WO2007125580A1 - Procédé de modulation adaptatif et appareil de communication - Google Patents

Procédé de modulation adaptatif et appareil de communication Download PDF

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Publication number
WO2007125580A1
WO2007125580A1 PCT/JP2006/308871 JP2006308871W WO2007125580A1 WO 2007125580 A1 WO2007125580 A1 WO 2007125580A1 JP 2006308871 W JP2006308871 W JP 2006308871W WO 2007125580 A1 WO2007125580 A1 WO 2007125580A1
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WIPO (PCT)
Prior art keywords
transmission
modulation
subcarrier
adjustment
sir
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PCT/JP2006/308871
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English (en)
Japanese (ja)
Inventor
Nobuhisa Kataoka
Original Assignee
Mitsubishi Denki Kabushiki Kaisha
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Application filed by Mitsubishi Denki Kabushiki Kaisha filed Critical Mitsubishi Denki Kabushiki Kaisha
Priority to JP2008513027A priority Critical patent/JP4700106B2/ja
Priority to PCT/JP2006/308871 priority patent/WO2007125580A1/fr
Publication of WO2007125580A1 publication Critical patent/WO2007125580A1/fr

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Classifications

    • 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—Arrangements for allocating sub-channels of the transmission path allocation of payload
    • H04L5/0046—Determination of how many bits are transmitted on different sub-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
    • H04L1/0002—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
    • H04L1/0009—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the channel coding

Definitions

  • the present invention relates to an adaptive modulation method for adaptively selecting and determining an encoding method and a modulation method at the time of data transmission by orthogonal frequency division multiplexing (OFDM).
  • the present invention relates to an adaptive modulation method in the case of selecting and determining a V-code scheme and a modulation scheme for each subcarrier based on communication quality for each subcarrier, and a communication apparatus for realizing the adaptive modulation method.
  • An adaptive modulation scheme is a scheme that selectively uses a combination of a coding scheme (coding rate and type of error correction code) and a modulation scheme according to the state of a transmission path.
  • a coding scheme coding rate and type of error correction code
  • a modulation scheme that is difficult to error are used in combination.
  • Patent Document 1 discloses a method of selecting and using an encoding method, a modulation method, or the like according to the state of a transmission path as an adaptive modulation method when performing communication using OFDM. .
  • a plurality of data are transmitted in parallel using a plurality of subcarriers.
  • Each subcarrier can use a different modulation method.
  • the same modulation method is used for all subcarriers. ing.
  • Patent Document 1 Japanese Patent Application Laid-Open No. 2002-261726
  • OFDM frequency division multiplexing
  • TDM Time Division
  • CDM Code Division Multiplexing
  • SDM Space Division Multiplexing
  • the present invention has been made in view of the above, and in communication using OFDM, It is an object of the present invention to provide an adaptive modulation method capable of realizing high-speed data transmission while satisfying desired communication quality and a communication apparatus for realizing the adaptive modulation method.
  • an adaptive modulation method adapts an encoding method and a modulation method at the time of data transmission by orthogonal frequency division multiplexing according to the state of a transmission path. For example, a modulation method for each subcarrier is selected from among modulation methods defined in advance, and a combination of modulation methods for each subcarrier (modulation method pattern).
  • a modulation scheme pattern determining step for determining the transmission method an encoding scheme selection step for selecting an encoding scheme to be used when encoding the transmission data from among the encoding schemes defined in advance, and a received signal Based on the SIR for each subcarrier, the transmission rate and communication quality (transmission quality) at the time of data transmission using the determined modulation method pattern and the selected encoding method are determined.
  • a transmission quality calculation step to be output, and further, by repeatedly executing the modulation scheme pattern determination step, the encoding scheme selection step, and the transmission quality calculation step, the modulation scheme pattern and the coding scheme are The transmission quality calculation step is executed for all the combinations, and the modulation method pattern and the encoding method when the transmission quality that achieves the maximum transmission speed while satisfying the desired communication quality is obtained in the transmission quality calculation result. It is characterized in that it is selected and determined as a formal modulation system pattern and encoding system used during data transmission.
  • the adaptive modulation method according to the present invention performs data transmission by selecting a combination of an optimal encoding method and an optimal modulation method for each subcarrier based on the reception quality of the signal. Therefore, while satisfying the desired communication quality, it is possible to perform data transmission at a higher speed than when the above-mentioned conventional technology is used, and in particular, transmission at the time of data transmission on a transmission line whose frequency characteristics are not flat. There is an effect that the speed can be increased.
  • FIG. 1 is a diagram showing a configuration example of a first embodiment of a communication system and a communication apparatus constituting the communication system for realizing an adaptive modulation method according to the present invention.
  • FIG. 2 is a flowchart showing an example of an operation for selecting and determining a coding scheme and a modulation scheme for each subcarrier.
  • FIG. 3 is a diagram for explaining an operation of selecting a modulation scheme for each subcarrier.
  • FIG. 4 is a diagram for explaining a selection operation of a sign key method.
  • FIG. 5 is a diagram for explaining an operation of selecting and determining a modulation method and a code key method for each subcarrier.
  • FIG. 6 is a flowchart showing an operation of generating adaptive modulation instruction information performed by the communication apparatus of the second embodiment.
  • Fig. 7-1 is a diagram for explaining the SIR threshold setting operation.
  • Fig. 7-2 is a diagram for explaining the SIR threshold setting operation.
  • FIG. 8 is a diagram showing a configuration example of a third embodiment of a communication system and a communication apparatus constituting the communication system for realizing the adaptive modulation method according to the present invention.
  • FIG. 9 is a flowchart showing an operation for adjusting a modulation scheme and a coding scheme for each subcarrier once determined.
  • FIG. 10 is a flowchart showing an SIR threshold adjustment operation.
  • FIG. 11 is a flowchart showing a sign key method adjustment operation.
  • FIG. 12 is a flowchart showing an operation of updating adaptive modulation instruction information in the adaptive modulation method of the fourth embodiment.
  • FIG. 13 is a flowchart showing an operation of changing the modulation scheme for each subcarrier in the adaptive modulation method of the fifth embodiment.
  • FIG. 14 is a flowchart showing an operation of changing the modulation scheme for each subcarrier in the adaptive modulation method of the fifth embodiment.
  • FIG. 15 is a flowchart showing an operation for updating adaptive modulation instruction information in the adaptive modulation method of the seventh embodiment.
  • FIG. 16-1 is a diagram for explaining an adaptive modulation method according to the eighth embodiment.
  • FIG. 16-2 is a diagram for explaining an adaptive modulation method according to the eighth embodiment.
  • FIG. 17-1 is a diagram for explaining an adaptive modulation method according to the ninth embodiment.
  • FIG. 17-2 is a diagram for explaining an adaptive modulation method according to the ninth embodiment.
  • FIG. 17-3 is a diagram for explaining an adaptive modulation method according to the ninth embodiment.
  • FIG. 17-4 is a diagram for explaining an adaptive modulation method according to the ninth embodiment.
  • FIG. 17-5 is a diagram for explaining an adaptive modulation method according to the ninth embodiment.
  • FIG. 18 is a flowchart showing an operation when the adaptive modulation method of the ninth embodiment is applied to the first embodiment.
  • FIG. 1 is a diagram showing a configuration example of a first embodiment of a communication system that implements an adaptive modulation method according to the present invention and a communication device that constitutes the communication system.
  • This communication system includes a communication device 1 and a communication device 2.
  • the communication device 1 includes an encoding unit 11
  • the communication apparatus 2 includes an OFDM demodulator 21, a decoder 22, and a determiner 23.
  • the determination unit 23 operates as a transmission condition selection unit, a transmission quality calculation unit, an iterative process control unit, and a transmission condition determination unit.
  • FIG. 1 shows a state in which the communication device 1 transmits data to the communication device 2. Therefore, each of the communication devices 1 and 2 includes only a signal transmission processing unit (corresponding to the encoding unit 11 and the modulation unit 12) and a reception processing unit (corresponding to the OFDM demodulating unit 21 and the decoding unit 22). In actuality, both have a transmission processing unit and a reception processing unit, and the communication device 2 transmits a signal to the communication device 1 as necessary.
  • a signal transmission processing unit corresponding to the encoding unit 11 and the modulation unit 12
  • a reception processing unit corresponding to the OFDM demodulating unit 21 and the decoding unit 22
  • encoding section 11 encodes transmission data in the encoding scheme indicated by "encoding scheme information" that constitutes the adaptive modulation instruction information notified in advance from the communication partner.
  • the OFDM modulation unit 12 is a modulation scheme indicated by “information indicating the modulation scheme for each subcarrier” that constitutes the adaptive modulation instruction information for which the communication partner power has been notified in advance, and the encoding received from the encoding unit 11
  • the transmission data is modulated to generate a transmission signal.
  • the generated transmission signal is transmitted from the antenna to the communication apparatus 2 that is the communication partner via the transmission path.
  • OFDM demodulator 21 demodulates the received signal from communication device 1.
  • Decoding section 22 performs error correction processing on the demodulated data obtained by OFDM demodulation section 21 demodulating the received signal, and outputs the processing result as received data.
  • the determination unit 23 determines the encoding method used by the data transmission source device (communication device 1) and the modulation method for each subcarrier. Then, adaptive modulation instruction information indicating the determination result is generated. Specifically, the determination unit 23 selects an encoding method that can maximize the transmission rate and a modulation method for each subcarrier according to the transmission path state estimated based on the received signal.
  • this is not a frequency characteristic S flat of the transmission path, so an optimum modulation method is selected for each frequency (subcarrier), and this is combined with an optimum coding method to perform communication. Is.
  • the generated adaptive modulation instruction information is notified (transmitted) to the communication device 1 via the transmission path.
  • FIG. 2 is a flowchart showing an operation for generating adaptive modulation instruction information.
  • the determination unit 23 receives the SIR (Signal to Interference Ratio) for each subcarrier measured by the OFDM demodulation unit 21 (step Sl 1).
  • the determination unit 23 selects a modulation scheme for each subcarrier (step S12). For example, if the number of subcarriers is 3 and the selectable modulation methods are BPSK and QPSK, select one of the eight patterns shown in Fig. 3 as the combination of modulation methods for each subcarrier. Will be. Note that the conditions for selecting a combination (combination pattern) of modulation methods for each subcarrier are not particularly specified. Therefore, for example, the combination pattern numbers shown in FIG. 3 may be selected in ascending order, or selectable combination patterns may be selected at random! /.
  • the determination unit 23 selects an encoding method (step S13).
  • the encoding method is selected from two types of encoding methods with different error correction capabilities as shown in Fig. 4, for example.
  • Figure 4 shows an example using Reed-Solomon (RS) codes.
  • RS 255, 239), which is the first encoding method, indicates an encoding method for generating a code in which 16 redundant bytes are added to 239 bytes of information.
  • RS (120, 104) which is the second encoding method, indicates a code method that generates a code in which 16 bytes of redundant bytes are added to 104 bytes of information.
  • the determination unit 23 holds the selection result in step S12 and the selection result in step S13 together (holds a combination of the selection results), and the next step S12 and subsequent times.
  • the determination unit 23 calculates a transmission rate and communication quality when communication is performed using the selection results in steps S 12 and S 13 (step S 14). For example, if No. 1 in the example shown in Fig. 3 is selected as the combination of modulation schemes for each subcarrier and No. 1 in the example shown in Fig.
  • the communication quality is calculated using the SIR for each subcarrier obtained in step S11.
  • Communication quality is the bit error rate (coded: BER: coded bit error rate) or packet error rate (PER: packet error rate) after error correction, so it can be calculated based on the SIR for each subcarrier. .
  • the decision unit 23 performs this uncoded-BER for all subcarriers. Then, the BER of the input signal to the decoding unit 22 is calculated.
  • the power shown in the case of using coded BER as the communication quality may be replaced with PER.
  • the method for calculating the communication quality by calculation is shown here, the SIR vs. BER characteristics are calculated by simulation in advance of the calculation, and a table showing the result is created and referred to this table. Even so,
  • step S 15 determines whether or not the transmission rate calculation and communication quality calculation have been completed for all combinations of the modulation scheme for each subcarrier and the encoding scheme.
  • step S15 it is not yet selected (transmission rate calculation and If there is a combination of the modulation scheme for each subcarrier and the encoding scheme (No in step S15), the process returns to step S12 and is still selected. Similar processing (steps S12 to S14) is performed for the combination of the modulation scheme for each subcarrier and the code key scheme.
  • the determination unit 23 compares the combination of the transmission speed and communication quality held as the processing result of step S14. From the processing results that are held, a combination that satisfies the desired communication quality (for example, the communication quality required by the communication system) and has the maximum transmission speed is selected. Finally, the combination of the modulation scheme for each subcarrier and the coding scheme corresponding to the selection result (where the selection result was obtained) is adaptive modulation instruction information (a combination used for data transmission). (Step S16).
  • FIG. 5 shows subcarrier numbers # 1, # 2, and # 3 during data transmission performed by combining any of the modulation schemes shown in FIG. 3 and any of the encoding schemes shown in FIG.
  • An example of the calculation result in step S14 is shown when the SIR of each subcarrier is 8 dB, 9 dB, and 10 dB, respectively.
  • No. 15 is the combination that gives the highest transmission rate. Therefore, when the calculation result shown in FIG.
  • the determination unit 23 selects and determines the combination of No. 15 in step S16. If there are a plurality of candidates having the same transmission rate among the combinations satisfying the communication quality, the combination having the best communication quality is selected and determined.
  • a combination of an optimal encoding scheme and an optimal modulation scheme for each subcarrier is selected based on the reception quality of the signal, and the selected combination is used.
  • Data transmission This makes it possible to perform data transmission at the highest transmission speed while satisfying the desired communication quality.
  • the transmission speed at the time of data transmission on the transmission line which is not the frequency characteristic force S flat, is higher than before. Speed up The
  • the adaptive modulation method and communication apparatus according to the second embodiment will be described.
  • an adaptive modulation method for reducing the amount of calculation and reducing the circuit scale by simplifying the processing described in Embodiment 1 will be described.
  • the configuration of the communication system that implements the adaptive modulation method of the present embodiment and the configuration of the communication device that constitutes the communication system are the same as those of the above-described first embodiment, and the adaptive modulation instruction information that is determined by the determination unit 23 Only the generation operation is different. Therefore, in the present embodiment, the description will focus on the adaptive modulation instruction information generation operation performed by the determination unit 23.
  • FIG. 6 is a flowchart showing an operation for generating adaptive modulation instruction information performed by communication apparatus 2 (determination unit 23) according to the second embodiment. Note that the same steps as those in the first embodiment are denoted by the same step numbers, and the description thereof is omitted.
  • the determination unit 23 sets the SIR threshold corresponding to the coding scheme selected in step S13 (step S21). Further, this SIR threshold is determined in advance for each selectable encoding method based on the communication quality (desired communication quality) that should be satisfied in the communication. To select and set the one corresponding to the selected encoding method.
  • FIGS. 7-1 and 7-2 are diagrams showing an example of a correspondence relationship between received signal quality before error correction execution (in this example, uncoded-BER, which is a BER before error correction execution), and SIR. More specifically, FIG. 7-1 is a diagram showing an example of a correspondence relationship between communication quality (coded-BER which is a BER after error correction) and uncoded-BER for each coding method. This correspondence can be calculated based on the coding rate for each coding method. Fig. 7-2 shows an example of the relationship between uncoded-BER and SIR for each modulation method.
  • the modulation scheme # 2 requires a larger SIR, and this is the case for modulation schemes with a large number of transmission bits.
  • the SIR of a certain subcarrier is between ⁇ and ⁇ , and the desired communication quality is coded-
  • modulation scheme # 2 can be used on the subcarrier. That is, ⁇ and ⁇ are signs
  • determination unit 23 selects SIR threshold value ⁇ for selecting modulation scheme # 1 and modulation scheme # 2.
  • determination unit 23 determines SIR threshold value ⁇ and modulation method for selecting modulation method # 1.
  • the determination unit 23 compares the SIR threshold set in step S21 with the SIR for each subcarrier acquired in step S11, and determines the modulation scheme for each subcarrier (step S 22). Specifically, based on FIGS. 7-1 and 7-2, for example, if the SIR of the subcarrier for which the modulation scheme is determined is between ⁇ and ⁇ , the determination unit 23 determines the subcarrier
  • the modulation method is determined to be modulation method # 1. Note that the determination unit 23 performs such processing (determination of the modulation scheme) for all subcarriers.
  • the determination unit 23 calculates a transmission rate (step S23). Note that the transmission rate calculation process is the same as the transmission rate calculation process performed in step S14 of the first embodiment described above, and the coding rate and step of the coding method selected in step S13 above. In step S22, the transmission rate is calculated when the modulation method (modulation method for each subcarrier) determined in step S22 is used. The determination unit 23 holds the calculated transmission rate. Next, the determination unit 23 determines whether or not the above-described series of processing (steps S13, S21, S22, S23) for all selectable encoding methods has been executed (step S24).
  • step S24, No If there is an encoding method (step S24, No) (if the above processing is executed) (step S24, No), the process returns to step S13 and the same processing is performed for the remaining encoding methods. (Steps S13, S21, S22, S23, S24) are performed. When the above-described series of processing is completed for all the code keys (step S24, Yes), the process proceeds to step S16.
  • the determination unit 23 selects and determines the combination of the modulation scheme for each subcarrier and the encoding scheme for which the maximum transmission rate is obtained in step S23 as a combination to be used during data transmission ( Step S 16).
  • the optimum coding scheme and the optimum for each subcarrier are described.
  • a combination with a suitable modulation method was selected, and data transmission was performed using the selected combination.
  • the selection accuracy of the combination is inferior to that of the first embodiment, but the amount of calculation is reduced. While reducing the circuit scale, the transmission speed during data transmission can be increased faster than before.
  • FIG. 8 is a diagram showing a configuration example of a third embodiment of a communication system for realizing an adaptive modulation method according to the present invention and a communication apparatus constituting the communication system.
  • the communication system according to the third embodiment includes a communication device 1 and a communication device 2a.
  • Communication device 1 is the same as communication device 1 of the first embodiment described above.
  • the communication device 2a includes a determination unit 23a instead of the determination unit 23 included in the communication device 2.
  • the determination unit 23a performs operations as a transmission condition selection unit, a transmission quality calculation unit, an iterative process control unit, and a transmission condition determination unit. Further, the determination unit 23a includes a comparison unit 31, a threshold setting unit 32, a selection unit 33, an encoding scheme holding unit 34, and a control unit 35. Note that parts other than the determination unit 23a have the same configurations as those of the first embodiment, and thus the same reference numerals are given and description thereof is omitted. In the present embodiment, an operation for adjusting the modulation scheme and the coding scheme for each subcarrier that is determined (in use) will be described.
  • the modulation scheme and code scheme can be adjusted (reselected) adaptively to increase the transmission speed. Is realized. Note that the present embodiment differs from the second embodiment described above only in the adaptive modulation instruction information generation operation (adaptive modulation instruction information update operation) performed by the determination unit 23a. Here, the operation of the determination unit 23a will be mainly described.
  • the determination unit 23a included in the communication device 2a of the present embodiment adjusts the modulation scheme and encoding scheme for each subcarrier once determined by the procedure shown in FIG. FIG.
  • FIG. 9 is a flowchart showing an operation (operation for updating adaptive modulation instruction information) in which the determination unit 23a adjusts the modulation scheme for each subcarrier once determined and the encoding scheme. Note that the same steps as those in the second embodiment are denoted by the same step numbers, and the description thereof is omitted.
  • the comparison unit 31 constitutes a modulation scheme pattern determination unit
  • the threshold setting unit 32 and the control unit 35 constitute an SIR threshold adjustment unit
  • the control unit 35 constitutes a reference communication quality acquisition unit
  • the selection unit 33, the code key scheme holding unit 34, and the control unit 35 constitute a coding scheme adjustment unit.
  • determination section 23a generates adaptive modulation instruction information by executing any of the adaptive modulation instruction information generation operations shown in Embodiment 1 or 2 at the start of communication (modulation for each subcarrier). System and coding system). Thereafter, the control unit 35 of the determination unit 23a acquires communication quality information indicating the communication quality measured by the decoding unit 22 (step S31). Note that the communication quality measured by the decoding unit 22 is a CRC error as is generally done. This is measured by the method of detecting the perception and obtaining PER. The communication quality acquired here is retained as the standard communication quality until the next step S31 is executed.
  • determination unit 23a adjusts the SIR threshold value (see step S21 in FIG. 6) set in the adaptive modulation instruction information generation operation at the start of communication (step S32). It should be noted that after the adjustment of the SIR threshold has already been performed, the latest SIR threshold value obtained by the previous adjustment is adjusted (readjustment).
  • step S32 the control unit 35 of the determination unit 23a has a good communication quality (reference communication quality) indicated by the communication quality information acquired in step S31 (the desired communication quality is satisfied).
  • the communication quality is determined based on a communication quality determination threshold value for determining whether the communication quality is good or not. Specifically, the control unit 35 determines that the communication quality is good when the communication quality is equal to or higher than the communication determination threshold, and otherwise the communication quality is not good.
  • step S41, No the control unit 35 instructs the value setting unit 32 to adjust the SIR threshold, and the threshold! /, Value setting unit 32
  • the SIR threshold value (updated SIR threshold value) is reset (step S42).
  • the threshold value setting unit 32 adjusts all the SIR thresholds for each of the plurality of modulation schemes. Based on the updated SIR threshold value and the SIR for each subcarrier received from OFDM demodulator 21, comparator 31 performs the same processing as step S22 in Embodiment 2 (see FIG. 6).
  • the modulation method for each carrier is determined (step S43). Note that the determined modulation scheme for each subcarrier is notified to the communication device 1.
  • control unit 35 acquires communication quality information in a state reflecting the determined modulation scheme for each subcarrier from the decoding unit 22, and confirms whether the communication quality is good (step S44). ).
  • step S44 If the communication quality is good (step S44, Yes), the process proceeds to step S33. On the other hand, if the communication quality is not good (step S44, No), the process proceeds to step S42 and the SIR Adjust the threshold (increase by the specified value) and execute step S43 above. Thereafter, the same processing (steps S42 to S44) is repeatedly executed until it is determined in step S44 that the communication quality is good (step S44, Yes).
  • step S42 when the SIR threshold value is increased, 16QAM and 64QAM, such as a large multi-value number! /, And a modulation method (weak to noise !, modulation method) are selected.
  • a modulation system with a small multi-level number such as BPSK and QPSK is easily selected.
  • the SIR threshold by adjusting the SIR threshold, it is possible to increase noise resistance and improve communication quality.
  • the amount of increase in the SIR threshold in step S42 can be finely adjusted as the value is reduced, and the number of executions of the adjustment process is reduced as the value is increased.
  • step S41 when it is determined in step S41 that the communication quality is good (step S41, Yes), the control unit 35 sets the SIR threshold value to the threshold setting unit 32.
  • the threshold value setting unit 32 resets the SIR threshold value (updated SIR threshold value) after reducing the SIR threshold value in use by a specified value.
  • Step S45 Note that there are a plurality of threshold V and value setting units 32, and the adjustment is performed according to all the SIR thresholds and values for each modulation method. However, even if the communication quality is good, the control unit 35 determines the communication quality, determines the excess quality with a certain margin for the value, and if it is less than the value, Does not issue an instruction to adjust the SIR threshold to the threshold setting unit 32. That is, the process of step S32 is terminated without adjusting the SIR threshold value.
  • step S46 Based on the SIR threshold value reset (adjusted) by the threshold value setting unit 32 and the SIR for each subcarrier received from the OFDM demodulation unit 21, the comparison unit 31 The same processing as in step S22 is executed to determine the modulation scheme for each subcarrier (step S46). Note that the determined modulation scheme for each subcarrier is notified to the communication apparatus 1.
  • control unit 35 acquires communication quality information in a state reflecting the determined modulation scheme for each subcarrier from the decoding unit 22, and based on the acquired communication quality! /, SIR threshold, It is checked whether the value can be further decreased (whether the communication quality is excessively good enough to further increase the transmission rate) (step S47). That is, this In step S47, it is determined whether or not the communication quality is within the above-mentioned quality judgment threshold and is in a range that is greater than the value and less than the above-mentioned excess quality judgment threshold value.
  • step S47 If the value cannot be further decreased (step S47, No), the process proceeds to step S33. On the other hand, if the SIR threshold can be further reduced (step S47, Yes), the process proceeds to step S45 to adjust the SIR threshold (decrease by the specified value) and Execute. Thereafter, in step S47, the same processing (steps S45 to S47) is repeatedly executed until it is determined that the SIR threshold cannot be further decreased (No in step S47).
  • steps S45 to S47 described above makes it easier to select a modulation scheme that can transmit a large number of bits at once, such as 16QAM and 64QAM, by reducing the SIR threshold. This is based on the characteristic. In other words, the transmission rate can be increased by adjusting the SIR threshold.
  • step S33 the control unit 35 checks whether or not the coding scheme selection count has reached the specified count (step S33). If the number of encoding method selections has reached the specified number (step S33, Yes), the process proceeds to step S16. On the other hand, if the number of selections of the coding scheme has reached the specified number (step S33, No), the determination unit 23a adjusts the coding scheme in use (step S34).
  • step S34 the control unit 35 of the determination unit 23a confirms whether or not the reference communication quality indicated by the communication quality information acquired in step S31 is good (satisfying the desired communication quality). (Step S51).
  • step S51 When the communication quality is not good (step S51, No), the control unit 35 instructs the selection unit 33 to adjust the encoding method, and the selection unit 33 uses the encoding used. Select a coding method with a higher error correction capability from the coding methods held in the coding method holding unit 34, and change the method to use this coding method thereafter (step S52). This increases the number of redundant bits included in the encoded data and increases noise resistance.
  • step S51 determines whether the communication quality is good (step (S51, Yes)
  • the control unit 35 instructs the selection unit 33 to adjust the encoding method, and the selection unit 33 sends the encoding method used to the encoding method holding unit 34.
  • a code scheme with a lower error correction capability is selected from the stored code schemes, and thereafter changed to use this code scheme (step S53). This reduces the number of redundant bits contained in the encoded data and increases the transmission rate.
  • the control unit 35 if it is less than the excess quality determination threshold value obtained by adding a certain margin to the communication quality determination threshold value, the selection unit 33 Does not give instructions for adjusting the encoding method. That is, the process of step S34 is terminated without adjusting the encoding method.
  • step S34 the process proceeds to step S31, and the series of processes (steps S31, S32, S23, S33) are executed again. Thereafter, in step S33, the same processing (steps S31, S32, S23, S33, S34) is continued until it is determined that the number of selections of the sign key method has reached the specified number (step S33, Yes).
  • the change in the code method is limited to the specified number of times because the number of processing executions is reduced and the time required to reset the combination of the coding method and the modulation method for each subcarrier. This is to shorten the time. However, if the time and circuit scale are sufficient, all the coding methods can be selected. In this case, it is possible to select a more appropriate code scheme and modulation scheme for each subcarrier.
  • control unit 35 obtains the combination of the modulation scheme for each subcarrier and the encoding scheme that has obtained the maximum transmission rate among the calculations and stored in step S23. Make a selection (step S16). The combination force selected and determined in step S16 When the combination of the modulation scheme for each subcarrier in use and the encoding scheme is different, the selected combination is notified to the communication apparatus 1.
  • the time variation of the transmission path is monitored, and the encoding scheme being used and the modulation scheme for each subcarrier are not optimal for the transmission path state.
  • the code scheme to be used and the modulation scheme for each subcarrier were appropriately changed. With this, for example, even if the communication quality cannot be satisfied, the communication quality becomes excessively good, etc., the change follows, A high transmission speed can always be realized while satisfying desired communication quality.
  • Embodiment 4 the adaptive modulation method and communication apparatus according to Embodiment 4 will be described.
  • the amount of calculation is reduced and the circuit scale is reduced.
  • the configuration of the communication system that implements the adaptive modulation method of the present embodiment and the communication device that constitutes the communication system are the same as those of the third embodiment described above, and the update of the adaptive modulation instruction information performed by the determination unit 23a Only the operation is different.
  • FIG. 12 is a flowchart illustrating an operation in which the determination unit 23a according to the fourth embodiment updates the adaptive modulation instruction information.
  • step S61 is executed instead of step S16.
  • the process of step S61 is a process for determining the modulation scheme for each subcarrier.
  • the adjusted SIR threshold! /, And the modulation scheme for each subcarrier using the value are set. Since it has been determined, it is adopted as the modulation method for each subcarrier after adjustment.
  • Other processing is the same as that in the adaptive modulation instruction information update operation of Embodiment 3 (see Fig. 9) with the same step number.
  • the adaptive modulation method and communication apparatus will be described.
  • an adaptive modulation method in which the processing described in Embodiment 3 is partially changed will be described.
  • the configuration of the communication system that implements the adaptive modulation method of the present embodiment and the communication device that configures the communication system are the same as those of the above-described third embodiment, and update of the adaptive modulation instruction information performed by the determination unit 23a Only the operation is different. Therefore, in the present embodiment, the update operation of adaptive modulation instruction information performed by determination unit 23a will be mainly described.
  • FIG. 13 is a flowchart showing an operation in which the determination unit 23a of the fifth embodiment changes the modulation scheme for each subcarrier, and is executed instead of step S32 of FIG. 9 described in the third embodiment. Operation (step S32b). Other processes in the adaptive modulation instruction information update operation (processes other than step S32 in FIG. 9) are the same as those in the third embodiment.
  • step S71 is added between steps S42 and S43.
  • step S45 and S46 are interspersed with step S72.
  • the other parts are the same as those shown in FIG.
  • step S71 and step S72 the same processing is executed. Specifically, in steps S42 and S45, each SIR threshold value, which is uniformly adjusted with the same adjustment amount, is added to each modulation method, and different offset values are added for each modulation method. adjust. The reason for adding this offset value will be described below.
  • modulation methods with a small number of multi-values generally tend to be less susceptible to disturbances such as noise and signal fluctuations (phase fluctuations) due to device imperfections. is there.
  • modulation methods with large multi-levels such as 16QAM and 64QAM, are generally vulnerable to disturbances.
  • 16QAM and 64QAM are generally vulnerable to disturbances.
  • the required SIR increases greatly in 16QAM and 64QAM compared to BPSK and QPSK.
  • FIG. 7-2 used in the description of Embodiment 2 it is necessary to increase the ⁇ force ldB. In a state where ⁇ is 2 dB, etc. (The numerical values are just examples.
  • the SIR threshold used in the modulation scheme adjustment operation for each subcarrier is given an offset corresponding to the modulation scheme corresponding to each value.
  • the SIR threshold can be adjusted with a different adjustment amount for each modulation method, and even when there is a disturbance such as signal fluctuation due to incompleteness of the device, a highly accurate modulation method for each subcarrier. Selection becomes possible.
  • Embodiment 6 an adaptive modulation method in which the processing described in Embodiment 3 is partially changed will be described.
  • the configuration of the communication system that implements the adaptive modulation method of the present embodiment and the communication device that configures the communication system are the same as those of the above-described third embodiment, and update of the adaptive modulation instruction information performed by the determination unit 23a Only the operation is different. Therefore, in the present embodiment, the update operation of adaptive modulation instruction information performed by determination unit 23a will be mainly described.
  • FIG. 14 is a flowchart showing an operation in which the determination unit 23a of the sixth embodiment changes the modulation scheme for each subcarrier, and is executed instead of step S32 of FIG. 9 described in the third embodiment. Operation (step S32c). Other processes in the adaptive modulation instruction information update operation (processes other than step S32 in FIG. 9) are the same as those in the third embodiment.
  • step S81 between steps S41 and S42 with respect to the operation shown in FIG. 10 (SIR threshold adjustment operation in the third embodiment).
  • Step S41 and S45 are interpolated from Step S82.
  • the other parts are the same as those shown in FIG.
  • step S81 and step S82 are the same, and the threshold value is adjusted. This is a process to limit the amount (increase / decrease amount). Specifically, when executing the process to increase and decrease the SIR threshold (step S42ZS45), the current adjustment amount is compared to the cumulative adjustment amount of the SIR threshold that has been increased and decreased in step S32c. When is added, it is confirmed whether or not the cumulative adjustment amount falls within the specified range (step S81ZS82). If the result of adding the current adjustment amount to the cumulative adjustment amount is within the specified range (steps S81, YesZS82, Yes), the SIR threshold value is increased and decreased (step S43ZS45). On the other hand, if the result of adding the current adjustment amount to the cumulative adjustment amount is not within the specified range (step S81, NoZS82, No), the process of step S32c is terminated.
  • the reason for adjusting the value by referring to the cumulative adjustment amount as described above will be explained as follows.
  • the higher the SIR threshold the easier it is to select a modulation scheme with a small multi-level number.
  • the transmission rate will be extremely reduced and transmission efficiency will deteriorate.
  • the smaller the SIR threshold the easier it is to select a modulation scheme with a large number of values, but it becomes weaker with respect to the time variation of the transmission path and communication becomes unstable.
  • the adjustment amount is set within a certain range.
  • the adjustment of the SIR threshold used in the modulation scheme adjustment operation for each subcarrier is performed only within a certain range.
  • the modulation scheme for each subcarrier is not excessively adjusted with respect to fluctuations in the transmission path state, and stable communication can be realized.
  • FIG. 15 is a flowchart illustrating an operation in which the determination unit 23a of the seventh embodiment updates the adaptive modulation instruction information.
  • step S91 is executed instead of step S 16.
  • the process of step S91 is a process of determining the encoding method, and the encoding method that obtained the maximum transmission rate in step S23 is selected and determined as the adjusted encoding method.
  • Other processing is the same as that in the adaptive modulation instruction information update operation (see FIG. 9) of Embodiment 3 to which the same step number is assigned.
  • the process of selecting (determining) the modulation scheme for each subcarrier in the above-described embodiment is performed collectively for each of a plurality of neighboring subcarriers. Therefore, the configuration of the communication system that implements the adaptive modulation method of the present embodiment and the communication device that constitutes the communication system is the same as that of either the first or third embodiment described above.
  • FIG. 16-1 and FIG. 16-2 are diagrams for explaining the adaptive modulation method of the eighth embodiment. is there.
  • Figure 16-1 is an example of the frequency characteristic (amplitude characteristic) of the transmission line, and shows that the signal easily passes in proportion to the magnitude of the amplitude characteristic shown on the vertical axis.
  • Figure 16-2 is an example of the received signal level of the OFDM signal received through the transmission line with the amplitude characteristics shown in Figure 16-1.
  • the reception level is proportional to the amplitude characteristics of the transmission line, and a subcarrier with a higher reception level can easily use a multi-level modulation method that can transmit many bits at a time.
  • a subcarrier with a low reception level has a small multi-level number and cannot be used as a modulation method, and can transmit only a few bits at a time.
  • the frequency characteristics of the transmission path are determined by the influence of the reflected wave (multipath wave) and the like.
  • the delay time of the multipath wave (the signal that arrives first and the signal that arrives after being delayed by reflection) If the time difference is not so large, the frequency characteristics undulation (number of peaks and valleys) is relatively small.
  • the ease of passing the signal (reception level) is almost the same in neighboring subcarriers. Therefore, even if a process for selecting a modulation scheme for each subcarrier as in the above-described embodiment is executed, the same modulation scheme may be used for neighboring subcarriers as a result. The amount of calculation is unnecessarily high.
  • a plurality of subcarriers that are not set for each subcarrier are grouped into a plurality of subcarriers (subcarrier group).
  • the same modulation method is set. For example, if there are 100 subcarriers and 2 waves are combined into a subcarrier group, the number of targets for which the modulation scheme is set (corresponding to the number of subcarriers in the above-described embodiment) is 1Z2.
  • the effort for setting the modulation method for each carrier processing for setting the modulation method for each subcarrier in the above-described embodiment
  • the modulation scheme setting processing that has been individually executed for each subcarrier in Embodiments 1 to 6 described above is performed by subcarriers having a plurality of neighboring subcarriers. It was decided to carry out every group. As a result, the processing time and circuit scale required for setting the modulation method can be reduced. [0092] Embodiment 9.
  • Embodiments 1 to 8 described above the power of explaining an adaptive modulation method in a communication system using OFDM
  • the adaptive modulation method described above is applied to a communication system using a method other than OFDM. The case where it does is demonstrated. Therefore, the configuration of the communication system that realizes the adaptive modulation method of the present embodiment is the same as that of either of the first or third embodiment described above, and only the multiplexing scheme to be used is different.
  • FIGS. 17-1 to 17-5 are diagrams for explaining the adaptive modulation method according to the ninth embodiment.
  • Figures 17-1 to 17-3 show an example of the spectrum of the OFDM signal, an example of the spectrum of the FDM signal, and an example of the spectrum of the CDM signal, respectively.
  • Fig. 17-4 schematically shows an example of the time waveform of the TDM signal
  • Fig. 17-5 shows a configuration example of a communication system that performs SDM.
  • Embodiments 1 to 8 are inventions based on OFDM signals as shown in FIG. 17-1, and in this system, data is transmitted in parallel using multiple subcarriers. To do.
  • the present invention can be applied to the above-described miscommunication system.
  • the transmission channel used in each communication system (communication system based on one of FDM, CDM, TDM, and SDM) is a process targeting subcarriers. (Channels multiplexed using one of frequency, code, time slot, and space) are changed.
  • the communication apparatus on the receiving side can execute the following processing to select and determine the modulation scheme and code scheme for each transmission channel.
  • the communication device on the receiving side first measures the SIR for each transmission channel (step S111), then selects the modulation method for each transmission channel (step S112), and then selects the coding method (step S112). S113), then calculate the transmission rate and communication quality (step S114), and determine all combinations of the modulation scheme for each transmission scheme selected in step S112 and the encoding scheme selected in step S113. After confirming whether or not step S114 has been executed (step S115), if all combinations have been executed!
  • step S112 and S113 Selects and determines the combination of the modulation method and the encoding method for each transmission channel corresponding to the combination that maximizes the transmission speed while satisfying the desired communication quality in the combination of the selection results. (Step S11 6). If it is determined in step S115 that step S114 has not been executed for all combinations (step S115, No), steps S112 to S112 are performed until the above processing is executed for all combinations. The process of S115 is repeatedly executed.
  • Embodiments 2 to 8 The operation procedure shown in Embodiments 2 to 8 is the same as the communication system using OFDM signals. In order to apply to communication systems other than the above, the operation procedure of each embodiment has been described above.
  • Embodiments 1 to 7 the adaptive modulation method shown in Embodiments 1 to 7 described above can be applied to a communication system that performs multiplex transmission other than OFDM. It was. That is, the transmission channels (frequency, code, time slot, space) of each communication system that performs multiplex transmission other than OFDM are handled in the same way as subcarriers in a communication system using OFDM, and are shown in Embodiments 1 to 8. By performing the operation, the same effects as those of the above-described embodiments can be obtained in each communication system. Industrial applicability
  • the adaptive modulation method according to the present invention is useful for, for example, a communication system using OFDM, and particularly based on the communication quality for each subcarrier. It is suitable for the adaptive modulation method of communication equipment that performs communication by adaptively selecting and determining each modulation method.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Detection And Prevention Of Errors In Transmission (AREA)
  • Time-Division Multiplex Systems (AREA)

Abstract

Procédé de modulation adaptatif pour la sélection et la fixation d'un programme de codage et d'un programme de modulation pour la transmission de données avec multiplexage par répartition orthogonale de la fréquence. Ce procédé englobe les opérations suivantes: fixation d'un schéma de programme de modulation pour le choix d'un programme de modulation pour chaque sous-porteuse et pour la fixation d'une combinaison de programme de modulation (schéma) pour chaque sous-porteuse; sélection d'un programme de codage; et calcul de la qualité de transmission consistant à calculer, sur la base du SIR de chaque sous-porteuse, un débit de transmission et une qualité de communication. Selon ce procédé, les opérations de fixation d'un schéma de programme de codage, de sélection d'un programme de codage et de calcul de la qualité de transmission sont exécutées de manière itérative, les opérations de calcul de la qualité de transmission étant exécutés pour toutes les combinaisons de schémas de programme de modulation et de programmes de codage. Ensuite, un schéma de programme de modulation et un programme de codage (pour lesquels est satisfaite une qualité requise de communication et est obtenue une qualité de transmission avec débit maximum de transmission dans les calculs correspondants) sont sélectionnés et fixés en tant que schéma de programme de modulation formel et programme de codage formel, respectivement.
PCT/JP2006/308871 2006-04-27 2006-04-27 Procédé de modulation adaptatif et appareil de communication WO2007125580A1 (fr)

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JP2010537494A (ja) * 2007-08-16 2010-12-02 イカノス・コミュニケーションズ・インコーポレーテッド マルチトーン・トランシーバにおけるビット誤り判定のための方法および装置
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