WO2022139875A1 - Apparatus and method for phase noise correction in wireless communication systems - Google Patents

Abstract

Embodiments of an apparatus and method for phase noise correction are disclosed. The apparatus receives an initial data signal and at least one reference signal, which includes a phase-tracking reference signal (PT-RS) in which either one or both of a time density and a frequency density is reduced based on the initial data signal. The apparatus obtains a first channel estimation. The apparatus initially demodulates the initial data signal to produce a demodulated data signal based on the first channel estimation. The apparatus regenerates a regenerated data signal based on a hard decision of the demodulated data signal. The apparatus estimates a phase noise based on the regenerated data signal. The apparatus calculates a second channel estimation based on the estimated phase noise. The apparatus obtains a corrected demodulated data signal based on the second channel estimation. The apparatus decodes the corrected demodulated data signal.

Description

APPARATUS AND METHOD FOR PHASE NOISE CORRECTION IN WIRELESS COMMUNICATION SYSTEMS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63/128,785 filed December 21, 2020, entitled “METHOD FOR PHASE TRACK REFERENCE SIGNAL IN WIRELESS COMMUNICATION SYSTEMS,” which is hereby incorporated by reference in its entirety.

BACKGROUND

[0002] Embodiments of the present disclosure relate to an apparatus and method for phase noise correction in wireless communication systems. Specifically, embodiments relate to an apparatus and method for phase noise correction using a phase tracking reference signal in wireless communication systems, such as in an orthogonal frequency division multiplexing (OFDM) system.

[0003] Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Orthogonal frequency division multiplexing (OFDM) is one of the most widely used and adopted digital multicarrier methods and has been used extensively for cellular communications, such as 4th-generation (4G) Long Term Evolution (LTE) and 5th-generation (5G) New Radio (NR).

SUMMARY

[0004] Embodiments of an apparatus and method for phase noise correction using a phase tracking reference signal (PT-RS), such as in an OFDMA or OFDM system, are disclosed herein. [0005] In one example, an apparatus including at least one processor and a memory storing instructions is disclosed. The instructions, when executed by the at least one processor, cause the apparatus to receive an initial data signal and at least one reference signal, wherein the at least one reference signal includes a phase-tracking reference signal (PT-RS) and either one or both of a time density of the PT-RS and a frequency density of the PT-RS is reduced based on the initial data signal, with respect to a PT-RS required without using the initial data signal. The instructions, when executed by the at least one processor, further cause the apparatus to obtain a first channel estimation based on the at least one reference signal. The instructions, when executed by the at least one processor, further cause the apparatus to initially demodulate an initial data signal to produce a demodulated data signal based on the first channel estimation. The instructions, when executed by the at least one processor, further cause the apparatus to regenerate a regenerated data signal based on a hard decision of the demodulated data signal. The instructions, when executed by the at least one processor, further cause the apparatus to estimate a phase noise based on the regenerated data signal. The instructions, when executed by the at least one processor, further cause the apparatus to calculate a second channel estimation based on the estimated phase noise. The instructions, when executed by the at least one processor, further cause the apparatus to obtain a corrected demodulated data signal based on the second channel estimation. The instructions, when executed by the at least one processor, further cause the apparatus to decode the corrected demodulated data signal.

[0006] In another example, a method for wireless communication is disclosed. The method includes receiving an initial data signal and at least one reference signal, wherein the at least one reference signal includes a phase-tracking reference signal (PT-RS) and either one or both of a time density of the PT-RS and a frequency density of the PT-RS is reduced based on the initial data signal, with respect to a PT-RS required without using the initial data signal. The method further includes obtaining a first channel estimation based on the at least one reference signal. The method further includes initially demodulating an initial data signal to produce a demodulated data signal based on the first channel estimation. The method further includes regenerating a regenerated data signal based on a hard decision of the demodulated data signal. The method further includes estimating a phase noise based on the regenerated data signal. The method further includes calculating a second channel estimation based on the estimated phase noise. The method further includes obtaining a corrected demodulated data signal based on the second channel estimation. The method further includes decoding the corrected demodulated data signal.

[0007] In still another example, a baseband chip is disclosed. The baseband chip includes a receiving circuit. The receiving circuit is configured to receive an initial data signal and at least one reference signal, wherein the at least one reference signal includes a phase-tracking reference signal (PT-RS) and either one or both of a time density of the PT-RS and a frequency density of the PT-RS is reduced based on the initial data signal, with respect to a PT-RS required without using the initial data signal. The baseband chip further includes a channel estimation circuit. The channel estimation circuit is configured to obtain a first channel estimation based on the at least one reference signal. The baseband chip further includes a demodulation circuit. The demodulation circuit is configured to initially demodulate an initial data signal to produce a demodulated data signal based on the first channel estimation. The baseband chip further includes a regeneration circuit. The regeneration circuit is configured to regenerate a regenerated data signal based on a hard decision of the demodulated data signal. The baseband chip further includes a phase noise estimation circuit. The phase noise estimation circuit is configured to estimate a phase noise based on the regenerated data signal. The baseband chip further includes one or more channel calculation circuits. The one or more channel calculation circuits are configured to calculate a second channel estimation based on the estimated phase noise. The one or more channel calculation circuits are further configured to obtain a corrected demodulated data signal based on the second channel estimation. The baseband chip further includes a decoding circuit. The decoding circuit is configured to decode the corrected demodulated data signal.

[0008] In one example, an apparatus including at least one processor and a memory storing instructions is disclosed. The instructions, when executed by the at least one processor, cause the apparatus to generate a phase-tracking reference signal (PT-RS) based on an initial data signal such that either one or both of a time density of the PT-RS and a frequency density of the PT-RS is reduced based on an initial data signal, with respect to a PT-RS required without using the initial data signal. The instructions, when executed by the at least one processor, further cause the apparatus to transmit a demodulation reference signal (DMRS) and the PT-RS to a receiver for channel estimation. The instructions, when executed by the at least one processor, further cause the apparatus to transmit the initial data signal to the receiver for receiving and decoding based on the DMRS, the PT-RS, and characteristics of the initial data signal.

[0009] In another example, a method for wireless communication is disclosed. The method includes generating a phase-tracking reference signal (PT-RS) based on an initial data signal such that either one or both of a time density of the PT-RS and a frequency density of the PT-RS is reduced based on an initial data signal, with respect to a PT-RS required without using the initial data signal. The method further includes transmitting a demodulation reference signal (DMRS) and the PT-RS to a receiver for channel estimation. The method further includes transmitting the initial data signal to the receiver for receiving and decoding based on the DMRS, the PT-RS, and characteristics of the initial data signal.

[0010] In another example, a baseband chip is disclosed. The baseband chip includes a generating circuit. The generating circuit is configured to generate a phase-tracking reference signal (PT-RS) based on an initial data signal such that either one or both of a time density of the PT-RS and a frequency density of the PT-RS is reduced based on an initial data signal, with respect to a PT-RS required without using the initial data signal. The baseband chip further includes a reference signal transmission circuit. The reference signal transmission circuit is configured to transmit a demodulation reference signal (DMRS) and the PT-RS to a receiver for channel estimation. The baseband chip further includes a data signal transmission circuit. The data signal transmission circuit is configured to transmit the initial data signal to the receiver for receiving and decoding based on the DMRS, the PT-RS, and characteristics of the initial data signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate embodiments of the present disclosure and, together with the description, further serve to explain the principles of the present disclosure and to enable a person skilled in the pertinent art to make and use the present disclosure.

[0012] FIG. 1A illustrates a wireless network, according to some embodiments of the present disclosure.

[0013] FIG. IB illustrates an example of a reference signal (RS) configuration.

[0014] FIG. 2 illustrates a detailed block diagram of a wireless communications process in a wireless communications system, in which a reference signal and a data signal are used for phase noise correction.

[0015] FIGS. 3A and 3B illustrate block diagrams of an apparatus including a host chip, a radio frequency (RF) chip, and a baseband chip implementing a wireless communication system, according to some embodiments of the present disclosure.

[0016] FIG. 4A is a block diagram of a phase noise correction circuit in a receiver, according to some embodiments of the present disclosure.

[0017] FIG. 4B is a block diagram of a phase noise correction circuit in a transmitter, according to some embodiments of the present disclosure.

[0018] FIG. 5A illustrates a flowchart of a method for phase noise correction in a receiver, according to some embodiments of the present disclosure.

[0019] FIG. 5B illustrates a flowchart of a method for phase noise correction in a transmitter, according to some embodiments of the present disclosure.

[0020] FIG. 6 illustrates a block diagram of a communications device for phase noise correction, according to some embodiments of the present disclosure.

[0021] Embodiments of the present disclosure will be described with reference to the accompanying drawings.

DETAILED DESCRIPTION

[0022] Although specific configurations and arrangements are discussed, it should be understood that this is done for illustrative purposes only. A person skilled in the pertinent art will recognize that other configurations and arrangements can be used without departing from the spirit and scope of the present disclosure. It will be apparent to a person skilled in the pertinent art that the present disclosure can also be employed in a variety of other applications.

[0023] It is noted that references in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” “some embodiments,” “certain embodiments,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it would be within the knowledge of a person skilled in the pertinent art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0024] In general, terminology may be understood at least in part from usage in context. For example, the term “one or more” as used herein, depending at least in part upon context, may be used to describe any feature, structure, or characteristic in a singular sense or may be used to describe combinations of features, structures, or characteristics in a plural sense. Similarly, terms, such as “a,” “an,” or “the,” again, may be understood to convey a singular usage or to convey a plural usage, depending at least in part upon context. In addition, the term “based on” may be understood as not necessarily intended to convey an exclusive set of factors and may, instead, allow for existence of additional factors not necessarily expressly described, again, depending at least in part on context.

[0025] Various aspects of wireless communication systems will now be described with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, units, components, circuits, steps, operations, processes, algorithms, etc. (collectively referred to as “elements”). These elements may be implemented using electronic hardware, firmware, computer software, or any combination thereof. Whether such elements are implemented as hardware, firmware, or software depends upon the particular application and design constraints imposed on the overall system.

[0026] The techniques described herein are principally described in the context of the operation of an orthogonal frequency division multiplexing (OFDM) or orthogonal frequency division multiple access (OFDMA) system. However, to the extent they are relevant, the techniques and ideas described herein may also be used for and in combination with various wireless communication networks, such as code division multiple access (CDMA) system, time division multiple access (TDMA) system, frequency division multiple access (FDMA) system, single-carrier frequency division multiple access (SC-FDMA) system, and other networks. For example, networks may include but are not limited to 4G LTE, and 5G NR cellular networks, as well as WI-FI wireless networks. The terms “network” and “system” are often used interchangeably. The techniques described herein may be used for the wireless networks mentioned above, as well as other wireless networks, though they are particularly adapted to and explained in the context of OFDM and OFDMA systems.

[0027] Orthogonal frequency-division multiple access (OFDMA) is a multi-user version of the popular orthogonal frequency-division multiplexing (OFDM) digital modulation scheme. Multiple access is achieved in OFDMA by assigning subsets of subcarriers to individual users. This allows simultaneous low-data-rate transmission from several users.

[0028] Phase noise causes significant challenges to a receiver in some bands (for example, mmW). A phase tracking reference signal (PT-RS) is a common way to help a receiver estimate phase noise and compensate for it. However, a PT-RS requires an overhead, which presents a significant challenge for a receiver in some bands. This disclosure provides a method to reduce resources occupied by a PT-RS according to a modulation and coding scheme (MCS), channel bandwidth, or new data indicator, and so on, while maintaining good receiver performance.

[0029] A PT-RS is a reference signal that is added in 5G. The PT-RS is a known pseudorandom sequence initialized based on different known parameters. For example, the resources of the PT-RS in a time domain and in a frequency domain are configured by a base station (BS) gNode B. Parameter frequencyDensity defines the presence and frequency density of UL PT-RS as a function of scheduled bandwidth (BW). Parameter timeDensity defines the presence and time density of uplink (UL) PT-RS as a function of MCS.

[0030] Thus, PT-RS is a predefined known sequence used to help estimate phase noise and compensate for the phase noise. The PT-RS is overhead data because it does not send information bits, but merely acts as a reference signal. While the PT-RS serves a purpose, the more resources PT-RS uses, the more resources the PT-RS wastes.

[0031] An aspect of the present disclosure is to reduce densities of PT-RS in an uplink (UL) by utilizing data resource elements (RE) to track phase noise in a base station such as a gNode B receiver for the RE in which hard decision of data RE is reliable. gNode B may control time and frequency density of UL PT-RS through different parameters when data RE based phase noise estimation is enabled in gNode B.

[0032] FIG. 1A illustrates a wireless network 100, in which certain aspects of the present disclosure may be implemented, according to some embodiments of the present disclosure. As shown in FIG. 1 A, wireless network 100 may include a network of nodes, such as a user equipment (UE) 102, an access node 104, and a core network element 106. User equipment 102 may be any terminal device, such as a mobile phone, a desktop computer, a laptop computer, a tablet, a vehicle computer, a gaming console, a printer, a positioning device, a wearable electronic device, a smart sensor, or any other device capable of receiving, processing, and transmitting information, such as any member of a vehicle to everything (V2X) network, a cluster network, a smart grid node, or an Internet-of-Things (loT) node. It is understood that user equipment 102 is illustrated as a mobile phone simply by way of illustration and not by way of limitation.

[0033] Access node 104 may be a device that communicates with UE 102, such as a wireless access point, a base station (BS), a Node B, an enhanced Node B (eNodeB or eNB), a next-generation Node B (gNodeB or gNB), a cluster master node, or the like. Access node 104 may have a wired connection to UE 102, a wireless connection to UE 102, or any combination thereof. Access node 104 may be connected to UE 102 by multiple connections, and UE 102 may be connected to other access nodes in addition to access node 104. Access node 104 may also be connected to other UEs. It is understood that access node 104 is illustrated by a radio tower by way of illustration and not by way of limitation.

[0034] Core network element 106 may serve access node 104 and user equipment 102 to provide core network services. Examples of core network element 106 may include a home subscriber server (HSS), a mobility management entity (MME), a serving gateway (SGW), or a packet data network gateway (PGW). These are examples of core network elements of an evolved packet core (EPC) system, which is a core network for the LTE system. Other core network elements may be used in LTE and in other communication systems. In some embodiments, core network element 106 includes an access and mobility management function (AMF) device, a session management function (SMF) device, or a user plane function (UPF) device, of a core network for the NR system. It is understood that core network element 106 is shown as a set of rack-mounted servers by way of illustration and not by way of limitation.

[0035] Core network element 106 may connect with a large network, such as the Internet 108, or another Internet Protocol (IP) network, to communicate packet data over any distance. In this way, data from user equipment 102 may be communicated to other user equipment connected to other access points, including, for example, a computer 110 connected to Internet 108, for example, using a wired connection or a wireless connection, or to a tablet 112 wirelessly connected to Internet 108 via a router 114. Thus, computer 110 and tablet 112 provide additional examples of possible user equipment, and router 114 provides an example of another possible access node.

[0036] A generic example of a rack-mounted server is provided as an illustration of core network element 106. However, there may be multiple elements in the core network including database servers, such as a database 116, and security and authentication servers, such as an authentication server 118. Database 116 may, for example, manage data related to user subscriptions to network services. A home location register (HLR) is an example of a standardized database of subscriber information for a cellular network. Likewise, authentication server 118 may handle authentication of users, sessions, and so on. In the NR system, an authentication server function (AUSF) device may be the specific entity to perform user equipment authentication. In some embodiments, a single server rack may handle multiple such functions, such that the connections between core network element 106, authentication server 118, and database 116, may be local connections within a single rack.

[0037] As described below in greater detail, in some embodiments, wireless communication can be established between any suitable nodes in wireless network 100, such as between UE 102 and access node 104, and between UE 102 and core network element 106 for sending and receiving data (e.g., OFDMA symbol(s)). A transmitting node (e.g., a UE) may generate the OFDMA symbol(s) and transmit the symbol(s) to a receiving device (e.g., a BS). When the receiving device receives the symbol(s), the receiver may perform the methods described in the present disclosure to use both a reference signal and a data signal to improve the ability of the receiver to successfully receive the symbol(s).

[0038] Each node of wireless network 100 in FIG. 1 A that is suitable for the reception of signals, such as OFDMA signals, may be considered as a receiving device. More detail regarding the possible implementation of a receiving device is provided by way of example in the description of a communications device 600 in FIG. 6. Communications device 600 may be configured as user equipment 102, access node 104, or core network element 106 in FIG. 1A. Similarly, communications device 600 may also be configured as computer 110, router 114, tablet 112, database 116, or authentication server 118 in FIG. 1 A. As shown in FIG. 6, communications device 600 may include a processor 602, a memory 604, and a transceiver 606. These components are shown as connected to one another by a bus, but other connection types are also permitted. When communications device 600 is user equipment 102, additional components may also be included, such as a user interface (UI), sensors, and the like. Similarly, communications device 600 may be implemented as a blade in a server system when communications device 600 is configured as core network element 106. Other implementations are also possible, and these enumerated examples are not to be taken as limiting.

[0039] Transceiver 606 may include any suitable device for sending and/or receiving data. Communications device 600 may include one or more transceivers, although only one transceiver 606 is shown for simplicity of illustration An antenna 608 is shown as a possible communication mechanism for communications device 600. If the communication is MIMO, multiple antennas and/or arrays of antennas may be utilized for such communication. Additionally, examples of communications device 600 may communicate using wired techniques rather than (or in addition to) wireless techniques. For example, access node 104 may communicate wirelessly to user equipment 102 and may communicate by a wired connection (for example, by optical or coaxial cables) to core network element 106. Other communication hardware, such as a network interface card (NIC), may be included in communications device 600 as well. [0040] As shown in FIG. 6, communications device 600 may include processor 602. Although only one processor is shown, it is understood that multiple processors can be included. Processor 602 may include microprocessors, microcontrollers, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functions described throughout the present disclosure. Processor 602 may be a hardware device having one or more processing cores. Processor 602 may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Software can include computer instructions written in an interpreted language, a compiled language, or machine code. Other techniques for instructing hardware are also permitted under the broad category of software. [0041] As shown in FIG. 6, communications device 600 may also include memory 604. Although only one memory is shown, it is understood that multiple memories can be included. Memory 604 can broadly include both memory and storage. For example, memory 604 may include random-access memory (RAM), read-only memory (ROM), static RAM (SRAM), dynamic RAM (DRAM), ferro-electric RAM (FRAM), electrically erasable programmable ROM (EEPROM), CD-ROM or other optical disk storage, hard disk drive (HDD), such as magnetic disk storage or other magnetic storage devices, Flash drive, solid-state drive (SSD), or any other medium that can be used to carry or store desired program code in the form of instructions that can be accessed and executed by processor 602. Broadly, memory 604 may be embodied by any computer-readable medium, such as a non-transitory computer-readable medium.

[0042] Processor 602, memory 604, and transceiver 606 may be implemented in various forms in communications device 600 for performing wireless communication with phase noise correction functions. In some embodiments, processor 602, memory 604, and transceiver 606 of communications device 600 are implemented (e g., integrated) on one or more system-on-chips (SoCs). In one example, processor 602 and memory 604 may be integrated on an application processor (AP) SoC (sometimes known as a “host,” referred to herein as a “host chip”) that handles application processing in an operating system environment, including generating raw data to be transmitted. In another example, processor 602 and memory 604 may be integrated on a baseband processor (BP) SoC (sometimes known as a modem, referred to herein as a “baseband chip”) that converts the raw data, e g., from the host chip, to signals that can be used to modulate the carrier frequency for transmission, and vice versa, which can run a real-time operating system (RTOS). In still another example, processor 602 and transceiver 606 (and memory 604 in some cases) may be integrated on an RF SoC (sometimes known as a transceiver, referred to herein as an “RF chip”) that transmits and receives RF signals with antenna 608. It is understood that in some examples, some or all of the host chip, baseband chip, and RF chip may be integrated as a single SoC. For example, a baseband chip and an RF chip may be integrated in a single SoC that manages all the radio functions for cellular communication.

[0043] Various aspects of the present disclosure related to phase noise correction may be implemented as software and/or firmware elements executed by a generic processor in a baseband chip (e.g., a baseband processor). It is understood that in some examples, one or more of the software and/or firmware elements may be replaced by dedicated hardware components in the baseband chip, including integrated circuits (ICs), such as application-specific integrated circuits (ASICs). Mapping to the wireless communication (e.g., WI-FI, 4G, LTE, 5G, etc.) layer architecture, the implementation of the present disclosure may be at Layer 1, e.g., the physical (PHY) layer.

[0044] FIG. IB illustrates an example of a reference signal (RS) configuration. The RS structure of 5G new radio (NR) basically follows that of long-term evolution (LTE) while achieving the flexibility to adapt to operation in various different frequency bands and scenarios. [0045] To increase protocol efficiency, and to keep transmissions contained within a slot or beam without having to depend on other slots and beams, 5G NR introduces the following four main reference signals. Specifically, 5G NR introduces a demodulation reference signal (DMRS), a phase tracking reference signal (PT-RS), a sounding reference signal (SRS), and a channel state information reference signal (CSLRS).

[0046] For example, these reference signals differentiate between NR and LTE. In NR, there is not a cell-specific reference signal (C-RS). Also, a new reference signal PT-RS has been introduced for time/frequency tracking. DMRS is used for both downlink and uplink channels. Further, in NR, reference signals are transmitted only when necessary, by contrast from LTE, where always exchanges reference signals to manage the link.

[0047] The reference signals include a DMRS. The DMRS is specific for specific UE and is used to estimate the radio channel. The system is able to beamform the DMRS, keep it within a scheduled resource, and transmit it only when necessary in either DL or UL. Further, multiple orthogonal DMRSs may be allocated to support MIMO transmission. Thus, the network presents users with DMRS information early on for the initial decoding requirement that low-latency applications need, but it only occasionally presents this information for low-speed scenarios in which the channel shows little change. In high-mobility scenarios, to track fast changes in a channel, a system might increase the rate of transmission of DMRS signal (called “additional DMRS”). As noted above, DMRS refers to the demodulation reference signal. DMRS is used by a receiver for radio channel estimation for demodulation of associated physical channel DMRS design, and mapping is specific to each Downlink (DL) and Uplink (UL) NR channels such as NR-PBCH, NR-PDCCH, NR-PDSCH, NR-PUSCH, and NR- PUSCH. A DMRS is specific for a specific UE and transmitted on demand. DMRS can be a beamformed DMRS, be kept within a scheduled resource, and transmit it only when necessary in either DL or UL. Also, multiple orthogonal DMRSs can be allocated to support MIMO transmission.

[0048] The reference signals may also include a PT-RS. The phase noise of a transmitter increases as the frequency of operation increases. The PT-RS plays an important role, especially at mmWave frequencies, to minimize the effect of the oscillator phase noise on system performance. One of the main problems that phase noise introduces into an OFDM signal appears as a common phase rotation of all the sub-carriers, known as common phase error (CPE). As noted above, PT-RS stands for phase tracking reference signal. The main function of the PT-RS is to track a phase of the local oscillator at a transmitter and a receiver. A PT-RS enables suppression of phase noise and common phase error especially at higher mm-wave frequencies. A PT-RS is present both in uplink (in NR-PUSCH) and downlink (in NR-PDSCH) channels.

[0049] Due to phase noise properties, PT-RS has a low density in a frequency domain and a high density in a time domain. PT-RS is associated with one DMRS port during transmission. Moreover, PT-RS is confined to a scheduled BW and a duration used for NR-PDSCH/NR- PUSCH. The NR system typically maps the PT-RS information to a few subcarriers per symbol because the phase rotation affects all sub-carriers within an OFDM symbol equally. However, the phase rotation shows a low correlation from symbol to symbol. The system configures the PT-RS depending on the quality of the oscillators, carrier frequency, subcarrier spacing, and modulation and coding schemes that the transmission uses.

[0050] However, as discussed below, the configuration of a PT-RS may be different in embodiments, because a data signal may substitute for all or part of a PT-RS.

[0051] The reference signals may also include an SRS. As a UL-only signal, the SRS is transmitted by the UE to help the gNB obtain the channel state information (CSI) for each user. CSI describes how the NR signal propagates from the UE to the gNB and represents the combined effect of scattering, fading, and power decay with distance. The system uses the SRS for resource scheduling, link adaptation, Massive MIMO, and beam management. As noted above, SRS refers to a sounding reference signal and is an uplink only signal. The SRS is configured specific to a UE. In the time domain, an SRS spans 1/2/4 consecutive symbols which are mapped within the last six symbols of the slot. Multiple SRS symbols may allow coverage extension and increased sounding capacity. The design of SRS and its frequency hopping mechanism are the same as that used in LTE for SRS.

[0052] The reference signals may also include a CSI-RS. As a DL-only signal, the CSI-RS the UE receives is used to estimate the channel and report channel quality information back to the gNB. During MIMO operations, NR uses different antenna approaches based on the carrier frequency. At lower frequencies, the system uses a modest number of active antennas for MU- MIMO and adds frequency division duplex (FDD) operations. In this case, the UE requires the CSI-RS to calculate the CSI and reports it back in the UL direction. As noted above, CSI-RS refers to channel state information reference signal, and the CSI-RS signals themselves are downlink only signal. For example, a CSI-RS is used for DL CSI acquisition. Also, a CSI-RS is used for RSRP measurements used during mobility and beam management, and also used for frequency/time tracking, demodulation, and UL reciprocity-based pre-coding. A CSI-RS is configured specific to a UE, but multiple users can also share the same resource. A 5G NR standard allows a high level of flexibility in CSI-RS configurations, such that a resource can be configured with up to 32 ports. A CSI-RS resource may start at any OFDM symbol of the slot, and it usually occupies 1/2/4 OFDM symbols depending upon the configured number of ports. CSI-RS may be periodic, semi-persistent or aperiodic, due to downlink control information (DCI) triggering. For time/frequency tracking, CSI-RS can either be periodic or aperiodic. A CSI-RS is transmitted in bursts of two or four symbols which are spread across one or two slots.

[0053] As discussed above, in high-frequency bands, phase noise would be a serious issue. Phase noise is phase fluctuation that occurs due to frequency components other than those of the carrier frequency in a local oscillator signal. Therefore, in NR, a Phase-Tracking Reference Signal (PT-RS) is newly specified as a UE-specific reference signal.

[0054] NR also involves beam control techniques. Beam control in LI (the first layer of the Open Systems Interconnection (OSI) reference model (physical layer)) and L2 (the second layer of the OSI reference model (data link layer)) can be divided into beam management and CSI acquisition. Beam management is a particularly effective technique at high frequencies and is generally aimed at establishing and maintaining transmitting/receiving analog beam pairs between the base station and user equipment. For example, the user equipment compares the Ll-Reference Signal Received Power (RSRP) of multiple SS/PBCH blocks and CSI-RS to which different beams have been applied by the base station. Here, RSRP refers to the received power of a signal measured at a receiver. RSRP is used as an indicator of the receiver sensitivity of a mobile terminal. The user equipment selects a suitable transmit beam to be reported to the base station. The base station reports the beam information applied to the downlink channel so that the user equipment can select the corresponding reception beam to receive the downlink channel. A beam failure recovery technique is also specified, whereby user equipment that detects deterioration in the characteristics of a base station beam can request a switch to a different beam.

[0055] On the other hand, CSI acquisition is used for purposes such as determining the choice of transmission rank. Transmission rank refers to the number of layers or spatial streams transmitted simultaneously in MIMO, digital beams, and a Modulation and Coding Scheme (MCS). An MCS refers to combinations of modulation scheme and coding rate decided on beforehand when performing Adaptive Modulation and Coding. The codebook used for digital beam control may be specified as Type I and Type II, which have relatively low and relatively high quantization granularity, respectively. Quantization granularity refers to the spatial granularity of beams that are capable of being formed. In Type II, digital beam control refers to information about two beams and their linear combination. A linear combination refers to a linear sum of vectors. The vectors are multiplied by constant factors and added together. Then, information is reported to the base station, enabling beam control with higher spatial granularity.

[0056] Thus, FIG. IB and the above discussion provide background for typical reference signals in 5G NR. These typical reference signals are modified, as described further below, in examples to improve performance.

[0057] FIG. 2 illustrates a detailed block diagram of a wireless communications process in a wireless communications system 200, in which a reference signal and a data signal are used to perform phase noise correction.

[0058] In the receiver, channel estimation is done on the basis of reference signals, including DMRS, and PT-RS if PT-RS is available. Thus, it is to be noted that in embodiments, a DMRS will be present, in that channel estimation requires a DMRS. However, in embodiments, the data signal substitutes for all or part of a PT-RS that would otherwise be used in a typical technology for phase noise estimation. A demodulator demodulates the received data symbol based on channel estimation results. The output of the demodulation is fed to be used for a hard decision. The hard decision result is used to regenerate transmitted data RE when hard decision quality is good. Because the hard decision quality is good, the regenerated transmitted data RE is reliable. With a reliable regenerated data RE, it is possible to estimate a phase noise by obtaining a phase change to data RE from the last symbol to a present symbol. By applying such a data RE assistance to phase noise estimation, channel estimation results are updated. Accordingly, a demodulator re-does demodulation for the data RE. Then, the demodulation output is fed to a decoder.

[0059] According to such a process, a reference signal is provided as an input for channel estimation module 210. As discussed, the reference signal includes a DMRS, and optionally includes a PT-RS. The presence and properties of the PT-RS are discussed further below. The result of the channel estimation module 210 is provided for use in the demodulation module 220. A data signal is also provided for use in the demodulation module. As noted, the data signal should be of high quality with respect to phase noise, so that it is reliable even without phase noise correction.

[0060] The demodulation module 220 performs a preliminary demodulation. The results of such a demodulation are provided to a hard decision module 230. The hard decision module 230 performs a hard decision on the demodulated data signal.

[0061] Hard decision decoding takes a stream of bits or a block of bits from the threshold stage of the receiver and decodes each bit by considering it as definitely 1 or 0. Hard decision decoding samples the received pulses and compares their voltages to threshold values. If a voltage is greater than the threshold value, it is decoded as 1 and otherwise decoded as 0. The decoding is done irrespective of how close the voltage is to the threshold. However, because embodiments provide for a preliminary demodulation that is of high quality, it is considered safe to assume that the hard decision is a correct decision. In some embodiments, hard decision quality can be measured according to some metric, including but not limited to the distance between received signal and threshold. If hard decision quality of a resource element is not high, it can be discarded. [0062] Accordingly, the results of such a hard decision module 230 are provided to a signal regeneration module 250. The signal regeneration module 250 uses such a hard decision and regenerates the original data signal. The regenerated original data signal is then provided to phase noise estimation module 240 and demodulation module 220.

[0063] The phase noise estimation module 240 receives the reliable regenerated data RE. Accordingly, the phase noise estimation module 240 estimates a phase noise by finding a phase change to the data RE from the last symbol to a current symbol. The phase noise estimation module 240 provides the estimated phase noise to channel estimation module 210 and demodulation module 220.

[0064] Based on the estimated phase noise, the channel estimation module 210 obtains updated channel estimation results. These updated channel estimation results are provided to the demodulation module 220. The demodulation module 220 then uses the updated channel estimation results to repeat the demodulation of the data RE. Because the updated channel estimation results are used, this demodulation is able to correct for phase noise. After the repeated demodulation, the output of the demodulation is provided to decoder module 260, which decodes the data RE accordingly.

[0065] Additional aspects of how the modules of FIG. 2 operate are discussed further herein. When data RE assisted phase noise estimation, as discussed above, is enabled in the receiver of a gNode B, other factors, like coding rate and scheduled bandwidth, can be considered in determining time density of PT-RS, i.e., time density of PT-RS is given by Equation 1 :

(Equation 1).

[0066] In Equation 1, I CS is a scheduled modulation and coding scheme (MCS) and

is a scheduled bandwidth of a physical uplink shared channel (PUSCH). In 5GNR, PUSCH is the physical uplink channel that carries user data DMRS and PT-RS are the reference signals associated with PUSCH. DMRS is used for channel estimation as part of the coherent demodulation of PUSCH. As discussed above, a PT-RS may also be used for phase estimation, but in some embodiments, PT-RS is omitted or minimized

[0067] Thus, embodiments differ from using a denser PT-RS required by a higher MCS in alternative technologies. With data RE-assisted phase noise estimation, coding rate also plays an important role. A higher coding rate with such data RE assisted phase noise estimation requires a lower raw bit error rate (BER) to make block error rate (BLER) occur at a certain level. A hard decision of data RE is more reliable in assisting with phase noise estimation. Thus, a new L_PT-RS is not necessarily monotonic with IMCS, in that coding rate also affects L_PT-RS . For example, 16QAM with R=0.64 may require a larger L_PT-RS than 64QAM with R=0.43.

[0068] With a larger number of PUSCH resource blocks (RBs), data RE-assisted phase noise estimation may be able to provide more accurate phase noise estimation. In general, each data RE provides more information that can be used to estimate phase noise. Therefore, the sparser time density is required by the receiver and the receiver instructs the transmitter to reduce time density.

[0069] In an embodiment, a time density of PT-RS is given by Equation 2: pT-RS ⁼ I_MCS •> RB •> NDI) (Equation 2).

[0070] In Equation 2, IMCS is a scheduled MCS,

is a scheduled bandwidth of a PUSCH, and NDI is a new data indicator. One example of how the new data indicator works is

Equation 3:

[0071] Thus, when the packet is new, the time density of the PT-RS is provided based on the MCS and the bandwidth, but if the packet is not new, the time density of the PT-RS is provided based on the MCS.

[0072] Also, differing from a frequency density of PT-RS being independent of MCS in a typical art, with data RE assisted phase noise estimation, a frequency density of PT-RS may also be a function of scheduled bandwidth (NRB) and MCS IMCS) or coding rate, as given by Equations 4A-4B: pT-RS ⁼ ( _MCS^ R ) (Equation 4A) or

(Equation 4B).

[0073] In Equation 4B, R denotes a coding rate. With a higher coding rate, only a sparser PT-RS in frequency direction may be required. As discussed, with a higher coding rate, the data RE is more reliable, and thus it becomes more feasible to substitute information obtained from reliable data RE for information that would otherwise be provided by the PT-RS. Similarly, with wider PUSCH resource allocation, more data RE may be used to assist phase error estimation, as more data RE are available. Thus, a fewer total number of PT-RS REs is required, as the additional data REs substitute for PT-RS RE. Such a feature is different from alternative approaches, in which a total number of PT-RS RE tends to be larger with larger N_w . Thus, instead of needing more PT-RS RE when bandwidth is larger, the larger bandwidth is actually exploited to take advantage of the greater quantity of high-quality data, which can be relied upon to provide information usable for improved channel estimation.

[0074] In an embodiment, a frequency density of PT-RS is given by Equations 5A-5B: PT-RS ⁼ IMCS -> RB •> NDI) (Equation 5A) or

(Equation 5B).

[0075] In Equations 5A and 5B, IMCS is a scheduled MCS, A is a coding rate, p.,, is a scheduled bandwidth of the PUSCH, and NDI is a new data indicator. One example is shown in

Equation (Equation 6).

[0076] Thus, when the packet is new, the frequency density of the PT-RS is provided based on the MCS and the bandwidth, but if the packet is not new, the frequency density of the PT-RS is provided based on the bandwidth.

[0077] There may be a larger processing latency in providing data RE-assisted phase noise estimation. Thus, the data RE-assisted phase noise estimation is enabled or disabled according to latency requirements for a given application. For example, ultra-reliable low-latency communication (URLLC) requires low latency and uses MCS to achieve low spectral efficiency. URLLC is a use case supported by the 5GNR standard. URLLC allows a network to be optimized for processing extremely large amounts of data with very little delay or latency. For example, URLLC is possibly relevant in applications that require latency-sensitive connected devices, such as factory automation, autonomous driving, the industrial internet, the smart grid, and robotic surgeries.

[0078] To help manage the latency aspects of the data RE assisted phase noise estimation, embodiments can add mes table into the time and frequency density function of PT-RS.

[0079] In an embodiment, a time density of PT-RS is given by Equation 7: pT-RS ~ J_MCS ’ RB 5 NDI , mes > table (Equation 7).

[0080] In an embodiment, a frequency density of PT-RS is given by Equation 8:

8).

[0081] Thus, Equations 7-8 are similar to Equations 2 and 5A, but utilize the MCS table to do a better trade-off between performance and latency when using the data RE-assisted phase noise estimation.

[0082] FIGS. 3A and 3B illustrate block diagrams of an apparatus including a host chip, a radio frequency (RF) chip, and a baseband chip implementing a wireless communication system according to some embodiments of the present disclosure. For example, the apparatus provided in FIGS. 3A and 3B may implement a UE that sends reference signals in a UL or implement a BS that receives reference signals in a UL, such that the reference signals aid in phase noise correction. [0083] It is contemplated that the wireless communication systems described above may be implemented either in software or hardware. For example, FIGS. 3A and 3B illustrate block diagrams of an apparatus 300 including a host chip, an RF chip, and a baseband chip implementing a wireless communication system with phase noise correction as presented in FIG. 2 in software and hardware, respectively, according to some embodiments of the present disclosure. Apparatus 300 may be an example of any node of wireless network 100 in FIG. 1A suitable for signal reception and/or transmission, such as user equipment 102, access node 104, or a core network element 106. As shown in FIGS. 3A and 3B, apparatus 300 may include an RF chip 302, a baseband chip 304A in FIG. 3A or baseband chip 304B in FIG. 3B, a host chip 306, and an antenna 310. In some embodiments, baseband chip 304A or 304B is implemented by processor 602 and memory 604, and RF chip 302 is implemented by processor 602, memory 604, and transceiver 606, as described in greater detail below, with respect to FIG. 6. Besides on-chip memory 312 (also known as “internal memory,” e.g., as registers, buffers, or caches) on each chip 302, 304A or 304B, or 306, apparatus 300 may further include a system memory 308 (also known as the main memory) that can be shared by each chip 302, 304A or 304B, or 306 through the main bus. Baseband chip 304A or 304B is illustrated as a standalone system on a chip (SoC) in FIGS. 3A and 3B. However, it is understood that in one example, baseband chip 304A or 304B and RF chip 302 may be integrated as one SoC; in another example, baseband chip 304A or 304B and host chip 306 may be integrated as one SoC; in still another example, baseband chip 304A or 304B, RF chip 302, and host chip 306 may be integrated as one SoC, as described above.

[0084] In the uplink, host chip 306 may generate original data and send it to baseband chip 304A or 304B for encoding, modulation, and mapping. Baseband chip 304A or 304B may access the original data from host chip 306 directly using an interface 314 or through system memory 308 and then prepare the data for processing upon receipt to perform the functions of modules 210, 220, 230, 240, 250, and 260, as described above in detail with respect to FIG. 2, as non-limiting examples. Baseband chip 304A or 304B then may pass the modulated signal (e.g., the OFDMA symbol) to RF chip 302 through interface 314. A transmitter (Tx) 316 of RF chip 302 may convert the modulated signals in the digital form from baseband chip 304A or 304B into analog signals, i.e., RF signals, and transmit the RF signals through antenna 310 into the channel.

[0085] In the downlink, antenna 310 may receive the RF signals (e g., the OFDMA symbol) through the channel and pass the RF signals to a receiver (Rx) 318 of RF chip 302. RF chip 302 may perform any suitable front-end RF functions, such as filtering, down-conversion, or samplerate conversion, and convert the RF signals into low-frequency digital signals (baseband signals) that can be processed by baseband chip 304A or 304B. In the downlink, interface 314 of baseband chip 304A or 304B may receive the baseband signals, for example, the OFDMA symbol. Baseband chip 304A or 304B then may perform the phase noise correction functions of modules 210, 220, 230, 240, 250, and 260, as described above in detail with respect to FIG. 2, as non-limiting examples. The original data may be extracted by baseband chip 304A or 304B from the baseband signals and passed to host chip 306 through interface 314 or stored into system memory 308.

[0086] In some embodiments, the phase noise correction schemes disclosed herein (e.g., by wireless communication system 200) may be implemented in firmware and/or software modules by baseband chip 304A in FIG. 3A having a phase noise correction module, which may include firmware and/or software, where the phase noise correction module may be implemented and executed by a phase noise correction processor 320, which may be implemented as a baseband processor 320 executing the stored instructions, as illustrated in FIG. 3 A. Baseband processor 320 may be a generic processor, such as a central processing unit or a digital signal processor (DSP), not dedicated to phase noise correction. That is, baseband processor 320 is also responsible for any other functions of baseband chip 304A and can be interrupted when performing phase noise correction due to other processes with higher priorities. Each element in apparatus 300 may be implemented as a software module executed by baseband processor 320 to perform the respective functions described above in detail. [0087] In some other embodiments, the phase noise correction schemes disclosed herein, for example, by wireless communication system 200, may be implemented in hardware by baseband chip 304B in FIG. 3B having a dedicated phase noise correction circuit 322, such as phase noise correction circuit 322 as illustrated in FIG. 3B. Phase noise correction circuit 322 may include one or more integrated circuits (ICs), such as application-specific integrated circuits (ASICs), dedicated to implementing the phase noise correction schemes disclosed herein. Each element in wireless communication system 200 may be implemented as a circuit to perform the respective functions described above in detail. One or more microcontrollers (not shown) in baseband chip 304B may be used to program and/or control the operations of phase noise correction circuit 322. It is understood that in some examples, the phase noise correction schemes disclosed herein may be implemented in a hybrid manner, e.g., in both hardware and software. For example, some elements in wireless communication system 200 may be implemented as a software phase noise correction module executed by baseband processor 320, while some elements in wireless communication system 200 may be implemented as circuits.

[0088] FIG. 4A is a block diagram of a phase noise correction circuit in a receiver, according to some embodiments of the present disclosure.

[0089] For example, FIG. 4A illustrates phase noise correction circuit 400, and illustrates the subunits that provide hardware to implement the phase noise correction of FIG. 2. Specifically, FIG. 4A shows a phase noise correction circuit 400A in a receiver. Phase noise correction circuit 400A may correspond to phase noise correction circuit 322 of FIG. 3B, implemented as a hardware circuit. However, there may be a mixture between hardware and firmware and/or software in the implementation of embodiments for phase noise correction, such that some of the phase noise correction of FIG. 2 is implemented as firmware and/or software modules executed by a baseband processor, and some of them are implemented as dedicate hardware circuits. Specifically, phase noise correction circuit 400A includes a receiving circuit 328, channel estimation circuit 330, a demodulation circuit 332, a regeneration circuit 334, a phase noise estimation circuit 336, one or more channel calculation circuits 338, and a decoding circuit 340. These constituent circuits generally correspond to the relevant corresponding modules of FIG. 2 and the relevant corresponding operations of method 500. However, the regeneration circuit 334 may also make the hard decision, and the one or more channel calculation circuits 338 may also obtain the demodulated data based on the calculated channel estimation, in examples or these operations may be performed in their own separate circuits. Thus, the circuits of FIG. 4 A illustrate how the functionality of FIGS. 2 and 5 may be implemented in portions of specialized hardware. Thus, FIG. 4A illustrates circuits that provide a potential way to reduce the time and/or frequency density of a PT-RS based on characteristics of the initial data signal. [0090] FIG. 4B is a block diagram of a phase noise management circuit 450 in a transmitter, according to some embodiments of the present disclosure. Specifically, FIG. 4B shows a phase noise management circuit 400B in a transmitter. As discussed above, the elements of FIG. 4B are not necessarily dedicated hardware but may instead be a combination of dedicated hardware as well as firmware and/or software implemented by a baseband processor.

[0091] FIG. 4B includes a generating circuit 348, a reference signal transmission circuit 350, and a data signal transmission circuit 352. These circuits provide functionality so that a transmitting UE is able to send information over a UL for receipt by a BS, such that the BS is able to perform the method of FIG. 5A using the elements of FIG. 4A. In particular, the generating circuit 348 generates a PT -RS which has a reduced time density and/or a reduced frequency density as described elsewhere in this disclosure. The reference signal transmission circuit 350 transmits these reference signals to the receiving BS. The data signal transmission circuit 352 transmits an initial data signal to the receiving BS, such that the receiving BS is to receive and decode based on the DMRS, the PT-RS, and characteristics of the initial data signal. The relevant characteristics are discussed above, with respect to quality metrics that govern how the data can substitute for the PT-RS. The PT-RS is chosen by reference signal transmission circuit 350 such that it has a reduced time density and/or a reduced frequency density, given characteristics of the data signal, as discussed above, such as in connection with FIG. 2.

[0092] FIG. 5A illustrates a flowchart of a method 500 for phase noise correction in a receiver, according to some embodiments of the present disclosure.

[0093] In operation S502, the method receives at least one reference signal and an initial data signal. For example, as discussed above, the method always receives a DMRS and a certain amount of data. In another embodiment, the method receives a PT-RS as well as the DMRS. However, if such a PT-RS is received, it follows the caveats discussed above. Specifically, the time density and the frequency density of the PT-RS consider various aspects of the quality of the data RE. As discussed further above, based on aspects of the data RE, it becomes possible to use a PT-RS with reduced time and/or frequency density because reference signal information that is otherwise derived from a PT-RS is derived from the data RE.

[0094] In operation S504, the method performs channel estimation based on the at least one reference signal. This channel estimation is a preliminary channel estimation and does not consider the data RE yet. The channel estimation uses a DMRS, where the DMRS refers to a demodulation reference signal. The DMRS is used by a receiver for radio channel estimation for demodulation of an associated physical channel. The channel estimation also uses a PT-RS, where the PT-RS is a signal that specifically helps identify phase noise that may interfere with the channel. However, as noted, in some embodiments, the PT-RS may have reduced time density and/or reduced frequency density, in that some of the information that would otherwise be conveyed by the PT-RS will be conveyed by the data RE and captured in the second channel estimation.

[0095] More specifically, the channel estimation may find a channel for a given transmit antenna, a given receive antenna, a symbol, and a reference signal, such that the reference signal represents a sum of the modulated signal and noise. The channel estimation is also based on a channel estimation algorithm used in a given embodiment.

[0096] In operation S506, the method initially demodulates the initial data signal to produce a demodulated data signal. As noted, such an initial demodulation is based on the channel estimation performed, which is based on a channel estimation algorithm.

[0097] For example, it may depend on a multiple-input multiple-output (MIMO) scheme that is being used to decide what algorithm is used in the demodulation. For example, different demodulation algorithms may be used depending on whether the MIMO scheme is 1 -layer or multiple-layer. Some demodulation algorithms are linear or non-linear.

[0098] In operation S508, the method produces a hard decision of the demodulated data signal. For example, the demodulated data signal may provide a soft-output decision, which can then be used to get a hard decision of the demodulated data signal. Such a hard decision should satisfy a quality threshold, as discussed with respect to the various metrics discussed elsewhere in this disclosure.

[0099] In operation S510, the method regenerates a regenerated data signal based on the hard decision. For example, the data signal is regenerated based on the hard decision by considering the characteristics of the channel along with the signal from the hard decision, in order to eliminate the noise from the data signal. While the original data signal includes a noise component, regenerating the regenerated data signal may provide a regenerated data signal where the noise component is reduced and/or eliminated.

[0100] In operation S512, the method estimates phase noise based on the regenerated data signal. More specifically, the phase noise is estimated by measuring a phase change with respect to the data RE from a last symbol to a present symbol. Because the data RE has been regenerated with an accurate aspect, due to the known quality aspects, the estimated phase noise can be used in lieu of all or part of the PT-RS.

[0101] In operation S514, the method calculates a channel estimation based on the estimated phase noise. In particular, a channel estimation can be performed based not only on the original DMRS and any PT-RS that is available, but also based on the estimated phase change provided from operation S512.

[0102] In operation S516, the method obtains the demodulated data signal based on the calculated channel estimation. For example, the demodulation is performed as described above, based on the data signal. However, instead of using the original channel estimation, which may be less than ideal, it is only based on the DMRS and a PT-RS that is reduced in time density and/or frequency density.

[0103] In operation S518, the method decodes the obtained demodulated data signal. Because the channel estimation is improved, as discussed above, it is possible to manage phase noise while managing to also minimize overhead due to PT-RS.

[0104] Thus, FIG. 5A illustrates a method that provides a potential way to reduce the time and/or frequency density of a PT-RS based on characteristics of the initial data signal.

[0105] It is to be noted that once the decoding is performed, the method may additionally output the results of the decoding, such as to other portions of the OFDMA system for further use or processing, such as in operation S520, at which point the method ends.

[0106] FIG. 5B illustrates a flowchart of a method 550 for phase noise correction in a transmitter, according to some embodiments of the present disclosure.

[0107] In operation S552, the method transmits the DMRS and the PT-RS. For example, these reference signals are sent over the UL by the UE to the BS. As discussed with respect to FIG. 4B, the PT-RS is generated such that it has a reduced time density and/or a reduced frequency, given characteristics of the data signal, as discussed above, such as in connection with FIG. 2.

[0108] In operation S554, the method transmits the initial data signal. As discussed above, the initial data signal is intended to substitute for part of the PT-RS, so characteristics of the initial data signal are also considered in operation S552 so that unnecessary resources are not used for the PT-RS. Thus, the initial data signal is sent for receiving and decoding at a receiver, considering the DMRS, the PT-RS, and characteristics of the initial data signal, such as those discussed in FIG. 2 about its ability to substitute for the PT-RS.

[0109] In operation S560, the method ends. At this point, the corresponding receiver has received the DMRS, the PT-RS, and the initial data signal, and is able to decode the data signal, accordingly, based on using the combination of information from the DMRS, the modified PT- RS, and the initial data signal, at the BS.

[0110] According to one aspect of the present disclosure, an apparatus including at least one processor and a memory storing instructions is disclosed. The instructions, when executed by the at least one processor, cause the apparatus to receive an initial data signal and at least one reference signal, wherein the at least one reference signal includes a phase-tracking reference signal (PT-RS) and either one or both of a time density of the PT-RS and a frequency density of the PT-RS is reduced based on the initial data signal, with respect to a PT-RS required without using the initial data signal. The instructions, when executed by the at least one processor, further cause the apparatus to obtain a first channel estimation based on at least one reference signal. The instructions, when executed by the at least one processor, further cause the apparatus to initially demodulate an initial data signal to produce a demodulated data signal based on the first channel estimation. The instructions, when executed by the at least one processor, further cause the apparatus to regenerate a regenerated data signal based on a hard decision of the demodulated data signal. The instructions, when executed by the at least one processor, further cause the apparatus to estimate a phase noise based on the regenerated data signal. The instructions, when executed by the at least one processor, further cause the apparatus to calculate a second channel estimation based on the estimated phase noise. The instructions, when executed by the at least one processor, further cause the apparatus to obtain a corrected demodulated data signal based on the second channel estimation. The instructions, when executed by the at least one processor, further cause the apparatus to decode the corrected demodulated data signal.

[OHl] In some embodiments, the instructions, when executed by the at least one processor, further cause the apparatus to receive the at least one reference signal and the initial data signal.

[0112] In some embodiments, the instructions, when executed by the at least one processor, further cause the apparatus to produce the hard decision of the demodulated data signal. [0113] In some embodiments, a quality of the hard decision exceeds a threshold quality value.

[0114] In some embodiments, the estimating includes determining a phase change between a previous resource element (RE) and a current RE of the regenerated data signal.

[0115] In some embodiments, the at least one reference signal further includes a demodulation reference signal (DMRS).

[0116] In some embodiments, the time density of the PT-RS is based on either one or both of a scheduled modulation and coding scheme (MCS) and a scheduled bandwidth of a physical uplink shared channel (PUSCH).

[0117] In some embodiments, the PT-RS has a sparser time density when the scheduled bandwidth is greater.

[0118] In some embodiments, the time density of the PT-RS is further based on a new data indicator.

[0119] In some embodiments, when the new data indicator is true, the time density of the PT-RS is based on the MCS and the scheduled bandwidth.

[0120] In some embodiments, when the new data indicator is false, the time density of the PT-RS is based on the MCS.

[0121] In some embodiments, the time density of the PT-RS is further based on an MCS table for the MCS.

[0122] In some embodiments, the frequency density of the PT-RS is based on a scheduled bandwidth of a physical uplink shared channel (PUSCH) and modulation and coding scheme (MCS) or based on the scheduled bandwidth and a coding rate.

[0123] In some embodiments, the frequency density of the PT-RS is sparser when the scheduled bandwidth is larger.

[0124] In some embodiments, the frequency density of the PT-RS is based on a new data indicator.

[0125] In some embodiments, when the new data indicator is true, the frequency density of the PT-RS is based on the MCS and the scheduled bandwidth.

[0126] In some embodiments, when the new data indicator is false, the time density of the PT-RS is based on the MCS.

[0127] In some embodiments, the frequency density of the PT-RS is further based on an MCS table for the MCS.

[0128] In some embodiments, the instructions, when executed by the at least one processor, further cause the apparatus to output the decoded data signal.

[0129] According to another aspect of the present disclosure, a method for wireless communication is disclosed. The method includes receiving an initial data signal and at least one reference signal, wherein the at least one reference signal includes a phase-tracking reference signal (PT-RS) and either one or both of a time density of the PT-RS and a frequency density of the PT-RS is reduced based on the initial data signal, with respect to a PT-RS required without using the initial data signal. The method further includes obtaining a first channel estimation based on the at least one reference signal. The method further includes initially demodulating an initial data signal to produce a demodulated data signal based on the first channel estimation. The method further includes regenerating a regenerated data signal based on a hard decision of the demodulated data signal. The method further includes estimating a phase noise based on the regenerated data signal. The method further includes calculating a second channel estimation based on the estimated phase noise. The method further includes obtaining a corrected demodulated data signal based on the second channel estimation. The method further includes decoding the corrected demodulated data signal.

[0130] According to another aspect of the present disclosure, a baseband chip is disclosed. The baseband chip includes a receiving circuit. The receiving circuit is configured to receive an initial data signal and at least one reference signal, wherein the at least one reference signal includes a phase-tracking reference signal (PT-RS) and either one or both of a time density of the PT-RS and a frequency density of the PT-RS is reduced based on the initial data signal, with respect to a PT-RS required without using the initial data signal. The baseband chip further includes a channel estimation circuit. The channel estimation circuit is configured to obtain a first channel estimation based on the at least one reference signal. The baseband chip further includes a demodulation circuit. The demodulation circuit is configured to initially demodulate an initial data signal to produce a demodulated data signal based on the first channel estimation. The baseband chip further includes a regeneration circuit. The regeneration circuit is configured to regenerate a regenerated data signal based on a hard decision of the demodulated data signal. The baseband chip further includes a phase noise estimation circuit. The phase noise estimation circuit is configured to estimate a phase noise based on the regenerated data signal. The baseband chip further includes one or more channel calculation circuits. The one or more channel calculation circuits are configured to calculate a second channel estimation based on the estimated phase noise. The one or more channel calculation circuits are further configured to obtain a corrected demodulated data signal based on the second channel estimation. The baseband chip further includes a decoding circuit. The decoding circuit is configured to decode the corrected demodulated data signal.

[0131] According to another aspect of the present disclosure, an apparatus including at least one processor and a memory storing instructions is disclosed. The instructions, when executed by the at least one processor, cause the apparatus to generate a phase-tracking reference signal (PT-RS) based on an initial data signal such that either one or both of a time density of the PT-RS and a frequency density of the PT-RS is reduced based on an initial data signal, with respect to a PT-RS required without using the initial data signal. The instructions, when executed by the at least one processor, further cause the apparatus to transmit a demodulation reference signal (DMRS) and the PT-RS to a receiver for channel estimation. The instructions, when executed by the at least one processor, further cause the apparatus to transmit the initial data signal to the receiver for receiving and decoding based on the DMRS, the PT-RS, and characteristics of the initial data signal.

[0132] In some embodiments, a time density of the PT-RS is based on either one or both of a scheduled modulation and coding scheme (MCS) and a scheduled bandwidth of a physical uplink shared channel (PUSCH).

[0133] In some embodiments, the PT-RS has a sparser time density when the scheduled bandwidth is greater.

[0134] In some embodiments, the time density of the PT-RS is further based on a new data indicator.

[0135] In some embodiments, when the new data indicator is true, the time density of the

PT-RS is based on the MCS and the scheduled bandwidth. [0136] In some embodiments, when the new data indicator is false, the time density of the PT-RS is based on the MCS.

[0137] In some embodiments, the time density of the PT-RS is further based on an MCS table for the MCS.

[0138] In some embodiments, a frequency density of the PT-RS is based on a scheduled bandwidth of a physical uplink shared channel (PUSCH) and modulation and coding scheme (MCS) or based on the scheduled bandwidth and a coding rate.

[0139] In some embodiments, the frequency density of the PT-RS is sparser when the scheduled bandwidth is larger.

[0140] In some embodiments, the frequency density of the PT-RS is based on a new data indicator.

[0141] In some embodiments, when the new data indicator is true, the frequency density of the PT-RS is based on the MCS and the scheduled bandwidth.

[0142] In some embodiments, when the new data indicator is false, the frequency density of the PT-RS is based on the MCS.

[0143] In some embodiments, the frequency density of the PT-RS is further based on an MCS table for the MCS.

[0144] According to another aspect of the present disclosure, a method for wireless communication is disclosed. The method includes generating a phase-tracking reference signal (PT-RS) based on an initial data signal such that either one or both of a time density of the PT-RS and a frequency density of the PT-RS is reduced based on an initial data signal, with respect to a PT-RS required without using the initial data signal. The method further includes transmitting a demodulation reference signal (DMRS) and the PT-RS to a receiver for channel estimation. The method further includes transmitting the initial data signal to the receiver for receiving and decoding based on the DMRS, the PT-RS, and characteristics of the initial data signal.

[0145] According to another aspect of the present disclosure, a baseband chip is disclosed. The baseband chip includes a generating circuit. The generating circuit is configured to generate a phase-tracking reference signal (PT-RS) based on an initial data signal such that either one or both of a time density of the PT-RS and a frequency density of the PT-RS is reduced based on an initial data signal, with respect to a PT-RS required without using the initial data signal. The baseband chip further includes a reference signal transmission circuit. The reference signal transmission circuit is configured to transmit a demodulation reference signal (DMRS) and a phase tracking reference signal (PT-RS) to a receiver for channel estimation. The baseband chip further includes a data signal transmission circuit. The data signal transmission circuit is configured to transmit the initial data signal to the receiver for receiving and decoding based on the DMRS, the PT-RS, and characteristics of the initial data signal.

[0146] A benefit of this technology is, at least, to significantly improve receiver performance by eliminating or reducing the overhead that would otherwise be required to send a PT-RS. Based on various quality metrics of the data, data RE substitutes for all or part of a PT-RS when performing phase noise estimation. Such estimation is required for successful operation but can be performed without all or some of the PT-RS when data RE of sufficient quality allows.

[0147] Thus, this solution reduces or eliminates the wasted resources that would otherwise be occupied by PT-RS and thereby increases spectral efficiency, such as in an OFDM or OFDMA communication system.

[0148] The foregoing description of the specific embodiments will so reveal the general nature of the present disclosure that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present disclosure. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance.

[0149] Embodiments of the present disclosure have been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed.

[0150] The Summary and Abstract sections may set forth one or more but not all embodiments of the present disclosure as contemplated by the inventor(s), and thus, are not intended to limit the present disclosure and the appended claims in any way.

[0151] Various functional blocks, modules, and steps are disclosed above. The particular arrangements provided are illustrative and without limitation. Accordingly, the functional blocks, modules, and steps may be re-ordered or combined in different ways than in the examples provided above. Likewise, certain embodiments include only a subset of the functional blocks, modules, and steps, and any such subset is permitted.

[0152] The breadth and scope of the present disclosure should not be limited by any of the above-described embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

28 WHAT IS CLAIMED IS:

1. An apparatus for wireless communication, comprising: at least one processor; and a memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive an initial data signal and at least one reference signal, wherein the at least one reference signal comprises a phase-tracking reference signal (PT-RS) and either one or both of a time density of the PT-RS and a frequency density of the PT-RS is reduced based on the initial data signal, with respect to a PT-RS required without using the initial data signal; obtain a first channel estimation based on the at least one reference signal; initially demodulate the initial data signal to produce a demodulated data signal based on the first channel estimation; regenerate a regenerated data signal based on a hard decision of the demodulated data signal; estimate a phase noise based on the regenerated data signal; calculate a second channel estimation based on the estimated phase noise; obtain a corrected demodulated data signal based on the second channel estimation; and decode the corrected demodulated data signal.

2. The apparatus of claim 1, wherein the instructions, when executed by the at least one processor, further cause the apparatus to receive the at least one reference signal and the initial data signal.

3. The apparatus of claim 1, wherein the instructions, when executed by the at least one processor, further cause the apparatus to produce the hard decision of the demodulated data signal.

4. The apparatus of claim 1 , wherein a quality of the hard decision exceeds a threshold quality value.

5. The apparatus of claim 1, wherein the estimating comprises determining a phase change between a previous resource element (RE) and a current RE of the regenerated data signal.

6. The apparatus of claim 1, wherein the at least one reference signal further comprises a demodulation reference signal (DMRS).

7. The apparatus of claim 1, wherein the time density of the PT-RS is based on either one or both of a scheduled modulation and coding scheme (MCS) and a scheduled bandwidth of a physical uplink shared channel (PUSCH).

8. The apparatus of claim 7, wherein the PT-RS has a sparser time density when the scheduled bandwidth is greater.

9. The apparatus of claim 7, wherein the time density of the PT-RS is further based on a new data indicator.

10. The apparatus of claim 9, wherein when the new data indicator is true, the time density of the PT-RS is based on the MCS and the scheduled bandwidth.

11. The apparatus of claim 9, wherein when the new data indicator is false, the time density of the PT-RS is based on the MCS.

12. The apparatus of claim 7, wherein the time density of the PT-RS is further based on an MCS table for the MCS.

13. The apparatus of claim 1, wherein the frequency density of the PT-RS is based on a scheduled bandwidth of a physical uplink shared channel (PUSCH) and modulation and coding scheme (MCS) or based on the scheduled bandwidth and a coding rate.

14. The apparatus of claim 13, wherein the frequency density of the PT-RS is sparser when the scheduled bandwidth is larger.

15. The apparatus of claim 13, wherein the frequency density of the PT-RS is based on a new data indicator.

16. The apparatus of claim 15, wherein when the new data indicator is true, the frequency density of the PT-RS is based on the MCS and the scheduled bandwidth.

17. The apparatus of claim 15, wherein when the new data indicator is false, the frequency density of the PT-RS is based on the MCS.

18. The apparatus of claim 13, wherein the frequency density of the PT-RS is further based on an MCS table for the MCS.

19. The apparatus of claim 1, wherein the instructions, when executed by the at least one processor, further cause the apparatus to output the decoded data signal.

20. A method for wireless communication, comprising: receiving an initial data signal and at least one reference signal, wherein the at least one reference signal comprises a phase-tracking reference signal (PT-RS) and either one or both of a time density of the PT-RS and a frequency density of the PT-RS is reduced based on the initial data signal, with respect to a PT-RS required without using the initial data signal; obtaining a first channel estimation based on at least one reference signal; initially demodulating an initial data signal to produce a demodulated data signal based on the first channel estimation; regenerating a regenerated data signal based on a hard decision of the demodulated data signal; estimating a phase noise based on the regenerated data signal; calculating a second channel estimation based on the estimated phase noise; obtaining a corrected demodulated data signal based on the second channel estimation; and decoding the corrected demodulated data signal.

21. A baseband chip, comprising: a receiving circuit configured to receive an initial data signal and at least one reference signal, wherein the at least one reference signal comprises a phase-tracking reference signal (PT- RS) and either one or both of a time density of the PT-RS and a frequency density of the PT-RS is reduced based on the initial data signal, with respect to a PT-RS required without using the initial data signal; a channel estimation circuit configured to obtain a first channel estimation based on the at least one reference signal; a demodulation circuit configured to initially demodulate an initial data signal to produce a demodulated data signal based on the first channel estimation; a regeneration circuit configured to regenerate a regenerated data signal based on a hard decision of the demodulated data signal; a phase noise estimation circuit configured to estimate a phase noise based on the regenerated data signal; one or more channel calculation circuits configured to calculate a second channel estimation based on the estimated phase noise and further configured to obtain a corrected demodulated data signal based on the second channel estimation; and a decoding circuit configured to decode the corrected demodulated data signal.

22. An apparatus for wireless communication, comprising: at least one processor; and a memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: generate a phase-tracking reference signal (PT-RS) based on an initial data signal such that either one or both of a time density of the PT-RS and a frequency density of the PT-RS is reduced based on an initial data signal, with respect to a PT-RS required without using the initial data signal; transmit a demodulation reference signal (DMRS) and the PT-RS to a receiver for channel estimation; and transmit the initial data signal to the receiver for receiving and decoding based on the DMRS, the PT-RS, and characteristics of the initial data signal.

23. The apparatus of claim 22, wherein a time density of the PT-RS is based on either one or both of a scheduled modulation and coding scheme (MCS) and a scheduled bandwidth of a physical uplink shared channel (PUSCH).

24. The apparatus of claim 23, wherein the PT-RS has a sparser time density when the scheduled bandwidth is greater.

25. The apparatus of claim 23, wherein the time density of the PT-RS is further based on a new data indicator.

26. The apparatus of claim 25, wherein when the new data indicator is true, the time density of the PT-RS is based on the MCS and the scheduled bandwidth.

27. The apparatus of claim 25, wherein when the new data indicator is false, the time density of the PT-RS is based on the MCS. 32

28. The apparatus of claim 23, wherein the time density of the PT-RS is further based on an MCS table for the MCS.

29. The apparatus of claim 22, wherein a frequency density of the PT-RS is based on a scheduled bandwidth of a physical uplink shared channel (PUSCH) and modulation and coding scheme (MCS) or based on the scheduled bandwidth and a coding rate.

30. The apparatus of claim 29, wherein the frequency density of the PT-RS is sparser when the scheduled bandwidth is larger.

31. The apparatus of claim 29, wherein the frequency density of the PT-RS is based on a new data indicator.

32. The apparatus of claim 31, wherein when the new data indicator is true, the frequency density of the PT-RS is based on the MCS and the scheduled bandwidth.

33. The apparatus of claim 32, wherein when the new data indicator is false, the frequency density of the PT-RS is based on the MCS.

34. The apparatus of claim 29, wherein the frequency density of the PT-RS is further based on an MCS table for the MCS.

35. A method for wireless communication, comprising: generating a phase-tracking reference signal (PT-RS) based on an initial data signal such that either one or both of a time density of the PT-RS and a frequency density of the PT-RS is reduced based on an initial data signal, with respect to a PT-RS required without using the initial data signal; transmitting a demodulation reference signal (DMRS) and the PT-RS to a receiver for channel estimation; and transmitting the initial data signal to the receiver for receiving and decoding based on the DMRS, the PT-RS, and characteristics of the initial data signal.

36. A baseband chip, comprising: a generating circuit configured to generate a phase-tracking reference signal (PT-RS) based 33 on an initial data signal such that either one or both of a time density of the PT-RS and a frequency density of the PT-RS is reduced based on an initial data signal, with respect to a PT-RS required without using the initial data signal; a reference signal transmission circuit configured to transmit a demodulation reference signal (DMRS) and the PT-RS to a receiver for channel estimation; and a data signal transmission circuit configured to transmit the initial data signal to the receiver for receiving and decoding based on the DMRS, the PT-RS, and characteristics of the initial data signal.