JP2018191357A - Base station, communication method, and integrated circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid PUCCH resource collision between a normal mode terminal and an MTC coverage enhancement mode terminal.SOLUTION: A receiving section 202 receives control information indicating assignment of downlink data, and the downlink data; and a transmitting section transmits a response signal using a resource in a first resource group when an own terminal is a first terminal to which repetition transmission is applied, and the transmitting section transmits the response signal using a resource in a second resource group that is different from the first resource group, when the own terminal is a second terminal to which the repetition transmission is not applied.SELECTED DRAWING: Figure 9

Description

  The present disclosure relates to a base station, a communication method, and an integrated circuit.

  In 3GPP LTE (3rd Generation Partnership Project Long Term Evolution), orthogonal frequency division multiple access (OFDMA) is adopted as a downlink communication method.

  In a wireless communication system to which 3GPP LTE is applied, a base station (sometimes referred to as an eNB) uses a predetermined communication resource and uses a synchronization signal (SCH: Synchronization Channel) and a broadcast signal (PBCH: Physical Broadcast Channel). ). Then, the terminal (sometimes called a UE (User Equipment)) secures synchronization with the base station by first capturing the SCH. Thereafter, the terminal acquires parameters (for example, a frequency bandwidth) unique to the base station by reading the BCH information (for example, refer to Non-Patent Documents 1 to 3).

  The terminal establishes communication with the base station by making a connection request to the base station after completing acquisition of the parameters unique to the base station. The base station transmits control information via a control channel such as PDCCH (Physical Downlink Control Channel) to a terminal with which communication has been established, as necessary. The terminal then performs “blind determination” on each of the plurality of control information included in the received PDCCH signal. That is, the control information includes a CRC (Cyclic Redundancy Check) part, and this CRC part is masked by the terminal ID of the transmission target terminal in the base station. Therefore, the terminal cannot determine whether or not the received control information is control information destined for the own device until the CRC portion of the received control information is demasked with the terminal ID of the own device. In this blind determination, if the CRC calculation is OK as a result of demasking, it is determined that the control information is addressed to the own device.

  In LTE, HARQ (Hybrid Automatic Repeat Request) is applied to downlink data from a base station to a terminal. That is, the terminal feeds back a response signal indicating the downlink data error detection result to the base station. The terminal performs CRC on the downlink data, and if CRC = OK (no error), an acknowledgment (ACK: Acknowledgement) is received, and if CRC = NG (with error), a negative acknowledgment (NACK: Negative Acknowledgement) ) As a response signal to the base station. An uplink control channel such as PUCCH (Physical Uplink Control Channel) is used for feedback of the response signal (that is, ACK / NACK signal).

  Here, the control information transmitted from the base station includes resource allocation information including resource information allocated to the terminal by the base station. As described above, the PDCCH is used for transmitting the control information. The PDCCH is composed of one or more L1 / L2 CCHs (L1 / L2 Control Channels). Each L1 / L2 CCH is composed of one or a plurality of CCEs (Control Channel Elements). That is, CCE is a basic unit for mapping control information to PDCCH. When one L1 / L2 CCH is composed of a plurality of CCEs, a plurality of consecutive CCEs are assigned to the L1 / L2 CCH. The base station allocates L1 / L2 CCH to the resource allocation target terminal according to the number of CCEs required for the control information notification to the resource allocation target terminal. Then, the base station maps and transmits the control information to the physical resource corresponding to the L1 / L2 CCH CCE.

  Each CCE is associated with a PUCCH configuration resource (hereinafter referred to as a PUCCH resource) in a one-to-one correspondence. Therefore, the terminal that has received the L1 / L2 CCH specifies a PUCCH resource corresponding to the CCE that constitutes the L1 / L2 CCH, and transmits an ACK / NACK signal to the base station using the PUCCH resource. However, when the L1 / L2 CCH occupies a plurality of consecutive CCEs, the terminal may use one resource (for example, PUCCH corresponding to the CCE with the smallest index) among the plurality of PUCCH resources respectively corresponding to the plurality of CCEs. Resource) to transmit an ACK / NACK signal to the base station.

  Also, as shown in FIG. 1, the transmission timing of the ACK / NACK signal on the PUCCH in the terminal is the subframe in which the received PDCCH signal and the PDSCH (Physical Downlink Shared Channel) signal to which data is assigned by the PDDCH signal are received. (Subframe n in FIG. 1) is a subframe (subframe n + K in FIG. 1) after K subframes (for example, K = 4 in FDD (Frequency Division Duplex)).

  A plurality of ACK / NACK signals transmitted from a plurality of terminals are, as shown in FIG. 2, a ZAC (Zero Auto-correlation) sequence having a Zero Auto-correlation characteristic on the time axis, a Walsh sequence, and a DFT ( Discrete Fourier Transform) sequence and code multiplexed in PUCCH. In FIG. 2, (W (0), W (1), W (2), W (3)) represents a Walsh sequence having a sequence length of 4, and (F (0), F (1), F (2) ) Represents a DFT sequence having a sequence length of 3.

  As shown in FIG. 2, at the terminal, the ACK / NACK signal is first spread on the frequency axis into frequency components corresponding to 1 SC-FDMA (Single-Carrier Frequency Division Multiple Access) symbols by a ZAC sequence (sequence length 12). Is done. That is, a ZAC sequence having a sequence length of 12 is multiplied by an ACK / NACK signal component represented by a complex number. Next, the first spread ACK / NACK signal and the ZAC sequence as a reference signal are a Walsh sequence (sequence length 4: W (0) to W (3)) and a DFT sequence (sequence length 3: F), respectively. (0) to F (2)) are secondarily diffused. That is, for each component of a sequence length 12 signal (ACK / NACK signal after first spreading or ZAC sequence as a reference signal), each orthogonal code sequence (Orthogonal sequence: Walsh sequence or DFT sequence) The components are multiplied. Further, the second-order spread signal is converted into a signal having a sequence length of 12 on the time axis by an inverse discrete Fourier transform (IDFT) or an inverse fast Fourier transform (IFFT). Then, a cyclic prefix (CP) is added to each of the signals after IFFT to form a one-slot signal composed of seven SC-FDMA symbols.

  PUCCH is arranged at both ends of the system band on the frequency axis. In PUCCH, radio resources are allocated to each terminal in units of subframes. One subframe is composed of two slots, and PUCCH is frequency hopped (inter-slot frequency hopping) between the first half slot and the second half slot.

  ACK / NACK signals from different terminals are spread using ZAC sequences corresponding to different cyclic shift amounts (Cyclic Shift Index) or orthogonal code sequences corresponding to different sequence numbers (OC Index: Orthogonal Cover Index). ing. An orthogonal code sequence is a set of a Walsh sequence and a DFT sequence. The orthogonal code sequence may also be referred to as a block-wise spreading code sequence. Therefore, the base station can separate a plurality of these code-multiplexed ACK / NACK signals by using conventional despreading and correlation processing (see, for example, Non-Patent Document 4). FIG. 3 shows PUCCH resources defined by a sequence number (OC index: 0 to 2) of an orthogonal code sequence and a cyclic shift index (Cyclic shift Index: 0 to 11) of a ZAC sequence. When a Walsh sequence with a sequence length of 4 and a DFT sequence with a sequence length of 3 are used, there are 3 * 12 = 36 PUCCH resources in the same subcarrier at the maximum. However, not all 36 PUCCH resources can be used. For example, FIG. 3 shows a case where 18 PUCCH resources (# 0 to # 17) can be used.

  By the way, as a mechanism to support the future information society, M2M (Machine-to-Machine) communication that realizes a service by autonomous communication between devices without user's judgment is expected in recent years. A smart grid is a specific application example of the M2M system. A smart grid is an infrastructure system that efficiently supplies lifelines such as electricity or gas, and is autonomous and effective by implementing M2M communication between a smart meter deployed in each home or building and a central server. Adjust the balance of demand for resources. Other application examples of the M2M communication system include a monitoring system for goods management or telemedicine, and remote management of vending machine inventory or billing.

  In the M2M communication system, the use of a cellular system having a wide communication area has attracted attention. In 3GPP, the examination of M2M on the premise of cellular network in the standardization of LTE and LTE-Advanced is being promoted under the name of machine type communication (MTC). In particular, “Coverage Enhancement” to further expand the communication area is being considered in order to cope with cases where MTC communication devices such as smart meters in the basement of buildings are located in places where existing communication areas cannot be used. (For example, see Non-Patent Document 5).

  In particular, in MTC coverage enhancement, repetition of transmitting the same signal multiple times is considered to be an important technique for expanding the communication area. Specifically, it is assumed that repetition transmission is performed in each channel such as PDCCH, PDSCH, and PUCCH.

3GPP TS 36.211 V11.5.0, “Physical channels and modulation (Release 11),” December 2013. 3GPP TS 36.212 V11.4.0, “Multiplexing and channel coding (Release 11),” December 2013. 3GPP TS 36.213 V11.5.0, “Physical layer procedures (Release 11),” December 2013. Seigo Nakao, Tomofumi Takata, Daichi Imamura, and Katsuhiko Hiramatsu, “Performance enhancement of E-UTRA uplink control channel in fast fading environments,” Proceeding of 2009 IEEE 69th Vehicular Technology Conference (VTC2009-Spring), April 2009. 3GPP TR 36.888 V12.0.0, “Study on provision of low-cost Machine-Type Communications (MTC) User Equipments (UEs) based on LTE,” June 2013.

  However, the PUCCH resource for transmitting the ACK / NACK signal by the terminal in the MTC coverage enhancement mode (terminal that performs repetition transmission) has not been sufficiently studied. In particular, when a terminal in MTC coverage enhancement mode and a terminal in normal mode (terminals that do not perform repetition transmission) coexist, the terminal in normal mode uses the PUCCH resource used by the terminal in MTC coverage enhancement mode. It is necessary to design so that it does not collide with the PUCCH resource to be used.

  One aspect of the present disclosure is to avoid collision of PUCCH resources between terminals in normal mode and terminals in MTC coverage enhancement mode without reducing the frequency utilization efficiency of PDCCH resources and increasing scheduling complexity. A base station, a communication method, and an integrated circuit.

  A base station according to an aspect of the present disclosure transmits downlink control information and downlink data from the terminal using a transmission unit that transmits the downlink control information and downlink data to the terminal, and an uplink control channel resource determined based on the control information. A reception unit configured to receive a response signal for the downlink data, and a coverage enhancement mode capable of performing repetition transmission of the response signal over a plurality of subframes is set in the terminal. The uplink control channel resource is determined using a first offset, and the first offset is different from a second offset used when the coverage enhancement mode is not set, and the response signal is a repetition factor. It is set for each repetition level transmitted.

  A base station according to an aspect of the present disclosure transmits downlink control information and downlink data from the terminal using a transmission unit that transmits the downlink control information and downlink data to the terminal, and an uplink control channel resource determined based on the control information. A receiving unit that receives a response signal for the downlink data, and transmitting the downlink control information capable of repetition transmission to the terminal over a plurality of subframes for which the coverage enhancement mode is set. The uplink control channel resource is determined using a first offset, and the first offset is different from the second offset used when the coverage enhancement mode is not set, and the response signal is a repeat signal. This is set for each repetition level transmitted.

  A communication method according to an aspect of the present disclosure includes a step of transmitting downlink control information and downlink data to a terminal, and the uplink control channel resource determined based on the control information is transmitted from the terminal Receiving a response signal for the downlink data, and when a coverage enhancement mode capable of repetition transmission of the response signal across a plurality of subframes is set in the terminal, The uplink control channel resource is determined using a first offset, and the first offset is different from the second offset used when the coverage enhancement mode is not set, and the response signal is transmitted by repetition. It is set for each repetition level.

  A communication method according to an aspect of the present disclosure includes a step of transmitting downlink control information and downlink data to a terminal, and the uplink control channel resource determined based on the control information is transmitted from the terminal Receiving a response signal for the downlink data, and transmitting to the terminal the downlink control information capable of repetition transmission over a plurality of subframes set with a coverage enhancement mode, The uplink control channel resource is determined using a first offset, and the first offset is different from the second offset used when the coverage enhancement mode is not set, and the response signal is a repetition transmission. It is set for each repetition level.

  The integrated circuit according to an aspect of the present disclosure is transmitted from the terminal using downlink control information and downlink data, a process of transmitting the downlink data to the terminal, and an uplink control channel resource determined based on the control information. Receiving a response signal for the downlink data, and when a coverage enhancement mode capable of repetition transmission of the response signal across a plurality of subframes is set in the terminal, The uplink control channel resource is determined using a first offset, and the first offset is different from the second offset used when the coverage enhancement mode is not set, and the response signal is transmitted by repetition. It is set for each repetition level.

  The integrated circuit according to an aspect of the present disclosure is transmitted from the terminal using downlink control information and downlink data, a process of transmitting the downlink data to the terminal, and an uplink control channel resource determined based on the control information. Receiving a response signal for the downlink data, and transmitting the downlink control information capable of repetition transmission over a plurality of subframes set with a coverage enhancement mode to the terminal, The uplink control channel resource is determined using a first offset, and the first offset is different from the second offset used when the coverage enhancement mode is not set, and the response signal is a repetition transmission. It is set for each repetition level.

  According to one aspect of the present disclosure, collision of PUCCH resources between a terminal in normal mode and a terminal in MTC coverage enhancement mode is avoided without reducing the frequency utilization efficiency of PDCCH resources and increasing the complexity of scheduling. can do.

Diagram showing the transmission timing of each channel The figure which shows the spreading | diffusion method of a response signal and a reference signal Diagram showing an example of PUCCH resources The figure which shows the transmission timing of each channel at the time of repetition transmission Diagram showing an example of PUCCH resource collision FIG. 3 is a block diagram showing a main configuration of the base station according to Embodiment 1. FIG. 3 is a block diagram showing a main configuration of a terminal according to Embodiment 1. FIG. 3 is a block diagram showing a configuration of a base station according to the first embodiment. A block diagram showing a configuration of a terminal according to the first embodiment The figure which shows the PUCCH resource which concerns on Embodiment 1. The figure which shows the PUCCH resource which concerns on Embodiment 2. The figure which shows the PUCCH resource which concerns on Embodiment 3. The figure which shows matching with CCE and PUCCH resource which concern on Embodiment 4. The figure which shows matching with CCE and PUCCH resource which concern on Embodiment 4. The figure which shows an example of the collision of the PUCCH resource which concerns on Embodiment 5 The figure which shows the transmission timing of each channel which concerns on Embodiment 5. FIG. The figure which shows an example of the collision of the PUCCH resource which concerns on Embodiment 6 The figure which shows the transmission timing of each channel which concerns on Embodiment 6. FIG.

FIG. 4 shows the transmission timing of each channel in MTC coverage enhancement assumed as one aspect of the present disclosure. In FIG. 4, the PDCCH repetition level (number of repetitions or repetition factor) is N _PDCCH , the PDSCH repetition level is N _PDSCH , and the PUCCH repetition level is N _PUCCH . Also, as shown in FIG. 4, in MTC coverage enhancement, repetition transmission of PDSCH to which data is allocated by the PDCCH is performed after repetition transmission of PDCCH. The transmission timing of the ACK / NACK signal (PUCCH) at the terminal is after the K _MTC subframe from the subframe in which the PDSCH has been received.

  For downlink control signal when MTC coverage enhancement mode terminal (terminal that performs repetition transmission) and normal mode terminal (terminal that does not perform repetition transmission) coexist in the area covered by the same base station If the control channels are separately provided, the frequency utilization efficiency is lowered. Therefore, it is conceivable to set the downlink control channel (PDCCH) using the same frequency for the terminal in the normal mode and the terminal in the MTC coverage enhancement mode.

  At this time, in the terminal in the normal mode and the terminal in the MTC coverage enhancement mode, the subframe in which the ACK / NACK signal is transmitted (the first subframe in which PUCCH repetition transmission is performed) and the transmission of the ACK / NACK signal are performed. The time interval differs from the subframe in which the PDCCH including the CCE associated with the PUCCH resource to be used is transmitted (the last subframe in which PDCCH repetition transmission is performed). Therefore, when both terminals transmit an ACK / NACK signal in the same subframe, the CCE number associated with the PUCCH resource to which the normal mode terminal transmits the ACK / NACK signal and the MTC coverage enhancement mode terminal ACK There is a possibility that the CCE number associated with the PUCCH resource that transmits the / NACK signal overlaps. In this case, the ACK / NACK signal is transmitted using the same PUCCH resource in both terminals.

  FIG. 5 shows an example when the PUCCH resource of the terminal in the normal mode collides with the PUCCH resource of the terminal in the MTC coverage enhancement mode. In FIG. 5, n is a subframe in which a PUCCH resource collision occurs.

In this case, for the terminal in the normal mode, the PDCCH is transmitted in the subframe nK, and the PDSCH allocated by the PDCCH is transmitted in the same subframe nK. On the other hand, for terminals in MTC coverage enhancement mode, PDCCH is transmitted in subframes nK _MTC -N _PDSCH -N _{PDCCH to} nK _MTC -N _PDSCH -1. The PDSCH allocated by the PDCCH is transmitted in subframes nK _MTC -N _{PDSCH to} nK _MTC −1.

  When a subframe in which a terminal in normal mode transmits PDCCH and a subframe in which a terminal in MTC coverage enhancement mode transmits PDCCH overlap, both terminals do not transmit PDCCH using the same CCE Scheduled. However, in other cases (for example, in the case of FIG. 5), the same CCE can be used for PDCCH transmission to a terminal in normal mode and PDCCH repetition transmission to a terminal in MTC coverage enhancement mode. For example, in FIG. 5, CCE # 0 to CCE # 3 are used for PDCCH for a terminal in MTC coverage enhancement mode, and the terminal corresponds to CCE # 0 (the smallest index among CCE # 0 to CCE # 3). PUCCH resource to use. Further, in FIG. 5, CCE # 0 and CCE # 1 are used for PDCCH for the terminal in the normal mode, and the terminal uses the PUCCH resource corresponding to CCE # 0 (the smaller index of CCE # 0 and CCE # 1). Is used.

  As a result, a collision of PUCCH resources for transmitting an ACK / NACK signal occurs between a terminal in the normal mode and a terminal in the MTC coverage enhancement mode.

  The PDCCH allocation of the normal mode terminal is performed on the base station side so that the PUCCH resource where the normal mode terminal transmits the ACK / NACK signal and the PUCCH resource where the MTC coverage enhancement mode terminal transmits the ACK / NACK signal do not collide. It is also possible to control (CCE used for terminals in MTC coverage enhancement mode in the past subframe is not assigned to terminals in normal mode). However, in this case, there are problems such as a decrease in utilization efficiency of PDCCH resources or an increase in scheduling complexity.

  Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[Outline of communication system]
In the following description, an FDD (Frequency Division Duplex) system will be described as an example.

  Also, the communication system according to each embodiment of the present disclosure is a system that supports LTE-Advanced, for example, and includes a base station 100 and a terminal 200.

  The terminal 200 is set to the normal mode or the MTC coverage enhancement mode. For example, when the MTC coverage enhancement mode is applied, the terminal 200 applies repetition transmission over a plurality of subframes when transmitting PDCCH, PDSCH, or PUCCH. That is, terminal 200 repeatedly transmits the same signal in consecutive subframes for a predetermined repetition level.

  FIG. 6 is a block diagram illustrating a main configuration of the base station 100 according to the embodiment of the present disclosure. In the base station 100 shown in FIG. 6, the transmission unit 112 transmits control information (PDCCH signal) indicating downlink data allocation and downlink data (PDSCH signal), and the control unit 101 adds the control information to the control information. Based on the ACK / NACK signal for the downlink data, the ACK / NACK signal receiving unit (PUCCH extracting unit 116, despreading unit 118, correlation processing unit 119) determines the determined resource. ACK / NACK signal is received using. Here, the receiving unit transmits an ACK / NACK signal transmitted from a first terminal to which repetition transmission is applied to the control information, downlink data, and ACK / NACK signal to a first resource group ( A second resource group (PUCCH resource) different from the first resource group is received from an ACK / NACK signal received from a second terminal to which repetition transmission is not applied, using a resource in the PUCCH resource region). Receive using the resources in the region.

  FIG. 7 is a block diagram illustrating a main configuration of the terminal 200 according to each embodiment of the present disclosure. In terminal 200 shown in FIG. 7, receiving section 202 receives control information indicating downlink data allocation and downlink data, and control section 213 receives ACK / for downlink data based on the control information. The resource used for the NACK signal is determined, and the ACK / NACK signal transmission unit (primary spreading unit 216, secondary spreading unit 217, IFFT unit 218) transmits the ACK / NACK signal using the determined resource. To do. Here, the transmission unit includes the first resource group when the terminal is a first terminal to which repetition transmission is applied to control information, downlink data, and an ACK / NACK signal. When an ACK / NACK signal is transmitted using a resource and the terminal is a second terminal to which repetition transmission is not applied, a resource in a second resource group different from the first resource group is used. Send an ACK / NACK signal.

(Embodiment 1)
[Base station configuration]
FIG. 8 is a block diagram showing a configuration of base station 100 according to Embodiment 1 of the present disclosure. In FIG. 8, the base station 100 includes a control unit 101, a control signal generation unit 102, a control signal encoding unit 103, a control signal modulation unit 104, a broadcast signal generation unit 105, a data encoding unit 106, Retransmission control unit 107, data modulation unit 108, signal allocation unit 109, IFFT unit 110, CP adding unit 111, transmitting unit 112, antenna 113, receiving unit 114, CP removing unit 115, PUCCH An extraction unit 116, a sequence control unit 117, a despreading unit 118, a correlation processing unit 119, and a determination unit 120 are included.

  The control unit 101 transmits, to the resource allocation target terminal 200, a downlink resource (downlink control information allocation resource) for transmitting control information and downlink data (transmission data) included in the control information. Downlink resources (downlink data allocation resources) are allocated. The downlink control information allocation resource is selected in a resource corresponding to PDCCH or EPDCCH (Enhanced PDCCH). Further, the downlink data allocation resource is selected within the resource corresponding to PDSCH. When there are a plurality of resource allocation target terminals 200 in the same subframe, the control unit 101 allocates different resources to each of the resource allocation target terminals 200. The downlink control information allocation resource is equivalent to the above-described L1 / L2 CCH. That is, the downlink control information allocation resource is composed of one or a plurality of CCEs. Further, as described above, when PUCCH is notified implicitly using CCE, each CCE is associated with a PUCCH resource in an uplink control channel region (PUCCH region).

  The control unit 101 identifies a PUCCH resource (frequency and code used for primary spreading / secondary spreading) corresponding to the CCE occupied by the PDCCH including the control information. The control unit 101 transmits information on ZAC sequences and orthogonal code sequences (that is, PUCCH resources) that may be used for spreading the PUCCH signals (ACK / NACK signals and reference signals) transmitted from the terminal 200 to the sequence control unit. 117 and output information about the frequency to the PUCCH extraction unit 116.

  Also, the control unit 101 determines a coding rate used when transmitting control information to the resource allocation target terminal 200 and outputs the determined coding rate to the control signal coding unit 103. Also, the control unit 101 determines a coding rate used when transmitting downlink data to the resource allocation target terminal 200, and outputs the determined coding rate to the data coding unit 106.

  Since the data amount of the control information varies depending on the determined coding rate, the control unit 101 allocates downlink control information allocation resources including CCEs to which the control information of this data amount can be mapped. The control unit 101 outputs information on downlink data allocation resources to the control signal generation unit 102. Also, the control unit 101 outputs information related to downlink data allocation resources and downlink control information allocation resources to the signal allocation unit 109.

  In addition, when the MTC coverage enhancement mode is set for the resource allocation target terminal 200, the control unit 101 provides information on the repetition level (number of repetitions) for each channel (PDCCH, PDSCH, or PUCCH) of the terminal 200. And output to the control signal generation unit 102 and the data encoding unit 106.

  Further, the control unit 101 instructs the notification signal generation unit 105 to generate a notification signal based on a parameter determined in advance for each base station.

  In addition, the control unit 101 generates information regarding the PUCCH resource and outputs the information to the control signal generation unit 102. The information regarding the PUCCH resource is, for example, a parameter for specifying the PUCCH resource used in the terminal in the normal mode and the terminal in the MTC coverage enhancement mode. In addition, the information regarding a PUCCH resource may be notified to the terminal 200 as broadcast information as a cell-specific value, or may be notified to the terminal 200 as higher layer signaling.

  The control signal generation unit 102 generates a control signal using information received from the control unit 101 (information on downlink data allocation resources, information on PUCCH repetition levels or information on PUCCH resources), and encodes the control signal into a control signal Output to the unit 103. When there are a plurality of resource allocation target terminals 200, the control signal includes the terminal ID of the destination terminal in order to distinguish the resource allocation target terminals 200 from each other. For example, the control signal includes a CRC bit masked by the terminal ID of the destination terminal. In addition, when the MTC coverage enhancement mode is set for the resource allocation target terminal 200, the control signal generation unit 102 generates a repetition signal according to information about the repetition level received from the control unit 101. That is, when the PDCCH repetition level is greater than 1, control signal generation section 102 sends the same control signal to control signal encoding section 103 over a plurality of consecutive subframes corresponding to the repetition level. Output.

  The control signal encoding unit 103 encodes the control signal received from the control signal generation unit 102 according to the coding rate received from the control unit 101, and outputs the encoded control signal to the control signal modulation unit 104.

  Control signal modulation section 104 modulates the control signal received from control signal encoding section 103 and outputs the modulated control signal to signal allocation section 109.

  The notification signal generation unit 105 generates a notification signal according to an instruction from the control unit 101, and outputs the notification signal to the signal allocation unit 109. The broadcast signal includes, for example, a signal related to the system bandwidth or the PUCCH resource. Also, the notification signal may be subjected to encoding processing and modulation processing.

  Data encoding section 106 encodes transmission data (bit sequence, that is, downlink data) for each destination terminal according to the encoding rate received from control section 101, and outputs the encoded data signal to retransmission control section 107. To do. In addition, when the MTC coverage enhancement mode is set for the resource allocation target terminal 200, the data encoding unit 106 generates a repetition signal according to information about the repetition level received from the control unit 101. That is, when the PDSCH repetition level is higher than 1, data encoding section 106 outputs the same data signal to retransmission control section 107 over a plurality of consecutive subframes corresponding to the repetition level. .

  Retransmission control section 107 holds the encoded data signal received from data encoding section 106 and outputs it to data modulation section 108 at the time of initial transmission. The retransmission control unit 107 holds the encoded data signal for each destination terminal. In addition, upon receiving a NACK for the transmitted data signal from determination unit 120 described later, retransmission control unit 107 outputs corresponding retained data to data modulation unit 108. When receiving the ACK for the transmitted data signal, retransmission control section 107 deletes the corresponding retained data.

  Data modulation section 108 modulates the data signal received from retransmission control section 107 and outputs the data modulation signal to signal allocation section 109.

  The signal allocation unit 109 receives a control signal received from the control signal modulation unit 104, a notification signal received from the notification signal generation unit 105, and a data modulation signal received from the data modulation unit 106 as downlink resources (downlink data signal allocation resources, downlink signals). And the mapped signal is output to IFFT section 110. Specifically, the signal allocation unit 109 maps the control signal to the resource indicated by the downlink control information allocation resource received from the control unit 101, and applies the data modulation signal to the resource indicated by the downlink data allocation resource received from the control unit 101. Map. The signal allocation unit 109 maps the broadcast signal to a preset time / frequency resource.

  IFFT section 110 converts the frequency domain signal into a time domain signal by performing IFFT processing on the signal received from signal allocation section 109. IFFT section 110 outputs the time domain signal to CP adding section 111.

  CP adding section 111 adds a CP to the signal received from IFFT section 110 and outputs the signal after the CP addition (OFDM signal) to transmitting section 112.

  Transmitting section 112 performs RF (Radio Frequency) processing such as D / A (Digital-to-Analog) conversion and up-conversion on the OFDM signal received from CP adding section 111, and wirelessly transmits to terminal 200 via antenna 113. Send a signal.

  The receiving unit 114 performs RF processing such as down-conversion or A / D (Analog-to-Digital) conversion on the radio signal from the terminal 200 received via the antenna 113, and the obtained received signal is subjected to CP. The result is output to the removal unit 115.

  CP removing section 115 removes the CP added to the received signal received from receiving section 114 and outputs the signal after CP removal to PUCCH extracting section 116.

  PUCCH extraction section 116 extracts the uplink control channel signal (PUCCH) from the signal received from CP removal section 115 based on the information received from control section 101, and outputs the extracted PUCCH to despreading section 118. Also, when there is a terminal 200 in the MTC coverage enhancement mode, the PUCCH extraction unit 116 performs in-phase combining on the PUCCH transmitted by repetition over a plurality of subframes and extracts a PUCCH (combined signal).

  Sequence control section 117, based on the ZAC sequence and orthogonal code sequence information received from control section 101, a ZAC sequence that may be used for spreading ACK / NACK signals and reference signals transmitted from terminal 200, and An orthogonal code sequence is generated. Sequence control section 117 outputs the orthogonal code sequence to despreading section 118 and outputs the ZAC sequence to correlation processing section 119.

  Despreading section 118 uses the orthogonal code sequence received from sequence control section 117 (orthogonal code sequence that terminal 200 should use for secondary spreading), and corresponds to the ACK / NACK signal in the signal received from PUCCH extraction section 116 Are despread, and the despread signal is output to the correlation processing unit 119.

  Correlation processing section 119 obtains a correlation value between a ZAC sequence input from sequence control section 117 (a ZAC sequence that terminal 200 may use in primary spreading) and a signal input from despreading section 118. The correlation value is output to the determination unit 120.

  Based on the correlation value received from correlation processing section 119, determination section 120 determines whether the ACK / NACK signal transmitted from terminal 200 indicates ACK or NACK for the transmitted data. The determination unit 120 outputs the determination result to the retransmission control unit 107.

[Terminal configuration]
FIG. 9 is a block diagram showing a configuration of terminal 200 according to Embodiment 1 of the present disclosure. In FIG. 9, terminal 200 includes antenna 201, receiving section 202, CP removing section 203, FFT (Fast Fourier Transform) section 204, extracting section 205, broadcast signal receiving section 206, and control signal demodulating section 207. A control signal decoding unit 208, a determination unit 209, a data demodulation unit 210, a data decoding unit 211, a CRC unit 212, a control unit 213, an ACK / NACK generation unit 214, a modulation unit 215, 1 A secondary spreading unit 216, a secondary spreading unit 217, an IFFT unit 218, a CP adding unit 219, and a transmitting unit 220 are included.

  Receiving section 202 performs RF processing such as down-conversion or AD conversion on the radio signal received from antenna 201 from base station 100 to obtain a baseband OFDM signal. Receiving section 202 outputs the OFDM signal to CP removing section 203.

  CP removing section 203 removes the CP added to the OFDM signal received from receiving section 202, and outputs the signal after CP removal to FFT section 204.

  The FFT unit 204 converts the time domain signal into a frequency domain signal by performing an FFT process on the signal received from the CP removal unit 203. The FFT unit 204 outputs the frequency domain signal to the extraction unit 205.

  The extraction unit 205 extracts a notification signal from the signal received from the FFT unit 204 and outputs the notification signal to the notification signal reception unit 206. Here, since the resource to which the broadcast signal is mapped is determined in advance, the extraction unit 205 obtains the broadcast signal by extracting information mapped to the resource. The extracted broadcast signal includes, for example, a system bandwidth or a signal related to PUCCH resources.

  Further, the extraction unit 205 extracts a downlink control channel signal (PDCCH signal) from the signal received from the FFT unit 204 and outputs it to the control signal demodulation unit 207. Further, the extraction unit 205 extracts downlink data (PDSCH signal) from the signal received from the FFT unit 204 based on the information regarding the downlink data allocation resource addressed to the terminal received from the determination unit 209 and supplies the downlink data (PDSCH signal) to the data demodulation unit 210. Output. The PDCCH signal includes, for example, information on downlink data allocation resources, information on PUCCH repetition levels, information on PUCCH resources, and the like.

  In addition, when the MTC coverage enhancement mode is set for the own device and the PDCCH signal is transmitted by repetition, the extraction unit 205 performs in-phase synthesis on the PDCCH signal transmitted by repetition over a plurality of subframes. Then, the PDCCH signal is extracted. Similarly, when downlink data (PDSCH signal) is transmitted by repetition, the extraction unit 205 performs in-phase synthesis on the PDSCH signal transmitted by repetition over a plurality of subframes, and performs downlink transmission. Extract data.

  The broadcast signal receiving unit 206 obtains information on the system bandwidth or PUCCH resource from the broadcast signal received from the extraction unit 205. The broadcast signal receiving unit 206 performs demodulation processing and decoding processing when the broadcast signal is encoded and modulated. The notification signal receiving unit 206 outputs the obtained notification signal to the determination unit 209 or the control unit 213.

  Control signal demodulation section 207 demodulates the PDCCH signal received from extraction section 205, and outputs the demodulated PDCCH signal to control signal decoding section 208.

  Control signal decoding section 208 decodes the PDCCH signal received from control signal demodulation section 207 and outputs the decoding result to determination section 209.

  The determination unit 209 blindly determines whether the control information included in the decoding result received from the control signal decoding unit 208 is control information addressed to the terminal itself. For example, the determination unit 209 demasks the CRC bits with the terminal ID of the own terminal, and determines that the control information in which CRC = OK (no error) is the control information addressed to the own terminal. Then, the determination unit 209 outputs information regarding the downlink data allocation resource included in the control information addressed to the own device to the extraction unit 205. Also, the determination unit 209 identifies the CCE to which the control information addressed to itself is mapped, and outputs the identified CCE identification information to the control unit 213.

  The data demodulator 210 demodulates the downlink data received from the extractor 205 and outputs the demodulated downlink data to the data decoder 211.

  The data decoding unit 211 decodes the downlink data received from the data demodulation unit 210 and outputs the decoded downlink data to the CRC unit 212.

  CRC section 212 performs error detection on the downlink data received from data decoding section 211 using CRC, and outputs the error detection result to ACK / NACK generation section 214. Also, the CRC unit 212 outputs, as received data, downlink data that has been determined to be error-free as a result of error detection.

  The control unit 213 holds in advance information related to the PUCCH resource and information related to the repetition level notified from the base station 100 to the terminal 200 through a broadcast signal, a PDCCH signal, or higher layer signaling.

  The control unit 213 uses the information about the PUCCH resource and the CCE identification information received from the determination unit 209 to use the PUCCH resource (frequency and primary spreading / secondary spreading) corresponding to the CCE indicated in the CCE identification information. ) Is specified. That is, the control unit 213 specifies the PUCCH resource of the uplink control channel based on the CCE identification information.

  Specifically, the control unit 213 generates a ZAC sequence corresponding to the PUCCH resource to be used, determines the cyclic shift amount to be used based on the set cyclic shift amount, and determines the primary spreading unit 216. Output to. Also, the control unit 213 outputs an orthogonal code sequence corresponding to the PUCCH resource to be used to the secondary spreading unit 217. Also, the control unit 213 outputs the frequency resource (subcarrier) corresponding to the PUCCH resource to be used to the IFFT unit 218.

  In addition, when the terminal is in the MTC coverage enhancement mode, the control unit 213 outputs information on the PUCCH repetition level to the ACK / NACK generation unit 214.

  The ACK / NACK generation unit 214 generates an ACK / NACK signal based on the error detection result received from the CRC unit 212. Specifically, ACK / NACK generation unit 214 generates a NACK when an error is detected, and generates an ACK when an error is not detected. The ACK / NACK generation unit 214 outputs the generated ACK / NACK signal to the modulation unit 215. In addition, when the own terminal is in the MTC coverage enhancement mode, the ACK / NACK generation unit 214 transmits a repetition signal according to the information regarding the repetition level received from the control unit 213. That is, when the PUCCH repetition level is greater than 1, the ACK / NACK generation unit 214 sends the same ACK / NACK signal to the modulation unit 215 over a plurality of consecutive subframes corresponding to the repetition level. Output.

  Modulation section 215 modulates the ACK / NACK signal received from ACK / NACK generation section 214 and outputs the modulated ACK / NACK signal to primary spreading section 216.

  The primary spreading section 216 performs primary spreading of the reference signal and the ACK / NACK signal received from the modulating section 215 using the ZAC sequence and cyclic shift amount set by the control section 213, and performs ACK after the primary spreading. The / NACK signal and the reference signal are output to the secondary spreading section 217.

  Secondary spreading section 217 performs second spreading of the ACK / NACK signal and reference signal using the orthogonal code sequence set by control section 213, and outputs the signal after the second spreading to IFFT section 218.

  The IFFT unit 218 uses the frequency resource set by the control unit 213 to perform time mapping by performing mapping to the subcarrier and IFFT processing on the ACK / NACK signal and the reference signal received from the secondary spreading unit 217. Generate a region signal. IFFT section 218 outputs the generated signal to CP adding section 219.

  CP adding section 219 adds a CP to the signal received from IFFT section 218 and outputs the signal after the CP addition to transmitting section 220.

  The transmitting unit 220 performs RF processing such as D / A conversion and up-conversion on the signal received from the CP adding unit 219 and transmits a radio signal to the base station 100 via the antenna 201.

[Operations of base station 100 and terminal 200]
The operations of base station 100 and terminal 200 having the above configuration will be described.

  Below, the case where the terminal of normal mode and the terminal of MTC coverage enhancement mode coexist in the cell of base station 100 is demonstrated.

  Base station 100 according to the present embodiment notifies each terminal 200 of information related to PUCCH resources in advance. The information on the PUCCH resource includes, for example, an offset value used when specifying the PUCCH number from the CCE number, and a PUCCH resource code-multiplexed per resource block (RB) arranged in each PUCCH region Information on the maximum number of

  In the present embodiment, the offset value is set independently for the terminal in the normal mode and the terminal in the MTC coverage enhancement mode.

Specifically, when the terminal in the normal mode receives the downlink allocation control information (PDCCH or EPDCCH), the PUCCH resource that transmits the ACK / NACK signal for the downlink data (PDSCH) indicated in the corresponding allocation control information Resource number n _PUCCH is determined according to the following equation.
n _PUCCH = n _CCE + N _PUCCH ⁽¹⁾ (1)

In the formula (1), n _CCE represents a CCE number (an integer of 0 or more) occupied by the PDCCH. Specifically, when the PDCCH occupies only one CCE, n _CCE is the number of the CCE. In addition, when the PUCCH occupies a plurality of CCEs, n _CCE is the smallest CCE number.

In Equation (1), N _PUCCH ⁽¹⁾ indicates an offset value for specifying the PUCCH resource number from the CCE number. For example, in 3GPP Release 11, N _PUCCH ⁽¹⁾ indicates the number of PUCCH resources reserved for SPS / SR (Semi-Persistent Scheduling / Scheduling Request) resources. N _PUCCH ⁽¹⁾ is, for example, a common value in the cell, and is notified from the base station 100 to the terminal 200 by a broadcast signal or higher layer signaling.

The terminal in the normal mode determines the OC index and the cyclic shift amount to be actually used based on the determined PUCCH resource number n _PUCCH .

On the other hand, when the terminal in the MTC coverage enhancement mode receives the downlink allocation control information (PDCCH or EPDCCH), the PUCCH resource that transmits the ACK / NACK signal for the downlink data (PDSCH) indicated in the corresponding allocation control information Resource number n _{PUCCH_MTC} is determined according to the following equation.
n _{PUCCH_MTC} = n _CCE + N _{PUCCH_MTC} ⁽¹⁾ (2)

In Expression (2), N _{PUCCH_MTC} ⁽¹⁾ indicates an offset value for specifying the PUCCH resource number from the CCE number for the terminal in the MTC coverage enhancement mode. That is, an independent offset value N _{PUCCH_MTC} ⁽¹⁾ different from the offset N _PUCCH ⁽¹⁾ of the terminal in the normal mode is set for the terminal in the MTC coverage enhancement mode. N _{PUCCH_MTC} ⁽¹⁾ may be, for example, an individual (UE specific) value depending on the terminal 200 or a value common to terminals in the MTC coverage enhancement mode.

The terminal in the MTC coverage enhancement mode determines the OC index and the cyclic shift amount to be actually used based on the determined PUCCH resource number n _{PUCCH_MTC} .

  FIG. 10 shows an example of PUCCH resources for a terminal in the normal mode and a terminal in the MTC coverage enhancement mode.

  In FIG. 10, as in FIG. 3, 18 PUCCH resources can be used out of a maximum of 36 PUCCH resources for each 1 RB (PRB (Physical RB)). In FIG. 10, PUCCH resource numbers (# 0 to # 53) are assigned to 54 usable PUCCH resources over three RBs.

In FIG. 10, the offset value N _PUCCH ⁽¹⁾ = 6 for the terminal in the normal mode and the offset value N _{PUCCH_MTC} ⁽¹⁾ = 30 for the terminal in the MTC coverage enhancement mode.

That is, the terminal in the normal mode transmits an ACK / NACK signal using the PUCCH resource with PUCCH resource number n _PUCCH = n _CCE +6. On the other hand, the terminal in the MTC coverage enhancement mode transmits an ACK / NACK signal using the PUCCH resource with PUCCH resource number n _{PUCCH_MTC} = n _CCE +30.

  That is, when the terminal 200 is a terminal in the normal mode, the terminal 200 transmits an ACK / NACK signal using the PUCCH resource in the PUCCH resource group for the terminal in the normal mode, and the terminal 200 When the terminal is in the enhancement mode, the ACK / NACK signal is transmitted using the PUCCH resource in the PUCCH resource group for the terminal in the MTC coverage enhancement mode different from the PUCCH resource group for the terminal in the normal mode.

  Similarly, the base station 100 receives the ACK / NACK signal transmitted from the terminal in the normal mode using the resources in the PUCCH resource group for the terminal in the normal mode, and the terminal in the MTC coverage enhancement mode. ACK / NACK signals transmitted from the terminal are received using resources in the PUCCH resource group for terminals in the MTC coverage enhancement mode different from the PUCCH resource group for terminals in the normal mode.

  Accordingly, as shown in FIG. 10, a PUCCH resource group that can be used for transmission of an ACK / NACK signal by a terminal in MTC coverage enhancement mode in which repetition transmission is applied to the PDCCH signal, the PDSCH signal, and the ACK / NACK signal. And a PUCCH resource group that can be used by a terminal in a normal mode to which repetition transmission is not applied to transmit an ACK / NACK signal. That is, the PUCCH resource region for both terminals is divided by changing the offset value for specifying the PUCCH resource number from the CCE number between the terminal in the normal mode and the terminal in the MTC coverage enhancement mode.

FIG. 10 shows a case where the number of CCEs that can be used for the terminal 200 in each mode is 24. However, the number of CCEs that can be used for terminal 200 in each mode is not limited to 24, and other values may be used, and the PUCCH resource area for terminal 200 in each mode is divided according to the number of CCEs that can be used. Thus, the offset values N _PUCCH ⁽¹⁾ and N _{PUCCH_MTC} ⁽¹⁾ may be set.

Here, as an example, as shown in FIG. 5, when the CCE number corresponding to the PUCCH resource used for the ACK / NACK signal transmitted in the same subframe is CCE # 0 (that is, n _CCE = 0) Will be described.

In this case, the terminal in the normal mode uses the PUCCH resource with the PUCCH resource number n _PUCCH = 6 (= 0 + 6) according to Equation (1).

On the other hand, the terminal in the MTC coverage enhancement mode uses the PUCCH resource with the PUCCH resource number n _{PUCCH_MTC} = 30 (= 0 + 30) according to Equation (2).

That is, when the terminal 200 (control unit 213) is a terminal in the normal mode, the terminal 200 (control unit 213) adds the offset value N _PUCCH ⁽¹⁾ to the _CCE index n _CCE used for the PDCCH, and actually receives the ACK. PUCCH resource used for / NACK signal is calculated. Further, when the terminal 200 is a terminal in the MTC coverage enhancement mode, the terminal 200 adds the offset value N _{PUCCH_MTC} ⁽¹⁾ to the _CCE index n _CCE used for the PDCCH, and actually transmits the ACK / NACK signal. Calculate PUCCH resources used for. However, the offset value N _PUCCH ⁽¹⁾ is different from the offset value N _{PUCCH_MTC} ⁽¹⁾ .

  Therefore, when both terminals transmit an ACK / NACK signal in the same subframe, the CCE number associated with the PUCCH resource in which the terminal in the normal mode transmits the ACK / NACK signal and the terminal in the MTC coverage enhancement mode are ACK. Even if the CCE number associated with the PUCCH resource for transmitting the / NACK signal is the same CCE # 0, the PUCCH resources used in both are different.

  That is, when both terminals transmit ACK / NACK signals in the same subframe, even if the CCE number (minimum index) used for the corresponding PDCCH is the same, the terminal in normal mode and MTC coverage enhancement mode PUCCH resource collision with other terminals can be avoided.

  Thus, according to the present embodiment, PUCCH resources are determined using different offset values for terminals in the normal mode and terminals in the MTC coverage enhancement mode. By doing so, the PUCCH resource that can be used by the terminal in the normal mode and the PUCCH resource that can be used by the terminal in the MTC coverage enhancement mode are separated. As a result, the PUCCH resources used for the ACK / NACK signal are different even if the CCE occupied by the PDCCH used for downlink data allocation corresponding to the ACK / NACK signal transmitted in the same subframe is the same. Can be made. Therefore, collision of PUCCH resources for transmitting ACK / NACK signals can be avoided.

  Also, as described above, since the offset value for specifying the PUCCH resource number is different between the terminal in the normal mode and the terminal in the MTC coverage enhancement mode, the collision of the PUCCH resource is avoided. There is no need to add any restrictions on allocation. For this reason, according to the present embodiment, the PDCCH resource usage efficiency does not decrease or the scheduling complexity does not increase.

  Therefore, according to the present embodiment, the PUCCH resource collision between the terminal in the normal mode and the terminal in the MTC coverage enhancement mode is performed without reducing the frequency utilization efficiency of the PDCCH resource and increasing the complexity of scheduling. It can be avoided.

Furthermore, allocation of PUCCH resources to terminals in the normal mode (see, for example, Equation (1)) has already been performed in the LTE system. Therefore, in the present embodiment, only the offset value N _{PUCCH_MTC} ⁽¹⁾ used independently when allocating the PUCCH resource to the terminal in the MTC coverage enhancement mode may be newly notified from the base station 100 to the terminal 200. Therefore, the influence on the operation of the existing system is small.

(Embodiment 2)
The basic configuration of the base station and terminal according to the present embodiment is the same as that of Embodiment 1, and will be described with reference to FIG. 8 (base station 100) and FIG. 9 (terminal 200).

  Hereinafter, as in Embodiment 1, a case where a terminal in the normal mode and a terminal in the MTC coverage enhancement mode coexist in the cell of base station 100 will be described.

  Base station 100 according to the present embodiment notifies each terminal 200 of information related to PUCCH resources in advance. The information on the PUCCH resource includes, for example, an offset value used when specifying the PUCCH number from the CCE number, and a PUCCH resource code-multiplexed per resource block (RB) arranged in each PUCCH region Information on the maximum number of

  In the present embodiment, the offset value is set in common for terminals in the normal mode and terminals in the MTC coverage enhancement mode. However, the correspondence between the CCE number and the PUCCH resource number is different between the terminal in the normal mode and the terminal in the MTC coverage enhancement mode.

Specifically, as in the first embodiment, the terminal in the normal mode determines the resource number n _PUCCH of the PUCCH resource that transmits the ACK / NACK signal according to Equation (1), and actually uses the OC index and the cyclic shift. Determine the amount.

On the other hand, when the terminal in the MTC coverage enhancement mode receives the downlink allocation control information (PDCCH or EPDCCH), the PUCCH resource that transmits the ACK / NACK signal for the downlink data (PDSCH) indicated in the corresponding allocation control information Resource number n _{PUCCH_MTC} is determined according to the following equation.
n _{PUCCH_MTC} = N _PUCCH ⁽¹⁾ -1-n _CCE (3)

In Expression (3), N _PUCCH ⁽¹⁾ is an offset value for specifying the PUCCH resource number from the CCE number, and is also included in Expression (1). That is, the same offset value N _PUCCH ^{(1) as} the offset N _PUCCH ⁽¹⁾ of the terminal in the normal mode is set for the terminal in the MTC coverage enhancement mode. N _PUCCH ⁽¹⁾ may be notified from base station 100 to terminal 200 by a broadcast signal or higher layer signaling, for example.

The terminal in the MTC coverage enhancement mode determines the OC index and the cyclic shift amount to be actually used based on the determined PUCCH resource number n _{PUCCH_MTC} .

That is, when the terminal 200 (control unit 213) is a terminal in the normal mode, the terminal 200 (control unit 213) adds the offset value N _PUCCH ⁽¹⁾ to the _CCE index n _CCE used for the PDCCH, and actually receives the ACK. PUCCH resource used for / NACK signal is calculated. On the other hand, when the terminal 200 is a terminal in the MTC coverage enhancement mode, the terminal 200 subtracts the _CCE index n _CCE used for the PDCCH from the offset value N _{PUCCH_MTC} ⁽¹⁾ , and actually receives the ACK / NACK. Calculate the PUCCH resource used for the signal.

  FIG. 11 shows an example of PUCCH resources for a terminal in normal mode and a terminal in MTC coverage enhancement mode.

  In FIG. 11, 18 PUCCH resources can be used out of a maximum of 36 PUCCH resources for each RB, as in FIG. 10. In FIG. 11, PUCCH resource numbers (# 0 to # 53) are assigned to 54 usable PUCCH resources over three RBs.

Also, in FIG. 11, the offset value N _PUCCH ⁽¹⁾ = 30 for each terminal 200.

That is, the terminal in the normal mode transmits an ACK / NACK signal using the PUCCH resource with the PUCCH resource number n _PUCCH = n _CCE +30. On the other hand, a terminal in the MTC coverage enhancement mode transmits an ACK / NACK signal using a PUCCH resource with a PUCCH resource number n _{PUCCH_MTC} = 30-1-n _CCE (= 29-n _CCE ).

  That is, as shown in FIG. 11, with the boundary between PUCCH resource numbers # 29 and # 30, PUCCH resources with numbers greater than or equal to # 30 are set in the PUCCH resource area for terminals in the normal mode, and numbers less than or equal to # 29 The PUCCH resource is set in the PUCCH resource area for terminals in the MTC coverage enhancement mode.

  Accordingly, as shown in FIG. 11, different PUCCH resource regions are set for each of the terminal in the normal mode and the terminal in the MTC coverage enhancement mode. That is, by changing the correspondence (formula (1) and formula (3)) for specifying the PUCCH resource number from the CCE number between the terminal in the normal mode and the terminal in the MTC coverage enhancement mode, The PUCCH resource area for the terminal is divided.

Here, as an example, as shown in FIG. 5, when the CCE number corresponding to the PUCCH resource used for the ACK / NACK signal transmitted in the same subframe is CCE # 0 (that is, n _CCE = 0) Will be described.

In this case, the terminal in the normal mode uses the PUCCH resource with the PUCCH resource number n _PUCCH = 30 (= 0 + 30) according to Equation (1).

On the other hand, the terminal in the MTC coverage enhancement mode uses the PUCCH resource with the PUCCH resource number n _{PUCCH_MTC} = 29 (= 29-0) according to Equation (3).

  That is, when both terminals transmit an ACK / NACK signal in the same subframe, the CCE number associated with the PUCCH resource to which the normal mode terminal transmits the ACK / NACK signal and the MTC coverage enhancement mode terminal ACK Even if the CCE number associated with the PUCCH resource for transmitting the / NACK signal is the same CCE # 0, the PUCCH resources used in both are different.

  That is, when both terminals transmit ACK / NACK signals in the same subframe, even if the CCE number (minimum index) used for the corresponding PDCCH is the same, the terminal in normal mode and MTC coverage enhancement mode PUCCH resource collision with other terminals can be avoided.

  As described above, according to the present embodiment, PUCCH resources are determined using associations between different CCEs for terminals in the normal mode and terminals in the MTC coverage enhancement mode. By doing so, the PUCCH resource that can be used by the terminal in the normal mode and the PUCCH resource that can be used by the terminal in the MTC coverage enhancement mode are separated. As a result, the PUCCH resources used for the ACK / NACK signal are different even if the CCE occupied by the PDCCH used for downlink data allocation corresponding to the ACK / NACK signal transmitted in the same subframe is the same. Can be made. Therefore, collision of PUCCH resources for transmitting ACK / NACK signals can be avoided.

  In addition, as described above, since the correspondence for specifying the PUCCH resource number is different between the terminal in the normal mode and the terminal in the MTC coverage enhancement mode, the collision of the PUCCH resource is avoided. There is no need to add any restrictions on allocation. For this reason, according to the present embodiment, the PDCCH resource usage efficiency does not decrease or the scheduling complexity does not increase.

  Therefore, according to the present embodiment, the PUCCH resource collision between the terminal in the normal mode and the terminal in the MTC coverage enhancement mode is performed without reducing the frequency utilization efficiency of the PDCCH resource and increasing the complexity of scheduling. It can be avoided.

Furthermore, allocation of PUCCH resources to terminals in the normal mode (see, for example, Equation (1)) has already been performed in the LTE system. In addition, the same parameter (offset value N _PUCCH ⁽¹⁾ ) as that of the terminal in the normal mode is also used when assigning the PUCCH resource to the terminal in the MTC coverage enhancement mode. Therefore, there is no parameter to be newly added to the terminal in the MTC coverage enhancement mode. Therefore, it does not affect the operation of the existing system.

  The association for specifying the PUCCH resource number from the CCE number may be reversed between the normal mode and the MTC coverage enhancement mode. That is, the terminal in the normal mode may determine the PUCCH resource number using Equation (3), and the terminal in the MTC coverage enhancement mode may determine the PUCCH resource number using Equation (1). Since it is assumed that the terminal does not communicate so frequently in MTC, it is assumed that the frequency of use of the PUCCH region of the terminal in the MTC coverage enhancement mode is low. In the uplink, a PUSCH area (Physical Downlink Shared Channel) is arranged at the center of the system band, PUCCH areas are arranged at both ends, and PUCCH resources (for example, see FIG. 11) are arranged from the outside to the inside of the PUCCH area. PUCCH resource numbers are assigned in ascending order. Therefore, the PUCCH region of the MTC coverage enhancement mode terminal, which is associated with Equation (1) and is used less frequently, is arranged in the frequency band inside the uplink, and is thus continuous with the frequency band for uplink data. be able to. In this way, when a terminal in the MTC coverage enhancement mode does not use a PUCCH resource, the resource can be used for uplink data (PUSCH). In addition, since the PUCCH region of a terminal in MTC coverage enhancement mode is continuous with the PUSCH region, a plurality of consecutive subcarriers are collectively allocated to a specific terminal, and a peak-to-transmission power ratio (PAPR: Peak-to- Increase in Average Power Ratio can be suppressed.

(Embodiment 3)
The basic configuration of the base station and terminal according to the present embodiment is the same as that of Embodiment 1, and will be described with reference to FIG. 8 (base station 100) and FIG. 9 (terminal 200).

  Below, the case where the terminal of normal mode and the terminal of MTC coverage enhancement mode coexist in the cell of base station 100 is demonstrated.

  Base station 100 according to the present embodiment notifies each terminal 200 of information related to PUCCH resources in advance. Information on PUCCH resources includes, for example, a difference in cyclic shift amount between available PUCCH resources adjacent to each other in one orthogonal sequence of PUCCH resources (for example, see FIG. 3), and 1 RB arranged in each PUCCH region. Contains information on the maximum number of code-multiplexed PUCCH resources.

  Also, different PUCCH resource regions are set for each of the terminal in the normal mode and the terminal in the MTC coverage enhancement mode. In the following description, a case will be described in which Implicit notification is made in association with a CCE number as allocation of a PUCCH resource to a terminal in MTC coverage enhancement mode. For example, the PUCCH resource for the terminal in the normal mode and the terminal in the MTC coverage enhancement mode may be set by the same method as in the first or second embodiment. However, in the present embodiment, as an allocation of the PUCCH resource to the terminal in the MTC coverage enhancement mode, Explicit notification may be sent from base station 100 to terminal 200 using higher layer signaling or the like.

  In the present embodiment, the difference in the cyclic shift amount is set independently for the terminal in the normal mode and the terminal in the MTC coverage enhancement mode.

  FIG. 12 shows an example of PUCCH resources for the terminal in the normal mode and the terminal in the MTC coverage enhancement mode according to the present embodiment. In FIG. 12, out of a total of 72 PUCCH resources of 2 RBs, 12 PUCCH resources are reserved for SPS / SR, 48 PUCCH resources are reserved for terminals in the normal mode, and the remaining Twelve PUCCH resources are reserved for terminals in the MTC coverage enhancement mode.

  As described above, the PUCCH resource shown in FIG. 12 is defined by a combination of an orthogonal code sequence (OC index) and a cyclic shift amount (Cyclic shift Index) of a ZAC sequence.

For a terminal in the normal mode, a difference Δ _shift ^PUCCH of the cyclic shift amount between adjacent resources available in one orthogonal code sequence defining the PUCCH resource is set. For example, in FIG. 12, Δ _shift ^PUCCH = 2 is set. That is, PUCCH resources corresponding to every other cyclic shift amount can be used for twelve cyclic shift amounts (Cyclic Shift Index = 0 to 11) that can be taken for one orthogonal code sequence. Therefore, for the terminal in the normal mode, 18 PUCCH resources out of a maximum of 36 PUCCH resources can be used for each 1 RB (PRB (Physical RB)).

In FIG. 12, when the terminal in the normal mode receives the downlink allocation control information, the resource number n _PUCCH of the PUCCH resource that transmits the ACK / NACK signal for the downlink data indicated in the corresponding allocation control information is expressed by the equation (1). ) (Where N _PUCCH ⁽¹⁾ = 6).

  In FIG. 12, PUCCH resource numbers # 6 to # 29 are selected from among the PUCCH resources to which the number corresponding to every other cyclic shift amount in each orthogonal code sequence is assigned starting from PUCCH resource # 0. Twenty-four PUCCH resources are PUCCH resources that can be used by terminals in the normal mode.

On the other hand, in a terminal in MTC coverage enhancement mode, a cyclic shift amount difference Δ _shift ^PUCCH_MTC between available resources adjacent to each other in one orthogonal code sequence defining a PUCCH resource is set. For example, in FIG. 12, Δ _shift ^PUCCH_MTC = 1 is set. That is, different parameters are set for the terminal in the normal mode and the terminal in the MTC coverage enhancement mode as the difference in the cyclic shift amount between the available PUCCH resources. Specifically, Δ _shift ^PUCCH_MTC is smaller than Δ _shift ^PUCCH .

  That is, a terminal in MTC coverage enhancement mode uses PUCCH resources corresponding to all cyclic shift amounts that are consecutive with respect to 12 cyclic shift amounts (Cyclic Shift Index = 0 to 11) that can be taken for one orthogonal code sequence. It becomes possible.

In FIG. 12, when the terminal in the MTC coverage enhancement mode receives the downlink allocation control information, the resource number n _{PUCCH_MTC} of the PUCCH resource that transmits the ACK / NACK signal for the downlink data indicated in the corresponding allocation control information is expressed. It may be determined according to (2) (however, N _{PUCCH_MTC} ⁽¹⁾ = 60).

  In FIG. 12, 12 PUCCH resource numbers # 60 to # 71 among PUCCH resources assigned numbers to resources corresponding to successive cyclic shift amounts in each orthogonal code sequence starting from PUCCH resource # 0. The PUCCH resource becomes a PUCCH resource that can be used by a terminal in the MTC coverage enhancement mode.

Terminal 200 determines the OC index and the cyclic shift amount to be actually used based on the PUCCH resource number. The association between the PUCCH resource number, the OC index, and the cyclic shift amount depends on the difference between adjacent cyclic shift amounts. Therefore, in the present embodiment, the correspondence for specifying the OC index and the cyclic shift amount actually used from the PUCCH resource number is different between the terminal in the normal mode and the terminal in the MTC coverage enhancement mode. Specifically, the terminal of the MTC coverage enhancement mode, a delta _Shift ^PUCCH in equation showing association specifying the OC index and a cyclic shift amount for actual use from PUCCH resource numbers in the existing system (not shown) delta _Shift ^{It can} be replaced with ^PUCCH_MTC .

  In the existing system (for example, 3GPP Release 11), the PUCCH resource for the terminal in the normal mode described above is secured. On the other hand, as shown in FIG. 12, when there is a terminal in the MTC coverage enhancement mode, in addition to the PUCCH resource for the terminal in the normal mode, the PUCCH resource for the terminal in the MTC coverage enhancement mode is additionally set. Is done.

Here, as shown in FIG. 12, the maximum number of codes that can be multiplexed in each RB is specified by the number of available cyclic shift amounts among the available cyclic shift amounts. Specifically, the maximum number of codes that can be multiplexed is specified by the number of cyclic shift amounts that can be used as PUCCH resources (that is, Δ _shift ^PUCCH and Δ _shift ^PUCCH_MTC ).

In the present embodiment, the maximum code multiplexing possible number (difference in cyclic shift amount) is set independently for each of the terminal in the normal mode and the terminal in the MTC coverage enhancement mode. Specifically, among the combinations of orthogonal code sequences and cyclic shift amounts defined as each resource of the PUCCH resource group for terminals in MTC coverage enhancement mode, the difference Δ between adjacent cyclic shift amounts in the same orthogonal code sequence Δ _shift ^PUCCH_MTC is the difference Δ _shift ^PUCCH between adjacent cyclic shift amounts in the same orthogonal code sequence among the combinations of orthogonal code sequences and cyclic shift amounts defined as each resource of the PUCCH resource group for terminals in the normal mode. Is also small.

  For this reason, in the PUCCH resource region for terminals in the MTC coverage enhancement mode, the ratio of available PUCCH resources to the entire PUCCH resource region is higher than in the PUCCH resource region for terminals in the normal mode. Specifically, as shown in FIG. 12, in the PUCCH resource area for terminals in the normal mode, 24 PUCCH resources out of 48 PUCCH resources can be used. On the other hand, in the PUCCH resource area for terminals in the MTC coverage enhancement mode, all 12 PUCCH resources can be used. That is, the maximum number of codes that can be multiplexed is maximized for a terminal in MTC coverage enhancement mode.

  That is, in the present embodiment, as described above, by increasing the maximum code multiplexing possible number in the PUCCH resource for the terminal in the MTC coverage enhancement mode than the maximum code multiplexing possible number in the PUCCH resource for the terminal in the normal mode, By increasing the number of PUCCH resources that can be used, the overhead of PUCCH resources can be minimized.

For example, in order to be able to use 12 PUCCH resources, it is necessary to secure 24 PUCCH resources when Δ _shift ^PUCCH_MTC = 2, whereas when Δ _shift ^PUCCH_MTC = 1, As shown in FIG. 12, it is only necessary to secure 12 PUCCH resources. Thus, delta is made smaller than the _shift ^PUCCH_MTC Δ _shift ^PUCCH, as compared with the case where the same as the difference delta _Shift ^PUCCH cyclic shift amount set in the normal mode terminals, minimizing the PUCCH resource overhead Can be suppressed.

  By the way, in the PUCCH resources in the same RB, the PUCCH resources that are not used for code multiplexing contribute to the reduction of intersymbol interference due to the effect of reducing the intersymbol interference by code spreading. For example, as illustrated in FIG. 12, in the PUCCH resource for the terminal in the normal mode, a PUCCH resource that is not used between adjacent resources of the available PUCCH resources # 6 to # 29 (a PUCCH resource that is not used for code multiplexing) Exists, and the PUCCH resource contributes to reduction of intersymbol interference.

  On the other hand, as shown in FIG. 12, there is no PUCCH resource that is not used for code multiplexing in the terminal PUCCH resource in the MTC coverage enhancement mode.

  However, considering the traffic characteristics in MTC, it is assumed that terminals in MTC do not communicate frequently. That is, the usage frequency of the terminal PUCCH resource in the MTC coverage enhancement mode is probabilistically low. Therefore, in the PUCCH resource for terminals in MTC coverage enhancement mode, even if the maximum number of codes that can be multiplexed in the same RB is increased, the number of terminals that are code-multiplexed at the same time is small. Are less likely to be used at the same time. That is, since the possibility of the occurrence of intersymbol interference due to the simultaneous use of resources corresponding to adjacent cyclic shift amounts is low, the transmission characteristics of the ACK / NACK signal are hardly deteriorated.

  Also, considering the communication environment in MTC, it is assumed that the coding rate of control information for terminals in MTC coverage enhancement mode is set low, and the number of CCEs occupied by the L1 / L2 CCH constituting the PDCCH is relatively large. Is done. For this reason, for example, as described above, when a PUCCH resource number is notified Implicitly by a CCE number to a terminal in MTC coverage enhancement mode, there is a possibility that the CCEs having adjacent numbers are used for the same terminal. Get higher. Therefore, the possibility that PUCCH resources having adjacent numbers (resources corresponding to adjacent cyclic shift amounts) are simultaneously used is low.

  In this way, for a terminal in MTC coverage enhancement mode, the PUCCH in which the maximum code multiplexable number in the same RB is increased even if the difference between adjacent cyclic shift amounts is set smaller than in the normal mode. Since the actual use probability in the resource area is low, the performance degradation of the ACK / NACK signal due to the increase in the maximum number of codes that can be multiplexed does not substantially occur.

  Thus, according to the present embodiment, PUCCH resources are used by using a difference in cyclic shift amount (that is, the maximum number of codes that can be multiplexed) that is different for a terminal in normal mode and a terminal in MTC coverage enhancement mode. Is set. Thereby, in a system in which a terminal in the normal mode and a terminal in the MTC coverage enhancement mode coexist, an increase in PUCCH resource overhead can be minimized.

Furthermore, PUCCH resource allocation to terminals in the normal mode has already been performed in the LTE system. Accordingly, in this embodiment, the difference Δ _shift ^PUCCH_MTC cyclic shift amount to be used independently when allocation of PUCCH resources to terminals MTC coverage enhancement mode need be newly notified from the base station 100 to the terminal 200. Therefore, the influence on the operation of the existing system is small.

  Also, according to the present embodiment, the PUCCH resource for transmitting the ACK / NACK signal is differentiated between the terminal in the normal mode and the terminal in the MTC coverage enhancement mode by using different PUCCH resources for the ACK / NACK signal. Can avoid collisions.

  Note that this embodiment is different in cyclic shift amount difference between terminals in normal mode (terminals that do not perform repetition) and terminals in MTC coverage enhancement mode (terminals that perform repetition) (that is, in other words, terminals that perform repetition). The case where the PUCCH resource is set using the maximum code multiplexing possible number) has been described. However, in the present embodiment, the difference in cyclic shift amount is different for each terminal group in the same cell (for example, a terminal under a macro base station and a terminal under a remote antenna station in the same cell) ( That is, the PUCCH resource may be set using the maximum code multiplexing possible number).

(Embodiment 4)
As described above, in the existing system, the CCE number and the PUCCH resource number are associated one-to-one. That is, M PUCCH resources corresponding to the number of CCEs are associated with M CCEs, respectively. For example, in FIG. 12, CCE # 0 and PUCCH # 60, CCE # 1 and PUCCH # 61, CCE # 2 and PUCCH # 62, and the like are associated with terminals in the MTC coverage enhancement mode.

  Also, it is assumed that the coding rate of control information is set to be low for a terminal in MTC coverage enhancement mode in order to suppress the deterioration of the error rate characteristic of the control information. That is, it is assumed that the number of CCEs occupied by the L1 / L2 CCH constituting the PDCCH for the terminal in the MTC coverage enhancement mode is relatively large. For example, for a terminal in MTC coverage enhancement mode, a larger value (4, 8) among possible values (for example, 1, 2, 4, 8) as the number of occupied CCEs (sometimes referred to as an aggregation level). ) Is assumed to be set.

  As described above, when the L1 / L2 CCH occupies a plurality of CCEs in the PDCCH for the terminal in the MTC coverage enhancement mode, the terminal uses the PUCCH corresponding to one CCE (CCE of the smallest index) among the plurality of CCEs. ACK / NACK signal is transmitted using resources. Therefore, PUCCH resources corresponding to other CCEs other than the CCE corresponding to the PUCCH resource used for transmitting the ACK / NACK signal are not used and are wasted. For example, in FIG. 12, when the L1 / L2 CCH constituting the PDCCH for the terminal in the MTC coverage enhancement mode occupies four CCEs CCE # 0 to CCE # 3, the terminal has the minimum index among the four CCEs. An ACK / NACK signal is transmitted using only PUCCH # 60 corresponding to CCE # 0. That is, the physical resources of PUCCH # 61 to PUCCH # 63 corresponding to CCE # 1 to CCE # 3 are wasted and are wasted.

  Also, considering the traffic characteristics in MTC, it is assumed that terminals in MTC do not frequently communicate. That is, the use frequency of the terminal PUCCH resource in the MTC coverage enhancement mode is probabilistically low.

  Therefore, in the present embodiment, M PUCCH resources are not associated with M CCEs in a one-to-one correspondence with M CCEs for MTC coverage enhancement mode terminals. Associate fewer PUCCH resources. In other words, for a terminal in MTC coverage enhancement mode, a plurality of CCEs are associated with one PUCCH resource.

  The basic configuration of the base station and terminal according to the present embodiment is the same as that of Embodiment 1, and will be described with reference to FIG. 8 (base station 100) and FIG. 9 (terminal 200).

  Base station 100 and terminal 200 hold in advance a correspondence between CCEs and PUCCH resources according to the present embodiment.

  Hereinafter, method 1 and method 2 related to the association between CCEs and PUCCH resources according to the present embodiment will be described.

In the present embodiment, for example, as shown in FIG. 12, different PUCCH resource areas are set for each of the terminal in the normal mode and the terminal in the MTC coverage enhancement mode. For example, the PUCCH resource for the terminal in the normal mode and the terminal in the MTC coverage enhancement mode may be set by the same method as in the first or second embodiment. However, in the present embodiment, as an allocation of the PUCCH resource to the terminal in the MTC coverage enhancement mode, Explicit notification may be sent from base station 100 to terminal 200 using higher layer signaling or the like. Also, the difference in cyclic shift amount between PUCCH resources that can be used by terminals in the MTC coverage enhancement mode is set to 1 (Δ _shift ^PUCCH_MTC = 1) as in the third embodiment.

  In the following, attention is paid to PUCCH resources (# 60 to # 71) for terminals in the MTC coverage enhancement mode.

<Method 1 (FIG. 13)>
Method 1 is a method in which the association between CCE numbers and PUCCH resources is N-to-1.

  For example, FIG. 13 shows an example of correspondence between CCE numbers and PUCCH resource numbers when N = 4.

  As shown in FIG. 13, four CCEs CCE # 0 to CCE # 3 are associated with PUCCH # 60, and four CCEs CCE # 4 to CCE # 7 are associated with PUCCH # 61. , CCE # 8 to CCE # 11 are associated with PUCCH # 62.

  For example, if the terminal in MTC coverage enhancement mode has a CCE with the smallest index among the CCEs that occupy the L1 / L2 CCH that constitutes the PDCCH addressed to the terminal, the PUCCH An ACK / NACK signal is transmitted using resource # 60. Similarly, the CCE of the smallest index among the CCEs allocated to the terminal in the MTC coverage enhancement mode is PCECH resource # 61 is used for transmitting the ACK / NACK signal in the case of CCE # 4 to CCE # 7, In the case of CCE # 8 to CCE # 11, PUCCH resource # 62 is used for transmission of the ACK / NACK signal.

For example, the PUCCH resource number n _{PUCCH_MTC} used by the terminal in the MTC coverage enhancement mode is determined according to the following equation.
n _{PUCCH_MTC} = floor (n _CCE / N) + N _{PUCCH_MTC} ⁽¹⁾ (4)

In equation (4), the function “floor (X)” represents a floor function that returns the largest integer less than or equal to X. Also, n _CCE indicates the smallest CCE number among the CCEs occupied by the PDCCH, and N indicates the number of CCEs associated with one PUCCH resource (N = 4 in FIG. 13). N _{PUCCH_MTC} ⁽¹⁾ indicates an offset value for the terminal in the MTC coverage enhancement mode. For example, in FIG. 13, N _{PUCCH_MTC} ⁽¹⁾ = 60.

  According to the method 1, the PUCCH resource area reserved for the terminal in the MTC coverage enhancement mode is reduced to 1 / N compared with the case where the CCE number and the PUCCH number are associated with each other on a one-to-one basis. Specifically, when there is a one-to-one correspondence between CCE numbers and PUCCH numbers, it is necessary to secure 12 PUCCH resources for 12 CCEs. In the case of 13 (N = 4), only 3 PUCCH resources need be secured for 12 CCEs.

<Method 2>
Method 2 is a method in which the number of CCEs associated with one PUCCH resource is set to a value that can be taken as the number of occupied CCEs (aggregation level).

  For example, in Method 2, it is assumed that the CCE occupation number N (> 1) is set for the terminal in the MTC coverage enhancement mode.

  For example, FIG. 14 shows an example of association between CCE numbers and PUCCH resource numbers when N = 4.

  As shown in FIG. 14, four CCEs CCE # 0 to CCE # 3 are associated with PUCCH # 60, and four CCEs CCE # 4 to CCE # 7 are associated with PUCCH # 61. , CCE # 8 to CCE # 11 are associated with PUCCH # 62. That is, one PUCCH resource is associated with every CCE occupied CCEs.

  A CCE is assigned to a terminal in the MTC coverage enhancement mode in units of four CCEs shown in FIG. For example, if the CCE that occupies the L1 / L2 CCH constituting the PDCCH destined for the terminal is CCE # 0 to CCE # 3, the terminal in the MTC coverage enhancement mode transmits an ACK / NACK signal using the PUCCH resource # 60. Send. Similarly, when CCE # 4 to CCE # 7 are assigned to terminals in MTC coverage enhancement mode, PUCCH resource # 61 is used for transmitting ACK / NACK signals, and CCE # 8 to CCE # 11 are When assigned, PUCCH resource # 62 is used for transmission of the ACK / NACK signal.

For example, the PUCCH resource number n _{PUCCH_MTC} used by the terminal in the MTC coverage enhancement mode is determined according to the following equation.
n _{PUCCH_MTC} = n _CCE / N + N _{PUCCH_MTC} ⁽¹⁾ (5)

In Equation (5), n _CCE indicates the smallest CCE number among the CCEs occupied by the PDCCH, and N indicates the number of CCE occupations for terminals in the MTC coverage enhancement mode (N = 4 in FIG. 13). N _{PUCCH_MTC} ⁽¹⁾ indicates an offset value for the terminal in the MTC coverage enhancement mode. For example, in FIG. 14, N _{PUCCH_MTC} ⁽¹⁾ = 60.

  According to the method 2, the PUCCH resource area reserved for the terminal in the MTC coverage enhancement mode is reduced to 1 / N as compared with the case where the CCE number and the PUCCH number are associated with each other on a one-to-one basis. Specifically, when there is a one-to-one correspondence between CCE numbers and PUCCH numbers, it is necessary to secure 12 PUCCH resources for 12 CCEs. In the case of 14 (when N = 4), only 3 PUCCH resources need be reserved for 12 CCEs.

  Also, since each PUCCH resource is associated with a CCE in units of the number of CCEs occupied by each terminal, N CCEs associated with one PUCCH resource must be used simultaneously among a plurality of terminals. There is no.

  The method 1 and the method 2 have been described above.

  Thus, in this embodiment, a plurality of CCEs are associated with one PUCCH resource for a terminal in MTC coverage enhancement mode. Thereby, it is possible to suppress an increase in resources reserved as PUCCH resources for terminals in the MTC coverage enhancement mode. Therefore, even in a system in which terminals in MTC coverage enhancement mode exist (when a PUCCH resource for terminals in MTC coverage enhancement mode is additionally set), an increase in overhead of PUCCH resources can be suppressed.

  Also, according to the present embodiment, the PUCCH resource for transmitting the ACK / NACK signal is differentiated between the terminal in the normal mode and the terminal in the MTC coverage enhancement mode by using different PUCCH resources for the ACK / NACK signal. Can avoid collisions.

(Embodiment 5)
In the MTC coverage enhancement mode, the PUCCH resource number is associated with the CCE number and Implicitly notified in the same manner as in the existing system. If there are terminals with different PDCCH and PUCCH repetition levels, the same PUCCH resource ACK / NACK signals may be transmitted simultaneously using PUCCH, causing a PUCCH resource collision.

FIG. 15 shows an example when PUCCH resources collide between terminals in the MTC coverage enhancement mode. In FIG. 15, the repetition levels of PDCCH and PDSCH of terminal 1 (UE # 1) and terminal 2 (UE # 2) are N _PDCCH and N _PDSCH , respectively. Further, the PUCCH repetition level of terminal 1 is set to N _PUCCH + α _PUCCH, and the PUCCH repetition level of terminal 2 is set to N _PUCCH . That is, in terminal 1, N _PDCCH and N _PDSCH are the same as in terminal 2, and the PUCCH repetition level is higher by α _PUCCH .

  Also, in FIG. 15, terminal 1 transmits PDCCH using CCE # 0 to CCE # 3. On the other hand, terminal 2 transmits PDCCH using CCE # 0 to CCE # 3 from the next subframe in which transmission of PDCCH of terminal 1 is completed. That is, both terminal 1 and terminal 2 transmit an ACK / NACK signal using the PUCCH resource associated with CCE # 0.

As shown in FIG. 15, terminal 1 transmits an ACK / NACK signal over N _PUCCH + α _PUCCH subframes, and terminal 2 transmits the next sub-frame after terminal 1 transmits an ACK / NACK signal for N _PUCCH subframes. An ACK / NACK signal is transmitted from the frame to N _PUCCH . Therefore, as shown in FIG. 15, PUCCH resources collide between terminals in the α _PUCCH subframe in the latter half of the PUCCH repetition of terminal 1 and the subframe corresponding to the α _PUCCH subframe in the first half of the PUCCH repetition of terminal 2. Resulting in.

  Therefore, in this embodiment, a method for avoiding a collision of PUCCH resources for transmitting ACK / NACK signals between terminals in the MTC coverage enhancement mode will be described.

  The basic configuration of the base station and terminal according to the present embodiment is the same as that of Embodiment 1, and will be described with reference to FIG. 8 (base station 100) and FIG. 9 (terminal 200).

  Specifically, when the PDCCH and the PUCCH have different repetition levels, the terminal 200 (MTC coverage enhancement mode terminal) has a CCE number (up to the same number of subframes as the PDCCH repetition level in PUCCH repetition). That is, an ACK / NACK signal is transmitted using a PUCCH resource that is notified implicitly in association with the smallest CCE number.

  On the other hand, terminal 200 transmits an ACK / NACK signal using a PUCCH resource assigned to Explicit in a subframe exceeding the PDCCH repetition level. The PUCCH resource is notified from the base station 100 to the terminal 200 in advance.

FIG. 16 shows the transmission timing of each channel according to the present embodiment. In FIG. 16, as in FIG. 15, the repetition levels of the PDCCH and PDSCH of terminal 1 (UE # 1) and terminal 2 (UE # 2) are N _PDCCH and N _PDSCH , respectively. Further, the PUCCH repetition level of terminal 1 is set to N _PUCCH + α _PUCCH, and the PUCCH repetition level of terminal 2 is set to N _PUCCH . In FIG. 16, N _PUCCH is the same as N _PDCCH .

  Further, in FIG. 16, terminal 1 transmits PDCCH using CCE # 0 to CCE # 3. On the other hand, terminal 2 transmits PDCCH using CCE # 0 to CCE # 3 from the next subframe in which transmission of PDCCH of terminal 1 is completed.

In this case, as illustrated in FIG. 16, in the PUCCH repetition, the terminal 1 is the smallest of the CCEs used for the PDCCH up to N _PUCCH subframes equal to the N _PDCCH among N _PUCCH + α _PUCCH subframes. An ACK / NACK signal is transmitted using a PUCCH resource associated with CCE # 0 having an index of.

On the other hand, the terminal 1 transmits an ACK / NACK signal using the PUCCH resource notified to Explicit after the α _PUCCH subframe exceeding the N _PUCCH subframe among the N _PUCCH + α _PUCCH subframes.

Also, as shown in FIG. 16, in the PUCCH repetition, the terminal 2 is used for the PDCCH over the N _PUCCH subframe from the next subframe in which the terminal 1 transmits the ACK / NACK signal for the N _PUCCH subframe. An ACK / NACK signal is transmitted using the PUCCH resource associated with CCE # 0 having the smallest index among the CCEs.

That is, in FIG. 16, the terminal 1 and the terminal 2 are different from each other in the α _PUCCH subframe in the latter half of the PUCCH repetition of the terminal 1 and the subframe corresponding to the α _PUCCH subframe in the first half of the PUCCH repetition of the terminal 2. PUCCH resources are used. Therefore, there is no PUCCH resource collision between the terminal 1 and the terminal 2.

  As described above, the terminal 200 includes the PUCCH resources for the terminal in the MTC coverage enhancement mode in the subframes below the repetition level of the PDCCH among the plurality of subframes in which the repetition transmission of the ACK / NACK signal is performed. ACK / NACK signals are transmitted using PUCCH resources associated with CCE used for PDCCH, and in subframes exceeding the PDCCH repetition level, ACK is used using one of PUCCH resources set in advance. / NACK signal is transmitted.

  In this way, when there are terminals in MTC coverage enhancement mode with different PDCCH and PUCCH repetition levels, ACK / NACK signals are simultaneously transmitted between terminals in MTC coverage enhancement mode that transmit PDCCH using the same CCE. Even if a subframe to be transmitted is generated, it is possible to avoid collision of PUCCH resources for transmitting ACK / NACK signals between terminals.

  In addition, you may combine this Embodiment with the operation | movement of Embodiment 1-4. That is, this embodiment is applied to a method for avoiding collision of PUCCH resources between terminals in MTC coverage enhancement mode, and a method for avoiding collision of PUCCH resources between a terminal in MTC coverage enhancement mode and a terminal in normal mode Any one of Embodiments 1 to 4 may be applied.

(Embodiment 6)
In the fifth embodiment, terminals having different PDCCH and PUCCH repetition levels have been described. In contrast, in the present embodiment, a case will be described in which the repetition levels of PDCCH and PUCCH in each terminal are the same, but the repetition levels between terminals are different.

  In this case, between the terminals in the MTC coverage enhancement mode, in the same way as in the existing system, the PUCCH resource number is associated with the CCE number and Implicitly notified. Therefore, the ACK / NACK signal is transmitted between the terminals using the same PUCCH resource. It may be transmitted at the same time and PUCCH resource collision may occur.

  FIG. 17 shows an example when PUCCH resources collide between terminals in the MTC coverage enhancement mode. In FIG. 17, the repetition level of PDCCH, PDSCH, and PUCCH of terminal 1 (UE # 1) is 8, and the repetition level of PDCCH, PDSCH, and PUCCH of terminal 2 (UE # 2) is 4.

  Also, in FIG. 17, terminal 1 transmits PDCCH using CCE # 0 to CCE # 3. On the other hand, terminal 2 transmits PDCCH using CCE # 0 to CCE # 3 from the next subframe in which transmission of PDCCH of terminal 1 is completed. That is, both terminal 1 and terminal 2 transmit an ACK / NACK signal using the PUCCH resource associated with CCE # 0.

  As shown in FIG. 17, the terminal 1 receives the PDCCH over 8 subframes and receives the PDSCH over the next 8 subframes. On the other hand, terminal 2 receives PDCCH over four subframes from the next subframe in which terminal 1 has completed reception of PDCCH, and receives PDSCH over the next four subframes. That is, terminal 1 and terminal 2 have the same PDSCH reception completion timing (or ACK / NACK signal transmission start timing).

  In this case, at the same timing, terminal 1 transmits an ACK / NACK signal over 8 subframes, and terminal 2 transmits an ACK / NACK signal over 4 subframes. For this reason, as shown in FIG. 17, PUCCH resources collide between terminals in the 4 subframes in the first half of PUCCH repetition of terminal 1 and the subframes corresponding to all 4 subframes of PUCCH repetition of terminal 2. End up.

  Therefore, in the present embodiment, a method for avoiding collision of PUCCH resources for transmitting ACK / NACK signals between terminals in MTC coverage enhancement modes having different repetition levels will be described.

  The basic configuration of the base station and terminal according to the present embodiment is the same as that of Embodiment 1, and will be described with reference to FIG. 8 (base station 100) and FIG. 9 (terminal 200).

  Specifically, the terminal 200 (the terminal in the MTC coverage enhancement mode), in the PUCCH repetition, is associated with the CCE number used for transmitting the PDCCH (that is, the smallest CCE number) and is notified to Implicit in the PUCCH resource. Is used to transmit an ACK / NACK signal. However, terminal 200 transmits an ACK / NACK signal using a PUCCH resource specified using a different offset value for each configured repetition level.

For example, the repeated tee Deployment level PUCCH resource numbers n _{PUCCH_MTC_4} in the case of 4 and,, PUCCH resource numbers n _{PUCCH_MTC_8} the case of the repeated tee Deployment level 8 is determined according to the following equation.
n _{PUCCH_MTC_4} = n _CCE + N _{PUCCH_MTC_4} ⁽¹⁾ (6)
n _{PUCCH_MTC_8} = n _CCE + N _{PUCCH_MTC_8} ⁽¹⁾ (7)

In Expressions (6) and (7), n _CCE represents a CCE number (an integer of 0 or more) occupied by PDCCH. In Equations (6) and (7), N _{PUCCH_MTC_4} ⁽¹⁾ indicates an offset value for identifying the PUCCH resource number from the CCE number when the repetition level is 4, and N _{PUCCH_MTC_8} ⁽¹⁾ When the repetition level is 8, an offset value for specifying the PUCCH resource number from the CCE number is shown.

N _{PUCCH_MTC_4} ⁽¹⁾ and N _{PUCCH_MTC_8} ⁽¹⁾ are set to different values. In other words, the PUCCH resource that can be used by the terminal 200 is divided into at least a PUCCH resource when the repetition level is 4 and a PUCCH resource when the repetition level is 8. That is, the PUCCH resource group that can be used by terminal 200 includes a plurality of sub resource groups for each repetition level of the ACK / NACK signal.

  Here, the case where the repetition level is 4 or 8 will be described, but the repetition level is not limited to 4 or 8, and when other values can be adopted, the offset value is similarly set for the value. Is set.

  FIG. 18 shows the transmission timing of each channel according to the present embodiment. In FIG. 18, similarly to FIG. 17, the repetition level of PDCCH, PDSCH, and PUCCH of terminal 1 (UE # 1) is 8, and the repetition level of PDCCH, PDSCH, and PUCCH of terminal 2 (UE # 2) is 4. It is. Further, in FIG. 18, terminal 1 transmits PDCCH using CCE # 0 to CCE # 3. On the other hand, terminal 2 transmits PDCCH using CCE # 0 to CCE # 3 from the next subframe in which transmission of PDCCH of terminal 1 is completed.

In this case, as shown in FIG. 18, the terminal 1 transmits an ACK / NACK signal in the PUCCH repetition using the PUCCH resource of N _{PUCCH_MTC_8} ⁽¹⁾ + n _CCE = N _{PUCCH_MTC_8} ⁽¹⁾ according to the equation (6). Send. On the other hand, in the PUCCH repetition, the terminal 2 transmits an ACK / NACK signal using the PUCCH resource of N _{PUCCH_MTC_4} ⁽¹⁾ + n _CCE = N _{PUCCH_MTC_4} ⁽¹⁾ according to the equation (7).

As described above, N _{PUCCH_MTC_4} ⁽¹⁾ and N _{PUCCH_MTC_8} ⁽¹⁾ are different from each other. Therefore, as shown in FIG. 18, in the subframes corresponding to the first four subframes of terminal 1 PUCCH repetition and all the four subframes of terminal 2 PUCCH repetition, both terminal 1 and terminal 2 mutually Different PUCCH resources are used. For this reason, the collision of the PUCCH resource between the terminal 1 and the terminal 2 does not occur.

  In this way, even if a subframe in which PDCCH is transmitted using the same CCE and ACK / NACK signals are transmitted simultaneously between terminals in MTC coverage enhancement mode having different repetition levels, ACK / NACK signals are generated. It is possible to avoid collision of PUCCH resources that transmit NACK signals between terminals.

  In addition, you may implement this Embodiment in combination with the operation | movement of Embodiment 1-4. That is, this embodiment is applied to a method for avoiding collision of PUCCH resources between terminals in MTC coverage enhancement mode, and a method for avoiding collision of PUCCH resources between a terminal in MTC coverage enhancement mode and a terminal in normal mode Any one of Embodiments 1 to 4 may be applied.

  The embodiments of the present disclosure have been described above.

  Note that although cases have been described with the above embodiment as examples where one aspect of the present disclosure is configured by hardware, the present disclosure can also be realized by software.

  Each functional block used in the description of each of the above embodiments is typically realized as an LSI which is an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include a part or all of them. The name used here is LSI, but it may also be called IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.

  Further, the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible. An FPGA (Field Programmable Gate Array) that can be programmed after manufacturing the LSI, or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used.

  Furthermore, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology. Biotechnology can be applied.

  The terminal of the present disclosure determines control information indicating downlink data allocation, a reception unit that receives the downlink data, and a resource used for a response signal to the downlink data based on the control information And a transmission unit that transmits the response signal using the determined resource, and the transmission unit is configured so that the own terminal responds to the control information, the downlink data, and the response signal. If the terminal is a first terminal to which repetition transmission is applied, the response signal is transmitted using a resource in the first resource group, and the terminal transmits a second signal to which the repetition transmission is not applied. In the case of a terminal, the response signal is transmitted using a resource in a second resource group different from the first resource group.

  In the terminal according to the present disclosure, the control unit adds a first offset value to an index of a control channel element (CCE) used for the control information, and adds the first offset value to the response signal in the first resource group. Calculating a resource to be used, adding a second offset value to an index of the CCE used for the control information, calculating a resource used for the response signal in the second resource group, and The first offset value and the second offset value are different.

  In the terminal according to the present disclosure, the control unit adds an offset value to an index of a control channel element (CCE) used for the control information, and is used for the response signal in the first resource group. A resource is calculated, and an index of the CCE used for the control information is subtracted from the offset value to calculate a resource used for the response signal in the second resource group.

  In the terminal of the present disclosure, each resource of the first resource group and the second resource group is defined by a combination of an orthogonal code sequence and a cyclic shift amount, and is defined as each resource of the first resource group Among the combinations, the difference between the cyclic shift amounts adjacent in the same orthogonal code sequence is the difference between the cyclic shift amounts adjacent in the same orthogonal code sequence among the combinations defined as the resources of the second resource group. Smaller than the difference.

  In the terminal of the present disclosure, one resource of the first resource group is associated with a plurality of control channel elements (CCEs) used for the control information.

  In the terminal of the present disclosure, the plurality is the number of CCEs occupied by the allocation information.

  In the terminal according to the present disclosure, the transmission unit includes, among the plurality of subframes in which the repetition transmission of the response signal is performed, out of the first resource group in a subframe equal to or less than the number of repetitions of the control information. The response signal is transmitted using a resource associated with a control channel element (CCE) used for the control information, and is set in advance in a subframe exceeding the number of repetitions of the control information. The response signal is transmitted using a resource.

  In the terminal according to the present disclosure, the first resource group includes a plurality of sub-resource groups for each repetition frequency of the response signal.

  The base station according to the present disclosure includes control information indicating downlink data allocation, a transmission unit that transmits the downlink data, and resources used for a response signal to the downlink data based on the control information. A controller for determining, and a receiver for receiving the response signal using the determined resource, wherein the receiver is configured to replicate the control information, the downlink data, and the response signal. The response signal transmitted from the first terminal to which the transmission is applied is received using a resource in the first resource group, and the response is transmitted from the second terminal to which the repetition transmission is not applied. A signal is received using a resource in a second resource group different from the first resource group.

  The transmission method of the present disclosure includes control information indicating downlink data allocation, a reception step of receiving the downlink data, and resources used for a response signal to the downlink data based on the control information. A control step for determining, and a transmission step for transmitting the response signal using the determined resource, wherein the transmission step is a repetition rate for the control information, the downlink data, and the response signal. The first terminal to which transmission is applied transmits the response signal using resources in the first resource group, and the second terminal to which the repetition transmission is not applied is different from the first resource group. The response signal is transmitted using a resource in the second resource group.

  The reception method of the present disclosure includes control information indicating downlink data allocation, a transmission step of transmitting the downlink data, and resources used for a response signal to the downlink data based on the control information. A control step for determining, and a reception step for receiving the response signal using the determined resource, wherein the reception step is a repetition rate for the control information, the downlink data, and the response signal. The response signal transmitted from the first terminal to which the transmission is applied is received using a resource in the first resource group, and the response is transmitted from the second terminal to which the repetition transmission is not applied. A signal is received using a resource in a second resource group different from the first resource group.

  One aspect of the present disclosure is useful for a mobile communication system.

DESCRIPTION OF SYMBOLS 100 Base station 200 Terminal 101,213 Control part 102 Control signal generation part 103 Control signal encoding part 104 Control signal modulation part 105 Broadcast signal generation part 106 Data encoding part 107 Retransmission control part 108 Data modulation part 109 Signal allocation part 110, 218 IFFT unit 111, 219 CP adding unit 112, 220 transmitting unit 113 antenna 114, 202 receiving unit 115, 203 CP removing unit 116 PUCCH extracting unit 117 sequence control unit 118 despreading unit 119 correlation processing unit 120, 209 determining unit 204 FFT Unit 205 extracting unit 206 broadcast signal receiving unit 207 control signal demodulating unit 208 control signal decoding unit 210 data demodulating unit 211 data decoding unit 212 CRC unit 214 ACK / NACK generation unit 215 modulation unit 216 primary spreading unit 217 secondary spreading unit

Claims (15)

A transmission unit for transmitting downlink control information and downlink data to the terminal;
A receiving unit that receives a response signal for the downlink data, transmitted from the terminal using an uplink control channel resource determined based on the control information;
Comprising
When a coverage enhancement mode capable of repetition transmission of the response signal over a plurality of subframes is set in the terminal, the uplink control channel resource is determined using a first offset,
Unlike the second offset used when the coverage enhancement mode is not set, the first offset is set for each repetition level at which the response signal is transmitted by repetition.
base station. A transmission unit for transmitting downlink control information and downlink data to the terminal;
A receiving unit that receives a response signal for the downlink data, transmitted from the terminal using an uplink control channel resource determined based on the control information;
Comprising
When transmitting the downlink control information capable of repetition transmission over a plurality of subframes for which coverage enhancement mode is set to the terminal, the uplink control channel resource is determined using a first offset,
Unlike the second offset used when the coverage enhancement mode is not set, the first offset is set for each repetition level at which the response signal is transmitted by repetition.
base station. The transmission unit repeats the downlink control information over a plurality of subframes to the terminal for which the coverage enhancement mode is set,
The base station according to claim 1 or 2. A combination of one of a plurality of orthogonal code sequences and one of a plurality of cyclic shift amounts is identified from the association with the uplink control channel resource,
The association in the coverage enhancement mode is different from the association when the coverage enhancement mode is not set.
The base station according to claim 1. The association is based on the difference between adjacent cyclic shift amounts combined in one orthogonal code sequence,
The difference in the cyclic shift amount in the coverage enhancement mode is set independently from the difference in the cyclic shift amount when the coverage enhancement mode is not set.
The base station according to claim 4. The receiving unit receives the response signal transmitted by repetition over a plurality of subframes from the terminal in which the coverage enhancement mode is set;
The base station according to any one of claims 1 to 5. The receiving unit receives the response signal from the terminal in which the coverage enhancement mode is set after a predetermined number of subframes from a subframe in which the downlink data is transmitted.
The base station according to claim 1. The first offset is specific to the terminal, and the second offset is common within the cell.
The base station according to claim 1. The first offset is common to terminals for which the coverage enhancement mode is set.
The base station according to claim 1. The transmitting unit transmits at least one of the first offset and the second offset by an upper layer;
The base station according to claim 1. The transmission unit repeats the downlink data over a plurality of subframes to the terminal for which the coverage enhancement mode is set.
The base station according to claim 1. A step of transmitting downlink control information and downlink data to the terminal;
Receiving a response signal for the downlink data transmitted from the terminal using an uplink control channel resource determined based on the control information;
Comprising
When a coverage enhancement mode capable of repetition transmission of the response signal over a plurality of subframes is set in the terminal, the uplink control channel resource is determined using a first offset,
Unlike the second offset used when the coverage enhancement mode is not set, the first offset is set for each repetition level at which the response signal is transmitted by repetition.
Communication method. A step of transmitting downlink control information and downlink data to the terminal;
Receiving a response signal for the downlink data transmitted from the terminal using an uplink control channel resource determined based on the control information;
Comprising
When transmitting the downlink control information capable of repetition transmission over a plurality of subframes for which coverage enhancement mode is set to the terminal, the uplink control channel resource is determined using a first offset,
Unlike the second offset used when the coverage enhancement mode is not set, the first offset is set for each repetition level at which the response signal is transmitted by repetition.
Communication method. A process of transmitting downlink control information and downlink data to the terminal;
A process of receiving a response signal to the downlink data transmitted from the terminal using an uplink control channel resource determined based on the control information;
Control
When a coverage enhancement mode capable of repetition transmission of the response signal over a plurality of subframes is set in the terminal, the uplink control channel resource is determined using a first offset,
Unlike the second offset used when the coverage enhancement mode is not set, the first offset is set for each repetition level at which the response signal is transmitted by repetition.
Integrated circuit. A process of transmitting downlink control information and downlink data to the terminal;
A process of receiving a response signal to the downlink data transmitted from the terminal using an uplink control channel resource determined based on the control information;
Control
When transmitting the downlink control information capable of repetition transmission over a plurality of subframes for which coverage enhancement mode is set to the terminal, the uplink control channel resource is determined using a first offset,
Unlike the second offset used when the coverage enhancement mode is not set, the first offset is set for each repetition level at which the response signal is transmitted by repetition.
Integrated circuit.

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