JP2004166123A - Base station apparatus and mcs selection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve throughput by performing MCS selection in consideration of demodulating characteristics in a radio communication system which conducts outgoing high-speed packet transmission. <P>SOLUTION: Demodulation portions 104, prepared with the number correspondent to the number of communication terminals which perform a radio communication conduct demodulation processings such as reverse diffusion for a receiving base-band signal, an RAKE composite, and an error correcting demodulation. Also, the demodulation portions 104 appear in a delay profile prepared at reverse diffusion, count the number of selected paths used for the RAKE composite, and output signals indicating the number of paths (path number information) to a scheduler 151. The scheduler 151 determines a communication terminal which transmits a packet based on a packet transmission control signal, a CQI signal from each communication terminal, and an ACK/NACK signal, and conducts MCS selection (determines modulation system and encoding ratio) based on the CQI signal and on the path number information signal. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a base station device and an MCS selection method used in a wireless communication system that performs downlink high-speed packet transmission.
[0002]
[Prior art]
In the field of wireless communication, a downlink high-speed packet transmission scheme has been developed in which a plurality of communication terminal devices share a high-speed, large-capacity downlink channel and transmit packets from the base station device to the communication terminal devices. In the downlink high-speed packet transmission scheme, a scheduling technique and an adaptive modulation technique are used to increase transmission efficiency.
[0003]
The scheduling technique is a technique in which a base station apparatus sets a communication terminal apparatus (hereinafter, referred to as a “destination apparatus”) to which a high-speed downlink packet is transmitted for each time slot, and allocates a packet to be transmitted to the transmission destination apparatus. . In addition, the adaptive modulation technique is a technique for adaptively selecting a modulation and coding scheme (MCS), that is, determining a modulation scheme, a coding rate, and the number of code multiplexes according to a state of a propagation path of a communication terminal apparatus that transmits a packet. is there.
[0004]
In a wireless communication system that performs high-speed packet transmission, ARQ (Automatic Repeat Request), in particular, H-ARQ (Hybrid-Automatic Repeat Request) is used to improve data reception performance. ARQ is a technology in which a transmitting device automatically retransmits a data unit (frame) in which an error is detected in a receiving device. H-ARQ is a technology in which a specific bit is transmitted when a transmitting device retransmits. This is a technique in which only the selected signal is transmitted to the receiving device and the retransmitted signal and the already received signal are combined in the receiving device.
[0005]
Hereinafter, the operation of the base station device and the communication terminal device of the wireless communication system that performs high-speed packet transmission will be outlined.
[0006]
The base station apparatus, based on the report value of the reception quality of the downlink transmitted from each communication terminal apparatus, sets the communication terminal apparatus having the best line quality as the destination apparatus, and in each time slot, the packet to the destination apparatus. Assign. Then, the base station apparatus transmits the packet indicating the result of the scheduling, the error-correction-encoded and modulated packet to the destination apparatus according to the scheme determined by the scheduling and the MCS selection. As a method of selecting a destination terminal, there is also a method of considering a transmission data amount, an average throughput, and the like for the terminal device.
[0007]
Each communication terminal apparatus performs demodulation in a time slot to which a packet addressed to the own station is allocated based on the received information indicating the scheduling result, performs CRC detection, and the like, and when the packet data is correctly demodulated, If the ACK signal indicating this cannot be demodulated correctly, the NACK signal indicating this is transmitted to the base station apparatus.
[0008]
Upon receiving the ACK signal, the base station device transmits new data, and upon receiving the NACK signal, retransmits data according to the HARQ procedure.
[0009]
As described above, in the downlink high-speed packet transmission system, all communication terminal devices existing in a sector share one channel and efficiently transmit packets, so that code resources and power resources can be effectively utilized. .
[0010]
2. Description of the Related Art In a conventional wireless communication system that performs downlink high-speed packet transmission, a communication terminal apparatus uses a carrier-to-interference ratio (CIR) such as a common control channel and reception power to determine a required quality (for example, block A modulation method or the like that can achieve an error rate of 10 ^-1 or less is selected, and a report value indicating the selection result is transmitted to the base station device.
[0011]
[Non-patent document 1]
"3GPP TS 25.214 V5.1.0 (2002-06)"
[0012]
[Problems to be solved by the invention]
However, the CIR does not necessarily reflect the demodulation characteristics of the modulation method. In particular, in the case of a multi-level modulation method with a small inter-symbol distance such as 16QAM, the demodulation characteristics are greatly affected by the characteristics of the delay profile. Even in this case, as the number of paths appearing in the delay profile increases and as the delay spread increases, the demodulation characteristics generally deteriorate and the throughput decreases. Also, as the propagation delay increases, the number of paths tends to increase, and the delay spread tends to increase. Similarly, the throughput decreases. Also, as the fading fluctuation speed increases, the demodulation characteristics similarly deteriorate and the throughput decreases.
[0013]
The present invention has been made in view of such a point, and in a wireless communication system performing downlink high-speed packet transmission, a base station apparatus and an MCS selection method capable of performing MCS selection in consideration of demodulation characteristics and improving throughput. The purpose is to provide.
[0014]
[Means for Solving the Problems]
The base station apparatus according to the present invention includes: a receiving unit that receives a report value indicating a reception quality of a downlink transmitted from a communication terminal apparatus; and a destination determination unit that determines a communication terminal apparatus to which data is to be transmitted based on the report value. Means, an MCS selecting means for setting a modulation scheme, a coding rate and a code multiplexing number, and a transmitting means for transmitting data with the set modulation scheme, a coding rate and a code multiplexing number, wherein the MCS selecting means is , The modulation scheme, the coding rate or the number of code multiplexes is determined in consideration of the report value and the line state not reflected in the report value.
[0015]
The MCS selection means in the base station apparatus of the present invention adopts a configuration in which a modulation scheme, a coding rate, or a code multiplex number is determined in consideration of the characteristics of the report value and the delay profile.
[0016]
The MCS selection means in the base station apparatus of the present invention is configured such that when at least one of each of the number of paths, delay spread or propagation delay is equal to or greater than a threshold, or when a determination value obtained from a combination of the respective elements is equal to or greater than a threshold. In some cases, a configuration is adopted in which one or a combination of a modulation scheme of a multi-level number lower than a predetermined value, a coding rate lower than the predetermined value, and a code multiplexing number lower than the predetermined value is set.
[0017]
With these configurations, it is possible to select a modulation method, a coding rate, or the number of code multiplexes in consideration of a report value indicating the reception quality of the downlink and a line state not reflected in the report value, particularly the characteristics of the delay profile. In addition, it is possible to prevent the demodulation characteristics from deteriorating and improve the throughput.
[0018]
The receiving means in the base station apparatus of the present invention employs a configuration for measuring a line state that is not reflected in the report value.
[0019]
In the base station apparatus of the present invention, the receiving means measures at least one of the number of uplink paths or delay spread or propagation delay, and the MCS selecting means determines the number of uplink paths or delay spread or propagation delay. A configuration for determining the modulation scheme, coding rate, or number of code multiplexes by using this is adopted.
[0020]
According to these configurations, it is not necessary to measure the characteristics of the delay profile other than the measurement and reporting of the reception quality of the downlink in the communication terminal apparatus, so that the processing load on the communication terminal apparatus can be reduced. Further, only the base station apparatus can select a modulation scheme, a coding rate, or the number of code multiplexes in consideration of the characteristics of the delay profile using processing required for normal reception, thereby preventing the demodulation characteristics from deteriorating and increasing the throughput. Can be improved.
[0021]
The MCS selection means in the base station apparatus of the present invention adopts a configuration in which a modulation scheme, a coding rate, or the number of code multiplexes is determined in consideration of the speed of fading fluctuation.
[0022]
The MCS selecting means in the base station apparatus of the present invention, when the speed of fading fluctuation is equal to or higher than a threshold value, a modulation scheme of a multilevel number lower than a predetermined value, a coding rate lower than the predetermined value, a code lower than the predetermined value A configuration is adopted in which one or a combination of multiplex numbers is set.
[0023]
With these configurations, the modulation scheme, coding rate, or number of code multiplexes can be selected in consideration of the speed of fading fluctuation, so that it is possible to prevent demodulation characteristics from deteriorating and maintain throughput.
[0024]
The MCS selection method of the present invention includes a step of acquiring the number of paths or delay spread, which is a characteristic of a delay profile, and a modulation method, a coding rate, and a settable modulation method based on the magnitude relationship between the number of paths or delay spread and a threshold. Alternatively, a method including a step of limiting any or a combination of the code multiplexing numbers and a step of determining the modulation scheme, the coding rate, and the code multiplexing number based on the downlink state from the limited number is adopted.
[0025]
According to this method, the modulation method, the coding rate, or the number of code multiplexes can be selected in consideration of the number of paths or delay spread, which are characteristics of the delay profile, so that the demodulation characteristics are prevented from deteriorating and the throughput is maintained. can do.
[0026]
The MCS selection method of the present invention includes a step of acquiring the speed of fading fluctuation, and a modulation method, a coding rate, or a code multiplexing number which can be set based on a magnitude relationship between the fading fluctuation and a threshold. And a step of determining a modulation scheme, a coding rate, and the number of code multiplexes based on the downlink state from the limited ones.
[0027]
According to this method, the modulation method, the coding rate, or the number of code multiplexes can be selected in consideration of the speed of the fading fluctuation, so that the demodulation characteristics can be prevented from deteriorating and the throughput can be maintained.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
The gist of the present invention is that, when MCS is selected, in addition to a report value indicating a downlink state, a line state that is not reflected in a report value such as a characteristic of a delay profile is also taken into consideration, and the number of paths is large, or delay spread is large. When it is large, it means to select a modulation method with a low multi-level number, to select a low coding rate, or to reduce the number of code multiplexes.
[0029]
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, HSDPA (High Speed Downlink Packet Access) is used as an example of the downlink high-speed packet transmission system. In HSDPA, HS-PDSCH (High Speed-Physical Downlink Shared Channel), HS-SCCH (Shared Control Channel of HS-PDSCH), and A-DPCH (Associated Shared-Phone Shared Digital Private Channel, etc.) .
[0030]
HS-PDSCH is a downlink shared channel used for packet transmission. The HS-SCCH is a downlink shared channel in which information related to resource allocation (TFRI: Transport-format and Resource related Information), information related to H-ARQ control, and the like are transmitted.
[0031]
The A-DPCH is a separate associated channel in the uplink and downlink directions, and its channel configuration, handover control, and the like are the same as those of the DPCH. In the A-DPCH, a pilot signal, a TPC command, and the like are transmitted. In the uplink, an HS-DPCCH for transmitting an ACK / NACK signal and a CQI (Channel Quality Indicator) signal is multiplexed on the A-DPCH.
[0032]
The CQI signal is a signal that reports a combination of MCSs that can achieve required quality in a downlink state estimated based on the CIR from the communication terminal apparatus to the base station apparatus. 1, a combination of a CQI signal (CQI value), a transport block size (TB size), the number of multicodes of packet data (Number of HS-PDSCH) and a modulation scheme (Modulation), an offset of transmission power, and the like. Are shared with each other. The communication terminal device selects an MCS capable of achieving the required quality from the CQI table and reports the selected MCS. The base station device performs MCS selection based on the CQI signal. In this case, the coding rate is changed by changing the puncturing rate of the redundant bits after error correction coding.
[0033]
(Embodiment)
FIG. 2 is a block diagram showing a configuration of the base station apparatus according to one embodiment of the present invention. Hereinafter, the operation of each component of base station apparatus 100 of FIG. 2 will be described.
[0034]
Duplexer 102 outputs a signal received by antenna 101 to reception RF section 103. Further, duplexer 102 wirelessly transmits the signal output from transmission RF section 166 from antenna 101.
[0035]
The reception RF unit 103 converts the radio frequency reception signal output from the duplexer 102 into a baseband digital signal, and outputs the baseband digital signal to the demodulation unit 104.
[0036]
Demodulation sections 104 are prepared by the number of communication terminal apparatuses that perform wireless communication, perform demodulation processing such as despreading, RAKE combining, and error correction decoding on the received baseband signal, and output the result to demultiplexing section 105. Also, the demodulation unit 104 counts the number of paths that appear in the delay profile created during despreading and is selected for use in RAKE combining, and indicates a signal indicating the number of paths (hereinafter, referred to as a “path number information signal”). ) Is output to the scheduler 151. The following is generally known as a path selection method. (1) In the delay profile, timings in which the levels fall within a predetermined window width in order from the highest level are selected as paths. (2) In the delay profile, a timing that falls within a predetermined window width before and after the timing of the maximum level and that is equal to or higher than the predetermined level is selected as a path. (3) In the delay profile, an average value excluding a value equal to or higher than a predetermined level is set as a noise level, and a timing having a level larger than the sum of the noise level and the predetermined value is selected as a path.
[0037]
Separation section 105 separates the output signal of demodulation section 104 into data and control signals. The control signal separated by the separating unit 105 includes a DL (Down Link) TPC command, a CQI signal, an ACK / NACK signal, and the like. The CQI signal and the ACK / NACK signal are output to scheduler 151, and the TPC command for DL is output to transmission power control section 158.
[0038]
The SIR measuring sections 106 are prepared by the number of communication terminal apparatuses for performing wireless communication, measure the uplink reception SIR based on the desired wave level and the interference wave level measured in the demodulation process, and send a signal indicating the SIR to the TPC command. Output to the generation unit 107.
[0039]
The TPC command generation units 107 are prepared by the number of communication terminal devices that perform wireless communication, and are used for UL (Up Link) for instructing increase or decrease of uplink transmission power according to the magnitude relationship between uplink reception SIR and target SIR. Generate a TPC command.
[0040]
The scheduler 151 uses a communication terminal device (hereinafter, referred to as a “destination device”) that transmits a packet based on a packet transmission control signal, a CQI signal from each communication terminal device, and an ACK / NACK signal as a transmission destination determining unit. The information indicating the destination device and the packet data to be transmitted is output to the buffer (Queue) 152. In addition, the scheduler 151 performs MCS selection (determination of a modulation scheme and a coding rate) based on the CQI signal and the number-of-paths information signal of the transmission destination apparatus as MCS selection means, and modulates the modulation scheme and the coding rate with the modulation unit 153. To instruct. Further, the scheduler 151 outputs a signal to be used when determining the transmission power of the packet data to the transmission power control unit 154. In the present invention, the transmission power control method for packet data is not limited, and the transmission power control for packet data need not be performed. In addition, the scheduler 151 outputs a signal to be transmitted to the destination apparatus via the HS-SCCH (hereinafter, referred to as “HS-SCCH signal”) to the amplification unit 161. The HS-SCCH signal includes information (TFRI) indicating the timing of transmitting packet data, the coding rate of the packet data, the modulation scheme, and the like. The details of the MCS selection of the scheduler 151 will be described later.
[0041]
The buffer 152 outputs the packet data for the destination device specified by the scheduler 151 to the modulator 153.
[0042]
Modulation section 153 performs error correction coding, modulation, and spreading on the packet data according to the instruction of scheduler 151, and outputs the result to amplification section 155.
[0043]
The transmission power control section 154 controls the transmission power of the output signal of the modulation section 153 to a value determined by the scheduler 151 by controlling the amount of amplification of the amplification section 155. The output signal of amplification section 155 is a signal transmitted on HS-PDSCH, and is output to multiplexing section 165.
[0044]
Multiplexing sections 156 are prepared by the number of communication terminal apparatuses that perform wireless communication, multiplex a pilot signal and a UL TPC command with individual data (including a control signal) to be transmitted to each communication terminal apparatus, and output the result to modulation section 157. I do.
[0045]
Modulation sections 157 are prepared by the number of communication terminal apparatuses that perform wireless communication, perform error correction coding, modulation, and spreading on the output signal of multiplexing section 156, and output the result to amplification section 159.
[0046]
The transmission power control section 158 is prepared by the number of communication terminal apparatuses performing wireless communication, and controls the transmission power of the output signal of the modulation section 157 by controlling the amplification amount of the amplification section 159 according to the DL TPC command. Further, transmission power control section 158 outputs a signal indicating the transmission power value to transmission power control section 160. The signal amplified by amplifying section 159 is a signal transmitted on DPCH (including A-DPCH), and is output to multiplexing section 165.
[0047]
The transmission power control section 160 controls the amplification amount of the amplification section 161 with a value obtained by adding an offset to the transmission power value of the transmission power control section 158, thereby reducing the transmission power of the HS-SCCH signal output from the scheduler 151. Control. The signal amplified by the amplification section 161 is a signal transmitted on the HS-SCCH, and is output to the multiplexing section 165. Note that transmission power control section 160 may correct the offset value based on the retransmission state, the number of A-DPCH handover connections, and the like.
[0048]
Modulating section 162 performs error correction coding, modulation and spreading on the common control data, and outputs the result to amplifying section 164. Transmission power control section 163 controls the transmission power of the output signal of modulation section 162 by controlling the amount of amplification of amplification section 164. The output signal of the amplification unit 164 is a signal transmitted by CPICH or the like, and is output to the multiplexing unit 165.
[0049]
The multiplexing unit 165 multiplexes each output signal of the amplifying unit 155, the amplifying unit 159, the amplifying unit 161, and the amplifying unit 164, and outputs the multiplexed signal to the transmission RF unit 166.
[0050]
Transmission RF section 166 converts the baseband digital signal output from modulation section 159 to a radio frequency signal and outputs the signal to duplexer 102.
[0051]
FIG. 3 is a block diagram showing a configuration of a communication terminal apparatus that performs wireless communication with the base station apparatus according to the present embodiment. The communication terminal device 200 in FIG. 3 receives the individual data, the common control data, the packet data, and the HS-SCCH signal from the base station device 100. Hereinafter, the operation of each component of the communication terminal device 200 of FIG. 3 will be described.
[0052]
Duplexer 202 outputs a signal received by antenna 201 to reception RF section 203. Further, duplexer 202 wirelessly transmits the signal output from transmission RF section 258 from antenna 201.
[0053]
The reception RF unit 203 converts the radio frequency reception signal output from the duplexer 202 into a baseband digital signal, outputs the HS-PDSCH signal to the buffer 204, and outputs the HS-SCCH signal to the demodulation unit 205. Then, the DPCH signal is output to the demodulation section 208, and the common control channel signal is output to the CIR measurement section 212.
[0054]
Buffer 204 temporarily stores the HS-PDSCH signal and outputs the signal to demodulation section 206.
[0055]
The demodulation unit 205 performs demodulation processing such as despreading, RAKE combining, and error correction decoding on the HS-SCCH signal, and calculates the arrival timing of packet data addressed to the own station, the coding rate of the packet data, the modulation scheme, and the like. Information necessary for demodulating packet data is obtained and output to demodulation section 206.
[0056]
The demodulation unit 206 performs demodulation processing such as despreading, RAKE combining, and error correction decoding on the HS-PDSCH signal stored in the buffer based on the information acquired by the demodulation unit 205. The obtained packet data is output to error detecting section 207.
[0057]
The error detection unit 207 performs error detection on the packet data output from the demodulation unit 206 and, if no error is detected, an ACK signal, and if an error is detected, a NACK signal. Output to
[0058]
Demodulation section 208 performs demodulation processing such as despreading, RAKE combining, and error correction decoding on the DPCH signal, and outputs the result to demultiplexing section 209. Separating section 209 separates the output signal of demodulating section 208 into data and control signals. The control signal separated by the separation unit 209 includes a UL TPC command and the like. The UL TPC command is output to transmission power control section 257.
[0059]
The SIR measuring section 210 measures the downlink reception SIR based on the desired wave level and the interference wave level measured in the demodulation process, and outputs all the measured reception SIRs to the TPC command generation section 211. TPC command generation section 211 generates a DL TPC command based on the magnitude relationship between the received SIR output from SIR measurement section 210 and the target SIR, and outputs the DL TPC command to multiplexing section 254.
[0060]
CIR measurement section 212 measures CIR using a signal of the common control channel from the base station apparatus, and outputs the measurement result to CQI generation section 213. CQI generating section 213 generates a CQI signal based on the CIR of the signal transmitted from the base station apparatus, and outputs the generated CQI signal to multiplexing section 251.
[0061]
Multiplexing section 251 multiplexes the CQI signal and the ACK / NACK signal and outputs the multiplexed signal to modulating section 252. Modulation section 252 performs error correction coding, modulation, and spreading on the output signal of multiplexing section 251 and outputs the result to multiplexing section 256.
[0062]
Modulating section 253 performs error correction coding, modulation, and spreading on data to be transmitted to base station apparatus 100 and outputs the result to multiplexing section 256.
[0063]
Multiplexing section 254 multiplexes the DL TPC command and pilot signal and outputs the result to modulating section 255. Modulating section 255 performs error correction coding, modulation, and spreading on the output signal of multiplexing section 254 and outputs the result to multiplexing section 256.
[0064]
Multiplexing section 256 multiplexes each output signal of modulating section 252, modulating section 253 and modulating section 255 and outputs the multiplexed signal to transmitting RF section 258.
[0065]
Transmission power control section 257 controls the transmission power of the output signal of multiplexing section 256 by controlling the amount of amplification of transmission RF section 258 according to the UL TPC command. Note that when connected to a plurality of base station apparatuses, the transmission power control unit 257 performs control to increase the transmission power only when all UL TPC commands instruct the transmission power to increase.
[0066]
RF transmitting section 258 amplifies the baseband digital signal output from multiplexing section 256, converts the signal into a radio frequency signal, and outputs the signal to duplexer 102.
[0067]
Next, details of the MCS selection of the scheduler 151 of the base station apparatus 100 will be described using the flowchart of FIG. It is assumed that the CQI table held in the base station device is as shown in FIG.
[0068]
First, in step (hereinafter abbreviated as “ST”) 301, scheduler 151 selects each communication terminal device that is a candidate for transmitting a packet from a packet transmission control signal, and sets a CQI from each of the selected communication terminal devices. A destination device is determined based on the signal. For example, a communication terminal device having the best reception quality is determined as a destination device based on the CQI signal.
[0069]
Then, in ST302, the scheduler 151 performs a magnitude comparison between a preset threshold value and the number of paths (threshold value determination), and when the number of paths is less than the threshold value (ST302: No), based on the CQI signal of the destination apparatus. MCS selection is performed (ST304).
[0070]
On the other hand, if the number of paths is equal to or larger than the threshold (ST302: Yes), 16QAM is not selected as the modulation method. That is, if the modulation scheme corresponding to the CQI signal of the destination device is QPSK (ST303: No), MCS selection is performed based on the CQI signal of the destination device (ST304), and the CCS signal corresponding to the CQI signal of the destination device is obtained. If the modulation scheme is 16QAM (ST303: Yes), the MCS having the closest transmission rate is selected from among the combinations of MCS when the modulation scheme uses 16QAM in QPSK (ST305).
[0071]
For example, FIG. 1 shows the CQI table held in the base station apparatus 100, and when the CQI signal from the destination apparatus is “7” and the number of paths is equal to or larger than the threshold, the base station apparatus sets the CQI signal “4”. Is selected.
[0072]
In the above ST305, MCS selection may be performed by lowering the number of multiplexed codes than the CQI signal from the transmission destination apparatus, and transmission power per code may be increased. For example, FIG. 1 shows the CQI table held in the base station apparatus 100, and when the CQI signal from the destination apparatus is “7” and the number of paths is equal to or greater than the threshold, the base station apparatus sets the CQI signal “5”. Is performed, and the transmission power per code is increased.
[0073]
As described above, in the present embodiment, the MCS is selected in consideration of the demodulation characteristics of the modulation scheme, and when the number of paths is larger than a certain number, the modulation scheme with a lower multilevel number is selected, or the number of code multiplexes is reduced. This can prevent the demodulation characteristics from deteriorating and maintain the throughput.
[0074]
In the present embodiment, when the number of paths is larger than a certain number, it is assumed that the influence of the multipath propagation path environment is large, and the CQI signal of the transmission destination device may be offset to have a lower CQI value. For example, when the CQI value indicated by the CQI signal of the destination device is “6” in FIG. 1 and the number of paths is larger than a certain number, the offset value “2” is subtracted to set the CQI value to “4”.
[0075]
Further, although a case has been described with the present embodiment where the base station apparatus performs a threshold determination on the number of paths selected for use in RAKE combining, the present invention is not limited to this, and the present invention is not limited to this. The number of unselected paths may be considered. Instead of the number of paths, a delay spread, which is one of the characteristics of the delay profile, may be used. The delay spread is described in detail in "Shuichi Sasaoka, edited by Mobile Communications (Ohm)".
[0076]
Further, the propagation delay time can be measured from a delay profile as a delay time (round trip time) from downlink transmission to uplink reception in the base station apparatus. From the magnitude of the propagation delay time, the base station apparatus and the communication terminal apparatus can be measured. You can get an indication of the distance. Therefore, the demodulation section 104 counts the propagation delay time and outputs information indicating the propagation delay time to the scheduler 151. When the distance is long, the line state is often inferior. When the time is equal to or longer than the threshold, selection of multi-level modulation such as 16QAM may be suppressed.
[0077]
Further, in the present embodiment, it is possible to apply to both the first transmission and the retransmission in the HARQ process.
[0078]
Further, in each of the above embodiments, a case has been described in which a preset fixed threshold value is used, but the threshold value may be variable according to the CIR. When a combination of the number of paths, delay spread, or propagation delay time is used, each threshold may be controlled independently. In addition, a determination value obtained from a combination of each element of the number of paths, delay spread, or propagation delay time may be compared. Further, in each of the above embodiments, a case has been described in which the modulation scheme and the like are controlled based on the characteristics of the delay profile. However, the present invention is not limited to this, and the modulation is performed based on other propagation path states such as fading fluctuation speed. The method can be controlled.
[0079]
Further, in each of the above-described embodiments, a case has been described where a modulation scheme of a multi-level number lower than a predetermined value is set when the number of paths or the like is equal to or greater than a threshold, but a coding rate lower than the predetermined value, Any or a combination of a small number of code multiplexes may be set. As a result, even if a multi-level modulation scheme such as 16QAM with a small inter-symbol distance is selected, the demodulation characteristics do not deteriorate and the throughput can be maintained.
[0080]
In the FDD scheme, the carrier frequency of the uplink / downlink is different, so that the fading fluctuation is independent, but the correlation of the average power delay profile is expected to be high. MCS selection can be performed in consideration of delay profile characteristics such as the number of paths / delay spread.
[0081]
【The invention's effect】
As described above, according to the present invention, at the time of MCS selection, in addition to the report value indicating the downlink reception quality, the modulation scheme is also considered in consideration of the line state that is not reflected in the report value such as the characteristic of the delay profile. By selecting the coding rate or the number of code multiplexes, it is possible to prevent the demodulation characteristics from deteriorating and maintain the throughput.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of a CQI table. FIG. 2 is a block diagram illustrating a configuration of a base station device according to an embodiment of the present invention. FIG. 3 is a diagram illustrating wireless communication with the base station device according to the embodiment. FIG. 4 is a block diagram showing a configuration of a communication terminal apparatus for performing MCS selection in the base station apparatus according to the above embodiment.
104 Demodulation unit 151 Scheduler 152 Buffer 153 Modulation unit

Claims (9)

Receiving means for receiving a report value indicating the reception quality of the downlink transmitted from the communication terminal apparatus; transmission destination determining means for determining a communication terminal apparatus to which data is to be transmitted based on the report value; MCS selecting means for setting the rate and the number of code multiplexes, and transmitting means for transmitting data at the set modulation scheme, coding rate and number of code multiplexes,
The base station apparatus, wherein the MCS selecting means determines a modulation scheme, a coding rate, or a code multiplex number in consideration of the report value and a line state that is not reflected in the report value. 2. The base station apparatus according to claim 1, wherein the MCS selection unit determines a modulation scheme, a coding rate, or a code multiplex number in consideration of the characteristics of the report value and the delay profile. The MCS selection unit is configured to determine whether the number of paths, delay spread, or propagation delay is at least one of the threshold values or more, or if the determination value obtained from the combination of the elements is at least the threshold value, 3. The base station apparatus according to claim 2, wherein any one or a combination of a modulation scheme with a low multilevel number, a coding rate lower than a predetermined value, and a code multiplexing number smaller than a predetermined value is set. 2. The base station apparatus according to claim 1, wherein the receiving unit measures a line state that is not reflected in the report value. The receiving means measures at least one of the number of paths, delay spread, and propagation delay of the uplink, and the MCS selecting means uses the number of paths, delay spread, or propagation delay of the uplink to perform modulation and coding. 4. The base station apparatus according to claim 2, wherein the rate or the number of code multiplexes is determined. 2. The base station apparatus according to claim 1, wherein the MCS selection unit determines a modulation scheme, a coding rate, or the number of code multiplexes in consideration of a fading fluctuation speed. The MCS selecting means, when the speed of the fading fluctuation is equal to or higher than a threshold value, any one or a combination of a multi-level modulation scheme lower than a predetermined value, a coding rate lower than the predetermined value, and a code multiplexing number lower than the predetermined value. 7. The base station apparatus according to claim 6, wherein A step of acquiring the number of paths or delay spread, which is a characteristic of the delay profile, and any one of a modulation method, a coding rate, and a code multiplex number that can be set based on the magnitude relationship between the number of paths or delay spread and a threshold. Alternatively, an MCS selection method comprising: a step of limiting a combination; and a step of determining a modulation scheme, a coding rate, and the number of code multiplexes based on a downlink state among limited ones. A step of acquiring the speed of fading fluctuation, and a step of limiting any or a combination of a modulation scheme, a coding rate, and a code multiplexing number that can be set based on the magnitude relationship between the fading fluctuation and a threshold. Determining a modulation scheme, a coding rate, and the number of code multiplexes based on a downlink state from among the MCSs.

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