JP6856726B2 - Communication equipment, communication methods and integrated circuits - Google Patents

Description

The present invention relates to communication devices, communication methods and integrated circuits.

In LTE (Long Term Evolution) Rel.8 (Release 8) formulated by 3GPP (3rd Generation Partnership Project Radio Access Network), SC-FDMA (single-carrier frequency-division multiple-access) is used as the uplink communication method. Was adopted (Non-Patent Documents 1, 2, and 3). SC-FDMA has a small PAPR (Peak-to-Average Power Ratio) and high power utilization efficiency of terminals (UE: User Equipment).

In the LTE uplink, both the data signal (Physical Uplink Shared Channel) and the control signal (Physical Uplink Control Channel) are transmitted in subframe units (Non-Patent Document 1). .. FIG. 1 shows an example of PUSCH subframe configuration in the case of Normal cyclic prefix. As shown in FIG. 1, one subframe consists of two time slots, and a plurality of SC-FDMA data symbols and pilot symbols (called DMRS (Demodulation Reference Signal)) are time-multiplexed in each slot. When the base station receives PUSCH, it uses DMRS to estimate the channel. After that, the base station demodulates / decodes the SC-FDMA data symbol using the channel estimation result. In LTE-A (LTE-Advanced) Rel.10 (Release 10), DFT-S-OFDM (Discrete-Fourier-Transform Spread Orthogonal Frequency Division Multiplexing), which is an extended version of SC-FDMA, can also be used. .. DFT-S-OFDM is a method of expanding the degree of freedom in scheduling by dividing the PUSCH obtained as shown in FIG. 1 into two spectra and mapping each spectrum to a different frequency.

The DMRS multiplexed on PUSCH is generated based on the CAZAC (Constant Amplitude Zero Auto-Correlation) series, which has excellent autocorrelation and cross-correlation characteristics. In LTE, 30 series groups are defined in which CAZAC series with various series lengths (bandwidths) and high correlation are grouped into one group (see, for example, FIG. 2). Each cell is assigned one of the 30 series groups based on the cell-specific ID (cell ID). As a result, a series group having a small correlation with each other is assigned between the cells.

The terminal generates DMRS using the CAZAC series corresponding to the allocated bandwidth among the series groups assigned to the cell to which it belongs, and time-multiplexes DNRS to PUSCH. As a result, DMRS with a large correlation is transmitted between terminals in the same cell, and DMRS with a small correlation is transmitted between terminals in different cells. Here, since the correlation of DMRS between cells is small, even if the interference of DMRS transmitted at the same timing occurs, the interference can be reduced by the window function method or the averaging. On the other hand, in the same cell, different frequencies or times are assigned between the terminals so that they can be orthogonalized so that they do not interfere with each other. It is also possible to assign the same frequency or time between terminals (called MU-MIMO (Multi-user multi-input multi-output)), in which case different cyclic shifts (CS) to the DMRS of each terminal. ), Or by multiplying the two DMRSs in PUSCH by a different orthogonal code (OCC (Orthogonal Cover Code)) between the terminals, the DMRS between the terminals can be orthogonally multiplexed.

In this way, spatial reuse of radio resources is realized by reducing mutual interference between cells by using different series groups. In addition, by applying MU-MIMO in the cell, wireless resources can be used efficiently. By doing so, LTE can realize highly efficient uplink transmission.

Furthermore, in LTE-A Rel.11 (Release 11), a virtual cell ID has been added that allows any series group to be assigned to any terminal regardless of the cell ID of the cell to which it belongs.

By the way, in recent years, the explosive increase in mobile traffic has occurred with the spread of smartphones, and in order to provide users with stress-free mobile data communication services, it is essential to dramatically improve the utilization efficiency of wireless resources. Therefore, in LTE-A Rel.12 (Release 12), Small cell enhancement, in which innumerable small cell base stations forming small cells are arranged, is being studied (Non-Patent Document 4). Small cell enhancement has the advantage that by reducing the coverage and the number of terminals per cell, the wireless resources that can be allocated to each cell can be expanded and the data rate of the terminals can be improved. On the other hand, it is unrealistic to cover all areas with small cells. Further, if a terminal having a high moving speed is connected to a small cell, there is a problem that the frequency of handover increases. Therefore, it is considered that the small cell is developed so as to overlap with the macro cell having a large coverage (see, for example, FIG. 3. It is also called a heterogeneous network (HetNet)). This makes it possible to support all terminals while eliminating coverage holes in macro cells, and to provide large-capacity communication to terminals that require high-speed data communication services with low moving speeds in small cells.

3GPP TS 36.211, “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channels and modulation,” v.11.1.0 3GPP TS 36.212, “Evolved Universal Terrestrial Radio Access (E-UTRA); Multiplexing and channel coding,” v.11.1.0 3GPP TS 36.213, “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures,” v.11.1.0 3GPP TR 36.932, “Scenarios and requirements of LTE small cell enhancements,” v.12.0.0

The network configuration (for example, FIG. 3) being studied in Small cell enhancement has the following characteristics.
(1) The condition and quality of the propagation path for the terminal connected to the small cell are often good. This is because there is a high probability that the distance between the small cell base station and the terminal is short, and communication is likely to occur due to a high received power or a high signal-to-noise ratio (SNR). Also, for the same reason, the transmission power required for the terminal is likely to be small.
(2) Since the coverage of small cells is small, the number of terminals operated at the same time is smaller than that of macro cells. In some cases, the small cell may communicate with only one or two terminals.
(3) Unlike macro cells, small cells are likely not evenly arranged. Small cells may be locally densely distributed or sparsely distributed over a large area.

From the above features, it is assumed that the base station can perform channel estimation with sufficiently high accuracy because the channel condition and quality are good in the uplink of the terminal communicating with the small cell in Small cell enhancement. In addition, since the number of terminals operated simultaneously in each small cell is small, the merit of applying MU-MIMO is small. Therefore, as shown in FIG. 1, it is not always necessary to use 14% or more (1/7 of the total) of PUSCH subframes as DMRS. That is, in the uplink of a terminal that communicates with a small cell, if the DMRS in the PUSCH subframe can be reduced and the reduced wireless resources can be diverted to data (PUSCH), higher terminal throughput can be achieved. ..

Against this background, Small cell enhancement is a technology that improves the data rate per terminal and per subframe by replacing some DMRS of PUSCH with data (in the following explanation, "Reduced DMRS (Reduced DMRS)". The application of) is being considered. For example, if the DMRS contained in the PUSCH subframe shown in Fig. 1 can be reduced by half, the data rate can be improved by about 7%, and if the DMRS can be reduced to 1/4, the data can be as high as 11%. Rate improvement can be realized.

FIG. 4 shows an arrangement pattern (Legacy DMRS pattern) showing arrangement in one subframe of DMRS (Legacy DMRS) up to Rel.11 and an example of an arrangement pattern (Reduced) showing arrangement in one subframe of DMRS in Reduced DMRS. DMRS patterns (1) to (4)) are shown. As shown in FIG. 4, the proportion of DMRS in the Reduced DMRS pattern is smaller than that in the Legacy DMRS pattern. That is, the Reduced DMRS pattern has fewer resources to which DMRS is mapped than the Legacy DMRS pattern.

The Legacy DMRS pattern (FIG. 4A) corresponds to the subframe configuration shown in FIG. 1, and is a pattern in which two DMRSs are arranged in one subframe.

Reduced DMRS patterns (1) and (2) (FIGS. 4B and 4C) are patterns in which one of the two DMRSs included in the Legacy DMRS pattern (FIG. 4A) is replaced with data, respectively. This makes it difficult to apply the Walsh-Hadamard Code (OCC), but it can increase the amount of data allocated and improve the data rate. In addition, if the PUSCH subframes of Reduced DMRS patterns (1) and (2) are connected in time and transmitted continuously, two DMRSs can be used across the two subframes. Multiplexing is also possible (see, for example, FIG. 5A). Similarly, if the PUSCH subframes of Reduced DMRS patterns (2) and (1) are connected in time and transmitted continuously, multiplexing by an orthogonal code becomes possible (see FIG. 5B). Further, in FIG. 5B, since the temporal distance between the DMRSs to be multiplied by the code is smaller than that in FIG. 5A, it is possible to apply MU-MIMO to a terminal having a high moving speed.

Reduced DMRS pattern (3) (Fig. 4D) is a method of distributed mapping of DMRS with a sequence length shorter than the allocated bandwidth into SC-FDMA symbols. By allocating data to resource elements (RE (Resource Element)) to which DMRS is not mapped, the data rate can be improved as in Reduced DMRS patterns (1) and (2). Also, in Reduced DMRS pattern (3), the configuration in which DMRS is placed on two different SC-FDMA symbols in one subframe is maintained, so as in Rel.11 (Fig. 4A), different terminals with orthogonal codes are used. DMRS orthogonal multiplexing is possible. Therefore, Reduced DMRS pattern (3) has the advantage that MU-MIMO can be easily applied. On the other hand, in Reduced DMRS pattern (3), considering that DMRS and data are frequency-multiplexed in the same SC-FDMA symbol, there is a concern that the PAPR of the terminal will increase. However, since the transmission power of the terminal connected to the small cell is likely to be small, increasing the PAPR of the terminal is not a big problem. Further, in Reduced DMRS pattern (3), the resource element to which DMRS is mapped may be shifted between two SC-FDMA symbols including DMRS (not shown). In this case, the channel estimation accuracy can be improved by averaging or interpolating the channel estimates using DMRS included in the two SC-FDMA symbols.

Reduced DMRS pattern (4) (Fig. 4E) is a method of locally mapping DMRS with a sequence length shorter than the allocated bandwidth into the SC-FDMA symbol. Reduced DMRS pattern (4) has the same effect as Reduced DMRS pattern (3) and estimates channel variation in the frequency direction within the band to which DMRS is mapped compared to Reduced DMRS pattern (3). It has the advantage of being easy to use. In the Reduced DMRS pattern (4), the frequency position to which DMRS is mapped and the relative frequency position of DMRS in the two SC-FDMA symbols are not limited to the example shown in FIG. 4E.

The example of Reduced DMRS has been described above.

However, Reduced DMRS is not always effective. For example, when the channel quality of the terminal is good, Reduced DMRS is effective, but when the channel quality is poor, it is desirable to improve the channel estimation accuracy by increasing the energy of DMRS by using Legacy DMRS. Further, when a large interference from the terminal to the peripheral cell is expected, it is necessary to keep the correlation of the interference with the DMRS of the terminal connected to the peripheral cell small by using Legacy DMRS. Furthermore, terminals that support only functions up to Rel.8-11 (Legacy terminals) can only use Legacy DMRS, so when applying MU-MIMO to terminals that support Rel.12 functions and Legacy terminals It is essential to use Legacy DMRS even for terminals that support the Rel.12 function.

It is desirable that such switching between Legacy DMRS and Reduced DMRS can be flexibly controlled according to the judgment of the base station in consideration of ensuring flexibility in uplink scheduling. Further, as described above (FIGS. 4B to 4E), it is conceivable to provide a plurality of arrangement patterns as Reduced DMRS. Therefore, the DMRS pattern suitable for the terminal is selected from the Legacy DMRS and a plurality of DMRS patterns including a plurality of Reduced DMRS patterns according to the channel quality of the terminal, the surrounding conditions, or the data rate required by the terminal. You need to be able to do it.

An object of the present invention is to provide a communication device, a communication method, and an integrated circuit capable of selecting an appropriate DMRS pattern for a terminal from a plurality of DMRS patterns including Legacy DMRS and Reduced DMRS.

The communication device according to one aspect of the present invention is control information used for allocation of PUSCH (Physical Uplink Shared Channel), and determines the arrangement of the uplink DMRS (Demodulation Reference Signal) in the resource element. A transmission unit that transmits the control information to the terminal and a DMRS (Demodulation Reference Signal) that is arranged in the resource element based on the control information and transmitted in combination with the PUSCH are received from the terminal. A configuration including a receiving unit and a circuit unit that estimates a channel based on the received DMRS is adopted.

The communication method according to one aspect of the present invention is control information used for allocation of PUSCH (Physical Uplink Shared Channel), and determines the arrangement of the uplink DMRS (Demodulation Reference Signal) in the resource element. The DMRS (Demodulation Reference Signal), which is transmitted to the terminal, is arranged in the resource element based on the control information, and is transmitted in combination with the PUSCH, is received from the terminal and received. Channel estimation is performed based on the DMRS.

The integrated circuit according to one aspect of the present invention is control information used for allocation of PUSCH (Physical Uplink Shared Channel), and determines the arrangement of the uplink DMRS (Demodulation Reference Signal) in the resource element. A process of transmitting the control information to the terminal and a process of receiving the DMRS (Demodulation Reference Signal) arranged in the resource element based on the control information and transmitted in combination with the PUSCH from the terminal. And the process of performing channel estimation based on the received DMRS, and so on.

According to the present invention, it is possible to select an appropriate DMRS pattern for a terminal from a plurality of DMRS patterns including Legacy DMRS and Reduced DMRS.

Diagram showing the uplink subframe configuration Diagram showing DMRS series group assignment Diagram showing network configuration in Small cell enhancement Diagram showing an example of Legacy DMRS pattern and Reduced DMRS pattern Diagram showing orthogonal multiplexing by OCC using the Reduced DMRS pattern The figure which shows the communication system which concerns on Embodiment 1 of this invention. A block diagram showing a configuration of a main part of a base station according to the first embodiment of the present invention. Block diagram showing the configuration of the base station according to the first embodiment of the present invention. A block diagram showing a configuration of a main part of a terminal according to a first embodiment of the present invention. Block diagram showing the configuration of the terminal according to the first embodiment of the present invention. The figure which shows the correspondence between the DPI and the DMRS pattern which concerns on Embodiment 1 of this invention. The figure which shows the correspondence between the DPI, the DMRS pattern, and the virtual cell ID which concerns on Embodiment 1 of this invention. The figure which shows the correspondence between the DPI and DMRS pattern which concerns on Embodiment 1 of this invention, and ON / OFF of base series group hopping. The figure which shows the notification example of the DMRS pattern which concerns on Embodiment 1 of this invention. The figure which shows the notification example of the DMRS pattern which concerns on Embodiment 1 of this invention. The figure which shows the relationship between the allocated band of PUSCH which concerns on Embodiment 2 of this invention, and each parameter of RIV. The figure which shows the DMRS pattern corresponding to each allocated bandwidth which concerns on Embodiment 2 of this invention. The figure which shows the DMRS pattern corresponding to each allocated bandwidth which concerns on Embodiment 2 of this invention. The figure which shows the correspondence between the allocated bandwidth and DMRS pattern which concerns on Embodiment 2 of this invention. The figure which shows the DMRS pattern corresponding to each allocated bandwidth which concerns on Embodiment 2 of this invention. The figure which shows the correspondence between the start position of the allocated bandwidth and the DMRS pattern which concerns on Embodiment 2 of this invention. The figure which shows the DMRS pattern corresponding to each start position of the allocated bandwidth which concerns on Embodiment 2 of this invention. The figure which shows the correspondence between the A-SRS trigger bit and DMRS pattern which concerns on Embodiment 3 of this invention. The figure which shows the correspondence between the control channel and DMRS pattern which concerns on Embodiment 4 of this invention. The figure which shows the correspondence between the CS field and DMRS pattern which concerns on Embodiment 5 of this invention. The figure which shows the correspondence between the CS field and DMRS pattern which concerns on Embodiment 5 of this invention. The figure which shows the data mapping order which concerns on Embodiment 6 of this invention. The figure which shows the DMRS pattern at the time of ACK / NACK multiplexing which concerns on other embodiment of this invention.

Hereinafter, each embodiment of the present invention will be described in detail with reference to the drawings. In each embodiment, the same components are designated by the same reference numerals, and the description thereof will be duplicated and will be omitted.

(Embodiment 1)
[Outline of communication system]
FIG. 6 shows a communication system according to the present embodiment. The communication system shown in FIG. 6 is composed of a base station 100 in a cell and one or more terminals 200. In FIG. 6, the base station 100 may be a macro cell base station or a small cell base station. Further, the communication system may be a HetNet system in which a macro cell base station and a small cell base station coexist, or a CoMP (Coordinated multipoint) system in which a plurality of base stations cooperate to communicate with a terminal. .. The macro cell and the small cell may be operated at different frequencies or may be operated at the same frequency.

[Configuration of base station 100]
FIG. 7 is a block diagram showing a main part of the base station 100.

The base station 100 shown in FIG. 7 includes a control signal generation unit 11, a transmission unit 12, a reception unit 13, a channel estimation unit 14, and a reception signal processing unit 15.

The control signal generation unit 11 generates a control signal for the terminal 200, and the transmission unit 12 transmits the generated control signal via the antenna. The control signal includes a UL grant that directs the allocation of PUSCH. The UL grant is composed of a plurality of bits and includes information instructing a frequency allocation resource (RB: Resource Block), a modulation / coding method, an SRS (Sounding Reference Signal) trigger, and the like. In addition, the UL grant includes a DMRS pattern indicator (DPI) to specify the DMRS placement pattern (DMRS pattern) when sending the assigned PUSCH. DPI consists of one or more bits. It is assumed that the DMRS pattern candidates that can be selected by DPI are notified or defined in advance to the terminal 200 by the upper layer. Further, the control signal is transmitted using a downlink control channel (PDCCH (Physical downlink control channel) or EPDCCH (Enhanced physical downlink control channel)). The EPDCCH is sometimes called an EPDCCH set, and is arranged in the PDSCH as a new control channel different from the PDCCH.

That is, the control signal generation unit 11 generates uplink control information based on the arrangement pattern instructed to the terminal 200 among the plurality of arrangement patterns of the DMRS of the uplink, and the transmission unit 12 generates the generated control. Send information.

The receiving unit 13 receives the PUSCH transmitted by the terminal 200 in accordance with UL grant via the antenna, and extracts data and DMRS. The channel estimation unit 14 performs channel estimation using DMRS. The received signal processing unit 15 demodulates / decodes the data based on the estimated channel estimated value.

FIG. 8 is a block diagram showing details of the base station 100.

The base station 100 shown in FIG. 8 includes a control unit 101, a control information generation unit 102, a coding unit 103, a modulation unit 104, a mapping unit 105, an IFFT (Inverse Fast Fourier Transform) unit 106, and a CP (Cyclic Prefix) addition unit 107. , Radio transmission unit 108, radio reception unit 109, CP removal unit 110, FFT (Fast Fourier Transform) unit 111, decoding unit 112, CSI (Channel State Information) measurement unit 113, channel estimation unit 114, equalization unit 115, It includes an IDFT (Inverse Discrete Fourier Transform) unit 116, a demodulation unit 117, a decoding unit 118, and a determination unit 119.

Of these, the control unit 101, the control information generation unit 102, the coding unit 103, and the modulation unit 104 mainly function as the control signal generation unit 11 (FIG. 7), and the mapping unit 105, the Fourier unit 106, and the CP addition unit 107. , The wireless transmission unit 108 mainly functions as the transmission unit 12 (FIG. 7). Further, the wireless reception unit 109, the CP removal unit 110, the FFT unit 111, and the demapping unit 112 mainly function as the reception unit 13 (FIG. 7), the channel estimation unit 114 functions as the channel estimation unit 14, and the equalization unit The 115, the IDFT unit 116, the demodulation unit 117, the decoding unit 118, and the determination unit 119 mainly function as the received signal processing unit 15 (FIG. 7).

In the base station 100 shown in FIG. 8, the control unit 101 determines the PUSCH subframe allocation to the terminal 200 according to the state of the terminal 200 or the reception status. For example, the control unit 101 uses the determination result (presence / absence of error; ACK or NACK) of the received data of the terminal 200 input from the determination unit 119, the channel information (CSI) of the terminal 200 input from the CSI measurement unit 113, and the like. Based on this, the PUSCH subframe allocation to the terminal 200 is determined. At this time, the control unit 101 indicates the frequency resource block (RB) allocation information instructed to the terminal 200, the coding method, the modulation method, the information indicating whether it is the first transmission or the retransmission, the process number of the hybrid automatic repeat request (HARQ), and the process number. , DMRS pattern information (DPI) and the like are determined, and the determined information is output to the control information generation unit 102.

Further, the control unit 101 determines the coding level for the control signal for the terminal 200, and outputs the determined coding level to the coding unit 103. The coding level is determined according to the amount of control information included in the control signal to be transmitted or the state of the terminal 200.

Further, the control unit 101 determines a radio resource element (RE) for mapping the control signal for the terminal 200, and instructs the mapping unit 105 of the determined RE.

The control information generation unit 102 generates a control information bit string using the control information for the terminal 200 input from the control unit 101, and outputs the generated control information bit string to the coding unit 103. Since the control information may be transmitted to a plurality of terminals 200, the control information generation unit 102 generates a bit string including the terminal ID of each terminal 200 in the control information for each terminal 200. For example, a CRC bit masked by the terminal ID of the destination terminal 200 is added to the control information.

The coding unit 103 encodes the control information bit string input from the control information generation unit 102 by using the coding level instructed by the control unit 101. The coding unit 103 outputs the obtained coded bit string to the modulation unit 104.

The modulation unit 104 modulates the coding bit string input from the coding unit 103, and outputs the obtained symbol string to the mapping unit 105.

The mapping unit 105 maps the control signal input as a symbol string from the modulation unit 104 to the radio resource instructed by the control unit 101. The control channel to which the control signal is mapped may be PDCCH or EPDCCH. The mapping unit 105 inputs the signal of the downlink subframe including the PDCCH or EPDCCH to which the control signal is mapped to the IFFT unit 106.

The IFFT unit 106 applies IFFT to the downlink subframe input from the mapping unit 105, and converts the signal sequence in the frequency domain into a time waveform. The IFFT unit 106 outputs the converted time waveform to the CP addition unit 107.

The CP addition unit 107 adds a CP to the time waveform input from the IFFT unit 106, and outputs the signal to which the CP is added to the wireless transmission unit 108.

The wireless transmission unit 108 performs transmission processing such as D / A conversion and up-conversion on the signal input from the CP addition unit 107, and transmits the signal after the transmission processing to the terminal 200 via the antenna.

The wireless reception unit 109 receives the uplink signal (PUSCH) transmitted from the terminal 200 via the antenna, performs reception processing such as down-conversion and A / D conversion on the received signal, and after the reception processing. The signal is output to the CP removal unit 110.

The CP removing unit 110 removes a waveform corresponding to the CP from the signal (time waveform) input from the wireless receiving unit 109, and outputs the signal after removing the CP to the FFT unit 111.

The FFT unit 111 applies the FFT to the signal (time waveform) input from the CP removal unit 110, decomposes it into a signal series (frequency elements in the subcarrier unit) in the frequency domain, and corresponds to the subframe of PUSCH. Take out the signal to do. The FFT unit 111 outputs the obtained signal to the demapping unit 112.

The demapping unit 112 extracts the PUSCH subframe portion assigned to the terminal 200 from the input signal. Further, the demapping unit 112 decomposes the extracted PUSCH subframe of the terminal 200 into DMRS and a data symbol (SC-FDMA data symbol), outputs DMRS to the channel estimation unit 114, and equalizes the data symbol. Output to 115. Further, when the terminal 200 transmits a sounding reference signal (SRS) in the subframe of the PUSCH, the demapping unit 112 extracts the SRS and outputs the extracted SRS to the CSI measurement unit 113. When SRS is transmitted, the final data symbol of the PUSCH subframe is replaced with SRS, so the demapping unit 112 may separate the SRS and the data symbol.

When SRS is input from the demapping unit 112, the CSI measurement unit 113 performs CSI measurement using the SRS. The CSI measurement unit 113 outputs the obtained CSI measurement result to the control unit 101.

The channel estimation unit 114 performs channel estimation using the DMRS input from the demapping unit 112. The channel estimation unit 114 outputs the obtained channel estimation value to the equalization unit 115.

The equalization unit 115 equalizes the SC-FDMA data symbol input from the demapping unit 112 by using the channel estimation value input from the channel estimation unit 114. The equalization unit 115 outputs the equalized SC-FDMA data symbol to the IDFT unit 116.

The IDFT unit 116 applies an IDFT having a bandwidth corresponding to the allocated bandwidth to the SC-FDMA data symbol in the frequency domain input from the equalization unit 115, and converts it into a time domain signal. The IDFT unit 116 outputs the obtained time domain signal to the demodulation unit 117.

The demodulation unit 117 demodulates the time domain signal input from the IDFT unit 116. Specifically, the demodulation unit 117 converts the symbol sequence into a bit sequence based on the modulation method instructed to the terminal 200, and outputs the obtained bit sequence to the decoding unit 118.

The decoding unit 118 performs error correction decoding on the bit sequence input from the demodulation unit 117, and outputs the decoded bit sequence to the determination unit 119.

The determination unit 119 detects an error in the bit sequence input from the decoding unit 118. Error detection is performed using CRC bits added to the bit sequence. If the determination result of the CRC bit is correct, the determination unit 119 takes out the received data and notifies the control unit 101 of ACK. On the other hand, if the determination result of the CRC bit is incorrect, the determination unit 119 notifies the control unit 101 of NACK.

[Configuration of terminal 200]
FIG. 9 is a block diagram showing a main part of the terminal.

The terminal 200 shown in FIG. 9 includes a receiving unit 21, a control signal extraction unit 22, a control unit 23, a DMRS generation unit 24, and a transmission unit 25.

The receiving unit 21 receives the control signal (UL grant) transmitted to the terminal 200 on the PDCCH or EPDCCH, and the control signal extraction unit 22 extracts information regarding the allocation of the PUSCH subframe from the control signal. Specifically, the control signal extraction unit 22 can blindly decode the control signal allocation candidates in the preset control channel and decode the control signal to which the CRC bit masked by the terminal ID of the terminal 200 is added. Then, the control signal is extracted as control information addressed to the terminal 200. The control information includes frequency resource block (RB) allocation information, modulation method, information indicating initial transmission or retransmission, HARQ process number, A-SRS trigger (Aperiodic SRS transmission request), and DMRS pattern information (DPI). Etc. are included.

The control unit 23 determines the PUSCH subframe configuration based on the extracted control information (UL grant). For example, the control unit 23 determines the DMRS pattern to be used according to the value of DPI included in the UL grant. The DMRS generation unit 24 generates DMRS according to the instruction from the control unit 23, and the transmission unit 25 transmits the signal of the PUSCH subframe including the DMRS according to the instruction from the control unit 23.

That is, the receiving unit 21 receives the uplink control information, and the control unit 23 determines a specific arrangement pattern from the plurality of uplink DMRS arrangement patterns based on the control information, and the DMRS generation unit. 24 generates DMRS according to a specific arrangement pattern.

FIG. 10 is a block diagram showing details of the terminal 200.

The terminal 200 shown in FIG. 10 has a wireless reception unit 201, a CP removal unit 202, an FFT unit 203, a control signal extraction unit 204, a control unit 205, a coding unit 206, a modulation unit 207, a DMRS generation unit 208, and an SRS generation unit 209. , A multiplex unit 210, a DFT (Discrete Fourier Transform) unit 211, a mapping unit 212, an IFFT unit 213, a CP addition unit 214, and a wireless transmission unit 215.

Of these, the wireless receiving unit 201, the CP removing unit 202, and the FFT unit 203 mainly function as the receiving unit 21 (FIG. 9). Further, the coding unit 206, the modulation unit 207, the SRS generation unit 209, the multiplexing unit 210, the DFT unit 211, the mapping unit 212, the IFFT unit 213, the CP addition unit 213, and the wireless transmission unit 215 are mainly the transmission units 25 (FIG. 9). ) Functions. Further, the control signal extraction unit 204 functions as the control signal extraction unit 22, the control unit 205 functions as the control unit 23, and the DMRS generation unit 208 functions as the DMRS generation unit 24.

In the terminal 200 shown in FIG. 10, the radio receiving unit 201 receives the control signal (PDCCH or EPDCCH) transmitted from the base station 100 (FIG. 8) via the antenna, down-converts the control signal, and A / Receive processing such as D conversion is performed, and the control signal after the reception processing is output to the CP removal unit 202.

The CP removal unit 202 removes the CP from the downlink subframe signal including the PDCCH or EPDCCH in the control signal input from the wireless reception unit 201, and outputs the signal after the CP removal to the FFT unit 203.

The FFT unit 203 applies the FFT to the signal (downlink subframe) input from the CP removal unit 202 and converts it into a frequency domain signal. The FFT unit 203 outputs the frequency domain signal to the control signal extraction unit 204.

The control signal extraction unit 204 blindly decodes the frequency domain signal (PDCCH or EPDCCH) input from the FFT unit 203, and attempts to decode the control signal. A CRC masked by the terminal ID of the terminal 200 is added to the control signal addressed to the terminal 200. Therefore, if the CRC determination is OK as a result of blind decoding, the control signal extraction unit 204 extracts the control signal and outputs it to the control unit 205.

The control unit 205 controls PUSCH transmission based on the control signal input from the control signal extraction unit 204.

Specifically, the control unit 205 instructs the mapping unit 212 to allocate RB at the time of PUSCH transmission based on the RB allocation information of PUSCH included in the control signal. Further, the control unit 205 instructs the coding unit 206 and the modulation unit 207 of the coding method and the modulation method at the time of PUSCH transmission, respectively, based on the information of the coding method and the modulation method included in the control signal. Further, the control unit 205 instructs the SRS generation unit 209 whether or not to transmit the SRS after a lapse of a certain period of time based on the SRS trigger included in the control signal. The SRS specified by this SRS trigger may be multiplexed to the PUSCH subframe specified by UL grant and transmitted, or may be transmitted at a time later than that subframe. Further, the control unit 205 determines the DMRS pattern at the time of PUSCH transmission based on the DPI included in the control signal, and instructs the DMRS generation unit 208 of the determined DMRS pattern.

The coding unit 206 adds a CRC bit masked by the terminal ID to the input transmission data and performs error correction coding. The coding rate, codeword length, and the like used by the coding unit 206 are instructed by the control unit 205. The coding unit 206 outputs the coded bit sequence to the modulation unit 207.

The modulation unit 207 modulates the bit sequence input from the coding unit 206. The modulation level (that is, the number of modulation multi-values) used by the modulation unit 207 is instructed by the control unit 205. The modulation unit 207 outputs the modulated data symbol sequence to the multiplexing unit 210.

The DMRS generation unit 208 generates DMRS according to the DMRS pattern instructed by the control unit 205, and outputs the DMRS to the multiplexing unit 210.

The SRS generation unit 209 generates SRS according to the instruction from the control unit 205, and outputs the SRS to the multiplexing unit 210. The SRS transmission timing is not always the same as the PUSCH subframe specified by UL grant.

The multiplexing unit 210 multiplexes the data symbol series, DMRS and SRS input from the modulation unit 207, the DMRS generation unit 208 and the SRS generation unit 209, respectively, and outputs the signal after the multiplexing to the DFT unit 211.

The DFT unit 211 applies DFT to the signal input from the multiplexing unit 210, decomposes the signal into a frequency component signal for each subcarrier, and outputs the obtained frequency component signal to the mapping unit 212. ..

The mapping unit 212 maps the signal (that is, data symbol sequence, DMRS and SRS) input from the DFT unit 211 to the time / frequency resource in the assigned PUSCH subframe according to the instruction from the control unit 205. The mapping unit 212 outputs the PUSCH subframe signal to the IFFT unit 213.

The IFFT unit 213 applies IFFT to the PUSCH subframe signal in the frequency domain input from the mapping unit 212 and converts it into a time domain signal. The IFFT unit 213 outputs the obtained time domain signal to the CP addition unit 214.

The CP addition unit 214 adds a CP to the time domain signal (for each output unit of the IFFT unit 213) input from the IFFT unit 213, and outputs the signal after the CP addition to the wireless transmission unit 215.

The wireless transmission unit 215 performs transmission processing such as D / A conversion and up-conversion on the signal input from the CP addition unit 214, and transmits the signal after the transmission processing to the base station 100 via the antenna.

[motion]
The processing flow of the base station 100 and the terminal 200 of the present embodiment will be described in steps (1) to (4).

Step (1): The base station 100 notifies the terminal 200 that a plurality of DMRS patterns can be specified prior to the transmission / reception of PUSCH. The DMRS pattern that can be specified may be defined in advance, and the base station 100 may notify the terminal 200 from a plurality of candidates via a higher layer. DMRS patterns that can be specified include, for example, Reduced DMRS patterns as shown in FIGS. 4B-4E and 5, in addition to the Legacy DMRS pattern used in Rel.8-10 (see, eg, FIG. 4A).

The notification to the terminal 200 in step (1) may be performed by the base station 100 that transmits / receives PUSCH, or may be performed by a base station 100 other than the base station that transmits / receives PUSCH. For example, the base station 100 for transmitting and receiving PUSCH may be a small cell base station, and the base station for notifying step (1) may be a macro cell base station.

Step (2): The base station 100 transmits a control signal (UL grant) to the terminal 200 via the PDCCH or EPDCCH to instruct the allocation of PUSCH. UL grants include a DMRS pattern indicator (DPI) that indicates a DMRS pattern. The DPI instructs the terminal 200 to specify any one specific DMRS pattern from the plurality of DMRS pattern candidates. That is, the base station 100 (control unit 101) generates a DPI based on a specific DMRS pattern instructed to the terminal 200.

FIG. 11 shows an example in which the DPI is 2 bits. In FIG. 11, Legacy DMRS pattern and Reduced DMRS patterns (1) to (3) are associated with each value of DPI.

The transmission of the UL grant including the DPI to the terminal 200 may be performed by the base station 100 that transmits / receives PUSCH, or may be performed by a base station 100 other than the base station that transmits / receives PUSCH. For example, the base station 100 that transmits and receives PUSCH may be a small cell base station, and the base station that transmits UL grant may be a macrocell base station.

Step (3): The terminal 200 blindly decodes the PDCCH or EPDCCH received in step (2) to obtain a control signal (UL grant) addressed to its own terminal. When the UL grant includes the DPI, the terminal 200 (control unit 205) determines a specific DMRS pattern used by the terminal 200 from a plurality of DMRS pattern candidates based on the DPI. Then, the terminal 200 (DMRS generation unit 208) generates DMRS to be used for PUSCH transmission according to a specific DMRS pattern.

Step (4): The base station 100 receives the PUSCH transmitted by the terminal 200 in the step (3), and performs channel estimation based on the DMRS extracted from the PUSCH subframe. Base station 100 uses the obtained channel estimates to equalize, demodulate, and decode data symbols.

When it is determined that the data can be correctly decoded, the base station 100 transmits an ACK to the terminal 200 to prompt the transmission of the next data. When it is determined that the data decoding result contains an error, the base station 100 transmits NACK to the terminal 200 to prompt the retransmission of HARQ.

[effect]
As described above, the base station 100 instructs the terminal 200 on any of a plurality of predetermined DMRS patterns by using the DPI included in the UL grant on the downlink control channel (PDCCH or EPDCCH). .. The terminal 200 identifies the DMRS pattern in the PUSCH subframe according to the DPI included in the UL grant transmitted from the base station 100.

By doing so, the DMRS pattern of the terminal 200 can be dynamically switched. Therefore, according to the present embodiment, it is possible to select an appropriate DMRS pattern for the terminal 200 from a plurality of DMRS patterns including Legacy DMRS and Reduced DMRS.

For example, the base station 100 dynamically switches between a DMRS pattern (Legacy DMRS pattern) that can be received with high channel estimation accuracy and a DMRS pattern (Reduced DMRS pattern) with low overhead according to the situation or environment of the terminal 200. be able to. Therefore, according to the present embodiment, high reliability and an increase in communication capacity can be flexibly realized.

Further, for example, when the Legacy terminal (for example, a terminal supporting the function of Rel.10) exists in the cell, the base station 100 instructs the terminal 200 to use the Legacy DMRS, and the Legacy terminal and the terminal 200. And may be spatially multiplexed by CS and OCC. Further, the base station 100 may instruct the terminal 200 to use Reduced DMRS and cause the terminal 200 to transmit data using a low overhead PUSCH subframe. In this way, the base station 100 can flexibly instruct the scheduling of the uplink to the terminal 200. Therefore, according to the present embodiment, it is possible to avoid characteristic deterioration due to scheduling restrictions.

Further, in particular, since the number of terminals that simultaneously communicate with each other is small in a small cell, it is assumed that the downlink control channel is not congested. Furthermore, in a small cell, the distance between the terminal and the small cell base station is relatively short, so even if a new DPI bit is added to the control signal, the reduction in coverage does not matter. That is, according to the present embodiment, by notifying the DMRS pattern using the DPI, it is possible to flexibly switch the DMRS pattern without any major demerit.

[Variation 1]
In variation 1, the DPI represents a DMRS pattern and a virtual cell ID (VCID) or cell ID (PCID).

Specifically, the base station 100 notifies the terminal 200 in advance not only the DMRS pattern that can be instructed but also the virtual cell ID corresponding to the value of each DPI. Then, the base station 100 uses the DPI to instruct the use of the DMRS pattern and the virtual cell ID (or cell ID) corresponding to the DMRS pattern. The terminal 200 identifies the DMRS pattern and the virtual cell ID (or cell ID) based on the DPI, and generates the DMRS.

FIG. 12 shows the correspondence between the DPI and the DMRS pattern and the virtual cell ID. For example, in FIG. 12, when the DPI is 00, the terminal 200 generates DMRS using the Legacy DMRS pattern and the base sequence corresponding to the cell ID. When the DPI is 10, the terminal 200 generates DMRS using the Reduced DMRS (Pattern 2) and the base sequence corresponding to the virtual cell ID 1 (VCID 1). The same applies when the DPI is 01 and 11.

As described above, Reduced DMRS is often used when the channel state of the terminal 200 is good (for example, when the distance between the terminal 200 and the base station 100 is relatively short). Such a case is likely to occur when the terminal 200 is connected to a small cell base station. Further, it is considered that the small cell base stations are arranged in a non-uniform manner, such as being arranged in a large number at a high density or being arranged at a low density and sparsely.

Therefore, the interference is orthogonalized by notifying a plurality of small cell base stations of the same virtual cell ID, or the interference is randomized by notifying different virtual cell IDs, and the virtual cell ID is used. Interference control between small cells may be performed more flexibly. In other words, Reduced DMRS and virtual cell ID are likely to be operated at the same time.

Therefore, as shown in FIG. 12, the DMRS pattern and the virtual cell ID are simultaneously notified from the base station 100 to the terminal 200 using the DPI, so that the use of both the Reduced DMRS and the virtual cell ID is instructed only by the DPI. Therefore, it is possible to more flexibly and appropriately realize interference control between small cells while suppressing an increase in overhead.

[Variation 2]
In variation 2, the DPI shows the DMRS pattern and the base series group hopping ON / OFF.

Here, base series group hopping has been introduced from Rel.8, and cells are created by hopping the group number of the base series group so that DMRS is generated using a different base series group for each DMRS transmission. This is a method for further reducing the interference between the two. On the other hand, when base series group hopping is performed, there is a problem that OCC cannot perform inter-terminal multiplexing because the base series used for each of the two DMRSs in the PUSCH subframe is different. Therefore, in Rel.10, the function to turn on / off the base series group hopping quasi-statically was added by the notification from the upper layer, and OCC multiplexing was realized.

Therefore, the base station 100 notifies the terminal 200 in advance of ON / OFF of the base series group hopping corresponding to the value of each DPI as well as the DMRS pattern that can be instructed. Then, the base station 100 uses DPI to instruct ON / OFF of the DMRS pattern and the base series group hopping corresponding to the DMRS pattern. The terminal 200 identifies the ON / OFF of the DMRS pattern and the base series group hopping based on the DPI, and generates the DMRS.

FIG. 13 shows the correspondence between DPI and ON / OFF of DMRS pattern and base series group hopping. For example, in FIG. 13, when the DPI is 00, the terminal 200 uses Legacy DMRS and turns on base series group hopping to generate DMRS. When the DPI is 11, the terminal 200 uses Reduced DMRS (Pattern 2) and turns off the base series group hopping to generate DMRS. The same applies when the DPI is 01 and 10.

FIG. 14 shows an example in the case where the DMRS pattern and the base series group hopping ON / OFF are notified using the DPI shown in FIG. 13 in each subframe. Note that FIG. 14 shows four subframes, and each subframe is composed of two slots.

As shown in FIG. 14, since the terminal 200 is instructed to have DPI = “00” in the first and fourth subframes, the base series of the two DMRSs in the subframes is used while using the Legacy DMRS. Hopping groups (series group numbers: # 3, # 15). This makes it possible to randomize interference with other cells.

Further, as shown in FIG. 14, since the terminal 200 is instructed to have DPI = “01” in the second subframe, the cell ID is not performed by using Legacy DMRS without hopping the base series group. Alternatively, DMRS is generated using a series determined by the virtual cell ID (here, series group number: # 3). This makes it possible for OCC to orthogonalize the interference.

Further, as shown in FIG. 14, since the terminal 200 is instructed to have DPI = “11” in the third subframe, DMRS is generated using Reduced DMRS without hopping the base series group. To do. This makes it possible to reduce the overhead of Reduced DMRS.

Interference can be randomized by turning on base series group hopping, but OCC cannot orthogonalize the interference. On the other hand, when the base series group hopping is turned off, orthogonalization by OCC is possible, but the interference is not randomized. On the other hand, as shown in FIG. 14, the base station 100 simultaneously instructs the DMRS pattern and the base series group hopping ON / OFF using the DPI. As a result, the terminal 200 can dynamically switch ON / OFF of the DMRS pattern and the base series group hopping according to the state of the terminal 200, interference with surrounding cells, or the presence or absence of spatially multiplexed terminals. it can. Therefore, according to the variation 2, interference suppression and increase in throughput can be realized more flexibly.

[Variation 3]
In variation 2 (FIG. 14), when the base sequence group hopping was OFF, the sequence determined by the cell ID or virtual cell ID was used in all slots (series group number: # 3 in FIG. 14). On the other hand, in variation 3, when the base series group hopping is OFF in a certain subframe, the terminal 200 is used in the first slot in the subframe when the series group hopping is ON. Series group is used in two slots in the subframe.

FIG. 15 shows an example of the case where the DMRS pattern and the base series group hopping ON / OFF are notified using the DPI shown in FIG. 13 in each subframe. Note that FIG. 15 shows four subframes as in FIG. 14, and each subframe is composed of two slots.

As shown in FIG. 15, since DPI = “01” is specified in the second subframe, hopping of the base series group is not performed. On the other hand, the DMRS series group number used in the first slot when the base series group is hopping in the second subframe is # 6. Therefore, in the second subframe, the terminal 200 uses the Legacy DMRS to generate the DMRS using the series group number # 6 without hopping the base series group.

Similarly, as shown in FIG. 15, since DPI = “11” is specified in the third subframe, hopping of the base series group is not performed. On the other hand, the DMRS series group number used in the first slot when the base series group is hopping in the third subframe is # 7. Therefore, in the third subframe, the terminal 200 generates DMRS using Reduced DMRS and series group number # 7 without hopping the base series group.

That is, in variation 2 (FIG. 14), DMRS of series group number # 3 was always used when series group hopping was OFF, whereas in variation 3 (FIG. 15), series group hopping was OFF. In the case (second and third subframes), the series group number is also changed.

By doing so, the DMRS series group used is switched at least every 1 ms (1 subframe) in any terminal 200, so in addition to the effect of variation 2, the interference given to other peripheral cells is randomized. The effect is obtained.

(Embodiment 2)
[Outline of communication system]
The communication system according to the present embodiment is composed of the base station 100 and one or more terminals 200 as in the first embodiment (FIG. 6).

However, in the present embodiment, unlike the first embodiment, the DPI that indicates the DMRS pattern is not used, and the RB allocation information and the DMRS pattern are simultaneously used depending on the value of the Resource Indication Value (RIV) included in the UL grant. Instructed. That is, the plurality of DMRS patterns are associated with each value of RIV, which is the existing RB allocation information of the uplink included in the control information transmitted from the base station 100 to the terminal 200. That is, the DMRS pattern is notified using the existing RIV.

Specifically, the terminal 200 is notified in advance of a plurality of DMRS patterns that can be instructed, and is notified in advance of DMRS patterns corresponding to each value of RIV. Then, the terminal 200 specifies the RB used for PUSCH subframe transmission based on the RIV value notified from the base station 100, and determines the DMRS pattern corresponding to the RIV as the DMRS pattern used in the PUSCH subframe. To do. The plurality of DMRS patterns that can be instructed and the DMRS patterns corresponding to each value of RIV may be notified in advance by the base station 100 to the terminal 200 in a higher layer or the like, and only a specified combination is used. You may.

[Configuration of base station 100]
The control unit 101 of the base station 100 determines the PUSCH subframe allocation to the terminal 200. At this time, the control unit 101 determines the value of the RB allocation information (RIV) in consideration of both the RB assigned to the terminal 200 and the DMRS pattern notified to the terminal 200.

[Configuration of terminal 200]
The control unit 205 of the terminal 200 instructs the mapping unit 212 to allocate the RB at the time of PUSCH transmission based on the value of the RIV included in the UL grant. Further, the control unit 205 determines the DMRS pattern at the time of PUSCH transmission based on the value of RIV.

[motion]
The operation of the base station 100 and the terminal 200 of this embodiment will be described. The processing flow of the base station 100 and the terminal 200 according to the present embodiment is substantially the same as in steps (1) to (4).

However, unlike the first embodiment, the UL grant does not include the DPI in the present embodiment. Instead, the base station 100 sets the RIV value based on the DMRS pattern instructed to the terminal 200, and the terminal 200 sets the DMRS pattern used in the PUSCH subframe based on the RIV value included in the UL grant. To determine.

Note that RIV is information notified by the number of bits according to the system bandwidth (for example, Log ₂ (N _RB ^UL (N _RB ^UL +1) / 2) bits when PUSCH is not frequency hopping), and is the information of RIV. The value is determined based on the following equation (1) (without PUSCH frequency hopping).

Here, N _RB ^UL represents the system bandwidth of the uplink, L _CRBs represents the number of allocated RBs _{of the terminal 200, and RB START} represents the lowest frequency RB of the allocated RBs of the terminal 200. Further, the equation (1) is used in the case of continuous band allocation. From the RIV value shown in the equation (1), the number of RBs assigned to the terminal 200 and the position of the RB are uniquely determined (see FIG. 16). There is a restriction that L _CRBs can only be selected in multiples of 2, 3, and 5. Therefore, in the mechanism up to Rel.11, the value of RIV corresponding to _{L CRBs} other than multiples of 2, 3 and 5 is not specified.

[effect]
In this way, the base station 100 notifies the terminal 200 of any of the plurality of DMRS patterns by using the frequency resource allocation information (RIV) that indicates the frequency resource allocation information bit included in the UL grant. The terminal 200 identifies the DMRS pattern to be used from the plurality of DMRS patterns based on the RIV value included in the received UL grant.

As described above, it is highly possible that the Reduced DMRS is instructed to the terminal 200 when communicating with a small cell base station. Further, it is highly possible that the number of terminals communicating with the small cell is small and the channel quality of the terminal communicating with the small cell is good. Therefore, in a small cell, the frequency scheduling gain cannot be increased even if the frequency scheduling granularity is made finer. In other words, even if the particle size of frequency scheduling is reduced and the DMRS pattern is specified accordingly, the effect of the disadvantages hardly occurs. Therefore, as in the present embodiment, by specifying the DMRS pattern used in the terminal 200 according to the value of RIV, the DMRS pattern can be flexibly switched.

Further, in the present embodiment, since the DMRS pattern is notified using the existing RIV, the additional bit for instructing the DMRS pattern becomes unnecessary, and the overhead does not increase.

Next, the notification / specific specific examples 1 to 4 of the DMRS pattern of the base station 100 and the terminal 200 in the present embodiment will be described in detail.

[Specific example 1]
The base station 100 sets the value of the number of allocated RBs (that is, the allocated bandwidth) L _{CRBs in} the RIV to either an even number or an odd number in consideration of the DMRS pattern. The terminal 200 specifies the DMRS pattern to be used according to whether the value of the number of allocated RBs (allocated bandwidth) L _{CRBs in the RIV included in the UL grant is even or odd.}

For example, a Legacy DMRS pattern is associated with an RIV indicating an odd number of RB allocations, and a Reduced DMRS pattern is associated with an RIV indicating an even number of RB allocations. That is, the terminal 200, the base station 100, using the Legacy DMRS if RIV where L _CRBS corresponds to an odd number of RB is informed, if the RIV where L _CRBS corresponds to an even number of RB is informed Reduced DMRS is used for.

The correspondence between the number of allocated RBs (even and odd numbers) shown in L _CRBs and whether or not to use Reduced DMRS is specified in advance, or the base station 100 and the terminal are notified by notification of the upper layer. It is shared with 200. Further, the pattern of Reduced DMRS specified by RIV may be defined in advance, or may be notified from the base station 100 to the terminal 200 in an upper layer or the like.

FIG. 17 shows an example of notification of the DMRS pattern in Specific Example 1. In FIG. 17, as the Reduced DMRS, for example, the Reduced DMRS pattern (3) shown in FIG. 4D is used.

As shown in FIG. 17, _{when the number of L CRBs} in the RIV notified by UL grant is an odd number (1RB or 3RB), the Legacy DMRS pattern is used as the DMRS pattern. _{On the other hand, when the number of L CRBs} in the RIV notified by UL grant is an even number (2RB or 4RB), the Reduced DMRS pattern (3) is used as the DMRS pattern.

In FIG. 17, one type of Reduced DMRS pattern is associated with an even number of _{L CRBs,} but among a plurality of Reduced DMRS patterns for different values of _{L CRBs (for example, 2RB and 4RB).} You may associate different patterns with each other.

Here, in the existing DMRS, the series length corresponding to the _{integer L CRBs is defined.} Therefore, if L _CRBs are even, there is a DMRS with half the sequence length of _{L CRBs.} On the other hand, when L _CRBs are odd, it is not possible to define a series length obtained by dividing _{L CRBs by a power of 2 (for example, 2).}

Therefore, when L _CRBS is even, the terminal 200, even with Reduced DMRS pattern such that DMRS half sequence length L _CRBS, using existing DMRS half sequence length L _CRBS be able to. That is, as shown in FIG. 17, by _specifying that Reduced DMRS is used only when _{L CRBs are even numbers and Legacy DMRS is used when L CRBs} are odd numbers, the terminal 200 is an existing series. Only long DMRS can be used to generate DMRS with half the bandwidth of PUSCH. In other words, when using Reduced DMRS, there is no need to newly define a DMRS with a series length other than the existing series length.

In addition, Reduced DMRS is likely to be used in small cells, has weak channel quality frequency selectivity, and is expected to have a small number of terminals that communicate simultaneously. In other words, Reduced DMRS is likely to be used in an environment where coarse frequency scheduling does not have any disadvantages. Therefore, by associating the number of allocated RBs (allocated bandwidth) in RIV with the DMRS pattern, the flexibility of RIV is restricted, but the disadvantages of this restriction have almost no effect, and dynamic notification of Reduced DMRS is realized. be able to.

[Variation of Specific Example 1]
Here, the RIV indicating the allocation of the odd number of RBs is associated with the allocation of the odd number + 1 RB and the Reduced DMRS pattern, and the RIV indicating the allocation of the even number of RBs is associated with the even number of RBs. Assignment and Legacy DMRS pattern are associated.

That is, the terminal 200, the base station 100, is used Reduced DMRS the RB number as (L _CRBS +1) when RIV where L _CRBS corresponds to an odd number of RB is informed, L _CRBS is an even number When the RIV corresponding to RB is notified, Legacy DMRS is used with the _{number of RBs as L CRBs.}

The correspondence between the number of allocated RBs (even and odd numbers) shown in L _CRBs and whether or not to use Reduced DMRS is specified in advance, or the base station 100 and the terminal are notified by notification of the upper layer. It is shared with 200. Further, the pattern of Reduced DMRS specified by RIV may be defined in advance, or may be notified from the base station 100 to the terminal 200 in an upper layer or the like.

FIG. 18 shows an example of notification of the DMRS pattern in the variation of Specific Example 1. In FIG. 18, as in FIG. 17, as the Reduced DMRS, for example, the Reduced DMRS pattern (3) shown in FIG. 4D is used.

As shown in FIG. 18, when the _{number of L CRBs} in the RIV notified by UL grant is an even number (2RB or 4RB), the allocated bandwidth is _{set according to the L CRBs} , and the Legacy DMRS pattern is used as the DMRS pattern. On the other hand, as shown in FIG. 18, _{when the number of L CRBs} in the RIV notified by UL grant is an odd number ( _1RB or 3RB), the allocated bandwidth is set according to (L CRBs +1, that is, 2RB or 4RB). Reduced DMRS pattern (3) is used as the DMRS pattern.

By doing so, unlike the specific example 1 (FIG. 17), the allocated bandwidth (odd number of allocated RBs) that cannot be specified for the terminal 200 that can notify the Reduced DMRS is generated, but the same allocated bandwidth (even number) is generated. Legacy DMRS and Reduced DMRS can be selected in the number of allocated RBs). That is, since the terminal 200 can select one DMRS pattern from a plurality of DMRS patterns including Legacy DMRS and Reduced DMRS in the same allocated bandwidth, it is necessary to change the bandwidth for DMRS pattern selection. Absent. Therefore, the circuit configuration and algorithm of the scheduler can be simplified.

The terminal 200 uses the Legacy DMRS the RB number as (L _CRBS +1) if the RIV where L _CRBS corresponds to an odd number of RB is informed, L _CRBS corresponds to an even number of RB RIV When notified, Reduced DMRS may be used with the number of RBs as L _CRBs.

Further, the RIV indicating the allocation of the odd number of RBs may be associated with the allocation of the odd number of RBs and the Reduced DMRS pattern.

[Specific example 2]
The base station 100 sets the value of the number of allocated RBs (allocated bandwidth) L _{CRBs in the RIV in consideration of the DMRS pattern. The terminal 200 compares} the value of the allocated RB number (allocated bandwidth) L CRBs with the predetermined value in the RIV included in the UL grant, and specifies the DMRS pattern to be used.

For example, a Legacy DMRS pattern is associated with a RIV showing an allocated bandwidth of a predetermined value x or less, and a Reduced DMRS pattern is associated with a RIV showing an allocated bandwidth wider than a predetermined value x. That is, the terminal 200, the RIV notified from the base station 100, if L _CRBS satisfies 0 <L _CRBs ≦ x by using the Legacy DMRS, if L _CRBS satisfies x <L _CRBs ≦ N _RB ^UL Reduced DMRS is used for.

That is, the DMRS pattern used by the terminal 200 is switched for each bandwidth range allocated to the terminal 200.

Whether or not to use Reduced DMRS when x <L _CRBs ≤ N _RB ^UL is satisfied is specified in advance or shared between the base station 100 and the terminal 200 by notification of the upper layer or the like. It is assumed that there is. Further, _{the pattern of Reduced DMRS specified by L CRBs} may be defined in advance, or may be notified from the base station 100 to the terminal 200 in an upper layer or the like.

Further, it is assumed that the predetermined value x (0 <x <N _RB ^UL ) is specified in advance or shared between the base station 100 and the terminal 200 by notification of an upper layer or the like.

Further, a plurality of values (x ₁ , x ₂ , ...) _Are notified as x, and the DMRS pattern used by the terminal 200 may be switched from among the plurality of DMRS patterns according to the value of L CRBs.

19 and 20 show an example of DMRS pattern notification when a plurality of predetermined values x ₁ , x ₂ , and x _{3 are used.}

In FIG. 19, x ₁ = 2, x ₂ = 8, and x ₃ = 15 are set. Let N _RB ^UL = 25. In this case, _{Legacy DMRS is used when 0 <L CRBs} ≤ x ₁ is satisfied (L _CRBs = 1 to 2), and when x ₁ <L _CRBs ≤ x ₂ is satisfied (L _CRBs = 3 to 8). When Reduced DMRS pattern (1) is used and x ₂ <L _CRBs ≤ x ₃ is satisfied (L _CRBs = 9 to 15), Reduced DMRS pattern (2) is used and x ₃ <L _CRBs ≤ N _RB ^UL. If the condition is satisfied (L _CRBs = 16 to 25), the Reduced DMRS pattern (3) is used. Here, as shown in FIG. 20, the Reduced DMRS pattern (1) shown in FIG. 19 corresponds to the Reduced DMRS pattern (1) shown in FIG. 4B, and the Reduced DMRS patterns (2) and (3) are The SC-FDMA symbol is used to replace one of the two DMRSs contained in the Legacy DMRS pattern (Fig. 4A) with data, and to replace the DMRS with a sequence length shorter than the allocated bandwidth in the remaining DMRS frequency resources. It is a method of distributed mapping inside.

As described above, in the specific example 2, when _{the bandwidth of the RB portion whose RIV is equal to or less than the predetermined value (x 1 in} FIGS. 19 and 20) is specified, the Legacy DMRS is selected, and the RB portion whose RIV is larger than the predetermined value is selected. When specifying the bandwidth of, one DMRS pattern is selected from one or more Reduced DMRS patterns.

The terminal 200 that can use Reduced DMRS is often connected to a small cell or has good channel quality. In such a case, there is a high possibility that the bandwidth allocated to the terminal 200 is wide. That is, the better the channel state of the terminal 200, the wider the band is likely to be allocated. Also, the better the channel state of the terminal 200, the more accurate the channel estimation can be with DMRS with less energy or less resources.

Therefore, as in Specific Example 2, the DMRS pattern is changed for each allocated bandwidth of the terminal 200, and at that time, the wider the bandwidth is allocated, the smaller the energy or resource of the DMRS is, and that amount is allocated to the data. Is possible. That is, as shown in FIGS. 19 and 20, the wider the allocated bandwidth, the lower the density of DMRS within the subframe.

In this way, the terminal 200, which has good channel quality and requires a high data rate, is given more data resources and high throughput by instructing a wide allocated bandwidth and Reduced DMRS. can do. On the other hand, for the terminal 200 that requires high channel estimation accuracy or the terminal 200 that requires MU-MIMO with the Legacy terminal, a narrow allocated bandwidth is instructed and a Legacy DMRS is instructed to channel. It is possible to improve the estimation accuracy or apply MU-MIMO.

[Specific example 3]
The base station 100 sets the value of the _{RB position RB START having} the lowest allocated bandwidth in the RIV in consideration of the DMRS pattern. _{The terminal 200 compares the value of the RB position RB START} with the predetermined value in the RIV included in the UL grant to specify the DMRS pattern to be used.

For example, a Legacy DMRS pattern is associated with a RIV whose lowest frequency in the allocated band is higher than a predetermined value y, and a Reduced DMRS pattern is associated with a RIV whose lowest frequency in the allocated band is equal to or less than a predetermined value y. That is, the terminal 200, the RIV notified from the base station 100, if the RB _START satisfies 0 ≦ RB _START ≦ y by using the Reduced DMRS, if RB _START satisfies y _{<RB START} <N RB ^UL Legacy DMRS is used for.

That is, the DMRS pattern used by the terminal 200 is switched for each start position of the band allocated to the terminal 200.

Whether or not to use Reduced DMRS when 0 ≤ RB _START ≤ y is satisfied is specified in advance or shared between the base station 100 and the terminal 200 by notification of the upper layer or the like. And. Further, _{the pattern of Reduced DMRS specified by RB START} may be defined in advance, or may be notified from the base station 100 to the terminal 200 in an upper layer or the like.

Further, it is assumed that the predetermined value y (0 ≦ y <N _RB ^UL ) is defined in advance or shared between the base station 100 and the terminal 200 by notification from the upper layer or the like.

Further, a plurality of values (y ₁ , y ₂ , ...) Are notified as y, and the DMRS pattern used by the terminal 200 may be switched from among the plurality of DMRS patterns according to the value of _{RB START.}

21 and 22 show an example of notification of the DMRS pattern when a plurality of predetermined values y ₁ , y ₂ , and y _{3 are used.}

In FIG. 21, y ₁ = 10, y ₂ = 15, and y ₃ = 20 are set. Let N _RB ^UL = 25. In this case, _{Reduced DMRS pattern (3) is used when 0 ≤ RB START} ≤ y ₁ is satisfied (RB _START = 0 to 10), and when y ₁ <RB _START ≤ y ₂ is satisfied (RB _START = 11 ~). Reduced DMRS pattern (2) is used for 15), and Reduced DMRS pattern (1) is used when y ₂ <RB _START ≤ y ₃ (RB _START = 16 to 20), and y ₃ <RB _START. Legacy DMRS is used when ≤ N _RB ^UL is satisfied (RB _{START = 21-25).} Here, as in Specific Example 2, as shown in FIG. 22, the Reduced DMRS pattern (1) shown in FIG. 21 corresponds to the Reduced DMRS pattern (1) shown in FIG. 4B, and the Reduced DMRS pattern (2). , (3) replace one of the two DMRSs included in the Legacy DMRS pattern (Fig. 4A) with data, and in the remaining DMRS frequency resources, the DMRS with a sequence length shorter than the allocated bandwidth. Is a method of distributed mapping in SC-FDMA symbols.

As described above, in the specific example 3, when the RIV _{specifies the RB start position larger than the predetermined value (y 3 in} FIGS. 21 and 22), the Legacy DMRS is selected, and the RB start position where the RIV is equal to or less than the predetermined value is selected. When specified, one DMRS pattern is selected from one or more Reduced DMRS patterns.

As mentioned above, PUSCH resource allocation is indicated by the starting position of the allocated RB (the lowest frequency RB number, the starting point) and the bandwidth from the starting position (the number of consecutive RBs in the high frequency direction) (Figure). 16). Therefore, in order to allocate a wide band to the terminal 200, the base station 100 _{must notify the RIV so that the start position RB START} is the RB number of the lower frequency (see, for example, FIG. 22). Further, Reduced DMRS is likely to be instructed by the terminal 200 having good channel quality, and is expected to be effective in an environment where RB allocation in a wider band is performed.

On the other hand, in Specific Example 3, Reduced DMRS is instructed when _{RB START} is a low frequency RB number, and Legacy DMRS is instructed when _{RB START is a high frequency RB number.} That is, according to the specific example 3, the base station 100 can allocate a wide band RB to the terminal 200 when instructing Reduced DMRS, and assigns a narrow band RB to the terminal 200 when instructing Legacy DMRS. It will be possible.

As a result, the terminal 200 can use the Reduced DMRS at the time of RB allocation in a wider band. Therefore, it is possible to reduce the overhead of the terminal 200 in good condition such that a wide band is allocated, and to achieve higher throughput.

Further, in the third embodiment, the base station 100 can concentrate the allocation of the terminal 200 instructed by the Legacy DMRS on the high frequency RB. This makes it possible to prevent interference between the Legacy terminal and the terminal 200 (terminal assigned to the low frequency RB) that can use Reduced DMRS.

[Specific example 4]
As mentioned above, in PUSCH before _Rel.11 , the bandwidth L CRBs that can be specified by UL grant are limited to the number of RBs that are multiples of 2, 3, and 5. Therefore, there are some RIV values that are not notified, for example, when the bandwidth (L _{CRBs) shows 7 RB.}

Therefore, in the fourth embodiment, the base station 100 notifies the terminal 200 of the use of Reduced DMRS by using the value of RIV that is not used in PUSCH before Rel.11. That is, the plurality of DMRS patterns are associated with the RIV value corresponding to the bandwidth other than the bandwidth that can be allocated by the RIV (that is, the bandwidth that cannot be allocated).

That is, when the RIV notified from the base station 100 is a value other than the RB number (bandwidth) which is a multiple of 2,3,5, the terminal 200 has any one of one or a plurality of Reduced DMRS patterns. Determine one Reduced DMRS.

Whether or not to use Reduced DMRS when RIVs that are not used in PUSCH before Rel.11 are notified is specified in advance, or between the base station 100 and the terminal 200 by notification of the upper layer or the like. It shall be shared. Further, the pattern of Reduced DMRS specified by RIV may be defined in advance, or may be notified from the base station 100 to the terminal 200 in an upper layer or the like.

_{In addition, the values of L CRBs} and RB _START in the RIV that indicates the Reduced DMRS pattern shall be notified in advance from the upper layer. _{Alternatively, the values of L CRBs} and RB _{START in} the RIV indicating the Reduced DMRS pattern may be used as the L CRBs and RB _START corresponding to the values of the RIV that can be actually indicated, which can be identified from the value of the _RIV. .. In this case, one RIV can be used to simultaneously realize Reduced DMRS instructions and flexible frequency scheduling.

In this way, by diverting the RIV value that is not used as the assigned RB information for the notification of the DMRS pattern, the terminal from the base station 100 can maintain the same degree of freedom of PUSCH frequency scheduling as before Rel.11. It is possible to instruct Reduced DMRS to 200.

(Embodiment 3)
[Outline of communication system]
The communication system according to the present embodiment is composed of the base station 100 and one or more terminals 200 as in the first embodiment (FIG. 6).

However, in the present embodiment, unlike the first embodiment, the DPI that indicates the DMRS pattern is not used, and the DMRS pattern is indicated by the value of the A-SRS trigger bit (SRS request field) included in the UL grant. .. That is, the plurality of DMRS patterns are associated with each value of the existing Aperiodic SRS trigger bit included in the control information transmitted from the base station 100 to the terminal 200.

The A-SRS trigger bit is a bit for instructing the transmission of A-SRS at the specified transmittable timing. That is, in the present embodiment, the A-SRS trigger bit simultaneously indicates whether or not the A-SRS transmission request is made and the DMRS pattern. That is, the DMRS pattern is notified using the existing A-SRS trigger.

Specifically, the terminal 200 is notified in advance of a plurality of DMRS patterns that can be instructed, and is notified in advance of the DMRS patterns corresponding to the A-SRS trigger bits. Then, the terminal 200 specifies the transmission timing of the A-SRS based on the value of the A-SRS trigger bit notified from the base station 100, and sets the DMRS pattern corresponding to the A-SRS trigger bit to the PUSCH sub. Determined as the DMRS pattern used in the frame. The plurality of DMRS patterns that can be instructed and the DMRS patterns corresponding to the respective values of the A-SRS trigger bits may be notified in advance by the base station 100 to the terminal 200 in a higher layer or the like, and are defined. Only combinations may be used.

Further, the transmission timing of A-SRS indicated by the A-SRS trigger bit and the transmission timing of PUSCH indicated by UL grant do not necessarily have to be the same. For example, the transmission timing of A-SRS may be the same timing for the entire cell, and the transmission timing of PUSCH may be the timing after the specified time from the reception of UL grant. By doing so, it is possible to easily control the interference of SRS between terminals while suppressing the delay of uplink data.

[Configuration of base station 100]
The control unit 101 of the base station 100 determines the PUSCH subframe allocation to the terminal 200. At this time, the control unit 101 determines the value of the A-SRS trigger bit in consideration of both the presence / absence of the A-SRS transmission request to the terminal 200 and the DMRS pattern notified to the terminal 200.

[Configuration of terminal 200]
The control unit 205 of the terminal 200 determines whether or not A-SRS is transmitted at the next A-SRS transmission timing based on the value of the A-SRS trigger bit included in the UL grant, and instructs the SRS generation unit 209. .. Further, the control unit 205 determines the DMRS pattern at the time of PUSCH transmission based on the value of the A-SRS trigger bit.

[motion]
The operation of the base station 100 and the terminal 200 of this embodiment will be described. The processing flow of the base station 100 and the terminal 200 according to the present embodiment is substantially the same as in steps (1) to (4).

However, unlike the first embodiment, the UL grant does not include the DPI in the present embodiment. Instead, the base station 100 sets the value of the A-SRS trigger bit based on the DMRS pattern instructed to the terminal 200, and the terminal 200 sets the PUSCH based on the value of the A-SRS trigger bit included in the UL grant. Determines the DMRS pattern used in the subframe.

The number of DMRS patterns that can be selected by the terminal 200 differs depending on the number of bits of the A-SRS trigger. FIG. 23A shows an example of notification of the DMRS pattern when the A-SRS trigger bit is 1 bit, and FIG. 23B shows an example of notification of the DMRS pattern when the A-SRS trigger bit is 2 bits.

For example, as shown in FIG. 23A (in the case of 1 bit), when the value of the A-SRS trigger bit is 0, it is instructed that there is no A-SRS transmission request (No trigger) and that it is Legacy DMRS. To. If the value of the A-SRS trigger bit is 1, it is instructed that there is an A-SRS transmission request and that it is the Reduced DMRS pattern (1).

Further, as shown in FIG. 23B (in the case of 2 bits), when the value of the A-SRS trigger bit is 00, it is instructed that there is no A-SRS transmission request and that it is Legacy DMRS, and A-SRS. When the value of the trigger bit is 01, it is instructed that there is an A-SRS transmission request and that it is the Reduced DMRS pattern (1). Similarly, if the value of the A-SRS trigger bit is 10, there is a transmission request for A-SRS and it is instructed that it is Legacy DMRS, and if the value of the A-SRS trigger bit is 11, A-SRS There is no transmission request for, and it is instructed that the Reduced DMRS pattern (2) is used.

In this way, the terminal 200 is instructed at the same time as the A-SRS transmission request and the DMRS pattern according to the value of the A-SRS trigger bit included in the UL grant. When the number of A-SRS trigger bits is multiple (for example, Fig. 23B), A-SRS and DMRS patterns with different configurations (1st SRS parameter set and 2nd SRS parameter set in Fig. 23) can be set for each value of the trigger bits. It becomes. In addition, the A-SRS Configuration and DMRS pattern corresponding to each value of the A-SRS trigger bit can be set independently.

[effect]
In this way, the base station 100 and the terminal 200 notify and select the DMRS pattern by associating the value of the A-SRS trigger bit with the DMRS pattern.

In LTE, in addition to A-SRS, Periodic SRS (P-SRS), which is transmitted periodically without a trigger bit, is specified. When the transmission cycle of P-SRS is short, it is considered that the necessity of transmission request of A-SRS is low. When the necessity of the transmission request of A-SRS is low, the base station 100 and the terminal 200 can divert the A-SRS trigger bit as an instruction bit of the DMRS pattern as in the present embodiment. By doing so, it is possible to select an appropriate DMRS pattern for the terminal 200 from a plurality of DMRS patterns including Legacy DMRS and Reduced DMRS as in the first embodiment without increasing the overhead.

(Embodiment 4)
[Outline of communication system]
The communication system according to the present embodiment is composed of the base station 100 and one or more terminals 200 as in the first embodiment (FIG. 6).

However, in the present embodiment, unlike the first embodiment, the DPI that indicates the DMRS pattern is not used, and the DMRS pattern is switched according to the downlink control channel (PDCCH or each EPDCCH set) to which the UL grant is transmitted. Be done. That is, the plurality of DMRS patterns are associated with the plurality of control channels used for transmitting the control information transmitted from the base station 100 to the terminal 200, respectively.

Specifically, the terminal 200 is notified in advance of a plurality of DMRS patterns that can be instructed, and the DMRS patterns corresponding to each control channel (PDCCH and each EPDCCH set) are notified in advance. Then, the terminal 200 determines the DMRS pattern corresponding to the control channel used for transmitting the UL grant notified from the base station 100 as the DMRS pattern used in the PUSCH subframe. The plurality of DMRS patterns that can be instructed and the DMRS patterns corresponding to each control channel may be notified in advance by the base station 100 to the terminal 200 in a higher layer or the like, and only the specified combinations are used. May be good.

[Configuration of base station 100]
The control unit 101 of the base station 100 determines the PUSCH subframe allocation to the terminal 200. At this time, the control unit 101 considers both the control channels (PDCCH and EPDCCH set) that map the control signals (including UL grant) to the terminal 200 and the DMRS pattern that notifies the terminal 200, and determines the control signal. Determine the mapping.

[Configuration of terminal 200]
The control unit 205 of the terminal 200 determines the DMRS pattern at the time of PUSCH transmission depending on whether the control channel to which the UL grant is transmitted is PDCCH or EPDCCH set.

[motion]
The operation of the base station 100 and the terminal 200 of this embodiment will be described. The processing flow of the base station 100 and the terminal 200 according to the present embodiment is substantially the same as in steps (1) to (4).

However, unlike the first embodiment, the UL grant does not include the DPI in the present embodiment. Instead, the base station 100 sets the control channel used for UL grant transmission based on the DMRS pattern instructed to the terminal 200, and the terminal 200 sets the control channel (PDCCH or EPDCCH set) used for UL grant transmission. Based on this, determine the DMRS pattern used in the PUSCH subframe.

Only one EPDCCH set may be set, or a plurality of EPDCCH sets may be set. FIG. 24 shows an example of notification of the DMRS pattern when PDCCH and three EPDCCH sets are set.

In FIG. 24, the terminal 200 blindly decodes three types of EPDCCH sets in addition to the PDCCH. Then, the terminal 200 determines the DMRS pattern in the PUSCH transmission instructed by the UL grant depending on which control channel the UL grant can be decrypted.

For example, as shown in FIG. 24, when the UL grant is transmitted using PDCCH or EPDCCH set 1, the terminal 200 determines that the Legacy DMRS has been instructed. Further, when the UL grant is transmitted using EPDCCH set 2, the terminal 200 determines that the Reduced DMRS pattern (1) is instructed, and when the UL grant is transmitted using EPDCCH set 3, the terminal 200 determines that the Reduced DMRS pattern (1) is instructed. , Reduced DMRS pattern (2) is judged to be instructed.

[effect]
In this way, the base station 100 and the terminal 200 notify and select the DMRS pattern by associating the control channel to which the UL grant is transmitted with the DMRS pattern.

PDCCH has a wide coverage and is supported by terminals from the past (Rel.8), so it is highly likely that macrocell base stations will use it to transmit UL grants. On the other hand, EPDCCH can set a plurality of sets (two EPDCCH sets in Rel.11) as blind decoding targets. From this, it is conceivable that different EPDCCH sets are associated with the macro cell base station and the small cell base station, and UL grants are transmitted from different base stations depending on the situation of the terminal 200. In this way, it is conceivable that different control channels (or different EPDCCH sets) are set for each of a plurality of base stations (or transmission / reception points) capable of communicating with the terminal 200.

For example, in FIG. 24, PDCCH and EPDCCH set 1 are used to transmit UL grants from a macrocell base station with high coverage and reliability, and EPDCCH set 2 and EPDCCH set 3 are UL grants from nearby small cell base stations. The operation used for transmission of is conceivable. In such a case, the Legacy DMRS pattern is associated with the control channel (PDCCH and EPDCCH set 1) used by the macro cell base station to transmit UL grant, and the control channel (EPDCCH) used by the small cell base station to transmit UL grant. A Reduced DMRS pattern is associated with set 2, 3).

By associating the control channel to which the UL grant is transmitted with the DMRS pattern in this way, it is possible to realize an operation in which the Reduced DMRS is used for the terminal 200 when communicating with a specific base station (transmission / reception point). it can. By doing so, the DMRS pattern can be appropriately switched without increasing the overhead and without restricting the control bits included in the UL grant.

(Embodiment 5)
[Outline of communication system]
The communication system according to the present embodiment is composed of the base station 100 and one or more terminals 200 as in the first embodiment (FIG. 6).

However, in the present embodiment, unlike the first embodiment, the DPI indicating the DMRS pattern is not used, and the DMRS is determined by the value of the cyclic shift notification bit (CS field or cyclic shift index) included in the UL grant. The pattern is indicated. That is, the plurality of DMRS patterns are associated with each value of the existing CS field included in the control information transmitted from the base station 100 to the terminal 200.

The CS field is a bit for indicating the cyclic shift amount and the OCC code number (OCC index) applied to the DMRS when the PUSCH specified by the UL grant is transmitted. That is, in the present embodiment, the CS field simultaneously indicates the cyclic shift amount and OCC code number applied to the DMRS, and the DMRS pattern. That is, the DMRS pattern is notified using the existing CS field.

Specifically, the terminal 200 is notified in advance of a plurality of DMRS patterns that can be instructed, and the DMRS patterns corresponding to each CS field are notified in advance. Then, the terminal 200 specifies the cyclic shift amount and the OCC code number based on the value of the CS field notified from the base station 100, and uses the DMRS pattern corresponding to the CS field in the PUSCH subframe. Determined as the DMRS pattern to be used. The plurality of DMRS patterns that can be instructed and the DMRS patterns corresponding to each value of the CS field may be notified in advance by the base station 100 to the terminal 200 in a higher layer or the like, and only a specified combination is used. You may.

[Configuration of base station 100]
The control unit 101 of the base station 100 determines the PUSCH subframe allocation to the terminal 200. At this time, the control unit 101 determines the value of the CS field in consideration of both the cyclic shift amount of DMRS with respect to the terminal 200, the code number of OCC, and the DMRS pattern notified to the terminal 200.

[Configuration of terminal 200]
The control unit 205 of the terminal 200 specifies the cyclic shift amount applied to the DMRS and the code number of the OCC based on the value of the CS field included in the UL grant, and instructs the DMRS generation unit 208. Further, the control unit 205 determines the DMRS pattern at the time of PUSCH transmission based on the value of the CS field, and instructs the DMRS generation unit 208.

[motion]
The operation of the base station 100 and the terminal 200 of this embodiment will be described. The processing flow of the base station 100 and the terminal 200 according to the present embodiment is substantially the same as in steps (1) to (4).

However, unlike the first embodiment, the UL grant does not include the DPI in the present embodiment. Instead, base station 100 sets the value of the CS field based on the DMRS pattern instructing terminal 200, and terminal 200 is used in the PUSCH subframe based on the value of CS field contained in the UL grant. Determine the DMRS pattern.

FIG. 25 shows an example of notification of the DMRS pattern using the CS field (3 bits). In FIG. 25, λ represents the layer number. The cyclic shift amount that can be notified by the CS field is 0 to 11, and the OCC code numbers are 0 and 1. Further, the OCC code number 0 corresponds to [+1 +1], and the OCC code number 1 corresponds to [+1 -1].

As shown in FIG. 25, the CS field values of 000, 001, 010, and 111 are associated with the Legacy DMRS, and the CS field values of 011 and 100 are associated with the Reduced DMRS pattern (1). , CS field values 101 and 110 are associated with Reduced DMRS pattern (2).

[effect]
In this way, the base station 100 and the terminal 200 notify and select the DMRS pattern by associating the value of the A-SRS trigger bit with the DMRS pattern.

Reduced DMRS is likely to be used when the terminal 200 is connected to a small cell base station and when the channel quality is sufficiently good. It is assumed that the number of such terminals is small and the interference with other cells is small. In other words, Reduced DMRS is likely to be used in situations where there is less need for orthogonalization and interference control using CS and OCC. Therefore, by instructing the DMRS pattern at the same time as CS / OCC using the CS field, there are certain restrictions on the notification of CS / OCC, but there is almost no effect of the disadvantages due to this restriction, and the DMRS pattern is switched appropriately. be able to. Moreover, since the DMRS pattern is notified using the existing CS field, no new bit is added and the overhead does not increase.

In this embodiment, the use of a DMRS pattern other than the Legacy DMRS (that is, any of the Reduced DMRS patterns) is limited to the case where the number of layers (transmission rank) is 1 (that is, when λ = 0). You may. Specifically, when the number of layers (transmission rank) is 1, the terminal 200 (control unit 205) determines a specific DMRS pattern used by the terminal 200 based on the CS field, and determines the number of layers (transmission rank). When is 2 or more, the Legacy DMRS pattern is determined as a specific DMRS pattern used by the terminal 200 regardless of the value of the CS field.

FIG. 26 shows a case where the use of the Reduced DMRS pattern is limited to λ = 0 (number of layers 1) in the CS field shown in FIG. 25. In FIG. 26, in the CS field to which the Reduced DMRS is associated, when the number of layers is 1 (λ = 0), the associated Reduced DMRS is used, but the number of layers is 2 or more (λ = 1 to 0). In the case of 3), Legacy DMRS is used instead of the associated Reduced DMRS.

When the number of layers is large, high throughput can be achieved by simultaneously transmitting (multiplexing) multiple data from different layers with the same time / frequency resource. At this time, DMRS is also multiplexed, so that it is easily affected by the channel estimation error. Therefore, when the number of layers is large, the throughput can be expected to be further improved by using Reduced DMRS as in the case of the number of layers 1, but the channel estimation is more accurate than the slight improvement in resource efficiency. It is desirable to do well and give priority to receiving data correctly without retransmission. Moreover, when the number of layers is large, it is possible to achieve a high data rate without relying on Reduced DMRS. Therefore, as shown in FIG. 26, by switching the DMRS pattern according to the number of layers, an appropriate DMRS according to the number of layers can be used.

Even if the DMRS is changed according to the format of the UL grant or the search space to which the UL grant is transmitted, the same as the above-described embodiment can be realized. For example, UL grant has DCI format 0 that can specify one-layer transmission and DCI format 4 that can specify two or more layers. Therefore, for UL grants that instruct 1-layer transmission (for example, DCI format 0), Legacy DMRS is used regardless of the value of CS field, and for UL grants that can instruct 2 or more layer transmissions (for example, DCI format 4), some Reduced DMRS may be used for the value of CS field of. Alternatively, the control channel that sends the UL grant has a common search space (CSS (Common Search Space)) that instructs one-layer transmission and a terminal individual search space (USS (UE specific Search Space)) that can instruct two or more layers. There is. Therefore, in the search space (CSS) that instructs 1-layer transmission, Legacy DMRS is used regardless of the value of CS field, and in the search space (USS) that can instruct 2 or more layer transmission, the value of some CS field is used. In some cases, Reduced DMRS may be used.

(Embodiment 6)
The communication system according to the present embodiment is composed of the base station 100 and one or more terminals 200 as in the first embodiment (FIG. 6).

However, in the present embodiment, unlike the first embodiment, the DPI indicating the DMRS pattern is not included in the UL grant and is transmitted as a control signal different from the UL grant in the control channel.

In the following description, the control signal when the DPI is 2 bits is called DCI format 3d, and the control signal when the DPI is 1 bit is called DCI format 3dA.

Specifically, the base station 100 transmits DCI format 3d or DCI format 3dA as DPI. On the other hand, the terminal 200 can blindly decode each DCI format 3d / 3dA and correctly decode the DCI format 3d / 3dA, and if the DPI addressed to the terminal 200 is included, the DMRS pattern instructed by the DPI is used. ..

The base station 100 notifies the terminal 200 in advance of the use of DCI format 3d / 3dA and the DMRS pattern instructed by the DPI of DCI format 3d / 3dA. Further, the base station 100 notifies the terminal 200 of the pseudo terminal ID required for decoding the DCI format 3d / 3dA in advance. The pseudo terminal ID may be a value common to a plurality of terminals 200. Then, the base station 100 transmits DCI format 3d / 3dA together with the UL grant. This DCI format 3d / 3dA includes DPI addressed to one or more terminals 200, and a CRC bit masked by a pseudo terminal ID is added. That is, the control signal transmitted from the base station 100 to the terminal 200 includes the DPI and the UL grant, and the DPI is masked differently from the masking (scramble) for the UL grant.

The terminal 200 blindly decodes the DCI format 3d / 3dA in addition to the UL grant. At this time, the terminal 200 determines the success or failure of decoding using the CRC masked by the terminal ID of the terminal 200 for UL grant, and the CRC masked by the pseudo terminal ID for DCI format 3d / 3dA. Is used to determine the success or failure of decoding. If the decoding of the DCI format 3d / 3dA is successful at the same time as the UL grant is successfully decrypted, the terminal 200 selects the DMRS pattern according to the value of the DPI addressed to the terminal 200 included in the DCI format 3d / 3dA, and the UL grant is selected. Sends the PUSCH assigned by.

The base station 100 receives the PUSCH transmitted by the terminal 200 and decodes the PUSCH. Since the base station 100 cannot determine whether the DCI format 3d / 3dA is correctly decoded at the terminal 200, it is assumed that the PUSCH is transmitted using either the Legacy DMRS or the DMRS pattern specified by the DPI, and the PUSCH Decryption is performed in sequence.

As described above, in the present embodiment, the DPI is transmitted / received using the scrambled control signal (DCI format 3 / 3A) different from the UL grant, and the DMRS pattern is switched according to the DPI value. ..

By doing so, it is possible to separately notify the Reduced DMRS while using the UL grant of Rel.11 or earlier as it is, so that the base station 100 operates the terminal using Legacy DMRS with the scheduler of Rel.11 or earlier. Only terminals that use Reduced DMRS can be notified of DMRS patterns with independent control signals. That is, the notification of Reduced DMRS can be realized only by adding the function of DCI format 3d / 3dA to the scheduler of the conventional base station 100, so that the implementation of the base station 100 becomes easy.

When the terminal 200 uses Reduced DMRS, more transmission data is transmitted than when Legacy DMRS is used. At this time, the terminal 200 maps the transmission data in the same manner as when using Legacy DMRS (that is, avoiding resources blanked by Reduced DMRS), and blanks the transmission data that could not be mapped by Reduced DMRS. It may be mapped to the resource that became. FIG. 27 shows an example of the data mapping order. When Reduced DMRS is used, the amount of transmitted data is determined according to the DMRS pattern. At this time, as shown in FIG. 27, first, data is mapped from the beginning of the subframe in the same manner as in the case of Legacy DMRS. Since data that cannot be mapped is generated by the amount of Reduced DMRS, finally, the data that cannot be mapped is mapped to the blank resource by Reduced DMRS.

As a result, the data mapping order is the same as in Legacy DMRS for resources other than the resources to which data is newly mapped by Reduced DMRS (resources that are blank due to Reduced DMRS). Therefore, the base station 100 considers a plurality of different data mapping patterns even if the terminal 200 cannot correctly determine whether or not the DCI format 3d / 3dA is correctly decoded (that is, whether it is a Legacy DMRS or a DMRS that is not). There is no need to decode the data according to the data mapping order of. Further, even if the terminal 200 transmits the PUSCH in the Legacy DMRS pattern, the base station 100 may be able to correctly decode the data in the data mapping order assuming the Reduced DMRS. By doing so, the receiver configuration in the base station 100 can be simplified, and the processing delay required for decoding can be shortened.

The embodiments of the present invention have been described above.

(Other embodiments)
[1] When the ACK / NACK response signal for the downlink data and the PUSCH transmission specified by UL grant are at the same timing, the ACK / NACK response signal is inserted by replacing the data in the PUSCH subframe. Since this ACK / NACK response signal requires high judgment accuracy (low error rate), it is stipulated that the ACK / NACK response signal is mapped to the SC-FDMA symbol adjacent to DMRS before Rel.11. It was. On the other hand, when Reduced DMRS is used, some DMRS are replaced with data, so the ACK / NACK response signal cannot be mapped to the SC-FDMA symbol adjacent to DMRS, and the channel estimation accuracy for determining the ACK / NACK response signal is improved. There is a possibility that it cannot be secured. FIG. 28 shows an example in which the ACK / NACK response signal is mapped into the PUSCH in the Legacy DMRS (FIG. 28A) and a certain Reduced DMRS pattern (FIG. 28B). For example, in FIG. 28B, it can be seen that the Reduced DMRS pattern (1) shown in FIG. 4B is used and the ACK / NACK response signal is mapped to a location away from the DMRS.

Therefore, when the ACK / NACK response signal is multiplexed on the PUSCH, the terminal 200 may always use the Legacy DMRS even when the Reduced DMRS is instructed. By doing so, the channel estimation accuracy for determining the ACK / NACK response signal can be made equivalent to that before Rel.11.

Alternatively, the Reduced DMRS that can be used when the ACK / NACK response signal is multiplexed on the PUSCH may be limited to the pattern in which the DMRS is arranged on the SC-FDMA adjacent to the ACK / NACK response signal. The pattern in which DMRS is arranged in SC-FDMA adjacent to the ACK / NACK response signal is, for example, the Reduced DMRS pattern (3) shown in FIG. 4D. By doing so, it is possible to suppress deterioration of the channel estimation accuracy for the determination of the ACK / NACK response signal.

Alternatively, when using Reduced DMRS, the location of the ACK / NACK response signal may be changed. For example, in the case of FIG. 28B, the ACK / NACK response signal may be mapped in a concentrated manner around the DMRS left in the Reduced DMRS. By doing so, the Reduced DMRS can be flexibly used while ensuring the channel estimation accuracy for the determination of the ACK / NACK response signal.

[2] Further, in the above-described embodiment, the case where the present invention is configured by hardware has been described as an example, but the present invention can also be realized by software in cooperation with hardware.

Further, each functional block used in the description of the above embodiment is typically realized as an LSI which is an integrated circuit. These may be individually integrated into one chip, or may be integrated into one chip so as to include a part or all of them. Although it is referred to as an LSI here, it may be referred to as an IC, a system LSI, a super LSI, or an ultra LSI depending on the degree of integration.

Further, the method of making an integrated circuit is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array) that can be programmed after the LSI is manufactured, or a reconfigurable processor that can reconfigure the connection and settings of circuit cells inside the LSI may be used.

Furthermore, if an integrated circuit technology that replaces an LSI appears due to advances in semiconductor technology or another technology derived from it, it is naturally possible to integrate functional blocks using that technology. There is a possibility of applying biotechnology.

The communication device of the present disclosure is control information used for allocation of PUSCH (Physical Uplink Shared Channel), and is said to determine the arrangement of an uplink DMRS (Demodulation Reference Signal) to a resource element. A transmitter that transmits the DMRS (Demodulation Reference Signal) to the terminal, a receiver that is arranged in the resource element based on the control information, and receives the DMRS (Demodulation Reference Signal) that is multiplexed and transmitted with the PUSCH from the terminal. A configuration including a circuit unit that estimates a channel based on the received DMRS is adopted.

In the communication device of the present disclosure, the arrangement of one of the plurality of arrangement patterns is determined based on the control information, and the plurality of arrangement patterns have at least two arrangements in which the number of resource elements for arranging the DMRS is different. Includes patterns.

In the communication device of the present disclosure, the arrangement of one of the plurality of arrangement patterns is determined based on the control information, and the plurality of arrangement patterns include at least two arrangement patterns in which the number of symbols for arranging the DMRS is different. Including.

In the communication device of the present disclosure, the arrangement of one of the plurality of arrangement patterns is determined based on the control information, and the plurality of arrangement patterns are the number of symbols for arranging the DMRS per slot or one subframe. Includes at least two different placement patterns.

In the communication device of the present disclosure, the arrangement of one of the plurality of arrangement patterns is determined based on the control information, and in the plurality of arrangement patterns, the resource for arranging the DMRS is increased in LTE-A release 11. Includes less placement patterns than the line DMRS is placed on.

In the communication device of the present disclosure, the arrangement of one of the plurality of arrangement patterns is determined based on the control information, and the plurality of arrangement patterns are notified to the terminal in an upper layer.

In the communication device of the present disclosure, the arrangement of one of a plurality of arrangement patterns is determined based on the control information, and the arrangement pattern in which the DMRS having a sequence length shorter than the frequency bandwidth to which the PUSCH is allocated is arranged. including.

In the communication device of the present disclosure, the arrangement of one of the plurality of arrangement patterns is determined based on the control information, and the plurality of arrangement patterns include hopping or non-hopping.

In the communication device of the present disclosure, the control information includes information for determining a cyclic shift and an orthogonal code, and the receiving unit is generated based on the determined cyclic shift and the orthogonal code. Receive DMRS.

In the communication device of the present disclosure, when ACK / NACK is multiplexed and transmitted with the PUSCH, the receiving unit is arranged adjacent to the DMRS arranged based on the determined arrangement. Receive NACK.

The communication method of the present disclosure is control information used for allocation of PUSCH (Physical Uplink Shared Channel), and the control information for determining the arrangement of an uplink DMRS (Demodulation Reference Signal) to a resource element. Is transmitted to the terminal, and the DMRS (Demodulation Reference Signal) that is arranged in the resource element based on the control information and transmitted in combination with the PUSCH is received from the terminal and sent to the received DMRS. Perform channel estimation based on this.

The integrated circuit of the present disclosure is control information used for allocation of PUSCH (Physical Uplink Shared Channel), and is said to determine the arrangement of an uplink DMRS (Demodulation Reference Signal) to a resource element. To the terminal, and to receive the DMRS (Demodulation Reference Signal), which is arranged in the resource element based on the control information and transmitted in combination with the PUSCH, from the terminal. It controls the process of performing channel estimation based on the DMRS.

The present invention can be applied to mobile communication systems.

100 Base station 200 Terminal 11 Control signal generator 12, 25 Transmitter 13,21 Receiver 14,114 Channel estimation 15 Received signal processing 101, 23,205 Control 102 Control information generator 103, 206 Coding 104 , 207 Modulation section 105,212 Mapping section 106,213 IFFT section 107,214 CP addition section 108,215 Wireless transmitter section 109,201 Wireless receiver section 110,202 CP removal section 111,203 FFT section 112 Demapping section 113 CSI measurement Part 115 Equalization part 116 IDFT part 117 Demodulation part 118 Decoding part 119 Judgment part 22,204 Control signal extraction part 24,208 DMRS generation part 209 SRS generation part 210 Multiplexing part 211 DFT part

Claims (11)

Transmission to transmit the control information used for allocation of PUSCH (Physical Uplink Shared Channel) to the terminal, which determines the arrangement of the uplink DMRS (Demodulation Reference Signal) to the resource element. Department and
A receiving unit that is arranged in the resource element based on the control information and receives the DMRS (Demodulation Reference Signal) that is multiplexed and transmitted with the PUSCH from the terminal.
A circuit unit that estimates the channel based on the received DMRS,
Equipped with
Based on the control information, one arrangement of a plurality of arrangement patterns are determined, each of the plurality of arrangement patterns, not chopsticks or the sequence group hopping of the DMRS, the are correlated association,
Communication device. The plurality of placement patterns include at least two placement patterns with different numbers of resource elements for placing the DMRS.
The communication device according to claim 1. The plurality of arrangement patterns include at least two arrangement patterns in which the number of symbols for arranging the DMRS is different.
The communication device according to claim 1. The plurality of arrangement patterns include at least two arrangement patterns in which the number of symbols for arranging the DMRS per slot or one subframe is different.
The communication device according to claim 1. The plurality of placement patterns include a placement pattern in which the resources for placing the DMRS are less than the resources for placing the uplink DMRS in LTE-A Release 11.
The communication device according to claim 1. Notifying the terminal of the plurality of arrangement patterns in an upper layer.
The communication device according to claim 1. The plurality of arrangement patterns include an arrangement pattern in which the DMRS having a series length shorter than the frequency bandwidth to which the PUSCH is allocated is arranged.
The communication device according to claim 1. The control information includes information for determining the cyclic shift and the quadrature code, and the receiving unit receives the DMRS generated based on the determined cyclic shift and the quadrature code.
The communication device according to claim 1. When the ACK / NACK is transmitted in combination with the PUSCH, the receiving unit receives the ACK / NACK arranged adjacent to the DMRS arranged based on the determined arrangement.
The communication device according to claim 1. The control information used for allocating the PUSCH (Physical Uplink Shared Channel), which determines the allocation of the uplink DMRS (Demodulation Reference Signal) to the resource element, is transmitted to the terminal.
The DMRS (Demodulation Reference Signal), which is arranged in the resource element based on the control information and transmitted in combination with the PUSCH, is received from the terminal.
Channel estimation is performed based on the received DMRS, and
Based on the control information, one arrangement of a plurality of arrangement patterns are determined, each of the plurality of arrangement patterns, not chopsticks or the sequence group hopping of the DMRS, the associated,
Communication method. A process of transmitting the control information used for allocating the PUSCH (Physical Uplink Shared Channel) to the terminal, which determines the allocation of the uplink DMRS (Demodulation Reference Signal) to the resource element. When,
A process of receiving the DMRS (Demodulation Reference Signal), which is arranged in the resource element based on the control information and transmitted in combination with the PUSCH, from the terminal.
Processing to perform channel estimation based on the received DMRS and
Control and
Based on the control information, one arrangement of a plurality of arrangement patterns are determined, each of the plurality of arrangement patterns, not chopsticks or the sequence group hopping of the DMRS, the associated,
Integrated circuit.

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