TECHNICAL FIELD

The present invention relates to a base station apparatus, a mobile station apparatus, and a transmission method for transmitting uplink scheduling information to the mobile station apparatus, for example, in independent uplink/downlink cell data transmission in which an uplink data channel and a downlink data channel are connected to their respective optimum cells.

BACKGROUND ART

In the 3rd generation partnership project radio access network long term evolution advanced (3GPP LTE-A), a method of connecting a channel for uplink user data information (hereinafter referred to as “uplink data”) and a channel for downlink user data information (hereinafter referred to as “downlink data”) to their respective optimum cells (independent uplink/downlink cell data transmission) is under consideration (see Non Patent Literature 1).

FIG. 1shows a situation of independent uplink/downlink cell data transmission in which a physical downlink shared channel (PDSCH) is connected to cell #1and a physical uplink shared channel (PUSCH) is connected to cell #2. A PDSCH is a downlink data channel in which downlink data is arranged and a PUSCH is an uplink data channel in which uplink data is arranged.

An independent base station apparatus (eNB, hereinafter referred as “base station”) is provided in each of cell #1and cell #2, and backhaul between cell #1and cell #2is configured with an X2 interface. Here, when cell #1is the cell having the best downlink channel quality for an LTE-A mobile station (hereinafter referred to as “mobile station”), and cell #2is the cell having the best uplink channel quality for the LTE-A mobile station, in independent uplink/downlink cell data transmission, as shown inFIG. 1, a PDSCH is connected to cell #1, and a PUSCH is connected to cell #2.

Further, because a channel (for example, a PUCCH) for controlling feedback (FB) such as acknowledgement/negative acknowledgement (ACK/NACK) needs to transmit a feedback at a high speed, the FB control channel is connected to the same cell as for a downlink data channel, not the same cell as for an uplink data channel which provides an optimum link connection. If the FB control channel is connected to the same cell as for an uplink data channel which provides an optimum link connection, and communication between independent cells is performed via backhaul, such communication would take time on the order of several to several dozens of subframes, making it difficult to transmit feedback in the FB control channel at a high speed. However, when connecting to the same cell as for a downlink data channel, it is possible to transmit feedback in the FB control channel at a high speed.

As described above, in independent uplink/downlink cell data transmission, an uplink data channel and a downlink data channel are connected to their respective optimum cells. At this time, scheduling information (control information for designating modulation coding scheme (MCS) or resource block (RB)) needs to be reported to an LTE-A mobile station at a high speed.

In an LTE downlink channel, downlink scheduling information is reported using a PDCCH in the same subframe as the subframe containing the PDSCH in which downlink data is arranged. Further, in an LTE uplink channel, uplink scheduling information is reported to an LTE mobile station using a PDCCH four subframes before the subframe containing a PUSCH in which uplink data is arranged.

In an LTE-A, as a method of reporting uplink scheduling information, a method in which uplink scheduling information is transferred from cell #2to cell #1in real time and reported to an LTE-A mobile station using a PDCCH of cell #1, is possible. However, because it will take time to communicate via Backhaul in which cell #1and cell #2are connected with an X2 interface, it is difficult to transfer uplink scheduling information from cell #2to cell #1at high speed.

As another method, a method in which the base station of cell #2transmits a PDCCH containing uplink scheduling information for an LTE-A mobile station to the LTE-A mobile station, is possible. For example, as shown inFIG. 2, downlink scheduling information for an LTE-A mobile station is transmitted using a PDCCH from the base station of cell #1to which a PDSCH is connected, and uplink scheduling information for the LTE-A mobile station is transmitted using a PDCCH from the base station of cell #2to which a PUSCH is connected. Here, if uplink scheduling information for an LTE mobile station is transmitted to the LTE mobile station in which the PUSCH is connected to cell #1by containing the information in the PDCCH, as is conventionally done, the LTE mobile station in cell #1can connect to cell #1, as is conventionally done, making it possible to maintain a backward compatibility with the LTE mobile station.

CITATION LIST

Non-Patent Literature

NPL 1

“Downlink/Uplink Radio Link Connection Methods in Heterogeneous Network for LTE-Advanced”, annual conference of the Institute of Electronics, Information and Communication Engineers (ISCIE), B-5-14, 2008.

SUMMARY OF INVENTION

Technical Problem

However, an LTE-A mobile station requires a plurality of circuits for receiving, at the same time, PDCCHs which are transmitted in the same resource element (RE) region from each of cell #1to which a PDSCH is connected and cell #2to which a PUSCH is connected, and demodulating and decoding the PDCCHs, making the reception circuit bigger and more complex.

It is therefore an object of the present invention to provide a base station apparatus, a mobile station, and a transmission method for suppressing the amount of increase in reception and demodulation and decoding processing of uplink scheduling information in independent uplink/downlink cell data transmission in which an uplink data channel and a downlink data channel are connected to their respective optimum cells.

Solution to Problem

A base station apparatus according to the present invention employs a configuration to have a base station apparatus in a radio communication system including a mobile station apparatus that receives downlink data that is transmitted in a downlink data region of a first base station apparatus and transmits uplink data in an uplink data region of a second base station apparatus, the first base station apparatus, and the second base station apparatus, the base station apparatus being the second base station apparatus and comprising; an arrangement section that arranges a control signal containing scheduling information of uplink data to transmit from the mobile station apparatus to the second base station apparatus, in the downlink data region of the first base station apparatus; and a transmission section that transmits the control signal to the mobile station apparatus.

A mobile station apparatus according to the present invention employs a configuration to have a mobile station apparatus in a radio communication system including a mobile station apparatus that receives downlink data that is transmitted in a downlink data region of a first base station apparatus, and transmits uplink data in an uplink data region of a second base station apparatus, the first base station apparatus, and the second base station apparatus, comprising; a reception section that receives a control signal containing scheduling information of uplink data for the second base station apparatus, that is arranged in the downlink data region of the first base station apparatus; an arrangement section that arranges the uplink data in a resource indicated by the scheduling information of uplink data; and a transmission section that transmits the arranged uplink data to the second base station apparatus.

A transmission method according to the present invention employs a transmission method in a radio communication system including a mobile station apparatus that receives downlink data that is transmitted in a downlink data region of a first base station apparatus, and transmits uplink data in an uplink data region of a second base station apparatus, the first base station apparatus, and the second base station apparatus, a method of transmitting scheduling information of uplink data to transmit from the mobile station apparatus to the second base station apparatus to the mobile station apparatus, the method comprising: arranging a control signal containing the scheduling information of uplink data to transmit from the mobile station apparatus to the second base station apparatus in the downlink data region of the first base station apparatus; and transmitting the control signal to the mobile station apparatus.

A transmission method according to the present invention employs a transmission method in a radio communication system including a mobile station apparatus that receives downlink data that is transmitted in a downlink data region of a first base station apparatus, and transmits uplink data in an uplink data region of a second base station apparatus, the first base station apparatus, and the second base station apparatus, a method of transmitting scheduling information of uplink data to transmit from the mobile station apparatus to the second base station apparatus to the mobile station apparatus, the method comprising: arranging a control signal containing the scheduling information of uplink data to transmit from the mobile station apparatus to the second base station apparatus in the downlink data region of the first base station apparatus; and transmitting the control signal to the mobile station apparatus.

Advantageous Effects of Invention

According to the present invention, it is possible to suppress the amount of increase in reception and demodulation and decoding processing of uplink scheduling information in independent uplink/downlink cell data transmission in which an uplink data channel and a downlink data channel are connected to their respective optimum cells.

