EP3878127A1

EP3878127A1 - Dm-rs sequence indication for uplink communication

Info

Publication number: EP3878127A1
Application number: EP19882556.4A
Authority: EP
Inventors: Avik SENGUPTA; Sameer PAWAR; Guotong Wang; Gregory V. Morozov; Alexei Davydov
Original assignee: Intel Corp
Current assignee: Intel Corp
Priority date: 2018-11-08
Filing date: 2019-11-07
Publication date: 2021-09-15
Also published as: WO2020097312A1; EP3878127A4

Abstract

Systems, methods, and apparatus are provided for enabling a user equipment device (UE) to determine a demodulation reference signal (DM-RS) sequence based on signaling from a base station. In one example, an apparatus for a UE includes baseband circuitry having a radio frequency (RF) interface configured to transmit and receive RF signals, and one or more processors. The one or more processors are configured to determine, based on signaling from a base station, a demodulation reference signal (DM-RS) sequence, wherein the DM-RS sequence comprises a sequence of binary values; modulate the determined DM-RS sequence using π/2 binary phase-shift keying (BPSK) to generate a π/2 BPSK modulated DM-RS signal in the pre-discrete Fourier transform (DFT) time domain; and transmit an uplink signal to the base station using one or multiple symbols of an orthogonal frequency division multiplexing (OFDM) waveform that includes the π/2 BPSK modulated DM-RS signal.

Description

DM-RS SEQUENCE INDICATION FOR UPLINK COMMUNICATION

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to US Provisional Patent Application

Number 62/757,626 filed on November 8, 2018, entitled“5G METHOD OF DM-RS SEQUENCE INDICATION FOR PUSCH AND PUCCH TRANSMISSION,” which is incorporated herein by reference for all purposes.

BACKGROUND

[0002] Various examples generally may relate to the field of wireless

communications.

BRIEF DESCRIPTION OF THE FIGURES

[0003] Fig. 1 depicts an exemplary wireless communication network that includes a base station and a user equipment device (UE) performing uplink communication in accordance with some examples.

[0004] Fig. 1 A illustrates two exemplary DM-RS resource allocation types.

[0005] Fig. 2 depicts DM-RS resource allocation according to various types.

[0006] Fig. 3 is a flow diagram depicting an exemplary method of determining a DM- RS sequence in accordance with some examples.

[0007] Fig. 4 illustrates a functional block diagram of an exemplary UE wireless communication device in accordance with some examples.

[0008] Fig. 5 illustrates a functional block diagram of an exemplary base station wireless communication device in accordance with some examples.

DETAILED DESCRIPTION

[0009] The following detailed description refers to the accompanying drawings. The same reference numbers may be used in different drawings to identify the same or similar elements. In the following description, for purposes of explanation and not limitation, specific details are set forth such as particular structures, architectures, interfaces, techniques, etc. in order to provide a thorough understanding of the various aspects of various examples. However, it will be apparent to those skilled in the art having the benefit of the present disclosure that the various aspects of the various examples may be practiced in other examples that depart from these specific details. In certain instances, descriptions of well-known devices, circuits, and methods are omitted so as not to obscure the description of the various examples with unnecessary detail. For the purposes of the present document, the phrase“A or B” means (A), (B), or (A and B).

[0010] The following detailed description refers to the accompanying drawings. The same reference numbers may be used in different drawings to identify the same or similar elements. In the following description, for purposes of explanation and not limitation, specific details are set forth such as particular structures, architectures, interfaces, techniques, etc. in order to provide a thorough understanding of the various aspects of various examples. However, it will be apparent to those skilled in the art having the benefit of the present disclosure that the various aspects of the various examples may be practiced in other examples that depart from these specific details. In certain instances, descriptions of well-known devices, circuits, and methods are omitted so as not to obscure the description of the various examples with unnecessary detail. For the purposes of the present document, the phrase“A or B” means (A), (B), or (A and B).

[0011] Fig. 1 illustrates a general overview of an exemplary uplink procedure for a wireless communication network that includes a base station 100 (e.g., eNB, gNB, serving cell, transmission/reception point (TRP, and so on (hereinafter“base station”)) and a user equipment device (UE) 120. An exemplary UE 120 is illustrated in Fig. 4 and an exemplary base station 100 is illustrated in Fig. 5. The base station 100 includes a baseband processor 1 10 that performs various functions for wireless communication. In the following description, if a base station is described as performing some function, it is to be understood that it is processor 1 10 that is performing the function. The UE 120 includes a baseband processor 130 that performs various functions for wireless communication. In the following description, if a UE is described as performing some function, it is to be understood that it is processor 130 that is performing the function.

[0012] Demodulation reference signals (DM-RSs) are predetermined (e.g., known to the recipient) reference signals transmitted between devices in predetermined resources for use in channel estimation and demodulation of physical channels. The DM-RSs are generated by modulating a predetermined sequence according to a predetermined modulation scheme. In Releasel 5 New Radio (NR), for the case of TT/2 binary phase-shift keying (BPSK) modulated discrete Fourier Transform-spread- orthogonal frequency-division multiplexing (DFT-s-OFDM) based physical uplink shared channel/physical uplink control channel (PUSCH/PUCCH) communication, the DM-RSs are generated in the frequency domain. For the case of resource allocation of up to 4 PRBs the DM-RSs are based on computer generated sequences (CGS) mapped to a quadrature phase-shift keying QPSK constellation. For larger resource allocations, the DM-RSs are generated based on cyclically extended Zadoff-Chu sequences .

[0013] When TT/2 BPSK modulation is used for data, the peak to average power ratio (PAPR) of the DM-RS (which is modulated using QPSK) becomes worse compared to the PAPR of the data especially when a pulse shaping filter is used. To resolve this issue the DM-RS sequence may also be modulated by the TT/2 BPSK modulation in the time domain prior to transform precoding or application of discrete Fourier transform (DFT) spreading. One of the problems of supporting such a DM-RS structure is that, depending on the subcarrier frequency, the sequence may provide non uniform power distribution in the frequency domain that degrades channel estimation performance of minimum mean square error (MMSE), zero forcing (ZF), or least squares (LS) based channel estimation schemes. Moreover, the power spectrum of the DM-RS in the frequency domain may contain null(s) that would require special handling at the receiver for channel estimation.

[0014] Described herein are techniques for a base station to indicate DM-RS sequence(s) that can be used by a UE for TT/2 BPSK modulation. As illustrated at (a) in Fig. 1 , to facilitate an uplink communication from the UE 120 to the base station 100, the base station 100 transmits information specifying a DM-RS sequence (or

sequences) to the UE 120. When the UE prepares to transmit an uplink

communication, the UE determines one or more DM-RS sequence(s) based on the specified DM-RS sequence(s). The UE modulates the determined DM-RS sequence(s) using TT/2 BPSK modulation to generate a TT/2 BPSK modulated DM-RS signal in the pre-DFT time domain. As illustrated in (b), the UE 120 transmits an uplink signal (e.g., a PUSCH and/or PUCCH) to the base station 100 that includes the TT/2 BPSK modulated DM-RS signal. In one example, the UE 120 transmits the uplink signal using one or multiple symbols of an OFDM waveform which contains the TT/2 BPSK modulated DM-RS signal with DFT or transform precoding enabled .

[0015] Referring to Fig. 1 A, in NR Release-15, two different DM-RS types were designed, namely Type-1 and Type-2 DM-RS. For the single symbol case, Type 1 DM- RS uses a comb-2 structure with 2 code division multiplexing (CDM)-Groups and length-2 frequency domain-orthogonal cover codes (FD-OCC) per pair of alternating resource elements (REs) within each CDM-Group. Type 2 DM-RS uses a comb-3 structure with 3 CDM-Groups and length-2 FD-OCC per pair of adjacent REs within each CDM-Group. The length-2 FD-OCC is given by [i i_{, i -i}] .

[0016] For uplink DM-RS, when a DFT-S-OFDM waveform is used, Type 1 DMRS is used in Release-15 NR. For this case,“base” DM-RS sequences (e.g., a set of possible DM-RS sequences) that can be used by a UE for TT/2 BPSK modulation are generated in the frequency domain. In one example, for base sequences of length {6, 12, 18, 24} are computer generated sequences mapped to QPSK constellation. For length 30, the sequence is also constant modulus and is based on points chosen from the unit circle in the l/Q plane. For base sequences of length 30 or larger, cyclically extended Zadoff-Chu sequence is used.

[0017] The base sequences are divided into u e {l,...,30} groups each containing a single base sequence for sequence length up to 24 and two base sequences for larger sequence length where ve {0,1} is the base sequence number. The DM-RS sequences are generated in the frequency domain (i.e. , they are not DFT-spread and are constant modulus signals in the frequency domain).

[0018] In the case when p/2-BPSK is used for modulating the PUSCH/PUCCH, the PAPR of the data becomes much lower than of the ZC or CGS based DM-RS.

However, the TT/2 BPSK modulated DM-RS has drawback of non-uniform power spectral density that may degrade the performance of minimum mean square error (MMSE) channel estimation schemes. Moreover, the power spectrum of the DM-RS in the frequency domain may contain null(s) that would require special handling at the MMSE.

[0019] Fig. 2 illustrates some examples of the power spectral density of different base DM-RS sequences modulated by TT/2 BPSK. It can be seen that presented sequences have zero power in the frequency domain for specific subcarriers. The base DM-RS sequences modulated by TT/2 BPSK can be obtained from modulation of pseudo random sequence or modulation of the tabulated base sequences b(i). The mapping of the binary sequence b(i) to TT/2 BPSK sequence d(i) is defined according to the following equation

After DFT-spreading of the p/2-BPSK modulated DM-RS sequence, frequency domain pulse/spectrum shaping can be applied.

[0020] An example of the base binary sequences b(i) that can be modulated by using TT/2 BPSK modulation to minimize frequency domain peak-to-average power ratio (PAPR-FD) for the DM-RS lengths of 6 are illustrated below.

[0021] An example of the base binary sequences that can be modulated by using TT/2 BPSK modulation to minimize PAPR-FD for the DM-RS lengths of 12 are illustrated below.

[0022] An example of the base binary sequences that can be modulated by using TT/2 BPSK modulation to minimize PAPR-FD for the DM-RS lengths of 18 are illustrated below.

[0023] An example of the base binary sequences that can be modulated by using TT/2 BPSK modulation to minimize PAPR-FD for the DM-RS lengths of 24 are illustrated below.

[0024] In one example, the nJD value can be configured for the UE. The n_ID range can be from 0 to 29 (or 1 to 30) and indicate the specific sequence to be used by the UE for pi/2 BPSK modulation. In one example the nJD value can be different for different resource allocation sizes. In this example, the UE can receive multiple nJD values - n_ID6, n_ID12, n_ID18 and n_ID24 corresponding to sequence lengths of 6, 12, 18 and 24 respectively. Each value indicates the specific sequence to be used by the UE for DM-RS.

[0025] In another example, the UE can receive signaling which is restricting / allowing specific set of the sequences for DM-RS. When sequence hopping is configured for the UE, UE may only choose the sequence from the allowed subset. For example, for each resource allocation a bitmap of length 30 can be defined, where each bit in the bitmap may be associated with one sequence. In another example, a bitmap of smaller length can be used. In this example, the each bit in the bitmap may be associated with group of sequences and may restrict / allow use of the particular sequence subset. The bitmap may be commonly or independently configured for different DM-RS sequence length. [0026] In another example, the UE may receive nJD configuration that should be translated to the binary domain according to DM-RS sequence length and modulated according to pi/2 BPSK modulation.

[0027] Fig. 3 is a flow diagram outlining a method 300 for a user equipment device (UE). The method 300 may be performed by a UE 120 or processor 130 of Fig. 1 . The method includes, at 310, determining, based on signaling from a base station, a demodulation reference signal (DM-RS) sequence, wherein the DM-RS sequence comprises a sequence of binary values. The method includes, at 320, modulating the determined DM-RS sequence using TT/2 binary phase-shift keying (BPSK) to generate a TT/2 BPSK modulated DM-RS signal in the pre-discrete Fourier transform (DFT) time domain. The method includes, at 330, transmitting an uplink signal to the base station using one or multiple symbols of an orthogonal frequency division multiplexing (OFDM) waveform that includes the TT/2 BPSK modulated DM-RS signal.

[0028] Fig. 4 illustrates a user device 120 (see also Figs. 1 and 2) in accordance with an aspect. The user device 120 may be a mobile device or a user equipment (UE) in some aspects. The device 120 is configured to transmit and receive RF signals and includes an application processor 405, baseband processor 130 (also referred to as a baseband module), radio front end module (RFEM) 415 (also referred to as a radio interface), memory 420, connectivity module 425, near field communication (NFC) controller 430, audio driver 435, camera driver 440, touch screen 445, display driver 450, sensors 455, removable memory 460, power management integrated circuit (PMIC) 465 and smart battery 470.

[0029] In some aspects, application processor 405 may include, for example, one or more CPU cores and one or more of cache memory, low drop-out voltage regulators (LDOs), interrupt controllers, serial interfaces such as serial peripheral interface (SPI), inter-integrated circuit (I2C) or universal programmable serial interface module, real time clock (RTC), timer-counters including interval and watchdog timers, general purpose input-output (IO), memory card controllers such as secure digital / multi-media card (SD/MMC) or similar, universal serial bus (USB) interfaces, mobile industry processor interface (Ml PI) interfaces and Joint Test Access Group (JTAG) test access ports.

[0030] In some aspects, baseband module 130 may be implemented, for example, as a solder-down substrate including one or more integrated circuits, a single packaged integrated circuit soldered to a main circuit board, and/or a multi-chip module containing two or more integrated circuits.

[0031] Fig. 5 illustrates an example base station or gNB/TRP/eNB 100 (See also Figs. 1 and 2) in accordance with an aspect. The eNB 100 is configured to transmit and receive RF signals and may include one or more of application processor 505, baseband modules 1 10 (also referred to as baseband processors), one or more radio front end modules 515 (also referred to as a radio interface), memory 520, power management circuitry 525, power tee circuitry 530, network controller 535, network interface connector 540, satellite navigation receiver module 545, and user interface 550.

[0032] In some aspects, application processor 505 may include one or more CPU cores and one or more of cache memory, low drop-out voltage regulators (LDOs), interrupt controllers, serial interfaces such as SPI, I2C or universal programmable serial interface module, real time clock (RTC), timer-counters including interval and watchdog timers, general purpose IO, memory card controllers such as SD/MMC or similar, USB interfaces, MIPI interfaces and Joint Test Access Group (JTAG) test access ports.

[0033] In some aspects, baseband processor 1 10 may be implemented, for example, as a solder-down substrate including one or more integrated circuits, a single packaged integrated circuit soldered to a main circuit board or a multi-chip module containing two or more integrated circuits.

[0034] In some aspects, memory 520 may include one or more of volatile memory including dynamic random access memory (DRAM) and/or synchronous dynamic random access memory (SDRAM), and nonvolatile memory (NVM) including high speed electrically erasable memory (commonly referred to as Flash memory), phase change random access memory (PRAM), magnetoresistive random access memory (MRAM) and/or a three-dimensional crosspoint memory. Memory 520 may be implemented as one or more of solder down packaged integrated circuits, socketed memory modules and plug-in memory cards.

[0035] In some aspects, power management integrated circuitry 525 may include one or more of voltage regulators, surge protectors, power alarm detection circuitry and one or more backup power sources such as a battery or capacitor. Power alarm detection circuitry may detect one or more of brown out (under-voltage) and surge (over-voltage) conditions. [0036] In some aspects, power tee circuitry 530 may provide for electrical power drawn from a network cable to provide both power supply and data connectivity to the base station radio head 100 using a single cable.

[0037] In some aspects, network controller 535 may provide connectivity to a network using a standard network interface protocol such as Ethernet. Network connectivity may be provided using a physical connection which is one of electrical (commonly referred to as copper interconnect), optical or wireless.

[0038] In some aspects, satellite navigation receiver module 545 may include circuitry to receive and decode signals transmitted by one or more navigation satellite constellations such as the global positioning system (GPS), Globalnaya

Navigatsionnaya Sputnikovaya Sistema (GLONASS), Galileo and/or BeiDou. The receiver 545 may provide data to application processor 505 which may include one or more of position data or time data. Application processor 505 may use time data to synchronize operations with other radio base stations.

[0039] In some aspects, user interface 550 may include one or more of physical or virtual buttons, such as a reset button, one or more indicators such as light emitting diodes (LEDs) and a display screen.

[0040] While the invention has been illustrated and described with respect to one or more implementations, alterations and/or modifications may be made to the illustrated examples without departing from the spirit and scope of the appended claims. In particular regard to the various functions performed by the above described

components or structures (assemblies, devices, circuits, circuitries, systems, etc.), the terms (including a reference to a "means") used to describe such components are intended to correspond, unless otherwise indicated, to any component or structure which performs the specified function of the described component (e.g., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary

implementations of the invention.

[0041] Various illustrative logics, logical blocks, modules, circuitries, and circuits described in connection with aspects disclosed herein can be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform functions described herein. A general-purpose processor can be a microprocessor, but, in the alternative, processor can be any conventional processor, controller, microcontroller, or state machine.

[0042] The above description of illustrated embodiments of the subject disclosure, including what is described in the Abstract, is not intended to be exhaustive or to limit the disclosed embodiments to the precise forms disclosed. While specific embodiments and examples are described herein for illustrative purposes, various modifications are possible that are considered within the scope of such embodiments and examples, as those skilled in the relevant art can recognize.

[0043] In this regard, while the disclosed subject matter has been described in connection with various embodiments and corresponding Figures, where applicable, it is to be understood that other similar embodiments can be used or modifications and additions can be made to the described embodiments for performing the same, similar, alternative, or substitute function of the disclosed subject matter without deviating therefrom. Therefore, the disclosed subject matter should not be limited to any single embodiment described herein, but rather should be construed in breadth and scope in accordance with the appended claims below.

[0044] In the present disclosure like reference numerals are used to refer to like elements throughout, and wherein the illustrated structures and devices are not necessarily drawn to scale. As utilized herein, terms“module”,“component,”“system,” “circuit,”“circuitry,”“element,”“slice,” and the like are intended to refer to a computer- related entity, hardware, software (e.g., in execution), and/or firmware. For example, circuitry or a similar term can be a processor, a process running on a processor, a controller, an object, an executable program, a storage device, and/or a computer with a processing device. By way of illustration, an application running on a server and the server can also be circuitry. One or more circuitries can reside within a process, and circuitry can be localized on one computer and/or distributed between two or more computers. A set of elements or a set of other circuitry can be described herein, in which the term“set” can be interpreted as“one or more.”

[0045] As another example, circuitry or similar term can be an apparatus with specific functionality provided by mechanical parts operated by electric or electronic circuitry, in which the electric or electronic circuitry can be operated by a software application or a firmware application executed by one or more processors. The one or more processors can be internal or external to the apparatus and can execute at least a part of the software or firmware application. As yet another example, circuitry can be an apparatus that provides specific functionality through electronic components without mechanical parts; the electronic components can include field gates, logical

components, hardware encoded logic, register transfer logic, one or more processors therein to execute software and/or firmware that confer(s), at least in part, the

functionality of the electronic components.

[0046] It will be understood that when an element is referred to as being“electrically connected” or“electrically coupled” to another element, it can be physically connected or coupled to the other element such that current and/or electromagnetic radiation can flow along a conductive path formed by the elements. Intervening conductive, inductive, or capacitive elements may be present between the element and the other element when the elements are described as being electrically coupled or connected to one another. Further, when electrically coupled or connected to one another, one element may be capable of inducing a voltage or current flow or propagation of an electro magnetic wave in the other element without physical contact or intervening components. Further, when a voltage, current, or signal is referred to as being“applied” to an element, the voltage, current, or signal may be conducted to the element by way of a physical connection or by way of capacitive, electro-magnetic, or inductive coupling that does not involve a physical connection.

[0047] Use of the word exemplary is intended to present concepts in a concrete fashion. The terminology used herein is for the purpose of describing particular examples only and is not intended to be limiting of examples. As used herein, the singular forms“a,”“an” and“the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,”“comprising,”“includes” and/or“including,” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.

[0048] For one or more examples, at least one of the components set forth in one or more of the preceding figures may be configured to perform one or more operations, techniques, processes, and/or methods as set forth in the example section below. For example, the baseband circuitry as described above in connection with one or more of the preceding figures may be configured to operate in accordance with one or more of the examples set forth below. For another example, circuitry associated with a UE, base station, network element, etc. as described above in connection with one or more of the preceding figures may be configured to operate in accordance with one or more of the examples set forth below in the example section.

EXAMPLES

[0049] Example 1 is an apparatus for a user equipment device (UE), including baseband circuitry having a radio frequency (RF) interface configured to transmit and receive RF signals, and one or more processors. The one or more processors are configured to: determine, based on signaling from a base station, a demodulation reference signal (DM-RS) sequence, wherein the DM-RS sequence includes a sequence of binary values; modulate the determined DM-RS sequence using TT/2 binary phase-shift keying (BPSK) to generate a TT/2 BPSK modulated DM-RS signal in the pre discrete Fourier transform (DFT) time domain; and transmit an uplink signal to the base station using one or multiple symbols of an orthogonal frequency division multiplexing (OFDM) waveform that includes the TT/2 BPSK modulated DM-RS signal.

[0050] Example 2 includes the subject matter of example 1 , including or omitting optional elements, wherein the one or more processors are configured to transmit the uplink signal with DFT or transform precoding enabled.

[0051] Example 3 includes the subject matter of example 1 , including or omitting optional elements, wherein the one or more processors are configured to transmit the uplink over a physical uplink shared channel (PUSCH) or a physical uplink control channel (PUCCH).

[0052] Example 4 includes the subject matter of any one of examples 1 -3, including or omitting optional elements, wherein the one or more processors are configured to determine the DM-RS sequence based on a sequence index received from the base station, wherein the sequence index identifies a unique sequence of binary values in a group of base sequences of binary values.

[0053] Example 5 includes the subject matter of example 4, including or omitting optional elements, wherein the one or more processors are configured to select the group of base sequences of binary values from a plurality of groups, wherein each group of base sequences of binary values in the plurality is associated with a different number of physical resource blocks allocated to DM-RS in the uplink signal.

[0054] Example 6 includes the subject matter of example 4, including or omitting optional elements, wherein the one or more processors are configured to determine the DM-RS sequence based on a bitmap that identifies a subset of allowed sequences of binary values in the group of base sequences of binary values, wherein each bit of the bitmap corresponds to a unique base sequence of binary values in the group.

[0055] Example 7 includes the subject matter of example 4, including or omitting optional elements, wherein the one or more processors are configured to determine the DM-RS sequence based on a bitmap that identifies a subset of allowed sequences of binary values in the group of base sequences of binary values, wherein each bit of the bitmap corresponds to a set of unique base sequence of binary values in the group.

[0056] Example 8 includes the subject matter of example 4, including or omitting optional elements, wherein the one or more processors are configured to: determine whether the UE is performing DM-RS sequence hopping; when the UE is not performing DM-RS sequence hopping determine the DM-RS sequence based on an entirety of the group of base sequences of binary values; and when the UE is performing DM-RS sequence hopping, determine the DM-RS sequence based on a subset of allowed sequences of binary values in a group of base sequences of binary values defined by a bitmap.

[0057] Example 9 includes the subject matter of any one of examples 1 -3, including or omitting optional elements, wherein the one or more processors are configured to convert a value or index received from the base station into a corresponding binary DM- RS sequence.

[0058] Example 10 includes the subject matter of any one of examples 1 -3, including or omitting optional elements, wherein the one or more processors are configured to modulate the sequence of binary values in the determined DM-RS sequence, from least significant bit to most significant using TT/2 BPSK modulation to generate the TT/2 BPSK modulated DM-RS signal.

[0059] Example 1 1 includes the subject matter of any one of examples 1 -3, including or omitting optional elements, wherein the one or more processors are configured to modulate the sequence of binary values in the determined DM-RS sequence b(i) to generate the TT/2 BPSK modulated DM-RS signal d(i) according to the following relationship:

[0060] Example 12 is a method for a user equipment device (UE), including determining, based on signaling from a base station, a demodulation reference signal (DM-RS) sequence, wherein the DM-RS sequence includes a sequence of binary values; modulating the determined DM-RS sequence using TT/2 binary phase-shift keying (BPSK) to generate a TT/2 BPSK modulated DM-RS signal in the pre-discrete Fourier transform (DFT) time domain; and transmitting an uplink signal to the base station using one or multiple symbols of an orthogonal frequency division multiplexing (OFDM) waveform that includes the TT/2 BPSK modulated DM-RS signal.

[0061] Example 13 includes the subject matter of example 12, including or omitting optional elements, including transmitting the uplink signal with DFT or transform precoding enabled.

[0062] Example 14 includes the subject matter of example 12, including or omitting optional elements, including transmitting the uplink over a physical uplink shared channel (PUSCH) or a physical uplink control channel (PUCCH).

[0063] Example 15 includes the subject matter of any one of examples 12-14, including or omitting optional elements, including determining the DM-RS sequence based on a sequence index received from the base station, wherein the sequence index identifies a unique sequence of binary values in a group of base sequences of binary values.

[0064] Example 16 includes the subject matter of any one of examples 12-14, including or omitting optional elements, including converting a value or index received from the base station into a corresponding binary DM-RS sequence.

[0065] Example 17 includes the subject matter of any one of examples 12-14, including or omitting optional elements, including modulating the sequence of binary values in the determined DM-RS sequence, from least significant bit to most significant using TT/2 BPSK modulation to generate the TT/2 BPSK modulated DM-RS signal.

[0066] Example 18 is a method for a base station, including transmitting a signal to a user equipment device (UE) specifying a demodulation reference signal (DM-RS) sequence, wherein the DM-RS sequence includes a sequence of binary values;

receiving an uplink signal from the UE; and demodulating using TT/2 binary phase-shift keying (BPSK) one or multiple symbols of the uplink signal based on the DM-RS sequence to determine channel information associated with the uplink signal.

[0067] Example 19 includes the subject matter of example 18, including or omitting optional elements, including transmitting a sequence index to the UE, wherein the sequence index identifies a unique sequence of binary values in a group of base sequences of binary values. [0068] Example 20 includes the subject matter of example 18, including or omitting optional elements, including transmitting a value or index that is converted into a corresponding binary DM-RS sequence by the UE.

[0069] Any of the above described examples may be combined with any other example (or combination of examples), unless explicitly stated otherwise. The foregoing description of one or more implementations provides illustration and description, but is not intended to be exhaustive or to limit the scope of examples to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of various examples.

Claims

CLAIMS We claim:

1 . An apparatus for a user equipment device (UE), comprising baseband circuitry having a radio frequency (RF) interface configured to transmit and receive RF signals, and one or more processors configured to:

determine, based on signaling from a base station, a demodulation reference signal (DM-RS) sequence, wherein the DM-RS sequence comprises a sequence of binary values;

modulate the determined DM-RS sequence using TT/2 binary phase-shift keying (BPSK) to generate a TT/2 BPSK modulated DM-RS signal in the pre-discrete Fourier transform (DFT) time domain; and

transmit an uplink signal to the base station using one or multiple symbols of an orthogonal frequency division multiplexing (OFDM) waveform that includes the TT/2 BPSK modulated DM-RS signal.

2. The apparatus of claim 1 , wherein the one or more processors are configured to transmit the uplink signal with DFT or transform precoding enabled.

3. The apparatus of claim 1 , wherein the one or more processors are configured to transmit the uplink signal over a physical uplink shared channel (PUSCH) or a physical uplink control channel (PUCCH).

4. The apparatus of any one of claims 1 -3, wherein the one or more processors are configured to determine the DM-RS sequence based on a sequence index received from the base station, wherein the sequence index identifies a unique sequence of binary values in a group of base sequences of binary values.

5. The apparatus of claim 4, wherein the one or more processors are configured to select the group of base sequences of binary values from a plurality of groups, wherein each group of base sequences of binary values in the plurality is associated with a different number of physical resource blocks allocated to DM-RS in the uplink signal.

6. The apparatus of claim 4, wherein the one or more processors are configured to determine the DM-RS sequence based on a bitmap that identifies a subset of allowed sequences of binary values in the group of base sequences of binary values, wherein each bit of the bitmap corresponds to a unique base sequence of binary values in the group.

7. The apparatus of claim 4, wherein the one or more processors are configured to determine the DM-RS sequence based on a bitmap that identifies a subset of allowed sequences of binary values in the group of base sequences of binary values, wherein each bit of the bitmap corresponds to a set of unique base sequence of binary values in the group.

8. The apparatus of claim 4, wherein the one or more processors are configured to: determine whether the UE is performing DM-RS sequence group hopping;

when the UE is not performing DM-RS sequence group hopping determine the

DM-RS sequence based on an entirety of the group of base sequences of binary values; and

when the UE is performing DM-RS sequence group hopping, determine the DM- RS sequence based on a subset of allowed sequences of binary values in a group of base sequences of binary values defined by a bitmap.

9. The apparatus of any one of claims 1 -3, wherein the one or more processors are configured to convert a value or index received from the base station into a

corresponding binary DM-RS sequence.

10. The apparatus of any one of claims 1 -3, wherein the one or more processors are configured to modulate the sequence of binary values in the determined DM-RS sequence, from least significant bit to most significant using TT/2 BPSK modulation to generate the TT/2 BPSK modulated DM-RS signal.

1 1 . The apparatus of claim 10, wherein the one or more processors are configured to modulate the sequence of binary values in the determined DM-RS sequence b(i) to generate the TT/2 BPSK modulated DM-RS signal d(i) according to the following relationship:

12. A method for a user equipment device (UE), comprising:

determining, based on signaling from a base station, a demodulation reference signal (DM-RS) sequence, wherein the DM-RS sequence comprises a sequence of binary values;

modulating the determined DM-RS sequence using TT/2 binary phase-shift keying (BPSK) to generate a TT/2 BPSK modulated DM-RS signal in the pre-discrete Fourier transform (DFT) time domain; and

transmitting an uplink signal to the base station using one or multiple symbols of an orthogonal frequency division multiplexing (OFDM) waveform that includes the TT/2 BPSK modulated DM-RS signal.

13. The method of claim 12, comprising transmitting the uplink signal with DFT or transform precoding enabled.

14. The method of claim 12, comprising transmitting the uplink over a physical uplink shared channel (PUSCH) or a physical uplink control channel (PUCCH).

15. The method of any one of claims 12-14, comprising determining the DM-RS sequence based on a sequence index received from the base station, wherein the sequence index identifies a unique sequence of binary values in a group of base sequences of binary values.

16. The method of any one of claims 12-14, comprising converting a value or index received from the base station into a corresponding binary DM-RS sequence.

17. The method of any one of claims 12-14, comprising modulating the sequence of binary values in the determined DM-RS sequence, from least significant bit to most significant using TT/2 BPSK modulation to generate the TT/2 BPSK modulated DM-RS signal.

18. A method for a base station, comprising:

transmitting a signal to a user equipment device (UE) specifying a demodulation reference signal (DM-RS) sequence, wherein the DM-RS sequence comprises a sequence of binary values;

receiving an uplink signal from the UE; and

demodulating using TT/2 binary phase-shift keying (BPSK) one or multiple symbols of the uplink signal based on the DM-RS sequence to determine channel information associated with the uplink signal.

19. The method of claim 18, comprising transmitting a sequence index to the UE, wherein the sequence index identifies a unique sequence of binary values in a group of base sequences of binary values.

20. The method of any one of claims 12-13, comprising transmitting a value or index that is converted into a corresponding binary DM-RS sequence by the UE.