Adaptive and distributed reference signal insertion in discrete Fourier transform extended orthogonal frequency division multiplexing (DFT-S-OFDM) signals

Abstract

Distributed, adaptive insertion of a reference signal (RS) in a Discrete Fourier Transform Extended Orthogonal Frequency Division Multiplexing (DFT-s-OFDM) transmission scheme may include pre-DFT insertion and / or post-DFT insertion of the distributed RS at various locations in the frequency domain. In an example configuration, a wireless transmit / receive unit (WTRU) may determine a first codebook including one or more demodulation reference signal (DM-RS) sequences, receive one or more DFT-s-OFDM symbols including the one or more DM-RS sequences, and determine a set of the one or more DM-RS sequences using blind detection based on the received one or more DFT-s-OFDM symbols. The RS insertion scheme may improve overhead, provide control of peak-to-average power ratio (PAPR), and mitigate adverse effects on spectral efficiency.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 399,759, filed on August 22, 2022, which is hereby incorporated by reference in its entirety. Background Art

[0003] Discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM) is a single carrier transmission scheme that can be used in fourth generation (4G) long term evolution (LTE) wireless cellular systems and fifth generation (5G) new radio (NR) wireless cellular systems. A reference signal (RS) can be inserted into the DFT-s-OFDM transmission scheme to measure various characteristics of the radio channel. The reference signal (RS) may include a plurality of reference symbols that can be inserted into the DFT-s-OFDM symbol. However, RS insertion may adversely affect performance. For example, RS insertion may increase the peak-to-average power ratio (PAPR), thereby deteriorating power amplifier efficiency. As another example, RS insertion may adversely affect spectral efficiency (e.g., the information rate that can be sent over a given bandwidth). Summary of the invention

[0004] Described herein are example methods, devices, and systems for distributed and adaptive insertion of one or more reference signals (RS) in a discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM) transmission scheme. The RS insertion scheme described herein can improve overhead and provide control over peak-to-average power ratio (PAPR).

[0005] The reference signal sequence may be dynamically selected by the transmitting node from a set of sequences specified in a predetermined codebook and interleaved with the DFT-precoded data symbols based on PAPR measurements performed by the transmitting node.

[0006] The reference signal sequence may be dynamically selected by the transmitting node from a set of sequences specified in a predetermined codebook. The selected reference signal sequence may be used to replace a set of DFT precoded symbols. The set of DFT precoded symbols replaced by the reference symbols is said to be "punctured". The selection of the RS sequence may be based on the PAPR measurement and / or the structure of the transmitted signal (e.g., DFT precoded data symbol).

[0007] The receiving node may detect the transmitted reference signal based on blind detection of a sequence of one or more sequences from a predetermined codebook or based on explicit signaling, and the detected reference signal may be used for channel estimation and signal equalization / decoding. Blind detection refers to a situation where the transmitting node does not transmit an indication of the RS sequence used during transmission. Therefore, the receiving node may not have an explicit indication of the RS sequence used by its transmitting node. Therefore, the receiving node may detect the transmitted reference signal sequence based on the received signal without explicit indication. This way of detecting the RS sequence from the received signal is called blind detection. For example, when the RS sequence is a limited part of a known larger sequence or a part of a known codebook or a predetermined codebook, blind detection at the receiving node can be achieved. Alternatively, the transmitting node may transmit an indication of the RS sequence selected by the receiving node to the receiving node through explicit signaling. This can facilitate RS sequence detection at the receiving node.

[0008] The padding sequence structure and the reference signal sequence may be dynamically selected by the transmitting node based on PAPR measurements and / or transmitted signals (e.g., DFT pre-coded data symbols), structures in a set of structures / sequences specified in a predetermined codebook. The padding sequence may be appended to the modulated data symbols by the transmitting node before the DFT stage, and the reference signal sequence may be used to replace the punctured samples of the DFT pre-coded data+padding sequence symbols.

[0009] The receiving node may detect the transmitted reference signal based on blind detection or explicit signaling of a sequence from one or more sequences in a predetermined codebook, use the detected reference signal for channel estimation and signal equalization, perform IDFT, detect the padding sequence structure via blind detection or explicit signaling, and use the detected sequence structure for interference cancellation and signal decoding.

[0010] An example method for inserting a reference signal may include receiving control information indicating a set of two or more demodulation reference signal (DM-RS) sequences. One or more discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM) symbols may be received, each of the one or more DFT-s-OFDM symbols including corresponding data, corresponding DM-RS, or a combination thereof. Using blind detection, a first subset of DM-RS sequences may be determined based on the set of one or more DM-RS sequences, wherein determining the first subset of DM-RS sequences may be based on the received one or more DFT-s-OFDM symbols. A performance parameter associated with the first subset of DM-RS sequences may be determined. It may be determined that the determined performance parameter associated with the first subset of DM-RS sequences is less than a threshold performance parameter. An indication of a second subset of DM-RS sequences may be transmitted based on determining that the performance parameter associated with the first subset of DM-RS sequences is less than the threshold performance parameter.

[0011] Further with respect to the method, the control information may include a codebook, the codebook including the set of one or more DM-RS sequences. The control information may be received via a downlink control information (DCI) related signal or a medium access control (MAC) control element (CE). The method may include: determining a channel estimate based on the first subset of DM-RS sequences, wherein the performance parameter is associated with the determined channel estimate. The method may include: determining a DFT-s-OFDM symbol equalization based on the first subset of DM-RS sequences, wherein the performance parameter is associated with the determined DFT-s-OFDM symbol equalization. The performance parameter may include a decoding performance parameter. The decoding performance parameter may include at least one of a block error rate (BLER) or a bit error rate (BER). The method may include: receiving a second control information indicating a second subset of DM-RS sequences. The method may include: receiving an additional DFT-s-OFDM symbol; and processing the additional DFT-s-OFDM symbol using the second subset of DM-RS sequences. The blind detection may be based on correlation of the indicated set of one or more DM-RS sequences with the received one or more DFT-s-OFDM symbols.

[0012] An example WTRU for inserting a reference signal may include a transceiver and a processor. The processor may be configured to receive control information via the transceiver, the control information indicating a set of two or more demodulation reference signal (DM-RS) sequences. The processor may be configured to receive one or more discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM) symbols via the transceiver, each of the one or more DFT-s-OFDM symbols including corresponding data, corresponding DM-RS, or a combination thereof. The processor may be configured to determine a first subset of DM-RS sequences based on the set of one or more DM-RS sequences using blind detection, wherein determining the first subset of DM-RS sequences is based on the received one or more DFT-s-OFDM symbols. The processor may be configured to determine a performance parameter associated with the first subset of DM-RS sequences. The processor may be configured to determine that the determined performance parameter associated with the first subset of DM-RS sequences is less than a threshold performance parameter. The processor may be configured to transmit, via the transceiver, an indication of a second subset of DM-RS sequences based on determining that the performance parameter associated with the first subset of DM-RS sequences is less than the threshold performance parameter.

[0013] Further with respect to the WTRU, the control information may include a codebook, the codebook including the set of one or more DM-RS sequences. The control information may be received via a downlink control information (DCI) related signal or a medium access control (MAC) control element (CE). The processor may be configured to determine a channel estimate based on the first subset of DM-RS sequences, wherein the performance parameter is associated with the determined channel estimate. The processor may be configured to determine a DFT-s-OFDM symbol equalization based on the first subset of DM-RS sequences, wherein the performance parameter is associated with the determined DFT-s-OFDM symbol equalization. The performance parameter includes a decoding performance parameter. The decoding performance parameter may include at least one of a block error rate (BLER) or a bit error rate (BER). The processor may be configured to receive second control information via the transceiver, the second control information indicating a second subset of DM-RS sequences. The processor may be configured to receive an additional DFT-s-OFDM symbol; and process an additional DFT-s-OFDM signal using the second subset of DM-RS sequences. The blind detection may be based on correlation of the indicated set of one or more DM-RS sequences with the received one or more DFT-s-OFDM symbols. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] A more detailed understanding can be obtained from the following detailed description, which is given by way of example in conjunction with its accompanying drawings. As with the detailed description, the figures in such drawings are examples. Therefore, the drawings and specific embodiments should not be considered limiting, and other equally effective examples are possible and intended. The same reference numerals ("ref." or "refs.") represent the same elements in the drawings.

[0015] Figure 1A is an example system diagram illustrating an example communication system in which one or more disclosed embodiments may be implemented.

[0016] Figure 1B is an example of a method that can be performed according to an embodiment of the present invention. Figure 1A An example system diagram of an example wireless transmit / receive unit (WTRU) for use within an example communication system.

[0017] Figure 1C is an example of a method that can be performed according to an embodiment of the present invention. Figure 1A An example system diagram of an example Radio Access Network (RAN) and an example Core Network (CN) for use within an illustrated communication system.

[0018] Figure 1D is an example of a method that can be performed according to an embodiment of the present invention. Figure 1A An example system diagram of another example RAN and another example CN used within the illustrated communication system.

[0019] Figure 2 Examples of pre-DFT insertion and post-DFT insertion of a reference signal (RS) in a discrete Fourier transform (DFT) spread orthogonal frequency division multiplexing (DFT-s-OFDM) system are depicted.

[0020] Figure 3 An example of interleaving insertion of RSs in a DFT-s-OFDM system is depicted.

[0021] Figure 4 An example of RS insertion by subcarrier puncturing with zero padding is depicted.

[0022] Figure 5 is a flow chart of an example process for dynamic RS insertion at the base station (BS) side.

[0023] Figure 6 is a flow chart of an example process for data detection and interference cancellation from RS insertion at the wireless transmit / receive unit (WTRU) side.

[0024] Figure 7 Depicts an example block diagram of the DFT-s-OFDM reception process.

[0025] Figure 8 is a flow chart of an example process for RS insertion selection by a sending node with the assistance of receiving node feedback.

[0026] Fig. 9 Depicted is a block diagram of an example transmitter architecture for reducing peak-to-average power ratio (PAPR) using an adaptive demodulation reference signal (DM-RS).

[0027] Fig.10 Depicted is a block diagram of an example receiver architecture for reducing PAPR using DM-RS.

[0028] Fig.11 is a flow chart of an example process for detecting shared DFT-s-OFDM symbols that support blind DM-RS detection and codebook change requests.

[0029] Fig.12 is a flow chart of an example process for using auxiliary information to detect shared DFT-s-OFDM symbols supporting blind DM-RS detection and codebook update.

[0030] Fig.13 is a flow chart of an example process for detecting shared DFT-s-OFDM symbols supporting interference cancellation of padding sequences, blind DM-RS detection, and padding sequence structure and codebook change requests.

[0031] Fig.14 is a flow chart of an example process for detecting shared DFT-s-OFDM symbols that supports interference cancellation of padding sequences, blind DM-RS detection, and dynamic selection of padding sequence structure and DM-RS codebook. DETAILED DESCRIPTION

[0032] Figure 1A 1 is a diagram illustrating an example communication system 100 in which one or more disclosed embodiments may be implemented. The communication system 100 may be a multiple access system that provides content such as voice, data, video, messaging, broadcast, etc. to multiple wireless users. The communication system 100 may enable multiple wireless users to access such content through sharing of system resources (including wireless bandwidth). For example, the communication system 100 may employ one or more channel access methods such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single carrier FDMA (SC-FDMA), zero tail unique word DFT spread OFDM (ZT UW DTS-s OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, and filter bank multi-carrier (FBMC), etc.

[0033] like Figure 1AAs shown, the communication system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, RAN 104 / 113, CN 106 / 115, public switched telephone network (PSTN) 108, Internet 110 and other networks 112, but 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. By way of example, the WTRUs 102a, 102b, 102c, 102d (any of which may be referred to as a “station” and / or “STA”) may be configured to send and / or receive wireless signals and may include user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular phone, a personal digital assistant (PDA), a smart phone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watch or other wearable device, a head-mounted display (HMD), a vehicle, a drone, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in an industrial and / or automated process chain environment), a consumer electronic device, a device operating on a commercial and / or industrial wireless network, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a UE.

[0034] The communication system 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device that is configured to interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106 / 115, the Internet 110, and / or other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node B, an eNode B, a Home Node B, a Home eNode B, a gNB, an NR Node B, 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.

[0035] Base station 114a may be part of RAN 104 / 113, which may also include other base stations and / or network elements (not shown), such as base station controllers (BSC), radio network controllers (RNC), relay nodes, etc. Base station 114a and / or base station 114b may be configured to send 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 a licensed spectrum and an unlicensed spectrum. A cell may provide coverage of wireless services to a specific geographic area, which may be relatively fixed or may change over time. The cell may be further divided into cell sectors. For example, the cell associated with base station 114a may be divided into three sectors. Therefore, in one embodiment, base station 114a may include three transceivers, i.e., one transceiver for each sector of the cell. In an embodiment, base station 114a may employ multiple-input multiple-output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to send and / or receive signals in a desired spatial direction.

[0036] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0037] More specifically, as noted above, the communication system 100 may be a multiple access system and may employ one or more channel access schemes such as CDMA, TDMA, FDMA, OFDMA, and SC-FDMA. For example, the 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 115 / 116 / 117. WCDMA may include communication protocols such as High Speed ​​Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High Speed ​​Downlink (DL) Packet Access (HSDPA) and / or High Speed ​​UL Packet Access (HSUPA).

[0038] 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 establish the air interface 116 using Long Term Evolution (LTE) and / or Advanced LTE (LTE-A) and / or Advanced LTE Pro (LTE-APro).

[0039] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR radio access, which may establish the air interface 116 using New Radio (NR).

[0040] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may together implement LTE radio access and NR radio access, for example using the dual connectivity (DC) principle. Thus, the air interface used by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions transmitted to / from multiple types of base stations (e.g., eNBs and gNBs).

[0041] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e., Wireless Fidelity (WiFi)), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile Communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), and GSM EDGE (GERAN).

[0042] Figure 1AThe base station 114b in may be, for example, a wireless router, a Home NodeB, a Home eNodeB, or an access point, and may utilize any suitable RAT to facilitate wireless connectivity in local areas such as commercial venues, homes, vehicles, campuses, industrial facilities, sky corridors (e.g., for use by drones), and roads. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In 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 yet another 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 a picocell or a femtocell. As Figure 1A As shown, base station 114b may have a direct connection to Internet 110. Therefore, base station 114b may not need to access Internet 110 via CN 106 / 115.

[0043] The RAN 104 / 113 may be in communication with the CN 106 / 115, which may be any type of network configured to provide voice, data, applications and / or Voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have different quality of service (QoS) requirements, such as different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 / 115 may provide call control, billing services, mobile location-based services, prepaid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions, such as user authentication. Although not described in detail in the text and video, the CN 106 / 115 may be configured to provide voice, data, applications and / or Voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have different quality of service (QoS) requirements, such as different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 / 115 may provide call control, billing services, mobile location-based services, prepaid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions, such as user authentication. Figure 1A Although not shown in the figure, it will be appreciated that the RAN 104 / 113 and / or the CN 106 / 115 may be in direct or indirect communication with other RANs that employ the same RAT as the RAN 104 / 113 or a different RAT. For example, in addition to being connected to the RAN 104 / 113, which may utilize NR radio technology, the CN 106 / 115 may also be in communication with another RAN (not shown) that employs GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0044] 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. The PSTN 108 may include a circuit-switched telephone network that provides plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and / or the Internet Protocol (IP) in the TCP / IP Internet protocol suite. The networks 112 may include wired communication networks and / or wireless communication networks owned and / or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, which may employ the same RAT as the RAN 104 / 113 or a different RAT.

[0045] 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 via different wireless links). Figure 1A The illustrated WTRU 102c may be configured to communicate with the base station 114a, which may employ a cellular-based radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0046] Figure 1B is a system diagram illustrating an example WTRU 102. Figure 1B As shown, the WTRU 102 may include, among other things, a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138. It will be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0047] 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 associated with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) circuit, any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal decoding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. Although Figure 1B The processor 118 and the transceiver 120 are depicted as separate components, but it is understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0048] The send / receive element 122 may be configured to send a signal to a base station (e.g., base station 114a) or receive a signal from a base station via an air interface 116. For example, in one embodiment, the send / receive element 122 may be an antenna configured to send and / or receive an RF signal. In an embodiment, the send / receive element 122 may be a transmitter / detector configured to send and / or receive, for example, an IR, UV, or visible light signal. In another embodiment, the send / receive element 122 may be configured to send and / or receive both an RF signal and an optical signal. It should be understood that the send / receive element 122 may be configured to send and / or receive any combination of wireless signals.

[0049] Although the transmit / receive element 122 Figure 1B Although depicted as a single element in the figure, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0050] The transceiver 120 may be configured to modulate signals to be transmitted by the transmit / receive element 122 and to demodulate signals received by the transmit / receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. For example, the transceiver 120 may include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11.

[0051] 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 (e.g., a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit). The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from and store data in any type of suitable memory, such as a non-removable memory 130 and / or a removable memory 132. The non-removable memory 130 may include a random access memory (RAM), a read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, and a secure digital (SD) memory card, among others. In other embodiments, the processor 118 may access information from and store data in a memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0052] The processor 118 may receive power from the power source 134, and may be configured to distribute and / or control power to the 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 cell batteries (e.g., nickel cadmium (NiCd), nickel zinc (NiZn), nickel metal hydride (NiMH), lithium ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0053] The processor 118 may also be coupled to the 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 the information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (e.g., base stations 114a, 114b) over the air interface 116 and / or determine its location based on the timing of signals received from two or more nearby base stations. It will be appreciated that the WTRU 102 may acquire location information by any suitable location-determination method while remaining consistent with an embodiment.

[0054] The processor 118 may also be coupled to other peripherals 138, which may include one or more software modules and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, module, FM radio unit, digital music player, media player, video game player module, Internet browser, virtual reality and / or augmented reality (VR / AR) device and activity tracker, etc. Peripheral device 138 may include one or more sensors, which may be one or more of the following: gyroscope, accelerometer, Hall effect sensor, magnetometer, orientation sensor, proximity sensor, temperature sensor, time sensor; geolocation sensor; altimeter, light sensor, touch sensor, magnetometer, barometer, gesture sensor, biometric sensor and / or humidity sensor.

[0055] The WTRU 102 may include a full-duplex radio for which transmission and reception of some or all signals (e.g., associated with specific subframes for both UL (e.g., for transmission) and downlink (e.g., for reception)) may be concurrent and / or simultaneous. The full-duplex radio may include an interference management unit 139 for reducing and / or substantially eliminating self-interference via signal processing performed by hardware (e.g., a choke) or via a processor (e.g., a separate processor (not shown) or via the 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 specific subframes for both UL (e.g., for transmission) or downlink (e.g., for reception)) may be concurrent and / or simultaneous.

[0056] Figure 1C 1 is a system diagram illustrating the RAN 104 and the CN 106 in accordance with an embodiment. As noted above, the RAN 104 may employ E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0057] The RAN 104 may include evolved Node-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of evolved Node-Bs while remaining consistent with an embodiment. The evolved Node-Bs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the evolved Node-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the evolved Node-B 160a, for example, may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a.

[0058] Each of the evolved Node Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, and scheduling of users in the UL and / or DL, among other things. Figure 1C As shown, the eNode-Bs 160a, 160b, 160c may communicate with one another via an X2 interface.

[0059] Figure 1C The illustrated CN 106 may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (or PGW) 166. While each of the foregoing elements is depicted as being 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.

[0060] The MME 162 may be connected to each of the evolved Node-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation / deactivation, and selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM and / or WCDMA.

[0061] The SGW 164 may be connected to each of the evolved Node-Bs 160a, 160b, 160c in the RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring the user plane during an inter-evolved Node-B handover, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, and managing and storing the context of the WTRUs 102a, 102b, 102c.

[0062] The SGW 164 may be connected to the PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0063] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include, or may be in communication with, an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that acts 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 networks and / or wireless networks owned and / or operated by other service providers.

[0064] Although the WTRU Figures 1A to 1D Although described as wireless terminals, it is contemplated that in certain representative embodiments, such terminals may (eg, temporarily or permanently) use a wired communications interface with a communications network.

[0065] In a representative embodiment, the other network 112 may be a WLAN.

[0066] A WLAN in infrastructure basic service set (BSS) mode may have an access point (AP) for a BSS and one or more stations (STAs) associated with the AP. The AP may have access or an interface to a distribution system (DS) or another type of wired / wireless network that carries traffic to and / or carries traffic away from the BSS. Traffic originating from outside the BSS and destined for the STA may arrive through the AP and may be delivered to the STA. Traffic originating from the STA and destined for a target outside the BSS may be transmitted to the AP to be delivered to the corresponding target. Traffic between STAs within the BSS may be transmitted through the AP, for example, wherein the source STA may transmit traffic to the AP, and the AP may deliver traffic to the destination STA. Traffic between STAs within the BSS may be considered and / or referred to as point-to-point traffic. Point-to-point traffic may be transmitted between the source STA and the target STA (e.g., directly between them) using a 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 within or using the IBSS (eg, all STAs in the STA) may communicate directly with each other. The IBSS communication mode may sometimes be referred to herein as an "ad hoc" communication mode.

[0067] When using the 802.11ac infrastructure operation mode or a similar operation mode, the AP may send beacons on a fixed channel (such as a primary channel). The primary channel may be a fixed width (e.g., a 20 MHz wide bandwidth) or a width dynamically set via signaling. The primary channel may be an operating channel of the BSS and may be used by the STA 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, a STA (e.g., each STA) (including the AP) may sense the primary channel. If the primary channel is sensed / detected and / or determined to be busy by a particular STA, the particular STA may back off. One STA (e.g., only one station) may transmit at any given time in a given BSS.

[0068] High throughput (HT) STAs may communicate using a 40 MHz wide channel (eg, via a combination of a primary 20 MHz channel and adjacent or non-adjacent 20 MHz channels) to form a 40 MHz wide channel.

[0069] Very high throughput (VHT) STA can support 20MHz, 40MHz, 80MHz and / or 160MHz wide channels. 40MHz channels and / or 80MHz channels can be formed by combining continuous 20MHz channels. 160MHz channels can be formed by combining 8 continuous 20MHz channels, or by combining two non-continuous 80MHz channels (this can be called 80+80 configuration). For 80+80 configuration, after channel coding, the data can pass through a segment parser that can divide the data into two streams. Each stream can be processed by inverse fast Fourier transform (IFFT) and time domain processing separately. These streams can be mapped to two 80MHz channels, and the data can be sent by the transmitter STA. At the receiver of the receiver STA, the above-mentioned operation for the 80+80 configuration can be reversed, and the combined data can be transmitted to the medium access control (MAC).

[0070] 802.11af and 802.11ah support operating modes below 1GHz. Channel operating bandwidths and carriers are reduced in 802.11af and 802.11ah relative to those used in 802.11n and 802.11ac. 802.11af supports 5MHz, 10MHz, and 20MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11ah supports 1MHz, 2MHz, 4MHz, 8MHz, and 16MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah may support instrument type control / machine type communications, such as MTC devices in macro coverage areas. MTC devices may have certain capabilities, such as limited capabilities, including support for (e.g., only support for) certain bandwidths and / or limited bandwidths. MTC devices may include batteries with battery life above a threshold (e.g., to maintain very long battery life).

[0071] 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 a STA (which supports the minimum bandwidth operating mode) from all STAs operating in the BSS. In the example of 802.11ah, for STAs (e.g., MTC-type devices) that support (e.g., only support) 1MHz mode, the primary channel may be 1MHz wide, even if the AP and other STAs in the BSS support 2MHz, 4MHz, 8MHz, 16MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or network allocation vector (NAV) settings may depend on the state of the primary channel. If the primary channel is busy, for example, because a STA (supporting only the 1MHz operating mode) is sending to the AP, the entire available band may be considered busy even if most of the band remains idle and may be available.

[0072] In the United States, the available frequency band for 802.11ah is 902MHz to 928MHz. In South 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.

[0073] Figure 1D 1 is a system diagram illustrating the RAN 113 and the CN 115 in accordance with an embodiment. As noted above, the RAN 113 may employ NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 113 may also be in communication with the CN 115.

[0074] The RAN 113 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 113 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, the gNBs 180a, 180b may utilize beamforming to send signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a may, for example, use multiple antennas to send wireless signals to and / or receive wireless signals from the WTRU 102a. In an embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, gNB 180a may transmit multiple component carriers to WTRU 102a (not shown). A subset of these component carriers may be on unlicensed spectrum, while the remaining component carriers may be on licensed spectrum. In an embodiment, gNBs 180a, 180b, 180c may implement coordinated multi-point (CoMP) technology. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and / or gNB 180c).

[0075] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with parameter sets that may be scalable. For example, OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or transmit time intervals (TTIs) of varying or scalable lengths (e.g., containing different numbers of OFDM symbols and / or varying absolute time lengths over time).

[0076] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c while not accessing other RANs (e.g., such as the eNodeBs 160a, 160b, 160c). In a standalone configuration, the WTRUs 102a, 102b, 102c may use one or more of the gNBs 180a, 180b, 180c as mobility anchor points. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration, the WTRUs 102a, 102b, 102c may communicate / connect with the gNBs 180a, 180b, 180c while also communicating / connecting with another RAN, such as the eNode-Bs 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement the DC principle to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the eNode-Bs 160a, 160b, 160c may act as mobility anchors for the WTRUs 102a, 102b, 102c, and the gNBs 180a, 180b, 180c may provide additional coverage and / or throughput for serving the WTRUs 102a, 102b, 102c.

[0077] Each of the gNBs 180a, 180b, 180c may be associated with a specific 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 slicing, dual connectivity, interworking between NR and E-UTRA, routing of user plane data towards a user plane function (UPF) 184a, 184b, routing of control plane information towards an access and mobility management function (AMF) 182a, 182b, etc. Figure 1D As shown, gNBs 180a, 180b, and 180c may communicate with each other via an Xn interface.

[0078] Figure 1DThe CN 115 shown may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and possible data networks (DNs) 185a, 185b. Although each of the foregoing elements is 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.

[0079] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via the N2 interface and may act as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRU 102a, 102b, 102c, support of network slicing (e.g., handling of different PDU sessions with different requirements), selecting a specific SMF 183a, 183b, management of registration areas, termination of NAS signaling and mobility management, etc. The AMF 182a, 182b may use network slicing to customize CN support for the WTRU 102a, 102b, 102c based on the type of services utilized by the WTRU 102a, 102b, 102c. For example, different network slices may be established for different use cases, such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced mobile broadband (eMBB) access, and / or services for machine type communication (MTC) access, etc. The AMF 162 may provide a control plane function for switching between the RAN 113 and other RANs (not shown) that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP (3rd Generation Partnership Project) access technologies, such as WiFi.

[0080] The SMF 183a, 183b may be connected to the AMF 182a, 182b in the CN 115 via the N11 interface. The SMF 183a, 183b may also be connected to the UPF 184a, 184b in the CN 115 via the N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b, and configure traffic routing through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions such as managing and allocating UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, and providing downlink data notifications. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0081] The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via the N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPF 184, 184b may perform other functions, such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering downlink packets, providing mobility anchoring, etc.

[0082] 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 acts 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 networks and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to local data networks (DNs) 185a, 185b via the UPF 184a, 184b via the N3 interface to the UPF 184a, 184b and the N6 interface between the UPF 184a, 184b and the DN 185a, 185b.

[0083] Given that Figures 1A to 1D as well as Figures 1A to 1D , one or more or all of the functions described herein with respect to one or more of the following items may be performed by one or more simulation devices (not shown): WTRU 102a-102d, base station 114a-114b, evolved Node B 160a-160c, MME 162, SGW 164, PGW 166, gNB 180a-180c, AMF 182a-182b, UPF 184a-184b, SMF 183a-183b, DN 185a-185b and / or any other device described herein. The simulation device may be one or more devices configured to mimic one or more or all of the functions described herein. For example, the simulation device may be used to test other devices and / or simulate network and / or WTRU functions.

[0084] The simulation device may be designed to implement one or more tests of other devices in a laboratory environment and / or in an operator network environment. For example, one or more simulation devices may perform one or more functions or all 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. One or more simulation devices may perform one or more functions or all functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The simulation device may be directly coupled to another device for testing purposes and / or may use over-the-air wireless communications to perform testing.

[0085] One or more simulation devices can perform one or more (including all) functions without being implemented / deployed as part of a wired and / or wireless communication network. For example, the simulation device can be used in a test scenario in a test laboratory and / or a non-deployed (e.g., testing) wired and / or wireless communication network to implement testing of one or more components. One or more simulation devices can be test equipment. Direct RF coupling and / or wireless communication performed via an RF circuit system (e.g., which can include one or more antennas) can be used by the simulation device to send and / or receive data.

[0086] Discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM) is a single-carrier waveform adopted by the Third Generation Partnership Project (3GPP) for the uplink of 4G Long Term Evolution (LTE) and 5G New Radio (NR) wireless cellular standards. Unlike other multi-carrier waveforms like cyclic prefix (CP)-orthogonal frequency division multiplexing (CP-OFDM), the single-carrier nature of DFT-s-OFDM allows for a reduction in peak-to-average power ratio (PAPR) while retaining other benefits, like DFT-based frequency domain equalization and simple inter-symbol interference (ISI) suppression. The efficiency of the power amplifier (PA) can be improved as the PAPR is reduced because the output power range over which the device maintains a linear response is larger, thus delivering a higher output power for the same power amplifier (PA) technology. For example, this property is applicable when the carrier frequency increases beyond frequency range 2 (FR2) (i.e., above 52.6 GHz) because the PA efficiency may begin to decrease significantly at these higher frequencies.

[0087] DFT-s-OFDM can be characterized by a transform precoding stage that is added to the processing steps in CP-OFDM. Transform precoding can achieve a single carrier waveform in the time domain when the subcarriers are mapped to continuous frequency positions, which can limit the flexibility of DFT-s-OFDM to allocate control information and data information in the frequency domain. For this reason, control channels and data channels in 5G NR may not be multiplexed in frequency, but instead be assigned different DFT-s-OFDM symbols so that the single carrier property is preserved. This also applies to some 5G NR reference signals, such as DM-RS, which do not allow data information to be multiplexed in the same symbol.

[0088] Figure 2 An example of pre-DFT and post-DFT insertion of reference signals (RS) in a DFT-spread orthogonal frequency division multiplexing (DFT-s-OFDM) system is depicted. RS insertion in DFT-s-OFDM can be classified into either of the following two mechanisms: pre-DFT or post-DFT, such as Figure 2 Depicted. RS insertion in 5G NR can utilize RS pre-DFT insertion. RS insertion in 5G NR can be performed before the DFT stage, referred to herein as pre-DFT RS insertion. When inserted before performing DFT, the RS symbol can be multiplexed with data in the time domain, or mapped separately in the symbol before transform precoding. Subcarriers can be mapped to continuous frequency positions to retain the single-carrier nature of the waveform. Therefore, it may not be possible to frequency multiplex control information and data information. For example, the 5G NR demodulation reference signal (DM-RS) can be mapped separately in the symbol and occupies up to four complete symbols per time slot in DFT-s-OFDM. Data information is not frequency multiplexed in those symbols, which may lead to inefficiencies caused by high resource utilization of control signals, especially when more than one DM-RS symbol is used per time slot. At frequencies exceeding 52.6GHz, it may be appropriate to increase the number of DM-RS symbols to more than one in order to effectively track Doppler changes at higher modulations. In these cases, the overhead from DM-RS may be quite high.

[0089] As another example, the 5G NR phase tracking reference signal (PT-RS) can be multiplexed with data in the time domain before DFT. Unlike DM-RS, PT-RS symbols can be multiplexed with data before DFT, and resource utilization can be adjusted as needed. However, the DFT operation spreads both data and PT-RS on the output subcarriers, and therefore may not be able to multiplex data information and control information in the frequency domain. Therefore, pre-DFT RS insertion in 5G NR may be limited to generating continuous RS in the frequency domain (with poor resource utilization) or generating RS multiplexed with data in the time domain (not able to be interleaved with data in the frequency domain).

[0090] When inserted after DFT (referred to as post-DFT insertion), RS symbols can be multiplexed with data at any frequency position required. The continuous allocation of data subcarriers in the frequency domain is not preserved, and the PAPR may increase compared to the case where RS is not inserted. However, by allocating only the required RS symbols, resource efficiency can be higher than that in pre-DFT insertion. Two example techniques for post-DFT insertion are described below: interleaved RS insertion and subcarrier puncturing.

[0091] Figure 3 An example method for post-DFT insertion using subcarrier interleaving is depicted. If L reference symbols are to be inserted in a distributed fashion into blocks of M consecutive subcarriers and multiplexed with (ML) modulated data symbols, then a (ML)-point DFT may be performed on the data and its output mapped to non-contiguous frequency locations, leaving room for further allocation of the L reference symbols in an interleaved fashion. In this manner, the L reference symbols and (ML) data symbols are effectively interleaved across the M subcarriers.

[0092] This process can be adapted to insert distributed RS at non-periodic positions in the frequency domain. However, this may have the effect of forcing the transceiver to use different DFT sizes for DFT-s-OFDM symbols carrying RS (ML) and DFT-s-OFDM symbols not carrying RS (M), thereby complicating the implementation. In addition, both (ML) and M must conform to the DFT sizes allowed in 3GPP LTE and NR, for example, This may limit the evolution of the standard to use different RS frequency densities. For example, a frequency density of one eighth of a resource element may not be allowed for RS signals because no matter what the value of M is, None of them fits the formula. Furthermore, this technique may not improve PAPR control. The complexity, measured by the number of complex multiplications and not taking into account the equalization step (common to all techniques), is given by (ML)log2(ML).

[0093] Figure 4 An example of RS insertion by subcarrier puncturing with zero padding is depicted. Using the same DFT size in all DFT-s-OFDM symbols may be more attractive for post-DFT insertion of RS. Figure 4 An example of this is depicted in , where the data symbols are padded with zeros up to size M, and an M-point DFT is performed, then the L data subcarriers are punctured at the output of the DFT stage, and the RS signal is inserted.

[0094] The process may be adapted to insert distributed RSs at periodic positions in the frequency domain. In this case, subcarrier puncturing may cause some interference to appear in the DFT-s-OFDM time domain signal in the form of periodic terms due to the periodic positions of the RS subcarriers, and these interferences may be compensated at reception before demodulating the data symbols. Such interference may cause an increase in both bit error rate (BER) statistics and PAPR. The increase in PAPR is added to the increase in PAPR caused by RS insertion due to the non-adjacency of the data subcarriers after DFT. The PAPR increase may not be necessary in a multi-user scenario based on DFT-s-OFDM, in which each user is assigned a different subcarrier cluster in the frequency domain, because the PAPR of multi-cluster transmissions may deteriorate with the dynamic load of the network. Techniques for post-DFT insertion based on subcarrier puncturing may rely on the receiver to perform interference suppression for data recovery, and may not provide any means to reduce the PAPR.

[0095] RS insertion by utilizing adaptive subcarrier puncturing may include post-DFT RS insertion techniques based on subcarrier puncturing and selecting an appropriate padding sequence structure for appending to data symbols prior to the DFT stage. Various examples may be identified based on, for example, the type of transmitting node (base station or user equipment / WTRU), the type of padding sequence adaptation (dynamic or semi-static), etc.

[0096] Figure 5 is a flow chart of an example process for dynamic RS insertion at the base station (BS). Error! Reference source not found. The base station (BS) or any appropriate network entity may perform Figure 5 The following steps depicted in for dynamically inserting distributed RS. The BS may dynamically select (502) one or more padding sequences from a set of padding sequence structures specified in a predetermined codebook based on, for example, PAPR measurements performed by the BS or time domain measurements performed by a user equipment (UE) (also referred to as a wireless transmit / receive unit (WTRU)) on a current symbol and / or several previous symbols and based on feedback reports transmitted by the WTRU in a periodic, semi-periodic, on-demand, or event-based manner. The padded sequence may be appended (504) to the modulated data symbol before the DFT stage. A permutation (506) may be applied to the resulting data block and padding symbols so that the complex modulation symbols after the permutation are uncorrelated and the permuted positions of the padding symbols are different from each other modulo L. An M-point DFT (508) may be performed and the subcarriers located at the target pilot positions may be punctured (508) and replaced (508) by L RS (e.g., complex valued, blank, etc.) symbols. DFT-s-OFDM processing is then performed to generate a time domain waveform, and the PAPR may be measured (510) to refine the padding sequence selection in subsequent time intervals. Figure 5The dashed lines in represent optional aspects. For example, a permutation (506) may be optionally included depending on the degree of correlation. The PAPR may be measured (510) and reported by the WTRU instead of being measured at the BS. There may be no signaling (512) in, for example, blind decoding performed by the WTRU.

[0097] The BS may signal (512) a padding sequence structure to the WTRU via one or more padding sequence structure identifier (PSeqS ID) fields, which may be transmitted once during session establishment and / or dynamically updated during data transfer, or alternatively, the sequence identifier may be blindly detected by the WTRU without explicit signaling. In the case where multiple transmit / receive points (TRPs) may be used to transmit data channels using fully / partially / non-overlapping time-frequency resources (e.g., using different DL beams) (e.g., using different or same transport blocks, different or same redundancy versions of the same transport block, or different or same codewords, etc.), the BS may transmit multiple PSeqS ID fields, or a combined PSeqS ID field, to the WTRU containing an indication of the padding sequence structure to be used for each TRP. Optionally, a feedback report containing a PSeqS report (514) may be transmitted to the BS in a periodic, semi-periodic, or on-demand manner to assist the padding sequence selection process, as well as a final time domain report message containing time domain measurements performed by the WTRU.

[0098] Figure 6 is a flow chart of an example process for data detection and interference cancellation from RS insertion at the wireless transmit / receive unit (WTRU) side. Figure 6 As depicted, a WTRU or any appropriate entity may perform the following steps for interference cancellation caused by, for example, subcarrier puncturing and RS insertion and data recovery. The WTRU may obtain periodic signaling information (602) from a BS or any appropriate network entity, the periodic signaling information including a padding sequence structure used in a sequence structure included in a predetermined codebook. Alternatively, the WTRU may know the sequence structure in advance or perform blind detection of the padding sequence structure without explicit signaling. A DFT-s-OFDM symbol (608) may be received, the symbol including complex modulated data symbols affected by interference caused by subcarrier puncturing. Interference may be cancelled (604), and the complex modulated symbols may be estimated and delivered to higher layers. A feedback report (606) including a PSeqS report may optionally be transmitted to the BS in a periodic, semi-periodic, or on-demand manner to assist in the padding sequence selection process, as well as a final time domain report message including time domain measurements performed by the WTRU.

[0099] Figure 7 Depicts an example block diagram of the DFT-s-OFDM reception process. Figure 7The DFT-s-OFDM symbol reception and interference cancellation processing steps are further described in detail. Regarding the reception of DFT-s-OFDM symbols, the DFT-s-OFDM processing can use the time domain received waveform s R [n] and deliver data symbols affected by interference from subcarrier puncturing. Figure 7 Depicted are processing blocks including at least CP removal (702), serial / parallel conversion (702), N-point DFT (704), extraction of subcarriers allocated to users (706), channel estimation (708), equalization (710), M-point inverse DFT (712), and parallel / serial conversion (714). Additional processing blocks may be possible depending on the specific implementation.

[0100] Cancellation of interference introduced during subcarrier puncturing may be performed at the BS side. The WTRU may exploit the presence of padding sequences to aid in the estimation and further removal of interference terms from the time domain symbols prior to demodulation. Any suitable detection strategy may be used, including successive interference cancellation (SIC), maximum likelihood (ML) detectors, etc., any suitable combination thereof.

[0101] To illustrate this, follow the pattern Subcarrier puncturing and RS insertion produce interference terms consisting of L periodic terms p[m] in the time domain, which are frequency shifted by p[6]:

[0102]

[0103] The DFT of p[m] is equal to the value of the inserted RS symbols minus the punctured subcarriers. After appropriately undoing the permutation step and the frequency shift p, the receiver can therefore use this term to estimate the interference with the aid of the padding symbols c[m] appended to the data.

[0104] Distributed RS patterns inserted in the frequency domain present several advantages compared to block RS patterns. Distributed RS patterns can have higher resource utilization efficiency compared to block RS patterns in pre-DFT RS insertion, as evident in 5G NR DM-RS for PUCCH format 3 with up to 50% overhead. Distributed RS can bring more flexibility than block RS to allocate multiple-input / multiple-output (MIMO) orthogonal layers. In multi-user (MU)-MIMO, the use of hybrid beamforming at high frequencies may require digital precoding to perform spatial multiplexing of the signals when the beams overlap spatially. In single-user (SU)-MIMO, future device evolution may lead to an increase in the number of supported MIMO layers. In both cases, DM-RS signals can be more flexibly mapped to resources when allocated in the frequency domain.

[0105] Systems using DFT-s-OFDM may envision pre-DFT insertion of RS based on occupying full OFDM symbol resource allocation (with poor resource utilization) or multiplexing with data signals in the time domain (cannot be interleaved with data in the frequency domain) so as not to compromise the low PAPR of a single carrier waveform. Post-DFT insertion of RS as an alternative solution may avoid the spectral inefficiency associated with the use of pre-DFT insertion of RS.

[0106] Post-DFT insertion based on interleaved RS insertion may have disadvantages such as increasing PAPR, limiting the achievable RS frequency pattern, and using different DFT sizes for symbols carrying RS and those not carrying RS. When implemented with zero padding, RS insertion by subcarrier puncturing may not provide the ability to control PAPR and performance except through optimized receiver structure.

[0107] An adaptive framework for pre-DFT insertion and / or post-DFT insertion of distributed RS in DFT-s-OFDM at periodic positions in the frequency domain is described herein, which provides flexibility in RS frequency pattern while providing a means to minimize PAPR and optimize demodulation performance. Additionally, WTRU assistance, such as in terms of WTRU capability signaling and measurements, is described.

[0108] In the subsequent implementation, it is assumed that L reference symbols (or pilots) are inserted into blocks of M consecutive subcarriers in a distributed manner and multiplexed with (ML) modulated data symbols {d[0], ..., d[ML-1]}. Depending on the application, the pilots can be complex values ​​known a priori or blank symbols.

[0109] Can be at equally spaced subcarrier positions Insert pilots at, where p can be the set and represents a priori known frequency shift. The combined frequency pattern may also be in a state with two a priori known frequency shifts Form (ML) will be a multiple of L.

[0110] Figure 8 A flow chart is depicted containing a process for RS insertion in a DFT-s-OFDM signal. More specifically, Figure 8An example process of RS insertion selection performed by a transmitting node using receiving node feedback is depicted. The transmitting node and the receiving node may first exchange some information (802), which includes but is not limited to any of the following elements related to their RS insertion capabilities: support for pre-DFT RS insertion; support for post-DFT RS insertion based on interleaved frequency division multiple access (IFDMA); support for RS insertion based on subcarrier puncturing via a padding sequence, and the supported padding sequence structure; support for fixed or adaptive RS sequences, and the RS sequences supported in the adaptive case; power amplifier (PA) related information, such as PA type / class or peak-to-average power ratio (PAPR) requirements / preferences; demodulation related information, such as support for SIC with a maximum number of iterations, or any other detection related parameters; etc. or any appropriate combination thereof.

[0111] The transmitting node may provide RS insertion configuration parameters (804) to the receiving node via, for example, downlink control information (DCI)-related signaling, MACCE (control element) or higher layer signaling. RS insertion configuration parameters may include RS insertion type, filling sequence structure detection mode (blind detection vs. explicit signaling), filling sequence structure identifier, RS codebook identifier, any other information required for RS insertion technology, or any appropriate combination thereof. RS insertion type may be dynamically selected from any of the following: pre-DFT RS insertion of full RS symbols, pre-DFT RS insertion based on IFDMA, post-DFT RS insertion based on filling sequence adaptation, post-DFT RS insertion with RS sequence adaptation, post-DFT RS insertion based on filling sequence adaptation and RS sequence adaptation, or any appropriate combination thereof. The transmitting node may decide to switch among these alternatives based on available transmit power, PAPR, complexity, and / or based on feedback reports or signaling information obtained from the receiving node (which includes information about demodulation performance, PAPR measurement, capability information, preferred RS insertion type, preferred filling sequence structure type, or similar indications, or any appropriate combination thereof).

[0112] After data transmission and RS insertion (806), the receiver may perform data reception and provide feedback (808) in an evented, triggered, or periodic manner to assist the sending node in selecting the most appropriate RS insertion technique for use by the node.

[0113] In response to feedback from the receiving node, the transmitting node may also dynamically update some or all of the configuration parameters related to RS insertion, such as a padding sequence structure identifier, RS sequence type, RS codebook, etc., or any suitable combination thereof.

[0114] Pre-DFT RS insertion of full RS symbols, pre-DFT RS insertion based on IFDMA, and post-DFT RS insertion based on padding sequence adaptation can be performed. Post-DFT RS insertion with RS sequence adaptation and post-DFT RS insertion based on padding sequence adaptation and RS sequence adaptation techniques are described in the following sections together with exemplary embodiments.

[0115] Example embodiments are described that reduce resource overhead associated with RS while providing flexibility in controlling PAPR.Example embodiments consider post-DFT RS insertion techniques based on subcarrier interleaving or puncturing, and dynamic adaptation of the selected RS sequence to control PAPR.

[0116] RS (e.g., DM-RS) may be adapted to share the transmitted data within a DFT-s-OFDM symbol based on an instantaneous or statistical evaluation of the impact of RS insertion on the PAPR of the entire transmitted signal. The RS sequence may be selected from one or more RS sequences in a defined codebook based on, for example, any of the following.

[0117] The RS sequence may be selected based on searching codebook elements to determine a sequence that minimizes the PAPR of the transmitted signal based on data symbols to be sent in the current DFT-s-OFDM symbol, slot, subframe, etc.

[0118] The RS sequence may be selected based on searching codebook elements to determine a sequence that minimizes an average PAPR of the transmitted signal based on data symbols sent over the previous one or more DFT-s-OFDM symbols, slots, subframes, etc.

[0119] The RS sequence may be selected based on searching codebook elements to determine a sequence that minimizes an average PAPR of a transmitted signal based on data symbols transmitted over current and previous one or more DFT-s-OFDM symbols, slots, subframes, etc.

[0120] The RS sequence may be selected based on minimizing the distance to a vector (same length as the RS) as determined, for example, by an inner product, and is determined by applying the DFT to the known structure of data symbols (to be sent in any of the current DFT-s-OFDM symbol, slot, and subframe) and selecting the DFT output at the subcarriers allocated to the RS.

[0121] The RS sequence may be selected based on minimizing the distance to a vector (same length as the RS) as determined, for example, by an inner product, and is determined by applying the DFT to the known structure of the data symbols (sent over the previous one or more DFT-s-OFDM symbols, time slots, or subframes) and selecting the DFT outputs at the subcarriers allocated to the RS.

[0122] The RS sequence may be selected based on minimizing the distance to a vector (same length as the RS) as determined, for example, by an inner product, and determined by applying the DFT to the known structure of data symbols (sent in the current and previous one or more DFT-s-OFDM symbols, time slots, or subframes) and selecting the DFT outputs at the subcarriers allocated to the RS.

[0123] When the size of the DFT utilized is the sum of the data symbol set size and the RS sequence length, the known structure of the data symbols may be, for example, a cyclic prefix structure (in which a set of data symbols is appended with repetitions of a subset of data symbols), a sign reversal structure (in which a set of data symbols is appended with sign-inverted repetitions of a subset of data symbols), a phase shift structure (in which a set of data symbols is appended with repetitions of a phase-shifted subset of data symbols), a sequence filling structure (in which a set of data symbols is appended with one or more sequences of constant envelope characteristics), a zero filling structure (in which a set of data symbols is appended with zeros up to the length of the sum of the data symbol set size and the RS sequence length), etc., or any suitable combination thereof.

[0124] The RS sequence may also be selected from one or more RS sequences in the defined codebook taking into account interference levels across data symbols that may be caused by RS insertion in the frequency domain using subcarrier puncturing methods / techniques.

[0125] The set of one or more RS sequences in one or more RS codebooks may include, for example, any one of a set of pseudo-random sequences or a set of Zadoff-Chu sequences or a set of any other low PAPR sequences or a combination thereof, which may be determined based on, for example, any one or more of the following items.

[0126] It can be based on the codebook size N cb And by fixing the offset O cb The set of initialization seeds related to each other determines the set of one or more RS sequences, and the fixed offset is obtained as L1 / MAC-CE / RRC (Radio Resource Control) signaling or as a pre-configuration. For example, the initialization seed c of the nth RS sequence init,n =c init,n-1 +O cb ,n∈{1,2,…N cb -1}.

[0127] It can be based on a fixed offset signaled (or pre-configured) via L1 / MAC-CE / RRC. cb,n The set of initialization seeds associated with the initial seed (as c init,n =c init,n-1 +O cb,n ,n∈{1,2,…Ncb -1}) to determine the set of one or more RS sequences.

[0128] It can be based on the codebook size N cb And the set of one or more RS sequences is determined by a set of initialization seeds related to each other by variable offsets. For example, for a function f(·) which can be, for example, linear, quadratic, parabolic, etc., the initialization seed c of the nth RS sequence init,n =c init,0 +f(n),n∈{1,2,…N cb -1}.

[0129] The set of one or more RS sequences may be based on, for example, using the parameter p i (where i∈{0,1,…,n rs -1}) to identify a set of one or more parameterized basis / root sequences, each parameterized basis / root sequence having one or more corresponding cyclic shifts (e.g., α l,i , where l∈{0,1,…,n cs,i -1}), so that the total number of sequences is limited by the codebook size (i.e., ∑ i n cs,i =N cb ) restrictions. Sequence p l,i [n] can be obtained from the base / root sequence p i [n] constructed as p l,i [n] = p i [(n-α l,i )modL], where mod represents the modulo operator and L represents the length of the sequence. The set of root sequence parameters and cyclic shift values ​​{p i ,α l,i}Can be pre-configured or signaled via L1, MAC-CE and / or Radio Resource Control (RRC) messages.

[0130] The one or more initialization seeds and / or offsets and / or cyclic shifts may also depend on, for example, any one or more of the following: the OFDM symbol number of the RS, the number of symbols per time slot, the serving cell ID, one or more signaled / configured scrambling IDs, and the code division multiplexing (CDM) group. Additionally, a known transform (e.g., a discrete Fourier transform (DFT)) may be applied to one or more RS sequences in the RS sequence after the RS sequence is generated. In addition, one or more elements in each RS sequence in the codebook may be scaled by one or more scaling factors, which may be shared across the one or more elements or unique to a single element or a group of elements across the one or more elements. The scaling factors and the mapping to the elements may be pre-specified / configured or signaled, and compliance with the specified RS transmit power should be ensured.

[0131] The RS codebook may be dynamically or semi-statically adjusted / updated based on one or more of the following: the distribution of channel parameters, the distribution of data sent / received, the signaling overhead incurred, and the receiver capabilities. The distribution of the data sent / received may be inferred directly at the sender entity without feedback from the receiver entity, while the distribution of the channel parameters may require feedback or assistance from the receiver entity to obtain at the sender entity. The adaptation of the RS codebook (its size or the relationship between sequences within the codebook) may be due to the quality of the channel estimation experienced at the receiver, especially in the case of blind RS detection. This adaptation may also be required to limit the number of blind detections by reducing the RS codebook size, thereby limiting the power consumption at the receiver, at the expense of a potentially higher PAPR at the transmitter.

[0132] RS adaptation is performed on a transmitter, the transmitter being configured to signal RS codebook generation parameters to a receiving entity or to assist the receiving entity in determining an RS sequence for use by the transmitting entity to limit blind detection complexity.

[0133] Therefore, the signaling overhead may depend on either the RS codebook size and the capability of the receiving entity in terms of blind detection. The trade-off between signaling overhead, dynamic channel conditions, and receiver capability may be considered by allowing the sending entity to split the large-sized RS codebook into subsets and dynamically signaling an indication of the considered subsets to the receiving entity, thereby reducing blind detection complexity with manageable signaling overhead. In addition, the signaling overhead associated with RS codebook generation parameters may be reduced by limiting the generation parameters to a known set at the receiver and allowing the sender to signal only an index of one of the known sets rather than explicit signaling of the parameters. Alternatively, a combination of explicit signaling and index signaling of RS codebook generation parameters may be considered.

[0134] Fig. 9An example transmitter architecture that uses dynamic insertion of distributed RS (e.g., DM-RS) to adjust PAPR is depicted. A transmitting entity (e.g., BS) may perform the following steps to generate a signal with low PAPR characteristics. At step 902, a (M-L) point DFT may be performed on (M-L) data symbols, and the output of the DFT may be interleaved, leaving L empty samples for RS insertion. At step 904, a RS (e.g., DM-RS) of length L may be selected from an RS codebook by an RS codebook and sequence selection module, and interleaved with the (M-L) data symbols using L empty samples. At step 906, an N-point IFFT may be performed on the data and RS symbols, and the PAPR may be evaluated at the output of the IFFT module and fed back to the RS codebook and sequence selection module. At step 908, a cyclic prefix (CP) may be appended to the DFT-s-OFDM symbol, and the signal may be provided to the RF front end for transmission over a channel at step 910.

[0135] In an alternative to step 902, the transmitting entity may perform an (M)-point DFT on the (ML) data symbols padded with L zero symbols and puncture the output of the DFT, replacing the L output samples with L null samples for RS insertion.

[0136] In another alternative to step 902, the transmitting entity may perform an (M)-point DFT on the (ML) data symbols padded with L cyclic prefix symbols and puncture the output of the DFT, replacing the L output samples with L null samples for RS insertion.

[0137] In an additional alternative to step 902, the transmitting entity may perform an (M)-point DFT on the (M-L) data symbols filled with L symbols corresponding to a constant envelope sequence, and puncture the output of the DFT, replacing the L output samples with L null samples for RS insertion. The constant envelope sequence may be randomly selected from a set of known sequences, or selected to meet a criterion, such as a minimum PAPR at the input of the DFT module.

[0138] In an additional alternative to step 902, the transmitting entity may perform an (M)-point DFT on the (ML) data symbols padded with L symbols corresponding to a sign-inverted or phase-inverted copy of a subset of the data symbols, and puncture the output of the DFT, replacing the L output samples with L null samples for RS insertion. The phase shift may be selected to meet a criterion, such as a minimum PAPR at the input of the DFT module.

[0139] In an alternative to step 906, the PAPR evaluation feedback may be considered for ongoing / current transmissions, where the second and third steps are repeated a certain number of times using different RSs at each iteration before finally selecting the RS to be used for the actual transmission by proceeding to the fourth step.

[0140] In another alternative to step 906, the PAPR estimation feedback may be considered for subsequent transmissions, where the RS selection in the second step considers the estimated PAPR history. In this alternative, the RS codebook and sequence selection module may instead consider the PAPR estimated and fed back by the receiving node.

[0141] Fig.10 An example receiver architecture employing dynamic / adaptive detection of a distributed RS (e.g., DM-RS) is depicted. A receiving entity (e.g., WTRU) may perform the following steps to receive a signal having adaptive RS (e.g., DM-RS) characteristics. At step 1002, a DFT-s-OFDM signal / symbol including data and RS (e.g., DM-RS) may be received from an RF front end, and a cyclic prefix (CP) sample may be removed during parallel-to-serial conversion. At step 1004, an N-point FFT may be performed on the DFT-s-OFDM symbol with the CP removed, L symbols corresponding to the RS may be delivered to an RS detection module, and (MM) data symbols may be delivered to an equalization module. At step 1006, the RS detection module may determine an RS sequence from a list of RS sequences in a codebook using blind detection, may estimate a channel using the determined RS, and may deliver a (MM) channel estimate vector to the equalization module. At step 1008, the equalization module may reverse the effect of the channel on the (ML) data symbols and may deliver the (ML) equalized symbols to an IDFT module 1010. At step 1012, the P / S and receiver module may receive the output of the IDFT module and perform symbol demodulation, decoding, and bit detection.

[0142] In an alternative to step 1004, both the (MM) data symbols and the M RS symbols may be delivered to the equalization module, and M equalized symbols are generated after the RS used is correctly identified by the RS detection module and the correct channel estimation is performed. An M-point IDFT is then performed on the M equalized symbols, and the P / S and receiver module extracts the (MM) data symbols from the M samples at the output of the IDFT module.

[0143] In one example, (ML) data symbols may be extracted from the M samples at the output of the IDFT module by simply discarding the M padding symbols appended to the data symbols during transmission. In another example, the structure of the padding symbols (e.g., zero or constant envelope sequence) may be used to estimate interference (e.g., caused by subcarrier puncturing for RS insertion (i.e., at the transmitter)) and cancel, as described in Section 2.3.3(ii), to obtain better decoding performance.

[0144] In one option, the codebook used for RS sequence detection in the third step may be static and may be pre-configured at the WTRU. In a second option, the codebook may be configurable and selected at the WTRU from one or more pre-configured codebooks using an index / indication signaled from the network as DCI in the PDCCH or a higher layer message such as a dedicated RRC message or through system information. In a third option, the sequences constituting the codebook may be explicitly signaled from the network to the UE using a higher layer message such as a dedicated RRC message or system information.

[0145] In addition to the above procedures, the WTRU may periodically evaluate the performance in terms of block error rate (BLER) and / or channel estimation quality to determine the need to update the codebook used for blind detection and channel estimation of the RS sequence. Upon determining that the performance metric is below a certain threshold, the UE may send a request to update the RS codebook, which may be pre-configured or signaled to the WTRU in a configuration message. The request may indicate a specific codebook or may only indicate the value of the performance metric.

[0146] In an example embodiment, the WTRU may determine a DM-RS codebook in a first step based on an indication received from the network (e.g., in a DCI sent via a PDCCH). In a second step, the WTRU may receive a DFT-s-OFDM signal / symbol including data and DM-RS symbols. In a third step, the WTRU may select a DM-RS sequence from one or more DM-RS sequences in the determined codebook using blind detection. The selected DM-RS sequence may be a DM-RS sequence with the maximum correlation with the received DM-RS sequence. In a fourth step, the WTRU may estimate the channel and equalize the received DFT-s-OFDM signal / symbol using the selected DM-RS sequence. In a fifth step, the WTRU may demodulate and decode the equalized DFT-s-OFDM signal and evaluate the decoding and / or channel estimation performance. Under the condition that the decoding performance drops below a certain threshold, the WTRU may send a request to update the DM-RS codebook.

[0147] In another example embodiment, the WTRU may determine a DM-RS codebook in a first step based on an indication received from the network, for example, through system information. In a second step, the WTRU may receive a DFT-s-OFDM signal / symbol including data and DM-RS symbols over one or more time slots or subframes. In a third step, the WTRU may select an ordered set of one or more DM-RS sequences from the one or more DM-RS sequences in the determined codebook using blind detection. The selected DM-RS sequence is the DM-RS sequence that has the maximum correlation with the received one or more DM-RS sequences over the one or more time slots / subframes. In a fourth step, the WTRU may estimate the channel and equalize the received DFT-s-OFDM signal / symbol using the selected DM-RS sequence. In a fifth step, the WTRU demodulates and decodes the equalized DFT-s-OFDM signal / symbol and evaluates the decoding and / or channel estimation performance. In a sixth step, the WTRU may send feedback information including an indication of the determined channel estimation performance and an indication of the determined ordered set of one or more DM-RS sequences. Alternatively, the WTRU may send an indication of only a subset of the ordered set of one or more DM-RS sequences.In a seventh step, the WTRU may receive a DCI including an indication of the new DM-RS codebook over the PDCCH.

[0148] In another example embodiment, the WTRU may determine the DM-RS codebook and padding sequence structure in a first step based on an indication received from the network, such as through system information. In a second step, the WTRU may receive a DFT-s-OFDM signal / symbol including padding data and DM-RS symbols. In a third step, the WTRU may select a DM-RS sequence from one or more DM-RS sequences in the determined codebook using blind detection. In a fourth step, the WTRU may estimate the channel and equalize the received DFT-s-OFDM signal / symbol using the selected DM-RS sequence. In a fifth step, the WTRU may perform an IDFT on the equalized DFT-s-OFDM signal and utilize the determined padding sequence structure to eliminate interference from subcarrier puncturing and DM-RS insertion at the transmitter in the data symbol. In a sixth step, the WTRU may demodulate and decode the equalized DFT-s-OFDM signal / symbol after interference cancellation and evaluate the decoding and / or channel estimation performance. Under a first condition that the decoding performance drops below a first threshold, the UE sends a request to update the DM-RS codebook. Under a second condition that the decoding performance drops below a second threshold, the WTRU may send a request to update the padding sequence structure. In one alternative, the first threshold and the second threshold are the same threshold. In another alternative, the first condition depends on the channel estimation performance. In another technical implementation of the sixth step, the WTRU may evaluate the interference leakage metric (e.g., a measurement of interference leakage from subcarrier puncturing and DM-RS insertion into the data symbols) and the channel estimation quality. Under a first condition that the interference leakage is above a first threshold and the channel estimation quality is above a second threshold, the WTRU may send a request to deactivate the pre-DFT sequence padding. Under a second condition that the interference leakage is above the first threshold and the channel estimation quality is below the second threshold, the UE sends a request to deactivate DM-RS sequence adaptation, i.e., only a static and known DM-RS sequence is sent with the data symbols without blind detection at the WTRU. Under a third condition that the interference leakage is below the first threshold and the channel estimation quality is below the second threshold, the WTRU may send a request to update the DM-RS codebook. Otherwise, the WTRU may continue to consider the determined DM-RS codebook and padding sequence structure.

[0149] Fig.11 is a flow chart of an example process for detecting shared DFT-s-OFDM symbols that support blind DM-RS detection and codebook change requests. Fig.11As depicted, a WTRU configured to receive a shared DFT-s-OFDM symbol between data and a reference signal (RS) may perform the following operations. At step 1102, the WTRU may determine a first codebook including one or more DM-RS sequences based on a received indication (e.g., a DCI in a PDCCH message). At step 1104, the WTRU may receive a DFT-s-OFDM symbol including data and a DM-RS. At step 1106, the WTRU may determine a DM-RS sequence from the one or more DM-RS sequences in the first codebook using blind detection. At step 1107, the WTRU may determine that an attempt to perform blind detection on the used DM-RS sequence failed. At step 1108, the WTRU may utilize the determined DM-RS sequence for channel estimation and DFT-s-OFDM symbol equalization. At step 1110, the WTRU may determine a decoding performance (e.g., a block error rate (BLER)) and compare the decoding performance with a first threshold and a second threshold. At step 1109, the WTRU may determine that the decoding performance (e.g., block error rate (BLER)) is below a first threshold and above a second threshold. At step 1112, the WTRU may send a request to select a second DM-RS codebook. At step 1144, the WTRU may perform link adaptation by measuring and reporting channel status, for example, with the assistance of CSI-RS.

[0150] The initial / first DM-RS codebook may be a default codebook indicated using a higher layer message (e.g., a dedicated RRC or system information). Blind detection of the DM-RS sequence may be based on the output of a correlation of the received sequence with one or more DM-RS sequences within the indicated DM-RS codebook. The received sequence may be obtained by extracting symbols according to a periodic allocation on subcarriers at the output of the FFT module. The determination of the DM-RS sequence may be based on blind detection and a received indication of a subset of the one or more DM-RS sequences in the default codebook. The determination of the DM-RS sequence may be based on explicit signaling of the sequence from the transmitting node. The request to select a new DM-RS codebook may include any one of an indication of channel estimation quality, a DM-RS codebook size, an experienced PAPR, and a blind detection capability (e.g., the number of sequences to be correlated simultaneously). The first threshold may indicate a requirement to update the DM-RS codebook, and the second threshold indicates a requirement to update the modulation and coding scheme.

[0151] Fig.12 is a flow chart of an example process for using auxiliary information to detect shared DFT-s-OFDM symbols supporting blind DM-RS detection and codebook update. Fig.12As depicted, a WTRU configured to receive shared DFT-s-OFDM symbols between data and a demodulation reference signal (DM-RS) and provide assistance information to a serving base station may perform the following operations. At step 1202, the WTRU may determine any one of a default codebook and a first codebook including one or more DM-RS sequences based on a received indication (e.g., system information or DL ​​control information). At step 1204, the WTRU may receive one or more DFT-s-OFDM symbols including data and DM-RS on one or more time slots. At step 1206, the WTRU may determine a set of one or more DM-RS sequences from the one or more DM-RS sequences in any one of the default codebook and the first codebook using blind detection based on the received one or more DFT-s-OFDM symbols. At step 1208, the WTRU may use the determined DM-RS sequence for channel estimation and DFT-s-OFDM symbol equalization. At step 1210, the WTRU may determine a channel estimation performance based on the determined set of one or more DM-RS sequences and compare the channel estimation performance with a threshold. At step 1212, the WTRU may determine that the channel estimation performance is below a threshold. At step 1214, the WTRU may send feedback information including an indication of the determined channel estimation performance and an indication of any of the determined sets or subsets of the one or more DM-RS sequences. At step 1216, the WTRU may receive DL control information including an indication of a second DM-RS codebook.

[0152] Blind detection of the DM-RS sequence may be based on an output of a correlation of the received sequence with one or more DM-RS sequences within an indicated DM-RS codebook. The received sequence may be obtained by extracting symbols at the output of the FFT module according to a periodic allocation on subcarriers. Determination of the DM-RS sequence may be based on blind detection and a received indication of a subset of the one or more DM-RS sequences in either of a default codebook and a first codebook. The subset of the one or more DM-RS sequences may be determined based on a decoding failure of an associated physical data shared channel (PDSCH), for example, from a gNB. Channel estimation performance may be determined based on a correlation peak detected across one or more DM-RS sequences in the DM-RS codebook.

[0153] Fig.13 1 is a flow chart of an example process for detecting a shared DFT-s-OFDM symbol supporting interference cancellation of a padding sequence, blind DM-RS detection, and padding sequence structure and codebook change request. Post-DFT RS insertion with padding and RS sequence adaptation may be performed. Fig.13As depicted, a WTRU configured to receive a shared DFT-s-OFDM symbol between padding data symbols and a demodulation reference signal (DM-RS) may perform the following operations. At step 1302, the WTRU may determine a pre-DFT padding sequence structure and a first codebook including one or more DM-RS sequences based on an indication received through, for example, a DCI in a PDCCH message. At step 1304, the WTRU may receive a DFT-s-OFDM symbol including padding data and a DM-RS. At step 1306, the WTRU may determine a DM-RS sequence from the one or more DM-RS sequences in the first codebook using blind detection. At step 1308, the WTRU may determine that an attempt to perform blind detection on the used DM-RS sequence has failed. At step 1310, the WTRU may utilize the determined DM-RS sequence for channel estimation and DFT-s-OFDM symbol equalization. At step 1312, the WTRU may eliminate interference from DM-RS puncturing / insertion based on the determined pre-DFT padding sequence structure. At step 1314, the WTRU may determine any one of a decoding performance (e.g., BLER) compared to a first threshold and a channel estimation quality compared to a second threshold. At step 1316, the WTRU may determine that the decoding performance (e.g., BLER) is below the first threshold and the channel estimation quality is above the second threshold. At step 1318, the WTRU may send a request to update / select any one of a DM-RS codebook and a pre-DFT padding sequence structure.

[0154] Any of the pre-DFT sequence structure and the initial / first DM-RS codebook may be determined by default based on an indication received in a dedicated RRC or through system information. The determination of the DM-RS sequence may be based on blind detection and a received indication of a subset of the one or more DM-RS sequences in the default codebook / first codebook. The request sent may include any of an indication of channel estimation quality, a DM-RS codebook size, an experienced PAPR, and a blind detection capability (e.g., the number of sequences to be correlated simultaneously).

[0155] Fig.14 1 is a flow chart of an example process for detecting a shared DFT-s-OFDM symbol supporting interference cancellation of a padding sequence, blind DM-RS detection, and dynamic selection of a padding sequence structure and a DM-RS codebook. Fig.14As depicted, a WTRU or any appropriate entity configured to receive a shared DFT-s-OFDM symbol between (filler) data symbols and (adaptive) demodulation reference signals (DM-RS) may perform the following operations. At step 1402, the WTRU may report support for cancellation of interference (e.g., due to subcarrier puncturing and DM-RS insertion and blind DM-RS sequence detection). At step 1404, the WTRU may determine a pre-DFT fill sequence structure and a default codebook consisting of one or more DM-RS sequences based on an indication received through, for example, system information or DL ​​control information; one or more DFT-s-OFDM symbols including filler data and adaptive DM-RS are received on one or more time slots. At step 1406, the WTRU may determine a set of one or more DM-RS sequences from the one or more DM-RS sequences in the default codebook using blind detection based on the received one or more DFT-s-OFDM symbols. At step 1408, the WTRU may use the determined DM-RS sequence for channel estimation and DFT-s-OFDM symbol equalization. At step 1410, the WTRU may cancel interference from subcarrier puncturing and DM-RS insertion based on the determined pre-DFT padding sequence structure. At step 1412, the WTRU may determine interference leakage compared to a first threshold and channel estimation quality compared to a second threshold. At step 1416, the WTRU may determine that the interference quality is above a threshold and the channel estimation quality is below another threshold; or the interference quality is above a threshold and the channel estimation quality is above another threshold; or the interference leakage is below a threshold. At step 1414, the WTRU may send a request to deactivate DM-RS adaptation. At step 1418, the WTRU may send a request to deactivate pre-DFT sequence padding.

[0156] Any of the pre-DFT sequence structure and the initial / first DM-RS codebook may be determined by default based on an indication received in a dedicated RRC or through system information. The determination of the DM-RS sequence may be based on blind detection and a received indication of a subset of the one or more DM-RS sequences in the default codebook / first codebook. The request sent may include any of an indication of channel estimation quality, a DM-RS codebook size, an experienced PAPR, and a blind detection capability (e.g., the number of sequences to be correlated simultaneously). The request sent may be to deactivate DM-RS adaptation when it is determined that the interference leakage is above a first threshold and the channel estimation quality is below a second threshold. The request sent may be to select / update a second DM-RS codebook when it is determined that the interference leakage is below a first threshold and the channel estimation quality is below a second threshold. The WTRU may continue to use the determined padding sequence structure and DM-RS codebook when it is determined that the interference leakage is below the first threshold and the channel estimation quality is above the second threshold.

[0157] Although features and elements are provided above in specific combinations, it will be understood by those of ordinary skill in the art that each feature or element may be used alone or in any combination with other features and elements. The present disclosure is not limited to the specific embodiments described in the present application, which are intended to be illustrative of various aspects. Many modifications and variations can be made without departing from the essence and scope of the present invention, as they will be apparent to those skilled in the art. Unless explicitly provided as such, any element, action or description used in the present application specification should not be understood as being essential or necessary to the present invention. According to the foregoing description, in addition to those listed herein, within the scope of the present disclosure, functionally equivalent methods, devices and articles will be apparent to those skilled in the art. Such modifications and variations are intended to fall within the scope of the appended claims. The present disclosure is limited only to the terms of the appended claims and the full range of equivalents of such entitled claims. It should be understood that the present disclosure is not limited to a specific method or system.

[0158] Although the foregoing embodiments may be discussed with respect to specific terminology and structures (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.) for simplicity, the embodiments discussed are not limited thereto and may be applied to other systems using, for example, other forms of electromagnetic waves or non-electromagnetic waves such as sound waves.

[0159] It should also be understood that the terms used herein are used only for the purpose of describing specific embodiments and are not intended to be limiting. As used herein, the term "video" or the term "imagery" may mean any of a snapshot, a single image, and / or multiple images displayed on a time basis, or any suitable combination thereof. For example, when 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 one of several embodiments of the WTRU; (iii) a wireless and / or wired (e.g., tetherable) device configured with (in particular) some or all of the structure and functionality of the WTRU; (iii) a wireless and / or wired device configured with less than all of the structure and functionality of the WTRU; or (iv), etc. References herein Figures 1A to 1DDetails of an example WTRU are provided that may represent any WTRU described herein. As another example, various disclosed embodiments herein above and below are described as utilizing a head mounted display. One 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 reality experience.

[0160] In addition, the methods provided herein may be implemented in a computer program, software, or firmware incorporated into a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (sent via a wired or wireless connection) and computer-readable storage media. Unlike signals, 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 built-in 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.

[0161] Variations of the methods, devices, articles, and systems provided above are possible without departing from the scope of the present invention. In view of the various embodiments that may be applied, it should be understood that the illustrated embodiments are merely examples and should not be considered to limit the scope of the following claims. For example, the embodiments provided herein include handheld devices that may include or be utilized with any suitable voltage source (such as a battery, etc.) that provides any suitable voltage.

[0162] In addition, in the embodiments provided herein, processing platforms, computing systems, controllers and other devices comprising processors are indicated. These devices may include at least one central processing unit ("CPU") and memory. According to the practice of those skilled in the art of computer programming, reference to the symbolic representation of actions and operations or instructions may be performed by various CPUs and memories. Such actions and operations or instructions may be referred to as "executed", "computer executed" or "CPU executed".

[0163] Those of ordinary skill in the art will appreciate that the actions and symbolic representations of operations or instructions include manipulation of electrical signals by the CPU. The electrical system represents data bits, which may result in the ultimate transformation of electrical signals or reduction of electrical signals and the retention of data bits at memory locations in the memory system, thereby reconfiguring or otherwise changing the operation of the CPU and performing other processing of signals. The memory location that holds the data bits is a physical location that has specific electrical, magnetic, optical, or organic properties that correspond to or represent the data bits. It should be understood that the embodiments are not limited to the above-mentioned platforms or CPUs, and other platforms and CPUs may also support the provided methods.

[0164] 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 include cooperating or interconnected computer-readable media that reside solely on the processing system or distributed across multiple interconnected processing systems that may be local or remote relative to the processing system. It should be understood that the embodiments are not limited to the above-mentioned memories, and other platforms and memories may also support the provided methods.

[0165] 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 a mobile unit, a network element, and / or any other computing device.

[0166] The above specific embodiments have been listed various embodiments of devices and / or processes by using block diagrams, flow charts and / or examples. In the case where such block diagrams, flow charts and / or examples contain one or more functions and / or operations, it should be understood by those skilled in the art that each function and / or operation within such block diagrams, flow charts or examples can be implemented individually and / or collectively by a wide range of hardware, software, firmware or almost any combination thereof. In example embodiments, several parts of the subject matter described herein can be implemented via application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), digital signal processors (DSPs) and / or other integrated formats. Those skilled in the art will recognize that some aspects of the embodiments disclosed herein can be implemented in whole or in part in an integrated circuit as one or more computer programs running on one or more computers (e.g., one or more programs running on one or more computer systems), one or more programs running on one or more processors (e.g., one or more programs running on one or more microprocessors), firmware or almost any combination thereof, and according to the present disclosure, designing circuit systems and / or writing codes for software and / or firmware will be within the technical scope of those skilled in the art. Those skilled in the art will appreciate that the mechanisms of the subject matter described herein may be distributed as a program product in various forms, and that the illustrative embodiments of the subject matter described herein apply regardless of the specific type of signal-bearing medium used to actually implement the distribution. Examples of signal-bearing media include, but are not limited to, the following: recordable type media (such as floppy disks, hard drives, CDs, DVDs, digital tapes, computer memory, etc.); and transmission type media (such as digital and / or analog communication media (e.g., fiber optic cables, waveguides, wired communication links, wireless communication links, etc.)).

[0167] 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 a data processing system. That is, at least a portion of the devices and / or processes described herein can 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 generally may include one or more of the following: a system unit housing; a video display device; a memory, such as a volatile memory and a non-volatile memory; a processor, such as a microprocessor and a digital signal processor; a computing entity, such as an operating system, a driver, a graphical user interface, and an application; one or more interactive devices, such as a touch pad or a screen; and / or a control system, including a feedback loop and a control motor (e.g., a feedback for sensing position and / or velocity, a control motor for moving and / or adjusting components and / or quantities). A typical data processing system may be implemented using any suitable commercially available components, such as those typically found in data computing / communication and / or network computing / communication systems.

[0168] The subject matter described herein sometimes illustrates different components contained in or connected to different other components. It should be understood that such depicted architectures are merely examples, and in fact many other architectures that achieve the same functionality can be implemented. In a conceptual sense, any arrangement of components that achieve the same functionality is effectively "associated" so that the desired functionality can be achieved. Therefore, any two components that are combined to achieve a specific functionality in this article can be considered to be "associated" with each other so that the desired functionality is achieved, regardless of the architecture or intermediate components. Similarly, any two components so associated can also be considered to be "operably connected" or "operably coupled" to each other to achieve the desired functionality, and any two components that can be so associated can also be considered to be "operably coupled" to each other to achieve the desired functionality. Specific examples of operable coupling include, but are not limited to, components that can physically cooperate and / or physically interact and / or components that can wirelessly interact and / or wirelessly interact and / or components that can logically interact and / or components that can logically interact.

[0169] With respect to substantially any plural and / or singular terms used herein, those skilled in the art may convert from the plural to the singular and / or from the singular to the plural as appropriate, depending on the context and / or application. For clarity, various singular / plural arrangements may be explicitly listed herein.

[0170] It will be understood by those skilled in the art that, in general, the terms used herein, and particularly in the appended claims (e.g., the bodies of the appended claims), are generally intended to be "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 also be understood by those skilled in the art that if a specific number of an introduced claim recitation is intended, such intent will be explicitly stated in the claim, and in the absence of such a recitation, there is no such intent. For example, where only one item is intended, the term "single" or similar language may be used. To aid understanding, the following appended claims and / or the description herein may contain 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 as implying that any particular claim containing such introduced claim recitations is limited to an embodiment containing only one such recitation by the indefinite article "a" or "an" to introduce the claim recitation. This is true even when the same claim includes the introductory phrase "one or more" or "at least one" and an indefinite article such as "a" or "a kind" (e.g., "a" and / or "a kind" should be interpreted as meaning "at least one" or "one or more"). The same applies to the use of definite articles used to introduce claim recitations. In addition, even if a specific number of introduced claim recitations is explicitly recited, one skilled in the art will recognize that such recitation should be interpreted as meaning at least the stated number (e.g., a 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 similar to "at least one of A, B, and C, etc." is used, generally speaking, the meaning of such construction is that one skilled in the art will understand the convention (e.g., "a system having at least one of A, B, and C" will include, but is not limited to, a system having A alone, B alone, C alone, A and B simultaneously, A and C simultaneously, B and C simultaneously, and / or A, B, and C simultaneously, etc.). In those instances where a convention similar to "at least one of A, B, or C, etc." is used, generally speaking, the meaning of such construction is that one skilled in the art will understand the convention (e.g., "a system having at least one of A, B, or C" will include, but is not 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.). One skilled in the art will also understand that, in fact, any discrete words and / or phrases presenting two or more alternative terms, whether in the specification, claims, or drawings, should be understood to contemplate the possibility of including one of the terms, any of the terms, or both of the terms.For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B." Furthermore, as used herein, the term "any of" followed by a listing of multiple items and / or multiple categories of items is intended to include "any of," "any combination," "any multiples," and / or "any combination of multiples" of the items and / or categories of items, either alone or in combination with other items and / or other categories of items. Furthermore, as used herein, the term "set" is intended to include any number of items, including zero. Additionally, as used herein, the term "quantity" is intended to include any number, including zero. And, as used herein, the term "plurality" is intended to be synonymous with "multiple."

[0171] In addition, where features or aspects of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also described in terms of any individual member or subgroup of members of the Markush group.

[0172] 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 subranges and combinations of their subranges. Any listed range can be easily identified as fully describing and enabling the same range to be divided into at least equal halves, one-third, one-quarter, one-fifth, one-tenth, etc. As a non-limiting example, each range discussed herein can be easily divided into a lower third, a middle third, and an upper third, etc. As will be understood by those skilled in the art, all languages ​​such as "up to", "at least", "greater than", and "less than", etc. include the cited numbers and refer to the ranges that can be subsequently divided into subranges as described above. Finally, as will be understood by those skilled in the art, the range includes each individual number. Therefore, for example, a group with 1 to 3 units refers to a group with 1, 2, or 3 units. Similarly, a group with 1 to 5 units refers to a group with 1, 2, 3, 4, or 5 units, etc.

Claims

1. A method performed by a wireless transmit / receive unit (WTRU), the method comprising: receiving control information indicating a set of two or more demodulation reference signal (DM-RS) sequences; receiving one or more discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM) symbols, each of the one or more DFT-s-OFDM symbols comprising corresponding data, a DM-RS, or a combination thereof; determining a first subset of DM-RS sequences based on the set of one or more DM-RS sequences using blind detection, wherein determining the first subset of DM-RS sequences is based on the received one or more DFT-s-OFDM symbols; determining a performance parameter associated with the first subset of DM-RS sequences; determining that the determined performance parameter associated with the first subset of DM-RS sequences is less than a threshold performance parameter; as well as An indication of a second subset of DM-RS sequences is transmitted based on a determination that the performance parameter associated with the first subset of DM-RS sequences is less than the threshold performance parameter. 2 . The method according to claim 1 , wherein the control information comprises a codebook, the codebook comprising the set of one or more DM-RS sequences.

3. The method of claim 1, wherein the control information is received via a downlink control information (DCI) related signal or a medium access control (MAC) control element (CE).

4. The method according to claim 1, further comprising: A channel estimate is determined based on the first subset of DM-RS sequences, wherein the performance parameter is associated with the determined channel estimate.

5. The method according to claim 1, further comprising: A DFT-s-OFDM symbol equalization is determined based on the first subset of DM-RS sequences, wherein the performance parameter is associated with the determined DFT-s-OFDM symbol equalization. The method of claim 1 , wherein the performance parameters comprise decoding performance parameters.

7. The method of claim 6, wherein the decoding performance parameter comprises at least one of a block error rate (BLER) or a bit error rate (BER).

8. The method according to claim 1, further comprising: Second control information is received, where the second control information indicates the second subset of DM-RS sequences.

9. The method of claim 1, wherein the second subset of DM-RS sequences is determined based on a decoding failure of a physical data shared channel (PDSCH).

10. The method according to claim 8, further comprising: receiving additional DFT-s-OFDM symbols; as well as The additional DFT-s-OFDM symbols are processed using the second subset of DM-RS sequences.

11. The method of claim 1 , wherein the blind detection is based on correlation of the indicated set of one or more DM-RS sequences with the received one or more DFT-s-OFDM symbols.

12. A wireless transmit / receive unit (WTRU), the wireless transmit / receive unit (WTRU) comprising: Transceiver; and A processor, the processor being configured to: receiving, via the transceiver, control information indicating a set of two or more demodulation reference signal (DM-RS) sequences; receiving, via the transceiver, one or more discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM) symbols, each of the one or more DFT-s-OFDM symbols comprising data, DM-RS, or a combination thereof; determining a first subset of DM-RS sequences based on the set of one or more DM-RS sequences using blind detection, wherein determining the first subset of DM-RS sequences is based on the received one or more DFT-s-OFDM symbols; determining a performance parameter associated with the first subset of DM-RS sequences; determining that the determined performance parameter associated with the first subset of DM-RS sequences is less than a threshold performance parameter; as well as An indication of a second subset of DM-RS sequences is transmitted via the transceiver based on determining that the performance parameter associated with the first subset of DM-RS sequences is less than the threshold performance parameter.

13. The WTRU of claim 12, wherein the control information comprises a codebook comprising the set of one or more DM-RS sequences.

14. The WTRU of claim 12, wherein the control information is received via a downlink control information (DCI) related signal or a medium access control (MAC) control element (CE).

15. The WTRU of claim 12, the processor further configured to determine a channel estimate based on the first subset of DM-RS sequences, wherein the performance parameter is associated with the determined channel estimate.

16. The WTRU of claim 12, wherein the processor is further configured to determine DFT-s-OFDM symbol equalization based on the first subset of DM-RS sequences, wherein the performance parameter is associated with the determined DFT-s-OFDM symbol equalization.

17. The WTRU of claim 12, wherein the performance parameters include decoding performance parameters.

18. The WTRU of claim 17, wherein the decoding performance parameter comprises at least one of a block error rate (BLER) or a bit error rate (BER).

19. The WTRU of claim 12, the processor further configured to receive, via the transceiver, second control information indicating the second subset of DM-RS sequences.

20. The WTRU of claim 12, wherein the second subset of DM-RS sequences is determined based on a decoding failure of a physical data shared channel (PDSCH).

21. The WTRU of claim 19, wherein the processor is further configured to: receiving additional DFT-s-OFDM symbols; and The additional DFT-s-OFDM signal is processed using the second subset of DM-RS sequences.

22. The WTRU of claim 12, wherein the blind detection is based on correlation of the indicated set of one or more DM-RS sequences with the received one or more DFT-s-OFDM symbols.

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