CN117616715A

CN117616715A - Methods, architectures, devices and systems relating to adaptive reference signal configuration

Info

Publication number: CN117616715A
Application number: CN202280048115.0A
Authority: CN
Inventors: A·绍贾埃法尔德; 阿兰·穆拉德; 阿夫欣·哈吉卡特; I·赫马德
Original assignee: InterDigital Patent Holdings Inc
Current assignee: InterDigital Patent Holdings Inc
Priority date: 2021-06-11
Filing date: 2022-06-09
Publication date: 2024-02-27

Abstract

Processes, methods, architectures, apparatuses, systems, devices and computer program products related to adaptive reference signal configuration are described. The method for adapting the reference signal configuration may be implemented in a WTRU. For example, the WTRU may receive transmissions from, for example, a base station in accordance with one or more first reference signal configurations. For example, channel estimation measurements 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 may be selected from a plurality of reference signal configurations based on the channel estimation measurements (e.g., for subsequent transmission). For example, an indication of the selected one or more second reference signal configurations may be transmitted (e.g., to the base station).

Description

Methods, architectures, devices and systems relating to adaptive reference signal configuration

Cross Reference to Related Applications

The present application claims the benefit of european patent application No. 21178929.2 filed on day 2021, month 6, 11 and european patent application 22167141.5 filed on day 2022, month 4, 7, each of which is incorporated herein by reference in its entirety.

Technical Field

The present disclosure relates generally to the field of communications, software, and coding, including, for example, methods, architectures, devices, systems related to adaptive reference signal configuration using any of Artificial Intelligence (AI) and Machine Learning (ML), for example.

Disclosure of Invention

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 configured according to one or more first reference signals. Channel estimation measurements are performed on the received transmissions based on the one or more first reference signal configurations. An indication of one or more second reference signal configurations to be used for subsequent transmissions is transmitted to the base station, wherein the one or more second reference signal configurations are selected from a plurality of reference signal configurations based on the channel estimation measurements.

Drawings

A more detailed understanding can be obtained from the following detailed description, which is given by way of example in connection with the accompanying drawings. As with the detailed description, the drawings in such figures are examples. Accordingly, the drawings (figures) and detailed description are not to be taken in a limiting sense, and other equally effective examples are possible and contemplated. In addition, like reference numerals ("ref") in the drawings denote like elements, and wherein:

FIG. 1A is a system diagram illustrating an exemplary communication system;

fig. 1B is a system diagram illustrating an exemplary wireless transmit/receive unit (WTRU) that may be used within the communication system shown in fig. 1A;

fig. 1C is a system diagram illustrating an exemplary Radio Access Network (RAN) and an exemplary Core Network (CN) that may be used within the communication system shown in fig. 1A;

fig. 1D is a system diagram illustrating a further exemplary RAN and a further exemplary CN that may be used within the communication system shown in fig. 1A;

fig. 2 is a diagram showing an example of a composite channel estimation process based on a user specific reference signal;

fig. 3 is a diagram showing an example of a 5G demodulation reference signal (DMRS) configuration;

fig. 4 is a system diagram showing a first example of an adaptive reference signal configuration method;

fig. 5 is a diagram showing an example of message exchange of a first example of an adaptive reference signal configuration method;

fig. 6 is a system diagram showing a second example of the adaptive reference signal configuration method;

fig. 7 is a diagram showing an example of message exchange of a second example of the adaptive reference signal configuration method;

fig. 8 is a diagram showing an example of reference signal adaptation;

fig. 9 is a diagram showing an example of a procedure of reference signal adaptation;

fig. 10A, 10B, and 10C are diagrams showing an example of determination of AI/ML-based reference signal configuration;

Fig. 11 is a diagram showing an example of a method for adapting a reference signal configuration; and is also provided with

Fig. 12 is a diagram showing an example of a method for reference signal adaptation by which the density of reference signal configurations can be modified.

Detailed Description

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 should 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 description below. Furthermore, embodiments and examples not specifically described herein may be practiced in place of or in combination with embodiments and other examples that are explicitly, implicitly, and/or inherently described, disclosed, or otherwise provided (collectively, "provided"). Although various embodiments are described and/or claimed herein, wherein an apparatus, system, device, etc., and/or any element thereof, performs an operation, procedure, algorithm, function, etc., and/or any portion thereof, it is to be understood that any embodiment described and/or claimed herein assumes that any apparatus, system, device, etc., and/or any element thereof, is configured to perform any operation, procedure, algorithm, function, etc., and/or any portion thereof.

Exemplary communication System

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 respect to fig. 1A-1D, wherein various elements of a network may utilize, perform, adapt and/or configure the methods, apparatuses and systems provided herein, according to and/or with respect to the methods, apparatuses and systems provided herein.

Fig. 1A is a system diagram illustrating an exemplary communication system 100 in which one or more disclosed embodiments may be implemented. Communication system 100 may be a multiple-access system that provides content, such as voice, data, video, messages, broadcasts, etc., to a plurality of wireless users. Communication system 100 may enable multiple wireless users to access such content through the sharing of system resources, including wireless bandwidth. For example, 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-sOFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, filter Bank Multicarrier (FBMC), and the like.

As shown in fig. 1A, the communication system 100 may include wireless transmit/receive units (WTRUs) 102a, 102b, 102c, 102d, radio Access Networks (RANs) 104/113, core Networks (CNs) 106/115, public Switched Telephone Networks (PSTN) 108, the internet 110, and other networks 112, although it should 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. As an example, the WTRUs 102a, 102b, 102c, 102d (any of which may be referred to as a "station" and/or a "STA") may be configured to transmit and/or receive wireless signals and may include (or may be) User Equipment (UE), mobile stations, fixed or mobile subscriber units, subscription-based units, pagers, cellular telephones, personal Digital Assistants (PDAs), smartphones, laptop computers, netbooks, personal computers, wireless sensors, hotspots or Mi-Fi devices, internet of things (IoT) devices, watches or other wearable devices, head-mounted displays (HMDs), vehicles, drones, medical devices and applications (e.g., tele-surgery), industrial devices and applications (e.g., robots and/or other wireless devices operating in an industrial and/or automated processing chain environment), consumer electronics devices, devices operating on a commercial and/or industrial wireless network, and the like. Any of the WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a UE.

Communication system 100 may also include base station 114a and/or 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, for example, to facilitate access to one or more communication networks, such as the CN 106/115, the internet 110, and/or the network 112. As an example, the base stations 114a, 114B may be any of a Base Transceiver Station (BTS), a Node B (NB), an evolved node B (eNB), a Home Node B (HNB), a home evolved node B (HeNB), a g node B (gNB), an NR node B (NR NB), a site controller, an Access Point (AP), a wireless router, and the like. Although the base stations 114a, 114b are each depicted as a single element, it should be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and/or network elements.

Base station 114a may be part of RAN 104/113 that may also include other base stations and/or network elements (not shown), such as Base Station Controllers (BSCs), radio Network Controllers (RNCs), relay nodes, and the like. Base station 114a and/or 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 cells (not shown). These frequencies may be in a licensed spectrum, an unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide coverage of wireless services to a particular geographic area, which may be relatively fixed or may change over time. The cell may be further divided into cell sectors. For example, a cell associated with base station 114a may be divided into three sectors. Thus, in an embodiment, the base station 114a may include three transceivers, i.e., one for each sector of a cell. In an embodiment, the base station 114a may employ multiple-input multiple-output (MIMO) technology and may utilize multiple transceivers for each or any sector of a cell. For example, beamforming may be used to transmit and/or receive signals in a desired spatial direction.

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, millimeter wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable Radio Access Technology (RAT).

More specifically, as noted above, communication system 100 may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, or the like. For example, a base station 114a in 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 use Wideband CDMA (WCDMA) to establish the air interface 116.WCDMA may include communication 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).

In an 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 use Long Term Evolution (LTE) and/or LTE-advanced (LTE-a) and/or LTE-advanced Pro (LTE-a Pro) to establish the air interface 116.

In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR radio access that may use a new air interface (NR) to establish the air interface 116.

In embodiments, 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 a Dual Connectivity (DC) principle. Thus, the air interface utilized by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and/or transmissions sent to/from multiple types of base stations (e.g., enbs and gnbs).

In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e., wireless fidelity (Wi-Fi)), IEEE 802.16 (i.e., worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000 1X, CDMA EV-DO, tentative standard 2000 (IS-2000), tentative standard 95 (IS-95), tentative standard 856 (IS-856), global system for mobile communications (GSM), enhanced data rates for GSM evolution (EDGE), GSM EDGE (GERAN), and the like.

The base station 114B in fig. 1A may be, for example, a wireless router, home node B, home evolved node B, or access point, and may utilize any suitable RAT to facilitate wireless connections in local areas such as businesses, homes, vehicles, campuses, industrial facilities, air corridors (e.g., for use by drones), roads, and the like. In an 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 an 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 an 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 any of a micro-cell, pico-cell, or femto-cell. As shown in fig. 1A, the base station 114b may have a direct connection with the internet 110. Thus, the base station 114b may not need to access the Internet 110 via the CN 106/115.

The RANs 104/113 may communicate with the CNs 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, 102 d. The data may have different quality of service (QoS) requirements, such as different throughput requirements, delay requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, and the like. The CN 106/115 may provide call control, billing services, mobile location based services, prepaid calls, internet connections, video distribution, etc., and/or perform advanced security functions such as user authentication. Although not shown in fig. 1A, it should be appreciated that the RANs 104/113 and/or CNs 106/115 may communicate directly or indirectly with other RANs that employ the same RAT as the RANs 104/113 or a different RAT. For example, in addition to being connected to the RAN 104/113 that may utilize NR radio technologies, the CN 106/115 may also communicate with another RAN (not shown) employing any of GSM, UMTS, CDMA, wiMAX, E-UTRA, or Wi-Fi radio technologies.

The CN 106/115 may also act as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and/or other networks 112.PSTN 108 may include circuit-switched telephone networks that provide Plain Old Telephone Services (POTS). The internet 110 may include a global system for interconnecting computer networks and devices using common communication protocols, such as Transmission Control Protocol (TCP), user Datagram Protocol (UDP), and/or Internet Protocol (IP) in the TCP/IP internet protocol suite. Network 112 may include wired and/or wireless communication networks owned and/or operated by other service providers. For example, network 112 may include another CN connected to one or more RANs, which may employ the same RAT as RANs 104/114 or a different RAT.

Some or all of the WTRUs 102a, 102b, 102c, 102d in the communication 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 employ a cellular-based radio technology, and with a base station 114b, which may employ an IEEE 802 radio technology.

Fig. 1B is a system diagram illustrating an exemplary WTRU 102. As shown in fig. 1B, the WTRU 102 may include a processor 118, a transceiver 120, a transmit/receive element 122, a speaker/microphone 124, a keypad 126, a display/touchpad 128, a non-removable memory 130, a removable memory 132, a power source 134, a Global Positioning System (GPS) chipset 136, and/or other elements/peripherals 138, etc. It should be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a Digital Signal Processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, application Specific Integrated Circuits (ASICs), field Programmable Gate Arrays (FPGAs) circuits, any other type of Integrated Circuit (IC), a state machine, or the like. The processor 118 may perform signal coding, data processing, power control, input/output processing, and/or any other functions that enable the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to a transceiver 120, which may be coupled to a transmit/receive element 122. Although fig. 1B depicts the processor 118 and the transceiver 120 as separate components, it should be understood that the processor 118 and the transceiver 120 may be integrated together, for example, in an electronic package or chip.

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

Although the transmit/receive element 122 is depicted as a single element in fig. 1B, the WTRU 102 may include any number of transmit/receive elements 122. For example, the WTRU 102 may employ MIMO technology. Thus, in an 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.

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

The processor 118 of the WTRU 102 may be coupled to and may receive user input data from a speaker/microphone 124, a keypad 126, and/or a display/touchpad 128, such as 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. Further, the processor 118 may access information from and store data in any type of suitable memory, such as the non-removable memory 130 and/or the 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. Removable memory 132 may include a Subscriber Identity Module (SIM) card, a memory stick, a Secure Digital (SD) memory card, and the like. In other embodiments, the processor 118 may never physically locate memory access information on the WTRU 102, such as on a server or home computer (not shown), and store the data in that memory.

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

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 the 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 base stations (e.g., base stations 114a, 114 b) over the air interface 116 and/or determine its location based on the timing of signals received from two or more nearby base stations. It should be appreciated that the WTRU 102 may obtain location information by any suitable location determination method while remaining consistent with an embodiment.

The processor 118 may also be coupled to other elements/peripherals 138 that may include one or more software modules/units and/or hardware modules/units that provide additional features, functionality, and/or wired or wireless connections. 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), universal Serial Bus (USB) port, vibration device, television transceiver, hands-free headset,Modules, frequency Modulation (FM) radio units, digital music players, media players, video game player modules, internet browsers, virtual reality and/or augmented reality (VR/AR) devices, activity trackers, and the like. The element/peripheral 138 may include one or more sensors, which may be one or more of the following: gyroscopes, accelerometers, hall effect sensors, magnetometers, orientation sensors, proximity sensors, temperature sensors, time sensors; a geographic position sensor; altimeters, light sensors, touch sensors, magnetometers, barometers, gesture sensors, biometric sensors, and/or humidity sensors.

WTRU 102 may include a full duplex radio for which transmission and reception of some or all signals (e.g., associated with a particular subframe for both uplink (e.g., for transmission) and downlink (e.g., for reception)) may be concurrent and/or simultaneous. The full duplex radio station may include an interference management unit for reducing and/or substantially eliminating self-interference via hardware (e.g., choke) or via signal processing by a processor (e.g., a separate processor (not shown) or via processor 118). In an embodiment, the WTRU 102 may include a half-duplex radio for which transmission and reception of some or all signals (e.g., associated with a particular subframe for uplink (e.g., for transmission) or downlink (e.g., for reception)).

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

RAN 104 may include enode bs 160a, 160B, 160c, but it should be understood that 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 to communicate with the WTRUs 102a, 102B, 102c over the air interface 116. In an embodiment, the evolved node bs 160a, 160B, 160c may implement MIMO technology. Thus, the enode B160 a may use multiple antennas to transmit wireless signals to and receive wireless signals from the WTRU 102a, for example.

Each of the evolved node bs 160a, 160B, and 160c may be associated with a particular cell (not shown) and may be configured to process radio resource management decisions, handover decisions, user scheduling in the Uplink (UL) and/or Downlink (DL), and so on. As shown in fig. 1C, the enode bs 160a, 160B, 160C may communicate with each other over an X2 interface.

The CN 106 shown in fig. 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 are depicted as part of the CN 106, it should be understood that any of these elements may be owned and/or operated by an entity other than the CN operator.

MME 162 may be connected to each of evolved node bs 160a, 160B, and 160c in RAN 104 via an S1 interface and may function as a control node. For example, the MME 162 may be responsible for authenticating the user of the WTRUs 102a, 102b, 102c, bearer activation/deactivation, selecting a particular serving gateway during initial attach of the WTRUs 102a, 102b, 102c, and the like. MME 162 may provide control plane functionality for switching between RAN 104 and other RANs (not shown) employing other radio technologies such as GSM and/or WCDMA.

SGW 164 may be connected to each of the evolved node bs 160a, 160B, 160c in RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to/from the WTRUs 102a, 102b, 102 c. The SGW 164 may perform other functions such as anchoring user planes during inter-enode B handover, triggering paging when DL data is available to the WTRUs 102a, 102B, 102c, managing and storing the contexts of the WTRUs 102a, 102B, 102c, etc.

The SGW 164 may be connected to a PGW 166 that may provide the WTRUs 102a, 102b, 102c with access to a packet switched network, such as the internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to a circuit-switched network (such as the PSTN 108) to facilitate communications between the WTRUs 102a, 102b, 102c and legacy landline communication devices. For example, the CN 106 may include or may 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.

Although the WTRU is depicted in fig. 1A-1D as a wireless terminal, it is contemplated that in some representative embodiments such a terminal may use a wired communication interface with a communication network (e.g., temporarily or permanently).

In representative embodiments, the other network 112 may be a WLAN.

A WLAN in an 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 to and/or from the BSS. Traffic originating outside the BSS and directed to the STA may arrive through the AP and may be delivered to the STA. Traffic originating from the STA and leading to a destination outside the BSS may be sent to the AP to be delivered to the respective destination. Traffic between STAs within the BSS may be sent through the AP, for example, where the source STA may send traffic to the AP and the AP may pass the traffic to the destination STA. Traffic between STAs within a BSS may be considered and/or referred to as point-to-point traffic. Point-to-point traffic may be sent between (e.g., directly between) the source and destination STAs using Direct Link Setup (DLS). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z Tunnel DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and STAs (e.g., all STAs) within or using the IBSS may communicate directly with each other. The IBSS communication mode may sometimes be referred to herein as an "ad-hoc" communication mode.

When using the 802.11ac infrastructure mode of operation or similar modes of operation, the AP may transmit beacons on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., 20MHz wide bandwidth) or a width dynamically set by signaling. The primary channel may be an operating channel of the BSS and may be used by STAs to establish a connection with the AP. In certain representative embodiments, carrier sense multiple access/collision avoidance (CSMA/CA) may be implemented, for example, in an 802.11 system. For CSMA/CA, STAs (e.g., each STA), including the AP, may listen to the primary channel. If the primary channel is listened to/detected by a particular STA and/or determined to be busy, the particular STA may backoff. One STA (e.g., only one station) may transmit at any given time in a given BSS.

High Throughput (HT) STAs may communicate using 40MHz wide channels, for example, via a combination of a primary 20MHz channel with an adjacent or non-adjacent 20MHz channel to form a 40MHz wide channel.

Very High Throughput (VHT) STAs may support channels that are 20MHz, 40MHz, 80MHz, and/or 160MHz wide. 40MHz and/or 80MHz channels may be formed by combining consecutive 20MHz channels. The 160MHz channel may be formed by combining 8 consecutive 20MHz channels, or by combining two non-consecutive 80MHz channels (this may be referred to as an 80+80 configuration). For the 80+80 configuration, after channel coding, the data may pass through a segment parser that may split the data into two streams. An Inverse Fast Fourier Transform (IFFT) process and a time domain process may be performed on each stream separately. These streams may be mapped to two 80MHz channels and data may be transmitted by the transmitting STA. At the receiver of the receiving STA, the operations described above for the 80+80 configuration may be reversed, and the combined data may be sent to a Medium Access Control (MAC) layer, entity, or the like.

The 802.11af and 802.11ah support modes of operation below 1 GHz. Channel operating bandwidth and carrier are reduced in 802.11af and 802.11ah relative to those used in 802.11n and 802.11 ac. The 802.11af supports 5MHz, 10MHz, and 20MHz bandwidths in the television white space (TVWS) spectrum, and the 802.11ah supports 1MHz, 2MHz, 4MHz, 8MHz, and 16MHz bandwidths using non-TVWS spectrum. According to representative embodiments, 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, such as limited capabilities, including supporting (e.g., supporting only) certain bandwidths and/or limited bandwidths. MTC devices may include batteries with battery lives above a threshold (e.g., to maintain very long battery lives).

WLAN systems that can support multiple channels, and channel bandwidths such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include channels that can be designated as primary channels. 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 set and/or limited by STAs from all STAs operating in the BSS (which support a minimum bandwidth mode of operation). In the example of 802.11ah, for STAs (e.g., MTC-type devices) that support (e.g., only) 1MHz mode, the primary channel may be 1MHz wide, even though the AP and other STAs in the BSS support 2MHz, 4MHz, 8MHz, 16MHz, and/or other channel bandwidth modes of operation. The carrier sense and/or Network Allocation Vector (NAV) settings may depend on the state of the primary channel. If the primary channel is busy, for example, because the STA (supporting only 1MHz mode of operation) is transmitting to the AP, the entire available frequency band may be considered busy even though most of the frequency band remains idle and possibly available.

The available frequency band for 802.11ah in the united states is 902MHz to 928MHz. In korea, the available frequency band is 917.5MHz to 923.5MHz. In Japan, the available frequency band is 916.5MHz to 927.5MHz. The total bandwidth available for 802.11ah is 6MHz to 26MHz, depending on the country code.

Fig. 1D is a system diagram illustrating RAN 113 and CN 115 according to one embodiment. As noted above, RAN 113 may employ NR radio technology to communicate with WTRUs 102a, 102b, 102c over an air interface 116. RAN 113 may also communicate with CN 115.

RAN 113 may include gnbs 180a, 180b, 180c, although it will be appreciated that RAN 113 may include any number of gnbs while remaining consistent with an embodiment. Each of the gnbs 180a, 180b, 180c may include one or more transceivers to communicate 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, 102 c. Thus, the gNB 180a may use multiple antennas to transmit wireless signals to the WTRU 102a and/or receive wireless signals from the WTRU 102a, for example. In an embodiment, the gnbs 180a, 180b, 180c may implement carrier aggregation techniques. 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 the unlicensed spectrum while the remaining component carriers may be on the licensed spectrum. In embodiments, the gnbs 180a, 180b, 180c may implement coordinated multipoint (CoMP) techniques. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and/or gNB 180 c).

The WTRUs 102a, 102b, 102c may communicate with the gnbs 180a, 180b, 180c using transmissions associated with the scalable parameter sets. For example, the OFDM symbol interval and/or OFDM subcarrier interval may vary from transmission to transmission, from cell to cell, and/or from part of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gnbs 180a, 180b, 180c using various or scalable length subframes or Transmission Time Intervals (TTIs) (e.g., including different numbers of OFDM symbols and/or continuously varying absolute time lengths).

The gnbs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in an independent configuration and/or in a non-independent configuration. In a standalone configuration, the WTRUs 102a, 102B, 102c may communicate with the gnbs 180a, 180B, 180c while also not accessing other RANs (e.g., such as the enode bs 160a, 160B, 160 c). In an independent configuration, the WTRUs 102a, 102b, 102c may use one or more of the gnbs 180a, 180b, 180c as mobility anchor points. In an independent configuration, the WTRUs 102a, 102b, 102c may use signals in unlicensed frequency bands to communicate with the gnbs 180a, 180b, 180 c. In a non-standalone configuration, the WTRUs 102a, 102B, 102c may communicate or connect with the gnbs 180a, 180B, 180c, while also communicating or connecting with other RANs (such as the enode bs 160a, 160B, 160 c). 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 enodebs 160a, 160B, 160c substantially simultaneously. In a non-standalone configuration, the enode bs 160a, 160B, 160c may serve as mobility anchors for the WTRUs 102a, 102B, 102c, and the gnbs 180a, 180B, 180c may provide additional coverage and/or throughput for serving the WTRUs 102a, 102B, 102 c.

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 UL and/or DL, support of network slices, 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, and so on. As shown in fig. 1D, gnbs 180a, 180b, 180c may communicate with each other through an Xn interface.

The CN 115 shown in fig. 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 are depicted as part of the CN 115, it should be understood that any of these elements may be owned and/or operated by an entity other than the CN operator.

AMFs 182a, 182b may be connected to one or more of gNB 180a, 180b, 180c in RAN 113 via an N2 interface and may function as a control node. For example, the AMFs 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, support for network slices (e.g., handling of different Protocol Data Unit (PDU) sessions with different requirements), selection of a particular SMF 183a, 183b, management of registration areas, termination of NAS signaling, mobility management, and so on. The AMFs 182a, 182b may use network slices to customize CN support for the WTRUs 102a, 102b, 102c, e.g., based on the type of service used by the WTRUs 102a, 102b, 102 c. For example, different network slices may be established for different use cases, such as services relying on ultra high reliability low latency (URLLC) access, services relying on enhanced large-scale mobile broadband (eMBB) access, services for MTC access, etc. AMF 162 may provide control plane functionality for switching between RAN 113 and other RANs (not shown) employing other radio technologies, such as LTE, LTE-A, LTE-a Pro, and/or non-3 GPP access technologies, such as Wi-Fi.

The SMFs 183a, 183b may be connected to AMFs 182a, 182b in the CN 115 via an N11 interface. The SMFs 183a, 183b may also be connected to UPFs 184a, 184b in the CN 115 via an N4 interface. SMFs 183a, 183b may select and control UPFs 184a, 184b and configure traffic routing through 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 notifications, etc. The PDU session type may be IP-based, non-IP-based, ethernet-based, etc.

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 a packet-switched network, such as the internet 110, for example, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. UPFs 184, 184b may perform other functions such as routing and forwarding packets, enforcing user plane policies, supporting multi-host PDU sessions, handling user plane QoS, buffering downlink packets, providing mobility anchoring, and the like.

The CN 115 may facilitate communications with other networks. For example, the CN 115 may include or may 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 embodiments, WTRUs 102a, 102b, 102c may connect to local Data Networks (DNs) 185a, 185b through UPFs 184a, 184b via an N3 interface to UPFs 184a, 184b and an N6 interface between UPFs 184a, 184b and DNs 185a, 185b.

In view of fig. 1A-1D and the corresponding descriptions of fig. 1A-1D, one or more or all of the functions described herein with reference to any one of the following may be performed by one or more emulation elements/devices (not shown): the WTRUs 102a-102d, base stations 114a-114B, eNodeBs 160a-160c, MME 162, SGW 164, PGW 166, gNB 180a-180c, AMFs 182a-182B, UPFs 184a-184B, SMFs 183a-183B, DNs 185a-185B, and/or any other elements/devices described herein. The emulated device may be one or more devices configured to emulate one or more or all of the functions described herein. For example, the emulation device may be used to test other devices and/or analog network and/or WTRU functions.

The simulation device may be designed to enable one or more tests of other devices in a laboratory environment and/or an operator network environment. For example, the one or more emulation devices can perform one or more or all of the functions while being fully or partially implemented and/or deployed as part of a wired and/or wireless communication network in order to test other devices within the communication network. The one or more emulation devices can perform one or more functions or all functions while being temporarily implemented/deployed as part of a wired and/or wireless communication network. The emulation device may be directly coupled to another device for testing purposes and/or may perform testing using over-the-air wireless communications.

The one or more emulation devices can perform one or more (including all) functions while not being implemented/deployed as part of a wired and/or wireless communication network. For example, the simulation device may be used in a test laboratory and/or a test scenario in a non-deployed (e.g., test) wired and/or wireless communication network in order to enable testing of one or more components. The one or more simulation devices may be test equipment. Direct RF coupling and/or wireless communication via RF circuitry (e.g., which may include one or more antennas) may be used by the emulation device to transmit and/or receive data.

Example of channel estimation

For example, a pilot-based scheme may be used in the network to enable coherent demodulation of a composite Channel Estimate (CE) of either of the precoded signal and the beamformed signal, e.g., at the receiver. For example, for this purpose, demodulation reference signals (DMRS) may be used in a 5G new air interface (NR).

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 of the precoded signal and the beamformed signal may be performed by applying the same precoding (e.g., beamforming) weights to reference signals that may be used on either of the downlink physical channel and the uplink physical channel. For example, the precoding weights 21, 22 may be applied to Physical Resource Blocks (PRBs) prior to transmission. The same precoding weights 21, 22 may be applied to the reference signal at the receiver side (e.g., precoding weights that may be known to the receiver) for channel estimation. For example, the first channel estimate may be based on the first precoding weights 21 and the second channel estimate may be based on the second precoding weights 22.

Different configurations of DMRS may be used in a 5G network to satisfy different deployment scenarios. For example, different configurations of DMRS may include various (e.g., different) time densities and frequency densities of reference signals. The configuration of DMRS (such as, for example, any of density and location in a resource grid, orthogonal cover codes, duration, start symbols, etc.) may affect (e.g., determine) CE performance. For example, the density of reference signal transmissions over any of time and frequency may be configured according to any of time and frequency selectivity (e.g., sensitivity) of the communication channel. For example, a (e.g., more) dense distribution of reference signals in the frequency domain may allow for higher frequency selectivity of the communication channel (e.g., as compared to a less dense distribution). For example, more frequent transmission of the reference signal may allow (e.g., support) higher fading rates in the time domain.

Described herein are mechanisms (e.g., methods, architectures, apparatuses, and systems) for adaptively transmitting Reference Signals (RSs) based on an indication of a (e.g., preferred) configuration of the RSs by a terminal for a network. For example, the selection of an RS (e.g., DMRS) configuration by a terminal may be based on (e.g., instantaneous) measurements, which may be performed by the terminal, e.g., based on any CE scheme. In another example, an RS (e.g., DMRS) configuration may be selected by the terminal by applying any of artificial intelligence and machine learning (AI/ML) based analysis to any of CE configuration and CE measurement (e.g., collected).

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

Throughout the embodiments described herein, the terms "explicitly" and "explicit" when associated with, for example, any of "transmitting," "indicating," and "reporting" a piece of information, may be used to designate a transmission (e.g., of a message) that includes a (e.g., explicit) information element that indicates the piece of information. A message including (e.g., explicit) information may be included in any one of a Physical Uplink Control Channel (PUCCH) and Uplink Control Information (UCI).

Throughout the embodiments described herein, the terms "implicitly" and "implicit" when associated with, for example, any of "transmitting," "indicating," and "reporting" a piece of information, may be used to designate transmission (e.g., of any type of information) in a resource (e.g., of a particular type) that may be associated with the piece of information. The (e.g., specific) resource may be, for example, any one of a specific PUCCH resource, a Random Access Channel (RACH) resource, a Sounding Reference Signal (SRS) resource, and a spatial relationship information (e.g., a spatial relationship info) resource, etc.

Throughout the embodiments described herein, the terms "serving base station," "gNB" (collectively, "network") may be used interchangeably to designate any network element, such as, for example, a network element that acts 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.

The 3GPP standard provides a certain flexibility in pilot configuration to meet different WTRU capabilities and use cases. For example, for a 5G NR Physical Downlink Shared Channel (PDSCH) DMRS, there may be a configuration including any of configuration type 1, configuration type 2, mapping type a, mapping type B, starting symbols for mapping type a, single symbol DMRS and dual symbol DMRS, DMRS additional locations and durations.

Fig. 3 is a diagram showing 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 exemplary DMRS pattern on one symbol and one resource block using downlink antenna ports 1000, 1001, 1002, and 1003 having CDM group 0 31 and CDM group 1 32 across frequency domain 30 and code domain in 5G NR having configuration type 1, mapping type a, and starting symbol 3.

For example, CE performance may depend on any of the configuration of the DMRS and the receiver implementation (e.g., characteristics).

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

For example, performing channel estimation across a larger number of Physical Resource Blocks (PRBs) (e.g., for a given implementation) may allow for improved performance (e.g., where the delay spread is small (e.g., negligible)). Increasing the number of PRBs for a CE (which may be referred to as "bundling") may decrease the resolution of frequency selective precoding.

For example, MU-MIMO (e.g., for a given implementation) may be based on Code Division Multiplexing (CDM) to distinguish antenna ports sharing the same Resource Elements (REs). For example, adding pilot REs across additional symbols may allow for increased CDM capability for higher order MIMO.

For example, where the density of the reference signals is the same (e.g., for a given implementation), the position of the pilot on the resource grid may affect the receiver computational complexity (e.g., the number of extrapolation operations and interpolation operations).

For example, in case of a limited number of options (e.g., including patterns that may be available in 5G NR) for reference signal configuration (e.g., even), the obtaining of (e.g., optimal) selection (e.g., of DMRS configuration) may also be complex. This may result in an inefficient (e.g., user-specific) reference signal configuration that may underutilize or over-utilize radio resources for the pilot, such as, for example, physical Resource Elements (PRE). In the event that the number of alternative reference signal configurations increases (e.g., has an increased number of different parameters), the complexity of selecting the configuration of the user-specific reference signal may further increase. For example, there may be DMRS configurations with flexible DMRS patterns. Implementations described herein may allow for improved DMRS configuration selection such that efficiency of radio resource utilization for pilots may be improved. Embodiments described herein may also allow DMRS-free transmission of physical channels in 5G NR.

The embodiments described herein may allow for facilitating (e.g., enabling) adaptive reference signal transmission by a mechanism that may allow a terminal to indicate (e.g., prefer) a configuration of a reference signal to a network (e.g., transmit an indication of the configuration). For example, an indication of the (e.g., preferred) reference signal configuration may be transmitted to the network in either of an implicit and explicit manner. Implementations described herein may provide benefits such as any of reduced DMRS resource usage overhead, reduced DMRS signaling overhead, and enhanced CE accuracy.

Adaptive reference signal configuration overview

Embodiments are described herein in terms of examples of cellular communication networks involving at least WTRUs and base stations. The WTRU may be any type of WTRU including, for example, any of a smart phone, a sensor, a repeater, etc. The embodiments described herein may be applicable to any type of transceiver chain including, for example, multiple antennas located at either (e.g., both) of a base station and a WTRU. For clarity, embodiments are described herein with downlink DMRS as an example. 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 any of downlink reference signals (such as, for example, CSI-RS, etc.) and uplink reference signals.

For example, a physical channel in either of the downlink and uplink directions may be accompanied by (e.g., user-specific) reference signals (e.g., DMRS), which may also be referred to herein as pilots, in order to facilitate composite channel estimation and coherent demodulation. This may be achieved, for example, by populating a PRE (e.g., transmitting a reference signal) based on a pseudo-random sequence, which may be generated based on system parameters (e.g., a combination of any 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.

For example, the configuration of DMRS may include any of the density and pattern of reference signals in the resource grid, the duration, the starting symbols (e.g., pre-loaded DMRS), and the cover code, e.g., to distinguish between antenna ports sharing the same time/frequency resources (for either of the single-user and multi-user MIMO cases). For example, the parameter set for the DMRS may be different depending on any of the physical channel and WTRU capabilities. For example, DMRSs may be grouped over multiple (e.g., contiguous) resource blocks, where the precoder may be constant, such that the receiver may perform wideband channel estimation. For example, the (e.g., specific) selection of 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., preconfigured) in the WTRU.

The embodiments described herein may enable a terminal (e.g., with appropriate WTRU capabilities) of wireless communications 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.

For example, a base station may use a plurality of higher layer parameters and dynamic (DCI-based) signaling to configure DMRSs accompanying the corresponding physical channels. For example, the base station may transmit 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 (e.g., indicate) any of a location and a density (e.g., any of PRBs, slots, ports), a cover code, a start symbol, an additional symbol, etc. of the reference signal in the resource grid. For example, depending on any of the type of physical channel (e.g., PDSCH, PBCH), WTRU capabilities, number and location of antennas, etc., there may be different reference signal configurations with different parameters (e.g., options). For example, a pseudo-random sequence (such as, for example, a GOLD sequence) may be used to generate a DMRS (e.g., pilot) based on system parameters that may be known by the receiver (e.g., preconfigured in the receiver). Parameters that may be used for control sequence generation may include any of scrambling identity, symbol position, number of OFDM symbols in a slot, etc. For example, after selecting a DMRS setting (e.g., a reference signal configuration), the base station may signal the selection to the WTRU (e.g., transmit signaling information indicating the selection). The selected DMRS settings (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). 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, for example, by a particular receiver filter implementation (e.g., least squares, least mean square error, etc.) that can broadly estimate the composite channel by mapping the transmitted layers onto the receiving antennas of the resource blocks that can be scheduled.

For example, the receiver may (e.g., initially) determine an estimate of the channel of pilot symbols based on the known locations of pilot symbols in the received slot. For example, an averaging window may be used to reduce the effects of noise.

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

For example, noise power estimation may be performed to improve performance by comparing either of the direct channel estimate and the average channel estimate.

For example, with channel estimation, the WTRU may continue (e.g., perform) coherent demodulation of the precoded/beamformed physical channels (e.g., including data symbols). For example, data may be demodulated based on the estimated channel. After the data may have been demodulated, a (e.g., real, current) channel may be obtained (e.g., based on the demodulated data) and may be compared to the estimated channel.

For example, accuracy of the channel estimate may be obtained, e.g., 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 Mean Square Error (MSE), bit Error Rate (BER) performance, and Error Vector Magnitude (EVM).

First example of adaptive reference Signal configuration method

For example, a WTRU may have the capability to allow the WTRU to assist (e.g., a base station) in the adaptive configuration and transmission of (e.g., user-specific) reference signals (e.g., DMRS) for composite channel estimation and coherent demodulation of physical channels. For example, the WTRU may receive configuration information indicating any number (e.g., anchor, default) of 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) configuration and channel estimation measurements in a database accessible (e.g., available) to the device. For example, the WTRU may select (e.g., determine, decide) a (e.g., preferred) configuration or a (e.g., preferred) configuration list of reference signals (e.g., DMRS) for any number of subsequent transmissions of the physical channel. The selection may be performed using AI/ML-based learning, for example, based 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 either a (e.g., preferred) configuration or a (e.g., preferred) configuration list of reference signals (e.g., DMRS) in either an explicit manner (e.g., by either of uplink control and data channels) and an implicit manner (e.g., by using either of specific uplink control and data channel resources) for subsequent use (e.g., transmission) on the physical channel.

For example, in the first step, the WTRU may be preconfigured with any number of (e.g., anchor, default) DMRS configurations. For example, the WTRU may have been pre-configured, for example, with factory settings. In another example, the WTRU may receive (e.g., from the network) first configuration information indicating any number of (e.g., anchor, default) DMRS configurations. For example, the (e.g., each) reference signal configuration may be associated with an index.

For example, in a second step, the WTRU may receive an indication of DMRS configuration for physical channel transmission from the network. The indication of the DMRS configuration may be included in second configuration information, which may be received via any one of RRC (e.g., 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).

For example, in a third step, the WTRU may use the (e.g., user specific) reference signal to perform composite CE and coherent demodulation of the corresponding physical channel.

For example, in a fourth step, where the WTRU has such capability, the WTRU may store any of the indicated DMRS configuration (e.g., according to any of pattern, density, RB, antenna ports, etc.) and CE measurements (such as, for example, complex channel coefficients) in, for example, a database.

For example, in a 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, selection of a (e.g., preferred) configuration of the DMRS may be performed by AI/ML-based learning of a history of any of the DMRS configuration and CE measurements, which history may have been collected, for example, over a certain period of time. In another example, a (e.g., preferred) configuration of the DMRS may be selected based on (e.g., instantaneous) measurements using, for example, CE techniques such as, for example, any of doppler, delay spread, etc.

For example, in a sixth step, the WTRU may indicate the selected (e.g., preferred) DMRS configuration to the network, e.g., where the corresponding WTRU capabilities are enabled. The indication of the determined (e.g., preferred) DMRS configuration may be transmitted either explicitly or implicitly. Explicitly transmitting an indication of a reference signal configuration may be referred to herein as transmitting a message including (e.g., explicit) information indicating a selected (e.g., preferred) configuration of the reference signal, such as, for example, an index of the reference signal configuration. A message including (e.g., explicit) configuration selection may be included in any one of a Physical Uplink Control Channel (PUCCH) and Uplink Control Information (UCI). Implicitly transmitting an indication of a reference signal configuration may be referred to herein as performing a transmission in a (e.g., particular) resource that may be associated with an indication of a selected reference signal configuration, such as, for example, an index of the reference signal configuration. For example, the (specific) resource may be any one of a specific PUCCH resource, a Random Access Channel (RACH) resource, a Sounding Reference Signal (SRS) resource, and a spatial relationship information (e.g., a spatialrelationship info) resource, etc. For example, it may be indicated that no pilot transmission may be accommodated (e.g., performed) e.g., in case the channel coherence interval is large, or in case a previous channel estimate may be applicable for a subsequent transmission.

Fig. 4 is a system diagram showing a first example of the 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 downlink transmissions 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 include 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, database 410 may include historical CE measurements such as, for example, frequency domain channel sampling, noise statistics, EVM, and the like. For example, the WTRU 41 may include an AI/ML module 411 (e.g., executing on a processor) that may be configured to perform any of the following: performing channel prediction (e.g., coherence interval, confidence level); and selecting a reference signal configuration (e.g., for subsequent transmission).

Fig. 5 is a diagram showing an example of message exchange of a first example of the adaptive reference signal configuration method.

For example, the WTRU may send a first message 51 including capability information indicating the WTRU's capability to perform an adaptive reference signal method according to, for example, the first example.

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

For example, the WTRU may receive PDSCH transmissions 53 (e.g., according to a reference signal configuration).

For example, in step 54, the WTRU may perform CE and demodulate PDSCH transmissions.

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

For example, in step 56, the WTRU may select a (e.g., preferred) reference signal configuration (e.g., a list of reference signal configurations) for subsequent transmission.

For example, the WTRU may transmit an indication 57 of the selected reference signal configuration to the base station. The indication transmission may be either one of an implicit transmission and an explicit transmission.

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

Second example of adaptive reference Signal configuration method

For example, a base station of wireless communication may adaptively configure transmission of (e.g., user-specific) reference signals (e.g., DMRS) for composite channel estimation and coherent demodulation of either of a beamformed physical channel and a precoded physical channel.

For example, in a first step, the base station may indicate any number of anchor (e.g., default) reference signal configurations to the WTRU (e.g., transmit information indicating any number of anchor reference signal configurations) via, for example, a downlink control channel. For example, the (e.g., each) reference signal configuration may be associated with an index. For example, the base station may receive an indication of a (e.g., preferred) configuration or list of configurations of reference signals used in a subsequent physical channel from a WTRU (e.g., with a particular WTRU capability). The indication may be received in either an explicit manner (e.g., by receiving a (e.g., preferred) configuration index via any of the uplink control and data channels) or an implicit manner (e.g., derived from WTRU parameter selections within any of the uplink control and data channel resources). For example, the base station may store the reference signal configuration in a database (e.g., according to any of pattern, density, RBs, antenna ports, etc.). The reference signal configuration may be acquired from any number of WTRUs for various (e.g., different) physical channels in either of the downlink and uplink.

For example, in a second step, the base station may utilize tools from AI/ML to assist the WTRU in any of database storage and AI/ML learning framework complexity. For example, the base station may provide input to the WTRU, e.g., based on any of the amount and type of data to be stored and AI/ML model details (e.g., such as any of architecture, learning rate, etc.). For example, the base station may determine parameters of an AI/ML learning scheme to be used at the WTRU for selecting a (e.g., preferred) configuration of the DMRS. For example, the historical DMRS configuration may be stored in a database in the network.

For example, in a third step, the base station may transmit a learning framework (e.g., input) that the WTRU will use to select the (e.g., preferred) reference signal configuration (e.g., transmit information indicating that the WTRU will use to select the learning framework (e.g., input) of the (e.g., preferred) reference signal configuration). The information indicating the learning framework to be used may be transmitted to the WTRU based on any type of signaling (e.g., DCI-based signaling). For example, in the case of deep learning, the learning framework information may include an indication of any of architecture, number of layers, activation functions, and the like.

For example, in a fourth step, the WTRU may use this information for custom storage of any of the historical DMRS configurations, channel estimation measurements (e.g., any of RB number, ports, duration, metrics, etc.). For example, the WTRU may adjust its policy of storing the history data based on information received from the base station.

For example, in a fifth step, the WTRU may use the received information to select a (e.g., preferred) configuration of the DMRS for the subsequent physical channel. This may be performed based on AI/ML-based analysis of the collected historical data and by executing any of the CEs. The selected reference signal configuration may be associated with (e.g., some) index(s) to facilitate feedback between the base station and the WTRU.

For example, in a sixth step (e.g., where WTRU capabilities are enabled), the WTRU may indicate the selected reference signal configuration (e.g., transmit information indicating the selected reference signal configuration) in either one of an explicit manner (e.g., via including information in PUCCH/UCI) and an implicit manner through selection of a particular uplink resource (e.g., any one of a particular PUCCH resource, RACH resource, SRS resource, spatial relationship information (e.g., a spatial relationship info resource), etc.). The adaptive reference signal configuration method according to the second example may allow for reducing complexity on the WTRU side by utilizing a network to assist AI/ML-based selection of reference signal configurations at the WTRU.

Fig. 6 is a system diagram showing a second example of the 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 downlink transmissions 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 include 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, database 610 may include historical CE measurements such as, for example, any of frequency domain channel sampling, noise statistics, EVM, and the like. For example, the WTRU 61 may include an AI/ML module 611 (e.g., executing on a processor) that may be configured to perform any of the following: performing channel prediction (e.g., coherence interval, confidence level); and selecting a reference signal configuration (e.g., for subsequent transmission).

For example, the base station 60 may include a database 600 for storing historical pilot configurations (e.g., a set of reference signal configurations that may have been used for previous transmissions with the WTRU 61). For example, database 600 may include historical CE measurements, such as, for example, a list of signaled pilot configurations. For example, the base station 60 may include an AI/ML module 601 (e.g., executing 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.). The AI/ML module 601 can also include an AI/ML training model (e.g., a neural network architecture).

Fig. 7 is a diagram showing an example of message exchange of a second example of the adaptive reference signal configuration method.

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

For example, the WTRU may send a first message 71 including capability information indicating the WTRU's capability to perform an adaptive reference signal method according to, for example, the second example.

For example, the WTRU may receive configuration information 72 indicating any of a reference signal configuration and a learning framework (e.g., parameters).

For example, the WTRU may receive PDSCH transmissions 73 (e.g., according to a reference signal configuration).

For example, in step 74, the WTRU may perform CE and demodulate PDSCH transmissions.

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

For example, in step 76, the WTRU may select (e.g., preferred) a reference signal configuration (e.g., list) for subsequent transmission, e.g., using the indicated learning framework. For example, the AI/ML learning module can be configured in accordance with parameters of an indicated learning framework.

For example, the WTRU may transmit an indication 77 of the selected reference signal configuration to the base station. The indication transmission may be either one of an implicit transmission and an explicit transmission.

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

Adaptive reference Signal configuration method examples

Examples of methods by which a WTRU decides (e.g., selects) and indicates the (e.g., preferred) setting of a DMRS for subsequent transmission via learning (e.g., of any of historical configuration and measurements) by performing any of CE measurements are described herein.

For example, a wireless communication system may include a multi-antenna base station in communication with a multi-antenna WTRU, wherein transmission of a data channel may be accompanied by a (e.g., user-specific) reference signal in order to facilitate (e.g., assist) composite channel estimation and coherent demodulation at a receiver. For example, the density of reference signal transmissions on any of time and frequency may be configured according to any of time and frequency selectivity of the communication channel. For example, the higher the frequency selectivity, the denser the distribution of the reference signal in the frequency domain may be. For example, the increased fading rate in the time domain may be compensated for by transmitting the reference signal more frequently.

For example, the WTRU may have the capability (e.g., may be able to select and signal the settings of the DMRS) to select and signal the (e.g., preferred) settings (e.g., preferred reference signal configurations) of the DMRS (e.g., either explicitly or implicitly). Capability information indicating this capability of the WTRU to the base station may be transmitted, for example, during initial registration, e.g., as part of an RRC message. For example, the capability information may be included in an information element of an RRC message that may allow the WTRU to indicate whether the WTRU supports additional DMRS patterns (e.g., beyond existing DMRS patterns), e.g., without a specific capability signaling configuration.

For example, a WTRU (e.g., with the ability to select (e.g., preferred) a reference signal configuration) may be configured with a default configuration for the reference signal (e.g., may receive configuration information indicating the default configuration for the reference signal), where, for example, the reference signal may be placed in either of the frequency domain and the time domain at an initially configured interval. For example, the time/frequency interval used in the default configuration may be based on the (e.g., most likely) separation in time and frequency. In another example, the time/frequency interval used in the default configuration may be based on any of historical configuration, deployment scenario, mobility configuration, MIMO pattern, traffic type, priority, delay, and the like. The reference signals placed based on the default configuration may be referred to herein as anchor reference signals.

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

For example, the WTRU may receive an indication (such as, for example, an index identifying the reference signal configurations or any type of identifier) from the base station to indicate (e.g., a pre-configured default) one of the reference signal configurations.

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

For example, any of N regions (e.g., ranges) of doppler values and M regions of delay spread values may be determined. For example, different regions may correspond to different anchor reference signal configurations. For example, the N and M regions with doppler and delay spread values, respectively, may perform any of the following operations: 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 the reference signal configuration and a value region).

For example, the WTRU may indicate its determined default reference signal configuration to the base station in either an implicit manner or an explicit manner. For example, the WTRU may explicitly indicate its determined configuration by an index (e.g., transmitting a message including the index). For example, the WTRU may implicitly indicate information by using any of specific PUCCH resources, RACH resources, SRS resources, spatial relationship information (e.g., spatial relationship info) resources, etc., which may be associated with a reference signal configuration (e.g., index).

For example, the WTRU may demodulate the received signal based on a default reference signal configuration (e.g., an attempt). For example, the WTRU may perform measurements on available anchor reference signals to estimate metrics that may correspond to performance attributes (such as, for example, accuracy of channel estimation). For example, the WTRU may determine whether the measured metric matches any of a range (e.g., configured) and a threshold that may be associated with (e.g., successful) operation of the channel estimator. For example, the accuracy of the channel estimate may be measured by any number of Key Performance Indicators (KPIs), such as, for example, any of correlation coefficients that measure the quality of the channel prediction and Mean Square Error (MSE) that reflects the difference between the estimated channel and the (e.g., real, current) channel.

For example, in the event that the WTRU determines that the measured metric does not match any of the (e.g., configured) range and threshold, the WTRU may request an increase or decrease in the density of the reference signal on any of the time and frequency domains (e.g., send information requesting an increase or decrease in the density of the reference signal on any of the time and frequency domains). For example, the WTRU may use separate indicators for time and frequency indication. For example, a reference signal grid may be determined (e.g., defined) that has the highest possible reference signal density over both frequency and time span (e.g., both). For example, the WTRU may indicate (e.g., a preferred) density of the (e.g., each) domain by information indicating a relative change in at least one step size (such as, for example, a simple up/down command, where, for example, the up command may indicate an increase in density of the reference signal), and vice versa. For example, considering that any of the reference signal frequency and time resource utilization is any value from 0 to 100%, a step size may be defined as (e.g., associated with) a (e.g., fixed) percent increase (or decrease) in the density of the reference signal. For example, a time occupancy of 0% and a frequency occupancy of 0% may correspond to no pilot transmission. In another example, there may be a set of reference signal configurations with different reference signal densities (which may be any of uniform and non-uniform distribution). Indicating a change (e.g., an increase or decrease) of one step may indicate a change to a reference signal configuration of a next (e.g., higher or lower) density of reference signals in the set of reference signal configurations.

For example, where the WTRU determines that the measured metric does not match any of the (e.g., configured) range and threshold, the WTRU may indicate any of the (e.g., preferred) density of the reference signal of the (e.g., each) domain, any measured metrics, etc. (e.g., transmit information indicating any of the density of the reference signal of the domain, any measured metrics, etc.). In a first example, the WTRU may transmit information reporting (e.g., indicating) the correlation of the measurements (e.g., between the estimated channel and the real channel) for the (e.g., each) domain. The reported correlation value may be an indicator of the accuracy of the channel estimate. For example, the (e.g., each) correlation level may trigger a different reference signal pattern. For example, in the event that 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). In the event that 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 a subsequent transmission from the base station with an updated reference signal configuration (e.g., with a new pattern). For example, the threshold may be any of the following: pre-configured in the WTRU; and receiving from the network via the configuration information. In a second example, the WTRU may determine (e.g., and employ) a pattern from, for example, a set of pre-configured patterns, and may indicate the employed reference signal pattern, for example, by any one of explicitly by index and implicitly by transmission of uplink resources. For example, the WTRU may explicitly indicate its determined configuration by explicit transmission of information indicating the index. For example, the WTRU may implicitly indicate the determined reference signal configuration by using any of specific PUCCH resources, RACH resources, SRS resources, and spatial relationship information (e.g., spatialrelationship info) resources, etc.

Fig. 8 is a diagram showing an example of reference signal adaptation. For example, the initial resource grid 80 may correspond to a default (e.g., initial) reference signal configuration. The initial resource grid may include resource blocks that may be allocated to the data 82 and the anchor reference signal 83. For example, the subsequent resource grid 81 may be obtained based on a (e.g., preferred) reference signal configuration that may have been selected by either of AI/ML-based learning and CE performance measurement. The subsequent resource grid 81 may include resource blocks that may be allocated to additional reference signals 84, resulting in a denser distribution of reference signals in the time and frequency domains (e.g., both).

For example, future transmissions of the indicated reference signal (e.g., corresponding to a (e.g., preferred) reference signal configuration) may begin within X time units from a reference time point (X is any integer value). The X time units may be any of fixed (e.g., one slot from a reference point in time), semi-statically and dynamically configured by the network (e.g., indicated in configuration information receivable from the network). In the case where X time units are configured by the network (e.g., semi-statically, dynamically), the WTRU may indicate the (e.g., supported) time interval as part of capability information (e.g., signaling) that may be transmitted to the network (e.g., information may be transmitted indicating the (e.g., supported) time interval as part of capability information (e.g., signaling) that may be transmitted to the network) such that the network may transmit configuration information indicating X time units greater than the indicated (e.g., supported) time interval.

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

In an example of an explicit indication, the WTRU may receive an explicit (e.g., accept, reject) indication, such as, for example, information received in any of a MAC control element (MAC CE) and DCI, through a dynamic indication.

In examples of implicit indications, the WTRU may detect an implicit (e.g., accept, reject) indication based on an association of use of a (e.g., particular) resource, which may be associated with a requested reference signal pattern, for example (such as receiving a (e.g., new) grant associated with the (e.g., particular) resource, e.g., in either of time and frequency). For example, in the case where the WTRU receives (e.g., new) scheduling information in a shorter time than the configured X time units, the WTRU may determine that the request for the new RS pattern may or may not have not been received.

In another example, the WTRU may determine whether a request for a new RS pattern has been accepted by blind processing of a received RS that may arrive (e.g., be received) after X time units. For example, the WTRU may detect the new RS pattern by performing any one of checking (e.g., analyzing, processing) resources associated with the requested pattern, power measurements, descrambling according to the coverage code, scrambling ID, etc.

For example, in the event that the WTRU determines that the 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 the (e.g., preferred) reference signal configuration.

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) via, for example, DCI/PDCCH as an acknowledgement of the (e.g., preferred) reference signal configuration indication.

Fig. 9 is a diagram showing an example of a procedure of reference signal adaptation.

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

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

For example, in step 92, the WTRU may determine whether any of the measured time and frequency related values match a (e.g., expected) threshold of the WTRU channel estimator. For example, the channel estimator threshold may be any of the following: pre-configured in the WTRU; and receiving from the network via the configuration information.

For example, in the event that either of the measured time and frequency correlation values does not match the channel estimator threshold, the WTRU may indicate (e.g., a preferred) reference signal configuration (either explicitly or implicitly) in step 93. For example, the WTRU may indicate a request for additional reference signals to be transmitted by the base station.

For example, in step 94, the WTRU may determine whether additional reference signals are received from the base station within a time window (e.g., corresponding to X time units from a reference time point, such as, for example, an indication transmission). In the event that it is determined that additional reference signals have not been received before X time units have elapsed, the WTRU may retransmit an indication of the (e.g., preferred) reference signal configuration in step 93. In the event that it is determined that an 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.

Fig. 12 is a diagram illustrating an example of a method for reference signal adaptation by which the density of reference signals (e.g., any one of increasing and decreasing) of a reference signal configuration may be modified in any one of the time domain and the frequency domain. For example, reference signals within a reference signal configuration may have a density in any of 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 that may be followed by a transmission 1220 of (e.g., scheduled) RSs, which may or may not be accompanied by a 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 allow for an initial capability to provide channel estimation. For example, the WTRU may receive configuration information indicating one or more (e.g., performance) criteria (such as, for example, a threshold) to be used in the determination (e.g., selection) of the DMRS pattern. One or more (e.g., performance) criteria (e.g., thresholds) may relate to (e.g., different) radio transmission characteristics. For example, different (e.g., performance) criteria (e.g., thresholds) may exist 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, for example, in step 1240, the performed measurements may be compared to one or more (e.g., configured) criteria (e.g., performance measurement thresholds). For example, the WTRU may use additional information based on historical performance (e.g., measurements), such as previous (e.g., optimal, selected) RS settings in (e.g., given) channel conditions and mobility. Depending on whether the measured performance meets or fails to meet one or more (e.g., configured) criteria (e.g., performance measurement thresholds), the WTRU may determine whether to maintain or change RS density at any of time and frequency. For example, in the event that the WTRU determines that the measured performance meets one or more (e.g., configured) criteria (e.g., performance measurement thresholds) in either of time and frequency, the WTRU may determine in step 1250 whether the density of RS-configured reference signals may be reduced in either of time and frequency (e.g., by comparing the density of RS-configured reference signals to a density bound of reference signals). In the case where the WTRU determines that the density of the RS configured reference signal may be reduced (e.g., in any of time and frequency), the WTRU may transmit any of an implicit and explicit indication of a density change (e.g., in any of time and frequency) in step 1270. In the event that the WTRU determines that the density of the RS configured reference signal may not be reduced (e.g., in either of time and frequency), the WTRU may not transmit any implicit or explicit indication of the density change in step 1260.

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

For example, one method may be implemented in a WTRU. The method may include:

● Receiving a transmission from a base station configured according to one or more default reference signals;

● Performing channel estimation measurements on the received transmissions based on a default reference signal configuration;

● Selecting one or more reference signal configurations to be used for subsequent transmissions, wherein the one or more reference signal configurations may be selected from a plurality of reference signal configurations based on channel estimation measurements; and

● An indication of the selected one or more reference signal configurations is transmitted to the base station.

For example, configuration information may be received, where the configuration information may indicate a default RS configuration and any of a plurality of RS configurations.

For example, the subsequent transmission may be any one of a downlink and an uplink transmission.

For example, the indication may be any of an explicit indication (e.g., based on explicit information) and an implicit indication (e.g., based on transmissions in a particular resource).

The indication may include any of various types of indications, such as, for example, an index associated with an RS pattern (e.g., configuration), an up/down command to increase/decrease the density of the reference signal.

For example, the selection of RS configuration may be based on AIML (e.g., performed on a history of CE measurements).

Fig. 10A, 10B, and 10C are three diagrams showing three examples of AI/ML-based determination of a reference signal configuration. There may be different examples of different architectures for AI/ML based determination of reference signal configuration. These three architectural examples are described as examples, and not limitations to the embodiments described herein. For example, the described examples of AI/ML blocks and deep learning may be considered merely as representative of an exemplary solution for a processor engine that can analyze and determine (e.g., preferred) reference signal patterns. (e.g., configuration). Any other type and architecture of adaptive processing engine may be suitable for the embodiments described herein.

Fig. 10A is a diagram showing 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 some measurements to evaluate at least one set of performance metrics, such as, for example, any of MSE and correlation coefficients, where a set of performance metrics may include any number of measurements. The performance metric may be referred to herein as any metric capable of capturing the accuracy of the channel estimation algorithm, e.g., in either of the time and frequency domains. For example, the performance metric may include a plurality of measurement points (e.g., values) corresponding to a plurality of reference signals.

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

For example, the WTRU 1000 may receive multiple (e.g., more than one) reference signal sets (e.g., corresponding to multiple reference signal configurations), e.g., to converge to one solution (e.g., a preferred reference signal configuration). For example, the reference signal sets may differ in any of shape and form. For example, the reference signal sets may differ in pattern density (e.g., in any of the time domain, frequency domain, and code domain). For example, the reference signal set 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 reference signal density (e.g., 10%) in the frequency domain, and the locations of the resource elements comprising the pilots may be different. For example, the WTRU may be configured with a (e.g., fixed) reference signal set (e.g., or slot) for (e.g., each potential) update of the reference signal configuration. In other words, the WTRU may not be able to arbitrarily determine the reference signal configurations that do not belong to the configured reference signal configuration set. For example, a (e.g., fixed) set of reference signal sets (e.g., configurations) may perform any of the following operations: pre-configured in the WTRU; and receiving from the base station via the configuration information.

Fig. 10B is a diagram showing a second example of AI/ML 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 some measurements to evaluate at least one set of performance metrics, such as, for example, any of MSE and correlation coefficients, where a set of performance metrics may include any number of measurements.

For example, the WTRU may report the set of evaluations of performance metrics (e.g., a reporting indication of the set of evaluations of the transmission performance metrics) to the base station, e.g., either explicitly (e.g., through either of the uplink control and data channels) and implicitly (e.g., through use of either of the specific uplink control and data channel resources). For example, transmitting the explicit indication of the set of performance metrics may include including explicit information indicating the set of performance metrics in any of a PUCCH/UCI information element and a Channel State Information (CSI) report. For example, the explicit indication may include, for example, an index of a pre-configured table of performance metric values (e.g., a pre-configured list of any of MSE and correlation coefficient values) and any of the (e.g., original) values of the performance metric to be reported. For example, transmitting an implicit indication of the set of performance metrics may include selecting (e.g., and for transmission) any of uplink control and channel resources (such as, for example, any of PUCCH resources, RACH resources, SRS resources, spatial relationship information (e.g., spatial relationship info) resources, etc.) that may be associated with the performance metric value (e.g., a range of values).

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, a (e.g., preferred) reference signal configuration may be transmitted to the WTRU as configuration information.

For example, the WTRU may receive multiple (e.g., more than one) reference signal sets to report a set (e.g., estimated) 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 time slot) for (e.g., each potential) reporting of the performance metric. In other words, the base station may not arbitrarily determine a reference signal configuration that may not belong to a set of (e.g., initially determined) reference signal configurations.

Fig. 10C is a diagram showing a third 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 some measurements to evaluate at least one set of performance metrics, such as, for example, any of MSE and correlation coefficients, where a set of performance metrics may include any number of measurements.

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, the WTRU may report a set of inter-node data (e.g., transmit report indications) to the base station based on the set of (e.g., estimated) performance metrics that may be provided to the input layer 1001C of the AI/ML engine. For example, taking a non-limiting example of deep learning (e.g., involving neural network architecture and parameters), performance metrics (e.g., any of MSE and correlation coefficients) may be used as inputs in the WTRU (e.g., to the input layer 1001C), e.g., to determine (e.g., select) any of the weights and biases of the layers of the inter-node data, such as, for example, the neural network. Running the output layer 1002C at the base station may allow for reduced terminal complexity and improved overall performance, where some learning and decisions about reference signal configuration, for example, may be performed by the base station, where data enters the output layer provided by the WTRU (which may be referred to herein as inter-node data). In this example, the AI/ML engine may be considered as distributed between the WTRU and the base station. The transmission of the reporting directive of the inter-node data may be either explicit or implicit.

For example, the WTRU may report any additional measurements (e.g., transmit reporting directives of any additional measurements) to the base station (e.g., as well). For example, the base station may perform additional processing on the report received from the WTRU to determine a (e.g., preferred) reference signal configuration.

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

For example, the WTRU may be configured with a (e.g., fixed) reference signal set (e.g., or time slot) for (e.g., each potential) reporting of any of the performance metrics and inter-node data.

Fig. 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 used (e.g., implemented) in a WTRU.

For example, in step 1120, a transmission may be received (e.g., downlink) from, for example, a base station in accordance with one or more first reference signal configurations.

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

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

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

For example, one or more first reference signal configurations may do any of the following: (1) pre-configured in a WTRU; and/or (2) indicated by (e.g., included in) first configuration information received from the base station.

For example, the multiple reference signal configuration may do any of the following: (1) pre-configured in a WTRU; and/or (2) indicated by second configuration information received from the base station.

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

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

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

For example, each of the plurality of reference signal configurations may be associated with an index.

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

For example, the 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 (e.g., in the database) one or more reference signal configurations.

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

For example, the reference signal configuration may have a different density in either of time and frequency.

For example, reference signals within a reference signal configuration may have a density in any of time and frequency, and there may be different densities of reference signals for different ones of the plurality of reference signal configurations.

For example, the indication of the (e.g., selected) one or more 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.

For example, the indication of the (e.g., selected) one or more second reference signal configurations may indicate an up command or a down command to apply to the one or more first reference signal configurations for increasing or decreasing the density in either of time and frequency, respectively.

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

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

For example, the relative change may indicate that the density of the reference signal is increased or decreased in fixed steps over any of time and frequency.

For example, one or more second reference signal configurations may be selected at an increased density of second reference signals over any of time and frequency, subject to failure of the performed channel estimation measurements to meet one or more first (e.g., performance) criteria, respectively, over any of time and frequency.

For example, the WTRU may receive third configuration information indicating one or more first (e.g., performance) criteria over any of time and frequency.

For example, one or more second reference signal configurations may be selected at a reduced density of second reference signals in either of time and frequency under the condition that the performed channel estimation measurements satisfy one or more second (e.g., performance) criteria, respectively, in either of time and frequency.

For example, the WTRU may receive fourth configuration information indicating one or more second (e.g., performance) criteria on either of time and frequency.

For example, the subsequent transmission may be any one of a (e.g., subsequent) downlink transmission and a (e.g., subsequent) uplink transmission.

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.

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

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

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

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

For example, one or more reference signal configurations (e.g., indications of the selected one or more reference signal configurations) may be indicated (e.g., transmitted) by transmissions in resources that may be associated with the selected one or more second reference signal configurations.

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

For example, the selection of the one or more second reference signal configurations may also be based on AI/ML performed on channel estimation measurements (e.g., last performed).

For example, the selection of one or more reference signal configurations may also be based on AI/ML performed on a set of channel estimation measurements (e.g., a history of channel estimation measurements).

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

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

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

For example, inter-node data may be transmitted to a base station, the inter-node data obtained based on historical channel estimation measurements (e.g., a history of channel estimation measurements).

For example, at least one performance metric may be transmitted to the base station, the at least one performance metric obtained based on at least one estimated measurement.

Throughout the embodiments described herein, (e.g., configuration) information may be described as being received by the WTRU from the network, e.g., through system information or via any kind of protocol message. Although not explicitly mentioned in the embodiments described herein, the same (e.g., configuration) information may be preconfigured in the WTRU (e.g., via any kind of preconfigured method, such as via factory settings) so that the (e.g., configuration) information may be used by the WTRU without being received from the network.

For clarity, the implementations described herein that satisfy, do not satisfy the conditions (e.g., performance criteria) and "configure condition parameters" are described with respect to threshold (e.g., greater than or less than) (e.g., threshold) values, configure (e.g., threshold) values, and so forth. For example, a condition (e.g., performance criteria) being met may be described as being above a (e.g., threshold) value, and a condition (e.g., performance criteria) being not being met may be described as being below a (e.g., threshold) value. The implementations described herein are not limited to threshold-based conditions (e.g., performance criteria). Any kind of other conditions and parameters (such as, for example, belonging to or not belonging to a range of values) may be suitable for the embodiments described herein.

Conclusion(s)

Although features and elements are provided above in particular combinations, one 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 to the specific embodiments described in this patent application, which are intended as illustrations of various aspects. Many modifications and variations may be made without departing from the spirit and scope of the invention, as will be apparent to those skilled in the art. No element, act, or instruction used in the description of the present application should be construed as critical or essential to the invention unless explicitly described as such. Functionally equivalent methods and apparatus, other than those enumerated herein, which are 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 should be understood that the present disclosure is not limited to a particular method or system.

For simplicity, the foregoing embodiments are discussed with respect to the terminology and structure of infrared-capable devices (i.e., infrared emitters and receivers). However, the embodiments discussed are not limited to these systems, but may be applied to other systems using other forms of electromagnetic waves or non-electromagnetic waves (such as acoustic waves).

It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the term "video" or the term "image" may mean any of a snapshot, a single image, and/or multiple images that are displayed on a temporal basis. As another example, as referred to herein, the term "user equipment" and its abbreviation "UE", the term "remote" and/or the term "head mounted display" or its abbreviation "HMD" may mean or include (i) a wireless transmit and/or receive unit (WTRU); (ii) Any of a number of embodiments of the WTRU; (iii) Devices with wireless capabilities and/or with wired capabilities (e.g., tethered) are configured with some or all of the structure and functionality of a WTRU, in particular; (iii) Wireless capability and/or wireline capability devices configured with less than the full structure and functionality of the WTRU; or (iv) etc. Details of an exemplary WTRU that may represent any of the WTRUs described herein are provided herein with respect to fig. 1A-1D. As another example, various disclosed embodiments herein are described above and below as utilizing a head mounted display. Those skilled in the art will recognize that devices other than head mounted displays may be utilized and that some or all of the present disclosure and various disclosed embodiments may be modified accordingly without undue experimentation. Examples of such other devices may include drones or other devices configured to stream information to provide an adapted real-world experience.

Additionally, the methods provided herein may be implemented in a computer program, software, or firmware incorporated in a computer readable medium for execution by a computer or processor. Examples of computer readable media include electronic signals (transmitted over a wired or wireless connection) 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 associated with the software may be used to implement a radio frequency transceiver for a WTRU, UE, terminal, base station, RNC, or any host computer.

Variations of the methods, apparatus, and systems provided above are possible without departing from the scope of the invention. In view of the various embodiments that may be employed, it should be understood that the illustrated embodiments are examples only and should not be taken as limiting the scope of the following claims. For example, embodiments provided herein include a handheld device that may include or be used with any suitable voltage source (such as a battery or the like) that provides any suitable voltage.

Furthermore, in the embodiments provided above, processing platforms, computing systems, controllers, and other devices including processors are indicated. These devices may include at least one central processing unit ("CPU") and memory. References to actions and symbolic representations of operations or instructions may be performed by various CPUs and memories in accordance with practices of persons skilled in the art of computer programming. Such acts and operations, or instructions, may be considered to be "executing," computer-executed, "or" CPU-executed.

Those of ordinary skill in the art will appreciate that the acts and symbolically represented operations or instructions include the manipulation of electrical signals by the CPU. The electrical system represents data bits that may result in a final transformation of the electrical signal or a reduction of the electrical signal and a retention of the data bits at memory locations in the memory system, thereby reconfiguring or otherwise altering the operation of the CPU and performing other processing of the signal. The memory location holding the data bit is a physical location having a particular electrical, magnetic, optical, or organic attribute corresponding to or representing the data bit. It should be understood that embodiments are not limited to the above-described platforms or CPUs, and that other platforms and CPUs may also support the provided methods.

The data bits may also be maintained on computer readable media 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 the CPU. The computer readable media may comprise cooperating or interconnected computer readable media that reside exclusively on the processing system or are distributed among a plurality of interconnected processing systems, which may be local or remote relative to the processing system. It should be understood that embodiments are not limited to the above-described memories, and that other platforms and memories may support the provided methods.

In an exemplary 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 the mobile unit, the network element, and/or any other computing device.

There is little distinction between hardware implementations and software implementations of aspects of the system. The use of hardware or software is often (but not always, as in some contexts the choice between hardware and software may become important) a design choice representing a tradeoff between cost and efficiency. There may be various media (e.g., hardware, software, and/or firmware) that may implement the processes and/or systems and/or other techniques described herein, and the preferred media may vary with the context in which the processes and/or systems and/or other techniques are deployed. For example, if the implementer determines that speed and accuracy are paramount, the implementer may opt for a medium of mainly hardware and/or firmware. If flexibility is paramount, the implementer may opt for a particular implementation of mainly software. Alternatively, the implementer may opt for some combination of hardware, software, and/or firmware.

The foregoing detailed description has set forth various embodiments of the devices and/or processes via the use of block diagrams, flowcharts, and/or examples. Where such block diagrams, flowcharts, and/or examples include one or more functions and/or operations, it will be understood by those skilled in the art that each function and/or operation within such block diagrams, flowcharts, or examples can be implemented, individually and/or collectively, by a wide range of hardware, software, firmware, or virtually any combination thereof. In an embodiment, portions of the subject matter described herein may be implemented via an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), a Digital Signal Processor (DSP), and/or other integrated format. However, those skilled in the art will recognize that some aspects of the embodiments disclosed herein, in whole or in part, can be equivalently implemented 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 virtually any combination thereof, and that designing the circuitry and/or writing the code for the software and/or firmware would be well within the skill of one of skill in the art in light of this disclosure. Furthermore, those skilled in the art will appreciate that the mechanisms of the subject matter described herein are capable of being distributed as a program product in a variety of forms, and that an illustrative embodiment of the subject matter described herein applies regardless of the particular type of signal bearing media used to actually carry out the distribution. Examples of signal bearing media include, but are not limited to, the following: recordable type media (such as floppy disks, hard disk drives, CDs, DVDs, digital tapes, computer memory, etc.); and transmission type media such as digital and/or analog communications media (e.g., fiber optic cable, waveguide, wired communications link, wireless communications link, etc.).

Those skilled in the art will recognize that it is common in the art to describe devices and/or processes in the manner set forth herein, and thereafter use engineering practices to integrate such described devices and/or processes into data processing systems. That is, at least a portion of the devices and/or processes described herein may be integrated into a data processing system via 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 the following: a system unit housing; a video display device; memories such as volatile memories and nonvolatile memories; a processor, such as a microprocessor and a digital signal processor; computing entities such as operating systems, drivers, graphical user interfaces, and applications; one or more interactive devices, such as a touch pad or screen; and/or a control system comprising a feedback loop and a control motor (e.g. feedback for sensing position and/or speed, a control motor for moving and/or adjusting components and/or amounts). Typical data processing systems may be implemented using any suitable commercially available components, such as those typically found in data computing/communication and/or network computing/communication systems.

The subject matter described herein sometimes illustrates different components included within or connected with different other components. It is to be understood that such depicted architectures are merely examples, and that in fact many other architectures can be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively "associated" such that the desired functionality is achieved. Thus, any two components herein combined to achieve a particular functionality can be seen as "associated with" each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being "operably connected," or "operably coupled," to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being "operably couplable," to each other to achieve the desired functionality. Specific examples of operably couplable include, but are not limited to, physically mateable and/or physically interactable components and/or wirelessly interactable components and/or logically interactable components.

With respect to substantially any plural and/or singular terms used herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. For clarity, various singular/plural permutations may be explicitly listed herein.

It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as "open" 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," the term "comprising" should be interpreted as "including but not limited to," etc.). It will be further understood by those with skill in the art that if a specific number of an introduced claim recitation is intended, such intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, where only one item is contemplated, the term "single" or similar language may be used. To facilitate understanding, the following appended claims and/or descriptions herein may include the use of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation object by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation object to embodiments containing only one such recitation object. Even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles 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 holds true for the use of definite articles used to introduce claim recitations. Furthermore, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, means at least two recitations, or two or more recitations). In addition, in those instances where a convention analogous to "at least one of A, B and C, etc." is used, in general such a construction has the meaning that one having skill in the art would understand the convention (e.g., "a system having at least one of A, B and C" would include but not be limited to systems that have a alone, B alone, C alone, a and B together, a and C together, B and C together, and/or A, B and C together, etc.). In those instances where a convention analogous to "at least one of A, B or C, etc." is used, in general such a construction has the meaning that one having skill in the art would understand the convention (e.g., "a system having at least one of A, B or C" would include but not be limited to systems having a alone, B alone, C alone, a and B together, a and C together, B and C together, and/or A, B and C together, etc.). It should also be understood by those within the art that virtually any separate word and/or phrase presenting two or more alternative terms, whether in the specification, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "a or B" will be understood to include the possibilities of "a" or "B" or "a and B". In addition, as used herein, the term "…" followed by listing a plurality of items and/or a plurality of item categories is intended to include items and/or item categories "any one of", "any combination of", "any multiple of" and/or any combination of multiples of "alone or in combination with other items and/or other item categories. Furthermore, as used herein, the term "collection" is intended to include any number of items, including zero. Furthermore, as used herein, the term "number" is intended to include any number, including zero. Also, as used herein, the term "multiple" is intended to be synonymous with "multiple".

Further, where features or aspects of the present disclosure are described in terms of markush groups, those skilled in the art will recognize thereby that the present disclosure is also described in terms of any individual member or subgroup of members of the markush group.

As will be understood by those skilled in the art, for any and all purposes (such as in terms of providing a written description), all ranges disclosed herein also encompass any and all possible sub-ranges and combinations of sub-ranges thereof. Any listed range can be readily identified as sufficiently descriptive and so that the same range can be divided into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein can be readily divided into a lower third, a middle third, an upper third, and the like. As will also be understood by those skilled in the art, all language such as "up to", "at least", "greater than", "less than", etc., include the recited numbers and refer to ranges that may be subsequently divided into sub-ranges as described above. Finally, as will be understood by those skilled in the art, the scope includes each individual number. Thus, for example, a group having 1 to 3 units refers to a group having 1, 2, or 3 units. Similarly, a group having 1 to 5 units refers to a group having 1, 2, 3, 4, or 5 units, or the like.

Furthermore, the claims should not be read as limited to the order or elements provided, unless stated to that effect. Furthermore, use of the term "means for … …" in any claim is intended to invoke 35U.S. C. ≡112,or a device plus function claim format, and any claims that do not have the term "device for … …" are not intended to be so. />

Claims

1. A method implemented in a wireless transmit/receive unit (WTRU), the method comprising:

receiving a transmission from a base station configured according to one or more first reference signals;

performing channel estimation measurements on the received transmissions based on the one or more first reference signal configurations; and

transmitting an indication of one or more second reference signal configurations to be used for subsequent transmissions to the base station, wherein the one or more second reference signal configurations are selected from a plurality of reference signal configurations based on the channel estimation measurements.

2. The method of claim 1, wherein the one or more first reference signal configurations do any of: (1) pre-configured in the WTRU; and/or (2) indicated by first configuration information received from the base station.

3. The method of any of claims 1-2, wherein the plurality of reference signal configurations do any of: (1) pre-configured in the WTRU; and/or (2) indicated by second configuration information received from the base station.

4. A method according to claims 2 and 3, wherein the first configuration information and the second configuration information are included in the same message.

5. A method according to claims 2 and 3, wherein the first configuration information and the second configuration information are included in different messages.

6. The method of any of claims 1-5, wherein each of the plurality of reference signal configurations is associated with an index.

7. The method of any of claims 2-6, wherein the first configuration information includes one or more first indices indicating the one or more first reference signal configurations.

8. The method of any of claims 1-7, wherein the indication of the one or more second reference signal configurations indicates a second index associated with one second reference signal configuration.

9. The method of any of claims 1-8, wherein reference signals within a reference signal configuration have a density in any of time and frequency, and wherein reference signals have different densities for different ones of the plurality of reference signal configurations.

10. The method of any of claims 1-9, wherein the indication of the one or more second reference signal configurations indicates one or more densities in any of time and frequency for the selected one or more second reference signal configurations.

11. The method of any of claims 1-10, wherein the indication of the one or more second reference signal configurations indicates a relative change in density of reference signals in any of time and frequency from a first density of first reference signals for the one or more first reference signal configurations to a second density of second reference signals for the selected one or more second reference signal configurations.

12. The method of claim 11, wherein the indication is selected as an index value based on a relative change in density of the reference signals between the one or more first reference signal configurations and the selected one or more second reference signal configurations.

13. The method of any of claims 11 to 12, wherein the relative change indicates increasing or decreasing the density of the reference signal in fixed steps over any of time and frequency.

14. The method of any of claims 1-13, wherein the one or more second reference signal configurations are selected with an increased density of second reference signals over any of time and frequency on condition that the performed channel estimation measurements fail to meet one or more first performance criteria over any of time and frequency, respectively.

15. The method of any of claims 1-13, wherein the one or more second reference signal configurations are selected at a reduced density of second reference signals in any of time and frequency, provided that the performed channel estimation measurements meet one or more second performance criteria in any of time and frequency, respectively.

16. The method of any of claims 1-15, wherein the subsequent transmission is a downlink transmission, and wherein the method comprises receiving the subsequent transmission using the one or more second reference signal configurations.

17. The method of any of claims 1-15, wherein the subsequent transmission is an uplink transmission, and wherein the method comprises transmitting the subsequent transmission using the one or more second reference signal configurations.

18. The method of any of claims 1 to 17, wherein the indication of the one or more second reference signal configurations is transmitted by transmitting first information indicative of the selected one or more second reference signal configurations.

19. The method of any of claims 1-17, wherein the indication of the one or more second reference signal configurations is transmitted by transmission in a resource associated with the selected one or more second reference signal configurations.

20. The method of claim 19, wherein the resource is any one of a physical uplink control channel resource, a random access channel resource, a sounding reference signal resource, and a spatial relationship information resource.

21. An apparatus comprising circuitry, the apparatus comprising any of a transmitter, a receiver, a processor, and a memory, the apparatus configured to perform the method of any of claims 1-20.