuration to each surface configuration included in the beam-sweeping pattern of the APD. To configure the APD, the base station can then identify the MIMO transmission configuration for the MIMO transmission based on the channel characterization process and the assigned APD phase vector that results in the highest or strongest signal metric for reflections reaching the UE or base station during channel characterization. Alternatively or additionally, the base station can determine a respective timing advance value for application of the APD or phase vector by the UE's uplink transmission based on the respective positions of the APD and UE and the subframe or slot timing of a shared physical channel (e.g., a physical downlink shared channel (PDSCH) or a physical uplink shared channel (PUSCH)) for scheduling the MIMO transmission. By doing so, the base station 120 can adjust the arrival of the MIMO transmission at the receiver within a sufficient amount of time (e.g., cyclic prefix) to allow for decoding of the received transmitted signal, taking into account different amounts of propagation delay (or distance) over the APD-enabled communication path.

[0080] Returning to FIG. 6 , base station 120 identifies a MIMO transmission configuration, including surface configurations of APDs 181 and 182, for downlink transmissions to UE 111 and UE 112 based on the results of a channel characterization process. In this example, the base station determines a surface configuration 611 for APD 181 and a surface configuration 612 for APD 182. Based on the results of the aforementioned channel characterization process, surface configuration 611 may include an indication of phase vector 7 for APD 181 and an APD timing advance (TA) value based on the propagation delay between the base station and APD 181. Surface configuration 612 may include an indication of phase vector 24 for APD 182 and another APD TA value based on the propagation delay between the base station and APD 182. In some cases, the APD surface configuration may further include a reference or indication to a slot or subframe of a physical shared channel for scheduling MIMO transmissions by the base station. 6 is not drawn to scale, and APD 181 may be located much farther from the base station than APD 182. Thus, the APD TA value of APD 181 may be much larger than the APD TA value of APD 182 or other APDs 180 near the base station.

[0081] Alternatively or additionally, the base station can identify a MIMO transmission configuration for UE uplink transmission, which may include a surface configuration and a UE timing advance value, based on the results of the channel characterization process. Based on the reciprocity principle, the uplink surface configurations 611 and 612 may use the same phase vector as a downlink configuration with the same timing advance value (e.g., similar path distance) or a different timing advance value (or vice versa). For example, the base station may determine the UE timing advance based on the total path length or propagation delay, and may determine the (uplink) APD timing advance based on the path length or propagation delay between the UE and the APD. Thus, a MIMO transmission configuration for a communication path may include a UE TA value and a surface configuration with an indication of the phase vector and an uplink APD TA value. As noted above, the downlink APD TA value and the uplink APD TA value may include different amounts of time, such as when the APD is not equidistant from the base station and the UE.

[0082] Continuing with the described example, base station 120 generates or updates a MIMO transmission configuration using uplink parameters for surface configuration 611 of APD 181, surface configuration 612 of APD 182, a UE TA value for UE 111, and a UE TA value for UE 112. For uplink transmission, surface configuration 611 may include an APD TA value based on an indication of phase vector 7 of APD 181 and a propagation delay between UE 111 and APD 181. Surface configuration 612 may include an indication of phase vector 24 of APD 182 and another APD TA value based on a propagation delay between UE 112 and APD 182. The base station may configure the uplink APD TA values ​​to apply each surface configuration to the APDs at a time coinciding with the arrival of an uplink transmission by the corresponding UE, resulting in a reflection of the uplink MIMO transmission to the base station. For UEs 111 and 112, the base station determines a UE TA value 631 for UE 111 based on the propagation delay between UE 111 and the base station, and determines a UE TA value 632 for UE 112 based on the propagation delay between UE 112 and the base station. The base station may configure the UE TA values ​​631 and 632 such that uplink MIMO transmissions arrive at the base station within a time window (e.g., a cyclic prefix) that allows the base station to simultaneously decode the received MIMO transmission signals.

[0083] In an aspect, base station 120 configures APD 180 and / or UE 110 for MIMO transmission by sending a surface configuration to the APD over an APD control channel (APD control channel 511 or 512) and a UE TA value to the UE over a low-band connection (e.g., low-band connection 512 or low-band connection 522). Base station 120 may send the surface configuration as a full configuration message (or command) or may send the surface configuration as a partial configuration message (or command). In some cases, a partial surface command may correspond to a subset of configuration parameters for an uplink APD MIMO setting or a different subset of configuration parameters for a downlink APD MIMO setting. Alternatively or additionally, the surface configuration sent by the base station may indicate an absolute value for a phase vector or TA setting or a delta value to be applied by the APD to a current (e.g., previously configured) phase vector or TA setting.

[0084] 6, the base station transmits a surface configuration 611 to the APD 181 using an APD control channel 511 and a UE TA value 631 (e.g., for uplink MIMO) to the UE 111 using a low-bandwidth connection 521 to enable a first communication path for MIMO transmission. The base station also transmits a surface configuration 612 to the APD 182 using an APD control channel 512 and a UE TA value 632 to the UE 112 using a low-bandwidth connection 521 to enable a second communication path for MIMO transmission. Based on the surface configurations 611 and 612, the base station 120 may cause the corresponding APDs 180 of the communication paths to implement multiple simultaneous phase vectors simultaneously or in the same time slot in accordance with various MIMO configurations described herein.

[0085] For downlink MU-MIMO transmissions, base station 120 uses the MIMO transmission configuration to coordinate the application of simultaneous phase vectors so that the respective phase vectors applied by the APDs are time-aligned with the PDSCH of the base station's downlink transmission. In some embodiments, the base station associates each APD phase vector with a downlink MU-MIMO antenna port or beam to a particular UE. As shown in FIG. 6, the base station may associate a first MU-MIMO downlink beam including signal ray 641 with phase vector 7 of APD 181, which is applied in alignment with the PDSCH of the MU-MIMO transmission (e.g., using the APD TA value). Base station 120 may also associate a second MU-MIMO downlink beam including signal ray 642 with phase vector 24 of APD 182, which is applied in alignment with the PDSCH of the MU-MIMO transmission. Based on the incident downlink signal rays 641 and 642, APD 181 directs reflected signal ray 651 of the first reflected beam toward UE 111, and APD 182 directs reflected signal ray 652 of the second reflected beam toward UE 112. Thus, base station 120 can use APDs 181 and 182 to perform downlink MU-MIMO transmissions to UEs 111 and 112 that utilize the same time and frequency resources, thereby improving the spectral efficiency of the wireless network.

[0086] When implementing uplink MU-MIMO transmission, base station 120 uses the MIMO transmission configuration to coordinate the application of simultaneous phase vectors so that the respective phase vectors applied by the APDs are time-aligned with the UE's respective PDSCHs. In some embodiments, the base station associates each APD phase vector with a respective uplink antenna port of the corresponding UE. In the context of FIG. 6, the base station may associate a first antenna port of an uplink beam including signal ray 661 with phase vector 7 of APD 181, which is applied in alignment with the PUSCH of the UE-originated MU-MIMO transmission (e.g., using the APD TA value). Base station 120 may also associate a second antenna port of an uplink beam including signal ray 662 with phase vector 24 of APD 182, which is applied in alignment with the PUSCH of the UE-originated MU-MIMO transmission.

[0087] As described herein, the base station 120 may transmit respective timing advance information to the APD to time-align the application of an APD phase vector associated with a UE with a corresponding PUSCH transmission from that UE. Accordingly, the base station may provide a TA value (if necessary) for each associated uplink phase vector associated with one of the corresponding UEs of a scheduled MU-MIMO transmission. Note that the base station 120 may transmit the APD TA value as a separate command to the APD (e.g., from a surface configuration) to control the timing of the implementation or application of the phase vector by the APD. In some cases, the APD timing advance command is separate (although related) from the timing advance command (e.g., TA value 631 or 632) that the base station transmits to the corresponding UE to adjust the UE's uplink transmission timing. Accordingly, the base station may calculate the APD TA value based on the timing advance command transmitted to the corresponding UE and / or the PUSCH timing of the corresponding UE.

[0088] Based on the incident uplink signal rays 661 and 662, APD 181 reflects signal ray 671 of the first reflected beam toward base station 120, and APD 182 reflects signal ray 672 of the second reflected beam toward base station 120. In an aspect, the base station may schedule each UE uplink transmission, configure a UE TA value, and / or configure an APD TA value to provide a reflected uplink MU-MIMO transmission that reaches the base station within an amount of time (e.g., a cyclic prefix) that allows decoding of the received MU-MIMO transmission signal. Thus, base station 120 can use APDs 181 and 182 to implement uplink MU-MIMO transmissions from UEs 111 and 112 that utilize the same time and frequency resources. This can improve the spectral efficiency of the wireless network.

[0089] FIG. 7 illustrates, at 700, an example of using multiple APDs for SU-MIMO transmission with a UE in accordance with one or more aspects. The environment of example 700 includes base station 120, APD 181, APD 182, and UE 111 of FIG. 1, which may communicate as described with reference to FIGS. 1-6. As shown in FIG. 7, base station 120 may communicate with UE 111 using a low-band connection 521 (e.g., less than 6 GHz, sub-6 GHz) in a manner similar to that described with respect to wireless link 130 of FIG. 1. In this example, base station 120 also communicates with UE 111 using a first high-band connection 721 including RIS 322 of APD 181 and a second high-band connection 722 including RIS 322 of APD 182.

[0090] Generally, the aspect of SU-MIMO transmission described with reference to FIG. 7 may be implemented similarly to the transmission with a single UE (UE 111) described with reference to FIG. 6. Here, assume that the CSI-RS index provided by UE 111 indicates that phase vector 8 and phase vector 27 of APD 181 provide the highest two RSRP values, and that no CSI-RS index has been received from another UE. Accordingly, base station 120 groups UE 111 with APD 181 and APD 182 for scheduling SU-MIMO transmission over the respective communication paths shown in FIG. 7. In this example, the base station determines a surface configuration 711 for APD 181 and a surface configuration 712 for APD 182. Based on the results of the channel characterization process described above, surface configuration 711 may include an indication of phase vector 8 of APD 181 and one or more APD TA values ​​based on the propagation delay between the base station and APD 181 or between UE 111 and APD 181. The surface configuration 712 may include an indication of the phase vector 27 of the APD 182 and one or more other APD TA values ​​based on the propagation delay between the base station and the APD 182 or between the UE 111 and the APD 182. In an aspect, the surface configuration may be implemented as a combined configuration including parameters for uplink and downlink MIMO transmissions described herein, or may be implemented as separate configurations. To configure the APD for SU-MIMO, the base station 120 transmits the surface configuration 711 to the APD 181 using the APD control channel 511 and the surface configuration 712 to the APD 182 using the APD control channel 512, as shown in FIG. 7 .

[0091] For uplink SU-MIMO transmission, the base station may determine a UE TA value 731 for the UE 111 based on the propagation delay between the UE 111 and the base station using the APD 181 and / or based on the propagation delay between the UE 111 and the base station using the APD 182. The base station may configure the UE TA value 731 so that the uplink MIMO transmission via each APD-enabled communication path arrives at the base station within a time window (e.g., a cyclic prefix) during which the base station can simultaneously decode the received SU-MIMO transmission signals. As shown in FIG. 7 , the base station transmits the UE TA value 731 (e.g., for uplink MIMO) to the UE 111 using the low bandwidth connection 521 to enable the first and second communication paths for the uplink SU-MIMO transmission. Based on the surface configurations 711 and 712, the base station 120 may cause the corresponding APDs 180 of the communication paths to implement multiple simultaneous phase vectors simultaneously or in the same time slot in accordance with various MIMO configurations described herein.

[0092] To implement downlink SU-MIMO transmission, base station 120 uses the MIMO transmission configuration to coordinate the application of simultaneous phase vectors so that each phase vector applied by the APD can be time-aligned with the PDSCH of the base station's downlink transmission. In some cases, the base station associates each APD phase vector with a downlink SU-MIMO antenna port or beam to the UE via a specific communication path. As shown in FIG. 7 , the base station may associate a first SU-MIMO downlink beam including signal ray 741 with phase vector 8 of APD 181, which is applied in alignment with the PDSCH of the SU-MIMO transmission (e.g., using the APD TA value). Base station 120 may further associate a second SU-MIMO downlink beam including signal ray 742 with phase vector 27 of APD 182, which is applied in alignment with the PDSCH of the SU-MIMO transmission. Based on the incident downlink signal rays 741 and 742, APD 181 directs reflected signal ray 751 of the first reflected beam toward UE 111, and APD 182 directs reflected signal ray 752 of the second reflected beam toward UE 111. Thus, base station 120 can use APDs 181 and 182 to perform downlink SU-MIMO transmission to UE 111 that utilizes the same time and frequency resources, thereby improving the spectral efficiency of the wireless network.

[0093] When implementing uplink SU-MIMO transmission, base station 120 uses the MIMO transmission configuration to coordinate the application of simultaneous phase vectors so that each phase vector applied by the APD is time-aligned with the UE's PDSCH. In some cases, the base station associates each APD phase vector with a respective uplink antenna port of the UE. As shown in FIG. 7 , the base station may associate a first antenna port of an uplink beam including signal ray 761 with phase vector 8 of APD 181, which is applied in alignment with the UE's PUSCH (e.g., using the APD TA value). Base station 120 may also associate a second antenna port of an uplink beam including signal ray 762 with phase vector 27 of APD 182, which is applied in alignment with the UE's PUSCH. Based on the incident uplink signal rays 761 and 762, APD 181 reflects signal ray 771 of a first reflected beam toward base station 120, and APD 182 reflects signal ray 772 of a second reflected beam toward base station 120. In an aspect, the base station may schedule UE uplink transmissions, configure a UE TA value, and / or configure an APD TA value to provide a reflected uplink SU-MIMO transmission that arrives at the base station within an amount of time (e.g., a cyclic prefix) that allows decoding of the received SU-MIMO transmission signal. Thus, base station 120 can use APDs 181 and 182 to implement uplink SU-MIMO transmissions from UE 111 that utilize the same time and frequency resources. This can improve the spectral efficiency of the wireless network.

[0094] FIG. 8 illustrates, at 800, an example of using multiple APD surface partitions for MU-MIMO transmission with multiple UEs in accordance with one or more aspects. The environment of example 800 includes base station 120, APD 181, UE 111, and UE 112 of FIG. 1, which may communicate as described with reference to FIGS. 1-7. As shown in FIG. 8, in a manner similar to that described with respect to wireless link 130 of FIG. 1, base station 120 may communicate with UE 111 using a low-band connection 521 (e.g., less than 6 GHz, sub-6 GHz) and may communicate with UE 112 using a low-band connection 522. In this example, base station 120 also communicates with UE 111 using a high-band connection 821 that includes a first partition 881 (e.g., a first RIS) of APD 181 and communicates with UE 112 using a high-band connection 822 that includes a second partition 882 (e.g., a second RIS) of APD 181.

[0095] Generally, the aspect of SU-MIMO transmission described with reference to Figure 8 may be implemented similarly to the transmission with a single APD (APD 181) described with reference to Figure 6. Here, assume that the CSI-RS index provided by UE 111 indicates that phase vector 5 of APD 181 provided the highest RSRP value, and the CSI-RS index of UE 112 indicates that phase vector 9 of APD 181 provided the highest RSRP value for the channel characterization process. In this MU-MIMO example, the CSI-RS index of each of UE 111 and UE 112 may not include measurements of the other APD, or may indicate that the CRS or SRS reflections provided by the other APD are unlikely to support MIMO transmission (e.g., low RSRP or excessive signal fading). Therefore, base station 120 pairs UE 111 with the first partition 881 of APD 181 and pairs UE 112 with the second partition 882 of APD 181 for scheduling MU-MIMO transmission over the respective communication paths shown in FIG. 8.

[0096] In some aspects, the base station 120 or the MIMO function 268 determines the APD partition and / or the MIMO transmission configuration for the UE by analyzing signal metrics of the channel characterization process described herein. The MIMO transmission configuration may include, for each APD partition, a respective phase vector, an APD partition TA value, a UE TA value, etc. Accordingly, the base station 120 can determine and / or select a surface configuration based on distributing access to the APD 180, such as panel-divided access or APD sub-panel access. As an example, the base station 120 selects the surface configuration 811 based on the panel division (e.g., allocation of configurable surface elements), and thus, the base station contemporaneously and / or simultaneously sends respective MIMO transmission signals to each receiving UE using APD partitions 881 and 882, as shown in example 800.

[0097] For example, base station 120 may distribute the configurable surface elements of APD 181 into subsets of configurable surface elements, such as a horizontal partition that groups a first subset of configurable surface elements (of the RIS) in the same horizontal row (e.g., APD partitions 881 and 882), a vertical partition that groups a second subset of configurable surface elements in the same vertical column, a quadrant partition that groups a subset of configurable surface elements in the same quadrant of the RIS, and / or any other combination of suitable partition geometries. Based on the distributed access, base station 120 may select a first surface configuration to modify the first subset of configurable surface elements of APD 181, select a second surface configuration to modify the second subset of configurable surface elements of APD 181, etc. If each surface configuration uses different configurable surface elements of the APD 181 and / or different APD timing advance values, the base station 120 can direct separate spatial streams of MIMO transmissions contemporaneously and / or simultaneously to the APD surface by directing the MIMO transmission spatial streams to respective subsets of the configurable surface elements. In some aspects, the same APD can be used for multiple streams of MIMO transmission by using respective different polarizations of the transmit signal and / or APD phase vectors. For example, a transmitter (e.g., a base station or UE(s)) can apply different polarizations (e.g., vertical, horizontal, linear, circular, etc.) to the separate streams of MIMO transmission, and the APD can apply corresponding polarization phase vectors to provide reflections of the MIMO transmissions to the receiver(s).

[0098] Briefly, base station 120 of FIG. 8 may determine a MIMO transmission configuration for an APD-enabled communication path formed by APD partition 881, APD partition 882, APD 182, and UE 111, similar to that described with respect to the transactions of FIGS. 5A-7, 9, 10, and 11, and / or the method of FIG. 12. In this example, the base station determines a surface configuration 811 for APD partition 881 of APD 181 and respective surface configuration APD partition 882. Based on the results of the channel characterization process described above, surface configuration 811 may include an indication of phase vector 5 for APD partition 881, an indication of phase vector 9 for APD partition 882, and one or more APD TA values ​​based on propagation delays between the base station and APD 181, between APD 181 and UE 111, or between APD 181 and UE 112. In some aspects, the surface configuration may be implemented as a combined configuration including parameters for uplink and downlink MIMO transmission as described herein, or may be implemented as separate configurations. To configure the APD for MU-MIMO, the base station 120 transmits the surface configuration 811 to the APD 181 using the APD control channel 511, as shown in FIG.

[0099] For uplink MU-MIMO transmission, the base station may determine a UE TA value 831 for UE 111 based on a propagation delay between UE 111 and the base station, and may determine a UE TA value 832 for UE 112 based on a propagation delay between UE 112 and the base station. The base station may configure UE TA values ​​831 and 832 to arrive at the base station within a time window (e.g., a cyclic prefix) that allows the uplink MIMO transmission to simultaneously decode the received MIMO transmission signals. As shown in FIG. 8 , the base station transmits UE TA value 831 to UE 111 using low-band connection 521 and UE TA value 832 to UE 112 using low-band connection 522, enabling first and second communication paths including APD partition 881 and APD partition 882 for uplink MU-MIMO transmission. Based on the surface configuration 711, the base station 120 may cause corresponding APD partitions 881 and 882 of the communication paths to implement multiple simultaneous phase vectors at the same time or in the same time slot according to various MIMO configurations described herein.

[0100] To implement downlink MU-MIMO transmission, base station 120 uses the MIMO transmission configuration to coordinate the application of simultaneous phase vectors so that each phase vector applied by the APD can be time-aligned with the PDSCH of the base station's downlink transmission. In some cases, the base station associates each APD partition phase vector with a downlink MU-MIMO antenna port or beam to a specific UE. As shown in FIG. 8, the base station may associate a first MU-MIMO downlink beam including signal ray 841 with phase vector 5 of APD partition 881, which is applied in alignment with the PDSCH of the MU-MIMO transmission (e.g., using the APD TA value). Base station 120 may also associate a second MU-MIMO downlink beam including signal ray 842 with phase vector 9 of APD partition 882, which is applied in alignment with the PDSCH of the MU-MIMO transmission. Based on incident downlink signal rays 841 and 842, APD partition 881 directs reflected signal ray 851 of the first reflected beam toward UE 111, and APD partition 882 directs reflected signal ray 852 of the second reflected beam toward UE 112. Thus, base station 120 can use APD partitions 881 and 882 to perform downlink MU-MIMO transmissions to UEs 111 and 112 that utilize the same time and frequency resources, thereby improving the spectral efficiency of the wireless network.

[0101] When implementing uplink MU-MIMO transmission, base station 120 uses the MIMO transmission configuration to coordinate the application of simultaneous phase vectors so that the respective phase vectors applied by the APDs are time-aligned with the respective PUSCHs of the UEs. In some embodiments, the base station associates each APD partition phase vector with a respective uplink antenna port of the corresponding UE. As shown in FIG. 8 , the base station may associate a first antenna port of an uplink beam including signal ray 861 with phase vector 5 of APD partition 881, which is applied in alignment with the PUSCH of UE 111 (e.g., using the APD TA value). Base station 120 may also associate a second antenna port of an uplink beam including signal ray 862 with phase vector 9 of APD partition 882, which is applied in alignment with the PUSCH of UE 112.

[0102] As described herein, base station 120 may transmit respective timing advance information to the APD to time-align the application of an APD phase vector associated with a UE with a corresponding PUSCH transmission from that UE. Accordingly, the base station may provide a TA value (if necessary) for each associated uplink phase vector associated with one of the corresponding UEs of a scheduled MU-MIMO transmission. Based on incident uplink signal rays 861 and 862, APD partition 881 reflects signal ray 871 of a first reflected beam toward base station 120, and APD partition 882 reflects signal ray 872 of a second reflected beam toward the base station. In an aspect, the base station may schedule each UE uplink transmission, configure the UE TA value, and / or configure the APD partition TA value to provide a reflected uplink MU-MIMO transmission that arrives at the base station within an amount of time (e.g., cyclic prefix) that enables decoding of the received MU-MIMO transmission signal. Therefore, base station 120 can use APD partitions 881 and 882 to implement uplink MU-MIMO transmissions from UEs 111 and 112 that utilize the same time and frequency resources, thereby improving the spectral efficiency of the wireless network.

[0103] FIG. 9 illustrates, at 900, an example of using multiple APD partitions for SU-MIMO transmission with a UE in accordance with one or more aspects. The environment of example 900 includes base station 120, APD 181, and UE 111 of FIG. 1, which may communicate as described with reference to FIGS. 1-8. As shown in FIG. 9, base station 120 may communicate with UE 111 using a low band connection 521 (e.g., below 6 GHz, sub-6 GHz) in a manner similar to that described with respect to wireless link 130 of FIG. 1. In this example, base station 120 also communicates with UE 111 using a first high band connection 921 including a first partition 881 (e.g., a first RIS) of APD 181 and a second high band connection 922 including a second partition 882 (e.g., a second RIS) of APD 181. To configure and operate the application of the downlink phase vector or uplink phase vector, the base station communicates with the APD 181 using an APD control channel 511 (which may be a wide-beam low-band APD control channel or a narrow-beam APD control channel).

[0104] To enable the SU-MIMO transmission shown in FIG. 9, base station 120 may select a group of candidate APDs 180, including APD 181, and perform a channel characterization process, such as described with reference to FIGS. 5A, 5B, 10, 11, and / or 12, to obtain uplink or downlink signal reports (e.g., signaling metrics). Based on the uplink and / or downlink signal reports, base station 120 selects one UE for performing MIMO transmission. Here, assume that the SRS received by the base station indicates that phase vector 6 of APD partition 881 provided UE 111 with the highest RSRP value and that phase vector 7 of APD partition 882 provided UE 111 with the next highest RSRP value. Further, assume that the base station has not received SRS reflections from other combinations of APDs and UEs that indicate viable APD-enabled communication paths. Therefore, base station 120 groups UE 111 with first partition 881 and second partition 882 of APD 181 for scheduling SU-MIMO transmissions over the respective communication paths shown in FIG.

[0105] In an aspect, a base station determines a MIMO transmission configuration for an APD partition and a selected UE by analyzing signal metrics from the channel characterization process described herein. The MIMO transmission configuration may include an APD partition phase vector, an APD partition TA value, a UE TA value, etc. Briefly, the base station 120 of FIG. 9 may determine a MIMO transmission configuration for an APD-enabled communication path formed by the APD partition 881, the APD partition 882, and the UE 111 in a manner similar to that described with respect to the transactions of FIGS. 5A-8, 10 and 11, and / or the method of FIG. 12. In this example, the base station determines a surface configuration 911 for the APD partitions 881 and 882 of the APD 181. Based on the results of the aforementioned channel characterization process, the surface configuration 911 may include an indication of phase vector 6 for both the APD partition 881 and the APD partition 882 and one or more APD TA values ​​based on propagation delays between the base station and the APD 181 or between the APD 181 and the UE 111. In other cases, such as for large APDs, the surface configuration may include different phase vectors for multiple partitions of the APD. In some aspects, the surface configuration may be implemented as a combined configuration including parameters for uplink and downlink MIMO transmissions as described herein, or may be implemented as separate configurations. To configure the APD for MU-MIMO, the base station 120 transmits the surface configuration 911 to the APD 181 using the APD control channel 511, as shown in FIG. 9.

[0106] For uplink SU-MIMO transmission, the base station may determine a UE TA value 931 for the UE 111 based on the propagation delay between the UE 111 and the base station when using the APD 181 and / or the UE 111's PUSCH. In some cases, the base station may determine multiple UE TA values ​​such that uplink MIMO transmissions via each APD partition-corresponding communication path arrive at the base station within a time window (e.g., a cyclic prefix) during which the base station can simultaneously decode the received SU-MIMO transmission signals. As shown in FIG. 9 , the base station transmits a UE TA value 951 to the UE 111 using the low-bandwidth connection 521 to enable the first and second communication paths for the uplink SU-MIMO transmission. Based on the surface configuration 911, the base station 120 may cause corresponding partitions of the APD 181 of the communication paths to implement multiple simultaneous phase vectors simultaneously or in the same time slot in accordance with various MIMO configurations described herein.

[0107] To implement downlink SU-MIMO transmission, base station 120 uses the MIMO transmission configuration to coordinate the application of simultaneous phase vectors so that each phase vector applied by the APD can be time-aligned with the PDSCH of the base station's downlink transmission. As described herein, the base station may associate each APD partition phase vector with a downlink SU-MIMO antenna port or beam to a UE via a particular communication path. As shown in FIG. 9 , the base station associates a first SU-MIMO downlink beam including signal ray 941 with phase vector 6 of APD partition 881, which is applied in alignment with the PDSCH of the SU-MIMO transmission (e.g., using the APD TA value). Base station 120 also associates a second SU-MIMO downlink beam including signal ray 942 with phase vector 6 of APD partition 882, which is applied in alignment with the PDSCH of the SU-MIMO transmission. Based on incident downlink signal rays 941 and 942, APD partition 881 directs reflected signal ray 951 of the first reflected beam toward UE 111, and APD partition 882 directs reflected signal ray 952 of the second reflected beam toward UE 111. Thus, base station 120 can use APD partitions 881 and 882 to perform downlink SU-MIMO transmission to UE 111 that utilizes the same time and frequency resources, thereby improving the spectral efficiency of the wireless network.

[0108] When implementing uplink SU-MIMO transmission, base station 120 uses the MIMO transmission configuration to coordinate the application of simultaneous phase vectors so that the respective phase vectors applied by the APDs are time-aligned with the UE's respective PUSCHs. In some cases, the base station associates each APD partition phase vector with a respective uplink antenna port of the UE. As shown in FIG. 9 , the base station associates a first antenna port of an uplink beam including signal ray 961 with phase vector 6 of APD partition 881, which is applied in alignment with the UE's PUSCH (e.g., using the APD TA value). Base station 120 also associates a second antenna port of an uplink beam including signal ray 962 with phase vector 6 of APD partition 882, which is applied in alignment with the UE's PUSCH. Based on the incident uplink signal rays 961 and 962, APD partition 881 reflects signal ray 971 of the first reflected beam toward base station 120, and APD partition 882 reflects signal ray 972 of the second reflected beam toward base station 120. In an aspect, the base station may schedule UE uplink transmissions, configure UE TA value(s), and / or configure APD TA values ​​to provide a reflected uplink SU-MIMO transmission that arrives at the base station within an amount of time (e.g., a cyclic prefix) that allows decoding of the received SU-MIMO transmission signal. Thus, base station 120 can use APD partitions 881 and 882 to implement uplink SU-MIMO transmissions by UE 111 that utilize the same time and frequency resources, thereby improving the spectral efficiency of the wireless network.

[0109] Transaction on MIMO Transmission Using APD Various aspects of MIMO transmission using APDs enable a base station to use one or more APDs in at least one communication path for MIMO transmission with each UE. Typically, the base station can select and configure one or more APDs to perform MU-MIMO transmission with multiple UEs or SU-MIMO transmission with a UE based on channel information or the results of a channel characterization process. By doing so, the base station can perform MIMO communication using the APDs to communicate with UEs that use the same time and frequency resources, thereby improving the spectral efficiency of the wireless network.

[0110] 10 and 11 illustrate some example signaling and control transactions performed between entities such as a base station (e.g., base station 120), APDs (e.g., APDs 181 and 182 and / or APD partitions 881 and 882), and UEs (e.g., UEs 111 and 112) to implement various aspects of MIMO transmission using APD 1. The illustrated examples include a base station configuring various combinations of APDs and UEs to communicate using MIMO transmission (e.g., FIG. 10) and APDs, and performing downlink or uplink channel characterization processes (e.g., FIG. 11). The various operations described with reference to FIGS. 10 and 11 may be performed by any of the entities described with reference to FIGS. 1-4, in combination with operations of the other examples of FIGS. 5A-9, and / or in combination with operations of the method illustrated in FIG. 12.

[0111] 10 illustrates example signaling and control transactions for MIMO transmission using APDs, according to one or more aspects. Signaling and control transaction diagram 1100 includes signaling and control transactions between base station 120, APD 181, APD 182, UE 111, and UE 112, which may be implemented as described with reference to FIGS. 1-9. Generally, the illustrated transactions may enable base station 120 or MIMO function 268 to configure and use APD 181 and / or APD 182 for SU-MIMO transmission with a UE (e.g., UE 111 or UE 112) or for MU-MIMO transmission with multiple UEs (e.g., UE 111 and UE 112).

[0112] At 1005, the base station 120 establishes a respective wireless connection with at least one of the UE 111 and the UE 112. Each wireless connection established with a UE may include a low-band connection that enables non-LoS communication between the base station and either of the UEs. In some cases, the base station may also establish a high-band connection with the UE, either directly or via a communication path that includes the surface of the APD 181 or the APD 182. For example, the base station may establish a low-band connection and a high-band connection with the UE to enable communication between the UE and the base station in frequency bands below 6 GHz and above 6 GHz.

[0113] In an aspect, the base station may also determine 1005 to use one or more APDs for MIMO transmission with at least one of the UEs. The base station may thus schedule downlink MIMO transmissions to one or more of the UEs or schedule uplink MIMO transmissions from one or more of the UEs. Alternatively or additionally, the base station may determine to include an APD-enabled communication path to enable MIMO transmission with at least one of the UEs. As an example, the base station may fail in an attempt to establish a high-bandwidth wireless connection with the UE. For example, base station 120 attempts to establish a high-bandwidth wireless link with UE 111, but signal failure occurs because an obstacle (e.g., obstacle 171 or 172) blocks the LoS communication path. In other cases, the base station may analyze signal and / or link quality measurements to detect channel impairments or detect that the signal and / or link quality measurements are trending below acceptable performance levels. As another example, base station 120 can use UE location information to analyze historical records to determine that a UE location has been historically associated with APD wireless communication or that UE 110 is moving toward a location historically associated with APD communication.

[0114] At 1010, the base station selects one or more APDs to use for MIMO transmission with UE 111 and / or UE 112. For example, the base station may select a set or group of candidate APDs for evaluation to use for MIMO transmission based on the proximity (e.g., within a threshold distance) of the APDs to the location of one of the UEs or based on historical usage records of APDs communicating with UEs proximate to the UE's location. Alternatively or additionally, the base station can monitor respective APD-broadcast signals from the APDs, access APD records indicating APDs within a cell coverage area, query a server that stores APD information, use UE location information to identify APDs within operating range of UE 110, and / or do other things.

[0115] At 1015, the base station performs a channel characterization process using one or more APDs to obtain uplink or downlink signal metrics. The channel characterization process may include binding resources or parameters of the channel characterization process with an APD beam sweeping pattern to enable a receiving device to identify a reflection of a reference signal received from the APD. In an aspect, while the base station is transmitting a downlink reference signal or while the UE is transmitting an uplink reference signal, the base station configures one or more APDs to perform a beam sweeping pattern to enable characterization of the channel between the base station and the UE. In some cases, the base station performs a CSI process (e.g., FIG. 5A ) with at least one APD and one or more UEs to obtain downlink signal reports for reflections of CSI-RSs reaching the one or more UEs from the at least one APD. Alternatively or additionally, the base station can perform an SRS process (e.g., FIG. 5B ) with at least one APD and one or more UEs to obtain uplink signal measurements of reflections of SRSs reaching the base station from the at least one APD.

[0116] At 1020, the base station 120 groups the APD(s) 180 and the UE(s) 110 for MIMO transmission. Based on the results of the channel characterization process, the base station can group various combinations of UEs and APDs to implement uplink and / or downlink MIMO transmission. In some aspects, the base station selects multiple UEs to communicate using MU-MIMO or selects one UE to communicate using SU-MIMO based on the channel characterization process. For example, the base station can group multiple UEs with respective APDs to implement MU-MIMO transmission as described with reference to FIG. 6. In other cases, the base station can group one UE with multiple APDs to implement SU-MIMO transmission as described with reference to FIG. 7. As another example, the base station can group multiple APDs with respective partitions of a single APD to implement MU-MIMO transmission as described with reference to FIG. 8. Alternatively, the base station can group a single UE with multiple partitions of an APD to implement SU-MIMO using one APD as described with reference to FIG. 9.

[0117] Optionally, at 1025, the base station determines a UE timing advance value for uplink MIMO transmission. For example, the base station 120 can determine uplink timing advance information including respective timing advance commands or values, which may account for different propagation distances through each APD-enabled communication path of the UE. Optionally, the UE timing advance commands are separate (although related) from the APD timing advance commands that the base station sends to the corresponding APD. As described herein, the APD timing advance can adjust the timing of application of a phase vector by the APD to coincide with the UE's uplink transmission timing, which is changed based on the UE timing advance.

[0118] At 1030, the base station determines a surface configuration of one or more APDs. Typically, the base station uses the results of a channel characterization process to determine respective phase vectors for one or more APDs or APD partitions to enable MIMO communication over APD-enabled communication paths. Alternatively or additionally, the base station may determine an APD timing advance value to time-align the application of the phase vectors by the APD with uplink or downlink transmissions. Thus, the surface configuration of an APD (or APD partition) may include a phase vector, an indication of the physical channel timing (e.g., PUSCH or PDSCH) or time slot (during which the phase vector is applied), and an APD timing advance value that adjusts the relative timing application of the phase vectors specified in the physical channel. In some cases, the APD timing adjustment value is based on the timing advance value of the corresponding UE for uplink communication. Each APD timing adjustment value may also be determined based on a propagation delay calculated for communication between the base station and the APD and / or between the UE and the APD.

[0119] At 1035, the base station transmits an indication of a respective surface configuration to at least one of the APDs selected for MIMO transmission. In some cases, the base station transmits the respective surface configurations to multiple APDs. Each surface configuration enables a respective APD-enabled communication path for MU-MIMO with multiple UEs (e.g., FIG. 6) or enables a respective APD-enabled communication path for SU-MIMO with a single UE (e.g., FIG. 7). In other cases, the base station transmits the surface configuration to a single APD. The surface configuration enables a respective communication path using an APD partition for MU-MIMO with multiple UEs (e.g., FIG. 8) or enables a respective communication path using an APD partition for SU-MIMO with a single UE (e.g., FIG. 9).

[0120] Optionally, at 1040, the base station transmits an indication of the respective UE timing advance value to at least one of the UEs selected for MIMO transmission. For example, the base station may transmit the indication of the respective UE timing advance value to multiple UEs to adjust corresponding uplink transmission times so that uplink MU-MIMO transmissions from the multiple UEs reach the base station within an amount of time (e.g., cyclic prefix) that allows for decoding of the received transmission signals. Alternatively, the base station may transmit a UE timing advance to a UE that communicates with the base station via multiple APD-enabled communication paths so that uplink SU-MIMO transmissions reach the base station within an amount of time that allows for decoding of the received transmission signals.

[0121] At 1045, the base station communicates with the UE using MIMO transmission. In some aspects, the base station may communicate with multiple UEs or a single UE (e.g., SU-MIMO) using surface configurations transmitted to one or more APDs. In some cases, the base station implements MU-MIMO (e.g., as indicated at 1045) and transmits downlink transmission signals to or receives uplink transmission signals from multiple UEs using multiple APDs as described with reference to FIG. 6. Alternatively, although not shown in the transaction at 1045, the base station may implement other aspects of MIMO transmission using APDs as described herein. For example, the base station may implement SU-MIMO and transmit downlink transmission signals to or receive uplink transmission signals from a single UE using multiple APDs as described with reference to FIG. 7. In other cases, the base station may implement MU-MIMO and transmit downlink transmission signals to or receive uplink transmission signals from multiple UEs using APD partitions as described with reference to FIG. 8. In still other cases, the base station may implement SU-MIMO and send downlink transmissions or receive uplink transmissions with one UE using APD partitions as described with reference to Figure 9. From transaction 1045, the base station may return to any of the preceding transactions, such as the transaction of subdiagram 1015, to recharacterize one or more communication paths and implement further iterations of MIMO transmission using APD.

[0122] 11 illustrates, at 1100, exemplary details of signaling and control transactions that can be used to perform channel characterization in accordance with one or more aspects. The illustrated transactions may enable base station 120 or MIMO function 268 to use one or more APDs to sweep a reflected downlink or uplink beam through a respective communication path that includes one of the APDs. While illustrated with transactions for two APDs 181 and 182 and two UEs 111 and 112, any of the transactions or subdiagrams illustrated in FIG. 11 can be implemented with any combination or group of APD(s), APD partitions, and UE(s) described herein.

[0123] The base station 120, the APD 180, and / or the UE 110 may be implemented similarly to the entities described with reference to Figures 1-9. While this example is shown in the context of performing a channel characterization process, the operations described with reference to Figure 11 may be initiated or performed by entities unrelated to the channel characterization process, e.g., to perform various transactions and / or operations described in connection with the methods of Figures 5A-10 or 12. For example, the base station 120 may select, group, configure, and / or control the APD 180 and the UE 110 to perform various aspects of MIMO transmission using the APD, as described with reference to Figures 5A-10 and / or 12. In an aspect, the transactions of Figure 11 may correspond to subdiagram 1015 of Figure 10, which performs a channel characterization process to obtain uplink or downlink signal metrics. These metrics may be used to enable aspects of MIMO transmission using the APD.

[0124] At 1105, the base station 120 configures the APD 180 and the UE for a channel characterization process. In an aspect, the base station may associate air interface resources for the uplink or downlink channel characterization process with the respective phase vectors of the beam sweeping patterns assigned to the APDs. The base station may then transmit indices of the beam sweeping patterns that the APDs 181 and 182 implement during the channel characterization process to reflect the beams of the downlink or uplink reference signals, as shown at 1105. Alternatively or additionally, the base station may transmit SRS parameters associated with the respective APD beam sweeping pattern phase vectors to the UEs 111 and 112 to enable the uplink channel characterization process shown at 1105. From 1105, the transaction may proceed to subdiagram 1110, where the base station, the APDs, and the UEs perform the transaction for the downlink channel characterization process. Alternatively, from 1105, the transaction may proceed to subdiagram 1115, where the base station, APD, and UE perform an uplink channel characterization process transaction.

[0125] The entities in FIG. 11 may perform the operations of subdiagram 1110 to execute a downlink channel characterization process for a communication path including APDs 181 and 182. For example, a base station may execute a downlink channel characterization process (CSI procedure) as described with reference to FIG. 5A. Based on the configuration in 1105, the first APD 181 applies a first surface configuration to the RIS of the first APD at 1120, and the second APD 182 applies a second surface configuration to the RIS of the second APD at 1125. At 1130, the base station transmits a downlink wireless signal (e.g., CSI-RS). The downlink wireless signal (e.g., CSI-RS) may utilize the surfaces of the APDs to cause reflections of the downlink wireless signal reaching one or both of UE 111 and UE 112. At 1135, the first UE 111 generates a downlink signal report (e.g., CSI feedback) of measurements on reflections of the downlink wireless signal reaching the first UE. Similarly, at 1140, the second UE 112 generates a downlink signal report of measurements of reflections of the downlink wireless signal reaching the second UE. If various combinations of downlink beams and APD phase vectors do not result in reflections reaching the UE, the UE may receive reflections of the downlink wireless signal from one APD, multiple APDs, or no APD, as described with reference to FIG. 5A. At 1145, the first UE 111 and the second UE 112 communicate their respective downlink signal reports to the base station. This enables the base station to perform other operations for MIMO transmission using APDs. Optionally, at 1150, the base station can perform another iteration of subdiagram 1110 to perform another channel characterization process. For example, the base station can use at least one of the downlink signal reports provided by the UEs 111 and 112 to refine parameters for downlink beam or APD phase vector selection for a subsequent iteration of channel characterization. Once the downlink channel characterization is complete, the base station may then group the APDs and UEs as described with reference to FIGS.

[0126] In an aspect, the entities in FIG. 11 may perform the operations of subdiagram 1110 to execute an uplink channel characterization process for a communication path including APDs 181 and 182. As an example, a base station may perform the uplink channel characterization process (SRS procedure) described with reference to FIG. 5B. Based on the configuration in 1105, the first APD 181 applies a first surface configuration to the RIS of the first APD at 1155, and the second APD 182 applies a second surface configuration to the RIS of the second APD at 1160. At 1165, the first UE and the second UE transmit respective uplink wireless signals (e.g., SRS). The respective uplink wireless signals (e.g., SRS) may utilize the surfaces of the APDs to cause reflections of the uplink wireless signals reaching one or both of UE 111 and UE 112. At 1170, the base station generates an uplink signal report of measurements (e.g., SRS metrics) on reflections of the uplink wireless signals reaching the base station. If various combinations of uplink beams and APD phase vectors do not result in reflections reaching the base station, the base station may receive reflections of the downlink wireless signal from one APD, multiple APDs, or no reflections of the downlink wireless signal from the APD, as described with reference to FIG. 5B. Based on the uplink signal reports, the base station may perform other operations for MIMO transmission using the APDs. Optionally, at 1175, the base station may perform another iteration of subdiagram 1115 to perform another channel characterization process. For example, the base station may use the uplink signal reports to refine parameters for uplink beam or APD phase vector selection for subsequent iterations of channel characterization. Once the uplink channel characterization is complete, the base station may then group the APDs and UEs, as described with reference to FIGS. 5B-10 and 12.

[0127] Example Method of MIMO Transmission Using APD 12 illustrates example method(s) 1200 that can be used to implement various aspects of MIMO transmission using APDs. In various embodiments, operations of method 1200 are performed by or in conjunction with a base station, UE(s), and APD(s), as described with reference to any of FIGS. 1-11. In some cases, aspects of method 1200 are performed in conjunction with operations described with reference to FIGS. 5A-9 and / or transactions described with reference to FIGS. 10 and 11 to implement aspects of MIMO transmission using APDs.

[0128] At 1205, the base station selects one or more APDs to use for at least one communication path for MIMO transmission with one or more UEs. For example, the base station can select candidate APDs within a threshold distance from one or more UEs experiencing degraded signal or link quality measurements. For example, the base station (e.g., base station 120) selects one or more APDs (e.g., APD 181, APD 182) for use on a communication path to one or more UEs (e.g., UE 111, UE 112) in response to identifying signal degradation indicated by signal and / or link quality measurements as described with reference to FIG. 6, FIG. 8, and / or FIG. 10.

[0129] At 1210, the base station performs a channel characterization process using one or more APDs and one or more UEs. The base station 120 performs the channel characterization process as described, for example, with reference to FIGS. 5A, 5B, 1015 of FIG. 10, and / or 11. This may include the base station 120 causing the APD 181 and / or the APD 182 to apply multiple surface configurations, the base station 120 transmitting a downlink CSI-RS, and / or the UE 110 transmitting an uplink SRS. In performing the channel characterization process, the base station 120 may receive downlink signal quality measurements from the UE 110 (e.g., subdiagram 1110 of FIG. 5A or FIG. 11) or may generate uplink signal quality measurements based on the uplink SRS (e.g., subdiagram 1115 of FIG. 5B or FIG. 11).

[0130] Optionally, at 1215, the base station groups multiple UEs with at least one APD for MU-MIMO transmission. For example, base station 120 selects UE 111 and UE 112 to be paired or grouped for MU-MIMO transmission, as described with reference to 1020 in FIG. 6, FIG. 8, or FIG. 10. Optionally, at 1220, the base station groups one UE with at least one APD for SU-MIMO transmission. For example, base station 120 groups UE 110 with multiple APDs 181 and 182 or partitions of APD 181 for SU-MIMO transmission, as described with reference to FIG. 7 and / or FIG. 9.

[0131] At 1225, the base station configures one or more APDs for MIMO transmission based on the channel characterization process. For example, the base station 120 causes the APD 181 to apply a first surface configuration and the APD 182 to apply a second surface configuration, as shown at 1035 in FIG. 10 . Alternatively or additionally, the base station 120 determines an APD timing adjustment (e.g., using link quality measurements, using UE location information, using APD location information), as shown at 1030, and configures one or more APDs with the timing adjustment, as shown at 1035. In some aspects, the base station 120 determines a UE timing adjustment and indicates the UE timing adjustment to the UE(s) 110, as shown at 1040 in FIG. 10 . In some cases, the base station 120 configures a single APD using panel division or sub-panels, as described with reference to FIG. 7 or FIG. 9 .

[0132] At 1230, the base station communicates with one or more UEs using MIMO transmissions and respective surfaces of one or more APDs. As a first example, base station 120 communicates with UE 111 and UE 112 using APD 181 and APD 182 for MU-MIMO transmissions, as shown at 1045 in FIG. 10 or with respect to FIG. 6. As a second example, base station 120 communicates with UE 111 using APD 181 and APD 182 for SU-MIMO transmissions, as described with respect to FIG. 7. As a third example, base station 120 communicates with UE 111 and UE 112 using APD 181 (with panel splitting) for MU-MIMO transmissions, as described with respect to FIG. 8. As a fourth example, base station 120 communicates with UE 111 using APD 181 (with panel splitting) for SU-MIMO transmissions, as described with respect to FIG. 9.

[0133] The order in which the method blocks are shown is not intended to be construed as a limitation, and any number of the shown method blocks may be omitted or any number of the shown method blocks may be combined in any order to implement one or another method. Generally, any of the components, modules, methods, and operations described herein may be implemented using software, firmware, hardware (e.g., fixed logic circuitry), manual processing, or any combination thereof. Some operations of the example methods may be described in the general context of executable instructions stored in a computer-readable storage memory that is local and / or remote to a computer processing system, and implementations may include software applications, programs, functions, etc. Alternatively, or additionally, any of the functionality described herein may be performed, at least in part, by one or more hardware logic components. Such hardware logic components may be, for example, but not limited to, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), systems-on-chip (SoCs), complex programmable logic devices (CPLDs), etc.

[0134] Although aspects of MIMO transmission using APDs have been described using language specific to features and / or methods, the subject matter of the appended claims is not necessarily limited to the specific features or methods described. Rather, certain features and methods are disclosed as exemplary implementations of MIMO transmission using APDs, and other equivalent features and methods are intended to be within the scope of the appended claims. Accordingly, features recited in the appended claims may be selected in "any combination," including combining the recited features in any number and in any combination. Furthermore, while various different aspects are described, it should be understood that each described aspect may be practiced independently or in conjunction with one or more of the other described aspects.

[0135] Next, some exemplary embodiments are presented. Aspect 1. A method performed by a base station for communicating with at least one user equipment (UE) in a wireless network using multiple-input multiple-output (MIMO) transmissions and at least one adaptive phase change device (APD), the method including: selecting the at least one APD for use in at least one communication path for the MIMO transmissions; performing a channel characterization process for the at least one communication path using the at least one APD and the at least one UE; configuring the at least one APD for the MIMO transmissions based on the channel characterization process; and communicating with the at least one UE via the at least one communication path using the MIMO transmissions and a respective surface of each of the at least one APD.

[0136] 2. The method of claim 1, further comprising: A single UE of the at least one UE may be selected based on the channel characterization process, and the MIMO transmission may be implemented as a single-user-MIMO (SU-MIMO) transmission between the base station and the single UE. Multiple UEs of the at least one UE may be selected based on the channel characterization process, and the MIMO transmission may be implemented as a multi-user-MIMO (MU-MIMO) transmission between the base station and the multiple UEs.

[0137] Performing the channel characterization process may include transmitting one or more channel state information reference signals (CSI-RS) toward the respective surfaces of at least one APD. Performing the channel characterization process may include receiving one or more sounding reference signals (SRS) from the at least one UE using the respective surfaces of the at least one APD. Performing the channel characterization process may include receiving quality measurements of one or more respective downlink signals or links from the at least one UE in response to transmitting the one or more CSI-RS. Performing the channel characterization process may include generating quality measurements of one or more respective uplink signals or links in response to receiving the one or more SRS. Configuring the at least one APD for MIMO transmission based on the channel characterization process may include analyzing at least one of the quality measurements of the one or more respective downlink signals or links or the quality measurements of the one or more respective uplink signals or links. A respective surface configuration may be selected for each of the at least one APD based on the analyzing.

[0138] Performing the channel characterization process may include selecting, for each APD of the at least one APD, a respective beam sweeping pattern to be applied during the channel characterization process. Each APD of the at least one APD may be caused to apply the respective beam sweeping pattern during the channel characterization process. Performing the channel characterization process may include associating each CSI-RS of the one or more CSI-RS with a respective surface configuration included in the respective beam sweeping pattern. Performing the channel characterization process may include associating each SRS of the one or more SRS with the respective surface configuration included in the respective beam sweeping pattern. Performing the channel characterization process may include assigning a respective MIMO transmission configuration to the respective surface configuration. Configuring the APD may include identifying a MIMO transmission configuration for the MIMO transmission based on the channel characterization process and the assigning. Communicating with the at least one UE may include communicating with each UE of the at least one UE using the MIMO transmission configuration for the MIMO transmission.

[0139] Configuring the at least one APD for MIMO transmission may include indicating a respective APD timing adjustment to each APD of the at least one APD. The at least one APD may be caused to adopt the surface configuration using the respective APD timing adjustment. The at least one APD may include at least two APDs, and a respective APD timing adjustment may be indicated to each APD of the at least two APDs.

[0140] Determining the respective APD timing adjustment may be based on at least one of a physical downlink shared channel (PDSCH) MIMO transmission time, a physical uplink shared channel (PUSCH) MIMO transmission time, a respective position of each UE in the at least one UE, or a respective position of each APD in the at least one APD.

[0141] Indicating the respective APD timing adjustment to each APD of the at least one APD may include communicating the respective APD timing adjustment to each APD of the at least one APD using an APD control channel utilizing frequency transmission in a frequency band lower than a frequency band of the MIMO transmission.

[0142] Selecting the at least one UE for MIMO transmission may include selecting a first UE and a second UE for MU-MIMO communication. Communicating with the first UE and the second UE using the MIMO transmission may include: communicating with the first UE by using a first MIMO transmission of the MIMO transmissions and including a first APD of the at least one APD in a first communication path for the first MIMO transmission; and communicating with the second UE by using a second MIMO transmission of the MIMO transmissions and including a second APD of the at least one APD in a second communication path for the second MIMO transmission, thereby performing the MU-MIMO communication.

[0143] Configuring the at least one APD for MIMO transmission may include at least one of selecting a first surface configuration of the first APD based at least in part on a first MU-MIMO transmission configuration specific to the first UE, or selecting a second surface configuration of the second APD based at least in part on a second MU-MIMO transmission configuration specific to the second UE.

[0144] Selecting at least one UE for MIMO transmission may include selecting a single UE for SU-MIMO communication. Communicating with the single UE using the MIMO transmission may include: communicating with the single UE by using a first MIMO transmission of the MIMO transmissions and including a first APD of the at least one APD in a first communication path for the first MIMO transmission; and communicating with the single UE by using a second MIMO transmission of the MIMO transmissions and including a second APD of the at least one APD in a second communication path for the second MIMO transmission, thereby implementing the SU-MIMO communication.

[0145] Configuring the at least one APD for MIMO transmission may include at least one of selecting a first surface configuration of the first APD based at least in part on a SU-MIMO transmission configuration of the single UE, or selecting a second surface configuration of the second APD based at least in part on a SU-MIMO transmission configuration of the single UE.

[0146] Selecting the at least one UE for MIMO transmission may include selecting a first UE and a second UE for MU-MIMO communication. Communicating with the first UE and the second UE using the MIMO transmission may include: communicating with the first UE by using a first MIMO transmission of the MIMO transmissions and including a first APD surface partition of a single APD of the at least one APD in a first communication path for the first MIMO transmission; and communicating with the second UE by using a second MIMO transmission of the MIMO transmissions and including a second APD surface partition of the single APD in a second communication path for the second MIMO transmission, thereby performing the MU-MIMO communication. Configuring the at least one APD for MIMO transmission includes at least one of selecting a first surface configuration of the first APD surface partition of the single APD based at least in part on a first MU-MIMO transmission configuration specific to the first UE, or selecting a second surface configuration of the second APD surface partition of the single APD based at least in part on a second MU-MIMO transmission configuration specific to the second UE.

[0147] Selecting at least one UE for MIMO transmission may include selecting a single UE for SU-MIMO communication. Communicating with the single UE using the MIMO transmission may include: communicating with the single UE by using a first MIMO transmission among the MIMO transmissions and including a first APD surface partition of a single APD among the at least one APD in a first communication path for the first MIMO transmission; and communicating with the single UE by using a second MIMO transmission among the MIMO transmissions and including a second APD surface partition of the single APD in a second communication path for the second MIMO transmission, thereby implementing the SU-MIMO communication. Configuring the at least one APD for MIMO transmission may include at least one of selecting a first surface configuration of the first APD surface partition of the single APD based at least in part on a SU-MIMO transmission configuration of the single UE, or selecting a second surface configuration of the second APD surface partition of the single APD based at least in part on a SU-MIMO transmission configuration of the single UE.

[0148] Aspect 2. A base station comprising: at least one wireless transceiver; at least one processor; and a computer-readable storage medium comprising instructions that, in response to execution by the at least one processor, cause the base station to perform the method of aspect 1.

[0149] Aspect 3. A computer-readable storage medium comprising instructions that, when executed by a processor, cause the method set forth in aspect 1 to be performed.

Claims

1. 1. A method performed by a base station for communicating with multiple user equipment units (UEs) in a wireless network using multiple-input multiple-output (MIMO) transmission and a first adaptive phase change device (APD), the method comprising: selecting a first APD to be used in at least one communication path for the MIMO transmission; selecting a first UE and a second UE for multi-user-MIMO (MU-MIMO) communication; performing a channel characterization process for the at least one communication path using the first APD and the first UE and the second UE; and configuring the first APD for the MIMO transmission based on the channel characterization process, wherein the configuring includes: applying a simultaneous phase vector applied by the first APD; a first APD surface partition is time-aligned with PDSCH and PUSCH transmissions between the first UE and the base station; such that a second APD surface partition is time-aligned with PDSCH and PUSCH transmissions between the second UE and the base station; adjusting, said method further comprising: communicating with the first UE using a first MIMO transmission of the MIMO transmissions and including the first APD surface partition in a first communication path for the first MIMO transmission; communicating with the second UE using a second MIMO transmission of the MIMO transmissions and including the second APD surface partition in a second communication path for the second MIMO transmission; A method comprising:

2. said performing said channel characterization process further comprising: transmitting one or more channel state information reference signals (CSI-RS) toward a surface of the first APD; The method of claim 1 , comprising:

3. said performing said channel characterization process further comprising: receiving one or more respective downlink signal or link quality measurements from the UE in response to transmitting the one or more CSI-RS; Configuring the first APD for the MIMO transmission based on the channel characterization process includes: analyzing said one or more respective downlink signal or link quality measurements; selecting a surface configuration for the first APD based on the analyzing; and The method of claim 2 , comprising:

4. The performing of the channel characterization process, receiving one or more sounding reference signals (SRS) from the UE using a surface of the first APD; The method of claim 1 , comprising:

5. The performing of the channel characterization process, generating one or more respective uplink signal or link quality measurements in response to receiving the one or more SRSs; Configuring the first APD for the MIMO transmission based on the channel characterization process includes: analyzing quality measurements of said one or more respective uplink signals or links; selecting a surface configuration for the first APD based on the analyzing; and The method of claim 4, comprising:

6. said performing said channel characterization process further comprising: selecting, for the first APD, a beam sweeping pattern to be applied during the channel characterization process; applying the beam sweeping pattern to the first APD during the channel characterization process; assigning a MIMO transmission configuration to the surface configuration; Configuring the first APD includes: identifying a MIMO transmission configuration for the MIMO transmission based on the channel characterization process and the allocating; The communicating with the first UE and the communicating with the second UE include: communicating using the MIMO transmission configuration for the MIMO transmission. The method according to claim 3 or 5.

7. said performing said channel characterization process further comprising: associating each CSI-RS of the one or more CSI-RS with a respective surface configuration included in the beam sweeping pattern; 7. The method of claim 6 when dependent on claim 3, comprising:

8. The performing of the channel characterization process, associating each SRS of the one or more SRSs with a respective surface configuration included in the beam sweeping pattern; 7. The method of claim 6 when dependent on claim 5, comprising:

9. The configuring of the first APD for the MIMO transmission comprises: indicating an APD timing adjustment to the first APD; causing the first APD to apply the surface configuration using the APD timing adjustment; The method of claim 3 or 5, comprising:

10. Physical Downlink Shared Channel (PDSCH) MIMO transmission time, Physical Uplink Shared Channel (PUSCH) MIMO transmission time; the respective location of each of said UEs; or the position of the first APD; 10. The method of claim 9, further comprising determining the APD timing adjustment based on at least one of:

11. The indicating the APD timing adjustment to the first APD includes: communicating the APD timing adjustment to the first APD using an APD control channel utilizing frequency transmission in a frequency band lower than a frequency band of the MIMO transmission; 10. The method of claim 9, comprising:

12. The method of claim 11, wherein the first APD for the MIMO transmission is configured to: Calculating a first timing advance value for the first UE; calculating a second timing advance value for the second UE; 10. The method of claim 9, wherein the indicating the APD timing adjustment to the first APD is based at least in part on the first timing advance value or the second timing advance value.

13. The configuring of the first APD for the MIMO transmission comprises: selecting a first surface configuration for the first APD surface partition of the first APD based at least in part on a first MU-MIMO transmission configuration specific to the first UE; or selecting a second surface configuration for the second APD surface partition of the first APD based at least in part on a second MU-MIMO transmission configuration specific to the second UE; The method of claim 1 , comprising at least one of:

14. The method of claim 1, wherein communicating with the first UE and communicating with the second UE includes simultaneously communicating with the first UE and the second UE.

15. The method of claim 1, wherein communicating with the first UE includes communicating user plane data with the first UE; The method of claim 1 , wherein communicating with the second UE includes communicating user plane data to and from the second UE.

16. The method of claim 15, wherein communicating with the first UE includes communicating control plane data with the first UE; The method of claim 1 , wherein communicating with the second UE includes communicating control plane data to and from the second UE.

17. A base station, at least one wireless transceiver; at least one processor; and 17. A base station comprising: a computer-readable storage medium containing instructions that, when executed by the at least one processor, cause the base station to perform the method of any one of claims 1 to 5 and 13 to 16.

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