Wireless communication methods and wireless communication systems

Abstract

To provide a wireless communication method and wireless communication system that can reliably communicate even under conditions of network congestion. [Solution] A wireless communication method for performing multi-carrier wireless communication using multiple subcarriers between a transmitter and a receiver, comprising: a first symbol sequence acquisition step of acquiring a first symbol sequence by multiplying a transmission symbol by a pseudo-random vector composed of 1 and -1; a transmission step of the transmitter transmitting a transmission signal based on the first symbol sequence; a second symbol sequence acquisition step of the receiver acquiring a second symbol sequence corresponding to the first symbol sequence based on a received signal corresponding to the transmission signal received by the receiver; a determination symbol acquisition step of acquiring a determination symbol which is the dot product of the second symbol sequence and the pseudo-random vector; and an estimation step of estimating the transmission symbol based on the determination symbol.

Description

TECHNICAL FIELD

[0001] The present invention relates to a wireless communication method and a wireless communication system.

[0002] When wireless communication is used for industrial purposes, reliable communication is required. For this reason, a mechanism that enables reliable communication even in the presence of interference from other communications or the like is necessary.

[0003] Conventionally, as a radio wave sharing scheme in wireless communication using OFDM (Orthogonal Frequency Division Multiplexing), there is a method using frequency division multiplexing or time division multiplexing. However, in conventional wireless communication using OFDM, frequency division multiplexing or time division multiplexing may not be possible under circumstances where communication is congested. For this reason, conventional wireless communication has a problem that accurate wireless communication is hindered when a plurality of wireless communications are performed at the same frequency and at the same time.

[0004] Here, a technology for providing a determination apparatus and a determination method that accurately determine whether communication is possible in a communication system with low power consumption is disclosed in, for example, Patent Document 1.

[0005] Specifically, Patent Document 1 discloses a technology that inserts pilot signals into a wireless signal at a constant frequency to acquire a correlation value of a discrete sample signal related to the wireless signal, and estimates the congestion degree of the communication system based on the peak of the correlation value.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0006]

PATENT DOCUMENT 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] However, the technology disclosed in Patent Document 1 is merely a technology for estimating the degree of congestion in communications, and does not provide a mechanism that can reliably communicate even during times of communication congestion. Therefore, there has been a problem in that it is difficult to achieve reliable communication in applications where delays or loss are unacceptable, such as emergency stop signals, safety signals, or synchronization signals in manufacturing sites.

[0008] The present invention was devised in view of the above-mentioned problems, and its objective is to provide a wireless communication method and wireless communication system that can reliably perform communication even under conditions of communication congestion. [Means for solving the problem]

[0009] The wireless communication method according to the first invention is a wireless communication method that performs multi-carrier wireless communication using a plurality of subcarriers between a transmitter and a receiver, and is characterized by comprising: a first symbol sequence acquisition step of acquiring a first symbol sequence by multiplying a transmission symbol by a pseudo-random vector composed of 1 and -1; a transmission step of the transmitter transmitting a transmission signal based on the first symbol sequence acquired in the first symbol sequence acquisition step; a second symbol sequence acquisition step of the receiver acquiring a second symbol sequence corresponding to the first symbol sequence based on a received signal corresponding to the transmission signal transmitted in the transmission step, which is received by the receiver; a determination symbol acquisition step of acquiring a determination symbol which is the dot product of the second symbol sequence acquired in the second symbol sequence acquisition step and the pseudo-random vector; and an estimation step of estimating the transmission symbol based on the determination symbol acquired in the determination symbol acquisition step.

[0010] The wireless communication method according to the second invention is characterized in that, in the first invention, the pseudo-random vector is set for each combination of the transmitter and the receiver, and when the combinations are different, the respective pseudo-random vectors are orthogonal to each other.

[0011] The wireless communication method according to the third invention is characterized in that, in the first invention, it further comprises a retransmission step in which the transmitter updates the transmission power related to the transmission signal based on the determination symbol obtained in the determination symbol acquisition step, and the transmitter newly transmits a transmission signal based on the updated transmission power.

[0012] The wireless communication method according to the fourth invention is characterized in that, in the first invention, it further comprises a retransmission step in which the number of subcarriers and the pseudo-random vector relating to the transmission signal are updated based on the determination symbol obtained in the determination symbol acquisition step, a first symbol sequence is newly obtained based on the updated number of subcarriers and the pseudo-random vector, and the transmitter transmits a transmission signal based on the newly obtained first symbol sequence.

[0013] The wireless communication method according to the fifth invention is characterized in that, in the first invention, it further comprises a retransmission step in which a pseudo-random matrix is ​​obtained based on the determination symbol obtained in the determination symbol acquisition step, a plurality of first symbol sequences are newly obtained by multiplying the transmission symbol by the pseudo-random matrix, and the transmitter transmits a transmission signal based on the plurality of newly obtained first symbol sequences.

[0014] The wireless communication system according to the sixth invention is a wireless communication system that performs multi-carrier wireless communication using a plurality of subcarriers, and is characterized by comprising: a first symbol sequence acquisition means for acquiring a first symbol sequence by multiplying a transmission symbol by a pseudo-random vector composed of 1 and -1; a transmission means for transmitting a transmission signal based on the first symbol sequence acquired by the first symbol sequence acquisition means; a reception means for receiving a reception signal corresponding to the transmission signal transmitted by the transmission means; a second symbol sequence acquisition means for acquiring a second symbol sequence corresponding to the first symbol sequence based on the reception signal received by the reception means; a determination symbol acquisition means for acquiring a determination symbol which is the dot product of the second symbol sequence acquired by the second symbol sequence acquisition means and the pseudo-random vector; and an estimation means for estimating the transmission symbol based on the determination symbol acquired by the determination symbol acquisition means. [Effects of the Invention]

[0015] According to the first to fifth inventions, the first symbol sequence acquisition step involves multiplying the transmitted symbol by a pseudo-random vector composed of 1 and -1 to obtain the first symbol sequence; the second symbol sequence acquisition step involves obtaining the second symbol sequence corresponding to the first symbol sequence; and the determination symbol acquisition step involves obtaining the determination symbol, which is the dot product of the second symbol sequence and the pseudo-random vector. As a result, the wireless communication method can estimate the transmitted symbol while minimizing the influence of interference from other communications. This makes it possible for the wireless communication method to achieve reliable communication even in situations where communications are congested.

[0016] In particular, according to the second invention, a pseudo-random vector is set for each combination of transmitter and receiver, and when the combination of transmitter and receiver is different, the respective pseudo-random vectors are orthogonal to each other. Therefore, the wireless communication method can separate wireless communications with different pseudo-random vectors. As a result, the wireless communication method can achieve more reliable communication even in situations where communications are congested.

[0017] In particular, according to the third invention, the retransmission step updates the transmission power related to the transmission signal based on the determination symbol, and the transmitter newly transmits a transmission signal based on the updated transmission power. Therefore, the wireless communication method can transmit and receive signals with the updated transmission power so as not to be affected by interference from other communications. As a result, the wireless communication method can achieve reliable communication even in situations where communications are congested.

[0018] In particular, according to the fourth invention, the retransmission step updates the number of subcarriers and pseudo-random vectors related to the transmission signal based on the determination symbol, acquires a new first symbol sequence based on the updated number of subcarriers and pseudo-random vectors, and the transmitter transmits a transmission signal based on the newly acquired first symbol sequence. Therefore, the wireless communication method can transmit and receive signals using the updated number of subcarriers and pseudo-random vectors so as not to be affected by interference from other communications. As a result, the wireless communication method can achieve more reliable communication even in situations where communications are congested.

[0019] In particular, according to the fifth invention, the retransmission step obtains a pseudo-random matrix based on the determination symbol, multiplies the transmission symbol by the pseudo-random matrix to obtain a new set of first symbol sequences, and the transmitter transmits a transmission signal based on the newly obtained set of first symbol sequences. Therefore, the wireless communication method can transmit and receive signals using a pseudo-random matrix set so as not to be affected by interference from other communications. As a result, the wireless communication method can achieve more reliable communication even in situations where communications are congested.

[0020] According to the sixth invention, the first symbol sequence acquisition means multiplies a transmission symbol by a pseudo-random vector composed of 1 and -1 to acquire a first symbol sequence, the second symbol sequence acquisition means acquires a second symbol sequence corresponding to the first symbol sequence, and the determination symbol acquisition means acquires a determination symbol that is an inner product of the second symbol sequence and the pseudo-random vector. For this reason, the wireless communication system can estimate the transmission symbol while reducing the influence of interference from other communications and the like. This enables the wireless communication system to realize reliable communication even in a situation where communication is congested. Brief Description of the Drawings

[0021] [Figure 1] Figure 1 is a schematic diagram showing an example of the overall configuration of a wireless communication system to which the present invention is applied. [Figure 2] Figure 2 is a schematic diagram showing an example of the functional configuration of the wireless communication system. [Figure 3] Figure 3 is a flowchart showing an example of steps of a wireless communication method in the first embodiment. [Figure 4] Figure 4 is a flowchart showing an example of steps of a wireless communication method in the second embodiment. [Figure 5] Figure 5 is a flowchart showing an example of specific steps of a retransmission step in the second embodiment. [Figure 6] Figure 6 is a flowchart showing a modification of the specific steps of the retransmission step in the second embodiment. Modes for Carrying Out the Invention

[0022] Hereinafter, embodiments of the wireless communication system 100 to which the present invention is applied will be described in detail with reference to the drawings.

[0023] <Wireless Communication System 100> Figure 1 is a schematic diagram showing an example of the overall configuration of the wireless communication system 100 to which the present invention is applied.

[0024] The wireless communication system 100 is a system that transmits and receives wireless signals. As shown in Figure 1, the wireless communication system 100 comprises a transmitter 1 and a receiver 2.

[0025] Transmitter 1 comprises an encoding device 11, a modulator 12, a DA (Digital to Analog) converter 13, an RF (Radio Frequency) circuit 14, and a transmitting antenna 15.

[0026] The encoding device 11 is connected to the modulator 12, the modulator 12 is connected to the DA converter 13, the DA converter 13 is connected to the RF circuit 14, and the RF circuit 14 is connected to the transmitting antenna 15.

[0027] The receiver 2 comprises a receiving antenna 21, an RF circuit 22, an AD (Analog to Digital) converter 23, a demodulator 24, and a decoding device 25.

[0028] The receiving antenna 21 is connected to the RF circuit 22, the RF circuit 22 is connected to the AD converter 23, the AD converter 23 is connected to the demodulator 24, and the demodulator 24 is connected to the decoding device 25.

[0029] In the wireless communication system 100, the transmitter 1 and the receiver 2 perform wireless communication using the transmitting antenna 15 and the receiving antenna 21.

[0030] The following explains each element in Figure 1.

[0031] <Transmitter 1> Transmitter 1 is a device that transmits a transmission signal to receiver 2. Here, the transmission signal is the signal transmitted from the transmitting antenna 15 of transmitter 1. There may also be multiple transmitters 1.

[0032] <Encoding device 11> The encoding device 11 is a device that multiplies a transmission symbol by a pseudo-random vector composed of 1 and -1 to obtain a first symbol sequence, and outputs the first symbol sequence to the modulator 12. Here, the transmission symbol is a symbol to be transmitted from the transmitter 1. For example, the transmission symbol may be a bit sequence related to information to be transmitted converted into a complex number. For example, the transmission symbol may be a bit sequence of a certain length converted into a complex symbol by a modulation scheme such as BPSK, QPSK, or 16QAM. The pseudo-random vector is a vector composed of 1 and -1. The number of elements of the pseudo-random vector may correspond to the number of subcarriers used for communication. The first symbol sequence is a vector obtained by multiplying the transmission symbol by the pseudo-random vector.

[0033] <Modulator 12> The modulator 12 is a device that performs inverse FFT (Fast Fourier Transform) on the first symbol sequence obtained by the encoding device 11 to generate a time-domain signal, and outputs the time-domain signal to the DA converter 13. The signal generated by the modulator 12 may be a discrete-time signal.

[0034] <DA converter 13> The DA converter 13 is a device that converts the discrete-time signal generated by the modulator 12 into a continuous-time signal, and outputs the continuous-time signal to the RF circuit 14.

[0035] <RF circuit 14> The RF circuit 14 is a device that performs frequency conversion and amplitude amplification so that the continuous-time signal obtained by the DA converter 13 can be used in the frequency band for transmission and reception, and generates a transmission signal. The generated transmission signal is output to the transmission antenna 15. The RF circuit 14 may adjust the transmission power related to the transmission signal.

[0036] <Transmission antenna 15> The transmission antenna 15 is an antenna that transmits the transmission signal generated by the RF circuit 14 to the receiver 2.

[0037] <Receiver 2> The receiver 2 is a device that receives a received signal corresponding to a transmission signal transmitted from the transmission antenna 15 and estimates a transmission symbol. The received signal is a signal corresponding to the transmission signal transmitted by the transmitter 1, and is a signal received by the reception antenna 21. Further, there may be a plurality of receivers 2.

[0038] <Reception Antenna 21> The reception antenna 21 is an antenna that receives a received signal.

[0039] <RF Circuit 22> The RF circuit 22 is a device that converts the received signal received by the reception antenna 21 into a low frequency and outputs the resulting signal to the AD converter 23. A known filter technique in communication may be used in the RF circuit 22.

[0040] <AD Converter 23> The AD converter 23 is a device that converts a continuous-time signal input from the RF circuit 22 into a discrete-time signal and outputs the resulting signal to the demodulator 24.

[0041] <Demodulator 24> The demodulator 24 is a device that obtains a second symbol sequence by performing FFT on the discrete-time signal input from the AD converter 23. The second symbol sequence is a vector corresponding to the first symbol sequence, and is a vector in which information on the first symbol sequence and the influence of interference or noise from other communications are reflected.

[0042] <Decoding Device 25> The decoding device 25 is a device that calculates the inner product of the second symbol sequence obtained by the demodulator 24 and a pseudo-random vector to obtain a decision symbol. The decision symbol is the inner product of the second symbol sequence and the pseudo-random vector, and is a symbol used to estimate a transmission symbol. The decision symbol may be a complex number. As the pseudo-random vector used in the decoding device 25, the same pseudo-random vector as that used in the encoding device 11 is used.

[0043] Figure 2 shows an example of the functional configuration of a wireless communication system 100 to which the present invention is applied.

[0044] The wireless communication system 100 includes, for example, a first symbol sequence acquisition unit 31, a transmission unit 32, a second symbol sequence acquisition unit 33, a determination symbol acquisition unit 34, and an estimation unit 35, as shown in Figure 2.

[0045] As shown in Figure 2, in the wireless communication system 100, the first symbol sequence acquisition unit 31 is connected to the transmission unit 32 and the determination symbol acquisition unit 34. The transmission unit 32 is connected to the first symbol sequence acquisition unit 31, the second symbol sequence acquisition unit 33, and the determination symbol acquisition unit 34. The second symbol sequence acquisition unit 33 is connected to the transmission unit 32 and the determination symbol acquisition unit 34. The determination symbol acquisition unit 34 is connected to the first symbol sequence acquisition unit 31, the transmission unit 32, the second symbol sequence acquisition unit 33, and the estimation unit 35. The estimation unit 35 is connected to the determination symbol acquisition unit 34. The elements in Figure 2 will be explained below.

[0046] <First Symbol Sequence Acquisition Unit 31> The first symbol sequence acquisition unit 31 acquires the first symbol sequence by multiplying the transmitted symbols by a pseudo-random vector consisting of 1s and -1s. The function of the first symbol sequence acquisition unit 31 is performed by the encoding device 11 in Figure 1.

[0047] <Transmitter 32> The transmitting unit 32 transmits a transmission signal based on the first symbol sequence acquired by the first symbol sequence acquisition unit 31. The functions of the transmitting unit 32 are performed by the modulator 12, DA converter 13, RF circuit 14, and transmitting antenna 15 shown in Figure 1.

[0048] <Second Symbol Sequence Acquisition Unit 33> The second symbol sequence acquisition unit 33 acquires a second symbol sequence corresponding to the first symbol sequence based on the received signal corresponding to the transmitted signal transmitted by the transmission unit 32. The function of the second symbol sequence acquisition unit 33 is performed by the receiving antenna 21, RF circuit 22, AD converter 23, and demodulator 24 in Figure 1.

[0049] <Determination Symbol Acquisition Unit 34> The determination symbol acquisition unit 34 calculates the dot product of the second symbol sequence acquired by the second symbol sequence acquisition unit 33 and the pseudo-random vector, and acquires the determination symbol. The function of the determination symbol acquisition unit 34 may also be performed by the decoding device 25 in Figure 1.

[0050] <Estimation part 35> The estimation unit 35 estimates the transmission symbol based on the determination symbol acquired by the determination symbol acquisition unit 34. The function of the estimation unit 35 may also be performed by the decoding device 25 in Figure 1.

[0051] <First Embodiment: Wireless Communication Method> Next, an example of the steps of the wireless communication method having the above-described configuration will be explained as the first embodiment.

[0052] Figure 3 is a flowchart showing an example of the steps of the wireless communication method in the first embodiment. Each step in Figure 3 will be described below.

[0053] <Step S11 for obtaining the first symbol sequence> In the first symbol sequence acquisition step S11, the first symbol sequence acquisition unit 31 acquires the first symbol sequence by multiplying the transmitted symbols by a pseudo-random vector consisting of 1s and -1s. The pseudo-random vector used in the first symbol sequence acquisition unit 31 may be predetermined.

[0054] The number of elements in the pseudorandom vector may be the same as the number of subcarriers N used in wireless communication.

[0055] <Transmission Step S12> In transmission step S12, the transmission unit 32 transmits a transmission signal based on the first symbol sequence.

[0056] In the transmission step S12, first, the modulator 12 performs an inverse FFT on the first symbol sequence acquired in the first symbol sequence acquisition step S11 to generate a discrete-time signal. Next, the DA converter 13 converts the discrete-time signal generated by the modulator 12 into a continuous-time signal. Next, the RF circuit 14 performs frequency conversion and amplitude amplification on the continuous-time signal obtained by the DA converter 13 to generate a transmission signal. Finally, the transmitting antenna 15 transmits the transmission signal generated by the RF circuit 14 to the receiver 2.

[0057] <Step S13 to obtain the second symbol sequence> In the second symbol sequence acquisition step S13, the second symbol sequence acquisition unit 33 acquires a second symbol sequence corresponding to the first symbol sequence based on the received signal corresponding to the transmitted signal transmitted in the transmission step S12.

[0058] In the second symbol sequence acquisition step S13, the receiving antenna 21 receives the received signal. Next, the RF circuit 22 converts the received signal received by the receiving antenna 21 into a low-frequency signal. Next, the AD converter 23 converts the continuous-time signal acquired by the RF circuit 22 into a discrete-time signal. Next, the demodulator 24 performs an FFT on the discrete-time signal acquired by the AD converter 23 to acquire the second symbol sequence.

[0059] <Judgment Symbol Acquisition Step S14> In the judgment symbol acquisition step S14, the judgment symbol acquisition unit 34 calculates the dot product of the second symbol sequence acquired in the second symbol sequence acquisition step S13 and the pseudo-random vector, and acquires the judgment symbol.

[0060] Here, the pseudo-random vector used in the judgment symbol acquisition step S14 is the same as the pseudo-random vector used in the first symbol sequence acquisition step S11.

[0061] <Estimated Step S15> In estimation step S15, the estimation unit 35 estimates the transmission symbol based on the determination symbol acquired in determination symbol acquisition step S14.

[0062] For example, let x be the transmission symbol and r be the pseudorandom vector. Assume that the number of elements in the pseudorandom vector is the same as the number of subcarriers N used in communication. In this case, the first symbol sequence obtained in the first symbol sequence acquisition step S11 is x·r. Then, the second symbol sequence obtained in the second symbol sequence acquisition step S13 is x·r+M. M is a vector representing the influence of interference from communication occurring outside of the transmitter 1 and receiver 2, and noise associated with communication, and may be multivariate white noise. Each element of M may also be a complex number. In this case, the decision symbol obtained in the decision symbol acquisition step S14 is (x·r+M)·r=x·N+M', where M'=M·r. If M is multivariate white noise, the expected value of M' is 0. Here, we use the fact that since r is a vector composed of 1s and -1s, the dot product r·r is N.

[0063] Here, if interference or noise from other communications is significant, the values ​​of M and M' will increase. When the transmission power or the number of subcarriers in wireless communication is high, the effects of interference and noise from other communications become relatively smaller.

[0064] Based on the determination symbol x·N+M', the transmission symbol x is estimated.

[0065] For example, when x = +1, the first symbol sequence is r, the second symbol sequence is r + M, and the decision symbol is N + M'. Also, when x = -1, the first symbol sequence is -r, the second symbol sequence is -r + M, and the decision symbol is -N + M'. If the sign of N in the decision symbol is +, the transmitted symbol x can be estimated to be +1, and if the sign of N in the decision symbol is -, the transmitted symbol can be estimated to be -1.

[0066] Thus, if the transmitted symbol is x=+1 or x=-1, and |N| is greater than |M|, i.e., |N|>|M|, then in estimation step S15, the transmitted symbol can be estimated based on the sign of the determination symbol.

[0067] Here, we used the cases x=+1 and x=-1 as examples, but even in cases such as x=0.5, if the value of |N| is sufficiently larger than |M'|, that is, |N|>>|M'|, the transmission symbol x can be estimated based on the value and sign of the judgment symbol.

[0068] Even when the transmitted symbol is an imaginary number, such as x=+i or x=-i, the transmitted symbol can be estimated. In the case of x=+i or x=-i, the judgment symbol is ±iN+M', and if |N|>|M'|, the transmitted symbol x can be estimated to be +i or -i based on the value and sign of the judgment symbol. Furthermore, even in the case of x=0.5i, for example, if |N|>>|M'|, the transmitted symbol x can be estimated based on the value and sign of the judgment symbol.

[0069] Even when the transmission symbol x is a complex number such as x = a + ib, it is possible to estimate the transmission symbol x. In the case of x = a + ib, the decision symbol is aN + ibN + M'. By separating the decision symbol into its real and imaginary parts and performing the same calculation as described above, the values ​​of a and b can be estimated, and the transmission symbol x can be estimated.

[0070] The above calculation may be performed in the receiver 2 or the decoding device 25 within the receiver 2.

[0071] In the first embodiment, a pseudo-random vector may be set for each combination of transmitter 1 and receiver 2. If the combinations of transmitter 1 and receiver 2 are different, the respective pseudo-random vectors may be set to be orthogonal.

[0072] By setting each pseudo-random vector to be orthogonal, it is possible to separate wireless communications with different pseudo-random vectors.

[0073] For example, suppose a pseudo-random vector r is used in wireless communication A between a transmitter 1 and a receiver 2, and a pseudo-random vector s is used in wireless communication B between a different transmitter 1 and receiver 2. Here, r and s are orthogonal, and r·s=0. For example, suppose a transmission signal sent from transmitter 1 for wireless communication A is received by receiver 2 for wireless communication B.

[0074] At this time, the first symbol sequence obtained by the encoding device 11 in the transmitter 1 for wireless communication A is x·r, where x is the transmission symbol, and a transmission signal based on the first symbol sequence x·r is transmitted from the transmitter 1 for wireless communication A.

[0075] If a receiver 2 for wireless communication B receives a transmission signal based on the first symbol sequence x·r, the second symbol sequence acquired by the demodulator 24 of receiver 2 for wireless communication B is x·r+M, and the decision symbol acquired by the decoder 25 of receiver 2 for wireless communication B is (x·r+M)·s=M·s due to the orthogonal relationship of the vectors. Here, the expected value of M·s is 0 when M is multivariate white noise. In this way, when receiver 2 receives a signal that was not anticipated, the quality of communication usually deteriorates due to interference, but in this embodiment, the wireless communication system can prevent interference between wireless communications by making the pseudo-random vectors orthogonal to each wireless communication.

[0076] The wireless communication method to which the first embodiment is applied is completed by the steps described above. Steps S11 to S15 may be repeated.

[0077] According to the first embodiment, the first symbol sequence acquisition step S11 acquires the first symbol sequence by multiplying the transmitted symbol by a pseudo-random vector composed of 1 and -1; the second symbol sequence acquisition step S13 acquires the second symbol sequence corresponding to the first symbol sequence; and the determination symbol acquisition step S14 acquires the determination symbol, which is the dot product of the second symbol sequence and the pseudo-random vector. As a result, the wireless communication method can estimate the transmitted symbol while minimizing the influence of interference from other communications. This makes it possible for the wireless communication method to which the first embodiment is applied to achieve reliable communication even in situations where communications are congested.

[0078] Furthermore, according to the first embodiment, a pseudo-random vector is set for each combination of transmitter 1 and receiver 2, and when the combinations of transmitter 1 and receiver 2 are different, the respective pseudo-random vectors are orthogonal to each other. Therefore, the wireless communication method can separate wireless communications with different pseudo-random vectors. As a result, the wireless communication method to which the first embodiment is applied can achieve reliable communication even in situations where communication is congested.

[0079] <Second Embodiment: Wireless Communication Method> Next, an example of the steps of the wireless communication method having the above-described configuration will be explained as a second embodiment. The main difference between the first embodiment and the second embodiment is that the retransmission step S22b is performed.

[0080] Figure 4 is a flowchart illustrating an example of the steps in the wireless communication method according to the second embodiment. Each step in Figure 4 will be described below. The details described in the first embodiment will be omitted.

[0081] First, the wireless communication method in the second embodiment performs steps S21 to S24. Steps S21 to S24 are the same as steps S11 to S14 in the first embodiment. Here, in the determination symbol acquisition step S24, it is determined whether |N|>|M'| or |N|>>|M'| is satisfied based on the determination symbol. As an example, the determination of |N|>|M'| is considered below.

[0082] For example, the determination of |N|>|M'| may be based on the determination symbol aN+ibN+M' obtained in the determination symbol acquisition step S24. If interference or noise from other communications is significant, |N|>|M'| will not be satisfied.

[0083] Furthermore, in order to determine if |N|>|M'|, a predetermined transmission symbol may be used in the wireless communication method of the second embodiment, and |N|>|M'| may be determined.

[0084] For example, if the transmission symbol is x=1, |N|>|M'| may be determined when the sign of the judgment symbol N+M' is positive. Also, for example, if the transmission symbol is x=1, |N|>|M'| may be determined when the judgment symbol N+M' is close to N. Furthermore, for example, in the judgment symbol acquisition step S24, if the transmission symbol is estimated and the estimated value is similar to the transmission symbol, |N|>|M'| may be determined.

[0085] If the determination symbol acquisition step S24 does not determine |N|>|M'|, the flow proceeds to the retransmission step S22b. Alternatively, if the determination symbol acquisition step S24 determines |N|>|M'|, the flow may proceed to the estimation step S25. In the estimation step S25, the same processing as in the estimation step S15 is performed to estimate the transmission symbol.

[0086] <Retransmission step S22b> In the retransmission step S22b, communication-related conditions are updated such that |N|>|M'| in the communication between the transmitter 1 and the receiver 2, and the transmitter 1 transmits a transmission signal again under the updated conditions.

[0087] <Specific Example 1 of S22b> In the retransmission step S22b, the transmission unit 32 may update the transmission power related to the transmission signal based on the determination symbol. Here, the transmission power is the strength of the radio wave that transmits the transmission signal. By increasing the transmission power, the influence of interference and noise from other wireless communications is relatively reduced. Therefore, reliable wireless communication can be realized.

[0088] For example, the transmission unit 32 updates the transmission power to increase by a certain amount, and the transmission unit 32 newly transmits a transmission signal with the updated transmission power. After that, as shown in FIG. 4, the second symbol sequence acquisition step S23 and the determination symbol acquisition step S24 are executed again, and it is determined whether or not |N|>|M'|. If it is not determined that |N|>|M'| in the determination symbol acquisition step S24, the process proceeds to the retransmission step S22b again. After that, in the retransmission step S22b, the transmission unit 32 updates the transmission power again so as to increase by a certain amount, and newly transmits a transmission signal with the updated transmission power.

[0089] By repeating this process, a transmission power that satisfies |N|>|M'| is determined. If it is determined that |N|>|M'| in the determination symbol acquisition step S24, the flow proceeds to the estimation step S25.

[0090] By determining the transmission power such that |N|>|M'|, transmission symbols can be accurately estimated.

[0091] <Specific Example 2 of S22b> In the retransmission step S22b, the first symbol sequence acquisition unit 31 may update the number of subcarriers and the pseudo-random vector related to the transmission signal based on the determination symbol. By increasing the number of subcarriers N in transmission and reception, reliable wireless communication can be achieved.

[0092] Figure 5 is a flowchart showing an example of a specific step in the retransmission step in the second embodiment. The flowchart in Figure 5 includes an update step S31, a first symbol sequence retrieval step S32, and a retransmission execution step S33.

[0093] In update step S31, the number of subcarriers N used in transmission and reception between the transmitter 1 and the receiver 2 is updated in the wireless communication system 100. For example, if |N|>|M'| is not satisfied, the number of subcarriers N may be updated in update step S31 to be larger by a predetermined amount. In addition, the pseudo-random vectors used in the first symbol sequence acquisition unit 31 and the determination symbol acquisition unit 34 are also updated in accordance with the update of the number of subcarriers N. For example, the number of elements in the pseudo-random vector may be updated to match the updated number of subcarriers N.

[0094] In the first symbol sequence reacquisition step S32, the first symbol sequence acquisition unit 31 acquires a new first symbol sequence based on the updated subcarrier count and pseudorandom vector. For example, the first symbol sequence acquisition unit 31 acquires a new first symbol sequence by multiplying the transmitted symbols by the updated pseudorandom vector.

[0095] In the retransmission execution step S33, the transmitting unit 32 transmits a transmission signal based on the newly acquired first symbol sequence.

[0096] Thereafter, as shown in FIG. 4, based on the updated pseudo-random vector and the newly transmitted transmission signal, the second symbol sequence acquisition step S23 and the decision symbol acquisition step S24 are executed again, and it is determined whether |N|>|M'| is satisfied. In the second symbol sequence acquisition step S23 and the decision symbol acquisition step S24, the number of subcarriers and the pseudo-random vector updated in the update step S31 are used. If it is not determined that |N|>|M'| in the decision symbol acquisition step S24, the process proceeds again to the retransmission step S22b. In this case, in the update step S31, the number of subcarriers and the pseudo-random vector are updated again. Next, in the first symbol sequence re-acquisition step S32, a new first symbol sequence is acquired based on the again updated number of subcarriers and pseudo-random vector. Next, in the retransmission execution step S33, the transmitting unit 32 transmits a transmission signal based on the newly acquired first symbol sequence. If it is determined that |N|>|M'| in the decision symbol acquisition step S24, the flow proceeds to the estimation step S25.

[0097] By repeating this process, the number of subcarriers and the pseudo-random vector that satisfy |N|>|M'| are determined.

[0098] By determining the number of subcarriers and the pseudo-random vector such that |N|>|M'|, the wireless communication system 100 can accurately estimate the transmission symbols.

[0099] <Specific Example 3 of S22b> In the retransmission step S22b, the first symbol sequence acquisition unit 31 acquires a pseudo-random matrix. By using a transmission signal based on the pseudo-random matrix, reliable wireless communication can be realized. Here, the pseudo-random matrix is a matrix composed of 1 and -1. The number of elements for each column of the pseudo-random matrix may correspond to the number of subcarriers used for wireless communication.

[0100] Figure 6 is a flowchart showing a modified example of the specific steps of the retransmission step in the second embodiment. The flowchart in Figure 6 includes a pseudo-random matrix acquisition step S41, a first symbol column reacquisition step S42, and a retransmission execution step S43.

[0101] In the pseudo-random matrix acquisition step S41, the first symbol sequence acquisition unit 31 acquires a pseudo-random matrix. For example, the first symbol sequence acquisition unit 31 acquires a pseudo-random matrix of size N×2, which is made up of two pseudo-random vectors placed side by side.

[0102] In the first symbol sequence reacquisition step S42, the first symbol sequence acquisition unit 31 calculates the product of the transmitted symbol and the pseudo-random matrix and acquires multiple first symbol sequences anew. For example, if the size of the pseudo-random matrix is ​​N × 2, two first symbol sequences are acquired.

[0103] In the retransmission execution step S43, the transmitting unit 32 transmits a transmission signal based on multiple first symbol sequences. For example, if two first symbol sequences have been acquired in the first symbol sequence reacquisition step S42, first, the modulator 12 performs an inverse FFT on each of the two first symbol sequences to generate discrete-time signals. At this time, the multiple acquired discrete-time signals are concatenated and combined into a single discrete-time signal. At this time, for example, the discrete-time signal generated from two first symbol sequences will be twice as long as the discrete-time signal generated from one first symbol sequence. Next, the DA converter 13 converts the discrete-time signal generated by the modulator 12 into a continuous-time signal. Next, the RF circuit 14 performs frequency conversion and amplitude amplification on the continuous-time signal obtained by the DA converter 13 to generate a transmission signal. Next, the transmitting antenna 15 transmits the transmission signal generated by the RF circuit 14 to the receiver 2. The transmitting unit 32 generates a transmission signal based on a pseudo-random matrix and transmits the generated transmission signal to the receiver 2 using these procedures.

[0104] Subsequently, as shown in Figure 4, the second symbol sequence acquisition step S23 and the determination symbol acquisition step S24 are executed again based on the pseudo-random vector and the transmitted signal. In the determination symbol acquisition step S24, each row of the pseudo-random matrix acquired in the first symbol sequence reacquisition step S42 may be used as the pseudo-random vector.

[0105] In the second symbol sequence acquisition step S23, for example, if the size of the pseudo-random matrix is ​​N × 2, two second symbol sequences are acquired. In the second symbol sequence acquisition step S23, for example, multiple second symbol sequences may be acquired by processing the transmitted signal in intervals of a certain amount of time.

[0106] In the judgment symbol acquisition step S24, the judgment symbols may be obtained for each second symbol sequence by multiplying it by a corresponding pseudorandom vector, using the same procedure as in the judgment symbol acquisition step S14. Then, the sum of these results may be treated as the final judgment symbol. In this case, for example, if the transmitted symbol is x=1 and the size of the pseudorandom matrix is ​​N×2, the judgment symbol will be 2N+M'. In this case, the judgment symbol acquisition step S24 determines whether |2N|>|M'|.

[0107] For example, if the determination symbol acquisition step S24 does not determine |2N|>|M'|, the process proceeds again to the retransmission step S22b. In this case, the pseudo-random matrix is ​​acquired or updated again in the pseudo-random matrix acquisition step S41. For example, in the pseudo-random matrix acquisition step S41, a new pseudo-random matrix of size N×3 is acquired. Next, in the first symbol sequence reacquisition step S42, the first symbol sequence acquisition unit 31 calculates the product of the transmission symbol and the pseudo-random matrix and acquires three new first symbol sequences. Next, in the retransmission execution step S43, the transmission unit 32 transmits a transmission signal based on the multiple first symbol sequences.

[0108] After this, the second symbol sequence acquisition step S23 and the judgment symbol acquisition step S24 are executed again based on the updated pseudorandom vector and the newly transmitted signal. Since the size of the pseudorandom matrix is ​​N × 3, in the judgment symbol acquisition step S24, it is determined whether |3N| > |M'|. By repeating this process, a pseudorandom matrix that satisfies |n·N| > |M'| is determined. Here, n is the number of elements in each row of the pseudorandom matrix. The value of n increases as the pseudorandom matrix acquisition step S41 is executed repeatedly. If it is determined in the judgment symbol acquisition step S24 that |n·N| > |M'|, the flow proceeds to the estimation step S25.

[0109] By determining a pseudo-random matrix such that |n·N|>|M'|, the transmitted symbol can be accurately estimated.

[0110] For example, when using an N×2 pseudorandom matrix, the question is whether |2N|>|M'| is satisfied. On the other hand, when implementing the wireless communication method of the first embodiment with 2N subcarriers, the question is whether |2N|>|M'| is satisfied. Thus, performing transmission and reception using a pseudorandom matrix has substantially the same effect as performing transmission and reception with an increased number of subcarriers N. Therefore, by determining a pseudorandom matrix such that |n·N|>|M'|, the transmission symbol can be accurately estimated.

[0111] The steps described above complete the wireless communication method to which the second embodiment is applied. Steps S23, S24, and S22b may also be repeated.

[0112] The wireless communication method to which the second embodiment described above is applied is performed continuously during wireless communication, and the optimal transmission power, number of subcarriers, pseudorandom vector, pseudorandom matrix, etc., may be constantly updated or acquired. Furthermore, when updating the transmission power, number of subcarriers, pseudorandom vector, pseudorandom matrix, etc., a predetermined transmission symbol may be used, and in communication after the transmission power, number of subcarriers, pseudorandom vector, pseudorandom matrix, etc., have been determined, any transmission symbol may be used to perform wireless communication.

[0113] According to the second embodiment, the retransmission step S22b updates the transmission power related to the transmission signal based on the determination symbol, and the transmitter 1 newly transmits a transmission signal based on the updated transmission power. Therefore, the wireless communication method can transmit and receive signals with the updated transmission power so as not to be affected by interference from other communications. As a result, the wireless communication method to which the second embodiment is applied can achieve reliable communication even in situations where communications are congested.

[0114] According to the second embodiment, the retransmission step S22b updates the number of subcarriers and the pseudo-random vector related to the transmission signal based on the determination symbol, acquires a new first symbol sequence based on the updated number of subcarriers and pseudo-random vector, and the transmitter 1 transmits a transmission signal based on the newly acquired first symbol sequence. Therefore, the wireless communication method to which the second embodiment is applied can transmit and receive signals using the updated number of subcarriers and pseudo-random vector so as not to be affected by interference from other communications. As a result, the wireless communication method to which the second embodiment is applied can achieve reliable communication even in situations where communications are congested.

[0115] According to the second embodiment, the retransmission step S22b obtains a pseudo-random matrix based on the determination symbol, multiplies the transmission symbol by the pseudo-random matrix to obtain a new set of first symbol sequences, and the transmitter 1 transmits a transmission signal based on the newly obtained set of first symbol sequences. Therefore, the wireless communication method can transmit and receive signals using a pseudo-random matrix set so as not to be affected by interference from other communications. As a result, the wireless communication method to which the second embodiment is applied can achieve reliable communication even in situations where communications are congested.

[0116] While embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0117] 1: Transmitter 2: Receiver 11: Encoding device 12: Modulator 13: DA converter 14:RF circuit 15: Transmitting antenna 21: Receiving antenna 22:RF circuit 23: AD converter 24: Demodulator 25: Decryption device 31: First Symbol Sequence Acquisition Unit 32: Transmitter 33: Second Symbol Sequence Acquisition Unit 34: Judgment Symbol Acquisition Unit 35: Estimation part 100: Wireless communication system S11: Step to obtain the first symbol sequence S12: Transmission Step S13: Step to obtain the second symbol sequence S14: Step to obtain judgment symbol S15: Estimated Step S21: Step to obtain the first symbol sequence S22: Sending Step S22b: Retransmission Step S23: Step to obtain the second symbol sequence S24: Step to obtain judgment symbol S25: Estimated Step S31: Update Steps S32: Step to retrieve the first symbol sequence S33: Retransmission execution step S41: Step to obtain a pseudo-random matrix S42: Step to retrieve the first symbol sequence S43: Retransmission execution step

Claims

1. A wireless communication method that performs multi-carrier wireless communication using multiple subcarriers between a transmitter and a receiver, A first symbol sequence acquisition step involves multiplying the transmitted symbol by a pseudo-random vector consisting of 1s and -1s to obtain a first symbol sequence, A transmission step in which the transmitter transmits a transmission signal based on the first symbol sequence acquired in the first symbol sequence acquisition step, A second symbol sequence acquisition step, in which the receiver receives a received signal corresponding to the transmitted signal transmitted in the transmission step, and acquires a second symbol sequence corresponding to the first symbol sequence; A determination symbol acquisition step, which acquires a determination symbol that is the dot product of the second symbol sequence acquired in the second symbol sequence acquisition step and the pseudo-random vector, The system includes an estimation step of estimating the transmission symbol based on the determination symbol obtained in the determination symbol acquisition step. A wireless communication method characterized by the following.

2. The aforementioned pseudo-random vector is set for each combination of the transmitter and the receiver, and if the combination is different, each of the aforementioned pseudo-random vectors is orthogonal to each other. The wireless communication method according to claim 1, characterized by the above.

3. The further step includes updating the transmission power for the transmission signal based on the determination symbol obtained in the determination symbol acquisition step, and a retransmission step in which the transmitter newly transmits a transmission signal based on the updated transmission power. The wireless communication method according to claim 1, characterized by the above.

4. Based on the determination symbol obtained in the determination symbol acquisition step, the number of subcarriers and the pseudo-random vector relating to the transmission signal are updated. Based on the updated number of subcarriers and the pseudo-random vector, a new first symbol sequence is obtained. The transmitter transmits a transmission signal based on the newly acquired first symbol sequence. Having an additional retransmission step The wireless communication method according to claim 1, characterized by the above.

5. Based on the determination symbol obtained in the determination symbol acquisition step, a pseudo-random matrix is ​​obtained, The aforementioned transmission symbol is multiplied by the aforementioned pseudo-random matrix to obtain a new sequence of first symbols. The transmitter transmits a transmission signal based on a newly acquired sequence of the first symbols. Having an additional retransmission step The wireless communication method according to claim 1, characterized by the above.

6. A communication system that performs multi-carrier wireless communication using multiple subcarriers, A first symbol sequence acquisition means that obtains a first symbol sequence by multiplying the transmitted symbol by a pseudo-random vector composed of 1 and -1, A transmitting means for transmitting a transmission signal based on the first symbol sequence acquired by the first symbol sequence acquisition means, A receiving means for receiving a received signal corresponding to the transmitted signal transmitted by the transmitting means, A second symbol sequence acquisition means that acquires a second symbol sequence corresponding to the first symbol sequence based on the received signal received by the receiving means, A determination symbol acquisition means that acquires a determination symbol which is the dot product of the second symbol sequence acquired by the second symbol sequence acquisition means and the pseudo-random vector, The system includes estimation means for estimating the transmission symbol based on the determination symbol obtained by the determination symbol acquisition means. A wireless communication system characterized by the following.

Images