Wireless communication system, wireless communication method, and receiving device

Abstract

The purpose of the present invention is to utilize a nonlinear region of an amplifier and ensure a high data rate without false transmission of data in a wireless communication system using a single-carrier multilevel modulation scheme. This reception device obtains, from a transmission device, specifications 62 about the input / output characteristics of a transmission signal amplifier, and transmission power 64 for data transmission. The constellation 66 of signal points are estimated on the basis of the specifications 62 and the transmission power 64. A reception point 58 of a reception signal that is a point of constellation coordinates is sensed, and, for the reception point, likelihood calculation 68 is performed with the signal points. A symbol intended by the reception point is identified on the basis of the result of the likelihood calculation 68.

Description

[Technical Field]

[0001] The present disclosure relates to a wireless communication system, a wireless communication method, and a receiving device, and more particularly to a wireless communication system, a wireless communication method, and a receiving device that use a single-carrier multi-level modulation scheme. [Background technology]

[0002] Non-Patent Document 1 below discloses a technology related to a wireless communication system using a single-carrier multi-level modulation scheme. In wireless communication using a single-carrier multi-level modulation scheme, the higher the transmission power, the higher the SNR (Signal to Noise Ratio).

[0003] On the other hand, amplifiers for transmission signals generally exhibit linear input / output characteristics when the input power is low, but exhibit nonlinear characteristics when the power is high. For this reason, in wireless communications, the higher the transmission power, the more likely distortion occurs in the transmission signal.

[0004] The above-mentioned Non-Patent Document 1 discloses a technique for limiting the transmission power to within the linear range of the amplifier in order to avoid the effects of such distortion. In this case, distortion is not superimposed on the transmission signal, so the signal can be correctly processed in the receiving device, and erroneous data transmission can be effectively prevented.

[0005] Furthermore, a technique disclosed in Patent Document 1 below is known as a technique for avoiding the problem of distortion that accompanies an increase in transmission power. When, for example, an APSK (Amplitude and Phase-Shift Keying) technique is used as a modulation method, in a region where the input power is large, a phase shift occurs in the transmission signal due to a change in the AM / PM characteristics. Patent Document 1 discloses a technique for dealing with such a phase shift.

[0006] FIG. 1 is a diagram for explaining an overview of the technology disclosed in Patent Document 1. More specifically, FIG. 1 shows a constellation corresponding to 32APSK. In 32APSK, 32 symbols, indicated by circles or circles in the diagram, are defined by changing the amplitude and phase of the transmission signal. More specifically, four symbols are defined on the first inner circumference 10, twelve on the second inner circumference 12, and sixteen on the outermost circumference 14.

[0007] Patent Document 1 discloses that one or more pilot signals 16 are arranged on each of the first inner circumference 10, the second inner circumference 12, and the outermost circumference 14. The positions of the pilot signals 16 are shared between the transmitting device and the receiving device. Therefore, the receiving device can detect the phase shift occurring in each concentric circle based on the difference between the position of the pilot signal 16 actually received and the previously shared position.

[0008] For example, when a signal belonging to the first inner circumference 10 is received, the signal is adjusted to reflect the phase shift occurring in the first inner circumference 10. When a signal belonging to another concentric circle is received, the phase shift is corrected in the same manner. With this method, even if a phase shift occurs in the received signal in an area with high transmission power, the shift can be properly corrected to prevent erroneous data transmission. [Prior art documents] [Non-patent literature]

[0009] [Non-Patent Document 1] High-Speed ​​Satellite Mobile Communications: Technologies and Challenges, MOHAMED IBNKAHLA, QUAZI MEHBUBAR RAHMAN, AHMED IYANDA SULYMAN, HISHAM ABDULHUSSEIN AL-ASADY, JUN YUAN, AND AHMED SAFWAT, p312-339, PROCEEDINGS OF THE IEEE, VOL. 92, NO. 2, February 2004 [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-59889 Summary of the Invention [Problem to be solved by the invention]

[0011] However, the technology of Non-Patent Document 1 solves the distortion problem by abandoning the use of the non-linear region of the amplifier. In other words, this technology does not allow the amplifier to fully demonstrate its inherent capabilities, which goes against the essential demand to use large amounts of power without excessive capital investment.

[0012] Furthermore, in the technology of Patent Document 1, the transmitting device needs to transmit to the receiving device at least the same number of pilot signals as the number of concentric circles that make up the constellation. Furthermore, the environment of the communication path of the wireless signal is not always constant. Therefore, the pilot signals need to be transmitted frequently, preferably for each data communication flow.

[0013] The technology described in Patent Document 1 further requires the transmission of a larger number of pilot signals when, for example, QAM (Quadrature Amplitude Modulation) is used as the modulation method. That is, as described in Patent Document 1, if the modulation method is APSK, multiple symbols arranged on concentric circles can be corrected with a single common phase shift. Therefore, the number of pilot signals required for multiple symbols arranged on concentric circles is one.

[0014] In contrast, in the case of QAM, the symbols in the constellation are arranged in a grid pattern. For example, 4 x 4 = 16 or 8 x 8 = 64 symbols are arranged in a grid pattern on the constellation. In this case, even if one pilot signal can be shared by several symbols, it is necessary to prepare a large number of pilot signals to properly correct all symbols.

[0015] If a large number of pilot signals are transmitted and received for each communication flow, the data rate will inevitably decrease. In this regard, the technology described in Patent Document 1 enables the use of large power commensurate with the amplifier's capacity, but there is still room for improvement in terms of data rate.

[0016] The present disclosure has been made in consideration of the above-mentioned problems, and has as its first object to provide a wireless communication system that utilizes the nonlinear region of an amplifier, does not cause erroneous data transmission, and ensures a high data rate.

[0017] A second object of the present disclosure is to provide a wireless communication method that utilizes the nonlinear region of an amplifier, does not cause erroneous data transmission, and ensures a high data rate.

[0018] A third object of the present disclosure is to provide a receiving device that does not erroneously recognize data and ensures a high data rate even when a signal that utilizes the nonlinear region of an amplifier is transmitted. [Means for solving the problem]

[0019] In order to achieve the above object, a first aspect is a wireless communication system including a transmitting device and a receiving device that perform wireless communication using a single-carrier multi-level modulation scheme, The transmitting device a transmission signal amplifier with variable transmission power; providing specifications relating to input / output characteristics of the transmission signal amplifier to the receiving device; and providing the receiving device with the transmission power used for data transmission; The receiving device a signal point estimation process for estimating a constellation of signal points based on the transmission power and the specifications; A process of detecting a reception point, which is a point on a constellation coordinate system of a received signal; A process of calculating likelihood between the reception point and the signal point; It is desirable that the receiver is configured to execute a process of identifying the symbol intended by the reception point based on the calculation result of the likelihood.

[0020] A second aspect is a wireless communication method using a transmitting device and a receiving device that perform wireless communication using a single-carrier multi-level modulation scheme, the transmitting device includes a transmission signal amplifier with variable transmission power; the transmitting device providing the receiving device with specifications regarding input / output characteristics of the transmitting signal amplifier; a step of the transmitting device providing the receiving device with transmission power used for data transmission; the receiving device estimating a constellation of signal points based on the transmission power and the specifications; a step in which the receiving device detects a reception point of a received signal, which is a point on a constellation coordinate system; The receiving device calculates the likelihood of the reception point and the signal point; The receiving device specifies a symbol intended by the receiving point based on the calculation result of the likelihood; It is desirable to include:

[0021] A third aspect is a receiving device for performing wireless communication using a single-carrier multi-level modulation scheme, A process of acquiring specifications relating to input / output characteristics of a transmission signal amplifier used by a transmission device of the wireless communication from the transmission device; A process of acquiring transmission power used by the transmitting device for data transmission; a signal point estimation process for estimating a constellation of signal points based on the transmission power and the specifications; A process of detecting a reception point, which is a point on a constellation coordinate system of a received signal; A process of calculating likelihood between the reception point and the signal point; A process of identifying a symbol intended by the receiving point based on the calculation result of the likelihood; Preferably, the system is configured to execute the following: [Effects of the Invention]

[0022] According to the first to third aspects, the receiving device can estimate the constellation of signal points based on the transmission power provided by the transmitting device and the specifications of the transmitting signal amplifier. Therefore, according to these aspects, it is possible to ensure a high data rate without causing erroneous data transmission while utilizing the nonlinear region of the amplifier. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a diagram for explaining an outline of the technology disclosed in Patent Document 1. [Figure 2] FIG. 1 is a diagram illustrating a configuration of a wireless communication system according to a first embodiment of the present disclosure. [Figure 3] FIG. 2 is a diagram illustrating the configuration of a transmission device to be compared with the transmission device according to the first embodiment of the present disclosure. [Figure 4] 10A and 10B are diagrams illustrating input / output characteristics of an amplifier built into a transmitter. [Figure 5] FIG. 10 is a diagram showing how distortion occurs in a constellation as transmission power increases. [Figure 6] FIG. 2 is a block diagram illustrating a configuration of a transmission device according to the first embodiment of the present disclosure. [Figure 7] 1 is a block diagram illustrating a configuration of a main part of a receiving device according to a first embodiment of the present disclosure. [Figure 8] FIG. 2 is a diagram illustrating a characteristic operation of the receiving device according to the first embodiment of the present disclosure. [Figure 9] FIG. 10 is a diagram illustrating a configuration of a communication device included in a wireless communication system according to a second embodiment of the present disclosure. [Figure 10] 10 is a flowchart illustrating a flow of processing executed by the communication device shown in FIG. 9 to control transmission power. [Figure 11]10 is a flowchart illustrating a modified example of the process executed by the communication device shown in FIG. 9 to control transmission power. DETAILED DESCRIPTION OF THE INVENTION

[0024] Embodiment 1 [Overall Configuration of First Embodiment] 2 shows an overall configuration of a wireless communication system according to the first embodiment of the present disclosure. As shown in FIG. 2, the wireless communication system according to the present embodiment includes a transmitting device 20 and a receiving device 50.

[0025] [Issues addressed by the first embodiment] 3 is a block diagram illustrating the configuration of a transmitting device 22 for comparison with the transmitting device 20 of this embodiment. The transmitting device 22 of the comparative example includes an information bit generating unit 24. The information bit generating unit 24 generates information bits to be transmitted to the receiving device 50. The information bit generating unit 24 may include an error correction coding function or an interleaving function.

[0026] The information bits generated by the information bit generator 24 are provided to a data signal modulator 26. The data signal modulator 26 modulates the provided information bits into a data signal. As a modulation method, for example, quadrature amplitude modulation (QAM) or APSK, which can be used for a single-carrier multi-level modulation method, can be considered.

[0027] The data signal generated by the data signal modulation unit 26 is provided to the digital-to-analog conversion unit 28. The digital-to-analog conversion unit 28 converts the digitally modulated data signal into an analog transmission signal.

[0028] The transmission signal generated in the digital-to-analog conversion unit 28 is provided to a transmission signal amplifier 30. The transmission signal amplifier 30 amplifies the transmission signal and provides it to an antenna 32. The transmission signal is then transmitted from the antenna 32 to a receiving device 50 in the form of a radio signal.

[0029] 4 shows the input / output characteristics of the transmission signal amplifier 30. As shown in FIG. 4, the output power (vertical axis) of the transmission signal amplifier 30 increases as the input power (horizontal axis) increases. B In smaller areas, it is proportional to the input power. B In the region beyond this, the proportional relationship is lost. Hereinafter, the region in which the two are proportional is referred to as the "linear region," and the region in which the proportional relationship is lost is referred to as the "nonlinear region."

[0030] Figure 5 shows how distortion occurs in an 8x8 = 64QAM constellation as transmission power increases. In the 64QAM modulation method, 64 symbols arranged in a grid pattern are defined by changing and adjusting the amplitude of two independent carrier waves. Hereinafter, the points on the constellation coordinates where each of these 64 symbols is defined will be referred to as "signal points." Furthermore, the points on the constellation coordinates of each actually transmitted data signal will be referred to as "reception points."

[0031] In the linear region of the transmission signal amplifier 30, the reception points form a distortion-free constellation as shown on the left side of Fig. 5 (transmission power P1). On the other hand, in the nonlinear region of the transmission signal amplifier 30, the reception points form a distortion-free constellation as shown on the right side of Fig. 5 (transmission power P N ), distortion is superimposed on the constellation at the receiving point.

[0032] The receiving device 50 calculates the likelihood of each reception point included in the transmission signal with respect to adjacent signal points, and recognizes each reception point as one of 64 symbols based on the result. The likelihood calculation can be performed, for example, by a method such as that described in the following document.

[0033] On the Optimality of Bit Detection of Certain Digital Modulations, Marvin K. Simon and Ramesh Annavajjala, p299-307, IEEE TRANSACTIONS ON COMMUNICATIONS, VOL. 53, NO. 2, FEBRUARY 2005

[0034] If the receiving device 50 performs the likelihood calculation using signal points that form a distortion-free constellation, the receiving points generated in the linear domain can be correctly recognized. However, the receiving points generated in the nonlinear domain cannot be correctly recognized because they are shifted from their original positions on the constellation. Therefore, if the transmission signal amplifier 30 uses the nonlinear domain, the receiving device 50 may misrecognize data.

[0035] [Features of the first embodiment] Even with the transmitter 22 of the comparative example, misidentification of data can be prevented by limiting the transmission power to the linear region of the transmission signal amplifier 30. However, in this case, the amplification capability of the transmission signal amplifier 30 cannot be fully utilized.

[0036] Fig. 6 is a block diagram for explaining the configuration of the transmitting device 20 in this embodiment. In Fig. 6, the same elements as those included in the transmitting device 22 of the comparative example (see Fig. 3) are denoted by the same reference numerals, and their explanations will be omitted or simplified.

[0037] In the transmitting device 20 of this embodiment, the information bit generator 24 in the transmitting device 22 of the comparative example is replaced with an information bit generator 34. The information bit generator 34 provided in this embodiment generates information bits related to the specifications of the transmitting device 20 when communication between the transmitting device 20 and the receiving device 50 starts. Specifically, the modulation method used by the transmitting device 20 and the input / output characteristics of the transmission signal amplifier 30 (see FIG. 4) are converted into information bits.

[0038] The information bits generated in this manner are transmitted from the transmitting device 20 to the receiving device 50 when communication between the transmitting device 20 and the receiving device 50 starts. Therefore, in this embodiment, the modulation method used by the transmitting device 20 and the input / output characteristics of the transmission signal amplifier 30 are shared between the two devices when communication between them starts.

[0039] The transmitting device 20 in this embodiment includes a transmission power control unit 36 ​​in the upstream stage of the transmission signal amplifier 30. The transmission power control unit 36 ​​controls the transmission power so as to obtain a desired communication quality. A transmission power command from the transmission power control unit 36 ​​is provided to the transmission signal amplifier 30 and also to a transmission power information notification unit 38.

[0040] The transmission power information notifying unit 38 provides the command value of the transmission power to the information bit generating unit 34. Then, the information bit generating unit 34 generates bit information related to the current transmission power and includes the information in the transmission data. As a result, a transmission signal including information on the transmission power set by the transmission power control unit 36 ​​is transmitted from the transmitting device 20 of this embodiment to the receiving device 50.

[0041] Incidentally, when transmitting data after starting communication, transmitting device 20 of this embodiment also transmits a training signal. In Fig. 6, the constellations of the data and training signal before and after amplification are shown below transmission signal amplifier 30. If transmission signal amplifier 30 uses a nonlinear region, as shown in this figure, the constellation of the amplified data will be distorted.

[0042] The training signal information is shared in advance between the transmitting device 20 and the receiving device 50, and is preferably transmitted with a power (amplitude) that falls within the linear region of the transmitting signal amplifier 30. During the process of reaching the receiving device 50, the training signal may experience phase and amplitude shifts due to the environment of the wireless signal communication path. The receiving device 50 detects the influence of the shift due to the communication path based on the shift between the reception point of the actually received training signal and the known signal point of the training signal. The receiving device 50 then eliminates the influence due to the communication path by reflecting the detection result in each of the reception points of the data.

[0043] Fig. 7 is a block diagram for explaining the configuration of the main parts of a receiving device 50 according to this embodiment. As shown in Fig. 7, the receiving device 50 according to this embodiment includes a data signal equalization unit 52. The data signal equalization unit 52 is a block that obtains an estimated value of a transmission signal by inversely calculating the amplitude and phase shift information of a communication channel response. Specifically, the data signal equalization unit 52 executes a process of reflecting a training result 56 in a data signal 54. This results in a receiving point 58 in which deviations due to the environment of the communication channel are canceled out.

[0044] The receiving device 50 of this embodiment further includes a likelihood calculation unit 60. The likelihood calculation unit 60 is a block that calculates likelihood in accordance with current constellation information. The likelihood calculation unit 60 first identifies a constellation 66 of the received signal based on specification information 62 of the transmitting device 20 acquired at the start of communication and current transmission power 64 received together with the data signal.

[0045] The modulation method used by the transmitter 20 and the input / output characteristics of the transmission signal amplifier 30 are known to the receiver 50. If this information is known, and the actually used transmission power is known, the constellation of the received signal can be reproduced. Here, as shown in the lower part of Figure 7, the transmission power P i (i=1 to N), a constellation 66 corresponding to the training point 58 is selected. After completing this process, the likelihood calculation unit 60 then uses the selected constellation 66 to perform likelihood calculation 68 for each of the reception points 58 to which the training results are reflected.

[0046] FIG. 8 is a diagram illustrating an overview of likelihood calculation 68. The left side of FIG. 8 shows an overview of likelihood calculation 68 when transmission power is P1. In this case, the constellation 66 of the received signal is distortion-free, with each signal point 70 properly arranged in a grid pattern. The likelihood calculation unit 60 refers to the constellation 66 and calculates the likelihood for some of the signal points 70 located near the reception point 58 using a normal distribution for the Euclidean distance between them. The signal point 70 for which the largest likelihood is obtained is then adopted as the symbol corresponding to that reception point 58.

[0047] The right side of Figure 8 shows the case where the transmission power is P N 1 shows an overview of likelihood calculation 68 when the constellation 66 of the received signal includes a deviation at each signal point 70 due to the nonlinearity of the transmission signal amplifier 30. The likelihood calculation unit 60 references the constellation 66 with the deviation and calculates the likelihood for the reception point 58 using the same method as above. Then, based on the result, the symbol represented by the reception point 58 is identified.

[0048] As described above, the wireless communication system of this embodiment allows the transmitting device 20 to transmit a high-power transmission signal by using the nonlinear region of the transmission signal amplifier 30. Furthermore, by transferring the specifications of the transmission signal amplifier 30 to the receiving device 50 at the start of communication, the receiving device 50 can reproduce a distorted constellation corresponding to the nonlinear region without requiring further information provision. Then, by performing likelihood calculations using this constellation, it is possible to prevent data from being erroneously recognized even for transmission signals using the nonlinear region. Furthermore, a training signal with an extremely small amount of data is used for each data transmission, thereby eliminating the effects of phase and amplitude deviations due to the communication path at all reception points. Therefore, the wireless communication system of this embodiment can utilize the nonlinear region of the transmission signal amplifier 30, prevent erroneous data transmission, and ensure a high data rate.

[0049] [Modification of the first embodiment] 7 shows how the likelihood calculation unit 60 reconstructs the constellations of the received signal for each of a plurality of transmission powers P1 and P2 that fall within the linear region of the transmission signal amplifier 30. However, the method for reconstructing the constellations of the received signal is not limited to this. That is, the likelihood calculation unit 60 may use the same distortion-free constellations in common for the transmission powers that fall within the linear region of the transmission signal amplifier 30, and reconstruct the constellations of the received signal only for the transmission powers that fall within the nonlinear region.

[0050] In the first embodiment described above, the transmitting device 20 provides the receiving device 50 with the specifications of the transmission signal amplifier 30 at the start of wireless communication. However, the present disclosure is not limited to this. For example, the transmitting device 20 may store the receiving device 50 that provided the specifications, and the receiving device 50 that received the specifications may store the information. Then, for the second and subsequent communications between the two devices, the exchange of the specifications may be omitted.

[0051] In the first embodiment described above, the transmitting device 20 provides the receiving device 50 with information about the modulation method used for wireless communication, along with the specifications of the transmission signal amplifier 30. However, the present disclosure is not limited to this. For example, if the modulation method used for communication between the transmitting device 20 and the receiving device 50 is determined in advance, provision of the information about the modulation method may be omitted.

[0052] Embodiment 2 Next, a wireless communication system according to a second embodiment of the present disclosure will be described with reference to FIGS. 9 to 11 as well as FIG. 2 above.

[0053] Fig. 9 is a block diagram illustrating the configuration of a communication device 80 used in the wireless communication system of this embodiment. The communication device 80 shown in Fig. 9 includes a transmitting unit for transmitting a wireless signal and a receiving unit for processing a received wireless signal. The communication device 80 can be used as either the transmitting device 20 or the receiving device 50 shown in Fig. 1. Below, a case will be described in which both the transmitting device 20 and the receiving device 50 are configured by the communication device 80 shown in Fig. 9.

[0054] A communication device 80 in this embodiment includes a transmitting unit having a configuration similar to that of the transmitting device 20 in embodiment 1. Similarly to the receiving device 50 in embodiment 1, the communication device 80 also includes a data signal equalization unit 52 and a likelihood calculation unit 60. Note that in Fig. 9, the same elements as those described in embodiment 1 are assigned the reference numerals shown in Fig. 6 or 7, and redundant description will be omitted or simplified.

[0055] The communication device 80 in this embodiment provides a signal received by the antenna 32 to a received signal amplifier 82. The received signal amplifier 82 amplifies the received signal with an appropriate gain and provides the amplified signal to an analog-to-digital converter 84.

[0056] The analog-to-digital converter 84 is a block for demodulating the received analog signal into a digital signal. The signal digitized by the analog-to-digital converter 84 is provided to the data signal equalizer 52.

[0057] The data signal equalization unit 52 and likelihood calculation unit 60 perform the same processing as in the first embodiment. This allows accurate data recognition to be achieved regardless of whether or not the constellation of the received signal contains distortion.

[0058] The signal symbolized in the likelihood calculation unit 60 is provided to an information bit detection unit 86. In this embodiment, the information bit detection unit 86 converts information related to the bit error rate (BER) of the signal into bits in addition to the data to be exchanged with the communication partner. The BER information is then provided to an information bit generation unit 34 in the transmission unit.

[0059] The information bit generator 34 performs bit generation processing to include BER information in a transmission signal in order to provide the BER information to the communication partner. In this embodiment, the communication device 80 thereby provides the communication device 80 of the communication partner with information on the BER achieved by the current transmission power.

[0060] Similarly, information about the BER achieved at the current transmission power is also provided by the communication partner to the communication device 80 shown in Fig. 9. This information is restored to a data signal by the receiving unit of the communication device 80, and then fed back to the transmission power control unit 36 ​​of the transmitting unit. Based on the information fed back in this way, the transmission power control unit 36 ​​controls the transmission power so as to improve communication quality.

[0061] Fig. 10 is a flowchart illustrating an example of processing executed by the transmission power control unit 36 ​​in this embodiment. The routine shown in Fig. 10 is started immediately after the communication device 80 establishes communication with the communication device 80 of the other party.

[0062] In this routine, first, the transmission power is set to the maximum power P N (Step 100). Next, it is determined whether the BER returned from the communication partner for the set transmission power is equal to or less than a threshold value (for example, 1E-6) (Step 102).

[0063] Maximum power P Nis the most advantageous power for obtaining a good SNR if the constellation distortion caused by the nonlinearity of the transmission signal amplifier 30 can be properly absorbed. If it is determined in step 102 above that the BER is equal to or less than the threshold, it can be determined that the transmission signal has been received sufficiently accurately. Therefore, in this case, it can be determined that the constellation distortion has been properly absorbed in the communication device 80 of the communication partner. In other words, it can be determined that the current transmission power is the maximum power that achieves the desired communication quality.

[0064] Such a transmission power is suitable for ensuring a high data rate and a high SNR. Therefore, if the determination in step 102 is positive, it is determined that the current transmission power is appropriate, and the power control routine is terminated.

[0065] On the other hand, if it is determined in step 102 that the BER exceeds the threshold, it can be determined that the communication device 80 of the other party is not able to accurately acquire data. In other words, it can be determined that the distortion of the constellation is likely to be too large for the communication device 80 of the other party. In this case, the transmission power control unit 36 ​​attempts to reduce the transmission power in order to alleviate the distortion of the constellation (step 104). For example, if the current transmission power is P N If so, the power is P N-1 will be changed to.

[0066] Thereafter, the process of step 102 is executed again. Then, as a result of repeating steps 102 and 104, if a transmission power that clears the BER is found, this routine is ended at that point.

[0067] According to the above process, the transmission power used by the communication device 80 is determined to be the largest power that clears the BER after communication starts. Therefore, according to the wireless communication system of this embodiment, in addition to the same effects as in the first embodiment, it is possible to obtain the effect of optimizing the transmission power and achieving the best communication quality.

[0068] [Modification of the second embodiment] Fig. 11 is a flowchart for explaining an example of another routine that can be executed by transmission power control unit 36 ​​to control transmission power instead of the routine shown in Fig. 10. Like the routine shown in Fig. 10, the routine shown in Fig. 11 is also started immediately after communication device 80 establishes communication with communication device 80 of the other party.

[0069] 11, first, the transmission power is set to a preset initial power (step 110). The initial power is the power that is expected to be the maximum power that clears the BER.

[0070] Next, it is determined whether the BER provided from the communication device 80 of the communication partner satisfies the condition of being equal to or less than a threshold (step 112). This process is substantially the same as the process of step 102 shown in FIG.

[0071] If it is determined in step 112 that the BER condition is met, it can be determined that there is still room to increase the transmission power. Therefore, in this case, the transmission power control unit 36 ​​attempts to increase the transmission power (step 114). Specifically, the transmission power is increased by the current power P i From there, the next level up, P i+1 Change to.

[0072] Next, it is determined again whether the BER provided by the communication device 80 of the communication partner for the increased transmission power satisfies the threshold condition (step 116). As a result, if the BER satisfies the threshold condition, the process of step 114 is executed again.

[0073] In this routine, if the determination in step 116 is negative, it can be determined that the transmission power has exceeded the upper limit of the power that can clear the BER by one level. In this case, it can be determined that a power that is one level lower than the current transmission power is the maximum power that can clear the BER. Therefore, if the determination in step 116 is negative, the transmission power is reduced by one level (step 118), and the current routine is terminated.

[0074] If it is determined in step 112 that the BER cannot be cleared with the initial power set as the transmission power, a process of lowering the transmission power is executed (step 120). Then, it is determined whether the BER for the changed transmission power satisfies the threshold condition (step 122).

[0075] If the BER is not cleared as a result, it can be determined that the transmission power is still excessive. Therefore, if the determination in step 122 is negative, the process of step 120 is executed again.

[0076] In this routine, if the determination in step 122 is affirmative, it can be determined that the transmission power has been reduced to the maximum power that can clear the BER at that point. In this case, the current transmission power is the optimum power, and the routine is then promptly terminated.

[0077] As described above, according to the routine shown in Fig. 11, the transmission power can be set to the maximum power that satisfies the desired BER, as in the case of the routine shown in Fig. 10. Furthermore, according to the routine shown in Fig. 11, when the optimum transmission power is sufficiently smaller than the maximum power PN, the optimum transmission power can be found earlier than the routine shown in Fig. 10. [Explanation of symbols]

[0078] 20 Transmitting device 30 Transmitting signal amplifier 34 Information bit generator 36 Transmission power control section 38 Transmission power information notification unit 50 Receiving device 52 Data signal equalization unit 60 Likelihood calculation unit 80 Communication equipment 86 Information bit detector

Claims

1. A wireless communication system including a transmitting device and a receiving device that perform wireless communication using a single-carrier multi-level modulation scheme, The transmitting device a transmission signal amplifier with variable transmission power; a process of providing specifications regarding input / output characteristics of the transmission signal amplifier to the receiving device at the start of the wireless communication; and a process of providing a transmission signal including information on transmission power used for the data transmission to the receiving device for each data transmission; The receiving device receiving the transmitted signal to generate a received signal; a signal point estimation process for estimating a constellation of signal points related to the received signal based on information about the transmission power included in the received signal and the specifications acquired at the start of the wireless communication; A process of detecting a reception point, which is a point on a constellation coordinate of the received signal; A process of calculating likelihood between the reception point and the signal point; and a process of identifying the symbol intended by the receiving point based on the calculation result of the likelihood.

2. A wireless communication system including a transmitting device and a receiving device that perform wireless communication using a single-carrier multi-level modulation scheme, The transmitting device a transmission signal amplifier with variable transmission power; providing specifications relating to input / output characteristics of the transmission signal amplifier to the receiving device; and providing information about the transmission power used for data transmission to the receiving device, The receiving device a signal point estimation process for estimating a constellation of signal points based on the transmission power information and the specifications; A process of detecting a reception point, which is a point on a constellation coordinate system of a received signal; A process of calculating likelihood between the reception point and the signal point; and a process of identifying a symbol intended by the reception point based on a result of the likelihood calculation, The transmitting device further configured to perform the operation of transmitting a training signal; The receiving device storing the original value of the training signal; a process of detecting an influence of a communication path on the received signal based on a difference between the original value and the value of a training signal actually received; and further performing a process of eliminating the influence of the communication channel from the reception point prior to calculating the likelihood, A wireless communication system in which the training signal is transmitted at a power level within the linear region of the transmission signal amplifier.

3. A wireless communication system including a transmitting device and a receiving device that perform wireless communication using a single-carrier multi-level modulation scheme, The transmitting device a transmission signal amplifier with variable transmission power; providing specifications relating to input / output characteristics of the transmission signal amplifier to the receiving device; and providing information about the transmission power used for data transmission to the receiving device, The receiving device a signal point estimation process for estimating a constellation of signal points based on the transmission power information and the specifications; A process of detecting a reception point, which is a point on a constellation coordinate system of a received signal; A process of calculating likelihood between the reception point and the signal point; and a process of identifying a symbol intended by the reception point based on a result of the likelihood calculation, The receiving device calculating an error rate of the received signal; providing the error rate to the transmitting device; The transmitting device The wireless communication system is further configured to execute a power control process for controlling the transmission power to a maximum power that satisfies the requirement regarding the error rate.

4. The power control process includes: setting the transmission power to maximum power at the start of wireless communication; obtaining the error rate from the receiving device; a process of determining whether the error rate satisfies the requirement; 4. The wireless communication system according to claim 3, further comprising a process of gradually reducing the transmission power until a result is obtained that the error rate satisfies the requirement.

5. A wireless communication method using a transmitting device and a receiving device that perform wireless communication using a single-carrier multi-level modulation scheme, the transmitting device includes a transmission signal amplifier with variable transmission power; a step of the transmitting device providing specifications regarding input / output characteristics of the transmitting signal amplifier to the receiving device at the start of the wireless communication; a step of the transmitting device providing a transmission signal including information on transmission power used for the data transmission to the receiving device for each data transmission; A process in which the receiving device receives the transmission signal and generates a received signal; a step in which the receiving device estimates a constellation of signal points related to the received signal based on information about the transmission power included in the received signal and the specifications acquired at the start of the wireless communication; The receiving device detects a reception point of the received signal, which is a point on a constellation coordinate system; The receiving device calculates the likelihood of the reception point and the signal point; The receiving device specifies a symbol intended by the receiving point based on the calculation result of the likelihood; A wireless communication method comprising:

6. A wireless communication method using a transmitting device and a receiving device that perform wireless communication using a single-carrier multi-level modulation scheme, the transmitting device includes a transmission signal amplifier with variable transmission power; the transmitting device providing the receiving device with specifications regarding input / output characteristics of the transmitting signal amplifier; a step of the transmitting device providing information on transmission power used for data transmission to the receiving device; a step of transmitting a training signal by the transmitting device at a power level within a linear region of the transmitting signal amplifier; the receiving device estimating a constellation of signal points based on the information on the transmission power and the specifications; the receiving device stores an original value of the training signal, and detects an influence of a communication path on the received signal based on a difference between the original value and the value of the training signal actually received; The receiving device detects a reception point of the received signal, which is a point on a constellation coordinate system; a step of the receiving device eliminating the influence of the communication path from the reception point; a step in which the receiving device calculates a likelihood between the signal point and a reception point from which the influence of the communication channel has been eliminated; The receiving device specifies a symbol intended by the receiving point based on the calculation result of the likelihood; A wireless communication method comprising:

7. A wireless communication method using a transmitting device and a receiving device that perform wireless communication using a single-carrier multi-level modulation scheme, the transmitting device includes a transmission signal amplifier with variable transmission power; the transmitting device providing the receiving device with specifications regarding input / output characteristics of the transmitting signal amplifier; a step of the transmitting device providing information on transmission power used for data transmission to the receiving device; the receiving device estimating a constellation of signal points based on the information on the transmission power and the specifications; a step in which the receiving device detects a reception point of a received signal, which is a point on a constellation coordinate system; The receiving device calculates the likelihood of the reception point and the signal point; The receiving device specifies a symbol intended by the receiving point based on the calculation result of the likelihood; the receiving device calculating an error rate of the received signal; the receiving device providing the error rate to the transmitting device; a step of the transmitting device controlling the transmission power to a maximum power at which the requirement regarding the error rate is satisfied; A wireless communication method comprising:

8. A receiving device for performing wireless communication using a single-carrier multi-level modulation scheme, a process of acquiring, at the start of the wireless communication, specifications relating to input / output characteristics of a transmission signal amplifier used by a transmission device of the wireless communication; A process of acquiring a transmission signal including information on transmission power used by the transmitting device for data transmission; receiving the transmitted signal to generate a received signal; a signal point estimation process for estimating a constellation of signal points related to the received signal based on information about the transmission power included in the received signal and the specifications acquired at the start of the wireless communication; A process of detecting a reception point, which is a point on a constellation coordinate of the received signal; A process of calculating likelihood between the reception point and the signal point; A process of identifying a symbol intended by the receiving point based on the calculation result of the likelihood; a receiving device configured to perform the

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