Patent Description:
In recent years, it has become common to transmit not only audio data but also large-volume data, such as still image data and moving image data in addition to audio data in cellular mobile communication systems, in response to spread of multimedia information. Active studies associated with techniques for achieving a high transmission rate in a high-frequency radio band have been conducted to achieve large-volume data transmission.

When a high frequency radio band is utilized, however, attenuation increases as the transmission distance increases, although a higher transmission rate can be expected within a short range. Accordingly, the coverage area of a radio communication base station apparatus (hereinafter, abbreviated as "base station") decreases when a mobile communication system using a high frequency radio band is actually put into operation. Thus, more base stations need to be installed in this case. The installation of base stations involves reasonable costs, however. For this reason, there has been a high demand for a technique that provides a communication service using a high-frequency radio band while limiting an increase in the number of base stations.

In order to meet such a demand, studies have been carried out on a relay technique in which a radio communication relay station apparatus (hereinafter, abbreviated as "relay station") is installed between a base station and a radio communication mobile station apparatus (hereinafter, abbreviated as "mobile station") to perform communication between the base station and mobile station via the relay station for the purpose of increasing the coverage area of each base station. The use of relay technique allows a mobile station not capable of directly communicating with a base station to communicate with the base station via a relay station.

It is required for an LTE-A (long-term evolution advanced) system for which the introduction of the relay technique described above has been studied, to maintain compatibility with LTE (long-term evolution) in terms of a smooth transition from and coexistence with LTE. For this reason, mutual compatibility with LTE is required for the relay technique as well.

<FIG> illustrates example frames in which control signals and data are assigned in the LTE system and the LTE-A system.

In the LTE system, DL (downlink) control signals from a base station to a mobile station are transmitted through a DL control channel, such as PDCCH (physical downlink control channel). In LTE, DL grant (also referred to as "DL assignment") indicating DL data assignment and UL (uplink) grant indicating UL data assignment are transmitted through PDCCH. A DL grant indicates that a resource in the subframe in which the DL grant is transmitted has been allocated to the mobile station. Meanwhile, in an FDD system, a UL grant indicates that a resource in the fourth subframe after the subframe in which the UL grant is transmitted has been allocated to the mobile station. In a TDD system, a UL grant indicates that the resource in a subframe transmitted after four or more subframes from the subframe in which the UL grant is transmitted has been allocated to the mobile station. In the TDD system, the subframe to be assigned to the mobile station, or the number of subframes before the assigned subframe in which the UL grant is transmitted is determined in accordance with the time-division pattern of the UL and DL (hereinafter referred to as "UL/DL configuration pattern"). Regardless of the UL/DL configuration pattern, the UL subframe is a subframe after at least four subframes from the subframe in which the UL grant is transmitted.

In the LTE-A system, relay stations, in addition to base stations, also transmit control signals to mobile stations in PDCCH regions in the top parts of subframes. With reference to a relay station, DL control signals have to be transmitted to a mobile station. Thus, the relay station switches the processing to reception processing after transmitting the control signals to the mobile station to prepare for receiving signals transmitted from the base station. The base station, however, transmits DL control signals to the relay station at the time the relay station transmits the DL control signals to the mobile station. The relay station therefore cannot receive the DL control signals transmitted from the base station. In order to avoid such inconvenience in LTE-A, studies have been carried out on providing a region for mapping downlink control signals for relay stations (i.e., relay PDCCH (R-PDCCH) region) in a data region as illustrated in <FIG> in LTE-A. Similar to the PDCCH, mapping a DL grant and UL grant to the R-PDCCH is studied. In the R-PDCCH, as illustrated in <FIG>, mapping a DL grant in the first slot and a UL grant in the second slot is studied (refer to Non-patent Literature <NUM>). Mapping the DL grant only in the first slot reduces a delay in decoding the DL grant and allows relay stations to prepare for ACK/NACK transmission for DL data (transmitted in the fourth subframes following reception of DL grant in FDD). Each relay station finds the downlink control signals intended for the relay station by performing blind-decoding on downlink control signals transmitted using an R-PDCCH region from a base station within a resource region indicated using higher layer signaling from the base station (i.e., search space). As described above, the base station notifies the relay station of the search space corresponding to the R-PDCCH by higher layer signaling.

Given the introduction of various apparatuses as radio communication terminals in the future M2M (machine to machine) communication, for example, there is a concern for a shortage of resources in the mapping region for PDCCH (i.e., "PDCCH region") due to an increase in the number of terminals. If PDCCH cannot be mapped due to such a resource shortage, the DL data cannot be assigned for the terminals. Thus, the resource region for mapping DL data (i.e., "PDSCH (physical downlink shared channel) region") cannot be used even if there is an available region, which may cause a decrease in the system throughput. Studies have been carried out to solve such resource shortage through mapping control signals for terminals served by a base station also in a data region to which R-PDCCH is mapped. The resource region to which control signals for terminals served by the base station are mapped and which can be utilized as a data region at different timings is called an "enhanced PDCCH (E-PDCCH) region, "new-PDCCH (N-PDCCH) region" or "X-PDCCH region" or the like. As described above, in LTE-A, a relay technique is introduced and relay control signals are mapped to the data region. Since the relay control signal may be expanded and used as a control signal for a terminal, the resource region to which control signals for terminals served by the base station are mapped and which can be utilized as a data region at different timings is also called "R-PDCCH. " Mapping the control signals (i.e., E-PDCCH) to a data region in such a manner enables transmission power control for control signals transmitted to terminals near a cell edge or interference control for interference to another cell by control signals to be transmitted or for interference to the cell from another cell. In LTE-Advance, a high transmission rate is achieved using a wideband radio bandwidth, multiple-input multiple-output (MIMO) transmission technique and interference control technique.

PDCCH and R-PDCCH have four aggregation levels, i.e., levels <NUM>, <NUM>, <NUM>, and <NUM> (for example, refer to Non-patent Literature (hereinafter, abbreviated as "NPL") <NUM>). Levels <NUM>, <NUM>, <NUM>, and <NUM> respectively have six, six, two, and two "resource region candidates. " The term "resource region candidate" refers to a candidate region to which control signals are to be mapped. Each resource region candidate is composed of as many control channel elements (CCE) as corresponding aggregation levels. In addition, when a single terminal is set with one aggregation level, control signals are actually mapped to one of the multiple resource region candidates of the aggregation level. <FIG> illustrates example search spaces corresponding to R-PDCCH. The ovals represent search spaces at various aggregation levels. The multiple resource region candidates in the search spaces at the different aggregation levels are arranged consecutively on VRBs (virtual resource blocks). The resource region candidates in the VRBs are mapped to PRBs (physical resource blocks) through higher layer signaling.

A search space corresponding to E-PDCCH is a resource region to which control signals transmitted from a base station to a terminal may be mapped. A search space corresponding to E-PDCCH is individually set for each terminal.

As described above, in the R-PDCCH region, a DL grant is mapped to the first slot and UL grant is mapped to the second slot. That is, the resource to which the DL grant is mapped is separated from the resource to which the UL grant is mapped in the time domain. In contrast, in E-PDCCH, as shown in <FIG>, studies are also underway to separate the resource to which the DL grant is mapped from the resource to which the UL grant is mapped in the frequency domain (that is, subcarriers or PRB pair). Here, the term "PRB (physical resource block) pair" refers to a set of PRBs of the first slot and the second slot, whereas the term "PRB" refers to each of the PRBs of the first slot and the second slot.

For the design of E-PDCCH, part of the design of R-PDCCH may be used or a design completely different from the design of R-PDCCH may be used. Actually, studies are underway to make the design of E-PDCCH different from the design of R-PDCCH.

NPL <NUM>
3GPP TS <NUM> V10. <NUM> Physical layer for relaying operation
<CIT> discloses an apparatus for transmitting and receiving control information for a repeater and a method thereof. The repeater for receiving control information in a wireless communication system comprises: a receiving module for receiving through higher layer signaling from a base station the information on a resource block (RB) which the repeater should search to receive the control information; a processor for detecting the control information from the first RB by blind-decoding at least one received RB which should be searched; and a receiving module for receiving through the first RB from the base station the control information detected by the processor.

When the resource to which a DL grant is mapped is separated from the resource to which a UL grant is mapped in the frequency domain (that is, subcarriers or RB pair), one PRB pair may be designated as a minimum unit (that is, a CCE) when resources are allocated to E-PDCCH. However, when a PRB pair made up of two slots is designated as a CCE, the resource amount of CCE increases. For this reason, a reception SINR of E-PDCCH increases and the possibility of receiving quality becoming excessively high, which results in an increased possibility of resources being wasted. Therefore, a "divided resource region" obtained by dividing one PRB pair may be used as a CCE of E-PDCCH.

However, when the division number per PRB pair increases, the resource amount of CCE for E-PDCCH (that is, the number of resource elements (REs) forming one CCE) decreases. Moreover, when the aggregation level of E-PDCCH is assumed to be <NUM>, <NUM>, <NUM> or <NUM> as in the cases of PDCCH and R-PDCCH, the number of terminals that can be supported decreases. That is, the receiving quality of terminals that can be supported is determined by the receiving quality of highest aggregation level <NUM>. When the resource amount of CCE for E-PDCCH is small, the receiving quality of E-PDCCH degrades, and therefore the number of terminals that satisfy the desired receiving quality decreases.

Furthermore, even when the division number per PRB pair is fixed, the number of REs forming a CCE varies from one subframe to another. The following is the description of factors that cause the number of REs forming a CCE to vary from one subframe to another even when the division number per PRB pair is fixed. In LTE and LTE-A, one PRB has <NUM> subcarriers in the frequency direction and has a width of <NUM> msec in the time direction as shown in <FIG>. A unit of two PRBs combined in the time direction is called a "PRB pair. " That is, a PRB pair has <NUM> subcarriers in the frequency direction and has a width of <NUM> msec in the time direction. However, when a PRB pair represents a block of <NUM> subcarriers in the frequency domain, the PRB pair may be simply called "RB. " In addition, a unit defined by one subcarrier and one OFDM symbol is a resource element (RE). The items described about PRBs here also apply to VRBs. The term "RB" is used to generically call a PRB and VRB.

The number of OFDM symbols per PRB varies depending on a CP (cyclic prefix) length of OFDM symbol. Therefore, the number of REs forming a CCE varies depending on the CP (cyclic prefix) length even if the division number per PRB pair is fixed.

To be more specific, a normal downlink subframe includes <NUM> OFDM symbols in the case of a normal CP and includes <NUM> OFDM symbols in the case of an extended CP. Furthermore, a DwPTS region of a special subframe shown in <FIG> (that is, region used for DL transmission) includes three, nine, ten, eleven or twelve OFDM symbols in the case of a normal CP and three, eight, nine or ten OFDM symbols in the case of an extended CP.

The number of REs to which reference signals are mapped in one PRB varies from one subframe to another. Therefore, the number of REs forming a CCE varies depending on the number of REs to which reference signals are mapped in one PRB even when the division number per PRB pair is fixed.

The number of OFDM symbols used for PDCCH is variable from one to four. Therefore, in such a setting that the PDCCH region is not used for E-PDCCH, the number of OFDM symbols available for E-PDCCH decreases as the number of OFDM symbols of the PDCCH region increases. That is, the number of REs forming a CCE varies depending on the number of OFDM symbols forming the PDCCH region even if the division number per PRB pair is fixed.

<FIG> and <FIG> illustrate the number of REs of the first slot and the second slot when resources of the fourth and subsequent OFDM symbols of the PRB pair are used for E-PDCCH. <FIG> and <FIG> illustrate an example where CSI-RS is mapped to the second slot in particular. <FIG> and <FIG> together form one table: <FIG> showing the first half of the table and <FIG> showing the second half of the table.

As described above, when the number of REs located in a PRB pair and available for E-PDCCH fluctuates considerably, receiving quality of a control signal is more likely to degrade.

An object of the present invention is to provide an integrated circuit which controls an communication apparatus capable of improving receiving quality of a control signal.

According to the present invention, it is possible to provide an integrated circuit for controlling a communication apparatus and a reception method that are capable of improving receiving quality of a control signal. The invention is illustrated in further detail below and understood by the following examples called "embodiments", which are not necessarily encompassed by the claims.

Embodiments of the present invention will be described in detail with reference to the drawings. In the embodiments, the same elements will be assigned the same reference numerals, and any duplicate description of the elements is omitted.

A communication system according to Embodiment <NUM> of the present invention includes a transmitting apparatus and a receiving apparatus. Specifically, in this embodiment of the present invention, a description will be provided while the transmitting apparatus is referred to as base station <NUM>, and the receiving apparatus is referred to as terminal <NUM>. The communication system is an LTE-A system, for example. Base station <NUM> is an LTE-A base station, and terminal <NUM> is an LTE-A terminal, for example.

<FIG> is a block diagram illustrating a main configuration of base station <NUM> according to Embodiment <NUM> of the present invention.

Base station <NUM> maps an assignment control signal to one of a plurality of "resource region candidates" forming a search space and transmits the mapped signal to terminal <NUM>. Each resource region candidate is composed of as many CCEs as the value of aggregation level.

Division number calculation section <NUM> calculates the division number of a PRB pair based on a first number of REs to which an assignment control signal in each PRB pair can be mapped, a second number of REs to which a signal other than the assignment control signal is mapped and a reference value. The reference value is the number of REs that satisfy receiving quality requirements of the assignment control signal in terminal <NUM>.

Control signal mapping control section <NUM> sets resource region candidates including at least one CCE obtained by dividing each PRB pair by the division number and determines a search space configured of a plurality of resource region candidates set for each PRB pair based on an aggregation level.

The assignment control signal is mapped by mapping section <NUM> to one of a plurality of "resource region candidates" forming a search space determined in control signal mapping control section <NUM> and transmitted to terminal <NUM>.

<FIG> is a block diagram illustrating a main configuration of terminal <NUM> according to Embodiment <NUM> of the present invention.

Terminal <NUM> receives an assignment control signal mapped by a transmitting apparatus to one of a plurality of "resource region candidates" forming a search space. Each "resource region candidate" is made up of as many control channel elements as the value of aggregation level.

Extracted resource identification section <NUM> sets resource region candidates including at least one CCE obtained by dividing each PRB pair by the division number and identifies a search space made up of the plurality of resource region candidates set in each PRB pair based on the aggregation level. The plurality of "resource region candidates" forming the identified search space correspond to a plurality of "resource regions to be extracted. " The assignment control signal mapped by the transmitting apparatus to one of the plurality of identified "resource region candidates" is extracted by signal demultiplexing section <NUM>, and the assignment control signal is thereby received.

<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 assignment control information generating section <NUM>, search space determining section <NUM>, division number calculation section <NUM>, control signal mapping control section <NUM>, error-correction coding section <NUM>, modulation section <NUM>, mapping section <NUM>, transmitting section <NUM>, receiving section <NUM>, demodulation section <NUM>, and error-correction decoding section <NUM>.

When there are a data signal to be transmitted and a data signal to be assigned to an uplink, assignment control information generating section <NUM> determines a resource to which the data signal is assigned and generates assignment control information (DL assignment and UL grant). The DL assignment includes information on mapping resources of a downlink data signal. On the other hand, the UL grant includes information on mapping resources of uplink data to be transmitted from terminal <NUM>. The DL assignment is outputted to mapping section <NUM> and the UL grant is outputted to receiving section <NUM>.

Search space determining section <NUM> determines a PRB pair candidate group (that is, corresponding to the above-described first group, and hereinafter may also be referred to as "search space PRB group") to which a control signal including at least one of DL grant and UL grant transmitted to terminal <NUM> and outputs information on the determined "search space PRB group" (hereinafter, may also be referred to as "search space information") to control signal mapping control section <NUM> and error-correction coding section <NUM>.

The information on the "search space PRB group" is a bit string composed, for example, of N bits and the N bits respectively correspond to N PRB pairs forming a communication band available to base station <NUM>. For example, a PRB pair corresponding to bit value <NUM> is a PRB pair included in a search space and a PRB pair corresponding to bit value <NUM> is a PRB pair not included in the search space.

Division number calculation section <NUM> receives the number of OFDM symbols available for E-PDCCH in one PRB pair and the number of REs used for RS in one PRB pair as input and calculates the division number D by which one PRB pair is divided based on these numbers. This division number D is calculated for each subframe because the number of REs available for E-PDCCH included in one PRB pair may vary from one subframe to another. The PRB pair is divided based on the calculated division number D, and D "divided resource regions" are thereby defined. Each divided resource region is used as a CCE of E-PDCCH.

To be more specific, the division number D is calculated from equation <NUM> below.

When PRS is taken into consideration, the number of REs used for PRS is further subtracted in symbols used for E-PDCCH.

Control signal mapping control section <NUM> determines a search space corresponding to a pair of the division number M calculated in division number calculation section <NUM> and an aggregation level based on the division number M, "search space information" received from search space determining section <NUM> and the aggregation level. Control signal mapping control section <NUM> selects one of a plurality of "resource region candidates" forming the determined search space as a "control signal mapping resource. " Here, the "control signal mapping resource" is a resource region to which a control signal intended for terminal <NUM> is actually mapped. Furthermore, each "resource region candidate" is made up of as many CCEs as aggregation levels. Furthermore, the "control signal mapping resource" is also made up of as many CCEs as aggregation levels. However, although the number of REs forming a CCE normally varies depending on the division number M, it is leveled.

Error-correction coding section <NUM> receives the transmission data signal and the search space information as input, performs error-correction coding on the inputted signal and outputs the coded signal to modulation section <NUM>.

Modulation section <NUM> applies modulation processing to the signal received from error-correction coding section <NUM> and outputs the modulated data signal to mapping section <NUM>.

Mapping section <NUM> maps the assignment control information generated in assignment control information generating section <NUM> to the "control signal mapping resource" determined in control signal mapping control section <NUM>.

Furthermore, mapping section <NUM> maps the data signal received from modulation section <NUM> to a downlink resource corresponding to the downlink resource allocation control information (DL assignment) generated in assignment control information generating section <NUM>.

The assignment control information and the data signal are mapped to predetermined resources in this way, and a transmission signal is thereby formed. The transmission signal thus formed is outputted to transmitting section <NUM>.

Transmitting section <NUM> applies radio transmission processing such as up-conversion to the input signal and transmits the signal to terminal <NUM> via an antenna.

Receiving section <NUM> receives the signal transmitted from terminal <NUM> and outputs the received signal to demodulation section <NUM>. To be more specific, receiving section <NUM> separates a signal corresponding to a resource indicated by UL grant from the received signal, applies reception processing such as down-conversion to the separated signal and outputs the signal to demodulation section <NUM>.

Demodulation section <NUM> applies demodulation processing to the input signal and outputs the signal obtained to error-correction decoding section <NUM>.

Error-correction decoding section <NUM> decodes the input signal and obtains a received data signal from terminal <NUM>.

<FIG> is a block diagram illustrating a configuration of terminal <NUM> according to Embodiment <NUM> of the present invention. In <FIG>, terminal <NUM> includes receiving section <NUM>, signal demultiplexing section <NUM>, demodulation section <NUM>, error-correction decoding section <NUM>, division number calculation section <NUM>, extracted resource identification section <NUM>, control signal receiving section <NUM>, error-correction coding section <NUM>, modulation section <NUM>, mapping section <NUM>, and transmitting section <NUM>.

Receiving section <NUM> receives a signal transmitted from base station <NUM>, applies reception processing such as down-conversion thereto and then outputs the signal to signal demultiplexing section <NUM>.

Signal demultiplexing section <NUM> extracts, from the received signal, a signal corresponding to a "resource region group to be extracted" indicated by an "extraction indication signal" received from extracted resource identification section <NUM> and outputs the extracted signal to control signal receiving section <NUM>. The "resource region group to be extracted" corresponds to the "resource region candidate group" determined in control signal mapping control section <NUM>.

Furthermore, signal demultiplexing section <NUM> extracts a signal corresponding to a data resource indicated by DL assignment outputted from control signal receiving section <NUM> (that is, downlink data signal) from the received signal and outputs the extracted signal to demodulation section <NUM>.

Demodulation section <NUM> demodulates the signals from signal demultiplexing section <NUM> and outputs the demodulated signals to error-correction decoding section <NUM>.

Error-correction decoding section <NUM> decodes the demodulated signals outputted from demodulation section <NUM> and outputs the decoded received data signals. Specifically, error-correction decoding section <NUM> outputs search space information transmitted from base station <NUM> to extracted resource identification section <NUM>.

Division number calculation section <NUM> has the same function as that of division number calculation section <NUM>. That is, division number calculation section <NUM> receives the number of OFDM symbols available for E-PDCCH in one PRB pair and the number of REs available for RS in one PRB pair as input and calculates the division number D by which one PRB pair is divided based on these numbers. The PRB pair is divided based on the calculated division number D and D "divided resource regions" are thereby defined. Each divided resource region is used as a CCE of E-PDCCH. The number of REs used by CRS in one PRB pair is indicated from base station <NUM> to terminal <NUM> through a broadcast channel. The number of REs used by DMRS in one PRB pair may vary from one terminal to another. Therefore, the number of REs used by DMRS may be previously specified from base station <NUM> to terminal <NUM> by a higher layer control signal during E-PDCCH transmission. Furthermore, the number of REs and the period used by CSI-RS in one PRB pair are specified from base station <NUM> to terminal <NUM> by a higher layer control signal for each terminal.

Extracted resource identification section <NUM> identifies a plurality of "resource regions to be extracted" (that is, search spaces) corresponding to a pair of the division number M calculated in division number calculation section <NUM> and an aggregation level based on the division number M, the search space information transmitted from base station <NUM> and the aggregation level. Extracted resource identification section <NUM> outputs information on the plurality of identified "resource regions to be extracted" to signal demultiplexing section <NUM> as an "extraction indication signal.

Control signal receiving section <NUM> performs blind decoding on the signal received from signal demultiplexing section <NUM> and thereby detects a control signal (DL assignment or UL grant) intended for terminal <NUM> of control signal receiving section <NUM>. The detected DL assignment intended for terminal <NUM> is outputted to signal demultiplexing section <NUM> and the detected UL grant intended for terminal <NUM> is outputted to mapping section <NUM>.

Error-correction coding section <NUM> uses the transmission data signals as input, performs error-correction coding on the transmission data signals, and outputs the coded signal to modulation section <NUM>.

Modulation section <NUM> modulates the signal outputted from error-correction coding section <NUM> and outputs the modulated signal to mapping section <NUM>.

Mapping section <NUM> maps the signal outputted from modulation section <NUM> according to the UL grant received from control signal receiving section <NUM> and outputs the mapped signal to transmitting section <NUM>.

Transmitting section <NUM> applies transmission processing such as up-conversion to the input signal and transmits the signal.

The operations of base station <NUM> and terminal <NUM> configured in the manner described above will be described.

Division number calculation section <NUM> in base station <NUM> receives the number of OFDM symbols available for E-PDCCH in one PRB pair and the number of REs used for RS in one PRB pair as input and calculates the division number D by which one PRB pair is divided based on these numbers. D "divided resource regions" are defined by dividing the PRB pair based on the calculated division number D. Each divided resource region is used as a CCE of E-PDCCH.

To be more specific, the division number is calculated using equation <NUM> described above. That is, the division number is calculated based on the "reference number of REs" and the number of REs that can be used for E-PDCCH in the PRB pair to be calculated so that the number of REs forming each CCE becomes at least equal to the "reference number of REs. " Even when the number of REs per PRB pair varies from one subframe to another, this allows the number of REs per PRB pair to be leveled among subframes, thus making it possible to secure receiving quality per CCE to a certain level or higher. That is, even when transmitting assignment control information to a terminal of poor receiving quality located near the cell edge, it is possible to use subframes having fewer REs per PRB pair. However, when the division number calculated according to equation <NUM> described above is zero, "<NUM>" is used as the division number. Furthermore, when the value that the division number can take is limited to <NUM>, <NUM> or <NUM>, "<NUM>" is used as the division number when the division number calculated by equation <NUM> is "<NUM>.

Control signal mapping control section <NUM> in base station <NUM> determines a search space corresponding to a pair of the division number M and the aggregation level based on the division number M calculated in division number calculation section <NUM>, "search space information" received from search space determining section <NUM> and the aggregation level. Control signal mapping control section <NUM> then selects one of the plurality of "resource region candidates" forming the determined search space as a "control signal mapping resource. " By being mapped to the determined control signal mapping resource, the assignment control information generated in assignment control information generating section <NUM> is transmitted from base station <NUM> to terminal <NUM>.

Division number calculation section <NUM> in terminal <NUM> receives the number of OFDM symbols available for E-PDCCH in one PRB pair and the number of REs used for RS in one PRB pair as input, and calculates the division number D by which one PRB pair is divided based on these numbers. D "divided resource regions" are defined by dividing the PRB pair based on the calculated division number D.

Extracted resource identification section <NUM> in terminal <NUM> identifies a plurality of "resource regions to be extracted" (that is, search spaces) corresponding to a pair of the division number M and the aggregation level based on the division number M calculated in division number calculation section <NUM>, the search space information transmitted from base station <NUM> and the aggregation level. Signals corresponding to the plurality of identified "resource regions to be extracted" in the received signal are subjected to blind decoding processing in control signal receiving section <NUM>.

As described above, according to the present embodiment, division number calculation section <NUM> in base station <NUM> calculates the division number of a PRB pair based on a first number of REs to which an assignment control signal in each PRB pair can be mapped, a second number of REs to which a signal other than the assignment control signal is mapped and a reference value. The reference value is the number of REs that satisfy receiving quality requirements of the assignment control signal in terminal <NUM>.

Control signal mapping control section <NUM> determines a search space by determining a control channel element group (that is, a physical channel CCE group used) forming a plurality of resource region candidates among CCE groups obtained by dividing each PRB pair included in the first group by the same number as the division number.

In this manner, the number of REs included in a CCE can be leveled even when there is a variation in the number of REs which are included in the PRB pair and to which an assignment control signal can be mapped. This makes it possible to improve receiving quality of the control signal.

According to the present embodiment, division number calculation section <NUM> in terminal <NUM> calculates the division number of a PRB pair based on a first number of REs to which an assignment control signal in each PRB pair can be mapped, a second number of REs to which a signal other than the assignment control signal is mapped and a reference value. The reference value is the number of REs that satisfy receiving quality requirements of the assignment control signal in terminal <NUM>.

Extracted resource identification section <NUM> identifies a search space by identifying a control channel element group forming a plurality of "resource region candidates" in a CCE group obtained by dividing each PRB pair included in the first group set in base station <NUM> into the same number as the division number. The plurality of "resource region candidates" forming the identified search space, correspond to a plurality of "resource regions to be extracted.

Embodiment <NUM> relates to a method for mapping a logical channel (VRB) to a physical channel (PRB). Since basic configurations of a base station and a terminal according to Embodiment <NUM> are common to those of base station <NUM> and terminal <NUM> according to Embodiment <NUM>, they will be described with reference to <FIG> and <FIG>.

In base station <NUM> of Embodiment <NUM>, control signal mapping control section <NUM> identifies a search space corresponding to a pair of the division number M calculated in division number calculation section <NUM> and an aggregation level based on the division number M, the "search space information" received from search space determining section <NUM> and the aggregation level.

To be more specific, a search space is identified based on a "VRB table," the division number M, "search space information," an aggregation level, and an "association rule" per pair of the division number M and the aggregation level. The search space is made up of a plurality of "resource region candidates" and each "resource region candidate" is made up of as many CCEs (hereinafter may also be referred to as "mapping candidate CCEs") as aggregation levels.

More specifically, as shown in <FIG>, control signal mapping control section <NUM> includes VRB table storage section <NUM>, search space identification section <NUM> and mapping resource selection section <NUM>.

VRB table storage section <NUM> stores a "VRB table. " The "VRB table" associates a plurality of VRB pairs with a divided resource region (that is, "virtual channel CCE") group per division number candidate of each VRB pair. The "VRB table" further associates a plurality of pairs of the division number candidate and aggregation level candidate with a plurality of "virtual channel unit resource region candidates" in accordance with each pair. Each "virtual channel unit resource region candidate" is made up of as many "virtual channel CCEs used" as aggregation levels.

Search space identification section <NUM> identifies the virtual channel CCE group used associated in the VRB table with a pair of the division number M calculated in division number calculation section <NUM> and the aggregation level. Search space identification section <NUM> then identifies a search space of the physical channel based on the identified virtual channel CCE group used, "search space information" received from search space determining section <NUM> and an "association rule" corresponding to the pair of the division number M calculated in division number calculation section <NUM> and the aggregation level. The "association rule" associates a "virtual channel unit resource region candidate" with a "physical channel resource region candidate. " The identified search space is made up of a plurality of "resource region candidates" and each "resource region candidate" is made up of as many "physical channel CCEs used" as aggregation levels. The "physical channel CCE used" means the same as the above-described "mapping candidate CCE.

In the "VRB table," the "unit resource region candidate" corresponding to the pair of the division number M and aggregation level L is common to the "unit resource region candidate" corresponding to the pair of the division number <NUM> and aggregation level <NUM>. Furthermore, the "association rule" corresponding to the pair of the division number M and aggregation level L is common to the "association rule" corresponding to the pair of the division number <NUM> and aggregation level <NUM>.

Mapping resource selection section <NUM> selects one of the plurality of "resource region candidates" forming the search space identified by search space identification section <NUM> as a control signal mapping resource.

In terminal <NUM> of Embodiment <NUM>, extracted resource identification section <NUM> identifies a plurality of "resource region groups to be extracted" (that is, search spaces) corresponding to the pair of the division number M calculated in division number calculation section <NUM> and an aggregation level based on the division number M, the search space information transmitted from base station <NUM> and the aggregation level.

To be more specific, a search space is identified based on the "VRB table," the division number M, the "search space information," the aggregation level, and the "association rule" per pair of the division number M and the aggregation level. Each search space is made up of a plurality of "resource regions to be extracted" and each "resource region to be extracted" is made up of as many CCEs (hereinafter, may also be referred to as "CCEs to be extracted") as aggregation levels.

More specifically, extracted resource identification section <NUM> includes VRB table storage section <NUM> and search space identification section <NUM> as shown in <FIG>.

VRB table storage section <NUM> stores the same "VRB table" as that of base station <NUM>. That is, the "VRB table" associates a plurality of VRB pairs with a divided resource region (that is, "virtual channel CCE") group per division number candidate of each VRB pair. The "VRB table" further associates the plurality of pairs of division number and aggregation level candidates with the plurality of "virtual channel resource regions to be extracted" corresponding to each pair. Each "virtual channel resource region to be extracted" is made up of as many "virtual channel CCE used" as aggregation levels.

Search space identification section <NUM> identifies a virtual channel CCE group used associated in the VRB table with the pair of the division number M calculated in division number calculation section <NUM> and the aggregation level. Search space identification section <NUM> then identifies a search space of the physical channel based on the identified virtual channel CCE group used, the "search space information," and the "association rule" corresponding to the pair of the division number M calculated in division number calculation section <NUM> and the aggregation level. The "association rule" associates a "virtual channel resource region to be extracted" with a "physical channel resource region to be extracted. " The identified search space is made up of a plurality of "resource regions to be extracted" and each "resource region to be extracted" is made up of as many "physical channel CCEs used" as aggregation levels. The "physical channel CCE used" means the same as the above-described "CCE to be extracted.

Here, the "unit resource region candidate" corresponding to the pair of the division number M and aggregation level L in the "VRB table" is common to the "unit resource region candidate" corresponding to the pair of the division number <NUM> and aggregation level <NUM>. Furthermore, the "association rule" corresponding to the pair of the division number M and aggregation level L is common to the "association rule" corresponding to the pair of the division number <NUM> and aggregation level <NUM>.

The operations of base station <NUM> and terminal <NUM> configured in the manner described above will be described. Here, in particular, a case will be described as an example where the division number = <NUM> and the division number = <NUM>. <FIG> is a diagram provided for describing the operations of base station <NUM> and terminal <NUM>.

The diagram on the left of <FIG> visually expresses contents of the "VRB table. " In the "VRB table" shown in <FIG>, there are four aggregation levels: levels <NUM>, <NUM>, <NUM> and <NUM>. Search spaces at levels <NUM>, <NUM>, <NUM> and <NUM> have <NUM>, <NUM>, <NUM> and <NUM> "virtual channel unit resource region candidates" respectively. Four virtual channel CCEs obtained by dividing VRB#X which is one VRB pair into <NUM> are called VRB#X(a), VRB#X(b), VRB#X(c) and VRB#X(d). On the other hand, four physical channel CCEs obtained by dividing PRB#X which is one PRB pair into <NUM> are called PRB#X(a), PRB#X(b), PRB#X(c) and PRB#X(d). Two virtual channel CCEs obtained by dividing VRB#X which is one VRB pair into <NUM> are called VRB#X(A) and VRB#X(B). On the other hand, two physical channel CCEs obtained by dividing PRB#X which is one PRB pair into <NUM> are called PRB#X(A) and PRB#X(B).

The "VRB table" in <FIG> includes eight VRB pairs: VRB#<NUM> to VRB#<NUM>. For search spaces, as many "virtual channel unit resource region candidates" as aggregation levels are continuously arranged in eight VRB pairs from VRB#<NUM>. In the "VRB table" in <FIG>, a resource combining VRB#X(a) and VRB#X(b) is VRB#X(A) and a resource combining VRB#X(c) and VRB#X(d) is VRB#X(B).

Search space identification section <NUM> identifies a virtual channel CCE group used associated in the VRB table with a pair of the division number M calculated in division number calculation section <NUM> and the aggregation level.

For example, when the division number = <NUM> and the aggregation level = <NUM>, VRB#<NUM>(a), VRB#<NUM>(b), VRB#<NUM>(c), VRB#X0(d), VRB#<NUM>(a) and VRB#<NUM>(b) are identified as a virtual channel CCE group used. Note that when the aggregation level = <NUM>, the virtual channel CCE used is equal to the "virtual channel unit resource region candidate.

For example, when the division number = <NUM> and the aggregation level = <NUM>, VRB#<NUM>(a), VRB#<NUM>(b), VRB#<NUM>(c), VRB#X0(d), VRB#<NUM>(a), VRB#<NUM>(b), VRB#<NUM>(c), VRB#X1(d), VRB#<NUM>(a), VRB#<NUM>(b), VRB#<NUM>(c) and VRB#X2(d) are identified as a virtual channel CCE group used. On the other hand, when the division number = <NUM> and the aggregation level = <NUM>, VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A) and VRB#<NUM>(B) are identified as a virtual channel CCE group used. As described above, a resource combining VRB#X(a) and VRB#X(b) is VRB#X(A) and a resource combining VRB#X(c) and VRB#X(d) is VRB#X(B) in the "VRB table. " The "virtual channel unit resource region candidate" in the case where the division number = <NUM> and the aggregation level = <NUM> matches that in the case where the division number = <NUM> and the aggregation level = <NUM>.

When the division number = <NUM> and aggregation level = <NUM>, VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A) and VRB#<NUM>(B) are identified as a virtual channel CCE group used. At this time, the "virtual channel unit resource region candidates" are {VRB#<NUM>(A), VRB#<NUM>(B)}, {VRB#<NUM>(A), VRB#<NUM>(B)}, {VRB#<NUM>(A), VRB#<NUM>(B)}, {VRB#<NUM>(A), VRB#<NUM>(B)}, {VRB#<NUM>(A), VRB#<NUM>(B)}, and {VRB#<NUM>(A), VRB#<NUM>(B)}. Here, a set of VRBs enclosed by {} makes up one "virtual channel unit resource region candidate. " The "virtual channel unit resource region candidate" in the case where the division number = <NUM> and the aggregation level = <NUM> matches that in the case where the division number = <NUM> and the aggregation level = <NUM>. However, when the division number = <NUM> and the aggregation level = <NUM>, since there are two "virtual channel unit resource region candidates," only {VRB#<NUM>(A), VRB#<NUM>(B)} and {VRB#<NUM>(A), VRB#<NUM>(B)} are used.

When the division number = <NUM> and the aggregation level = <NUM>, VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A), and VRB#<NUM>(B) are identified as a virtual channel CCE group used. At this time, there are two "virtual channel unit resource region candidates": {VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A), VRB#<NUM>(B)} and {VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A), VRB#<NUM>(B)}. The "virtual channel unit resource region candidate" in the case where the division number = <NUM> and the aggregation level = <NUM> matches that in the case where the division number = <NUM> and the aggregation level = <NUM>.

When the division number = <NUM> and the aggregation level = <NUM>, the "virtual channel unit resource region candidates" are {VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A), VRB#<NUM>(B)}, and {VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A), VRB#<NUM>(B)}.

Search space identification section <NUM> identifies a search space of the physical channel based on the identified virtual channel CCE group used, "search space information" received from search space determining section <NUM>, and the "association rule" corresponding to the pair of the division number M calculated in division number calculation section <NUM> and the aggregation level.

For example, when the division number = <NUM> and the aggregation level = <NUM>, as shown in the diagram in the middle of <FIG>, VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A) and VRB#<NUM>(B) are mapped to PRB#<NUM>(A), PRB#<NUM>(A), PRB#<NUM>(A), PRB#<NUM>(A), PRB#<NUM>(A) and PRB#<NUM>(B) according to the "association rule. " When the division number = <NUM> and the aggregation level = <NUM>, as shown in the diagram on the right of <FIG>, VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A) and VRB#<NUM>(B) are mapped to PRB#<NUM>(A), PRB#<NUM>(A), PRB#<NUM>(A), PRB#<NUM>(A), PRB#<NUM>(A) and PRB#<NUM>(B) according to the "association rule. " That is, the "association rule" in the case where the division number = <NUM> and the aggregation level = <NUM> matches that in the case where the division number = <NUM> and the aggregation level = <NUM>.

On the other hand, terminal <NUM> performs processing similar to that of base station <NUM>. That is, search space identification section <NUM> identifies the virtual channel CCE group used associated in the VRB table with the pair of the division number M calculated in division number calculation section <NUM> and the aggregation level. Search space identification section <NUM> identifies a search space of the physical channel based on the identified virtual channel CCE group used, "search space information" and the "association rule" corresponding to the pair of the division number M calculated in division number calculation section <NUM> and the aggregation level.

As described above, according to the present embodiment, control signal mapping control section <NUM> in base station <NUM> determines a search space by determining a control channel element group forming a plurality of resource region candidates among CCE groups obtained by dividing each PRB pair included in the first group into the same number as the division number. The plurality of resource region candidates are common when the division number is M (M is a natural number) and the value of the aggregation level is A (A is a natural number) and when the division number is <NUM> and the value of the aggregation level is 2A.

Even when the division number of a PRB pair varies from one subframe to another, assignment of physical resources can be made common in this way, and it is thereby possible to reduce the amount of signaling when base station <NUM> indicates the physical resources to terminal <NUM>. Furthermore, if a PRB pair having good quality is included in the first group in the first subframe, it is possible to continue to use the PRB pair even when the division number varies from one subframe to another.

According to the present embodiment, extracted resource identification section <NUM> in terminal <NUM> identifies a search space by identifying a control channel element group forming a plurality of resource region candidates in the CCE group obtained by dividing each PRB pair included in the first group into the same number as the division number. The plurality of resource region candidates forming the identified search space correspond to the plurality of "resource regions to be extracted. " The plurality of "resource regions to be extracted" are common when the division number is M (M is a natural number) and the value of the aggregation level is A (A is a natural number) and when the division number is <NUM> and the value of the aggregation level is 2A.

Embodiment <NUM> relates to variations of a method for mapping a logical channel (VRB) to a physical channel (PRB). Note that since basic configurations of a base station and a terminal according to Embodiment <NUM> are common to those of base station <NUM> and terminal <NUM> according to Embodiment <NUM> and Embodiment <NUM>, they will be described with reference to <FIG> and <FIG>.

In base station <NUM> according to Embodiment <NUM>, control signal mapping control section <NUM> identifies a search space corresponding to a pair of the division number M calculated in division number calculation section <NUM> and an aggregation level based on the division number M, the "search space information" received from search space determining section <NUM> and the aggregation level.

To be more specific, a search space is identified based on a "VRB table", the division number M, "search space information," aggregation level, a "first type association rule" and a "second type association rule. " Here, the "first type association rule" is a rule that associates "virtual channel unit resource region candidates" with "physical channel unit resource region candidates" regarding the pair of the division number M/<NUM> and the aggregation level as in the case of Embodiment <NUM>. On the other hand, the "second type association rule" is a rule that associates "resource region candidates" regarding the pair of the division number M/<NUM> and the aggregation level with "resource region candidates" regarding the pair of the division number M and the aggregation level. That is, the "second type association rule" is a rule that associates "physical channel CCEs" regarding the division number M/<NUM> with "physical channel CCEs" regarding the division number M in a given PRB pair. Here, in the case of the division number M, up to M/<NUM> of M physical channel CCEs included in one PRB pair may be designated as physical channel CCEs used.

More specifically, control signal mapping control section <NUM> includes search space identification section <NUM> as shown in <FIG>.

Search space identification section <NUM> identifies a virtual channel CCE group used associated in the VRB table with the pair of the "reference division number" and the aggregation level. Search space identification section <NUM> identifies a search space of the physical channel corresponding to the pair of the "reference division number" and the aggregation level based on the identified virtual channel CCE group used, the "search space information" and the "first type association rule" corresponding to the pair of the "reference division number" and the aggregation level. Here, when the division number calculated in division number calculation section <NUM> is <NUM>, the "reference division number" is M.

Search space identification section <NUM> identifies a search space of the physical channel corresponding to the division number calculated in division number calculation section <NUM> based on the search space of the physical channel corresponding to the pair of the "reference division number" and the aggregation level, and the "second type association rule.

Extracted resource identification section <NUM> in terminal <NUM> of Embodiment <NUM> identifies a plurality of "resource region groups to be extracted" (that is, search space) corresponding to the pair of the division number M calculated in division number calculation section <NUM> and an aggregation level based on the division number M, the search space information transmitted from base station <NUM> and the aggregation level.

To be more specific, a search space is identified based on the "VRB table," the division number M, "search space information," aggregation level, "first type association rule" and "second type association rule. " Here, the "first type association rule" is a rule that associates the "virtual channel resource regions to be extracted" with the "physical channel resource regions to be extracted" regarding the pair of the division number M/<NUM> and aggregation level as in the case of Embodiment <NUM>. On the other hand, the "second type association rule" is a rule that associates the "physical channel resource regions to be extracted" regarding the pair of the division number M/<NUM> and aggregation level with the "physical channel resource regions to be extracted" regarding the pair of the division number M and aggregation level. That is, the "second type association rule" is a rule that associates the "physical channel CCEs" regarding the division number M/<NUM> with the "physical channel CCEs" regarding the division number M in a given PRB pair.

More specifically, extracted resource identification section <NUM> includes search space identification section <NUM> as shown in <FIG>.

Search space identification section <NUM> identifies a virtual channel CCE group used associated in the VRB table with the pair of the "reference division number," i.e., the division number M and the aggregation level. Search space identification section <NUM> identifies a search space of the physical channel corresponding to the pair of the "reference division number" and the aggregation level based on the identified virtual channel CCE group used, "search space information" and the "first type association rule" corresponding to the pair of the "reference division number" and the aggregation level.

The diagram on the left of <FIG> visually expresses contents of a "VRB table" when the division number = <NUM>.

When the division number = <NUM> calculated in division number calculation section <NUM>, search space identification section <NUM> identifies a virtual channel CCE group used associated in the VRB table with the pair of the reference division number = <NUM> and the aggregation level using the "VRB table" shown in the diagram on the left of <FIG>.

Search space identification section <NUM> identifies a search space of the physical channel corresponding to the pair of the reference division number = <NUM> and the aggregation level based on the identified virtual channel CCE group used, "search space information" and the "first type association rule" corresponding to the pair of the reference division number = <NUM> and the aggregation level. For example, when the division number = <NUM> and the aggregation level = <NUM>, as shown in the diagram in the middle of <FIG>, VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A) and VRB#<NUM>(B) are mapped to PRB#<NUM>(A), PRB#<NUM>(A), PRB#<NUM>(A), PRB#<NUM>(A), PRB#<NUM>(A) and PRB#<NUM>(B) according to the "first type association rule.

Search space identification section <NUM> then identifies a search space of the physical channel corresponding to the division number calculated in division number calculation section <NUM> based on the search space of the physical channel corresponding to the pair of the "reference division number" and the aggregation level, and the "second type association rule. " Here, according to "second type association rule" in <FIG>, PRB#X(a) and PRB#X(c) are associated with PRB#X(A), and PRB#X(b) and PRB#X(d) are associated with PRB#X(B). However, PRB#X(a) and PRB#X(c) associated with PRB#X(A) are never used simultaneously as physical channel CCEs used. Similarly, PRB#X(b) and PRB#X(d) associated with PRB#X(B) are never used simultaneously as physical channel CCEs used.

Search space identification section <NUM> of terminal <NUM> perform basically the same operation as that of search space identification section <NUM>.

As described above, according to the present embodiment, control signal mapping control section <NUM> in base station <NUM> determines a search space by determining a control channel element group forming a plurality of resource region candidates among CCE groups obtained by dividing each PRB pair included in the first group into the same number as the division number. Control signal mapping control section <NUM> then identifies a second search space in the physical channel when the division number is <NUM> (M is a natural number) and the value of the aggregation level is 2A (A is a natural number) based on the first search space in the logical channel and the first type association rule when the division number is <NUM> and the value of the aggregation level is 2A. Control signal mapping control section <NUM> further identifies a third search space in the physical channel when the division number is M and the value of the aggregation level is A based on the second search space and the second type association rule. The second type association rule associates CCEs when the division number in each PRB pair is <NUM> with CCEs when the division number is M.

By so doing, even when the division number of a PRB pair varies from one subframe to another, if base station <NUM> indicates physical resources to terminal <NUM> for the division number <NUM>, indication for the division number M is unnecessary, and it is thereby possible to reduce the amount of signaling when base station <NUM> indicates physical resources to terminal <NUM>. If a PRB pair of good quality is included in the first group in the first subframe, it is possible to continue to use the PRB pair even when the division number varies from one subframe to another.

According to the present embodiment, extracted resource identification section <NUM> in terminal <NUM> identifies a search space by identifying a control channel element group forming a plurality of resource region candidates among CCE groups obtained by dividing each PRB pair included in the first group into the same number as the division number. The plurality of resource region candidates forming this identified search space, correspond to the plurality of "resource regions to be extracted. " Extracted resource identification section <NUM> then identifies a second search space in the physical channel when the division number is <NUM> (M is a natural number) and the value of the aggregation level is 2A (A is a natural number) based on the first search space in the logical channel and the first type association rule when the division number is <NUM> and the value of the aggregation level is 2A. Furthermore, extracted resource identification section <NUM> identifies a third search space in the physical channel when the division number is M and the value of the aggregation level is A based on the second search space and the second type association rule. The second type association rule associates CCEs when the division number in each PRB pair is <NUM> with CCEs when the division number is M.

As with Embodiment <NUM>, Embodiment <NUM> relates to a variation of a method for mapping a logical channel (VRB) to a physical channel (PRB). However, the relationship between the calculated division number and the "reference division number" in Embodiment <NUM> is opposite to the relationship in Embodiment <NUM>. Since basic configurations of a base station and a terminal according to Embodiment <NUM> are common to those of base station <NUM> and terminal <NUM> according to Embodiment <NUM> and Embodiment <NUM>, they will be described with reference to <FIG>, <FIG>, <FIG> and <FIG>.

In base station <NUM> of Embodiment <NUM>, search space identification section <NUM> identifies a virtual channel CCE group used associated in a VRB table with a pair of the "reference division number" and the aggregation level. Search space identification section <NUM> identifies a search space of the physical channel corresponding to the pair of the "reference division number" and the aggregation level based on the identified virtual channel CCE group used, "search space information" and the "first type association rule" corresponding to the pair of the "reference division number" and the aggregation level. Here, when the division number calculated in division number calculation section <NUM> is M, the "reference division number" is <NUM>.

In terminal <NUM> of Embodiment <NUM>, search space identification section <NUM> identifies a virtual channel CCE group used associated in a VRB table with the pair of the "reference division number," i.e., the division number M and the aggregation level. Search space identification section <NUM> then identifies a search space of the physical channel corresponding to the pair of the "reference division number" and the aggregation level based on the identified virtual channel CCE group used, "search space information" and the "first type association rule" corresponding to the pair of the "reference division number" and the aggregation level.

Search space identification section <NUM> then identifies a search space of the physical channel corresponding to the division number calculated in division number calculation section <NUM> based on a search space of the physical channel corresponding to the pair of the "reference division number" and the aggregation level, and the "second type association rule.

Search space identification section <NUM> identifies a search space of the physical channel corresponding to the pair of the reference division number = <NUM> and the aggregation level based on the identified virtual channel CCE group used, "search space information" and the "first type association rule" corresponding to the pair of the reference division number = <NUM> and the aggregation level. For example, when the division number = <NUM> and the aggregation level = <NUM>, as shown in the diagram in the middle of <FIG>, VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A), VRB#<NUM>(B), VRB#<NUM>(A) and VRB#<NUM>(B) are mapped to PRB#<NUM>(A), PRB#<NUM>(B), PRB#<NUM>(A), PRB#<NUM>(B), PRB#<NUM>(A), PRB#<NUM>(B), PRB#<NUM>(A), PRB#<NUM>(B), PRB#<NUM>(A), PRB#<NUM>(B), PRB#<NUM>(A) and PRB#<NUM>(B) according to the "first type association rule.

Search space identification section <NUM> then identifies a search space of the physical channel corresponding to the division number calculated in division number calculation section <NUM> based on a search space of the physical channel corresponding to the pair of the "reference division number" and the aggregation level, and the "second type association rule". The "second type association rule" in <FIG> associates PRB#X(A) with PRB#X(a) and associates PRB#X(B) with PRB#X(c) in PRB#<NUM> or the like. On the other hand, the "second type association rule" in <FIG> associates PRB#X(A) with PRB#X(b) and associates PRB#X(B) with PRB#X(d) in PRB#<NUM> or the like. That is, the method of association is changed between the first PRB pair and the second PRB pair. However, the "second type association rule" is not limited to this example, and a common method of association may be used between the first PRB pair and the second PRB pair.

As described above, according to the present embodiment, control signal mapping control section <NUM> in base station <NUM> determines a search space by determining a control channel element group forming a plurality of resource region candidates among CCE groups obtained by dividing each PRB pair included in the first group into the same number as the division number. Control signal mapping control section <NUM> identifies a second search space in the physical channel when the division number is M (M is a natural number) and the value of the aggregation level is A (A is a natural number) based on the first search space in the logical channel and the first type association rule when the division number is M and the value of the aggregation level is A. Control signal mapping control section <NUM> identifies a third search space in the physical channel when the division number is <NUM> and the value of the aggregation level is 2A based on the second search space and the second type association rule. The second type association rule associates control channel elements when the division number is <NUM> in each physical channel resource block with control channel elements when the division number is M.

By so doing, even when the division number of a PRB pair varies from one subframe to another, if base station <NUM> indicates physical resources to terminal <NUM> for the division number M, indication for the division number <NUM> becomes unnecessary, and it is thereby possible to reduce the amount of signaling when base station <NUM> indicates physical resources to terminal <NUM>. Furthermore, if a PRB pair of good quality is included in the first group in the first subframe, it is possible to continue to use the PRB pair even when the division number varies from one subframe to another.

According to the present embodiment, extracted resource identification section <NUM> in terminal <NUM> identifies a search space by identifying a control channel element group forming a plurality of resource region candidates among CCE groups obtained by dividing each PRB pair included in the first group into the same number as the division number. The plurality of resource region candidates forming the identified search space, correspond to a plurality of "resource regions to be extracted. " Extracted resource identification section <NUM> identifies a second search space in the physical channel when the division number is M (M is a natural number) and the value of the aggregation level is A (A is a natural number) based on the first search space in the logical channel and the first type association rule when the division number is M and the value of the aggregation level is A. Furthermore, extracted resource identification section <NUM> identifies a third search space in the physical channel when the division number is <NUM> and the value of the aggregation level is 2A based on the second search space and the second type association rule. The second type association rule associates control channel elements when the division number is <NUM> in each physical channel resource block with control channel elements when the division number is M.

The functional blocks described in the embodiments are achieved by an LSI, which is typically an integrated circuit. The functional blocks may be provided as individual chips, or part or all of the functional blocks may be provided as a single chip. Depending on the level of integration, the LSI may be referred to as an IC, a system LSI, a super LSI, or an ultra LSI.

In addition, the circuit integration is not limited to LSI and may be achieved by dedicated circuitry or a general-purpose processor other than an LSI. After fabrication of LSI, a field programmable gate array (FPGA), which is programmable, or a reconfigurable processor which allows reconfiguration of connections and settings of circuit cells in LSI may be used.

Should a circuit integration technology replacing LSI appear as a result of advancements in semiconductor technology or other technologies derived from the technology, the functional blocks could be integrated using such a technology.

Claim 1:
An integrated circuit which, in operation, controls a process of a communication apparatus, the process comprising:
calculating, for each subframe, a division number based on a number of OFDM symbols available for an Enhanced PDCCH, EPDCCH, in a resource block pair and a number of resource elements, REs, used for reference signals in the resource block pair, the EPDCCH being mapped into a resource region available for a transmission of either of downlink control information and downlink data;
setting resource region candidates including at least one Control Channel Element, CCE, by dividing the resource block pair by the division number and to identify a search space formed of the plurality of resource region candidates set in the resource block pair based on an aggregation level; and
acquiring the downlink control information by blind-decoding a received signal at the plurality of resource region candidates.