Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L27/00—Modulated-carrier systems
  • H04L27/26—Systems using multi-frequency codes
  • H04L27/2601—Multicarrier modulation systems
  • H04L27/2626—Arrangements specific to the transmitter only
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
  • H04L1/0002—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate
  • H04L1/0003—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate by switching between different modulation schemes
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
  • H04L1/0023—Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the signalling
  • H04L1/0028—Formatting
  • H04L1/0029—Reduction of the amount of signalling, e.g. retention of useful signalling or differential signalling
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
  • H04L1/0072—Error control for data other than payload data, e.g. control data
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
  • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
  • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
  • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
  • H04L1/1812—Hybrid protocols; Hybrid automatic repeat request [HARQ]
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
  • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
  • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
  • H04L1/1867—Arrangements specially adapted for the transmitter end
  • H04L1/1896—ARQ related signaling
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L5/00—Arrangements affording multiple use of the transmission path
  • H04L5/0001—Arrangements for dividing the transmission path
  • H04L5/0003—Two-dimensional division
  • H04L5/0005—Time-frequency
  • H04L5/0007—Time-frequency the frequencies being orthogonal, e.g. OFDM(A) or DMT
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L5/00—Arrangements affording multiple use of the transmission path
  • H04L5/003—Arrangements for allocating sub-channels of the transmission path
  • H04L5/0044—Allocation of payload; Allocation of data channels, e.g. PDSCH or PUSCH
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L5/00—Arrangements affording multiple use of the transmission path
  • H04L5/003—Arrangements for allocating sub-channels of the transmission path
  • H04L5/0053—Allocation of signalling, i.e. of overhead other than pilot signals
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
  • H04W52/04—Transmission power control [TPC]
  • H04W52/30—Transmission power control [TPC] using constraints in the total amount of available transmission power
  • H04W52/34—TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading
  • H04W52/346—TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading distributing total power among users or channels
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
  • H04L1/0009—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the channel coding
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
  • H04L1/0023—Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the signalling
  • H04L1/0025—Transmission of mode-switching indication
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
  • H04L1/0023—Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the signalling
  • H04L1/0026—Transmission of channel quality indication
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W72/00—Local resource management
  • H04W72/50—Allocation or scheduling criteria for wireless resources
  • H04W72/54—Allocation or scheduling criteria for wireless resources based on quality criteria

Definitions

• the present invention relates to a technical field of wireless communication, and more particularly to a transmission apparatus and a transmission method used in a communication system that performs packet scheduling in the downlink.
• IMT-2000 International Mobile Telecommunications_2000
• an information transmission rate of 2 Mbps or more is realized using a 5 MHz frequency band in the downlink.
• the IMT-2000 uses a single-carrier wideband code division multiple access (W-CDMA) system.
• W-CDMA wideband code division multiple access
• High Speed Downlink Packet Access (HSDPA) is based on Adaptive Modulation and Channel Coding (AMC), automatic retransmission of packets at the MAC layer (ARQ: Automatic Repeat). Request) and high-speed packet scheduling are used to increase the transmission rate and quality.
• AMC is described in Non-Patent Document 1, for example.
• ARQ is described in Non-Patent Document 2, for example.
• FIG. 1 is a conceptual diagram for explaining the AMC method.
• the terminal 11 close to the base station 10 can receive a signal with higher power than the terminal 12 far from the base station 10. Therefore, since the channel state for the terminal 11 is estimated to be good, a large value is adopted for the modulation multilevel number and the code rate.
• the terminal 12 can receive a signal with less power than the terminal 11. Therefore, since the channel state for the terminal 12 is expected to be not good, a small value is used for the modulation level and the coding rate.
• FIG. 2 shows an example of combinations of modulation schemes (modulation multilevel numbers) and channel coding rates.
• the combination of the channel state quantity, modulation method and coding rate (MCS number) is determined in advance in a table as shown in the figure, and an appropriate MCS number is appropriately selected according to the channel state. Is done.
• the quantity indicating the channel state is generally managed as channel state information (CQI: Channel Quality Indicator).
• CQI Channel Quality Indicator
• the channel state information CQI may be expressed, for example, as a power ratio between a desired signal and an undesired signal. Typically, it may be expressed as an SIR (Signal to Interference power ratio) or SINR of the received signal. ,.
• FIG. 3 is a conceptual diagram for explaining the ARQ (precisely, hybrid ARQ) method.
• the hybrid ARQ method is a technology that combines the ARQ method that requests retransmission of packets according to the error detection (CRC: Cyclic Redundancy Check) result, and the error correction coding (or channel coding) method that performs error correction. It is.
• CRC Cyclic Redundancy Check
• S3 error correction decoding
• S4 error detection
• the sender is requested to retransmit the packet (S5).
• FIG. 4 there are several ways of how to retransmit.
• a packet P1 is transmitted from the transmission side to the reception side, and when an error is detected on the reception side, the packet P1 is discarded and retransmission is requested.
• the transmitting side retransmits a packet (indicated by P2) having the same contents as packet P1.
• packet P1 is transmitted from the transmission side to the reception side, and even if an error is detected on the reception side, packet P1 is maintained without being discarded.
• the transmission side retransmits a packet (indicated by P2) having the same contents as packet P1.
• the receiving side combines the previously received packet and the packet received this time to generate packet P3.
• the contents of packet P1 correspond to those transmitted at twice the power, so the demodulation accuracy improves.
• the packet P1 is maintained without being discarded.
• the transmitting side transmits the redundant data derived by performing a certain operation on the packet PI as the packet P2. For example, it is assumed that multiple sequences such as PI, PI ', P1 ", ... are derived by signing packet P1. Depending on the algorithm of the sign used.
• the transmission side when the transmission side receives a retransmission request, it transmits P1 ′ as a packet P2. On the receiving side, the receiving side combines the previously received packet and the packet received this time to generate packet P3. Since packet P3 has increased redundancy, the demodulation accuracy is more probable. For example, if the coding rate of the packet P1 is 1Z2, the reliability of the packet P3 becomes 1/4 because the coding rate of the packet P3 is 1/4. However, information such as what the encoding algorithm is and what redundant data is transmitted (puncture pattern) needs to be known to the receiving side.
• the high-speed packet scheduling method is a technique for improving the frequency utilization efficiency in the downlink.
• the channel state between the mobile station (user) and the base station changes with time.
• it is possible to improve the frequency utilization efficiency by determining whether the channel state is good or bad for each user and preferentially assigning shared data packets to users with good channel state.
• Power S can be.
• FIG. 5 is a conceptual diagram for explaining a high-speed packet scheduling method.
• a shared data packet is allocated to a user having a good channel condition (a user related to a large value of SINR).
• a plurality of codes may be used to multiplex data addressed to different users within one time slot (frame).
• codes # 1 to # 10 are used, and two types of data for user # 1 and user # 2 are multiplexed in the third frame among the five frames.
• Patent Document 2 S. Lin, Costello, Jr. and M. Miller, “Automatic-Repeat-Request Error control Schemes", IEEE Communication Magazine, vol.12, No.12, pp.5-17, Dec.198 4
• FIG. 19 schematically shows the reception level of a signal affected by frequency selective fading.
• Fig. 19 (A) if the frequency band used for radio transmission is relatively narrow, the reception level within that band can be treated as being constant.
• FIG. 19 (B) when it becomes a wide band, the frequency dependence of the reception level becomes significant.
• dividing the entire radio band into a plurality of frequency blocks and applying adaptive modulation / decoding coding, ARQ, and packet scheduling for each frequency block may be effective for high speed and large capacity. Les. However, when all of these controls are performed in the minimum data unit, many control signals are required, and there is a concern that the data transmission efficiency may be deteriorated.
• An object of the present invention is to efficiently transmit a control signal necessary for improving frequency utilization efficiency in a communication system that preferentially transmits data to a communication partner in a better channel state. It is to provide a transmission device and a transmission method.
• a transmission device that uses one or more frequency blocks including one or more carrier frequencies and preferentially transmits data to a communication partner in a better channel state.
• the transmission device evaluates the channel state for each frequency block for each of a plurality of communication partners, and selects means for selecting one or more communication partners from the plurality of communication partners;
• a determination means for determining at least a modulation method according to the evaluated channel state, one or more frequency blocks that can be used by the selected communication partner to receive data, and a control channel indicating the determined modulation method.
• FIG. 1 is a conceptual diagram for explaining an AMC scheme.
• FIG. 2 is a diagram illustrating an example of combinations of modulation schemes and channel coding rates.
• FIG. 3 is a conceptual diagram for explaining a hybrid ARQ scheme.
• FIG. 4 is a diagram showing a specific example of a retransmission method.
• FIG. 5 is a diagram showing reception quality that changes with time.
• FIG. 6 is a diagram showing how a plurality of users are code-multiplexed.
• FIG. 7 is a block diagram of a transmitter according to an embodiment of the present invention.
• FIG. 8 is a diagram illustrating a state in which time multiplexing is performed in a radio resource allocation unit.
• FIG. 9 is a diagram illustrating a state in which frequency multiplexing is performed in a radio resource allocation unit.
• FIG. 10 is a diagram illustrating a state where code multiplexing is performed in a radio resource allocation unit.
• FIG. 11 is a diagram showing how radio resources are allocated using a plurality of frequency blocks
• FIG. 12A is a diagram showing a transmission procedure of a base station according to one embodiment of the present invention.
• FIG. 12B is a flowchart (1) for explaining the transmission procedure in more detail.
• FIG. 12C is a flowchart (2) for explaining the transmission procedure in more detail.
• FIG. 12D is a flowchart (3) for explaining the transmission procedure in more detail.
• FIG. 13 is a chart listing the contents of control information.
• FIG. 14 is a diagram showing several examples of mapping control information and other information on a downlink physical channel.
• FIG. 15A is a diagram showing an example of mapping control information for each frequency block in a downlink physical channel.
• FIG. 15B shows an example of a localized FDM.
• FIG. 15C is a diagram showing an example of distributed FDM.
• FIG. 16 is a diagram showing a state in which error detection coding is applied to control information.
• FIG. 17 is a diagram showing a state in which error correction coding is performed on control information.
• FIG.18 A chart comparing various transmission methods.
• FIG. 32 is a block diagram of a transmitter according to an embodiment of the present invention.
• FIG. 33 is a diagram illustrating a correspondence relationship between modulation schemes and transmission power.
• FIG. 34 is a diagram illustrating a correspondence relationship between MCS numbers and transmission power.
• FIG. 35A is a diagram showing transmission power for each resource block when conventional AMC control is performed.
• G] 35B] is a diagram showing transmission power for each resource block when AMC control and transmission power control are performed according to the present embodiment.
• FIG. 37 is a diagram showing a schematic allocation example of resource blocks.
• FIG. 38 is a diagram showing an example of transmission power for each resource block.
• FIG. 39 is a diagram showing another example of transmission power for each resource block.
• the channel state is evaluated for each frequency block for each of a plurality of communication partners, and one or more communication partners are selected based on the evaluation result, and according to the evaluated channel state. At least a modulation method is determined, and a control channel indicating one or more frequency blocks that can be used for receiving data by the selected communication partner and the determined modulation method is created. The data channel modulated by the modulation method is transmitted to the selected communication partner.
• the modulation method that can be specified with a small number of bits and the number of bits greatly affects the data transmission efficiency. Therefore, in a communication system that performs packet scheduling and AMC control using a wide frequency band, The control information can be efficiently transmitted to the mobile station, and the frequency utilization efficiency can be further improved.
• the channel coding rate may also be determined according to the channel state for each frequency block.
• a data channel modulated by the modulation method and encoded at the channel coding rate and a control channel may be transmitted.
• the channel coding rate is determined for each frequency block.
• adaptive modulation codes can be performed for each frequency block.
• the channel coding rate may be set to the same value for a plurality of frequency blocks. This is because the channel coding rate does not affect the data transmission efficiency and the like as much as the modulation multi-level number.
• Means for receiving a data retransmission request from the communication partner may be provided in the transmission apparatus, and the transmission means may retransmit the data in response to the retransmission request. Data retransmission in response to a retransmission request may be performed for each frequency block. As a result, retransmission control can be performed for each frequency block.
• an error correction code means for performing error correction code on the control channel may be provided in the transmission apparatus.
• the error correction encoding means may perform error correction encoding of the control channel for each frequency block from the viewpoint of reducing the occurrence of errors.
• the control information of the physical layer and the control information of the layer higher than the physical layer may be separately error correction encoded.
• the data transmitted from the transmission means may include an error detection code for the control information.
• Error detection codes may be added separately to the two types of control information for the physical layer and higher layers than the physical layer.
• the present invention is applied to a system that employs an orthogonal frequency division multiplexing (OFDM) system in the downlink, which describes a system that employs an orthogonal frequency division multiplexing (OFDM) system, and other multicarrier systems. May be applied.
• the wide downlink frequency band is divided into multiple frequency blocks.
• one frequency block is Although one or more carrier frequencies are included, in this embodiment, it is assumed that each frequency block includes a plurality of subcarriers.
• Such a frequency block is also called a resource block or a chunk.
• a frequency block or chunk may be used as a unit for allocating radio resources.
• FIG. 7 shows a transmitter 700 according to one embodiment of the present invention.
• the transmitter 700 is typically provided in a base station of a mobile communication system as in the present embodiment, but may be provided in another device.
• the base station and the transmitter are used interchangeably unless otherwise noted.
• FIG. 7 showing a part of the transmitter 700 shows a common control channel processing unit 720, a shared control channel processing unit 740, a shared data channel processing unit 760, a radio resource allocation unit 702, and an inverse Fourier transform unit 704.
• a guard interval processing unit 706 is shown.
• the common control channel processing unit 720 performs channel coding, modulation, and spreading for transmitting a common control channel.
• the common control channel includes certain information such as a base station scramble code.
• the shared control channel processing unit 740 performs coding, modulation, and spreading for transmitting a shared control channel.
• the shared control channel includes scheduling information necessary for the mobile station to demodulate the shared data channel.
• the common control channel processing unit 720 includes a channel encoding unit 722, a data modulation unit 724, and a spreading unit 726.
• the shared control channel processing unit 740 also includes a channel encoding unit 742, a data modulation unit 744, and a spreading unit 746.
• Channel coding sections 722 and 742 code the signals input thereto according to some coding algorithm, and output them. For example, convolutional encoding may be performed in the channel encoding unit.
• Data modulation sections 724 and 744 modulate and output a signal input thereto.
• modulation such as QPSK may be performed.
• Spreading sections 726 and 746 spread the signal input thereto and output it.
• Shared data channel processing section 760 performs packet scheduling in addition to channel coding, modulation and spreading of the shared data channel (transmission data).
• the shared data channel processing unit 760 includes a packet scheduling unit 761, a channel coding unit 762, and a data
• the data modulation unit 764 and the diffusion unit 766 are included.
• Packet scheduling section 761 receives data to be transmitted to one or more mobile stations, and performs data transmission scheduling based on feedback information from each mobile station.
• Data to be transmitted to the mobile station is received from a device or network higher than the base station, and stored in a transmission buffer (not shown) for each mobile station.
• the feedback information includes channel state information (CQI) measured by the mobile station.
• CQI is expressed by SIR.
• the packet scheduling unit 761 evaluates the state of the propagation path for each mobile station based on the channel state information CQI reported from each mobile station, and selects a mobile station with a better channel state. As will be described later, channel state information CQI from the mobile station is reported for each frequency block (or chunk).
• the packet scheduling unit 761 determines the combination (MCS number) of the modulation scheme and coding rate corresponding to the downlink data transmission.
• the MCS number is determined according to a table as shown in FIG.
• the packet scheduling unit 761 also performs processing related to packet retransmission based on the feedback information.
• Information such as the selected mobile station, MCS number, and retransmission control information is output as control information, and the control information is provided to the shared control channel processing unit 740. Data to be transmitted to the selected mobile station is given to channel coding section 762 as transmission data.
• Channel encoding section 762 encodes the signal input thereto according to some code algorithm and outputs it. For example, turbo coding may be performed in the channel coding unit.
• the data modulation unit 764 modulates and outputs a signal input thereto.
• Various modulations such as QPSK :, 16QAM, and 64QAM may be performed in the data modulation unit.
• Spreading section 766 spreads the signal input thereto and outputs it.
• Radio resource allocation section 702 appropriately multiplexes and outputs the signals after spreading the common control channel, shared control channel, and shared data channel. Multiplexing may be performed by any one of time multiplexing, frequency multiplexing, or code multiplexing, or two or more methods may be combined.
• Figure 8 shows the situation when two signals are time multiplexed. In the figure, Channel # 1 and channel # 2 represent any two of the common control channel, shared control channel, and shared data channel. For simplicity of illustration, the power of the multiplexing of two signals is shown. Three signals may be time multiplexed. Fig. 9 shows how two signals are frequency-multiplexed, and Fig. 10 shows how two signals are code-multiplexed.
• appropriate radio resources time slot, frequency and Z or code
• Inverse Fourier transform section 704 performs OFDM modulation by performing fast inverse Fourier transform (IFFT) on the signal input thereto, and outputs the modulated signal.
• IFFT fast inverse Fourier transform
• the guard interval processing unit 706 adds a guard interval to the signal input thereto, creates a symbol in the OFDM scheme (OFDM symbol), and outputs it.
• the OF DM symbol is input to a radio unit (not shown) and transmitted by radio.
• FIG. 11 is a conceptual diagram for explaining an operation example of a transmitter according to an embodiment of the present invention.
• a wide downlink frequency band is divided into a plurality of frequency blocks or chunks, and in this embodiment, each frequency block includes a plurality of subcarriers.
• radio resources are allocated not only for each time slot (shown as a transmission slot in the figure) but also for each frequency block. As will be described later, this time slot may be one transmission time interval (TTI) or the duration of some packet.
• TTI transmission time interval
• the entire downlink frequency band is divided into eight frequency blocks, and each frequency block includes the same number of subcarriers. The channel state is monitored for each of these eight frequency blocks, and a frequency block is assigned to a mobile station with a better channel state.
• FIG. 12A is a flowchart showing a transmission procedure performed in the base station.
• the base station receives channel state information CQI from one or more mobile stations and analyzes their contents. For example, the channel state information CQI, which is the received SIR, is reported for each frequency block. That is, before this flow starts, the mobile station measures, for example, the received signal quality of a pilot signal and measures the downlink channel state for each frequency block.
• step 122 based on the reported received SIR for each frequency block, a better The mobile station in the channel state is identified for each frequency block, and the mobile station that reported the best received SIR for each frequency block is selected. In addition, the combination of modulation scheme and coding rate (MCS number) corresponding to the received SIR is also determined. This combination is also determined for each frequency block.
• MCS number modulation scheme and coding rate
• step 123 of FIG. 12A a common control channel, a shared control channel, and a shared data channel are created. These processes are performed by the processing units 720, 740, and 760 in FIG. However, each channel does not necessarily have to be created at the same time in this step.
• the shared control channel is created based on the control information output from the packet scheduling unit 761 in FIG. This control information includes information (MCS number, etc.) necessary for demodulating the shared data channel. Details of the control information and its transmission method will be described later.
• step 124 of FIG. 12A an OFDM symbol is created. This processing is mainly performed in the radio resource allocation unit 702, IFFT unit 704, guard interval insertion unit 706, etc. in FIG.
• step 125 of FIG. 12A downlink data transmission is performed on one or more frequency blocks according to the determined MCS number for the mobile station selected in step 122.
• FIG. 12B is a flowchart for explaining an example of the operation performed in steps 123 and 124 of FIG. 12A.
• step S1 a bit for error detection is added to the transmission data sequence.
• CRC cyclic redundancy detection
• step S2 channel codes are performed. As described above, the channel coding is performed by the channel coding unit 762 in FIG. 7, and the channel coding for the data channel is performed by the channel coding unit 762.
• step S3 processing relating to hybrid ARQ is performed. More specifically, send For example, information indicating whether the packet to be retransmitted is a new packet or information indicating the redundant version of the retransmission packet is created.
• the redundant purge can be changed by puncturing or repetition.
• the channel code rate may be changed in this step.
• step S4 harm ij is assigned to the physical channel, and the encoded symbol is assigned to each frequency block.
• This processing is mainly performed by the radio resource allocation unit 702 in FIG.
• the frequency scheduling determines which user's symbol is assigned to which frequency block.
• steps S5_1 to N data modulation is performed for each frequency block, and a transmission symbol is created.
• N is the total number of frequency blocks. Thereafter, a process (not shown) for wirelessly transmitting the transmission symbol is performed.
• the modulation scheme is determined for each frequency block, so that a transmission rate suitable for each frequency block is set individually. Therefore, the illustrated operation example is preferable from the viewpoint of increasing transmission throughput.
• steps S1 to S4 are the same as in FIG. 12B.
• step S5 ' it is shown that a modulation scheme common to all frequency blocks is determined. More generally, the modulation scheme may be determined in common for a plurality of frequency blocks. By using a common modulation method for multiple frequency blocks, the number of control bits (information amount) required to notify the receiving side of the modulation method can be reduced compared to the case of FIG. 12B.
• the modulation scheme not only the modulation scheme but also the channel coding rate may be determined for each frequency block.
• the signal is transmitted by the method shown in FIGS. 12B and 12C.
• frequency block # 1 including the lowest subcarrier for frequency block # 1 including the lowest subcarrier, user # 1 is selected in a certain transmission slot, and user # 2 is selected in the next transmission slot.
• user # 1 is in the best channel condition at that frequency block
• user # 2 is in the best channel condition.
• the mobile station in the best channel state in each frequency block is determined for each transmission slot, and data transmission is performed with an adaptive modulation scheme suitable for the mobile station, so that a wide frequency band can be used very efficiently. can do.
• FIG. 13 shows details of main control information given to the shared control channel processing unit 740 by the packet scheduling unit 761 of FIG.
• the control information includes chunk allocation information, modulation scheme information, coding rate information, hybrid ARQ process information, redundant version, packet state information, and UE identity information. Is included.
• Chunk allocation information indicates which frequency block is allocated to which mobile station (user). The number of frequency blocks allocated to a certain mobile station (user) is determined according to the required data rate, and generally a numerical value of 1 or more is also acceptable.
• user # 1 is assigned to two frequency blocks # 1 and # 4, and one frequency block is assigned to the remaining users # 2 to 6,8.
• one frequency block is assigned to each user.
• This frequency block allocation state is shown in the chunk allocation information.
• This information belongs to physical layer control information. Since this information indicates how a plurality of frequency blocks are allocated, it is not necessary to notify the mobile station for each frequency block.
• Modulation scheme information indicates a modulation scheme used for downlink data transmission, and is specified by an MCS number. For example, various multilevel modulation schemes such as QPSK, 16QAM, 64 QAM, 128QAM, etc. may be used. This information belongs to physical layer control information. This information is preferably notified to the mobile station for each frequency block, but may be notified to a plurality of frequency blocks in common.
• the channel coding rate is managed for each frequency block together with the modulation method, and may be notified to the mobile station for each frequency block, or is managed separately from the modulation method, and the same value is used for a plurality of frequency blocks. May be. Figure “Yes” in the rightmost column of 13 corresponds to the former case, and “none” corresponds to the latter case.
• Hybrid ARQ process information indicates a packet number related to retransmission control. This information belongs to layer 2 control information. Retransmission of packets in hybrid ARQ may be performed for each frequency block, or may be performed for each transmission slot without distinguishing the frequency block. “Yes” in the rightmost column in FIG. 13 corresponds to the former case, and “No” corresponds to the latter case.
• the redundancy version indicates what puncture pattern is used for retransmission control.
• This information belongs to layer 2 control information.
• redundant data may be transmitted for each frequency block, or may be performed for each transmission slot without distinguishing the frequency block. “Yes” in the rightmost column in FIG. 13 corresponds to the former case, and “none” corresponds to the latter case.
• Packet status information distinguishes whether a packet transmitted to the mobile station of the base station is a packet transmitted for the first time (new packet) or a retransmitted packet (retransmitted packet). This information belongs to layer 2 control information. No, retransmission of packets in the hybrid ARQ may be performed for each frequency block, or may be performed for each transmission slot without distinguishing the frequency block. “Yes” in the rightmost column in FIG. 13 corresponds to the former case, and “No” corresponds to the latter case.
• UE identity information distinguishes a mobile station or a user receiving data transmitted on the downlink, and is also referred to as a user identifier or identification information. This information belongs to the physical layer control information. This information does not need to be notified to the mobile station for each frequency block, similar to the chunk allocation information.
• FIG. 14 shows several examples of mapping a control channel and other channels on a downlink physical channel.
• the control channels are mapped or multiplexed over a certain frequency range and total duration.
• the frequency range may be the same as or different from the frequency block range.
• the control channel is mapped over the entire frequency and over a certain period.
• Configuration example 3 shows an example of the mapping combination shown in configuration example 1 and configuration example 2. That is, in the configuration example 3, the control channel is mapped over a certain frequency range and a certain period.
• control channel frequency Wide mapping in the direction increases the frequency diversity effect, which is preferable from the viewpoint of improving the received signal quality.
• Configuration Example 4 is an example in which the control channel is mapped for each frequency block in the downlink physical channel. Since control channels include those whose data size varies depending on the number of users and frequency blocks, when all control channels are mapped using the method of Configuration Example 2, the period occupied by the control channels is constant over time. There is a risk that the demodulation process becomes complicated.
• the control channel (unspecified control channel) related to all frequency blocks is mapped over the entire frequency as in configuration example 2, and the control channel (specific control channel ( A specific control channel can be mapped only to that frequency block. As a result, the efficiency and quality of the demodulation process of the control channel can be improved.
• the configuration example of the mapping shown in FIG. 4 is merely an example, and the control channel and the other channels may be variously multiplexed by a single method or a combination method of time, frequency, or code. Good.
• the target of multiplexing is not limited to the control channel and other channels, and any channel may be multiplexed.
• various multiplexing methods may be used.
• one or more frequency blocks may be allocated to each of a plurality of users, and the modulation scheme may be determined for each frequency block by the method shown in FIG. 12B.
• each of the four users may be assigned a frequency block, and the modulation scheme may be set separately for each of these frequency blocks.
• a modulation scheme common to multiple frequency blocks may be determined as shown in FIG. 12C.
• Frequency direction multiplexing as shown in Figure 15B, is called a localized frequency division multiplexing (localized FDM) scheme because a specific band is occupied by a specific user.
• localized FDM localized frequency division multiplexing
• distributed FDM distributed frequency division multiplexing
• each channel is It has a plurality of frequency components (subcarrier components) distributed at equal intervals or unequal intervals on the wavenumber axis, and different channels are orthogonal to each other in the frequency domain.
• each user's channel is distributed over the entire system band, and each user's channel is orthogonal to each other in the frequency domain.
• At least one of the modulation scheme and the channel coding rate may be determined for each frequency block or for a plurality of frequency blocks, and may be determined in units of smaller frequencies. Theoretically, for each of a number of subcarriers, they may be determined individually. Therefore, when multiplexing as shown in FIG. 15C is performed, a modulation scheme or the like may be determined for each subcarrier. However, even if the modulation method is determined in such a small unit, it is expected that the improvement effect of such a large throughput will not be obtained, and a control channel for specifying all of them is required. In addition, processing burden and control information amount may increase.
• FIG. 16 shows a state in which error detection coding is performed on the control channel.
• Error detection coding may be performed, for example, using a cyclic redundancy check (CRC) code.
• CRC cyclic redundancy check
• By performing error detection coding for example, it is possible to deal with problems such as a certain user demodulating data of a different user or performing erroneous retransmission control.
• the control information of the physical layer and the control information of the higher layer 2 are separately error detection coded. Performing the error detection code according to the type of control information is advantageous for mapping for each frequency block as in configuration example 4 in FIG. In the example shown in Fig.
• FIG. 17 shows a state where error correction coding is performed on the control information.
• Error correction coding may be performed by using, for example, convolutional coding. By performing error correction coding, for example, resistance to multipath fading can be increased.
• the control information of the physical layer and the control information of the higher layer 2 are separately error-corrected and encoded.
• the physical layer control information and the higher layer 2 control information are encoded together with error correction coding. That is, error correction coding is performed on the entire control information. This is desirable from the viewpoint of reducing overhead.
• the ability to correct errors (encoding gain) is advantageous when the unit of encoding is longer (B).
• the unit of the code key is long, a certain bit error may be chained to the subsequent bits. In other words, the probability that an error will occur tends to increase as the unit of the sign key increases. Therefore, in actuality, the encoding unit may be determined by comparing these characteristics.
• FIG. 18 shows a chart listing various methods for performing one or more of frequency-domain packet scheduling, adaptive modulation and coding (AMC), and hybrid ARQ for each frequency block. The contents of one method are shown in one line.
• AMC adaptive modulation and coding
• Method 1 controls packet scheduling, data modulation, channel coding rate, and hybrid ARQ in the frequency domain for each frequency block. In this way, frequency resources can be used most efficiently and data transmission efficiency is very good. However, since much of the control information listed in Fig. 13 has to be managed for each frequency block, the overhead becomes very large. Specifically, modulation scheme information, code rate information, hybrid ARQ process information, redundant version, and packet status information are all reported to the mobile station for each frequency block.
• a double circle ( ⁇ ) in the “Characteristics” column indicates that the data transmission efficiency is very good
• a circle ( ⁇ ) indicates that the data transmission is very good
• a triangle ( ⁇ ) indicates good
• the cross (X) indicates not good.
• the double circle ( ⁇ ) in the “overhead” column indicates that the amount of overhead is very small
• the circle ( ⁇ ) indicates that it is small
• the triangle ( ⁇ ) indicates that the intersection of overhead
• Method 2 packet scheduling, data modulation, and hybrid A RQ in the frequency domain are controlled for each frequency block, and the channel coding rate is controlled for each transmission time interval TTI.
• Transmission time interval TTI is a fixed unit time specific to the system.
• Method 2 only the channel coding rate is set to a value common to all frequency blocks. Therefore, Method 2 can reduce the overhead as compared with Method 1 in that the channel coding rate need not be managed for each frequency block.
• modulation scheme information, no, hybrid ARQ process information, redundant version, and packet status information are reported to the mobile station for each frequency block, and coding rate information is reported to all frequency blocks in common.
• Method 3 controls packet scheduling, data modulation, and hybrid A RQ in the frequency domain for each frequency block, and controls the channel coding rate for each packet.
• the length (duration) of the bucket is a relative quantity determined by the upper network, for example, and may be the same or different from the absolute unit time (TTI) inherent to the system. Good.
• TTI absolute unit time
• Method 3 only the channel coding rate is set to a value common to all power frequency blocks. Therefore, method 3 can also reduce overhead compared to method 1 in that the channel coding rate need not be managed for each frequency block. More specifically, modulation scheme information, no, hybrid ARQ process information, redundant version, and packet status information are notified to the mobile station for each frequency block, and coding rate information is reported in common to all frequency blocks. However, coding rate information needs to be reported for each packet.
• Method 4 controls packet scheduling, data modulation, and channel coding in the frequency domain for each frequency block, and controls No. and Abrid ARQ for each packet. That is, retransmission control is performed without distinguishing frequency blocks, and overhead can be reduced accordingly.
• the packet length is one unit of information that is actually communicated, and retransmission is performed for each packet. This is preferable from the viewpoint of improving throughput. Specifically, modulation scheme information and coding rate information are reported to the mobile station for each frequency block, and hybrid ARQ process information, redundant version, and packet status information are commonly reported to all frequency blocks. However, information regarding retransmission control must be notified for each packet.
• Method 5 packet scheduling and data modulation in the frequency domain are controlled for each frequency block, the channel code is controlled for each transmission time interval TTI, and the ARQ is controlled for each packet.
• channel coding rate control and retransmission control are performed without distinguishing frequency blocks, and overhead can be reduced accordingly.
• modulation scheme information is reported to the mobile station for each frequency block, and coding rate information, hybrid ARQ process information, redundant version, and packet status information are reported to all frequency blocks in common. However, information regarding retransmission control must be notified for each packet.
• Method 6 controls packet scheduling and data modulation in the frequency domain for each frequency block, and controls channel code rate and hybrid ARQ for each packet.
• channel coding rate control and retransmission control are performed without distinguishing frequency blocks, and overhead can be reduced accordingly.
• modulation scheme information is reported to the mobile station for each frequency block, and coding rate information, hybrid ARQ process information, redundant version, and packet status information are commonly reported to all frequency blocks.
• encoding rate information and information on retransmission control must be notified for each packet.
• Method 7 controls packet scheduling, data modulation, and channel coding in the frequency domain for each frequency block, and controls No. and ARQ for each transmission time interval TTI. That is, only retransmission control is performed without distinguishing frequency blocks. Method 7 can reduce overhead in that retransmission control is not required for each frequency block. In addition, since retransmission is performed at every transmission time interval TTI regardless of the length of the packet, retransmission control can be simplified. Specifically, modulation scheme information and coding rate information are reported to the mobile station for each frequency block, and hybrid ARQ process information, redundant version, and packet status information are commonly reported to all frequency blocks. However, information regarding retransmission control must be notified at every transmission time interval TTI.
• Method 8 packet scheduling and data modulation in the frequency domain are controlled for each frequency block, and channel codes and hybrid ARQ are controlled for each transmission time interval TTI. That is, channel coding rate control and retransmission control are performed without distinguishing frequency blocks, and overhead can be reduced accordingly.
• the modulation scheme information is It is notified to the mobile station for each frequency block, and the coding rate information, noise, hybrid ARQ process information, redundant version, and packet status information are commonly reported to all frequency blocks.
• coding rate information and information on retransmission control must be notified at every transmission time interval TTI.
• Method 9 packet scheduling and data modulation in the frequency domain are controlled for each frequency block, channel code is controlled for each packet, and noble ARQ is controlled for each transmission time interval TTI.
• channel coding rate control and retransmission control are performed without distinguishing frequency blocks, and overhead can be reduced accordingly.
• modulation scheme information is reported to the mobile station for each frequency block, and coding rate information, hybrid ARQ process information, redundant version, and packet status information are reported to all frequency blocks in common.
• coding rate information is notified for each packet, and information related to retransmission control must be notified for each transmission time interval TTI.
• the method 10 controls packet scheduling in the frequency domain for each frequency block, but controls data modulation, channel code and hybrid ARQ for each transmission time interval TTI. That is, data modulation, channel coding rate control, and retransmission control are performed without distinguishing frequency blocks, and overhead can be extremely reduced. Specifically, modulation scheme information, coding rate information, hybrid ARQ process information, redundant version, and packet status information are commonly reported to frequency blocks. However, these must be notified at every transmission time interval TTI.
• the modulation scheme (modulation multi-level number) control greatly affects the data transmission efficiency, throughput or frequency utilization efficiency, but the amount of information specifying the modulation scheme is Very little compared to control information or the like. Therefore, data modulation should be controlled for each frequency block.
• the control of the channel coding rate does not significantly affect the data transmission efficiency (characteristics) and overhead amount. Therefore, from the viewpoint of simplification of signal processing, it is effective to perform the channel coding rate at every transmission time interval TTI.
• Retransmission control The retransmission unit of ARQ has a large effect on the amount of overhead. It can be seen that the larger the amount of overhead, the better the data transmission efficiency.
• the information that is actually communicated is more than performed based on the transmission time interval TTI. It is desirable to carry out based on the unit of information (per packet). However, from the viewpoint of simplifying retransmission control, it is desirable to perform it at every transmission time interval TTI.
• CRC bit assignment, channel coding, and retransmission control are performed only for one data sequence.
• CRC bit assignment, channel coding, and retransmission control are performed for each of a plurality of data sequences.
• FIG. 20 is a flowchart (1) showing a main transmission procedure according to an embodiment of the present invention.
• step S1 the transmission data sequence is divided into a plurality of sequences.
• the processing after the division is the same as the flowchart (1) in FIG. 12B.
• the division of the data series may be performed by, for example, a serial / parallel conversion unit (S / P). Division may be called subdivision, segmentation, segmentation, etc.
• the size of the divided data may be the minimum unit at the time of retransmission. From the viewpoint of retransmitting the minimum necessary information, it is desirable that the data size after division is small, but from the viewpoint of reducing overhead related to retransmission, it is desirable that the data size after division is large.
• the transmission data sequence is shown as being divided into two sequences for simplicity of explanation, but the transmission data sequence may be divided into more than two sequences.
• the two system flows in FIG. 20 do not necessarily have to be performed simultaneously (if the data size is small, only the left or right flow is executed). You can do that.
• an error detection bit is added to each of the divided transmission data sequences.
• the data size after division may be the same in a plurality of series, or may be different for each series.
• steps S13 and S23 channel coding is performed on each of the divided transmission data sequences.
• R2 is determined independently and may be set to different values or the same value.
• each of the divided transmission data sequences is associated with a hybrid ARQ. Processing is performed. More specifically, information indicating whether the packet to be transmitted is a packet to be retransmitted or a new packet is created, and information for specifying a redundant version of the retransmission packet is created.
• the redundancy version at step 14 and the redundancy version at step 24 are also determined independently and may be different or the same.
• each of the divided transmission data sequences is assigned to a physical channel, and a symbol after the sign is assigned to each frequency block.
• This processing is mainly performed by the radio resource allocation unit 702 in FIG. Which user's symbol is assigned to which frequency block is determined by frequency scheduling.
• the illustrated operation example is preferable from the viewpoint of increasing the transmission throughput.
• FIG. 21 is another flowchart (1) ′ for explaining the main transmission procedure. This is generally the same as the flow in FIG. 20, but step S3 is different.
• FIG. 22 is another flowchart for explaining the main transmission procedure (2).
• the processing after the division in step S1 is the same as the flowchart (2) in FIG. 12C.
• This flow is generally the same as the flow in Fig. 20 except for the force steps S16 'and S26'.
• the modulation scheme is determined independently for each of the transmission data sequences divided into two, but the modulation scheme applied to the same series of data is the same.
• the modulation method may be different for each frequency block. Since the same modulation method is applied to multiple frequency blocks, The number of control bits required to notify the receiving side of the modulation scheme can be saved.
• FIG. 23 is another flowchart for explaining the main transmission procedure (2) ′. This is generally the same as the flow of FIG. 22, but step S3 is different.
• the modulation method applied to the same series of data is the same. Since the same modulation scheme is applied to multiple frequency blocks with the same channel code rate for each sequence, the number of control bits required to notify the receiving side of the channel coding rate and modulation scheme is saved. Can do.
• FIG. 24 is another flow chart for explaining the main transmission procedure. (2) “ 0 ” This is generally the same as the flow of FIG. 23, but step S6 is different.
• R1 R2
• the number of control bits required to notify the receiving side of the channel coding rate and the modulation scheme because the channel coding ratio for each sequence is equal and the same modulation scheme is applied to all frequency blocks. Can be further saved.
• FIG. 25 is another flowchart for explaining the main transmission procedure (3).
• the processing after the division in step S1 is the same as the flowchart (3) in FIG. 12D.
• this flow is generally the same as the flow of FIG. 20 except for the force steps S13— :! to K, 23—1 to L.
• the channel code can be performed for each frequency block.
• the signal is transmitted by the method shown in FIGS.
• Dividing the data series to be transmitted into a plurality of series may be performed in various product applications and processing environments.
• the data series to be transmitted is divided in accordance with a plurality of transmission antennas.
• FIG. 26 is a flowchart (1) for explaining a main transmission procedure according to the third embodiment.
• the transmission data sequence is generally transmitted from one transmitting antenna in the end, and in Fig. 26, it is divided.
• Each series of data is transmitted from separate transmit antennas # 1 and # 2.
• any number of sequences can be divided, that is, any number of transmitting antennas.
• the processing power for one transmit antenna (eg, # 1) in FIG. 26 may be replaced with any of the processes described in FIGS. That is, the data series transmitted from one transmission antenna may be divided into a plurality of pieces.
• the data sequence to be transmitted is divided into a larger number of sequences than the total number of transmission antennas.
• the channel coding rate is set for each transmission antenna, and the modulation scheme is set for each frequency block. Therefore, this method is preferable from the viewpoint of achieving high throughput.
• FIG. 27 is another flowchart for explaining the main transmission procedure (2).
• the data of each divided sequence is the same as the example shown in FIG. 22 except that it is transmitted from separate transmitting antennas # 1 and # 2.
• the same modulation scheme is used for a plurality of (all in the illustrated example) frequency blocks for data transmitted from the same transmission antenna. Therefore, the number of control bits required to notify the receiving side of the modulation method can be saved. Since this saving effect increases in proportion to the number of transmitting antennas, the saving effect of the number of control bits is greater than in the second embodiment.
• FIG. 28 is another flowchart (3) for explaining the main transmission procedure. Except for the fact that the data of each divided sequence is transmitted from separate transmit antennas # 1 and # 2, it is the same as the example shown in FIG.
• the fourth embodiment of the present invention is also related to the multi-antenna system as in the third embodiment.
• FIG. 29 is a flowchart (1) for explaining the main transmission procedure. Since the processing content performed in each step has already been described, redundant description is omitted.
• processing related to the CRC bit force Q, channel coding, and retransmission control is performed in common for all transmission antennas. Therefore, CRC bits are added to a packet having a relatively large data size and channel coding is performed. Thereafter, this packet is divided and transmitted separately from multiple transmit antennas. Therefore, according to the present embodiment, in order to notify the receiving side of the channel coding rate or CR The number of control bits required for c bits can be saved.
• FIG. 30 is a flowchart (2) for explaining the main transmission procedure.
• processing related to CRC bit allocation, channel coding, and retransmission control is performed in common for all transmission antennas.
• the modulation scheme applied to data transmitted from the same transmit antenna is the same regardless of the frequency block. Since the same modulation scheme is applied to multiple frequency blocks, the number of control bits required to notify the receiver of the modulation scheme can be saved.
• FIG. 31 is a flowchart (3) for explaining the main transmission procedure.
• processing related to CRC bit addition, channel coding, and retransmission control is performed in common for all transmission antennas.
• the channel code rate is also determined for each frequency block.
• AMC adaptive modulation and coding
• MCS modulation scheme and coding scheme
• the signal processing (encoding, decoding, modulation, demodulation, etc.) methods on the transmission side and the reception side differ depending on the combination contents of the modulation method and the coding method. Therefore, if the number of MCS is large, the number of signal processing method changes and the computation burden also increase. This is preferable from the viewpoint of simplifying signal processing (particularly for simple communication terminals).
• the fifth embodiment of the present invention can cope with such a problem.
• FIG. 32 shows a block diagram of a transmitter according to the present embodiment.
• This transmitter is generally similar in power to the transmitter already described in FIG. 7.
• the main difference is that the power control unit 768 is depicted in the shared data channel processing unit 760 in FIG.
• Common control channel and shared control channel There are also elements that set some transmit power for the channel, but they are not shown because they are not directly related to the present invention.
• fixed values are used for the channel coding rate, modulation scheme and transmission power for the common control channel.
• fixed values are also used for the channel coding rate and the modulation scheme for the shared control channel.
• the transmission power control of the shared control channel may be controlled by open-loop or closed-loop transmission power control, and furthermore, power control based on the downlink pilot channel reception quality (CQI information) reported from the mobile station is performed. It may be broken.
• CQI information downlink pilot channel reception quality
• the power control unit 768 adjusts the transmission power of the data channel based on the power control information of the packet scheduling unit 761.
• the power control information includes information that specifies the transmission power of the shared data channel for each resource block (frequency block).
• the power control information is determined by the packet scheduling unit 761.
• the power control information may be derived based on a predetermined correspondence relationship between the modulation scheme (or MCS) and transmission power, or may be calculated regardless of such a prior correspondence relationship.
• the update frequency of the power control information may be every subframe (or TTI), and may be higher or lower.
• FIG. 33 shows an example of a correspondence relationship that may be used when the power control information is calculated based on a predetermined correspondence relationship.
• transmission power P1 is used when the modulation scheme is QPSK
• transmission power P2 is used when 16QAM
• transmission power P3 is used when 64QAM.
• Some relationship may or may not be established between the transmission powers PI, P2, and P3.
• the type of data modulation method and transmission power value is not limited to 3, and may be more or less.
• the modulation method and transmission power may or may not correspond to one to one.
• the same transmission power P1 may be used for QPSK and 16QAM.
• Figure 34 shows an example of the correspondence between MCS and transmission power.
• Various correspondence relationships are not limited to those shown in Figs. 33 and 34, and may be set in advance. In any case, it is sufficient that the transmission power can be derived from the modulation scheme or the like.
• FIGS. 35A and 35B show the transmission power for each resource block.
• Figure 35A shows all The same transmission power is set for the source block, which corresponds to the state of transmission power in the existing AMC control.
• Fig. 35B shows how transmission power is set for each resource block in response to AMC control for each resource block. Since the transmission power can be changed adaptively with MCS alone, higher throughput can be achieved compared to when only AMC control is performed.
• FIG. 36 schematically shows the relationship between throughput and signal-to-noise ratio SNR that can be achieved with a given MCS.
• MCS1 has a lower relative bit rate than MCS2, and MCS2 has a lower relative bit rate than MCS3.
• the maximum throughput achievable with MCS1, MCS2, and MCS3 is assumed to be Tphl, Tph2, and Tph3, respectively.
• the signal-to-noise ratio at a certain transmission power is a value indicated by “E” in the figure.
• a throughput greater than Thpl can be achieved if a force MCS2 is used where the throughput achievable with MCS1 is about Tphl.
• MCS2 is not prepared in the system and only MCS1 and MCS3 are prepared in the system.
• the transmission power can be increased.
• the signal to noise ratio can be increased from E to F.
• the signal-to-noise ratio becomes F, not only MCS1 but also MCS3 can be selected.
• MCS 3 a larger throughput can be achieved. That is, according to the present embodiment, three types of MCS1, 2, and 3 are not prepared, and even if two types of MCS1 and MCS3 are not prepared in the force system, high throughput can be achieved. . In other words, by changing the value of the transmission power, it is possible to reduce the types of MCS while achieving high throughput.
• the value of the transmission power may be derived from a predetermined correspondence between the modulation scheme and the transmission power, or may be calculated regardless of such a prior correspondence.
• power information indicating a predetermined correspondence relationship is stored in each memory as common information between the base station and the mobile station.
• the mobile station can know what the transmission power was by referring to the correspondence relationship for the MCS notified from the base station. Therefore, in this example, the base station does not have to transmit information indicating what the transmission power is through the shared control channel or the like.
• Predetermined correspondence is notified to the mobile station through a common control channel such as broadcast information It may be sent to the mobile station at the time of call setup as layer 3 information, or it may be written to ROM as system specific information.
• the base station individually derives transmission power so that throughput is the best when allocating individual resource blocks to users.
• This method is particularly advantageous in terms of improving the achievable throughput, since not only the MCS but also the transmission power is optimized. However, it is necessary to notify the mobile station of information indicating the power with which the data channel is transmitted with which transmission power in which resource block by the shared control channel.
• the base station may measure the reception quality for each resource block allocated to itself and estimate the transmission power.
• the frequency of notifying the mobile station of the resource block allocation status (information indicating which resource block is allocated to which user) may be every 1 subframe (1 TTI) or less. Good. More generally, the frequency of notifying the mobile station of the resource block allocation status, the MCS number, and the transmission power may be the same in all or part of them, or may be all different.
• the channel used for notification may be a shared control channel.
• FIG. 37 shows a schematic example of resource block allocation.
• a shaded resource block indicates that a certain user is being harmed by IJ.
• the allocation status of the resource block is notified to the mobile station every 3 subframes (resource allocation notification), and the allocation contents change as necessary.
• the resource block allocation status remains unchanged for three subframes.
• the resource block is presumed to have good channel conditions, but is preferentially allocated to the user, but there is no guarantee that all of the resource blocks will remain in good channel condition during the above three subframes. In some cases, the channel condition may get worse.
• the resource block indicated by “X” in the figure indicates that the channel status has become worse.
• the resource block indicated by the X should not be used for data channel transmission. Therefore, in this embodiment, such resource blocks are used.
• the transmit power is set to zero for them. Even if the resource block update frequency is low, useless data transmission can be avoided by setting the transmission power for resource blocks with poor channel conditions to zero.
• FIG. 38 and FIG. Fig. 38 (A) schematically shows how some data is transmitted with the same transmission power in all eight resource blocks that have been hit by a certain user. This corresponds to the state of conventional AMC control, and is the same as shown in FIG. 35A.
• Figure 38 (B) shows the transmission power for resource blocks RB3 and RB5 set to zero. In this case, the base station should increase the transmission power for resource blocks other than resource blocks RB3 and RB5, and keep the total transmission power of the base station as constant as possible.
• FIGs 39 (A) and 39 (B) show the situation before and after the transmission power for resource blocks RB3 and RB5 is set to zero, and transmission power control is also performed in the same way as in Figure 35B. As shown in Fig. 39 (B), the transmission power for each resource block is increasing.
• Information on which resource block transmission power is set to zero may be notified to the mobile station through a shared control channel different from the shared control channel indicating the allocation status of the resource block. However, it is not essential to prepare such a shared control channel. For example, the mobile station may try to receive all the resource blocks assigned to itself, and the signal of resource blocks (RB3 and RB5 in the above example) with less than the required reception quality may be ignored. However, when information indicating what resource block has zero transmission power is notified to the mobile station, the mobile station determines each resource block based on the information, the total transmission power and the reception power related to the mobile station. The reception quality can be measured with high accuracy.

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