WO2018229953A1 - Base station, terminal, communication system, and processing method - Google Patents

Abstract

A base station (110) is provided with a communication unit (111) and a control unit (112). The communication unit (111) wirelessly communicates with a first terminal (120) and a second terminal (130) that differs from the first terminal (120). By controlling the communication unit (111), the control unit (112) transmits, to the first terminal (120), a first data channel that is transmitted in a frame format including a reference signal having a repeated pattern in the temporal direction. In addition, the control unit (112) transmits, to the second terminal (130), control information indicating a wireless resource of the first data channel. In addition, the control unit (112) transmits, to the second terminal (130), a second data channel in which there are fewer reference signals than in the first data channel or that includes no reference signals.

Description

Base station, terminal, communication system and processing method

The present invention relates to a base station, a terminal, a communication system, and a processing method.

Conventionally, in 3GPP, specifications of mobile communication systems such as the third generation mobile communication system (3G), LTE corresponding to the 3.9th generation mobile communication system, LTE-Advanced corresponding to the fourth generation mobile communication system have been studied. ing. 3GPP is an abbreviation for 3rd Generation Partnership Project. LTE is an abbreviation for Long Term Evolution. In addition, studies on technologies relating to the fifth generation mobile communication system (5G) have also started. Also, a configuration is known in which individual RS (Reference Signal: Reference Signal) patterns are assigned to each terminal that performs wireless communication with a base station (see, for example, Patent Documents 1 to 4 below).

Special table 2016-518758 gazette JP 2010-283863 A JP 2011-142454 A JP 2014-143605 A

However, in the above-described conventional technology, for example, if an RS pattern in which the reference signal repeats in the time direction is assigned to each terminal, the overhead of the radio signal due to the reference signal increases, and transmission efficiency may decrease. In addition, a terminal to which an RS pattern that does not repeat a reference signal in time is assigned, for example, it may be difficult to compensate for a frequency offset, and reception quality may deteriorate.

In one aspect, an object of the present invention is to provide a base station, a terminal, a communication system, and a processing method that can improve overhead by reducing overhead while suppressing deterioration in reception quality.

In order to solve the above-described problems and achieve the object, in one embodiment, a base station that performs wireless communication between a first terminal and a second terminal different from the first terminal is configured to A first data channel transmitted in a frame format including a reference signal having a repetitive pattern is transmitted to the first terminal, and control information indicating a radio resource of the first data channel is transmitted to the second terminal. Then, a base station, a communication system, and a communication method are proposed in which a second data channel that has fewer reference signals than the first data channel or does not include a reference signal is transmitted to the second terminal.

In another embodiment, the terminal performs wireless communication with another terminal and the own terminal, and transmits a first data channel transmitted in a frame format including a reference signal having a repetition pattern in the time direction. Control information indicating radio resources of the first data channel from the base station that transmits to the other terminal, and a second data channel that includes fewer reference signals than the first data channel or does not include a reference signal , Receiving the first data channel based on the received control information, and receiving the frequency of the second data channel based on a reference signal included in the received first data channel A terminal, a communication system, and a communication method that compensate for the offset are proposed.

In one aspect, the present invention has an effect that transmission efficiency can be improved by reducing overhead while suppressing deterioration in reception quality.

FIG. 1 is a diagram illustrating an example of a communication system according to an embodiment. FIG. 2 is a diagram illustrating an example of a mobile communication system according to the embodiment. FIG. 3 is a diagram illustrating an example of an RS pattern for a low-speed terminal according to the embodiment. FIG. 4 is a diagram illustrating an example of an RS pattern for a high-speed terminal according to the embodiment. FIG. 5 is a sequence diagram illustrating an example of processing in the mobile communication system according to the embodiment. FIG. 6 is a diagram of an example of the base station according to the embodiment. FIG. 7 is a diagram illustrating an example of a hardware configuration of the base station apparatus according to the embodiment. FIG. 8 is a diagram illustrating an example of a terminal according to the embodiment. FIG. 9 is a diagram illustrating an example of a hardware configuration of the terminal according to the embodiment. FIG. 10 is a flowchart illustrating an example of processing performed by the base station apparatus according to the embodiment. FIG. 11 is a flowchart illustrating an example of processing performed by the terminal according to the embodiment. FIG. 12 is a diagram illustrating an example of a DCI format for a low-speed terminal according to the embodiment. FIG. 13 is a diagram illustrating an example of a DCI format for a high-speed terminal according to the embodiment. FIG. 14 is a diagram illustrating another example of the RS pattern for low-speed terminals according to the embodiment. FIG. 15 is a diagram illustrating another example of the RS pattern for the high-speed terminal according to the embodiment.

Embodiments of a base station, a terminal, a communication system, and a processing method according to the present invention will be described in detail below with reference to the drawings.

(Embodiment)
(Communication system according to embodiment)
FIG. 1 is a diagram illustrating an example of a communication system according to an embodiment. As illustrated in FIG. 1, the communication system 100 according to the embodiment includes a base station 110, a first terminal 120, and a second terminal 130. Further, the communication system 100 may further include a third terminal 140.

The base station 110 includes a communication unit 111 and a control unit 112. The communication unit 111 is a communication unit that performs wireless communication with the first terminal 120, the second terminal 130, and the third terminal 140. Wireless communication by the communication unit 111 is controlled by the control unit 112.

The control unit 112 controls the communication unit 111 to transmit a radio signal to the first terminal 120, the second terminal 130, and the third terminal 140. For example, the control unit 112 transmits a first data channel transmitted in a frame format including a reference signal having a repetition pattern in the time direction, that is, a first data channel including a reference signal repeated in the time direction to the first terminal 120. Send to. The reference signal that repeats in the time direction is a reference signal having a predetermined pattern that enables frequency offset compensation on the receiving side. For example, the reference signals repeated in the time direction are a plurality of reference signals assigned to different time resources with the same frequency resource in the first data channel.

In addition, the control unit 112 transmits control information indicating radio resources for transmitting the first data channel to the first terminal 120 to the second terminal 130. The control information can be realized by DCI (Downlink Control Information) as an example. Further, the control information may include information indicating the arrangement of reference signals in the first data channel.

Further, the control unit 112 transmits a second data channel having a reference signal smaller than that of the first data channel to the second terminal 130. The second data channel having fewer reference signals than the first data channel is, for example, a data channel to which a reference signal that is not repeated in time is assigned.

When the reference signal repeats three or more times in the first data channel, the second data channel may include a plurality of reference signals that repeat in the time direction a smaller number of times than the reference signal of the first data channel. . Alternatively, the second data channel may not include the reference signal.

When the control unit 112 transmits the control information described above to the second terminal 130, the frequency offset of the second data channel based on the reference signal included in the first data channel with respect to the second terminal 130. Can be compensated.

The first terminal 120 compensates the frequency offset of the first data channel based on the reference signal included in the first data channel transmitted from the base station 110 to the own terminal. Then, the first terminal 120 decodes user data and the like included in the first data channel compensated for the frequency offset.

The second terminal 130 includes a receiving unit 131 and a processing unit 132. The receiving unit 131 receives control information indicating the radio resource of the first data channel described above and the second data channel described above from the base station 110. Further, the reception unit 131 receives a first data channel transmitted from the base station 110 to the first terminal 120 based on the received control information. Then, the reception unit 131 outputs the received first data channel and second data channel to the processing unit 132.

The processing unit 132 compensates the frequency offset of the second data channel output from the receiving unit 131 based on at least one of the reference signals included in the first data channel output from the receiving unit 131. For example, the processing unit 132 estimates a frequency offset based on the reference signal included in the first data channel, and compensates the frequency offset of the second data channel based on the estimated frequency offset.

Alternatively, the processing unit 132 estimates the phase rotation amount based on the reference signal included in the first data channel, and compensates the phase rotation amount of the second data channel based on the estimated phase rotation amount. The frequency offset of the two data channels may be compensated.

For example, the processing unit 132 can estimate the frequency offset and the phase rotation amount by performing correlation calculation between a plurality of reference signals repeated in the time direction in the first data channel, and can compensate the frequency offset. Compensation of frequency offset by correlation calculation between a plurality of reference signals will be described later.

In addition, the processing unit 132 calculates a frequency offset of the second data channel based on at least a part of the reference signals included in the first data channel and the reference signal included in the second data channel. You may compensate. However, in this case, reference signals used for frequency offset compensation are reference signals having different times.

In addition, the processing unit 132 decodes user data included in the second data channel in which the frequency offset is compensated. As a result, even in the second terminal 130 that receives the second data channel that has fewer reference signals than the first data channel, it is possible to compensate for the frequency offset using the reference signal included in the first data channel. it can. For this reason, the reception quality of the second data channel can be improved. Also, the reference signal included in the second data channel to the second terminal 130 can be reduced. For this reason, the overhead by the reference signal in a radio signal can be reduced and transmission efficiency can be improved.

Thus, according to the base station 110, the first data channel transmitted in the frame format including the reference signal having the repetition pattern in the time direction can be transmitted to the first terminal 120. Further, according to the base station 110, the second data channel that has fewer reference signals than the first data channel or does not include the reference signal can be transmitted to the second terminal 130. Thereby, the overhead in a radio signal can be reduced and the transmission efficiency can be improved.

Further, according to the base station 110, the control information indicating the radio resource of the first data channel transmitted in the frame format including the reference signal having the repetition pattern in the time direction can be transmitted to the second terminal 130. it can. Accordingly, the second terminal 130 can compensate for the frequency offset based on the reference signal of the first data channel, and can suppress a decrease in reception quality. For this reason, it is possible to improve the transmission efficiency by reducing the overhead in the radio signal while suppressing the deterioration of the reception quality.

The control information can be, for example, information directly indicating the radio resource (for example, frequency) of the first data channel. Further, the control information may be information indicating a difference between the radio resource of the second data channel to the second terminal 130 and the radio resource of the first data channel to the first terminal 120. . Thereby, the second terminal 130 allocates the radio resource of the first data channel to the first terminal 120 based on the radio resource of the second data channel to the own terminal and the difference indicated by the control information. A first data channel can be received. In this case, for example, it is possible to reduce the information amount of the control information as compared with the case where the control information directly indicates the radio resource of the first data channel.

Further, the communication unit 111 of the base station 110 may be capable of wireless communication with each terminal including the first terminal 120 and the second terminal 130. In the example illustrated in FIG. 1, it is assumed that the communication unit 111 is communicating with the first terminal 120, the second terminal 130, and the third terminal 140. In this case, the control unit 112 identifies a plurality of terminals (for example, high-speed terminals described later) that are in a predetermined movement state among the terminals that the communication unit 111 is communicating with. The predetermined moving state is, for example, a state where the moving speed is a certain speed or higher and the fading frequency is a predetermined value or higher. The fading frequency is, for example, the amount of change in radio frequency due to the Doppler effect accompanying the movement of the terminal.

For example, the control unit 112 specifies a fading frequency for each terminal with which the communication unit 111 is communicating. As an example, the control unit 112 measures the fading frequency of each terminal based on the radio signal received from each terminal by the communication unit 111. Or the control part 112 may specify the fading frequency of each terminal by receiving the information which shows the fading frequency which each terminal measured based on the radio signal which the communication part 111 transmitted to each terminal from each terminal. . And the control part 112 judges whether each terminal is a predetermined | prescribed movement state by determining whether the specified fading frequency is more than predetermined value about each terminal.

Alternatively, the control unit 112 may specify the moving speed of each terminal with which the communication unit 111 is communicating. As an example, the control part 112 specifies the moving speed of each terminal by receiving the measurement result of the moving speed of each terminal from each terminal. And the control part 112 judges whether each terminal is a predetermined | prescribed movement state by determining whether the specified moving speed is more than predetermined value about each terminal.

In the example shown in FIG. 1, the first terminal 120 and the second terminal 130 are in a predetermined movement state (for example, during high-speed movement), and the third terminal 140 is not in a predetermined movement state (for example, during stoppage or low-speed movement). Suppose that it is determined that

The control unit 112 transmits the first data channel described above to some of the plurality of terminals determined to be in the predetermined movement state. In addition, the control unit 112 transmits the above-described control information and the second data channel to a terminal different from the above-described some terminals among the plurality of terminals determined to be in the predetermined movement state.

In the example illustrated in FIG. 1, the control unit 112 transmits the first data channel described above to the first terminal 120 out of the first terminal 120 and the second terminal 130 that are determined to be in the predetermined movement state. To do. In addition, the control unit 112 transfers the control information and the second information to the second terminal 130 that is different from the part of the first terminal 120 and the second terminal 130 that are determined to be in the predetermined movement state. Send the data channel.

In addition, the control unit 112 transmits the third data channel to the third terminal 140 (for example, a low-speed terminal described later) that is not in a predetermined moving state. The third data channel is, for example, a data channel having a reference signal that is less than the first data channel. As an example, the third data channel is a data channel including the same number of reference signals as the reference signals included in the second data channel.

Thus, according to the base station 110, the first data channel transmitted in the frame format including the reference signal having the repetition pattern in the time direction to only some of the plurality of terminals in the predetermined movement state. Can be sent. In addition, according to the base station 110, the second data channel including the reference signal having fewer reference signals than the first data channel or not including the reference signal is transmitted to the remaining terminals among the plurality of terminals in the predetermined movement state. Control information can be transmitted. Further, the base station 110 can transmit a third data channel having a reference signal smaller than the first data channel to a terminal that is not in a predetermined movement state.

As a result, the terminal (for example, the second terminal 130) excluding a part (for example, the first terminal 120) out of the terminals that need to compensate for the frequency offset based on the reference signal repeated in the time direction has a small number of reference signals. A data channel can be transmitted. In addition, the third data channel with few reference signals can be transmitted to a terminal (for example, the third terminal 140) that does not require frequency offset compensation based on the reference signal repeated in the time direction. Thereby, the overhead by a reference signal can be reduced and the transmission efficiency can be improved.

In addition, the terminals of the first data channel transmitted in the frame format including the reference signal having the repetition pattern in the time direction are transmitted to terminals excluding a part of the terminals that need to compensate the frequency offset based on the reference signal repeated in the time direction. Control information indicating radio resources can be transmitted. Thereby, a terminal (for example, the second terminal 130) excluding this part can compensate for the frequency offset based on the reference signal of the first data channel, and can suppress a decrease in reception quality.

Further, the amount of signaling can be reduced by not transmitting the above-described control information to a terminal (for example, the third terminal 140) that does not require frequency offset compensation based on a reference signal repeated in the time direction.

In addition, the control unit 112 of the base station 110 controls the communication unit 111 to obtain information indicating the possible range of the radio resources of the first data channel and the second data channel in advance for the first terminal 120 and the first terminal. It may be transmitted to the second terminal 130. This range is, for example, a partial range of the system band that can be used by the base station 110 (for example, a specific subband). In this case, the control unit 112 controls the communication unit 111 to transmit the first data channel and the second data channel using the radio resource selected from the range indicated by the transmitted information.

Also, this range may be a range that can be taken by radio resources of the first data channel, the second data channel, and the third data channel. In this case, the control unit 112 controls the communication unit 111 to set the first data channel, the second data channel, and the third data channel according to the radio resource selected from the range indicated by the transmitted information. Send.

In addition, the control unit 112 can transmit information indicating this range by higher level signaling such as an RRC (Radio Resource Control) message.

Thereby, the base station 110, the first terminal 120, and the second terminal 130 can set the reception process in the range indicated by the information received from the base station 110. When the radio signal transmitted from the base station 110 is an OFDM signal, this reception processing includes, for example, FFT. OFDM is an abbreviation for Orthogonal Frequency Division Multiplexing. FFT is an abbreviation for Fast Fourier Transform.

(Mobile communication system according to embodiment)
FIG. 2 is a diagram illustrating an example of a mobile communication system according to the embodiment. The communication system 100 shown in FIG. 1 can be realized by the mobile communication system 200 shown in FIG. 2, for example. Mobile communication system 200 includes a base station 210, terminals 221 to 223, and a core network 230.

The base station 210 is a radio base station apparatus that performs radio communication with the terminals 221 to 223. Base station 210 is connected to core network 230. As an example, the base station 210 is an eNB (evolved Node B) defined by 3GPP.

Each of the terminals 221 to 223 is a wireless terminal device that performs wireless communication with the base station 210. For example, the terminal 221 is a terminal whose moving speed is lower than that of the terminals 222 and 223 (including a stop). Terminals 222 and 223 are terminals having a higher moving speed than terminal 221. Each of the terminals 221 to 223 is, for example, a UE (User Equipment) defined by 3GPP. For example, the core network 230 is an EPC (Evolved Packet Core) defined by 3GPP.

The base station 110 shown in FIG. 1 can be realized by the base station 210, for example. The first terminal 120, the second terminal 130, and the third terminal 140 shown in FIG. 1 can be realized by the terminals 221 to 223, for example.

(RS pattern for low-speed terminals according to the embodiment)
FIG. 3 is a diagram illustrating an example of an RS pattern for a low-speed terminal according to the embodiment. A low-speed wireless format 300 shown in FIG. 3 is a wireless format to which an RS pattern for low-speed terminals is applied. In the low-speed wireless format 300, the horizontal direction indicates time and the vertical direction indicates frequency. Control information 310 (Control) and a data channel 320 (Data) are assigned to the low-speed wireless format 300.

In the control information 310, downlink control information is transmitted. The downlink control information includes, for example, DCI. The control information 310 is transmitted as a PDCCH as an example. PDCCH is an abbreviation for Physical Downlink Control Channel (physical downlink control channel).

The data channel 320 includes downlink user data. As an example, the data channel 320 is a PDSCH for 1 TTI transmitted by the base station 210. TTI is an abbreviation for Transmission Time Interval (transmission time interval). PDSCH is an abbreviation for Physical Downlink Shared Channel (physical downlink shared channel).

Also, the data channel 320 includes reference signals 331 and 332. Reference signals 331 and 332 are downlink reference signals. Reference signals 331 and 332 are reference signals having different frequencies. In the example illustrated in FIG. 3, the reference signals 331 and 332 are reference signals at different times, but the reference signals 331 and 332 may be reference signals at the same time.

Each reference signal is, for example, a reference signal that is individually transmitted to each terminal, and is, for example, DMRS (Data Demodulation Reference Signal).

As shown in FIG. 3, as an RS pattern for a low-speed terminal, for example, an RS pattern in which a reference signal is arranged once for each frequency in a data channel 320 for 1 TTI can be used. With respect to the data channel 320 of a low speed terminal (for example, the terminal 221) with a small frequency offset, the arrangement of reference signals can be reduced and the arrangement of user data and the like can be increased, so that transmission efficiency can be improved.

(RS pattern for high-speed terminals according to the embodiment)
FIG. 4 is a diagram illustrating an example of an RS pattern for a high-speed terminal according to the embodiment. A high-speed wireless format 400 shown in FIG. 4 is a wireless format to which an RS pattern for high-speed terminals is applied. In the high-speed wireless format 400, the horizontal direction indicates time and the vertical direction indicates frequency. Control information 410 and a data channel 420 are assigned to the high-speed wireless format 400. The control information 410 is downlink control information. The downlink control information includes, for example, DCI. The control information 410 is a PDCCH as an example. The data channel 420 includes downlink user data. As an example, the data channel 420 is a PDSCH for 1 TTI transmitted by the base station 210.

The data channel 420 includes reference signals 431 to 434. Reference signals 431 to 434 are downlink reference signals. The reference signals 431 and 433 are reference signals having the same frequency and different times. The reference signals 432 and 434 have the same frequency, are different from the reference signals 431 and 433, and are reference signals at different times. In the example illustrated in FIG. 4, the reference signals 431 and 432 are reference signals having different times, but the reference signals 431 and 432 may be reference signals having the same time. In the example shown in FIG. 4, the reference signals 433 and 434 are reference signals at different times, but the reference signals 433 and 434 may be reference signals at the same time.

As shown in FIG. 4, for example, an RS pattern in which a reference signal is arranged twice for each frequency in a data channel 420 for 1 TTI can be used as an RS pattern for a high-speed terminal. Thereby, even a high-speed terminal (for example, the terminals 222 and 223) having a large frequency offset can compensate for the frequency offset with high accuracy.

However, the RS pattern for high-speed terminals with a large number of reference signals arranged in this way has a larger overhead than the RS pattern for low-speed terminals with a small number of arranged reference signals, so that the transmission efficiency is low. On the other hand, the base station 210 according to the embodiment applies the RS pattern for high-speed terminals only to some high-speed terminals (for example, the terminals 222 and 223), for example, and low-speed to the remaining high-speed terminals. Apply RS pattern for terminal.

In addition, the base station 210 performs high-speed radio format resource position information indicating a position of a radio resource allocated to a high-speed terminal to which the RS pattern for high-speed terminals is applied, for a high-speed terminal that does not apply the RS pattern for high-speed terminals Is notified by DCI.

As an example, the base station 210 assigns radio resources that apply an RS pattern for high-speed terminals to the terminal 222 that is a high-speed terminal, and applies radio resources that apply an RS pattern for low-speed terminals to the terminal 223 that is a high-speed terminal. Make assignments. In this case, the base station 210 notifies high-speed radio format resource position information indicating the position of the radio resource allocated to the terminal 222 by DCI to the terminal 223.

The terminal 223 receives the data channel 420 (see FIG. 4) of the radio resource allocated to the terminal 222 based on the high-speed radio format resource position information notified from the base station 210. Then, the terminal 222 uses the reference signals 431 to 434 included in the received data channel 420 to compensate for its own frequency offset.

The high-speed radio format resource position information indicating the position of the radio resource allocated to the terminal 222 is information directly indicating, for example, a radio resource (time and frequency) allocated to the terminal 222 using a bitmap or the like. Alternatively, the high-speed radio format resource position information may be information indicating a difference (offset) between the position of the radio resource allocated to the terminal 222 and the position of the radio resource allocated to the terminal 223. In this case, the high-speed wireless format resource position information indirectly indicates the position of the wireless resource allocated to the terminal 222. For example, the terminal 223 is allocated to the terminal 222 based on the position of the radio resource allocated to the terminal 223 indicated by the DCI transmitted from the base station 210 to the terminal 223 and the difference indicated by the high-speed radio format resource position information. Identified radio resources.

(Frequency offset compensation)
As an example, frequency offset compensation by a terminal 223 to which a low-speed wireless format 300 of an RS pattern for a low-speed terminal is assigned will be described. For example, it is assumed that the low-speed wireless format 300 (see FIG. 3) is assigned to the terminal 223 from the base station 210, and the high-speed wireless format 400 (see FIG. 4) is assigned to the terminal 222 from the base station 210.

In this case, the terminal 223 specifies the resource position of the data channel 320 transmitted from the base station 210 to the own terminal based on the DCI included in the control information 310 transmitted from the base station 210. Also, the terminal 223 specifies the resource position of the data channel 420 transmitted from the base station 210 to the terminal 222 based on the high-speed wireless format resource position information included in the control information 310. Then, the terminal 223 receives the reference signals 431 to 434 based on the identified resource position of the data channel 420.

In addition, the terminal 223 performs decoding of user data included in the data channel 320 by compensating for the frequency offset of the data channel 320 received from the base station 210 based on the received reference signals 431 to 434.

First, a case where the pilot sequences of the reference signals 431 and 433 are the same as each other and the pilot sequences of the reference signals 432 and 434 are the same as each other will be described. In this case, the terminal 223 can compensate for the frequency offset even if the pilot sequence s of the reference signals 431 to 434 is unknown.

For example, the received symbol x [k] at time k can be expressed by the following equation (1). In the following equation (1), Δθ represents the amount of phase rotation. E indicates the frequency deviation within the symbol. H indicates propagation path distortion. It is assumed that the frequency deviation E and the channel distortion H in the symbol are time invariant. The radio signal transmitted from the base station 210 to the terminals 221 to 223 is an OFDM signal, and W in the following equation (1) is a DFT matrix. DFT is an abbreviation for Discrete Fourier Transform.

x [k] = e ^j Δθ ^UEk EHW ⁻¹ s (1)

From the above equation (1), the received symbol x [k + τ] at time k + τ can be expressed as the following equation (2). τ is a time length between the reference signals 431 and 433 (= time length between the reference signals 432 and 434).

x [k + τ] = e ^j Δθ ^{(k +} τ ⁾ EHW ⁻¹ s = e ^j Δθτx [k] (2)

From the above equation (2), the following equation (3) is established. In the following equation (3), x ^H [k] is a conjugate transpose of the received symbol x [k].

x ^H [k] x [k + τ] = e ^j Δθτ || EHW ⁻¹ s || ² (3)

Therefore, the terminal 223 can calculate the phase rotation amount Δθτ at the time length τ, for example, by the following equation (4). The terminal 223 can compensate for the frequency offset of the received signal by compensating the phase rotation amount of the received signal based on the calculated phase rotation amount Δθτ.

arg (x ^H [k] x [k + τ]) = Δθτ (4)

Next, the case where the pilot sequences of the reference signals 431 and 433 are different from each other and the pilot sequences of the reference signals 432 and 434 are different from each other will be described. In this case, it is assumed that pilot sequence s of reference signals 431 to 434 is known at terminal 223. In this case, the phase rotation amount of the received signal can be estimated by removing the pilot sequence s.

For example, the following equation (5) is established by the above equation (1). In the following equation (5), diag (s) ^H is a diagonal matrix and is multiplicative.

diag (s) ^H x [k] = e ^j Δθ ^k EHW ⁻¹ diag (s) ^H s (5)

Here, the following formula (6) and the following formula (7) hold. In the following equation _{(7), s n (n = 0,} ..., N-1) assumes the amplitude of 1.

From the above formula (5), it can be expressed as the following formula (8) and the following formula (9).

diag (s) ^H x [k] = e ^j Δθ ^k EHW ⁻¹ (8)

diag (s) x ^H [k] x [k + τ] diag ^H (s)
= E ^j Δθτ || EHW ^-1 || ² (9)

Therefore, the terminal 223 can calculate the phase rotation amount Δθτ in the time length τ, for example, by the following equation (10). The terminal 223 can compensate for the frequency offset of the received signal by compensating the phase rotation amount of the received signal based on the calculated phase rotation amount Δθτ.

^{arg (diag (s) x H} [k] x [k + τ] diag H (s))
= Δθτ (10)

Note that, according to the frequency offset compensation method described above, the frequency offset can be compensated even when the reference signals are transmitted from the plurality of antennas of the base station 210.

(Processing in Mobile Communication System According to Embodiment)
FIG. 5 is a sequence diagram illustrating an example of processing in the mobile communication system according to the embodiment. In the mobile communication system 200 shown in FIG. 2, for example, the steps shown in FIG. 5 are executed. In the example illustrated in FIG. 2, it is assumed that the base station 210 assigns a high-speed wireless format 400 (see FIG. 4) to which a high-speed terminal RS pattern is applied to a terminal 222 that is a high-speed terminal. Further, it is assumed that the base station 210 assigns a low-speed wireless format 300 (see FIG. 3) in which an RS pattern for low-speed terminals is applied to a terminal 221 that is a low-speed terminal and a terminal 223 that is a high-speed terminal.

First, the base station 210 transmits DCI for a low-speed terminal to the terminal 221 (step S501). The DCI transmitted in step S501 includes information indicating the position of the radio resource of the data channel transmitted from the base station 210 to the terminal 221 in step S504, for example. Also, the DCI transmitted in step S501 includes information that can specify the RS pattern in the data channel that the base station 210 transmits to the terminal 221 in step S504.

Also, the base station 210 transmits DCI for the high speed terminal to the terminal 222 (step S502). The DCI transmitted at step S502 includes, for example, information indicating the position of the radio resource of the data channel transmitted from the base station 210 to the terminal 222 at step S505. Also, the DCI transmitted in step S502 includes information that can specify the RS pattern in the data channel that the base station 210 transmits to the terminal 222 in step S505, for example.

In addition, the base station 210 transmits DCI for the high speed terminal to the terminal 223 (step S503). The DCI transmitted at step S503 includes information indicating the position of the radio resource of the data channel transmitted from the base station 210 to the terminal 223 at step S506, for example. Also, the DCI transmitted in step S503 includes information that can specify the RS pattern in the data channel that the base station 210 transmits to the terminal 223 in step S506, for example. Also, the DCI transmitted in step S503 includes, for example, high-speed radio format resource position information indicating the position of the radio resource of the data channel transmitted from the base station 210 to the terminal 222 in step S505.

Next, the base station 210 transmits the data channel 320 (see FIG. 3) to which the RS pattern for low-speed terminals is applied to the terminal 221 (step S504). Based on the DCI received in step S501, the terminal 221 receives the data channel 320 transmitted in step S504, and decodes the received data channel 320.

Further, the base station 210 transmits the data channel 420 (see FIG. 4) to which the RS pattern for high-speed terminals is applied to the terminal 222 (step S505). The terminal 222 receives the data channel 420 transmitted in step S505 based on the DCI received in step S502. Then, the terminal 222 performs frequency offset compensation for the received data channel 420 based on the reference signals 431 to 434 included in the received data channel 420, and decodes the data channel 420 that has been compensated for frequency offset.

Also, the base station 210 transmits the data channel 320 (see FIG. 3) to which the RS pattern for low-speed terminals is applied to the terminal 223 (step S506). The terminal 223 receives the data channel transmitted in step S506 based on the DCI received in step S503. Also, the terminal 223 identifies the position of the radio resource of the data channel 420 that the base station 210 transmits to the terminal 222 in step S505 based on the high-speed radio format resource position information included in the DCI received in step S503. Further, the terminal 223 receives the data channel 420 based on the specified position of the radio resource.

Then, the terminal 223 compensates the received frequency offset of the data channel 320 to the own terminal based on the reference signals 431 to 434 included in the data channel 420 to the terminal 222, and compensates the frequency offset. The data channel 320 is decoded. Alternatively, the terminal 223 compensates for the frequency offset based on the received reference signals 331 and 332 included in the data channel 320 to the own terminal and the received reference signals 433 and 434 included in the data channel 420 to the terminal 222. You may go.

In the example shown in FIG. 5, it is assumed that the data channels transmitted in steps S504 to S506 are normally decoded by the terminals 221 to 223, respectively. In this case, the terminal 221 transmits an ACK response for the data channel 320 transmitted in step S504 to the base station 210 (step S507). Also, the terminal 222 transmits an ACK response for the data channel 420 transmitted in step S505 to the base station 210 (step S508). In addition, the terminal 223 transmits an ACK response for the data channel 320 transmitted in step S506 to the base station 210 (step S509).

If the data channel 320 transmitted in step S504 is not normally decoded by the terminal 221, the terminal 221 transmits a NACK response to the base station 210 in step S507. If the data channel 420 transmitted in step S505 is not normally decoded by the terminal 222, the terminal 222 transmits a NACK response to the base station 210 in step S508. If the data channel 320 transmitted in step S506 is not normally decoded by the terminal 223, the terminal 223 transmits a NACK response to the base station 210 in step S509.

(Base station according to the embodiment)
FIG. 6 is a diagram of an example of the base station according to the embodiment. As illustrated in FIG. 6, the base station 210 includes, for example, an antenna 601, an RF reception unit 602, a baseband reception unit 603, a line termination unit 604, a baseband transmission unit 605, an RF transmission unit 606, A scheduling unit 607. RF is an abbreviation for Radio Frequency.

Antenna 601 receives a signal wirelessly transmitted from another communication device (for example, terminals 221 to 223), and outputs the received signal (uplink reception signal) to RF reception unit 602. The RF reception unit 602 performs an RF reception process on the uplink reception signal output from the antenna 601. The RF reception processing by the RF reception unit 602 includes, for example, amplification, frequency conversion from the RF band to the baseband, conversion from an analog signal to a digital signal, and the like. The RF reception unit 602 outputs a signal (uplink baseband signal) subjected to the RF reception process to the baseband reception unit 603.

The uplink baseband signal output from the RF receiving unit 602 to the baseband receiving unit 603 is a signal from which an uplink carrier wave has been removed. The baseband receiving unit 603 demodulates the uplink baseband signal output from the RF receiving unit 602, and decodes the demodulated signal. For example, the baseband receiving unit 603 demodulates and decodes the uplink baseband signal based on the uplink scheduling setting from the scheduling unit 607. Baseband reception section 603 then outputs a signal (reception signal) obtained by decoding to line termination section 604.

The line termination unit 604 performs a line termination process based on the received signal output from the baseband reception unit 603, and transmits the uplink signal obtained by the line termination process to the upper network. The upper network is, for example, the core network 230 shown in FIG. Also, the line termination unit 604 performs a line termination process based on the downlink signal received from the upper network, and outputs a transmission signal obtained by the line termination process to the baseband transmission unit 605.

The baseband transmission unit 605 encodes the transmission signal output from the line termination unit 604 and modulates the encoded signal. For example, the baseband transmission unit 605 demodulates and decodes the transmission signal based on the downlink scheduling setting from the scheduling unit 607. Baseband transmission section 605 then outputs a signal (downlink baseband signal) obtained by modulation to RF transmission section 606. Further, the baseband transmission unit 605 generates control information such as DCI based on the downlink scheduling setting from the scheduling unit 607, and outputs a signal (downlink baseband signal) including the generated control information to the RF transmission unit 606. To do.

The RF transmission unit 606 performs RF transmission processing of the downlink baseband signal output from the baseband transmission unit 605. The RF transmission processing by the RF transmission unit 606 includes, for example, conversion from a digital signal to an analog signal, frequency conversion from a baseband to an RF band, amplification, and the like. The RF transmission unit 606 outputs the signal (downlink modulated signal) subjected to the RF transmission process to the antenna 601. The antenna 601 wirelessly transmits the downlink modulated signal output from the RF transmission unit 606 to other communication devices (for example, terminals 221 to 223).

The scheduling unit 607 performs downlink scheduling for assigning radio resources in radio transmission from the base station 210 to the terminals 221 to 223. Then, the scheduling unit 607 performs downlink scheduling setting for the baseband transmission unit 605 based on the result of downlink scheduling.

In addition, the scheduling unit 607 performs uplink scheduling that allocates radio resources in radio transmission from the terminals 221 to 223 to the base station 210. Then, the scheduling unit 607 performs uplink scheduling setting based on the uplink scheduling result for the baseband receiving unit 603.

The communication unit 111 illustrated in FIG. 1 can be realized by, for example, the antenna 601, the RF reception unit 602, the baseband reception unit 603, the baseband transmission unit 605, and the RF transmission unit 606. The control unit 112 illustrated in FIG. 1 can be realized by the scheduling unit 607, for example.

(Hardware configuration of base station apparatus according to embodiment)
FIG. 7 is a diagram illustrating an example of a hardware configuration of the base station apparatus according to the embodiment. In FIG. 7, the same parts as those shown in FIG. The base station 210 illustrated in FIG. 6 can be realized by an antenna 601, an RF circuit 701, an FPGA 702, a CPU 703, and a memory 704, for example, as illustrated in FIG. FPGA is an abbreviation for Field Programmable Gate Array. CPU is an abbreviation for Central Processing Unit.

The RF circuit 701 includes circuits such as an amplifier, a mixer, an ADC, and a DAC. ADC is an abbreviation for Analog / Digital Converter (analog / digital converter). DAC stands for Digital / Analog Converter (digital / analog converter). The RF receiving unit 602 and the RF transmitting unit 606 shown in FIG. 6 can be realized by the RF circuit 701, for example.

The FPGA 702 is a circuit that performs baseband digital processing. The baseband receiving unit 603 and the baseband transmitting unit 605 illustrated in FIG. 6 can be realized by the FPGA 702, for example.

The CPU 703 is a CPU that controls the entire base station 210. The memory 704 includes, for example, a main memory and an auxiliary memory. The main memory is, for example, a RAM (Random Access Memory). The main memory is used as a work area for the CPU 703. The auxiliary memory is a non-volatile memory such as a magnetic disk, an optical disk, or a flash memory. Various programs for operating the base station 210 are stored in the auxiliary memory. The program stored in the auxiliary memory is loaded into the main memory and executed by the CPU 703. The line termination unit 604 and scheduling unit 607 shown in FIG. 6 can be realized by the CPU 703 and the memory 704, for example.

(Terminal according to the embodiment)
FIG. 8 is a diagram illustrating an example of a terminal according to the embodiment. Although the configuration of the terminal 221 will be described, the configurations of the terminals 222 and 223 are the same as the configuration of the terminal 221. As illustrated in FIG. 8, the terminal 221 includes, for example, an antenna 801, an RF reception unit 802, a baseband reception unit 803, a control unit 804, a baseband transmission unit 805, and an RF transmission unit 806. .

The antenna 801 receives a signal wirelessly transmitted from another communication device (for example, the base station 210), and outputs the received signal (downlink reception signal) to the RF reception unit 802. The RF reception unit 802 performs an RF reception process on the downlink reception signal output from the antenna 801. The RF reception processing by the RF receiver 802 includes, for example, amplification, frequency conversion from the RF band to the baseband, conversion from an analog signal to a digital signal, and the like. The RF reception unit 802 outputs the signal (downlink baseband signal) subjected to the RF reception process to the baseband reception unit 803.

The downlink baseband signal output from the RF reception unit 802 to the baseband reception unit 803 is a signal from which a downlink carrier wave has been removed. The baseband receiving unit 803 demodulates the downlink baseband signal output from the RF receiving unit 802 and decodes the demodulated signal. Then, the baseband receiving unit 803 outputs a signal (reception signal) obtained by decoding to the control unit 804.

The control unit 804 performs processing (for example, application processing) based on the received signal output from the baseband receiving unit 803. In addition, a transmission signal based on processing (for example, application processing) is generated, and the generated transmission signal is output to baseband transmission section 805. In addition, the control unit 804 performs a reception process based on a control signal such as DCI included in the reception signal output from the baseband reception unit 803 and a reference signal.

The baseband transmission unit 805 encodes the transmission signal output from the control unit 804 and modulates the encoded signal. Then, the baseband transmission unit 805 outputs a signal (uplink baseband signal) obtained by the modulation to the RF transmission unit 806.

The RF transmission unit 806 performs RF transmission processing on the uplink baseband signal output from the baseband transmission unit 805. The RF transmission processing by the RF transmission unit 806 includes, for example, conversion from a digital signal to an analog signal, frequency conversion from a baseband to an RF band, amplification, and the like. The RF transmission unit 806 outputs a signal (uplink modulated signal) subjected to RF transmission processing to the antenna 801. The antenna 801 wirelessly transmits the uplink modulated signal output from the RF transmission unit 806 to another communication device (for example, the base station 210).

The receiving unit 131 of the second terminal 130 illustrated in FIG. 1 can be realized by, for example, the antenna 801, the RF receiving unit 802, the baseband receiving unit 803, and the control unit 804. The processing unit 132 of the second terminal 130 illustrated in FIG. 1 can be realized by at least one of the baseband receiving unit 803 and the control unit 804, for example.

(Hardware configuration of terminal according to embodiment)
FIG. 9 is a diagram illustrating an example of a hardware configuration of the terminal according to the embodiment. In FIG. 9, the same parts as those shown in FIG. Although the hardware configuration of the terminal 221 will be described, the hardware configurations of the terminals 222 and 223 are the same as the hardware configuration of the terminal 221. The terminal 221 illustrated in FIG. 8 can be realized by an antenna 801, an RF circuit 901, a baseband circuit 902, a memory 903, a processor 904, and a memory 905, for example, as illustrated in FIG. it can.

The RF circuit 901 includes circuits such as an amplifier, a mixer, an ADC, and a DAC. The RF receiver 802 and the RF transmitter 806 shown in FIG. 8 can be realized by the RF circuit 901, for example.

The baseband circuit 902 is a circuit that performs baseband digital processing. The baseband circuit 902 can be realized by a digital circuit such as an FPGA or a DSP, for example. DSP is an abbreviation for Digital Signal Processor. The memory 903 is a storage area connected to the baseband circuit 902. The baseband circuit 902 performs baseband processing by accessing the memory 903, for example. The baseband receiving unit 803 and the baseband transmitting unit 805 illustrated in FIG. 8 can be realized by the baseband circuit 902 and the memory 903, for example.

The processor 904 is a circuit that performs signal processing (for example, host processing), and is, for example, a CPU that controls the entire terminal 221. The memory 905 includes, for example, a main memory and an auxiliary memory. The main memory is, for example, a RAM. The main memory is used as a work area for the processor 904. The auxiliary memory is a non-volatile memory such as a magnetic disk, an optical disk, or a flash memory. Various programs for operating the terminal 221 are stored in the auxiliary memory. The program stored in the auxiliary memory is loaded into the main memory and executed by the processor 904. The control unit 804 illustrated in FIG. 8 can be realized by the processor 904 and the memory 905, for example.

(Processing by base station apparatus according to embodiment)
FIG. 10 is a flowchart illustrating an example of processing performed by the base station apparatus according to the embodiment. The base station 210 according to the embodiment executes, for example, each step shown in FIG. Each step illustrated in FIG. 10 is executed by control or processing by the scheduling unit 607 of the base station 210 illustrated in FIG. 6, for example.

First, the base station 210 performs radio scheduling processing (step S1001). The radio scheduling process in step S1001 includes, for example, terminal selection for selecting a terminal that performs radio communication and resource allocation for assigning radio resources (for example, a combination of frequency and time) to the selected terminal.

Also, the base station 210 initializes a high-speed format allocation flag (step S1002). For example, the base station 210 sets the high-speed format allocation flag Flag_HS to False (Flag_HS: = False). The high speed format assignment flag Flag_HS is information indicating whether or not the high speed wireless format 400 is assigned to the high speed terminal. Further, the high-speed format allocation flag Flag_HS is stored in the memory of the base station 210 (for example, the memory 704 shown in FIG. 7).

Next, the base station 210 performs the processing of steps S1003 to S1009 by looping U times while incrementing the index u (u: = u + 1) (u: = 0 to U-1). U is the number of terminals selected by the terminal selection in step S1001 (the number of selected terminals). u is an index from 0 to U−1 indicating the current processing target terminal among the U terminals selected by the terminal selection in step S1001.

For example, it is assumed that the base station 210 selects the terminals 221 to 223 by the terminal selection in step S1001. In this case, U = 3. Further, it is assumed that base station 210 assigns indexes = 0 to 2 to terminals 221 to 223, respectively. In this case, the terminal u when the index u = 0 indicates the terminal 221, the terminal u when the index u = 1 indicates the terminal 222, and the terminal u when the index u = 2 indicates the terminal 223.

First, the base station 210 performs high-speed movement determination that determines whether or not the fading frequency estimation result fd [u] of the terminal u is larger than a predetermined threshold value Θfd (step S1003). The estimation result fd [u] of the fading frequency of the terminal u can be calculated by the base station 210 based on the radio signal from the terminal u. Alternatively, the fading frequency estimation result fd [u] of the terminal u can be calculated by the terminal u based on a radio signal from the base station 210, for example. In this case, the base station 210 receives information indicating the estimation result fd [u] calculated by the terminal u from the terminal u.

In step S1003, when the fading frequency estimation result fd [u] of the terminal u is not larger than the threshold Θfd (step S1003: No), the base station 210 determines the terminal u as a low speed terminal (step S1004). For example, the base station 210 sets the mobility Mobility [u] of the terminal u to Normal (Mobility [u]: = Normal). Mobility Mobility [u] is information stored in a memory of base station 210 (for example, memory 704 shown in FIG. 7).

Next, the base station 210 allocates the low-speed wireless format 300 to the terminal u (step S1005), and ends the processes of steps S1003 to S1009 for the terminal u. In step S1005, for example, the base station 210 sets the radio format ChannelFormat [u] of the terminal u to Normal (ChannelFormat [u]: = Normal). The radio format ChannelFormat [u] is information stored in the memory of the base station 210 (for example, the memory 704 shown in FIG. 7).

In step S1003, when the fading frequency estimation result fd [u] of the terminal u is larger than the threshold Θfd (step S1003: Yes), the base station 210 determines the terminal u as a high-speed terminal (step S1006). For example, the base station 210 sets the mobility Mobility [u] of the terminal u to HighSpeed (Mobility [u]: = HighSpeed). Mobility Mobility [u] is information stored in a memory of base station 210 (for example, memory 704 shown in FIG. 7).

Next, the base station 210 determines whether or not the high-speed format allocation flag Flag_HS is True (step S1007). If the high speed format assignment flag Flag_HS is True (step S1007: Yes), it can be determined that the high speed wireless format 400 has already been assigned to the high speed terminal, and the base station 210 moves to step S1005. In this case, the terminal u is determined as a high-speed terminal, but the low-speed wireless format 300 is assigned.

In step S1007, if the high-speed format assignment flag Flag_HS is not True (step S1007: No), it can be determined that the high-speed wireless format 400 has not yet been assigned to the high-speed terminal. In this case, the base station 210 assigns the high speed wireless format 400 to the terminal u (step S1008). For example, the base station 210 sets the radio format ChannelFormat [u] of the terminal u to HighSpeed (ChannelFormat [u]: = HighSpeed).

Next, the base station 210 stores the terminal u as a high-speed format terminal and changes the high-speed format assignment flag Flag_HS (step S1009). In step S1009, for example, the base station 210 sets the high-speed format terminal HSFormatUE to u (HSFormatUE: = u). The high-speed format terminal HSFormatUE is information stored in the memory of the base station 210 (for example, the memory 704 shown in FIG. 7). In addition, the base station 210 sets the high-speed format assignment flag Flag_HS to True (Flag_HS: = True). Then, the base station 210 ends the processes of steps S1003 to S1009 for the terminal u.

When the base station 210 performs the processes of steps S1003 to S1009 in U loops, the base station 210 performs the processes of steps S1010 to S1015 in U loops while incrementing the index u (u: = u + 1) (u: = 0 to U-1).

First, the base station 210 determines whether or not the mobility Mobility [u] of the terminal u is High Speed (step S1010). When mobility Mobility [u] is not High Speed (step S1010: No), base station 210 transmits DCI (for example, see FIG. 12) for low-speed terminals to terminal u (step S1011). The DCI for low-speed terminals includes high-speed radio format resource position information indicating the positions of radio resources allocated to the terminals indicated by the high-speed format terminal HSFormatUE.

In step S1010, when mobility Mobility [u] is High Speed (step S1010: Yes), base station 210 transmits DCI for high-speed terminals (for example, see FIG. 13) to terminal u (step S1012).

Next, the base station 210 determines whether or not the radio format ChannelFormat [u] of the terminal u is HighSpeed (step S1013). When the radio format ChannelFormat [u] is not High Speed (step S1013: No), the base station 210 transmits the data channel 320 to the terminal u in the low speed radio format 300 (see FIG. 3) (step S1014). Then, the base station 210 ends the processes of steps S1010 to S1015 for the terminal u.

In step S1013, when the radio format ChannelFormat [u] is HighSpeed (step S1013: Yes), the base station 210 moves to step S1015. That is, the base station 210 transmits the data channel 420 to the terminal u in the high-speed wireless format 400 (see FIG. 4) (step S1015), and ends the processes of steps S1010 to S1015 for the terminal u.

In the example shown in FIG. 10, the process of setting the first selected high-speed terminal as the high-speed format terminal has been described, but the present invention is not limited to such a process. For example, the base station 210 may set a high-speed format terminal to be a high-speed terminal to which the frequency resource closest to the center of the subband used by these high-speed terminals is assigned. Thereby, the maximum value of the difference between the frequency resource allocated to each other high-speed terminal and the frequency resource allocated to the high-speed format terminal can be reduced. For this reason, it is possible to suppress a decrease in frequency offset compensation accuracy caused by other high-speed terminals referring to the reference signal of the high-speed format terminal.

Also, the base station 210 may use a plurality of high-speed terminals among the high-speed terminals as high-speed format terminals. In this case, the base station 210 transmits, to each high-speed terminal that is not a high-speed format terminal, high-speed radio format resource position information indicating the radio resource of the high-speed format terminal that is closest to the allocated frequency resource among the plurality of high-speed format terminals. . As a result, it is possible to suppress a decrease in frequency offset compensation accuracy caused by other high-speed terminals referring to the reference signal of the high-speed format terminal. In this case, the base station 210 may use a plurality of high-speed terminals among the high-speed terminals as high-speed format terminals so that the frequency resources allocated to the high-speed format terminals are evenly arranged within the subband. As a result, it is possible to suppress a decrease in frequency offset compensation accuracy caused by other high-speed terminals referring to the reference signal of the high-speed format terminal.

Also, the base station 210 may select a high-speed terminal having the highest fading frequency (or the highest moving speed) among the high-speed terminals as a high-speed format terminal. As a result, the terminal having the largest frequency offset can compensate for the frequency offset by the reference signal assigned to the own terminal, and can suppress a decrease in the frequency offset compensation accuracy.

(Processing by the terminal according to the embodiment)
FIG. 11 is a flowchart illustrating an example of processing performed by the terminal according to the embodiment. The processing by the terminal 221 will be described, but the processing by the terminals 222 and 223 is the same as the processing by the terminal 221. The terminal 221 executes, for example, each step shown in FIG. Each step shown in FIG. 11 is executed by, for example, control or processing by the control unit 804 shown in FIG.

First, the terminal 221 receives DCI from the base station 210 to the terminal (step S1101). For example, the terminal 221 can determine whether the DCI is the DCI for the terminal by attempting to demodulate and decode the DCI transmitted from the base station 210 (blind reception or blind decoding).

Next, the terminal 221 determines whether or not the DCI received in step S1101 is DCI for high-speed terminals (step S1102). For example, the terminal 221 determines whether the DCI is DCI for a high-speed terminal based on the value of a field indicating the format of the DCI (for example, see FIGS. 12 and 13) included in the received DCI. .

In step S1102, if the DCI is not for high-speed terminals (step S1102: No), the terminal 221 proceeds to step S1105. In this case, the terminal 221 may not perform frequency offset compensation. If the DCI is for high-speed terminals (step S1102: Yes), the terminal 221 proceeds to step S1103. That is, the base station 210 extracts the high-speed radio format resource position information indicating the position of the radio resource allocated to the terminal to which the high-speed radio format 400 is applied from the DCI received in step S1101 (step S1103).

Next, the terminal 221 estimates the frequency offset using the reference signals (reference signals 431 to 434) of the high speed wireless format 400 at the resource position indicated by the extracted high speed wireless format resource position information (step S1104).

Next, the terminal 221 extracts information indicating the position of the radio resource of the data channel addressed to the terminal and various parameters from the DCI received in step S1101 (step S1105). Various parameters are parameters for receiving a data channel addressed to the terminal itself.

Next, the terminal 221 decodes the data channel for the terminal itself using the information extracted in step S1105 (step S1106), and ends a series of processing. At this time, when performing step S1104, the base station 210 can improve the reception quality of the data channel by performing frequency offset compensation based on the frequency offset estimated in step S1104.

In the process shown in FIG. 11, even when the terminal 221 does not determine whether or not the terminal 221 is a high-speed terminal, it is determined whether or not the DCI to the terminal is DCI for the high-speed terminal. Thus, processing according to whether or not the terminal 221 is a high-speed terminal can be performed. When the terminal 221 determines whether or not the terminal 221 is a high-speed terminal, the process may be branched depending on whether or not the terminal 221 is a high-speed terminal in step S1102. In this case, information indicating whether DCI is DCI for high-speed terminals (for example, high-speed DCI format determination flags 1201 and 1301 shown in FIGS. 12 and 13) may not be included in DCI.

(DCI format for low-speed terminals according to the embodiment)
FIG. 12 is a diagram illustrating an example of a DCI format for a low-speed terminal according to the embodiment. DCI 1200 shown in FIG. 12 is DCI for low-speed terminals. The DCI 1200 includes a high-speed DCI format determination flag 1201 and high-speed wireless format resource position information 1202.

The high-speed DCI format determination flag 1201 is information indicating that the DCI 1200 is DCI for low-speed terminals. In the example shown in FIG. 12, the high-speed DCI format determination flag 1201 is stored at the head of the DCI 1200. The high-speed wireless format resource position information 1202 is information indicating the position of the wireless resource to which the high-speed wireless format 400 is assigned to the high-speed terminal. In the example shown in FIG. 12, the high-speed wireless format resource position information 1202 is stored at the end of the DCI 1200.

(DCI format for high-speed terminals according to the embodiment)
FIG. 13 is a diagram illustrating an example of a DCI format for a high-speed terminal according to the embodiment. DCI 1300 shown in FIG. 13 is DCI for high-speed terminals. The DCI 1300 includes a high-speed DCI format determination flag 1301. The high-speed DCI format determination flag 1301 is information indicating that the DCI 1300 is DCI for low-speed terminals. In the example shown in FIG. 13, the high-speed DCI format determination flag 1301 is stored at the head of the DCI 1300.

Also, the DCI for high-speed terminals does not include information indicating the position of the radio resource assigned the high-speed radio format to the high-speed terminal, such as the high-speed radio format resource position information 1202 shown in FIG. Also good.

Note that the high-speed DCI format determination flags 1201 and 1301 may be omitted from the DCIs 1200 and 1300 shown in FIGS. In this case, for example, the number of bits is made different between the DCIs 1200 and 1300, and the terminals 221 to 223 try to decode the received DCI with the respective number of bits, so that the DCI is either DCI 1200 or 1300 Can be determined.

(Another example of the RS pattern for low-speed terminals according to the embodiment)
FIG. 14 is a diagram illustrating another example of the RS pattern for low-speed terminals according to the embodiment. In FIG. 14, the same parts as those shown in FIG. As shown in FIG. 14, a reference signal 1411 may be included in the data channel 320 of the low-speed wireless format 300. The reference signal 1411 is a reference signal assigned to the entire frequency of the low speed wireless format 300. As described above, the reference signal of the data channel 320 may not be a reference signal having a different time for each frequency included in the low-speed wireless format 300.

(Another example of the RS pattern for high-speed terminals according to the embodiment)
FIG. 15 is a diagram illustrating another example of the RS pattern for the high-speed terminal according to the embodiment. In FIG. 15, the same parts as those shown in FIG. As shown in FIG. 15, reference signals 1511 and 1512 may be included in the data channel 420 of the high-speed wireless format 400. Each of the reference signals 1511 and 1512 is a reference signal assigned to the entire frequency of the high-speed wireless format 400. Reference signals 1511 and 1512 are reference signals having different times. As described above, the reference signal of the data channel 420 may not be a reference signal having a different time for each frequency included in the high-speed wireless format 400.

As described above, according to the embodiment, the data channel 320 of the low-speed wireless format 300 can be transmitted to the terminal 223 excluding a part (terminal 222) of the high-speed terminals and the terminal 221 that is a low-speed terminal. Thereby, the overhead by a reference signal can be reduced and the transmission efficiency can be improved. Further, DCI including high-speed radio format resource position information indicating the radio resource of the data channel 420 of the high-speed radio format 400 can be transmitted to the terminal 223 which is a high-speed terminal. As a result, the terminal 223 can compensate for the frequency offset based on the reference signals 431 to 434 of the data channel 420, and can suppress a decrease in reception quality. For this reason, it is possible to improve the transmission efficiency by reducing the overhead due to the reference signal while suppressing the deterioration of the reception quality.

As described above, according to the base station, the terminal, the communication system, and the processing method, it is possible to improve the transmission efficiency by reducing the overhead while suppressing the deterioration of the reception quality.

Conventionally, the use of high-frequency waves such as a millimeter wave band is assumed in 5G. At high frequencies, the frequency offset caused by the accuracy of the transmitter and the Doppler frequency increases, and correction of this frequency offset becomes a problem.

For example, in 4G downlink, a cell common pilot (CS-RS: Cell Specific Reference Signal) is mainly used for frequency offset estimation. On the other hand, in 5G, cell common pilots are abolished to improve operational efficiency, and studies are proceeding in a direction in which user-specific pilots (UE-RS: UE specific Reference Signal) are allocated.

In order to realize both a wide range of frequency offset correction and efficiency improvement of radio resources in user-specific pilots, for example, it is discussed to have a plurality of DMRS patterns for PDSCH. For example, as a reference signal arrangement pattern for a terminal moving at high speed, a pattern that repeats in the time direction is supported in order to facilitate frequency offset compensation. However, if the number of reference signals arranged is large, the overhead becomes large and the transmission efficiency deteriorates.

On the other hand, according to the above-described embodiment, only a part of the terminals moving at high speed transmits a data channel in which the reference signal repeats in the time direction, and the other terminals moving at high speed move the data. You can refer to the channel. As a result, the ratio of the reference signal in the radio resource can be reduced, the utilization efficiency of the radio resource can be improved, and the cell throughput can be improved.

DESCRIPTION OF SYMBOLS 100 Communication system 110,210 Base station 111 Communication part 112,804 Control part 120 1st terminal 130 2nd terminal 131 Reception part 132 Processing part 140 3rd terminal 200 Mobile communication system 221-223 Terminal 230 Core network 300 Low- speed wireless format 310, 410 Control information 320, 420 Data channel 331, 332, 431-434, 1411, 1511, 1512 Reference signal 400 High- speed wireless format 601, 801 Antenna 602, 802 RF receiver 603, 803 Baseband receiver 604 Line termination unit 605, 805 Baseband transmission unit 606, 806 RF transmission unit 607 Scheduling unit 701, 901 RF circuit 702 FPGA
703 CPU
704, 903, 905 Memory 902 Baseband circuit 904 Processor 1200, 1300 DCI
1201, 1301 High-speed DCI format determination flag 1202 High-speed wireless format resource position information

Claims (12)

1. A communication unit that performs wireless communication between the first terminal and a second terminal different from the first terminal;
   A first data channel transmitted in a frame format including a reference signal having a repetition pattern in a time direction is transmitted to the first terminal, and control information indicating a radio resource of the first data channel is transmitted to the second terminal Transmitting to the terminal and transmitting a second data channel having a reference signal less than the first data channel or not including the reference signal to the second terminal;
   A base station characterized by that.
2. By transmitting the control information to the second terminal, the second terminal is compensated for a frequency offset of the second data channel based on a reference signal included in the first data channel. The base station according to claim 1.
3. The base station according to claim 1 or 2, wherein the second data channel includes a reference signal that does not repeat in time.
4. 4. The control information according to claim 1, wherein the control information is information indicating a difference between a radio resource of the second data channel and a radio resource of the first data channel. The listed base station.
5. The communication unit selects some terminals from a plurality of terminals that are in a predetermined movement state among the terminals that are communicating, and a reference signal is sent to the terminal that is not in the predetermined movement state among the terminals. A third data channel that is less than the data channel of
   The first terminal is the selected part of the terminals;
   The second terminal is a terminal different from the some of the plurality of terminals.
   The base station according to any one of claims 1 to 4, wherein:
6. 6. The base station according to claim 1, wherein the control information is DCI (Downlink Control Information).
7. Radio information selected from the possible range is transmitted to the first terminal and the second terminal by transmitting information indicating the possible range of the radio resource of the first data channel and the second data channel. The base station according to any one of claims 1 to 6, wherein the base station transmits the first data channel and the second data channel.
8. The base station according to claim 7, wherein information indicating the possible range is transmitted to the first terminal and the second terminal by an RRC (Radio Resource Control) message.
9. From the base station that transmits to the other terminal a first data channel that is transmitted in a frame format including a reference signal that performs wireless communication between the other terminal and the own terminal and has a repetition pattern in the time direction. Receiving control information indicating radio resources of one data channel and a second data channel having a reference signal less than the first data channel or not including the reference signal, and based on the received control information A receiver for receiving the first data channel;
   A processing unit for compensating a frequency offset of the second data channel received by the receiving unit based on a reference signal included in the first data channel received by the receiving unit;
   A terminal comprising:
10. A first terminal;
    A second terminal different from the first terminal;
    A base station that performs radio communication between the first terminal and the second terminal, wherein a first data channel transmitted in a frame format including a reference signal having a repetitive pattern in a time direction is defined as the first data channel. Control information indicating radio resources of the first data channel is transmitted to the second terminal, and a reference signal is less than the first data channel or does not include a reference signal. A base station transmitting a data channel to the second terminal;
    Including
    The second terminal receives the control information and the second data channel from the base station, receives the first data channel based on the received control information, and receives the received first data Compensating for a frequency offset of the received second data channel based on a reference signal included in the channel;
    A communication system characterized by the above.
11. A base station that performs wireless communication between a first terminal and a second terminal different from the first terminal,
    Transmitting a first data channel transmitted in a frame format including a reference signal having a repetition pattern in a time direction to the first terminal;
    Transmitting control information indicating radio resources of the first data channel to the second terminal;
    Transmitting a second data channel with fewer reference signals than the first data channel or no reference signal to the second terminal;
    A processing method characterized by the above.
12. The device
    From the base station that transmits to the other terminal a first data channel that is transmitted in a frame format including a reference signal that performs wireless communication between the other terminal and the own terminal and has a repetition pattern in the time direction. Receiving control information indicating radio resources of one data channel and a second data channel having a reference signal less than the first data channel or not including the reference signal;
    Receiving the first data channel based on the received control information;
    Compensating a frequency offset of the received second data channel based on a reference signal included in the received first data channel;
    A processing method characterized by the above.

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