JP2015139106A - User terminal, radio base station and radio communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately feed back feedback signals such as a transmission acknowledgement signal in a dynamic TDD.SOLUTION: A user terminal, that communicates with a radio base station which changes and controls UL/DL configurations by using a time division communication, includes: a selection unit which selects an uplink HARQ reference UL/DL configuration to be used for the uplink HARQ timing control; and a control unit which controls a feedback of transmission acknowledgement signals for a downlink data signal by using a prescribed PUCCH format. The control unit determines the PUCCH format on the basis of the number of downlink data signal transmissions for an uplink UL sub-frame when using a first uplink HARQ reference UL/DL configuration as an uplink HARQ reference UL/DL configuration, while it determines the PUCCH format on the basis of the number of downlink data signal transmissions for a UL sub-frame regardless of a DAI when using the second uplink HARQ reference UL/DL configuration.

Description

  The present invention relates to a user terminal, a radio base station, and a radio communication method applicable to a next generation communication system.

  In the UMTS (Universal Mobile Telecommunications System) network, Long Term Evolution (LTE) has been specified for the purpose of higher data rate and low delay (Non-patent Document 1). LTE uses a multi-access scheme based on OFDMA (Orthogonal Frequency Division Multiple Access) for the downlink (downlink) and SC-FDMA (single carrier frequency division multiple access) for the uplink (uplink). Is used. In addition, a successor system of LTE (for example, sometimes referred to as LTE Advanced or LTE enhancement (hereinafter referred to as “LTE-A”)) has been studied and specified for the purpose of further broadbandization and higher speed from LTE. ing.

  As a duplex format in radio communication of LTE and LTE-A systems, frequency division duplex (FDD) that divides uplink (UL) and downlink (DL) by frequency, and uplink and downlink are divided by time. There is time division duplex (TDD). In the case of TDD, the same frequency region is applied to uplink and downlink communication, and uplink and downlink are divided by time from one transmission / reception point, and signals are transmitted and received.

  In the TDD of the LTE system, a plurality of frame configurations (UL / DL configuration (UL / DL configuration)) with different transmission ratios between uplink subframes (UL subframes) and downlink subframes (DL subframes) are defined. Yes. Specifically, as shown in FIG. 1, seven frame configurations of UL / DL configurations 0 to 6 are defined, subframes # 0 and # 5 are allocated to the downlink, and subframe # 2 is the uplink. Assigned to a link. The acknowledgment signal (HARQ) for the downlink shared channel (PDSCH) transmitted in each DL subframe is fed back using a predetermined UL subframe defined for each UL / DL configuration.

3GPP TS 36.300 “Evolved UTRA and Evolved UTRAN Overall description”

  In general, the ratio of DL traffic to UL traffic is not constant and varies with time or location. Therefore, when TDD is applied, from the viewpoint of effective use of radio resources, the UL / DL configuration shown in FIG. 1 is not fixed, but is temporally or spatially dependent on actual traffic fluctuations. It is desirable to change to

  Therefore, in the TDD after the LTE-A system (Rel. 12), the transmission ratio of the DL subframe and the UL subframe is dynamically changed in the time domain for each transmission / reception point (which may be a radio base station or a cell). ) Or changing to semi-static (dynamic time configuration scenario) is under consideration.

  However, in the existing LTE system, it is defined that a feedback signal (such as a delivery confirmation signal) corresponding to each DL subframe is transmitted in a predetermined UL subframe. Therefore, if the feedback timing before the UL / DL configuration change is applied as it is when the UL / DL configuration is changed, the delivery confirmation signal or the like may not be appropriately transmitted in the radio frame after the UL / DL configuration change.

  In TDD, when a user terminal feeds back an acknowledgment signal using an uplink control channel (PUCCH), the user terminal selects a predetermined PUCCH format based on the UL / DL configuration to be used. Therefore, in TDD (dynamic TDD) that dynamically changes the UL / DL configuration, there are problems such as how to select a PUCCH format and control feedback of a delivery confirmation signal.

  The present invention has been made in view of such points, and an object of the present invention is to provide a user terminal, a radio base station, and a radio communication method capable of appropriately feeding back a feedback signal such as a delivery confirmation signal in dynamic TDD. To do.

  The user terminal of the present invention is a user terminal that communicates with a radio base station that is controlled by changing the UL / DL configuration by time division duplex, and is used for uplink HARQ reference UL / DL used for uplink HARQ timing control. A selection unit that selects a configuration, and a control unit that controls feedback of an acknowledgment signal for a downlink data signal using a predetermined PUCCH format, the control unit as an UL / DL configuration for uplink HARQ reference, When the first uplink HARQ reference UL / DL configuration is used, the PUCCH format is determined based on the number of downlink data signals transmitted to the uplink UL subframe and the DAI (Downlink Assignment Index), and the second uplink HARQ reference is made. When the UL / DL configuration for use is used, it is based on the number of downlink data signal transmissions for UL subframes regardless of DAI. Then, the PUCCH format is determined.

  According to the present invention, in dynamic TDD, a feedback signal such as a delivery confirmation signal can be appropriately fed back.

It is a figure for demonstrating an example of UL / DL structure in TDD. It is a figure for demonstrating the allocation method of the PUCCH resource corresponding to each DL sub-frame in TDD. It is a figure which shows an example in the case of changing UL / DL structure. It is a figure which shows an example which changes the feedback mechanism of the uplink control signal of each DL sub-frame according to the change of UL / DL structure. It is a figure which shows an example of PUCCH format selection in a 1st aspect. It is a figure which shows DL sub-frame with respect to UL sub-frame of each UL / DL structure. It is a figure which shows an example of the table of M = 4 in TDD. It is a figure which shows an example of the mapping method of the channel selection in a 2nd aspect. It is a figure which shows an example of the A / N bundling in a modification. It is the schematic which shows an example of the radio | wireless communications system which concerns on this Embodiment. It is explanatory drawing of the whole structure of the wireless base station which concerns on this Embodiment. It is explanatory drawing of a function structure of the wireless base station which concerns on this Embodiment. It is explanatory drawing of the whole structure of the user terminal which concerns on this Embodiment. It is explanatory drawing of a function structure of the user terminal which concerns on this Embodiment.

  First, in time division duplex (TDD), a method of feeding back an acknowledgment signal (also referred to as HARQ-ACK or ACK / NACK) for a downlink data signal (PDSCH signal) via a PUCCH of a predetermined uplink subframe. This will be described with reference to FIG.

  FIG. 2A shows a radio frame configuration in TDD (here, UL / DL Configuration 2 (hereinafter also referred to as “DL / UL Configuration 2”)). Moreover, FIG. 2B has shown the schematic diagram in the case of applying the channel selection based on a PUCCH format for the delivery confirmation signal with respect to several DL sub-frame.

  In FIG. 2A, the acknowledgment signal for the downlink data signal in the fifth to ninth DL subframes and the special subframes (hereinafter also simply referred to as “DL subframes”) from the left is the 13th UL subframe from the left. This shows a case where feedback is assigned to the PUCCH. The seventh special subframe from the left (Special subframe) has a guard period necessary for switching between the uplink and the downlink, and PDSCH, PUSCH, and the like are allocated through the guard period. In FIG. 2A, since the number of subframes to be fed back is 4 (M = 4), the numbers m of subframes constituting these are m = 0, 1, 2, and 3. In FIG. 2A, the number m is assigned to the DL subframe in preference to the special subframe, the fifth subframe from the left is m = 0, and the sixth subframe is m = 1,7. The third subframe is m = 3, and the ninth subframe is m = 2. Note that the numbering method of the subframe number m is not limited to this. In the following description, the special subframe is regarded as a DL subframe.

  The acknowledgment signal for each DL subframe can be generated with 1 bit (ACK / NACK). Therefore, 4 bits are required to feed back the acknowledgment signals of the four DL subframes in one UL subframe. The existing LTE system (Rel. 10) uses 4 bits combining 2 bits (QPSK) based on the PUCCH format 1b and 2 bits based on channel selection of the PUCCH resource (channel) corresponding to each DL subframe. (See FIG. 2B).

  The PUCCH resource corresponding to each DL subframe can be determined based on the control channel element (CCE) of the downlink control signal (PDCCH) transmitted in each DL subframe. For example, as shown in FIG. 2A, when feedback acknowledgment signals of a plurality of DL subframes are fed back via a predetermined UL subframe, the PUCCH resource (channel) corresponding to each DL subframe is expressed by the following formula (1 ) Can be determined.

In channel selection based on the PUCCH format 1b (PUCCH format 1b with channel selection), information (2 bits) represented by QPSK and selection information (maximum) of PUCCH resources (channels) secured corresponding to each DL subframe 2 bits) are used in combination. For example, in the case of FIG. 2A (M = 4), a maximum of 4 bits combining PUCCH resources (n _{PUCCH, 0 to} n _{PUCCH, 3} ) corresponding to four DL subframes and information represented by QPSK are included. Used to feed back the acknowledgment signal for each DL subframe (see FIG. 2B).

  As described above, PUCCH format 1b with channel selection (hereinafter, also simply referred to as “channel selection”) can support a delivery confirmation signal having a maximum of 4 bits. When the UL / DL configuration is not changed, the number of DL subframes corresponding to one UL subframe is 4 or less except for the UL / DL configuration 5 shown in FIG. Therefore, the delivery confirmation signal fed back in one UL subframe is 4 bits or less except for UL / DL configuration 5. For this reason, in a conventional system (Rel. 10 or the like), in a UL / DL configuration other than the UL / DL configuration 5, channel selection is applied and a delivery confirmation signal is fed back.

  By the way, as described above, Rel. 12 and later, a dynamic TDD (dynamic time configuration scenario) in which the transmission ratio of DL subframes and UL subframes is changed in the time domain for each transmission / reception point has been studied. The dynamic TDD can be controlled to change the UL subframe to the DL subframe in the set UL / DL configuration.

  In the following, as an example, when the wireless base station applies UL / DL configuration 4, the third subframe is changed from UL to DL (corresponding to UL / DL configuration 2). This will be described with reference to FIG.

  When the UL / DL configuration is not changed (see FIG. 3A), the acknowledgment signal for each PDSCH signal transmitted in subframes 0, 1, 4, and 5 is fed back in subframe 2 of the next frame. In addition, an acknowledgment signal for each PDSCH signal transmitted in subframes 6 to 9 is fed back in subframe 3 of the next frame.

  However, when the UL / DL configuration is changed (see FIG. 3B), the third subframe is a DL subframe in the changed UL / DL configuration. That is, with the change of the UL / DL configuration, the transmission direction of the third subframe is changed from UL to DL. As a result, the user terminal cannot feed back the acknowledgment signal corresponding to the DL subframes 6 to 9 of UL / DL configuration 4.

  In this way, when the UL / DL configuration is changed, Rel. If the feedback mechanism of the delivery confirmation signal in FIG. 10 is applied as it is, a problem occurs when the delivery confirmation signal or the like is fed back. Therefore, it has been studied to change the HARQ timing when the UL / DL configuration is changed.

  Specifically, separately from the UL / DL configuration that is actually applied, the HARQ reference UL / DL configuration (HARQ reference configuration) to be used for HARQ timing may be defined to control feedback such as a delivery confirmation signal. It is being considered. For example, an uplink HARQ reference UL / DL configuration (UL HARQ reference configuration) and / or a downlink HARQ reference UL / DL configuration (DL HARQ reference configuration) is set.

  Here, the uplink HARQ reference UL / DL configuration is a reference UL / DL configuration applied to the transmission timing of A / N from the radio base station to the user terminal in the DL subframe in UL HARQ. Note that UL HARQ is an operation in which A / N transmission is performed from a radio base station to a user terminal via DL via PHICH, and retransmission data is transmitted from the user terminal to the radio base station via UL. Of course, the UL / DL configuration actually set and the UL / DL configuration for uplink HARQ reference may be the same UL / DL configuration.

  The UL / DL configuration with many UL subframes is selected as the uplink HARQ reference UL / DL configuration. Also, information related to the uplink HARQ reference UL / DL configuration can be notified by being included in the system information (for example, SIB1 configuration).

  The downlink HARQ reference UL / DL configuration is a reference UL / DL configuration applied to A / N transmission timing from the user terminal to the radio base station in the UL subframe in DL HARQ. Note that DL HARQ is an operation in which A / N transmission is performed via a PUCCH from a user terminal to a radio base station in UL, and retransmission data transmission is performed from the radio base station to the user terminal in DL. Of course, the UL / DL configuration actually set and the UL / DL configuration for downlink HARQ reference may be the same UL / DL configuration.

  As the UL / DL configuration for downlink HARQ reference, an UL / DL configuration with many DL subframes (for example, UL / DL configurations 2, 4, and 5) is selected. Also, information related to the downlink HARQ reference UL / DL configuration can be notified by being included in higher layer signaling (for example, RRC signaling).

  FIG. 4 shows a case where UL / DL configuration 5 is selected as the UL / DL configuration for downlink HARQ reference. In FIG. 4, the delivery confirmation signals of DL subframes 0, 1, 4 to 8 in the radio frame before the UL / DL configuration change are fed back in the UL subframe 2 in the radio frame after the UL / DL configuration change.

  In this way, by setting the reference UL / DL configuration used for HARQ timing, even when the UL / DL configuration is dynamically changed, the delivery confirmation signal can be appropriately fed back. It becomes. On the other hand, when the feedback mechanism is changed as described above, the number of DL subframes corresponding to one UL subframe may be larger than four. For example, in the case shown in FIG. 4, it is necessary to feed back the acknowledgment signals of seven DL subframes 0, 1, 4 to 8 using UL subframe 2 in the radio frame immediately after the UL / DL configuration change. is there.

  In this case, if the delivery confirmation signal of each DL subframe is generated with 1 bit, if the DL subframe corresponding to the UL subframe is larger than 4, there is a problem that cannot be supported by the above-described PUCCH format 1b with channel selection. . In channel selection, it is necessary to secure a maximum of four PUCCH resources (channels). However, when the number of DL subframes corresponding to one UL subframe is larger than 4, the number of PUCCH resources to be reserved becomes larger than four, resulting in a problem that resource utilization efficiency is lowered.

  As a method for solving this problem, it is conceivable to apply a different PUCCH format (for example, PUCCH format 3 having a large number of transmittable bits). PUCCH format 3 is a PUCCH format newly defined in LTE-A, and can transmit a large number of ACK / NACK bits (20 bits). In PUCCH format 3, as in PDSCH, a signal is generated by DFT (Discrete Fourier Transform) -based precoding, and different UEs can be multiplexed by orthogonal codes (OCC: Orthogonal Cover Code).

  In addition, when applying PUCCH format 3, as a resource for allocating a delivery confirmation signal, a PUCCH resource candidate is notified to the user terminal by RRC signaling, and an identifier (ARI: A / N Resource Indicator) indicating a specific PUCCH resource candidate is used. Notification is included in downlink control information.

  However, when PUCCH format 3 is applied, there is a problem that the reliability of PUCCH transmission is lowered and a signaling overhead is increased as compared with the case where PUCCH format 1b is applied. Therefore, in the dynamic TDD, even when the PUCCH format 3 is set, application of another PUCCH format (for example, PUCCH format 1a / 1b) is considered when a predetermined condition is satisfied. Yes.

  Specifically, when the number of DL subframes (number of PDSCH transmissions) for the UL subframe is 1, the DAI included in the downlink control channel is 1, and the UL / DL configuration of the primary cell is UL / DL configurations 1 to 6 Change from PUCCH format 3 to another PUCCH format. The number of DL subframes for the UL subframe corresponds to the number of downlink data signals transmitted to the UL subframe (that is, the number of DL subframes to which the downlink data signal is transmitted).

  A DAI (Downlink Assignment Index) is used for a DL subframe counter in TDD to which A / N bundling is applied, and is included in downlink control information (DCI). Below, DAI is demonstrated.

  In the TDD cell, DL subframes are allocated over a plurality of subframes, and A / Ns for the plurality of DL subframes are fed back in one UL subframe. At this time, if the user terminal cannot perform DL allocation (PDCCH signal) of a DL subframe in the middle of a plurality of DL subframes, A / N feedback cannot be performed appropriately.

  For example, it is assumed that a DL signal is transmitted in four consecutive subframes (SF # 0 to # 3) to the user terminal. In this case, if the user terminal misdetects the DL assignment (PDCCH signal) of SF # 1, the user terminal determines that the DL signal is transmitted in three subframes of SF # 0, # 2, and # 3. Therefore, when the user terminal performs A / N bundling in the subframe direction, if these three subframes (SF # 0, # 2, # 3) are OK (ACK), ACK is fed back. As described above, if detection error occurs on the user terminal side, DL HARQ cannot be performed correctly.

  In order to solve such a problem, TDD supports 2-bit DAI in downlink control information (DCI). The DAI serves as a counter, and the value increases by one for each DL allocation. That is, when the user terminal misdetects the DL assignment on the way, the increase in the DAI count value is not 1, so that the detection error can be grasped.

  In this way, DAI is supported in TDD in which application of A / N bundling is assumed in the subframe direction. Further, DAI is supported in UL / DL configurations 1 to 6 that perform A / N feedback with one UL for a plurality of DLs. That is, in the TDD UL / DL configuration, the UL / DL configuration 0 with a low DL subframe ratio (high UL subframe ratio) does not feed back A / N for multiple DLs in one UL subframe. Therefore, DAI is not supported.

  Therefore, as described above, in UL / DL configurations 1 to 6, even when PUCCH format 3 is set, the number of DL subframes (number of PDSCH transmissions) for the UL subframe is 1, and the DAI is If it is 1, the PUCCH format 1a / 1b can be used.

  However, the present inventors focused on the fact that DAI is not included in DCI (DAI does not exist) when UL / DL configuration 0 is set as the UL / DL configuration for uplink HARQ reference. In this case, even if the UL / DL configuration actually set is not UL / DL configuration 0, there is no DAI. Therefore, if PUCCH format 3 is set, the number of DL subframes for the UL subframe is 1. However, other formats (PUCCH format 1a / 1b) cannot be used.

  Therefore, the present inventors, as a first aspect of the present embodiment, include the first uplink HARQ reference UL / DL including DAI in the uplink HARQ reference UL / DL configuration used for uplink HARQ timing control. When using the configuration, determine the PUCCH format based at least on the DAI, and when using the second uplink HARQ reference UL / DL configuration not including the DAI, determine the PUCCH format regardless of the DAI. Inspired. The first uplink HARQ reference UL / DL configuration is one of the UL / DL configurations 1 to 6 used in the TDD of the LTE system, and the second uplink HARQ reference UL / DL configuration is the TDD of the LTE system. The UL / DL configuration 0 used in FIG. Hereinafter, the first aspect will be described in detail.

(First aspect)
FIG. 5 shows an example of the PUCCH format selected when the UL / DL configuration 2 is used and when the UL / DL configuration 0 is used. In FIG. 5, it is assumed that UL / DL configuration 2 is applied as the downlink HARQ reference UL / DL configuration and UL / DL configuration 0 is applied as the uplink HARQ reference UL / DL configuration. The UL / DL configuration actually set may be the UL / DL configuration 0 or another UL / DL configuration.

  In the UL / DL configuration 2 in FIG. 5, three DL subframes (the number of PDSCH transmissions is 3) correspond to a predetermined UL subframe (eighth from the top of the subframe). Here, the special subframe is also regarded as a DL subframe. In this case, the user terminal applies feedback such as A / N by applying PUCCH format 3 in the UL subframe.

  On the other hand, in the UL / DL configuration 0 in FIG. 5, one DL subframe (the number of PDSCH transmissions is 1) corresponds to a predetermined UL subframe (the eighth from the top of the subframe). Also, in UL / DL configuration 0, DAI is not provided in PDCCH, but in this embodiment, PUCCH format is selected based on the number of PDSCH transmissions for UL / DL configuration 0 regardless of DAI. Therefore, here, since the number of PDSCH transmissions is 1, the user terminal performs A / N feedback using PUCCH format 1a / 1b instead of PUCCH format 3.

  Thus, in this embodiment, in dynamic TDD, when UL / DL configuration 0 (for example, primary cell) is set as the uplink HARQ reference UL / DL configuration, the number of PDSCH transmissions is set regardless of DAI. Based on this, the PUCCH format is selected. Thereby, when PUCCH format 3 is set, even if DAI is not included in DCI, it can be changed to PUCCH format 1a / 1b and applied. As a result, it is possible to use the PUCCH format with a small DL transmission amount in an environment where the traffic load is low (suppress resource consumption by the PUCCH format 3), thereby improving system efficiency.

  Although FIG. 5 shows a case where a user terminal using dynamic TDD selects the PUCCH format regardless of DAI, the present embodiment is not limited to this. For example, when UL / DL configuration 0 is set as the uplink HARQ reference UL / DL configuration, a configuration in which PUCCH format 3 is always used may be used.

  The first mode is not limited to dynamic TDD, and may be applied to other usage forms including TDD (for example, TDD-TDD CA, TDD-FDD CA, etc.).

(Second aspect)
In the second aspect, control of channel selection based on PUCCH format 1b when a downlink HARQ reference UL / DL configuration (DL HARQ reference configuration) is set will be described.

  As described above, in dynamic TDD (eIMTA), a predetermined UL / DL configuration is used as a reference for HARQ timing. In order to cope with the change of the UL / DL configuration, it is assumed that a configuration having a large number of DL subframes corresponding to one UL subframe is selected as the downlink HARQ UL / DL configuration. FIG. 6A shows a DL subframe corresponding to a UL subframe in each UL / DL configuration.

  In UL / DL configurations 2, 4, and 5, four or more DL subframes (number of PDSCH transmissions) correspond to one UL subframe. Accordingly, the present inventors are considering applying UL / DL configurations 2, 4, and 5 as downlink HARQ reference UL / DL configurations in dynamic TDD. In this case, the downlink HARQ reference UL / DL configuration 2 can be applied to the UL / DL configurations 0, 1, 2, and 6 that are actually set (see FIG. 6B). Further, the downlink HARQ reference UL / DL configuration 4 can be applied to UL / DL configurations 0, 1, 3, 4, and 6 that are actually set. Also, the downlink HARQ reference UL / DL configuration 5 can be applied to UL / DL configurations 0, 1, 2, 3, 4, 5, and 6 that are actually set.

  In particular, in the UL / DL configurations 2 and 4, the number of DL subframes corresponding to one UL subframe is 4, so the channel selection based on the PUCCH format 1b in the case of M = 4 is applied to apply A / N Give feedback.

  In channel selection in TDD, the number of PUCCH resource candidates to which A / N can be allocated is determined according to the number of M (M = 2, 3 or 4) as shown in the above equation (1). A mapping table to be applied is defined according to each M value, and the user terminal controls the mapping according to the M value.

  In the case of M = 4, not all ACK, NACK, and DTX combinations can be defined with 4 bits, so a plurality of ACK / NACK / DTX combinations overlap for the same QPSK symbol and PUCCH resource candidate combination. (See FIG. 7). Therefore, ambiguity occurs when channel selection is performed using a table at M = 4.

  When the UL / DL configurations 2 and 4 are used as the downlink HARQ reference UL / DL configuration, the present inventors have a number of DL subframes corresponding to the UL depending on the UL / DL configuration actually set. We focused on the fact that it is not necessarily 4. That is, it has been found that the number of DL subframes may be 3 or less in an area corresponding to four DL subframes (including special subframes) of UL / DL configurations 2 and 4.

  Therefore, the present inventors applied the downlink HARQ reference UL / DL configuration for the downlink HARQ timing in the dynamic TDD, and the mapping method applied to channel selection is not the downlink HARQ reference UL / DL configuration. It has been found that the control is based on the number of downlink subframes (M) of the UL / DL configuration that is actually set.

  FIG. 8A is a schematic diagram illustrating an example of the second mode. FIG. 8A shows a case where the UL / DL configuration actually set is UL / DL configuration 1, and the UL / DL configuration set as the downlink HARQ reference UL / DL configuration is UL / DL configuration 2. Yes. In this case, the user terminal controls the A / N feedback by applying DL HARQ timing in the UL / DL configuration 2.

  Specifically, according to the HARQ timing of UL / DL configuration 2, DL subframes (including special subframes) corresponding to 5 to 9 from the top of the subframe are fed back in a predetermined UL subframe. In UL / DL configuration 2, the number of DL subframes corresponding to 5 to 9 from the top of the subframe is 4 (M = 4), whereas in UL / DL configuration 1 that is actually set, 3 (M = 3).

  Therefore, the user terminal applies a channel selection mapping method based on the number of PDSCH transmissions for the UL / DL configuration actually set (here, UL / DL configuration 1). Specifically, a mapping table (number of PUCCH resource candidates) corresponding to M = 3 is selected and channel selection is performed.

For example, when a mapping table of M = 4 is selected according to UL / DL configuration 2 for downlink HARQ reference 2, a combination of the same QPSK symbol and PUCCH resource candidate (for example, n ⁽¹⁾ _{PUCCH, 1} , b (0 ), b (1) = 1,0), the same ACK / NACK / DTX combination is defined redundantly (see FIG. 8B). In this case, even if only A / N for three DL subframes is actually transmitted, it is difficult for the radio base station to clearly determine the status of each ACK, NACK, and DTX.

  On the other hand, as shown in the present embodiment, by controlling the channel selection mapping method (table selection, PUCCH resource candidate setting) based on the actually set UL / DL configuration, a mapping table in which M is 3 or less Can be used. Thereby, the ambiguity of the ACK, NACK, and DTX states in channel selection can be suppressed, and HARQ feedback can be performed appropriately.

  Note that the mapping method shown in FIG. 8A can be suitably used when the UL / DL configuration for downlink HARQ reference is UL / DL configuration 2 or 4.

(Modification)
In the existing LTE system, channel selection is limited to the support of acknowledgment signals of up to 4 bits. Therefore, in UL / DL configuration 5 in which the number of DL subframes for one UL subframe is greater than 4, channel selection is not possible. It was not supported.

  However, in dynamic TDD, it is assumed that only a change from a UL subframe to a DL subframe is allowed in each subframe of the UL / DL configuration actually set. In this case, the UL / DL configuration 5 can support more UL / DL configurations that are actually set as the downlink HARQ reference UL / DL configuration (see FIG. 6B above).

  Therefore, the present inventors have found that when dynamic TDD is applied, the UL / DL configuration 5 is controlled to support channel selection. Specifically, in the dynamic TDD, when the number of DL subframes for one UL subframe is larger than 4, at least a part of A / N is bundled in the time direction (subframe direction) (A / N bundling). ). For example, when UL / DL configuration 5 is used as a downlink HARQ reference UL / DL configuration), and the number of PDSCH transmissions is greater than 4, A / N bundling arranged in the time direction is performed. A / N bundling can be performed for each codeword.

  For example, as shown in FIG. 9, a case is assumed where UL / DL configuration 5 is applied as DL HARQ in dynamic TDD. In this case, a maximum of 9 DL subframes correspond to one UL subframe. Therefore, when M> 4 in dynamic TDD, a part of A / N is bundled so that M is 4 or less (M ≦ 4), and channel selection is applied. Note that, among the plurality of DL subframes, the subframe to which A / N bundling is applied, the number of bundling, and the like can be set as appropriate.

  Thus, in dynamic TDD, even when the UL / DL configuration 5 is a downlink HARQ reference UL / DL configuration, channel selection can be applied.

(Configuration of wireless communication system)
Hereinafter, an example of the radio communication system according to the present embodiment will be described in detail.

  FIG. 10 is a schematic configuration diagram of a radio communication system according to the present embodiment. Note that the radio communication system shown in FIG. 10 is a system including, for example, an LTE system or SUPER 3G. In this radio communication system, carrier aggregation (CA) in which a plurality of basic frequency blocks (component carriers) having the system bandwidth of the LTE system as one unit can be applied. Further, this radio communication system may be called IMT-Advanced, or may be called 4G, FRA (Future Radio Access).

  A radio communication system 1 shown in FIG. 10 includes a radio base station 11 that forms a macro cell C1, and radio base stations 12a and 12b that are arranged in the macro cell C1 and form a small cell C2 that is narrower than the macro cell C1. . Moreover, the user terminal 20 is arrange | positioned at the macrocell C1 and each small cell C2. The user terminal 20 can be connected to both the radio base station 11 and the radio base station 12. Further, intra-base station CA (Intra-eNB CA) or inter-base station CA (Inter-eNB CA) is applied between the radio base station 11 and the radio base station 12. Further, as the CA between the radio base station 11 and the radio base station 12, TDD-TDD CA, TDD-FDD CA, or the like can be applied.

  Communication between the user terminal 20 and the radio base station 11 can be performed using a carrier having a relatively low frequency band (for example, 2 GHz) and a narrow bandwidth (referred to as an existing carrier or a legacy carrier). On the other hand, a carrier having a relatively high frequency band (for example, 3.5 GHz) and a wide bandwidth may be used between the user terminal 20 and the radio base station 12, or between the user base 20 and the radio base station 11. The same carrier may be used. A new carrier type (NCT) may be used as a carrier type between the user terminal 20 and the radio base station 12. The wireless base station 11 and the wireless base station 12 (or between the wireless base stations 12) are wired (Optical fiber, X2 interface, etc.) or wirelessly connected.

  The radio base station 11 and each radio base station 12 are connected to the upper station apparatus 30 and connected to the core network 40 via the upper station apparatus 30. The upper station device 30 includes, for example, an access gateway device, a radio network controller (RNC), a mobility management entity (MME), and the like, but is not limited thereto. Each radio base station 12 may be connected to the higher station apparatus 30 via the radio base station 11.

  The radio base station 11 is a radio base station having a relatively wide coverage, and may be referred to as an eNodeB, a macro base station, a transmission / reception point, or the like. The radio base station 12 is a radio base station having local coverage, and may be called a small base station, a pico base station, a femto base station, a Home eNodeB, a micro base station, a transmission / reception point, or the like. Hereinafter, when the radio base stations 11 and 12 are not distinguished, they are collectively referred to as a radio base station 10. Each user terminal 20 is a terminal that supports various communication schemes such as LTE and LTE-A, and may include not only mobile communication terminals but also fixed communication terminals.

  In a radio communication system, OFDMA (Orthogonal Frequency Division Multiple Access) is applied to the downlink and SC-FDMA (Single Carrier Frequency Division Multiple Access) is applied to the uplink as radio access schemes. OFDMA is a multi-carrier transmission scheme that performs communication by dividing a frequency band into a plurality of narrow frequency bands (subcarriers) and mapping data to each subcarrier. SC-FDMA is a single-carrier transmission scheme that reduces interference between terminals by dividing the system bandwidth into bands composed of one or continuous resource blocks for each terminal, and a plurality of terminals using different bands. is there.

  Here, communication channels used in the wireless communication system shown in FIG. 10 will be described. The downlink communication channel includes a PDSCH (Physical Downlink Shared Channel) shared by each user terminal 20 and a downlink L1 / L2 control channel (PDCCH, PCFICH, PHICH, extended PDCCH). User data and higher control information are transmitted by the PDSCH. PDSCH and PUSCH scheduling information and the like are transmitted by PDCCH (Physical Downlink Control Channel). The number of OFDM symbols used for PDCCH is transmitted by PCFICH (Physical Control Format Indicator Channel). HARQ ACK / NACK for PUSCH is transmitted by PHICH (Physical Hybrid-ARQ Indicator Channel). Moreover, scheduling information of PDSCH and PUSCH may be transmitted by the extended PDCCH (EPDCCH). This EPDCCH is frequency division multiplexed with PDSCH (downlink shared data channel).

  The uplink communication channel includes a PUSCH (Physical Uplink Shared Channel) as an uplink data channel shared by each user terminal 20 and a PUCCH (Physical Uplink Control Channel) that is an uplink control channel. User data and higher control information are transmitted by this PUSCH. Also, downlink radio quality information (CQI: Channel Quality Indicator), ACK / NACK, and the like are transmitted by PUCCH and PUSCH (when transmitting simultaneously with user data).

  FIG. 11 is an overall configuration diagram of radio base station 10 (including radio base stations 11 and 12) according to the present embodiment. The radio base station 10 includes a plurality of transmission / reception antennas 101 for MIMO transmission, an amplifier unit 102, a transmission / reception unit 103, a baseband signal processing unit 104, a call processing unit 105, and a transmission path interface 106. Yes.

  User data transmitted from the radio base station 10 to the user terminal 20 via the downlink is input from the higher station apparatus 30 to the baseband signal processing unit 104 via the transmission path interface 106.

  The baseband signal processing unit 104 performs PDCP layer processing, user data division / combination, RLC layer transmission processing such as RLC (Radio Link Control) retransmission control transmission processing, MAC (Medium Access Control) retransmission control, for example, HARQ transmission processing, scheduling, transmission format selection, channel coding, inverse fast Fourier transform (IFFT) processing, and precoding processing are performed and transferred to each transceiver 103. The downlink control channel signal is also subjected to transmission processing such as channel coding and inverse fast Fourier transform, and is transferred to each transceiver 103.

  Moreover, the baseband signal processing part 104 notifies the control information for communication in the said cell with respect to the user terminal 20 by upper layer signaling (RRC signaling, an alerting signal, etc.). Information for communication in the cell includes, for example, information on UL / DL configuration used in the TDD cell, information on uplink / downlink HARQ reference UL / DL configuration, system bandwidth in uplink or downlink, and feedback Resource information and the like.

  Each transmission / reception unit 103 converts the baseband signal output by precoding for each antenna from the baseband signal processing unit 104 to a radio frequency band. The amplifier unit 102 amplifies the frequency-converted radio frequency signal and transmits the amplified signal using the transmission / reception antenna 101. The transmission / reception unit 103 functions as a transmission unit that transmits information on the UL / DL configuration used in the TDD cell by higher layer signaling (broadcast signal, RRC signaling, etc.).

  On the other hand, for data transmitted from the user terminal 20 to the radio base station 10 via the uplink, radio frequency signals received by the respective transmission / reception antennas 101 are amplified by the amplifier units 102 and frequency-converted by the respective transmission / reception units 103. It is converted into a baseband signal and input to the baseband signal processing unit 104.

  The baseband signal processing unit 104 performs FFT processing, IDFT processing, error correction decoding, MAC retransmission control reception processing, RLC layer, and PDCP layer reception processing on user data included in the input baseband signal. The data is transferred to the higher station apparatus 30 via the transmission path interface 106. The call processing unit 105 performs call processing such as communication channel setting and release, status management of the radio base station 10, and radio resource management.

  FIG. 12 is a main functional configuration diagram of the baseband signal processing unit 104 included in the radio base station 10 according to the present embodiment. As shown in FIG. 12, the baseband signal processing unit 104 included in the radio base station 10 includes a control unit 301, a DL signal generation unit 302, a UL / DL configuration determination unit 303, and a UL / DL configuration determination for HARQ reference. Unit 304, mapping unit 305, UL signal decoding unit 306, and determination unit 307.

  The control unit 301 controls scheduling of downlink user data transmitted on the PDSCH, downlink control information transmitted on the PDCCH and / or enhanced PDCCH (EPDCCH), downlink reference signals, and the like. The control unit 301 also performs control (allocation control) of uplink data transmitted on the PUSCH, uplink control information transmitted on the PUCCH or PUSCH, and uplink reference signal scheduling. Information related to allocation control of uplink signals (uplink control signals, uplink user data) is notified to user terminals using downlink control signals (DCI).

  Specifically, the control unit 301 controls allocation of radio resources for the downlink signal and the uplink signal based on the instruction information from the higher station apparatus 30 and the feedback information from each user terminal 20. That is, the control unit 301 has a function as a scheduler. Further, when the radio base station 10 uses TDD, the allocation of the downlink signal and the uplink signal to each subframe is controlled based on the UL / DL configuration and the special subframe configuration to be used.

  The DL signal generation unit 302 generates a downlink control signal (PDCCH signal and / or EPDCCH signal) and a downlink data signal (PDSCH signal) whose assignment has been determined by the control unit 301. Specifically, the DL signal generation unit 302, based on an instruction from the control unit 301, a DL allocation (DL assignment) for notifying downlink signal allocation information and a UL grant (DL grant) for notifying uplink signal allocation information ( UL grant).

  Further, the DL signal generation unit 302 generates information on the UL / DL configuration determined by the UL / DL configuration determination unit 303 and information on the UL / DL configuration determined by the HARQ reference UL / DL configuration determination unit 304. To do. Also, the DL signal generation unit 302 generates DAI when the uplink HARQ reference UL / DL configuration is UL / DL 1 to 6.

  The UL / DL configuration determining unit 303 determines the UL / DL configuration to be used in TDD in consideration of UL and DL traffic and the like. The UL / DL configuration determining unit 303 can determine the UL / DL configuration based on information from the higher station apparatus 30 or the like.

  The HARQ reference UL / DL configuration determination unit 304 determines a UL / DL configuration to be applied as HARQ timing in dynamic TDD. For example, UL / DL configuration 0 can be selected as the UL / DL configuration for uplink HARQ reference, and UL / DL configurations 2, 4, and 5 can be selected as the UL / DL configuration for downlink HARQ reference. Of course, selectable configurations are not limited to this.

  The mapping unit 305 controls allocation of the downlink control signal and downlink data signal generated by the DL signal generation unit 302 to radio resources based on an instruction from the control unit 301.

  The UL signal decoding unit 306 decodes a feedback signal (such as a delivery confirmation signal) transmitted from the user terminal and outputs the decoded signal to the control unit 301. Also, the UL signal decoding unit 306 decodes the uplink data signal transmitted from the user terminal through the uplink shared channel (PUSCH), and outputs the decoded signal to the determination unit 307. The determination unit 307 performs retransmission control determination (ACK / NACK) based on the decoding result of the UL signal decoding unit 306 and outputs the result to the control unit 301.

  FIG. 13 is an overall configuration diagram of the user terminal 20 according to the present embodiment. The user terminal 20 includes a plurality of transmission / reception antennas 201 for MIMO transmission, an amplifier unit 202, a transmission / reception unit (reception unit) 203, a baseband signal processing unit 204, and an application unit 205.

  For downlink data, radio frequency signals received by a plurality of transmission / reception antennas 201 are respectively amplified by an amplifier unit 202, frequency-converted by a transmission / reception unit 203, and converted into a baseband signal. The baseband signal is subjected to FFT processing, error correction decoding, retransmission control reception processing, and the like by the baseband signal processing unit 204. Among the downlink data, downlink user data is transferred to the application unit 205. The application unit 205 performs processing related to layers higher than the physical layer and the MAC layer. Also, broadcast information in the downlink data is also transferred to the application unit 205.

  The transmission / reception unit 203 functions as a reception unit that receives information on the UL / DL configuration and information on the UL / DL configuration for HARQ reference when the user terminal 20 is connected to the TDD cell.

  On the other hand, uplink user data is input from the application unit 205 to the baseband signal processing unit 204. The baseband signal processing unit 204 performs retransmission control (H-ARQ (Hybrid ARQ)) transmission processing, channel coding, precoding, DFT processing, IFFT processing, and the like, and forwards them to each transmission / reception unit 203. The transmission / reception unit 203 converts the baseband signal output from the baseband signal processing unit 204 into a radio frequency band. Thereafter, the amplifier unit 202 amplifies the frequency-converted radio frequency signal and transmits the amplified signal using the transmitting / receiving antenna 201.

  FIG. 14 is a main functional configuration diagram of the baseband signal processing unit 204 included in the user terminal 20. As shown in FIG. 14, the baseband signal processing unit 204 included in the user terminal 20 includes a DL signal decoding unit 401, a UL / DL configuration selection unit 402, a HARQ reference UL / DL configuration selection unit 403, and a determination unit. 404, a control unit 405, a UL signal generation unit 406, and a mapping unit 407 are included at least.

  The DL signal decoding unit 401 decodes the downlink control signal (PDCCH signal) transmitted on the downlink control channel (PDCCH), and outputs scheduling information (allocation information to uplink resources) to the control unit 405. Also, the DL signal decoding unit 401 decodes the downlink data signal transmitted through the downlink shared channel (PDSCH), and outputs it to the determination unit 404. The determination unit 404 performs retransmission control determination (ACK / NACK) based on the decoding result of the DL signal decoding unit 401 and outputs the result to the control unit 405.

  When the received downlink signal includes information on the UL / DL configuration and information on the UL / DL configuration for HARQ reference, the DL signal decoding unit 401 stores the decoded information in the UL / DL configuration selection unit 402 or The data is output to the HARQ reference UL / DL configuration selection unit 403.

  The UL / DL configuration selection unit 402 selects the UL / DL configuration to be applied by the user terminal based on information on the UL / DL configuration notified from the radio base station. Further, the UL / DL configuration selection unit 402 outputs information on the UL / DL configuration to be applied to the control unit 405 or the like.

  The HARQ reference UL / DL configuration selection unit 403 selects the HARQ timing to be applied by the user terminal in dynamic TDD based on information notified from the radio base station. Also, the HARQ reference UL / DL configuration selection unit 403 outputs information on the selected uplink HARQ reference UL / DL configuration and / or downlink HARQ reference UL / DL configuration to the control unit 405 or the like.

  The control unit 405 controls generation of an uplink control signal (feedback signal) and an uplink data signal based on a downlink control signal (PDCCH signal) transmitted from the radio base station and a retransmission control determination result for the received PDSCH signal. . The downlink control signal is output from the DL signal decoding unit 401, and the retransmission control determination result is output from the determination unit 404.

  Further, the control unit 405 is based on information on the UL / DL configuration output from the UL / DL configuration selection unit 402 and information on the UL / DL configuration output from the HARQ reference UL / DL configuration selection unit 403. The PUCCH format used for transmission of the uplink control signal is controlled.

  When the first aspect is applied, the control unit 405 transmits the number of downlink data signals for uplink UL subframes when UL / DL configurations 1 to 6 are used as UL / DL configurations for uplink HARQ reference. And the PUCCH format is determined based on the DAI. On the other hand, when UL / DL configuration 0 is used as the uplink HARQ reference UL / DL configuration, the control unit 405 determines the PUCCH format based on the number of downlink data signal transmissions for the UL subframe regardless of DAI. To do.

  Specifically, when the PUCCH format 3 is set and the UL / DL configuration 0 is set as the uplink HARQ reference UL / DL configuration, the control unit 405 sets the downlink data signal corresponding to the UL subframe. When the number of transmissions is 1, the PUCCH format 3 is changed to the PUCCH format 1a / 1b and applied.

  Also, when the second aspect is applied, the control section 405, among the DL subframes with the UL / DL configuration to be set, the DL subframe corresponding to the UL subframe with the downlink HARQ reference UL / DL configuration. Based on the number of frames, the setting of the number of PUCCH resource candidates in channel selection based on PUCCH format 1b is controlled.

  Thus, the control unit 405 also functions as a feedback control unit that controls the feedback of the delivery confirmation signal (A / N) with respect to the PDSCH signal.

  The UL signal generation unit 406 generates an uplink control signal (feedback signal such as a delivery confirmation signal or channel state information (CSI)) based on an instruction from the control unit 405. Further, the UL signal generation unit 406 generates an uplink data signal based on an instruction from the control unit 405.

  The mapping unit 407 (allocation unit) controls allocation of uplink control signals (such as delivery confirmation signals) and uplink data signals to radio resources (PUCCH, PUSCH) based on an instruction from the control unit 405.

  Although the present invention has been described in detail using the above-described embodiments, it is obvious to those skilled in the art that the present invention is not limited to the embodiments described in this specification. The present invention can be implemented as modified and changed modes without departing from the spirit and scope of the present invention defined by the description of the scope of claims. For example, the above-described plurality of aspects can be applied in appropriate combination. Therefore, the description of the present specification is for illustrative purposes and does not have any limiting meaning to the present invention.

DESCRIPTION OF SYMBOLS 1 ... Wireless communication system 10 ... Wireless base station 11 ... Wireless base station (macro base station)
12, 12a, 12b ... wireless base station (small base station)
DESCRIPTION OF SYMBOLS 20 ... User terminal 30 ... Host station apparatus 40 ... Core network 101 ... Transmission / reception antenna 102 ... Amplifier unit 103 ... Transmission / reception unit 104 ... Baseband signal processing unit 105 ... Call processing unit 106 ... Transmission path interface 201 ... Transmission / reception antenna 202 ... Amplifier unit 203 ... Transmission / reception unit 204 ... Baseband signal processing unit 205 ... Application unit 301 ... Control unit 302 ... DL signal generation unit 303 ... UL / DL configuration determination unit 304 ... HARQ reference UL / DL configuration determination unit 305 ... Mapping unit 306 ... UL signal decoding unit 307 ... determination unit 401 ... DL signal decoding unit 402 ... UL / DL configuration selection unit 403 ... HARQ reference UL / DL configuration selection unit 404 ... determination unit 405 ... control unit 406 ... UL signal generation unit 407 ... mapping Part

Claims (10)

A user terminal that communicates with a radio base station that controls the UL / DL configuration by changing the time division duplex,
A selector that selects an uplink HARQ reference UL / DL configuration used for uplink HARQ timing control;
A control unit that controls feedback of a delivery confirmation signal for a downlink data signal using a predetermined PUCCH format,
When the first uplink HARQ reference UL / DL configuration is used as the uplink HARQ reference UL / DL configuration, the control unit transmits the number of downlink data signals for the uplink UL subframe and DAI (Downlink Assignment Index). PUCCH format is determined based on the UL, and when the second uplink HARQ reference UL / DL configuration is used, the PUCCH format is determined based on the number of downlink data signal transmissions for the UL subframe regardless of DAI. Characteristic user terminal.   The first uplink HARQ reference UL / DL configuration is one of the UL / DL configurations 1 to 6 used in the TDD of the LTE system, and the second uplink HARQ reference UL / DL configuration is the TDD of the LTE system. The user terminal according to claim 1, wherein the user terminal has a UL / DL configuration of 0.   When the PUCCH format 3 is set and the uplink HARQ reference UL / DL configuration is set as the second uplink HARQ reference UL / DL configuration, the control unit transmits downlink data corresponding to the UL subframe. The user terminal according to claim 1 or 2, wherein when the number of signal transmissions is 1, PUCCH format 3 is changed to PUCCH format 1a / 1b.   The user terminal according to any one of claims 1 to 3, wherein the selection unit selects a predetermined uplink HARQ reference UL / DL configuration based on system information transmitted from a radio base station. .   The user according to claim 1, wherein the control unit uses the PUCCH format 3 when using the second uplink HARQ reference UL / DL configuration as the uplink HARQ reference UL / DL configuration. Terminal. A wireless communication method of a user terminal that communicates by time division duplex to a wireless base station that changes and controls a UL / DL configuration,
The user terminal selects an uplink HARQ reference UL / DL configuration to be used for uplink HARQ timing control based on information transmitted from the radio base station, and provides feedback of a delivery confirmation signal for the downlink data signal. Controlling using a predetermined PUCCH format,
When the first uplink HARQ reference UL / DL configuration is used as the uplink HARQ reference UL / DL configuration, the PUCCH format is based on the number of downlink data signals transmitted to the uplink UL subframe and the DAI (Downlink Assignment Index). In the case of using the second uplink HARQ reference UL / DL configuration, the PUCCH format is determined based on the number of downlink data signal transmissions for the UL subframe regardless of the DAI. Method. A user terminal that communicates with a radio base station that controls the UL / DL configuration by changing the time division duplex,
A selection unit that selects a downlink HARQ reference UL / DL configuration to be used for downlink HARQ timing control;
A control unit that controls feedback of a delivery confirmation signal for a downlink data signal using channel selection based on the PUCCH format 1b, and
The control unit performs channel selection based on the PUCCH format 1b based on the number of DL subframes corresponding to the UL subframes configured for downlink HARQ reference UL / DL among the DL subframes configured for UL / DL. The user terminal which controls the setting of the number of PUCCH resource candidates in.   The user terminal according to claim 7, wherein the selection unit selects one of UL / DL configurations 2, 4, and 5 used in TDD of the LTE system as a downlink HARQ reference UL / DL configuration. . A radio base station that communicates with a user terminal by time division duplex and changes and controls the UL / DL configuration,
A UL / DL configuration to be set in the user terminal, and a determination unit that determines a UL / DL configuration for downlink HARQ reference to be used for downlink HARQ timing control,
A transmission unit that transmits information on the UL / DL configuration for downlink HARQ reference to the user terminal;
Receiving a delivery confirmation signal fed back from the user terminal,
The receiving unit is configured to determine a PUCCH resource candidate determined based on the number of DL subframes corresponding to a UL subframe with a downlink HARQ reference UL / DL configuration among DL subframes with a UL / DL configuration set in a user terminal A radio base station receiving a number of acknowledgment signals. A wireless communication method of a user terminal that communicates by time division duplex to a wireless base station that changes and controls a UL / DL configuration,
The user terminal selects a downlink HARQ reference UL / DL configuration used for downlink HARQ timing control, and controls the feedback of a delivery confirmation signal for the downlink data signal using channel selection based on the PUCCH format 1b. And having
Number of PUCCH resource candidates in channel selection based on PUCCH format 1b based on the number of DL subframes corresponding to UL subframes configured for downlink HARQ reference UL / DL among DL subframes configured for UL / DL A wireless communication method characterized by controlling the setting.

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