Patent ID: 12218753

DESCRIPTION OF EMBODIMENT

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.

Embodiment 1

[Base Station Configuration]

FIG.2is a block diagram illustrating a configuration of base station100according to Embodiment 1 of the present invention. InFIG.2, base station100includes configuration section101, memory102, control section103, PDCCH generating section104, coding sections105,106, and107, modulating sections108,109, and110, allocation section111, PCFICH generating section112, multiplexing section113, IFFT (Inverse Fast Fourier Transform) section114, CP (Cyclic Prefix) adding section115, RF transmitting section116, RF receiving section117, CP removing section118, FFT (Fast Fourier Transform) section119, extraction section120, IDFT (Inverse Discrete Fourier Transform) section121, and data receiving section122.

Configuration section101configures one or a plurality of CCs used for uplink and downlink, for each 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 section101also changes the UE CC set once configured.

When initially configuring the UE CC set and every time changing the UE CC set, configuration section101corrects (updates) a CIF table (that is, a labeling rule) stored in memory102. In this CIF table stored in memory102, 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 section101adds the new CC, while maintaining the CCs forming the currently configured UE CC set. Also, when correcting the CIF table, configuration section101allocates 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 section101also 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 section101deletes 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 section101notifies later described terminal200of the following information via a process system going through coding section106. That is, when adding a CC, configuration section101notifies terminal200of the CC number to be added, the PDCCH CC number, and the CIF code point allocated to the CC to be added, to terminal200. Meanwhile, when deleting a CC, configuration section101notifies terminal200of 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 section101outputs the CC numbers and the PDCCH CC numbers forming the UE CC set, to control section103and PDCCH generating section104. Hereinafter, the pieces of information output from configuration section101may be collectively referred to as “configuration information.”

Control section103generates 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 terminal200is allocated. Meanwhile, the downlink resource allocation information represents a downlink resource (for example, PDSCH) to which downlink data addressed to allocation-target terminal200is 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 section103outputs the resource allocation information to PDCCH generating section104and multiplexing section113.

Here, based on the configuration information received from configuration section101, control section103allocates the resource allocation information for allocation-target terminal200, to the PDCCH arranged in the downlink component carrier configured in corresponding terminal200. This allocation process is allocated on a subframe unit basis. In particular, control section103allocates the resource allocation information for allocation-target terminal200, to the PDCCH arranged in the downlink component carrier indicated by the PDCCH CC number configured in the terminal200. Control section103allocates a CIF code point to each CC subject to the resource allocation, according to the CIF table updated by configuration section101. A PDCCH is formed by one or a plurality of CCEs. Furthermore, the number of CCEs used by base station100is configured based on the propagation path quality (CQI: Channel Quality Indicator) and the control information size of allocation-target terminal200. By this means, terminal200can receive control information at a necessary and sufficient error rate.

Control section103determines 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 section103generates the CFI information indicating the determined number of the OFDM symbols. Then, control section103outputs the CFI information for each downlink component carrier, to PCFICH generating section112and multiplexing section113.

PDCCH generating section104generates 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 section101. This PDCCH signal includes the uplink resource allocation information and the downlink resource allocation information output from control section103. Furthermore, PDCCH generating section104adds a CRC bit to the PDCCH signal and then masks (or scrambles) the CRC bit with a terminal ID. Then, PDCCH generating section104outputs the masked PDCCH signal to coding section105.

The process described above is performed for each processing target terminal200.

Coding section105performs a channel coding process on the PDCCH signal of each component carrier input from PDCCH generating section104and outputs the PDCCH signal that has been subjected to the channel coding process to modulation section108.

Modulation section108modulates the PDCCH signal input from coding section105and outputs the modulated PDCCH signal to allocation section111.

Allocation section111allocates the PDCCH signals of terminals input from modulation section108, to CCEs inside of the search space of each terminal in each downlink component carrier. Allocation section111outputs the PDCCH signal allocated to the CCE to multiplexing section113.

PCFICH generating section112generates a PCFICH signal to be transmitted every downlink component carrier, based on the CFI information every downlink component carrier input from control section103. PCFICH generating section112then outputs the generated PCFICH signal to multiplexing section113.

Coding section106encodes the configuration information input from configuration section101and outputs the encoded configuration information to modulating section109.

Modulation section109modulates the encoded configuration information and outputs the modulated configuration information to multiplexing section113.

Coding section107performs 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 section110.

Modulation section110modulates the transmission data (downlink data) that has been subjected to the channel coding process and outputs the modulated transmission data signal to multiplexing section113.

Multiplexing section113multiplexes the PDCCH signal input from allocation section111, the PCFICH signal input from PCFICH generating section112, the configuration information input from modulation section109, and the data signal (that is, the PDSCH signal) input from modulation section110. Here, based on the CFI information of each downlink component carrier input from control section103, multiplexing section113determines the number of OFDM symbols to arrange the PDCCHs every downlink component carrier. Furthermore, multiplexing section113maps the PDCCH signal and the data signal (PDSCH signal) to each downlink component carrier, based on the downlink resource allocation information input from control section103. Multiplexing section113may also map the configuration information to the PDSCH. Multiplexing section113then outputs a multiplexed signal to IFFT section114.

IFFT section114converts the multiplexed signal input from multiplexing section113into a time domain waveform. CP adding section115then obtains an OFDM signal by adding a CP to this time domain waveform.

RF transmitting section116applies a radio transmission process (such as up-conversion and D/A conversion) on the OFDM signal input from CP adding section115and transmits the result via an antenna.

Meanwhile, RF receiving section117performs 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 section118.

CP removing section118removes a CP from the received signal, and FFT section119converts the received signal from which the CP is removed into a frequency domain signal.

Extraction section120extracts the uplink data of each terminal and the PUCCH signal (e.g., ACK/NACK signal) from the frequency domain signal input from FFT section119, based on the uplink resource allocation information (e.g., the uplink resource allocation information in four subframes ahead) input from control section103. IDFT section121converts the signal extracted by extraction section120into a time domain signal and outputs the time domain signal to data receiving section122.

Data receiving section122decodes uplink data out of the time domain signal input from IDFT section121. Then, data receiving section122outputs the decoded uplink data as received data.

[Terminal Configuration]

FIG.3is a block diagram illustrating a configuration of terminal200according to Embodiment 1 of the present invention. Terminal200communicates with base station100by using a plurality of downlink component carriers. When the received data includes an error, terminal200stores 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.

InFIG.3, terminal200includes RF receiving section201, CP removing section202, FFT section203, demultiplexing section204, configuration information receiving section205, PCFICH receiving section206, CIF table configuring section207, PDCCH receiving section208, PDSCH receiving section209, modulating sections210and211, DFT (Discrete Fourier Transform) section212, mapping section213, IFFT section214, CP adding section215, and RF transmitting section216.

RF receiving section201is capable of changing a reception band, and changes the reception band, based on the band information input from configuration information receiving section205. Then, RF receiving section201applies 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 section202.

CP removing section202removes a CP from the reception signal. FFT section203converts the received signal from which the CP is removed into a frequency domain signal and outputs this frequency domain signal to demultiplexing section204.

Demultiplexing section204demultiplexes the signal input from FFT section203into 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 section204outputs the control signal to configuration information receiving section205, the PCFICH signal to PCFICH receiving section206, the PDCCH signal to PDCCH receiving section208, and the PDSCH signal to PDSCH receiving section209.

Configuration information receiving section205reads the following information from the control signal received from demultiplexing section204. 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 section205outputs the read information to CIF table configuring section207, PDCCH receiving section208, RF receiving section201, and RF transmitting section216. Furthermore, configuration information receiving section205reads the terminal ID configured to the terminal from the control signal received from demultiplexing section204and outputs the read information to PDCCH receiving section208.

PCFICH receiving section206extracts the CFI information from the PCFICH signal received from demultiplexing section204. That is, PCFICH receiving section206obtains 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 section206outputs the extracted CFI information to PDCCH receiving section208and PDSCH receiving section209.

CIF table configuring section207corrects (updates) the CIF table held by PDCCH receiving section208, based on an added or removed CC number received from configuration information receiving section205and the CIF code point allocated to the CC. This correction process corresponds to the correction process in base station100.

PDCCH receiving section208performs blind decoding on the PDCCH signal received from demultiplexing section204, 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 section205.

To be more specific, for each downlink component carrier, PDCCH receiving section208specifies the number of OFDM symbols in which the PDCCH is arranged, based on the CFI information received from PCFICH receiving section206. PDCCH receiving section208then calculates the search space of the terminal by using the terminal ID received from configuration information receiving section205.

PDCCH receiving section208then demodulates and decodes the PDCCH signal allocated to each CCE in the calculated search space.

PDCCH receiving section208performs 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 1 and downlink component carrier 2) and the PDCCH signals of both component carriers are transmitted from CC1, PDCCH receiving section208performs the blind decoding on the PDCCH signal performing data allocation of downlink component carrier 1 and blind decoding on the PDCCH signal performing data allocation of downlink component carrier 2, on CC1.

PDCCH receiving section208determines 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 section208outputs the downlink resource allocation information included in the PDCCH signal addressed to the terminal to PDSCH receiving section209, and outputs the uplink resource allocation information to mapping section213. Meanwhile, when no PDCCH signal resulting in CRC=OK is detected, PDCCH receiving section208determines 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 section207, PDCCH receiving section208converts 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 section209. Here, the CIF table is stored in the memory (not shown) included in PDCCH receiving section208.

PDSCH receiving section209extracts the received data (downlink data) from the PDSCH signal received from demultiplexing section204, based on the downlink resource allocation information and CFI information of a plurality of downlink component carriers received from PDCCH receiving section208, and the CFI information of the CC where the PDCCH signal is transmitted, the CFI information received from PCFICH receiving section206. 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 section209performs error detection on the extracted reception data (downlink data). As a result of the error detection, PDSCH receiving section209generates a NACK signal as an ACK/NACK signal when the reception data includes an error, whereas PDSCH receiving section209generates an ACK signal as the ACK/NACK signal when the reception data includes no error. Then, PDSCH receiving section209outputs the ACK/NACK signal to modulation section210. When the reception data includes an error, PDSCH receiving section209stores the extracted reception data in an HARQ buffer (not shown). Upon receipt of retransmitted data, PDSCH receiving section209combines 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 station100transmits the PDSCH signal using spatial multiplexing, for example, MIMO (Multiple-Input Multiple-Output) and thereby transmits two data blocks (Transport Blocks), PDSCH receiving section209generates ACK/NACK signals for the respective data blocks.

Modulation section210modulates the ACK/NACK signal received from PDSCH receiving section209. When base station100transmits two data blocks by spatially-multiplexing the PDSCH signal in each downlink component carrier, modulation section210applies QPSK modulation on the ACK/NACK signal. Meanwhile, when base station100transmits one data block, modulation section210applies BPSK modulation on the ACK/NACK signal. That is, modulation section210generates one QPSK signal or BPSK signal as the ACK/NACK signal of each downlink component carrier. Modulation section210then outputs the modulated ACK/NACK signal to mapping section213.

Modulation section211modulates transmission data (uplink data) and outputs the modulated data signal to DFT section212.

DFT section212converts the data signal input from modulation section211into a frequency domain signal and outputs the resulting plurality of frequency components to mapping section213.

Mapping section213maps the data signal input from DFT section212to the PUSCH arranged in the uplink component carrier, according to the uplink resource allocation information input from PDCCH receiving section208. Mapping section213also maps the ACK/NACK signal input from modulation section210onto the PUCCH arranged in the uplink component carrier.

Here, modulation sections210and211, DFT section212, and mapping section213may also be provided every uplink component carrier.

IFFT section214converts a plurality of frequency components mapped to the PUSCH into a time-domain waveform, and CP adding section215adds a CP to the time-domain waveform.

RF transmitting section216is capable of changing a transmission band, and configures the transmission band, based on the band information received from configuration information receiving section205. Then, RF transmitting section216applies 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 Station100and Terminal200]

Operations of base station100and terminal200having 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.4illustrates how CCs forming a UE CC set vary with time.FIG.5illustrates the conditions of the CIF table in time intervals illustrated inFIG.4. When the CIF consists of two bits, there are four code points represented by bit sequences 00, 01, 10, and 11, respectively. Here, a case will be described assuming that CIs=1, 2, 3, and 4 correspond to the bit sequences 00, 01, 10, and 11, respectively.

As illustrated inFIG.4, when the power of terminal200is turned on, terminal200starts to communicate with base station100in one CC (inFIG.4, CC2) according to operations such as a cell search and random access as in LTE.

Base station100then adds a CC to terminal200due to, for example, increase of the amount of data. Here, configuration section101corrects (updates) the CIF table stored in memory102in base station100. To be more specific, when adding a new CC to the UE CC set, configuration section101adds the new CC while maintaining the CCs forming the currently configured UE CC set. In the correction of the CIF table, configuration section101allocates 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 section101also allocates “PDCCH CC number.”

For example, inFIG.4, 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 inFIGS.5B, C, and E, respectively. For example, CC1 is added betweenFIG.5BandFIG.5C. InFIG.5C, CC1 is associated with CIF code point 3 unused inFIG.5B, while the relationship between the CCs forming the UE CC set and the CIF code point inFIG.5Bis maintained.

As illustrated inFIG.4, in interval C, the information of data (PDSCH) allocation in CC1, 2, and 3 is notified to terminal200by the PDCCH of CC2. That is, “PDCCH CC number” is 2 at this time.

Also, when deleting a CC from the CCs forming the UE CC set, configuration section101deletes only the CC, while maintaining the correspondence between the CIF code points and the CCs not to be deleted.

For example, CC1 is deleted betweenFIG.5CandFIG.5D. InFIG.5D, the correspondence between the CIF code points and CCs 2 and 3 other than CC1 inFIG.5Cis maintained.

The correction process by CIF table configuring section207of terminal200corresponds to the correction process in base station100.

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 terminal200, the number of bits required for notifying terminal200of the CCs from base station100can be only the number of CCs supported by terminal200. For example, even in case of a system supporting eight CCs, the number of bits required for notifying terminal200of the CCs from base station100can be only two bits when the number of CCs supported by terminal200is 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 station100, when adding a component carrier to a component carriers set (UE CC set), configuration section101corrects 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 section103forms 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 section101. The transmission section including configuration section101, coding section106, and modulating section109transmits a notification signal including the information related to the correction of the CIF table to terminal200.

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 memory102may 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 ofFIG.4B). Here, in case of adding CC1 and CC4, CC1 may be configured as the PDCCH CC of CC1 and CC4, and CIF code points 1 and 2 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.

Embodiment 2

In Embodiment 2, 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 2 are common to Embodiment 1, and will therefore be described usingFIGS.2and3.

When adding a CC, configuration section101of base station100according to Embodiment 2 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 2, configuration section101basically 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 section101deletes 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 section207of terminal200corrects (updates) the CIF table held by PDCCH receiving section208, based on the added or deleted CC number received from configuration information receiving section205, the CIF code point and the CFI value allocated to the CC.

Operations of base station100and terminal200having the above mentioned configurations will be described.

In the present embodiment, base station100and terminal200share 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=1, 2, and 3 are allocated, and then the information related to the allocated CIF code points is notified to terminal200from base station100. 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 terminal200of the information related to the CC in case of adding a CC, base station100also notifies terminal200of the number of allocated code points. This notification format is illustrated inFIG.7.

FIG.6illustrates how the CIF table varies when CCs are added. In particular,FIG.6illustrates how the CIF table varies when CC1 and CC4 are sequentially added to terminal200performing communication using CC2 and CC3. Here, it is assumed that the CC used to transmit a PDCCH is CC2.

As illustrated inFIG.6, when adding CC1, configuration section101allocates 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=1, 2, and 3 are prepared here, different CIF code points are allocated to the three pairs of CC1 and CFIs=1, 2, and 3, respectively. In the state ofFIG.6A, since CIF code points 5 to 8 are unused, three of these CIF code points are allocated to the three pairs of CC1 and CFIs=1, 2, and 3, respectively. Here, in particular, the CIF code point with a smaller number is preferentially allocated in ascending order.

As illustrated inFIG.6C, when adding CC4, configuration section101allocates 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=2 is allocated to CIF code point 8 which is unused. Meanwhile, instead of the pair of CC3 and CFI=3, the pair of CC4 and CFI=1 is allocated to CIF code point 4 which has been previously allocated to the pair of CC3 and CFI=3. That is, the pair of CC3 and CFI=3 is overwritten by the pair of CC4 and CFI=1.

That is, depending on conditions, configuration section101may 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 section101can 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=3 is overwritten inFIG.6C, the pair of CC3 and CFI=1 or the pair of CC3 and CFI=2 may be overwritten instead.

Configuration section101can 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=1 and 2 are selected from three pairs of CC4 and CFIs=1, 2, and 3 inFIG.6C, two pairs of CC4 and CFIs=2 and 3 may be selected or two pairs of CC4 and CFIs=1 and 3 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, 2 or 3) 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, 1 or 2, 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, 1 or 3 may be selected as the CFI value. Then, the information related to the selected pair is separately notified.

FIG.7illustrates the notification formats of the CIF code points. InFIG.7, 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 inFIG.7, 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 ofFIG.6C, it is possible to separately allocate CIF code point 4 to the pair of CC3 and CFI=3, or to automatically return to the table ofFIG.6Bwhich 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 terminal200of pairs in case of allocating only pairs of the CC to be added and some of the CFI values to CIF code points.

(Variation 1)

In variation 1, the CIF table associates the CIF code points with the CFI values, respectively, in advance. That is, in the example ofFIG.8, the CFI values are fixedly allocated to CIF code points 2 to 8, 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 section101can be simplified. Also, when base station100notifies terminal200of a CIF code point, the corresponding CFI value is specified. For this reason, base station100need not separately notify terminal200of the CFI value.

(Variation 2)

Variation 2 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 inFIG.7.

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=2, 2, and 3, respectively, this means that the CFI values corresponding to CIF code points=2 and 3 are 1 and 3, respectively. Also, in a case where the three notification fields report CIF code points=2, 3, and 3, respectively, this means that the CFI values corresponding to CIF code points=2 and 3 are 1 and 2, respectively. Also, in a case where the three notification fields report CIF code points=2, 3, and 2, respectively, this means that the CFI values corresponding to CIF code points=2 and 3 are 2 and 3, 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 3)

Variation 3 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 ofFIG.7is 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 6 and 8 are to be associated with CFIs=2 and 3, respectively, three notification fields store CIF code points=1, 6, and 8, respectively. Here, when the added CC and the CC used to transmit a PDCCH are the same, CIF=1 is used as a rule regardless of the notification content of the CIF code point. By this means, when CIF=1 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=1, 6, and 8, respectively, only CIF code points 6 and 8 are valid. Thus, CFI values=2 and 3 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 3

Embodiment 3 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.

The basic configurations of a base station and a terminal according to Embodiment 3 are common to Embodiment 1, and will therefore be described usingFIGS.2and3.

Memory102of base station100according to Embodiment 3 stores a group of CIF table formats.FIG.9illustrates an example of the group of the CIF table formats. As illustrated inFIG.9, 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 terminal200, configuration section101selects and configures which table format to use from a plurality of CIF table formats stored in memory102. The information of this configured CIF table format is notified to terminal200as configuration information. This table format is configured and notified to terminal200when terminal200transitions 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 terminal200, configuration section101notifies terminal200of the subset number of the CIF table format that is configured in advance every terminal200and that is allocated to the CC to be added. By this means, terminal200can associate the additional CC with all CIF code points included in the notified subset number.

CIF table configuring section207of terminal200according to Embodiment 3 configures the table format notified from the base station in PDCCH receiving section208. Also, CIF table configuring section207updates the CIF table by the subset number notified in case of CC addition.

Operations of base station100and terminal200having the above mentioned configurations will be described referring toFIG.9.

As illustrated inFIG.9, 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 1, each subset includes three CIF code points. In each of table formats 2 to 4, 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 1 differs from table formats 2 to 4, in the number of the CIF code points included in the subsets. Also, table formats 2 to 4 differ each other in the combination of CFI values included in the subsets. That is, in table format 2, the combination of the CFI values included in the subsets is 1 and 2, while the combination of the CFI values included in the subsets is 2 and 3 in table format 3, and the combination of the CFI values included in the subsets is 1 and 3 in table format 4.

In each table format, the subset including CIF=8 includes only one CIF. For CIF=8, the largest CFI value is selected and configured from CFI values allocatable for each table format. That is, as the CFI value, 2, 3 and 3 are respectively configured in table formats 2, 3 and 4. 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 terminal200, as long as the first OFDM symbol to which a data signal (PDSCH) addressed to the terminal200is 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=8, the number of OFDM symbols in a control channel region of a certain CC often exceeds the CFI value configured in CIF=8. 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=8, the largest CFI value is selected and configured from the CFI values allocatable in each table format.

For each terminal200, configuration section101selects and configures which table format to use, from a plurality of CIF table formats stored in memory102, and then notifies each terminal200of the configuration information.

Configuration section101configures table format 1 for the terminal capable of receiving signals using up to three CCs, and configures table formats 2 to 4 for the terminal capable of receiving signals using equal to or more than four CCs. Also, configuration section101configures table formats 2 to 4 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 1 for the terminal without the requirement of high speed transmission.

Also, configuration section101can configure the table format on a cell unit basis. For example, configuration section101assigns and configures table formats 2 to 4 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 1 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 section101configures 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, 2 and 3) is allocated to each subset is configured in such a cell.

In contrast, in a cell with a small cell radius, configuration section101configures 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, 1 and 2) 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 section101configures the table format in which both a large CFI value and a small CFI value (for example, 1 and 3) are allocated to each subset.

As described above, for each terminal200, configuration section101selects and configures which table format to use, from a plurality of CIF table formats stored in memory102. Also, a plurality of the CIF table formats stored in memory102differ 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 section101only has to notify each terminal200of 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 5 as illustrated inFIG.10may be defined in advance in memory102. 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 1 is described as a format for three CCs and table formats 2 to 4 are each described as a format for four CCs or five CCs inFIG.9. It is, however, possible to separately define, as a format for four CCs, the table format in which subset 1 includes CIFs=2, 3, and 4, subset 2 includes CIFs=5 and 6, and subset 3 includes CIFs=7 and 8. By this means, it is possible to maximize the number of CFIs that can be notified every CC.

[Other Embodiments]

(1) The above embodiments have explained that a PDCCH of each CC is used to report a CFI of the CC, while a PDCCH of a certain CC is used to report a CFI of another CC. However, the present invention is not limited to this, and the PDCCH of each CC may not need to report the CFI of the CC. That is, the configuration in which only the PDCCH of a certain CC reports the CFI of another CC is also possible. In this case, when a CC used to transmit a PDCCH including information of a CC to be added at the moment of CC addition is the same as the CC to be added, terminal200considers that the PDCCH does not include any CIF and thus determines that no CIF code point is notified or that the CIF code point is notified, but the allocation is invalid. Meanwhile, when the CC used to transmit the PDCCH including the information of the CC at the moment of CC addition is different from the CC to be added, terminal200considers that the PDCCH includes a CIF and thus determines that the CIF code point is notified. In this case, there is no need to separately report the information indicating whether or not the CIF is included, every PDCCH. Also, even in the system performing operations with a CIF and without the CIF every CC, when adding a CC to a UE CC set, terminal200only needs to determine whether the CC to be added performs CIF notification or the CC different from the CC to be added performs the CIF notification. Here, terminal200only has to operate commonly in both cases. Thus, it is possible to simplify the system and the terminal.

(2) The above embodiments have explained that RRC signaling is performed at addition or deletion of the UE CC set. However, the present invention is not limited to this and is applicable even when more dynamic control than RRC signaling is performed. For example, it is also possible to designate the CIF code point even when a MAC header or a PDCCH reports the addition or deletion of the CC (that is, CC activation/deactivation).

(3) The above embodiments have explained that one PDCCH is transmitted per CC. However, the present invention is not limited to this, and two or more PDCCHs may be transmitted per CC. In case of this configuration, at the addition of a CC, CIF code points are allocated to two ore more PDCCH CCs included in one CC.

(4) The above embodiments have explained that CFI indicates a control channel region. However, the present invention is not limited to this, and the CFI may be the information indicating the first OFDM symbol to which data is mapped. For example, while CFI=2 holds true in a certain CC (that is, up to two OFDM symbols are used for control channel), the first OFDM symbol number to which data for a certain terminal200is mapped may be 4. For example, even in a case where only CFI=3 can be notified to a certain terminal200in a certain CC, it is possible to configure a small control channel region (for example, two OFDM symbols) when the amount of control channel of the CC is small.

(5) Although a case where the number of bits in the CIF is 2 bits and 3 bits has been described in the above, another number of bits is also possible. Also, a case where a cell or a terminal uses a different number of bits may be possible.

(6) Although an example to report the CI and CFI in the CIF has been described in the above, the present invention is applicable for reporting information other than the CFI.

(7) Although the above embodiments have described allocation of downlink CC, the techniques described in embodiments are also applicable for allocation of uplink CC. Also, a CC may be added or deleted in a pair of uplink and downlink, or may be added or deleted in uplink and downlink separately.

(8) The above described UE CC set may be referred to as “UE DL CC set” for a downlink CC and “UE UL CC set” for an uplink CC.

(9) The above mentioned PDCCH format may be referred to as “DCI (Downlink Control Information) format.”

(10) The above mentioned “carrier aggregation” may also be referred to as “band aggregation.” Furthermore, discontinuous frequency bands may be aggregated in the carrier aggregation.

(11) Although the above mentioned “component carrier” has been defined as the band having a width of maximum 20 MHz and the basic unit of communication bands, the component carrier may be defined as follows. A “component carrier” in downlink (hereinafter referred to as “downlink component carrier”) may be defined as the band divided by downlink frequency band information in the BCH broadcasted from a base station, or the band defined by a bandwidth where a physical downlink control channel (PDCCH) is placed in the frequency domain in a distributed manner. Also, a “component carrier” in uplink (hereinafter referred to as “uplink component carrier”) may be defined as the band divided by uplink frequency band information in the BCH broadcasted from a base station, or the reference unit in the communication band which is equal to or below 20 MHz and includes a PUCCH near the center and PUCCHs at both end parts. Also, in 3GPP LTE, “component carrier(s) (CC)” may be expressed as “Component Carrier(s)” in English. Also, “component carrier(s)” may be referred to as “component band(s).” Furthermore, “Component Carrier” may be defined by a physical cell number and a carrier frequency number, and may be referred to as “cell.”

(12) The PDCCH may be set to be always transmitted by the primary component carrier. Here, the primary component carrier may be the component carrier determined by a system (for example, the component carrier used for transmitting an SCH or PBCH), a common component carrier among terminals200may be set for each cell, or a different component carrier may be set for each terminal200.

(13) Although the above embodiments have described an example where the present invention is implemented with hardware, the present invention can be implemented with software.

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 LSI,” 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.

The disclosure of Japanese Patent Application No. 2010-030267, filed on Feb. 15, 2010, including the specification, drawings and abstract, is incorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

The transmission apparatus and the transmission method of the present invention are useful as an apparatus and a 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.

REFERENCE SIGNS LIST

100Base station101Configuration section102Memory103Control section104PDCCH generating section105,106,107Coding section108,109,110,210,211Modulating section111Allocation section112PCFICH generating section113Multiplexing section114,214IFFT section115,215CP adding section116,216RF transmitting section117,201RF receiving section118,202CP removing section119,203FFT section120Extraction section121IDFT section122Data receiving section200Terminal204Demultiplexing section205Configuration information receiving section206PCFICH receiving section207CIF table configuring section208PDCCH receiving section209PDSCH receiving section212DFT section213Mapping section