JP2011097616A - Terminal device, and radio communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a terminal device of a communication system which can simultaneously transmit control channel having a large number of aggregations, i.e., control information including a large number of redundant bits to a plurality of terminals. <P>SOLUTION: The terminal device performs communication with a base station for transmitting a control signal using a control channel formed by coupling a plurality of control channel elements including a plurality of sub-carriers. The terminal device is configured so that out of a plurality of control channel candidate groups each including a plurality of control channel candidates consisting of connection of a plurality of control channel elements, a first control channel candidate group corresponding to its own device is observed to detect a control channel corresponding to the own device, and the first control channel candidate group includes a control channel candidate which is common with a second control channel candidate group corresponding to another terminal device out of the plurality of control channel candidate groups. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention is composed of at least one base station and one or more terminals belonging to the service area covered by the base station, and the base station uses a plurality of communication channel scheduling information (communication channel assignment result to each terminal). The present invention relates to a communication system that separately notifies a terminal through a control channel.

Currently, the standardization body ^{3GPP (3 rd Generation Partnership Project)} , and standardized working of a wireless network adopting a new radio system is performed under the name of LTE (Long Term Evolution). In this radio system, OFDMA (Orthogonal Frequency Division Multiple Access) is adopted in the downlink (base station → terminal direction), and a plurality of communication channels and control channels are defined in a certain frequency bandwidth. This is shown in FIG. The operation of assigning a radio channel to a terminal, so-called scheduling, is performed in units of subframes consisting of 14 OFDM symbols, and up to the first three OFDM symbols can be used as a control signal region in the unit, and the remaining OFDM symbols Can be used as a data signal region.

  The 3OFDM symbols are not always limited to use as a control signal region. That is, it is recognized that only one OFDM symbol or only two OFDM symbols are used as the control signal region, and in this case, the remaining 13 or 12 OFDM symbols can be used as the data signal region.

  Note that the modulation symbols (composed of one subcarrier and one OFDM symbol) written as R1 to R4 in FIG. 8 are places where a prescribed bit pattern, a so-called pilot signal enters. In LTE, this is called “Reference Signal”. This Reference Signal is a prescribed signal pattern, and the transmission path state can be estimated by the change of the signal when it is received, and is finally used for the demodulation operation of the control signal and the data signal. Therefore, when this modulation symbol is used for transmission of a pilot signal, this modulation symbol cannot be used for transmission of a control signal or a data signal. The numerical parts R1 to R4 are mapped in a one-to-one relationship with the numbers of a plurality of transmission antennas of the base station, and R1 to R4 are reference signals transmitted from four different antennas. There is a case where the number of transmission antennas is less than 4, and in this case, the reference signal is not transmitted to the portion of Rn (n = 2, 3, 4) corresponding to the non-existing antenna, and the data signal or control is performed. A signal can be transmitted.

  Here, the contents of the control signal described above include which part of the downlink data signal area (see FIG. 8) is allocated to the target terminal or the uplink (terminal → base station direction) data signal. Information indicating which part of the area (not shown) is allocated to the target terminal is described. Therefore, each terminal must periodically monitor the control signal area in order to know whether it has been assigned to itself or if it has been assigned, which part of the data signal area has been assigned. In addition, since control signals for a plurality of terminals are simultaneously placed in the control signal area, the terminal needs to receive a plurality of control channels and detect a control signal addressed to itself among them. Each terminal is notified in advance of a plurality of control channels (control channel candidates) to be received from the network side (the candidates may be different for each terminal). Although the control signals described so far are in the physical layer, the control signal signaling protocol in a higher layer (Higher Layer) than the physical layer is used for notification of control channel candidates from the network side.

  FIG. 9 shows the definition of control channel candidates. In LTE, a unit called “Control Channel Element” (hereinafter referred to as CCE) is defined, and one or two or more of these units are combined to form one control channel. In the example of FIG. 9, the number of control channel candidates to be received by a certain terminal is 11. Among these, candidates 1 to 6 constitute a control channel with one CCE, candidates 7 to 9 constitute two CCEs, and candidates 10 to 11 constitute a control channel with three CCEs. The terminal monitors a plurality of control channel candidates designated from the network side. Hereinafter, a plurality of control channels (a group of a plurality of control channel candidates designated from the network side to be monitored) that the terminal must monitor will be referred to as a “control channel candidate set”.

  Next, an operation when the base station transmits a control signal to the terminal in LTE will be described. When the base station sends a control signal to the terminal, the CRC bit for error check of the control signal is further multiplied by the terminal ID, and the encoded control signal is placed on any control channel in the control channel candidate set. The terminal decodes all control channel candidate sets notified from the network, and finally performs a CRC check using the terminal ID of its own station, and acquires the only control channel determined to be error-free as the control channel addressed to itself. To do. As a reference for selecting a control channel on which a base station carries a control signal, there is mainly the quality of a radio transmission path. For example, when the target terminal is located at a location far from the base station, the transmission path quality is poor and transmission errors are likely to occur. Therefore, in such a case, a robust error correction code for preventing errors is used. Conversely, when the target terminal is located near the base station, the transmission path quality is good and transmission errors are unlikely to occur, so there is no need to use a strong error correction code. Usually, when the strength of the error correction code is changed, the allowable number of redundant bits generated by error correction coding is changed. That is, when the strength is increased, many redundant bits are required. As the redundant bits increase, the encoded control signal bits cannot be accommodated in 1 CCE, and 2CCE, 3CCE, and multiple CCEs are required. In other words, the lower the wireless transmission path quality, the greater the required number of CCEs.

  FIG. 10 is a diagram illustrating a definition example of a control channel candidate set. Currently, the definition of the control channel candidate set is not determined in 3GPP, but the control channel candidate set having the configuration shown in FIG. As shown in FIG. 10, in the proposal proposed in Non-Patent Document 1 below, CCE0 to CCE7 are determined as candidates for configuring a control channel with 1 CCE, and a control channel composed of a plurality of CCEs is configured. Includes only those configurable from CCE0 to CCE7 in the control channel candidate set. Here, the configuration of a plurality of CCEs to form one control channel is referred to as “aggregation” here.

“3GPP Contribution R1-0772607” May7-11, 2007

  Non-Patent Document 1 includes an example indicating a control channel candidate set (see FIG. 10). However, when the technique described in Non-Patent Document 1 is applied, the following problems are expected to occur.

  For example, when there are more terminals than the number of control channel candidate sets in a communication system that employs the configuration shown in Non-Patent Document 1, the following problems may occur. FIG. 11 is a diagram for explaining this problem, and shows how a control channel candidate set is allocated to each terminal. Specifically, there is shown an example in which four control channel candidate sets S0 to S3 exist on the system and each is assigned to each terminal. That is, in this example, terminal 0 to terminal 3 are assigned to different control channel candidate sets (sets S0 to S3), respectively, and terminal 4 is assigned to set S0. There is a problem here. In the example shown in FIG. 11, each control channel candidate set includes only one control channel of 8 aggregation (control channel obtained by aggregating 8 CCEs). Therefore, if both terminal 0 and terminal 4 are located far from the base station and 8 aggregation is required as a control channel, a control signal cannot be sent to these two terminals simultaneously. was there.

  Conventionally, the transmission path quality of each terminal has not been considered. For example, the definition of the control channel candidate set as shown in FIG. 10 includes all of the aggregation levels without CCE aggregation, those with CCE aggregation, regardless of the transmission path quality of each terminal. In this case, according to the definition of the control channel candidate set as in this example, the terminal that is far from the base station is not used even if the control signal is always sent on the aggregated control channel. Decoding operations are also performed for channel candidates (those without aggregation and those with a small number of aggregations), and there is a problem that wasteful processing time is required and power consumption is increased.

  In addition, there is another problem. This problem will be described with reference to FIGS. 12-1 to 12-3. These figures show the state of the control channel candidate set definition accompanying the change of the control signal area. As described above, in the LTE system, the control signal region changes from 1 OFDM symbol to 3 OFDM symbols. This means that the number of CCEs that can be defined in the control signal region changes, and accordingly, the definition of the control channel candidate set also changes. In the example of FIGS. 12-1 to 12-3, when the control signal area is as large as 3 OFDM symbols, the number of CCEs can be defined large, and the number of control channel candidate sets can also be defined (in the case of FIG. 12-1). Equivalent). On the other hand, when the control signal area is as small as 1 OFDM symbol, the number of CCEs that can be defined is small, and only one control channel candidate set is defined (corresponding to the case of FIG. 12-3). When such a control signal region is variable, conventionally, the control channel candidate set must be individually notified from the network side to the terminal for each OFDM symbol number case in the control signal region. There has been a problem that the amount of control signal signaling in (a layer higher than the physical layer) increases.

  The present invention has been made in view of the above, and is a control channel having a large number of aggregations for a plurality of terminals, that is, a terminal device of a communication system capable of simultaneously transmitting control information including many redundant bits, and a radio The purpose is to obtain a communication method.

  It is another object of the present invention to provide a communication system terminal device and a wireless communication method that perform efficient control channel transmission / reception operations in consideration of transmission path quality.

  Another object of the present invention is to obtain a terminal device and a wireless communication method of a communication system that reduce the amount of signaling when transmitting / receiving control information.

  In order to solve the above-described problems and achieve the object, the present invention communicates with a base station that transmits a control signal using a control channel configured by combining a plurality of control channel elements including a plurality of subcarriers. A plurality of control channel candidates each including a plurality of control channel candidates each formed by combining a plurality of control channel elements, and observing a first control channel candidate group corresponding to the own device from the plurality of control channel candidate groups. The first control channel candidate group is controlled in common with a second control channel candidate group corresponding to another terminal device among the plurality of control channel candidate groups. It includes channel candidates.

  According to the present invention, it is possible to avoid with high probability a situation in which control channel selection flexibility is increased in a base station, and control signals cannot be sent simultaneously to a plurality of terminals located far from the base station. In other words, it is possible to simultaneously transmit a control channel having a large number of aggregations to a plurality of terminals (a control channel using an extension region generated by aggregating unit regions of a predetermined number or more). .

FIG. 1 is a diagram illustrating an example of a control channel candidate set used in the communication system according to the first embodiment. FIG. 2 is a diagram illustrating an example of functional configuration blocks included in a base station and a terminal that perform High Layer signaling. FIG. 3 is a diagram illustrating an example of functional configuration blocks included in a base station and a terminal that transmit and receive control signals in the physical layer. FIG. 4 is a diagram illustrating an example of a control channel candidate set used in the communication system according to the second embodiment. FIG. 5-1 is a diagram illustrating an operation example in which the terminal according to Embodiment 3 identifies a control channel candidate set. FIG. 5-2 is a diagram illustrating an operation example in which the terminal according to Embodiment 3 identifies a control channel candidate set. FIG. 5-3 is a diagram illustrating an operation example in which the terminal according to Embodiment 3 identifies a control channel candidate set. FIG. 6 is a diagram illustrating an example of a control channel candidate set. FIG. 7 is a diagram illustrating a configuration example of the CCE. FIG. 8 is a diagram for explaining a conventional communication system. FIG. 9 is a diagram for explaining a conventional communication system. FIG. 10 is a diagram for explaining a conventional communication system. FIG. 11 is a diagram for explaining a problem in the conventional communication system. FIG. 12A is a diagram for explaining a problem in the conventional communication system. FIG. 12-2 is a diagram for explaining problems in the conventional communication system. FIG. 12C is a diagram for explaining a problem in the conventional communication system.

  Embodiments of a communication system and a base station according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
Before describing the operation of each component in the communication system of the present embodiment, first, a method of sharing the same control channel with different control channel candidate sets in the communication system of the present embodiment will be described. FIG. 1 is a diagram illustrating an example of a control channel candidate set used in the communication system according to the present embodiment. The communication system of the present embodiment is characterized in that control channels having a large number of aggregations are shared among a plurality of control channel candidate sets (simultaneously assigned to a plurality of terminals).

  In FIG. 1, different control channel candidate sets are distinguished by different hatching patterns (in this example, S0: left oblique stripe, S1: horizontal stripe, S2: right oblique stripe, S3: vertical stripe of the control channel candidate set). However, the hatching pattern of the control channel shared from a plurality of channel candidate sets is represented by overlapping each pattern. At the 4 aggregation level (when the number of aggregation is 4), a total of 8 control channel candidates having index numbers 0 to 3 are shared by S0 and S2 of the control channel candidate set (S0 and S2). And index numbers 4 to 7 are shared by the control channel candidate sets S1 and S3. In addition, in the 8 aggregation level, a total of 8 control channel candidates in total are shared by S0 to S3 of the control channel candidate set.

  Then, if each control channel candidate set shown in FIG. 1 is used, a plurality of terminals are assigned to a specific control channel set, and the transmission path quality between these terminals and the base station is poor, that is, a plurality of terminals. Control information can be transmitted to a plurality of terminals using 8 aggregation control channel candidates even when the terminal needs to receive control information (control channel) using 8 aggregation control channel candidates. . This is because four control channel candidates for eight aggregations are shared by all control channel candidate sets (S0 to S3), and the control channel candidates for eight aggregations (8 This is because four control channel candidates (obtained by aggregating two CCEs) are secured.

  For example, in the system to which the control channel candidate set shown in FIG. 1 is applied, four terminals (terminal 0 to terminal 3) are assigned to different control channel candidate sets (sets S0 to S3), respectively, and the terminal 4 Is assigned to set S0, there are four 8-aggregation control channel candidates for each of the five terminals (four control channel candidates for each of the control channel candidate sets are four). To do). Therefore, the flexibility of selecting a control channel when sending a control signal to a terminal increases, and a situation in which a control signal cannot be sent simultaneously to a plurality of terminals located far from the base station can be avoided with high probability. .

  Next, the operation (high-layer processing) when the base station of the present embodiment notifies the terminal of a control channel candidate set (control channel information to be monitored) will be described. For example, if a rule that “any control channel candidate set includes M control channels at each aggregation level (including no aggregation)” is determined in advance, the base station uses the higher layer signaling to set the set number. It is only necessary to notify (control channel candidate set number), and each terminal can identify a control channel candidate (control channel to be monitored) from the notified set number. To give a specific example, a terminal that has been notified of set Si from the base station has M consecutive control channel candidates from the index control channel corresponding to the calculation result of “M * i” at each aggregation level. Judge that there is. More specifically, for example, in the system to which the control channel candidate set of FIG. 1 is applied, if M = 4 is determined in advance, the terminal notified as set S1 is index 4 (= M * i = 4 × It is determined that four control channels from the control channel corresponding to 1), that is, control channels from index 4 to index 7, are control channel candidates given to the own station at each aggregation level. As in the example of the 8-aggregation level in FIG. 1, when the number of control channels is smaller than “M * i”, the index is returned to the control channel with index 0 and indexed. Here, the case where M common to all the aggregation levels is used has been described, but M may be set to a different value for each level.

  FIG. 2 is a diagram illustrating an example of a functional configuration block for realizing the above-described signaling (notification of a control channel candidate set from the base station to the terminal) included in the base station and the terminal. As shown in FIG. 2, the base station has a configuration for performing higher layer signaling (notification of a set number to the terminal), a control channel candidate set determination unit 11, a high layer (high layer) signaling transmission unit 12, and A wireless transmission unit 13 is provided. On the other hand, the terminal includes a radio reception unit 21, a high layer signaling reception unit 22, and a control channel candidate set analysis unit 23.

  In the base station, the control channel candidate set determination unit 11 determines a control channel candidate set to be assigned to the target terminal. Information determined by the control channel candidate set determination unit 11 (control channel candidate set) is converted into a signaling protocol-defined format by the higher layer signaling transmission unit 12 and passed to the radio transmission unit 13. The wireless transmission unit 13 converts the received information into a wireless section transmission format and transmits it to the terminal. The information sent by the radio signal is received by the radio receiving unit 21 of the terminal, and is sent to the high layer signaling receiving unit 22 after removing header information and the like necessary for radio transmission. The higher layer signaling receiver 22 further removes header information on the protocol from the received information and passes it to the control channel candidate set analyzer 23. The control channel candidate set analysis unit 23 uses the received information to define a rule defined in advance in the system (for example, the above-described rule that any control channel candidate set includes M control channels at each aggregation level). To determine the position of a control channel candidate.

  Next, operations when the base station and the terminal according to the present embodiment transmit and receive control signals in the physical layer will be described. In the following description, it is assumed that the control channel candidate set notification from the base station to each terminal has already been performed.

  FIG. 3 is a diagram illustrating an example of a functional configuration block for realizing transmission / reception of a control signal in a physical layer included in a base station and a terminal. The base station includes a buffer unit 31, a scheduler unit 32, a data encoding unit 33, a control channel table 34, a control signal encoding unit 35, a wireless transmission unit 36, and a wireless reception unit 37. On the other hand, the terminal includes a radio reception unit 41, a signal separation unit 42, a control signal decoding unit 43, a control channel candidate table 44, a data decoding unit 45, a transmission path quality measurement unit 46, and a radio transmission unit 47.

  In the base station, the buffer unit 31 stores data to be transmitted to the terminal. The scheduler unit 32 monitors the data storage status of the buffer unit 31 and selects a terminal that transmits data at the current transmission timing from among a plurality of candidate terminals under its control. The scheduler unit 32 that has selected the terminal instructs the data encoding unit 33 to encode the target data, and refers to the control channel table 34 to select control channel candidates (control channel candidate set) on which the control signal of the target terminal is placed. know. Note that information on the control channel candidate set notified to each base station is registered in the control channel table. As described above, in this example, since the control channel candidate set notification from the base station to each terminal has already been performed, the control channel table 34 includes correspondence information (correspondence relationship) between each subordinate terminal and each control channel candidate set. ) Is registered.

  The scheduler unit 32 selects a control channel from among a plurality of control channel candidates corresponding to the selected terminal (scheduling target terminal). At this time, the wireless transmission path quality information for the target terminal and the presence of other terminals that simultaneously transmit control signals are considered. When the control channel is determined (selected), the scheduler unit 32 sends control information to the control signal encoding unit 35 together with the terminal ID (ID of the target terminal), transmission path quality information (transmission path quality with the target terminal), and Control channel information (information of selected control channel candidates) is notified. The control signal encoding unit 35 encodes the control information using the terminal ID and the transmission path quality information, and passes it to the wireless transmission unit 36 together with the control channel information. The wireless transmission unit 36 transmits control information through the instructed control channel, and also transmits encoded data through the data channel assigned for data. In addition to receiving data from the terminal, the wireless receiving unit 37 receives transmission path quality information reported from the terminal, and notifies the scheduler unit 32 of it.

  A signal transmitted from the base station to the terminal is received by the wireless reception unit 41 of the terminal and passed to the signal separation unit 42. The signal separation unit 42 separates the received signal received into a control signal and a data signal and sends them to the respective decoding units. The control signal decoding unit 43 recognizes the control channel candidate of the own station from the control channel candidate table 44 and executes a decoding process for each recognized control channel candidate. Of the control channel candidates that have been subjected to decoding processing, the control channel that can be determined to be addressed to itself by CRC check knows the frequency and modulation scheme to which the data signal is assigned from the contents of the control signal. Information on these frequencies and modulation schemes is sent to the data decoding unit 45. The data decoding unit 45 cuts out the corresponding part from the data signal according to the notified frequency information and modulation method, and performs data decoding. Further, the transmission path quality measurement unit 46 measures the signal power of the received signal from the base station, and converts the measured value into a prescribed format. The converted power measurement value is periodically notified to the base station via the wireless transmission unit 47 as transmission path quality information.

  As described above, in the communication system according to the present embodiment, the base station assigns control channel candidates obtained by aggregating (aggregating) a certain number or more of CCEs to a plurality of control channel candidate sets, and each terminal is a base station. Each control channel candidate in the control channel candidate set designated by is monitored. As a result, each control channel candidate set includes a plurality of control channel candidates having a large number of aggregations, which increases the flexibility of control channel selection in the base station. As a result, it is possible to avoid with high probability a situation in which control signals cannot be sent simultaneously to a plurality of terminals that are located far from the base station. That is, it is possible to simultaneously transmit control channels having a large number of aggregations to a plurality of terminals.

Embodiment 2. FIG.
Next, the communication system according to the second embodiment will be described. Note that the configurations of the base station and terminal of the present embodiment are the same as those of the first embodiment (see FIGS. 2 and 3). In Embodiment 1, a communication system capable of transmitting a control channel with a large number of aggregations to a plurality of terminals has been described. In the present embodiment, a communication system that performs control in consideration of transmission path quality is further described. To do. FIG. 4 is a diagram for explaining a method for determining a control channel candidate set based on transmission path quality. As shown in FIG. 4, the communication system according to the present embodiment uses a control channel candidate set composed of control channel candidates with a small number of aggregations and a control channel candidate set composed of control channel candidates with a large number of aggregations. The station determines a control channel candidate set to be assigned to each terminal based on the distance to the terminal. In this example, a control channel candidate set that is assigned to a terminal close to the base station (a terminal that is assumed to have good transmission path quality) includes a control channel without aggregation and a control channel with two aggregations, and is based on four aggregations and eight aggregations. A control channel candidate set to be assigned to a terminal far away from the base station (a terminal that is presumed to have poor transmission path quality) includes a control channel. Although not shown, control channel candidates with a large number of aggregations are shared among a plurality of control channel candidate sets as in the first embodiment. That is, in the communication system according to the present embodiment, a control channel candidate set is configured with a large number of aggregations (four or more) and a small number of aggregations, and a terminal that is far from the base station has a large number of aggregations. On the other hand, a terminal close to the base station is assigned to a control channel candidate set having a small number of aggregations.

  Therefore, the base station according to the present embodiment determines the distance (“near / far”) from each terminal using path loss or CQI (Channel Quality Indicator), and sets the terminal as a control channel candidate set based on the determination result. Assign to. In the base station, the control channel candidate set determining unit 11 (see FIG. 2) performs a process of assigning the terminal to the control channel candidate set based on the determination result.

  The path loss is the difference between the power of the signal transmitted by the base station (transmission power value) and the signal power (reception power) when the terminal receives the signal. That is, it is information obtained by subtracting the reception power value at the terminal of the signal from the transmission power value when the base station transmits the signal. This is obtained when the terminal reports the received power value to the base station and the base station calculates the path loss, or the base station notifies the terminal of the transmission power value and the terminal calculates the path loss. If this value is large, it can be determined that the distance from the base station is small, and if it is small, it is close to the base station. Note that, when the path loss is calculated in the base station, for example, the scheduler unit 32 calculates the path loss. On the other hand, when calculating the path loss at the terminal, for example, the transmission path quality measurement unit 46 calculates the path loss.

  CQI is already defined in LTE, and the terminal measures the transmission path quality, converts the measured value into a defined index (CQI), and reports it to the base station. This measurement value is the ratio of the power of the signal that should be received and the power of the signal that is causing interference including noise. If this value is large, it can be judged that the quality state is good, and if it is small, the quality state is bad, and it can be replaced with information on the distance between the base station and the terminal (“near / far”). In the terminal, the transmission path quality measurement unit 46 measures the transmission path quality and converts it into CQI.

  Whichever path loss or CQI is used, the obtained path loss or CQI is finally passed to the control channel candidate set determination unit 11 of the base station.

  As described above, in this embodiment, the control channel candidate set to be allocated to the terminal is determined based on the distance between the base station and the terminal or the transmission quality in the terminal. Only the aggregation level that is truly used, that is, only an appropriate control channel candidate is assigned to each terminal, so that a useless decoding operation in the terminal is omitted. As a result, the processing time and power consumption on the terminal side can be reduced.

  Further, as in the first embodiment, control channel candidates obtained by aggregating (aggregating) a certain number or more of CCEs are shared among a plurality of control channel candidate sets, so that a control channel having a large number of aggregations. It is possible to reduce the processing time and power consumption in the terminal while realizing simultaneous transmission to the plurality of terminals.

  In the above description, a case has been described in which there are two types of control channel candidate sets defined based on quality information (near / far from the base station), but three or more types may be used. When two or more types are defined, the number of control channel candidates constituting each control channel candidate set may be the same or different. When the number is different, for example, the number of control channel candidates is adjusted according to the distribution of terminals. That is, when there are many terminals far from the base station, the number of control channel candidates included in the control channel candidate set defined for terminals close to the base station is the number of control channel candidates included in the control channel candidate set defined in them. More than that. In the present invention, the number of control channel candidates included in each control channel candidate set is not particular.

Embodiment 3 FIG.
Next, Embodiment 3 will be described. Note that the configurations of the base station and terminal of the present embodiment are the same as those of the first embodiment (see FIGS. 2 and 3). In this embodiment, a communication system is described in which the base station notifies the terminal of the relative number of the control channel candidate set, so that the control channel candidate set can be notified to the terminal even when the control signal area is changed. . The control channel candidate set satisfies the condition described in the first embodiment “control channel candidates obtained by aggregating a certain number of CCEs or more are shared among a plurality of control channel candidate sets”. And

  In the communication system of the present embodiment, the same control channel candidate set number (relative number) that does not depend on the number of OFDM symbols in the control signal region is assigned to the control channel candidate set having the same configuration. , The base station notifies the terminal of the control channel candidate set.

  On the other hand, when the terminal is notified of the control channel candidate set number (S) from the base station, the terminal changes Sm (the number of control channel candidate sets on the system) according to the change of the notified number S and the control signal area. ) To calculate “Sd = S% Sm”. Here, “%” indicates a remainder calculation, and this calculation formula means that the remainder generated by dividing S by Sm is Sd. FIGS. 5A to 5C are diagrams illustrating an example of an operation in which the terminal according to the present embodiment specifies a control channel candidate set.

  An example of operation when the control signal area of the communication system corresponds to 1, 2, 3 OFDM symbols, and the number of control channel candidate sets Sm existing on the system is 1, 2, 4 will be described below. Considering the case where “3” is notified as the control channel candidate set number S from the base station to the target terminal under this condition, the system that does not apply the method for identifying the control channel candidate set shown in the present embodiment When Sm = 1 and Sm = 2, there is no control channel candidate set corresponding to the notified 3 and the terminal cannot specify the set number. On the other hand, in the communication system according to the present embodiment, the set number can be specified by performing the above-described remainder calculation.

  That is, when the control signal area shown in FIG. 5A is 3 OFDM symbols and Sm = 4, the remainder obtained by dividing the notified S = 3 by Sm (= 4) is 3, and Sd = 3 is derived (set) S3 is specified). When the control signal area shown in FIG. 5B is 2 OFDM symbols and Sm = 2, the remainder obtained by dividing the notified S = 3 by Sm (= 2) is 1 (Sd = 1). S1 is specified. When the control signal area shown in FIG. 5A is 1 OFDM symbol and Sm = 1, the remainder obtained by dividing the notified S = 3 by Sm (= 1) is 0 (Sd = 0). S0 is specified.

  An example in which the number of control channel candidate sets is small is shown in FIG. FIG. 6 shows an example when there are two control channel candidate sets (Sm = 2). In this case, if the set number S = 3 is notified, the terminal performs a remainder calculation. Sd = 1 is obtained, and the terminal can specify its own control channel candidate set as S1.

  Further, in the present embodiment, the communication system using the same control channel candidate set as that used in the communication system of the first embodiment has been described. However, the same control channel as that used in the communication system of the second embodiment is shown. Candidate sets can also be used.

  As described above, in the communication system of the present embodiment, the base station notifies the terminal of the relative number of the control channel candidate set, and the terminal that has received the notification of the relative number receives the notified relative number and the control signal area. The control channel candidate set (Sd) is specified based on the control channel candidate set number Sm on the system, which is a parameter that changes in accordance with the change. Also, the control channel candidate set shown in the first or second embodiment is used. Thereby, in addition to the effect obtained in the communication system of the first or second embodiment, the effect that the control channel candidate set can be notified from the base station to the terminal with a small amount of signaling, that is, the amount of signaling in the higher layer is reduced. The effect of is obtained.

  Note that the control channel candidate set notification method shown in the present embodiment is equivalent to virtually assuming that “the number of control channel candidate sets on the system is the same regardless of the number of OFDM symbols”. For example, in the case of Sm = 2 shown in FIG. 5B, considering that the set S0 is also the set S2 and the set S1 is also the set S3, the control channel candidate set is not different from the case of Sm = 4. It can be seen that the number is four.

  Further, in each of the above embodiments, the CCEs constituting the control channel candidates have been described as if they were one unit in which subcarriers that are physically adjacent to each other are grouped together. Absent. That is, a plurality of smaller chunks may be collected to form one CCE. FIG. 7 shows such a state. Considering that the radio environment has deteriorated in a specific small frequency band, when the control channel is transmitted only in the frequency band, the reception quality at the terminal strongly depends on the specific radio environment. However, as shown in FIG. 7, when the CCE is configured by a plurality of small frequency bands separated from each other on the frequency axis, the dependency on the radio environment of the specific frequency band is reduced, and the effect of stabilizing the reception quality is reduced. Expected (frequency diversity effect).

  As described above, the present invention is useful as a communication system in which a base station uses a band that can be used in common among a plurality of terminals and individually transmits control information for each terminal. This is suitable for realizing a communication system capable of simultaneously transmitting control information including a large number of redundant bits to a plurality of terminals having poor performance.

DESCRIPTION OF SYMBOLS 11 Control channel candidate set determination part 12 High Layer signaling transmission part 13, 36, 47 Radio transmission part 21, 37, 41 Radio reception part 22 High Layer signaling reception part 23 Control channel candidate set analysis part 31 Buffer part 32 Scheduler part 33 Data Encoding unit 34 Control channel table 35 Control signal encoding unit 42 Signal demultiplexing unit 43 Control signal decoding unit 44 Control channel candidate table 45 Data decoding unit 46 Transmission path quality measurement unit

Claims (7)

A terminal device that communicates with a base station that transmits a control signal using a control channel configured by combining a plurality of control channel elements including a plurality of subcarriers,
Among a plurality of control channel candidate groups each including a plurality of control channel candidates composed of a combination of a plurality of control channel elements, the first control channel candidate group corresponding to the own device is observed to detect the control channel corresponding to the own device. Configured to
The first control channel candidate group includes a control channel candidate common to a second control channel candidate group corresponding to another terminal device among the plurality of control channel candidate groups. Each of the first control channel candidate group and the second control channel candidate group includes a control channel candidate composed of a combination of a plurality of types of control channel elements, and the first control channel candidate group and the second control channel candidate group The terminal apparatus according to claim 1, wherein the control channel candidates that are commonly included in the channel candidate group include a combination of a predetermined number or more of control channel elements. The control channel elements are numbered consecutively, and the control channel candidates included in the first control channel candidate group and the second control channel candidate group are each a plurality of controls numbered consecutively in a predetermined range. The terminal device according to claim 2, comprising a combination of channel elements. Each of the first control channel candidate group and the second control channel candidate group includes a control channel candidate composed of a combination of 2, 4 or 8 control channel elements, and the first control channel candidate group and The terminal apparatus according to claim 1, wherein the control channel candidates that are commonly included in the second control channel candidate group include a combination of four or eight control channel elements. The control channel elements have a total number of 32 and are assigned consecutive numbers, and the control channel candidates included in the first control channel candidate group and the second control channel candidate group are assigned consecutive index numbers. The terminal device according to claim 4, comprising a combination of control channel elements. The control channel comprises one control channel element;
The terminal apparatus according to claim 1, 2 or 4, wherein the control channel candidates include one consisting of one control channel element. A wireless communication method in a terminal device that communicates with a base station that transmits a control signal using a control channel configured by combining a plurality of control channel elements including a plurality of subcarriers,
Among a plurality of control channel candidate groups each including a plurality of control channel candidates composed of a combination of a plurality of control channel elements, the first control channel candidate group corresponding to the own device is observed to detect the control channel corresponding to the own device. Control channel detection step,
With
The first control channel candidate group includes a control channel candidate common to a second control channel candidate group corresponding to another terminal device among the plurality of control channel candidate groups.

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