Patent Description:
3GPP-LTE (3rd Generation Partnership Project Radio Access Network Long Term Evolution, hereinafter referred to as "LTE") adopts OFDMA (Orthogonal Frequency Division Multiple Access) as a downlink communication scheme, and SC-FDMA (Single Carrier Frequency Division Multiple Access) as an uplink communication scheme (e.g., see non-patent literatures <NUM>, <NUM> and <NUM>).

In LTE, a radio communication base station apparatus (hereinafter abbreviated as "base station") communicates with radio communication terminal apparatuses (hereinafter abbreviated as "terminals") by allocating resource blocks (RBs) in a system band to terminals, per time unit referred to as a subframe. In addition, the base station transmits to the terminals the control information (resource allocation information) to notify the terminals of the result of resource allocation of downlink data and uplink data. This control information is transmitted to the terminals using downlink control channels such as PDCCHs (Physical Downlink Control Channels). Here, according to, for example, an allocation number of terminals, the base station controls the amount of resources used in transmission of the PDCCHs, that is, the number of OFDM symbols on a subframe unit basis. To be more specific, the base station transmits to the terminals using a PCFICH (Physical Control Format Indicator Channel), the CFI (Control Format Indicator), which is the information indicating the number of OFDM symbols capable of being used in transmission of the PDCCHs in the first OFDM symbols of the subframes. Each of terminals receives the PDCCH in accordance with the CFI detected from the received PCFICH. Here, each PDCCH occupies a resource formed of one or a plurality of consecutive CCEs (Control Channel Elements). In LTE, according to the number of information bits of the control information or the channel state of the terminal, one of <NUM>, <NUM>, <NUM>, and <NUM> is selected as the number of CCEs occupied by the PDCCH (the number of linked CCEs: CCE aggregation level). Here, LTE supports the frequency band with the maximum width of <NUM> as a system bandwidth.

In addition, the base station simultaneously transmits a plurality of PDCCHs to allocate a plurality of terminals to one subframe. At this time, in order to identify the destination terminal of each of the PDCCHs, the base station includes a CRC bit masked (or scrambled) with the ID of the destination terminal in the PDCCH for transmission. Then, the terminal detects the PDCCH addressed to the terminal by performing blind decoding on a plurality of PDCCHs which may be addressed to the terminal, by demasking (or descrambling) CRC bits using its own terminal ID.

Furthermore, studies have been underway for a technique to limit the CCE to be the target of blind decoding every terminal, for the purpose of reducing the number of blind decoding attempts at the terminal. This technique limits the CCE area (hereinafter, referred to as "search space") to be the target of the blind decoding every terminal. In LTE, the search space is randomly formed every terminal, and the number of CCEs forming the search space is defined every CCE aggregation level of the PDCCH. For example, for CCE aggregation levels <NUM>, <NUM>, <NUM>, and <NUM>, the numbers of CCEs forming the search spacesthat is, the numbers of CCEs to be the targets of the blind decodingare limited to six candidates (<NUM> (=<NUM>×<NUM>) CCEs), six candidates (<NUM> (=<NUM>×<NUM>) CCEs), two candidates (<NUM> (=<NUM>×<NUM>) CCEs), and two candidates (<NUM> (=<NUM>×<NUM>) CCEs), respectively. Thus, each terminal needs to perform blind decoding only on the CCEs in the search space allocated to the terminal, thus making it possible to reduce the number of blind decoding attempts. Here, the search space of each terminal is configured using the terminal ID of each terminal and a hash function for randomization.

Also, LTE adopts ARQ (Automatic Repeat reQuest) for downlink data from the base station to the terminals. That is, each of the terminals sends a response signal indicating the error detection result of downlink data to the base station as a feedback. The terminal performs a CRC on the downlink data, and then, transmits a response signal (that is, ACK/NACK signal) indicating an ACK (Acknowledgement) in case of CRC=OK (no error) or a NACK (Negative Acknowledgement) in case of CRC=NG (error exists) as a feed back to the base station. When the response signal transmitted as a feedback indicates the NACK, the base station transmits retransmission data to the terminal. Moreover, in LTE, the control technique for retransmitting data, referred to as HARQ (Hybrid ARQ), which combines error correction coding and ARQ, has been examined. In HARQ, when receiving retransmitted data, the terminal can improve reception quality at the terminal side by combining the retransmitted data and the previously-received data including an error.

Moreover, standardization of 3GPP LTE-Advanced (hereinafter referred to as "LTE-A") to realize faster communication than the LTE has been started. In LTE-A, in order to realize the downlink transmission speed equal to or higher than the maximum <NUM> Gbps and the uplink transmission speed equal to or higher than the maximum <NUM> Mbps, it is expected to introduce base stations and terminals (hereinafter referred to as "LTE-A terminals") capable of communicating with each other at the wideband frequency equal to or higher than <NUM>. In addition, an LTE-Advanced system is required to accommodate not only LTE-A terminals but also the terminals supporting an LTE system (hereinafter referred to as "LTE terminals").

In LTE-A, the carrier aggregation scheme whereby communication is performed by aggregating a plurality of frequency bands has been proposed to realize wideband communication of <NUM> or above (e.g., see non-patent literature <NUM>). For example, the frequency band having a width of <NUM> is defined as the base unit (hereinafter referred to as "component carrier (CC)") of communication bands. Thus, LTE-A realizes the system bandwidth of <NUM> by aggregating two component carriers. Also, a single component carrier accommodates both an LTE terminal and an LTE-A terminal. Additionally, in the following explanation, the component carrier in an uplink is referred to as "uplink component carrier", and the component carrier in a downlink is referred to as "downlink component carrier.

While it has been studied to support the carrier aggregation by at least five component carriers in the LTE-A system, the number of actually used component carriers differs every terminal according to, for example, a required transmission rate and the reception capability of each terminal with the number of component carriers. Here, which component carrier to be used is configured every terminal. The configured component carrier is referred to as "UE CC set. " The UE CC set is semi-statically controlled by the required transmission rate of the terminal.

In LTE-A, as a method to notify terminals of the resource allocation information of each component carrier from a base station, it has been discussed to allocate data of different component carriers by a PDCCH transmitted using a certain component carrier (e.g., see non-patent literature <NUM>). In particular, studies have been underway to indicate the component carrier which is the allocation target of the PDCCH by using a carrier indicator (CI) in the PDCCH. That is, the CI labels each component carrier. The CI is transmitted in a field inside of the PDCCH, referred to as "carrier indicator field (CIF).

Also, it has been considered to report the CIF value of the component carrier which is the allocation target, in addition to the CI in the CIF (e.g., see non-patent literature <NUM>).

Also, the above non-patent literature <NUM> discloses the correspondence between a CI value (that is, a code point) and the CC number indicated by the CI value. That is, when the same CC as the CC which has transmitted a PDCCH is allocated, CI=<NUM> (when CI starts from <NUM>) is allocated. CI values are associated in ascending frequency order with other CCs. For example, as illustrated in <FIG>, when there are three CCs (CC1, CC2, and CC3 in ascending frequency order) and all three CCs are configured to a terminal (that is, when a UE CC set includes CC1, CC2, and CC3), in the PDCCH transmitted in CC2, CI=<NUM> indicates data allocation of CC2, CI=<NUM> indicates the data allocation of CC1, and CI=<NUM> indicates the data allocation of CC3. Meanwhile, as illustrated in <FIG>, two out of three CCs are configured to the terminal (for example, when a UE CC set includes CC2 and CC3), CI=<NUM> indicates the data allocation of CC2 and CI=<NUM> indicates the data allocation of CC3. In this case, every time the CC configuration of each terminal (that is, the UE CC set) is changed, the correspondence between the CIs and the CC numbers varies, the CIs being other than the CI allocating the same CC. In the above example, when CC1 is added to the UE CC set in the terminal for which CC2 and CC3 are configured, the code point of the CI allocating CC3 varies before and after adding the CC.

Here, use of RRC signaling described in non-patent literature <NUM> to change the UE CC set (that is, addition and deletion of a CC), for example, has been considered. To be more specific, an RRC connection reconfiguration procedure is used to change the UE CC set. In case of changing a UE CC set, a base station firstly transmits an RRC connection reconfiguration message to a terminal to notify the terminal of the change. The terminal receiving this message changes its configuration, and then, after the change is completed, and sends an RRC connection reconfiguration complete message to the base station. By receiving the RRC connection reconfiguration complete message, the base station learns that the configuration change has been correctly made in the terminal. Here, it normally takes several <NUM> to <NUM> to communicate these messages with each other.

<NPL> relates to carrier aggregated systems, component carrier (CC) management operating on different carriers, e.g. CC addition/modification/removal etc. Each operation shall address a specific component carrier, i.e. which CC this operation applies to. A component carrier can be identified by the carrier frequency and possibly other parameters such as physical cell ID (PCI). While such detailed information can always be used wherever a component carrier shall be addressed, using a CC index is beneficial in terms of signaling overhead.

<NPL> relates to agreements for the design of carrier indication and carrier indication field (CIF). It discusses that whether CIF to component carrier index mapping is UE specific or system specific is still For Further Study. It discusses how to define or interpret the meaning of <NUM>-bit CIF.

<CIT> relates to a method and an apparatus of receiving data in a wireless communication system. The method includes receiving a downlink (DL) grant on a physical downlink control channel (PDCCH) through a first DL component carrier (CC), and receiving data based on the DL grant through a second DL CC.

However, according to the correspondence between the CIs and the CC numbers in the above non-patent literature <NUM>, the addition of a CC varies the correspondence between the CI code points and the CCs. For this reason, during the above RRC connection reconfiguration procedure (that is, a period from transmission of an RRC connection reconfiguration message from the base station to reception of an RRC connection reconfiguration complete message), the base station cannot allocate a CC other than the CC used to transmit the PDCCH (CC2 in the above example). To put it differently, even though the CC is added for the purpose of increasing the amount of data to be transmitted, for example, it is impossible to allocate data not only to the CC to be newly added (in the above example, CC2) but also to the CC in use (CC3), until the above reconfiguration is completed. As a result, a delay in data transmission occurs.

On the other hand, when the correspondence between the CIs and the CC numbers are fixed, the above mentioned problem of the delay in the data transmission does not occur. For example, when CI=<NUM>, CI=<NUM>, and CI=<NUM> are fixedly associated with CC1, CC2 and CC3, respectively, no change occurs in the correspondence. However, in this case, the number of code points (for example, <NUM> bits in the system of eight CCs) corresponding to the total number of CCs in the system is required for notification of the CCs, regardless of the number of CCs configured to the terminal. As a result, the number of CIF bits increases. For example, it is always required to use <NUM> bits for notification, even for allocation of four CCs (representable by <NUM> bits) every terminal. In other words, the number of CCs supportable by the system is limited by the number of CIF bits in this case.

It is therefore an object of the present invention to provide a transmission apparatus and a transmission method capable of preventing, when adding a CC to be used in carrier aggregation communication, a delay in data transmission while suppressing an increase in the number of bits required for notification of the CCs in use.

The problem is solved by the appended claims. A communication apparatus comprises a receiver configured to receive configuration information from a base station apparatus, the configuration information including a first component carrier, CC, identification index of an added CC, a second component carrier, CC, identification index indicating a downlink component carrier used for a transmission by the base station apparatus of physical downlink control information, including resource allocation information of data transmitted in the added CC and a carrier indicator field value, CIF value, assigned to the added CC and circuitry configured to configure the downlink component carrier based on the second component carrier identification index indicated by the configuration information, and to add a correspondence relationship between the CIF value and the first component carrier identification index into one-to-one correspondence relationships between one or more CIF values and one or more component carrier identification indices based on the CIF value indicated by the configuration information, wherein the one-to-one correspondence relationships are maintained when the correspondence relationship between the CIF value and the first component carrier identification index is added, wherein the correspondence relationship between the CIF value and the first component carrier identification index is deleted based on further configuration information, received from the base station apparatus, indicating the deletion of the added CC, while maintaining the one-to-one correspondence relationships of undeleted component carriers.

A base station apparatus comprises circuitry configured to configure a downlink component carrier used for a transmission by the base station apparatus of physical downlink control information, including resource allocation information of data transmitted in an added component carrier, CC, and a carrier indicator field value, CIF value, assigned to the added CC, wherein a correspondence relationship between the CIF value and a first component carrier identification index of the added CC is added into one-to-one correspondence relationships between one or more CIF values and one or more component carrier identification indices and a transmitter configured to transmit configuration information including the first component carrier identification index of the added CC, a second component carrier identification index indicating the downlink component carrier and the CIF value, wherein the one-to-one correspondence relationships are maintained when the correspondence relationship between the CIF value and the first component carrier identification index is added, wherein the correspondence relationship between the CIF value and the first component carrier identification index is deleted while maintaining the one-to-one correspondence relationships of undeleted component carriers and the transmitter is configured to transmit further configuration information that indicates the deletion of the added CC.

According to the present invention, it is possible to provide the transmission apparatus and the transmission method capable of preventing, when adding a CC to be used in carrier aggregation communication, a delay in data transmission while suppressing an increase in the number of bits required for notification of the CCs in use.

Now, embodiments of the present invention will be explained in detail with reference to the accompanying drawings. Here, in embodiments, the same components are denoted by the same reference numerals and their overlapping explanations are omitted.

<FIG> is a block diagram illustrating a configuration of base station <NUM> according to Embodiment <NUM> of the present invention. In <FIG>, base station <NUM> includes configuration section <NUM>, memory <NUM>, control section <NUM>, PDCCH generating section <NUM>, coding sections <NUM>, <NUM>, and <NUM>, modulating sections <NUM>, <NUM>, and <NUM>, allocation section <NUM>, PCFICH generating section <NUM>, multiplexing section <NUM>, IFFT (Inverse Fast Fourier Transform) section <NUM>, CP (Cyclic Prefix) adding section <NUM>, RF transmitting section <NUM>, RF receiving section <NUM>, CP removing section <NUM>, FFT (Fast Fourier Transform) section <NUM>, extraction section <NUM>, IDFT (Inverse Discrete Fourier Transform) section <NUM>, and data receiving section <NUM>.

Configuration section <NUM> configures one or a plurality of CCs used for uplink and downlink every terminal, that is, configures a UE CC set. This UE CC set is configured according to, for example, a required transmission rate of each terminal, the data amount to be transmitted in a transmission buffer, the tolerable amount of delay, and QoS (Quality of Service). Configuration section <NUM> also changes the UE CC set once configured.

When initially configuring the UE CC set and every time changing the UE CC set, configuration section <NUM> corrects (updates) a CIF table (that is, a labeling rule) stored in memory <NUM>. In this CIF table stored in memory <NUM>, CCs forming the UE CC set are associated with code points of the CIFs, respectively.

To be more specific, when adding a new CC to the UE CC set, configuration section <NUM> adds the new CC, while maintaining the CCs forming the currently configured UE CC set. Also, when correcting the CIF table, configuration section <NUM> allocates a currently unused CIF code point to the added CC, while maintaining the relationship between the CIF code points and the CCs forming the currently configured UE CC set. In addition, configuration section <NUM> also allocates the CC number (hereinafter, this number may be simply referred to as "PDCCH CC number") used to transmit a PDCCH signal including the resource allocation information related to data transmitted by the added CC. When deleting a CC from the CCs forming the UE CC set, configuration section <NUM> deletes only the CC, while maintaining the correspondence between the CIF code points and the undeleted CCs. The details of this CIF table and the correction process of the CIF table will be described later.

When changing the UE CC set, configuration section <NUM> notifies later described terminal <NUM> of the following information via a process system going through coding section <NUM>. That is, when adding a CC, configuration section <NUM> notifies terminal <NUM> of the CC number to be added, the PDCCH CC number, and the CIF code point allocated to the CC to be added, to terminal <NUM>. Meanwhile, when deleting a CC, configuration section <NUM> notifies terminal <NUM> of the CC number to be deleted. The above configuration is used relatively in a long span. That is, the configuration is not changed on a subframe unit basis.

When initially configuring the UE CC set and every time changing the UE CC set, configuration section <NUM> outputs the CC numbers and the PDCCH CC numbers forming the UE CC set, to control section <NUM> and PDCCH generating section <NUM>. Hereinafter, the pieces of information output from configuration section <NUM> may be collectively referred to as "configuration information.

Control section <NUM> generates the resource allocation information (that is, uplink resource allocation information and downlink resource allocation information). The uplink resource allocation information represents an uplink resource (for example, PUSCH) to which uplink data of allocation-target terminal <NUM> is allocated. Meanwhile, the downlink resource allocation information represents a downlink resource (for example, PDSCH) to which downlink data addressed to allocation-target terminal <NUM> is allocated. Here, the resource allocation information includes: the allocation information of a resource block (RB); the MCS information of data; the information relating to HARQ retransmission such as the information (NDI: New Data Indicator) or the RV (Redundancy Version) information which indicates whether the data is new or retransmission data; the information (CI: Carrier Indicator) of the CC subject to the resource allocation; and the CFI information of the allocation-target CC.

Control section <NUM> outputs the resource allocation information to PDCCH generating section <NUM> and multiplexing section <NUM>.

Here, based on the configuration information received from configuration section <NUM>, control section <NUM> allocates the resource allocation information for allocation-target terminal <NUM>, to the PDCCH arranged in the downlink component carrier configured in corresponding terminal <NUM>. This allocation process is allocated on a subframe unit basis. In particular, control section <NUM> allocates the resource allocation information for allocation-target terminal <NUM>, to the PDCCH arranged in the downlink component carrier indicated by the PDCCH CC number configured in the terminal <NUM>. Control section <NUM> allocates a CIF code point to each CC subject to the resource allocation, according to the CIF table updated by configuration section <NUM>. A PDCCH is formed by one or a plurality of CCEs. Furthermore, the number of CCEs used by base station <NUM> is configured based on the propagation path quality (CQI: Channel Quality Indicator) and the control information size of allocation-target terminal <NUM>. By this means, terminal <NUM> can receive control information at a necessary and sufficient error rate.

Control section <NUM> determines the number of OFDM symbols used to transmit the PDCCH every downlink component carrier, based on the number of CCEs used to transmit the PDCCH. Control section <NUM> generates the CFI information indicating the determined number of the OFDM symbols. Then, control section <NUM> outputs the CFI information for each downlink component carrier, to PCFICH generating section <NUM> and multiplexing section <NUM>.

PDCCH generating section <NUM> generates the PDCCH signal to be transmitted in the downlink component carrier indicated by the configuration information (in particular, the PDCCH CC number) received from configuration section <NUM>. This PDCCH signal includes the uplink resource allocation information and the downlink resource allocation information output from control section <NUM>. Furthermore, PDCCH generating section <NUM> adds a CRC bit to the PDCCH signal and then masks (or scrambles) the CRC bit with a terminal ID. Then, PDCCH generating section <NUM> outputs the masked PDCCH signal to coding section <NUM>.

The process described above is performed every processing target terminal <NUM>.

Coding section <NUM> performs a channel coding process on the PDCCH signal of each component carrier input from PDCCH generating section <NUM> and outputs the PDCCH signal that has been subjected to the channel coding process to modulation section <NUM>.

Modulation section <NUM> modulates the PDCCH signal input from coding section <NUM> and outputs the modulated PDCCH signal to allocation section <NUM>.

Allocation section <NUM> allocates the PDCCH signals of terminals input from modulation section <NUM>, to CCEs inside of the search space of each terminal in each downlink component carrier. Allocation section <NUM> outputs the PDCCH signal allocated to the CCE to multiplexing section <NUM>.

PCFICH generating section <NUM> generates a PCFICH signal to be transmitted every downlink component carrier, based on the CFI information every downlink component carrier input from control section <NUM>. PCFICH generating section <NUM> then outputs the generated PCFICH signal to multiplexing section <NUM>.

Coding section <NUM> encodes the configuration information input from configuration section <NUM> and outputs the encoded configuration information to modulating section <NUM>.

Modulation section <NUM> modulates the encoded configuration information and outputs the modulated configuration information to multiplexing section <NUM>.

Coding section <NUM> performs a channel coding process on the input transmission data (downlink data) and outputs the transmission data signal that has been subjected to the channel coding process to modulating section <NUM>.

Modulation section <NUM> modulates the transmission data (downlink data) that has been subjected to the channel coding process and outputs the modulated transmission data signal to multiplexing section <NUM>.

Multiplexing section <NUM> multiplexes the PDCCH signal input from allocation section <NUM>, the PCFICH signal input from PCFICH generating section <NUM>, the configuration information input from modulation section <NUM>, and the data signal (that is, the PDSCH signal) input from modulation section <NUM>. Here, based on the CFI information of each downlink component carrier input from control section <NUM>, multiplexing section <NUM> determines the number of OFDM symbols to arrange the PDCCHs every downlink component carrier. Furthermore, multiplexing section <NUM> maps the PDCCH signal and the data signal (PDSCH signal) to each downlink component carrier, based on the downlink resource allocation information input from control section <NUM>. Multiplexing section <NUM> may also map the configuration information to the PDSCH. Multiplexing section <NUM> then outputs a multiplexed signal to IFFT section <NUM>.

IFFT section <NUM> converts the multiplexed signal input from multiplexing section <NUM> into a time domain waveform. CP adding section <NUM> then obtains an OFDM signal by adding a CP to this time domain waveform.

RF transmitting section <NUM> applies a radio transmission process (such as up-conversion and D/A conversion) on the OFDM signal input from CP adding section <NUM> and transmits the result via an antenna.

Meanwhile, RF receiving section <NUM> performs a radio reception process (such as down-conversion and A/D conversion) on the reception radio signal received in a reception band via the antenna and outputs the resulting received signal to CP removing section <NUM>.

CP removing section <NUM> removes a CP from the received signal, and FFT section <NUM> converts the received signal from which the CP is removed into a frequency domain signal.

Extraction section <NUM> extracts the uplink data of each terminal and the PUCCH signal (e.g., ACK/NACK signal) from the frequency domain signal input from FFT section <NUM>, based on the uplink resource allocation information (e.g., the uplink resource allocation information in four subframes ahead) input from control section <NUM>. IDFT section <NUM> converts the signal extracted by extraction section <NUM> into a time domain signal and outputs the time domain signal to data receiving section <NUM>.

Data receiving section <NUM> decodes uplink data out of the time domain signal input from IDFT section <NUM>. Then, data receiving section <NUM> outputs the decoded uplink data as received data.

<FIG> is a block diagram illustrating a configuration of terminal <NUM> according to Embodiment <NUM> of the present invention. Terminal <NUM> communicates with base station <NUM> by using a plurality of downlink component carriers. When the received data includes an error, terminal <NUM> stores the received data in an HARQ buffer, and at the time of retransmission, combines retransmission data with the received data stored in the HARQ buffer and decodes the resulting combined data.

In <FIG>, terminal <NUM> includes RF receiving section <NUM>, CP removing section <NUM>, FFT section <NUM>, demultiplexing section <NUM>, configuration information receiving section <NUM>, PCFICH receiving section <NUM>, CIF table configuring section <NUM>, PDCCH receiving section <NUM>, PDSCH receiving section <NUM>, modulating sections <NUM> and <NUM>, DFT (Discrete Fourier Transform) section <NUM>, mapping section <NUM>, IFFT section <NUM>, CP adding section <NUM>, and RF transmitting section <NUM>.

RF receiving section <NUM> is capable of changing a reception band, and changes the reception band, based on the band information input from configuration information receiving section <NUM>. Then, RF receiving section <NUM> applies a radio reception process (such as, down-conversion and A/D conversion) to the reception radio signal (here, OFDM signal) received in the reception band via an antenna and outputs the resulting received signal to CP removing section <NUM>.

CP removing section <NUM> removes a CP from the reception signal. FFT section <NUM> converts the received signal from which the CP is removed into a frequency domain signal and outputs this frequency domain signal to demultiplexing section <NUM>.

Demultiplexing section <NUM> demultiplexes the signal input from FFT section <NUM> into a higher layer control signal (e.g., RRC signaling) including configuration information, a PCFICH signal, a PDCCH signal, and a data signal (i.e., PDSCH signal. ) Then, demultiplexing section <NUM> outputs the control signal to configuration information receiving section <NUM>, the PCFICH signal to PCFICH receiving section <NUM>, the PDCCH signal to PDCCH receiving section <NUM>, and the PDSCH signal to PDSCH receiving section <NUM>.

Configuration information receiving section <NUM> reads the following information from the control signal received from demultiplexing section <NUM>. That is, this read information means the information configured to the terminal, the information including: uplink component carrier and downlink component carrier for use in data transmission; information indicating a downlink component carrier for use in transmitting a PDCCH signal to which resource allocation information for each component carrier is allocated; and the CIF code point corresponding to an added or removed CC.

Configuration information receiving section <NUM> outputs the read information to CIF table configuring section <NUM>, PDCCH receiving section <NUM>, RF receiving section <NUM>, and RF transmitting section <NUM>. Furthermore, configuration information receiving section <NUM> reads the terminal ID configured to the terminal from the control signal received from demultiplexing section <NUM> and outputs the read information to PDCCH receiving section <NUM>.

PCFICH receiving section <NUM> extracts the CFI information from the PCFICH signal received from demultiplexing section <NUM>. That is, PCFICH receiving section <NUM> obtains the CFI information indicating the number of OFDM symbols used for the PDCCH to which the resource allocation information is allocated, for each of a plurality of downlink component carriers configured in the terminal. PCFICH receiving section <NUM> outputs the extracted CFI information to PDCCH receiving section <NUM> and PDSCH receiving section <NUM>.

CIF table configuring section <NUM> corrects (updates) the CIF table held by PDCCH receiving section <NUM>, based on an added or removed CC number received from configuration information receiving section <NUM> and the CIF code point allocated to the CC. This correction process corresponds to the correction process in base station <NUM>.

PDCCH receiving section <NUM> performs blind decoding on the PDCCH signal received from demultiplexing section <NUM>, to obtain the PDCCH signal (resource allocation information) addressed to the terminal. Here, the PDCCH signal is allocated to each CCE (i.e., PDCCH) arranged in the downlink component carrier configured to the terminal, the CCE indicated by the information received from configuration information receiving section <NUM>.

To be more specific, for each downlink component carrier, PDCCH receiving section <NUM> specifies the number of OFDM symbols in which the PDCCH is arranged, based on the CFI information received from PCFICH receiving section <NUM>. PDCCH receiving section <NUM> then calculates the search space of the terminal by using the terminal ID received from configuration information receiving section <NUM>.

PDCCH receiving section <NUM> then demodulates and decodes the PDCCH signal allocated to each CCE in the calculated search space.

PDCCH receiving section <NUM> performs blind decoding on each PDCCH signal performing resource allocation of data of each component carrier. For example, when there are two component carriers (downlink component carrier <NUM> and downlink component carrier <NUM>) and the PDCCH signals of both component carriers are transmitted from CC1, PDCCH receiving section <NUM> performs the blind decoding on the PDCCH signal performing data allocation of downlink component carrier <NUM> and blind decoding on the PDCCH signal performing data allocation of downlink component carrier <NUM>, on CC1.

PDCCH receiving section <NUM> determines the decoded PDCCH signal as the signal addressed to the terminal, the decoded PDCCH signal resulting in CRC=OK (no error) after demasking a CRC bit using the terminal ID of the terminal indicated by the terminal ID information.

PDCCH receiving section <NUM> outputs the downlink resource allocation information included in the PDCCH signal addressed to the terminal to PDSCH receiving section <NUM>, and outputs the uplink resource allocation information to mapping section <NUM>. Meanwhile, when no PDCCH signal resulting in CRC=OK is detected, PDCCH receiving section <NUM> determines that the current subframe does not include data allocation addressed to the terminal and stands by until the next subframe.

Here, in the downlink resource allocation information included in the PDCCH signal, the CIF code point indicates the CC used for transmitting downlink data. Thus, with reference to the CIF table updated by CIF table configuring section <NUM>, PDCCH receiving section <NUM> converts the CIF code point included in the downlink resource allocation information into a CC number and then outputs the downlink resource allocation information to PDSCH receiving section <NUM>. Here, the CIF table is stored in the memory (not shown) included in PDCCH receiving section <NUM>.

PDSCH receiving section <NUM> extracts the received data (downlink data) from the PDSCH signal received from demultiplexing section <NUM>, based on the downlink resource allocation information and CFI information of a plurality of downlink component carriers received from PDCCH receiving section <NUM>, and the CFI information of the CC where the PDCCH signal is transmitted, the CFI information received from PCFICH receiving section <NUM>. Also, when the CC used to transmit the PDCCH signal is different from the CC used to transmit the PDSCH signal, the CFI information is obtained from the decoded PDCCH signal.

Furthermore, PDSCH receiving section <NUM> performs error detection on the extracted reception data (downlink data). As a result of the error detection, PDSCH receiving section <NUM> generates a NACK signal as an ACK/NACK signal when the reception data includes an error, whereas PDSCH receiving section <NUM> generates an ACK signal as the ACK/NACK signal when the reception data includes no error. Then, PDSCH receiving section <NUM> outputs the ACK/NACK signal to modulation section <NUM>. When the reception data includes an error, PDSCH receiving section <NUM> stores the extracted reception data in an HARQ buffer (not shown). Upon receipt of retransmitted data, PDSCH receiving section <NUM> combines the previously-received data stored in the HARQ buffer with the retransmitted data and performs the error detection on the resulting combined signal. When base station <NUM> transmits the PDSCH signal using spatial multiplexing, for example, MIMO (Multiple-Input Multiple-Output) and thereby transmits two data blocks (Transport Blocks), PDSCH receiving section <NUM> generates ACK/NACK signals for the respective data blocks.

Modulation section <NUM> modulates the ACK/NACK signal received from PDSCH receiving section <NUM>. When base station <NUM> transmits two data blocks by spatially-multiplexing the PDSCH signal in each downlink component carrier, modulation section <NUM> applies QPSK modulation on the ACK/NACK signal. Meanwhile, when base station <NUM> transmits one data block, modulation section <NUM> applies BPSK modulation on the ACK/NACK signal. That is, modulation section <NUM> generates one QPSK signal or BPSK signal as the ACK/NACK signal of each downlink component carrier. Modulation section <NUM> then outputs the modulated ACK/NACK signal to mapping section <NUM>.

Modulation section <NUM> modulates transmission data (uplink data) and outputs the modulated data signal to DFT section <NUM>.

DFT section <NUM> converts the data signal input from modulation section <NUM> into a frequency domain signal and outputs the resulting plurality of frequency components to mapping section <NUM>.

Mapping section <NUM> maps the data signal input from DFT section <NUM> to the PUSCH arranged in the uplink component carrier, according to the uplink resource allocation information input from PDCCH receiving section <NUM>. Mapping section <NUM> also maps the ACK/NACK signal input from modulation section <NUM> onto the PUCCH arranged in the uplink component carrier.

Here, modulation sections <NUM> and <NUM>, DFT section <NUM>, and mapping section <NUM> may also be provided every uplink component carrier.

IFFT section <NUM> converts a plurality of frequency components mapped to the PUSCH into a time-domain waveform, and CP adding section <NUM> adds a CP to the time-domain waveform.

RF transmitting section <NUM> is capable of changing a transmission band, and configures the transmission band, based on the band information received from configuration information receiving section <NUM>. Then, RF transmitting section <NUM> applies a radio transmission process (such as, up-conversion and D/A conversion) to the signal to which the CP is added, to transmit the result via an antenna.

Operations of base station <NUM> and terminal <NUM> having the above mentioned configurations will be described. Here, in particular, the process to correct a CIF table will be explained, the process being performed for a change in a UE CC set.

<FIG> illustrates how CCs forming a UE CC set vary with time. <FIG> illustrates the conditions of the CIF table in time intervals illustrated in <FIG>. When the CIF consists of two bits, there are four code points represented by bit sequences <NUM>, <NUM>, <NUM>, and <NUM>, respectively. Here, a case will be described assuming that CIs=<NUM>, <NUM>, <NUM>, and <NUM> correspond to the bit sequences <NUM>, <NUM>, <NUM>, and <NUM>, respectively.

As illustrated in <FIG>, when the power of terminal <NUM> is turned on, terminal <NUM> starts to communicate with base station <NUM> in one CC (in <FIG>, CC2) according to operations such as a cell search and random access as in LTE.

Base station <NUM> then adds a CC to terminal <NUM> due to, for example, increase of the amount of data. Here, configuration section <NUM> corrects (updates) the CIF table stored in memory <NUM> in base station <NUM>. To be more specific, when adding a new CC to the UE CC set, configuration section <NUM> adds the new CC while maintaining the CCs forming the currently configured UE CC set. In the correction of the CIF table, configuration section <NUM> allocates the currently unused CIF code point to the added CC, while maintaining the relationship between the CIF code points and the CCs forming currently configured UE CC set. Configuration section <NUM> also allocates "PDCCH CC number.

For example, in <FIG>, CCs are added at the start timings of intervals B, C, and E, respectively. The conditions of the CIF tables in the intervals B, C, and E are illustrated in <FIG>, C, and E, respectively. For example, CC1 is added between <FIG>. In <FIG>, CC1 is associated with CIF code point <NUM> unused in <FIG>, while the relationship between the CCs forming the UE CC set and the CIF code point in <FIG> is maintained.

As illustrated in <FIG>, in interval C, the information of data (PDSCH) allocation in CC1, <NUM>, and <NUM> is notified to terminal <NUM> by the PDCCH of CC2. That is, "PDCCH CC number" is <NUM> at this time.

Also, when deleting a CC from the CCs forming the UE CC set, configuration section <NUM> deletes only the CC, while maintaining the correspondence between the CIF code points and the CCs not to be deleted.

For example, CC1 is deleted between <FIG>. In <FIG>, the correspondence between the CIF code points and CCs <NUM> and <NUM> other than CC1 in <FIG> is maintained.

The correction process by CIF table configuring section <NUM> of terminal <NUM> corresponds to the correction process in base station <NUM>.

As described above, even when the CIF table is changed in association with the change of the UE CC set (that is, addition or deletion of a CC), the correspondence between the CIF code points and CCs unrelated to the change is maintained. That is, it is possible to allocate data to the CCs unrelated to the change by using the previously allocated code points as is, even during an RRC connection reconfiguration procedure required on changing the UE CC set. By this means, it is possible to prevent a delay in data transmission. Also, the usage of more CCs can improve the data throughput.

Furthermore, since the CIF code points are allocated only to the CCs actually configured to terminal <NUM>, the number of bits required for notifying terminal <NUM> of the CCs from base station <NUM> can be only the number of CCs supported by terminal <NUM>. For example, even in case of a system supporting eight CCs, the number of bits required for notifying terminal <NUM> of the CCs from base station <NUM> can be only two bits when the number of CCs supported by terminal <NUM> is four. That is, even when the number of CCs in the entire system increases, there is no need to increase the number of CIF bits and hence it is possible to reduce the amount of control information.

According to the present embodiment described above, in base station <NUM>, when adding a component carrier to a component carriers set (UE CC set), configuration section <NUM> corrects the CIF table associating the identification information of the component carriers with the code points used as the labels of the component carriers included in the UE CC set, and then allocates an unused code point to the component carrier to be added, while maintaining the correspondence between the identification information of the component carriers and the code points in the state before the CIF table is corrected. Control section <NUM> forms control signals (PDCCHs) related to data transmission using a plurality of component carriers, respectively, and the control signals of the respective component carriers are labeled by the code points according to the CIF table corrected by configuration section <NUM>. The transmission section including configuration section <NUM>, coding section <NUM>, and modulating section <NUM> transmits a notification signal including the information related to the correction of the CIF table to terminal <NUM>.

As a result, it is possible to suppress the number of bits required for notification of the CCs in use and also to prevent the delay in the data transmission.

In addition, the CIF table in memory <NUM> may be maintained every CC used to transmit a PDCCH. That is, in case of adding a CC, the CIF table of the allocated PDCCH CC is corrected. For example, since CC2 is allocated as a PDCCH CC, the CIF table of CC2 is corrected in the above example. As another example, let us consider a case where CC2 is configured as the PDCCH CC for both CC2 and CC3 in the UE CC set (that is, the state of FIG. Here, in case of adding CC1 and CC4, CC1 may be configured as the PDCCH CC of CC1 and CC4, and CIF code points <NUM> and <NUM> may be allocated to CC1 and CC4. In this case, the CIF table of CC1 is corrected. In a case where the CIF table is maintained every CC as above, allocation of the same CIF code point numbers is possible when the PDCCH CCs are different. Thus, the number of CIF bits required for CC notification can be reduced.

In Embodiment <NUM>, the CIF code point reports a CFI value in addition to the CC number which is the target of the data allocation. That is, in the CIF table, the pair of the CC number and the CFI value is associated with the CIF code point. Here, the CFI value at the top of the subframe is transmitted to all terminals from each of the CCs by a PCFICH (Physical Control Format Indicator Channel). In a heterogeneous network environment where a macrocell and a femtocell exist, the PCFICH may not be received with sufficient reliability. In such an environment, it is possible to increase the reliability in CFI notification, by including the CFI value related to a certain CC in a PDCCH signal transmitted from another CC.

The basic configurations of a base station and a terminal according to Embodiment <NUM> are common to Embodiment <NUM>, and will therefore be described using <FIG> and <FIG>.

When adding a CC, configuration section <NUM> of base station <NUM> according to Embodiment <NUM> basically allocates pairs each including the CC to be added and a corresponding one of all CFI values to different CIF code points, respectively. Also in Embodiment <NUM>, configuration section <NUM> basically allocates a currently unused CIF code point to the added CC, while maintaining the relationship between the CIF code points and the CCs forming the currently configured UE CC set. When deleting a CC from the CCs forming the UE CC set, configuration section <NUM> deletes only the CC, while maintaining the correspondence between the CIF code points and the CCs not to be deleted. At this time, the correspondence related to the CC to be deleted is all deleted.

Also, CIF table configuring section <NUM> of terminal <NUM> corrects (updates) the CIF table held by PDCCH receiving section <NUM>, based on the added or deleted CC number received from configuration information receiving section <NUM>, the CIF code point and the CFI value allocated to the CC.

Operations of base station <NUM> and terminal <NUM> having the above mentioned configurations will be described.

In the present embodiment, base station <NUM> and terminal <NUM> share the table representing the relationship of the CIF code points, the CC numbers, and the CFI values. In case of adding a CC, up to three CIF code points corresponding to CFIs=<NUM>, <NUM>, and <NUM> are allocated, and then the information related to the allocated CIF code points is notified to terminal <NUM> from base station <NUM>. When the number of configured CCs is large, the number of CFI values that can be notified for the added CCs may be two or one. Thus, when notifying terminal <NUM> of the information related to the CC in case of adding a CC, base station <NUM> also notifies terminal <NUM> of the number of allocated code points. This notification format is illustrated in <FIG>.

<FIG> illustrates how the CIF table varies when CCs are added. In particular, <FIG> illustrates how the CIF table varies when CC1 and CC4 are sequentially added to terminal <NUM> performing communication using CC2 and CC3. Here, it is assumed that the CC used to transmit a PDCCH is CC2.

As illustrated in <FIG>, when adding CC1, configuration section <NUM> allocates the pairs each including the CC to be added and a corresponding one of all CFI values to different CIF code points, respectively. That is, since CFIs=<NUM>, <NUM>, and <NUM> are prepared here, different CIF code points are allocated to the three pairs of CC1 and CFIs=<NUM>, <NUM>, and <NUM>, respectively. In the state of <FIG>, since CIF code points <NUM> to <NUM> are unused, three of these CIF code points are allocated to the three pairs of CC1 and CFIs=<NUM>, <NUM>, and <NUM>, respectively. Here, in particular, the CIF code point with a smaller number is preferentially allocated in ascending order.

As illustrated in <FIG>, when adding CC4, configuration section <NUM> allocates the pairs each including the CC to be added and a corresponding one of all CFI values to different CIF code points, respectively. Here, the pair of CC4 and CFI=<NUM> is allocated to CIF code point <NUM> which is unused. Meanwhile, instead of the pair of CC3 and CFI=<NUM>, the pair of CC4 and CFI-<NUM> is allocated to CIF code point <NUM> which has been previously allocated to the pair of CC3 and CFI=<NUM>. That is, the pair of CC3 and CFI=<NUM> is overwritten by the pair of CC4 and CFI=<NUM>.

That is, depending on conditions, configuration section <NUM> may allocate the pairs each including the CC to be added and a corresponding one of some CFI values to different CIF code points, respectively.

Configuration section <NUM> can select which CIF code point corresponding to a CFI value to overwrite, from a plurality of CIF code points allocated to any CC. That is, while the pair of CC3 and CFI=<NUM> is overwritten in <FIG>, the pair of CC3 and CF1=<NUM> or the pair of CC3 and CFI=<NUM> may be overwritten instead.

Configuration section <NUM> can also select which pair to allocate to the CIF code point, from the pairs each including the CC to be added and a corresponding one of all the CFI values. That is, while two pairs of CC4 and CFIs=<NUM> and <NUM> are selected from three pairs of CC4 and CFIs=<NUM>, <NUM>, and <NUM> in <FIG>, two pairs of CC4 and CFIs=<NUM> and <NUM> may be selected or two pairs of CC4 and CFIs=<NUM> and <NUM> may be selected instead. The pair actually allocated to the CIF code point is selected according to, for example, the cell environment. For example, since a cell with a large cell radius (for example, macrocell) accommodates a large number of terminals, many PDCCH resources are often required. Thus, a large value (for example, <NUM> or <NUM>) is preferable as the CFI value representing a PDCCH resource region. In contrast, since the cell with a small cell radius (for example, picocell and femtocell) accommodates a small number of terminals, the CFI value representing the PDCCH resource region may be small. Thus, <NUM> or <NUM>, for example, is selected as the CFI value in this case. In a cell such as a hotspot where the number of terminals increases or decreases drastically, <NUM> or <NUM> may be selected as the CFI value. Then, the information related to the selected pair is separately notified.

<FIG> illustrates the notification formats of the CIF code points. In <FIG>, the upper part illustrates a format to report three CIF code points, the middle part illustrates a format to report two CIF code points, and the lower part illustrates a format to report one CIF code point.

As illustrated in <FIG>, each format provides the same number of regions to store the CIF code points as the number of CFI values required to be notified. Furthermore, each storage region is associated with a different CFI value. This storage region may be referred to as "notification field.

As described above, even when the CIF table is changed in association with a change in the UE CC set (that is, addition or deletion of a CC), the correspondence between the CIF code points and the CCs unrelated to the change is maintained. Even when a pair related to a previously allocated CC is overwritten, only some of the pairs related to the CC is overwritten, so that the CIF code points of the pairs not overwritten are maintained.

That is, it is possible to allocate data to the pairs unrelated to the change by using the previously allocated code points as is, even during an RRC connection reconfiguration procedure required on changing the UE CC set. By this means, it is possible to prevent the delay in the data transmission.

By selecting the code point to overwrite according to the necessary CFI value, it is possible to select the CFI value likely to be used according to a cell environment, for example. Also, configuring the CFI value in association with the CC in case of adding the CC makes it possible to configure the CFI value according to the cell environment, for example.

When deleting CC4 from the state of <FIG>, it is possible to separately allocate CIF code point <NUM> to the pair of CC3 and CFI=<NUM>, or to automatically return to the table of <FIG> which is the previous state. By this means, when the number of CCs included in the UE CC set decreases, it is possible to set three CFI values to be reportable, without separately reporting the CIF code point.

Here, there are some variations of the technique for notifying terminal <NUM> of pairs in case of allocating only pairs of the CC to be added and some of the CFI values to CIF code points,.

In variation <NUM>, the CIF table associates the CIF code points with the CFI values, respectively, in advance. That is, in the example of <FIG>, the CFI values are fixedly allocated to CIF code points <NUM> to <NUM>, respectively.

Thus, once the CFI value to be used is determined, the candidate usable CIF code points are narrowed down. Thus, the selection process of configuration section <NUM> can be simplified. Also, when base station <NUM> notifies terminal <NUM> of a CIF code point, the corresponding CFI value is specified. For this reason, base station <NUM> need not separately notify terminal <NUM> of the CFI value.

Variation <NUM> uses a notification format capable of storing a larger number of CIF code points than the number of actually required CFI values. Here, for ease of explanation, a case to use the notification format of the upper part in <FIG>.

Here, when only two out of three CFI values are allocated to additional CCs, it is notified as follows.

That is, in a case where three notification fields included in the notification format report CIF code points=<NUM>, <NUM>, and <NUM>, respectively, this means that the CFI values corresponding to CIF code points=<NUM> and <NUM> are <NUM> and <NUM>, respectively. Also, in a case where the three notification fields report CIF code points=<NUM>, <NUM>, and <NUM>, respectively, this means that the CFI values corresponding to CIF code points-<NUM> and <NUM> are <NUM> and <NUM>, respectively. Also, in a case where the three notification fields report CIF code points=<NUM>, <NUM>, and <NUM>, respectively, this means that the CFI values corresponding to CIF code points=<NUM> and <NUM> are <NUM> and <NUM>, respectively. To put it more specifically, the mapping patterns of the CIF code points to a plurality of notification fields are associated with the combinations of a plurality of CFI values.

By this means, it is possible to report the CFI value to be actually used, without additional signaling to report which CFI value is used.

Variation <NUM> uses a notification format capable of storing the same number of CIF code points as the maximum number of CFI values. Here, for ease of explanation, an explanation will be given of a case where the notification format shown in the upper part of <FIG> is used.

Here, when only two out of three CFI values are allocated to the additional CCs, it is notified as follows.

For example, when two CIF code points <NUM> and <NUM> are to be associated with CFIs=<NUM> and <NUM>, respectively, three notification fields store CIF code points =<NUM>, <NUM>, and <NUM>, respectively. Here, when the added CC and the CC used to transmit a PDCCH are the same, CIF=<NUM> is used as a rule regardless of the notification content of the CIF code point. By this means, when CIF=<NUM> is stored in a notification format, this CIF code point can be treated as invalid. Thus, as described above, when three notification fields store CIF code points=<NUM>, <NUM>, and <NUM>, respectively, only CIF code points <NUM> and <NUM> are valid. Thus, CFI values=<NUM> and <NUM> corresponding to the fields storing those code points, respectively, can be notified.

By this means, it is possible to report a CFI value to be actually used, without additional signaling to report which CFI value is used.

Embodiment <NUM> defines a plurality of CIF tables with different numbers of code points usable per CC, and configures in advance which table to use every terminal. By this means, it is possible to use the CIF table appropriate for the reception capability (UE capability) of each terminal, the communication status of each terminal, and the cell environment.

Memory <NUM> of base station <NUM> according to Embodiment <NUM> stores a group of CIF table formats. <FIG> illustrates an example of the group of the CIF table formats. As illustrated in <FIG>, each of the CIF table formats includes a plurality of subsets. This subset is a unit to be allocated to one CC. Each subset includes one or a plurality of CIF code points. Also, the CIF table formats differ each other in at least one of the number of CIF code points included in the subsets (in other words, the number of subsets included in each CIF table), and the combination of the CFI values included in a subset.

For each terminal <NUM>, configuration section <NUM> selects and configures which table format to use from a plurality of CIF table formats stored in memory <NUM>. The information of this configured CIF table format is notified to terminal <NUM> as configuration information. This table format is configured and notified to terminal <NUM> when terminal <NUM> transitions from an idle mode to an active mode to start communication or when a radio bearer is established. That is, the configuration or notification of the table format is set in a longer interval than a change in the UE CC set.

When adding a CC to terminal <NUM>, configuration section <NUM> notifies terminal <NUM> of the subset number of the CIF table format that is configured in advance every terminal <NUM> and that is allocated to the CC to be added. By this means, terminal <NUM> can associate the additional CC with all CIF code points included in the notified subset number.

CIF table configuring section <NUM> of terminal <NUM> according to Embodiment <NUM> configures the table format notified from the base station in PDCCH receiving section <NUM>. Also, CIF table configuring section <NUM> updates the CIF table by the subset number notified in case of CC addition.

Operations of base station <NUM> and terminal <NUM> having the above mentioned configurations will be described referring to <FIG>.

As illustrated in <FIG>, each CIF table format includes a plurality of subsets. A CIF code point is allocated to the subsets, by defining one or a plurality of CIF code points as an allocation unit. In table format <NUM>, each subset includes three CIF code points. In each of table formats <NUM> to <NUM>, basically, each subset includes two CIF code points.

Also, the CIF table formats differ each other in at least one of the number of CIF code points included in the subsets (in other words, the number of subsets included in each CIF table), and the combination of the CFI values included in a subset. That is, table format <NUM> differs from table formats <NUM> to <NUM>, in the number of the CIF code points included in the subsets. Also, table formats <NUM> to <NUM> differ each other in the combination of CFI values included in the subsets. That is, in table format <NUM>, the combination of the CFI values included in the subsets is <NUM> and <NUM>, while the combination of the CFI values included in the subsets is <NUM> and <NUM> in table format <NUM>, and the combination of the CFI values included in the subsets is <NUM> and <NUM> in table format <NUM>.

In each table format, the subset including CIF=<NUM> includes only one CIF. For CIF=<NUM>, the largest CFI value is selected and configured from CFI values allocatable for each table format. That is, as the CFI value, <NUM>, <NUM> and <NUM> are respectively configured in table formats <NUM>, <NUM> and <NUM>. The reason for the above configurations is as follows. That is, even when the number of OFDM symbols in the control channel region of a certain CC is lower than the CFI value reportable by a table format configured in a certain terminal <NUM>, as long as the first OFDM symbol to which a data signal (PDSCH) addressed to the terminal <NUM> is mapped, corresponds to the value notified by CFI, it is possible to prevent the control channel and the data signal from overlapping each other. Meanwhile, when a small CFI value is configured in CIF=<NUM>, the number of OFDM symbols in a control channel region of a certain CC often exceeds the CFI value configured in CIF=<NUM>. As a result, the control channel and the data signal overlap each other in this case. Thus, one of channels may not be able to be transmitted. In view of the above, for CIF=<NUM>, the largest CFI value is selected and configured from the CFI values allocatable in each table format.

For each terminal <NUM>, configuration section <NUM> selects and configures which table format to use, from a plurality of CIF table formats stored in memory <NUM>, and then notifies each terminal <NUM> of the configuration information.

Configuration section <NUM> configures table format <NUM> for the terminal capable of receiving signals using up to three CCs, and configures table formats <NUM> to <NUM> for the terminal capable of receiving signals using equal to or more than four CCs. Also, configuration section <NUM> configures table formats <NUM> to <NUM> which can configure a large number of CCs (that is, a large number of included subsets), for the terminal with the requirement of high speed transmission, and configures table <NUM> for the terminal without the requirement of high speed transmission.

Also, configuration section <NUM> can configure the table format on a cell unit basis. For example, configuration section <NUM> assigns and configures table formats <NUM> to <NUM> for each terminal in a cell operated with a large number of CCs causing other CCs to perform data allocation notification, and assigns and configures table format <NUM> in a cell operated with a small number of CCs causing other CC to perform data allocation notification,.

In a cell with a large cell radius, configuration section <NUM> configures a table format in which a large CFI value is allocated to each subset. That is, the cell with a large cell radius (for example, macrocell) accommodates a large number of terminals. For this reason, many PDCCH resources are often required. Thus, the table format in which a large CFI value (for example, <NUM> and <NUM>) is allocated to each subset is configured in such a cell.

In contrast, in a cell with a small cell radius, configuration section <NUM> configures a table format in which a small CFI value is allocated to each subset. That is, the cell with a small cell radius (for example, pico cell or femtocell) accommodates a small number of terminals. For this reason, the required amount of PDCCH resource region is small in many cases. Thus, the table format in which a small CFI value (for example, <NUM> and <NUM>) is allocated to each subset is configured in such a cell.

In a cell where the number of terminals increases or decreases drastically (for example, a hotspot), configuration section <NUM> configures the table format in which both a large CFI value and a small CFI value (for example, <NUM> and <NUM>) are allocated to each subset.

As described above, for each terminal <NUM>, configuration section <NUM> selects and configures which table format to use, from a plurality of CIF table formats stored in memory <NUM>. Also, a plurality of the CIF table formats stored in memory <NUM> differ each other in at least one of the number of CIF code points included in the subsets (in other words, the number of subsets included in each CIF table), and the combination of the CFI values included in a subset.

Accordingly, when adding a CC, configuration section <NUM> only has to notify each terminal <NUM> of a subset number. Thus, it is possible to reduce the number of bits used for notification. Defining the table format in advance limits the combination of a plurality of CIF code points used for allocation to a certain CC. By this means, it is possible to simplify a system and a terminal and also to reduce the amount of work for testing the system and the terminal.

Table format <NUM> as illustrated in <FIG> may be defined in advance in memory <NUM>. That is, the combination of CFI values differs every subset in this type of table format. This type of table format is useful as the table format capable of allocating four CCs or five CCs.

Here, table format <NUM> is described as a format for three CCs and table formats <NUM> to <NUM> are each described as a format for four CCs or five CCs in <FIG>. It is, however, possible to separately define, as a format for four CCs, the table format in which subset <NUM> includes CIFs=<NUM>, <NUM>, and <NUM>, subset <NUM> includes CIFs=<NUM> and <NUM>, and subset <NUM> includes CIFs=<NUM> and <NUM>. By this means, it is possible to maximize the number of CFIs that can be notified every CC.

Furthermore, each function block employed in the explanation of each of the aforementioned embodiments may typically be implemented as an LSI constituted by an integrated circuit. These may be individual chips or partially or totally contained on a single chip. "LSI" is adopted here but this may also be referred to as "IC," "system LSI," "super LS1," or "ultra LSI" depending on differing extents of integration.

Furthermore, the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible. After LSI manufacture, utilization of a programmable FPGA (Field Programmable Gate Array) or a reconfigurable processor where connections and settings of circuit cells within an LSI can be reconfigured is also possible.

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

Claim 1:
A communication apparatus comprising:
a receiver configured to receive configuration information from a base station apparatus, the configuration information including
• a first component carrier, CC, identification index of an added CC,
• a second component carrier, CC, identification index indicating a downlink component carrier used for a transmission by the base station apparatus of physical downlink control information, including resource allocation information of data transmitted in the added CC and
• a carrier indicator field value, CIF value, assigned to the added CC; and
circuitry configured to configure the downlink component carrier based on the second component carrier identification index indicated by the configuration information, and to add a correspondence relationship between the CIF value and the first component carrier identification index into one-to-one correspondence relationships between one or more CIF values and one or more component carrier identification indices based on the CIF value indicated by the configuration information;
wherein the one-to-one correspondence relationships are maintained when the correspondence relationship between the CIF value and the first component carrier identification index is added,
wherein the correspondence relationship between the CIF value and the first component carrier identification index is deleted based on further configuration information, received from the base station apparatus, indicating the deletion of the added CC, while maintaining the one-to-one correspondence relationships of undeleted component carriers.