JP4418294B2 - Communication apparatus and modulation method determination method - Google Patents

Description

  The present invention relates to a communication apparatus and a modulation method determination method.

  In a communication system using the link adaptation method, a plurality of modulation / demodulation methods are used while being switched according to the state of the transmission path. Specifically, for example, in the link adaptation method in the communication using the multi-level phase shift keying method, the fineness of phase division is switched according to the transmission path state. In the multi-level phase shift keying method, when the transmission line condition is good, the phase is finely divided to perform high-speed communication, and when the transmission line condition is bad, the phase is roughly divided to make it low speed but surely. It enables communication that can be demodulated.

In Patent Document 1, in a receiver capable of receiving a plurality of broadcasts having the same content with different frequencies, the electric field strength of the first frequency is measured by the reception strength detection means and detected to be equal to or higher than a predetermined level. A receiver is provided that includes means for receiving the first frequency and turning on the audio output when the signal is received, and means for receiving the frequency received immediately before the first frequency when the predetermined level is not detected. Yes.
JP-A-8-251049

  Here, in the conventional method, the transmitting communication device transmits information indicating the modulation method used when the transmission wave is modulated, and the receiving communication device receives the information to change the modulation method of the received wave. get. However, there are cases where the modulation method of the received wave cannot be normally acquired due to an instantaneous interruption of communication between the communication devices. In such a case, there is a problem that demodulation cannot be performed normally and communication cannot be performed normally.

  The present invention has been made in view of the above problems, and its object is to increase the possibility that communication can be normally performed even when the reception-side communication apparatus cannot acquire the modulation method of the received wave. It is to provide a communication apparatus and a modulation method determination method.

  The communication apparatus according to the present invention for solving the above-described problem is based on the first frame modulation scheme acquisition means for acquiring information indicating the modulation scheme of one frame, and on the basis of the information indicating the modulation scheme of the first frame. A demodulated signal is obtained by demodulating the first frame using a first frame modulation scheme determining means for determining a modulation scheme for one frame and the modulation scheme determined by the first frame modulation scheme determining means. First frame demodulating means; modulation scheme storage means for storing information indicating the modulation scheme of the first frame used by the first frame demodulating means; and modulation of the second frame received after the first frame. Information indicating the modulation scheme of the first frame stored in the second frame modulation scheme acquisition means for acquiring information indicating the scheme, and the modulation scheme storage means; Selects information indicating one modulation scheme from the information indicating the modulation scheme of the second frame acquired by the second frame modulation scheme acquisition means, and the second based on the information indicating the selected modulation scheme A second frame modulation method determining means for determining a modulation method of a frame; and a second frame modulation method determining means for acquiring a demodulated signal by demodulating the second frame using the modulation method determined by the second frame modulation method determining means. Two-frame demodulation means.

  By doing so, it is possible to increase the possibility that communication can be normally performed even when the reception-side communication apparatus cannot acquire the modulation method of the received wave. In the present application, the word frame is used as a word meaning a demodulation unit.

  Further, in the communication apparatus, the first frame modulation scheme acquisition unit acquires information indicating a modulation scheme included in a frame including information indicating a modulation scheme of the first frame, thereby modulating the first frame. It is good also as acquiring the information which shows a system.

  In the communication apparatus, the second frame modulation scheme acquisition unit acquires information indicating a modulation scheme included in a frame including information indicating a modulation scheme of the second frame, thereby modulating the second frame. It is good also as acquiring the information which shows a system.

  The communication apparatus further includes error detection means for detecting an error in the demodulated signal acquired by the first frame demodulation means, wherein the modulation method storage means detects an error by the error detection means. In addition, the storage of information indicating the modulation scheme used by the first frame demodulation means may be limited.

  In the communication apparatus, the second frame modulation scheme determination unit includes a determination unit that determines whether information indicating the modulation scheme of the second frame has been acquired by the second frame modulation scheme acquisition unit, When the determination means determines that the second frame modulation method acquisition means has acquired the information indicating the modulation method of the second frame, the second frame modulation method acquisition means acquires the second frame modulation method acquisition means. It is good also as selecting the information to show.

  The modulation scheme determination method according to the present invention includes a first frame modulation scheme acquisition step for acquiring information indicating a modulation scheme of the first frame, and the first frame based on the information indicating the modulation scheme of the first frame. A first frame modulation scheme determination step for determining a modulation scheme of the first frame, and a demodulated signal obtained by demodulating the first frame using the modulation scheme determined in the first frame modulation scheme determination step. A frame demodulation step; a modulation scheme storage step for storing information indicating a modulation scheme of the first frame used in the first frame demodulation step; and a modulation scheme of a second frame received after the first frame. A second frame modulation scheme acquisition step for acquiring information to be indicated, and a first frame stored in the modulation scheme storage step. Information indicating one modulation scheme is selected from information indicating a modulation scheme of a frame or information indicating a modulation scheme of the second frame acquired in the second frame modulation scheme acquisition step, and the selected modulation scheme is A second frame modulation scheme determination step for determining a modulation scheme of the second frame based on the indicated information; and the second frame is demodulated using the modulation scheme determined in the second frame modulation scheme determination step. And a second frame demodulating step for obtaining a demodulated signal.

  Embodiments of the present invention will be described with reference to the drawings.

  A mobile communication system 1 according to the present embodiment includes a base station apparatus 2, a mobile station apparatus 3, and a communication network 4 as shown in FIG. The base station device 2 communicates with the normal communication network 4 and the mobile station device 3.

  As shown in FIG. 2, the communication device 5 used as the base station device 2 includes a control unit 10, a wireless communication unit 11, a storage unit 12, and a network interface unit 13. The control unit 10 controls each unit of the communication device 5 and executes processes related to telephone calls and data communication. Specifically, the radio section signal input from the wireless communication unit 11 is demodulated / decoded, processed to be output to the network interface unit 13, and the signal input from the network interface unit 13 is encoded / modulated. Processing to output to the wireless communication unit 11 is also performed. The network interface unit 13 is connected to the communication network 4 and receives an audio signal, a communication packet, and the like from the communication network 4 and outputs them to the control unit 10, or according to an instruction from the control unit 10. A packet or the like is transmitted to the communication network 4. The wireless communication unit 11 includes an antenna, receives a voice signal, a communication packet, and the like from the mobile station device 3 and performs frequency conversion to output to the control unit 10 or according to an instruction input from the control unit 10 Processing such as generating a signal in the carrier frequency band based on an audio signal or a communication packet input from the control unit 10 and outputting the signal via an antenna is performed. The storage unit 12 operates as a work memory for the control unit 10. Further, the storage unit 12 holds programs and parameters related to various processes performed by the control unit 10.

  As shown in FIG. 3, the communication device 6 used as the mobile station device 3 includes a control unit 14, a wireless communication unit 15, a storage unit 16, a display unit 17, and an operation unit 18. Has been. The control unit 14 controls each unit of the communication device 6 and executes processing related to a call and data communication. The wireless communication unit 15 includes an aerial line, and modulates an audio signal, a communication packet, and the like according to an instruction input from the control unit 14 and outputs the modulated signal or the like via the aerial line. Is received, demodulated, and output to the control unit 14. The storage unit 16 operates as a work memory for the control unit 14. The storage unit 16 holds programs and parameters related to various processes performed by the control unit 14. The display unit 17 includes, for example, a liquid crystal display device, and displays and outputs information according to a signal input from the control unit 14. The operation unit 18 is, for example, a numeric keypad, and receives a telephone number or character string input from the user and outputs it to the control unit 14.

  In the wireless communication unit 11 or the wireless communication unit 15, an adaptive array antenna can be used. In that case, the radio communication unit 11 or the radio communication unit 15 includes an adaptive array antenna, an analog radio circuit that generates a signal in a carrier frequency band, a reference signal circuit that provides a modulation frequency to the analog radio circuit, A digital upsampling converter (DUC) for converting the frequency of a transmission signal input to the analog radio circuit; and a digital downsampling converter (DDC) for converting the frequency of a reception signal output by the analog radio circuit; It is comprised including. Further, the control unit 10 or the control unit 14 outputs to the DSP a transmission / reception digital signal processor (DSP) that performs signal processing of an input transmission signal to the DUC and an output reception signal from the DDC, and a reception signal from the DDC. A path control circuit (Path Controller) that combines a transmission signal from the DSP and a transmission antenna weight and conveys it to the DUC, and a central processing element (CPU) connected to the DSP included in the control unit 10 or the control unit 14 Consists of including.

  Here, the background art will be described again in detail.

  In a time-division multicarrier system employed in a mobile communication system such as a PHS (Personal Handyphone System), signals are multiplexed on the frequency axis using orthogonality between signals. When using an adaptive array antenna, it is possible to insert a reference signal for each time-divided received signal and obtain signal reproduction using the antenna weight calculated based on the correlation between the received signal and the reference signal. I have to. In other words, in order to mitigate the effects of selective fading, time-division signals are transmitted by multicarrier and interference waves existing in the transmission band are removed using an adaptive array antenna. We are trying to improve. In addition to these, a method called link adaptation is used in which communication is performed while appropriately changing two or more types of modulation methods according to transmission conditions.

  In the link adaptation method, an uplink signal transmitted from the mobile station device 3 to the base station device 2 includes a signal including a modulation method identifier (Modulation Class) that is information indicating a modulation method used for modulation of the uplink signal. FACCH (Fast Associated Control CHannel) is included, the base station apparatus 2 acquires a modulation scheme identifier from the FACCH, and performs reception processing using a demodulation scheme according to the modulation scheme indicated by the modulation scheme identifier. Similarly, a downlink signal transmitted from the base station apparatus 2 to the mobile station apparatus 3 includes a FACCH including a modulation scheme identifier that is information indicating a modulation scheme used for modulation of the downlink signal, and the mobile station apparatus 3 acquires a modulation scheme identifier from the FACCH, and performs reception processing using a demodulation scheme according to the modulation scheme indicated by the modulation scheme identifier.

  Conventionally, as shown in FIG. 5, the modulation scheme identifier (CMC) of the uplink signal is included in the FACCH during an odd frame of the traffic channel (TCH). In the case of an even frame, a coefficient (Rx Parameter) for performing power control or the like is included in the FACCH. That is, the mobile station apparatus 3 transmits the FACCH including the modulation scheme identifier in the 2k + 1 frame, and transmits the FACCH including the coefficient for power control and the like in the 2k + 2 frame.

  For this reason, the uplink modulation scheme is determined by the mobile station device 3 based on the instruction information from the base station device 2 when transmitting the odd frame of the TCH and included in the FACCH. Used. That is, the base station apparatus 2 demodulates and decodes the 2k + 1th frame and the 2k + 2th frame by the modulation scheme indicated by the modulation scheme identifier included in the 2k + 1th frame. Such link adaptation is usually referred to as link adaptation composed of two frames.

  Here, in the time division multi-carrier scheme, a super frame including a RACH (random access channel), a normal frame including the TCH, and a configuration channel such as a broadcast channel (BCH) is transmitted as the multi-carrier. A superframe is shown in FIG. The mobile station apparatus 3 receives the superframe for frequency and time synchronization with the base station apparatus 2 and for registration procedures of the mobile station apparatus 3 in the communication network 4. In addition, while registration is completed and traffic channel transmission / reception is performed, the mobile station device 3 maintains a radio wave propagation environment with the base station device 2 that changes from moment to moment, or a connected base station device. In order to select another base station apparatus 2 having higher superframe reception characteristics than 2 and to perform handover to the base station apparatus 2, the superframe transmitted from the base station apparatus 2 can be received. Normally, superframes from a plurality of base station apparatuses 2 are received at regular intervals.

  The super frame is used as a BCH in every other frame. A frame that is not used as a BCH is used as a TCH. In this way, effective use of frequency resources is achieved. On the other hand, the mobile station apparatus 3 is influenced by the reception of the super frame, and the mobile station apparatus 3 may not be able to include the FACCH in the transmission of the odd frame of the normal frame. In this case, the base station apparatus 2 cannot receive the FACCH in the odd frame, and the base station apparatus 2 cannot determine the modulation method of the odd frame and the immediately following even frame. For this reason, there is a case where the demodulation process of the frame is performed by an incorrect modulation method. In such a case, transmission / reception of TCH is interrupted and communication performance deteriorates. Alternatively, since communication with the mobile station device 3 is once disconnected and reconnected in the base station device 2, the communication transfer rate characteristics deteriorate. For this reason, it is necessary to acquire an appropriate modulation scheme in the base station apparatus 2 so that communication is not interrupted or disconnected in such a case.

  Therefore, in the present embodiment, an appropriate modulation scheme can be acquired by adopting a configuration in which the control section 10 of the communication apparatus 5 used as the base station apparatus 2 stores the modulation scheme. In order to describe the configuration, processing in the control unit 10 will be described in detail with reference to a functional block diagram of the control unit 10.

  FIG. 4 is a functional block diagram of the control unit 10. The control unit 10 functionally includes a receiving unit 20, a modulation scheme determining unit 22, a modulation scheme identifier selecting unit 24, a link adaptation switch 26, a MODn decoding unit 28-n, and a modulation scheme identifier storage unit 30. Yes. The link adaptation switch 26 and the MODn decoding unit 28-n constitute a decoding function unit 32. The link adaptation switch 26 includes switchers 34-1 and 34-2.

  The receiving unit 20 accepts a reception signal output from the wireless communication unit 11. Then, the received signal is output to the decoding function unit 32 as a reception frame which is a demodulation unit of the decoding function unit 32. For example, when the wireless communication unit 11 uses an adaptive array antenna, the receiving unit 20 receives a modulated signal discretized at a predetermined sampling time transmitted from the DDC as a received signal. A detector for calculating an antenna weight for extracting a desired signal, a correction coefficient, and a coefficient representing reception performance is included. At this time, a reference signal may be required, and a carrier frequency, an arrival direction, a modulation method, a polarization, and the like are generally used as the reference signal. Further, the receiving unit 20 includes a combining unit that combines the modulated signal received using the correction coefficient and the antenna weight to extract a desired signal. The desired signal is output to the decoding function unit 32 as a received frame.

  The modulation scheme determination unit 22 determines the modulation scheme of the received frame and the frame received thereafter by acquiring information indicating the modulation scheme of the reception frame included in the reception frame accepted by the reception unit 20. That is, the mobile station device 3 that is a communication partner transmits a signal while switching the modulation method by a conventionally known link adaptation method. In this case, the mobile station apparatus 3 transmits the modulation method included in the transmission signal. Specifically, as described above, a control code called FACCH is included in the transmission frame, and the reception side acquires the modulation scheme identifier, which is information indicating the modulation scheme of the reception frame, by acquiring the FACCH. Note that the modulation scheme determination unit 22 can acquire the modulation scheme identifier when the odd frame is received. As described above, the odd frame may not include the modulation scheme identifier. In this case, the modulation scheme identifier cannot be acquired, and the modulation scheme of the received frame cannot be determined.

  The modulation scheme identifier selection unit 24 selects a modulation scheme identifier used for demodulation of a received frame from a modulation scheme identifier stored in a modulation scheme identifier storage unit 30 to be described later and a modulation scheme identifier determined by the modulation scheme determination unit 22. This is selected and output to the link adaptation switch 26 and the modulation scheme identifier storage unit 30. That is, the modulation scheme identifier selection unit 24 determines the modulation scheme of the received frame (second frame) based on the selected modulation scheme identifier. When the modulation scheme identifier stored in the modulation scheme identifier storage unit 30 is selected, the previously received received frame (first frame) is decoded without using the modulation scheme identifier determined by the modulation scheme determination unit 22. The functional unit 32 performs demodulation and decoding using the modulation method demodulated and decoded. Note that the modulation scheme identifier is selected by the modulation scheme identifier selection unit 24 when the modulation scheme determination unit 22 determines whether or not the modulation scheme of the received frame has been determined. The modulation scheme identifier acquired by the unit 22 can be selected.

  The decoding function unit 32 demodulates and decodes the reception frame output from the reception unit 20. Specifically, the link adaptation switch 26 controls the switches 34-1 and 34-2 according to the modulation scheme identifier output from the modulation scheme identifier selection unit 24. That is, for example, when the modulation scheme identifier indicates that the modulation scheme of the received frame is a modulation scheme performed by the MOD1 decoding unit 28-1, each switch is switched to the MOD1 decoding unit 28-1, thereby performing MOD1 decoding. The unit 28-1, the receiving unit 20, and the output destination are electrically connected. Then, the MOD1 decoding unit 28-1 demodulates and decodes the reception frame output from the reception unit 20. That is, the MODn decoding unit 28-n is configured to be able to demodulate and decode using the assigned modulation scheme. The link adaptation switch 26 is configured to realize an electrical connection of each MODn decoding unit 28-n to which a modulation scheme corresponding to the modulation scheme identifier is assigned.

  Also, each MODn decoding unit 28-n checks for errors included in the received frame. Specifically, an error can be inspected by inspecting cyclic redundancy checking (CRC). When the received frame passes the inspection (hereinafter referred to as error check), the decoded received frame is output to a signal processing unit (not shown). If the received frame does not pass the inspection, a conventionally known retransmission control process is started.

  Then, the modulation scheme identifier storage unit 30 is a modulation scheme identifier that indicates the modulation scheme when the received frame passes the error check in the decoding function unit 32, that is, when the error included in the received frame is within a permissible range. Remember. On the other hand, when the received frame does not pass the error check, that is, when the error included in the received frame is in an unacceptable range, it is possible to limit storage of the modulation scheme identifier indicating the modulation scheme. That is, it can be prevented from storing.

  Next, the modulation scheme identifier selection processing in the modulation scheme identifier selection unit 24 will be described in detail with reference to the flowchart.

  FIG. 7 is a flowchart showing an example of processing in the modulation scheme identifier storage unit 30. First, it is determined whether or not the frame number of the frame used as the TCH is 0 or more (S100). That is, since the frame number is 0 at the start of communication, in such a case, the modulation scheme identifier determined in the random access channel is substituted into the variable LastCMC (S102). In addition, since the frame in which the modulation scheme identifier is included in the FACCH is an odd frame, the modulation scheme identifier determined in the random access channel is used for demodulation and decoding when the frame number is 0. Also, the modulation scheme identifier determined in the random access channel is output from the modulation scheme identifier selection unit 24. If the frame number is not 0, it is determined whether the frame number is an even number (S104). If the frame number is an even number, it is determined whether the received frame has passed the CRC check (S106). . The CRC check is performed in each MODn decoding unit 28-n, and the modulation scheme identifier storage unit 30 acquires the result. If the error check by CRC is passed, the modulation scheme identifier used for demodulation and decoding of the received frame is substituted into the variable LastCMC (S108). The modulation scheme identifier used for demodulation and decoding of the received frame is output from the modulation scheme identifier selection unit 24. Then, by storing the variable LastCMC, the modulation scheme identifier is stored. On the other hand, when the frame number is not an even number and when the received signal does not pass the error check by CRC, the modulation scheme identifier stored in the process so far is stored as it is.

  FIG. 8 is a flowchart showing an example of processing in the modulation scheme identifier selection unit 24. Here, description will be made assuming that an adaptive array antenna is used in the wireless communication unit 11. First, it is determined whether the frame number of the carrier used as the TCH is 0 or more (S120). That is, since the frame number is 0 when communication is started, in such a case, the modulation scheme identifier determined in the random access channel is substituted into the variable CMC (S122). If the frame number is an odd number (S124), it is determined whether or not the even frame immediately before the received frame is synchronized with the reference signal (S126). Is assigned to the variable CMC (S128). If not, the modulation scheme identifier stored in the modulation scheme identifier storage unit 30 is read and substituted into the variable CMC. Note that, for example, the mobile station apparatus 3 transmits a known signal called a training sequence included in all frames and compares the signal with a training sequence that is a reference signal held on the base station apparatus 2 side. When it is determined that the station apparatus 2 can correctly receive the training sequence, it can be assumed that synchronization is established.

  That is, as a modulation method used for demodulation at the time of receiving TCH included in an even frame or TCH included in a super frame, when a modulation method identifier included in FACCH that is a signal included in an odd frame of a normal frame can be obtained, The modulation system identifier is substituted into the variable CMC. If the modulation scheme identifier cannot be acquired, the modulation scheme identifier stored in the modulation scheme identifier storage unit 30 is read and substituted into the variable CMC. Then, the modulation scheme identifier stored in the variable CMC is output to the link adaptation switch 26 and the modulation scheme identifier storage unit 30. The decoding function unit 32 demodulates at least one TCH included in the TCH or superframe in the odd frame or the even frame, using the modulation scheme identifier. On the other hand, when the modulation scheme identifier included in the FACCH can be normally acquired, the modulation scheme identifier is output to the link adaptation switch 26 and the modulation scheme identifier storage unit 30 as in the known link adaptation technique. .

  By doing as described above, it is possible to perform communication normally even when the receiving-side communication apparatus cannot acquire the received frame modulation method. In particular, it is possible to reduce the influence of the case where the modulation scheme identifier cannot be acquired with the BCH reception when the time division data transmission / reception is performed by the multicarrier scheme, and to improve the data transmission performance. As a result, retransmission of data is reduced, and resources can be effectively used. Furthermore, even when the modulation scheme of the received frame cannot be obtained, by storing and using the previous modulation scheme, at least a past received frame can be demodulated and decoded with a modulation scheme that has passed the CRC check. By doing so, it is possible to demodulate and decode the received frame more reliably.

  The present invention is not limited to the above embodiment.

  For example, in the above embodiment, a base station apparatus used in a mobile communication system is described as an example, but communication is performed by designating a modulation scheme on the transmission side even if it is not a mobile communication system. It can be applied to a communication device. That is, according to the present invention, it is possible to use a modulation scheme with a proven record of demodulation and decoding for demodulation and decoding of a received wave that is received later.

1 is a configuration diagram of a mobile communication system according to an embodiment of the present invention. 1 is a configuration block diagram of a communication device according to an embodiment of the present invention. 1 is a configuration block diagram of a communication device according to an embodiment of the present invention. It is a functional block diagram of the communication apparatus which concerns on embodiment of this invention. It is a sequence diagram of the signal used by PHS. It is a block diagram of the super frame used by PHS. It is a flowchart of the process which concerns on embodiment of this invention. It is a flowchart of the process which concerns on embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Mobile communication system, 2 Base station apparatus, 3 Mobile station apparatus, 4 Communication network, 5, 6 Communication apparatus, 10, 14 Control part, 11, 15 Wireless communication part, 12, 16 Storage part, 13 Network interface part, 17 Display unit 18 Operation unit 20 Reception unit 22 Modulation method determination unit 24 Modulation method identifier selection unit 26 Link adaptation switch 28-n MODn decoding unit 30 Modulation method identifier storage unit 32 Decoding function unit 34 -N switcher.

Claims (4)

The first frame and the second frame that includes the information indicating the modulation scheme and that follows the first frame are repeatedly received, and the second frame and the first frame that follows the second frame are included in the second frame In a communication device that demodulates based on information indicating the modulation method,
A modulation scheme acquisition unit acquire information indicating the modulation scheme,
A first frame modulation scheme decision means for deciding a modulation scheme of the first frame based on the information indicating the pre-Symbol modulation scheme,
First frame demodulation means for obtaining a demodulated signal by demodulating the first frame using the modulation scheme determined by the first frame modulation scheme determination means;
Modulation scheme storage means for storing information indicating the modulation scheme of the first frame used by the first frame demodulation means ;
Information indicating the one modulation scheme from the information indicating the modulation scheme of the previous SL modulation scheme and the second frame to be acquired by the information or pre-Symbol modulation scheme acquisition unit indicating the modulation scheme of the first frame stored by the storage means A second frame modulation scheme determining means for determining the modulation scheme of the second frame based on information indicating the selected modulation scheme;
Second frame demodulation means for obtaining a demodulated signal by demodulating the second frame using the modulation scheme determined by the second frame modulation scheme determination means;
A communication device comprising: The communication device according to claim 1 ,
Error detecting means for detecting an error in the demodulated signal acquired by the first frame demodulating means,
The modulation method storage means restricts storing information indicating the modulation method used by the first frame demodulation means when an error is detected by the error detection means;
A communication device. The communication apparatus according to any one of claims 1 and 2 ,
The second frame modulation scheme determining means includes
Includes determination means are decision can be acquired that indicates the previous SL modulation scheme by the modulation scheme acquisition unit,
When the information indicating the pre-Symbol modulation scheme by the modulation scheme acquisition unit by the determining means is determined to be acquired, selecting information indicating the modulation scheme to be acquired by the previous SL modulation scheme acquisition unit ,
A communication device. The first frame and the second frame that includes the information indicating the modulation scheme and that follows the first frame are repeatedly received, and the second frame and the first frame that follows the second frame are included in the second frame A modulation method determination method in a communication device that demodulates based on information indicating the modulation method,
A modulation scheme acquisition step you acquire the information indicating the modulation scheme,
A first frame modulation scheme determining step of determining a modulation scheme of the first frame based on the information indicating the pre-Symbol modulation scheme,
A first frame demodulation step of obtaining a demodulated signal by demodulating the first frame using the modulation scheme determined in the first frame modulation scheme determination step;
A modulation scheme storage step for storing information indicating a modulation scheme of the first frame used in the first frame demodulation step ;
Information indicating the one modulation scheme from the information indicating the modulation scheme of the previous SL modulation scheme and the second frame to be acquired in the first frame information or pre-Symbol modulation scheme acquisition step indicates a modulation scheme that is stored in the storage step A second frame modulation scheme determination step for determining the modulation scheme of the second frame based on information indicating the selected modulation scheme;
A second frame demodulation step of obtaining a demodulated signal by demodulating the second frame using the modulation scheme determined in the second frame modulation scheme determination step;
A modulation method determination method comprising:

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