Method for configuring a phase-tracking reference signal

Abstract

Describes a technique for transmitting and receiving configuration messages for phase-tracking reference signals PT-RS over a radio channel between a radio access node and a radio device. The radio channel includes a plurality of subcarriers in a physical resource block PRB (602). A subset of the subcarriers (608) in the PRB (602) is allocated to demodulation reference signals DM-RS. In terms of the method aspect of the technique, a configuration message is transmitted to the radio device. The configuration message includes a bit field indicating at least one subcarrier allocated to PT-RS among the subset of subcarriers allocated to DM-RS.

Description

Technical Field

[0001] Generally, the present disclosure relates to a technique for configuring a phase-tracking reference signal (PT-RS). More specifically, methods and apparatuses for transmitting and receiving configuration messages for PT-RS and radio signal structures representing such configuration messages are provided. Background Art

[0002] The 3rd Generation Partnership Project (3GPP) has specified the physical signal structure of the next-generation radio access technology as the New Radio (NR). NR has a lean design that minimizes always-on transmissions to enhance network energy efficiency and ensure forward compatibility. Compared with the existing 3GPP Long-Term Evolution (LTE), reference signals in NR are transmitted only when necessary. The four main reference signals include: Demodulation Reference Signal (DM-RS), Phase-Tracking Reference Signal (PT-RS), Sounding Reference Signal (SRS), and Channel State Information Reference Signal (CSI-RS).

[0003] PT-RS is introduced in NR to enable compensation for oscillator phase noise. Generally, phase noise increases with the oscillator carrier frequency. Therefore, PT-RS can be utilized at high carrier frequencies such as millimeter waves to mitigate phase noise. One of the main degradations caused by phase noise in Orthogonal Frequency Division Multiplexing (OFDM) signals is the same phase rotation of all subcarriers, called Common Phase Error (CPE). PT-RS has a low density in the frequency domain and a high density in the time domain because the phase rotation caused by CPE is the same for all subcarriers within an OFDM symbol, but there is less correlated phase noise across OFDM symbols. PT-RS is specific to a User Equipment (UE) and is confined to the scheduled resources. The number of DM-RS ports used for transmitting PT-RS can be lower than the total number of DM-RS ports.

[0004] For example, the exact PT-RS subcarriers can be implicitly defined based on one or more of the following parameters: DM-RS port index, DM-RS scrambling ID (SCID), and cell ID. Additionally, explicit (e.g., Radio Resource Control RRC) signaling of the conventional parameter "PTRS-RE-offset" can override the above implicit association rules, which is important, for example, to be able to force avoidance of conflicts between PT-RS and poor-performing direct current (DC) subcarriers. Therefore, simple or existing solutions would signal an explicit offset or position "PTRS-RE-offset" that can take any value from 0 to 11. In other words, the existing explicit signaling can be used to map PT-RS to any subcarrier in a Physical Resource Block (PRB).

[0005] In existing signaling, the parameter "PTRS-RE-offset" for signaling can be set to any value from 0 to 11. Then, the problem is that "PTRS-RE-offset" signaled using RRC signaling implies gNB scheduling restrictions because the DM-RS for PDSCH or PUSCH transmission must use the subcarriers indicated by "PTRS-RE-offset", which is not desirable.

[0006] For example, if "PTRS-RE-offset = 0", if DM-RS configuration type 1 is configured, the DM-RS subcarrier comb (i.e., the subset of subcarriers {1, 3, 5, 7, 9, 11} assigned to DM-RS) cannot be used when scheduling a UE because the PT-RS must be mapped to the subcarriers used by the DM-RS (i.e., within the said subset).

[0007] Another problem is the high overhead in existing signaling. If "PTRS-RE-offset" can be set to values from 0 to 11, each indication of "PTRS-RE-offset" requires 4 bits. Moreover, since the PT-RS ports for the downlink (DL) and uplink (UL) can be associated with different DM-RS ports, independent indications of "PTRS-RE-offset" are required for UL and DL, thus increasing the overhead. Similarly, existing signaling must independently indicate the parameter "PTRS-RE-offset" for each PT-RS port in SU-MIMO, further increasing the signaling overhead. Summary of the Invention

[0008] Therefore, a technique is needed that allows for more efficient and / or flexible configuration of PT-RS. More specifically, a technique is needed to reduce the signaling overhead caused by this configuration. Alternatively or additionally, a technique is needed to avoid scheduling restrictions.

[0009] Regarding one aspect, a method for transmitting a configuration message for a phase-tracking reference signal (PT-RS) over a radio channel between a radio access node and a radio device is provided. The radio channel includes a plurality of subcarriers in a physical resource block (PRB). A subset of the subcarriers in the PRB is assigned to a demodulation reference signal (DM-RS). The method includes or triggers the step of transmitting the configuration message to the radio device. The configuration message includes a bit field indicating at least one subcarrier assigned to the PT-RS among the subset of subcarriers assigned to the DM-RS.

[0010] This subcarrier allocated to PT-RS can also be referred to as the PT-RS subcarrier of PT-RS. The subcarriers allocated to DM-RS can also be referred to as DM-RS subcarriers. A subset of subcarriers allocated to DM-RS (i.e., a subset including DM-RS subcarriers) can also be referred to as a DM-RS subset. The DM-RS subset can be an appropriate subset of multiple subcarriers in a PRB. In other words, this subset can include fewer subcarriers than a PRB.

[0011] With the help of a bit field, a configuration message can signal, for example, a relative offset with respect to a relevant subset of subcarriers allocated to DM-RS. The parameter or function represented by the bit field can be referred to as the subcarrier offset or resource element offset (RE-offset) of PT-RS, or simply "PTRS-RE-offset". This method can be implemented as the RE offset signaling of PT-RS.

[0012] The actual subcarriers used for PT-RS can depend on both the parameter "PTRS-RE-offset" and the subset of subcarriers allocated to DM-RS. For example, if the DM-RS ports are identified by DM-RS port numbers, the actual subcarriers used for PT-RS can depend on both the parameter "PTRS-RE-offset" and the DM-RS port numbers.

[0013] In addition, multiple different DM-RSs can be transmitted on corresponding DM-RS ports. The DM-RS port number p can be among the set of DM-RS ports for a radio channel, for example, in order to perform channel estimation of the radio channel and / or demodulate the radio channel into a data channel on the receiving side of the radio channel.

[0014] To avoid scheduling restrictions and reduce signaling overhead, the value of the bit field (i.e., the parameter "PTRS-RE-offset") represents the relative subcarrier index in the subset of subcarriers assigned to a DM-RS port in a specific transmission.

[0015] By transmitting the parameter "PTRS-RE-offset" as a configuration parameter in the bit field of the configuration message, scheduling restrictions can be avoided at least in some embodiments because the group of possible PT-RS subcarriers is limited to the subset of subcarriers used by, allocated to, or scheduled for the DM-RS ports associated with the PT-RS ports.

[0016] The same embodiment (e.g., the embodiment in the above paragraph) or additional embodiments may require much less signaling overhead than existing offset signaling because a common indication of "PTRS-RE-offset" can be used for both DL and UL. Alternatively or additionally, a common indication can be used for different PT-RS ports in SU-MIMO.

[0017] The bit field may include n bits indicating at least one sub - carrier among the subset of sub - carriers allocated to DM - RS that is allocated to PT - RS. The number of the plurality of sub - carriers in the PRB may be greater than 2 n .

[0018] The subset of sub - carriers allocated to DM - RS may be signaled dynamically.

[0019] The bit field may include 2 or 3 bits indicating at least one sub - carrier among the subset of sub - carriers allocated to DM - RS that is allocated to PT - RS. The number of the plurality of sub - carriers in the PRB may be 12.

[0020] The size of the bit field may be determined to represent any one of the sub - carriers in the subset of sub - carriers allocated to DM - RS as a sub - carrier allocated to PT - RS.

[0021] The bit field may include n bits. The number of sub - carriers in the subset of sub - carriers allocated to DM - RS may be equal to or less than 2 n .

[0022] Each sub - carrier in the subset of sub - carriers allocated to DM - RS may be uniquely identified by an index. The bit field may indicate the index corresponding to the sub - carrier allocated to PT - RS.

[0023] The radio channel may be accessed via one or more DM - RS ports. Each transmission of DM - RS may be associated with one of the one or more DM - RS ports.

[0024] Each DM - RS port among the one or more DM - RS ports may be uniquely identified by a DM - RS port index. Each transmission of DM - RS (abbreviation: DM - RS transmission) may be defined by or associated with the DM - RS port index.

[0025] One or more DM - RS ports may be located at (or may define) the transmission side of the radio channel. One or more DM - RS ports may be available for a radio access node (e.g., located at the radio access node) for downlink transmission. Alternatively or additionally, one or more DM - RS ports may be available for a radio device (e.g., located at the radio device) for uplink transmission.

[0026] Alternatively or additionally, one or more DM-RS ports may be located (or may be defined) on the receiving side of a radio channel. For example, the transmitting side may initially define the DM-RS ports by transmitting DM-RS, and the receiving side may define combined weights for beamforming reception based on the received DM-RS. One or more DM-RS ports are available for a radio access node (e.g., located at the radio access node) for uplink reception. Alternatively or additionally, one or more DM-RS ports are available for a radio device (e.g., located at the radio device) for downlink transmission.

[0027] Transmissions on a radio channel may include one or more layers (also referred to as spatial streams). The number of layers may be equal to the number of DM-RS ports used for transmission on the radio channel. The radio channel may be a multiple-input multiple-output (MIMO) channel, which is accessed at the transmitting side (i.e., the input of the MIMO channel) through DM-RS ports, optionally mapped to multiple transmitter antennas, and received at the receiver side (i.e., the output of the MIMO channel) through multiple receiver ports formed by the antennas.

[0028] The multiple transmitted layers may be separated in the spatial and / or polarization domain by a transmit precoder and separated in the receiver by performing channel estimation on the radio channel based on the DM-RS and / or PT-RS received at the receiving side and optional interference layer suppression. For example, the transmission may be a multi-layer single-user MIMO (SU-MIMO) transmission, where two or more layers may be accessed through two or more DM-RS ports.

[0029] DM-RS may be used to perform at least one of precoding at the transmitting side and demodulation at the receiving side of a radio channel.

[0030] The subset of subcarriers allocated to DM-RS may depend on the corresponding DM-RS port. For each DM-RS port, a subset of subcarriers in the PRB may be allocated to the DM-RS transmitted (or to be transmitted) through the corresponding DM-RS port. That is, the subset of subcarriers allocated to DM-RS is associated with each DM-RS port. At least some of the subsets of subcarriers used to transmit DM-RS through different DM-RS ports may be different. For example, the different subsets may be disjoint.

[0031] The PRB may include 12 subcarriers given by the index k ∈ {0,..., 11}. The subset of subcarriers allocated to the DM-RS transmitted through DM-RS port p may be given by the following formula:

[0032] {2·R·m + S·k′ + Δ(p) ∈ {0, ..., 11} | k′ ∈ {0, 1}, 0 ≤ m < 6 / R}, where R = 1, 2, or 3; S = 1 or 2; and the offset Δ(p) depends on the DM-RS port p.

[0033] For DM-RS configuration type 1, the parameters can be R = 2, S = 2, and Δ(p) ∈ {0, 1}. For DM-RS configuration type 2, the parameters can be R = 3, S = 1, and Δ(p) ∈ {0, 2, 4}. In the above expressions of these sets, the upper limit "11" can be replaced by and the upper limit 6 / R can be replaced by

[0034] The DM-RS can be derived from the sequence r(2·m + k′ + n0), where is the starting point of the carrier bandwidth part in terms of PRB, and is the number of subcarriers per PRB.

[0035] Different DM-RS can be transmitted through each DM-RS port. Since different DM-RS (e.g., orthogonal signals) are transmitted through different DM-RS ports, any dependency on "DM-RS" can be equivalently represented as a dependency on the corresponding "DM-RS port".

[0036] The DM-RS transmitted through different DM-RS ports can be distinguished by at least one of orthogonal covering codes in the frequency domain, orthogonal covering codes in the time domain, and the subset of subcarriers assigned to the DM-RS.

[0037] For example, each DM-RS transmitted through different DM-RS ports can use a disjoint subset of subcarriers or be orthogonally encoded in the frequency domain.

[0038] One of the DM-RS ports in the DM-RS ports can be associated with the PT-RS. The PT-RS can be transmitted through the DM-RS port associated with the PT-RS. The PT-RS can be transmitted on the subcarriers assigned to the PT-RS according to the bit field among the subset of subcarriers assigned to the DM-RS transmitted through the said one DM-RS port.

[0039] PT-RS and DM-RS can be transmitted simultaneously or separately (e.g., transmitted in an OFDM symbol or different PRBs, i.e., in different time slots or transmission time intervals TTI). In addition, the transmission of PT-RS and the transmission of DM-RS can overlap. The transmission duration of PT-RS can be longer than the transmission duration of DM-RS (e.g., multiple times the transmission duration of DM-RS). For example, PT-RS can be transmitted during one PRB including 14 OFDM symbols. DM-RS can be transmitted during one or two OFDM symbols.

[0040] The subcarriers assigned to PT-RS can be derived from or can be exportable from a bit field for at least one of the uplink transmission of PT-RS and the downlink transmission of PT-RS.

[0041] The radio access node can be configured to access a radio channel through a DM-RS port for downlink transmission to a radio device. The method can further include or trigger the step of transmitting PT-RS on a subcarrier through at least one DM-RS port, and allocating the subcarrier to PT-RS according to a bit field among a subset of DM-RS assigned to the corresponding DM-RS port of the subcarrier.

[0042] Alternatively or additionally, the radio device can be configured to access a radio channel through a DM-RS port for uplink transmission to a radio access node. The method can further include or trigger the step of receiving PT-RS transmitted on a subcarrier through at least one DM-RS port, and allocating the subcarrier to PT-RS according to a bit field among a subset of DM-RS assigned to the corresponding DM-RS port.

[0043] The DM-RS port through which PT-RS is transmitted can also be referred to as a PT-RS port. The expression "PT-RS" can collectively refer to different PT-RS (port-specific PT-RS) transmitted on different DM-RS ports. Alternatively or additionally, the expression "PT-RS" can refer to port-specific PT-RS in the context of, for example, a certain PT-RS port.

[0044] The radio access node can provide radio access to at least one radio device on a radio channel. For each radio device, PT-RS can be transmitted through each DM-RS port of one or two DM-RS ports.

[0045] A radio channel may include a single-user multiple-input multiple-output (SU-MIMO) channel accessed via two or more DM-RS ports. PT-RS may be transmitted or received on each of at least two of the two or more DM-RS ports. A radio channel may include two or more layers and / or two or more DM-RS ports. PT-RS may be transmitted or received for each of the two or more layers or via each of the two or more DM-RS ports.

[0046] A radio channel may include a multi-user multiple-input multiple-output (MU-MIMO) channel. Different DM-RS groups of DM-RS ports may provide access to different radio devices. PT-RS may be transmitted or received via at least one DM-RS port in each DM-RS group.

[0047] For each of the plurality of radio devices, the MU-MIMO channel may include at least one layer or at least one DM-RS port. For each of the plurality of radio devices, PT-RS may be transmitted or received on at least one layer or via at least one DM-RS port.

[0048] The subcarriers allocated to PT-RS may be uniquely determined among a subset of subcarriers allocated to DM-RS based on a bit field in a configuration message and a combination of the DM-RS ports via which PT-RS is transmitted or received.

[0049] The same value of the bit field may indicate different subcarriers allocated to PT-RS transmitted or received via different DM-RS ports.

[0050] The bit field may indicate two candidate subcarriers for PT-RS among a subset of subcarriers allocated to DM-RS. The subcarrier allocated to PT-RS may be determined among the two candidate subcarriers based on the DM-RS port via which PT-RS is transmitted or received.

[0051] The subcarriers allocated to PT-RS transmitted or received via DM-RS port p may be given by 2·R·m + S·k′ + Δ(p). The bit field may indicate m. The value of k′ may be determined as p mod 2 by DM-RS port p.

[0052] PT-RS may be transmitted or received via each of at least two different DM-RS ports. Alternatively or in combination, PT-RS may be transmitted in each of an uplink transmission and a downlink transmission.

[0053] The DM-RS transmitted through DM-RS port p may be subjected to an orthogonal cover code OCC (TD-OCC) in the time domain. Alternatively or additionally, the DM-RS transmitted through DM-RS port p may be subjected to an OCC in the frequency domain (FD-OCC). The subcarriers assigned to PT-RS may be determined among the subset of subcarriers assigned to DM-RS based on a combination of a bit field, the DM-RS port dependency of TD-OCC, and the DM-RS port dependency of FD-OCC. The combination may include a summation.

[0054] For example, for DM-RS port p, the DM-RS port dependency of TD-OCC may include:

[0055] TD_offset p = (p - 1000 div 2) div R, or

[0056] TD_offset p = floor((p - 1000) / (2·R)).

[0057] Alternatively or additionally, for DM-RS port p, the DM-RS port dependency of FD-OCC may include:

[0058] FD_offset p = p mod 2.

[0059] Herein, for DM-RS configuration type 1, R may be equal to 2, and for DM-RS configuration type 2, R may be equal to 3.

[0060] TD-OCC may include a factor (e.g., symbol) according to the following formula:

[0061] w t (I′) = [1 - 2·(TD_offset p )] / ′ .

[0062] Alternatively or additionally, FD-OCC may include a factor (e.g., symbol) according to the following formula:

[0063] w f (k′) = [1 - 2·(FD_offset p )] k′ .

[0064] For each DM-RS port through which PT-RS is transmitted or received, the configuration message may include an instance of a bit field indicating the subcarriers assigned to PT-RS among the subset of subcarriers assigned to DM-RS transmitted through the corresponding DM-RS port.

[0065] PT-RS can be transmitted or received through one of the DM-RS ports in the DM-RS port. This one DM-RS port can be determined according to predefined rules. For example, the DM-RS ports can be grouped into two or more non-overlapping DM-RS groups, and PT-RS can be transmitted or received through one of the DM-RS ports in each DM-RS group. This one DM-RS port can be determined according to the predefined rules applied to each DM-RS group.

[0066] This one DM-RS port through which PT-RS is transmitted or received may not be specified in the configuration message. Each of the radio access node and the radio device can determine this one DM-RS port through which PT-RS is transmitted or received by independently applying the predefined rules.

[0067] Each DM-RS port can be uniquely identified by a port index. One of the DM-RS ports determined according to the predefined rules can be the DM-RS port with the lowest port index.

[0068] PT-RS can include tones on the subcarriers assigned to PT-RS. The tones can correspond to the tones of the DM-RS transmitted on the same subcarrier through the corresponding DM-RS port. Herein, a tone can include a complex (e.g., Fourier) coefficient (e.g., for the duration of one OFDM symbol) carried by one subcarrier or one resource element. Each OFDM symbol can include multiple tones, and each tone is transmitted simultaneously on the corresponding subcarrier. During the duration of the symbol length, the tones can correspond to harmonic Fourier components in the time domain. Alternatively or additionally, a tone can refer to a modulation on one RE.

[0069] PT-RS can be transmitted or received in multiple PRBs. The same subcarriers relative to the corresponding PRB can be assigned to PT-RS in each PRB. In addition, the same subset of subcarriers can be assigned to DM-RS in each PRB.

[0070] The transmitted waveform can include orthogonal frequency division multiplexing (OFDM), especially cyclic prefix (CP) OFDM (CP-OFDM). The tones can be OFDM tones. The transmission can include multiple OFDM symbols per PRB, such as one time slot in the time domain. Each OFDM symbol can include one OFDM tone per subcarrier.

[0071] Each DM-RS port can be mapped to multiple antenna ports according to a precoder. Different DM-RS ports can be mapped according to different precoders.

[0072] Some or each DM-RS port may be beamformed according to a precoder. For example, for single-layer (Tx) beamforming on a radio channel, one DM-RS port may be used to access the radio channel. Alternatively, the DM-RS ports may be mapped to antenna ports (e.g., one-to-one correspondence or one-to-many correspondence).

[0073] The number of subcarriers according to DM-RS configuration type 1 in the subset of subcarriers allocated to DM-RS may be twice the number of subcarriers according to DM-RS configuration type 2 in the subset of subcarriers allocated to DM-RS. The same-sized bit field may be used for each of DM-RS configuration type 1 and DM-RS configuration type. The most significant bit of the bit field may be ignored or set to zero in order to determine the subcarriers allocated to PT-RS in DM-RS configuration type 2.

[0074] This aspect may be implemented at the RAN and / or by a radio access node of the RAN, for example. In this document, the expression radio access node may be used interchangeably with a base station or cell of the RAN. A radio access node may cover any station configured to provide radio access to one or more radio devices.

[0075] According to another aspect, a method is provided for receiving a configuration message of a phase-tracking reference signal PT-RS on a radio channel between a radio access node and a radio device. The radio channel includes a plurality of subcarriers in a physical resource block PRB. A subset of the subcarriers in the PRB is allocated to a demodulation reference signal DM-RS. The method includes or triggers a step of receiving a configuration message from the radio access node. The configuration message includes a bit field indicating at least one subcarrier allocated to PT-RS in the subset of subcarriers allocated to DM-RS.

[0076] A subcarrier allocated to PT-RS may also be referred to as a PT-RS subcarrier of PT-RS. A subcarrier allocated to DM-RS may also be referred to as a DM-RS subcarrier. A subset of the subcarriers allocated to DM-RS (i.e., the subset including the DM-RS subcarriers) may also be referred to as a DM-RS subset. The DM-RS subset may be a proper subset of the plurality of subcarriers in the PRB. In other words, the subset may include fewer subcarriers than the PRB.

[0077] By means of the bit field, the configuration message may signal, for example, a relative offset with respect to a relevant subset of the subcarriers allocated to DM-RS. The parameter or function represented by the bit field may be referred to as a subcarrier offset or resource element offset (RE-offset) of PT-RS, or simply "PTRS-RE-offset". The method may be implemented as RE-offset signaling of PT-RS.

[0078] The actual subcarriers for PT-RS can depend on both the parameter "PTRS-RE-offset" and the subset of subcarriers allocated for DM-RS. For example, if the DM-RS ports are identified by DM-RS port numbers, the actual subcarriers for PT-RS can depend on both the parameter "PTRS-RE-offset" and the DM-RS port numbers.

[0079] In addition, multiple different DM-RSs can be transmitted on corresponding DM-RS ports. The DM-RS port number p can be among the set of DM-RS ports for a radio channel, e.g., in order to perform channel estimation of the radio channel and / or demodulate the radio channel into a data channel on the receiving side of the radio channel.

[0080] To avoid scheduling restrictions and reduce signaling overhead, the value of the bit field (i.e., the parameter "PTRS-RE-offset") represents a relative subcarrier index in the subset of subcarriers assigned to a DM-RS port in a particular transmission.

[0081] By transmitting the parameter "PTRS-RE-offset" as a configuration parameter in the bit field of a configuration message, scheduling restrictions can be avoided in at least some embodiments because the group of possible PT-RS subcarriers is limited to the subset of subcarriers used, allocated to, or scheduled for the DM-RS ports associated with the PT-RS ports.

[0082] The same embodiments (e.g., the embodiments in the above paragraph) or additional embodiments may require much less signaling overhead than existing offset signaling because a common indication of "PTRS-RE-offset" can be used for both DL and UL. Alternatively or additionally, a common indication can be used for different PT-RS ports in SU-MIMO.

[0083] The bit field can include n bits indicating at least one subcarrier allocated to PT-RS among the subset of subcarriers allocated to DM-RS. The number of the plurality of subcarriers in a PRB can be greater than 2 n 。

[0084] The subset of subcarriers allocated for DM-RS can be signaled dynamically.

[0085] The bit field can include 2 or 3 bits indicating at least one subcarrier allocated to PT-RS among the subset of subcarriers allocated to DM-RS. The number of the plurality of subcarriers in a PRB can be 12.

[0086] The size of the bit field can be determined to represent any one of the subcarriers in the subset of subcarriers allocated to DM-RS as a subcarrier allocated to PT-RS.

[0087] The bit field may include n bits. The number of subcarriers in the subset of subcarriers assigned to DM-RS may be equal to or less than 2 n .

[0088] Each subcarrier in the subset of subcarriers assigned to DM-RS may be uniquely identified by an index. The bit field may indicate the index corresponding to the subcarriers assigned to PT-RS.

[0089] The radio channel may be accessed through one or more DM-RS ports. DM-RS may be transmitted or received through each DM-RS port. The subset of subcarriers assigned to DM-RS may depend on the corresponding DM-RS port.

[0090] The subcarriers assigned to PT-RS may be derived from the bit field for use in at least one of the uplink transmission of PT-RS and the downlink transmission of PT-RS.

[0091] Each DM-RS port among one or more DM-RS ports may be uniquely identified by a DM-RS port index. Each transmission of DM-RS (abbreviation: DM-RS transmission) may be defined by or associated with the DM-RS port index.

[0092] One or more DM-RS ports may be located at (or may define) the transmission side of the radio channel. One or more DM-RS ports may be available for a radio access node (e.g., located at the radio access node) for downlink transmission. Alternatively or additionally, one or more DM-RS ports may be available for a radio device (e.g., located at the radio device) for uplink transmission.

[0093] Alternatively or additionally, one or more DM-RS ports may be located at (or may define) the receiving side of the radio channel. For example, the transmission side may initially define the DM-RS ports by transmitting DM-RS, and the receiving side may define the combining weights for beamforming reception based on the received DM-RS. One or more DM-RS ports may be available for a radio access node (e.g., located at the radio access node) for uplink reception. Alternatively or additionally, one or more DM-RS ports may be available for a radio device (e.g., located at the radio device) for downlink transmission.

[0094] The transmission on the radio channel may include one or more layers (also known as spatial streams). The number of layers may be equal to the number of DM-RS ports used for the transmission on the radio channel. The radio channel may be a multiple-input multiple-output (MIMO) channel, which is accessed through DM-RS ports on the transmission side (i.e., the input of the MIMO channel), optionally mapped to multiple transmitter antennas, and received through multiple receiver ports formed by antennas on the receiver side (i.e., the output of the MIMO channel).

[0095] Multiple transmitted layers can be separated by a transmission precoder in the spatial and / or polarization domain and separated in the receiver by performing channel estimation on the radio channel based on DM-RS and / or PT-RS received on the receiving side and optional interference layer suppression. For example, the transmission can be a multi-layer single-user MIMO (SU-MIMO) transmission, where two or more layers can be accessed through two or more DM-RS ports.

[0096] The DM-RS can be used for at least one of precoding on the transmission side and demodulation on the receiving side of the radio channel.

[0097] The subset of subcarriers allocated to the DM-RS can depend on the corresponding DM-RS port. For each DM-RS port, a subset of subcarriers in the PRB can be allocated to the DM-RS transmitted (or to be transmitted) through the corresponding DM-RS port. That is, the subset of subcarriers allocated to the DM-RS is associated with each DM-RS port. At least some of the subsets of subcarriers used for transmitting the DM-RS through different DM-RS ports can be different. For example, the different subsets can be disjoint.

[0098] The PRB can include 12 subcarriers given by the index k ∈ {0,..., 11}. The subset of subcarriers allocated to the DM-RS transmitted through the DM-RS port p can be given by:

[0099] {2·R·m + S·k′ + Δ(p) ∈ {0,..., 11}|k′ ∈ {0, 1}, 0 ≤ m < 6 / R}, where R = 1, 2 or 3; S = 1 or 2; and the offset Δ(p) depends on the DM-RS port p.

[0100] For DM-RS configuration type 1, the parameters can be R = 2, S = 2, and Δ(p) ∈ {0, 1}. For DM-RS configuration type 2, the parameters can be R = 3, S = 1, and Δ(p) ∈ {0, 2, 4}. In the above expressions of these sets, the upper limit "11" can be replaced by and the upper limit 6 / R can be replaced by

[0101] The DM-RS can be derived from the sequence r(2·m + k′ + n0), where is the starting point of the carrier bandwidth part in terms of PRBs, and is the number of subcarriers per PRB.

[0102] Different DM-RSs can be transmitted through each DM-RS port. Since different DM-RSs (e.g., orthogonal signals) are transmitted through different DM-RS ports, any dependency on "DM-RS" can be equivalently expressed as a dependency on the corresponding "DM-RS port".

[0103] The DM-RSs transmitted through different DM-RS ports can be distinguished by at least one of orthogonal covering codes in the frequency domain, orthogonal covering codes in the time domain, and subsets of subcarriers assigned to the DM-RS.

[0104] For example, each DM-RS transmitted through a different DM-RS port can use a disjoint subset of subcarriers or be orthogonally encoded in the frequency domain.

[0105] One of the DM-RS ports can be associated with the PT-RS. The PT-RS can be transmitted or received through the DM-RS port associated with the PT-RS. The PT-RS can be transmitted or received on the subcarriers assigned to the PT-RS according to a bit field among the subsets of subcarriers assigned to the DM-RS transmitted through the one DM-RS port.

[0106] The PT-RS and the DM-RS can be transmitted simultaneously or separately (e.g., in OFDM symbols or different PRBs, i.e., in different time slots or transmission time intervals TTI). In addition, the transmission of the PT-RS and the transmission of the DM-RS can overlap. The transmission duration of the PT-RS may be longer than the transmission duration of the DM-RS (e.g., multiple times the transmission duration of the DM-RS). For example, the PT-RS can be transmitted or received during a PRB including 14 OFDM symbols. The DM-RS can be transmitted during one or two OFDM symbols.

[0107] The subcarriers assigned to the PT-RS can be derived from a bit field or can be derived for at least one of the uplink transmission and the downlink transmission of the PT-RS.

[0108] The radio access node can be configured to access a radio channel through a DM-RS port for downlink transmission to a radio device. The method can further include or trigger the step of receiving the PT-RS transmitted or transmitted through at least one DM-RS port on a subcarrier, where the subcarrier is assigned to the PT-RS according to a bit field among the subsets of subcarriers assigned to the DM-RS corresponding to the DM-RS port.

[0109] Alternatively or additionally, the radio device may be configured to access a radio channel via a DM-RS port for uplink transmission to a radio access node. The method may further comprise or trigger the step of transmitting or receiving PT-RS on a subcarrier via at least one DM-RS port, where the subcarrier is assigned to PT-RS according to a bit field among a subset of subcarriers of DM-RS assigned to the corresponding DM-RS port.

[0110] The DM-RS port through which PT-RS is transmitted or received may also be referred to as a PT-RS port. The expression "PT-RS" may collectively refer to different PT-RS (port-specific PT-RS) transmitted or received on different DM-RS ports. Alternatively or additionally, the expression "PT-RS" may refer to port-specific PT-RS in the context of, for example, a certain PT-RS port.

[0111] The radio access node may provide radio access to at least one radio device on a radio channel. For each radio device, PT-RS may be transmitted or received through each of one or two DM-RS ports.

[0112] The radio channel may include a single-user multiple-input multiple-output (SU-MIMO) channel accessed via two or more DM-RS ports. PT-RS may be transmitted or received through each of at least two of the two or more DM-RS ports. The radio channel may include two or more layers and / or two or more DM-RS ports. PT-RS may be transmitted or received for each of the two or more layers or through each of the two or more DM-RS ports.

[0113] The radio channel may include a multi-user multiple-input multiple-output (MU-MIMO) channel. Different DM-RS groups of DM-RS ports may provide access to different radio devices. PT-RS may be transmitted or received through at least one DM-RS port in each DM-RS group.

[0114] For each of the plurality of radio devices, the MU-MIMO channel may include at least one layer or at least one DM-RS port. For each of the plurality of radio devices, PT-RS may be transmitted or received on at least one layer or through at least one DM-RS port.

[0115] The subcarrier assigned to PT-RS may be uniquely determined among a subset of subcarriers assigned to DM-RS based on a combination of a bit field in a configuration message and the DM-RS port through which PT-RS is transmitted or received.

[0116] The same value of a bit field may indicate different subcarriers assigned to PT-RS transmitted or received via different DM-RS ports.

[0117] The bit field may indicate two or more candidate subcarriers for PT-RS among a subset of subcarriers assigned to DM-RS. The subcarriers assigned to PT-RS may be determined among the candidate subcarriers based on the DM-RS port through which PT-RS is transmitted or received (e.g., according to the DM-RS port index p or based on the DM-RS port through which PT-RS is transmitted or received).

[0118] The subcarriers assigned to PT-RS transmitted or received via DM-RS port p may be given by 2·R·m + S·k′ + Δ(p). The bit field may indicate m. The value of k′ may be determined as p mod 2 by DM-RS port p.

[0119] PT-RS may be transmitted or received via each of at least two different DM-RS ports. Alternatively or in combination, PT-RS may be transmitted in each of uplink transmission and downlink transmission.

[0120] The DM-RS transmitted via DM-RS port p may be subject to an orthogonal cover code OCC (TD-OCC) in the time domain. Alternatively or additionally, the DM-RS transmitted via DM-RS port p may be subject to an OCC (FD-OCC) in the frequency domain. The subcarriers assigned to PT-RS may be determined among a subset of subcarriers assigned to DM-RS based on a combination of the bit field, the DM-RS port dependence of TD-OCC, and the DM-RS port dependence of FD-OCC. This combination may include summation.

[0121] For example, for DM-RS port p, the DM-RS port dependence of TD-OCC may include:

[0122] TD_offset p = (p - 1000 div 2) div R, or

[0123] TD_offset p = floor((p - 1000) / (2·R))

[0124] Alternatively or additionally, for DM-RS port p, the DM-RS port dependence of FD-OCC may include:

[0125] FD_offset p = p mod 2.

[0126] In this document, for DM-RS configuration type 1, R may be equal to 2, and for DM-RS configuration type 2, R may be equal to 3.

[0127] TD - OCC may include a factor (e.g., a symbol) according to the following formula:

[0128] w t (I′) = [1 - 2·(TD_offset p )] / ′ .

[0129] Alternatively or additionally, FD - OCC may include a factor (e.g., a symbol) according to the following formula:

[0130] w f (k′) = [1 - 2·(FD_offset p )] k′ .

[0131] For each DM - RS port through which PT - RS is transmitted or received, the configuration message may include an instance of a bit field indicating the sub - carriers assigned to PT - RS among the sub - carrier subset of the DM - RS assigned to be transmitted through the corresponding DM - RS port.

[0132] PT - RS may be transmitted or received through one of the DM - RS ports. This one DM - RS port may be determined according to a predefined rule. For example, the DM - RS ports may be grouped into two or more non - overlapping DM - RS groups, and PT - RS may be transmitted or received through one of the DM - RS ports in each DM - RS group. This one DM - RS port may be determined according to the predefined rule applied to each DM - RS group.

[0133] This one DM - RS port through which PT - RS is transmitted or received may not be specified in the configuration message. Each of the radio access node and the radio device may determine this one DM - RS port by independently applying the predefined rule.

[0134] Each DM - RS port may be uniquely identified by a port index. This one DM - RS port determined according to the predefined rule may be the DM - RS port with the lowest port index.

[0135] The PT-RS may include tones on subcarriers allocated to the PT-RS. The tones may correspond to the tones of the DM-RS transmitted on the same subcarriers through the corresponding DM-RS ports. Herein, a tone may include a complex (e.g., Fourier) coefficient (e.g., for the duration of one OFDM symbol) carried by one subcarrier or one resource element. Each OFDM symbol may include multiple tones, and each tone is transmitted simultaneously on the corresponding subcarrier. During the duration of the symbol length, the tones may correspond to harmonic Fourier components in the time domain. Alternatively or additionally, a tone may refer to a modulation on one RE.

[0136] The PT-RS may be transmitted or received in multiple PRBs. The same subcarriers relative to the corresponding PRB may be allocated to the PT-RS in each PRB. Additionally, the same subset of subcarriers may be allocated to the DM-RS in each PRB.

[0137] The transmitted waveform may include orthogonal frequency division multiplexing (OFDM), particularly cyclic prefix (CP) OFDM (CP-OFDM). The tones may be OFDM tones. The transmission may include multiple OFDM symbols for each PRB, such as one time slot in the time domain. Each OFDM symbol may include one OFDM tone for each subcarrier.

[0138] Each DM-RS port may be mapped to multiple antenna ports according to a precoder. Different DM-RS ports may be mapped according to different precoders.

[0139] Some or each DM-RS port may be beamformed according to a precoder. For example, for single-layer (Tx) beamforming on a radio channel, one DM-RS port may be used to access the radio channel. Alternatively, the DM-RS ports may be mapped to antenna ports (e.g., one-to-one correspondence or one-to-many correspondence).

[0140] The number of subcarriers according to DM-RS configuration type 1 in the subset of subcarriers allocated to the DM-RS may be twice the number of subcarriers according to DM-RS configuration type 2 in the subset of subcarriers allocated to the DM-RS. The same-sized bit field may be used for each of DM-RS configuration type 1 and DM-RS configuration type. The most significant bit of the bit field may be ignored or set to zero in order to determine the subcarriers allocated to the PT-RS in DM-RS configuration type 2.

[0141] Another method aspect may further include any feature or step disclosed in the context of any one method aspect. Additionally, another method aspect may include a feature or step corresponding to any feature or step of this aspect.

[0142] Another method aspect may be performed by one or more radio devices in, for example, the RAN. The radio device or each radio device among these radio devices may be a user equipment (UE).

[0143] Regarding a system aspect, a method is provided for transmitting and receiving a configuration message for a phase tracking reference signal (PT-RS) over a radio channel between a radio access node and a radio device. The radio channel includes a plurality of subcarriers in a physical resource block (PRB). A subset of the subcarriers in the PRB is allocated to a demodulation reference signal (DM-RS). The method includes or triggers a step of transmitting the configuration message to the radio device. The configuration message includes a bit field indicating at least one subcarrier allocated to the PT-RS among the subset of subcarriers allocated to the DM-RS. The method further includes or triggers a step of receiving the configuration message from the radio access node. The configuration message includes a bit field indicating at least one subcarrier allocated to the PT-RS among the subset of subcarriers allocated to the DM-RS.

[0144] Regarding another system aspect, a system is provided for transmitting and receiving a configuration message for a phase tracking reference signal (PT-RS) over a radio channel between a radio access node and a radio device. The radio channel includes a plurality of subcarriers in a physical resource block (PRB). A subset of the subcarriers in the PRB is allocated to a demodulation reference signal (DM-RS). The system is configured to perform or trigger a step of transmitting the configuration message to the radio device. The configuration message includes a bit field indicating at least one subcarrier allocated to the PT-RS among the subset of subcarriers allocated to the DM-RS. The system is further configured to perform or trigger a step of receiving the configuration message from the radio access node. The configuration message includes a bit field indicating at least one subcarrier allocated to the PT-RS among the subset of subcarriers allocated to the DM-RS.

[0145] The system may be embodied by at least one of the radio access node and the radio device.

[0146] In any aspect, the radio device can be configured to perform peer-to-peer communication (e.g., on a sidelink) and / or access the RAN (e.g., uplink UL and / or downlink DL). The radio device can be a user equipment (UE, e.g., 3GPP UE), a mobile station or a portable station (STA, e.g., Wi-Fi STA), a device for machine-type communication (MTC), or a combination thereof. Examples of UEs and mobile stations include mobile phones and tablet computers. Examples of portable stations include laptop computers and televisions. Examples of MTC devices include robots, sensors, and / or actuators in, for example, manufacturing, automotive communication, and home automation. MTC devices can be implemented in household appliances and consumer electronics. Examples of combinations include autonomous vehicles, inter-door communication systems, and automated teller machines.

[0147] Examples of base stations can include 3G base stations or Node Bs, 4G base stations or eNodeBs, 5G base stations or gNodeBs, access points (e.g., Wi-Fi access points), and network controllers (e.g., according to Bluetooth, ZigBee, or Z-Wave).

[0148] The RAN can be implemented according to the Global System for Mobile Communications (GSM), Universal Mobile Telecommunications System (UMTS), Long-Term Evolution (LTE), and / or New Radio (NR).

[0149] The technology can be implemented on the physical layer (PHY), media access control (MAC) layer, radio link control (RLC) layer, and / or radio resource control (RRC) layer of the protocol stack of radio communication.

[0150] In another aspect, a computer program product is provided. The computer program product includes a program code portion for performing any one of the steps of the method aspects disclosed herein when the computer program product is executed by one or more computing devices. The computer program product can be stored on a computer-readable recording medium. The computer program product can also be provided for downloading via a data network, e.g., via the RAN and / or via the Internet and / or through a base station. Alternatively or additionally, the method can be encoded in a field-programmable gate array (FPGA) and / or an application-specific integrated circuit (ASIC), or the functionality can be provided for downloading by means of a hardware description language.

[0151] One device aspect relates to a device configured to perform one method aspect. Alternatively or additionally, the device can include units or modules configured to perform any of the steps of one method aspect. Another device aspect relates to a device configured to perform another method aspect. Alternatively or additionally, the device can include units or modules configured to perform any of the steps of another method aspect.

[0152] In addition, for each method aspect, the apparatus may include at least one processor and a memory. The memory includes instructions executable by the at least one processor, whereby the apparatus is operable to perform the corresponding method aspect.

[0153] The apparatus (or any node or station for embodying the technology) may further include any feature disclosed in the context of the method aspect. In particular, any one of the units and modules, or dedicated units or modules, may be configured to perform or trigger one or more steps of any one method aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0154] Further details of embodiments of the present technology are described with reference to the accompanying drawings, in which:

[0155] Figure 1 A schematic block diagram of an apparatus for transmitting a configuration message for a phase-tracking reference signal is shown;

[0156] Figure 2 A schematic block diagram of an apparatus for receiving a configuration message for a phase-tracking reference signal is shown;

[0157] Figure 3 A flowchart of a method for transmitting a configuration message for a phase-tracking reference signal, which method may be implemented by an apparatus of Figure 1 is shown;

[0158] Figure 4 A flowchart of a method for receiving a configuration message for a phase-tracking reference signal, which method may be implemented by an apparatus of Figure 2 is shown;

[0159] Figure 5 Schematically shows Figure 1 and Figure 2 an exemplary deployment of an embodiment of the apparatus;

[0160] Figure 6 Schematically shows a first example of allocating resource elements for different demodulation reference signal ports;

[0161] Figure 7 Schematically shows a second example of allocating resource elements for different demodulation reference signal ports;

[0162] Figure 8 Schematically shows an example of an effective allocation of resource elements of a phase-tracking reference signal;

[0163] Figure 9 Schematically shows an example of an ineffective allocation of resource elements of a phase-tracking reference signal;

[0164] Figure 10 Shows Figure 1Schematic block diagram of a first embodiment of the apparatus;

[0165] Figure 11 Shows Figure 1 Schematic block diagram of a second embodiment of the apparatus;

[0166] Figure 12 Shows Figure 2 Schematic block diagram of a first embodiment of the apparatus; and

[0167] Figure 13 Shows Figure 2 Schematic block diagram of a second embodiment of the apparatus. Detailed implementation

[0168] In the following description, for purposes of explanation and not limitation, specific details such as a particular network environment are set forth in order to provide a thorough understanding of the technology disclosed herein. Those skilled in the art will appreciate that the technology may be practiced in other embodiments that depart from these specific details. Additionally, although the following embodiments are primarily described in the context of 5G New Radio (NR) implementations, it will be readily understood that the technology described herein may also be implemented in any other radio network (including 3GPP LTE or its successors), wireless local area network (WLAN) according to the IEEE 802.11 standard series, Bluetooth (particularly Bluetooth Low Energy and Bluetooth Broadcast) according to the Bluetooth Special Interest Group (SIG), and / or ZigBee based on IEEE 802.15.4.

[0169] Furthermore, those skilled in the art will appreciate that the functions, steps, units, and modules explained herein may be implemented using software operating in conjunction with a programmed microprocessor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), digital signal processor (DSP), or general purpose computer (e.g., including an Advanced RISC Machine (ARM)). It will also be understood that although the following embodiments are primarily described in the context of methods and apparatuses, the present invention may also be embodied in a computer program product and a system including at least one computer processor and a memory coupled to the at least one processor, wherein the memory is encoded with one or more programs that can execute the functions and steps disclosed herein or implement the units and modules disclosed herein.

[0170] Figure 1A block diagram of a device that schematically shows a configuration message for transmitting a phase-tracking reference signal (PT-RS) on a radio channel between a radio access node and a radio device. The device is generally denoted by reference numeral 100. The radio channel includes a plurality of subcarriers in a physical resource block (PRB). A subset of the subcarriers in the PRB is allocated to a demodulation reference signal (DM-RS). Device 100 includes a configuration transmission module 102 that transmits the configuration message to the radio device. The configuration message includes a bit field indicating at least one subcarrier allocated to the PT-RS among the subset of subcarriers allocated to the DM-RS.

[0171] Device 100 may be connected to a RAN and / or may be part of a RAN. Device 100 may be embodied by or in a radio access node (e.g., a base station of a RAN), a node connected to the RAN to control the base station, or a combination thereof.

[0172] Optionally, device 100 includes a PT-RS module 104 for performing at least one of transmitting, receiving, and processing the PT-RS according to the configuration. Alternatively or additionally, device 100 includes a DM-RS module 106 for transmitting, receiving, and processing at least one of the DM-RS. The PT-RS module 104 may be a function or sub-module of the DM-RS module 106.

[0173] Any module of device 100 may be implemented by a unit configured to provide the corresponding functionality.

[0174] Figure 2 A block diagram of a device that schematically shows a configuration message for receiving a phase-tracking reference signal (PT-RS) on a radio channel between a radio access node and a radio device. The device is generally denoted by reference numeral 200. The radio channel includes a plurality of subcarriers in a physical resource block (PRB). A subset of the subcarriers in the PRB is allocated to a demodulation reference signal (DM-RS). Device 200 includes a configuration reception module 202 that receives the configuration message from the radio access node. The configuration message includes a bit field indicating at least one subcarrier allocated to the PT-RS among the subset of subcarriers allocated to the DM-RS.

[0175] Device 200 may be embodied by or in a radio device.

[0176] Optionally, device 200 includes a PT-RS module 204 for performing at least one of transmitting, receiving, and processing the PT-RS according to the configuration. Alternatively or additionally, device 200 includes a DM-RS module 206 for performing at least one of transmitting, receiving, and processing the DM-RS. The PT-RS module 204 may be a function or sub-module of the DM-RS module 206.

[0177] Any module of apparatus 200 may be implemented by a unit configured to provide the corresponding functionality.

[0178] In this document, a radio access node may cover a network controller (e.g., a Wi-Fi access point) or a cellular radio access node (e.g., a 3G Node B, a 4G eNodeB or a 5G gNodeB). The radio access node may be configured to provide radio access to a radio device. Alternatively or additionally, the radio device may include a mobile station or a portable station, a user equipment (UE), in particular a device for machine type communication (MTC) and a narrowband Internet of Things (NB-IoT) device. Two or more instances of the radio device may be configured to be wirelessly connected to each other, for example, in an ad-hoc radio network or via a 3GPP sidelink.

[0179] Figure 3 A flowchart of a method 300 for transmitting a PT-RS on a radio channel between a radio access node and a radio device is shown. The radio channel includes a plurality of subcarriers in (e.g., each) PRB. A subset of the subcarriers in the PRB is allocated to the DM-RS. In step 302 of method 300, a configuration message is transmitted to the radio device. The configuration message includes a bit field indicating at least one subcarrier allocated to the PT-RS among the subset of subcarriers allocated to the DM-RS.

[0180] In this document, a "subcarrier allocated to the PT-RS" may cover a subcarrier used for transmitting the PT-RS or scheduled for transmitting the PT-RS. In addition, a "subcarrier allocated to the PT-RS" may cover two or more candidate subcarriers, and finally one of the candidate subcarriers is allocated to the PT-RS (e.g., used for or scheduled for the PT-RS). For example, a "subcarrier allocated to the PT-RS" may cover a zero-power PT-RS, that is, the subcarrier is a PT-RS subcarrier, but the radio access node (e.g., a gNB) does not transmit anything on the PT-RS subcarrier. This PT-RS subcarrier is available for another radio access node (e.g., another gNB) to use. Thus, interference to the subcarrier can be avoided.

[0181] Optionally, in step 304, the PT-RS is processed, transmitted and / or received on the subcarrier allocated to the PT-RS according to the bit field.

[0182] The allocated subcarriers may further depend on the DM-RS ports through which the PT-RS is transmitted. For example, the index of the subcarriers allocated to the PT-RS can be a function of a bit field and the index of the DM-RS port. In one embodiment compatible with any embodiment disclosed herein, the bit field may uniquely determine the subcarriers allocated to the PT-RS among a subset of the subcarriers allocated to the DM-RS. In another embodiment compatible with any embodiment disclosed, the bit field alone cannot uniquely indicate the subcarriers of the PT-RS within the subset of the subcarriers allocated to the DM-RS. An additional dependence on the DM-RS ports used to transmit the PT-RS may eliminate the latter ambiguity, such that the combination of the port index and the bit field uniquely determines the subcarriers for the PT-RS.

[0183] In step 306, which may occur simultaneously with step 304, the DM-RS is processed, transmitted, and / or received. Alternatively or additionally, the radio access node may signal a change in the configuration of the DM-RS at and / or to the radio device.

[0184] Method 300 may be performed by device 100, for example, at or using a radio access node (e.g., a radio access node of a RAN). For example, modules 102, 104, and 106 may perform steps 302, 304, and 306, respectively.

[0185] Figure 4 A flowchart illustrating method 400 for receiving a configuration message for PT-RS on a radio channel between a radio access node and a radio device is shown. The radio channel includes a plurality of subcarriers in (e.g., in each) PRB. A subset of the subcarriers in the PRB is allocated to the DM-RS. In step 402 of method 400, a configuration message is received from the radio access node. The configuration message includes a bit field indicating at least one subcarrier allocated to the PT-RS among the subset of the subcarriers allocated to the DM-RS.

[0186] Optionally, in step 404, the PT-RS is processed, transmitted, and / or received on the subcarriers allocated to the PT-RS according to the bit field. For example, the subcarriers allocated to the PT-RS may be determined in step 404 based on the bit field and optionally the DM-RS port transmitting the PT-RS.

[0187] The radio device may process, transmit, and / or receive the DM-RS in step 406 according to the configuration message or another configuration received from the access node.

[0188] Method 400 may be performed by device 200, for example, at or using a radio device. For example, modules 202, 204, and 206 may perform steps 402, 404, and 406, respectively.

[0189] Figure 5 An exemplary environment 500 for implementing the present technology is schematically shown, such as a stand-alone or cellular radio access network (RAN). The environment 500 accordingly includes a plurality of radio channels 502 between embodiments of apparatuses 100 and 200. In Figure 5 the environment 500, the apparatus 100 is embodied by at least one base station or radio access node 510, which provides radio access to or controls the radio communication of at least one radio apparatus 512 embodying the apparatus 200. All radio apparatuses 512 that communicate radio 502 with the radio access node 510 do not necessarily embody the apparatus 200.

[0190] In NR, phase-tracking reference signals (PT-RS) can be configured for downlink and uplink transmissions to enable a receiver to correct phase-noise related errors. The PT-RS configuration is UE-specific, and it is agreed that the PT-RS is associated with one of the DM-RS ports used for transmission, which means that the same precoder is used to transmit the DM-RS and its associated PT-RS, and it means that the modulation symbols for the PT-RS are taken from the DM-RS, regardless of what DM-RS sequence is configured. It means that there is no specific configuration of the PT-RS sequence because it borrows from the DM-RS.

[0191] The UE shall assume that the PDSCH DM-RS is mapped to physical resources according to type 1 or type 2 given by the higher layer parameter DL-DM-RS-config-type.

[0192] The UE shall assume that, on the condition that a resource element (RE) is within the resources allocated for PDSCH transmission, the sequence r(m) is mapped to physical resource elements according to the following formula:

[0193]

[0194]

[0195] k′ = 0, 1

[0196]

[0197] According to Tables 7.4.1.1.2-1 and 7.4.1.1.2-2 in Section 7.4 of the document 3GPP TS 38.211 (e.g., version 1.0.0) or the following example table, the functions w f (k′), w t (I′) and Δ depend on the DM-RS port p.

[0198] The reference point of subcarrier label k is the start of carrier bandwidth part i, where the physical downlink shared channel (PDSCH) is transmitted, and where k = 0 corresponds to the lowest numbered subcarrier in the bandwidth part.

[0199] The offset n0 is given by:

[0200]

[0201] where is the start of the carrier bandwidth part where the physical uplink shared channel (PUSCH) is transmitted.

[0202] In the time domain (TD), the position I0 and the reference point of I of the first DM-RS symbol depend on the mapping type. For PDSCH mapping type A, I is defined relative to the start of the slot, and if the higher layer parameter DL-DMRS-typeA-pos is equal to 3, then I0 = 3, otherwise I0 = 2. For PDSCH mapping type B, I is defined relative to the start of the scheduled PDSCH resource, and I0 = 0.

[0203] According to Table 7.4.1.1.2-3 and 7.4.1.1.2-4 in Section 7.4 of document 3GPP TS 38.211 (e.g., version 1.0.0) or the following example table, and the last OFDM symbol for PDSCH in the slot give the position(s) of one or more additional DM-RS symbols.

[0204] The time domain index I′ and the supported antenna port p are given by Table 7.4.1.1.2-5 in Section 7.4 of document 3GPP TS 38.211 (e.g., version 1.0.0) or the following example table. If the higher layer parameter DL-DMRS-Ien is equal to 1, single-symbol DM-RS is used. If the higher layer parameter DL-DMRS-Ien is equal to 2, it is determined whether to use single-symbol DM-RS or double-symbol DM-RS through the associated DCI.

[0205] Table 7.4.1.1.2-1: Parameters for PDSCH DM-RS configuration type 1

[0206]

[0207] Table 7.4.1.1.2-2: Parameters for PDSCH DM-RS configuration type 2

[0208]

[0209] Table 7.4.1.1.2-3: Additional PDSCH DMRS positions for single-symbol DM-RS

[0210]

[0211]

[0212] Table 7.4.1.1.2-4: Additional PDSCH DMRS Positions for Dual Symbol DM-RS

[0213]

[0214] Table 7.4.1.1.2-5: PDSCH DM-RS Time Index I′ and Antenna Port p

[0215]

[0216] In Figure 6 and Figure 7 it shows the mapping of different DM-RS ports for DM-RS configuration types 1 and 2 for a single front-loaded case. In some embodiments, when using orthogonal cover codes for DM-RS in the time domain (i.e., using TD-OCC for DM-RS), PT-RS is not scheduled. In such embodiments, when using DM-RS ports 1004 to 1007 for DM-RS configuration type 1 and ports 1006 to 1011 for DM-RS configuration type 2, PT-RS is not transmitted.

[0217] Regarding the mapping of PT-RS in the frequency domain, 3GPP agreed to schedule each PT-RS port with up to 1 subcarrier per PRB. It was also agreed that the subcarrier used for a PT-RS port must be one of the subcarriers that are simultaneously used for DM-RS ports and associated with the PT-RS port.

[0218] Figure 8 An example of radio resource allocation 600 in PRB 602 is schematically shown for a grid of resource elements (RE) 604 including time 606 (e.g., in OFDM symbols) and frequency 608 (e.g., in subcarriers). Although the allocation 600 schematically shown in Figure 8 also includes a time domain (TD) 606 to illustrate the different durations and densities of PT-RS compared to DM-RS, the present technology can be implemented by a configuration mechanism that restricts the allocation 600 in the frequency domain (FD) (i.e., in terms of subcarrier k).

[0219] The duration of PRB 602 can correspond to one time slot 610.

[0220] An example allocation 600 of subcarriers to PT-RS is valid. In other words, mapping PT-RS to RE 604 is allowed because the subcarriers allocated to PT-RS are within the subset of subcarriers allocated to DM-RS. In contrast, Figure 9 the example allocation 600 schematically shown in Figure 9 is not an allowed PT-RS mapping.

[0221] Thus, if a comb-based structure is used for DM-RS with a repetition factor (RPF) R = 2 (as in DM-RS configuration type 1), then DM-RS is mapped to every second subcarrier, i.e., the subset of subcarriers allocated to DM-RS only covers every second subcarrier in PRB 602. Therefore, this technique ensures that PT-RS is only mapped to one of the 6 DM-RS subcarriers in the subset of the 12 subcarriers in this exemplary PRB 602.

[0222] In NR, a PRB has 12 subcarriers. Thus, the set of subcarriers of PRB 602 is {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}. In existing solutions, "PTRS-RE-offset" can be set to any value in this set. However, such a solution may lead to unsupported scenarios where the PT-RS port is not mapped to the subcarriers associated with the PT-RS port that are within the subset of subcarriers used for the DM-RS port. For example, for DM-RS configuration type 1 where PT-RS is associated with DM-RS port 1000, and port 1000 is mapped to subcarriers {0, 2, 4, 8, 10, 12} or {0, 2, 4, 6, 8, 10} or even all subcarriers, then configuring "PTRS-RE-offset" to be equal to any value among 1, 3, 5, 7, 9, or 11 via RRC will result in unsupported scenarios that imply scheduling restrictions.

[0223] If the conventional "PTRS-RE-offset" configured via the RRC layer is equal to any value among 1, 3, 5, 7, 9, or 11, then only DM-RS ports {1002, 1003, 1006, 1007} of DM-RS configuration type 1 can be used for PDSCH or PUSCH (because according to Table 7.4.1.1.2-1 above, these DM-RS ports have a subcarrier offset Δ = 1), and this is a scheduling restriction.

[0224] Table 1 and Table 2 below respectively represent the existing encodings of the conventional parameter "PTRS-RE-offset" for DM-RS configuration types 1 and 2. In addition, the last column indicates the group of DM-RS ports for which the corresponding values of the conventional "PTRS-RE-offset" result in supported scenarios.

[0225] Existing encodings require 4 bits to represent a regular "PTRS-RE-offset". Table 1 below outlines the bitmaps of the existing encodings of regular "PTRS-RE-offset" for DM-RS configuration type 1.

[0226]

[0227]

[0228] Similarly, Table 2 below outlines the bitmaps of the existing encodings of regular "PTRS-RE-offset" for DM-RS configuration type 2.

[0229] PTRS-RE-offset value Subcarriers for PT-RS Compatible DM-RS ports 0000 0 1000 / 1001 / 1006 / 1007 0001 1 1000 / 1001 / 1006 / 1007 0010 2 1002 / 1003 / 1008 / 1009 0011 3 1002 / 1003 / 1008 / 1009 0100 4 1004 / 1005 / 1010 / 1011 0101 5 1004 / 1005 / 1010 / 1011 0110 6 1000 / 1001 / 1006 / 1007 0111 7 1000 / 1001 / 1006 / 1007 1000 8 1002 / 1003 / 1008 / 1009 1001 9 1002 / 1003 / 1008 / 1009 1010 10 1004 / 1005 / 1010 / 1011 1011 11 1004 / 1005 / 1010 / 1011

[0230] The present technique can reduce signaling overhead (e.g., compared to the existing encodings of regular parameters) by transmitting a parameter "PTRS-RE-offset" (i.e., a bit field) that is used or can be used to generate a relative index to an element associated with PT-RS in a subset of elements of a subcarrier subset used or allocated for a DM-RS port.

[0231] Any embodiment described herein can implement at least one of the following features. Define a subset S of subcarriers within PRB602 that are used (or allocated) for DM-RS port p p . p Represent the relative index to one of the elements of S Rel as I

[0232] l Rel = f(PTRS-RE-offset, p).

[0233] Determine the PT-RS subcarrier via S p (I Rel ) where S p (·) represents an ordered subset S of an array, for example p .

[0234] Tables 3 and 4 below show, respectively, for the single-symbol DM-RS case, the subsets S of subcarriers for DM-RS ports for DM-RS configuration types 1 and 2 p .

[0235] Table 3 below lists the subsets of subcarriers for DM-RS configuration type 1 assuming single-symbol DM-RS. These subsets depend on DM-RS port p.

[0236] DM-RS port, p <![CDATA[Subset of DM-RS subcarriers in PRB, S p > 1000 {0,2,4,6,8,10} 1001 {0,2,4,6,8,10} 1002 {1,3,5,7,9,11} 1003 {1,3,5,7,9,11}

[0237] Table 4 below lists subsets of subcarriers for DM-RS configuration type 2 assuming single-symbol DM-RS. These subsets depend on DM-RS port p.

[0238] DM-RS port, p <![CDATA[Subset of DM-RS subcarriers in PRB, S p > 1000 <![CDATA[S p ={0, 1, 6, 7}]]> 1001 <![CDATA[S p ={0, 1, 6, 7}]]> 1002 <![CDATA[S p ={2, 3, 8, 9}]]> 1003 <![CDATA[S p = {2, 3, 8, 9}]]> 1004 <![CDATA[S p = {4, 5, 10, 11}]]> 1005 <![CDATA[S p = {4, 5, 10, 11}]]>

[0239] In a first variant that can be implemented in any of the embodiments described herein, a bit field indicates a relative index. The first variant can provide sufficient flexibility for the base station or network when configuring subcarriers to be used for PT-RS.

[0240] For sufficient indication of flexibility, the relative index can be used as the bit field, i.e., the function can be:

[0241] f(PTRS-RE-offset,p) = PTRS-RE-offset (Equation 1)

[0242] Thus, the relative index is fixed and equal to the parameter PTRS-RE-offset configured by RRC. The relative index does not depend dynamically on the associated DM-RS port.

[0243] The relative index selects a subcarrier among the subcarriers used for the DM-RS port for a particular PDSCH or PUSCH scheduling. If more than one DM-RS port is used for data scheduling, a predefined rule is used such that the PT-RS port is associated with the DM-RS port with the lowest index.

[0244] Based on the subsets defined for the respective DM-RS configuration types in Tables 3 and 4, the bit field value (i.e., the relative index PTRS-RE-offset) can indicate the subcarriers in the PRB for PT-RS. Since the subsets are complete for a given DM-RS port, the coding according to the first variant provides sufficient flexibility when configuring the corresponding PT-RS subcarriers for the DM-RS port. By way of non-limiting example, Tables 5 and 6 show the coding according to the present technique for DM-RS configuration types 1 and 2, respectively.

[0245] The following is an example for implementing the first variant. If PT-RS ports associated with DM-RS port 1000 (where S 1000 = {0,2,4,6,8,10}) and PTRS-RE-offset = 2 (i.e., 010 in binary) have been configured for the UE using RRC signaling, then PT-RS is mapped to subcarrier S 1000(2) = 4. If MIMO transmission is used, where DM-RS ports 1000, 1001, 1002, and 1003 are used, the predefined rule applies, i.e., the DM-RS port with the lowest index (in this case 1000) is used to determine the subcarriers of the PT-RS port according to the described rules (i.e., Table 3 or Table 4).

[0246] In the case of configuring multiple DM-RS groups, this process is applied per DM-RS group, so each DM-RS group selects one PT-RS subcarrier.

[0247] When receiving the PDSCH, the UE shall assume that the PT-RS exists on this subcarrier, and when transmitting the PUSCH, the UE shall transmit the PT-RS on this subcarrier assigned in the PRB for PT-RS transmission.

[0248] Embodiments of the first variant can reduce the RRC signaling overhead to 3 bits. In addition, a common indication of "PTRS-RE-offset" for the downlink (DL) and uplink (UL) can be used, because any value of the parameter "PTRS-RE-offset" can be used with any DM-RS port. Therefore, a common indication of "PTRS-RE-offset" can be applied for both DL and UL. The signaling overhead is reduced compared to the existing coding, and / or the signaling overhead is further reduced for both UL and DL relative to the implementation of this technology.

[0249] In addition, the first variant can be implemented to avoid the DC subcarrier, because the RRC signaling can control which subcarrier the PT-RS can be mapped to (which depends on the DM-RS port used).

[0250] To have coordinated signaling for DM-RS configuration types 1 and 2, for DM-RS configuration type 2, only 2 LSBs (e.g., the 2 least significant bits) of PTRS-RE-offset are used to generate the relative index. Therefore, the value and / or the common size (or signal format) of PTRS-RE-offset (i.e., the bit field) can be used with both DM-RS configuration types 1 and 2. In addition, when changing the DM-RS configuration type used in the transmission, it is not necessary to re-transmit or signal the configuration message (i.e., the PTRS-RE-offset parameter) again (e.g., to comply with the configuration type-related format of the bit field).

[0251] However, for the SU-MIMO case with more than 1 scheduled PT-RS port, each PT-RS port requires an independent indication of PTRS-RE-offset. The main reason is that if a PT-RS port is associated with a DM-RS port having the same subcarrier subset and has a common PTRS-RE-offset indication, the PT-RS ports will be mapped to the same subcarriers (which means a high level of interference between the PT-RS ports). Therefore, independent indications are needed.

[0252] As an implementation of the present technology, Table 5 below represents subcarrier indices (i.e., the actual indices in the PRB, rather than the relative indices in the subset) derived from a bit field (i.e., the parameter "PTRS-RE-offset" in the first column). Table 5 can be implemented as a coding mechanism with sufficient flexibility based on the parameter "PTRS-RE-offset".

[0253] Without limitation, Table 5 below assumes DM-RS configuration type 1 and single-symbol DM-RS.

[0254]

[0255] As an implementation of the present technology, Table 6 below represents subcarrier indices derived from a bit field (i.e., the parameter "PTRS-RE-offset" in the first column). Table 6 can be implemented as a coding mechanism with full flexibility based on the parameter "PTRS-RE-offset".

[0256] Table 6 below relates to DM-RS configuration types with a smaller subset such that the MSB (e.g., the most significant bit) in the parameter "PTRS-RE-offset" is ignored. Without limitation, Table 6 assumes DM-RS configuration type 2 and single-symbol DM-RS.

[0257]

[0258] In a second variant that can be implemented in any of the embodiments described herein, the bit field indicates a relatively reduced flexibility index.

[0259] To further reduce signaling overhead and enable the use of a common indication of "PTRS-RE-offset" for all PT-RS ports scheduled for SU-MIMO, an alternative function for generating the relative index (i.e., the function applied in the second variant) can be defined.

[0260] An example of the function according to the second variant is:

[0261] f(PTRS-RE-offset, p) = 2 · PTRS-RE-offset + offsetp (Equation 2)

[0262] where offsPt p is a parameter related to the OCC value used for DM-RS port p. Therefore, the relative index also dynamically depends on this one or more DM-RS ports selected for scheduling.

[0263] The offset of DM-RS port p can be obtained as offset p = p mod 2 p The function in Equation 2 reduces the indication flexibility because not all PT-RS ports can be mapped to any subcarrier. However, this reduction in flexibility has no impact on performance because, for example, the base station 510 or the RAN is still enabled to avoid the DC subcarrier of any PT-RS port.

[0264] The parameter offset p ensures that for the same value of PTRS-RE-offset, two PT-RS ports associated with DM-RS ports having the same comb but different OCCs are mapped to different subcarriers. Thus, a common indication of PTRS-RE-offset is achieved for SU-MIMO (i.e., for the case where the number of PT-RS ports is greater than 1). Alternatively or additionally, in the case where the same PTRS-RE-offset parameter has been configured (e.g., via RRC) for two or more UEs 512, two or more UEs 512 can still be scheduled in MU-MIMO scheduling each with a single layer (e.g., for DM-RS ports 1000 and 1001 respectively) because it is ensured that each DM-RS port maps PT-RS to a unique subcarrier.

[0265] In Tables 7 and 8 below, the offset p values of different DM-RS ports of DM-RS configuration types 1 and 2 are shown respectively. Based on the previous tables and the function in Equation 2, the relative index is generated. The implementation of the second variant is shown in Tables 9 and 10 below, and Tables 9 and 10 respectively outline the coding of PTRS-RE-offsct using the DM-RS ports in DM-RS configuration types 1 and 2 and the corresponding PT-RS subcarriers.

[0266] The following is an example for implementing the second variant. If a PT-RS port is associated with DM-RS port 1000 (where S 1000 = {0, 2, 4, 6, 8, 10}, and offset 1000 = 0) and PTRS-RE-offset = 2, then the PT-RS is mapped to subcarrier S 1000(2·2 + 0) = 8。

[0267] The following Table 7 indicates the offset according to DM-RS port p p . Without limitation, DM-RS configuration type 1 is assumed in Table 7.

[0268] DM-RS port, p <![CDATA[offset p > 1000 0 1001 1 1002 0 1003 1

[0269] The following Table 8 indicates the offset according to DM-RS port p p . Without limitation, DM-RS configuration type 2 is assumed in Table 8.

[0270] DM-RS port, p <![CDATA[offset p > 1000 0 1001 1 1002 0 1003 1 1004 0 1005 1

[0271] The implementation of a second variant is shown in the following Table 9. The subcarriers for PT-RS are derived from the combination of the DM-RS port p (i.e., offset p ). Table 9 can be implemented as a mechanism for encoding and decoding "PTRS-RE-offset". Without limitation, the following Table 9 assumes DM-RS configuration type 1 and single-symbol DM-RS. The checks in Table 9 show that each DM-RS port maps PT-RS to a unique subcarrier.

[0272]

[0273] Another implementation of a second variant that can be combined with the previous implementation is shown in the following Table 10. The subcarriers for PT-RS are derived from the combination of the DM-RS port p (i.e., offset p ). The following Table 10 applies to a smaller subset of DM-RS configuration types. Therefore, the MSB in the bit field is ignored.

[0274] The following Table 10 can be implemented as a mechanism for encoding and decoding "PTRS-RE-offset". Without limitation, Table 10 assumes DM-RS configuration type 2 and single-symbol DM-RS. The checks in Table 10 show that each DM-RS port maps PT-RS to a unique subcarrier.

[0275]

[0276] The implementation of the second variant can reduce the required overhead to 2 bits. Additionally, a common indication can be used for DL and UL, since the second variant enables the use of any value of the parameter "PTRS-RE-offset" with any DM-RS port. Also, for the case of SU-MIMO scheduling more than one PT-RS, a single indication of PTRS-RE-offset (e.g., a single transmission of a bit field) can provide different subcarriers for PT-RS ports associated with different DM-RS ports, thus reducing the overhead relative to the existing use of offsets.

[0277] To have coordinated signaling for DM-RS configuration types 1 and 2, for DM-RS configuration type 2, only 1 LSB (e.g., 1 least significant bit) of PTRS-RE-offset is used to generate a relative index. Thus, when changing the DM-RS configuration type used in a transmission, the value of the parameter PTRS-RE-offset (i.e., the bit field) can be used for or applied to both DM-RS configuration types 1 and 2, e.g., without having to re-signal PTRS-RE-offset.

[0278] For clarity and not limitation, the above embodiments and variants have been described for DM-RS ports without applying coding in the time domain. The following implementations utilize DM-RS ports applying such time coding (e.g., orthogonal cover codes in the time domain (TD-OCC)) to provide a relative index with reduced flexibility. The following implementations can be combined with any other embodiment or variant described herein.

[0279] To make the PTRS-RE-offset signaling compatible with the case where TD-OCC applied to DM-RS together with PT-RS is used (i.e., for the sub-6 (below 6) scenario, ports 1004 - 1007 are used for DM-RS type 1 and ports 1006 - 1011 are used for DM-RS type 2), an additional function f for determining the relative index is provided. The function can be implemented to generate a relative index for DM-RS ports without TD-OCC as described in the second variant. That is, for suitable DM-RS ports, the following implementation can be compatible with the above second variant.

[0280] An exemplary function for DM-RS type 1 is:

[0281] f(PTRS-RE-offset, p) = PTRS-RE-offset

[0282] + FD_offset p + 2·TD_offset p mod 6, Equation (Eq. 3-1)

[0283] where FD_offset p is a parameter related to the value of the frequency-domain OCC (FD-OCC) used for DM-RS port p. The parameter TD_offset p is related to the TD-OCC value used for DM-RS port p. Thus, the relative index also dynamically depends on the selected DM-RS port(s) for scheduling.

[0284] More specifically, and without limitation:

[0285] FD_offset p = p mod 2, and

[0286]

[0287] In Tables 11 and 12 below, encoding the PTRS-RE-offset, i.e., the bit field, using the proposed scheme is shown.

[0288] An exemplary function for DM-RS type 2 is:

[0289] f(PTRS-RE-offset, p) = PTRS-RE-offset

[0290] + FD_offset p + 2·TD_offset p mod 4, Equation (Eq. 3-2)

[0291] where FD_offset p is a parameter related to the FD-OCC value used for DM-RS port p, and TD_offset p is a parameter related to the TD-OCC value used for DM-RS port p.

[0292] Similar definitions of FD_offset p and TD_offset p can be applied, for example,

[0293] FD_offset p = p mod 2, and

[0294]

[0295] Thus, the relative index generated by the function f also dynamically depends on the one or more selected DM-RS ports for scheduling. In Tables 13 and 14 below, encoding the bit field, i.e., PTRS-RE-offset, using the proposed scheme is shown.

[0296] The solutions for DM-RS types 1 and 2 provide different PT-RS subcarriers for different DM-RS ports.

[0297] Table 11 below outlines the encoding of "PTRS-RE-offset" for DM-RS configuration type 1, where 2 DM-RS symbols are assumed for ports 1000 to 1003. It can be seen that each DM-RS port maps PT-RS to a unique subcarrier.

[0298]

[0299] Table 12 below outlines the encoding of "PTRS-RE-offset" for DM-RS configuration type 1, where 2 DM-RS symbols are assumed for ports 1004 to 1008. It can be seen that each DM-RS port maps PT-RS to a unique subcarrier.

[0300]

[0301] Table 13 below outlines the encoding of "PTRS-RE-offset" for DM-RS configuration type 2, where 2 DM-RS symbols are assumed for ports 1000 to 1005. It can be seen that each DM-RS port maps PT-RS to a unique subcarrier.

[0302]

[0303] Table 14 below outlines the encoding of "PTRS-RE-offset" for DM-RS configuration type 2, where 2 DM-RS symbols are assumed for ports 1006 to 1011. It can be seen that each DM-RS port maps PT-RS to a unique subcarrier.

[0304]

[0305] Figure 10 A schematic block diagram showing an embodiment of apparatus 100. Apparatus 100 includes one or more processors 1004 for performing method 300 and a memory 1006 coupled to processor 1004. For example, the memory 1006 can be encoded with instructions that at least implement module 102.

[0306] One or more processors 1004 may be a microprocessor, a controller, a microcontroller, a central processing unit, a digital signal processor, an application specific integrated circuit, a field programmable gate array, or a combination of one or more of any other suitable computing device, resource, or a combination of hardware, microcode, and / or encoded logic operable to provide base station and / or radio access functionality alone or in combination with other components of apparatus 100, such as memory 1006. For example, one or more processors 1004 may execute instructions stored in memory 1006. Such functionality may include providing the various features and steps discussed herein, including any benefits disclosed herein. The phrase "apparatus operable to perform an action" may mean that apparatus 100 is configured to perform the action.

[0307] As Figure 10 Schematically illustrated, apparatus 100 may be embodied by a base station 510 of a RAN, for example. Base station 510 includes a radio interface 1002 coupled or connected to apparatus 100 to form a radio channel with one or more radio devices. Base station 510 or apparatus 100 may communicate with one or more radio devices via radio interface 1002.

[0308] In a variant schematically illustrated as, for example, Figure 11 the functionality of apparatus 100 is provided by another node (e.g., in a RAN or a core network linked to a RAN). That is, the node performs method 300. The functionality of apparatus 100 is provided to base station 510 by the node via, for example, interface 1002 or a dedicated wired or wireless interface.

[0309] Figure 12 Schematic block diagram showing an embodiment of apparatus 200. Apparatus 200 includes one or more processors 1204 for performing method 400 and a memory 1206 coupled to processor 1204. For example, memory 1206 may be encoded with instructions that at least implement module 202.

[0310] One or more processors 1204 may be a microprocessor, a controller, a microcontroller, a central processing unit, a digital signal processor, an application specific integrated circuit, a field programmable gate array, or a combination of one or more of any other suitable computing device, resource, or a combination of hardware, microcode, and / or encoded logic operable to provide radio device and / or terminal functionality alone or in combination with other components of apparatus 200, such as memory 1206. For example, one or more processors 1204 may execute instructions stored in memory 1206. Such functionality may include providing the various features and steps discussed herein, including any benefits disclosed herein. The phrase "apparatus operable to perform an action" may mean that apparatus 200 is configured to perform the action.

[0311] AsFigure 12 is schematically shown that the apparatus 200 may be embodied by a radio apparatus 512 such as, for example, a RAN. The radio apparatus 512 includes a radio interface 1202 coupled or connected to the apparatus 200 to form a radio channel with one or more radio access nodes. The radio apparatus 512 or the apparatus 200 may communicate with one or more radio access nodes via the radio interface 1202.

[0312] In a variant schematically shown as, for example, Figure 13 the functionality of the apparatus 200 is provided by another node (e.g., in a RAN or a core network linked to the RAN). That is, this node executes the method 200. The functionality of the apparatus 200 is provided to the radio apparatus 512 by this node via, for example, the interface 1202 or a dedicated wired or wireless interface.

[0313] It has become apparent from the above description that embodiments of the present technology enable reduction of the signaling overhead of control signaling. It does not require independent indication of "PTRS-RE-offset" for DL and UL. Alternatively or in combination, it does not require independent indication of "PTRS-RE-offset" for all scheduled PT-RS ports in SU-MIMO.

[0314] The same or additional embodiments may avoid scheduling limitations, such as incompatibility between PTRS-RE-offset and the scheduled DM-RS ports.

[0315] In addition, even if only one value of the offset parameter (i.e., bit field) is transmitted for multiple PT-RS ports, orthogonality between PT-RS ports (i.e., PT-RS transmitted through different DM-RS ports) may be achieved by means of frequency-division multiplexing (FDM).

[0316] The configuration message may enable configuring the PT-RS depending on the quality of the oscillator, the carrier frequency, the OFDM subcarrier spacing, and the modulation and coding scheme (MCS) used for transmission.

[0317] Many advantages of the present invention will be fully understood from the above description, and it will be apparent that various changes may be made in the form, construction, and arrangement of the units and apparatuses without departing from the scope of the present invention and / or sacrificing all of its advantages. Since the present invention may be modified in various ways, it will be appreciated that the present invention should be limited only by the scope of the appended claims.

[0318] In addition, according to the following description of additional embodiments (where the port index "p" may be represented by "x") (including those described as "proposals"), the present technology may be implemented independently or in combination with any of the above embodiments, implementations, or variants.

[0319] 91st Meeting of 3GPP TSG RAN WG1

[0320] November 27 - December 1, 2017, Reno, USA

[0321] Source: Ericsson

[0322] Title: Remaining Details on PTRS Design

[0323] Agenda Item: 7.2.3.4

[0324] Document: Discussion and Decision

[0325] —————————————————————————————————

[0326] 1 Introduction

[0327] In RAN1-90bis, the following agreements were reached:

[0328]

[0329]

[0330]

[0331] In this document, we discuss different aspects related to the design of the Phase Tracking Reference Signal (PTRS) that is used to estimate and compensate for errors related to phase noise and support frequency offset estimation.

[0332] ——————————————————————————————————

[0333] 2 Discussion

[0334] This document is divided into two main parts. One part focuses on the outstanding issues of PTRS design for CP-OFDM waveforms (for both DL and UL), and the second part focuses on the outstanding issues of PTRS design for DFT-S-OFDM waveforms.

[0335] 2.1 PTRS Design for CP-OFDM

[0336] 2.1.1 Association Table of PTRS Time / Frequency Density

[0337] At the previous RAN1 meeting, it was agreed to support a time density of 1 PTRS per OFDM symbol, every second OFDM symbol, and every fourth OFDM symbol, and a frequency density of 1 PTRS subcarrier per second and every fourth PRB. In transmissions using a small scheduled BW, denser PTRS in the frequency domain are needed to obtain accurate phase noise estimation (as shown in [1]), and particularly to obtain accurate frequency offset estimation (as shown in [2]). Therefore, we consider it important to also support a frequency density of 1 PTRS subcarrier per PRB.

[0338] - In the density tables that can be configured separately for UL and DL via RRC, add support for a frequency density of 1 PTRS subcarrier per PRB.

[0339] It was also agreed that Table 1 and Table 2 (i.e., the time density associated with the scheduled MCS and the frequency density associated with the scheduled BW) should be used to select the selected PTRS configuration. However, the evaluation results we presented in [3] showed that the PTRS time density can be selected independently of the coding rate, i.e., it is sufficient if the PTRS time density is only associated with the modulation scheme (QPSK, 16QAM, 64QAM, and 256QAM).

[0340] To achieve this, we propose to simplify Table 2, where only the modulation scheme is used for MSC association since the granularity of the code rate is not required. Therefore, the MCS can only select the modulation constellation, where MCS = 1 is QPSK, MCS = 2 is 16QAM, and so on.

[0341] An important advantage of this method is that a single association table can be used with different MCS tables because multiple MCS tables will be defined (so far, it has been agreed that two different MCS tables will be used for NR ([4])). At the same time, this proposal does not require special handling of the reserved MCS entries, thus simplifying the design.

[0342] - The MCS thresholds in the PTRS time density table only have the granularity of the modulation constellation size and do not include the code rate.

[0343] Scheduled BW Frequency density <![CDATA[N RB <ptrsthRB0]]> Without PT-RS <![CDATA[ptrsthRB0≤N RB ≤ptrsthRB1]]> 1 <![CDATA[PtrsthRB1 ≤ N RB ≤ ptrsthRB2]]> 1 / 2 <![CDATA[PtrsthRB2≤N RB > <![CDATA[1 / 4]]>

[0344] Table 1. Association table between PTRS frequency density and scheduled BW

[0345] Scheduled MCS Time density <![CDATA[MCS<ptrsthMCS0]]> Without PT-RS <![CDATA[PtrsthMCS1≤MCS≤ptrsthMCS2]]> 1 / 4 <![CDATA[PtrsthMCS2≤MCS≤ptrsthMCS3]]> 1 / 2 <![CDATA[PtrsthMCS3≤MCS]]> 1

[0346] Table 2. Association table between PTRS time density and MCS

[0347] 2.1.2 Default configuration of PTRS in the time domain / frequency domain

[0348] Having agreed on the default configuration, the PTRS is mapped to each OFDM symbol and every other PRB. It was up to the FFS to decide whether this default configuration should be used for all scheduled BW and MCS, i.e., whether the PTRS should always be on. From the evaluation presented in [5], it can be seen how for low MCS and small scheduled BW, the PTRS does not need to compensate for the phase noise impact. However, in some cases, the PTRS can be used to perform frequency offset estimation, e.g., in UL transmissions (sub-6 or mmWave) with pre-loaded DMRS as shown in [7] and in DL transmissions in mmWave (where the TRS may require too much overhead).

[0349] For these cases, due to the requirements for frequency offset estimation, the PTRS should be on even for low MCS and small scheduled BW. Therefore, to meet the phase noise and frequency offset compensation requirements, we propose using a default association table where the PTRS is always on for both DL and UL. The proposed default thresholds for DL and UL are shown in Tables 3 and 4, respectively.

[0350] Since the maximum number of RBs per carrier in NR is 275, we can use the value 276 to indicate the unavailable threshold for the scheduled BW.

[0351] - For DL, support ptrsthRB0 DL = ptrsthRB1 DL = 0, ptrsthRB2 DL = 276 and ptrsthMS1 DL = ptrsthMS2 DL = ptrsthMS3 DL = 0 as the default threshold.

[0352] - For UL, support ptrsthRB0 U L = ptrsthRB1 U L = 0, ptrsthRB2 UL = 276 and ptrsthMS1 UL = ptrsthMS2 UL = ptrsthMS3 UL = 0 as the default threshold.

[0353] RB threshold <![CDATA[ptrsthRB0 DL = ptrsthRB1 DL = 0, ptrsthRB2 DL = 276]]> MS threshold <![CDATA[ptrsthMS1 DL = ptrsthMS2 DL = ptrsthMS3 DL = 0]]>

[0354] Table 3. Proposed default thresholds for DL

[0355] RB threshold <![CDATA[ptrsthRB0 DL = ptrsthRB1 DL = 0, ptrsthRB2 DL = 276]]> MS threshold <![CDATA[ptrsthMS1 DL = ptrsthMS2 DL = ptrsthMS3 DL = 0]]>

[0356] Table 4. Proposed default thresholds for UL

[0357] It is important to clarify that the fact that PTRS is always on as the default configuration does not mean that PTRS is always transmitted, but rather that RRC signaling can be used to activate or deactivate PTRS transmission when needed. An important detail regarding the existence of PTRS is that it should be independent for DL and UL, as each case has different requirements. For example, for the sub-6 GHz scenario, PTRS is not needed in DL because the impact of phase noise is not significant and frequency offset tracking is performed by TRS. However, for UL, PTRS is needed in sub-6 GHz to perform frequency offset compensation. Therefore, we propose to independently indicate the existence of PTRS for DL and UL via RRC.

[0358] - Higher layer configuration independently indicates the possible existence of PTRS for DL and UL, i.e.,

[0359] UL-PTRS-present and DL-PTRS-present are RRC parameters.

[0360] 2.1.3 RRC Signaling for Thresholds

[0361] It was previously agreed that the UE can suggest the value of the threshold in the association table via RRC signaling to override the default threshold. Regarding the signaling of the threshold, two important aspects should be studied: what values are allowed for the threshold (e.g., for the scheduled BW, do we need the flexibility of 275 possible thresholds?) and how to efficiently encode these allowed thresholds.

[0362] 2.1.3.1 Association Table for Frequency Density

[0363] First, we will focus on the thresholds of the association table (Table 1) between the scheduled BW and the PTRS frequency density. For this table, each threshold is set to a specific number of PRBs. In NR, the maximum scheduled BW is X = 275 PRBs ([6]), and then with full flexibility of choice, each threshold in the table can take any value in the vector S = [0, 1, 2, 3, 4,..., X, Inf], where "276" can also be used instead of "Inf". When X = 275, the choice with full flexibility requires 9 bits to encode each threshold, which means 27 bits are needed to encode 3 thresholds. However, this flexible choice does not provide any advantage because the values taken by the thresholds are usually limited, as can be seen from the evaluations presented in [1]. To reduce complexity and signaling overhead, we propose a choice with reduced flexibility where the number of allowed values for the threshold is restricted.

[0364] The preferred option is to limit the value of the threshold to a multiple of the number of PRBs of the RBG size, i.e., the threshold can take any value in the vector S = [0, RBG, 2*RBG, 3*RBG,..., Y*RBG, Inf], where if RBG = 4, then S = [0, 4, 8, 16,..., 272, Inf], which contains 70 elements (7 bits are required to encode one threshold, and 21 bits are required to encode 3 thresholds).

[0365] - Limit the value of the threshold ptrsthRB x to the set of elements that are multiples of the RBG size, i.e., [0, RBG, 2*RBG, 3*RBG,..., Y*RBG, 276], where and X is the maximum scheduled BW in NR.

[0366] If efficient coding is used instead of bitmap coding, further reduction of signaling overhead can be achieved. This is used for EPDCCH configuration in LTE, where a limited set of RBs is selected from all available RB sets.

[0367] With bitmap coding, each threshold can take any value in S, so the number of bits required to encode each threshold is where N is the length of the vector S. However, to improve the coding, we can utilize the relative relationship between the thresholds, i.e., ptrsthRB0 ≤ ptrsthRB1 ≤ ptrsthRB2.

[0368] Therefore, considering the previous relationship, we propose an efficient coding scheme for the set of thresholds in the association table in Algorithm 1.

[0369]

[0370] In Table 5, we show the comparison of the overhead for encoding the threshold set of the frequency density association table using full flexibility selection and reduced flexibility selection, as well as bitmap and efficient coding. We can see that using the proposed coding, the overhead is reduced by 5 bits for both full flexibility and reduced flexibility selections, and when combining these two methods, we reduce the signaling overhead from 27 bits to 16 bits.

[0371] Therefore, the proposed coding should be adopted to efficiently encode the thresholds of the association table, which is similar to the coding performed for EPDCCH in LTE.

[0372] - Encode the threshold set of the frequency density association table using the coding scheme described in Algorithm 1.

[0373]

[0374] Table 5. Overhead comparison for three threshold signaling, two types of selection, and two types of coding

[0375] 2.1.3.2 Association table of time density

[0376] As proposed in 2.1.1, Table 2 should be used to associate the PTRS time density and the modulation scheme. Since NR using CP - OFDM supports the modulation schemes QPSK, 16QAM, 64QAM, and 256QAM, the thresholds in such a table are set to one of the values in the vector S = [0, 1, 2, 3, 4, Inf].

[0377] - Limit the value of ptrsthMCS x to [0, 1, 2, 3, 4, Inf].

[0378] To efficiently code the three thresholds of the association table, we can use the same coding scheme proposed for the association table of frequency density. In Table 6, we show the overhead required to signal the threshold set using bitmap coding and the proposed coding scheme. The overhead reduction achieved using the proposed coding is significant, and thus this coding should be adopted for NR.

[0379] - Use the coding scheme described in Algorithm 1 to code the threshold set of the time density association table.

[0380] Bitmap Encoding in Algorithm 1 9 bits 6 bits (overhead reduced by 33.3%)

[0381] Table 6. Overhead comparison for three threshold signaling, two types of coding 2.1.4 RB - level offset of PTRS

[0382] RAN1 agreed to support the RB - level offset for selecting RBs among the scheduled RBs to map PTRS. It also agreed to implicitly derive the offset from the C - RNTI, but was unsure how to do it specifically. To design the implicit association rule between the C - RNTI and the RB - level offset, we should consider that for different densities, the maximum offset is different. Therefore, for a frequency density with 1 PTRS sub - carrier per 4th PRB, the maximum RB - offset is 3, for every 2nd PRB it is 1, and for every PRB it is 0. Thus, we propose the following equation to implicitly derive the RB - level offset from the C - RNTI (considering the frequency density used):

[0383] RB offset = C - RNTI mod n PTRS_step

[0384] where, for frequency density 1, n PTRS_step = 1, for frequency 1 / 2, n PTRS_step= 2, and for frequency density 1 / 4, n PTRS_step = 4.

[0385] When it comes to broadcast transmission using PTRS, the association between RB-level offset and C-RNTI is invalid. In this case, the RB-level offset must be implicitly derived from a different parameter (e.g., SI-RNTI). Similar to the previous case, the association rule for the broadcast case can be set as RB offset = SI-RNTI mod n PTRS_step .

[0386] - For broadcast transmission, the RB-level offset of PTRS is associated with SI-RNTI.

[0387] - The implicit relationship between the RB-level offset of PTRS and RNTI depends on the frequency density and is given by the equation RB offset = C-RNTI mod n PTRS_step where n PTRS_step = 1 / (freq_density).

[0388] 2.1.5 RE-level offset of PTRS

[0389] The RE-level offset indicates which subcarrier within the PRB the PTRS is mapped to. In the last RAN1 meeting, the association of the RE-level offset to one of the following parameters was discussed:

[0390] · Index of the DMRS port associated with the PTRS port

[0391] · SCID

[0392] · Cell ID

[0393] Some companies claim that if the RE-level is associated with the DMRS port index, the impact of PTRS on inter-cell interference of PTRS may cause some performance degradation. It has been suggested to randomize the PTRS mapping between cells by associating the RE-level offset with SCID or cell ID to avoid this degradation.

[0394] However, in [1], the evaluation results we presented show that the PTRS of adjacent cells has better performance against PTRS interference than PDSCH against PTRS interference (when using a generally recognized constant modulation symbol sequence for PTRS in CP-OFDM). Also, in Appendix 5.1 of [3], we introduced the derivation supporting this argument.

[0395] In addition, the PTRS mapping is closely related to the multiplexing of PTRS and CSI-RS. In the case of FDM for CSI-RS and PTRS, CSI-RS resources cannot be mapped to the subcarriers that map PTRS. It has been agreed that in all cases, CSI-RS resources with more than 1 port use FD2, and thus each CSI-RS port includes 2 adjacent CSI-RS REs in the frequency domain. This fact results in that in some cases, the RE-level offset associated with the SCID or cell ID may lead to a lower number of available REs for the CSI-RS resources, as Figure 1 shown.

[0396]

[0397] a) RE-level offset associated with the DM-RS port index

[0398]

[0399] b) RE-level offset associated with the SCID / cell ID

[0400] Figure 1 .Examples of PTRS fixed and configurable mapping and available CSI-RS ports

[0401] In summary, we believe that the best option for PTRS mapping is to associate the RE-level offset with the index of the DMRS port associated with the PTRS port, because it has a lower degradation due to inter-cell interference and it has good characteristics for FDM with CSI-RS. In Tables 7 and 8, we show the proposed RE-level offsets associated with each DMRS port index for DMRS types 1 and 2.

[0402] - Support the implicit association of the RE-level offset with the index of the DMRS port associated with the PTRS port.

[0403] - Use Tables 7 and 8 to derive the RE-level offset (for DMRS types 1 and 2) for a PTRS port based on its associated DRMS port index.

[0404] DMRS port 1000 1001 1002 1003 1004 1005 1006 1007 RE-level offset 0 2 1 3 4 6 5 7

[0405] Table 7. Implicit association of RE-level offset and DMRS port index for DMRS type 1

[0406]

[0407] Table 8. Implicit association of RE-level offset and DMRS port index for DMRS type 2 2.1.6 RRC "RE-level-offset" signaling

[0408] In addition to the implicit association of the RE-level offset, in RAN190bis, it was also agreed to support the RRC parameter "PTRS-RE-offset", which explicitly indicates the RE-level offset and replaces the obtained RE-level offset with the default association rule. The main purpose of introducing this parameter in the RRC signaling is to avoid mapping PTRS to the DC subcarrier. The convention regarding this parameter indicates that "PTRS-RE-offset" can take any value from 0 to 11. However, there are several drawbacks, which will be considered next.

[0409] First, if "PTRS-RE-offset" can be set to any value from 0 to 11, it means gNB scheduling restrictions because the DMRS for PDSCH or PUSCH transmission must use the subcarrier indicated by "PTRS-RE-offset" (since it was agreed that PTRS is mapped to one of the subcarriers to which its associated DMRS port is mapped). For example, if "PTRS-RE-offset" = 0, then if DMRS type 1 is configured, the DMRS ports mapped to the comb using subcarriers {1, 3, 5, 7, 9, 11} cannot be used when scheduling the UE. In the following table, we show the restrictions mentioned for DMRS type 1.

[0410]

[0411]

[0412] Table 9. Bitmap coding of "PTRS-RE-offset" using DM-RS type 1

[0413] Another issue is related to signaling overhead. If "PTRS-RE-offset" can be set to any value from 0 to 11, then each "PTRS-RE-offset" indication requires 4 bits. In addition, since the PTRS ports for DL and UL can be associated with different DMRS ports, the "PTRS-RE-offset" needs to be indicated independently for UL and DL, thereby increasing the overhead. Similarly, in SU-MIMO, the "PTRS-RE-offset" needs to be indicated independently for each PTRS port (further increasing the overhead).

[0414] Therefore, more efficient signaling is needed to avoid scheduling limitations and reduce overhead. We propose a different approach where "PTRS-RE-offset" is used to generate a relative index for one of the elements in the subset of subcarriers used for the DMRS port associated with the PTRS port. Thus, the relative index selects subcarriers among those used for the DMRS port for a specific PDSCH or PUSCH scheduling (without introducing any scheduling limitations). The proposed solution is summarized in Algorithm 2.

[0415]

[0416]

[0417] Based on the proposed method, we show in Tables 10 and 11 the coding of the PTRS subcarriers and "PTRS-RE-offset" for the selection of DMRS ports in DMRS types 1 and 2 (based on Algorithm 2). The proposed solution avoids limitations in scheduling while reducing the required overhead. Only 2 bits are needed to code "PTRS-RE-offset". In addition, a common indication of "PTRS-RE-offset" can be used for both DL and UL, since with the proposed solution, any value of "PTRS-RE-offset" can be used for any DMRS port. Also, for the SU-MIMO case with more than 1 PT-RS port, a single indication of "PTRS-RE-offset" can be used, as it will provide different subcarriers for the PTRS ports associated with different DMRS ports.

[0418] - Use a 2-bit bitmap coding in RRC to code "PTRS-RE-offset", where "PTRS-RE-offset" can take values {0, 1, 2, 3}.

[0419] - Use Algorithm 2 to determine which subcarrier to map the PTRS port to based on the value of "PTRS-RE-offset".

[0420]

[0421] Table 10. Coding of "PTRS-RE-offset" proposed for DM-RS type 1

[0422]

[0423]

[0424] Table 11. Encoding of "PTRS-RE-offset" proposed for DM-RS type 2 2.1.7 PTRS port signaling in DL of UCI

[0425] At the last RAN1 meeting, it was agreed that the UE should report in the UCI information about the preferred DL transport layer within the CW with a higher CQI. Using this information, the gNB can perform a permutation of the columns of the precoder in order to transmit in the best transport ports the DMRS port with the lowest index in the DMRS group and its associated PTRS port. Here, we define the concept of a Column Permutation Indicator (CPI) which indicates which columns of the selected precoder must be permuted in the gNB. For example, if CPI = 0, then no permutation is performed; if CPI = 2, then the first and third columns of the precoder are permuted. By including the CPI in the CSI-feedback, we are signaling information about the best transport ports.

[0426] RAN1 agreed to support transmission ranks from 1 to 8, where the RI is part of the CSI-feedback with 3-bit overhead. Importantly, the number of possible CPIs is related to the rank and the maximum number of ports per CW available for each rank (since it was agreed to signal only information about the best transport ports associated with the CW with a higher CQI). For example, for rank 5, up to 3 ports can be associated with 1 CW, so 3 different CPI values can be selected. Thus, 1 CPI value is allowed for rank 1, 2 CPI values for rank 2, 3 CPI values for rank 3, 4 CPI values for rank 4, 3 CPI values for ranks 5 and 6, and 4 CPI values for ranks 7 and 8. So, in total, 1+2+3+4+3+3+4+4 = 24 states are needed to jointly encode the RI and the CPI, and thus 5 bits are needed to jointly encode the RI and the CPI (with full flexibility in CPI selection). In a previous document such as [8], we proposed a less flexible CPI selection where for ranks higher than 4, only 2 out of 4 CPI values can be selected. For this case, we need in total 1+2+3+2*5 = 16 states, i.e., 4 bits are needed to jointly encode the RI and the CPI.

[0427] An important aspect to consider is that RAN1 agreed that it is possible to limit the ranks that can be used and signaled in the CSI-feedback by means of a rank restriction indicator. Thus, when rank restriction is used, some of the 16 states proposed in the previous solution are not used due to the restriction and can be used to increase the flexibility of CPI selection. Next, in Algorithm 3, we propose steps for efficiently encoding the RI and the CPI and reducing the DCI payload for signaling the RI and the CPI taking into account rank restriction.

[0428]

[0429] In Table 12, we show examples of previous encodings (a) without using rank constraints and (b) with using rank constraints. We can see how the previously proposed encoding is the same as the encoding proposed in [8] for the case without rank constraints. At the same time, we can see that when using rank constraints, we can increase the flexibility in CPI selection for ranks > 3 while still using a 4-bit overhead. Thus, the proposed joint encoding provides high flexibility in CPI selection while reducing the CPI feedback overhead by 1 bit. It is worth mentioning that since we use joint encoding of RI and CPI, the CPI information will still be signaled even when there is no PTRS transmission. This is because the static UCI payload is preferred.

[0430] - Use Algorithm 3 to jointly encode RI and CPI with 4 bits.

[0431]

[0432]

[0433] Table 1. Examples of the proposed joint encoding of RI and CPI

[0434] 2.1.8 Power Boost of PTRS

[0435] PTRS power boost is beneficial because it increases the estimation accuracy. However, the principle of PTRS power boost is different from the principle of power boost used in other reference signals such as DMRS. In DMRS, we use the unused power of the blank REs in a DMRS port to boost the power of some REs (i.e., transfer power between REs in the same port without allowing power transfer between ports). However, for PTRS, we have two different types of power boost. Power boost type 1 follows the same principle as used for DMRS power boost, i.e., transfer power between REs in the same port. Power boost type 2 transfers power between different ports for the same RE.

[0436] Which power boosting type to use depends on the transmitter architecture. For an analog beamforming transmitter, power boosting type 1 should be used because each port is directly mapped to a power amplifier (so power cannot be transferred between ports). For digital and hybrid beamforming, both type 1 and type 2 can be used. With type 1, the power scaling of the PTRS ports is related to the number of PTRS ports in SU-MIMO transmission (maximum 2 PTRS ports), while with type 2, the power scaling of the PTRS ports is related to the number of PDSCH / PUSCH layers in the DMRS group in SU-MIMO (up to 8 PDSCH layers and 4 PUSCH layers ([6])). Therefore, for digital and hybrid beamforming transmitters, power boosting type 2 provides better power utilization and is thus preferred. In Figure 2 and Figure 3 we show examples of power boosting for digital and analog beamforming with 1 and 2 PTRS ports in an SU-MIMO transmission with 3 DMRS ports and 3 PDSCH layers.

[0437] - Supports power boosting type 1, which uses power transfer between REs in the same port. It should be used for transmitters with analog beamforming.

[0438] - Supports power boosting type 2, which uses power transfer between ports for the same RE. It should be used for transmitters with digital and hybrid beamforming.

[0439] - For DL and UL, power boosting type 2 should be used by default.

[0440] - Supports the RRC signaling parameters "PTRS_boosting_type DL " and "PTRS_boosting_type UL " to independently indicate the power boosting type for DL and UL.

[0441]

[0442] Figure 2 . Examples of power boosting types 1 and 2 for a transmission with 1 PTRS port, 3 DMRS ports, and 3 PDSCH layers

[0443]

[0444]

[0445] Figure 3 . Examples of power boosting types 1 and 2 for a transmission with 2 PTRS ports, 3 DMRS ports, and 3 PDSCH layers

[0446] 2.1.8.1 DL Power Boost

[0447] For DL, the PDSCH to PTRS EPRE ratio is used as a metric to indicate the power boost level (where EPRE refers to the power of all ports in the transmission in one RE and it is not the EPRE per port). For power boost types 1 and 2, the EPRE is implicitly derived from different parameters.

[0448] For power boost type 1, power transfer between ports is not allowed. Thus, in this case, the PDSCH to PTRS EPRE ratio is related to the number of PTRS ports (N PTRS ) in the transmission and the number of PDSCH layers (N PDSCH ) in the DMRS group. The EPRE level is calculated as follows:

[0449] EPRE PDsCH_to_PTRS = 10 * log 10 (N PDSCH ) - 10 * log 10 (N PTRS ) [dB]

[0450] For power boost type 2, power transfer between ports is allowed. Thus, for this type of power boost, for any N PTRS and N PDSCH , EPRE PDSCH_to_PTRS = 0 dB.

[0451] - For power boost type 1, the PDSCH to PTRS EPRE ratio is implicitly calculated according to EPRE PDSCH_to_PTRS = +10 * log10(N PDSCH) - 10 * log 10 (N PTRS ) [dB], where N PTRS is the number of PTRS ports in the transmission and N PDSCH is the number of PDSCH layers in the DMRS group.

[0452] - For power boost type 2, for any number of PTRS ports in the transmission and any number of PDSCH layers in the DMRS group, the PDSCH to PTRS EPRE ratio is always 0 dB.

[0453] It was also agreed at the last RAN1 meeting to support RRC signaling for PDSCH to PTRS EPRE. However, this indication raises some issues which will be discussed next. For power boost type 1, from N PTRS and N PDSCH(Parameters derived from the DCI that can be dynamically changed) implicitly derive the EPRE ratio. Therefore, with respect to N PTRS and N PDSCH in the DCI, the EPRE level indicated by the RRC may be outdated (resulting in incorrect power scaling). For power boost type 2, for all cases, the EPRE ratio is equal to 0 dB, so the RRC indication of different EPRE levels will result in incorrect power scaling. Therefore, we believe that the EPRE indication via the RRC must be excluded to avoid the problems pointed out.

[0454] - Do not include explicit EPRE indication in the RRC signaling. Instead, use the RRC to configure the boost type.

[0455] 2.1.8.2 UL Power Boost

[0456] For UL, the power of the PTRS port is used as a metric to indicate the power boost level.

[0457] For power boost type 1, the power of the PTRS port is related to the power of the PUSCH RE in a layer (P PUSCH ) and the number of PTRS ports (N PTRS ). The PTRS power is given by:

[0458] P PTRS = 10 * log 10 (N PTRS ) + P PUSCH

[0459] For power boost type 2, the power of the PTRS port is related to the number of PUSCH layers in the DMRS group (N PUSCH ) and the power of the PUSCH RE in a layer (P PUSCH ). Therefore, the power of the PTRS port is given by:

[0460] P PTRS = 10 * log10(N PUSCH ) + P PUSCH

[0461] - If power boost type 1 is used in UL, then the power of the PTRS port is implicitly given by P PTRS = 10 * log 10 (N PTRS ) + P PUSCH where N PTRS is the number of PTRS ports and P PUSCH is the power of the PUSCH RE in a layer.

[0462] - If power boost type 2 is used in UL, then through P PTRS = 10 * log 10 (N PUSCH ) + P PUSCH implicitly gives the power of the PTRS port,

[0463] where N PUSCH is the number of PUSCH layers in the DMRS group, and P PUSCH is the power of the PUSCH RE in one layer.

[0464] 2.1.9 Mapping in time domain

[0465] An agreement has been reached on how to map PTRS within a time slot, but no agreement has been reached on the conflict between PTRS and SSB in the time slot. In this case, two different options can be used. Either puncture the PTRS RE that conflicts with the SSB, or shift it to the first OFDM symbol after the SSB. In some cases, puncturing may lead to a situation where the extrapolation of phase estimation cannot provide good accuracy due to a large distance between the last PTRS symbol and the PDSCH symbol. For example, in Figure 4 we show an example with a lower PTRS time density (1 PTRS per 4th OFDM symbol). It can be seen that when puncturing, within this time slot, there are 7 symbols between the last PDSCH symbol and the last PTRS RE, while with shifting, this distance is reduced to 1 symbol (thus improving phase estimation). Therefore, when PTRS conflicts with SSB, we prefer PTRS shifting.

[0466] - When PTRS conflicts with SSB, the PTRS should be shifted to the first OFDM symbol after the SSB, and the mapping algorithm should be restarted.

[0467]

[0468] Figure 4 . Example of PTRS and SSB conflict in the case of PTRS time density of 1 / 4

[0469] 2.1.10 PTRS design for mini-slots

[0470] For time-slot-based and non-time-slot-based transmissions, the same PTRS configuration should be used.

[0471] - For Rel.15, the PTRS configuration through RRC is applicable to both time-slot-based scheduling and non-time-slot-based scheduling.

[0472] 2.2 PTRS design for DFT-S-OFDM

[0473] 2.2.1 Association Table

[0474] RAN1 agreed that the configuration of block-based PTRS must be associated with the scheduled BW. The following issues regarding the association table remain unresolved:

[0475] · Whether the configuration is also associated with the scheduled MCS

[0476] · Whether the block size K = 1 is supported

[0477] · Whether the configuration with K = 4 and X > 4 is supported

[0478] · The default values for the thresholds in the table

[0479] In [9], we showed that the configuration of PTRS in the DFT domain is independent of the scheduled MCS, so the association table should only depend on the scheduled BW. Also, in [9], we showed that the configuration with K = 1 does not provide any performance gain for large scheduled BW, so it should not be supported. Thus, the overhead of signaling the thresholds in the association table is reduced (since one less threshold is used). Additionally, we showed in [9] that in some cases, the configuration with X = 8 and K = 4 provides performance gain (especially for large BW and UEs with low-quality oscillators), so Y = 8 needs to be supported. Therefore, Table 13 must be used to select the configuration of PTRS in the DFT domain.

[0480] - Exclude the configuration with K = 1.

[0481] - For large scheduled BW, support Y = 8.

[0482] - The PTRS configuration in the DFT domain is not associated with the scheduled MCS.

[0483] Scheduled BW XxK <![CDATA[N RB ≤N RB0 > Without PT-RS <![CDATA[N RB0 <N RB ≤N RB1 > 2x2 <![CDATA[N RB1 <N RB ≤N RB2 > 2x4 <![CDATA[N RB2 <N RB ≤N RB3 > 4x2 <![CDATA[N RB3 <N RB ≤N RB4 > 4x4 <![CDATA[N RB4 <N RB > 8x4

[0484] Table 13. Association Table between Scheduled BW and Block-Based Configuration

[0485] As mentioned before, an important outstanding issue is the default values for the thresholds in the association table. In [9], the evaluation results we provided indicate that the best choices for the default thresholds in Table 13 are N RB0 = 0, N RB1 = 8, N RB2 = N RB3 = 32, and N RB4 = 108. An important aspect of the proposed default thresholds is that they provide a configuration with PTRS always on for DFT-S-OFDM, thus allowing frequency offset estimation.

[0486] - For the thresholds in the association table between the scheduled BW and the block-based configuration, use N RB0 = 0, N RB1 = 8, N RB2 = N RB3 = 32 and N RB4 = 108 as the default value.

[0487] 2.2.2 RRC Signaling for Thresholds

[0488] As in the case of CP-OFDM, the UE can suggest new thresholds via RRC signaling to overwrite the default values in association table 13. The same principle for the thresholds of the association table used to signal the frequency density of PTRS for CP-OFDM introduced in section 2.1.3 can be applied to the thresholds of the association table for signaling the DFT configuration. In Table 14, we show the overhead required to signal the 5 thresholds of the association table using full flexibility and reduced flexibility selections as well as bitmaps and efficient coding. In this case, the benefits of the reduced flexibility selection and the proposed efficient coding are even greater than in the case of the thresholds of the PTRS frequency density table (because the number of thresholds to be encoded is larger).

[0489] - Limit the value of N RBx to a set of elements that are multiples of the RBG size, i.e., [0, RBG, 2*RBG, 3*RBG,..., Y*RBG, 276], where and X is the maximum scheduled BW in NR.

[0490] - Use the coding scheme described in Algorithm 1 to efficiently encode the thresholds of the association table based on the PTRS block configuration.

[0491] Bitmap Encoding in Algorithm 1 Full flexibility 45 bits 34 bits (overhead reduced by 24.4%) Reduced flexibility, PRG = 4 35 bits 24 bits (overhead reduced by 28.5%)

[0492] Table 14. Overhead Comparison for Signaling 5 Thresholds, 2 Types of Selections, and 2 Types of Coding

[0493] 2.2.3 Placement of Blocks for K = 2

[0494] In the previous RAN1 meeting, it was agreed that for the case of K = 2, place the blocks from sample n to sample n+K-1 within intervals dedicated to each block. In

[10] , we showed the evaluation results for different block placements for K = 2 and X = 2, where it was shown that the performance differences for different block placements are very small. Therefore, to have a coordinated design between cases K = 4 and K = 2, we believe that the best option for K = 2 is to place the blocks in the center of the intervals.

[0495] - For K = 2, map the PTRS blocks in the middle of each interval, i.e., where N is the number of samples in the interval.

[0496] —————————————————————————————————

[0497] 3 Conclusions

[0498] We propose the following additional proposals:

[0499] Proposal 1 In the density tables that can be configured separately for UL and DL via RRC, add support for the frequency density of 1 PTRS subcarrier in each PRB.

[0500] Proposal 2 The MCS thresholds in the PTRS time density table only have the granularity of the modulation constellation size and do not include the coding rate.

[0501] Proposal 3 For DL, support ptrsthRB0 DL = ptrsthRB1 DL = 0, ptrsthRB2 DL = 276 and ptrsthMS1 DL = ptrsthMS2 DL = ptrsthMS3 DL = 0 as the default threshold.

[0502] Proposal 4 For UL, support ptrsthRB0 UL = ptrsthRB1 UL = 0, ptrsthRB2 UL = 276 and ptrsthMS1 UL = ptrsthMS2 UL = ptrsthMS3 UL = 0 as the default threshold.

[0503] Proposal 5 The higher layer configuration independently indicates the possible presence of PTRS for DL and UL, i.e., UL-PTRS-present and DL-PTRS-present are RRC parameters.

[0504] Proposal 6 Limit the value of the threshold ptrsthRB x to a set of elements that are multiples of the RBG size, i.e., [0, RBG, 2*RBG, 3*RBG,..., Y*RBG, 276], where Y = XRBG and X is the maximum scheduled BW in NR.

[0505] Proposal 7 Use the coding scheme described in Algorithm 1 to encode the threshold set of the frequency density association table.

[0506] Proposal 8 Set ptrsthMCSx The value is restricted to [0, 1, 2, 3, 4, Inf].

[0507] Proposal 9 uses the encoding scheme described in Algorithm 1 to encode the threshold set of the time density correlation table.

[0508] Proposal 10 For broadcast transmission, the RB-level offset of PTRS is associated with SI-RNTI.

[0509] Proposal 11 The implicit relationship between the RB-level offset of PTRS and RNTI depends on the frequency density and is given by the equation RB offset = C-RNTI mod n PTRS_step Given, where n PTRS_step = 1 / (freq_density).

[0510] Proposal 12 Support the implicit association of the RB-level offset with the index of the DMRS port associated with the same PTRS port.

[0511] Proposal 13 Use Tables 7 and 8 to derive the RE-level offset (for DMRS types 1 and 2) for a PTRS port based on its associated DMRS port index.

[0512] Proposal 14 Use 2-bit bitmap encoding in RRC to encode "PTRS-RE-offset", where "PTRS-RE-offset" can take values {0, 1, 2, 3}.

[0513] Proposal 15 Use Algorithm 2 to determine which subcarrier to map the PTRS port to based on the value of "PTRS-RE-offset".

[0514] Proposal 16 Use Algorithm 3 to jointly encode RI and CPI with 4 bits.

[0515] Proposal 17 Support power boosting type 1, which uses power transfer between REs in the same port. It should be used for transmitters with analog beamforming.

[0516] Proposal 18 Support power boosting type 2, which uses power transfer between ports of the same RE. It should be used for transmitters with digital and hybrid beamforming.

[0517] Proposal 19 For DL and UL, power boosting type 2 should be used by default.

[0518] Proposal 20 Support the RRC signaling parameters "PTRS_boosting_type DL " and "PTRS_boosting_type UL” to independently indicate the power boost types for DL and UL.

[0519] Proposal 21 For power boost type 1, according to EPRE PDSCH_to_PTRS = +10 * log 10 (N PDSCH ) - 10 * log 10 (N PTRS ) [dB] implicitly calculates the PDSCH to PTRS EPRE ratio, where N PTRS is the number of PTRS ports in transmission, and N PDSCH is the number of PDSCH layers in the DMRS group.

[0520] Proposal 22 For power boost type 2, for any number of PTRS ports in transmission and any number of PDSCH layers in the DMRS group, the PDSCH to PTRS EPRE ratio is always 0 dB.

[0521] Proposal 23 Do not include explicit EPRE indication in RRC signaling. Instead, use RRC to configure the boost type.

[0522] Proposal 24 If power boost type 1 is used in UL, then the power of the PTRS port is implicitly given by P PTRS = 10 * log 10 (N PTRS ) + P PUSCH , where N PTRS is the number of PTRS ports, and P PUSCH is the power of the PUSCH RE in one layer.

[0523] Proposal 25 If power boost type 2 is used in UL, then the power of the PTRS port is implicitly given by P PTRS = 10 * log 10 (N PUSCH ) + P PUSCH , where N PUSCH is the number of PUSCH layers in the DMRS group, and P PUSCH is the power of the PUSCH RE in one layer.

[0524] Proposal 26 When PTRS conflicts with SSB, PTRS should be shifted to the first OFDM symbol after SSB, and the mapping algorithm should be restarted.

[0525] Proposal 27 For Rel.15, the PTRS configuration via RRC applies to both slot-based scheduling and non-slot-based scheduling.

[0526] Proposal 28 Exclude the configuration with K = 1.

[0527] Proposal 29 supports Y = 8 for large scheduling BW.

[0528] Proposal 30: The PTRS configuration in the DFT domain is not associated with the scheduled MCS.

[0529] Proposal 31: For the threshold in the association table between the scheduled BW and the block-based configuration, adopt N RB0 = 0, N RB1 = 8, N RB2 = N RB3 = 32, N RB4 = 108 as the default value.

[0530] Proposal 32: Limit the value of N RBx to a set of elements that are multiples of the RBG size, i.e., [0, RBG, 2*RBG, 3*RBG,..., Y*RBG, 276], where Y = XRBG and X is the maximum scheduled BW in NR.

[0531] Proposal 33: Efficiently encode the threshold of the association table for the PTRS block-based configuration using the coding scheme described in Algorithm 1.

[0532] Proposal 34: For K = 2, map the PTRS block in the middle of each interval, i.e., n = N2 - K2, where N is the number of samples in the interval.

[0533] 4 References

[0534] [1] R1-1718750, “Further evaluations on PTRS for CP-OFDM”, Ericsson

[0535] [2] R1-1720981, “TRS above-6GHz evaluations”, Ericsson

[0536] [3] R1-1716373, “Details on PTRS design”, Ericsson

[0537] [4] Chairman’s Notes RAN190bis

[0538] [5] R1-1714314, “On DL PTRS design”, Ericsson

[0539] [6] 3GPP TS 38.211v1.1.2

[0540] [7]R1-1718749, “Further evaluations on DMRS”, Ericsson

[0541] [8]R1-1718449, “Remaining details on PTRS design”, Ericsson

[0542] [9]R1-1720725, “Further evaluations on PTRS”, Ericsson

[0543]

[10] R1-1718751, “Further evaluations on PTRS for DFT-S-OFDM”, Ericsson

Claims

1. A method for transmitting a configuration message for a phase-tracking reference signal PT-RS over a radio channel between a radio access node and a radio device, the radio channel comprising a plurality of subcarriers in a physical resource block PRB, a subset of the subcarriers in the PRB being allocated to a demodulation reference signal DM-RS, the method comprising the steps of: Transmitting the configuration message to the radio device, the configuration message including a bit field indicating at least one subcarrier allocated to the PT-RS among the subset of subcarriers allocated to the DM-RS, wherein the radio channel is accessed via one or more DM-RS ports, each transmission of the DM-RS being associated with one of the one or more DM-RS ports, and wherein the subcarrier allocated to the PT-RS is uniquely determined among the subset of subcarriers allocated to the DM-RS based on the combination of the bit field in the configuration message and the DM-RS port through which the PT-RS is transmitted or received.

2. The method according to claim 1, wherein the bit field comprises n bits indicating the at least one subcarrier allocated to the PT-RS among the subset of subcarriers allocated to the DM-RS.

3. The method according to claim 2, wherein the number of the plurality of subcarriers in the PRB is greater than 2 n .

4. The method according to any one of claims 1 to 3, wherein the subset of subcarriers allocated to the DM-RS is signaled dynamically.

5. The method according to any one of claims 1 to 3, wherein the bit field comprises 2 or 3 bits indicating the at least one subcarrier allocated to the PT-RS among the subset of subcarriers allocated to the DM-RS, and the number of the plurality of subcarriers in the PRB is 12.

6. The method according to any one of claims 1 to 3, wherein the size of the bit field is determined to represent any one of the subcarriers in the subset of subcarriers allocated to the DM-RS as a subcarrier allocated to the PT-RS.

7. The method according to any one of claims 1 to 3, wherein the bit field includes n bits, and the number of subcarriers allocated to the subset of the subcarriers for the DM-RS is equal to or less than 2 n .

8. The method according to any one of claims 1 to 3, wherein each subcarrier in the subset of subcarriers allocated to the DM-RS is uniquely identified by an index, and the bit field indicates the index corresponding to the subcarrier allocated to the PT-RS.

9. The method according to any one of claims 1 to 3, wherein the subcarrier allocated to the PT-RS is derived from the bit field for at least one of an uplink transmission of the PT-RS and a downlink transmission of the PT-RS.

10. The method according to any one of claims 1 to 3, wherein the radio access node is configured to access the radio channel via the DM-RS port for a downlink transmission to the radio device, the method further comprising the steps of: Transmit the PT-RS on the subcarriers assigned to the PT-RS according to the bit field among the subset of the DM-RS assigned to the corresponding DM-RS port through at least one of the DM-RS ports.

11. The method according to any one of claims 1 to 3, wherein the radio device is configured to access the radio channel through the DM-RS port for uplink transmission to the radio access node, and the method further comprises the following steps: Receive the PT-RS transmitted on the subcarriers assigned to the PT-RS according to the bit field among the subset of the DM-RS assigned to the corresponding DM-RS port through at least one of the DM-RS ports.

12. The method according to any one of claims 1 to 3, wherein the radio channel comprises a multi-user multiple-input multiple-output (MU-MIMO) channel, wherein different DM-RS groups of the DM-RS ports provide access to different radio devices, and the PT-RS is transmitted or received through at least one of the DM-RS ports in each DM-RS group.

13. The method according to any one of claims 1 to 3, wherein the assignment of subcarriers to the subset of the DM-RS depends on the corresponding DM-RS port.

14. The method according to claim 13, wherein the PRB comprises 12 subcarriers given by an index k ∈ {0,..., 11}, and wherein the assignment of subcarriers to the subset of the DM-RS transmitted through the DM-RS port p is given by: {2·R·m + S·k′ + Δ(p) ∈ {0,..., 11}|k′ ∈ {0, 1}, 0 ≤ m < 6 / R}, where R = 1, 2 or 3; S = 1 or 2; and the offset Δ(p) depends on the DM-RS port p.

15. The method according to any one of claims 1 to 3, wherein the bit field indicates two candidate subcarriers for the PT-RS among the subset of the subcarriers assigned to the DM-RS, and wherein the subcarrier assigned to the PT-RS is determined among the two candidate subcarriers based on the DM-RS port through which the PT-RS is transmitted.

16. The method according to claim 14, wherein the subcarrier assigned to the PT-RS transmitted through the DM-RS port p is given by 2·R·m + S·k′ + Δ(p), wherein the bit field indicates m, and k′ = p mod 2.

17. The method according to claim 13, wherein different DM-RS are transmitted through each of the DM-RS ports.

18. The method according to claim 17, wherein the DM-RS transmitted through different DM-RS ports is distinguished by at least one of an orthogonal cover code in the frequency domain, OCC FD-OCC, an orthogonal cover code in the time domain, TD-OCC, and the allocation of subcarriers to the subset of the DM-RS.

19. The method according to any one of claims 1 to 3, wherein the radio channel comprises a single-user multiple-input multiple-output, SU-MIMO, channel accessed through two or more DM-RS ports, and the PT-RS is transmitted or received at each of at least two of the two or more DM-RS ports.

20. The method according to any one of claims 1 to 3, wherein the PT-RS is transmitted at each of at least two different DM-RS ports and / or in each of uplink transmission and downlink transmission.

21. The method according to any one of claims 1 to 3, wherein the DM-RS transmitted through the DM-RS port p is subjected to an orthogonal cover code in the time domain, OCC TD-OCC, and is subjected to OCC FD-OCC in the frequency domain, and wherein the subcarriers allocated to the PT-RS are determined among the subset of subcarriers allocated to the DM-RS based on a combination of the bit field, the DM-RS port correlation of the TD-OCC, and the DM-RS port correlation of the FD-OCC.

22. The method according to claim 21, wherein for the DM-RS port p, the DM-RS port correlation of the TD-OCC comprises: TD_offset p = (p - 1000 div 2) div R, or TD_offset p = floor(p - 1000) / (2·R)).

23. The method according to claim 21, wherein for the DM-RS port p, the DM-RS port correlation of the FD-OCC comprises: FD + offset p = p mod 2。 24. The method according to claim 21, wherein the TD-OCC comprises a factor: wt(I′) = [1 - 2·(TD_offset p )] I′ , and / or The FD-OCC comprises a factor: w f (k′) = [1 - 2·(FD_offset p )] k′ 。 25. The method according to claim 21, wherein for each DM-RS port through which the PT-RS is transmitted, the configuration message comprises an instance of the bit field indicating the subcarriers allocated to the PT-RS among the subset of subcarriers allocated to the DM-RS transmitted through the corresponding DM-RS port.

26. The method according to any one of claims 1 to 3, wherein the PT-RS is transmitted through one of the DM-RS ports, the one DM-RS port being determined according to a predefined rule; or wherein the DM-RS ports are grouped into two or more non-overlapping DM-RS groups, and the PT-RS is transmitted through one of the DM-RS ports in each of the DM-RS groups, the one DM-RS port being determined according to the predefined rule applied to each of the DM-RS groups.

27. The method according to claim 26, wherein each DM-RS port in the DM-RS ports is uniquely identified by a port index, and according to the predefined rule, the one DM-RS port in the DM-RS ports is the DM-RS port having the lowest port index.

28. The method according to any one of claims 1 to 3, wherein the PT-RS includes tones on the subcarriers allocated to the PT-RS, and the tones correspond to the tones of the DM-RS transmitted on the same subcarriers through the corresponding DM-RS ports.

29. The method according to any one of claims 1 to 3, wherein each DM-RS port is mapped to a plurality of antenna ports according to a precoder.

30. The method according to any one of claims 1 to 3, wherein the number of subcarriers in the subset of subcarriers allocated to the DM-RS according to DM-RS configuration type 1 is twice the number of subcarriers in the subset of subcarriers allocated to the DM-RS according to DM-RS configuration type 2, wherein the same-sized bit field is used for each of the DM-RS configuration type 1 and the DM-RS configuration type 2, and wherein the most significant bit of the bit field is ignored or set to zero so as to determine the subcarriers allocated to the PT-RS in the DM-RS configuration type 2.

31. A method of receiving a configuration message of a phase tracking reference signal PT-RS on a radio channel between a radio access node and a radio device, the radio channel including a plurality of subcarriers in a physical resource block PRB, a subset of the subcarriers in the PRB being allocated to a demodulation reference signal DM-RS, the method comprising the steps of: Receiving the configuration message from the radio access node, the configuration message including a bit field indicating at least one subcarrier allocated to the PT-RS among the subset of subcarriers allocated to the DM-RS, wherein the radio channel is accessed through one or more DM-RS ports, DM-RS is transmitted or received through each DM-RS port, and wherein the subcarriers allocated to the PT-RS are uniquely determined among the subset of subcarriers allocated to the DM-RS based on a combination of the bit field in the configuration message and the DM-RS port through which the PT-RS is transmitted or received.

32. The method according to claim 31, wherein the bit field includes n bits indicating the at least one subcarrier allocated to the PT-RS among the subset of subcarriers allocated to the DM-RS.

33. The method according to claim 32, wherein the number of the plurality of subcarriers in the PRB is greater than 2 n .

34. The method according to any one of claims 31 to 33, wherein the subset of subcarriers allocated to the DM-RS is signaled dynamically.

35. The method according to any one of claims 31 to 33, wherein the bit field includes 2 or 3 bits indicating at least one subcarrier among the subset of subcarriers of the DM-RS allocated to the PT-RS, and the number of subcarriers in the PRB is 12.

36. The method according to any one of claims 31 to 33, wherein the size of the bit field is determined to represent any one of the subcarriers in the subset of subcarriers of the DM-RS allocated to the PT-RS.

37. The method according to any one of claims 31 to 33, wherein the bit field comprises n bits, and the number of subcarriers of the subcarriers allocated to the subset of the DM-RS is equal to or less than 2 n .

38. The method according to any one of claims 31 to 33, wherein each subcarrier in the subset of subcarriers of the DM-RS allocated to the DM-RS is uniquely identified by an index, and the bit field indicates the index corresponding to the subcarrier allocated to the PT-RS.

39. The method according to any one of claims 31 to 33, wherein the subcarriers allocated to the PT-RS are derived from the bit field for at least one of the uplink transmission of the PT-RS and the downlink transmission of the PT-RS.

40. The method according to any one of claims 31 to 33, wherein the radio access node is configured to access the radio channel through the DM-RS port for downlink transmission to the radio device, and the method further includes the following steps: Receiving the PT-RS transmitted on the subcarriers allocated to the PT-RS according to the bit field among the subset of the DM-RS allocated to the corresponding DM-RS port through at least one of the DM-RS ports.

41. The method according to claim 31, wherein the radio device is configured to access the radio channel through the DM-RS port for uplink transmission to the radio access node, and the method further includes the following steps: Transmitting the PT-RS on the subcarriers allocated to the PT-RS according to the bit field among the subset of the DM-RS allocated to the corresponding DM-RS port through at least one of the DM-RS ports.

42. The method according to any one of claims 31 to 33, wherein the radio channel includes a multi-user multiple input multiple output (MU-MIMO) channel, wherein different DM-RS groups of the DM-RS ports provide access to different radio devices, and the PT-RS is transmitted or received through at least one of the DM-RS ports in each DM-RS group.

43. The method according to any one of claims 31 to 33, wherein the subset of subcarriers of the DM-RS allocated depends on the corresponding DM-RS port.

44. The method according to claim 43, wherein the PRB comprises 12 subcarriers given by an index k ∈ {0, ..., 11}, and wherein the assignment of subcarriers to the subset of the DM-RS transmitted or received through the DM-RS port p is given by: {2·R·m + S·k′ + Δ(p)′ {0, ..., 11}|k′ ∈ {0, 1}, 0 ≤ m < 6 / R}, where R = 1, 2 or 3; S = 1 or 2; and the offset Δ(p) depends on the DM-RS port p.

45. The method according to any one of claims 31 to 33, wherein the bit field indicates two candidate subcarriers for the PT-RS among the subset of subcarriers assigned to the DM-RS, and wherein the subcarrier assigned to the PT-RS is determined among the two candidate subcarriers based on the DM-RS port through which the PT-RS is transmitted.

46. The method according to claim 44, wherein the subcarrier assigned to the PT-RS transmitted through the DM-RS port p is given by 2·R·m + S·k′ + Δ(p), where the bit field indicates m, and k′ = p mod 2.

47. The method according to claim 43, wherein different DM-RS are transmitted or received through each of the DM-RS ports.

48. The method according to claim 47, wherein the DM-RS transmitted through different DM-RS ports are distinguished by at least one of an orthogonal cover code OCC FD-OCC in the frequency domain, an orthogonal cover code TD-OCC in the time domain, and the subset of subcarriers assigned to the DM-RS.

49. The method according to any one of claims 31 to 33, wherein the radio channel comprises a single-user multiple-input multiple-output SU-MIMO channel accessed through two or more DM-RS ports, and the PT-RS is transmitted or received through each of at least two of the two or more DM-RS ports.

50. The method according to any one of claims 31 to 33, wherein the PT-RS is transmitted through each of at least two different DM-RS ports and / or in each of an uplink transmission and a downlink transmission.

51. The method according to any one of claims 31 to 33, wherein the DM-RS transmitted through the DM-RS port p is subject to an orthogonal cover code OCC TD-OCC in the time domain and an OCC FD-OCC in the frequency domain, and wherein the subcarrier assigned to the PT-RS is determined among the subset of subcarriers assigned to the DM-RS based on a combination of the bit field, the DM-RS port correlation of the TD-OCC, and the DM-RS port correlation of the FD-OCC.

52. The method according to claim 51, wherein for the DM-RS port p, the DM-RS port correlation of the TD-OCC includes: TD_offset p = (p - 1000 div 2) div R, or TD_offset p = floor((p - 1000) / (2·R)).

53. The method according to claim 51, wherein for the DM-RS port p, the DM-RS port correlation of the FD-OCC includes: FD_offset p = p mod 2.

54. The method according to claim 51, wherein the TD-OCC includes factors: w t (I′) = [1 - 2·(TD_offset p )] I′ , and / or The FD-OCC includes factors: w f (k′) = [1 - 2·(FD_offset p )] k′ 。 55. The method according to any one of claims 31 to 33, wherein for each DM-RS port through which the PT-RS is transmitted, the configuration message includes an instance of the bit field indicating the subcarriers allocated to the PT-RS among the subset of subcarriers allocated to the DM-RS transmitted through the corresponding DM-RS port.

56. The method according to any one of claims 31 to 33, wherein the PT-RS is transmitted through one of the DM-RS ports, and the one DM-RS port is determined according to a predefined rule; or wherein the DM-RS ports are grouped into two or more non-overlapping DM-RS groups, and the PT-RS is transmitted through one of the DM-RS ports in each of the DM-RS groups, and the one DM-RS port is determined according to the predefined rule applied to each of the DM-RS groups.

57. The method according to claim 56, wherein each of the DM-RS ports is uniquely identified by a port index, and according to the predefined rule, the one DM-RS port among the DM-RS ports is the DM-RS port with the lowest port index.

58. The method according to any one of claims 31 to 33, wherein the PT-RS includes tones on the subcarriers allocated to the PT-RS, and the tones correspond to the tones of the DM-RS transmitted on the same subcarrier through the corresponding DM-RS port.

59. The method according to any one of claims 31 to 33, wherein each DM-RS port is mapped to a plurality of antenna ports according to a precoder.

60. The method according to any one of claims 31 to 33, wherein the number of subcarriers according to DM-RS configuration type 1 in the subset of subcarriers allocated to the DM-RS is twice the number of subcarriers according to DM-RS configuration type 2 in the subset of subcarriers allocated to the DM-RS, wherein the same-sized bit field is used for each of the DM-RS configuration type 1 and the DM-RS configuration type 2, and wherein the most significant bit of the bit field is ignored or set to zero in order to determine the subcarriers allocated to the PT-RS in the DM-RS configuration type 2.

61. A computer program product comprising a program code portion for performing the steps according to any one of claims 1 to 60 when the computer program product is executed on one or more computing devices.

62. The computer program product according to claim 61, stored on a computer-readable recording medium.

63. A radio access node for transmitting a configuration message of a phase-tracking reference signal PT-RS on a radio channel between the radio access node and a radio device, the radio channel including a plurality of subcarriers in a physical resource block PRB, a subset of the subcarriers in the PRB being allocated to a demodulation reference signal DM-RS, the radio access node being configured to perform the following steps: Transmit the configuration message to the radio device, the configuration message including a bit field indicating at least one subcarrier allocated to the PT-RS among the subset of subcarriers allocated to the DM-RS, wherein the radio channel is accessed through one or more DM-RS ports, each transmission of the DM-RS being associated with one of the one or more DM-RS ports, and wherein, based on the combination of the bit field in the configuration message and the DM-RS port through which the PT-RS is transmitted or received, the subcarrier allocated to the PT-RS is uniquely determined among the subset of subcarriers allocated to the DM-RS.

64. The radio access node according to claim 63, further configured to perform the steps according to any one of claims 2 to 30.

65. A radio device for receiving a configuration message of a phase-tracking reference signal PT-RS on a radio channel between a radio access node and the radio device, the radio channel including a plurality of subcarriers in a physical resource block PRB, a subset of the subcarriers in the PRB being allocated to a demodulation reference signal DM-RS, the radio device being configured to perform the following steps: Receive the configuration message from the radio access node, the configuration message including a bit field indicating at least one subcarrier allocated to the PT-RS among the subset of subcarriers allocated to the DM-RS, wherein the radio channel is accessed through one or more DM-RS ports, and DM-RS is transmitted or received through each DM-RS port, and wherein, based on the combination of the bit field in the configuration message and the DM-RS port through which the PT-RS is transmitted or received, the subcarrier allocated to the PT-RS is uniquely determined among the subset of subcarriers allocated to the DM-RS.

66. The radio device according to claim 65, further configured to perform the steps according to any one of claims 31 to 60.

67. A radio access node for transmitting a configuration message of a phase-tracking reference signal PT-RS on a radio channel between the radio access node and a radio device, the radio channel including a plurality of subcarriers in a physical resource block PRB, a subset of the subcarriers in the PRB being assigned to a demodulation reference signal DM-RS, the radio access node including at least one processor and a memory, the memory including instructions executable by the at least one processor, whereby the radio access node is operable to: Transmit the configuration message to the radio device, the configuration message including a bit field indicating at least one subcarrier assigned to the PT-RS among the subset of subcarriers assigned to the DM-RS, wherein the radio channel is accessed via one or more DM-RS ports, each transmission of the DM-RS being associated with one of the one or more DM-RS ports, and wherein the subcarrier assigned to the PT-RS is uniquely determined among the subset of subcarriers assigned to the DM-RS based on a combination of the bit field in the configuration message and the DM-RS port through which the PT-RS is transmitted or received.

68. The radio access node according to claim 67, further operable to perform the steps according to any one of claims 2 to 30.

69. A radio device for receiving a configuration message of a phase-tracking reference signal PT-RS on a radio channel between a radio access node and the radio device, the radio channel including a plurality of subcarriers in a physical resource block PRB, a subset of the subcarriers in the PRB being assigned to a demodulation reference signal DM-RS, the radio device including at least one processor and a memory, the memory including instructions executable by the at least one processor, whereby the radio device is operable to: Receive the configuration message from the radio access node, the configuration message including a bit field indicating at least one subcarrier assigned to the PT-RS among the subset of subcarriers assigned to the DM-RS, wherein the radio channel is accessed via one or more DM-RS ports, and DM-RS is transmitted or received through each DM-RS port, and wherein the subcarrier assigned to the PT-RS is uniquely determined among the subset of subcarriers assigned to the DM-RS based on a combination of the bit field in the configuration message and the DM-RS port through which the PT-RS is transmitted or received.

70. The radio device according to claim 69, further operable to perform the steps according to any one of claims 31 to 60.

71. A method for transmitting and receiving a configuration message for a phase tracking reference signal PT-RS over a radio channel between a radio access node and a radio device, the radio channel comprising a plurality of subcarriers in a physical resource block PRB, a subset of the subcarriers in the PRB being allocated to a demodulation reference signal DM-RS, the method comprising the steps of: Transmitting the configuration message to the radio device, the configuration message comprising a bit field indicating at least one subcarrier allocated to the PT-RS among the subset of subcarriers allocated to the DM-RS; and Receiving the configuration message from the radio access node, the configuration message comprising the bit field indicating at least one subcarrier allocated to the PT-RS among the subset of subcarriers allocated to the DM-RS, wherein the radio channel is accessed via one or more DM-RS ports, and each transmission of the DM-RS is associated with one of the one or more DM-RS ports, wherein, based on the combination of the bit field in the configuration message and the DM-RS port through which the PT-RS is transmitted or received, the subcarrier allocated to the PT-RS is uniquely determined among the subset of subcarriers allocated to the DM-RS.

72. A system embodied in at least one of a radio access node and a radio device for transmitting and receiving a configuration message for a phase tracking reference signal PT-RS over a radio channel between the radio access node and the radio device, the radio channel comprising a plurality of subcarriers in a physical resource block PRB, a subset of the subcarriers in the PRB being allocated to a demodulation reference signal DM-RS, the system configured to perform the steps of: Transmitting the configuration message to the radio device, the configuration message comprising a bit field indicating at least one subcarrier allocated to the PT-RS among the subset of subcarriers allocated to the DM-RS; and Receiving the configuration message from the radio access node, the configuration message comprising the bit field indicating at least one subcarrier allocated to the PT-RS among the subset of subcarriers allocated to the DM-RS, wherein the radio channel is accessed via one or more DM-RS ports, and each transmission of the DM-RS is associated with one of the one or more DM-RS ports, wherein, based on the combination of the bit field in the configuration message and the DM-RS port through which the PT-RS is transmitted or received, the subcarrier allocated to the PT-RS is uniquely determined among the subset of subcarriers allocated to the DM-RS.

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