Patent Description:
Long Term Evolution (LTE) has been specified for achieving a higher data rate, lower latency, and/or the like in a Universal Mobile Telecommunication System (UMTS) network (NPL <NUM>). Further, future systems of LTE have been also studied for achieving a broader bandwidth and higher speed based on the LTE. Examples of the future systems of the LTE include, for example, systems called LTE-Advanced (LTE-A), Future Radio Access (FRA), 5th generation mobile communication system (<NUM>), <NUM> plus (<NUM>+) and New Radio Access Technology (New-RAT).

The future radio communication systems (for example, <NUM>) are expected to support a broad range of frequencies ranging from a low carrier frequency to a high carrier frequency. For example, the future radio communication systems are desired to flexibly support arrangement (mapping) of reference signals, and/or the like, since propagation channel environments (for example, communication quality and frequency selectivity) and/or requirements (moving speed of a terminal to be supported, and/or the like) greatly differ for each frequency band such as a low carrier frequency and a high carrier frequency.

For example, in the future radio communication systems, switching of a mapping pattern among a plurality of mapping patterns in which positions and/or the number of reference signals are different is being studied.

PL1 describes a plurality of DM-Rs patterns. The information about the RS pattern that is (to be) used is part of a Downlink Control Information (DCI) message.

PL2 describes a method of generating a demodulation reference signal (DMRS) including: receiving uplink control information; determining a specific mapping pattern based on the control information from among a plurality of mapping patterns for an uplink DMRS; and generating a DMRS according to the specific mapping pattern.

PL3 describes that a base station dynamically indicates a DM RS pattern, together with the set of DMRS indices, using a DL grant transmitted in PDCCH.

However, in the case where a mapping pattern indicating arrangement of reference signals which are to be transmitted by one radio communication apparatus (for example, a radio base station (gNB)) to the other radio communication apparatus (for example, a user terminal (UE)) is switched among a plurality of mapping pattern, variance occurs between mapping patterns assumed by the two radio communication apparatuses. As a result, because the radio communication apparatus (for example, the user terminal (UE)) which receives the reference signals cannot appropriately receive the transmitted reference signals, there is a possibility that channel estimation accuracy may deteriorate.

The present invention has been made in view of such points, and an object of the present invention is to provide a user terminal and a channel estimation method which can appropriately receive reference signals and which can avoid deterioration of channel estimation accuracy.

According to an aspect of the present invention, it is possible to appropriately receive reference signals and suppress deterioration of channel estimation accuracy.

Hereinafter, each embodiment of the present invention will be described in detail with reference to the accompanying drawings.

A radio communication system according to the present embodiment includes at least radio base station <NUM> (also referred to as gNodeB (gNB), for example) as illustrated in <FIG>, and user terminal <NUM> (also referred to as User Equipment (UE), for example) as illustrated in <FIG>. User terminal <NUM> is connected to radio base station <NUM>.

Radio base station <NUM> transmits a downlink (DL) control signal to user terminal <NUM> using a downlink control channel (for example, Physical Downlink Control Channel (PDCCH)) and transmits a DL data signal and a demodulation reference signal (hereinafter, a DMRS) for demodulating the DL data signal using a downlink data channel (for example, Physical Downlink Shared Channel (PDSCH)). Further, user terminal <NUM> transmits an uplink (UL) control signal to radio base station <NUM> using an uplink control channel (for example, Physical Uplink Control Channel (PUCCH)) or an uplink data channel (for example, Physical Uplink Shared Channel (PUSCH)) and transmits an UL data signal and a DMRS using an uplink data channel (for example, Physical Uplink Shared Channel (PUSCH).

Note that, the downlink channel and the uplink channel through which radio base station <NUM> and user terminal <NUM> perform transmission and reception are not limited to the aforementioned PDCCH, PDSCH, PUCCH, PUSCH, and/or the like, and may be other channels such as, for example, a Physical Broadcast Channel (PBCH) and a Random Access Channel (RACH).

Additionally, in <FIG> and <FIG>, a signal waveform of the DL/UL signal generated at radio base station <NUM> and user terminal <NUM> may be a signal waveform based on Orthogonal Frequency Division Multiplexing (OFDM) modulation, or a signal waveform based on Single Carrier-Frequency Division Multiple Access (SC-FDMA) or DFT-Spread-OFDM (DFT-S-OFDM), or other signal waveforms. Illustration of component sections for generating a signal waveform (for example, an IFFT processor, a CP adder, a CP remover, an FFT processor, and/or the like) are omitted in <FIG> and <FIG>.

<FIG> is a block diagram illustrating an example of an entire configuration of radio base station <NUM> according to the present embodiment. Radio base station <NUM> illustrated in <FIG> includes scheduler <NUM>, transmission signal generator <NUM>, encoder and modulator <NUM>, mapper <NUM>, transmitter <NUM>, antenna <NUM>, receiver <NUM>, controller <NUM>, channel estimator <NUM>, and demodulator and decoder <NUM>. Note that, radio base station <NUM> may have a configuration for Multi-User Multiple-Input Multiple-Output (MU-MIMO) in which radio base station <NUM> simultaneously communicates with a plurality of user terminals <NUM> or may have a configuration for Single-User Multiple-Input Multiple-Output (SU-MIMO) in which radio base station <NUM> communicates with a single user terminal <NUM>.

Scheduler <NUM> performs scheduling (for example, resource allocation) of a DL signal (a DL data signal, a DL control signal, a DMRS, and/or the like). In addition, scheduler <NUM> performs scheduling (for example, resource allocation and layer (port) allocation) of an UL signal (an UL data signal, an UL control signal, a DMRS, or the like). The port means a mapping pattern of the DMRS logically allocated for each user terminal <NUM> in a plurality of layers. Note that, while description will be provided in the present embodiment assuming that ports correspond to layers on a one-to-one basis, the present invention is not limited to this. The port and/or the layer may be defined with different terms.

In scheduling, scheduler <NUM> configures a layer (port number) to be allocated to each user terminal <NUM>.

Further, in scheduling, scheduler <NUM> prepares in advance a plurality of mapping patterns indicating resource elements on which the DMRS of a DL signal is to be mapped, and, for example, selects one mapping pattern by switching the mapping pattern among the plurality of mapping patterns on the basis of the number of multiplexing of user terminal <NUM> and a layer (port number) to be allocated to each user terminal <NUM>. The prepared plurality of mapping patterns have arrangement of the DMRS which is partly different from each other. Further, the mapping pattern specifies resource elements on which the DMRS is to be mapped over a plurality of layers.

Each user terminal <NUM> may be notified of information (allocation information) indicating a port number allocated to each user terminal <NUM> and information (pattern information) indicating the selected mapping pattern through higher layer (for example, Radio Resource Control (RRC) or Medium Access Control (MAC)) signaling, or each user terminal <NUM> may be notified through physical layer (PHY) signaling.

Further, signaling may be individually performed at each user terminal <NUM> or may be performed in specific units. For example, common signaling may be performed for each resource unit to be allocated, for each subband, for each Resource Block Group (RBG), for each Component Carrier (CC), for each cell or for each carrier frequency.

Further, signaling may be periodically executed or may be dynamically executed.

Scheduler <NUM> outputs scheduling information including the allocation information and/or the pattern information to transmission signal generator <NUM> and mapper <NUM>.

Specific examples of the mapping pattern and specific examples of the pattern information at scheduler <NUM> will be described later.

Further, scheduler <NUM>, for example, configures a Modulation and Coding Scheme (MCS) (such as a coding rate and a modulation scheme) of a DL data signal and an UL data signal on the basis of channel quality between radio base station <NUM> and user terminal <NUM> and outputs MCS information to transmission signal generator <NUM> and encoder and modulator <NUM>. Note that the MCS is not limited to one configured by radio base station <NUM>, and may be configured by user terminal <NUM>. In the case where user terminal <NUM> configures the MCS, radio base station <NUM> may receive the MCS information from user terminal <NUM> (not illustrated).

Transmission signal generator <NUM> generates a transmission signal (including the DL data signal and the DL control signal). For example, the DL control signal includes the scheduling information (for example, resource allocation information on the DL data signal) or Downlink Control Information (DCI) including the MCS information output from scheduler <NUM>. Transmission signal generator <NUM> outputs the generated transmission signal to encoder and modulator <NUM>.

Encoder and modulator <NUM>, for example, performs encoding processing and modulation processing on the transmission signal input from transmission signal generator <NUM> on the basis of the MCS information input from scheduler <NUM>. Encoder and modulator <NUM> outputs the modulated transmission signal to mapper <NUM>.

Mapper <NUM> maps the transmission signal input from encoder and modulator <NUM> to a predetermined radio resource (DL resource) on the basis of the scheduling information (for example, DL resource allocation, a port number allocated to each user terminal <NUM> and a mapping pattern of the DMRS) input from scheduler <NUM>. Further, mapper <NUM> maps a reference signal (for example, the DMRS) to a predetermined radio resource (DL resource) on the basis of the scheduling information. Mapper <NUM> outputs the DL signal mapped to the radio resource to transmitter <NUM>.

Transmitter <NUM> performs transmission processing such as up-conversion and amplification on the DL signal input from mapper <NUM> and transmits a radio frequency signal (DL signal) from antenna <NUM>.

Receiver <NUM> performs reception processing such as amplification and down-conversion on the radio frequency signal (UL signal) received at antenna <NUM> and outputs the UL signal to controller <NUM>.

Controller <NUM> separates (de-maps) the UL data signal and the DMRS from the UL signal input from receiver <NUM> on the basis of the scheduling information (UL resource allocation) input from scheduler <NUM>. Then, controller <NUM> outputs the UL data signal to demodulator and decoder <NUM> and outputs the DMRS to channel estimator <NUM>.

Channel estimator <NUM> performs channel estimation using the DMRS of the UL signal and outputs a channel estimation value which is an estimation result to demodulator and decoder <NUM>.

Demodulator and decoder <NUM> performs demodulation and decoding processing on the UL data signal input from controller <NUM> on the basis of the channel estimation value input from channel estimator <NUM>. Demodulator and decoder <NUM> transfers the demodulated UL data signal to an application section (not illustrated). Note that the application section performs processing, and/or the like, relating to layers higher than a physical layer or a MAC layer.

<FIG> is a block diagram illustrating an example of an entire configuration of user terminal <NUM> according to the present embodiment. User terminal <NUM> illustrated in <FIG> includes antenna <NUM>, receiver <NUM>, controller <NUM>, channel estimator <NUM>, demodulator and decoder <NUM>, transmission signal generator <NUM>, encoder and modulator <NUM>, mapper <NUM> and transmitter <NUM>.

Receiver <NUM> performs reception processing such as amplification and down-conversion on the radio frequency signal (DL signal) received at antenna <NUM> and outputs the DL signal to controller <NUM>. The DL signal includes at least the DL data signal and the DMRS.

Controller <NUM> separates (de-maps) the DL control signal and the DMRS from the DL signal input from receiver <NUM>. Then, controller <NUM> outputs the DL control signal to demodulator and decoder <NUM> and outputs the DMRS to channel estimator <NUM>.

At this time, controller <NUM> controls reception of the DMRS in allocated layers (port numbers) indicated by the allocation information on the basis of the mapping pattern indicated by the pattern information which is notified to user terminal <NUM> in advance.

Further, controller <NUM> separates (de-maps) the DL data signal from the DL signal on the basis of the scheduling information (for example, DL resource allocation information) input from demodulator and decoder <NUM> and outputs the DL data signal to demodulator and decoder <NUM>.

Channel estimator <NUM> performs channel estimation using the separated DMRS and outputs a channel estimation value which is an estimation result to demodulator and decoder <NUM>.

Demodulator and decoder <NUM> demodulates the DL control signal input from controller <NUM>. Further, demodulator and decoder <NUM> performs decoding processing (for example, blind detection processing) on the demodulated DL control signal. Demodulator and decoder <NUM> outputs the scheduling information (DL/UL resource allocation) which is addressed to the own apparatus and which is obtained by decoding the DL control signal, to controller <NUM> and mapper <NUM> and outputs the MCS information for the UL data signal to encoder and modulator <NUM>.

Further, demodulator and decoder <NUM> performs demodulation and decoding processing on the DL data signal input from controller <NUM> using the channel estimation value input from channel estimator <NUM> on the basis of the MCS information for the DL data signal included in the DL control signal input from controller <NUM>. Further, demodulator and decoder <NUM> transfers the demodulated DL data signal to an application section (not illustrated). Note that the application section performs processing, and/or the like, relating to layers higher than the physical layer or the MAC layer.

Transmission signal generator <NUM> generates a transmission signal (including the UL data signal or the UL control signal) and outputs the generated transmission signal to encoder and modulator <NUM>.

Encoder and modulator <NUM>, for example, performs encoding processing and modulation processing on the transmission signal input from transmission signal generator <NUM> on the basis of the MCS information input from demodulator and decoder <NUM>. Encoder and modulator <NUM> outputs the modulated transmission signal to mapper <NUM>.

Mapper <NUM> maps the transmission signal input from encoder and modulator <NUM> to a predetermined radio resource (UL resource) on the basis of the scheduling information (UL resource allocation) input from demodulator and decoder <NUM>. Further, mapper <NUM> maps a reference signal (for example, the DMRS) to a predetermined radio resource (UL resource) on the basis of the scheduling information (for example, a mapping configuration including a user pattern of the DMRS).

Transmitter <NUM> performs transmission processing such as up-conversion and amplification on the UL signal (including at least the UL data signal and the DMRS) input from mapper <NUM> and transmits the radio frequency signal (UL signal) from antenna <NUM>.

Specific examples of the mapping pattern and specific examples of the pattern information will be described next.

First, as a first example, examples of a mapping pattern of the DMRS in eight layers and a mapping pattern of the DMRS in four layers will be described.

Note that, in the following description, to distinguish among a plurality of user terminals <NUM>, user terminal <NUM> will be described as user terminal #<NUM>, user terminal #<NUM>, and/or the like, and, to distinguish among user patterns configured for each user terminal <NUM>, the user patterns will be described as user patterns #<NUM>, #<NUM>, and/or the like.

<FIG> illustrates mapping patterns in a first example. <FIG> illustrates mapping pattern #<NUM> of the DMRS in eight layers and mapping pattern #<NUM> of the DMRS in four layers. Each mapping pattern indicates mapping positions of the DMRS in each layer in a Resource Unit (RU) (which is also referred to as a resource block, a resource block pair, and/or the like) which becomes a resource allocation unit.

The RU has a configuration in which <NUM> Resource Elements (REs) are arranged such that <NUM> REs are arranged in a time direction and <NUM> REs are arranged in a frequency direction. <NUM> RE is a radio resource region defined with one symbol and one subcarrier. That is, one RU is configured with <NUM> symbols and <NUM> subcarriers.

Note that, in the following description, <NUM> symbols in the time direction of the RU will be referred to as SB <NUM> to SB <NUM> starting from the left. Further, <NUM> subcarriers in the frequency direction of the RU will be referred to as SC <NUM> to SC <NUM> starting from the bottom.

In the REs of first two symbols (that is, SB <NUM> and SB <NUM>) of the RU, a control signal channel (for example, a PDCCH) is arranged.

Mapping pattern #<NUM> is a pattern in which the DMRS in eight layers of layer #<NUM> to layer #<NUM> is arranged in two successive symbols (SB <NUM> and SB <NUM>). Mapping pattern #<NUM> is a pattern in which the DMRS in four layers of layer #<NUM> to layer #<NUM> is arranged in one symbol (SB <NUM>).

In mapping pattern #<NUM>, the DMRS in different layers which is arranged in the same REs (for example, the DMRS in layer #<NUM>, layer #<NUM>, layer #<NUM> and layer #<NUM> arranged in SB <NUM> and SB <NUM> of SC <NUM>) is multiplexed by, for example, Repetition or TD-OCC (multiplexing by Orthogonal Cover Code (OCC) sequence in a time direction).

Arrangement of the DMRS in layer #<NUM> to layer #<NUM> in SB <NUM> in mapping pattern #<NUM> is similar to arrangement of the DMRS in layer #<NUM> to layer #<NUM> in SB <NUM> in mapping pattern #<NUM>. That is, arrangement in mapping pattern #<NUM> is configured from part of arrangement in mapping pattern #<NUM>, and arrangement in mapping pattern #<NUM> includes arrangement in mapping pattern #<NUM>.

Radio base station <NUM> allocates layers (port numbers) to each user terminal <NUM>, selects one of mapping pattern #<NUM> and mapping pattern #<NUM>, and transmits a downlink signal including the DMRS in the layers (port numbers) allocated to each user terminal <NUM> on the basis of the selected mapping pattern.

Here, an example where radio base station <NUM> allocates layer #<NUM> and layer #<NUM> (port #<NUM> and port #<NUM>) and layer #<NUM> to layer #<NUM> (port #<NUM> to port #<NUM>) to each of the plurality of user terminals <NUM> (for example, user terminals #<NUM> and #<NUM>) will be described.

<FIG> illustrates arrangement of the DMRS in layer #<NUM> and layer #<NUM> in respective mapping patterns in <FIG>.

Radio base station <NUM> allocates layer #<NUM> and layer #<NUM> (port #<NUM> and port #<NUM>) to user terminal #<NUM>, makes a notification of information on the allocated port numbers to user terminal #<NUM>, allocates layer #<NUM> to layer #<NUM> (port #<NUM> to port #<NUM>) to user terminal #<NUM> and makes a notification of information on the allocated port numbers to user terminal #<NUM>.

For example, in the case where a mapping pattern to be applied is uniquely determined in accordance with the number of transmission layers such that, upon transmission in one to four layers, mapping pattern #<NUM> is applied, and upon transmission in five to eight layers, mapping pattern #<NUM> is applied, radio base station <NUM> configures mapping pattern #<NUM> in <FIG> as the mapping pattern to be applied, and transmits the DMRS addressed to each user terminal <NUM>. Meanwhile, user terminal #<NUM> which is notified of only information on the port number allocated to the own terminal recognizes that the mapping pattern to be applied by radio base station <NUM> is mapping pattern #<NUM> in <FIG>. Therefore, while the pattern of the DMRS to be transmitted by radio base station <NUM> to user terminal #<NUM> is DMRS pattern #<NUM> in <FIG>, user terminal #<NUM> which receives only a notification of the information on the port number allocated by radio base station <NUM> separates the DMRS and performs channel estimation on the basis of the DMRS pattern #<NUM> in <FIG>.

That is, in such a case, there occurs variance between the mapping pattern of the DMRS transmitted by radio base station <NUM> and the mapping pattern assumed (recognized) by user terminal #<NUM>. As a result, because user terminal #<NUM> cannot appropriately receive the DMRS transmitted by radio base station <NUM>, channel estimation accuracy based on a reception result of the DMRS deteriorates.

To avoid such deterioration of the channel estimation accuracy, radio base station <NUM> notifies each user terminal <NUM> including user terminal #<NUM> of the pattern information.

First to third variations of the pattern information will be described below.

In the first variation, radio base station <NUM> notifies each user terminal <NUM> of the total number of DMRS transmission ports (the total number of transmission layers) as the pattern information.

For example, in the case where the total number of transmission ports with which radio base station <NUM> performs transmission is eight, radio base station <NUM> makes a notification that the total number of DMRS transmission ports is "<NUM>" as the pattern information.

When user terminal <NUM> receives the total number of DMRS transmission ports of "<NUM>" as the pattern information, user terminal <NUM> recognizes that the mapping pattern applied by radio base station <NUM> is switched to mapping pattern #<NUM>. Then, user terminal <NUM> receives the DMRS transmitted by radio base station <NUM> and performs channel estimation based on a reception result of the DMRS, on the basis of mapping pattern #<NUM> and information on the transmission port numbers allocated to user terminal <NUM>, which has been already notified.

For example, an example will be described where, in 4UE-MIMO in which transmission in eight layers is performed to four user terminals (user terminal #<NUM> to user terminal #<NUM>) as in mapping pattern #<NUM> in <FIG>, radio base station <NUM> allocates layer #<NUM> and layer #<NUM> (DMRS port numbers #<NUM> and #<NUM>) to user terminal #<NUM>, allocates layer #<NUM> and layer #<NUM> (DMRS port numbers #<NUM> and #<NUM>) to user terminal #<NUM>, allocates layer #<NUM> and layer #<NUM> (DMRS port numbers #<NUM> and #<NUM>) to user terminal #<NUM>, and allocates layer #<NUM> and layer #<NUM> (DMRS port numbers #<NUM> and #<NUM>) to user terminal #<NUM>.

In this case, radio base station <NUM> notifies user terminal #<NUM> of DMRS transmission port numbers #<NUM> and #<NUM> as the allocation information and of the total number of DMRS transmission ports of "<NUM>" as the pattern information. In a similar manner, radio base station <NUM> notifies user terminal #<NUM> of DMRS transmission port numbers #<NUM> and #<NUM> as the allocation information and of the total number of DMRS transmission ports of "<NUM>" as the pattern information. Radio base station <NUM> notifies user terminal #<NUM> of DMRS transmission port numbers #<NUM> and #<NUM> as the allocation information and of the total number of DMRS transmission ports of "<NUM>" as the pattern information. Radio base station <NUM> notifies user terminal #<NUM> of DMRS transmission port numbers #<NUM> and #<NUM> as the allocation information and of the total number of DMRS transmission ports of "<NUM>" as the pattern information.

In the second variation, radio base station <NUM> notifies each user terminal <NUM> of the number of transmission symbols of the DMRS in the mapping pattern as the pattern information.

For example, in the case where the total number of DMRS transmission ports with which radio base station <NUM> performs transmission is eight, and mapping pattern #<NUM> is applied, radio base station <NUM> makes a notification of the number of transmission symbols of the DMRS of "<NUM>" in mapping pattern #<NUM> as the pattern information.

When user terminal <NUM> receives the number of transmission symbols of the DMRS of "<NUM>" as the pattern information, user terminal <NUM> recognizes that the mapping pattern applied by radio base station <NUM> is switched to mapping pattern #<NUM>. Then, user terminal <NUM> receives the DMRS transmitted by radio base station <NUM> and performs channel estimation based on a reception result of the DMRS, on the basis of mapping pattern #<NUM> and information on the transmission port numbers allocated to user terminal <NUM>, which has already been notified.

For example, an example will be described where, in 4UE MU-MIMO in which transmission in eight layers is performed to four user terminals (user terminal #<NUM> to user terminal #<NUM>) as in mapping pattern #<NUM> in <FIG>, radio base station <NUM> allocates layer #<NUM> and layer #<NUM> (DMRS port numbers #<NUM> and #<NUM>) to user terminal #<NUM>, allocates layer #<NUM> and layer #<NUM> (DMRS port numbers #<NUM> and #<NUM>) to user terminal #<NUM>, allocates layer #<NUM> and layer #<NUM> (DMRS port numbers #<NUM> and #<NUM>) to user terminal #<NUM>, and allocates layer #<NUM> and layer #<NUM> (DMRS port numbers #<NUM> and #<NUM>) to user terminal #<NUM>.

In this case, radio base station <NUM> notifies user terminal #<NUM> of DMRS transmission port numbers #<NUM> and #<NUM> as the allocation information and of the number of transmission symbols of the DMRS of "<NUM>" as the pattern information. In a similar manner, radio base station <NUM> notifies user terminal #<NUM> of DMRS transmission port numbers #<NUM> and #<NUM> as the allocation information and of the number of transmission symbols of the DMRS of "<NUM>" as the pattern information. Radio base station <NUM> notifies user terminal #<NUM> of DMRS transmission port numbers #<NUM> and #<NUM> as the allocation information and of the number of transmission symbols of the DMRS of "<NUM>" as the pattern information. Radio base station <NUM> notifies user terminal #<NUM> of DMRS transmission port numbers #<NUM> and #<NUM> as the allocation information and of the number of transmission symbols of the DMRS of "<NUM>" as the pattern information.

In the third variation, radio base station <NUM> notifies each user terminal <NUM> of an index value indicating the mapping pattern as the pattern information.

For example, in the case where radio base station <NUM> applies mapping pattern #<NUM> which supports transmission in five to eight layers, radio base station <NUM> makes a notification of an index value of "<NUM>" corresponding to mapping pattern #<NUM> as the pattern information. Meanwhile, in the case where radio base station <NUM> switches the mapping pattern to mapping pattern #<NUM> which supports transmission in one to four layers, radio base station <NUM> makes a notification of an index value of "<NUM>" corresponding to mapping pattern #<NUM> as the pattern information.

In the case where user terminal <NUM> receives the index value of "<NUM>" as the pattern information, user terminal <NUM> recognizes that the mapping pattern applied by radio base station <NUM> is mapping pattern #<NUM>. Then, user terminal <NUM> receives the DMRS transmitted by radio base station <NUM> and performs channel estimation based on a reception result of the DMRS, on the basis of mapping pattern #<NUM> and information on the transmission port numbers allocated to user terminal <NUM>, which has already been notified.

In this case, radio base station <NUM> notifies user terminal #<NUM> of DMRS port numbers #<NUM> and #<NUM> as the allocation information and of the index value of "<NUM>" as the pattern information. In a similar manner, radio base station <NUM> notifies user terminal #<NUM> of DMRS port numbers #<NUM> and #<NUM> as the allocation information and of the index value of "<NUM>" as the pattern information. Radio base station <NUM> notifies user terminal #<NUM> of DMRS port numbers #<NUM> and #<NUM> as the allocation information and of the index value of "<NUM>" as the pattern information. Radio base station <NUM> notifies user terminal #<NUM> of DMRS port numbers #<NUM> and #<NUM> as the allocation information and of the index value of "<NUM>" as the pattern information.

In the first example and each variation of the pattern information in the first example described above, examples where the number of layers are different between two mapping patterns have been described. Subsequently, as a second example, examples of two mapping patterns of the DMRS in four layers will be described.

<FIG> illustrates mapping patterns in the second example. <FIG> illustrates mapping pattern #<NUM> and mapping pattern #<NUM> of the DMRS in four layers. Each mapping pattern indicates mapping positions of the DMRS in each layer in an RU which becomes a resource allocation unit.

In REs of first two symbols (that is, SB <NUM> and SB <NUM>) of the RU, a control signal channel (for example, a PDCCH) is arranged.

Mapping pattern #<NUM> is a pattern in which the DMRS in four layers of layer #<NUM> to layer #<NUM> is arranged in two successive symbols (SB <NUM> and SB <NUM>). Mapping pattern #<NUM> is a pattern in which the DMRS in four layers of layer #<NUM> to layer #<NUM> is arranged in one symbol (SB <NUM>).

The DMRS in layers different in the time direction in mapping pattern #<NUM> (for example, the DMRS in layer #<NUM> and layer #<NUM> arranged in SB <NUM> and SB <NUM> of SC <NUM>) is multiplexed by, for example, Repetition or TD-OCC.

Here, an example where radio base station <NUM> allocates layer #<NUM> and layer #<NUM> (port #<NUM> and port #<NUM>) and layer #<NUM> and layer #<NUM> (port #<NUM> and port #<NUM>) to each of the plurality of user terminals <NUM> (for example, user terminals #<NUM> and #<NUM>) will be described.

Arrangement of the DMRS in layer #<NUM> and layer #<NUM> in mapping pattern #<NUM> in <FIG> is similar to DMRS pattern #<NUM> in <FIG>, and arrangement of the DMRS in layer #<NUM> and layer #<NUM> in mapping pattern #<NUM> in <FIG> is similar to DMRS pattern #<NUM> in <FIG>.

That is, as described in the first example, even in the case where one of the two mapping patterns in <FIG> in which the number of layers (the number of port numbers) is the same, is applied, there occurs variance between the mapping pattern of the DMRS transmitted by radio base station <NUM> and the mapping pattern assumed (recognized) by user terminal #<NUM> (and/or user terminal #<NUM>). As a result, because user terminal #<NUM> (and/or user terminal #<NUM>) cannot appropriately receive the DMRS transmitted by radio base station <NUM>, channel estimation accuracy based on a reception result of the DMRS deteriorates.

To avoid such deterioration of the channel estimation accuracy, radio base station <NUM> notifies each user terminal <NUM> including user terminal #<NUM> (and user terminal #<NUM>) of pattern information indicating the mapping pattern.

Because the pattern information notified in the second example is similar to that in the first example, detailed description will be omitted. However, in the second example, as illustrated in <FIG>, because the total number of DMRS transmission ports is the same between the two mapping patterns to be applied, the first variation of the pattern information described in the first example is not used. The second variation and the third variation of the pattern information described in the first example are also used in the second example.

Note that, while, in the above-described example, MU-MIMO for two user terminals (user terminal #<NUM> and user terminal #<NUM>) is described, the present invention can be also applied to SU-MIMO for one user terminal (user terminal #<NUM>).

For example, in the case where layer #<NUM>, layer #<NUM>, layer #<NUM> and layer #<NUM> (DMRS transmission port numbers #<NUM> to #<NUM>) are allocated to user terminal #<NUM>, radio base station <NUM> notifies user terminal #<NUM> of DMRS transmission port numbers #<NUM> to #<NUM> as the allocation information.

Then, in the case where radio base station <NUM> uses the above-described second variation as the pattern information, radio base station <NUM> makes a notification of one of "<NUM> " and "<NUM>" which is the number of transmission symbols of the DMRS in the mapping pattern to be applied in accordance with which of mapping pattern #<NUM> and mapping pattern #<NUM> is to be applied. Further, in the case where radio base station <NUM> uses the above-described third variation as the pattern information, radio base station <NUM> makes a notification of "<NUM>" or "<NUM>" which is an index value associated with the mapping pattern to be applied in accordance with which of mapping pattern #<NUM> and mapping pattern #<NUM> is to be applied.

Note that, while, in the above-described first example and second example, the mapping patterns in the RU having a configuration where <NUM> REs are arranged such that <NUM> REs are arranged in the time direction and <NUM> REs are arranged in the frequency direction have been described, the present invention is not limited to this. For example, the present invention can be also applied to mapping of the DMRS in which resources are allocated in units called mini-slots. An example of the mapping pattern of the DMRS in the case where resources are allocated in units of mini-slots will be described below.

<FIG> illustrates mapping patterns in a mini-slot in a first example. <FIG> illustrates mapping pattern #A of the DMRS in eight layers, and mapping pattern #B of the DMRS in four layers. Each mapping pattern indicates mapping positions of the DMRS in each layer in a mini-slot which is a resource allocation unit.

The mini-slot in <FIG> has a configuration in which <NUM> REs are arranged in the frequency direction, and K REs (where K is an integer equal to or greater than <NUM> and equal to less than <NUM>) are arranged in the time direction (part of the configuration is not illustrated).

In the RE in the first one symbol (that is, SB <NUM>) in the mini-slot, a control signal channel (for example, a PDCCH) is arranged.

Mapping pattern #A is a pattern in which the DMRS in eight layers of layer #<NUM> to layer #<NUM> is arranged in two successive symbols (SB <NUM> and SB <NUM>). Mapping pattern #B is a pattern in which the DMRS in four layers of layer #<NUM> to layer #<NUM> is arranged in one symbol (SB <NUM>).

In mapping pattern #A and mapping pattern #B, the DMRS in the same layer is arranged at intervals corresponding to one subcarrier. This arrangement may be referred to as "Comb2" or "IFDM (RPF = <NUM>)".

In mapping pattern #A, the DMRS in different layers arranged in the same REs (for example, the DMRS in layer #<NUM>, layer #<NUM>, layer #<NUM> and layer #<NUM> arranged in SB <NUM> and SB <NUM> of SC <NUM>) is multiplexed by, for example, Cyclic Shift (CS) and TD-OCC. Alternatively, the DMRS in different layers arranged in the same REs is multiplexed by CS and Repetition.

Further, in mapping pattern #B, the DMRS in different layers arranged in the same RE (for example, the DMRS in layer #<NUM> and layer #<NUM> arranged in SB <NUM> of SC <NUM>) is multiplexed by, for example, CS.

Arrangement of the DMRS in layer #<NUM> to layer #<NUM> in SB <NUM> in mapping pattern #B is similar to arrangement of the DMRS in layer #<NUM> to layer #<NUM> in SB <NUM> in mapping pattern #A. That is, the arrangement in mapping pattern #B is configured from part of the arrangement in mapping pattern #A, and the arrangement in mapping pattern #A includes the arrangement in mapping pattern #B.

Radio base station <NUM> allocates layers (port numbers) to each user terminal <NUM>, selects one of mapping pattern #A and mapping pattern #B, and transmits a downlink signal in a mini-slot configuration including the DMRS in the layers (port numbers) allocated to each user terminal <NUM> on the basis of the selected mapping pattern.

<FIG> illustrates mapping patterns in a mini-slot in a second example. <FIG> illustrates mapping pattern #C of the DMRS in eight layers and mapping pattern #D of the DMRS in four layers. Each mapping pattern indicates mapping positions of the DMRS in each layer in a mini-slot which is a resource allocation unit.

The mini-slot in <FIG> has a configuration in which <NUM> REs are arranged in the frequency direction, and K REs (where K is an integer equal to or greater than <NUM> and equal to or less than <NUM>) are arranged in the time direction.

In the RE of the first one symbol (that is, SB <NUM>) of the mini-slot, a control signal channel (for example, a PDCCH) is arranged.

Mapping pattern #C is a pattern in which the DMRS in eight layers of layer #<NUM> to layer #<NUM> is arranged in two successive symbols (SB <NUM> and SB <NUM>). Mapping pattern #D is a pattern in which the DMRS in four layers of layer #<NUM> to layer #<NUM> is arranged in one symbol (SB <NUM>).

In mapping pattern #C and mapping pattern #D, the DMRS in the same layers is arranged at intervals corresponding to three subcarriers. This arrangement may be referred to as "Comb4" or "IFDM (RPF = <NUM>)".

In mapping pattern #C, the DMRS in different layers arranged in the same REs (for example, the DMRS in layer #<NUM> and layer #<NUM> arranged in SB <NUM> and SB <NUM> of SC <NUM>) is multiplexed by, for example, CS and Repetition.

Arrangement of the DMRS in layer #<NUM> to layer #<NUM> in SB <NUM> in mapping pattern #D is similar to arrangement of the DMRS in layer #<NUM> to layer #<NUM> in SB <NUM> in mapping pattern #C. That is, the arrangement in mapping pattern #D is configured from part of the arrangement in mapping pattern #C, and the arrangement in mapping pattern #C includes the arrangement in mapping pattern #D.

Radio base station <NUM> allocates layers (port numbers) to each user terminal <NUM>, selects one of mapping pattern #C and mapping pattern #D and transmits a downlink signal in a mini-slot configuration including the DMRS in the layers (port numbers) allocated to each user terminal <NUM> on the basis of the selected mapping pattern.

<FIG> illustrates mapping patterns in a mini-slot in a third example. <FIG> illustrates mapping pattern #E of the DMRS in <NUM> layers and mapping pattern #F of the DMRS in six layers. Each mapping pattern indicates mapping positions of the DMRS in each layer in a mini-slot which is a resource allocation unit.

The mini-slot in <FIG> has a configuration in which <NUM> REs are arranged in the frequency direction and K REs (where K is an integer equal to or greater than <NUM> and equal to or less than <NUM>) are arranged in the time direction.

In the REs of the first two symbols (that is, SB <NUM> and SB <NUM>) in the mini-slot, a control signal channel (for example, a PDCCH) is arranged.

Mapping pattern #E is a pattern in which the DMRS in <NUM> layers of layer #<NUM> to layer #<NUM> is arranged in two successive symbols (SB <NUM> and SB <NUM>). Mapping pattern #F is a pattern in which the DMRS in six layers of layer #<NUM> to layer #<NUM> is arranged in one symbol (SB <NUM>).

In mapping pattern #E, the DMRS in different layers arranged in the same REs (for example, the DMRS in layer #<NUM> and layer #<NUM> arranged in SB <NUM> of SC <NUM> and SC <NUM>) is multiplexed by, for example, FD-OCC (multiplexing by an OCC sequence in the frequency direction). Then, the DMRS in respective layers is multiplexed by combination of FD-OCC, Frequency Division Multiplexing (FDM) and Time Division Multiplexing (TDM).

In mapping pattern #F, the DMRS in different layers arranged in the same REs (for example, the DMRS in layer #<NUM> and layer #<NUM> arranged in SB <NUM> of SC <NUM> and SC <NUM>) is multiplexed by, for example, FD-OCC. Then, the DMRS in the respective layers is multiplexed by combination of FD-OCC and FDM.

Arrangement of the DMRS in layer #<NUM> to layer #<NUM> in SB <NUM> in mapping pattern #F is similar to arrangement of the DMRS in layer #<NUM> to layer #<NUM> in SB <NUM> in mapping pattern #E. That is, the arrangement in mapping pattern #F is configured from part of the arrangement in mapping pattern #E, and the arrangement in mapping pattern #E includes the arrangement in mapping pattern #F.

Radio base station <NUM> allocates layers (port numbers) to each user terminal <NUM>, selects one of mapping pattern #E and mapping pattern #F, and transmits a downlink signal in a mini-slot configuration including the DMRS in the layers (port numbers) allocated to each user terminal <NUM> on the basis of the selected mapping pattern.

<FIG> illustrates mapping patterns in a mini-slot in a fourth example. <FIG> illustrates mapping pattern #G of the DMRS in <NUM> layers and mapping pattern #H of the DMRS in six layers. Each mapping pattern indicates mapping positions of the DMRS in each layer in a mini-slot which is a resource allocation unit.

Mapping pattern #G is a pattern in which the DMRS in <NUM> layers of layer #<NUM> to layer #<NUM> is arranged in two successive symbols (SB <NUM> and SB <NUM>). Mapping pattern #H is a pattern in which the DMRS in six layers of layer #<NUM> to layer #<NUM> is arranged in one symbol (SB <NUM>).

In mapping pattern #G, the DMRS in different layers arranged in the same REs (for example, the DMRS in layer #<NUM>, layer #<NUM>, layer #<NUM> and layer #<NUM> arranged in SB <NUM> and SB <NUM> of SC <NUM> and SC <NUM>) is multiplexed by, for example, FD-OCC and TD-OCC. Then, the DMRS in respective layers is multiplexed by combination of FD-OCC, TD-OCC and FDM.

In mapping pattern #H, the DMRS in different layers arranged in the same REs (for example, the DMRS in layer #<NUM> and layer #<NUM> arranged in SB <NUM> of SC <NUM> and SC <NUM>) is multiplexed by, for example, FD-OCC. Then, the DMRS in respective layers is multiplexed by combination of FD-OCC and FDM.

Arrangement of the DMRS in layer #<NUM> to layer #<NUM> in SB <NUM> in mapping pattern #H is similar to arrangement of the DMRS in layer #<NUM> to layer #<NUM> in SB <NUM> in mapping pattern #G. That is, the arrangement in mapping pattern #H is configured from part of the arrangement in mapping pattern #G, and the arrangement in mapping pattern #G includes the arrangement in mapping pattern #H.

Radio base station <NUM> allocates layers (port numbers) to each user terminal <NUM>, selects one of mapping pattern #G and mapping pattern #H, and transmits a downlink signal in a mini-slot configuration including the DMRS in the layers (port numbers) allocated to each user terminal <NUM>.

In the above-described respective examples (the first example to the fourth example) in the mini-slot, in a similar manner to the above-described examples of the resource unit (the first example and the second example), radio base station <NUM> notifies each user terminal <NUM> of the pattern information indicating the mapping pattern.

As the pattern information in the case where the resource allocation unit is a mini-slot, any of the first variation to the third variation may be used in a similar manner to the pattern information in a case of the above-described resource unit.

In the present embodiment, one mapping pattern is selected by the mapping pattern of the DMRS being switched among a plurality of mapping patterns prepared in advance. Then, by radio base station <NUM> notifying user terminal <NUM> of the pattern information indicating the mapping pattern, because user terminal <NUM> uniquely determines the mapping positions (and/or the number of DMRS) of the DMRS addressed to user terminal <NUM>, so that it is possible to avoid variance between user terminal <NUM> and radio base station <NUM>, it is possible to appropriately receive a reference signal such as a DMRS and avoid deterioration of channel estimation accuracy.

Note that, while, in the present embodiment, an example has been described where one RU is configured with <NUM> symbols and <NUM> subcarriers, the present invention is not limited to this. A size of the RU may be changed.

Further, while, in the present embodiment, an example has been described where a control signal channel (for example, a PDCCH) is arranged in the REs of the first two symbols of the RU (that is, SB <NUM> and SB <NUM>) and the REs of first one symbol (SB <NUM>) or two symbols (SB <NUM> and SB <NUM>) of the mini-slot, arrangement of the control signal channel is not limited to this. Further, the control signal channel does not have to be arranged in the RU or may be arranged only in part of the REs.

Further, the number of layers (the number of ports) in the present embodiment is merely an example, and the present invention is not limited to this.

Further, while, in respective examples of the present embodiment, examples where there are two mapping patterns have been mainly described, the present invention is not limited to this. For example, there may be three or more mapping patterns. Further, while examples have been described where, out of two mapping patterns (for example, mapping pattern #<NUM> and mapping pattern #<NUM>), arrangement in one mapping pattern (for example, mapping pattern #<NUM>) is configured from part of arrangement in the other mapping pattern (for example, mapping pattern #<NUM>), the present invention is not limited to this.

Further, while, in the present embodiment, examples have been mainly described where the DMRS is arranged in the third symbol (SB <NUM>) or the fourth symbol (SB <NUM>) of the RU, the present invention is not limited to this. The DMRS may be arranged in the fifth symbol and the subsequent symbols or may be arranged in the second symbol and before the second symbol. Further, the arrangement may be determined in accordance with a size of the control channel.

For example, in addition to the DMRS (for example, a Front-loaded DMRS) arranged on the head side of the RU, an Additional DMRS may be arranged. The Additional DMRS is, for example, a DMRS arranged for improving capability of following temporal fluctuation of a channel in the case where user terminal <NUM> moves at high speed.

Further, the DMRS to which the present invention is applied is not particularly limited. For example, the present invention may be applied only to the above-described Front loaded DMRS, may be applied only to the Additional DMRS or may be applied to the both.

Further, while, in the above-described embodiment, the DMRS in a downlink signal to be transmitted by radio base station <NUM> to user terminal <NUM> has been mainly described using an example, the present invention is not limited to this. The present invention is also applied to the DMRS in an uplink signal to be transmitted by user terminal <NUM> to radio base station <NUM>. In this case, radio base station <NUM> configures a layer (reception port number) in which radio base station <NUM> receives the DMRS and selects a mapping pattern of the DMRS in the uplink signal. Then, radio base station <NUM>, for example, makes a notification of the total number of DMRS reception ports in the selected mapping pattern, the number of reception symbols or the index value as pattern information. By this means, because user terminal <NUM> can uniquely determine mapping positions (and/or the number of DMRS) of the DMRS to be transmitted by user terminal <NUM> (that is, to be received by radio base station <NUM>), so that it is possible to avoid variance between user terminal <NUM> and radio base station <NUM>, radio base station <NUM> can appropriately receive a reference signal such as the DMRS, so that it is possible to avoid deterioration of channel estimation accuracy.

Further, the RU and/or the mini-slot to which the present invention is applied is not particularly limited. In the case where a wide range of carrier frequencies are supported, the present invention may be applied to RUs and/or mini-slots in all the carrier frequencies, or the present invention may be applied to RUs and/or mini-slots in part of the carrier frequencies.

Each embodiment of the present invention has been described above.

Note that the block diagrams used to describe the embodiments illustrate blocks on the basis of functions. These functional blocks (constituent sections) are implemented by any combination of hardware and/or software. A means for realizing the functional blocks is not particularly limited. That is, the functional blocks may be implemented by one physically and/or logically coupled apparatus. Two or more physically and/or logically separated apparatuses may be directly and/or indirectly (for example, wired and/or wireless) connected, and the plurality of apparatuses may implement the functional blocks.

For example, the radio base station, the user terminal, and/or the like, according to an embodiment of the present invention may function as computers which perform processing of the radio communication method of the present invention. <FIG> illustrates an example of hardware configurations of the radio base station and the user terminal according to an embodiment of the present invention. The above-described radio base station <NUM> and user terminal <NUM> may be physically configured as a computer apparatus including processor <NUM>, memory <NUM>, storage <NUM>, communication apparatus <NUM>, input apparatus <NUM>, output apparatus <NUM>, bus <NUM>, and/or the like.

Note that the term "apparatus" in the following description can be replaced with a circuit, a device, a unit, and/or the like. The hardware configurations of radio base station <NUM> and user terminal <NUM> may include one or a plurality of apparatuses illustrated in the drawings or may not include part of the apparatuses.

For example, although only one processor <NUM> is illustrated, there may be a plurality of processors. The processing may be executed by one processor, or the processing may be executed by one or more processors at the same time, in succession, or in another manner. Note that processor <NUM> may be implemented by one or more chips.

The functions in radio base station <NUM> and user terminal <NUM> are implemented by predetermined software (program) loaded into hardware, such as processor <NUM>, memory <NUM>, and/or the like, according to which processor <NUM> performs the arithmetic and controls communication performed by communication apparatus <NUM> or reading and/or writing of data in memory <NUM> and storage <NUM>.

Processor <NUM> operates an operating system to entirely control the computer, for example. Processor <NUM> may be composed of a central processing unit (CPU) including an interface with peripheral apparatuses, control apparatus, arithmetic apparatus, register, and/or the like. For example, the above-described scheduler <NUM>, controllers <NUM> and <NUM>, transmission signal generators <NUM> and <NUM>, encoder and modulators <NUM> and <NUM>, mappers <NUM> and <NUM>, channel estimators <NUM> and <NUM>, demodulator and decoders <NUM> and <NUM>, and/or the like, may be realized with processor <NUM>.

Processor <NUM> reads out a program (program code), a software module, or data from storage <NUM> and/or communication apparatus <NUM> to memory <NUM> and executes various types of processing according to the read-out program and/or the like. The program used is a program for causing the computer to execute at least part of the operation described in the embodiments. For example, scheduler <NUM> of radio base station <NUM> may be implemented by a control program stored in memory <NUM> and operated by processor <NUM>, and the other functional blocks may also be implemented in the same way. While it has been described that the various types of processing as described above are executed by one processor <NUM>, the various types of processing may be executed by two or more processors <NUM> at the same time or in succession. Processor <NUM> may be implemented by one or more chips. Note that the program may be transmitted from a network through a telecommunication line.

Memory <NUM> is a computer-readable recording medium and may be composed of, for example, at least one of a ROM (Read Only Memory), an EPROM (Erasable Programmable ROM), an EEPROM (Electrically Erasable Programmable ROM), and a RAM (Random Access Memory). Memory <NUM> may be called a register, a cache, a main memory (main storage apparatus), and/or the like. Memory <NUM> can save a program (program code), a software module, and/or the like that can be executed to carry out the radio communication method according to an embodiment of the present invention.

Storage <NUM> is a computer-readable recording medium and may be composed of, for example, at least one of an optical disk such as a CD-ROM (Compact Disc ROM), a hard disk drive, a flexible disk, a magneto-optical disk (for example, a compact disc, a digital versatile disc, or a Blu-ray (registered trademark) disc), a smart card, a flash memory (for example, a card, a stick, or a key drive), a floppy (registered trademark) disk, and a magnetic strip. Storage <NUM> may also be called an auxiliary storage apparatus. The storage medium as described above may be a database, server, or other appropriate media including memory <NUM> and/or storage <NUM>.

Communication apparatus <NUM> is hardware (transmission and reception device) for communication between computers through a wired and/or wireless network and is also called, for example, a network device, a network controller, a network card, or a communication module. For example, transmitters <NUM> and <NUM>, antennas <NUM> and <NUM>, receivers <NUM> and <NUM>, and/or the like, as described above may be implemented by communication apparatus <NUM>.

Input apparatus <NUM> is an input device (for example, a keyboard, a mouse, a microphone, a switch, a button, or a sensor) that receives input from the outside. Output apparatus <NUM> is an output device (for example, a display, a speaker, or an LED lamp) which outputs to the outside. Note that input apparatus <NUM> and output apparatus <NUM> may be integrated (for example, a touch panel).

The apparatuses, such as processor <NUM> and memory <NUM>, are connected by bus <NUM> for communication of information. Bus <NUM> may be composed of a single bus or by buses different among the apparatuses.

Furthermore, radio base station <NUM> and user terminal <NUM> may include hardware, such as a microprocessor, a digital signal processor (DSP), an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), and an FPGA (Field Programmable Gate Array), and the hardware may implement part or all of the functional blocks. For example, processor <NUM> may be implemented by at least one of these pieces of hardware.

The notification of information is not limited to the aspects or embodiments described in the present specification, and the information may be notified by another method. For example, the notification of information may be carried out by one or a combination of physical layer signaling (for example, DCI (Downlink Control Information) and UCI (Uplink Control Information)), higher layer signaling (for example, RRC (Radio Resource Control) signaling, MAC (Medium Access Control) signaling, broadcast information (MIB (Master Information Block), and SIB (System Information Block))), and other signals. The RRC signaling may be called an RRC message and may be, for example, an RRC connection setup message, an RRC connection reconfiguration message, and/or the like.

The aspects and embodiments described in the present specification may be applied to a system using LTE (Long Term Evolution), LTE-A (LTE-Advanced), SUPER <NUM>, IMT-Advanced, <NUM>, <NUM>, FRA (Future Radio Access), W-CDMA (registered trademark), GSM (registered trademark), CDMA2000, UMB (Ultra Mobile Broadband), IEEE <NUM> (Wi-Fi), IEEE <NUM> (WiMAX), IEEE <NUM>, UWB (Ultra-WideBand), Bluetooth (registered trademark), or other appropriate systems and/or to a next-generation system extended based on the above systems.

The orders of the processing procedures, the sequences, the flow charts, and/or the like of the aspects and embodiments described in the present specification may be changed as long as there is no contradiction. For example, elements of various steps are presented in exemplary orders in the methods described in the present specification, and the methods are not limited to the presented specific orders.

Specific operations which are described in the specification as being performed by the base station (radio base station) may sometimes be performed by an upper node depending on the situation. Various operations performed for communication with a terminal in a network constituted by one network node or a plurality of network nodes including a base station can be obviously performed by the base station and/or a network node other than the base station (examples include, but not limited to, MME (Mobility Management Entity) or S-GW (Serving Gateway)). Although there is one network node in addition to the base station in the case illustrated above, a plurality of other network nodes may be combined (for example, MME and S-GW).

The information, the signals, and/or the like can be output from a higher layer (or a lower layer) to a lower layer (or a higher layer). The information, the signals, and/or the like may be input and output through a plurality of network nodes.

The input and output information and/or the like may be saved in a specific place (for example, memory) or may be managed by a management table. The input and output information and/or the like can be overwritten, updated, or additionally written. The output information and/or the like may be deleted. The input information and/or the like may be transmitted to another apparatus.

The determination may be made based on a value expressed by one bit (<NUM> or <NUM>), based on a Boolean value (true or false), or based on comparison with a numerical value (for example, comparison with a predetermined value).

Regardless of whether the software is called software, firmware, middleware, a microcode, or a hardware description language or by another name, the software should be broadly interpreted to mean an instruction, an instruction set, a code, a code segment, a program code, a program, a subprogram, a software module, an application, a software application, a software package, a routine, a subroutine, an object, an executable file, an execution thread, a procedure, a function, and/or the like.

The software, the instruction, and/or the like may be transmitted and received through a transmission medium. For example, when the software is transmitted from a website, a server, or another remote source by using a wired technique, such as a coaxial cable, an optical fiber cable, a twisted pair, and a digital subscriber line (DSL), and/or a wireless technique, such as an infrared ray, a radio wave, and a microwave, the wired technique and/or the wireless technique is included in the definition of the transmission medium.

The information, the signals, and/or the like described in the present specification may be expressed by using any of various different techniques. For example, data, instructions, commands, information, signals, bits, symbols, chips, and/or the like that may be mentioned throughout the entire description may be expressed by one or an arbitrary combination of voltage, current, electromagnetic waves, magnetic fields, magnetic particles, optical fields, and photons.

Note that the terms described in the present specification and/or the terms necessary to understand the present specification may be replaced with terms with the same or similar meaning. For example, the channel and/or the symbol may be a signal. The signal may be a message. The component carrier (CC) may be called a carrier frequency, a cell, and/or the like.

The terms "system" and "network" used in the present specification can be interchangeably used.

The information, the parameters, and/or the like described in the present specification may be expressed by absolute values, by values relative to predetermined values, or by other corresponding information. For example, radio resources may be indicated by indices.

The names used for the parameters are not limited in any respect. Furthermore, the numerical formulas and/or the like using the parameters may be different from the ones explicitly disclosed in the present specification. Various channels (for example, PUCCH and PDCCH) and information elements (for example, TPC) can be identified by any suitable names, and various names assigned to these various channels and information elements are not limited in any respect.

The base station (radio base station) can accommodate one cell or a plurality of (for example, three) cells (also called sector). When the base station accommodates a plurality of cells, the entire coverage area of the base station can be divided into a plurality of smaller areas, and each of the smaller areas can provide a communication service based on a base station subsystem (for example, small base station for indoor, remote radio head(RRH)). The term "cell" or "sector" denotes part or all of the coverage area of the base station and/or of the base station subsystem that perform the communication service in the coverage. Furthermore, the terms "base station," "eNB," "gNB," "cell," and "sector" can be interchangeably used in the present specification. The base station may be called a fixed station, a NodeB, a gNodeB, an eNodeB (eNB), an access point, a femto cell, a small cell, and/or the like.

The user terminal may be called, by those skilled in the art, a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communication device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or UE (User Equipment) or by some other appropriate terms.

As used herein, the term "determining" may encompass a wide variety of actions. For example, "determining" may be regarded as judging, calculating, computing, processing, deriving, investigating, looking up (for example, looking up in a table, a database or another data structure), ascertaining and/or the like. Also, "determining" may be regarded as receiving (for example, receiving information), transmitting (for example, transmitting information), inputting, outputting, accessing (for example, accessing data in a memory) and/or the like. Also, "determining" may be regarded as resolving, selecting, choosing, establishing and/or the like. That is, "determining" may be regarded as a certain type of action related to determining.

The terms "connected" and "coupled" as well as any modifications of the terms mean any direct or indirect connection and coupling between two or more elements, and the terms can include cases in which one or more intermediate elements exist between two "connected" or "coupled" elements. The coupling or the connection between elements may be physical or logical coupling or connection or may be a combination of physical and logical coupling or connection. When the terms are used in the present specification, two elements can be considered to be "connected" or "coupled" to each other by using one or more electrical wires, cables, and/or printed electrical connections or by using electromagnetic energy, such as electromagnetic energy with a wavelength of a radio frequency domain, a microwave domain, or an optical (both visible and invisible) domain that are non-limiting and non-inclusive examples.

The reference signal can also be abbreviated as RS and may also be called a pilot depending on the applied standard. Further, the DMRS may be referred to as different corresponding name, for example, a demodulation RS or a DM-RS, and/or the like.

The description "based on" used in the present specification does not mean "based only on," unless otherwise specifically stated. In other words, the description "based on" means both of "based only on" and " based at least on.

The "section" in the configuration of each apparatus may be replaced with "means," "circuit," "device," and/or the like.

The terms "including," "comprising," and modifications of these terms are intended to be inclusive just like the term "having," as long as the terms are used in the present specification or the appended claims. Furthermore, the term "or" used in the present specification or the appended claims is not intended to be an exclusive or.

The radio frame may be constituted by one frame or a plurality of frames in the time domain. The one frame or each of the plurality of frames may be called a subframe, a time unit, and/or the like in the time domain. The subframe may be further constituted by one slot or a plurality of slots in the time domain. The slot may be further constituted by one symbol or a plurality of symbols (OFDM (Orthogonal Frequency Division Multiplexing) symbol, SC-FDMA (Single Carrier-Frequency Division Multiple Access) symbol, and/or the like) in the time domain.

The radio frame, the subframe, the slot, the mini-slot, and the symbol indicate time units in transmitting signals. The radio frame, the subframe, the slot, the mini-slot, and the symbol may be called by other corresponding names.

For example, in the LTE system, the base station creates a schedule for assigning radio resources to each mobile station (such as frequency bandwidth that can be used by each mobile station and transmission power). The minimum time unit of scheduling may be called a TTI (Transmission Time Interval).

For example, one subframe may be referred to as a TTI, a plurality of successive subframes may be referred to as a TTI, one slot may be referred to as a TTI, or one mini-slot may be referred to as a TTI.

The resource unit is a resource assignment unit in the time domain and the frequency domain, and the resource unit may include one subcarrier or a plurality of continuous subcarriers in the frequency domain. In addition, the resource unit may include one symbol or a plurality of symbols in the time domain, and may have a length of one slot, one mini-slot, one subframe, or one TTI. One TTI and one subframe may be constituted by one resource unit or a plurality of resource units. The resource unit may be called a resource block (RB), a physical resource block (PRB: Physical RB), a PRB pair, an RB pair, a scheduling unit, a frequency unit, or a subband. The resource unit may be constituted by one RE or a plurality of REs. For example, one RE only has to be a resource smaller in unit size than the resource unit serving as a resource assignment unit (for example, one RE only has to be a minimum unit of resource), and the naming is not limited to RE.

The structure of the radio frame described above is illustrative only, and the number of subframes included in the radio frame, the number of slots included in the subframe, the number of mini-slots included in the subframe, the numbers of symbols and resource blocks included in the slot, and the number of subcarriers included in the resource block can be changed in various ways.

When articles, such as "a," "an," and "the" in English, are added by translation in the entire disclosure, the articles include plural forms unless otherwise clearly indicated by the context.

The aspects and embodiments described in the present specification may be independently used, may be used in combination, or may be switched and used along the execution. Furthermore, notification of predetermined information (for example, notification indicating "it is X") is not limited to explicit notification, and may be performed implicitly (for example, by not notifying the predetermined information).

Claim 1:
A terminal (<NUM>) in a new radio, NR, system, comprising:
a reception section (<NUM>) adapted to receive downlink control information (DCI) including information indicating a mapping pattern of a demodulation reference signal and to receive a downlink signal including at least a downlink data signal and the demodulation reference signal;
a control section (<NUM>) adapted to de-map the downlink data signal from the received downlink signal and to de-map the demodulation reference signal from the received downlink signal based on the information indicating the mapping pattern of the demodulation reference signal and reception of a downlink signal;
a channel estimator (<NUM>) adapted to perform channel estimation using the demodulation reference signal; and
a demodulator and decoder (<NUM>) adapted to demodulate and decode the downlink data signal using the channel estimation value input from the channel estimator, wherein the terminal is characterized in that
the information indicating the mapping pattern of the demodulation reference signal notifies a number of symbols to which the demodulation reference signal is mapped.