JP4750898B2 - Mobile communication system - Google Patents

Description

  The present invention relates to a technical field of wireless communication, and more particularly to a base station, a communication terminal, a transmission method, and a reception method used in a communication system in which frequency scheduling and multicarrier transmission are performed.

  In this type of technical field, it is becoming increasingly important to realize broadband wireless access that efficiently performs high-speed and large-capacity communication. Especially in the downlink, the multicarrier method-more specifically, the Orthogonal Frequency Division Multiplexing (OFDM) method-is promising from the viewpoint of high-speed and large-capacity communication while effectively suppressing multipath fading. Is being viewed. From the standpoint of improving the frequency utilization efficiency and improving the throughput, it is also proposed to perform frequency scheduling in the next generation system.

  As shown in FIG. 1, the frequency band that can be used in the system is divided into a plurality of resource blocks (divided into three in the illustrated example), and each resource block includes one or more subcarriers. A resource block may also be called a frequency chunk. One or more resource blocks are allocated to the terminal. In frequency scheduling, a resource block is preferentially allocated to a terminal with good channel state according to the received signal quality or channel state information (CQI: Channel Quality Indicator) for each resource block of the downlink pilot channel reported from the terminal. Therefore, it is intended to improve the transmission efficiency or throughput of the entire system. The pilot channel is a known signal on the transmission side and the reception side, and may be referred to as a reference signal, a reference signal, a known signal, a training signal, or the like. When frequency scheduling is performed, it is necessary to notify the terminal of the contents of scheduling, and this notification is performed by a control channel (which may be referred to as an L1 / L2 control signaling channel or an accompanying control channel). Furthermore, using this control channel, the modulation scheme (eg, QPSK, 16QAM, 64QAM, etc.) used in the scheduled resource block, channel coding information (eg, channel coding rate, etc.), and hybrid automatic retransmission request ( HARQ: Hybrid Auto Repeat ReQuest) will also be sent. The control channel configuration used in this type of mobile communication system is described in Non-Patent Documents 1, 2, and the like.

  By the way, if a specific resource block common to all terminals is fixedly allocated for the control channel, the channel state of the terminal is generally different for each resource block. May not be received. If the control channel is distributed to all resource blocks, any terminal may be able to receive the control channel with a certain level of reception quality, but it is difficult to expect a higher reception quality. Therefore, it is desired to transmit the control channel to the terminal with higher quality.

  In addition, when adaptive modulation and coding (AMC) control is performed in which the modulation scheme and channel coding rate are adaptively changed, the number of symbols required to transmit the control channel is determined for each terminal. Different. This is because the amount of information transmitted per symbol differs depending on the combination of AMC. In a future system, it is also considered to transmit and receive different signals with a plurality of antennas respectively prepared on the transmission side and the reception side. In this case, the aforementioned control information such as scheduling information may be required for each signal communicated by each antenna. Therefore, in this case, the number of symbols necessary for transmitting the control channel is not only different for each terminal, but may be different depending on the number of antennas used for the terminal. When the amount of information to be transmitted on the control channel differs from terminal to terminal, it is necessary to use a variable format that can flexibly cope with fluctuations in the amount of control information in order to use resources efficiently. There is a concern that the signal processing burden on the reception side and the reception side will increase. Conversely, when the format is fixed, it is necessary to secure a dedicated field for the control channel according to the maximum amount of information. However, in this case, even if a field dedicated to the control channel is vacant, that part of the resource is not used for data transmission, which is contrary to a request for effective use of the resource. Therefore, it is desired to transmit the control channel simply and efficiently.

  However, it does not seem to have been studied enough to transmit the control channel to meet the above various requirements.

3GPP, TR25.848, "Physical layer aspects of UTRA High Speed Downlink Packet Access" 3GPP, TR25.896, "Feasibility study of enhanced uplink for UTRA FDD"

  An object of the present invention is to control a communication terminal in a communication system in which a communication terminal includes many resource blocks including subcarriers having one or more frequency bands allocated to the communication system, and the communication terminal performs communication using one or more resource blocks. It is to transmit the channel efficiently.

This communication system
A mobile communication system that uses an OFDM scheme in the downlink and uses a subframe formed by a plurality of OFDM symbols,
A mapping unit that maps a control channel to a predetermined number of OFDM symbols from the beginning of a subframe, and maps a data channel to an OFDM symbol that is behind the OFDM symbol to which the control channel is mapped;
A transmission unit for transmitting the control channel and the data channel mapped in the mapping unit,
In the control channel mapped in the mapping unit, a plurality of control resource blocks are multiplexed, and each control resource block is mapped to all OFDM symbols to which the control channel is mapped,
And the base station transmission format of the control channel for some users but is kept unchanged, the transmission format of the control channel to another user characterized by Rukoto is variably controlled located in the cell,
A receiver for receiving the control channel and the data channel ;
Having a terminal and a processing unit for processing the control and data channels received at the receiver.

  According to the present invention, a communication terminal includes a number of resource blocks including one or more subcarriers having a frequency band allocated to the communication system, and the communication terminal controls the communication terminal in a communication system that performs communication using the one or more resource blocks. The channel can be transmitted efficiently.

The figure for demonstrating frequency scheduling is shown. It is a figure which shows the frequency band used by one Example of this invention. The partial block diagram (the 1) of the base station by one Example of this invention is shown. The partial block diagram (the 2) of the base station by one Example of this invention is shown. It is a figure which shows the signal processing element regarding one frequency block. It is a figure which shows the signal processing element regarding one frequency block. It is a figure which shows the information item example of a control signaling channel. It is a figure which shows the localized FDM system and the distributed FDM system. It is a figure which shows the symbol number of the L1 / L2 control channel which changes according to the number of simultaneous multiplex users. It is a figure which shows the example of mapping of part 0 information and a paging indicator. It is a figure which shows a mode that a unit information part is used for a paging indicator. 4 streams of two of the user equipment _A (UE A), another two are a diagram showing a state where precoding vectors W _A to face the user equipment _B (UE B), is W _B are set respectively. It is a figure which shows the unit of error correction encoding. It is a figure which shows the example of mapping of a data channel and a control channel. It is a figure which shows the example of mapping of a data channel and a control channel. It is an example which shows the format of the L1 / L2 control channel when notifying the number of symbols of the L1 / L2 control channel in Part 0. It is an example which shows the format of the L1 / L2 control channel when notifying the number of simultaneously allocated users of each MCS in Part 0. It is an example which shows the mapping of the part 0 in the L1 / L2 control channel in the case of 3 sector structure. It is a figure which shows the example of a multiplexing system of an unspecified control channel. It is a figure which shows the example of mapping of the common control information which does not contain a cell edge user. It is a figure which shows the example of a mapping of the common control information containing a cell edge user. It is a figure which shows the example of multiplexing of the unspecified control channel in the case of multiplexing a plurality of users. FIG. 2 shows a partial block diagram of a terminal according to an embodiment of the present invention. FIG. 2 shows a partial block diagram of a terminal according to an embodiment of the present invention. The block diagram regarding the receiving part of a terminal is shown. 6 is a flowchart illustrating an operation example according to an embodiment of the present invention. It is a flowchart which shows the example of a receiving operation of a parallel system. It is a flowchart which shows the example of a receiving operation of a serial system. It is FIG. (The 1) which shows the error detection coding of a non-specific control channel, and channel coding. It is FIG. (The 2) which shows the error detection coding of a non-specific control channel, and channel coding. It is FIG. (The 3) which shows the error detection encoding of an unspecified control channel, and channel encoding. It is a figure which shows a mode that TPC is performed. It is a figure which shows a mode that AMC control is performed. It is a figure which shows the relationship between the level of MCS level and data size. 4 schematically shows how the L1 / L2 control channel is transmitted with various multiplexing numbers in four TTIs. It is a figure which shows the specific example of various parameters regarding multiple number. It is a figure which shows a mode that the mapping positional relationship of control information is restrict | limited. It is a figure which shows a mode that the number of blind position detection decreases. It is a chart for comparing Method 1 to Method 7. It is a figure which shows the example in which the part to which the same channel coding system is applied to all the users, and the part which is not so exist in a control signal (the 1). It is a figure which shows the example in which the part to which the same channel coding system is applied to all the users, and the part which is not so exist in a control signal (the 2). It is a figure which shows the decoding method of a downlink scheduling grant. It is a figure which shows the example from which the channel encoding system of a control signal differs for every user. It is a chart which shows the comparative example of each method. It is a chart which shows an example of the data size used for each information item. It is a chart which shows the comparative example of each method.

  In one form of the present invention, the control channel is unspecified control information (common control information) decoded by an unspecified communication terminal and specific control information decoded by a specific communication terminal to which one or more resource blocks are allocated. And they may be encoded and modulated separately. The control channel is created by time-multiplexing non-specific control information and specific control information according to scheduling information, and is transmitted in a multi-carrier scheme. Thereby, even if the amount of control information differs for each communication terminal, it is possible to efficiently transmit the control channel in a fixed format without wasting resources.

  The non-specific control information may be mapped so as to be distributed over the entire system band, and the specific control information related to a specific communication terminal may be mapped only to the resource block allocated to the specific communication terminal. The quality of the specific control information can be improved while ensuring the quality of the unspecified control information to a certain level or more over all users. This is because the specific control information is mapped to a resource block having a good channel state for each specific communication terminal.

  The downlink pilot channel may also be mapped so as to be distributed over a plurality of resource blocks allocated to a plurality of communication terminals. By mapping the pilot channel over a wide band, the channel estimation accuracy and the like can be improved.

  In one aspect of the present invention, transmission power control is performed for an unspecified control channel, and transmission power control and adaptive modulation are performed for the specified control channel from the viewpoint of maintaining or improving the reception quality of control channels including unspecified and specified control channels. One or both of the encoding controls are performed.

  Transmission power control of the unspecified control channel may be performed so that the specific communication terminal to which the resource block is allocated can receive the unspecified control channel with high quality. This is because all users or communication terminals that have received an unspecified control channel have an obligation to attempt demodulation, but ultimately a user to whom a resource block is actually allocated may succeed in demodulation.

  The unspecified control channel may include information on one or both of the modulation scheme and the coding scheme applied to the specific control channel. Since the combination of the modulation scheme and the coding scheme is fixed for the unspecified control channel (because it is limited to at least one of the predetermined options), the user assigned with the resource block uses the unspecified control channel. By demodulating, it is possible to obtain information such as a modulation scheme and a coding scheme regarding a specific control channel. As a result, adaptive modulation and coding control can be performed on the specific control channel portion of the control channel, and the reception quality of that portion can be improved.

  When transmission power control and adaptive modulation and coding are controlled for a control channel, the total number of combinations of modulation schemes and coding schemes for a specific control channel is based on the total number of combinations of modulation schemes and coding schemes for a shared data channel Less may be prepared. This is because even if the required quality cannot be achieved by the adaptive modulation and coding control, it is sufficient that the required quality can be achieved by performing the transmission power control.

  FIG. 2 shows the frequency band used in one embodiment of the present invention. For convenience of explanation, specific numerical values are used, but the numerical values are merely examples, and various numerical values may be used. As an example, the frequency band (total transmission band) given to the communication system has a bandwidth of 20 MHz. The entire transmission band includes four frequency blocks 1 to 4, and each frequency block includes a plurality of resource blocks including one or more subcarriers. In the illustrated example, a state in which a large number of subcarriers are included in each frequency block is schematically illustrated. In this embodiment, four types of bandwidths of 5 MHz, 10 MHz, 15 MHz, and 20 MHz are prepared as communication bandwidths, and user devices (including communication terminals, mobile terminals, fixed terminals, etc.) have one or more frequencies. A block is used to communicate with any one of the four bandwidths. A terminal that communicates within a communication system may be able to communicate in any of the four bands, or may be able to communicate only in any bandwidth. However, it is necessary to be able to communicate at least in the 5 MHz band. Alternatively, the standard may be determined so that any communication terminal can communicate over the entire system bandwidth without preparing such four types of bands. In order to give a more general explanation, the following embodiment describes a case where four types of bandwidth options are prepared. However, it will be appreciated that the present invention is applicable with or without such bandwidth options.

  In this embodiment, the control channel (L1 / L2 control signaling channel or low layer control channel) for notifying the terminal of the scheduling content of the data channel (shared data channel) is configured with a minimum bandwidth (5 MHz), and the control channel Are prepared independently for each frequency block. For example, when a terminal that performs communication in a bandwidth of 5 MHz performs communication in the frequency block 1, it can receive the control channel prepared in the frequency block 1 and obtain the contents of scheduling. Which frequency block the terminal can communicate with may be notified in advance using a broadcast channel, for example. Moreover, the frequency block to be used may be changed after the start of communication. When a terminal that communicates with a bandwidth of 10 MHz communicates with frequency blocks 1 and 2, the terminal uses two adjacent frequency blocks, and both control channels prepared in frequency blocks 1 and 2 are used. The content of the scheduling over the range of 10 MHz can be obtained. A terminal that performs communication with a bandwidth of 15 MHz uses three adjacent frequency blocks. When communication is performed using frequency blocks 1, 2, and 3, the terminals are all prepared in frequency blocks 1, 2, and 3. And control content over a 15 MHz range can be obtained. A terminal that performs communication with a bandwidth of 20 MHz can receive all the control channels prepared in all frequency blocks, and obtain scheduling contents over a range of 20 MHz.

  In the figure, four discrete blocks are shown in the frequency block for the control channel, and this shows how the control channel is distributed and mapped to a plurality of resource blocks in the frequency block. A specific mapping example of the control channel will be described later.

  FIG. 3A shows a partial block diagram of a base station according to one embodiment of the present invention. 3A shows a frequency block allocation control unit 31, a frequency scheduling unit 32, a control signaling channel generation unit 33-1 and a data channel generation unit 34-1 in the frequency block 1, and a control signaling channel in the frequency block M. Generating unit 33-M and data channel generating unit 34-M, broadcast channel (or paging channel) generating unit 35, first multiplexing unit 1-1 for frequency block 1, ... first multiplexing unit 1 for frequency block M M, a second multiplexing unit 37, a third multiplexing unit 38, another channel generation unit 39, an inverse fast Fourier transform unit 40 (IFFT), and a cyclic prefix (CP) addition unit 41 are illustrated.

  The frequency block allocation control unit 31 confirms the frequency block used by the terminal based on the information on the maximum communicable bandwidth reported from the terminal (which may be a mobile terminal or a fixed terminal). The frequency block allocation control unit 31 manages the correspondence between individual terminals and frequency blocks, and notifies the frequency scheduling unit 32 of the contents. As to which frequency block a terminal that can communicate with a certain bandwidth may communicate with may be broadcast in advance on a broadcast channel. For example, the broadcast channel may allow a user communicating with a bandwidth of 5 MHz to use any one of the frequency blocks 1, 2, 3, and 4 or use any of them. May be limited. Moreover, use of a combination of two adjacent frequency blocks such as frequency blocks (1, 2), (2, 3) or (3,4) is permitted for a user communicating with a bandwidth of 10 MHz. . Use of all of these may be permitted, or use may be limited to any combination. A user communicating with a bandwidth of 15 MHz is allowed to use a combination of three adjacent frequency blocks such as frequency block (1, 2, 3) or (2, 3, 4). Use of both may be permitted, or use may be restricted to one combination. All frequency blocks are used for users communicating in a 20 MHz bandwidth. The usable frequency block may be changed after the start of communication according to a predetermined frequency hopping pattern.

  The frequency scheduling unit 32 performs frequency scheduling in each of the plurality of frequency blocks. In the frequency scheduling within one frequency block, scheduling information is determined so that resource blocks are preferentially allocated to terminals having good channel conditions based on channel state information CQI for each resource block reported from the terminals.

  The control signaling channel generation unit 33-1 in the frequency block 1 configures a control signaling channel for notifying the terminal of scheduling information in the frequency block 1 using only resource blocks in the frequency block 1. Similarly, other frequency blocks use only resource blocks in the frequency block to configure a control signaling channel for notifying the terminal of scheduling information in the frequency block.

  The data channel generation unit 34-1 in the frequency block 1 generates a data channel to be transmitted using one or more resource blocks in the frequency block 1. Since the frequency block 1 may be shared by one or more terminals (users), N data channel generators 1-1 to N are prepared in the illustrated example. Similarly, for other frequency blocks, data channels of terminals sharing the frequency block are generated.

  The first multiplexing unit 1-1 related to the frequency block 1 multiplexes signals related to the frequency block 1. This multiplexing includes at least frequency multiplexing. How the control signaling channel and the data channel are multiplexed will be described later. The other first multiplexing unit 1-x similarly multiplexes the control signaling channel and data channel transmitted in the frequency block x.

  The second multiplexing unit 37 performs an operation of changing the positional relationship on the frequency axis of various multiplexing units 1-x (x = 1,..., M) according to a predetermined hopping pattern. This will be described in the second embodiment.

  The broadcast channel (or paging channel) generation unit 35 generates broadcast information for notifying a subordinate terminal such as station data. Information indicating the relationship between the maximum frequency band in which a terminal can communicate and the frequency block that can be used by the terminal may be included in the control information. When the usable frequency block is changed variously, information specifying a hopping pattern indicating how the frequency block changes may be included in the broadcast information. Note that the paging channel may be transmitted in the same band as the broadcast channel, or may be transmitted in a frequency block used in each terminal.

  The other channel generation unit 39 generates a channel other than the control signaling channel and the data channel. For example, the other channel generation unit 39 generates a pilot channel.

  The third multiplexing unit 38 multiplexes the control signaling channel and data channel of each frequency block and the broadcast channel and / or other channels as necessary.

  The inverse fast Fourier transform unit 40 performs inverse fast Fourier transform on the signal output from the third multiplexing unit 38 and performs OFDM modulation.

  A cyclic prefix (CP) adding unit 41 adds a guard interval to the OFDM-modulated symbol, and generates a transmission symbol. The transmission symbol may be created, for example, by adding a series of data at the end (or the beginning) of the OFDM symbol to the beginning (or the end).

  FIG. 3B shows elements following the CP adding unit 41 in FIG. 3A. As shown in the figure, the symbol to which the guard interval is added is subjected to processing such as digital analog conversion, frequency conversion and band limitation by an RF transmission circuit, amplified to an appropriate power by a power amplifier, a duplexer, and a transmission / reception antenna. Sent through.

  Although not essential to the present invention, in this embodiment, antenna diversity reception by two antennas is performed during reception. Uplink signals received by the two antennas are input to the uplink signal receiver.

  FIG. 4A shows signal processing elements for one frequency block (xth frequency block). x is an integer of 1 or more and M or less. In general, a control signaling channel generation unit 33-x and a data channel generation unit 34-x, a multiplexing unit 43-A, B, and a multiplexing unit 1-x related to the frequency block x are illustrated. The control signaling channel generation unit 33-x includes an unspecific control channel generation unit 41 and one or more specific control channel generation units 42-A, B,.

  The unspecified control channel generation unit 41 may be called an unspecified control channel (unspecified control information, which all terminals using the frequency block of the control signaling channel must decode and demodulate, The channel coding and multi-level modulation are performed on the portion of which may be called) and output.

  The specific control channel generation units 42-A, B,..., Among the control signaling channels, specific control channels (terminals to which one or more resource blocks allocated in the frequency block must be decoded and demodulated ( Channel coding and multi-level modulation are performed on the portion of (which may be referred to as specific control information) and output.

  The data channel generators x-A, B,... Perform channel coding and multilevel modulation for the data channels addressed to the individual terminals A, B,. Information regarding this channel coding and multi-level modulation is included in the specific control channel.

  The multiplexing units 43-A, B,... Associate the specific control channel and the data channel with the resource block for each terminal to which the resource block is assigned.

  As described above, the coding (and modulation) for the unspecified control channel is performed by the unspecified control channel generating unit 41, and the coding (and modulation) for the specified control channel is performed by the specified control channel generating units 42-A and B. , ... done individually. Therefore, in this embodiment, as conceptually shown in FIG. 6, the unspecified control channel includes information for all the users to which the frequency block x is assigned, and these are collectively included in the error correction coding target. It may be.

  In another embodiment, the unspecified control channel may also be error correction coded for each user. In this case, each user cannot uniquely identify which of the individual error correction coded blocks contains the information of the own station, so it is necessary to decode all the blocks. In this alternative embodiment, since the encoding process is closed for each user, addition and change of users are relatively easy. Each user needs to decode and demodulate the unspecified control channel for all the users.

  On the other hand, the specific control channel includes only information related to users to which resource blocks are actually allocated, and is error-correction coded for each user. The user to whom the resource block is assigned can be determined by decoding and demodulating the unspecified control channel. Therefore, it is not necessary for everyone to decode the specific control channel, and only the user to whom the resource block is assigned needs to decode it. Note that the channel coding rate and the modulation scheme for the specific control channel are appropriately changed during communication, but the channel coding rate and the modulation scheme for the non-specific control channel may be fixed. However, it is desirable to perform transmission power control (TPC) to ensure a certain level of signal quality. The specific control channel is transmitted with a good resource block after being subjected to error correction coding. Therefore, the amount of downlink data may be reduced to a certain degree by performing puncturing.

  FIG. 5A shows an example of the types and information items of the downlink control signaling channel. The downlink control signaling channel includes a broadcast channel (BCH), a dedicated L3 signaling channel (upper layer control channel or higher layer control channel) and an L1 / L2 control channel (lower layer control channel). The L1 / L2 control channel may include not only information for downlink data transmission but also information for uplink data transmission. The L1 / L2 control channel may include the transmission format of the L1 / L2 control channel (data modulation scheme, channel coding rate, number of simultaneously allocated users, etc.). The information items transmitted in each channel will be outlined below.

(Broadcast channel)
The broadcast channel is used to notify a communication terminal (which may be a mobile terminal or a fixed terminal or may be called a user apparatus) of information that does not change in a cell or information that changes only at a low speed. For example, information that changes only in a cycle of about 1000 ms (1 second) may be notified as broadcast information. The broadcast information may include the transmission format of the downlink L1 / L2 control channel, the maximum number of simultaneously allocated users, resource block arrangement information, and MIMO scheme information. The maximum number of simultaneously allocated users (user multiplexing number) indicates how many pieces of control information are multiplexed in the downlink L1 / L2 control channel of one subframe. This number may be specified separately for the uplink and the downlink (N _UMAX , N _DMAX ), or may be expressed as a total number (N _all ) combining the uplink and the downlink.

  The transmission format is specified by the data modulation scheme and the channel coding rate. The data size may be notified instead of the channel coding rate. This is because the channel coding rate can be uniquely derived from the data modulation scheme and data size. This transmission format may be notified in the L1 / L2 control channel (part 0) described later.

  The maximum number of simultaneously allocated users represents the maximum number that can be multiplexed using one or more of FDM, CDM, and TDM in 1 TTI. This number may be the same in the uplink and downlink, or may be different.

  The resource block arrangement information is information for specifying the frequency block and the position on the time axis of the resource block used in the cell. In this embodiment, two types of frequency division multiplexing (FDM) systems, a localized FDM system and a distributed FDM system, can be used. In the localized FDM scheme, a continuous band is preferentially allocated to users in a channel state that is locally good on the frequency axis. This method is advantageous for communication of users with low mobility, high-quality and large-capacity data transmission, and the like. In the distributed FDM system, a downlink signal is created so as to have a plurality of frequency components intermittently over a wide band. This method is advantageous for communication of users with high mobility, data transmission of periodic and small data size such as voice packet (VoIP), and the like. Regardless of which method is used, the frequency resource is allocated according to information specifying a continuous band or a plurality of discrete frequency components.

  As shown in the upper part of FIG. 5B, for example, when the resource is specified as “No. 4” in the localized FDM method, the resource of physical resource block number 4 is used. In the distributed FDM system as shown in the lower side of FIG. 5B, when a resource is specified by “No. 4”, two left halves of physical resource blocks 2 and 8 are used. In the illustrated example, one physical resource block is divided into two. The numbering and the number of divisions in the distributed FDM method may be different for each cell. For this reason, the resource block arrangement information is notified to the communication terminals in the cell through the broadcast channel.

  MIMO system information includes single user mimo (SU-MIMO) or multi user mimo (MU-MIMO: Multi-User MIMO) when multiple antennas are provided in the base station. Which of the schemes is performed is indicated. The SU-MIMO scheme is a scheme in which one multi-antenna communication terminal and a multi-antenna base station communicate with each other, and the MU-MIMO scheme is a scheme in which a base station communicates with a plurality of communication terminals simultaneously.

In the downlink MU-MIMO scheme, a signal addressed to a certain user apparatus UE _A is transmitted from one or more antennas (for example, a first antenna of two antennas) of a base station, and another one or more antennas (for example, A signal addressed to another user apparatus UE _B is transmitted from the second antenna of the two antennas. In the uplink MU-MIMO scheme, a signal from one user apparatus UE _A and a signal from another user apparatus UE _B are simultaneously received by a plurality of antennas of the base station. A signal from each user apparatus may be distinguished by a reference signal assigned to each user apparatus. It is desirable to use a CAZAC code sequence for the reference signal for this purpose. This is because even if the Kazak code sequence is the same sequence, it has the property of being orthogonal to each other if the cyclic shift amount is different, for example, it is possible to easily prepare an orthogonal sequence.

(Dedicated L3 signaling channel)
The dedicated L3 signaling channel is also used to notify the communication terminal of information changing at a low speed such as a 1000 ms period. The broadcast channel is notified to all communication terminals in the cell, but the dedicated L3 signaling channel is notified only to a specific communication terminal. The dedicated L3 signaling channel includes the FDM type and persistent scheduling information. The dedicated L3 signaling channel may be classified as a specific control channel.

  The type of the FDM system indicates whether the specified individual communication terminal is multiplexed by the localized FDM system or the distributed FDM system.

  The persistent scheduling information specifies the transmission format (data modulation scheme and channel coding rate) of the uplink or downlink data channel, the resource block to be used, and the like when persistent scheduling is performed.

(L1 / L2 control channel)
The downlink L1 / L2 control channel may include not only information related to downlink data transmission but also information related to uplink data transmission. Furthermore, an information bit (part 0) indicating the transmission format of the L1 / L2 control channel may be included. Information related to downlink data transmission can be classified into three types, part 1, part 2a and part 2b as follows. Part 1 and part 2a can be classified as non-specific control channels, and part 2b can be classified as specific control channels.

(Part 0)
Part 0 information (hereinafter referred to as “Part 0” for the sake of brevity) includes the transmission format of the L1 / L2 control channel (modulation method and channel coding rate, the number of simultaneously allocated users or the total number of control bits). It is. In the case where the information notified by the broadcast channel is used as the transmission format of the L1 / L2 control channel, part 0 includes the number of simultaneously allocated users (or the total number of control bits).

  The number of symbols required for the L1 / L2 control channel depends on the number of simultaneously multiplexed users and the reception quality of the users to be multiplexed. As shown in the left side of FIG. 5C, typically, the number of symbols of the L1 / L2 control channel is made sufficiently large. When changing the number of symbols, control can be performed with a period of about 1000 ms (1 second), for example, according to the transmission format of the L1 / L2 control channel notified by the broadcast channel. However, if the number of simultaneously multiplexed users is small as shown on the right side of FIG. 5C, the number of symbols required for the control channel can be reduced. Therefore, when the number of simultaneously multiplexed users and the reception quality of the users to be multiplexed change in a short period, if a large amount of resources for the L1 / L2 control channel remains reserved, a lot of waste may occur. is there.

  In order to reduce the waste of the L1 / L2 control channel, part 0 (modulation method and channel coding rate, the number of simultaneously allocated users (or the total number of control bits)) is notified in the L1 / L2 control channel. May be. By notifying the modulation scheme and channel coding rate in the L1 / L2 control channel, it becomes possible to change the modulation scheme and channel coding rate in a shorter cycle than the notification by the broadcast channel. When the number of symbols occupied by the L1 / L2 control channel in one subframe is restricted by the category of a certain option, the transmission format can be specified by specifying which option is used. . For example, as described later, when four patterns of transmission formats are prepared, this part 0 information may be expressed by 2 bits.

(Part 1)
Part 1 includes a paging indicator (PI). Each communication terminal can confirm whether or not a call is made to the terminal by demodulating the paging indicator. More specifically, the communication terminal checks whether or not the group number assigned to itself is in the paging indicator, and demodulates the paging channel (PCH) if it is found. The positional relationship between PI and PCH is made known. The communication terminal can check whether there is an incoming call by confirming whether or not there is identification information of the terminal (for example, the telephone number of the terminal) in the paging channel (PCH).

  As a method of transmitting the paging indicator (PI) on the L1 / L2 control channel, (1) a method using an information part prepared exclusively for PI in the L1 / L2 control channel, and (2) such It is conceivable that a dedicated information part is not prepared.

  FIG. 5D shows an example when a paging indicator is transmitted by the method of (1). One subframe includes a predetermined number (for example, 10) of OFDM symbols in time series. For example, the first three symbols are assigned to common control information or the like. In the illustrated example, part 0 and paging indicator information are mapped to a certain band near the center frequency of the system band by the distributed FDM system. Control information related to the downlink (DL) and the uplink (UL) is mapped to the other part by the distributed FDM method. These control information and the paging channel (PCH) are time-multiplexed. In this method, a predetermined band is reserved exclusively for the paging indicator regularly or irregularly.

  (2) The L1 / L2 control channel includes a plurality of unit information portions of a predetermined size, and the number of unit information portions is allowed up to the maximum number specified by the broadcast information. Each unit information portion includes control information related to a specific user apparatus, and usually includes user identification information (UE-ID), resource allocation information, and the like. It is also conceivable to use any of such unit information portions for the paging indicator regularly or irregularly without securing a dedicated resource for the paging indicator (PI). However, it must be properly distinguished whether a certain unit information part includes information addressed to a specific user device or includes a paging indicator. For example, dedicated identification information (PI-ID) may be prepared for the paging indicator. In this case, what the PI-ID is is known to the user apparatus by broadcast information or the like.

  The number of bits of each unit information part may be kept the same or different. As will be described later, when MCS is variably controlled for each user in the common control information (when MCS of L1 / L2 control channel is variably controlled for each user), the number of bits depends on the MCS level. Because it may change.

  FIG. 5E shows how the unit information portion is used for the paging indicator regularly or irregularly. When each user device detects the PI-ID when decoding the unit information part, it processes the unit information part as a paging indicator (whether or not the group ID for the terminal is indicated in the unit information part) And if it is found, PCH is confirmed.) When the unit information portion is used as a paging indicator, it is desirable that the paging indicator is included in the head unit information portion from the viewpoint of promptly detecting the presence or absence of an incoming call.

(Part 2a)
Part 2a includes resource allocation information, allocation time length, and MIMO information of the downlink data channel.

  The resource allocation information of the downlink data channel specifies a resource block including the downlink data channel. Various methods known in the art can be used for specifying the resource block. For example, a bitmap method, a tree branch number method, or the like may be used.

  The allocated time length indicates how long the downlink data channel is continuously transmitted. The resource allocation contents change most frequently every TTI, but from the viewpoint of reducing overhead, the data channel may be transmitted with the same resource allocation contents over a plurality of TTIs.

  The MIMO information specifies the number of antennas, the number of streams, and the like when the MIMO scheme is used for communication. The number of streams may be called the number of information sequences. The number of antennas and the number of streams may be any suitable numbers, but may be four as an example.

  Although it is not essential that the part 2a includes user identification information, for example, all or part of 16-bit user identification information may be included.

(Part 2b)
Part 2b includes precoding information, a downlink data channel transmission format, hybrid retransmission control (HARQ) information, and CRC information when the MIMO scheme is used.

  The precoding information when the MIMO scheme is used specifies a weighting factor applied to each of a plurality of antennas. The directivity of the communication signal is adjusted by adjusting the weighting coefficient (precoding vector) applied to each antenna. The receiving side (user device) needs to perform channel estimation according to such directivity.

FIG. 5F shows precoding so that streams 1 and 2 (codeword 1) of the four streams are directed to user apparatus A (UE _A ) and streams 3 and 4 (codeword 2) are directed to user apparatus B (UE _B ). The manner in which the vectors W _A and W _B are set is shown. The reference signal is transmitted omnidirectionally. User devices A and B are notified of their precoding vectors W _A and W _B , respectively. The user device A introduces a weight after which or received reception taking into account the weight by the pre-coding vectors W _A when receiving the reference signal. Thereby, the channel estimation about the signal suitable for the user apparatus A can be performed appropriately. Similarly the user equipment B, and introduced into the weight after to or received reception taking into account the weight by precoding vector W _B when receiving the reference signal. Thereby, the channel estimation about the signal suitable for the user apparatus B can be performed appropriately.

  The transmission format of the downlink data channel is specified by the data modulation scheme and the channel coding rate. Instead of the channel coding rate, the data size or the payload size may be notified. This is because the channel coding rate can be uniquely derived from the data modulation scheme and data size. As an example, the transmission format may be expressed by about 8 bits.

  Hybrid retransmission control (HARQ: Hybrid Automatic Repeat ReQuest) information includes information necessary for downlink packet retransmission control. Specifically, the retransmission control information includes a process number, redundant version information indicating a packet combining method, and a new and old indicator (New Data Indicator) for distinguishing whether the packet is a new packet or a retransmission packet. As an example, the hybrid retransmission control information may be expressed by about 6 bits.

  CRC information indicates a CRC detection bit in which user identification information (UE-ID) is convoluted when the cyclic redundancy check method is used for error detection.

  Information related to uplink data transmission can be classified into four types of part 1 to part 4 as follows. In principle, these pieces of information may be classified into unspecified control channels, but may be transmitted as specific control channels to communication terminals to which resources are allocated for downlink data channels.

(Part 1)
Part 1 includes acknowledgment information for past uplink data channels. Acknowledgment information includes an acknowledgment (ACK) indicating that there was no error in the packet, or if it was within the allowable range, or a negative response (NACK) indicating that the packet had an error exceeding the allowable range. ). The delivery confirmation information may be substantially expressed by 1 bit.

(Part 2)
Part 2 includes resource allocation information for a future uplink data channel, a transmission format of the uplink data channel, transmission power information, and CRC information.

  The resource allocation information specifies resource blocks that can be used for uplink data channel transmission. Various methods known in the art can be used for specifying the resource block. For example, a bitmap method, a tree branch number method, or the like may be used.

  The transmission format of the uplink data channel is specified by the data modulation scheme and the channel coding rate. Instead of the channel coding rate, the data size or the payload size may be notified. This is because the channel coding rate can be uniquely derived from the data modulation scheme and data size. As an example, the transmission format may be expressed by about 8 bits.

The transmission power information indicates how much power the data channel transmitted in the uplink should transmit. In one form of the present invention, the uplink pilot channel is repeatedly transmitted from the communication terminal to the base station with a relatively short period Tref of, for example, several milliseconds. The transmission power Pref of the uplink pilot channel is longer than the period Tref according to the transmission power control information (TPC command) notified from the base station apparatus so as to be equal to or higher than the transmission power of the uplink pilot channel transmitted in the past. Updated with period T _TPC . The uplink L1 / L2 control channel is transmitted at a power _obtained by adding the first offset power _ΔL1L2 notified from the base station to the transmission power Pref of the uplink pilot channel. The uplink data channel is transmitted with power obtained by adding the second offset power Δ _data notified from the base station to the transmission power Pref of the uplink pilot channel. The offset power Δ _data related to such a data channel is included in the transmission power information of Part 2. The offset power _ΔL1L2 for the L1 / L2 control channel is included in transmission power information of Part 4 described later. Part 4 also includes a TPC command for updating the transmission power of the pilot channel.

The first offset power information Δ _L1L2 may be maintained unchanged or may be variably controlled. In the latter case, the user apparatus may be notified as broadcast information BCH or as layer 3 signaling information. The second offset power information Δ _data may be notified to the user apparatus with an L1 / L2 control signal. The first offset power information _ΔL1L2 may be determined such that the first offset power also increases or decreases according to the amount of information included in the control signal. The first offset power information _ΔL1L2 may be determined so as to differ depending on whether the reception quality of the control signal is good or bad. The second offset power information Δ _data may be determined so as to differ depending on whether the reception quality of the data signal is good or bad. In cooperation with a request for lower power (overload indicator) from the neighboring cells of the cell where the communication terminal is located, the uplink data channel is less than the sum of the transmission power Pref and the second offset power Δ _data of the uplink pilot channel. It may be transmitted with power.

  CRC information indicates a CRC detection bit in which user identification information (UE-ID) is convoluted when the cyclic redundancy check method is used for error detection. In the response signal (downlink L1 / L2 control channel) for the random access channel (RACH), the random ID of the RACH preamble may be used as the UE-ID.

(Part 3)
Part 3 includes transmission timing control bits related to the uplink signal. This is a control bit for synchronizing the communication terminals in the cell. This information may be notified as specific control information if resource blocks are allocated to the downlink data channel, or may be notified as non-specific control information.

(Part 4)
Part 4 includes transmission power information relating to the transmission power of the communication terminal, and this information indicates how much power the communication terminal, for which no resource has been allocated for transmission of the uplink data channel, reports, for example, downlink CQI. Indicates whether the uplink control channel should be transmitted. The offset power _ΔL1L2 and the TPC command are included in the information of Part 4.

  FIG. 4B shows signal processing elements related to one frequency block, similar to FIG. 4A, but looks different from FIG. 4A in that each control information is clearly specified. The same reference numerals in FIGS. 4A and 4B indicate the same elements. In the figure, “mapping within a resource block” indicates that mapping is limited to one or more resource blocks assigned to a specific communication terminal. “Outside resource block mapping” indicates mapping across the entire frequency block including a large number of resource blocks. Part 0 in the L1 / L2 control channel is transmitted throughout the frequency block as an unspecified control channel. Information related to uplink data transmission (parts 1 to 4) in the L1 / L2 control channel is the resource as a specific control channel if a resource is allocated for the downlink data channel, and unspecified control otherwise. It is transmitted as a channel over the entire frequency block.

  FIG. 7A shows an example of data channel and control channel mapping. The illustrated mapping example relates to one frequency block and one subframe, and generally corresponds to the output content of the first multiplexing unit 1-x (however, the pilot channel and the like are multiplexed by the third multiplexing unit 38). .) One subframe may correspond to, for example, one transmission time interval (TTI) or may correspond to a plurality of TTIs. In the illustrated example, seven resource blocks RB1 to RB7 are included in the frequency block. These seven resource blocks are allocated to terminals having good channel states by the frequency scheduling unit 32 in FIG. 3A.

  In general, unspecified control channels, pilot channels, and data channels are time-multiplexed. Unspecified control channels (including part 0 in the L1 / L2 control channel) are distributed and mapped over the entire frequency block. That is, the unspecified control channel is distributed over the entire band occupied by the seven resource blocks. In the illustrated example, the non-specific control channel (including part 0 in the L1 / L2 control channel) and other control channels (excluding the specific control channel) are frequency-multiplexed. Other channels may include, for example, a synchronization channel (distinguishment of such channels is not essential, and a synchronization channel may be included in an unspecified control channel). In particular, since part 0 in the L1 / L2 control channel needs to have a short delay time, it is preferably multiplexed with the first OFDM symbol. In the illustrated example, the unspecified control channel and the other control channels are frequency-multiplexed so that each has a plurality of frequency components arranged at some interval. Such a multiplexing scheme is called a distributed frequency division multiplexing (distributed FDM) scheme. The distributed FDM system is advantageous in that a frequency diversity effect can be obtained. The intervals between the frequency components may all be the same or different. In any case, it is necessary that unspecified control channels are distributed over a plurality of resource blocks (in the embodiment, the entire system band). Furthermore, in order to cope with an increase in the number of multiplexed users, it is also possible to apply the CDM method as another method. The CDM method has an advantage that the frequency diversity effect is further increased, but also has a disadvantage that the reception quality is deteriorated due to the loss of orthogonality.

  In the illustrated example, pilot channels and the like are also mapped over the entire frequency block. From the viewpoint of accurately performing channel estimation and the like for various frequency components, it is desirable that the pilot channel is mapped over a wide range as illustrated.

  In the illustrated example, resource blocks RB1, RB2, and RB4 are assigned to user 1 (UE1), resource blocks RB3, RB5, and RB6 are assigned to user 2 (UE2), and resource block RB7 is assigned to user 3 (UE3). . As described above, such allocation information is included in the unspecified control channel. Furthermore, a specific control channel for user 1 is mapped to the head of resource block RB1 among the resource blocks allocated to user 1. A specific control channel related to user 2 is mapped to the head of resource block RB3 among the resource blocks allocated to user 2. A specific control channel related to the user 3 is mapped to the head of the resource block RB7 assigned to the user 3. In the figure, it should be noted that the sizes occupied by the specific control channels of the users 1, 2 and 3 are drawn unevenly. This represents that the amount of information of a specific control channel may differ depending on the user. The specific control channel is mapped locally only to the resource block allocated to the data channel. In this regard, unlike distributed FDM that is distributed and mapped across various resource blocks, such a mapping scheme is also called localized frequency division multiplexing (localized FDM).

  FIG. 7B shows another example of mapping of unspecified control channels. The specific control channel of user 1 (UE1) is mapped to only one resource block RB1 in FIG. 7A, but over the entire resource blocks RB1, RB2, and RB4 (entire resource blocks assigned to user 1) in FIG. 7B. The distributed FDM method is discretely distributed and mapped. Also, the specific control channel for user 2 (UE2) is also mapped over the entire resource blocks RB3, RB5, RB6, unlike the case shown in FIG. 7A. User 2's specific control channel and shared data channel are time-division multiplexed. As described above, the specific control channel and the shared data channel of each user are time-division multiplexed (TDM) and / or frequency division multiplexed among all or a part of one or more resource blocks allocated to each user. Multiplexing may be performed in a system (including localized FDM system and distributed FDM system). By mapping the specific control channel over two or more resource blocks, the frequency diversity effect can be expected for the specific control channel, and the signal quality of the specific control channel can be further improved.

  Next, a specific format of the part 0 information in the L1 / L2 control channel will be described.

  FIG. 7C shows a format example of the L1 / L2 control channel. In the illustrated example, four patterns are prepared as the format of the L1 / L2 control channel, and the number of symbols (or the number of simultaneously allocated users) of the L1 / L2 control channel differs for each pattern. Which of the four patterns is used is notified by part 0 information. When using the modulation scheme and coding rate (MCS) reported by the communication terminal on the broadcast channel for the L1 / L2 control channel, the symbols required for the L1 / L2 control channel according to the number of simultaneously allocated users The number depends on the MCS level. In order to identify this, a control bit (2 bits in FIG. 7C) is provided as part 0 information of the L1 / L2 control channel. For example, by notifying the control bit of 00 as part 0 information, it is possible to know that the number of symbols of the L1 / L2 control channel is 100 by decoding this control bit at the communication terminal. 7C corresponds to part 0, and the variable control channel corresponds to an unspecified control channel (part 1 and part 2a in the case of downlink). In FIG. 7C, MCS is reported on the broadcast channel, but MCS may be reported on the L3 signaling channel.

  FIG. 7D shows a format example of the L1 / L2 control channel when the number of simultaneously allocated users of each MCS is notified in part 0. If an appropriate MCS is used in accordance with the reception quality of the communication terminal among predetermined types of MCS, the number of symbols required for the L1 / L2 control channel changes according to the reception quality of the communication terminal. In order to identify this, a control bit (8 bits in FIG. 7D) is provided as part 0 information of the L1 / L2 control channel. FIG. 7D shows a case where there are four types of MCSs as an example, and the maximum value of the number of simultaneously allocated users in each MCS is three. Since the number of simultaneously allocated users is 0 to 3, this information can be represented by 2 bits (00 = 0 user, 01 = 1 user, 10 = 2 user, 11 = 3 user). Since 2 bits are required for each MCS, part 0 in this case is 8 bits. For example, by notifying the control bit of 01100001 as the information of part 0, the communication terminal can know the control information (part 2a in the case of downlink) according to its reception quality based on this control bit. In the illustrated example, it can be seen that the number of multiplexed users is 1, 2, 0, 1 based on the information of 01, 10, 00, 01. If the quality of reception is expressed in four levels (minimum, low, medium and high), these correspond to the reception quality being low, medium, minimum and high, and this relationship is also reflected in MCS. (The higher the quality, the higher the MCS is used and the greater the multiplexing number).

  FIG. 7E is an example showing mapping of information bits (part 0) in the L1 / L2 control channel in the case of a three-sector configuration. In the case of a three-sector configuration, three types of patterns are prepared for transmitting information bits (part 0) indicating the transmission format of the L1 / L2 control channel so that the patterns do not overlap in the frequency domain. It may be assigned to each sector. By selecting patterns so that transmission patterns in adjacent sectors (or cells) are different from each other, the effect of interference coordination can be obtained.

  FIG. 7F shows examples of various multiplexing methods. In the above example, various unspecified control channels are multiplexed using the distributed FDM method, but various appropriate multiplexing methods such as code division multiplexing (CDM) and time division multiplexing (TDM) are used. Also good. FIG. 7F (1) shows a state in which multiplexing is performed by the distributed FDM method. By using numbers 1, 2, 3, and 4 that specify a plurality of discrete frequency components, the signals of each user can be appropriately orthogonalized. However, it does not have to be regular as in this example. Further, by using different rules between adjacent cells, the amount of interference when performing transmission power control can be randomized. FIG. 7F (2) shows how multiplexing is performed by the code division multiplexing (CDM) method. By using the codes 1, 2, 3, and 4, the signals of each user can be appropriately orthogonalized. This method is preferable from the viewpoint of effectively reducing interference from other cells. FIG. 7F (3) shows a situation in which the user multiplexing number is changed to 3 in the distributed FDM system. By redefining the numbers 1, 2, and 3 that specify a plurality of discrete frequency components, the signals of each user can be appropriately orthogonalized. When the number of simultaneously allocated users is less than the maximum number, the base station may increase the transmission power of the downlink control channel as shown in FIG. 7F (4). This is preferable from the viewpoint of improving the received signal quality, but when such transmission is performed at the cell edge, there is a possibility that interference from other cells may increase. A hybrid of CDM and FDM is also applicable.

  By the way, regarding the transmission method for part 0 information, both MCS (combination of modulation scheme channel coding rates) and transmission power applied to part 0 information may be kept constant, or MCS is kept constant. However, the transmission power may be variably controlled. Furthermore, the part 0 information may be maintained in common for all users residing in the cell, and the transmission format of the L1 / L2 control channel may differ depending on the user. For example, for users near the base station, the transmission format is optimized by appropriately changing the contents of the part 0 information, but for the users at the cell edge, the transmission format is not changed as such. (It may be kept constant.) However, information indicating whether or not each user belongs to the cell edge group needs to be notified to the user, for example, in the downlink L1 / L2 control channel. If it does not belong to the cell edge group, part 0 information is notified in a transmission format that is changed appropriately (extremely every TTI), and if it belongs to the cell edge group, control information is notified in a certain transmission format. Is done.

  FIG. 7G shows an example of L1 / L2 control channel mapping when only users 1 to 4 near the base station exist in the cell. The numbers in the figure correspond to individual users. For example, “1” corresponds to user 1. Users 1 to 4 are notified of the transmission format, for example, for each TTI through part 0 information. FIG. 7H shows an example of L1 / L2 control channel mapping when users 11 to 14 exist at the cell edge in addition to users 1 to 4 near the base station. The users 11 to 14 are not notified explicitly about the transmission format, but use a predetermined transmission format. Users 1 to 4 are explicitly notified of the same transmission format as the predetermined transmission format through part 0 information.

  FIG. 7I shows an example of multiplexing unspecified control channels when a plurality of users are multiplexed. The L1 / L2 control channel is mapped within 3 OFDM symbols in each subframe.

  For example, the subcarriers allocated to the L1 / L2 control channel constitute a plurality of control resource blocks (Control Resource blocks). For example, one control resource block is configured by X subcarriers (X is an integer satisfying X> 0). An optimum value X is prepared depending on the system bandwidth and the like. A plurality of control resource blocks use FDM or a hybrid of CDM and FDM. When multiple OFDM symbols are used for the L1 / L2 control channel, each control resource block is mapped to all OFDM symbols. This number of control resource blocks is reported on the broadcast channel.

The control channel is QPSK or 16QAM data modulated. When a plurality of coding rates are used (R1, R2,... Rn), Rn is R1 / n.
Even when the uplink scheduling information and the downlink scheduling information have different numbers of bits, control resource blocks having the same size are used by rate matching.

  FIG. 8A shows a partial block diagram of a mobile terminal used in one embodiment of the present invention. 8A shows a carrier frequency tuning unit 81, a filtering unit 82, a cyclic prefix (CP) removal unit 83, a fast Fourier transform (FFT) 84, a CQI measurement unit 85, a broadcast channel (or paging channel) decoding unit 86, A specific control channel (part 0) decoding unit 87-0, an unspecific control channel decoding unit 87, a specific control channel decoding unit 88, and a data channel decoding unit 89 are depicted.

  The carrier frequency tuning unit 81 appropriately adjusts the center frequency of the reception band so that the signal of the frequency block assigned to the terminal can be received.

  The filtering unit 82 filters the received signal.

  The cyclic prefix removing unit 83 removes the guard interval from the received signal and extracts the effective symbol portion from the received symbol.

  A fast Fourier transform unit (FFT) 84 performs fast Fourier transform on information included in the effective symbol and performs OFDM demodulation.

  CQI measuring section 85 measures the received power level of the pilot channel included in the received signal, and feeds back the measurement result to the base station as channel state information CQI. CQI is performed for every resource block in the frequency block, and they are all reported to the base station.

  The broadcast channel (or paging channel) decoding unit 86 decodes the broadcast channel. If a paging channel is included, it is also decoded.

  The unspecified control channel (part 0) decoding unit 87-0 decodes the information of part 0 in the L1 / L2 control channel. This part 0 makes it possible to recognize the transmission format of the unspecified control channel.

  The unspecified control channel decoding unit 87 decodes the unspecified control channel included in the received signal and extracts scheduling information. The scheduling information includes information indicating whether or not a resource block is allocated to the shared data channel addressed to the terminal, information indicating a resource block number when the resource block is allocated, and the like.

  The specific control channel decoding unit 88 decodes the specific control channel included in the received signal. The specific control channel includes data modulation, channel coding rate, and HARQ information regarding the shared data channel.

  The data channel decoding unit 89 decodes the shared data channel included in the received signal based on the information extracted from the specific control channel. An acknowledgment (ACK) or a negative acknowledgment (NACK) may be reported to the base station according to the decoding result.

  FIG. 8B shows a partial block diagram of the mobile terminal as in FIG. 8A, but it looks different from FIG. 8A in that individual control information is specifically shown. The same reference numerals in FIG. 8A and FIG. 8B indicate the same elements. In the figure, “in-resource block demapping” indicates that information mapped to one or more resource blocks allocated to a specific communication terminal is extracted. “Outside resource block demapping” indicates that information mapped over the entire frequency block including a large number of resource blocks is extracted.

  FIG. 8C shows elements associated with the receiver of FIG. 8A. Although not essential to the present invention, in this embodiment, antenna diversity reception by two antennas is performed during reception. The downlink signals received by the two antennas are respectively input to the RF receiving circuits (81, 82), the guard interval (cyclic prefix) is removed (83), and fast Fourier transformed (84). Signals received by the respective antennas are combined by an antenna diversity combining unit. The combined signal is supplied to each decoding unit in FIG. 8A or to the separation unit in FIG. 8B.

  FIG. 9A is a flowchart showing an operation example according to one embodiment of the present invention. As an example, it is assumed that a user having a mobile terminal UE1 that can communicate with a bandwidth of 10 MHz enters a cell or a sector that performs communication with a bandwidth of 20 MHz. It is assumed that the minimum frequency band of the communication system is 5 MHz, and the entire band is divided into four frequency blocks 1 to 4 as shown in FIG.

  In step S11, the terminal UE1 receives the broadcast channel from the base station, and confirms what frequency blocks the local station can use. The broadcast channel may be transmitted in a 5 MHz band including the center frequency of the entire 20 MHz band. In this way, any terminal having a different receivable bandwidth can easily receive the broadcast channel. The broadcast channel allows users communicating with a bandwidth of 10 MHz to use a combination of two adjacent frequency blocks such as frequency blocks (1, 2), (2, 3) or (3,4). To do. Use of all of these may be permitted, or use may be limited to any combination. As an example, it is assumed that use of the frequency blocks 2 and 3 is permitted.

  In step S12, the terminal UE1 receives the downlink pilot channel and measures the received signal quality regarding the frequency blocks 2 and 3. The measurement is performed for each of a number of resource blocks included in each frequency block, and all of them are reported to the base station as channel state information CQI.

  In step S21, the base station performs frequency scheduling for each frequency block based on the channel state information CQI reported from the terminal UE1 and other terminals. It is confirmed and managed by the frequency block allocation control unit (31 in FIG. 3A) that the data channel addressed to UE1 is transmitted from frequency block 2 or 3.

  In step S22, the base station creates a control signaling channel for each frequency block according to the scheduling information. The control signaling channel includes a common control channel (unspecified control channel) and a specific control channel.

  In step S23, the control channel and the shared data channel are transmitted from the base station for each frequency block according to the scheduling information.

  In step S13, the terminal UE1 receives signals transmitted in the frequency blocks 2 and 3.

  In step S14, the terminal UE1 recognizes the transmission format of the common control channel from the part 0 of the control channel received in the frequency blocks 2 and 3.

  In step S15, the common control channel is separated from the control channel received in the frequency block 2, is decoded, and scheduling information is extracted. Similarly, the common control channel is separated from the control channel received by the frequency block 3, is decoded, and the scheduling information is extracted. Any scheduling information includes information indicating whether or not a resource block is allocated to the shared data channel addressed to the terminal UE1, information indicating a resource block number when the resource block is allocated, and the like. When no resource block is assigned to the shared data channel addressed to the own station, the terminal UE1 returns to the standby state and waits for reception of the control channel. If any resource block is allocated to the shared data channel addressed to the own station, the terminal UE1 separates the specific control channel included in the received signal in step S16 and decodes it. The specific control channel includes data modulation, channel coding rate, and HARQ information regarding the shared data channel.

  In step S17, the terminal UE1 decodes the shared data channel included in the received signal based on the information extracted from the specific control channel. An acknowledgment (ACK) or a negative acknowledgment (NACK) may be reported to the base station according to the decoding result. Thereafter, the same procedure is repeated.

  9B and 9C show details of the procedure relating to steps S14-S16. FIG. 9B is a flowchart illustrating an example of a parallel reception operation. In step S1, the part 0 information in the common control information is confirmed. For example, a 2-bit value indicating part 0 information is confirmed, and the L1 / L2 control channel pattern is identified from among predetermined options.

In step S2, the number of symbols in one subframe of the L1 / L2 control channel is specified according to the specified pattern. It is assumed that the simultaneous allocation maximum number of users N _UMAX and N _DMAX are notified separately for the upper and lower links in the broadcast information. The data size per user is derived based on the number of L1 / L2 control channel symbols in one subframe and the maximum number of simultaneously allocated users.

In each step S3-1~N _DMAX, for each data size per user that is derived in step S2, demodulation is performed. This information part of one data size corresponds to the unit information part mentioned in connection with the description of the paging indicator (FIG. 5E). In these steps, each unit information portion is demodulated as control information related to the downlink. Actually, it is expected that only users having a maximum user multiplexing number N _DMAX or less are communicating. In the illustrated example, since these processes are performed in parallel, the processing time is the time required to demodulate one unit information portion.

  In step S4, the communication terminal checks whether or not there is downlink communication control information addressed to itself.

In each step S5-1~N _UMAX, for each data size per user that is derived in step S2, demodulation is performed. These steps S5-1～N _UMAX, unlike step S3-1～N _DMAX, demodulates the control information associated with the unit information portion uplink. In this case, the unit information portion related to the downlink and the unit information portion related to the uplink may have the same data size or different data sizes. Also in this case, it is expected that only users having the maximum user multiplexing number N _UMAX are actually communicating. Since these processes are performed in parallel, the processing time is the time required to demodulate one unit information portion.

In step S6, the communication terminal confirms the presence / absence of uplink communication control information addressed to itself.
In the above example, the maximum number of multiplexed users is specified separately for the upper and lower links. However, as described above, it is conceivable that only the total number (N _all ) of the upper and lower links combined is specified in the broadcast information. In this case, since it is unclear how many of Nall are for uplink or downlink, the demodulation of the unit information portion must be repeated for the total number Nall in the step S3 for the downlink. Similarly, for the uplink, demodulation must be repeated for the total number Nall in the step S5. Therefore, the number of times of demodulation at the communication terminal may increase considerably, but instead, the amount of information indicating the number of multiplexed users that must be notified by broadcast information can be reduced (rather than notifying both _NDMAX and _NUMAX) However, the amount of information is smaller if only Nall is notified.)

  FIG. 9C is a flowchart illustrating an example of a serial reception operation. As in the case of FIG. 9B, the part 0 information in the common control information is confirmed in step S1. In step S2, the number of symbols in one subframe of the L1 / L2 control channel is specified according to the specified pattern. The data size per user is derived based on the number of L1 / L2 control channel symbols in one subframe and the maximum number of simultaneously allocated users.

  In step S3, a parameter for designating the number of calculations is set to an initial value (n = 0).

  In step S4, demodulation is performed for each data size per user derived in step S2. In this step, each unit information portion is demodulated as control information related to the downlink.

In step S5, it is confirmed whether or not downlink communication control information addressed to the terminal itself has been obtained. If not, the flow proceeds to step S6, the parameter value is incremented by 1, and the flow returns to step S4 to demodulate another unit information portion. Thereafter, the same procedure is repeated until an event occurs in which the downlink communication control information addressed to the terminal is acquired or the parameter reaches the maximum value N _DMAX .

  In step S7, the parameter for designating the number of calculations is set to the initial value again (n = 0).

  In step S8, demodulation is performed for each data size per user derived in step S2. In this step, each unit information portion is demodulated as control information related to the uplink.

In step S9, it is confirmed whether or not uplink communication control information addressed to the terminal itself has been obtained. If not, the flow proceeds to step S10, the parameter value is incremented by one, and the flow returns to step S8 to demodulate another unit information portion. Thereafter, the same procedure is repeated until one of the events that the uplink communication control information addressed to the own terminal is acquired or the parameter reaches the maximum value N _UMAX occurs, and the flow is thus terminated.

In the example shown in the figure, these unit information parts are demodulated in series, so that the processing time is the shortest, and it takes time to demodulate the downlink unit information part once and the uplink unit information part once, longest and downlink unit information portion N _DMAX times and the uplink information unit portion takes time extent of N _UMAX recover tone.

Also in this example, it is conceivable that only the total number (N _all ) including the upper and lower links is specified in the broadcast information. Since it is unclear how many of Nall are for uplink or downlink, the demodulation of the unit information portion must be repeated for the downlink by a number equal to or less than the total number Nall in step S5. Similarly, for the uplink, demodulation must be repeated by a number equal to or less than the total number Nall in step S9. Therefore, the number of times of demodulation at the communication terminal may increase considerably, but instead, the amount of information indicating the number of multiplexed users that must be notified by broadcast information can be reduced (rather than notifying both _NDMAX and _NUMAX) However, the amount of information is smaller if only Nall is notified.)

  The unspecified control channel (including part 0) is information required by all users, and in order to decode the data channel based on this unspecified control channel, error detection (CRC) coding and channel are added to the unspecified control channel. Encoding is performed. In the second embodiment of the present invention, a specific example of this error detection coding and channel coding will be described. FIG. 4B is a diagram corresponding to a configuration in which L1 / L2 control information (part 0) and L1 / L2 control information (parts 2a and 2b) are separately channel-coded (channel coding / (Including diffusion / data modulation units 41 and 42-A). This alternative configuration is described below.

  FIG. 10A shows a case where part 0 and parts 2a and 2b are combined with error detection coding, and part 0 and parts 2a and 2b are separately channel coded. The communication terminals UE1 and UE2 detect an error by combining part 0 and parts 2a and 2b, and use the L1 / L2 control channel for the own communication terminal from among parts 2a and 2b based on part 0.

  Since the error detection (CRC) code of part 0 may be larger than the control bits of part 0, it is possible to reduce the error detection coding overhead in this case.

  FIG. 10B shows a case where part 0 and parts 2a and 2b are separately subjected to error detection coding, and part 0 and parts 2a and 2b are separately subjected to channel coding. Compared to the case of FIG. 10A, the overhead becomes larger, but there is an advantage that it is not necessary to perform the processes of parts 2 a and 2 b when the error detection of part 0 fails.

  FIG. 10C shows a case where part 0 and parts 2a and 2b are error-coded together and part 0 and parts 2a and 2b are channel-coded together. In this case, if the part 0 and the parts 2a and 2b are not decoded together, the information of the part 0 cannot be extracted, but there is an advantage that the efficiency of the channel coding rate is increased.

  Although FIGS. 10A to 10C describe error detection coding and channel coding of part 0 and parts 2a and 2b, the present invention can be similarly applied to unspecified control channels other than parts 2a and 2b.

  By the way, it is desirable to perform link adaptation from the viewpoint of improving the received signal quality of the control channel. In the third embodiment of the present invention, transmission power control (TPC) and adaptive modulation and coding (AMC) control are used as methods for performing link adaptation. FIG. 11 shows how transmission power control is performed, and it is intended to achieve the required quality on the receiving side by controlling the transmission power of the downlink channel. More specifically, since the channel state for the user 1 far from the base station is expected to be bad, the downlink channel is transmitted with a large transmission power. On the contrary, it is expected that the channel state is good for the user 2 close to the base station. In this case, if the transmission power of the downlink channel to the user 2 is large, the received signal quality for the user 2 may be good, but interference will be large for other users. Since the channel state of the user 2 is good, the required quality can be ensured even if the transmission power is small. Therefore, in this case, the downlink channel is transmitted with a relatively small transmission power. When transmission power control is performed independently, the modulation scheme and the channel coding scheme are kept constant, and a known combination is used on the transmission side and the reception side. Therefore, it is not necessary to separately notify the modulation scheme and the like in order to demodulate the channel under transmission power control.

  FIG. 12 shows how adaptive modulation and coding control is performed. The required quality on the receiving side is achieved by adaptively changing either or both of the modulation method and the coding method according to the quality of the channel state. Is intended. More specifically, if the transmission power from the base station is constant, the channel state for the user 1 far from the base station is expected to be poor, so the modulation multilevel number is small and / or the channel coding rate. Is also set small. In the example shown in the figure, QPSK is used as the modulation scheme for user 1 and 2 bits of information are transmitted per symbol. On the other hand, the user 2 close to the base station is expected to have a good channel state, and the modulation multi-level number is set large and / or the channel coding rate is set large. In the illustrated example, 16QAM is used as a modulation scheme for the user 2, and information of 4 bits per symbol is transmitted. As a result, the required quality is achieved by increasing the reliability for users with poor channel conditions, and the throughput can be improved while maintaining the required quality for users with good channel conditions. In adaptive modulation and coding control, when demodulating a received channel, information such as the modulation method, coding method, and number of symbols applied to that channel is required, so that information is notified to the receiving side by some means. It is necessary to. In addition, since the number of bits that can be transmitted per symbol differs depending on whether the channel state is good or not, information can be transmitted with a small number of symbols if the channel state is good, but on the other hand, a large number of symbols is required.

In the third embodiment of the present invention, transmission power control is performed for an unspecified control channel that an unspecified user must decode, and transmission is performed for a specified control channel that a specific user to which a resource block is allocated may decode. One or both of power control and adaptive modulation and coding control are performed. Specifically, the following three methods can be considered.
(1) TPC-TPC
In the first method, transmission power control is performed on an unspecified control channel, and only transmission power control is performed on a specific control channel. In the transmission power control, since the modulation scheme and the like are fixed, if the channel is received well, it can be demodulated without prior notification regarding the modulation scheme and the like. Since the unspecified control channel is distributed over the entire frequency block, it is transmitted with the same transmission power over the entire frequency range. In contrast, a specific control channel for a user occupies only a specific resource block for that user. Therefore, the transmission power of the specific control channel may be individually adjusted so that the received signal quality is improved for each user to which the resource block is assigned. For example, in the example shown in FIGS. 7A and 7B, the non-specific control channel is transmitted with the transmission power P ₀ , the specific control channel of the user 1 (UE1) is transmitted with the transmission power P ₁ suitable for the user 1, and the user 2 (UE2 ) May be transmitted with the transmission power P ₂ suitable for the user 2, and the specific control channel of the user 3 (UE 3) may be transmitted with the transmission power P ₃ suitable for the user 3. Incidentally portion of the shared data channel may be transmitted in the same or a different transmission power P _D.

As described above, the unspecified control channel must be decoded by all unspecified users. However, the main purpose of transmitting the control channel is to notify the user to which the resource block is actually allocated that there is data to be received and scheduling information thereof. Therefore, the transmission power when transmitting the unspecified control channel may be adjusted so that the required quality is satisfied for the user to which the resource block is allocated. For example, in the example of FIGS. 7A and 7B, when all users 1, 2 and 3 to which resource blocks are allocated are located in the vicinity of the base station, the transmission power P ₀ of the unspecified control channel is set to be relatively small. Good. In this case, for example, users at the cell edge other than the users 1, 2 and 3 may not be able to decode the unspecified control channel satisfactorily.

(2) TPC-AMC
In the second method, transmission power control is performed on an unspecified control channel, and only adaptive modulation and coding control is performed on the specific control channel. In general, when AMC control is performed, it is necessary to notify the modulation scheme and the like in advance. In this method, information such as the modulation scheme for the specific control channel is included in the non-specific control channel. Accordingly, each user first receives an unspecified control channel, decodes and demodulates it, and determines whether there is data addressed to the user station. If it exists, in addition to extracting scheduling information, information on the modulation scheme, coding scheme, number of symbols, etc. applied to the specific control channel is also extracted. Then, the specific control channel is demodulated according to information such as scheduling information and modulation scheme, information such as the modulation scheme of the shared data channel is acquired, and the shared data channel is demodulated.

  The control channel does not require much transmission at a higher throughput than the shared data channel. Therefore, when AMC control is performed for an unspecified control channel, the total number of combinations of modulation schemes and the like may be smaller than the total number of combinations of modulation schemes for shared data channels. As an example, as a combination of AMC of unspecified control channels, the modulation scheme may be fixed to QPSK, and the coding rate may be changed to 7/8, 3/4, 1/2, 1/4.

  According to the second method, it is possible to improve the quality of the specific control channel while ensuring the quality of the non-specific control channel at a certain level or higher for all users. This is because the specific control channel is mapped to a resource block having a good channel state for each specific communication terminal, and an appropriate modulation scheme and / or encoding scheme is used. By performing adaptive modulation and coding control on a specific control channel portion of the control channel, the reception quality of that portion can be improved.

  Note that the number of combinations of modulation schemes and channel coding rates may be limited to be extremely small, and demodulation may be attempted for all combinations on the receiving side. The content that has been successfully demodulated is finally adopted. In this way, a certain amount of AMC control can be performed even if information on the modulation scheme or the like is not notified in advance.

(3) TPC-TPC / AMC
In the third method, transmission power control is performed on an unspecified control channel, and both transmission power control and adaptive modulation and coding control are performed on the specific control channel. As described above, when AMC control is performed, in principle, it is necessary to notify the modulation scheme and the like in advance. In addition, it is desirable that the total number of combinations of modulation schemes and channel coding rates is large from the viewpoint of ensuring required quality even when fading varies greatly. However, if the total number is large, the determination process such as the modulation method becomes complicated, the amount of information required for notification increases, and the calculation burden and overhead increase. In the third method, transmission power control is used in combination with AMC control, and the required quality is maintained by both controls. Therefore, it is not necessary to compensate for all fading that varies greatly only by AMC control. Specifically, a modulation method that reaches the vicinity of the required quality is selected, and the required quality is ensured by adjusting the transmission power under the selected modulation method. For this reason, the total number of combinations of modulation schemes and channel coding schemes may be limited.

  In any of the above methods, only transmission power control is performed on the unspecified control channel, so that the user can easily obtain control information while maintaining required quality. Unlike AMC control, the amount of information transmitted per symbol does not change and can be easily transmitted in a fixed format. Since the unspecified control channel is distributed over the entire frequency block or over many resource blocks, the frequency diversity effect is large. Therefore, it can be expected that the required quality can be sufficiently achieved by simple transmission power control that adjusts the long-period average level. Note that it is not essential to the present invention that only transmission power control is performed for the non-characteristic control channel. For example, the transmission format used for the non-characteristic control channel may be controlled at a low speed using the broadcast channel.

  By including AMC control information (information for specifying a modulation scheme or the like) for a specific control channel in the non-specific control channel, AMC control can be performed for the specific control channel. For this reason, the transmission efficiency and quality of a specific control channel can be improved. The number of symbols required for the unspecified control channel is substantially constant, but the number of symbols required for the specified control channel varies depending on the content of AMC control, the number of antennas, and the like. For example, if the number of symbols required is N when the channel coding rate is 1/2 and the number of antennas is 1, the number of symbols required when the channel coding rate is 1/4 and the number of antennas is 2 is 4N. It increases to. Thus, even if the number of symbols required for the control channel changes, in this embodiment, the control channel can be transmitted in a simple fixed format as shown in FIGS. 7A and 7B. The content of the changing number of symbols is not included in the non-specific control channel, but is included only in the specific control channel. Therefore, it is possible to flexibly cope with such a change in the number of symbols by changing the ratio of the specific control channel and the shared data channel in the specific resource block.

  The data channel transmission format is reported on the L1 / L2 control channel. Therefore, the transmission format of the L1 / L2 control channel needs to be known to the user equipment. The simplest method is to fix the transmission format of the L1 / L2 control channel to one for all users in the serving cell. However, from the viewpoint of effective use of radio resources or link adaptation, it is desirable to adaptively change even the transmission format of the L1 / L2 control channel for each user. However, when the transmission format changes, it is necessary to notify each user apparatus which transmission format is used. In the fourth embodiment of the present invention, the transmission format of the L1 / L2 control channel is variably controlled.

  In general, even if the number of information bits to be transmitted is constant, the data size required for actual transmission differs depending on the transmission format. The transmission format is specified by parameters including a combination of modulation scheme and channel coding scheme (MCS information). The MCS information may be specified by a combination of a modulation scheme and a data size.

  As shown in FIG. 13, in order to transmit certain information with MCS2 (modulation scheme = QPSK, channel coding scheme R = 1/4), MCS1 (modulation scheme = QPSK, channel coding scheme R = 1/2). ) Requires twice the data size required for transmission. To transmit this information with MCS3 (modulation method = QPSK, channel coding method R = 1/6), the data required to transmit with MCS1 (modulation method = QPSK, channel coding method R = 1/2) Requires 3 times the size. In this way, when the MCS applied to the L1 / L2 control channel is variably controlled, the data size expressing it is different. Therefore, if the MCS is unknown at the time of decoding, the decoding process must be repeated as many times as possible. In order to finally determine the presence or absence of control information addressed to the device in the decoding process performed for each MCS, it is necessary to know how many control information are multiplexed on the L1 / L2 control channel (at most) This is because the control information destined to the own apparatus can be extracted (if any) by performing the decoding process for the number of times of multiplexing.

  As mentioned in FIGS. 9B and 9C of the first embodiment, the number of users multiplexed in the L1 / L2 control channel (user multiplexing number) may be notified to the user equipment separately on the uplink and downlink. The total number of both upper and lower links may be notified. However, the amount of radio resources required for notification, the amount of processing burden on the user device side, and the like differ depending on how the notification is made.

  Before describing the various methods according to the fourth embodiment of the present invention, symbols used in the description are defined in advance.

N _MCS : Represents the total number of MCSs prepared for the L1 / L2 control channel. That is, the combination of the data modulation scheme and the channel coding scheme used for the L1 / L2 control channel is expressed by any one of MCS-1 to _MCS -N _MCS .

N _{L1L2 (max)} : Represents the number of L1 / L2 control channels that can be multiplexed in 1 TTI (however, the number when the most efficient MCS is used) = N ′ _D + N ′ _U.

N _{UE, D} (m): Represents the number of MCS-m users in the downlink (assuming that a lower number is used for MCS with higher transmission efficiency).

N _{UE, U} (m): Represents the number of users of MCS-m in the uplink (assuming that MCS with higher transmission efficiency uses a lower number).

N _D : represents the number of downlink L1 / L2 control channels multiplexed related to downlink transmission (N ′ _D represents N _D when MCS with the highest transmission efficiency is used).

N _U: represents the number of multiplexed related L1 / L2 control channel for transmission of uplink (N _'U represents N _u in the case where the most efficient MCS is used.).

N _Dmax : represents the maximum number of multiplexed L1 / L2 control channels related to downlink transmission (N _D ≦ N _DMAX ).

N _Umax represents the maximum number of multiplexed L1 / L2 control channels related to uplink transmission (N _U ≦ N _UMAX ).

N _{L1L2 (max)} represents the maximum number that can be multiplexed for an arbitrary subframe, and (N ′ _D + N ′ _U ) represents the maximum number that can be multiplexed in a specific subframe.

FIG. 14A schematically shows how the downlink L1 / L2 control channel is transmitted with various multiplexing numbers in four TTIs. FIG. 14B shows a specific example of the multiplex number defined as described above with reference to FIG. 14A. In FIG. 14A, “D” indicates information related to the downlink, and “U” indicates information related to the uplink. It is shown that the data size is different depending on the applied MCS. 14A and 14B, only two types of MCS (MCS1 has higher transmission efficiency than MCS2) are shown for the sake of simplicity. For example, the bandwidth used in TTI1 can transmit information for nine users (N _{L1 / L2 (max)} = 9) if all users are transmitted in MCS1. On the downlink, U3 uses MCS1 with high efficiency, while U1 and U2 use MCS2 with low transmission efficiency (for this reason, “1” and “2” are shown for N _{UE and D.} ). As described with reference to FIG. 13, the higher the efficiency, the smaller the data size. Regarding uplink, U2 and U3 use MCS1 with high efficiency, but U1 uses MCS2 with low transmission efficiency (for this reason, “2” and “1” are shown for N _{UE and U.} ). In TTI1, a maximum of 5 users can be multiplexed on the downlink (N ′ _D = 5), but only 3 users are actually multiplexed (N _D = 3). Further, although up to 4 users can be multiplexed in the uplink (N ′ _U = 4), only 3 users are actually multiplexed (N _U = 3). Similarly, other TTIs are listed with numerical values for each parameter.

  Hereinafter, when the transmission format (specifically, the MCS number) applied to the L1 / L2 control channel is variably controlled, how to report the user multiplex number to the user equipment is described in the methods 1 to 7. Be considered. The main features of each method are shown in FIG.

(Method 1)
In the first method, the number of users (N _{UE, D} (m), N _{UE, U} (m)) is notified to the user apparatus for each TTI and for each MCS. Since the number of multiplexed users is notified separately for the upper and lower links, the user equipment is at most N _{UE, D} (m) + N _{UE, U} (m) times (hereinafter, this number is also referred to as “the number of blind detection positions”). ), It is possible to identify control information addressed to the own device (if it exists). In this method, the MCS-m of each user can be freely set for each user, so that the L1 / L2 control channel can be transmitted most efficiently (the highest radio resource efficiency). Since the number of symbols required for the L1 / L2 control channel is reported as part 0 information, the boundary between the L1 / L2 control channel and the shared data channel may change for each TTI.

(Method 2)
Also in the second method, the MCS of the L1 / L2 control channel is variably controlled for each user for each TTI. In this method, the number of multiplexed L1 / L2 control channels (values in the most efficient case: N ′ _D , N ′ _U ) is notified to the user equipment separately for each uplink and downlink for each TTI. Although MCS is variably controlled for each TTI, it is not specifically notified what the MCS of each user apparatus is. Therefore, the number of blind detection positions is N _MCS x (N ′ _D + N ′ _U ).

  Compared with method 1, the number of blind detections is greatly increased, but the number of bits required to express the multiplex number is small. This method is preferable from the viewpoint of saving the number of bits of the part 0 information. Since the MCS is controlled for each user for each TTI, the use efficiency of radio resources is as high as that of the method 1.

(Method 3)
Also in the third method, the MCS of the L1 / L2 control channel is variably controlled for each TTI. In this method, the sum of the number of multiplexed L1 / L2 control channels (the total number of multiplexed data in the most efficient case: N ′ _D + N ′ _U ) is reported collectively for each TTI. Even in this method, the MCS is variably controlled, but it is not specifically notified what the MCS of each user apparatus is. Accordingly, the number of blind detection positions is 2 × N _MCS × (N ′ _D + N ′ _U ).

  Compared with method 2, the number of blind detections is further increased (twice that of method 2), but the number of bits of part 0 information can be further saved. Since the MCS is controlled for each user for each TTI, the use efficiency of radio resources is as high as that of the method 1.

(Method 4)
In the fourth method, the MCS of each user is not controlled for each TTI, and it is notified in a higher layer (for example, with L3 control information) in a longer cycle, but the number of multiplexed users is separate for each uplink and downlink for each TTI. Will be notified. The MCS of each user is controlled at a lower speed than in the method 1-3. For instantaneous fading, it is preferable to maintain the quality by performing transmission power control. In this method, the number of multiplexed L1 / L2 control channels (the number of multiplexing in the most efficient case: N ′ _D , N ′ _U ) is reported separately for each uplink and downlink for each TTI. The number of blind detection positions depends on MCS, but N ′ _D + N ′ _U at most is sufficient.

  Since this method notifies each user's MCS only at a low speed, the number of bits of the part 0 information can be saved as compared with the case of the method 1. On the other hand, since the MCS is not updated frequently, the utilization efficiency of radio resources may be inferior to that of the method 1.

(Method 5)
Even in the fifth method, the MCS of each user is not controlled for each TTI, and it is notified in the upper layer (for example, with L3 control information) in a longer cycle. The number of user multiplexes is reported together for the upper and lower links for each TTI. As in the case of Method 4, since the MCS of each user is controlled only at a low speed, it is preferable to maintain the quality by performing transmission power control for instantaneous fading. In this method, the sum of the number of multiplexed L1 / L2 control channels (the total number of multiplexed data in the most efficient case: N ′ _D + N ′ _U ) is notified for each TTI. The number of blind detection positions depends on MCS, but is 2x (N ′ _D + N ′ _U ) at the maximum.

  Since this method also notifies each user's MCS only at a low speed, the utilization efficiency of radio resources is similar to that of Method 4. In this method, the number of multiplexed users is reported together in the upper and lower links, so the number of blind detections increases, but part 0 information can be saved more than in the case of method 4.

(Method 6)
Also in the sixth method, the MCS of each user is not controlled for each TTI, and it is notified in the upper layer (for example, with L3 control information) in a longer cycle. In this method, the maximum total number that can be multiplexed for each TTI is notified to the user collectively in the uplink and downlink, and the maximum number (N _Dmax , N _Umax ) that can be multiplexed separately for the uplink and downlink in a period longer than the TTI is ( Notified by broadcast information (BCH). Even in this method, the MCS of each user is controlled only at a low speed. Therefore, it is preferable to maintain the quality by performing transmission power control for instantaneous fading. The number of multiplexed L1 / L2 control channels notified for each TTI is expressed by the total number of multiplexing (N ′ _D + N ′ _U ) that can be realized when MCS with the highest transmission efficiency is used.

  In this method, the mapping positional relationship (arrangement of radio resources) between control information related to the uplink and control information related to the downlink is determined in advance. More specifically, for example, control information related to the downlink is arranged in order for each user, and then control information related to the uplink is arranged in order for each user. For example, the control information is forced to be mapped as indicated by “◯” in FIG. 15, and the mapping as indicated by “x” is prohibited. The mapping method itself is not limited to the arrangement shown in the figure, but any appropriate method may be used, but it is necessary that the mapping method is fixed in advance. Thus, by fixing the positional relationship of mapping in advance, the number of blind detections can be reduced.

In FIG. 16, as an example, when N _Dmax = 6, N _Umax = 4, and N _D + N _U = 9, the portion to be subjected to blind detection is indicated by a broken line. The user apparatus does not have to perform blind detection for a portion not surrounded by a broken line. By predetermining the mapping positional relationship of the control information related to the up and down links, the number of times of blind detection performed by the user apparatus can be reduced.

  Since this method also notifies each user's MCS only at a low speed, the utilization efficiency of radio resources is similar to that of Method 4. In this method, the number of multiplexed users is reported together in the upper and lower links, so part 0 information can be saved more than in method 4.

(Method 7)
In the seventh method, the MCS is fixed in common to all users residing in the cell. The maximum total number that can be multiplexed for each TTI (total number of multiplexing possible when transmission efficiency is the best: N ' _D + N' _U ) is notified to the users of the uplink and downlink together, and multiplexed separately for the uplink and downlink in a period longer than TTI. The maximum possible number (N _Dmax , N _Umax ) is reported in the upper layer (for example, by broadcast information (BCH)).

  Similarly to the method 6, the number of blind detections performed by the user apparatus can be reduced by predetermining the mapping position relationship of the control information related to the up and down links. In this method, since the MCS of each user is uniquely fixed, the utilization efficiency of radio resources may be inferior to any method. However, in this method, the number of multiplexed users is reported together in the upper and lower links. It can save more than in the case of method 4.

  As described above, the number of control bits required for downlink data transmission related information (Down Link Scheduling Grant-information) including precoding vector, transmission format, HARQ related information, etc. is determined when MIMO transmission is performed. Is expected to vary depending on the selected MIMO transmission scheme. For example, the number of streams, the number of codewords, the number of frequency selective precoding vectors, etc. may change.

  Even with such a change in the number of control bits, the channel coding scheme of downlink scheduling grant information is efficient transmission (which leads to a larger coding gain), rapid decoding processing (at the shortest) It is desirable to enable a single decoding process) and a reduction in the number of brand detections (encoding block size is fixed or known in advance). Although channel coding is outlined in connection with FIG. 6, the fifth embodiment of the present invention describes the invention related to channel coding in more detail.

  Hereinafter, three example methods for the channel coding scheme of the downlink scheduling grant information will be described.

(Method 1)
FIG. 18 illustrates an example in which a control signal includes a portion where the same channel coding scheme is applied to all users and a portion where it is not. In the first method, the control signal is divided into a basic data size part and an additional part. The basic data size is set large enough to include all information necessary for one stream transmission. The same channel coding scheme is applied to all users who need only control information smaller than the basic data size. When the number of streams is larger than 1, an additional part is prepared separately from the basic data size part. The data size of the additional part may be different for each user. Accordingly, channel coding is performed independently for each user in the additional portion (a different channel coding scheme may be used for each user, but even if the same channel coding scheme happens to be used by multiple users) Good.) When receiving the control signal, the user apparatus first decodes the basic data size portion and obtains control information. When it is found that the control information for the own device includes more contents than one stream, the user device can acquire all the control information for all the streams by decoding the additional part. According to this method, a user apparatus that transmits only one stream needs only one decoding process, and can maintain high coding efficiency even if the amount of control information differs for each user.

(Method 2)
FIG. 19A shows another example in which a portion where the same channel coding scheme is applied to all users and a portion where the same channel coding scheme is not present exist in the control signal. The second method is different in that the basic data size in the first method is fixed to be smaller. In the first method, the amount of control information necessary for one stream transmission may change. In the second method, the fixed length portion and the variable length portion of the control information are fixed in advance by the system. The fixed length part (Fixed Part) may include downlink resource allocation information and stream number information. The variable length part may include precoding information, transmission format, and HARQ related information for all streams. This method can also maintain high encoding efficiency as in the first method.

  FIG. 19B shows a downlink scheduling grant (Downlink Scheduling Grant) decoding method performed in the user apparatus when a part to which the same channel coding scheme is applied to all users and a part to which the same channel coding scheme is not present exist in the control signal. .

(Option 1) Decoding is performed separately for the basic data size portion and the additional portion.
In this case, the additional part is mapped to the control resource block (Control Resource Block), and the index of the additional control resource block is determined in advance. For example, in FIG. 19B, the basic data size portion is mapped to the first block (1stblock), and the additional portion is mapped to the second block (2ndblock) adjacent to the first block. The second block may be a resource block assigned to the shared data channel.

(Option 2) Decoding is performed separately for a fixed-length part and a variable part.
For example, in FIG. 19B, the basic data size portion is mapped to the 1st block, and the additional portion is a part of a predetermined resource block, eg, a resource block assigned to a control resource block or a shared data channel. To be mapped.

(Method 3)
FIG. 20 shows an example in which the channel coding scheme of the control signal is different for each user. In the third method, it is not intended that a common channel coding scheme is applied to all users (the same channel coding scheme may happen to be applied to all users as a result depending on the communication situation). .) All control information including a variable amount of control information related to MIMO is channel-coded together for each user. In this method, the unit of channel coding is ensured as long as possible for each user apparatus, so this method is preferable in that the coding gain can be kept high.

  FIG. 21 is a chart showing a comparative example of each method.

  FIG. 22 is a chart showing an example of the data size used for each information item.

FIG. 23 shows an example in which each method is compared in terms of the number of symbols. More specifically, the number of symbols required for downlink scheduling grant information is shown when the data sizes of precoding information, transmission format information, and HARQ related information are fixed and the number of blind detections is kept small. . In this comparative calculation example, a data size as shown in FIG. 22 is used. With respect to method 1, the CRC is only added to the basic data size portion (ie, the CRC is the result of the operation for both the basic data size portion and the additional portion). The combination of modulation scheme and channel coding scheme (MCS) for downlink scheduling grant information is {QPSK and R = 1/2}. The number of bits (B) of precoding vector information and the number of codewords N _codeword are changed as parameters.

As shown in the comparison result of FIG. 23, when the number of control bits of the precoding information is small (case A), the overhead increase amount of method 1 with respect to method 2 can be ignored. On the other hand, the maximum value of the overhead increase amount is about 30% at 5 MHz in Method 3 and about 16% at 20 MHz. When the number of control bits of the precoding information is large (case B), the amount of overhead increase in methods 1 and 3 is larger than that in method 2.

The following items are further disclosed regarding the embodiment including the above examples.

(1) A base station used in a mobile communication system that uses the OFDM scheme in the downlink,
A scheduler that schedules allocation of radio resources for each subframe so that a user apparatus communicates using one or more resource blocks;
Means for preparing a control channel including common control information mapped over a system band and specific control information mapped to one or more resource blocks allocated to a specific user device;
Means for time-multiplexing the common control information and the specific control information in accordance with an instruction from the scheduler to create a transmission signal;
And the common control information includes a format indicator indicating which number of symbols occupied by the common control information in one subframe is a predetermined option,
The common control information includes unit information portions having a predetermined data size by a number equal to or less than the designated multiplexing number.

(2) The base station according to (1), wherein the one or more unit information portions include a paging indicator regularly or irregularly.

(3) The base station according to (2), wherein the unit information portion including the paging indicator includes identification information for a paging indicator different from the identification information of the user apparatus.

(4) The base station as set forth in (1), wherein a paging indicator is included in an information portion reserved exclusively for the unit information portion.

(5) Among predetermined combinations of the modulation scheme and the channel coding scheme, a combination applied to the common control information portion of each user apparatus is controlled for each subframe, and information on user apparatuses using the same combination The base station as set forth in (1), wherein the number of specified multiplexes is separately indicated for uplink and downlink to indicate how many people are included in the common control information.

(6) Among predetermined combinations of modulation scheme and channel coding scheme, a combination applied to common control information of each user apparatus is controlled for each subframe,
The designated multiplex number includes information for how many persons in the common control information when a combination having the maximum transmission rate among the predetermined combinations of the modulation scheme and the channel coding scheme is applied to the common control information. The base station according to (1), wherein the uplink and downlink are separately indicated.

(7) Among the predetermined combinations of the modulation scheme and the channel coding scheme, the combination applied to the common control information of each user apparatus is controlled for each subframe,
The designated multiplex number includes information for how many persons in the common control information when a combination having the maximum transmission rate among the predetermined combinations of the modulation scheme and the channel coding scheme is applied to the common control information. The base station as set forth in (1), characterized by:

(8) The common control information is transmitted for each subframe as low layer control information,
MCS information indicating what combination of modulation scheme and channel coding scheme is applied to the common control information is transmitted as high layer control information,
(1) The base station according to (1), wherein information indicating how many people can be included in the common control information is indicated separately for uplink and downlink.

(9) The common control information is transmitted for each subframe as low layer control information,
MCS information indicating what combination of modulation scheme and channel coding scheme is applied to the common control information is transmitted as high layer control information,
The number of persons included in the common control information is indicated by the total number of uplink and downlink. The base station according to (1),

(10) The common control information is transmitted for each subframe as low layer control information,
MCS information indicating what combination of modulation scheme and channel coding scheme is applied to the common control information is transmitted as high layer control information,
Information indicating the maximum number of people included in the common control information for any subframe is transmitted in broadcast information separately in the uplink and downlink,
Information indicating the maximum number of people included in the common control information transmitted in a specific subframe is indicated by the total number of up and down links,
The base station according to (1), wherein a positional relationship in common control information between control information related to uplink and control information related to downlink is determined in advance.

(11) The common control information is transmitted as low layer control information for each subframe,
Information indicating the maximum number of information that may be included in the common control information transmitted in an arbitrary subframe is indicated in the broadcast information separately in the uplink and downlink,
Information indicating the maximum number of people included in the common control information transmitted in a specific subframe is indicated by the total number of up and down links,
The base station according to (1), wherein a positional relationship in the common control information between control information related to uplink and control information related to downlink is determined in advance.

(12) The base station according to (1), wherein transmission power control is performed for each user at least for transmission of common control information.

(13) Although the transmission format of the common control information for some users residing in the cell remains unchanged, the transmission format of the common control information for other users is variably controlled (1 ) Base station described.

(14) The base station according to (13), wherein the some users are users at a cell edge.

(15) The base station according to (1), wherein in the control information of each user apparatus, a portion having a predetermined basic data size or less and another portion are separately channel-coded.

(16) The base station according to (15), wherein the predetermined basic data size is set to a fixed length smaller than a data size of control information addressed to any user apparatus.

(17) The base station according to (1), wherein a channel coding unit is different for each user apparatus.

(18) A method used in a base station of a mobile communication system that uses an OFDM scheme for a downlink,
Planning the allocation of radio resources by the scheduler for each subframe so that the user apparatus communicates using one or more resource blocks, common control information mapped over the system band, and one or more allocated to a specific user apparatus Providing a control channel including specific control information mapped to a resource block of
In accordance with an instruction from the scheduler, time-multiplexing the common control information and the specific control information to create a transmission signal;
And the common control information includes a format indicator indicating which number of symbols occupied by the common control information in one subframe is a predetermined option,
The common control information includes a unit information portion having a predetermined data size by a number equal to or less than a designated multiplexing number.

(19) A user apparatus used in a mobile communication system that uses an OFDM scheme for a downlink,
Means for receiving a signal including a control channel having common control information mapped over a system band and specific control information mapped to one or more resource blocks assigned to a specific user equipment;
Means for separating the control channel and other channels from the received signal;
Control channel decoding means for decoding the common control information and the specific control information;
And the control channel decoding means analyzes a format indicator in the common control information, and identifies which of the predetermined options the number of symbols occupied by the common control information in one subframe. And
The control channel decoding means confirms whether or not control information addressed to its own device is included in a plurality of unit information portions of a predetermined data size in the common control channel. It is performed by decoding the common control information as many times as the designated multiplex number in a predetermined decoding method,
When control information addressed to the own device is included, a resource block for the own device is specified from the control information, and a data channel is derived by demodulating the resource block.

(20) The user device according to (19), wherein the one or more unit information portions include a paging indicator regularly or irregularly.

(21) The user device according to (20), wherein the unit information portion including the paging indicator includes identification information for a paging indicator different from the identification information for the user device.

(22) The user device according to (19), wherein a paging indicator is included in an information portion reserved exclusively for the unit information portion.

(23) Among predetermined combinations of modulation scheme and channel coding scheme, a combination applied to the common control information portion of each user apparatus is controlled for each subframe, and information on user apparatuses using the same combination (19) The user equipment according to (19), wherein the number of designated multiplexes is separately indicated for uplink and downlink to indicate how many people are included in the common control information.

(24) Among predetermined combinations of modulation scheme and channel coding scheme, a combination applied to common control information of each user apparatus is controlled for each subframe,
The designated multiplex number includes information for how many persons in the common control information when a combination having the maximum transmission rate among the predetermined combinations of the modulation scheme and the channel coding scheme is applied to the common control information. The user equipment according to (19), wherein the user equipment is indicated separately for uplink and downlink.

(25) Of the predetermined combinations of the modulation scheme and the channel coding scheme, the combination applied to the common control information of each user apparatus is controlled for each subframe,
The designated multiplex number includes information for how many persons in the common control information when a combination having the maximum transmission rate among the predetermined combinations of the modulation scheme and the channel coding scheme is applied to the common control information. (19) The user device according to (19), wherein

(26) The common control information is transmitted as sub-layer control information for each subframe,
MCS information indicating what combination of modulation scheme and channel coding scheme is applied to the common control information is transmitted as high layer control information,
(19) The user apparatus according to (19), wherein information indicating how many people can be included in the common control information is indicated separately for uplink and downlink.

(27) The common control information is transmitted as sub-layer control information for each subframe,
MCS information indicating what combination of modulation scheme and channel coding scheme is applied to the common control information is transmitted as high layer control information,
(19) The user apparatus according to (19), wherein the number of persons included in the common control information is indicated by the total number of up and down links.

(28) The common control information is transmitted for each subframe as low layer control information,
MCS information indicating what combination of modulation scheme and channel coding scheme is applied to the common control information is transmitted as high layer control information,
Information indicating the maximum number of people included in the common control information for any subframe is transmitted in broadcast information separately in the uplink and downlink,
Information indicating the maximum number of people included in the common control information transmitted in a specific subframe is indicated by the total number of up and down links,
(19) The user apparatus according to (19), wherein the positional relationship in the common control information between the control information related to the uplink and the control information related to the downlink is determined in advance.

(29) The common control information is transmitted as low layer control information for each subframe,
Information indicating the maximum number of information that may be included in the common control information transmitted in an arbitrary subframe is indicated in the broadcast information separately in the uplink and downlink,
Information indicating the maximum number of people included in the common control information transmitted in a specific subframe is indicated by the total number of up and down links,
(19) The user apparatus according to (19), wherein a positional relationship in the common control information between control information related to uplink and control information related to downlink is determined in advance.

(30) The user apparatus according to (19), wherein control information in which a part having a predetermined basic data size or less and another part are channel-coded separately is received.

(31) The user device according to (30), wherein the predetermined basic data size is set to a fixed length smaller than a data size of control information addressed to any user device.

(32) The base station according to (19), wherein a channel coding unit is different for each user apparatus.

(33) A method used in a user apparatus of a mobile communication system that uses an OFDM scheme for a downlink,
Receiving a signal including a control channel having common control information mapped over a system band and specific control information mapped to one or more resource blocks assigned to a specific user equipment;
Separating the control channel and other channels from the received signal;
A control channel decoding step for decoding the common control information and the specific control information;
And the control channel decoding step analyzes a format indicator in the common control information and specifies which number of symbols occupied by the common control information in one subframe is a predetermined option. And
The control channel decoding step confirms whether or not control information addressed to its own device is included in a plurality of unit information portions of a predetermined data size in the common control channel. It is performed by decoding the common control information as many times as the designated multiplex number in a predetermined decoding method, and the designated multiplex number is included in the broadcast information,
When control information addressed to the own device is included, a resource block for the own device is specified from the control information, and a data channel is derived by demodulating the resource block.

  (34) The subcarriers to which the common control information is allocated constitute a plurality of control resource blocks composed of one or more subcarriers, and when the common control information is mapped within a plurality of OFDM symbols, The base station according to (1), wherein the control resource block is mapped to all OFDM symbols.

(35) The control information in which the other part is channel-coded is mapped to a part of the resource block allocated to the control resource block or the shared data channel,
The user according to (30) or (31), wherein the control information in which the portion below the predetermined basic data size is channel-coded and the control information in which the other portion is channel-coded are separately decoded apparatus.

31 frequency block allocation control unit 32 frequency scheduling unit 33-x control signaling channel generation unit in frequency block x 34-x data channel generation unit in frequency block x 35 broadcast channel (or paging channel) generation unit 1-x frequency block first multiplexing unit 37 related to x 37 second multiplexing unit 38 third multiplexing unit 39 other channel generation unit 40 inverse fast Fourier transform unit 41 cyclic prefix addition unit 41 unspecified control channel generation unit 42 specific control channel generation unit 43 multiplexing unit 81 Carrier frequency tuning unit 82 Filtering unit 83 Cyclic prefix removal unit 84 Fast Fourier transform unit (FFT)
85 CQI measurement unit 86 Broadcast channel decoding unit 87-0 Unspecified control channel (part 0) decoding unit 87 Unspecified control channel decoding unit 88 Specific control channel decoding unit 89 Data channel decoding unit

Claims (1)

A mobile communication system that uses an OFDM scheme in the downlink and uses a subframe formed by a plurality of OFDM symbols,
A mapping unit that maps a control channel to a predetermined number of OFDM symbols from the beginning of a subframe, and maps a data channel to an OFDM symbol that is behind the OFDM symbol to which the control channel is mapped;
A transmission unit for transmitting the control channel and the data channel mapped in the mapping unit,
In the control channel mapped in the mapping unit, a plurality of control resource blocks are multiplexed, and each control resource block is mapped to all OFDM symbols to which the control channel is mapped,
And the base station transmission format of the control channel for some users but is kept unchanged, the transmission format of the control channel to another user characterized by Rukoto is variably controlled located in the cell,
A receiver for receiving the control channel and the data channel ;
A mobile communication system comprising: a terminal including a processing unit that processes a control channel and a data channel received by the receiving unit.

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