WO2011136207A1

WO2011136207A1 - Base station, mobile station, control signal transmission method, and control signal reception method

Info

Publication number: WO2011136207A1
Application number: PCT/JP2011/060140
Authority: WO
Inventors: 啓之石井; 貞行安部田; 哲士阿部; 尚人大久保; 信彦三木; 大將梅田
Original assignee: 株式会社エヌ・ティ・ティ・ドコモ
Priority date: 2010-04-30
Filing date: 2011-04-26
Publication date: 2011-11-03
Also published as: JP2011238989A; JP5427103B2

Abstract

The disclosed base station, which applies carrier aggregation and communicates with a mobile station, has: a management unit that manages a subcarrier positioned at the direct-current component of a baseband signal at the aforementioned mobile station; a mapping unit that, when the subcarrier positioned at the direct-current component of the baseband signal is used in a predetermined control channel, maps the predetermined control channel for the aforementioned mobile station to a wireless resource that differs from the wireless resource of the subcarrier positioned at the direct-current component of the baseband signal; and a control signal transmission unit that transmits a control signal of the predetermined control channel.

Description

Base station, mobile station, control signal transmission method, and control signal reception method

The present invention relates to a base station, a mobile station, a control signal transmission method, and a control signal reception method.

The Orthogonal Frequency Division Multiplexing (OFDM) system is a technique for transmitting a signal on a plurality of subcarriers. In general, in the OFDM method, an additional subcarrier (DC subcarrier) is set at the center of the carrier, and this subcarrier is not used for signal transmission (see 3GPP TS 36.101 V9.3.0 (2010-03)). .

This is because, in a receiver such as a mobile station, the subcarrier (DC subcarrier) added to the center is located in the direct current component after down-conversion to the baseband signal, so the signal on the DC subcarrier is This is because it cannot be decrypted.

In next-generation wireless access, application of carrier aggregation that integrates a plurality of frequency bands called component carriers to increase the bandwidth is being studied. The component carrier refers to a continuous frequency region of a predetermined unit. For example, a 10 MHz component carrier and a 20 MHz component carrier can be integrated to increase the system bandwidth. There may be a frequency region of another system between the component carriers.

Even when carrier aggregation is applied to communication, the mobile station cannot decode the signal at the position of the DC component after down-conversion to the baseband signal. For example, when a subcarrier located in a direct current component after down-conversion to a baseband signal is used for a data channel or a control channel, the mobile station cannot decode the subcarrier, so that the data channel (that is, the data channel) Data signal) or a control channel (that is, a control signal included in the control channel) reception quality deteriorates. In particular, this problem becomes significant in a control channel in which the number of symbols of the physical channel is small and deterioration due to the inability to decode the subcarrier cannot be compensated by redundant bits or coded bits. More specifically, the problem becomes significant when the number of subcarriers used for the control channel is small.

The present invention aims to improve the reception quality of the control channel even when carrier aggregation is applied to communication.

The base station of the present invention
A base station that communicates with a mobile station by applying carrier aggregation,
A management unit for managing subcarriers located in a DC component of a baseband signal in the mobile station;
When a subcarrier located in the DC component of the baseband signal is used for a predetermined control channel, the predetermined control for the mobile station is transferred to a radio resource different from the radio resource of the subcarrier located in the DC component of the baseband signal. A mapping unit for mapping channels;
A control signal transmitter for transmitting a control signal of a predetermined control channel;
It is characterized by having.

The control signal transmission method of the present invention includes:
A control signal transmission method in a base station that communicates with a mobile station by applying carrier aggregation,
Managing a subcarrier located in a DC component of a baseband signal at the mobile station;
When a subcarrier located in the DC component of the baseband signal is used for a predetermined control channel, the predetermined control for the mobile station is transferred to a radio resource different from the radio resource of the subcarrier located in the DC component of the baseband signal. Mapping the channel;
Transmitting a control signal of a predetermined control channel;
It is characterized by having.

The mobile station of the present invention
A mobile station that communicates with a base station by applying carrier aggregation,
When subcarriers located in the DC component of the baseband signal are used for a predetermined control channel, mapping information holding that holds radio resource mapping information used instead of the radio resources of the subcarrier located in the DC component of the baseband signal And
A control signal receiving unit that receives a control signal of a predetermined control channel based on the mapping information held in the mapping information holding unit;
It is characterized by having.

The control signal receiving method of the present invention includes:
A control signal reception method in a mobile station that communicates with a base station by applying carrier aggregation,
When subcarriers located in the DC component of the baseband signal are used for a predetermined control channel, holding radio resource mapping information used instead of the radio resources of the subcarrier located in the DC component of the baseband signal;
Receiving a control signal of a predetermined control channel based on the mapping information held in the mapping information holding unit;
It is characterized by having.

The base station of the present invention
A base station that communicates with a mobile station by applying carrier aggregation,
A management unit for managing subcarriers located in a DC component of a baseband signal in the mobile station;
When a subcarrier located in the DC component of the baseband signal is used for a predetermined control channel, the transmission power of the subcarrier located in the DC component of the baseband signal is reduced and transmission of the remaining subcarriers in the predetermined control channel is performed. A transmission power control unit for increasing power;
A control signal transmitter for transmitting a control signal of a predetermined control channel;
It is characterized by having.

The control signal transmission method of the present invention includes:
A control signal transmission method in a base station that communicates with a mobile station by applying carrier aggregation,
Managing a subcarrier located in a DC component of a baseband signal at the mobile station;
When a subcarrier located in the DC component of the baseband signal is used for a predetermined control channel, the transmission power of the subcarrier located in the DC component of the baseband signal is reduced and transmission of the remaining subcarriers in the predetermined control channel is performed. Increasing power, and
Transmitting a control signal of a predetermined control channel;
It is characterized by having.

The base station of the present invention
A base station that communicates with a mobile station by applying carrier aggregation,
A management unit for managing subcarriers located in a DC component of a baseband signal in the mobile station;
When a subcarrier located in the DC component of the baseband signal is used for a predetermined control channel, a generation unit that generates a control signal for the predetermined control channel as a message or broadcast information addressed to the mobile station;
A transmitter for transmitting a message or broadcast information addressed to the mobile station;
It is characterized by having.

The control signal transmission method of the present invention includes:
A control signal transmission method in a base station that communicates with a mobile station by applying carrier aggregation,
Managing a subcarrier located in a DC component of a baseband signal at the mobile station;
When a subcarrier located in the DC component of the baseband signal is used for a predetermined control channel, generating a control signal for the predetermined control channel as a message or broadcast information addressed to the mobile station;
Transmitting a message or broadcast information addressed to the mobile station;
It is characterized by having.

According to the embodiment of the present invention, it is possible to improve the reception quality of the control channel even when carrier aggregation is applied to communication.

The figure which shows the position of the direct current | flow component of a baseband signal in a mobile station in case a carrier aggregation is applied to communication Conceptual diagram of resource element group The figure which shows the frame structure of a downlink channel The block diagram of the base station which concerns on the Example of this invention An example in which a subcarrier located in the DC component of a baseband signal is used in PCFICH 7 is a flowchart of a control signal transmission method in a base station according to an embodiment of the present invention. The block diagram of the mobile station which concerns on the Example of this invention Flowchart of control signal reception method in mobile station according to an embodiment of the present invention The block diagram of the base station which concerns on the 1st modification of this invention The conceptual diagram which shows the transmission power control in the base station which concerns on the 1st modification of this invention The flowchart of the control signal transmission method in the base station which concerns on the 1st modification of this invention.

In the embodiment of the present invention, carrier aggregation is applied to communication between a mobile station and a base station. The mobile station cannot decode the signal of the subcarrier located in the DC component after the down conversion to the baseband signal. When such a subcarrier is used for a predetermined control channel, the reception quality of the control channel at the mobile station deteriorates. For example, control channels such as PCFICH (Physical Control Format Indicator Indicator Channel) and PHICH (Physical Hybrid-ARQ Indicator Channel) are mapped to the entire band, but the number of subcarriers to be mapped is small. That is, since such a control channel is mapped to a predetermined number or less of subcarriers, reception quality is significantly degraded. In order to avoid such degradation of reception quality, the base station manages the subcarriers located in the DC component of the baseband signal in the mobile station that communicates by applying carrier aggregation. When the subcarrier is used for a predetermined control channel, the base station maps the predetermined control channel to a radio resource different from the radio resource of the managed subcarrier.

Alternatively, when a subcarrier located in the DC component of the baseband signal is used for a predetermined control channel, the base station may decrease the transmission power of the subcarrier and increase the transmission power of the remaining subcarriers. . Further, the base station may transmit a control signal transmitted through a predetermined control channel as broadcast information or an RRC message.

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

FIG. 1 is a diagram showing a position of a direct current component of a baseband signal in a mobile station when carrier aggregation is applied to communication. The carrier aggregation may be constituted by two 20 MHz component carriers as shown in FIG. The component carrier refers to a continuous frequency region of a predetermined unit. Although the frequency region of another system may exist between the component carriers, FIG. 2 shows a case where each component carrier is set continuously in frequency. A mobile station (called an LTE mobile station) using a bandwidth of 20 MHz according to LTE (Long Term Evolution) receives a signal within one 20 MHz component carrier. For such an LTE mobile station, the center subcarrier (DC subcarrier) of each component carrier of 20 MHz is not used for signal transmission.

On the other hand, a mobile station using a total bandwidth of 40 MHz by carrier aggregation can receive signals by integrating two 20 MHz component carriers. In this case, since the two component carriers are symmetrical on the frequency axis, the position of the direct current component of the baseband signal is between the two component carriers for a mobile station using a bandwidth of 40 MHz. Normally, no signal is transmitted between the component carriers, so that the reception quality is not deteriorated due to the DC component of the baseband signal.

Further, as shown in FIG. 1B, the carrier aggregation may be configured symmetrically on the frequency axis by one 10 MHz component carrier and two 20 MHz component carriers. In this case, for a mobile station using a bandwidth of 50 MHz, the position of the DC component of the baseband signal matches the center subcarrier (DC subcarrier) of the 10 MHz component carrier. As described above, since the center subcarrier of each component carrier is not used for signal transmission, reception quality deterioration due to the DC component of the baseband signal does not occur.

However, the carrier aggregation may be composed of a 10 MHz component carrier and a 20 MHz component carrier as shown in FIG. Also in this case, the center subcarrier (DC subcarrier) of each component carrier of 10 MHz and 20 MHz is not used for signal transmission.

On the other hand, a mobile station using a total bandwidth of 30 MHz can receive a signal by integrating a 10 MHz component carrier and a 20 MHz component carrier. In this case, since the two component carriers are asymmetric on the frequency axis, the position of the direct current component of the baseband signal is the subcarrier for signal transmission of the 20 MHz component carrier for a mobile station using a bandwidth of 30 MHz. May overlap.

Further, as shown in FIG. 1D, the carrier aggregation may be configured asymmetrically on the frequency axis by one 10 MHz component carrier and two 20 MHz component carriers. Similarly, in this case, for a mobile station using a bandwidth of 50 MHz, the position of the DC component of the baseband signal may overlap with the signal transmission subcarrier of the 20 MHz component carrier.

Thus, when the carrier aggregation is configured asymmetrically on the frequency axis, the mobile station cannot decode the signal on the subcarrier located in the DC component of the baseband signal, and the reception quality deteriorates.

Next, the influence of the DC component of the baseband signal on the downlink channel will be described.

The downlink channel includes a downlink shared channel (PDSCH: Physical Downlink Shared Channel), a downlink control channel, and a downlink reference signal (DL RS: Downlink Reference Signal). The downlink control channel includes PDCCH (Physical Downlink Control Channel), PCFICH (Physical Control Format Indicator Channel), PHICH (Physical Hybrid-ARQ Indicator Channel), and the like.

PDSCH is a channel used for transmitting downlink data addressed to a mobile station. In general, PDSCH is encoded and mapped to the entire band or a part of the band. Due to the coding gain, the influence of reception quality degradation due to the DC component of the baseband signal is small. Even when the coding gain is small, if the HARQ retransmission is performed in a different band, the influence of the deterioration of the reception quality is small.

The PDCCH is a channel used for transmitting control information (DCI: Downlink Control Information) necessary for uplink and downlink data channel transmission. For example, resource allocation information, a modulation scheme, etc. are transmitted by PDCCH. The downlink control information includes control information for all mobile stations and control information for individual mobile stations (or for individual mobile station groups in which a plurality of mobile stations are combined). In general, the PDCCH is encoded and mapped to the entire band. Due to the coding gain, the influence of reception quality degradation due to the DC component of the baseband signal is small.

PCFICH is a channel used to transmit CFI (Control Format Indicator) indicating the number of OFDM symbols used for a control channel among 14 OFDM symbols constituting one subframe. Although PCFICH is mapped to the entire band, the number of mapped subcarriers is small. Therefore, the influence of the degradation of the reception quality due to the DC component of the baseband signal is great.

PHICH is a channel used to transmit acknowledgment information (ACK / NACK) (HI: HARQ Indicator) for the uplink data channel. Although PHICH is mapped to the entire band, the number of mapped subcarriers is small. Therefore, the influence of the degradation of the reception quality due to the DC component of the baseband signal is great.

DL RS is a predetermined signal sequence used for channel estimation, CQI measurement, cell search, and the like. In DL RS, the same signal sequence is mapped to subcarriers spread over the entire band. Therefore, even if the DL RS is deteriorated due to the direct current component of the baseband signal, the influence of the deterioration of the reception quality is small by not using the DL RS for channel estimation or the like.

Next, the frame structure of PCFICH and PHICH that are greatly affected by the degradation of the reception quality due to the DC component of the baseband signal will be described in more detail.

Radio resources are allocated to PDCCH, PCFICH, and PHICH in units of resource element groups (REG). The physical resources of the downlink control channel are divided in the time direction and the frequency direction. One subcarrier × 1 OFDM symbol is called a resource element (RE), and one resource element group is composed of four resource elements.

Figure 2 shows a conceptual diagram of the resource element group. FIG. 2 shows a case where the first 3 OFDM symbols of one subframe are used for the downlink control channel. In the first OFDM symbol, DL RSs (R1, R2) are arranged every 6 subcarriers. R1 is a reference signal for one antenna in the case of two transmitting antennas, and R2 is a reference signal for the other antenna. Although the number of resource element groups in one resource block (RB: Resource における Block) differs depending on the number of transmission antennas, for simplicity, when the number of transmission antennas is one, the radio resource of R2 is punctured. Accordingly, in the case of FIG. 2, eight resource element groups can be secured in one resource block in the first OFDM symbol.

Fig. 3 shows the frame structure of the downlink channel. For convenience of explanation, DL RS is omitted in FIG. The downlink control channel can use the top 3 OFDM symbols of 1 subframe at the maximum (4 OFDM symbols in the 1.4 MHz band). CFI is transmitted in PCFICH to indicate the number of OFDM symbols used for the control channel. Since it is not possible to recognize how many OFDM symbols are used for the control channel unless the PCFICH is demodulated, the PCFICH is mapped to the first OFDM symbol. Four resource element groups are used for PCFICH, and the four resource element groups are mapped so as to be substantially equally spaced over the entire band. Specifically, the mapping positions of the four resource element groups are determined by a predetermined calculation formula based on the cell ID and the system bandwidth.

PHICH may be mapped to the first OFDM symbol or may be mapped over 3 OFDM symbols. FIG. 3 shows a case where PHICH is mapped to the first OFDM symbol. Three resource element groups are used for PHICH, and the three resource element groups are mapped so as to be substantially equally spaced over the entire band. Specifically, the mapping positions of the three resource element groups are determined by a predetermined calculation formula based on the cell ID and the number of resource element groups excluding PCFICH.

Thus, although PCFICH and PHICH are mapped to the entire band, the number of mapped subcarriers is small. Therefore, the influence of the degradation of the reception quality due to the DC component of the baseband signal is great. Base stations and mobile stations for avoiding such influence will be described below.

<Configuration and operation of base station and mobile station according to embodiments of the present invention>
FIG. 4 shows a block diagram of a base station according to an embodiment of the present invention. The base station 10 includes a management unit 101, a mapping unit 103, a control signal transmission unit 105, and a data signal transmission unit 107.

The management unit 101 manages subcarriers located in the DC component of the baseband signal in a mobile station that communicates by applying carrier aggregation. In particular, when the component carriers constituting the carrier aggregation are asymmetric on the frequency axis, it is managed which subcarrier is located in the DC component of the baseband signal in the mobile station. The position of the DC component of the baseband signal may be calculated in advance before operation and stored in the management unit 101.

The mapping unit 103 maps PCFICH and PHICH to resource element groups. For example, PCFICH and PHICH are mapped to predetermined positions as shown in FIG. Next, mapping section 103 determines whether or not a subcarrier located in a DC component of a baseband signal in a mobile station that performs communication using the above-described carrier aggregation is used for PCFICH or PHICH. When the subcarrier located in the DC component of the baseband signal is used for PCFICH or PHICH, the mapping unit 103 secures another radio resource in addition to the above-described PCFICH and PHICH radio resources, and maps the PCFICH or PHICH. To do. That is, the mapping unit 103 performs normal PCFICH and PHICH radio resources when a subcarrier located in a DC component of a baseband signal in a mobile station that communicates by applying the above-described carrier aggregation is used for PCFICH or PHICH. In addition to the above, another radio resource is secured, and the PCFICH and PHICH are transmitted using both radio resources. Another radio resource may be reserved according to a predetermined rule determined in advance between the mobile station and the base station. As described above, generally, radio resources are allocated to the PCFICH and PHICH in units of resource element groups, and therefore, another radio resource to be secured may be one resource element group.

Alternatively, the mapping unit 103 may reserve the same number of resource element groups as the number of resource element groups used by the PCFICH or PHICH instead of securing one resource element group.

As described above, when the mapping 103 reserves another radio resource for PCFICH or PHICH, a mobile station that communicates by applying carrier aggregation uses another radio resource for the PCFICH or PHICH. The mobile station that decodes PCFICH or PHICH and communicates without applying carrier aggregation uses the radio resource for normal PCFICH or PHICH instead of the other radio resource for PCFICH or PHICH. Alternatively, PHICH may be decoded.

FIG. 5 shows an example in which the subcarrier located in the DC component of the baseband signal is used for PCFICH. In such a case, for example, the mapping unit 103 may map the PCFICH to the resource element group (REG2) adjacent to the resource element group (REG1) including the subcarrier located in the DC component of the baseband signal. When the adjacent resource element group (REG2) is used for PHICH, the mapping unit 103 may further map PCFICH to the adjacent resource element group. Here, the adjacent resource element group is secured, but not limited to the adjacent resource element group, any resource element group different from the resource element group (REG1) including the subcarrier located in the DC component of the baseband signal is used. May be secured. FIG. 5 shows an example in which the subcarrier located in the DC component of the baseband signal is used for PCFICH, but the same applies to the case where PHICH is mapped to the position of the DC component of the baseband signal. Another radio resource is secured. Note that the resource element group secured in this way is not used for PDCCH transmission.

The mapping unit 103 may reserve one resource element instead of the entire resource element group when securing another radio resource. Since the subcarrier located in the DC component of the baseband signal corresponds to one resource element, it is sufficient if one resource element can be secured without securing four resource elements. The remaining three resource elements may be used for transmission of PDCCH. However, since a normal LTE mobile station cannot recognize how to use such a resource element group, the remaining three resource elements are not used for transmission of PDCCH for the LTE mobile station. However, depending on the mobile station, the resource element corresponding to the subcarrier located in the DC component of the baseband signal can be regarded as null and decoded. For such mobile stations, the remaining three resource elements may be used for transmission of PDCCH.

The control signal transmission unit 105 transmits a control signal (DCI, CFI, HI) using a control channel (PDCCH, PCFICH, PHICH) mapped to a radio resource.

The data signal transmission unit 107 transmits a data signal addressed to the mobile station. The data signals include U-plane signals (user data) such as best-effort IP packets and voice signals, and C-plane signals (control data) such as broadcast information and RRC messages. When the mapping unit 103 maps the PCFICH or PHICH to another radio resource, the data signal transmission unit 107 may transmit information on the other radio resource as an RRC message. Or the information of another radio | wireless resource may be transmitted as alerting | reporting information. In this case, instead of the data signal transmission unit 107, a broadcast information transmission unit (not shown) may transmit information on another radio resource.

FIG. 6 shows a flowchart of a control signal transmission method in the base station according to the embodiment of the present invention.

The management unit 101 identifies the subcarrier located in the DC component of the baseband signal in the mobile station that communicates by applying carrier aggregation (S101).

The mapping unit 103 maps the PCFICH to a predetermined position as shown in FIG. 3 (S103). Next, mapping section 103 determines whether or not a subcarrier located in a DC component of a baseband signal in a mobile station that communicates by applying carrier aggregation is used for PCFICH (S105). When the subcarrier located in the DC component of the baseband signal is used for PCFICH, mapping section 103 maps PCFICH to another radio resource (S107). In this case, the mapping unit 103 maps the PCFICH to the other radio resource in addition to the normal radio resource. When the subcarrier located in the DC component of the baseband signal is not used for PCFICH, mapping section 103 does not need to map PCFICH to another radio resource.

The control signal transmission unit 105 transmits a control signal (CFI) by PCFICH mapped to the radio resource (S109).

The data signal transmission unit 107 transmits information (mapping information) of another radio resource secured by the mapping unit 103 as an RRC message or broadcast information (S111).

FIG. 6 illustrates PCFICH as an example in particular, but the control signal transmission method according to the embodiment of the present invention can be similarly applied to the case of PHICH.

FIG. 7 shows a block diagram of a mobile station according to an embodiment of the present invention. The mobile station 20 includes a mapping information holding unit 201, a control signal receiving unit 203, and a data signal receiving unit 205.

When subcarriers located in the DC component of the baseband signal are used for PCFICH or PHICH when performing carrier aggregation, the mapping information holding unit 201 replaces the radio resource of the subcarrier located in the DC component of the baseband signal. Holds mapping information of another radio resource to be used. Such mapping information may be determined according to a predetermined rule determined in advance between the mobile station and the base station. Also, the mapping information may be transmitted from the base station as an RRC message or broadcast information.

Alternatively, the mobile station may notify the base station of information on subcarriers located in the DC component of the baseband signal when the mobile station performs carrier aggregation. In this case, the base station may determine the mapping information based on information on subcarriers located in the DC component of the baseband signal.

For example, as shown in FIG. 5, when the PCFICH is mapped to the position of the DC component of the baseband signal, the mapping information holding unit 201 moves to the resource element group (REG2) next to the resource element group (REG1). Mapping information that the PCFICH is mapped may be held. When the adjacent resource element group (REG2) is used for PHICH, mapping information that PCFICH is mapped to the adjacent resource element group may be held.

The control signal receiving unit 203 receives PDCCH, PCFICH, and PHICH control signals (DCI, CFI, HI) based on the mapping information held in the mapping information holding unit 201. For example, the control information receiving unit 203 determines whether a subcarrier located in the DC component of the baseband signal is used for PCFICH or PHICH. When used for PCFICH or PHICH, the control signal receiving unit 203 receives PCFICH and PHICH control signals (CFI, HI) using another radio resource indicated by the mapping information. When not used for PCFICH or PHICH, the control signal receiving unit 203 receives PCFICH and PHICH control signals (CFI, HI) at a predetermined position as shown in FIG.

The data signal receiving unit 205 receives a data signal addressed to the mobile station 20. When the mapping information is transmitted from the base station as an RRC message or broadcast information, the data signal receiving unit 205 receives the mapping information and notifies the mapping information holding unit 201 of the mapping information. When the mapping information is transmitted from the base station as broadcast information, a broadcast information reception unit (not shown) may receive the mapping information instead of the data signal reception unit 205.

FIG. 8 shows a flowchart of the control signal receiving method in the mobile station according to the embodiment of the present invention.

The data signal receiving unit 205 receives mapping information of another radio resource used in place of the subcarrier radio resource located in the DC component of the baseband signal (S201). The received mapping information is held in the mapping information holding unit 201.

The control signal receiving unit 203 determines whether the subcarrier located in the DC component of the baseband signal is used for PCFICH (S203). When used for PCFICH, the control signal (CFI) of PCFICH is received using another radio resource indicated by the mapping information (S205). If not used in PCFICH, a PCFICH control signal (CFI) is received at a predetermined position as shown in FIG. 3 (S207).

In FIG. 8, the PCFICH is described as an example in particular, but the control signal receiving method according to the embodiment of the present invention can be similarly applied to the case of PHICH.

<Configuration and operation of base station and mobile station according to first modification of the present invention>
FIG. 9 shows a block diagram of a base station according to the first modification of the present invention. The base station 15 includes a management unit 151, a mapping unit 153, a transmission power control unit 154, a control signal transmission unit 155, and a data signal transmission unit 157.

The management unit 151 manages subcarriers located in the DC component of the baseband signal in a mobile station that communicates by applying carrier aggregation. In particular, when the component carriers constituting the carrier aggregation are asymmetric on the frequency axis, it is managed which subcarrier is located in the DC component of the baseband signal in the mobile station.

The mapping unit 153 maps the PCFICH and PHICH to the resource element group. For example, PCFICH and PHICH are mapped to predetermined positions as shown in FIG.

The transmission power control unit 154 determines whether a subcarrier located in the DC component of the baseband signal is used for PCFICH. When used for PCFICH, the transmission power of the subcarrier is decreased and the transmission power of the remaining subcarriers is increased. As described with reference to FIG. 3, four resource element groups (that is, 16 resource elements) are used for PCFICH. The amplitude of PCFICH transmission power is shown in FIG. FIG. 10A shows the amplitude when transmission power control is not performed. When the subcarrier located in the DC component of the baseband signal in the mobile station corresponds to one of the 16 resource elements, the transmission power control unit 154 may decrease the transmission power of the resource element. More specifically, the transmission power may be set to null. Furthermore, as shown in FIG. 10B, the transmission power of the remaining three subcarriers belonging to the same resource element group may be increased. Alternatively, the transmission power of the remaining 15 subcarriers may be increased.

The control signal transmission unit 155 transmits a control signal (DCI, CFI, HI) using a control channel (PDCCH, PCFICH, PHICH) mapped to a radio resource.

The data signal transmission unit 157 transmits a data signal addressed to the mobile station.

FIG. 11 shows a flowchart of a control signal transmission method in the base station according to the first modification of the present invention.

The management unit 151 identifies a subcarrier located in a DC component of a baseband signal in a mobile station that communicates by applying carrier aggregation (S151).

The mapping unit 153 maps the PCFICH to a predetermined position as shown in FIG. 3 (S153).

The transmission power control unit 154 determines whether the subcarrier located in the DC component of the baseband signal is used for PCFICH (S155). When the subcarrier located in the DC component of the baseband signal is used for PCFICH, the transmission power control unit 154 decreases the transmission power of the subcarrier and increases the transmission power of the remaining subcarriers (S157). When the subcarrier located in the DC component of the baseband signal is not used for PCFICH, the transmission power control unit 154 does not need to control the transmission power of PCFICH.

The control signal transmission unit 105 transmits a control signal (CFI) by PCFICH (S159).

When the mobile station communicating with the base station 15 shown in FIG. 9 communicates by applying carrier aggregation, the mobile station ignores the subcarrier located in the DC component of the baseband signal, and controls the control signal ( CFI).

In the first modified example, the PCFICH transmission power control has been described as an example, but the concept of the first modified example can be similarly applied to PHICH.

<Configuration and operation of base station and mobile station according to second modification of the present invention>
With reference to FIG.4 and FIG.7, the base station and mobile station which concern on the 2nd modification of this invention are demonstrated. In the second modification, the CFI transmitted by PCFICH is controlled for a longer period without notifying every subframe. The CFI may be fixed.

The management unit 101 of the base station 10 manages subcarriers located in the DC component of the baseband signal in the mobile station that communicates by applying carrier aggregation. In particular, when the component carriers constituting the carrier aggregation are asymmetric on the frequency axis, it is managed which subcarrier is located in the DC component of the baseband signal in the mobile station. The position of the DC component of the baseband signal may be calculated in advance before operation and stored in the management unit 101.

When there is a possibility that the subcarrier located in the DC component of the baseband signal is used for PCFICH, the CFI transmitted by PCFICH is generated as an RRC message addressed to the mobile station and transmitted from the data signal transmission unit 107. Alternatively, the CFI transmitted by PCFICH may be generated as broadcast information and transmitted as broadcast information from a broadcast information transmission unit (not shown).

The mapping unit 103 maps PCFICH and PHICH to resource element groups. For example, PCFICH and PHICH are mapped to predetermined positions as shown in FIG.

The data signal receiving unit 205 of the mobile station 20 receives the CFI transmitted as the RRC message. When CFI is transmitted as broadcast information, a broadcast information reception unit (not shown) of mobile station 20 receives CFI transmitted as broadcast information.

Since the frame structure is known from the received CFI, the control signal receiving unit 203 can receive the control signal regardless of whether or not the subcarrier located in the DC component of the baseband signal is used for PCFICH.

<Configuration and Operation of Base Station According to Third Modification of Present Invention>
With reference to FIG.4 and FIG.7, the base station which concerns on the 3rd modification of this invention is demonstrated. In the third modification, when the base station allocates the PUSCH radio resource, the corresponding PHICH radio resource is located in the DC component of the baseband signal in the mobile station when communicating by applying carrier aggregation. You may allocate the radio | wireless resource of PUSCH so that a subcarrier may not be included.

When the control signal transmission unit 105 of the base station 10 transmits an uplink scheduling grant for an uplink shared channel (PUSCH), the PHICH radio resource corresponding to the PUSCH communicates by applying carrier aggregation The radio resources of PUSCH may be allocated so as not to include subcarriers located in the DC component of the baseband signal in the mobile station. Alternatively, when the control signal transmission unit 105 of the base station 10 transmits an uplink scheduling grant for the uplink shared channel (PUSCH), the PHICH radio resource corresponding to the PUSCH communicates by applying carrier aggregation. In this case, information regarding the cyclic shift in the uplink scheduling grant may be set so as not to include a subcarrier located in the DC component of the baseband signal in the mobile station. In addition, the position of the radio resource of PHICH is changed by the information regarding the cyclic shift.

According to this modification, since the subcarrier located in the DC component of the baseband signal in the mobile station that communicates by applying carrier aggregation is not included in the radio resources of PHICH, the characteristics of the DC component of the baseband signal are Deterioration can be avoided.

<Effect of the embodiment of the present invention>
As described above, according to the embodiment of the present invention, it is possible to improve the reception quality of the control channel even when carrier aggregation is applied to communication.

More specifically, even when a subcarrier located in the DC component of the baseband signal is used for PCFICH or PHICH, it is possible to improve the reception quality of PCFICH or PHICH using another radio resource.

Further, when another radio resource is secured, when not one resource element group but one resource element is secured, the remaining three resource elements can be effectively used for transmission of PDCCH or the like.

In addition, when transmission power control is performed as in the first modification, the mobile station ignores the subcarrier located in the DC component of the baseband signal and decodes the control signal with the remaining subcarriers. At this time, since the transmission power of the remaining subcarriers has increased, there is a high possibility that the control signal can be decoded.

In addition, the second modification is effective when it is not necessary to dynamically change the CFI.

For convenience of explanation, the base station and the mobile station according to the embodiments of the present invention are described using functional block diagrams, but the present invention may be realized by hardware, software, or a combination thereof. Further, two or more embodiments and modifications may be used in combination as necessary.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and applications are possible within the scope of the claims.

This international application claims priority based on Japanese Patent Application No. 2010-105993 filed on April 30, 2010, and the entire contents of 2010-105993 are incorporated herein by reference.

10 base station 101 management unit 103 mapping unit 105 control signal transmission unit 107 data signal transmission unit 20 mobile station 201 mapping information holding unit 203 control signal reception unit 205 data signal reception unit 15 base station 151 management unit 153 mapping unit 154 transmission power control 155 Control signal transmitter 157 Data signal transmitter

Claims

A base station that communicates with a mobile station by applying carrier aggregation,
A management unit for managing subcarriers located in a DC component of a baseband signal in the mobile station;
When a subcarrier located in the DC component of the baseband signal is used for a predetermined control channel, the predetermined control for the mobile station is transferred to a radio resource different from the radio resource of the subcarrier located in the DC component of the baseband signal. A mapping unit for mapping channels;
A control signal transmitter for transmitting a control signal of a predetermined control channel;
Base station with
The base station according to claim 1, wherein the mapping unit maps a predetermined control channel to a resource element group different from a resource element group including a subcarrier located in a DC component of a baseband signal according to a predetermined rule.
The mapping unit maps a predetermined control channel to one resource element in a resource element group different from a resource element group including a subcarrier located in a DC component of a baseband signal according to a predetermined rule. The base station according to claim 1.
The base station according to claim 1, further comprising a mapping information transmission unit that transmits information on different radio resources.
The base station according to claim 1, wherein the predetermined control channel is PCFICH or PHICH.
A control signal transmission method in a base station that communicates with a mobile station by applying carrier aggregation,
Managing a subcarrier located in a DC component of a baseband signal at the mobile station;
When a subcarrier located in the DC component of the baseband signal is used for a predetermined control channel, the predetermined control for the mobile station is transferred to a radio resource different from the radio resource of the subcarrier located in the DC component of the baseband signal. Mapping the channel;
Transmitting a control signal of a predetermined control channel;
A control signal transmission method comprising:
A mobile station that communicates with a base station by applying carrier aggregation,
When subcarriers located in the DC component of the baseband signal are used for a predetermined control channel, mapping information holding that holds radio resource mapping information used instead of the radio resources of the subcarrier located in the DC component of the baseband signal And
A control signal receiving unit that receives a control signal of a predetermined control channel based on the mapping information held in the mapping information holding unit;
A mobile station.
A control signal reception method in a mobile station that communicates with a base station by applying carrier aggregation,
When subcarriers located in the DC component of the baseband signal are used for a predetermined control channel, holding radio resource mapping information used instead of the radio resources of the subcarrier located in the DC component of the baseband signal;
Receiving a control signal of a predetermined control channel based on the mapping information held in the mapping information holding unit;
A control signal receiving method comprising:
A base station that communicates with a mobile station by applying carrier aggregation,
A management unit for managing subcarriers located in a DC component of a baseband signal in the mobile station;
When a subcarrier located in the DC component of the baseband signal is used for a predetermined control channel, the transmission power of the subcarrier located in the DC component of the baseband signal is reduced and transmission of the remaining subcarriers in the predetermined control channel is performed. A transmission power control unit for increasing power;
A control signal transmitter for transmitting a control signal of a predetermined control channel;
Base station with
A control signal transmission method in a base station that communicates with a mobile station by applying carrier aggregation,
Managing a subcarrier located in a DC component of a baseband signal at the mobile station;
When a subcarrier located in the DC component of the baseband signal is used for a predetermined control channel, the transmission power of the subcarrier located in the DC component of the baseband signal is reduced and transmission of the remaining subcarriers in the predetermined control channel is performed. Increasing power, and
Transmitting a control signal of a predetermined control channel;
A control signal transmission method comprising:
A base station that communicates with a mobile station by applying carrier aggregation,
A management unit for managing subcarriers located in a DC component of a baseband signal in the mobile station;
When a subcarrier located in the DC component of the baseband signal is used for a predetermined control channel, a generation unit that generates a control signal for the predetermined control channel as a message or broadcast information addressed to the mobile station;
A transmitter for transmitting a message or broadcast information addressed to the mobile station;
Base station with
A control signal transmission method in a base station that communicates with a mobile station by applying carrier aggregation,
Managing a subcarrier located in a DC component of a baseband signal at the mobile station;
When a subcarrier located in the DC component of the baseband signal is used for a predetermined control channel, generating a control signal for the predetermined control channel as a message or broadcast information addressed to the mobile station;
Transmitting a message or broadcast information addressed to the mobile station;
A control signal transmission method comprising: