Method, architecture, apparatus, and system directed to adaptive reference signal construction

Abstract

Procedures, methods, architectures, apparatus, systems, devices, and computer program products directed to adaptive reference signal configurations are described. The method for adapting a reference signal configuration may be implemented in a WTRU. For example, the WTRU may receive a transmission from, for example, a base station according to one or more first reference signal configurations. For example, a channel estimation measurement may be performed on the received transmission based on the indicated one or more first reference signal configurations. For example, one or more second reference signal configurations (e.g., to be used for a subsequent transmission) may be selected from a plurality of reference signal configurations based on the channel estimation measurement. For example, an indication of the selected one or more second reference signal configurations may be transmitted (e.g., to a base station).

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of European Patent Application No. 21178929.2, filed June 11, 2021, and European Patent Application No. 22167141.5, filed April 07, 2022, the disclosures of which are incorporated by reference in their entireties into this application.

[0002] The present disclosure is generally directed to the fields of communications, software, and coding, including methods, architectures, devices, and systems directed to adaptive reference signal construction using any of artificial intelligence (AI) and machine learning (ML), for example. Summary of the Invention

[0003] Briefly, in accordance with one embodiment of the present disclosure, a method implemented in a wireless transmit / receive unit (WTRU) includes receiving a transmission from a base station according to one or more first reference signal configurations. Channel estimation measurements are performed for the received transmission based on the one or more first reference signal configurations. An indication of one or more second reference signal configurations to be used for a subsequent transmission is transmitted to the base station, and the one or more second reference signal configurations are selected from the plurality of reference signal configurations based on the channel estimation measurements. [Brief description of the drawings]

[0004] A more detailed understanding may be had from the following detailed description, taken by way of example in conjunction with the accompanying drawings. Such drawing figures, like the detailed description, are examples. Thus, the figures and detailed description should not be considered as limiting, as other equally effective examples are possible and likely. Moreover, like reference numerals ("references") in the figures indicate like elements. [Figure 1A] FIG. 1 is a system diagram illustrating an example communication system. [Figure 1B] 1A is a system diagram illustrating an example wireless transmit / receive unit (WTRU) that may be used within the communications system illustrated in FIG. 1A. [Figure 1C] FIG. 1B is a system diagram illustrating an example radio access network (RAN) and an example core network (CN) that may be used within the communication system illustrated in FIG. 1A. [Figure 1D] FIG. 1B is a system diagram illustrating a further exemplary RAN and a further exemplary CN that may be used within the communication system illustrated in FIG. 1A. [Diagram 2] 1 illustrates an example of a composite channel estimation procedure based on a user-specific reference signal; [Diagram 3] A diagram illustrating an example of a 5G demodulation reference signal (DMRS) configuration. [Figure 4] FIG. 2 is a system diagram illustrating a first example of an adaptive reference signal construction method. [Diagram 5] 10A-10C illustrate example message exchanges for a first example adaptive reference signal configuration method. [Figure 6] FIG. 11 is a system diagram illustrating a second example of an adaptive reference signal construction method. [Figure 7] 11 illustrates example message exchanges for a second example adaptive reference signal configuration method. [Figure 8] 1 is a diagram illustrating an example of reference signal adaptation. [Figure 9] 1 illustrates an example of a procedure for reference signal adaptation. [Figure 10A] FIG. 13 illustrates an example of AI / ML-based determination of reference signal configuration. [Figure 10B] FIG. 13 illustrates an example of AI / ML-based determination of reference signal configuration. [Figure 10C] FIG. 13 illustrates an example of AI / ML-based determination of reference signal configuration. [Figure 11] 1 illustrates an example of a method for adapting a reference signal configuration. [Figure 12] FIG. 13 illustrates an example of a method for reference signal adaptation in which the density of the reference signal configuration may be modified. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0005] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments and / or examples disclosed herein. However, it will be understood that such embodiments and examples may be practiced without some or all of the specific details set forth herein. In other instances, well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the following description. Furthermore, embodiments and examples not specifically described herein may be practiced in place of or in combination with embodiments and other examples explicitly, implicitly and / or inherently (collectively "provided") herein. Although various embodiments are described and / or claimed herein in which apparatus, systems, devices, etc. and / or any elements thereof perform operations, processes, algorithms, functions, etc. and / or any portions thereof, it should be understood that any embodiment described and / or claimed herein assumes that any apparatus, system, device, etc. and / or any elements thereof are configured to perform any operations, processes, algorithms, functions, etc. and / or any portions thereof.

[0006] Exemplary Communication Network The methods, apparatus, and systems provided herein are well suited for communications involving both wired and wireless networks. An overview of various types of wireless devices and infrastructure is provided with reference to Figures 1A-1D, in which various elements of a network may utilize, execute, be arranged in accordance with, and / or be adapted and / or configured for the methods, apparatus, and systems provided herein.

[0007] 1A is a system diagram illustrating an example communication system 100 in which one or more disclosed embodiments may be implemented. The communication system 100 may be a multiple access system that provides content, such as voice, data, video, messaging, broadcasts, etc., to multiple wireless users. The communication system 100 may enable the multiple wireless users to access such content through sharing of system resources, including wireless bandwidth. For example, the communication system 100 may employ one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tail (ZT) unique-word (UW) discrete Fourier transform (DFT) spread OFDM (ZT UW DTS-s OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, filter bank multicarrier (FBMC), etc.

[0008] 1A, the communications system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a radio access network (RAN) 104 / 113, a core network (CN) 106 / 115, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, although it will be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d, any of which may be referred to as a “station” and / or “STA,” may be configured to transmit and / or receive wireless signals and may include (or be) user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a mobile phone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in industrial and / or automated processing chain contexts), household electronic devices, devices operating in commercial and / or industrial wireless networks, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be referred to interchangeably as a UE.

[0009] The communication system 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as, for example, the CN 106 / 115, the Internet 110, and / or the network 112. By way of example, the base station 114a, 114b may be any of a base transceiver station (BTS), a Node-B (Node-B, NB), an eNode-B (eNode-B, eNB), a Home Node-B (Home Node-B, HNB), a Home eNode-B (Home eNode-B, HeNB), a gNode-B (gNode-B, gNB), a NR Node-B (NR NB), a site controller, an access point (AP), a wireless router, etc. Although the base stations 114a, 114b are each depicted as a single element, it will be understood that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0010] The base station 114a may be part of the RAN 104 / 113, which may also include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), a relay node, etc. The base station 114a and / or the base station 114b may be configured to transmit and / or receive wireless signals on one or more carrier frequencies, which may be referred to as a cell (not shown). These frequencies may be licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide wireless service coverage for a particular geographic area, which may be relatively fixed or may change over time. A cell may be further divided into cell sectors. For example, the cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, one transceiver for each sector of the cell. In one embodiment, the base station 114a may employ multiple-input multiple output (MIMO) technology and may utilize multiple transceivers for each or any sector of the cell, for example, using beamforming to transmit and / or receive signals in a desired spatial direction.

[0011] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0012] More specifically, as noted above, the communications system 100 may be a multiple access system and may use one or more channel access schemes, such as, for example, CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. For example, the base stations 114a of the RAN 104 / 113 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may establish the air interface 116 using wideband CDMA (WCDMA). WCDMA may include communications protocols such as High-Speed ​​Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High-Speed ​​Downlink Packet Access (HSDPA) and / or High-Speed ​​Uplink Packet Access (HSUPA).

[0013] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or LTE-Advanced (LTE-Advanced, LTE-A) and / or LTE-Advanced Pro (LTE-A Pro).

[0014] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR radio access, which may establish the air interface 116 using New Radio (NR).

[0015] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may implement LTE radio access and NR radio access together, e.g., using dual connectivity (DC) principles. Thus, the air interface utilized by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions transmitted to / from multiple types of base stations (e.g., eNBs and gNBs).

[0016] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a wireless technology such as IEEE 802.11 (i.e., Wireless Fidelity, Wi-Fi), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access, WiMAX), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile communication (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), or the like.

[0017] 1A may be, for example, a wireless router, a Home NodeB, a Home eNodeB, or an access point, and may utilize any suitable RAT to facilitate wireless connectivity in a localized area, such as, for example, an office, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a road, etc. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In one embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.) to establish either a small cell, a pico cell, or a femto cell. As shown in FIG. 1A, the base station 114b may have a direct connection to the Internet 110. Thus, the base station 114b may not need to access the Internet 110 via the CN 106 / 115.

[0018] The RAN 104 / 113 may communicate with the CN 106 / 115, which may be any type of network configured to provide voice, data, application, and / or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have various quality of service (QoS) requirements, such as, for example, different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 / 115 may provide call control, billing services, mobile location-based services, prepaid calls, Internet connectivity, video distribution, etc., and / or perform high-level security functions such as user authentication. Although not shown in FIG. 1A, it will be understood that the RAN 104 / 113 and / or the CN 106 / 115 may communicate directly or indirectly with other RANs employing the same RAT as the RAN 104 / 113 or a different RAT. For example, the CN 106 / 115, in addition to being connected to the RAN 104 / 113, which may utilize NR radio technology, may communicate with another RAN (not shown) that employs any of GSM, UMTS, CDMA2000, WiMAX, E-UTRA, or Wi-Fi radio technologies.

[0019] The CN 106 / 115 may also serve as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a public switched telephone network that provides plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the transmission control protocol (TCP), user datagram protocol (UDP), and / or the internet protocol (IP) of the TCP / IP Internet protocol suite. The network 112 may include wired and / or wireless communication networks owned and / or operated by other service providers. For example, the network 112 may include another CN connected to one or more RANs, which may employ the same RAT as the RAN 104 / 114 or a different RAT.

[0020] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links). For example, the WTRU 102c shown in FIG. 1A may be configured to communicate with a base station 114a, which may use a cellular-based wireless technology, and a base station 114b, which may use an IEEE 802 wireless technology.

[0021] 1B is a system diagram illustrating an example WTRU 102. As shown in FIG. 1B, the WTRU 102 may include, among other things, a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other elements / peripherals 138. It will be understood that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0022] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), multiple microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) circuit, any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. Although FIG. 1B depicts the processor 118 and the transceiver 120 as separate components, it will be understood that the processor 118 and the transceiver 120 may be integrated into an electronic package or chip, for example.

[0023] The transmit / receive element 122 may be configured to transmit signals to or receive signals from a base station (e.g., base station 114a) over the air interface 116. For example, in one embodiment, the transmit / receive element 122 may be an antenna configured to transmit and / or receive RF signals. In one embodiment, the transmit / receive element 122 may be an emitter / detector configured to transmit and / or receive IR, UV, or visible light signals, for example. In one embodiment, the transmit / receive element 122 may be configured to transmit and / or receive both RF and light signals. It will be appreciated that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0024] 1B as a single element, the WTRU 102 may include any number of transmit / receive elements 122. For example, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0025] The transceiver 120 may be configured to modulate signals transmitted by the transmit / receive element 122 and demodulate signals received by the transmit / receive element 122. As mentioned above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers to enable the WTRU 102 to communicate via multiple RATs, such as, for example, NR and IEEE 802.11.

[0026] The processor 118 of the WTRU 102 may be coupled to and may receive user-entered data from a speaker / microphone 124, a keypad 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light-emitting diode (OLED) display unit). The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from and store data in any type of suitable memory, such as non-removable memory 130 and / or removable memory 132. The non-removable memory 130 may include random-access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, etc. In other embodiments, the processor 118 may access information from, and store data in, memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0027] The processor 118 may receive power from the power source 134, but may be configured to distribute and / or control the power to other components in the WTRU 102. The power source 134 may be any suitable device for providing power to the WTRU 102. For example, the power source 134 may include one or more dry batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0028] The processor 118 may also be coupled to a GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding a current location of the WTRU 102. In addition to or in lieu of information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (e.g., base stations 114a, 114b) over the air interface 116 and / or determine its location based on the timing of signals being received from two or more nearby base stations. It will be understood that the WTRU 102 may obtain location information by way of any suitable location determination method while remaining consistent with an embodiment.

[0029] The processor 118 may be further coupled to other elements / peripherals 138, which may include one or more software and / or hardware modules / units that provide additional features, functions, and / or wired or wireless connectivity. For example, the elements / peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (e.g., for photos and / or videos), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, a Bluetooth® module, a frequency modulated (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, a virtual reality and / or augmented reality (VR / AR) device, an activity tracker, and the like. The elements / peripherals 138 may include one or more sensors, which may be one or more of a gyroscope, an accelerometer, a Hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor, a geolocation sensor, an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, and / or a humidity sensor.

[0030] The WTRU 102 may include a full-duplex radio where transmission and reception of some or all of the signals (e.g., associated with a particular subframe for both the uplink (e.g., for transmission) and downlink (e.g., for reception)) may be parallel and / or simultaneous. The full-duplex radio may include an interference management unit to reduce and or substantially eliminate self-interference either through hardware (e.g., chokes) or signal processing via a processor (e.g., via a separate processor (not shown) or processor 118). In one embodiment, the WTRU 102 may include a half-duplex radio for transmission and reception of some or all of the signals (e.g., associated with a particular subframe for either the uplink (e.g., for transmission) or downlink (e.g., for reception)).

[0031] 1C is a system diagram illustrating the RAN 104 and the CN 106 according to one embodiment. As mentioned above, the RAN 104 may communicate with the WTRUs 102a, 102b, and 102c over the air interface 116 using E-UTRA radio technology. The RAN 104 may also communicate with the CN 106.

[0032] The RAN 104 may include eNode-Bs 160a, 160b, 160c, although it will be understood that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. The eNode-Bs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In an embodiment, the eNode-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the eNode-B 160a may, for example, use multiple antennas to transmit wireless signals to, and receive wireless signals from, the WTRU 102a.

[0033] Each of the eNodeBs 160a, 160b, 160c may be associated with a particular cell (not shown) and configured to handle radio resource management decisions, handover decisions, scheduling of users in the uplink (UL) and / or downlink (DL), etc. As shown in FIG 1C, the eNode-Bs 160a, 160b, 160c may communicate with one another via an X2 interface.

[0034] 1C may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (PGW) 166. Although each of the foregoing elements is depicted as part of the CN 106, it will be understood that any one of these elements may be owned and / or operated by an entity other than the CN operator.

[0035] The MME 162 may be connected to each of the eNode-Bs 160a, 160b, and 160c in the RAN 104 via an S1 interface and may function as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, activating / deactivating bearers, selecting a particular serving gateway during initial attachment of the WTRUs 102a, 102b, 102c, etc. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM and / or WCDMA.

[0036] The SGW 164 may be connected to each of the eNodeBs 160a, 160b, 160c in the RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions such as fixing the user plane during inter-eNodeB handover, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, and managing and storing the context of the WTRUs 102a, 102b, 102c.

[0037] The SGW 164 may be connected to a PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0038] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include or communicate with an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers.

[0039] Although the WTRU is illustrated in FIGS. 1A-1D as a wireless terminal, it is contemplated that in certain representative embodiments, such a terminal may use a wired communications interface (e.g., temporarily or permanently) with the communications network.

[0040] In an exemplary embodiment, the other network 112 may be a WLAN.

[0041] A WLAN in infrastructure basic service set (BSS) mode may have an access point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may have access or interface to a distribution system (DS) or another type of wired / wireless network that carries traffic within and / or outside the BSS. Traffic originating from outside the BSS to the STAs may arrive through the AP and be delivered to the STAs. Traffic originating from the STAs to destinations outside the BSS may be sent to the AP and delivered to the respective destination. Traffic between STAs in the BSS may be sent, for example, through the AP, where the source STA may send traffic to the AP, which may deliver the traffic to the destination STA. Traffic between STAs in the BSS may be considered and / or referred to as peer-to-peer traffic. Peer-to-peer traffic may be sent in a direct link setup (DLS) between the source STA and the destination STA (e.g., directly between them). In one representative embodiment, the DLS may use 802.11e DLS or 802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and STAs (e.g., all of the STAs) within or using the IBSS may communicate directly with each other. The IBSS communication mode is sometimes referred to herein as an "ad-hoc" communication mode.

[0042] When using an 802.11ac infrastructure mode of operation or a similar mode of operation, an AP may transmit a beacon on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., a 20 MHz wide bandwidth) or a width that is dynamically set via signaling. The primary channel may be an operating channel of a BSS and may be used by STAs to establish a connection with an AP. In one representative embodiment, Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) may be implemented, for example, in an 802.11 system. With CSMA / CA, STAs (e.g., all STAs), including the AP, may sense the primary channel. If the primary channel is sensed / detected and / or determined to be busy by a particular STA, the particular STA may back off. One STA (e.g., only one station) may transmit at any given time in a given BSS.

[0043] High throughput (HT) STAs may use, for example, a 40 MHz wide channel for communication via a combination of a primary 20 MHz channel with adjacent or non-adjacent 20 MHz channels to form a 40 MHz wide channel.

[0044] A Very High Throughput (VHT) STA may support 20 MHz, 40 MHz, 80 MHz, and / or 160 MHz wide channels. The above 40 MHz and / or 80 MHz wide channels may be formed by combining multiple contiguous 20 MHz channels. A 160 MHz channel may be formed by combining eight contiguous 20 MHz channels or by combining two non-contiguous 80 MHz channels, which may be referred to as an 80+80 configuration. For the 80+80 configuration, after channel encoding, the data may pass through a segment parser that may split the data into two streams. Inverse fast fourier transform (IFFT) processing and time domain processing may be performed separately on each stream. The streams may be mapped to two 80 MHz channels and the data may be transmitted by the transmitting STA. At the receiver of the receiving STA, the above-mentioned operations for the 80+80 configuration may be reversed and the combined data may be transmitted to a medium access control (MAC) layer, entity, etc.

[0045] Sub-1 GHz operating modes are supported by 802.11af and 802.11ah. Channel operating bandwidths and carriers are reduced in 802.11af and 802.11ah compared to those used in 802.11n and 802.11ac. 802.11af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in TV white space (TVWS) spectrum, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah may support meter-type control / machine-type communication (MTC) such as MTC devices in macro coverage areas. MTC devices may have certain capabilities, including, for example, support for (e.g., only support for) certain and / or limited bandwidths. MTC devices may include batteries with battery life above a threshold (e.g., to maintain very long battery life).

[0046] WLAN systems that may support multiple channels and channel bandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include a channel that may be designated as a primary channel. The primary channel may have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be configured and / or limited by the STAs among all STAs operating in the BSS that support the smallest bandwidth operating mode. In an 802.11ah example, the primary channel may be 1 MHz wide for STAs (e.g., MTC type devices) that support (e.g., only) the 1 MHz mode, even if the AP and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or network allocation vector (NAV) settings may depend on the state of the primary channel. For example, if the primary channel is busy due to STAs (that only support 1 MHz mode of operation) transmitting to the AP, the entire available frequency band may be considered busy even though most of the frequency band may remain idle and available for use.

[0047] In the United States, the available frequency bands that can be used by 802.11ah are 902MHz to 928MHz. In South Korea, the available frequency bands are 917.5MHz to 923.5MHz. In Japan, the available frequency bands are 916.5MHz to 927.5MHz. The total bandwidth available for 802.11ah is 6MHz to 26MHz depending on the country code.

[0048] 1D is a system diagram illustrating the RAN 113 and the CN 115 according to one embodiment. As mentioned above, the RAN 113 may communicate with the WTRUs 102a, 102b, 102c over the air interface 116 using NR radio technology. The RAN 113 may also communicate with the CN 115.

[0049] The RAN 113 may include gNBs 180a, 180b, 180c, although it will be understood that the RAN 113 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In an embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, the gNBs 180a, 180b may utilize beamforming to transmit signals to and / or receive signals from the WTRUs 102a, 102b, 102c. Thus, the gNB 180a may transmit wireless signals to and / or receive wireless signals from the WTRUs 102a, 102b, 102c using, for example, multiple antennas. In one embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, the gNB 180a may transmit multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers may be on an unlicensed spectrum, and the remaining component carriers may be on a licensed spectrum. In one embodiment, the gNBs 180a, 180b, 180c may implement Coordinated Multi-Point (CoMP) technology. For example, the WTRU 102a may receive coordinated transmissions from the gNBs 180a and 180b (and / or gNB 180c).

[0050] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with a scalable numerology. For example, the OFDM symbol spacing and / or OFDM subcarrier spacing may be different for different transmissions, different cells, and / or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or transmission time intervals (TTIs) of different or scalable lengths (e.g., including varying numbers of OFDM symbols and / or varying lengths of absolute time durations).

[0051] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c without accessing another RAN (e.g., eNode-Bs 160a, 160b, 160c, etc.). In a standalone configuration, the WTRUs 102a, 102b, 102c may utilize one or more of the gNBs 180a, 180b, 180c as mobility anchor points. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in unlicensed bands. In a non-standalone configuration, the WTRUs 102a, 102b, 102c may communicate with and connect to a gNB 180a, 180b, 180c while also communicating with and connecting to another RAN, such as an eNode-B 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement DC principles to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the eNode-Bs 160a, 160b, 160c may act as mobility anchors for the WTRUs 102a, 102b, 102c, while the gNBs 180a, 180b, 180c may provide additional coverage and / or throughput for serving the WTRUs 102a, 102b, 102c.

[0052] Each of the gNBs 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, support for network slicing, dual connectivity, interworking between NR and E-UTRA, routing of user plane data towards user plane functions (UPFs) 184a, 184b, routing of control plane information towards access and mobility management functions (AMFs) 182a, 182b, etc. As shown in FIG. 1D, the gNBs 180a, 180b, 180c may communicate with each other via an Xn interface.

[0053] 1D may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and at least one Data Network (DN) 185a, 185b. Although each of the foregoing elements is depicted as part of the CN 115, it will be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0054] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N2 interface and may function as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, support for network slicing (e.g., handling different protocol data unit (PDU) sessions with different requirements), selecting a particular SMF 183a, 183b, managing registration areas, terminating NAS signaling, mobility management, etc. Network slicing may be used by the AMF 182, 182b, for example, to customize the CN support of the WTRUs 102a, 102b, 102c based on the type of service being utilized by the WTRUs 102a, 102b, 102c. For example, different network slices may be established for different use cases, such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for MTC access, etc. The AMF 162 may provide a control plane function for switching between the RAN 113 and other RANs (not shown) that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies such as Wi-Fi.

[0055] The SMFs 183a, 183b may be connected to the AMFs 182a, 182b in the CN 115 via an N11 interface. The SMFs 183a, 183b may also be connected to the UPFs 184a, 184b in the CN 115 via an N4 interface. The SMFs 183a, 183b may select and control the UPFs 184a, 184b and configure the routing of traffic through the UPFs 184a, 184b. The SMFs 183a, 183b may perform other functions such as managing and assigning UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, providing downlink data notification, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0056] The UPFs 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks such as the Internet 110, for example to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPFs 184, 184b may perform other functions such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering downlink packets, providing mobility anchoring, etc.

[0057] The CN 115 may facilitate communication with other networks. For example, the CN 115 may include or communicate with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves as an interface between the CN 115 and the PSTN 108. In addition, the CN 115 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers. In an embodiment, the WTRUs 102a, 102b, 102c may be connected to local data networks (DNs) 185a, 185b via the UPFs 184a, 184b via an N3 interface with the UPFs 184a, 184b and an N6 interface between the UPFs 184a, 184b and the DNs 185a, 185b.

[0058] 1A-1D and the corresponding description thereof, one or more or all of the functions described herein with respect to any of the WTRUs 102a-d, base stations 114a-b, eNodeBs 160a-c, MME 162, SGW 164, PGW 166, gNBs 180a-c, AMFs 182a-b, UPFs 184a-b, SMFs 183a-b, DNs 185a-b, and / or any other elements / devices described herein may be performed by one or more emulation elements / devices (not shown). The emulation devices may be one or more devices configured to emulate one or more or all of the functions described herein. For example, the emulation devices may be used to test other devices and / or simulate network and / or WTRU functions.

[0059] The emulation devices may be designed to implement one or more tests of other devices in a lab environment and / or an operator network environment. For example, one or more emulation devices may perform one or more or all functions while fully or partially implemented and / or deployed as part of a wired and / or wireless communication network to test other devices in the communication network. One or more emulation devices may perform one or more or all functions while temporarily implemented / deployed as part of a wired and / or wireless communication network. The emulation devices may be directly coupled to another device for testing purposes and / or may perform testing using terrestrial wireless communication.

[0060] The one or more emulation devices may perform one or more functions, including but not limited to, while not implemented / deployed as part of a wired and / or wireless communication network. For example, the emulation devices may be utilized in test scenarios in a test lab and / or in an undeployed (e.g., test) wired and / or wireless communication network to implement testing of one or more components. The one or more emulation devices may be test equipment. Direct RF coupling and / or wireless communication via RF circuitry (which may include, for example, one or more antennas) may be used by the emulation devices to transmit and / or receive data.

[0061] Channel Estimation Example A pilot-based scheme may be used, for example, in a network to enable joint channel estimation (CE) coherent demodulation of either precoded and beamformed signals, for example at a receiver. For example, a demodulation reference signal (DMRS) may be used in 5G New Radio (NR) for this purpose.

[0062] FIG. 2 is a diagram illustrating an example of a composite channel estimation procedure based on a (e.g., user-specific) reference signal. For example, composite channel estimation (CE) coherent demodulation of either precoded or beamformed signals can be performed by applying the same precoding (e.g., beamforming) weight to a reference signal that may be used in either a downlink physical channel or an uplink physical channel. For example, precoding weights 21, 22 can be applied to a physical resource block (PRB) before transmission. The same precoding weights 21, 22 (e.g., may be known to the receiver) can be applied to the reference signal at the receiver side for channel estimation. For example, a first channel estimation can be based on a first precoding weight 21, and a second channel estimation can be based on a second precoding weight 22.

[0063] To accommodate different deployment scenarios, different configurations of DMRS may be used in 5G networks. For example, different configurations of DMRS may include various (e.g., different) time and frequency densities of reference signals. The configuration of DMRS, such as any of the density and location in the resource grid, orthogonal cover codes, duration, starting symbol, etc., may affect (e.g., dictate) CE performance. For example, the density of reference signal transmission in any of the time and frequency may be configured according to any of the time and frequency selectivity (e.g., sensitivity) of the communication channel. For example, a dense (e.g., tighter) distribution of reference signals in the frequency domain may enable a higher frequency selectivity of the communication channel (e.g., than a sparser distribution). For example, more frequent transmission of reference signals may enable (e.g., support) a higher rate of fading in the time domain.

[0064] Described herein are mechanisms (e.g., methods, architectures, devices, and systems) for adaptive transmission of a reference signal (RS) to a network based on a terminal indication of an (e.g., preferred) configuration of the RS. For example, the selection of an RS (e.g., DMRS) configuration by a terminal may be based on (e.g., instantaneous) measurements that may be performed by the terminal based on any CE scheme. In another example, an RS (e.g., DMRS) configuration may be selected by a terminal by applying any of artificial intelligence and a machine learning (AI / ML) based analyses to any of the (e.g., collected) CE configurations and CE measurements.

[0065] For clarity, the embodiments are described herein with the example of downlink DMRS. The embodiments described herein are not limited to downlink DMRS and may be applicable to any other reference signal (e.g., any of CSI-RS and uplink reference signals). Throughout the embodiments described herein, the terms "reference signal configuration", "DMRS configuration", "reference signal configuration", and "DMRS configuration" may be used interchangeably to specify a reference signal configuration. Throughout the embodiments described herein, the terms "default reference signal configuration" and "first reference signal configuration" may be used interchangeably. Throughout the embodiments described herein, the terms "second reference signal configuration", "(e.g., preferred) reference signal configuration", and "selected reference signal configuration" may be used interchangeably to specify a reference signal configuration that may be selected (e.g., requested) by a WTRU for a subsequent transmission, for example. Throughout the embodiments described herein, the terms "terminal", "receiver", and "WTRU" may be used interchangeably to specify any device capable of receiving wireless signals, performing channel estimation, and selecting a (e.g., preferred) reference signal configuration. In the embodiments described herein, either AI or ML may be referred to as AI / ML. In the embodiments described herein, the terms "reference signal" and "pilot" may be used interchangeably.

[0066] Throughout the embodiments described herein, the terms "explicit" and "explicit," e.g., when associated with any of "transmitting," "indicating," and "reporting" a piece of information, may be used to designate a transmission (e.g., of a message) that includes an information element that indicates (e.g., explicit) information. The message that includes the (e.g., explicit) information may be included in any of the physical uplink control channel (PUCCH) and uplink control information (UCI).

[0067] Throughout the embodiments described herein, the terms "implicitly" and "implicit", when associated with, for example, any of "transmitting", "indicating" and "reporting" information, may be used to specify transmission (e.g., of any type of information) in (e.g., specific) resources that may be associated with the information. The (e.g., specific) resources may be, for example, specific PUCCH resources, random-access channel (RACH) resources, any of sounding reference signal (SRS) resources, spatial relationship information (e.g., spatialrelationInfo) resources, etc.

[0068] Throughout the embodiments described herein, the terms "serving base station," "base station," "gNB," and collectively the "network" may be used interchangeably to designate a network element that serves as a serving base station. The embodiments described herein are not limited to gNBs and are applicable to any other type of serving base station.

[0069] The 3GPP standard provides some flexibility in pilot configuration to cater for different WTRU capabilities and use cases. For example, for 5G NR physical downlink shared channel (PDSCH) DMRS, there may be configurations including any of configuration type 1, configuration type 2, mapping type A, mapping type B, starting symbol for mapping type A, single vs. double symbol DMRS, DMRS addition position, and duration.

[0070] 3 is a diagram illustrating an example of a 5G NR DMRS configuration. The DMRS configuration may be a single symbol configuration type 1 that may support up to 4×4 MIMO. FIG. 3 shows an example DMRS pattern over one symbol and one resource block in 5G NR with configuration type 1, mapping type A, and starting symbol 3, using downlink antenna ports 1000, 1001, 1002, and 1003 with CDM group 0 31 and CDM group 1 32 across frequency 30 and code domain.

[0071] For example, the CE performance may depend on any of the configuration and receiver implementation (eg, characteristics) of the DMRS.

[0072] For example, a higher density of reference signals (e.g., for a given implementation) may increase CE accuracy (and, e.g., overhead) and may decrease spectral efficiency. In the case of multi-user multiple-input multiple-output (MU-MIMO), a higher density of reference signals may reduce the range for spatial multiplexing.

[0073] For example, performing channel estimation over a larger number of physical resource blocks (PRBs) (e.g., for a given implementation) may allow for improved performance (e.g., when delay spread is small, e.g., negligible). Increasing the number of PRBs for CE (which may be referred to as "bundling") may reduce the resolution for frequency selective precoding.

[0074] For example, (e.g., for a given implementation) MU-MIMO may be based on code division multiplexing (CDM) to distinguish antenna ports sharing the same resource element (RE). For example, adding pilot REs across additional symbols may allow for increased CDM capacity for higher order MIMO.

[0075] For example, (eg, for a given implementation), if the density of reference signals is the same, the location of the pilots on the resource grid may affect the computational complexity of the receiver (eg, the number of extrapolation versus interpolation operations).

[0076] For example, when (e.g., even) using a limited number of options for reference signal configurations (including patterns that may be available in 5G NR), a (e.g., optimal) selection (e.g., of a DMRS configuration) may be complex to obtain. This may result in inefficient (e.g., user-specific) reference signal configurations that may under- or over-utilize radio resources for pilots, such as physical resource elements (PREs). The complexity of selecting a configuration of a user-specific reference signal may further increase when an increased number of reference signal configurations (e.g., with an increased number of different parameters) are available for selection. For example, there may be DMRS configurations with flexible DMRS patterns. The embodiments described herein may enable improved DMRS configuration selection such that the efficiency of radio resource utilization for pilots may be improved. The embodiments described herein may further enable enabling DMRS-less transmission of physical channels in 5G NR.

[0077] The embodiments described herein may facilitate (e.g., enable) adaptive reference signal transmission through mechanisms that may enable a terminal to indicate (e.g., transmit an indication of) a (e.g., preferred) configuration of a reference signal to the network. For example, an indication of the (e.g., preferred) reference signal configuration may be transmitted to the network either implicitly and explicitly. The embodiments described herein may provide benefits such as reduced DMRS resource usage overhead, reduced DMRS signaling overhead, and / or improved CE accuracy.

[0078] Overview of Adaptive Reference Signal Configuration The embodiments are described herein using an example of a cellular communication network including at least a WTRU and a base station. The WTRU may be any type of WTRU, including, for example, any of a smartphone, a sensor, a relay, etc. The embodiments described herein may be applicable to any type of transceiver chain, including, for example, multiple antennas in any (e.g., both) of the base station and the WTRU. For clarity, the embodiments are described herein using an example of a downlink DMRS. The embodiments described herein are not limited to downlink DMRS and may be applicable to any other reference signal. For example, the embodiments described herein may be applicable to both a downlink reference signal (e.g., CSI-RS, etc.) and an uplink reference signal.

[0079] For example, a physical channel in either the downlink or uplink direction may be accompanied by a (e.g., user-specific) reference signal (e.g., DMRS), which may also be referred to herein as a pilot, to facilitate composite channel estimation and coherent demodulation. This may be accomplished by populating the PRE (e.g., transmitting the reference signal) based on a pseudo-random sequence, which may be generated based on system parameters (e.g., any combination of slot number, symbol number, and scrambling identity) that may be known to the receiver. For example, in 5G NR (e.g., basic), DMRS may be supported in the WTRU, e.g., without capability signaling.

[0080] For example, the configuration of the DMRS may include any of the following: density and pattern of reference signals in the resource grid, duration, starting symbol (e.g., frontloading DMRS), and cover code, for example, to distinguish between antenna ports sharing the same time / frequency resource (for either single-user MIMO case or multi-user MIMO case). For example, the set of parameters for the DMRS may vary depending on any of the physical channel and WTRU capabilities. For example, the DMRS may be grouped over several (e.g., consecutive) resource blocks for which the precoder may be constant so that the receiver may perform wideband channel estimation. For example, the (e.g., specific) selection of the DMRS may be performed by any of higher layer configuration and dynamic (e.g., DCI-based) signaling. For example, one or more default configurations may be available (e.g., pre-configured) in the WTRU.

[0081] The embodiments described herein may enable a wireless communication terminal (e.g., having suitable WTRU capabilities) to assist in the configuration of (e.g., user-specific) reference signals that may be used for composite channel estimation and coherent demodulation of physical channels.

[0082] For example, the base station may configure the DMRS with the corresponding physical channel using some higher layer parameters and dynamic (DCI-based) signaling. For example, the base station may send DMRS configuration information to the WTRU via any type of signaling. For example, the configuration information may indicate one or more default configurations of the DMRS. For example, the (e.g., default) configuration of the DMRS may include any of the following: location and density of the reference signal in the resource grid (e.g., PRB, slot, port), cover code, starting symbol, additional symbols. There may be different reference signal configurations with different parameters (e.g., options) depending on, for example, any of the types of physical channels (e.g., PDSCH, PBCH), WTRU capabilities, antenna number and location, etc. For example, the DMRS (e.g., pilot) may be generated using a pseudo-random sequence (e.g., GOLD sequence, etc.) based on system parameters that may be known to the receiver (e.g., pre-configured in the receiver). Parameters that may be used to control this sequence generation may include any of the following: scrambling identity, symbol location, number of OFDM symbols in a slot, etc. For example, after selecting a DMRS setting (e.g., reference signal configuration), the base station may signal the selection to the WTRU (e.g., transmit signaling information indicating the selection). The selected DMRS setting (e.g., reference signal configuration) may be indicated to the WTRU based on any of a radio resource control (RRC) message, a MAC control element (MAC-CE), and a physical downlink control channel (PDCCH) DCI. For example, the WTRU may perform composite channel estimation and coherent demodulation of the corresponding physical channel based on the DMRS. This may be achieved through a specific receiver filter implementation (e.g., least squares, minimum mean squared error, etc.) that may broadly estimate the composite channel by mapping transmitted layers onto receive antennas for scheduled resource blocks.

[0083] For example, the receiver may (e.g., initially) determine an estimate of the channel of the pilot symbols from their known positions in the received slot. For example, an averaging window may be used to reduce the effects of noise.

[0084] For example, multi-dimensional interpolation and extrapolation operations may be used to estimate the missing values ​​from the channel estimation grid.

[0085] For example, a noise power estimation may be performed to improve performance by comparison of either a direct channel estimate and an average channel estimate.

[0086] For example, using the channel estimation, the WTRU may proceed (e.g., perform) coherent demodulation of the precoded / beamformed physical channel (e.g., including data symbols). For example, the data may be demodulated based on the estimated channel. After the data may be demodulated, a (e.g., actual, current) channel may be obtained (e.g., based on the demodulated data) and compared to the estimated channel.

[0087] For example, the accuracy of the channel estimation may be obtained in relation to an error (e.g., performance) metric that may be obtained (e.g., measured) on the demodulated data symbols. For example, the error (e.g., performance) metric may be any of the mean-square-error (MSE), bit-error-rate (BER) performance, and error-vector-magnitude (EVM).

[0088] First Example of Adaptive Reference Signal Construction Method For example, the WTRU may have capabilities that enable the WTRU to assist (e.g., a base station) in adaptive configuration and transmission of (e.g., user-specific) reference signals (e.g., DMRS) used for composite channel estimation and coherent demodulation of physical channels. For example, the WTRU may receive configuration information indicating any number of (e.g., anchor, default) reference signal (e.g., DMRS) configurations, where (e.g., each) reference signal configuration may be associated with an index. For example, the WTRU may store any of the reference signal (e.g., DMRS) configurations and channel estimation measurements in a database that may be accessible (e.g., available) to the device. For example, the WTRU may select (e.g., determine, decide) a (e.g., preferred) configuration or a list of (e.g., preferred) configurations of reference signals (e.g., DMRS) for any number of subsequent transmissions of the physical channel. The selection may be performed, for example, using AI / ML-based learning on stored historical data. In another example, the selection may be based (e.g., solely) on (e.g., instantaneous CE) measurements. For example, the WTRU may indicate to the network a (e.g., preferred) configuration or a list of (e.g., preferred) configurations of reference signals (e.g., DMRSs) for subsequent use (e.g., transmission) on a physical channel, either explicitly (e.g., through transferring a (e.g., preferred) configuration index over any of the uplink control and data channels) and implicitly (e.g., by using specific uplink control and data channel resources).

[0089] For example, in a first step, the WTRU may be pre-configured with any number of (e.g., anchor, default) DMRS configurations. For example, the WTRU may be pre-configured, e.g., at a factory setting. In another example, the WTRU may receive (e.g., from a network) first configuration information indicating any number of (e.g., anchor, default) DMRS configurations. For example, each (e.g.) reference signal configuration may be associated with an index.

[0090] For example, in the second step, the WTRU may receive an indication of a DMRS configuration for transmission of the physical channel from the network. The indication of the DMRS configuration may be included in second configuration information that may be received via any of RRC (e.g., a message), MAC-CE, and PDCCH (e.g., DCI). For example, the first configuration information and the second configuration information may be received in any of the same message (e.g., transmission) and different messages (e.g., transmission).

[0091] For example, in a third step, the WTRU may use a (eg, user-specific) reference signal to perform joint CE and coherent demodulation of the corresponding physical channel.

[0092] For example, in a fourth step, if the WTRU has this capability, the WTRU may store the indicated DMRS configuration (e.g., in terms of any of pattern, density, RB, antenna port, etc.) and any of the CE measurements (e.g., complex channel coefficients, etc.) in, for example, a database.

[0093] For example, in the fifth step, the WTRU may select (e.g., determine, decide) a (e.g., preferred) configuration of the DMRS for any of the subsequent downlink and uplink transmissions. For example, the selection of the (e.g., preferred) configuration of the DMRS may be performed using AI / ML-based learning on a history of any of the DMRS configurations and CE measurements, which may have been collected over a period of time. In another example, the (e.g., preferred) configuration of the DMRS may be selected based on (e.g., instantaneous) measurements, e.g., using CE techniques, such as, e.g., any of Doppler, delay spread, etc.

[0094] For example, in the sixth step, the WTRU may indicate a selected (e.g., preferred) configuration of the DMRS to the network, e.g., if the corresponding WTRU capability is enabled. An indication of the determined (e.g., preferred) configuration of the DMRS may be transmitted either explicitly and implicitly. Explicitly transmitting an indication of a reference signal configuration may be referred to herein as transmitting a message including (e.g., explicit) information (e.g., an index of a reference signal configuration, etc.) indicating a selected (e.g., preferred) configuration of a reference signal. A message including a (e.g., explicit) configuration selection may be included in either a physical uplink control channel (PUCCH) and an uplink control information (UCI). Implicitly transmitting an indication of a reference signal configuration may be referred to herein as performing a transmission in (e.g., a specific) resource that may be associated with a selected reference signal configuration (e.g., an index of a reference signal configuration, etc.). The (e.g., specific) resource may be, for example, any of a specific PUCCH resource, a Random Access Channel (RACH) resource, a Sounding Reference Signal (SRS) resource, a spatial relationship information (e.g., spatialrelationInfo) resource, etc. For example, it may be indicated that pilotless transmission may be adapted (e.g., performed) if the channel coherence interval is large or if previous channel estimates are applicable for a subsequent transmission.

[0095] FIG. 4 is a system diagram illustrating a first example of an adaptive reference signal configuration method. The WTRU 41 may communicate with the base station 40 via a cellular wireless network. For example, the WTRU 41 may receive a downlink transmission from the base station 40. The WTRU 41 may perform any of multi-carrier signal reception, channel estimation, MIMO equalization, layer demapping, and coherent demodulation. The WTRU 41 may comprise a database 410 for storing historical pilot configurations (e.g., a set of reference signal configurations that may have been used for previous transmissions). For example, the database 410 may include historical CE measurements, such as, for example, frequency domain channel samples, noise statistics, EVM, etc. For example, the WTRU 41 may comprise an AI / ML module 411 (e.g., running on a processor) that may be configured to perform any of channel predictions (e.g., coherence interval, confidence level) and select a reference signal configuration (e.g., for a subsequent transmission).

[0096] FIG. 5 is a diagram illustrating example message exchanges for a first example adaptive reference signal configuration method.

[0097] For example, the WTRU may transmit a first message 51 including capability information indicating the WTRU's capability to perform an adaptive reference signal method, eg, according to the first example.

[0098] For example, the WTRU may receive configuration information 52 indicating a reference signal configuration.

[0099] For example, the WTRU may receive a PDSCH transmission 53 (eg, in accordance with a reference signal configuration).

[0100] For example, in step 54, the WTRU may perform CE and demodulate the PDSCH transmission.

[0101] For example, in step 55, the WTRU may store the reference signal configuration used in the PDSCH transmission and any CE measurements performed for the PDSCH transmission.

[0102] For example, in step 56, the WTRU may select a (eg, preferred) reference signal configuration (eg, a list thereof) for a subsequent transmission.

[0103] For example, the WTRU may transmit an indication of the selected reference signal configuration 57 to the base station. This indication transmission may be either implicit or explicit.

[0104] For example, the WTRU may receive information 58 indicating that the reference signal configuration may have been updated.

[0105] Second Example of Adaptive Reference Signal Construction Method For example, a wireless communication base station may adaptively configure transmission of (e.g., user-specific) reference signals (e.g., DMRS) for composite channel estimation and coherent demodulation of any of beamformed and precoded physical channels.

[0106] For example, in a first step, the base station may indicate (e.g., transmit information indicative of) any number of anchor (e.g., default) reference signal configurations to the WTRU, e.g., via a downlink control channel. For example, (e.g., each) reference signal configuration may be associated with an index. For example, the base station may receive an indication from a WTRU (e.g., having certain WTRU capabilities) of a (e.g., preferred) configuration or list of configurations of reference signals to use in a subsequent physical channel. This indication may be received either explicitly (e.g., through receiving a (e.g., preferred) configuration index over any of the uplink control and data channels) and implicitly (e.g., inferred from a WTRU selection of parameters internal to any of the uplink control and data channel resources). For example, the base station may store the reference signal configurations (e.g., in terms of any of pattern, density, RB, antenna port, etc.) in a database. Reference signal configurations may be captured for various (e.g., different) physical channels in any of the downlink and uplink from any number of WTRUs.

[0107] For example, in a second step, the base station may utilize tools from AI / ML to assist the WTRU with any of the database storage and AI / ML learning framework complexities. For example, the base station may provide input to the WTRU with respect to, for example, any of the number and type of data to be stored, as well as the AI / ML model specifications (e.g., any of the architecture, learning rate, etc.). For example, the base station may determine parameters of the AI / ML learning scheme to be used in the WTRU for selection of a (e.g., preferred) configuration of the DMRS. For example, historical DMRS configurations may be stored in a database in the network.

[0108] For example, in the third step, the base station may communicate (e.g., transmit information indicative of) a learning framework (e.g., input) used by the WTRU to select a (e.g., preferred) reference signal configuration. The information indicative of the learning framework to be used may be transmitted to the WTRU based on any type of signaling (e.g., DCI-based). For example, in the case of deep learning, the learning framework information may include an indication of any of the architecture, number of layers, activation function, etc.

[0109] For example, in a fourth step, the WTRU may direct this information to adjusted storage of any of the past DMRS configurations, channel estimation measurements (e.g., any of the number of RBs, ports, duration, metrics, etc.). For example, the WTRU may adapt its policy of storing historical data based on the information received from the base station.

[0110] For example, in the fifth step, the WTRU may utilize the received information to select a (e.g., preferred) configuration of DMRS for the subsequent physical channel. This may be performed based on either an AI / ML-based analysis of collected historical data and through performing CE. The selected reference signal configuration may be associated with an index (e.g., a certain) to facilitate feedback between the base station and the WTRU.

[0111] For example, in the sixth step (e.g., if WTRU capability is enabled), the WTRU may indicate (e.g., send information indicating) the selected reference signal configuration either explicitly (e.g., by including information in the PUCCH / UCI) and implicitly by selection of certain uplink resources (e.g., any of specific PUCCH resources, RACH resources, SRS resources, spatial relationship information (e.g., spatialrelationInfo) resources, etc.). The adaptive reference signal configuration method according to the second example may enable reducing complexity on the WTRU side by utilizing the network to assist in AI / ML-based selection of a reference signal configuration at the WTRU.

[0112] FIG. 6 is a system diagram illustrating a second example of an adaptive reference signal configuration method. The WTRU 61 may communicate with the base station 60 via a cellular wireless network. For example, the WTRU 61 may receive a downlink transmission from the base station 60. The WTRU 61 may perform any of multi-carrier signal reception, channel estimation, MIMO equalization, layer demapping, and coherent demodulation. The WTRU 61 may comprise a database 610 for storing historical pilot configurations (e.g., a set of reference signal configurations that may have been used for previous transmissions). For example, the database 610 may include historical CE measurements, such as, for example, frequency domain channel samples, noise statistics, EVM, etc. For example, the WTRU 61 may comprise an AI / ML module 611 (e.g., running on a processor) that may be configured to perform any of channel predictions (e.g., coherence interval, confidence level) and select a reference signal configuration (e.g., for a subsequent transmission).

[0113] For example, base station 60 may comprise a database 600 for storing historical pilot configurations (e.g., a set of reference signal configurations that may have been used for previous transmissions by WTRU 61). For example, database 600 may include historical CE measurements, such as, for example, a signaled pilot configuration list. For example, base station 60 may comprise an AI / ML module 601 (e.g., running on a processor) that may be configured to assist the WTRU in selecting a (e.g., optimal) reference signal configuration (e.g., density, location, etc.). AI / ML module 601 may further comprise an AI / ML training model (e.g., a neural network architecture).

[0114] FIG. 7 is a diagram illustrating example message exchanges for the second example adaptive reference signal configuration method.

[0115] For example, in step 70, the base station may store any of the reference signal configurations and the CE measurements in a database.

[0116] For example, the WTRU may transmit a first message 71 including capability information indicating the WTRU's capability to perform an adaptive reference signal method, eg, according to the second example.

[0117] For example, the WTRU may receive configuration information 72 indicating any of the reference signal configuration and the learning framework (eg, parameters).

[0118] For example, the WTRU may receive a PDSCH transmission 73 (eg, in accordance with a reference signal configuration).

[0119] For example, in step 74, the WTRU may perform CE and demodulate the PDSCH transmission.

[0120] For example, in step 75, the WTRU may store the reference signal configuration used in the PDSCH transmission and any CE measurements performed for the PDSCH transmission.

[0121] For example, in step 76, the WTRU may select (e.g., a list of) (e.g., preferred) reference signal configurations for a subsequent transmission, e.g., using the indicated learning framework. For example, an AI / ML learning module may be configured according to parameters of the indicated learning framework.

[0122] For example, the WTRU may transmit an indication of the selected reference signal configuration 77 to the base station. This indication transmission may be either implicit or explicit.

[0123] For example, the WTRU may receive information 78 indicating that the reference signal configuration may have been updated.

[0124] Example of an adaptive reference signal configuration method Described herein are example methods for a WTRU to determine (e.g., select) and indicate a (e.g., preferred) configuration of a DMRS for a subsequent transmission, either through learning (e.g., of past configurations and measurements) and through performing CE measurements.

[0125] For example, a wireless communication system may comprise a multi-antenna base station communicating with a multi-antenna WTRU, and transmissions of a data channel may be accompanied by a (e.g., user-specific) reference signal to facilitate (e.g., aid) composite channel estimation and coherent demodulation at a receiver. For example, the density of the reference signal transmissions in either time or frequency may be configured according to either the time and frequency selectivity of the communication channel. For example, the higher the frequency selectivity, the denser the distribution of the reference signal may be in the frequency domain. For example, an increased rate of fading in the time domain may be compensated for by more frequent transmission of the reference signal.

[0126] For example, a WTRU may have (e.g., be capable of) selecting and signaling (e.g., either explicitly and implicitly) a (e.g., preferred) configuration of a DMRS (e.g., a preferred reference signal configuration). Capability information indicating such a capability of the WTRU to the base station may be transmitted, e.g., as part of an RRC message, e.g., within an initial registration process. For example, this capability information may be included in an information element of the RRC message, which may enable the WTRU to indicate, e.g., whether it supports additional DMRS patterns (e.g., beyond the existing DMRS patterns) without a specific capability signaling configuration.

[0127] For example, a WTRU (e.g., having the capability to select a (e.g., preferred) reference signal configuration) may be configured with (e.g., may receive configuration information indicative of) a default configuration for reference signals, e.g., the reference signals may be placed at initial configured intervals in any of the frequency and time domains. For example, the time / frequency intervals used in the default configuration may be based on (e.g., maximum possible) separation in time and frequency. In another example, the time / frequency intervals used in the default configuration may be based on any of the historical configuration, deployment scenario, mobility configuration, MIMO mode, traffic type, priority, and latency, etc. A reference signal placed based on a default configuration may be referred to herein as an anchor reference signal.

[0128] In an example, a WTRU may be configured with (e.g., may receive configuration information indicating) one or more default reference signal configurations. For example, the (e.g., each) default reference signal configuration may be associated with an index.

[0129] For example, the WTRU may receive an indication (e.g., an index, or any type of identifier that identifies a reference signal configuration, etc.) from the base station to indicate one of the (e.g., pre-configured, default) reference signal configurations.

[0130] For example, the WTRU may (e.g., self) determine a default reference signal configuration based on measurements such as, for example, any of Doppler, delay spread, etc. The determination of the default reference signal configuration may be performed, for example, without receiving any indication of the default configuration from the base station.

[0131] For example, any of N ranges (e.g., ranges) of Doppler values ​​and M ranges of delay spread values ​​may be determined. For example, different ranges may correspond to different anchor reference signal configurations. For example, the N and M ranges of Doppler and delay spread values, respectively, may be any of pre-configured in the WTRU and configured by the network (e.g., based on receiving configuration information). The WTRU may determine a default reference signal configuration based on (e.g., Doppler, delay spread) measurements (e.g., based on an association between reference signal configurations and ranges of values).

[0132] For example, the WTRU may indicate its determined default reference signal configuration to the base station either implicitly or explicitly. For example, the WTRU may explicitly indicate its determined configuration by an index (e.g., by sending a message including the index). For example, the WTRU may implicitly indicate the information by using any of a particular PUCCH resource, RACH resource, SRS resource, spatial relationship information (e.g., spatialrelationInfo) resource, etc. (which may, for example, be associated with the reference signal configuration (e.g., index)).

[0133] For example, the WTRU may demodulate (e.g., attempt to demodulate) a received signal based on a default reference signal configuration. For example, the WTRU may perform measurements on available anchor reference signals to estimate a metric that may correspond to a performance attribute such as, for example, the accuracy of the channel estimation. For example, the WTRU may determine whether the measured metric matches any of the (e.g., configured) ranges and thresholds that may be associated with the (e.g., successful) operation of the channel estimator. For example, the accuracy of the channel estimation may be measured through any number of key performance indicators (KPIs), such as any of a correlation coefficient, which measures the quality of the channel prediction, and a mean squared error (MSE), which reflects the difference between an estimated channel and the (e.g., actual, current) channel.

[0134] For example, if the WTRU determines that the measured metric does not match any of the (e.g., configured) ranges and thresholds, the WTRU may request (e.g., transmit information requesting) an increase or decrease in the density of the reference signals in either the time and frequency domains. For example, the WTRU may use separate indicators for time and frequency indices. For example, a grid of reference signals having the highest possible density of reference signals in frequency and time period (e.g., both) may be determined (e.g., defined). For example, the WTRU may indicate its (e.g., preferred) density for (e.g., each) domain by (e.g., by transmitting) information indicating a relative change (e.g., a simple up / down command, e.g., an up command may indicate an increase in the density of the reference signals) by at least one step, or vice versa. For example, considering that either of the reference signal frequency and time resource utilization may be any value between 0 and 100%, a step may be defined as (e.g., associated with) a (e.g., fixed) percentage increase (or decrease) in the density of the reference signals. For example, 0% in time and 0% in frequency occupancy may correspond to pilotless transmission. In another example, there may be a set of reference signal configurations having different densities of reference signals (which may be either uniformly and non-uniformly distributed). Indicating a one step change (e.g., increase or decrease) may indicate a change to a reference signal configuration with the next (e.g., higher or lower) density of reference signals in the set of reference signal configurations.

[0135] For example, if the WTRU determines that the measured metric does not match any of the (e.g., configured) ranges and thresholds, the WTRU may indicate (e.g., transmit information indicative of) any of the (e.g., preferred) densities of the reference signals for the (e.g., each) domain, any measured metrics, etc. In a first example, the WTRU may transmit a message reporting (e.g., indicating) the measured correlation (e.g., between the estimated channel and the actual channel) for the (e.g., each) domain. The reported correlation value may be an indication of the channel estimation accuracy. For example, the (e.g., each) level of correlation may trigger a different reference signal pattern. For example, if the reported correlation value is within a (e.g., desired) range of values, a new reference pattern may not be transmitted (e.g., subsequent transmissions may be performed by the base station based on the same reference signal configuration). If the reported correlation value is not within a (e.g., desired) range of values, e.g., below or above a (e.g., configured) threshold, the WTRU may receive subsequent transmissions from the base station using an updated reference signal configuration (e.g., using a new pattern). For example, this threshold may be either preconfigured in the WTRU and received from the network via configuration information. In a second example, the WTRU may, for example, determine (e.g., adopt) a pattern from a set of preconfigured patterns and may indicate the adopted reference signal pattern either explicitly, for example, via an index, and implicitly, via transmission of an uplink resource. For example, the WTRU may explicitly indicate its determined configuration by explicit transmission of information indicating an index. For example, the WTRU may implicitly indicate the determined reference signal configuration by using any of a specific PUCCH resource, RACH resource, SRS resource, spatial relationship information (e.g., spatialrelationInfo) resource, etc.

[0136] 8 is a diagram illustrating an example of reference signal adaptation. For example, an initial resource grid 80 may correspond to a default (e.g., initial) reference signal configuration. The initial resource grid may comprise resource blocks that may be assigned to data 82 and an anchor reference signal 83. For example, a subsequent resource grid 81 may have been obtained based on a (e.g., preferred) reference signal configuration that may have been selected through either AI / ML-based learning and CE performance measurements. The subsequent resource grid 81 may comprise resource blocks that may be assigned to additional reference signals 84, resulting in a tighter distribution of reference signals over time and frequency domains (e.g., both).

[0137] For example, future transmissions of an indicated reference signal (e.g., corresponding to a (e.g., preferred) reference signal configuration) may start within X time units from a reference time instant, where X is any integer value. The number of time units X may be either semi-statically and dynamically configured by the network (e.g., indicated in configuration information that may be received from the network) and may be fixed, e.g., one slot, from the reference time instant. If the number of time units X is configured by the network (e.g., semi-statically, dynamically), the WTRU may indicate (e.g., transmit) the (e.g., supported) time interval as part of capability information (e.g., signaling) that may be sent to the network, such that the network may transmit configuration information indicating a number of time units X that is greater than the indicated (e.g., supported) time interval.

[0138] After the WTRU may have transmitted an indication of a (e.g., preferred, requested) reference signal pattern, the WTRU may receive either an implicit or explicit indication indicating whether the (e.g., preferred, requested) reference signal pattern is accepted by the network.

[0139] In an example of an explicit indication, the WTRU may receive an explicit (e.g., accept, reject) indication via a dynamic indication, such as information received in either a MAC control element (MAC CE) and a DCI.

[0140] In an example of an implicit indication, the WTRU may detect an implicit (e.g., accept, reject) indication based on, for example, an association of use of a (e.g., specific) resource (e.g., receiving a (e.g., new) grant associated with the (e.g., specific) resource in any of time and frequency) that may be associated with the requested reference signal pattern. For example, if the WTRU receives (e.g., new) scheduling information within less than the configured X time units, the WTRU may determine that a request for a new RS pattern may not have been accepted or may not have been received.

[0141] In another example, the WTRU may determine whether the request for a new RS pattern has been accepted by blind processing of a received RS that may arrive (e.g., received) after X time units. For example, the WTRU may detect the new RS pattern by performing any of the following: inspection (e.g., analysis, processing) of resources associated with the requested pattern, power measurement, descrambling with a cover code, scrambling IDs, etc.

[0142] For example, if the WTRU determines that a requested configuration has not been activated within a (e.g., configured) time window, this may be interpreted as a decoding failure at the base station. For example, the WTRU may retransmit an indication of a (e.g., preferred) reference signal configuration.

[0143] In another example, the indication of the (e.g., preferred) reference signal configuration may be acknowledged by the base station. For example, the WTRU may receive an explicit indication of an updated reference signal pattern (e.g., configuration), e.g., over the DCI / PDCCH, as an acknowledgement of the (e.g., preferred) reference signal configuration indication.

[0144] FIG. 9 is a diagram illustrating an example of a procedure for reference signal adaptation.

[0145] For example, in step 90, configuration information may be received by the WTRU indicating one or more default reference signal configurations.

[0146] For example, the WTRU may perform measurements on an anchor reference signal in step 91. For example, the WTRU may estimate any of the time and frequency correlations between available reference signals of a default reference signal configuration.

[0147] For example, in step 92, the WTRU may determine whether any of the measured time and frequency correlation values ​​match (e.g., expected) thresholds for the WTRU channel estimator. For example, the channel estimator thresholds may be either pre-configured in the WTRU and received from the network via configuration information.

[0148] For example, if any of the measured time and frequency correlation values ​​do not match the channel estimator thresholds, the WTRU may indicate (either explicitly or implicitly) a (e.g., preferred) reference signal configuration in step 93. For example, the WTRU may indicate a request for transmission of additional reference signals by the base station.

[0149] For example, in step 94, the WTRU may determine whether an additional reference signal has been received from the base station within a time window (e.g., corresponding to X time units from a reference time instant, such as an indicator transmission). If it is determined that the additional reference signal has not been received before X time units have elapsed, the WTRU may retransmit an indicator of the (e.g., preferred) reference signal configuration in step 93. If it is determined that the additional reference signal has been received before X time units have elapsed, the WTRU may perform channel estimation and demodulation based on the additional reference signal in step 95.

[0150] FIG. 12 is a diagram illustrating an example of a method for reference signal adaptation in which the density of reference signals of a reference signal configuration may be modified (e.g., either increased or decreased) in any of the time and frequency domains. For example, the reference signals in a reference signal configuration may be of density in any of the time and frequency, and there may be different densities of reference signals for different reference signal configurations (e.g., in multiple reference signal configurations). For example, in step 1210, the WTRU may receive configuration information indicating an initial (e.g., default) RS configuration, followed by (e.g., scheduled) transmission 1220 of RS with or without data transmission. For example, the initial (e.g., default) RS configuration information may include information indicating a set of (e.g., basic) RSs, e.g., anchor RSs. The anchor RS may enable providing initial capabilities for channel estimation. For example, the WTRU may receive configuration information indicating one or more (e.g., performance) criteria (e.g., thresholds, etc.) to be used in determining (e.g., selecting) a DMRS pattern. One or more (e.g., performance) criteria (e.g., thresholds) may relate to (e.g., different) radio transmission characteristics. For example, there may be different (e.g., performance) criteria (e.g., thresholds) for channel variations in time and frequency. For example, in step 1230, the WTRU may perform (e.g., channel estimation) measurements on the anchor RS, such as, for example, channel estimation accuracy, and may compare the performed measurements to one or more (e.g., configured) criteria (e.g., performance measurement thresholds), for example, in step 1240. For example, the WTRU may use additional information based on past performance (e.g., measurements), such as previous (e.g., optimal, selected) RS configurations in (e.g., given) channel conditions and mobility. Depending on whether the measured performance meets or does not meet one or more of the (e.g., configured) criteria (e.g., performance measurement thresholds), the WTRU may decide to maintain or change the RS density in either time and frequency.For example, if the WTRU determines that the measured performance meets one or more (e.g., configured) criteria (e.g., performance measurement thresholds) in either time and frequency, the WTRU may determine whether the density of the reference signal of the RS configuration may be reduced in either time and frequency (e.g., by comparing the density of the reference signal of the RS configuration to a reference signal density limit) in step 1250. If the WTRU determines that the density of the reference signal of the RS configuration may be reduced (e.g., in either time and frequency), the WTRU may transmit either an implicit or explicit indication of the density change (e.g., in either time and frequency) in step 1270. If the WTRU cannot determine that the density of the reference signal of the RS configuration may be reduced (e.g., in either time and frequency), the WTRU may not transmit any implicit or explicit indication of the density change in step 1260.

[0151] If the WTRU determines to change the density of the reference signals (e.g., in either time or frequency), the WTRU may transmit information indicating one of the (e.g., pre-configured) RS patterns (e.g., configurations). In another example (e.g., in the case of a density change), the WTRU may request either an increase or decrease in the RS density in either frequency or time by transmitting information indicating a relative change, such as either an up command or a down command indicating either an increase or decrease in the density of the reference signals in either time or frequency. For example, the transmitted information may indicate an index value that may be associated with either an absolute change or a relative change. For example, an index value associated with an absolute change may indicate an index of the selected reference signal configuration. In another example, an index value associated with a relative change (e.g., up, down, increase, decrease) may indicate a second density of a second reference signal of a selected second reference signal configuration relative to a first density of a first reference signal of a current (e.g., default) reference signal configuration. For example, a change in the density of the reference signals may be indicated by at least one (e.g., any number) step according to any embodiment described herein. For example, the transmitted information (e.g., indicative of the selected reference signal configuration) may be selected as an index value based on the relative change in reference signal density between the current (e.g., default) reference signal configuration and the selected reference signal configuration.

[0152] For example, the method may be implemented in a WTRU. receiving a transmission from a base station in accordance with one or more default reference signal configurations; performing channel estimation measurements for the received transmission based on a default reference signal configuration; and selecting one or more reference signal configurations to be used for a subsequent transmission, where the one or more reference signal configurations may be selected from a plurality of reference signal configurations based on channel estimation measurements; and • Transmitting an indication of the selected one or more reference signal configurations to the base station.

[0153] For example, configuration information may be received, where the configuration information may indicate either a default RS configuration or a plurality of RS configurations.

[0154] For example, the subsequent transmission may be either a downlink transmission or an uplink transmission.

[0155] For example, the indication may be either explicit (eg, based on explicit information) or implicit (eg, based on transmissions on particular resources).

[0156] The indicator may include different types of indicators, such as, for example, an index associated with an RS pattern (eg, configuration), an up / down command to increase / decrease the density of the reference signal, or the like.

[0157] For example, the selection of the RS configuration may be based on AIML (eg, performed on historical CE measurements).

[0158] 10A, 10B, and 10C are three diagrams illustrating three examples of AI / ML-based determination of reference signal configuration. There may be different examples of different architectures of AI / ML-based determination of reference signal configuration. The three architecture examples are described as examples, not as limitations of the embodiments described herein. For example, the described AI / ML block and deep learning examples may be considered merely as exemplary solutions for representing a processor engine that may analyze and determine a (e.g., preferred) reference signal pattern (e.g., configuration). Any other type and architecture of an adaptive processing engine may be applicable to the embodiments described herein.

[0159] FIG. 10A is a diagram illustrating a first example of AI / ML-based determination of a reference signal configuration. For example, the WTRU 1000 may receive configuration information indicating an initial (e.g., default) reference signal configuration. For example, the WTRU 1000 may perform a number of measurements to evaluate at least one set of performance metrics, such as, for example, any of MSE and correlation coefficient, where the set of performance metrics may include any number of measurements. A performance metric may be referred to herein as any metric capable of capturing the accuracy of a channel estimation algorithm, for example, in any of the time and frequency domains. For example, a performance metric may include multiple measurement points (e.g., values) corresponding to multiple reference signals.

[0160] For example, the obtained (e.g., evaluated) set of performance metrics may be provided to the AI / ML engine 1001A to determine a (e.g., preferred) reference signal configuration. For example, the WTRU 1000 may indicate (e.g., transmit an indication of) the (e.g., preferred) configuration to the base station in either an implicit or explicit manner. For example, transmitting an explicit indication may include transmitting (e.g., explicit) information indicating the (e.g., preferred) reference signal configuration (e.g., included in a transmitted message) in either a control channel and a data channel. For example, transmitting an implicit indication may include performing a transmission (e.g., of any information) using any of specific uplink control and data channel resources (e.g., which may be associated with the (e.g., preferred) reference signal configuration).

[0161] For example, the WTRU 1000 may receive multiple (e.g., two or more) reference signal sets (e.g., corresponding to multiple reference signal configurations) to converge to a solution (e.g., a preferred reference signal configuration). For example, the reference signal sets may differ in any of shapes and forms. For example, the reference signal sets may differ in pattern density (e.g., in any of the time, frequency, and code domains). For example, the reference signal sets may differ in the location of pilot symbols across any of the symbols and subcarriers. For example, two reference signal sets (e.g., configurations) may have the same density (e.g., 10%) of reference signals in the frequency domain, and the location of resource elements containing pilots may differ. For example, the WTRU may be configured with a (e.g., fixed) reference signal set (e.g., or slot) for (e.g., all potential) updates of the reference signal configuration. In other words, the WTRU may not arbitrarily determine a reference signal configuration that may not belong to the set of configured reference signal configurations. For example, the (eg, fixed) set of reference signal sets (eg, configurations) may be either pre-configured in the WTRU and received from the base station via configuration information.

[0162] 10B is a diagram illustrating a second example of an AI / ML-based determination of a reference signal configuration. For example, the WTRU 1000 may receive configuration information indicating an initial (e.g., default) reference signal configuration. For example, the WTRU 1000 may perform a number of measurements to evaluate at least one set of performance metrics, such as, for example, any of MSE and correlation coefficient, and the set of performance metrics may include any number of measurements.

[0163] For example, the WTRU may report (e.g., transmit a report indication thereof) the evaluated set of performance metrics to the base station, e.g., explicitly (e.g., over any of the uplink control and data channels) and implicitly (e.g., by using any of the specific uplink control and data channel resources). For example, transmitting an explicit indication of the set of performance metrics may include including explicit information indicating the set of performance metrics in any of the PUCCH / UCI information elements and channel state information (CSI) reports. For example, the explicit indication may include, for example, an index into a preconfigured table of performance metric values ​​(e.g., a preconfigured list of any of the MSE and correlation coefficient values) and the (e.g., raw) values ​​of the performance metrics to be reported. For example, transmitting an implicit indication of the set of performance metrics may include selecting (e.g., using for transmission) any of the uplink control and data channel resources (e.g., any of the PUCCH resources, RACH resources, SRS resources, spatial relationship information (e.g., spatialrelationInfo) resources, etc.) that may be associated with the performance metric value (e.g., a range of values).

[0164] For example, the base station may include an AI / ML engine 1002B (e.g., running on a processor) that may be configured to process the received report to determine a (e.g., preferred) reference signal configuration. For example, the (e.g., preferred) reference signal configuration may be transmitted to the WTRU as configuration information.

[0165] For example, the WTRU may receive multiple (e.g., two or more) reference signal sets for reporting a (e.g., evaluated) set of performance metrics to the base station. For example, the WTRU may be configured with a (e.g., fixed) reference signal set (e.g., or slot) for (e.g., all potential) reporting of performance metrics. In other words, the base station may not arbitrarily determine a reference signal configuration that may not belong to a (e.g., pre-determined) set of reference signal configurations.

[0166] 10C is a diagram illustrating a third example of an AI / ML-based determination of a reference signal configuration. For example, the WTRU 1000 may receive configuration information indicating an initial (e.g., default) reference signal configuration. For example, the WTRU 1000 may perform a number of measurements to evaluate at least one set of performance metrics, such as, for example, any of MSE and correlation coefficient, and the set of performance metrics may include any number of measurements.

[0167] For example, the processing of the AI / ML engine may be split into two parts 1001C, 1002C, where the input layer may be included in the WTRU and the output layer may be included in the base station. For example, based on a (e.g., evaluated) set of performance metrics that may be provided to the input layer 1001C of the AI / ML engine, the WTRU may report (e.g., send a report indicator) a set of inter-node data to the base station. For example, with reference to a non-limiting example of deep learning (e.g., involving a neural network architecture and parameters), the performance metrics (e.g., any of MSE and correlation coefficients) may be used as inputs (e.g., to the input layer 1001C) in the WTRU to determine (e.g., select) inter-node data, such as any of the weights and biases of a layer of a neural network. Performing the output layer 1002C in the base station may enable reducing the complexity of the terminal and improving overall performance, where some of the learning and, e.g., decisions regarding reference signal configurations may be performed by the base station with data that goes into the output layer (which may be referred to herein as inter-node data) provided by the WTRU. In this example, the AI / ML engine may be viewed as being distributed between the WTRU and the base station. Transmission of inter-node data reporting indicators may be either explicit or implicit.

[0168] For example, the WTRU may (e.g., further) report (e.g., transmit a report indicator thereof) any additional measurements to the base station. For example, the base station may perform additional processing on reports that may be received from the WTRU to determine a (e.g., preferred) reference signal configuration.

[0169] For example, the WTRU may receive multiple (e.g., two or more) reference signal sets and report (e.g., transmit a reporting indication thereof) any of the evaluated set of performance metrics and inter-node data to the base station. For example, the (e.g., preferred) reference signal configuration may be either determined by the WTRU and received from the base station according to any of the examples described herein.

[0170] For example, the WTRU may be configured with a (eg, fixed) reference signal set (eg, or slots) for reporting any (eg, all potential) of performance metrics and inter-node data.

[0171] 11 is a diagram illustrating an example of a method 1100 for adapting a reference signal configuration. For example, the method 1100 for adapting a reference signal configuration may be for use (e.g., may be implemented) in a WTRU.

[0172] For example, in step 1120, a (eg, downlink) transmission may be received from a base station, eg, according to one or more first reference signal configurations.

[0173] For example, in step 1130, channel estimation measurements may be obtained (eg, performed) for a received (eg, downlink) transmission based on the one or more first reference signal configurations.

[0174] For example, in step 1140, one or more second reference signal configurations (eg, to be used for a subsequent transmission) may be selected from a plurality of reference signal configurations based on the channel estimation measurements.

[0175] For example, an indication of the (e.g., selected) one or more second reference signal configurations may be transmitted (e.g., to a base station) in step 1150. For example, in step 1150, the indication may indicate one or more second reference signal configurations to be used for a subsequent transmission, and the one or more second reference signal configurations may be selected from a plurality of reference signal configurations based on channel estimation measurements.

[0176] For example, the one or more first reference signal configurations may be either (1) pre-configured in the WTRU and / or (2) received from the base station, e.g., included in or indicated by the first configuration information.

[0177] For example, the multiple reference signal configurations may either (1) be pre-configured in the WTRU and / or (2) be indicated by second configuration information received from the base station.

[0178] For example, the first configuration information and the second configuration information may be included in the same message.

[0179] For example, the first configuration information and the second configuration information may be included in different messages.

[0180] For example, the reference signal configuration may be associated with an index in, for example, a database.

[0181] For example, each of a number of reference signal configurations may be associated with an index.

[0182] For example, the first configuration information may include one or more first indexes indicating one or more first reference signal configurations.

[0183] For example, an indication of the (e.g., selected) one or more second reference signal configurations may include (e.g., indicate) one or more second indexes associated with the one or more reference signal configurations (e.g., in a database).

[0184] For example, the index of the one or more second reference signal configurations may indicate a second index associated with one second reference signal configuration.

[0185] For example, the reference signal configurations may be of different densities in either time or frequency.

[0186] For example, the reference signals in a reference signal configuration may be of any density in time and frequency, and there may be different densities of reference signals for different reference signal configurations in the multiple reference signal configurations.

[0187] For example, an index of one or more (e.g., selected) second reference signal configurations may indicate one or more densities of reference signals in any of time and frequency for the selected one or more second reference signal configurations.

[0188] For example, an index of one or more (e.g., selected) second reference signal configurations may indicate an up or down command to be applied to one or more first reference signal configurations to increase or decrease density, respectively, in any of time and frequency.

[0189] For example, the indication of one or more second reference signal configurations may indicate a relative change (e.g., an increase or decrease) in the density of the reference signal in either time and frequency from a first density of a first reference signal for one or more first reference signal configurations to a second density of a second reference signal for selected one or more second reference signal configurations.

[0190] For example, an index of one or more second reference signal configurations may be selected as an index value based on a relative change in density of the reference signal between one or more first reference signal configurations and the selected one or more second reference signal configurations.

[0191] For example, the relative change may refer to increasing or decreasing the density of the reference signal by a fixed step in either time or frequency.

[0192] For example, one or more second reference signal configurations may be selected increasing the density of the second reference signal in either time or frequency, provided that the performed channel estimation measurements do not satisfy one or more first (e.g., performance) criteria in either time or frequency, respectively.

[0193] For example, the WTRU may receive third configuration information indicating one or more first (eg, performance) criteria in any of time and frequency.

[0194] For example, one or more second reference signal configurations may be selected that reduce the density of the second reference signal in any of time and frequency, provided that the performed channel estimation measurements satisfy one or more second (e.g., performance) criteria in any of time and frequency, respectively.

[0195] For example, the WTRU may receive fourth configuration information indicating one or more second (eg, performance) criteria in any of time and frequency.

[0196] For example, the subsequent transmission may be either a (eg, subsequent) downlink transmission or a (eg, subsequent) uplink transmission.

[0197] For example, the subsequent transmission may be a downlink transmission, and the subsequent transmission may be received using one or more second reference signal configurations.

[0198] For example, the subsequent transmission may be an uplink transmission, and the subsequent transmission may be received using one or more second reference signal configurations.

[0199] For example, the indication of the (eg, selected) one or more second reference signal configurations may include first information included in any of a physical uplink control channel and uplink control information.

[0200] For example, an indication of the (e.g., selected) one or more second reference signal configurations may be transmitted by transmitting first information indicating the selected one or more second reference signal configurations.

[0201] For example, the first information may be included in any of a physical uplink control channel and uplink control information.

[0202] For example, one or more reference signal configurations (e.g., an indication of a selected reference signal configuration) may be indicated (e.g., transmitted) by a transmission on resources that may be associated with the selected one or more second reference signal configurations.

[0203] For example, the resource may be any of a physical uplink control channel resource, a random access channel resource, a sounding reference signal resource, and a spatial relationship information resource.

[0204] For example, the selection of the one or more second reference signal configurations may be further based on an AI / ML performed on a (eg, last performed) channel estimation measurement.

[0205] For example, the selection of one or more reference signal configurations may be further based on AI / ML performed on a set (eg, a history) of channel estimation measurements.

[0206] For example, an AI / ML model may have been trained on a set of (e.g., a history of) channel estimation measurements.

[0207] For example, the second information indicating an AI / ML framework to be used for selection of the one or more second reference signal configurations may be received from a base station.

[0208] For example, the second information indicating the AI / ML framework to be used may be received via a downlink control channel.

[0209] For example, the node-to-node data may be transmitted to a base station, where the node-to-node data is obtained based on past (eg, historical) channel estimation measurements.

[0210] For example, at least one performance metric may be transmitted to a base station, where the at least one performance metric is obtained based on the at least one estimated measurement.

[0211] Throughout the embodiments described herein, the (e.g., configuration) information may be described as being received by the WTRU from the network, e.g., through system information or via any type of protocol message. Although not explicitly mentioned throughout the embodiments described herein, the same (e.g., configuration) information may be pre-configured in the WTRU (e.g., via any type of pre-configuration method, such as, for example, via a factory setting) such that this (e.g., configuration) information may be used by the WTRU without being received from the network.

[0212] For clarity, satisfying, not satisfying a condition (e.g., performance criterion), and "constituting a condition parameter" are described throughout the embodiments described herein with respect to a threshold (e.g., greater than or less than a value (e.g., threshold), constituting a value (e.g., threshold), etc.). For example, satisfying a condition (e.g., performance criterion) may be described as exceeding a value (e.g., threshold), and not satisfying a condition (e.g., performance criterion) may be described as being below a value (e.g., threshold). The embodiments described herein are not limited to threshold-based conditions (e.g., performance criterion). Any type of other condition and parameter (e.g., falling within or not falling within a range of values, etc.) may be applicable to the embodiments described herein.

[0213] conclusion Although features and elements are provided above in specific combinations, those of ordinary skill in the art will understand that each feature or element can be used alone or in any combination with other features and elements. The present disclosure is not limited in terms of the specific embodiments described in this application, which are intended as illustrations of various aspects. As will be apparent to those skilled in the art, many modifications and variations can be made without departing from the spirit and scope of the present invention. No element, operation, or instruction used in the description of this application should be construed as critical or essential to the invention unless expressly set forth as such. In addition to those enumerated herein, functionally equivalent methods and apparatuses within the scope of the present disclosure will be apparent to those skilled in the art from the foregoing description. Such modifications and variations are intended to fall within the scope of the appended claims. The present disclosure is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled. It is to be understood that the present disclosure is not limited to any particular method or system.

[0214] The foregoing embodiments are discussed with respect to the terminology and structure of infrared-enabled devices (i.e., infrared emitters and receivers) for simplicity, however, the discussed embodiments are not limited to these systems and may also be applied to other systems that use other forms of electromagnetic waves, or non-electromagnetic waves such as acoustic waves.

[0215] It should also be understood that the terms used herein are for purposes of describing particular embodiments only and are not intended to be limiting. As used herein, the term "video" or "image" may mean any of a snapshot, a single image, and / or multiple images displayed over time. As another example, the term "user equipment" and its abbreviation "UE", the term "remote" and / or the term "head mounted display" and its abbreviation "HMD" as referred to herein may mean or include (i) a wireless transmitting and / or receiving unit (WTRU), (ii) any of multiple embodiments of a WTRU, (iii) a wireless enabled and / or wired enabled (e.g., tetherable) device specifically configured to have some or all of the structure and functionality of a WTRU, (iii) a wireless enabled and / or wired enabled device configured to have less than all of the structure and functionality of a WTRU, or (iv) otherwise. Details of an exemplary WTRU that may represent any WTRU listed herein are provided herein with respect to FIGS. 1A-1D. As another example, various embodiments disclosed herein above and below are described as utilizing a head-mounted display. Those skilled in the art will recognize that devices other than a head-mounted display may be utilized and that the present disclosure and various disclosed embodiments may be modified in part or in whole accordingly without undue experimentation. Examples of such other devices may include drones or other devices configured to stream information to provide an adaptive reality experience.

[0216] In addition, the methods provided herein may be implemented in a computer program, software, or firmware embodied in a computer readable medium for execution by a computer or processor. Examples of computer readable media include electronic signals (transmitted over wired or wireless connections) and computer readable storage media. Examples of computer readable storage media include, but are not limited to, read only memory (ROM), random access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks and digital versatile disks (DVDs). A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, UE, terminal, base station, RNC, or any host computer.

[0217] Modifications of the methods, devices, and systems provided above are possible without departing from the scope of the present invention. In view of the wide variety of possible embodiments, it should be understood that the illustrated embodiments are merely examples and should not be construed as limiting the scope of the appended claims. For example, the embodiments provided herein include a handheld device, which may include or be utilized with any suitable voltage source, such as a battery providing any suitable voltage.

[0218] Further, in the above embodiments, it should be noted that processing platforms, computing systems, controllers, and other devices include processors. These devices may include at least one Central Processing Unit ("CPU") and memory. In accordance with the practices of those skilled in the art of computer programming, references to operations and symbolic representations of operations or instructions may be performed by various CPUs and memories. Such operations and operations or instructions may be referred to as being "executed," "executed by a computer," or "executed by a CPU."

[0219] Those of ordinary skill in the art will understand that the operations and symbolically represented operations or instructions include the manipulation of electrical signals by the CPU. The electrical system represents data bits that can cause a resultant transformation or reduction of the electrical signals, and maintains the data bits in memory locations of the memory system, thereby reconfiguring or otherwise altering the operation of the CPU and the processing of other signals. The memory locations in which the data bits are maintained are physical locations that have particular electrical, magnetic, optical, or organic properties that correspond to or represent the data bits. It should be understood that the embodiments are not limited to the platforms or CPUs mentioned above, and that other platforms and CPUs may support the methods provided.

[0220] The data bits may also be maintained on a computer readable medium including magnetic disks, optical disks, and any other volatile (e.g., random access memory (RAM)) or non-volatile (e.g., read only memory (ROM)) mass storage system readable by a CPU. The computer readable medium may include computer readable media that resides exclusively on a processing system or distributed, cooperative or interconnected among multiple interconnected processing systems that may be local or remote to a processing system. It should be understood that the embodiments are not limited to the memories mentioned above and that other platforms and memories may support the methods provided.

[0221] In an illustrative embodiment, any of the operations, processes, etc. described herein may be implemented as computer-readable instructions stored on a computer-readable medium. The computer-readable instructions may be executed by a processor of a mobile unit, a network element, and / or any other computing device.

[0222] There is little distinction between hardware and software implementations of aspects of the system. Whether to use hardware or software is generally a design choice that represents a cost vs. efficiency tradeoff (although in some circumstances the choice between hardware and software may be important). There may be a variety of vehicles (e.g., hardware, software, and / or firmware) in which the processes and / or systems and / or other techniques described herein may be effective, and the preferred vehicle may vary depending on the context in which the processes and / or systems and / or other techniques are deployed. For example, if an implementer determines that speed and accuracy are paramount, the implementer may select a primarily hardware and / or firmware vehicle. If flexibility is paramount, the implementer may select a primarily software implementation. Alternatively, the implementer may select some combination of hardware, software, and / or firmware.

[0223] The foregoing detailed description has illustrated various embodiments of devices and / or processes through the use of block diagrams, flow charts, and / or examples. To the extent that such block diagrams, flow charts, and / or examples include one or more functions and / or operations, it will be appreciated by those skilled in the art that each function and / or operation within such block diagrams, flow charts, or examples may be individually and / or collectively implemented by a wide range of hardware, software, firmware, or substantially any combination thereof. In one embodiment, some portions of the subject matter described herein may be implemented via application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), digital signal processors (DSPs), and / or other integrated forms. However, those skilled in the art will recognize that certain aspects of the embodiments disclosed herein may be equivalently implemented, in whole or in part, in integrated circuits, as one or more computer programs running on one or more computers (e.g., as one or more programs running on one or more computer systems), as one or more programs running on one or more processors (e.g., as one or more programs running on one or more microprocessors), as firmware, or as substantially any combination thereof, and that designing circuitry and / or writing software and / or firmware code is within the skill of those skilled in the art in light of this disclosure. In addition, those skilled in the art will recognize that the subject mechanisms described herein may be distributed as program products in a variety of forms, and that the illustrative embodiments of the subject matter described herein apply regardless of the particular type of signal-bearing medium used to actually effect the distribution. Examples of signal bearing media include, but are not limited to, recordable type media such as floppy disks, hard disk drives, CDs, DVDs, digital tape, computer memory, and transmission type media such as digital and / or analog communications media (e.g., fiber optic cables, wave guides, wired communications links, wireless communications links, etc.).

[0224] Those skilled in the art will recognize that it is common in the art to describe devices and / or processes in the manner described herein and then use engineering techniques to integrate such described devices and / or processes into a data processing system. That is, at least a portion of the devices and / or processes described herein may be integrated into a data processing system through a reasonable amount of experimentation. Those skilled in the art will recognize that a typical data processing system may generally include one or more of a system unit housing, a video display device, memory such as volatile and non-volatile memory, a processor such as a microprocessor and a digital signal processor, computing entities such as an operating system, drivers, a graphic user interface and application programs, one or more interaction devices such as a touchpad or screen, and / or a control system such as feedback loops and control motors (e.g., feedback to sense position and / or velocity, control motors to move and / or adjust components and / or quantities). A typical data processing system may be implemented utilizing any suitable commercially available components, such as those typically found in data computing / communication systems and / or network computing / communication systems.

[0225] The subject matter described herein may illustrate different components that are included within or connected to different other components. It should be understood that such depicted architectures are merely examples, and that in fact many other architectures that achieve the same functionality may be implemented. Conceptually, any arrangement of components to achieve the same functionality is effectively "associated" such that the desired functionality may be achieved. Thus, any two components herein that are combined to achieve a particular functionality may be considered to be "associated" with one another such that the desired functionality is achieved, regardless of the architecture or intervening components. Similarly, any two components so associated may be considered to be "operably connected" or "operably coupled" with one another to achieve the desired functionality, and any two components that can be so associated may be considered to be "operably coupleable" with one another to achieve the desired functionality. Examples of operably coupleable include, but are not limited to, physically matable and / or physically interacting components, and / or wirelessly interacting and / or wirelessly interacting components, and / or logically interacting and / or logically interacting components.

[0226] With respect to the use of substantially any plural and / or singular term herein, one of ordinary skill in the art can convert from plural to singular and / or from singular to plural as appropriate to the context and / or application. Various singular / plural permutations may be expressly set forth herein for purposes of clarity.

[0227] In general, those skilled in the art will understand that the terms used in this specification, and particularly in the appended claims (e.g., the body of the appended claims), are generally intended as "non-limiting" terms (e.g., the term "including" should be interpreted as "including, but not limited to," the term "having" should be interpreted as "having at least," and the term "including" should be interpreted as "including, but not limited to"). Furthermore, those skilled in the art will understand that where a specific number of recitations of an introduced claim are intended, such intent is expressly set forth in the claim, and in the absence of such recitation, no such intent exists. For example, where only one item is intended, the term "single" or similar language may be used. To aid in understanding, the following appended claims and / or description of this specification may include the use of the introductory phrases "at least one" and "one or more" to introduce the claim recitations. However, the use of such phrases should not be interpreted as meaning that the introduction of a claim recitation with the indefinite article "a" or "an" limits any particular claim that includes such an introduced claim recitation to an embodiment that includes only one such recitation, even if the same claim contains the introductory phrase "one or more" or "at least one" and an indefinite article such as "a" or "an" (e.g., "a" and / or "an" should be interpreted to mean "at least one" or "one or more"). The same applies to the use of definite articles used to introduce claim recitations. In addition, those skilled in the art will recognize that even if a specific number of recitations of an introduced claim are explicitly recited, such recitation should be interpreted to mean at least the recited number (e.g., the simple recitation "two recitations" without other qualifiers means at least two recitations, or more than two recitations).Furthermore, when notation similar to "at least one of A, B, and C" is used, such structure is generally intended as a person of ordinary skill in the art would understand the notation (e.g., "a system having at least one of A, B, and C" includes, but is not limited to, systems having only A, only B, only C, A and B together, A and C together, B and C together, and / or A, B, and C together). When notation similar to "at least one of A, B, or C" is used, such structure is generally intended as a person of ordinary skill in the art would understand the notation (e.g., "a system having at least one of A, B, or C" includes, but is not limited to, systems having only A, only B, only C, A and B together, A and C together, B and C together, and / or A, B, and C together). Those skilled in the art will further appreciate that virtually any disjunctive word and / or phrase presenting two or more alternative terms, whether in the specification, claims, or drawings, should be understood to contemplate the possibility of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" should be understood to include the possibility of "A" or "B" or "A and B." Additionally, as used herein, the term "any of" followed by a list of items and / or a list of categories of items is intended to include "any of," "any combination of," "any more than," and / or "any more than," of the items and / or categories of items, individually or in combination with other items and / or categories of items. Additionally, as used herein, the term "set" is intended to include any number of items, including zero. Additionally, as used herein, the term "number" is intended to include any number, including zero. Additionally, as used herein, the term "multiple" is intended to be synonymous with "plurality."

[0228] In addition, where features or aspects of the disclosure are described in terms of a Markush group, those skilled in the art will recognize that the disclosure is also described thereby in terms of any individual members or subgroups of members of the Markush group.

[0229] As will be understood by those skilled in the art, for all purposes, including in terms of providing a written description, all ranges disclosed herein encompass any possible subranges and combinations of subranges thereof. Any recited range can be readily recognized as fully descriptive and allowing the same range to be broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, a middle third, and an upper third, etc. Also, as will be understood by those skilled in the art, all words such as "up to," "at least," "greater than," "less than," etc., refer to a range that includes the recited number and that can be further broken down into subranges as discussed above. Finally, as will be understood by those skilled in the art, a range includes each individual element. Thus, for example, a group having 1 to 3 cells refers to a group having 1, 2, or 3 cells. Similarly, a group having 1 to 5 cells refers to a group having 1, 2, 3, 4, or 5 cells, and so on.

[0230] Moreover, the claims should not be read as limited to the provided order or to the provided elements unless specifically so recited. In addition, the use of the term "means for" in any claim is intended to be relied upon under 35 U.S.C. 112, paragraph 6, or means-plus-function claim format, and no claim without the term "means for" is so intended.

Claims

1. A wireless transmit / receive unit (WTRU) comprising a circuit including any one of a transmitter, a receiver, a processor, and a memory, wherein the circuit is configured to: receive a first transmission from a base station according to one or more first reference signal configurations; perform channel estimation measurements for the first transmission based on the one or more first reference signal configurations; transmit to the base station one or more commands indicating to increase or decrease the density of reference signals based on the channel estimation measurements, wherein at least one of the one or more commands indicates to increase or decrease the density of reference signals at one of time or frequency.

2. The WTRU according to claim 1, wherein the at least one command indicates to increase or decrease the density of reference signals by only one step at one of time or frequency to the next higher or lower density in a set of densities of reference signals.

3. The WTRU according to claim 2, wherein the density of reference signals is uniformly distributed within the set of densities of reference signals.

4. The WTRU according to any one of claims 1 to 3, wherein the one or more commands include a first command and a second command, the first command indicates to increase the density of reference signals in time, and the second command indicates to decrease the density of reference signals in frequency.

5. The WTRU according to claim 1, wherein the circuit is configured to receive information indicating whether the one or more commands have been received.

6. The WTRU according to claim 1, wherein the circuit is configured to determine that a second reference signal configuration corresponding to the one or more commands is not activated within a time window.

7. wherein the circuit is configured to blindly decode a second transmission received during the time window; and analyze a time or frequency resource associated with one or more second reference signal configurations corresponding to the one or more commands, the WTRU of claim 6, configured for.

8. wherein the circuit is configured to retransmit the one or more commands based on the determination that the second reference signal configuration corresponding to the one or more commands is not activated within the time window, the WTRU of claim 6.

9. wherein the circuit is configured to receive configuration information indicating a first duration of the time window, the WTRU of claim 6.

10. wherein the circuit is configured to transmit capability information indicating a second duration of the time window, the first duration indicated in the configuration information being longer than the second duration indicated in the capability information, the WTRU of claim 9.

11. A method implemented in a wireless transmit / receive unit (WTRU), the method comprising: receiving, from a base station, a first transmission according to one or more first reference signal configurations; performing channel estimation measurements for the first transmission based on the one or more first reference signal configurations; transmitting, to the base station, one or more commands indicating to increase or decrease a density of a reference signal based on the channel estimation measurements, at least one of the one or more commands indicating to increase or decrease the density of the reference signal at one of time or frequency.

12. The method according to claim 11, wherein the at least one command indicates increasing or decreasing the density of the reference signal by only one step in one of time or frequency to the next higher or lower density in a set of densities of the reference signal.

13. The method according to claim 12, wherein the density of the reference signal is uniformly distributed within the set of densities of the reference signal.

14. The method according to any one of claims 11 to 13, wherein the one or more commands include a first command and a second command, the first command indicating increasing the density of the reference signal in time, and the second command indicating decreasing the density of the reference signal in frequency.

15. The method according to claim 11, including receiving information indicating whether the one or more commands have been received.

16. The method according to claim 11, including determining that a second reference signal configuration corresponding to the one or more commands is not activated within a time window.

17. Blind decoding a second transmission received during the time window, Analyzing time or frequency resources associated with one or more second reference signal configurations corresponding to the one or more commands, The method according to claim 16, including.

18. The method according to claim 16, including retransmitting the one or more commands based on the determination that a second reference signal configuration corresponding to the one or more commands is not activated within the time window.

19. The method according to claim 16, including receiving configuration information indicating a first duration of the time window.

20. The method according to claim 19, comprising transmitting capability information indicating a second duration of the time window, wherein the first duration indicated in the configuration information is longer than the second duration indicated in the capability information.

Images