Uplink low-PAPR DMRS sequence design

An apparatus of user equipment (UE) includes processing circuitry coupled to a memory, where to configure the UE for DMRS processing in an NR network, the processing circuitry is to generate a plurality of binary sequences of length L, the binary sequences being arranged according to a signal quality metric. A set of CGSs is generated using the binary sequences, based on minimizing cross-correlation between subsets of binary sequences of different lengths selected from the plurality of binary sequences. A CGS is selected from the set of CGSs as a DMRS, based on uplink PRB resource allocation. The DMRS is encoded for transmission, where the encoding includes BPSK modulation and discrete Fourier transformation (DFT) spreading of the DMRS.

TECHNICAL FIELD

BACKGROUND

Mobile communications have evolved significantly from early voice systems to today's highly sophisticated integrated communication platform. With the increase in different types of devices communicating with various network devices, usage of 3GPP LTE systems has increased. The penetration of mobile devices (user equipment or UEs) in modern society has continued to drive demand for a wide variety of networked devices in a number of disparate environments. Fifth-generation (5G) wireless systems are forthcoming and are expected to enable even greater speed, connectivity, and usability. Next generation 5G networks (or NR networks) are expected to increase throughput, coverage, and robustness and reduce latency and operational and capital expenditures. 5G-NR networks will continue to evolve based on 3GPP LTE-Advanced with additional potential new radio access technologies (RATs) to enrich people's lives with seamless wireless connectivity solutions delivering fast, rich content and services. As current cellular network frequency is saturated, higher frequencies, such as millimeter wave (mmWave) frequency, can be beneficial due to their high bandwidth.

Potential LTE operation in the unlicensed spectrum includes (and is not limited to) the LTE operation in the unlicensed spectrum via dual connectivity (DC), or DC-based LAA, and the standalone LTE system in the unlicensed spectrum, according to which LTE-based technology solely operates in unlicensed spectrum without requiring an “anchor” in the licensed spectrum, called MulteFire. MulteFire combines the performance benefits of LTE technology with the simplicity of Wi-Fi-like deployments.

Further enhanced operation of LTE systems in the licensed as well as unlicensed spectrum is expected in future releases and 5G systems. Such enhanced operations can include configuring uplink low-PAPR DMRS sequence design.

DETAILED DESCRIPTION

The following description and the drawings sufficiently illustrate aspects to enable those skilled in the art to practice them. Other aspects may incorporate structural, logical, electrical, process, and other changes. Portions and features of some aspects may be included in or substituted for, those of other aspects. Aspects set forth in the claims encompass all available equivalents of those claims.

FIG. 1Aillustrates an architecture of a network in accordance with some aspects. The network140A is shown to include user equipment (UE)101and UE102. The UEs101and102are illustrated as smartphones (e.g., handheld touchscreen mobile computing devices connectable to one or more cellular networks) but may also include any mobile or non-mobile computing device, such as Personal Data Assistants (PDAs), pagers, laptop computers, desktop computers, wireless handsets, drones, or any other computing device including a wired and/or wireless communications interface. The UEs101and102can be collectively referred to herein as UE101, and UE101can be used to perform one or more of the techniques disclosed herein.

Any of the radio links described herein (e.g., as used in the network140A or any other illustrated network) may operate according to any exemplary radio communication technology and/or standard.

LTE and LTE-Advanced are standards for wireless communications of high-speed data for UE such as mobile telephones. In LTE-Advanced and various wireless systems, carrier aggregation is a technology according to which multiple carrier signals operating on different frequencies may be used to carry communications for a single UE, thus increasing the bandwidth available to a single device. In some aspects, carrier aggregation may be used where one or more component carriers operate on unlicensed frequencies.

Aspects described herein can be used in the context of any spectrum management scheme including, for example, dedicated licensed spectrum, unlicensed spectrum, (licensed) shared spectrum (such as Licensed Shared Access (LSA) in 2.3-2.4 GHz, 3.4-3.6 GHz, 3.6-3.8 GHz, and further frequencies and Spectrum Access System (SAS) in 3.55-3.7 GHz and further frequencies).

Aspects described herein can also be applied to different Single Carrier or OFDM flavors (CP-OFDM, SC-FDMA, SC-OFDM, filter bank-based multicarrier (FBMC), OFDMA, etc.) and in particular 3GPP NR (New Radio) by allocating the OFDM carrier data bit vectors to the corresponding symbol resources.

In some aspects, any of the UEs101and102can include enhanced MTC (eMTC) UEs or further enhanced MTC (FeMTC) UEs.

The UEs101and102may be configured to connect, e.g., communicatively couple, with a radio access network (RAN)110. The RAN110may be, for example, an Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN), a NextGen RAN (NG RAN), or some other type of RAN. The UEs101and102utilize connections103and104, respectively, each of which comprises a physical communications interface or layer (discussed in further detail below); in this example, the connections103and104are illustrated as an air interface to enable communicative coupling and can be consistent with cellular communications protocols, such as a Global System for Mobile Communications (GSM) protocol, a code-division multiple access (CDMA) network protocol, a Push-to-Talk (PTT) protocol, a PTT over Cellular (POC) protocol, a Universal Mobile Telecommunications System (UMTS) protocol, a 3GPP Long Term Evolution (LTE) protocol, a fifth-generation (5G) protocol, a New Radio (NR) protocol, and the like.

In an aspect, the UEs101and102may further directly exchange communication data via a ProSe interface105. The ProSe interface105may alternatively be referred to as a sidelink interface comprising one or more logical channels, including but not limited to a Physical Sidelink Control Channel (PSCCH), a Physical Sidelink Shared Channel (PSSCH), a Physical Sidelink Discovery Channel (PSDCH), and a Physical Sidelink Broadcast Channel (PSBCH).

Any of the RAN nodes111and112can terminate the air interface protocol and can be the first point of contact for the UEs101and102. In some aspects, any of the RAN nodes111and112can fulfill various logical functions for the RAN110including, but not limited to, radio network controller (RNC) functions such as radio bearer management, uplink and downlink dynamic radio resource management and data packet scheduling, and mobility management. In an example, any of the nodes111and/or112can be a new generation Node-B (gNB), an evolved node-B (eNB), or another type of RAN node.

The S-GW122may terminate the S interface113towards the RAN110, and routes data packets between the RAN110and the CN120. In addition, the S-GW122may be a local mobility anchor point for inter-RAN node handovers and also may provide an anchor for inter-3GPP mobility. Other responsibilities of the S-GW122may include a lawful intercept, charging, and some policy enforcement.

The P-GW123may further be a node for policy enforcement and charging data collection. Policy and Charging Rules Function (PCRF)126is the policy and charging control element of the CN120. In a non-roaming scenario, in some aspects, there may be a single PCRF in the Home Public Land Mobile Network (HPLMN) associated with a UE's Internet Protocol Connectivity Access Network (IP-CAN) session. In a roaming scenario with a local breakout of traffic, there may be two PCRFs associated with a UE's IP-CAN session: a Home PCRF (H-PCRF) within an HPLMN and a Visited PCRF (V-PCRF) within a Visited Public Land Mobile Network (VPLMN). The PCRF126may be communicatively coupled to the application server184via the P-GW123.

In some aspects, the communication network140A can be an IoT network or a 5G network, including 5G new radio network using communications in the licensed (5G NR) and the unlicensed (5G NR-U) spectrum. One of the current enablers of IoT is the narrowband-IoT (NB-IoT).

An NG system architecture can include the RAN110and a 5G network core (5GC)120. The NG-RAN110can include a plurality of nodes, such as gNBs and NG-eNBs. The core network120(e.g., a 5G core network or 5GC) can include an access and mobility function (AMF) and/or a user plane function (UPF). The AMF and the UPF can be communicatively coupled to the gNBs and the NG-eNBs via NG interfaces. More specifically, in some aspects, the gNBs and the NG-eNBs can be connected to the AMF by NG-C interfaces, and to the UPF by NG-U interfaces. The gNBs and the NG-eNBs can be coupled to each other via Xn interfaces.

In some aspects, the NG system architecture can use reference points between various nodes as provided by 3GPP Technical Specification (TS) 23.501 (e.g., V15.4.0, 2018-12). In some aspects, each of the gNBs and the NG-eNBs can be implemented as a base station, a mobile edge server, a small cell, a home eNB, and so forth. In some aspects, a gNB can be a master node (MN) and NG-eNB can be a secondary node (SN) in a 5G architecture.

FIG. 1Billustrates a non-roaming 5G system architecture in accordance with some aspects. Referring toFIG. 1B, there is illustrated a 5G system architecture140B in a reference point representation. More specifically, UE102can be in communication with RAN110as well as one or more other 5G core (5GC) network entities. The 5G system architecture140B includes a plurality of network functions (NFs), such as access and mobility management function (AMF)132, session management function (SMF)136, policy control function (PCF)148, application function (AF)150, user plane function (UPF)134, network slice selection function (NSSF)142, authentication server function (AUSF)144, and unified data management (UDM)/home subscriber server (HSS)146. The UPF134can provide a connection to a data network (DN)152, which can include, for example, operator services, Internet access, or third-party services. The AMF132can be used to manage access control and mobility and can also include network slice selection functionality. The SMF136can be configured to set up and manage various sessions according to network policy. The UPF134can be deployed in one or more configurations according to the desired service type. The PCF148can be configured to provide a policy framework using network slicing, mobility management, and roaming (similar to PCRF in a 4G communication system). The UDM can be configured to store subscriber profiles and data (similar to an HSS in a 4G communication system).

In some aspects, the 5G system architecture140B includes an IP multimedia subsystem (IMS)168B as well as a plurality of IP multimedia core network subsystem entities, such as call session control functions (CSCFs). More specifically, the IMS168B includes a CSCF, which can act as a proxy CSCF (P-CSCF)162BE, a serving CSCF (S-CSCF)164B, an emergency CSCF (E-CSCF) (not illustrated inFIG. 1B), or interrogating CSCF (I-CSCF)166B. The P-CSCF162B can be configured to be the first contact point for the UE102within the IM subsystem (IMS)168B. The S-CSCF164B can be configured to handle the session states in the network, and the E-CSCF can be configured to handle certain aspects of emergency sessions such as routing an emergency request to the correct emergency center or PSAP. The I-CSCF166B can be configured to function as the contact point within an operator's network for all IMS connections destined to a subscriber of that network operator, or a roaming subscriber currently located within that network operator's service area. In some aspects, the I-CSCF166B can be connected to another IP multimedia network170E, e.g. an IMS operated by a different network operator.

In some aspects, the UDM/HSS146can be coupled to an application server160E, which can include a telephony application server (TAS) or another application server (AS). The AS160B can be coupled to the IMS168B via the S-CSCF164B or the I-CSCF166B.

A reference point representation shows that interaction can exist between corresponding NF services. For example,FIG. 1Billustrates the following reference points: N1(between the UE102and the AMF132), N2(between the RAN110and the AMF132), N3(between the RAN110and the UPF134), N4(between the SMF136and the UPF134), N5(between the PCF148and the AF150, not shown), N6(between the UPF134and the DN152), N7(between the SMF136and the PCF148, not shown), N8(between the UDM146and the AMF132, not shown), N9(between two UPFs134, not shown), N10(between the UDM146and the SMF136, not shown), N11(between the AMF132and the SMF136, not shown), N12(between the AUSF144and the AMF132, not shown), N13(between the AUSF144and the UDM146, not shown), N14(between two AMFs132, not shown), N15(between the PCF148and the AMF132in case of a non-roaming scenario, or between the PCF148and a visited network and AMF132in case of a roaming scenario, not shown), N16(between two SMFs, not shown), and N22(between AMF132and NSSF142, not shown). Other reference point representations not shown inFIG. 1Ecan also be used.

FIG. 1Cillustrates a 5G system architecture140C and a service-based representation. In addition to the network entities illustrated inFIG. 1B, system architecture140C can also include a network exposure function (NEF)154and a network repository function (NRF)156. In some aspects, 5G system architectures can be service-based and interaction between network functions can be represented by corresponding point-to-point reference points Ni or as service-based interfaces.

In some aspects, as illustrated inFIG. 1C, service-based representations can be used to represent network functions within the control plane that enable other authorized network functions to access their services. In this regard, 5G system architecture140C can include the following service-based interfaces: Namf158H (a service-based interface exhibited by the AMF132), Nsmf1581(a service-based interface exhibited by the SMF136), Nnef158B (a service-based interface exhibited by the NEF154), Npcf158D (a service-based interface exhibited by the PCF148), a Nudm158E (a service-based interface exhibited by the UDM146), Naf158F (a service-based interface exhibited by the AF150), Nnrf158C (a service-based interface exhibited by the NRF156), Nnssf158A (a service-based interface exhibited by the NSSF142), Nausf158G (a service-based interface exhibited by the AUSF144). Other service-based interfaces (e.g., Nudr, N5g-eir, and Nudsf) not shown inFIG. 1Ccan also be used.

Techniques discussed herein can be performed by a UE or a base station (e.g., any of the UEs or base stations illustrated in connection withFIG. 1A-FIG. 1C).

Techniques discussed herein are associated with 3GPP NR Rel-16 and NR MIMO low PAPR reference signal design. For PUSCH/PUCCH DMRS for pi/2 modulation, new DMRS sequences may be specified to reduce the PAPR to the same level as for data symbols. In some aspects, for length 6 computer-generated sequences (CGS), 8-PSK may be used.

In Rel-15 NR, for the case of pi/2 BPSK modulated DFT-S-OFDM based PUSCH/PUCCH, the corresponding demodulation reference signals (DMRSs) may be generated in the frequency domain based on computer-generated sequences (CGS) mapped to QPSK constellation for the case of resource allocation of up to 3 physical resource blocks (PRBs) or based on extended Zadoff-Chu sequences for larger resource allocations. For the case when pi/2 BPSK modulation is used for data, the PAPR of the DMRS is degraded compared to the data especially when pulse shaping is used.

Techniques discussed herein can be used for low PAPR reference signal design for DFT-S-OFDM based PUSCH/PUCCH with pi/2 BPSK modulation for large and small resource allocation.

FIG. 2illustrates example type I and type II DMRS, in accordance with some aspects. In NR Rel-15, two different DMRS types were designed namely Type-1 DMRS (202and204) and Type-2 DMRS (206and208) which are shown inFIG. 2.

For the single symbol case, Type 1 DMRS uses a comb-2 structure with 2 CDM-Groups and length-2 FD-OCC per pair of alternating REs in each CDM-Group, while Type 2 DMRS uses a comb-3 structure with 3 CDM-Groups and length-2 FD-OCC per pair of adjacent REs in each CDM-Group. The length-2 FD-OCC is given by [1 1, 1 −1].

For Uplink DMRS, when the DFT-S-OFDM waveform is used, only Type 1 DMRS is used in Rel-15 NR. For this case, the DMRS base sequence is generated in the frequency domain according to the following:

(a) Case I (Small Resource Allocation): For base sequences of length {6, 12, 18, 24} computer-generated sequences mapped to QPSK constellation are used. For length 30, the sequence is also constant modulus and is based on points chosen from the unit circle in the I/Q plane.

(b) Case II (Larger Resource Allocation): For base sequences of length 36 or larger, cyclically extended Zadoff-ChuZC) sequence is used.

In some aspects, the base sequences are divided into u∈{1, . . . , 30} each containing a single base sequence for sequence length up to 5scRB(where NscRB=12 for NR) and two base sequences for larger sequence length where v∈{0,1} is the base sequence number. In some aspects, the DMRS sequences are generated in the frequency domain i.e., they are not DFT-spread and are constant modulus signals in the frequency domain. In the case when pi/2-BPSK is used for modulating the PUSCH/PUCCH, the PAPR of the data becomes much lower than of the ZC or CGS based DMRS. In this IDF, we propose sequence design for the case of PUSCH/PUCCH when pi/2 BPSK modulation and DFT-s-OFDM waveform is used. We discuss sequence design for the aforementioned cases separately.

In some embodiments, for the case of Rel-16 NR, the DMRS for pi/2 BPSK modulated PUSCH and PUCCH can be generated in the time domain as a binary sequence, mapped to a pi/2 BPSK constellation and then transmitted after DFT-spreading and OFDM symbol generation similar to PUSCH/PUCCH. For this case, a Type 1 DMRS mapping in the frequency domain, with the following sequence options can be used:

(a) Case I (Resource Allocations of 1-4 PRB): Sequence lengths {6, 12, 18 and 24} use binary CGS sequences; and

(b) Case II (Resource Allocations of more than 4 PRB): Sequence lengths of 30 and above use PN sequences based on Gold Code.

In some aspects, the mapping of the binary sequence b(i) to pi/2 BPSK sequence d(i) is defined according to the following equation:

In some aspects, after DFT-spreading of the pi/2-BPSK modulated DMRS sequence, frequency-domain pulse/spectrum shaping can be applied.

Sequence Design for Case I (Small Resource Allocation. 1-4 PRB)

FIG. 3is a block diagram of an example system300for generating computer-generated sequences (CGS), in accordance with some aspects. Referring toFIG. 3, system300can include circuitry, interfaces, logic, and code configured to perform the functions referenced as302,304,306,308,310,312, and314.

For the case of resource allocation of less than 5 PRB, the following techniques performed by system300may be used in connection with the design of computer-generated sequences (CGS). In one embodiment of this invention, a method as shown inFIG. 3can be used.

As an example of the method shown inFIG. 3, the CGS generation may start with the smallest, i.e., length 6, sequence design. Then based on the sequences designed in this case, the length 12 sequences are designed such that cross-correlation between chosen length 6 and length 12 sequences are minimized (e.g., at312and314). Similarly, for length 18 sequence design, the cross-correlation between the selected length 6, 12 sequences and length 18 sequences are minimized and for length 24, the cross-correlation between chosen length 6, 12, 18 sequences and length 24 sequences are minimized.

In one embodiment, the function xCorr(⋅) inFIG. 3measures the maximum linear cross-correlation in the time domain after OFDM symbol generation between two sequences. Furthermore, the maximum linear cross-correlation between the first sequence and all possible shifted and zero-padded versions (in the frequency domain) of the second sequence where the shifts are in multiples of 6 subcarriers and replicate the impact of non-overlapping frequency allocation for all sequences. The methodology for evaluation of autocorrelation and frequency domain shift is illustrated inFIG. 4.

FIG. 4is a block diagram of an example system400for performing linear cross-correlation in the time domain, in accordance with some aspects. Referring toFIG. 4, the system400can initiate the linear cross-correlation processing using time-domain binary sequences402. The time-domain binary sequences are then modulated using pi/2-BPSK modulation404and discrete Fourier transformation (DFT)406to obtain frequency domain complex sequences408. The frequency-domain complex sequences are then used for OFDM symbol generation410, and the linear cross-correlation in the time domain412is applied to the generated OFDM symbols.

The function ƒT(⋅) denotes a shifting of the sequence in the frequency domain. In one embodiment, the shifting can be done after mapping the complex frequency domain sequence to alternate sub-carriers after multiplying with OCC i.e., after Type 1 DMRS resource mapping. The reference point is subcarrier zero of the lowest numbered sub-carrier in the UE's uplink resource allocation.

FIG. 5inFIG. 6illustrate example frequency domain complex sequences500and600that can be used for linear cross-correlation, in accordance with some aspects.

As an example, the different cases for ƒT(⋅) for sequences with the same or different lengths are illustrated inFIG. 5andFIG. 6. In some aspects, use cases can be generalized to sequences of any two lengths. The sequences are then mapped to the subcarriers based on Type 1 DMRS mapping and linear cross-correlation is calculated in the time domain after OFDM symbol generation (as seen inFIG. 4).

In another embodiment, in addition to linear cross-correlation of a sequence with equal and smaller length sequences, circular cross-correlation may also be evaluated. Final cross-correlation, i.e., max(xCorr(⋅)) for a given sequence is the maximum linear cross-correlation values among all shifts and all chosen sequences of shorter length. Finally, the sequence with a minimum of this value is chosen in each iteration.

The sequence design in this embodiment depends on the values of the metric Mlwhich is selected. The metric can be selected to optimize sequence design and improve channel estimation performance. The following aspects discuss example selection choices for the metric.

In some aspects, the metric can be chosen to be the minimization of frequency domain PAPR (FD-PAPR). The FD-PAPR may be is defined as the ratio of maximum to mean power of the pi/2 BPSK-modulated sequence in the frequency domain after DFT spreading. Minimizing FD-PAPR may leave the option for an overall non-flat power profile even with some zero power samples. An example of sequences generated using this metric (i.e., FD-PAPR minimization) with K=30 sequences each for lengths L={6, 12, 18 and 24} are illustrated in Tables 1-4 below.

In another embodiment of this invention, the metric can be a minimization of the following ratio:

wherePlis the vector of powers of the reference signal sequence in the frequency domain after pi/2 BPSK modulation and DFT-spreading. The value of p can be determined as follows: (a) sort the values inPlin ascending order, and (b) select the n-th value in this sorted set and assign to p. The value of n can be {2, 3, 4, 5 . . . }. The significance of n is that it allows the frequency domain signal to possibly have n number of zero power samples.

Note that when this metric is minimized with n=2, one zero power sample may still be allowed in the frequency domain. An example of sequences generated using this metric (Max to 2ndMin Power Ratio) with K=30 sequences each for lengths L={6, 12, 18 and 24} and n=2 are illustrated in Tables 5-8 below.

In another embodiment of this invention, the metric can be the maximization of the Pth percentile power of the frequency domain samples of the reference signal after pi/2-BPSK modulation and DFT-spreading, where P={10, 20, 30, 40, 50}.

An example of sequences generated using this metric with K=30 sequences each for lengths L={6, 12, 18 and 24} and P=10 is provided in Tables 9-12 below.

An example of sequences generated using this metric with K=30 sequences each for lengths L={6, 12, 18 and 24} and P=40 is provided in Tables 13-16 below.

In one embodiment, the value K of a number of sequence groups can be less than 30 (as in Rel-15 NR). In one embodiment, the sequences may be selected by computing cyclic auto-correlation of sequence d(i) according to the following equation:

In some aspects, the set of sequences can be selected to searching the sequence that ‘n’ non-zero elements R(j) for j≠0 which has x times value lower that R(j) for j=0, i.e. R(j)/R(0)≤x. The value of ‘n’ can vary according to the following order ‘n’=0, 1, 2, etc.

FIG. 7is an example graph700of an auto-correlation sequence, in accordance with some aspects. The example of the sequence, which has n=1 and x=−3 dB, is shown inFIG. 7.

In another example embodiment, the sequence can be selected to minimize the sum of the elements of signal auto-correlation function d(i)=argmin Σj=0n−1R(j).

In another embodiment, computer-generated sequences can be chosen based on the frequency domain properties of π/2 BPSK modulated DFT-spread binary sequences that correspond to previous time-domain autocorrelation properties. For example, sequences that are perfectly flat in terms of frequency-domain power yield perfect autocorrelation with R(j)≠0; j=0 and R(j)=0, j≠0.

Similarly, for sequences length N, which can be decomposed into two sequences, each with flat power profile in the frequency domain, yield autocorrelation with two peaks such that R(j)≠0; j=0, N/2 and R(j)=0 otherwise.

This property is a direct consequence of the linearity of the DFT operation and that the autocorrelation of the two superposed sub-sequences which form the sequences are also superposed. Similarly, sequences that can be decomposed into three sub-sequences, each with a flat power in the frequency domain will have almost perfect autocorrelation with 3 peaks in the time domain at lags 0, N/3, and 2N/3, respectively. These sequences are defined to be sequences with almost-perfect autocorrelation. Examples of such sequences are illustrated inFIG. 8.

FIG. 8illustrates example graphs800with different samples of auto-correlation sequences, in accordance with some aspects.

Based on this observation, sequences with almost perfect autocorrelation or ones that can be decomposed into two/three or four sub-sequences with flat or relatively power profiles in the frequency domain may be selected for DMRS generation. Note that for channel estimation using such sequences, if adjacent samples are combined (for example in the two-level sequence case), the time domain autocorrelation of the sequences is further improved. Such sequences are further termed as frequency complementary sequences. For selecting such sequences an exhaustive search over all π/2-BPSK modulated binary sequences is conducted as shown in the previous figure with the metric being the levels of the sequences and final choice is based on pairwise partial cross-correlation.

An example of sequences generated using this method with K=30 sequences each for lengths L={12, 18 and 24} is provided in Tables 17-19 below.

For the case of length-12 CGS the sequence is generated as follows:

The binary sequence b(0), b(1), . . . , b(11) is chosen from the u-th row of the following Table 17.

For the case of length-12 CGS the sequence is generated as follows:

The binary sequence b(0), b(1), . . . , b(17) is chosen from the u-th row of the following Table 18.

For the case of length-12 CGS the sequence is generated as follows:

The binary sequence b(0), b(1), . . . , b(23) is chosen from the u-th row of the following Table 19.

FIG. 9illustrates example QPSK constellations900, in accordance with some aspects. In another embodiment, CGS sequences of length 6 for the case of 1 PRB allocation do not use binary sequences with π/2 BPSK modulation. Instead, sequences are generated using a π/4-QPSK constellation as shown inFIG. 9. The sequences are directly DFT-spread and mapped to REs using DMRS type 1 mapping.

In some aspects, for π/4-QPSK, two QPSK constellations are used wherein one constellation uses the real/imaginary axis (as shown by the black circles) while the other constellation is rotated in phase by π/4 on the unit circle (as shown by the blue circles). For such sequences, one sample uses the black dot constellation while the following sample uses the dot-circle constellation as seen inFIG. 9. Note that these sequences are a subset of the possible sequences that can be generated using an 8-PSK constellation.

In some aspects, for length 6 CGS a set K=30 π/4-QPSK modulated sequences are given by

In another embodiment, length 6 CGS sequences for 1 PRB allocation are generated from a 16-PSK constellation in the time domain, DFT-Spread and mapped to the frequency domain resources using Type 1 DMRS mapping. For length 6 CGS a set K=30 16-PSK modulated sequences are given by ru(n)=ejπϕ(n)/8; n=0, . . . , 5 and are illustrated in Table 21 below.

In another embodiment of this invention, length 6 CGS sequences for 1 PRB allocation are generated from an 8-PSK constellation in the time domain, DFT-Spread and mapped to the frequency domain resources using Type 1 DMRS mapping. For length 6 CGS a set K=30 8-PSK modulated sequences are given by ru(n)=ejπϕ(n)/8; n=0, . . . , 5 and are illustrated in Table 22 below.

In another embodiment of this invention, length 6 CGS sequences for 1 PRB allocation are generated from an 8-PSK constellation in the time domain, DFT-Spread and mapped to the frequency domain resources using Type 1 DMRS mapping. In this case, the chosen sequences provide low PAPR for both comb 0 and comb 1 i.e., when mapped to even or odd subcarriers.

For length 6 CGS a set K=30 8-PSK modulated sequences with Rel-15 Type mapping and good PAPR for both port 0 (comb 0) and port 2 (comb 1) are given by ru(n)=ejπϕ(n)/8; n=0, . . . , 5 and are illustrated in Table 22-a below.

In another embodiment, length 6 CGS sequences for 1 PRB allocation are generated from an 8-PSK constellation in the time domain. The Type 1 comb mapping is implemented using pre-DFT TD-OCC and block repetition. For any given length-6 sequence X, Port 0⇒DFT([X; X]) Port 2⇒DFT([X;−X]).

For length 6 CGS a set K=30 8-PSK modulated sequences with the TD-OCC based port mapping and good PAPR for both port 0 (comb 0) and port 2 (comb 1) are given by ru(n)=ejπϕ(n)/8; n=0, . . . , 5 and are illustrated in Table 22-b below.

In some embodiments, based on the CGS sequences generated using any of the above metrics, additional sequences can be generated using the following operations on the sequence:

(a) Frequency domain cyclic shift of the generated sequence. In one embodiment, the cyclic shift which is multiple of 6 subcarriers may be excluded in the generation procedure to avoid high cross-correlation between partially overlapping resource allocation in the frequency domain.

(b) Time-domain cyclic shifts of the pi/2 BPSK-modulated sequence, i.e. d′(j)=d(mod(j+offset, n)). In one embodiment, the cyclic shift defined by parameter offset which has a value lower the pre-determined threshold ‘y’ and larger than pre-determined threshold ‘n-y’ may not be considered to accommodate propagation delay difference between different UEs in different cells. In one example, the threshold ‘y’ can be selected according to the CP duration of the DFT-s-OFDM signal.

(c) Repetition of the generated sequence in time/frequency.

Complementary Sequences

In another embodiment, for the case of two-symbol DMRS, i.e., DMRS occupying two adjacent symbols or DMRS configuration with two or more symbols, complementary sequences (e.g., a, b, etc.) can be used. The complimentary DMRS signal can be defined to have a sum of auto-correlation function close to the delta function. For example, for two sequences da and db, the sum of auto-correlation function can be defined as follows: R(j)=Rda(j)+Rdb(j).

In one example, the following condition may be fulfilled, where x is pre-determined threshold:

In another example, x=0.

The example of the sequence da and db assignment is shown inFIG. 10.

In another embodiment, complementary sequences can be chosen such that the combined autocorrelation of the two sequences have almost-perfect autocorrelation as defined before. Examples of such complementary sequences are shown in the following Tables 23-31. For length 6 CGS with π/4 QPSK modulation, the sequences are given by

For the case of CGS sequences of length 12, 18 and 24, the complementary sequences are given in the following tables for a case of binary CGS using π/2-BPSK modulation.

For the case of CGS sequences of length 12, 18 and 24, the complementary CGS sequences are given in the following tables.

In another embodiment of this invention, for the case of CGS sequences of length 12, 18 and 24 which were agreed in RAN WG1 NRAH1901 and presented in R1-1901362, a set of complementary sequences may be chosen from the set of sequences in R1-1901362 i.e., for each sequence in the sets of sequences provided in R1-1901362, a corresponding sequence is selected from the same set such that the frequency domain properties of the two sequences when used in adjacent DMRS symbols or adjacent occurring DMRS symbols in time domain. In this case, this deterministic choice of sequences behaves similar to a fixed group-hopping pattern. The following tables provide an example of complementary sequences chosen from the set of 30 sequences for length 12 (Table 1), 18 (Table 2) and 24 (Table 3) from R1-1901362. The indexing is with reference to the indexing provided in R1-1901362 and can also be found in the first two columns of Tables 29-31.

Sequence Group Hopping when Transform Precoding is Enabled

In one embodiment, when transform precoding is enabled and π/2-BPSK modulated PUSCH/PUCCH is used, for a case of smaller resource allocation of 1-4 PRBs, sequence hopping can be employed where the CGS sequences to be used for each symbol is determined as follows:

In one embodiment, per-symbol group hopping can be enabled where ƒgh=(Σm=072mc(8(Nsymbslotns,ƒu+l)+m)) mod 3 0,

where Nsymbslot, ns,ƒuare defined in TS 38.211 (v15.1.0) and 1 is the symbol number within the slot. The gold sequence c(i) is defined in TS 38.211 (v15.1.0), section 5.2.1 and may be initialized with cinit=└nIDRS/30┘.

In one embodiment, when two symbol DMRS is used, per-symbol-pair group hopping can be enabled using ƒgh=(Σm=072mc(8(Nsymbslotns,ƒu+l)+m)) mod 3 0; l=l+l′, wherelis the DMRS position within the slot and is defined in Tables 6.4.1.1.3-3/4 of TS 38.211 (v15.1.0) and l′∈{0,1} is the time domain DMRS symbol index defined in TS 38.211 (v15.1.0). In another embodiment, for the case when l′=1, i.e., for the second time domain DMRS symbol, the sequences are chosen from the set of corresponding complementary sequences relative to the primary sequence chosen for the l′=0 i.e., the first DMRS symbol.

In another embodiment, per-symbol-pair group hopping can be enabled using ƒgh=(Σm=072mc(8(Nsymbslotns,ƒu+l)+m)) mod 3 0, where for every pair of adjacent occurring DMRS symbols, l is the symbol index of the first occurring DMRS symbol of the pair.

In another embodiment, when per-symbol-pair group hopping is used, for every pair of adjacent occurring DMRS symbols a deterministic hopping pattern can be chosen i.e., sequence A can be used in the first symbol of the pair while a corresponding sequence B can be used in the second symbol of the pair, where sequence A and B pairs are pre-determined for example as in Tables 32-34. In another example, the complementary sequence B can be a sequence that belongs to a different set of sequences than set A as in previous tables. The choice of one of 30 pairs is determined by u for each slot. Furthermore, in the case of more than two DMRS symbols in the slot, group hopping is used to determine the sequence sets in the second pair of symbols. For example, if there are four DMRS symbols in the slot, the first two symbols can use sequence pairs A and B while the second two symbols can use pairs C and D where the choice of each pair is based on per-symbol pair sequence hopping as above.

In one embodiment, per-slot group hopping can be enabled using ƒgh=(Σm=072mc(8(Nsymbslotns,ƒu)+m)) mod 3 0.

In another embodiment, per-slot group hopping can be enabled using ƒgh=(Σm=072mc(8(Nsymbslotns,ƒu+l)+m)) mod 3 0, where for every slot, l is the symbol index of the first occurring DMRS symbol in the slot.

In another embodiment, when per-slot group hopping is used, for every pair of adjacent occurring DMRS symbols a deterministic hopping pattern can be chosen i.e., sequence A can be used in the first symbol of the pair while a corresponding sequence B can be used in the second symbol of the pair, where sequence A and B pairs are pre-determined for example as in Tables 32-34. In another example, the complementary sequence B can be a sequence that belongs to a different set of sequences than set A as in previous tables. The choice of one of 30 pairs may be determined by u for each slot. Furthermore, in case of more than two DMRS symbols in the slot, the same pattern is repeated i.e., symbols 1 and 2 use sequences A and B respectively; symbols 3 and 4 use sequences A and B respectively.

In another embodiment, the Gold sequence in the above embodiments can be initialized by cinit=└(nIDRS+nSCID)/30┘.

In yet another embodiment, the Gold sequence in the above embodiments can be initialized by cinit=└(nIDRS,nSCID)/30┘.

In some aspects, two RS IDs are configured by higher layer parameters nPUSCH-Identity0, nPUSCH-Identity1 and one of them is selected by using nSCID. Modification of DMRS indication table to jointly signal port and nSCIDis proposed in the following description and applies to small resource allocation as well.

For all the embodiments above, in yet another embodiment, the value of sequence hopping parameter v=0, i.e., sequence hopping is disabled.

Sequence Design for Case II (Larger Resource Allocation)

For pi/2 BPSK-modulated PUSCH or PUCCH DMRS with resources allocations larger than 4 PRBs, Gold Code based binary PN sequences as in Rel-15 NR CP-OFDM based PUSCH DMRS are used with the following initialization:

cinit=(217(Nsymbslotns,ƒμ+l+1)(2NID+1)+2NID)mod 231, where the sequence generation using Gold sequences is defined in TS 38.211 (v15.1.0), Section 5.2.

In another embodiment, the DMRS sequence can be initialized with cinit=(217(Nsymbslotns,ƒμ+l+1)(2NIDnSCID+1)+2NIDnSCID+nSCID) mod 231, where the scrambling ID i.e., nSCID∈{0,1} can be signaled as follows:

In one embodiment, the nSCID∈{0,1} can be signaled dynamically by using a bit in DCI 0_0 or 0_1 for the case when transform precoding for UL is enabled by RRC configuration.

In another embodiment, the nSCID∈{0,1} can be signaled to the UE dynamically in the DCI by using entries in the DMRS antenna port indication tables 7.3.1.1.2-6 and 7.3.1.1.2-7 in TS 38.212 (v15.1.0).

In one embodiment of this embodiment, for maxLength=1, when one symbol front-loaded DMRS is used and only one DMRS port per CDM group is supported i.e., only port 0 and port 2 from TS 38.211 (v15.1.0) Table 6.4.1.1.3-1 are supported, then Table 7.3.1.1.2-6 in TS 38.212 (v15.1.0) can be modified as follows in Table 35:

In one embodiment, for maxLength=1, when one symbol front-loaded DMRS is used and two DMRS ports per CDM group is supported as in TS 38.211 (v15.1.0), Table 6.4.1.1.3-1, then Table 7.3.1.1.2-6 in TS 38.212 (v15.1.0) can be extended as follows in Table 36 by increasing the bit-width by 1 bit:

In another embodiment, for maxLength=2, when up to 2 front loaded DMRS symbols are used and ports 0, 2, 4 and 6 from TS 38.211 (v15.1.0) Table 6.4.1.1.3-1, i.e., 2 orthogonal ports per CDM group are supported, Table 7.3.1.1.2-6 TS 38.212 (v15.1.0) can be modified as follows in:

In another embodiment of this embodiment, for maxLength=2, when up to 2 front-loaded DMRS symbols are used and ports 0-7 from TS 38.211 (v15.1.0) Table 6.4.1.1.3-1, i.e., 4 orthogonal ports per CDM group are supported, Table 7.3.1.1.2-6 TS 38.212 (v15.1.0) can be modified as follows:

In this case, the scrambling ID-based initialization is allowed only for the case 1 symbol front-loaded DMRS.

In another embodiment, for maxLength=2, when up to 2 front-loaded DMRS symbols are used and ports 0 and 2 TS 38.211 (v15.1.0) Table 6.4.1.1.3-1, i.e., 1 orthogonal ports per CDM group are supported, Table 7.3.1.1.2-6 TS 38.212 (v15.1.0) can be modified as follows: Table 39:

In another embodiment, the bit-width can be reduced to 3 in this case and no reserved entries are used.

In another embodiment of this invention, the nSCIDcan be used to configure one of two possible sequences where the better sequence is configured for use, and better is defined as one of:

(a) The gold sequence which after π/2-BPSK modulation and DFT precoding has a flatter frequency response with flatter being defined as the ratio of the minimum sample power to the maximum sample power; and

(b) The gold sequence which after π/2-BPSK modulation has lower energy in the autocorrelation function across the first X lags after the zero-th lag where X can be defined as 10%, 20%, 30% or 40% of the total number of lags.

Support of Multiple Antenna Ports

To support MU-MIMO and SU-MIMO transmission scenarios with multiple MIMO layers, multiple orthogonal DMRS sequences may be supported to facilitate channel estimation on each layer while mitigating interference from other DMRS sequences transmission. According to an example embodiment, additional DMRS sequence which is orthogonal to the sequence, proposed above can be obtained by using an alternative approach to generate the pi/2 BPSK sequence as shown in the equation below, where λ=0 for the 1st DMRS ports and λ=1 for the 2nd DMRS port:

The cover code (w1, w2, w3, w4) can be used to provide a larger number of orthogonal DMRS sequences as follows:

In another embodiment, for large resource allocations, an M-PSK constellation (with numbered constellation points) in the time domain may be used along with a binary Gold Code based PN sequence with c_init as above configured to each UE. In one embodiment, a UE can start modulation with the 1st constellation point. In another embodiment, the constellation starting point is configured to the UE by DCI. When a sequence bit is 1, the bit is modulated using the next clockwise constellation point. If a bit is zero, the bit is modulated using the next anti-clockwise point. The modulation of the next bit may be clockwise or anti-clockwise w.r.t the current state (constellation point).

In another embodiment, the Rel-16 UL DMRS sequences can be configured to the UE for PUSCH scheduled by DCI format 0_1 or for PUSCH scheduled by DCI format 0_0 in the UE specific search space with CRC scrambled by C-RNTI, MCS-C-RNTI or CS-RNTI.

FIG. 11illustrates a block diagram of a communication device such as an evolved Node-B (eNB), a next generation Node-B (gNB), an access point (AP), a wireless station (STA), a mobile station (MS), or a user equipment (UE), in accordance with some aspects and to perform one or more of the techniques disclosed herein. In alternative aspects, the communication device1100may operate as a standalone device or may be connected (e.g., networked) to other communication devices.

Circuitry (e.g., processing circuitry) is a collection of circuits implemented in tangible entities of the device1100that include hardware (e.g., simple circuits, gates, logic, etc.). Circuitry membership may be flexible over time. Circuitries include members that may, alone or in combination, perform specified operations when operating. In an example, the hardware of the circuitry may be immutably designed to carry out a specific operation (e.g., hardwired). In an example, the hardware of the circuitry may include variably connected physical components (e.g., execution units, transistors, simple circuits, etc.) including a machine-readable medium physically modified (e.g., magnetically, electrically, moveable placement of invariant massed particles, etc.) to encode instructions of the specific operation.

In connecting the physical components, the underlying electrical properties of a hardware constituent are changed, for example, from an insulator to a conductor or vice versa. The instructions enable embedded hardware (e.g., the execution units or a loading mechanism) to create members of the circuitry in hardware via the variable connections to carry out portions of the specific operation when in operation. Accordingly, in an example, the machine-readable medium elements are part of the circuitry or are communicatively coupled to the other components of the circuitry when the device is operating. For example, any of the physical components may be used in more than one member of more than one circuitry. For example, under operation, execution units may be used in a first circuit of a first circuitry at one point in time and reused by a second circuit in the first circuitry, or by a third circuit in a second circuitry at a different time. Additional examples of these components with respect to the device1100follow.

In some aspects, the device1100may operate as a standalone device or may be connected (e.g., networked) to other devices. In a networked deployment, the communication device1100may operate in the capacity of a server communication device, a client communication device, or both in server-client network environments. In an example, the communication device1100may act as a peer communication device in peer-to-peer (P2P) (or other distributed) network environment. The communication device1100may be a UE, eNB, PC, a tablet PC, a STB, a PDA, a mobile telephone, a smartphone, a web appliance, a network router, switch or bridge, or any communication device capable of executing instructions (sequential or otherwise) that specify actions to be taken by that communication device. Further, while only a single communication device is illustrated, the term “communication device” shall also be taken to include any collection of communication devices that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein, such as cloud computing, software as a service (SaaS), and other computer cluster configurations.

Communication device (e.g., UE)1100may include a hardware processor1102(e.g., a central processing unit (CPU), a graphics processing unit (GPU), a hardware processor core, or any combination thereof), a main memory1104, a static memory1106, and mass storage1107(e.g., hard drive, tape drive, flash storage, or other block or storage devices), some or all of which may communicate with each other via an interlink (e.g., bus)1108.

The communication device1100may further include a display device1110, an alphanumeric input device1112(e.g., a keyboard), and a user interface (UI) navigation device1114(e.g., a mouse). In an example, the display device1110, input device1112and UI navigation device1114may be a touchscreen display. The communication device1100may additionally include a signal generation device1118(e.g., a speaker), a network interface device1120, and one or more sensors1121, such as a global positioning system (GPS) sensor, compass, accelerometer, or another sensor. The communication device1100may include an output controller1128, such as a serial (e.g., universal serial bus (USB), parallel, or other wired or wireless (e.g., infrared (IR), near field communication (NFC), etc.) connection to communicate or control one or more peripheral devices (e.g., a printer, card reader, etc.).

The storage device1107may include a communication device-readable medium1122, on which is stored one or more sets of data structures or instructions1124(e.g., software) embodying or utilized by any one or more of the techniques or functions described herein. In some aspects, registers of the processor1102, the main memory1104, the static memory1106, and/or the mass storage1107may be, or include (completely or at least partially), the device-readable medium1122, on which is stored the one or more sets of data structures or instructions1124, embodying or utilized by any one or more of the techniques or functions described herein. In an example, one or any combination of the hardware processor1102, the main memory1104, the static memory1106, or the mass storage1116may constitute the device-readable medium1122.

As used herein, the term “device-readable medium” is interchangeable with “computer-readable medium” or “machine-readable medium”. While the communication device-readable medium1122is illustrated as a single medium, the term “communication device-readable medium” may include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) configured to store the one or more instructions1124. The term “communication device-readable medium” is inclusive of the terms “machine-readable medium” or “computer-readable medium”, and may include any medium that is capable of storing, encoding, or carrying instructions (e.g., instructions1124) for execution by the communication device1100and that cause the communication device1100to perform any one or more of the techniques of the present disclosure, or that is capable of storing, encoding or carrying data structures used by or associated with such instructions. Non-limiting communication device-readable medium examples may include solid-state memories and optical and magnetic media. Specific examples of communication device-readable media may include non-volatile memory, such as semiconductor memory devices (e.g., Electrically Programmable Read-Only Memory (EPROM), Electrically Erasable Programmable Read-Only Memory (EEPROM)) and flash memory devices; magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; Random Access Memory (RAM); and CD-ROM and DVD-ROM disks. In some examples, communication device-readable media may include non-transitory communication device-readable media. In some examples, communication device-readable media may include communication device-readable media that is not a transitory propagating signal.

The instructions1124may further be transmitted or received over a communications network1126using a transmission medium via the network interface device1120utilizing any one of a number of transfer protocols. In an example, the network interface device1120may include one or more physical jacks (e.g., Ethernet, coaxial, or phone jacks) or one or more antennas to connect to the communications network1126. In an example, the network interface device1120may include a plurality of antennas to wirelessly communicate using at least one of single-input-multiple-output (SIMO), MIMO, or multiple-input-single-output (MISO) techniques. In some examples, the network interface device1120may wirelessly communicate using Multiple User MIMO techniques.

The term “transmission medium” shall be taken to include any intangible medium that is capable of storing, encoding or carrying instructions for execution by the communication device1100, and includes digital or analog communications signals or another intangible medium to facilitate communication of such software. In this regard, a transmission medium in the context of this disclosure is a device-readable medium.

Although an aspect has been described with reference to specific exemplary aspects, it will be evident that various modifications and changes may be made to these aspects without departing from the broader scope of the present disclosure. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense. This Detailed Description, therefore, is not to be taken in a limiting sense, and the scope of various aspects is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled.