Multi-layer discrete fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM) for single downlink control information (DCI) simultaneous transmission from multiple panels (STXMP)

Abstract

A method, network node and wireless device (WD) for multi-layer discrete Fourier transform (DFT) spread orthogonal frequency division multiplexing (DFT-s-OFDM) for single downlink control information (DCI) simultaneous multipanel transmission (STxMP) are disclosed. According to one aspect, a method in a network node includes determining a first mapping of phase tracking reference signal (PTRS) ports to different spatial layers. The method also includes configuring the WD with multiple PTRS ports for multilayer data transmission with discrete Fourier transform spread orthogonal frequency division multiplexing, DFT-s-OFDM. The method further includes separating PTRS ports for signals received from the WD on different layers according to the first mapping.

Description

[0001]MULTI-LAYER DISCRETE FOURIER TRANSFORM SPREAD ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING (DFT-S-OFDM) FOR SINGLE DOWNLINK CONTROL INFORMATION (DCI) SIMULTANEOUS TRANSMISSION FROM MULTIPLE PANELS (STxMP) TECHNICAL FIELD The present disclosure relates to wireless communications, and in particular, to multi-layer discrete Fourier transform (DFT) spread orthogonal frequency division multiplexing (DFT-s-OFDM) for single downlink control information (DCI) simultaneous multipanel transmission (STxMP). BACKGROUND The Third Generation Partnership Project (3GPP) has developed and is developing standards for Fourth Generation (4G) (also referred to as Long Term Evolution (LTE)) and Fifth Generation (5G) (also referred to as New Radio (NR)) wireless communication systems. Such systems provide, among other features, broadband communication between network nodes, such as base stations, and mobile wireless devices (WD), as well as communication between network nodes and between WDs. The 3GPP is also developing standards for Sixth Generation (6G) wireless communication networks. Numerology In the time domain, NR downlink (DL) and uplink (UL) transmissions are organized into equally sized subframes of 1 ms each. A subframe is further divided into multiple slots of equal duration. The slot length depends on the numerology (i.e., on the subcarrier spacing (SCS) and the cyclic prefix (CP)). For 15 kHz SCS, there is only one slot per subframe. In general, for 15 ∙ 2ఓkHz SCS, where ^^ ∈ ^0,1,2,3,4^ is the SCS configuration, there are 2ఓslots per subframe. Each slot consists of 14 symbols (unless extended CP is configured for which each slot consists of 12 symbols). In the frequency domain, a system bandwidth is divided into resource blocks (RBs) each corresponding to 12 contiguous subcarriers. One subcarrier during one symbol interval forms one RE, which is the smallest physical resource in NR. Bandwidth parts NR is designed to support very large channel bandwidths (up to 400 MHz), but not all WDs are capable of handling such large channel bandwidth. For this reason, a WD may operate in a contiguous subset, which may not be centered around the carrier frequency, of the common resource blocks (CRBs) within a cell. This subset is called a bandwidth part (BWP). A WD may be configured with up to four DL BWPs and up to four UL BWPs per serving cell, where different numerologies may be configured for different BWPs. In the case of supplementary uplink (SUL), there may be up to four additional UL BWPs on the SUL carrier The starting position and bandwidth of a BWP is radio resource control (RRC) configured. Only one DL and one UL BWP may be active at the same time per serving cell. For time division duplex (TDD), the active DL and UL BWP must share the same center frequency. For frequency division duplex (FDD), this is not required. In the DL, a WD does not expect to receive, e.g., physical downlink control channel (PDCCH) and / or physical downlink shared channel (PDSCH) outside the active BWP. In the UL, a WD is not expected to transmit, e.g., physical uplink control channel (PUCCH) and / or PUCCH outside of the active BWP. The network (NW), such as via a network node, may switch active BWP, e.g., via downlink control information (DCI) signaling. For example, DCI Format 1_1 (used for scheduling DL data transmissions) and DCI Format 0_1 (used for scheduling UL data transmissions) includes a 1 or 2 bit “BWP indicator” field for switching BWPs for DL and UL transmissions, respectively. The RBs within a BWP are known as physical resource blocks (PRBs) and are numbered starting from 0. When the NW schedules a DL or UL transmission, a set of virtual resource blocks (VRBs), which are mapped to PRBs, are signaled. In the DL, interleaved and non-interleaved mapping is supported. In the UL, only non-interleaved mapping is supported, for which there is a one-to-mapping between VRBs and CRBs. In what follows, unless otherwise stated, assume a one-to-one mapping between VRBs and PRBs, and simply use RBs to refer to both VRBs and CRBs. PUSCH The channel that carries data in the NR UL is called the physical uplink shared channel (PUSCH), which may be dynamically or semi-statically scheduled. In NR, there are two possible waveforms that may be used for PUSCH: cyclic prefix orthogonal frequency division multiplex (CP-OFDM) and discrete Fourier transform (DFT)-S- OFDM. The time-and-frequency domain resource allocation of said PUSCH is signaled by the NW to the WD. Furthermore, there are two transmission schemes specified for PUSCH: codebook (CB)-based precoding and non-codebook (NCB)-based precoding. PUSCH scheduling UL data transmissions may be dynamically scheduled by a dynamic grant (DG) (via DCI signaling) or semi-statically scheduled by a configured grant (CG) (via RRC signaling). PUSCH scheduling with DG PUSCH transmissions may be dynamically scheduled by sending from the NW to a WD a DG via the DCI in PDCCH. After decoding the DCI, the WD transmits data (unless the transmission buffer is empty) over PUSCH according to the DG. The DG may be carried, e.g., over DCI Format 0_1 (non-fallback format) or DCI Format 0_0 (fallback format). The non-fallback format supports all NR features but is larger in size compared to the fallback format which offers limited functionality but with a smaller overhead. Contents that are common for both the non-fallback and fallback formats include, e.g., BWP indication, frequency-domain resource allocation, time-domain resource allocation, transport-block related information (modulation and coding scheme (MCS), new data indicator (NDI), and redundance version (RV)), and PUSCH power-control parameters. Contents that are only in the non-fallback format (DCI Format 0_1) include, e.g., multi-antenna related information. PUSCH scheduling with CG NR supports two schemes for scheduling PUSCH transmissions without a DG: ^ CG type 1: PUSCH transmission parameters, periodicity, and offset is RRC configured and PUSCH is periodically transmitted; and ^ CG type 2: PUSCH periodicity and offset is RRC configured but PUSCH transmission is activated / deactivated using dynamic signaling. With CG type 1, PUSCH transmission parameters are RRC configured (see ConfiguredGrantConfig IE in 3GPP Technical Standard (TS) 38.331). The PUSCH periodicity and offset are also RRC configured, which allows the NW to control when the WD should transmit PUSCH. With CG type 2, the PUSCH periodicity and offset are RRC configured. Activation and deactivation of the PUSCH transmission is via PDCCH scrambled by CS-radio network temporary identifier (RNTI) and PUSCH transmission parameters are signaled via DCI in said PDCCH (e.g., DCI Format 0_0 or DCI Format 0_1). PUSCH waveform NR supports two different PUSCH waveforms: CP-OFDM and DFT-S-OFDM. The NW decides the waveform for PUSCH via RRC signaling. Specifically, for PUSCH scheduled by a DG, if the higher-layer parameter transformPrecoder in PUSCH-Config (see below snippet of ASN code from 3GPP Technical Standard (TS) 38.331 version 17.2.0) is enabled, the waveform is DFT-S-OFDM; if it is disabled, the waveform is CP- OFDM. If this field is not present, the WD applies the value of the higher-layer parameter msg3-transformPrecoding in RACH-ConfigCommon. PUSCH-Config ::= SEQUENCE { … transformPrecoder ENUMERATED {enabled, disabled} OPTIONAL, -- Need S … } CP-OFDM CP-OFDM is the baseline UL waveform. With CP-OFDM. non-contiguous frequency allocation is possible, which may simplify UL scheduling. CP-OFDM may also make the receiver less complex compared to DFT-s-OFDM (e.g., simplified channel equalization and layer separation) and supports coherent precoding. In NR 3GPP Technical Release 17 (3GPP Rel-17), CP-OFDM supports up to four-layer UL transmission. DFT-S-OFDM The main benefit with DFT-S-OFDM compared to CP-OFDM is that UL coverage may be improved as higher power-amplifier efficiency is possible due to a lower cubic metric. Drawbacks with DFT-S-OFDM include scheduling restrictions as only contiguous allocation in the frequency domain, for which the number of RBs must be a multiple of 2, 3, and 5, is possible. Furthermore, UL precoding is more restrictive, as coherent precoding (i.e., coherent combining of layers over antenna ports) is not possible. In fact, only single- layer UL transmission is supported with DFT-S-OFDM in NR 3GPP Rel-17. PUSCH precoding For PUSCH scheduled by a DG, the NW configures in RRC the transmission scheme by the higher-layer parameter txConfig in PUSCH-Config IE (see below snippet of ASN code from 3GPP TS 38.331 version 17.2.0). Two transmission schemes are supported: CB-based precoding and NCB-based precoding. CB-based precoding may be used for non-calibrated WDs and / or for FDD (i.e., UL / DL reciprocity does not need to hold). NCB-based precoding, on the other hand, relies on UL / DL reciprocity and is, hence, intended for TDD. PUSCH-Config ::= SEQUENCE { … txConfig ENUMERATED {codebook, nonCodebook} OPTIONAL, -- Need S … codebookSubset ENUMERATED {fullyAndPartialAndNonCoherent, partialAndNonCoherent,nonCoherent} OPTIONAL, -- Cond codebookBased maxRank INTEGER (1..4) OPTIONAL, -- Cond codebookBased … } CB-based precoding With CB-based precoding for the NR uplink, the NW configures the WD to transmit sounding reference signals (SRS) over a number of WD antennas. Based on SRS- based channel measurements, the NW signals a transmit precoding matrix indicator (TPMI), which indicates the transmission rank and precoder that the WD should apply over the WD antennas when transmitting PUSCH. The precoder candidates are tabulated in Clause 6.3.1.5 of 3GPP TS 38.211. CB-based PUSCH is enabled if the higher-layer parameter txConfig in PUSCH- Config IE is set to codebook. For dynamically scheduled PUSCH, CB-based PUSCH transmission may be summarized in the following steps. 1. The WD transmits a sounding reference signal (SRS), configured in an SRS resource set with higher-layer parameter usage in SRS-Config IE set to codebook. Up to two SRS resources (for testing up to two virtualizations / beams / panels) each with up to four ports, may be configured in the SRS resource set. ^ The network node determines the number of layers (i.e., the rank) and a preferred precoder (i.e., TPMI) from a codebook subset based on the received SRS from one of the SRS resources. The codebook subset is configured via the higher-layer parameter codebookSubset in PUSCH-Config IE (see above snippet of ASN code from 3GPP TS 38.331 version 17.2.0), based on reported WD capability, and is one of fully coherent, partially coherent, or non- coherent. 2. If two SRS resources are configured in the SRS resource set, the network node indicates the selected SRS resource via the 1-bit SRS resource indicator (SRI) field in the DCI scheduling the PUSCH transmission. If only one SRS resource is configured in the SRS resource set, the SRI field is not present in the DCI. 3. The network node indicates, via the DCI field “Precoding information and number of layers”, the number of layers and the TPMI. The maximum number of layers is limited by the higher-layer parameter maxRank in PUSCH-Config IE (see above snippet of ASN code from 3GPP TS 38.331 version17.2.0). Demodulation reference signal (DMRS) port(s) associated with the layer(s) are also indicated in DCI via the field “Antenna ports”. Unless UL full-power mode 1 is configured, the number of bits in DCI used for indicating the number of layers (if transform precoding is enabled, the number of PUSCH layers is limited to 1) and the TPMI is determined as follows: - 4, 5, or 6 bits if the number of antenna ports is 4, if transform precoding is disabled, and if the higher-layer parameter maxRank in PUSCH-Config IE is set to 2, 3, or 4 (see Table 1); - 2, 4, or 5 bits if the number of antenna ports is 4, if transform precoding is disabled or enabled, and if the higher-layer parameter maxRank in PUSCH-Config IE is set to 1 (see Table 2); - 2 or 4 bits if the number of antenna ports is 2, if transform precoding is disabled, and if the higher-layer parameter maxRank in PUSCH-Config IE is set to 2 (see Table 3); - 1 or 3 bits if the number of antenna ports is 2, if transform precoding is disabled or enabled, and if the higher-layer parameter maxRank in PUSCH-Config IE is set to 1 (see Table 4); - 0 bits if 1 antenna port is used for PUSCH transmission. 4. The WD performs PUSCH transmission over the antenna ports corresponding to the SRS ports in the indicated SRS resource. Table 1 Precoding information and number of layers, for 4 antenna ports, if transform precoding is disabled and maxRank = 2, 3 or, 4 (reproduced from Table 7.3.1.1.2-2 of 3GPP TS 38.212 version 17.2.0) Bit Bit Bit codebookSu field codebookSubset = field codebookSubset = field bset = mapp fullyAndPartialAndNonC mapp partialAndNonCoh mapp nonCoheren ed to oherent ed to erent ed to t index index index 0 1 layer: TPMI=0 0 1 layer: TPMI=0 0 1 layer: TPMI=0 1 layer: 1 1 layer: TPMI=1 1 1 layer: TPMI=1 1 TPMI=1 … … … … … … 1 layer: 3 1 layer: TPMI=3 3 1 layer: TPMI=3 3 TPMI=3 4 2 layers: TPMI=0 4 2 layers: TPMI=0 4 2 layers: TPMI=0 … … … … … … 9 2 layers: TPMI=5 9 2 layers: TPMI=5 9 2 layers: TPMI=5 10 3 layers: TPMI=0 10 3 layers: TPMI=0 10 3 layers: TPMI=0 11 4 layers: TPMI=0 11 4 layers: TPMI=0 11 4 layers: TPMI=0 12 1 layer: TPMI=4 12 1 layer: TPMI=4 12-15 reserved … … … … 19 1 layer: TPMI=11 19 1 layer: TPMI=11 20 2 layers: TPMI=6 20 2 layers: TPMI=6 … … … … 27 2 layers: TPMI=13 27 2 layers: TPMI=13 28 3 layers: TPMI=1 28 3 layers: TPMI=1 29 3 layers: TPMI=2 29 3 layers: TPMI=2 30 4 layers: TPMI=1 30 4 layers: TPMI=1 31 4 layers: TPMI=2 31 4 layers: TPMI=2 32 1 layer: TPMI=12 … … 47 1 layer: TPMI=27 48 2 layers: TPMI=14 … … 55 2 layers: TPMI=21 56 3 layers: TPMI=3 … … 59 3 layers: TPMI=6 60 4 layers: TPMI=3 61 4 layers: TPMI=4 62-63 reserved Table 2 Precoding information and number of layers, for 4 antenna ports, if transform precoding is disabled / enabled and maxRank = 1 (reproduced from Table 7.3.1.1.2-3 of 3GPP TS 38.212 version 17.2.0) Bit Bit Bit codebookSubs field codebookSubset = field field codebookSub et= mapped fullyAndPartialAndN mappe mappe set= partialAndNon to onCoherent d to d to nonCoherent Coherent index index index 0 1 layer: TPMI=0 0 1 layer: 0 1 layer: TPMI=0 TPMI=0 1 layer: 1 layer: 1 1 layer: TPMI=1 1 1 TPMI=1 TPMI=1 … … … … … … 1 layer: 1 layer: 3 1 layer: TPMI=3 3 3 TPMI=3 TPMI=3 4 1 layer: TPMI=4 4 1 layer: TPMI=4 … … … … 11 1 layer: TPMI=11 11 1 layer: TPMI=11 12 1 layer: TPMI=12 12-15 reserved … … 27 1 layer: TPMI=27 28-31 reserved Table 3 Precoding information and number of layers, for 2 antenna ports, if transform precoding is disabled and maxRank = 2 (reproduced from Table 7.3.1.1.2-4 of 3GPP TS 38.212 version 17.2.0). Bit codebookSubset = Bit codebookSubset = field fullyAndPartialAndNonCoherent field nonCoherent mapped mapped to to index index 0 1 layer: TPMI=0 0 1 layer: TPMI=0 1 1 layer: TPMI=1 1 1 layer: TPMI=1 2 2 layers: TPMI=0 2 2 layers: TPMI=0 3 1 layer: TPMI=2 3 reserved 4 1 layer: TPMI=3 5 1 layer: TPMI=4 6 1 layer: TPMI=5 7 2 layers: TPMI=1 8 2 layers: TPMI=2 9-15 reserved Table 4 Precoding information and number of layers, for 2 antenna ports, if transform precoding is disabled / enabled and maxRank = 1 (reproduced from Table 7.3.1.1.2-5 of 3GPP TS 38.212 version 17.2.0). Bit Bit field field codebookSubset = codebookSubset mapped mapped fullyAndPartialAndNonCoherent = nonCoherent to to index index 0 1 layer: TPMI=0 0 1 layer: TPMI=0 1 layer: 1 1 layer: TPMI=1 1 TPMI=1 2 1 layer: TPMI=2 3 1 layer: TPMI=3 4 1 layer: TPMI=4 5 1 layer: TPMI=5 6-7 reserved NCB-based precoding NCB-based PUSCH is enabled if the higher-layer parameter txConfig in PUSCH- Config IE is set to nonCodebook and is intended for reciprocity-based UL transmission in which SRS precoding is derived at a WD based on CSI-RS received in the DL. Specifically, the WD measures received CSI-RS and deduces a suitable precoder for SRS transmission(s), resulting in one or more (virtual) SRS ports, each corresponding to a spatial layer. A WD may be configured with up to four SRS resources, each with a single (virtual) SRS port, in an SRS resource set with higher-layer parameter usage in SRS- Config IE set to nonCodebook. A WD transmits the up to four SRS resources. The NW measures the UL channel based on the received SRS, selects the preferred SRS resource(s), and indicates the selection via the SRI field in DCI. The WD uses this information to precode PUSCH with a transmission rank that equals the number of indicated SRS resources (and, hence, the number of SRS ports). The size of the SRI field in the DCI format scheduling the PUSCH is: ୫୧୬^^^^౮,ே^^^^^logଶ^^ ^^^ୗୖୗ^^^ ^^ bits. Here, ^^ୗୖୗis the number of number of layers. DMRS for PUSCH DMRS for PUSCH is an UL RS (that consists of a pseudo-random quadrature phase shift keyed (QPSK) sequence for CP-OFDM or a low-peak to average power ratio (PAPR) sequence for DFT-S-OFDM) that is used for demodulating PUSCH such that the receiver (i.e., the network node) may handle time-varying and / or frequency-selective channels. DMRS is confined to the scheduled PUSCH time-and-frequency-domain allocation. The mapping of DMRS to resource elements (REs) is configurable in both the frequency domain and the time domain. In the frequency domain, there are two mapping types: type 1 (comb based) or type 2 (non-comb based). In the time-domain, DMRS may be either single symbol or double symbol, where the latter means that DMRS is mapped in pairs of two adjacent symbols. Furthermore, a WD may be configured with one, two, three, or four single-symbol DMRS, or one or two double-symbol DMRS. In low-Doppler scenarios, one DMRS symbol may be sufficient whereas in high-Doppler scenarios, additional DMRS symbols are required. The frequency-domain starting position of DMRS is the same as the frequency- domain starting position of PUSCH. The time-domain starting position of DMRS depends on the PUSCH mapping type: ^ For PUSCH mapping type A (slot-based scheduling), the first DMRS symbol is in the third or fourth (i.e., symbol 2 or 3) of a slot. ^ For PUSCH mapping type B (non-slot-based scheduling), the first DMRS symbol of a slot is the same as the first PUSCH symbol of a slot. DMRS for PUSCH configuration DMRS for PUSCH is RRC configured through the DMRS-UplinkConfig IE (see below for ASN code in 3GPP TS 38.331 version 17.2.0). DMRS-UplinkConfig ::= SEQUENCE { dmrs-Type ENUMERATED {type2} OPTIONAL, -- Need S dmrs-AdditionalPosition ENUMERATED {pos0, pos1, pos3} OPTIONAL, -- Need S phaseTrackingRS SetupRelease { PTRS-UplinkConfig } OPTIONAL, -- Need M maxLength ENUMERATED {len2} OPTIONAL, -- Need S transformPrecodingDisabled SEQUENCE { scramblingID0 INTEGER (0..65535) OPTIONAL, -- Need S scramblingID1 INTEGER (0..65535) OPTIONAL, -- Need S ..., [[ dmrs-Uplink-r16 ENUMERATED {enabled} OPTIONAL -- Need R ]] } OPTIONAL, -- Need transformPrecodingEnabled SEQUENCE { nPUSCH-Identity INTEGER(0..1007) OPTIONAL, -- Need S sequenceGroupHopping ENUMERATED {disabled} OPTIONAL, -- Need S sequenceHopping ENUMERATED {enabled} OPTIONAL, -- Need S ..., [[ dmrs-UplinkTransformPrecoding-r16 SetupRelease {DMRS- UplinkTransformPrecoding-r16} OPTIONAL -- Need M ]] } OPTIONAL, -- Need R ... } DMRS for PUSCH is configurable with respect to, e.g.: ^ The DMRS frequency-domain mapping type (type 1 or type 2), configured by the higher-layer parameter dmrs-Type (if this parameter is not configured, type 1 is used). Type 1 is comb based with 2 code division multiplex (CDM) groups, whereas type 2 is not comb based with 3 CDM groups. For DFT-S-OFDM, only type 1 is supported. FIG.1 is an illustration of the two DMRS types. Note that there are multiple DMRS ports per CDM group, which are separated using frequency-domain (and time-domain, for double-symbol DMRS) OCC(s): - For single-symbol DMRS, there exist 4 and 6 orthogonal DMRS ports (2 DMRS ports per CDM group, separated using a length-2 frequency domain orthogonal cover code (FD-OCC)) for type 1 and type 2, respectively; - For double-symbol DMRS, there exist 8 and 12 orthogonal DMRS ports (4 DMRS ports per CDM group, separated using a length-2 FD-OCC combined with a length-2 time domain orthogonal cover code (TD-OCC)) for type 1 and type 2, respectively; ^ Any additional DMRS symbols (0, 1, 2 or 3 for single-symbol DMRS and 0 or 1 for double-symbol DMRS), configured by the higher-layer parameter dmrs- AdditionalPosition. The position of additional DMRS depends on the PUSCH mapping type and PUSCH duration according to a predefined table. Note that it is not possible to configure a TD-OCC over additional (i.e., non-contiguous) DMRS. FIG.2 is an example of single-symbol (left part of the figure) and double-symbol (right part of the figure) DMRS with 2 and 1 additional DMRS symbol(s), respectively; ^ The associated phase tracking reference signal (PTRS) (if any), configured by the higher-layer parameter phaseTrackingRS; and ^ The maximum number of adjacent DMRS symbols (1 or 2), configured by the higher-layer parameter maxLength. If transform precoding is disabled (i.e., if the waveform is CP-OFDM), DMRS for PUSCH may be additionally and optionally configured with respect to scrambling ID 0 and 1, configured by RRC parameters scramblingID0 and scramblingID1, respectively, which are used for generating the pseudo-random DMRS sequence. If transform precoding is enabled (i.e., if the waveform is DFT-S-OFDM), DMRS group hopping or sequence hopping may be configured by the higher-layer parameters sequenceGroupHopping and sequenceHopping. If ^^ / 2-binary phase shift keying (BPSK) modulation is not used for PUSCH, the higher-layer parameter nPUSCH-Identity determines the low-PAPR sequence. In NR 3GPP Rel-16, to reduce PAPR for DMRS for CP-OFDM combined with fully coherent precoding, the higher-layer parameter dmrs-Uplink-r16 may be enabled. Doing so makes the DMRS sequence depend on the CDM group, which may be shown to reduce PAPR. If this field is not present, the same DMRS sequence is used over all CDM groups. Furthermore, to reduce PAPR for DMRS for DFT-S-OFDM when ^^ / 2-BPSK is used together with spectrum shaping, two different scrambling seeds may be configured via the higher-layer parameter dmrs-UplinkTransformPrecoding-r16. If this field is not present, the cell ID is used as scrambling seed. DMRS for PUSCH port mapping FIG.2 shows DMRS ports mapped to resource elements within one CDM group. DMRS ports that belong to the same CDM group are separated by a length-2 FD-OCC (and a length-2 TD-OCC, for double-symbol DMRS). Specifically, the DMRS sequence is mapped to the following subcarriers (for DFT-S-OFDM, only DMRS type 1 is supported): ^^ ൌ ^4 ^^ ^ 2 ^^ᇱ ^ ∆, for type 1,6^^ ^ ^^ᇱ ^ ∆, for 2.Here, ^^ is the subcarrier subcarrier within the scheduled PUSCH bandwidth), ^^ ∈ ^0,1,2, … ^, ^^ᇱ∈ ^0,1^, and ∆ is an offset that depends on the CDM group. In Table 5 and Table 6, port-specific parameters for DMRS type 1 and type 2 are given. Here, ^^^^ ^^′^, where ^^ᇱ∈ ^0,1^, is the FD-OCC and ^^^^ ^^′^, where ^^ᇱൌ 0 for single- symbol DMRS and ^^ᇱ∈ ^0,1^ for double-symbol DMRS, is the TD-OCC. Note that DMRS ports in different CDM groups are separated by different offsets and that DMRS ports within the same CDM group are separated through coding. Table 5: Parameters for PUSCH DMRS configuration type 1 (reproduced from Table 6.4.1.1.3-1 of 3GPP TS 38.211). Here, ^^^ denotes the DMRS port. ~pCDM wf ( k^) wt( l^)group ^^k^^ 0 k^^ 1 l^^ 0 l^^ 1^^ 0 0 0 +1 +1 +1 +1 1 0 0 +1 -1 +1 +1 2 1 1 +1 +1 +1 +1 3 1 1 +1 -1 +1 +1 4 0 0 +1 +1 +1 -1 5 0 0 +1 -1 +1 -1 6 1 1 +1 +1 +1 -1 7 1 1 +1 -1 +1 -1 Table 6: Parameters for PUSCH DMRS configuration type 2 (reproduced from Table 6.4.1.1.3-2 of 3GPP TS 38.211). Here, ^^^ denotes the DMRS port. ~pCDM wf ( k^) wt( l^)group ^^k^^ 0 k^^ 1 l^^ 0 l^^ 1^^ 0 0 0 +1 +1 +1 +1 1 0 0 +1 -1 +1 +1 2 1 2 +1 +1 +1 +1 3 1 2 +1 -1 +1 +1 4 2 4 +1 +1 +1 +1 5 2 4 +1 -1 +1 +1 6 0 0 +1 +1 +1 -1 7 0 0 +1 -1 +1 -1 8 1 2 +1 +1 +1 -1 9 1 2 +1 -1 +1 -1 10 2 4 +1 +1 +1 -1 11 2 4 +1 -1 +1 -1 From the transmitter’s perspective, the number of DMRS ports used for PUSCH transmission coincides with the rank, i.e., one DMRS port per transmitted layer. The DMRS port mapping is signaled to the WD from the network node via the field “Antenna ports” in the DCI scheduling the PUSCH. Table 7 and Table 8 give examples of what an indication looks like for DCI Format 0_1, CP-OFDM, single-symbol DMRS type 1, and for transmission rank 1 and 2, respectively. Similar tables may be found in 3GPP TS 38.212 for rank 3 and 4, double-symbol DMRS, and for DMRS type 2. REs, which are associated with a CDM group, that are not used for DMRS may be used for PUSCH. After layer mapping, the DMRS and the associated PUSCH are mapped to physical antennas through PUSCH precoding. Table 7 Antenna ports for single-symbol DMRS type 1, transform precoding is disabled, rank-1 transmission (reproduced from Table 7.3.1.1.2-8 of 3GPP 38.212). Value Number of DMRS CDM group(s) without data DMRS port(s) 0 1 0 1 1 1 2 2 0 3 2 1 4 2 2 5 2 3 6-7 Reserved Reserved Table 8 Antenna ports for single-symbol DMRS type 1, transform precoding is disabled, rank-2 transmission (reproduced from Table 7.3.1.1.2-9 of 3GPP 38.212). Value Number of DMRS CDM group(s) without data DMRS port(s) 0 1 0,1 1 2 0,1 2 2 2,3 3 2 0,2 4-7 Reserved Reserved PTRS for PUSCH In NR, a phase tracking reference signal (PTRS) may be configured for downlink and uplink transmissions in order for the receiver to correct phase noise related errors. The PTRS configuration is WD-specific and the PTRS is associated with one of the DMRS ports used for the PDSCH or PUSCH transmission, meaning that DMRS and its associated PTRS are transmitted using the same precoder and meaning that the modulated symbol used for the PTRS is based on whatever DMRS sequence is configured. It means that there is no specific configuration of the PTRS sequence as it borrows from the DMRS. In UL, for PUSCH scheduled by DCI format 0_0 or by activation DCI format 0_0, the UL PTRS port is associated to DM-RS port 0. For PUSCH scheduled by DCI format 0_1 and DCI format 0_2, the PTRS port to DMRS port association is dynamically indicated in DCI and is described in clause 6.2.2 in GPP TS 38.214. The presence of PTRS is indicated by RRC signaling for UL and DL independently. The uplink and downlink PTRS configurations in 3GPP TS 38.331 v17.2.0 are shown as following. PTRS-DownlinkConfig information element -- ASN1START -- TAG-PTRS-DOWNLINKCONFIG-START PTRS-DownlinkConfig ::= SEQUENCE { frequencyDensity SEQUENCE (SIZE (2)) OF INTEGER (1..276) OPTIONAL, -- Need S timeDensity SEQUENCE (SIZE (3)) OF INTEGER (0..29) OPTIONAL, -- Need S epre-Ratio INTEGER (0..3) OPTIONAL, -- Need S resourceElementOffset ENUMERATED {offset01, offset10, offset11 } OPTIONAL,-- Need S ..., [[ maxNrofPorts-r16 ENUMERATED {n1, n2} OPTIONAL -- Need R ]] } -- TAG-PTRS-DOWNLINKCONFIG-STOP -- ASN1STOP PTRS-UplinkConfig information element -- ASN1START -- TAG-PTRS-UPLINKCONFIG-START PTRS-UplinkConfig ::= SEQUENCE { transformPrecoderDisabled SEQUENCE { frequencyDensity SEQUENCE (SIZE (2)) OF INTEGER (1..276) OPTIONAL, -- Need S timeDensity SEQUENCE (SIZE (3)) OF INTEGER (0..29) OPTIONAL, -- Need S maxNrofPorts ENUMERATED {n1, n2}, resourceElementOffset ENUMERATED {offset01, offset10, offset11 } OPTIONAL, -- Need S ptrs-Power ENUMERATED {p00, p01, p10, p11} } OPTIONAL, -- Need R transformPrecoderEnabled SEQUENCE { sampleDensity SEQUENCE (SIZE (5)) OF INTEGER (1..276), timeDensityTransformPrecoding ENUMERATED {d2} OPTIONAL -- Need S } OPTIONAL, -- Need R ... } -- TAG-PTRS-UPLINKCONFIG-STOP -- ASN1STOP In current NR standards, at most two PTRS ports may be configured per user, which is configured by maxNrofPorts. Furthermore, there may be at most 4 orthogonal PTRS ports in total for MU-MIMO for Type1 DMRS and 6 in total for Type2 DMRS. PTRS are not mapped to resource elements used for DMRS, SSB (Synchronization Signal Block), CSI-RS (Channel State Information Reference Signal), etc. The supported time and frequency densities for PTRS in case of CP-OFDM include: ^ Time densities: 1, ½, or ¼ (i.e., one PTRS symbol every symbol, every 2nd, and every 4thOFDM symbol, respectively); and ^ Freq. densities: ½ or ¼ (i.e., one PTRS subcarrier every 2ndand 4thPRB, respectively). Time and frequency density are associated with DCI parameters, such as MCS (modulation and coding scheme) and scheduled bandwidth (BW) and are specified by Clause 5.1.6.3 in 3GPP TS 38.214 v17.2.0 for DL and clause 6.2.3 in 3GPP TS 38.214 v17.2.0 for UL. PTRS is confined in the scheduling RBs. PTRS for PUSCH CP-OFDM For PUSCH CP-OFDM, PTRS is mapped on one DMRS subcarrier of the associated DMRS port in each allocated RB. Also, the subcarrier used for a PTRS port must be one of the subcarriers also used for the DM-RS port associated with the PTRS port. PTRS sub-carrier ^^ in the scheduled PDSCH or PUSCH RBs is determined as: ^^ ൌ ^^^ோ^ா^ ^ ൫ ^^ ^^^்ିோௌ^ ^^^ோ^^^ ൯ ^^^ோ^^. Here: ^ ^^ ൌ 0,1,2, …; ^ ^^^ோ^ா^ is the sub-carrier offset and is given in Table 6.4.1.2.2.1-1 for UL in 3GPP TS 38.211 v17.2.0. The table are copied below, where resourceElementOffset is a parameter configured by RRC. If resourceElementOffset is not configured, the column corresponding to 'offset00' shall be used; ^ ^^^்ିோௌis the frequency density of PTRS and ^^PTRS∈ ^2,4^; ^ ^^^ோ^^^ is the RB offset for PTRS and is given by: o^^^ோ^^^ൌ ^ ^^ோே்ூ ^^ ^^ ^^ ^^^்ିோௌ if ^^ோ^ ^^ ^^ ^^ ^^^்ିோௌ ൌ 0^^ோே்ூ ^^ ^^ ^^ ^ ^^ோ^ ^^ ^^ ^^ ^^^்ିோௌ ^ ^^ ^^ℎ ^^ ^^ ^^ ^^ ^^ ^^;^ ^ ^^ோ^is the number of scheduled RBs; and ^ nRNTIis the RNTI associated with the DCI scheduling the transmission. Within each RB allocated for PTRS, the subcarrier for PTRS, also referred to as resource element offset k RE ref, is determined by both the index of the associated DMRS port and a RRC parameter resourceElementOffset. Table 6.4.1.2.2.1-1: The parameter k RE ref(UL). krefDM-RS antenna DM-RS Configuration type 1 DM-RS Configuration type 2 port resourceElementOffset resourceElementOffset ~poffset offset offset offset offset offset offset offset 00 01 10 11 00 01 10 11 0 0 2 6 8 0 1 6 7 1 2 4 8 10 1 6 7 0 2 1 3 7 9 2 3 8 9 3 3 5 9 11 3 8 9 2 4 - - - - 4 5 10 11 5 - - - - 5 10 11 4 For PTRS time domain mapping, the mapping starts at the first symbol containing PDSCH / PUSCH in a slot. Then it is mapped to every ^^ symbols (according to the time density 1 / ^^). PTRS is not transmitted in OFDM symbols that contain PDSCH / PUSCH DMRS. PTRS mapping is restarted at each DMRS symbol and then mapped relative to this symbol. In case of two adjacent DMRS symbols, the mapping is restarted using the second DMRS symbol as a reference. An example of PTRS REs in a PTRS RB is shown in FIG.3 for time domain density is ½ ( ^^ ൌ 2), where the PTRS port is associated with type 1 DMRS port 1 and the RRC parameter resourceElementOffset is configured as ‘offset10’ with a single symbol DMRS in the left figure and a double symbol DMRS in the right figure. Another example is shown in FIG. 4, where the PTRS port is associated with a single symbol type 1 DMRS port 1 (shown on the left) and a single symbol type 2 DMRS port 1 (shown on the right), and again both with the RRC parameterresourceElementOffset configured as ‘offset10’ but with a PTRS time density of 1 ( ^^ ൌ1).For CP-OFDM, in each subcarrier allocated for PTRS, the DMRS symbol in that subcarrier and the first front-loaded DMRS OFDM symbol before applying FD-OCC is used also for the PTRS. PTRS for PUSCH DFT-s-OFDM In existing NR specifications, when transform precoding or DFT-s-OFDM is enabled, only single layer PUSCH is supported. Also, only a single PTRS port is supported. For each OFDM symbol containing PTRS, a length ^^^^^்^ି௨ோ^ௌ^^^^^௨^^^^^PTRSsequence ^^ ^ ^^ᇱ^ ^ ^^ᇱ ൌ ^^^^^௨^ ^^ᇱ ^ ᇱ ᇱ ^்ିோௌ ᇱ ^^^௨^^ ^^^^ ^^ , ^^ ൌ 0,1, ... , ^^^^^௨^ െ 1, ^^ ൌ 0,1, … , ^^^^^^ െ1 ^ for is illustrated in FIG.5, where the DFT block indicates the transform precoding. The PTRS may be configured in every OFDM symbol (density =1) or every other OFDM symbols (density=2) scheduled for the PUSCH. The PTRS sequence is divided into ^^^^^்^ି௨ோ^ௌgroups and each group contains ^^^^^௨^^^^^samples, where ^^^^^௨^^^^^∈ ^2,4^ and ^^^^^்^ି௨ோ^ௌ∈ ^2,4,8^ are determined by the scheduled PUSCH BW, ^^ோ^, using Table 9, where ^ ^^ோ^^, … , ^^ோ^ସ^ are the thresholds in number of RBs and configured by network node. For each OFDM symbol containing PTRS, ^^^^^^ᇱ^is mapped in position ^^ before transform precoding. ^^ is dependent on the values of ^^^^^்^ି௨ோ^ௌand ^^^^^௨^^^^^and is determined according to Table 6.4.1.2.2.2-1 in is illustrated in FIG.6 for ^^^^^்^ି௨ோ^ௌൌ 4 , ^^^^^௨^^^^^ൌ 2, and ^^^^^^ௌ^ுൌ 24, where ^^^^^^ௌ^ுis the number Table 9 Scheduled BW (RBs) X x K NRB0^NRB^NRB12x2 NRB1 ^NRB^NRB2 2x4 NRB2^NRB^NRB34x2 NRB3^NRB^NRB4 4x4 NRB^ NRB48x4 Table 6.4.1.2.2.2-1: PTRS symbol mapping (3GPP TS 38.211). Numbe Numbe Index ^^ of PTRS samples in OFDM symbol l prior to r of r of transform precoding PTRS samples groups per N PTRS group N group samp22^^^ ^^sPcUSCH⁄ 4 ^ ^ ^^ െ 1 where ^^ ൌ 1,3 and ^^ ൌ 0,124^^ ^^sPcUSCH^ ^^ where ^^^ ൌ 0 and ^^ ൌ 0,1,2,3^^ ൌ 1 and ^^ ൌ െ4,െ3,െ2,െ142^ ^^ ^^sPcUSCH⁄ 8 ^ ^ ^^ െ 1 where ^^ ൌ 1,3,5,7 and ^^ ൌ 0,144^^ ^^sPcUSCH⁄ 4 ^ ^^ ^ ^^ where^^ ൌ 0 and ^^ ൌ 0,1,2,3 ^^ ൌ 0 ^ ^^ ൌ 1,2 and ^^ ൌ െ2,െ1,0,1 ^^ ൌ ^ ^^sPcUSCH⁄ 8 ^ ^^ ൌ 4 and ^^ ൌ െ4,െ3,െ2,െ1 ^^ ൌ 08 4^ ^^ ^^sPcUSCH⁄8 ^ ^ ^^ ^ ^^ where^^ ൌ 0 and ^^ ൌ 0,1,2,3 ^^ ൌ 0 ^ ^^ ൌ 1,2,3,4,5,6 and ^^ ൌ െ2,െ1,0,1 ^^ ൌ ^ ^^sPcUSCH⁄16 ^ ^^ ൌ 8 and ^^ ൌ െ4,െ3,െ2,െ1 ^^ ൌ 0SUMMARY Some embodiments advantageously provide methods, network nodes and wireless devices (WD) for multi-layer discrete Fourier transform (DFT) spread orthogonal frequency division multiplexing (DFT-s-OFDM) for single downlink control information (DCI) simultaneous multipanel transmission (STxMP). Methods are disclosed for configuring a WD with multiple PTRS ports for DFT-s- OFDM based on WD capability signaling. Method are disclosed for associating different PTRS ports to different WD panels, and for separating the PTRS ports transmitted in different WD panels. Methods disclosed herein include using different PTRS sequences for different PTRS ports, using different PTRS sample allocations for different PTRS Ports before transform precoding or using spatial division multiplexing to separate the same PTRS port transmitted from two different WD panels. Some embodiments enhance PTRS transmission for rank larger than 1 for DFT-S- OFDM transmission (e.g., STxMP SDM), which may increase UL throughput and reliability in coverage-limited scenarios. According to one aspect, a method in a wireless device configured to communicate with a network node is provided. The method includes a method in a wireless device, WD, configured to communicate with a network node. The method includes receiving a configuration of multiple phase tracking reference signal, PTRS, ports for multilayer data transmission with discrete Fourier transform spread orthogonal frequency division multiplexing, DFT-s-OFDM. The method includes determining a first mapping of the multiple PTRS ports to different spatial layers. The method also includes transmitting via the PTRS ports according to the first mapping. According to this aspect, in some embodiments, the method includes transmitting an indication of a first maximum number of supported PTRS ports. In some embodiments, the method includes receiving a second maximum number of PTRS ports by radio resource control, RRC, signaling. In some embodiments, the first mapping includes allocating PTRS symbols of a first PTRS port to a first set of time and frequency resources and allocating PTRS symbols of a second PTRS port to a second set of time and frequency resources, wherein the first and the second resources are different and not overlapping if the first and the second PTRS ports are different. In some embodiments, the PTRS symbols of a first PTRS port can be the same as or different from the PTRS symbols of a second PTRS port. In some embodiments, the first PTRS port is associated to a first spatial layer and the second PTRS port is associated to a second spatial layer. In some embodiments, multilayer data transmission is a simultaneous data transmission over multiple antenna panels, STxMP, scheduled by single downlink control information, DCI. In some embodiments, the first mapping includes associating sounding reference signal, SRS, resource sets to the PTRS ports. In some embodiments, the method includes associating different PTRS ports with different sequences. In some embodiments, the associating is performed according to a list of different sequences indicated by radio resource control, RRC, signaling. In some embodiments, the method includes receiving an indication of a first sequence for a first PTRS port and determining sequences of remaining PTRS ports according to a rule. In some embodiments, the method includes determining a second mapping between the PTRS ports and demodulation reference signal, DMRS, ports. In some embodiments, the PTRS ports transmitted from two or more panels are identical. In some embodiments, determining the first mapping includes determining a PTRS port for each of a plurality of sounding reference signal, SRS, resource sets associated with a physical uplink shared channel, PUSCH. According to another aspect, a wireless device, WD, configured to communicate with a network node is provided. The WD is configured to receive a configuration of multiple phase tracking reference signal, PTRS, ports for multilayer data transmission with discrete Fourier transform spread orthogonal frequency division multiplexing, DFT-s- OFDM. The WD is also configured to determine a first mapping of the multiple PTRS ports to different spatial layers. The WD is further configured to transmit via the PTRS ports according to the first mapping. According to this aspect, in some embodiments, the WD is configured to transmit an indication of a first maximum number of supported PTRS ports. In some embodiments, the WD is configured to receive a second maximum number of PTRS ports by radio resource control, RRC, signaling. In some embodiments, the first mapping includes allocating PTRS symbols of a first PTRS port to a first set of time and frequency resources and allocating PTRS symbols of a second PTRS port to a second set of time and frequency resources, wherein the first and the second resources are different and not overlapping if the first and the second PTRS ports are different. In some embodiments, the PTRS symbols of a first PTRS port can be the same as or different from the PTRS symbols of a second PTRS port. In some embodiments, the first PTRS port is associated to a first spatial layer and the second PTRS port is associated to a second spatial layer. In some embodiments, multilayer data transmission is a simultaneous data transmission over multiple antenna panels, STxMP, scheduled by single downlink control information, DCI. In some embodiments, the PTRS port mapping includes associating sounding reference signal, SRS, resource sets to the PTRS ports. In some embodiments, the WD is configured to associate different PTRS ports with different sequences. In some embodiments, the associating is performed according to a list of different sequences received by radio resource control, RRC, signaling. In some embodiments, the WD is configured to receive an indication of a first sequence for a first PTRS port and determining a sequence of remaining PTRS ports according to a rule. In some embodiments, the WD is configured to determine a second mapping between the PTRS ports and demodulation reference signal, DMRS, ports. In some embodiments, PTRS ports transmitted from two or more panels are identical. In some embodiments, determining the first mapping includes determining a PTRS port for each of a plurality of sounding reference signal, SRS, resource sets associated with a physical uplink shared channel, PUSCH. According to yet another aspect, a method in a network node configured to communicate with a wireless device, WD is provided. The method includes determining a first mapping of phase tracking reference signal, PTRS, ports to different spatial layers. The method also includes configuring the WD with multiple phase tracking reference signal, PTRS, ports for multilayer data transmission with discrete Fourier transform spread orthogonal frequency division multiplexing, DFT-s-OFDM. The method further includes separating PTRS ports for signals received from the WD on different layers according to the first mapping. According to this aspect, in some embodiments, the method includes receiving from the WD an indication of a first maximum number of supported PTRS ports. In some embodiments, a second maximum number of PTRS ports is configured by radio resource control, RRC, signaling. In some embodiments, the first mapping includes allocating PTRS symbols of a first PTRS port to a first set of time and frequency resources and allocating PTRS symbols of a second PTRS port to a second set of time and frequency resources, wherein the first and the second resources are different and not overlapping if the first and the second PTRS ports are different. In some embodiments, the PTRS symbols of a first PTRS port can be the same as or different from the PTRS symbols of a second PTRS port. In some embodiments, the first PTRS port is associated to a first spatial layer and the second PTRS port is associated to a second spatial layer. In some embodiments, multilayer data transmission is a simultaneous data transmission over multiple antenna panels, STxMP, scheduled by single downlink control information, DCI. In some embodiments, the PTRS port mapping includes associating sounding reference signal, SRS, resource sets and PTRS ports. In some embodiments, separating the PTRS ports includes associated different PTRS ports to different sequences. In some embodiments, a list of the different sequences for different PTRS ports is signaled to the WD by radio resource control, RRC, signaling. In some embodiments, configuring the WD includes sending an indication of a first PTRS port to enable the WD to determine a sequence of remaining PTRS ports according to a rule. In some embodiments, configuring the WD includes sending indication of an association between each PTRS port and at least one layer. In some embodiments, separating PTRS ports includes determining PTRS sample positions before transform precoding, and mapping different layers to the PTRS sample positions. In some embodiments, first PTRS sample positions before transform precoding for a first PTRS port are determined based on a table and second PTRS sample positions before transform precoding for a second PTRS port are allocated to not fully overlap the first PTRS sample positions. In some embodiments, non-overlapped PTRS sample positions are determined based at least in part on shifting the second PTRS sample positions relative to the first PTRS sample positions. In some embodiments, configuring the WD includes indicating to the WD a second mapping between the PTRS ports and demodulation reference signal, DMRS, ports. In some embodiments, configuring the WD includes enabling a parameter in a physical uplink shared channel, PUSCH, configuration information element. In some embodiments, the separating PTRS ports includes determining a PTRS port for each of a plurality of sounding reference signal, SRS, resource sets associated with the PUSCH. According to yet another aspect, a network node configured to communicate with a wireless device, WD, is provided. The network node is configured to determine a first mapping of phase tracking reference signal, PTRS, ports to different spatial layers. The network node is also configured to configure the WD with multiple phase tracking reference signal, PTRS, ports for multilayer data transmission with discrete Fourier transform spread orthogonal frequency division multiplexing, DFT-s-OFDM. The network node is further configured to separate PTRS ports for signals received from the WD on different layers according to the first mapping. According to this aspect, in some embodiments, the network node is configured to receive from the WD, an indication of a first maximum number of supported PTRS ports. In some embodiments, a second maximum number of PTRS ports is configured by radio resource control, RRC, signaling. In some embodiments, the first mapping includes allocating PTRS symbols of a first PTRS port to a first set of time and frequency resources and allocating PTRS symbols of a second PTRS port to a second set of time and frequency resources, wherein the first and the second resources are different and not overlapping if the first and the second PTRS ports are different. In some embodiments, the PTRS symbols of a first PTRS port can be the same as or different from the PTRS symbols of a second PTRS port. In some embodiments, the first PTRS port is associated to a first spatial layer and the second PTRS port is associated to a second spatial layer. In some embodiments, multilayer data transmission is a simultaneous data transmission over multiple antenna panels, STxMP, scheduled by single downlink control information, DCI. In some embodiments, the PTRS port mapping includes associating sounding reference signal, SRS, resource sets and PTRS ports. In some embodiments, separating the PTRS ports includes associated different PTRS ports to different sequences. In some embodiments, a list of the different sequences for different PTRS ports is signaled to the WD by radio resource control, RRC, signaling. In some embodiments, configuring the WD includes sending an indication of a first PTRS port to enable the WD to determine a sequence of remaining PTRS ports according to a rule. In some embodiments, configuring the WD includes sending indication of an association between each PTRS port and at least one layer. In some embodiments, separating PTRS ports includes: determining PTRS sample positions before transform precoding; and mapping different layers to the PTRS sample positions. In some embodiments, first PTRS sample positions before transform precoding for a first PTRS port are determined based on a table and second PTRS sample positions before transform precoding for a second PTRS port are allocated to not fully overlap the first PTRS sample positions. In some embodiments, non-overlapped PTRS sample positions are determined based at least in part on shifting the second PTRS sample positions relative to the first PTRS sample positions. In some embodiments, configuring the WD includes indicating to the WD a second mapping between the PTRS ports and demodulation reference signal, DMRS, ports. In some embodiments, configuring the WD includes enabling a parameter in a physical uplink shared channel, PUSCH, configuration information element. In some embodiments, the separating PTRS ports includes determining a PTRS port for each of a plurality of sounding reference signal, SRS, resource sets associated with the PUSCH. BRIEF DESCRIPTION OF THE DRAWINGS A more complete understanding of the present embodiments, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: FIG.1 illustrates Type 1 and Type 2 DMRS; FIG.2 illustrates single and double symbol DMRS; FIG.3 is an example of PTRS time domain mapping; FIG.4 is an example of PTRS subcarrier mapping; FIG.5 illustrates existing PTRS transmission; FIG.6 illustrates PTRS positions before transform precoding; FIG.7 is a schematic diagram of an example network architecture illustrating a communication system according to principles disclosed herein; FIG.8 is an example of a wireless device and network node configured according to principles disclosed herein; FIG.9 is a flowchart of an example process in a network node for multi-layer discrete Fourier transform (DFT) spread orthogonal frequency division multiplexing (DFT-s-OFDM) for single downlink control information (DCI) simultaneous multipanel (STxMP); FIG.10 is a flowchart of an example process in a wireless device for multi-layer discrete Fourier transform (DFT) spread orthogonal frequency division multiplexing (DFT-s-OFDM) for single downlink control information (DCI) simultaneous multipanel (STxMP); FIG.11 is a flowchart of another example process in a network node for multi- layer discrete Fourier transform (DFT) spread orthogonal frequency division multiplexing (DFT-s-OFDM) for single downlink control information (DCI) simultaneous multipanel (STxMP); FIG.12 is a flowchart of another example process in a wireless device for multi- layer discrete Fourier transform (DFT) spread orthogonal frequency division multiplexing (DFT-s-OFDM) for single downlink control information (DCI) simultaneous multipanel (STxMP); FIG.13 illustrates transmitting two PTRS ports for DFT-s-OFDM with multiple layers according to principles disclosed herein; and FIG.14 is an example of PTRS positions according to principles disclosed herein. DETAILED DESCRIPTION Before describing in detail example embodiments, it is noted that the embodiments reside primarily in combinations of apparatus components and processing steps related to multi-layer discrete Fourier transform (DFT) spread orthogonal frequency division multiplexing (DFT-s-OFDM) for single downlink control information (DCI) simultaneous multipanel transmission (STxMP). Accordingly, components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Like numbers refer to like elements throughout the description. As used herein, relational terms, such as “first” and “second,” “top” and “bottom,” and the like, may be used solely to distinguish one entity or element from another entity or element without necessarily requiring or implying any physical or logical relationship or order between such entities or elements. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the concepts described herein. 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. In embodiments described herein, the joining term, “in communication with” and the like, may be used to indicate electrical or data communication, which may be accomplished by physical contact, induction, electromagnetic radiation, radio signaling, infrared signaling or optical signaling, for example. One having ordinary skill in the art will appreciate that multiple components may interoperate and modifications and variations are possible of achieving the electrical and data communication. In some embodiments described herein, the term “coupled,” “connected,” and the like, may be used herein to indicate a connection, although not necessarily directly, and may include wired and / or wireless connections. The term “network node” used herein may be any kind of network node comprised in a radio network which may further comprise any of base station (BS), radio base station, base transceiver station (BTS), base station controller (BSC), radio network controller (RNC), g Node B (gNB), evolved Node B (eNB or eNodeB), Node B, multi- standard radio (MSR) radio node such as MSR BS, multi-cell / multicast coordination entity (MCE), integrated access and backhaul (IAB) node, relay node, donor node controlling relay, radio access point (AP), transmission points, transmission nodes, Remote Radio Unit (RRU) Remote Radio Head (RRH), a core network node (e.g., mobile management entity (MME), self-organizing network (SON) node, a coordinating node, positioning node, MDT node, etc.), an external node (e.g., 3rd party node, a node external to the current network), nodes in distributed antenna system (DAS), a spectrum access system (SAS) node, an element management system (EMS), etc. The network node may also comprise test equipment. The term “radio node” used herein may be used to also denote a wireless device (WD) such as a wireless device (WD) or a radio network node. In some embodiments, the non-limiting terms wireless device (WD) or a user equipment (UE) are used interchangeably. The WD herein may be any type of wireless device capable of communicating with a network node or another WD over radio signals, such as wireless device (WD). The WD may also be a radio communication device, target device, device to device (D2D) WD, machine type WD or WD capable of machine to machine communication (M2M), low-cost and / or low-complexity WD, a sensor equipped with WD, Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles, Customer Premises Equipment (CPE), an Internet of Things (IoT) device, or a Narrowband IoT (NB-IOT) device, etc. Also, in some embodiments the generic term “radio network node” is used. It may be any kind of a radio network node which may comprise any of base station, radio base station, base transceiver station, base station controller, network controller, RNC, evolved Node B (eNB), Node B, gNB, Multi-cell / multicast Coordination Entity (MCE), IAB node, relay node, access point, radio access point, Remote Radio Unit (RRU) Remote Radio Head (RRH). Note that although terminology from one particular wireless system, such as, for example, 3GPP LTE and / or New Radio (NR), may be used in this disclosure, this should not be seen as limiting the scope of the disclosure to only the aforementioned system. Other wireless systems, including without limitation Wide Band Code Division Multiple Access (WCDMA), Worldwide Interoperability for Microwave Access (WiMax), Ultra Mobile Broadband (UMB) and Global System for Mobile Communications (GSM), may also benefit from exploiting the ideas covered within this disclosure. Note further, that functions described herein as being performed by a wireless device or a network node may be distributed over a plurality of wireless devices and / or network nodes. In other words, it is contemplated that the functions of the network node and wireless device described herein are not limited to performance by a single physical device and, in fact, may be distributed among several physical devices. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. Some embodiments provide multi-layer discrete Fourier transform (DFT) spread orthogonal frequency division multiplexing (DFT-s-OFDM) for single downlink control information (DCI) simultaneous multipanel (STxMP). Returning now to the drawing figures, in which like elements are referred to by like reference numerals, there is shown in FIG.7 a schematic diagram of a communication system 10, according to an embodiment, such as a 3GPP-type cellular network that may support standards such as LTE and / or NR (5G), which comprises an access network 12, such as a radio access network, and a core network 14. The access network 12 comprises a plurality of network nodes 16a, 16b, 16c (referred to collectively as network nodes 16), such as NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 18a, 18b, 18c (referred to collectively as coverage areas 18). Each network node 16a, 16b, 16c is connectable to the core network 14 over a wired or wireless connection 20. A first wireless device (WD) 22a located in coverage area 18a is configured to wirelessly connect to, or be paged by, the corresponding network node 16a. A second WD 22b in coverage area 18b is wirelessly connectable to the corresponding network node 16b. While a plurality of WDs 22a, 22b (collectively referred to as wireless devices 22) are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole WD is in the coverage area or where a sole WD is connecting to the corresponding network node 16. Note that although only two WDs 22 and three network nodes 16 are shown for convenience, the communication system may include many more WDs 22 and network nodes 16. Also, it is contemplated that a WD 22 may be in simultaneous communication and / or configured to separately communicate with more than one network node 16 and more than one type of network node 16. For example, a WD 22 may have dual connectivity with a network node 16 that supports LTE and the same or a different network node 16 that supports NR. As an example, WD 22 may be in communication with an eNB for LTE / E-UTRAN and a gNB for NR / NG-RAN. A network node 16 is configured to include a NN configuration unit 24 which is configured to configure the WD with a plurality of phase tracking reference signal, PTRS, ports for discrete Fourier transform (DFT)-spread orthogonal frequency division multiplexing, OFDM. A wireless device 22 is configured to include a WD configuration unit 26 which is configured to configure a plurality of phase tracking reference signal, PTRS, ports for discrete Fourier transform (DFT)-spread orthogonal frequency division multiplexing, OFDM. Example implementations, in accordance with an embodiment, of the WD 22 and network node 16 discussed in the preceding paragraphs will now be described with reference to FIG.12. The communication system 10 includes a network node 16 provided in a communication system 10 and including hardware 28 enabling it to communicate with the WD 22. The hardware 28 may include a radio interface 30 for setting up and maintaining at least a wireless connection 32 with a WD 22 located in a coverage area 18 served by the network node 16. The radio interface 30 may be formed as or may include, for example, one or more RF transmitters, one or more RF receivers, and / or one or more RF transceivers. The radio interface 30 includes an array of antennas 34 to radiate and receive signal(s) carrying electromagnetic waves. In the embodiment shown, the hardware 28 of the network node 16 further includes processing circuitry 36. The processing circuitry 36 may include a processor 38 and a memory 40. In particular, in addition to or instead of a processor, such as a central processing unit, and memory, the processing circuitry 36 may comprise integrated circuitry for processing and / or control, e.g., one or more processors and / or processor cores and / or FPGAs (Field Programmable Gate Array) and / or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions. The processor 38 may be configured to access (e.g., write to and / or read from) the memory 40, which may comprise any kind of volatile and / or nonvolatile memory, e.g., cache and / or buffer memory and / or RAM (Random Access Memory) and / or ROM (Read-Only Memory) and / or optical memory and / or EPROM (Erasable Programmable Read-Only Memory). Thus, the network node 16 further has software 42 stored internally in, for example, memory 40, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the network node 16 via an external connection. The software 42 may be executable by the processing circuitry 36. The processing circuitry 36 may be configured to control any of the methods and / or processes described herein and / or to cause such methods, and / or processes to be performed, e.g., by network node 16. Processor 38 corresponds to one or more processors 38 for performing network node 16 functions described herein. The memory 40 is configured to store data, programmatic software code and / or other information described herein. In some embodiments, the software 42 may include instructions that, when executed by the processor 38 and / or processing circuitry 36, causes the processor 38 and / or processing circuitry 36 to perform the processes described herein with respect to network node 16. For example, processing circuitry 36 of the network node 16 may include a network node (NN) configuration unit 24 which is configured to configure the WD with a plurality of phase tracking reference signal, PTRS, ports for discrete Fourier transform (DFT)-spread orthogonal frequency division multiplexing, OFDM. The communication system 10 further includes the WD 22 already referred to. The WD 22 may have hardware 44 that may include a radio interface 46 configured to set up and maintain a wireless connection 32 with a network node 16 serving a coverage area 18 in which the WD 22 is currently located. The radio interface 46 may be formed as or may include, for example, one or more RF transmitters, one or more RF receivers, and / or one or more RF transceivers. The radio interface 46 includes an array of antennas 48 to radiate and receive signal(s) carrying electromagnetic waves. The hardware 44 of the WD 22 further includes processing circuitry 50. The processing circuitry 50 may include a processor 52 and memory 54. In particular, in addition to or instead of a processor, such as a central processing unit, and memory, the processing circuitry 50 may comprise integrated circuitry for processing and / or control, e.g., one or more processors and / or processor cores and / or FPGAs (Field Programmable Gate Array) and / or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions. The processor 52 may be configured to access (e.g., write to and / or read from) memory 54, which may comprise any kind of volatile and / or nonvolatile memory, e.g., cache and / or buffer memory and / or RAM (Random Access Memory) and / or ROM (Read-Only Memory) and / or optical memory and / or EPROM (Erasable Programmable Read-Only Memory). Thus, the WD 22 may further comprise software 56, which is stored in, for example, memory 54 at the WD 22, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the WD 22. The software 56 may be executable by the processing circuitry 50. The software 56 may include a client application 58. The client application 58 may be operable to provide a service to a human or non-human user via the WD 22. The processing circuitry 50 may be configured to control any of the methods and / or processes described herein and / or to cause such methods, and / or processes to be performed, e.g., by WD 22. The processor 52 corresponds to one or more processors 52 for performing WD 22 functions described herein. The WD 22 includes memory 54 that is configured to store data, programmatic software code and / or other information described herein. In some embodiments, the software 56 and / or the client application 58 may include instructions that, when executed by the processor 52 and / or processing circuitry 50, causes the processor 52 and / or processing circuitry 50 to perform the processes described herein with respect to WD 22. For example, the processing circuitry 50 of the WD 22 may include a WD configuration unit 26 which is configured to configure a plurality of phase tracking reference signal, PTRS, ports for discrete Fourier transform (DFT)-spread orthogonal frequency division multiplexing, OFDM. In some embodiments, the inner workings of the network node 16 and WD 22 may be as shown in FIG.8 and independently, the surrounding network topology may be that of FIG.7. The wireless connection 32 between the WD 22 and the network node 16 is in accordance with the teachings of the embodiments described throughout this disclosure. More precisely, the teachings of some of these embodiments may improve the data rate, latency, and / or power consumption and thereby provide benefits such as reduced user waiting time, relaxed restriction on file size, better responsiveness, extended battery lifetime, etc. In some embodiments, a measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. Although FIGS.7 and 8 show various “units” such as NN configuration unit 24, and WD configuration unit 26 as being within a respective processor, it is contemplated that these units may be implemented such that a portion of the unit is stored in a corresponding memory within the processing circuitry. In other words, the units may be implemented in hardware or in a combination of hardware and software within the processing circuitry. FIG.9 is a flowchart of an example process in a network node 16 for multi-layer discrete Fourier transform (DFT) spread orthogonal frequency division multiplexing (DFT-s-OFDM) for single downlink control information (DCI) simultaneous multipanel (STxMP). One or more blocks described herein may be performed by one or more elements of network node 16 such as by one or more of processing circuitry 36 (including the NN configuration unit 24), processor 38, and / or radio interface 30. Network node 16 such as via processing circuitry 36 and / or processor 38 and / or radio interface 30 is configured to configure the WD 22 with a plurality of phase tracking reference signal, PTRS, ports for discrete Fourier transform (DFT)-spread orthogonal frequency division multiplexing, OFDM (Block S10). In some embodiments, configuring the WD 22 includes configuring the WD 22 with a parameter indicating a sequence of PTRS ports. In some embodiments, configuring the WD 22 includes sending a parameter indicating a first PTRS port to enable the WD 22 to determine a sequence of remaining PTRS ports according to a rule. In some embodiments, configuring the WD 22 includes sending a parameter indicating an association between each PTRS port and at least one layer. In some embodiments, configuring the WD 22 includes indicating a mapping between each PTRS port and at least one demodulation reference signal, DMRS, port. FIG.10 is a flowchart of an example process in a wireless device 22 according to some embodiments of the present disclosure. One or more blocks described herein may be performed by one or more elements of wireless device 22 such as by one or more of processing circuitry 50 (including the WD configuration unit 26), processor 38, and / or radio interface 46. Wireless device 22 such as via processing circuitry 50 and / or processor 38 and / or radio interface 46 is configured to configure a plurality of phase tracking reference signal, PTRS, ports for discrete Fourier transform (DFT)-spread orthogonal frequency division multiplexing, OFDM (Block S12). In some embodiments, configuring the plurality of PTRS ports includes applying a sequence of PTRS ports. In some embodiments, configuring the plurality of PTRS ports includes determining a sequence of remaining PTRS ports according to a rule and a first PTRS port. In some embodiments, configuring the plurality of PTRS ports includes forming an association between each PTRS port and at least one layer. In some embodiments, configuring the plurality of PTRS ports includes mapping each PTRS port to at least one demodulation reference signal, DMRS, port. FIG.11 is a flowchart of an example process in a network node 16 for multi-layer discrete Fourier transform (DFT) spread orthogonal frequency division multiplexing (DFT-s-OFDM) for single downlink control information (DCI) simultaneous multipanel (STxMP). One or more blocks described herein may be performed by one or more elements of network node 16 such as by one or more of processing circuitry 36 (including the NN configuration unit 24), processor 38, and / or radio interface 30. Network node 16 such as via processing circuitry 36 and / or processor 38 and / or radio interface 30 is configured to determine a first mapping of phase tracking reference signal, PTRS, ports to different spatial layers (Block S14). The method also includes configuring the WD 22 with multiple phase tracking reference signal, PTRS, ports for multilayer data transmission with discrete Fourier transform spread orthogonal frequency division multiplexing, DFT- s-OFDM (Block S16). The method further includes separating PTRS ports for signals received from the WD 22 on different layers according to the first mapping (Block S18). According to this aspect, in some embodiments, the method includes receiving from the WD 22 an indication of a first maximum number of supported PTRS ports. In some embodiments, a second maximum number of PTRS ports is configured by radio resource control, RRC, signaling. In some embodiments, the first mapping includes allocating PTRS symbols of a first PTRS port to a first set of time and frequency resources and allocating PTRS symbols of a second PTRS port to a second set of time and frequency resources, wherein the first and the second resources are different and not overlapping if the first and the second PTRS ports are different. In some embodiments, the PTRS symbols of a first PTRS port can be the same as or different from the PTRS symbols of a second PTRS port. In some embodiments, the first PTRS port is associated to a first spatial layer and the second PTRS port is associated to a second spatial layer. In some embodiments, multilayer data transmission is a simultaneous data transmission over multiple antenna panels, STxMP, scheduled by single downlink control information, DCI. In some embodiments, the PTRS port mapping includes associating sounding reference signal, SRS, resource sets and PTRS ports. In some embodiments, separating the PTRS ports includes associated different PTRS ports to different sequences. In some embodiments, a list of the different sequences for different PTRS ports is signaled to the WD 22 by radio resource control, RRC, signaling. In some embodiments, configuring the WD 22 includes sending an indication of a first PTRS port to enable the WD 22 to determine a sequence of remaining PTRS ports according to a rule. In some embodiments, configuring the WD 22 includes sending indication of an association between each PTRS port and at least one layer. In some embodiments, separating PTRS ports includes determining PTRS sample positions before transform precoding, and mapping different layers to the PTRS sample positions. In some embodiments, first PTRS sample positions before transform precoding for a first PTRS port are determined based on a table and second PTRS sample positions before transform precoding for a second PTRS port are allocated to not fully overlap the first PTRS sample positions. In some embodiments, non- overlapped PTRS sample positions are determined based at least in part on shifting the second PTRS sample positions relative to the first PTRS sample positions. In some embodiments, configuring the WD 22 includes indicating to the WD 22 a second mapping between the PTRS ports and demodulation reference signal, DMRS, ports. In some embodiments, configuring the WD 22 includes enabling a parameter in a physical uplink shared channel, PUSCH, configuration information element. In some embodiments, the separating PTRS ports includes determining a PTRS port for each of a plurality of sounding reference signal, SRS, resource sets associated with the PUSCH. FIG.12 is a flowchart of an example process in a wireless device 22 according to some embodiments of the present disclosure. One or more blocks described herein may be performed by one or more elements of wireless device 22 such as by one or more of processing circuitry 50 (including the WD configuration unit 26), processor 38, and / or radio interface 46. Wireless device 22 such as via processing circuitry 50 and / or processor 38 and / or radio interface 46 is configured to receive a configuration of multiple phase tracking reference signal, PTRS, ports for multilayer data transmission with discrete Fourier transform spread orthogonal frequency division multiplexing, DFT-s-OFDM (Block S22). The method includes determining a first mapping of the multiple PTRS ports to different spatial layers (Block S20). The method also includes transmitting via the PTRS ports according to the first mapping (Block S24). According to this aspect, in some embodiments, the method includes transmitting an indication of a first maximum number of supported PTRS ports. In some embodiments, the method includes receiving a second maximum number of PTRS ports by radio resource control, RRC, signaling. In some embodiments, the first mapping includes allocating PTRS symbols of a first PTRS port to a first set of time and frequency resources and allocating PTRS symbols of a second PTRS port to a second set of time and frequency resources, wherein the first and the second resources are different and not overlapping if the first and the second PTRS ports are different. In some embodiments, the PTRS symbols of a first PTRS port can be the same as or different from the PTRS symbols of a second PTRS port. In some embodiments, the first PTRS port is associated to a first spatial layer and the second PTRS port is associated to a second spatial layer. In some embodiments, multilayer data transmission is a simultaneous data transmission over multiple antenna panels, STxMP, scheduled by single downlink control information, DCI. In some embodiments, the first mapping includes associating sounding reference signal, SRS, resource sets to the PTRS ports. In some embodiments, the method includes associating different PTRS ports with different sequences. In some embodiments, the associating is performed according to a list of different sequences indicated by radio resource control, RRC, signaling. In some embodiments, the method includes receiving an indication of a first sequence for a first PTRS port and determining sequences of remaining PTRS ports according to a rule. In some embodiments, the method includes determining a second mapping between the PTRS ports and demodulation reference signal, DMRS, ports. In some embodiments, the PTRS ports transmitted from two or more panels are identical. In some embodiments, determining the first mapping includes determining a PTRS port for each of a plurality of sounding reference signal, SRS, resource sets associated with a physical uplink shared channel, PUSCH. Having described the general process flow of arrangements of the disclosure and having provided examples of hardware and software arrangements for implementing the processes and functions of the disclosure, the sections below provide details and examples of arrangements for multi-layer discrete Fourier transform (DFT) spread orthogonal frequency division multiplexing (DFT-s-OFDM) for single downlink control information (DCI) simultaneous multipanel (STxMP). UE capability signaling In some embodiments, the WD 22 indicates during WD capability signaling the maximum number of supported PTRS port for PUSCH STxMP. In some embodiments, the WD 22 indicates during WD capability signaling the maximum number of supported PTRS port for PUSCH STxMP for DFT-s-OFDM (i.e., a separate indication is used compared to PUSCH STxMP CP-OFDM). In some embodiments, the WD 22 indicates support for PUSCH STxMP DFT-s- OFDM with support for up to X number of WD panels, then the WD 22 automatically supports up to X number of PTRS ports for the PUSCH STxMP DFT-s-OFDM transmission. In some embodiments, in cases where the WD capability indicates support of multiple PTRS ports for PUSCH STxMP DFT-s-OFDM transmission, the WD capability signaling in addition could include information related to one or more of: ^ Support of separating the PTRS ports using different sequences (as described herein); ^ Support of separating the ports using different time domain codes (e.g., TD-OCC); and / or ^ Support of separating the ports using different frequency allocation (as described herein). Number of PTRS port for STxMP In some embodiments, the maximum number of PTRS ports for STxMP DFT-s- OFDM transmission may be RRC configured. In some embodiments, the RRC configuration is done using a new parameter in PTRS-UplinkConfig information element as defined in 3GPP TS 38.331 version 17.2.0. In some embodiments, a previous parameter “maxNrofPorts” in PTRS-UplinkConfig is re-used also for indicating the maximum number of PTRS ports for STxMP DFT-s-OFDM transmission. In some embodiments, each PTRS port is associated with one WD panel (and / or SRS resource set). So, for example, in case the WD 22 is configured for STxMP with up to 4 WD panels (and / or 4 SRS resource sets), and the WD 22 is configured with maximum 4 PTRS ports, then the number of PTRS ports that are used depends on the number of used WD panels during the coming PUSCH transmission. So, for example, in case a WD 22 is configured with STxMP with 2 WD panels, and is configured with a maximum of two PTRS ports, and the WD 22 is triggered with PUSCH transmission using only one of the two WD panels (i.e., PUSCH transmission associated with only one of two SRS resource set with usage codebook or nonCodebook), then the WD 22 will only transmit one of the maximum two PTRS ports (i.e., the PTRS port that is associated with the WD panel used for the transmission). In NR 3GPP Rel-18 it has been considered that during STxMP operation with two WD panels, the WD 22 is configured with two SRS resource sets with usage ‘codebook’ or ‘nonCodebook’, and where each SRS resource set should be transmitted from one WD panel each. In case a WD 22 is configured with STxMP with up to X WD panels, and with maximum X PTRS ports, it is desirable that the network node 16 knows which PTRS port that is associated with which WD panel (i.e., SRS resource set), in order to properly decode the PTRS ports. In some embodiments, to solve this, there is an association between an SRS resource set with usage ‘codebook’ or ‘nonCodebook’ and an PTRS port. E.g., in some embodiments, in case a WD 22 is configured with maximum two PTRS ports, and STxMP with up to two WD panels, a first PTRS port is associated with a first SRS resource set with usage ‘codebook’ or ‘nonCodebook’ (e.g., the SRS resource set with lowest SRS resource set ID as specified in SRS-config IE in 3GPP TS 38.3331 version 17.2.0), and the second PTRS port is associated with the second SRS resource set with usage ‘codebook’ or ‘nonCodebook’(e.g., the SRS resource set with second lowest SRS resource set ID as specified in SRS-config IE in 3GPP TS 38.3331 version 17.2.0). “Separation by sequence” Some embodiments are relevant both for STxMP with DFT-S-OFDM (i.e., different PTRS ports are transmitted over different panels, as discussed in NR 3GPP Rel- 18) and for multi-layer DFT-s-OFDM (i.e., as proposed for NR 3GPP Rel-19). For PUSCH STxMP with DFT-s-OFDM, where one PTRS port is transmitted per WD panel, it could be beneficial to not use the same PTRS port for the two (or more) WD panels, since if there is cross interference between the PUSCH transmission of the two WD panels, it will be difficult for the network to separate the two PTRS, and hence do a correct phase noise estimation for respective WD panel. For multi-layer DFT-s-OFDM, more than one PTRS port may be needed in case different local oscillator are used for different PUSCH layers. One way to separate multiple PTRS ports for DFT-s-OFDM (e.g., from different WD panels if STxMP is configured for DFT-s-OFDM) is to use different sequences for the different PTRS ports. The sequence generation for PTRS port for PUSCH DFT-s- OFDM is currently defined by the parameter nPUSCH-Identity in the field “transformPrecodingEnabled” as specified in DMRS-UplinkConfig information element of 3GPP TS 38.331 v17.2.0. In some embodiments, the WD 22 supporting DFT-s-OFDM may be configured with more than one parameter that indicates the sequence of the PTRS ports. In some embodiments, a second parameter (e.g., called “nPUSCH-Identity-r18” is introduced, where the parameter “nPUSCH-Identity-r18” may be used to indicate the sequence for a second PTRS port. In some embodiments, in case X number of PTRS Ports is supported for PUSCH DFT-s-OFDM, a list of X sequences or IDs to be used for deriving the sequences may be RRC configured where each configured sequence / ID is associated with one PTRS port. In some embodiments, when the WD 22 is configured with more than one PTRS port for PUSCH DFT-s-OFDM, the sequence of the first PTRS port is defined in RRC by a parameter (e.g., defined based on the parameter “nPUSCH-Identity) and the sequences for the remaining PTRS ports are determined based on a rule, where the parameter used to indicate the sequence of the first PTRS port is used as input. One example of such a rule is that if the WD 22 is configured with X PTRS ports, and the RRC configured parameter determining the sequence of the first PTRS ports is Y, then the sequence for the remaining X-1 PTRS ports may be : n = mod(Y + m, k), where n is the sequence number of PTRS Port m, m is the PTRS port number for the remaining X-1 PTRS ports (1,2,3…X-1), and k is the total number of available sequences (which is 1008 in legacy NR specification). Other rules are possible. In some embodiments, the sequence of remaining PTRS ports are determined based on a rule, in order to save RRC signaling overhead. “Separation by mapping to different PTRS sample positions before transform precoding ” When two or more layers are supported for DFT-s-OFDM and two PTRS ports are configured, each PTRS port may be associated to one of the two or more layers. For each PTRS port, which layer to be associated may be indicated by the network node 16. Typically, for better performance, a PTRS port should be associated to a layer with a higher signal to noise ratio (SNR). An example is shown in FIG 13. In FIG.13, a different precoder is applied to each PTRS port (and associated PUSCH layer). This corresponds, e.g., to a STxMP transmission, where a different precoder is applied for each panel. It could also correspond to a multi-layer PUSCH transmission, for which the antenna precoding is such that not more than one layer is mapped to a single antenna port (which is required to preserve the low-PAPR property of a DFT-s-OFDM waveform). In some embodiments, the PTRS sample positions before transform precoding for a first PTRS port may be determined based on the existing Table 6.4.1.2.2.2-1 in 3GPP TS 38.211, while the PTRS sample positions before transform precoding for a second PTRS port may be allocated such that they are not overlapped or not fully overlapped with the positions of the first PTRS port. This would avoid potential interference between the two PTRS ports. An example is shown in FIG.14, where the PTRS samples for the 2ndPTRS port are shifted by 3 samples to the left with respect to the PTRS samples of the 1stPTRS port and thus, the PTRS sample positions of the two PTRS ports do not overlap. This may be achieved by using different values of s and / or k in Table 6.4.1.2.2.2-1 for the second PTRS ports. An example is shown Table 10. Table 10: PTRS symbol mapping for PTRS port p (p=0,1) . Numbe Numbe Index ^^ of PTRS samples in OFDM symbol l prior to r of r of transform precoding PTRS sample groups s per N PTRS group N group samp22^^^ ^^sPcUSCH⁄ 4 ^ ^ ^^ െ 1 ^ 2 ^^ where ^^ ൌ 1,3 and ^^ ൌ 0,124^^ ^^sPcUSCH^ ^^ where ^^^ ൌ 0 and ^^ ൌ 0,1,2,3 ^ 4 ^^^^ ൌ 1 and ^^ ൌ െ4,െ3,െ2,െ1 െ 4 ^^42^ ^^ ^^sPcUSCH⁄8 ^ ^ ^^ െ 1 ^ 2 ^^ where ^^ ൌ 1,3,5,7 and ^^ ൌ 0,144^^ ^^sPcUSCH⁄4 ^ ^^ ^ ^^ where^^ ൌ 0 and ^^ ൌ 0,1,2,3 ^ 4 ^^ ^^ ൌ 0 ^^^ ൌ 1,2 and ^^ ൌ െ2,െ1,0,1 െ 4 ^^ ^^ ൌ ^ ^^sPcUSCH⁄8 ^^^ ൌ 4 and ^^ ൌ െ4,െ3,െ2,െ1 െ 4 ^^ ^^ ൌ 084^ ^^ ^^sPcUSCH⁄ 8 ^ ^ ^^ ^ ^^ where^^ ൌ 0 and ^^ ൌ 0,1,2,3 ^ 4 ^^ ^^ ൌ 0 ^ ^^ ൌ 1,2,3,4,5,6 and ^^ ൌ െ2,െ1,0,1 െ 4 ^^ ^^ ൌ ^ ^^sPcUSCH⁄ ^^ ൌ 8 and ^^ ൌ െ4,െ3,െ2,െ1 െ 4 ^^ ^^ ൌ 0 The formulas in the above table may be extended to support 4 PTRS ports, with p = 0,1,2,3. Below other alternatives that may be used to support up to 2 and 4 PTRS ports are given. ^ One alternative extension for first entry may be: 22^ ^^ െ ^ ^^ ^^ ^^ ^^ 2^^^ ^^sPcUSCH⁄ 4 ^ ^ ^^ െ 1 where ^^ ൌ 1,3 and ^^ ൌ 0,1 + ⌊ ^^⁄ 2 ⌋ ^ One alternative extension for the third entry may be: 42^^ ^^ െ ^ ^^ ^^ ^^ ^^ 2^^ ^^sPcUSCH⁄ 8 ^ ^ ^^ െ 1 where ^^ ൌ 1,3,5,7 and^^ ൌ 0,1+⌊ ^^⁄ 2 ⌋ ^ One alternative extension for the fourth entry may be: 4 4 ^^ ^^sPcUSCH⁄ 4 ^ ^^ ^ ^^ where ì ^^ ൌ 0 and ^^ ൌ 0,1,2,3 ^ 4 ^^ ^^ ൌ 0 ï^^ ൌ 1 and ^^ ൌ െ2,െ1,0,1 ^ 4 ^^ ^^ ൌ^^^sPcUSCH⁄ 8^íPUSCHï^^ ൌ 2 and ^^ ൌ െ2,െ1,0,1 െ 4 ^^ ^^ ൌ ^ ^^sc⁄8 ^î ^^ ൌ 4 and ^^ ൌ െ4,െ3,െ2,െ1 െ 4 ^^ ^^ ൌ 0^ One alternative extension for the fifth entry may be: 84^ ^^ ^^sPcUSCH⁄8 ^ ^ ^^ ^ ^^ whereì ^^ ൌ 0 and ^^ ൌ 0,1,2,3 ^ 4 ^^ ^^ ൌ 0 ï ^^ ൌ 1,2,3 and ^^ ൌ െ2,െ1,0,1 ^ 4 ^^ ^^ ൌ ^ ^^sPcUSCH⁄ 16 ^ í ^^ ൌ 4,5,6 and ^^ ൌ െ2,െ1,0,1 െ 4 ^^ ^^ ൌ ^ ^^sPcUSCH⁄ 16 ^ ï î^^ ൌ 8 and ^^ ൌ െ4,െ3,െ2,െ1 െ 4 ^^ ^^ ൌ 0In some embodiments, to achieve non-overlapping PTRS ports, the index position to insert PTRS sequence for a second port is shifted one or multiple times of “Number of samples per PTRS group” (N group samp) relative to the first port. As used in some of the formulas above, the 2p and 2 and 4 are the val N group ues used forsamp. In some embodiments, partially overlapping PTRS ports is supported. Instead of shifting 2p or 4p for the index position, a different value than N group sampmay be used for a second port. The PTRS in the sequence index for the second port may shift 1p , 2p (N group samp= 4),3p ,4p(N group samp=2) . Same PTRS port is mapped to different DMRS ports In some embodiments, when using DFT-s-OFDM together with STxMP (SDM and / or SFN scheme), one PTRS port is transmitted per used WD panel and the PTRS port transmitted from each of the two (or more) WD panels are the same (i.e., same frequency, allocation, time allocation and sequence). However, the mapping of the PTRS port to antenna ports may be different over the two or more panels. For the SDM scheme, the PUSCH layer associated with the PTRS port may additionally be different over the two or more panels. One benefit with this solution is that the specification and RRC configuration impact is kept at a minimum. One drawback may be that there might be cross interference between the PTRS transmitted from different WD panels, which might have a negative impact on the phase noise estimation associated with the different WD panels. For a PUSCH scheduled by a DG, if the higher-layer parameter transformPrecoder in PUSCH-Config is enabled at the same time as an STxMP scheme is configured (e.g., if new parameter multipanelScheme-r18 is set to sdm-r18 or sfn-r18), and if PTRS is configured via PTRS-UplinkConfig IE, then this configuration is used to determine the PTRS port for all of the two or more SRS resource sets associated with the PUSCH. PUSCH-Config ::= SEQUENCE { … transformPrecoder ENUMERATED {enabled, disabled} OPTIONAL, -- Need S … multipanelScheme-r18 CHOICE { sdm-r18 SetupRelease { SDM-Scheme-r18 } sfn-r18 SetupRelease { SFN-Scheme-r18 } } OPTIONAL, -- Need M } Some embodiments may include one or more of the following: Embodiment A1. A network node configured to communicate with a wireless device (WD), the network node configured to, and / or comprising a radio interface and / or comprising processing circuitry configured to: configure the WD with a plurality of phase tracking reference signal, PTRS, ports for discrete Fourier transform (DFT)-spread orthogonal frequency division multiplexing, OFDM. Embodiment A2. The network node of Embodiment A1, wherein configuring the WD includes configuring the WD with a parameter indicating a sequence of PTRS ports. Embodiment A3. The network node of Embodiment A1, wherein configuring the WD includes sending a parameter indicating a first PTRS port to enable the WD to determine a sequence of remaining PTRS ports according to a rule. Embodiment A4. The network node of any of Embodiments A1-A3, wherein configuring the WD includes sending a parameter indicating an association between each PTRS port and at least one layer. Embodiment A5. The network node of any of Embodiments A1-A4, wherein configuring the WD includes indicating a mapping between each PTRS port and at least one demodulation reference signal, DMRS, port. Embodiment B1. A method implemented in a network node configured to communicate with a wireless device, WD, the method comprising: configuring the WD with a plurality of phase tracking reference signal, PTRS, ports for discrete Fourier transform (DFT)-spread orthogonal frequency division multiplexing, OFDM. Embodiment B2. The method of Embodiment B1, wherein configuring the WD includes configuring the WD with a parameter indicating a sequence of PTRS ports. Embodiment B3. The method of Embodiment B1, wherein configuring the WD includes sending a parameter indicating a first PTRS port to enable the WD to determine a sequence of remaining PTRS ports according to a rule. Embodiment B4. The method of any of Embodiments B1-B3, wherein configuring the WD includes sending a parameter indicating an association between each PTRS port and at least one layer. Embodiment B5. The method of any of Embodiments B1-B4, wherein configuring the WD includes indicating a mapping between each PTRS port and at least one demodulation reference signal, DMRS, port. Embodiment C1. A wireless device (WD) configured to communicate with a network node, the WD configured to, and / or comprising a radio interface and / or processing circuitry configured to: configure a plurality of phase tracking reference signal, PTRS, ports for discrete Fourier transform (DFT)-spread orthogonal frequency division multiplexing, OFDM. Embodiment C2. The WD of Embodiment C1, wherein configuring the plurality of PTRS ports includes applying a sequence of PTRS ports. Embodiment C3. The WD of Embodiment C1, wherein configuring the plurality of PTRS ports includes determining a sequence of remaining PTRS ports according to a rule and a first PTRS port. Embodiment C4. The WD of any of Embodiments C1-C3, wherein configuring the plurality of PTRS ports includes forming an association between each PTRS port and at least one layer. Embodiment C5. The WD of any of Embodiments C1-C4, wherein configuring the plurality of PTRS ports includes mapping each PTRS port to at least one demodulation reference signal, DMRS, port. Embodiment D1. A method implemented in a wireless device (WD), the method comprising: configuring a plurality of phase tracking reference signal, PTRS, ports for discrete Fourier transform (DFT)-spread orthogonal frequency division multiplexing, OFDM. Embodiment D2. The method of Embodiment D1, wherein configuring the plurality of PTRS ports includes applying a sequence of PTRS ports. Embodiment D3. The method of Embodiment D1, wherein configuring the plurality of PTRS ports includes determining a sequence of remaining PTRS ports according to a rule and a first PTRS port. Embodiment D4. The method of any of Embodiments D1-D3, wherein configuring the plurality of PTRS ports includes forming an association between each PTRS port and at least one layer. Embodiment D5. The method of any of Embodiments D1-D4, wherein configuring the plurality of PTRS ports includes mapping each PTRS port to at least one demodulation reference signal, DMRS, port. As will be appreciated by one of skill in the art, the concepts described herein may be embodied as a method, data processing system, computer program product and / or computer storage media storing an executable computer program. Accordingly, the concepts described herein may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects all generally referred to herein as a “circuit” or “module.” Any process, step, action and / or functionality described herein may be performed by, and / or associated to, a corresponding module, which may be implemented in software and / or firmware and / or hardware. Furthermore, the disclosure may take the form of a computer program product on a tangible computer usable storage medium having computer program code embodied in the medium that may be executed by a computer. Any suitable tangible computer readable medium may be utilized including hard disks, CD-ROMs, electronic storage devices, optical storage devices, or magnetic storage devices. Some embodiments are described herein with reference to flowchart illustrations and / or block diagrams of methods, systems and computer program products. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, may be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer (to thereby create a special purpose computer), special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks. These computer program instructions may also be stored in a computer readable memory or storage medium that may direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instruction means which implement the function / act specified in the flowchart and / or block diagram block or blocks. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks. It is to be understood that the functions / acts noted in the blocks may occur out of the order noted in the operational illustrations. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality / acts involved. Although some of the diagrams include arrows on communication paths to show a primary direction of communication, it is to be understood that communication may occur in the opposite direction to the depicted arrows. Computer program code for carrying out operations of the concepts described herein may be written in an object oriented programming language such as Python, Java® or C++. However, the computer program code for carrying out operations of the disclosure may also be written in conventional procedural programming languages, such as the "C" programming language. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer. In the latter scenario, the remote computer may be connected to the user's computer through a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). Many different embodiments have been disclosed herein, in connection with the above description and the drawings. It will be understood that it would be unduly repetitious and obfuscating to literally describe and illustrate every combination and subcombination of these embodiments. Accordingly, all embodiments may be combined in any way and / or combination, and the present specification, including the drawings, shall be construed to constitute a complete written description of all combinations and subcombinations of the embodiments described herein, and of the manner and process of making and using them, and shall support claims to any such combination or subcombination. Abbreviations that may be used in the preceding description include: Abbreviation Explanation 3GPP Third Generation Partnership Project ASN Abstract Syntax Notation BPSK Binary Phase Shift Keying BWP Bandwidth Part CA Carrier Aggregation CB Codebook CDM Code Division Multiplexing CE Control Element CP-OFDM Cyclic Prefix OFDM CRB Carrier RB CG Configured Grant CS Cyclic Shift CS-RNTI Configured Scheduling RNTI CSI Channel State Information DCI Downlink Control Information DFT Discrete Fourier Transform DFT-S-OFDM DFT Spread OFDM DG Dynamic Grant DL Downlink DMRS Demodulation RS FD-OCC Frequency Domain OCC FDD Frequency-Division Multiplexing FR1 Frequency Range 1 FR2 Frequency Range 2 IDFT Inverse DFT gNB gNodeB IE Information Element LSBw Least Significant Bit LTE Long Term Evolution MAC Medium Access Control MCS Modulation and Coding Scheme MIB Master Information Block MIMO Multiple-Input Multiple-Output MSB Most Significant Bit NCB Non-Codebook NDI New Data Indicator NR New Radio NW Network OCC Orthogonal Cover Code OFDM Orthogonal Frequency Division Multiplexing PA Power Amplifier PAPR Peak-to-Average Power Ratio PC Power Control PCell Primary Cell PDCCH Physical Downlink Control Channel PDSCH Physical Downlink Shared Channel PRB Physical RB PSD Power Spectral Density PTRS Phase Tracking Reference Signal PUCCH Physical Uplink Control Channel PUSCH Physical Uplink Shared Channel QPSK Quadrature Phase-Shift Keying RB Resource Block RBG Resource Block Group RE Resource Element RF Radio Frequency RS Reference Signal RSRP RS Received Power RIV Resource Indication Value RNTI Radio Network Temporary Identifier RRC Radio Resource Control RV Redundancy Version SCS Subcarrier Spacing SCell Secondary Cell SDM Spatial Division Multiplexing SFN Single Frequency Network SIB1 System Information Block 1 SLIV Start and Length Indicator Value SNR Signal-to-Noise Ratio SRI SRS Resource Indicator SRS Sounding Reference Signal SRSI SRS Resource Set Indicator SSB Synchronization Signal Block STxMP Simultaneous Transmission from Multiple Panels SUL Supplementary Uplink TB Transport Block TD-OCC Time Domain OCC TDD Time-Division Duplexing TRP Transmission and Reception Point UE User Equipment UL Uplink VRB Virtual RB It will be appreciated by persons skilled in the art that the embodiments described herein are not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope of the following claims.

Claims

What is claimed is:

1. A method in a wireless device, WD (22), configured to communicate with a network node (16), the method comprising: receiving (S22) a configuration of multiple phase tracking reference signal, PTRS, ports for multilayer data transmission with discrete Fourier transform spread orthogonal frequency division multiplexing, DFT-s-OFDM; determining (S24) a first mapping of the multiple PTRS ports to different spatial layers; and transmitting (S26) via the PTRS ports according to the first mapping.

2. The method of Claim 1, further comprising transmitting an indication of a first maximum number of supported PTRS ports.

3. The method of any of Claims 1 and 2, further comprising receiving a second maximum number of PTRS ports by radio resource control, RRC, signaling.

4. The method of any of Claims 1-3, wherein the first mapping includes allocating PTRS symbols of a first PTRS port to a first set of time and frequency resources and allocating PTRS symbols of a second PTRS port to a second set of time and frequency resources, wherein the first and the second resources are different and not overlapping if the first and the second PTRS ports are different.

5. The method of Claim 4, wherein the PTRS symbols of a first PTRS port can be the same as or different from the PTRS symbols of a second PTRS port.

6. The method of any of Claims 4 and 5, wherein the first PTRS port is associated to a first spatial layer and the second PTRS port is associated to a second spatial layer.

7. The method of Claim 1, wherein multilayer data transmission is a simultaneous data transmission over multiple antenna panels, STxMP, scheduled by single downlink control information, DCI.

8. The method of any of Claims 1-7, wherein the first mapping includes associating sounding reference signal, SRS, resource sets to the PTRS ports.

9. The method of any of Claims 1-8, further comprising associating different PTRS ports with different sequences.

10. The method of Claim 9, wherein the associating is performed according to a list of different sequences indicated by radio resource control, RRC, signaling.

11. The method of any of Claims 9 and 10, further comprising receiving an indication of a first sequence for a first PTRS port and determining sequences of remaining PTRS ports according to a rule.

12. The method of any of Claims 1-11, further comprising determining a second mapping between the PTRS ports and demodulation reference signal, DMRS, ports.

13. The method of any of Claims 1-12, wherein the PTRS ports transmitted from two or more panels are identical.

14. The method of any of Claims 1-13, wherein determining the first mapping includes determining a PTRS port for each of a plurality of sounding reference signal, SRS, resource sets associated with a physical uplink shared channel, PUSCH.

15. A wireless device, WD (22), configured to communicate with a network node (16), the WD (22) configured to: receive a configuration of multiple phase tracking reference signal, PTRS, ports for multilayer data transmission with discrete Fourier transform spread orthogonal frequency division multiplexing, DFT-s-OFDM; determine a first mapping of the multiple PTRS ports to different spatial layers; and transmit via the PTRS ports according to the first mapping.

16. The WD (22) of Claim 15, wherein the WD (22) is configured to transmitan indication of a first maximum number of supported PTRS ports.

17. The WD (22) of any of Claims 15 and 16, wherein the WD (22) is configured to receive a second maximum number of PTRS ports by radio resource control, RRC, signaling.

18. The WD (22) of any of Claims 15-17, wherein the first mapping includes allocating PTRS symbols of a first PTRS port to a first set of time and frequency resources and allocating PTRS symbols of a second PTRS port to a second set of time and frequency resources, wherein the first and the second resources are different and not overlapping if the first and the second PTRS ports are different.

19. The WD (22) of Claim 18, wherein the PTRS symbols of a first PTRS port can be the same as or different from the PTRS symbols of a second PTRS port.

20. The WD (22) of any of Claims 18 and 19, wherein the first PTRS port is associated to a first spatial layer and the second PTRS port is associated to a second spatial layer.

21. The WD (22) of Claim 15, wherein multilayer data transmission is a simultaneous data transmission over multiple antenna panels, STxMP, scheduled by single downlink control information, DCI.

22. The WD (22) of any of Claims 15-21, wherein the PTRS port mapping includes associating sounding reference signal, SRS, resource sets to the PTRS ports.

23. The WD (22) of any of Claims 15-22, wherein the WD (22) is configured to associate different PTRS ports with different sequences.

24. The WD (22) of Claim 23, wherein the associating is performed according to a list of different sequences received by radio resource control, RRC, signaling.

25. The WD (22) of any of Claims 23 and 24, wherein the WD (22) is configured to receive an indication of a first sequence for a first PTRS port anddetermining a sequence of remaining PTRS ports according to a rule.

26. The WD (22) of any of Claims 15-25, wherein the WD (22) is configured to determine a second mapping between the PTRS ports and demodulation reference signal, DMRS, ports.

27. The WD (22) of any of Claims 15-26, wherein PTRS ports transmitted from two or more panels are identical.

28. The WD (22) of any of Claims 15-27, wherein determining the first mapping includes determining a PTRS port for each of a plurality of sounding reference signal, SRS, resource sets associated with a physical uplink shared channel, PUSCH.

29. A method in a network node (16) configured to communicate with a wireless device, WD (22), the method comprising: determining (S14) a first mapping of phase tracking reference signal, PTRS, ports to different spatial layers; configuring (S16) the WD (22) with multiple phase tracking reference signal, PTRS, ports for multilayer data transmission with discrete Fourier transform spread orthogonal frequency division multiplexing, DFT-s-OFDM; and separating (S18) PTRS ports for signals received from the WD (22) on different layers according to the first mapping.

30. The method of Claim 29, further comprising receiving from the WD (22) an indication of a first maximum number of supported PTRS ports.

31. The method of any of Claims 29 and 30, wherein a second maximum number of PTRS ports is configured by radio resource control, RRC, signaling.

32. The method of any of Claims 29-31, wherein the first mapping includes allocating PTRS symbols of a first PTRS port to a first set of time and frequency resources and allocating PTRS symbols of a second PTRS port to a second set of time and frequency resources, wherein the first and the second resources are different and not overlapping if the first and the second PTRS ports are different.

33. The method of Claim 32, wherein the PTRS symbols of a first PTRS port can be the same as or different from the PTRS symbols of a second PTRS port.

34. The method of any of Claims 32 and 33, wherein the first PTRS port is associated to a first spatial layer and the second PTRS port is associated to a second spatial layer.

35. The method of Claim 29, wherein multilayer data transmission is a simultaneous data transmission over multiple antenna panels, STxMP, scheduled by single downlink control information, DCI.

36. The method of any of Claims 29-35, wherein the PTRS port mapping includes associating sounding reference signal, SRS, resource sets and PTRS ports.

37. The method of any of Claims 29-36, wherein separating the PTRS ports includes associated different PTRS ports to different sequences.

38. The method of Claim 37, wherein a list of the different sequences for different PTRS ports is signaled to the WD (22) by radio resource control, RRC, signaling.

39. The method of any of Claims 37 and 38, wherein configuring the WD (22) includes sending an indication of a first PTRS port to enable the WD (22) to determine a sequence of remaining PTRS ports according to a rule.

40. The method of any of Claims 29-39, wherein configuring the WD (22) includes sending indication of an association between each PTRS port and at least one layer.

41. The method of any of Claims 29-40, wherein separating PTRS ports includes: determining PTRS sample positions before transform precoding; and mapping different layers to the PTRS sample positions.

42. The method of Claim 29, wherein first PTRS sample positions before transform precoding for a first PTRS port are determined based on a table and second PTRS sample positions before transform precoding for a second PTRS port are allocated to not fully overlap the first PTRS sample positions.

43. The method of Claim 42, wherein non-overlapped PTRS sample positions are determined based at least in part on shifting the second PTRS sample positions relative to the first PTRS sample positions.

44. The method of any of Claims 29-43, wherein configuring the WD (22) includes indicating to the WD (22) a second mapping between the PTRS ports and demodulation reference signal, DMRS, ports.

45. The method of any of Claims 29-44, wherein configuring the WD (22) includes enabling a parameter in a physical uplink shared channel, PUSCH, configuration information element.

46. The method of Claim 45, wherein the separating PTRS ports includes determining a PTRS port for each of a plurality of sounding reference signal, SRS, resource sets associated with the PUSCH.

47. A network node (16) configured to communicate with a wireless device, WD (22), the network node (16) configured to: determine a first mapping of phase tracking reference signal, PTRS, ports to different spatial layers; configure the WD (22) with multiple phase tracking reference signal, PTRS, ports for multilayer data transmission with discrete Fourier transform spread orthogonal frequency division multiplexing, DFT-s-OFDM; and separate PTRS ports for signals received from the WD (22) on different layers according to the first mapping.

48. The network node (16) of Claim 47, wherein the network node (16) is configured to receive from the WD (22), an indication of a first maximum number of supported PTRS ports.

49. The network node (16) of any of Claims 47 and 48, wherein a second maximum number of PTRS ports is configured by radio resource control, RRC, signaling.

50. The network node (16) of any of Claims 47-49, wherein the first mapping includes allocating PTRS symbols of a first PTRS port to a first set of time and frequency resources and allocating PTRS symbols of a second PTRS port to a second set of time and frequency resources, wherein the first and the second resources are different and not overlapping if the first and the second PTRS ports are different.

51. The network node (16) of Claim 50, wherein the PTRS symbols of a first PTRS port can be the same as or different from the PTRS symbols of a second PTRS port.

52. The network node (16) of any of Claims 50 and 51, wherein the first PTRS port is associated to a first spatial layer and the second PTRS port is associated to a second spatial layer.

53. The network node (16) of Claim 47, wherein multilayer data transmission is a simultaneous data transmission over multiple antenna panels, STxMP, scheduled by single downlink control information, DCI.

54. The network node (16) of any of Claims 47-53, wherein the PTRS port mapping includes associating sounding reference signal, SRS, resource sets and PTRS ports.

55. The network node (16) of any of Claims 47-54, wherein separating the PTRS ports includes associated different PTRS ports to different sequences.

56. The network node (16) of Claim 55, wherein a list of the different sequences for different PTRS ports is signaled to the WD (22) by radio resource control, RRC, signaling.

57. The network node (16) of any of Claims 55 and 56, wherein configuringthe WD (22) includes sending an indication of a first PTRS port to enable the WD (22) to determine a sequence of remaining PTRS ports according to a rule.

58. The network node (16) of any of Claims 47-57, wherein configuring the WD (22) includes sending indication of an association between each PTRS port and at least one layer.

59. The network node (16) of any of Claims 47-58, wherein separating PTRS ports includes: determining PTRS sample positions before transform precoding; and mapping different layers to the PTRS sample positions.

60. The network node (16) of Claim 59, wherein first PTRS sample positions before transform precoding for a first PTRS port are determined based on a table and second PTRS sample positions before transform precoding for a second PTRS port are allocated to not fully overlap the first PTRS sample positions.

61. The network node (16) of Claim 60, wherein non-overlapped PTRS sample positions are determined based at least in part on shifting the second PTRS sample positions relative to the first PTRS sample positions.

62. The network node (16) of any of Claims 47-61, wherein configuring the WD (22) includes indicating to the WD (22) a second mapping between the PTRS ports and demodulation reference signal, DMRS, ports.

63. The network node (16) of any of Claims 47-62, wherein configuring the WD (22) includes enabling a parameter in a physical uplink shared channel, PUSCH, configuration information element.

64. The network node (16) of Claim 63, wherein the separating PTRS ports includes determining a PTRS port for each of a plurality of sounding reference signal, SRS, resource sets associated with the PUSCH.

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