Wireless communication system and wireless receiver

Abstract

To improve reception quality.SOLUTION: A wireless communication system includes a wireless transmitter and a wireless receiver. The wireless transmitter prepends a preamble signal known with the wireless receiver, and transmits a transmission frame. The wireless receiver includes: a correspondence relationship calculation unit which calculates correspondence relationships between a predetermined reference signal and preamble signals obtained by dividing a signal in a preamble section of the received transmission frame into multiple sections, to output correspondence relationship results; a delay detection calculation unit which performs delay detection on each of the correspondence relationship results of the divided sections to calculate phase change vectors; and a phase change vector selection unit which selects a phase change vector for use in synchronization acquisition, using maximum detection power of each of the phase change vectors calculated from the sum of the results of the delay detection of the sections.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a wireless communication system and a wireless receiving device. [Background technology]

[0002] Generally, in a wireless communication system, a preamble signal for the purpose of synchronization acquisition and AFC (Auto Frequency Control) is added to the beginning of a transmission frame.

[0003] The receiver performs a synchronization acquisition process to detect the peak of the correlation value by performing a cross-correlation calculation between the preamble signal and a predetermined fixed pattern, and detects the frequency offset from the phase change vector that represents the phase change amount of the cross-correlation calculation, and corrects the frequency offset.

[0004] The following prior art is included as background art in this technical field. For example, Patent Document 1 (JP Patent Publication 2012-257115A) describes a single carrier receiving device for a transmission device that transmits a single carrier signal having a preamble signal and a data signal in one frame, the single carrier receiving device including a complex multiplication unit that performs complex multiplication of a received sampling sequence converted from the single carrier signal and a complex conjugate signal of the preamble signal, a weighting coefficient multiplication unit that multiplies each output result of the complex multiplication unit by a weighting coefficient forming a low-pass filter, and a filter unit that performs convolution operation of the addition result with a window function having a predetermined time width W (W is a natural number).

[0005] Furthermore, Patent Document 2 (JP 2012-186537 A) describes a single carrier receiving device in a transmission device that transmits a single carrier signal having a preamble signal and a data signal in one frame, the single carrier receiving device comprising: a complex multiplication unit that performs complex multiplication of a received sampling sequence converted from the single carrier signal and a complex conjugate signal of the preamble signal; a differential processing unit that performs complex multiplication of a complex conjugate signal of a signal delayed by one sample on the complex multiplication result and an undelayed signal; an integrator that integrates the calculation result over a predetermined sample period NP; an averaging unit 8 that averages the integration result in the frame direction; and a rectangular filter unit that performs a convolution operation on the averaging result with a window function having a predetermined time width W (W is a natural number). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2012-257115 A [Patent Document 2] JP 2012-186537 A Summary of the Invention [Problem to be solved by the invention]

[0007] In the receiving devices described in the above-mentioned Patent Documents 1 and 2, a preamble signal is divided into small sections and a phase change vector is added. However, these receiving devices calculate the received power in a low SNR environment, such as an SNR less than 0 dB.

[0008] However, there is a trade-off between the frequency offset detection range, determined by the symbol length or number of samples for cross-correlation (hereinafter referred to as correlation width), and the detection accuracy. Specifically, if the correlation width is shortened, the frequency offset detection range becomes wider but the frequency offset detection accuracy decreases, whereas if the correlation width is lengthened, the frequency offset detection range becomes narrower but the frequency offset detection accuracy improves. Furthermore, if the correlation width is lengthened, the correlation gain also becomes larger, improving the detection accuracy.

[0009] Furthermore, if the correlation width is increased, the amount of phase change per correlation width becomes larger. If the frequency offset is large, the amount of phase change per correlation width may exceed ±π (±180°), making the direction of rotation unclear, and it may not be possible to detect the correct frequency offset.

[0010] Furthermore, generally, a cross-correlation or auto-correlation calculation is performed on the signal after frequency offset correction processing to perform synchronization acquisition processing. This is because a sufficient correlation peak value cannot be obtained unless the cross-correlation or auto-correlation calculation is performed after correcting the frequency offset and removing the effect of the frequency offset. [Means for solving the problem]

[0011] A representative example of the invention disclosed in the present application is as follows: That is, a wireless communication system includes a wireless transmitting device and a wireless receiving device, the wireless transmitting device transmits a transmission frame by adding a known preamble signal to the beginning of the transmission frame between the wireless receiving device, and the wireless receiving device has a cross-correlation calculation unit that calculates a cross-correlation between a preamble signal obtained by dividing a signal of a preamble section of the received transmission frame into a plurality of sections and a predetermined reference signal, and outputs the cross-correlation result, a differential detection calculation unit that performs differential detection on each of the cross-correlation results of the divided sections and calculates a phase change vector, and a phase change vector selection unit that selects a phase change vector to be used for synchronization acquisition using a maximum detection power of each of the phase change vectors calculated by the sum of the differential detection results of each of the sections.

[0012] In addition, in a wireless communication system according to an embodiment of the present invention, the wireless receiving device has a plurality of the cross-correlation calculation units and a plurality of the differential detection calculation units, each of the cross-correlation calculation units calculates the cross-correlation between a preamble signal divided into different division numbers and the reference signal, and each of the differential detection calculation units performs differential detection on the cross-correlation results corresponding to the different division numbers, and calculates a phase change vector corresponding to each division number.

[0013] In addition, in a wireless communication system according to one example of the present invention, the phase change vector selection unit selects a phase change vector having the largest maximum value among the maximum detection powers of phase change vectors having a plurality of division numbers, or compares the maximum detection powers of phase change vectors having a plurality of division numbers with a predetermined threshold value, and selects a phase change vector having a maximum detection power of the phase change vector that exceeds the predetermined threshold value and has the smallest number of divisions.

[0014] In addition, in a wireless communication system according to an example of the present invention, the wireless receiving device is characterized in having a frequency offset calculation unit that outputs a frequency offset using a change angle of the maximum power position of the selected phase change vector.

[0015] In a wireless communication system according to an embodiment of the present invention, the wireless receiving device includes a rotator section that corrects a received signal in accordance with the frequency offset.

[0016] In addition, in a wireless communication system according to one example of the present invention, the wireless receiving device has a plurality of the cross-correlation calculation units, a plurality of the differential detection calculation units, and a plurality of the frequency offset calculation units, and a processing block composed of one of the cross-correlation calculation units, one of the differential detection calculation units, and one of the frequency offset calculation units is connected in multiple stages, and the processing blocks perform calculation processing by reducing the number of divisions of the section as they progress to the later stages.

[0017] In addition, in a wireless communication system according to an example of the present invention, the processing block has a rotator unit, which is located downstream of the frequency offset calculation unit and calculates a cumulative frequency offset up to that stage, and the rotator unit outputs a received signal corrected by the frequency offset.

[0018] Moreover, in a wireless communication system according to an example of the present invention, the wireless receiving device has a frequency offset integration unit that adds the frequency offset at a predetermined timing, the rotator unit corrects the received signal by the frequency offset added by the frequency offset integration unit, and the cross-correlation calculation unit calculates the cross-correlation between a preamble signal obtained by dividing a signal of a preamble section of the received signal corrected by the rotator unit into a plurality of sections and a predetermined reference signal, outputs a plurality of cross-correlation results, and performs calculation processing by reducing the number of divisions according to the number of times of iterative processing.

[0019] In the wireless communication system according to one example of the present invention, the frequency offset calculation section outputs the tail of the power peak value obtained by the cross-correlation calculation as a synchronization capture position.

[0020] Moreover, a wireless receiving device according to an example of the present invention is characterized in that it comprises a cross-correlation calculation unit that calculates the cross-correlation between a preamble signal obtained by dividing a signal of a preamble section of the received transmission frame into a plurality of sections and a predetermined reference signal, and outputs the cross-correlation result, a differential detection calculation unit that performs differential detection on each of the cross-correlation results of the divided sections and calculates a phase change vector, and a phase change vector selection unit that selects a phase change vector to be used for synchronization acquisition using the maximum detection power of each of the phase change vectors calculated by the sum of the differential detection results of each of the sections. Effect of the Invention

[0021] According to one aspect of the present invention, it is possible to improve reception quality. Problems, configurations, and effects other than those described above will become apparent from the following description of the preferred embodiment of the present invention. [Brief description of the drawings]

[0022] [Figure 1] FIG. 2 is a diagram illustrating an AFC and synchronization acquisition processing unit according to the first embodiment of the present invention. [Diagram 2] FIG. 1 is a diagram illustrating a conventional phase change vector calculation method. [Diagram 3] FIG. 1 is a diagram illustrating a conventional phase change vector calculation method. [Figure 4] FIG. 2 is a diagram illustrating a configuration of a cross-correlation calculation unit according to the first embodiment. [Diagram 5] FIG. 2 is a diagram illustrating a configuration of a differential detection calculation unit according to the first embodiment. [Figure 6] FIG. 4 is a diagram illustrating a configuration of a phase change vector selection unit according to the first embodiment. [Figure 7] FIG. 2 illustrates a configuration of a frequency offset calculation unit according to the first embodiment; [Figure 8] FIG. 2 is a diagram illustrating a configuration of a rotator unit according to the first embodiment. [Figure 9] FIG. 11 illustrates an AFC and synchronization acquisition processing unit according to a second embodiment. [Figure 10] FIG. 13 is a diagram illustrating a configuration of a rotator unit according to a second embodiment. [Figure 11] FIG. 13 illustrates an AFC and synchronization acquisition processing unit according to a third embodiment. [Figure 12] FIG. 13 is a diagram illustrating a configuration of a frequency offset integration unit according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] In an embodiment of the present invention, in order to solve the above-mentioned problems, as a first solution, the cross-correlation between a preamble signal obtained by dividing a signal in a preamble section into a plurality of sections and a predetermined reference signal is calculated, a phase change vector described later is calculated for each divided section, the number of divisions at which a frequency offset can be detected is determined, and the phase change vector with the longest correlation width, i.e., the smallest number of divisions, is selected.

[0024] For phase change vectors with a small number of divisions, for example, the maximum detected power of the phase change vector for each division number can be compared and the division number resulting in the maximum detected power can be selected, or the maximum power of the phase change vector for each division number can be compared with a predetermined threshold value and the phase change vector with the smallest division number that exceeds the threshold value can be selected.

[0025] The change angle of the maximum power position of the selected phase change vector is used to calculate the frequency offset.

[0026] As a second solution, automatic frequency control (AFC) is performed in the first stage based on the frequency offset detection value in a phase change vector in which the number of divisions of the preamble section is large, and frequency offset correction is performed in a multi-stage connection based on the frequency offset detection value in a phase change vector in which the number of divisions of the preamble section in the next stage is smaller than that in the previous stage, thereby widening the frequency detection range and reducing the detection error by the multi-stage connection processing.

[0027] Furthermore, as a third solution, a frequency offset in a phase change vector having a large number of divisions of the preamble section of the received signal is detected and fed back initially, and the sum of the frequency offset detection value in a phase change vector having a small number of divisions of the preamble section of the signal that has been reverse-rotated and corrected using the fed back frequency offset and the previous frequency offset detection value is fed back, and the above-mentioned steps are repeated to widen the frequency detection range and reduce the detection error.

[0028] When the phase change vector matches the original preamble, a power peak value is obtained, and the position of the maximum value indicates the end of the preamble signal. This position is the same as the maximum peak position of the cross-correlation calculation result with the preamble signal in general synchronization acquisition processing, and detection equivalent to synchronization acquisition processing is possible.

[0029] <First Example> FIG. 1 is a diagram showing an AFC and synchronization acquisition processing unit of a reception processing unit of a wireless communication device according to a first embodiment of the present invention.

[0030] The AFC and synchronization acquisition processing unit of the first embodiment has a cross-correlation calculation unit 1, a differential detection calculation unit 2, a phase change vector selection unit 3, a frequency offset calculation unit 4, and a rotator 5. In the following description, when it is not necessary to distinguish between the calculation units of each series, the suffixes will be omitted.

[0031] The cross-correlation calculation unit 1-m and the differential detection calculation unit 2-m perform calculations for different division numbers, where m=1, 2, 3, ..., M, and M is the number of types of division numbers.

[0032] The conventional phase change vector calculation method that is the premise of the method will be described with reference to Fig. 2. A cross-correlation calculation is performed on successive preamble signals P1 and P2, and a phase change vector is calculated by performing differential detection of the maximum peak values ​​of each signal.

[0033] In this embodiment, the phase change vector is calculated by dividing the original preamble signal as shown in Fig. 3 into small sections. Here, L is the original preamble size, N is the number of original preambles, and S is the number of divisions. When S=1, it is the same as the conventional method in which no division is performed. This preamble signal has a signal pattern that is known between the wireless transmitting device and the wireless receiving device, and the wireless transmitting device adds the preamble signal to the beginning of the transmission frame and transmits it.

[0034] FIG. 4 is a diagram showing the configuration of the cross-correlation calculation unit 1. As shown in FIG.

[0035] The cross-correlation calculation unit 1 performs a cross-correlation calculation between the input received signal and a reference signal (transmission preamble signal), and outputs the calculation result to the differential detection calculation unit 2 .

[0036] As shown in Fig. 4, the cross-correlation calculation unit 1 has a complex multiplier 11 and a summation calculator 12. When the preamble length is L, the cross-correlation calculation unit 1 calculates a cross-correlation value Ci(n) of the n-th sample in the i-th preamble section by using the complex multiplier 11 and the summation calculator 12 according to Equation 1. In Equation 1, y(n) is the received signal, i is the index of a small section where i = 1, 2, 3, ..., S·N, ri(k) is the signal value of the reference signal in that small section, k is the sample index of the reference signal in that small section, and * is the complex conjugate.

[0037]

number

[0038] FIG. 5 is a diagram showing the configuration of the differential detection calculation unit 2. As shown in FIG.

[0039] The differential detection calculation unit 2 performs differential detection calculation on the cross-correlation values ​​Ci(n) of the short interval obtained by the cross-correlation calculation unit 1 to calculate a phase change vector, and outputs it to the phase change vector selection unit 3.

[0040] 5, the differential detection calculation unit 2 has a complex conjugator 21, a complex multiplier 22, and a summation calculator 23. The differential detection calculation unit 2 performs differential detection calculation and summation calculation using the complex conjugator 21, the complex multiplier 22, and the summation calculator 23, and calculates the phase change vector D(n) by Equation 2.

[0041]

number

[0042] FIG. 6 is a diagram showing a configuration of the phase change vector selection unit 3. As shown in FIG.

[0043] The phase change vector selection unit 3 selects a phase change vector D′m(n) that satisfies the frequency offset detection range and has the maximum correlation gain from the phase change vectors Dm(n) calculated for each division number, and outputs the selected vector to the frequency offset calculation unit 4 .

[0044] 6, the phase change vector selection unit 3 has a power calculator 31, a maximum value detector 32, and a selector 33. The phase change vector selection unit 3 uses the power calculator 31 and the maximum value detector 32 to calculate the maximum value detection value Dm,max according to Equation 3. In Equation 3, a in [a,b]=max(·) indicates the maximum value, b indicates the index of the maximum value, and Pm indicates the maximum value position of each |Dm(n)|2.

[0045]

number

[0046] The selector 33 compares each Dm,max with a threshold value γν, selects a phase change vector with the minimum division number that exceeds the threshold value, and outputs it as D'(n) to the frequency offset calculation unit 4. Note that the selector 33 may select a phase change vector with the largest maximum value detection power among phase change vectors with multiple division numbers.

[0047] The frequency offset calculation unit 4 calculates a phase Δθ for compensating for the frequency offset using the input phase change vector D'(n), and outputs it to the rotator unit 5. In addition, although it is not directly used for frequency offset compensation, it outputs the detected frequency offset Δf for confirmation display or logging.

[0048] FIG. 7 is a diagram showing the configuration of the frequency offset calculation unit 4. As shown in FIG.

[0049] The frequency offset calculation unit 4 has a power calculator 41, a maximum value position detector 42, an angle calculator 43, and an offset calculator 44. Using the power calculator 41 and the maximum value position detector 42, the frequency offset calculation unit 4 calculates the maximum value D'max and the maximum value position PSYNC according to Equation 4, and outputs the maximum value position PSYNC to an angle calculator 72. The maximum value position PSYNC is the synchronization capture position, and indicates the tail end position of the preamble.

[0050]

number

[0051] Angle calculator 43 uses the maximum value D(Pk) to calculate the change angle Δθ per sample according to formula 5, and outputs the result to frequency offset calculation 74 and rotator unit 5. In formula 5, Re[ ] indicates the real part, and Im[ ] indicates the imaginary part. If the numerator of formula 5 exceeds ±π, the rotation direction becomes unclear and there is a possibility of erroneous frequency offset detection. If L / S is large, that is, if the number of divisions is small, the numerator of formula 5 is more likely to exceed ±π, and the frequency offset detection range in which it can be detected correctly becomes narrower.

[0052]

number

[0053] The offset calculator 44 uses the inputted change angle Δθ to calculate and output the frequency offset Δf according to Equation 6. In Equation 6, fs is the sampling frequency.

[0054]

number

[0055] The rotator unit 5 uses the inputted change angle Δθ to perform reverse rotation correction of the rotation caused by the frequency offset on the received signal y(n), and outputs a frequency offset correction signal yAFC(n).

[0056] FIG. 8 is a diagram showing the configuration of the rotator unit 5. As shown in FIG.

[0057] The rotator unit 5 has an adder 51, a one-sample delay unit 52, an exponential function converter 53, and a complex multiplier 54. The rotator unit 5 uses the adder 51 and the one-sample delay unit 52 to perform an integral calculation of the angle according to Equation 7, and outputs the calculation result to the exponential function converter 53.

[0058]

number

[0059] The exponential function converter 53 uses the input Δθc(n) to obtain e -jθc(n) Convert to e -jθc(n) to the complex multiplier 54. Here, j is the imaginary unit. Also, e -jθc(n) According to Euler's formula, cosθ c (n) and sinθ c Since it is expressed as (n), in reality it is converted to a trigonometric function.

[0060]

number

[0061] The complex multiplier 54 multiplies the received signal y(n) and e by Equation 9. -jθc(n) and outputs the frequency offset correction result yAFC(n).

[0062]

number

[0063] According to the first embodiment described above, the optimum frequency offset can be detected by selecting the correlation width that satisfies the frequency offset detection range and has the highest detection accuracy, and the reception performance can be improved by automatic frequency control. In addition, the intermediate calculation results of the frequency offset detection are used to perform synchronization acquisition processing, so the amount of calculation can be reduced.

[0064] <Second Example> FIG. 9 is a diagram showing an AFC and synchronization acquisition processing unit in a reception processing unit of a wireless communication device according to a second embodiment of the present invention.

[0065] The AFC and synchronization acquisition processing unit of the second embodiment has a cross-correlation calculation unit 1, a differential detection calculation unit 2, a frequency offset calculation unit 4, and a rotator unit 6. Since the cross-correlation calculation unit 1, the differential detection calculation unit 2, and the frequency offset calculation unit 4 are the same as those of the first embodiment, their description will be omitted.

[0066] The AFC and synchronization acquisition processing unit of the second embodiment is configured by connecting a cross-correlation calculation unit 1, a differential detection calculation unit 2, a frequency offset calculation unit 4, and a rotator 6 in multiple stages. The first stage has a large division number S, i.e., a wide frequency offset detection range, and the later stages have a smaller division number S, i.e., the frequency offset detection range becomes narrower but the detection accuracy becomes higher. The final M stages are preferably configured with a division number S=1, i.e., no division. For example, in the case of a four-stage configuration, the division number S of the first stage is preferably 8, the division number S of the second stage is preferably 4, the division number S of the third stage is preferably 2, and the division number S of the final fourth stage is preferably 1. The first stage performs coarse frequency offset detection, and the later stages perform fine frequency offset detection of the remaining difference.

[0067] FIG. 10 is a diagram showing the configuration of the rotator unit 6 of the second embodiment.

[0068] The rotator unit 6 has an adder 61, an adder 51, a one-sample delay unit 52, an exponential function converter 53, and a complex multiplier 54. The adder 51, the one-sample delay unit 52, the exponential function converter 53, and the complex multiplier 54 are the same as those in the first embodiment, so their description will be omitted.

[0069] The adder 61 calculates an angle Δθ corresponding to the frequency offset of the previous stage. AFC(m-1) and the angle Δθm corresponding to the frequency offset calculated at that stage is added, and the angle Δθ corresponding to the cumulative frequency offset up to that stage is calculated by Equation 10. AFCm The Δθ input to the first stage is calculated and output to the rotator 6-m+1 in the subsequent stage and the adder 51. AFC(m-1) is set to 0.

[0070]

number

[0071] According to the second embodiment described above, multiple frequency offset detection stages are provided, so that the division number S is reduced with each stage, and even if the frequency offset is large, the reception performance can be improved compared to the first embodiment. However, the implementation scale increases by the number of stages.

[0072] <Third Example> FIG. 11 is a diagram showing an AFC and synchronization acquisition processing unit in a reception processing unit of a wireless communication device according to a third embodiment of the present invention.

[0073] The AFC and synchronization acquisition processing unit of the third embodiment has a rotator 5, a cross-correlation calculation unit 1, a differential detection calculation unit 2, a frequency offset calculation unit 4, and a frequency offset integration unit 7. The rotator 5, the cross-correlation calculation unit 1, the differential detection calculation unit 2, and the frequency offset calculation unit 4 are the same as those of the first embodiment, so their description will be omitted.

[0074] The AFC and synchronization acquisition processing unit of the third embodiment is configured to repeatedly process at a predetermined timing (for example, the calculation period from the rotator 5 to the frequency offset integration unit 7) using the rotator 5, the cross-correlation calculation unit 1, the differential detection calculation unit 2, the frequency offset calculation unit 4, and the frequency offset integration unit 7. The division number S is large at the first time, i.e., the frequency offset detection range is wide, and as the number of repetitions increases, the division number S is made smaller, i.e., the frequency offset detection range is made narrower, thereby successively increasing the detection accuracy. It is desirable to repeat the process with the division number S=1 at the final time, i.e., no division. For example, if the number of repetitions is four, it is desirable to repeat the process with the division number S=8 at the first time, the division number S=4 at the second time, the division number S=2 at the third time, and the division number S=1 at the fourth time. Coarse frequency offset detection is performed at the first time, and fine frequency offset detection of the remaining difference is performed at the second and subsequent repetitions.

[0075] FIG. 12 is a diagram showing a configuration of the frequency offset integrator 7 of the third embodiment.

[0076] The frequency offset integrator 7 has an adder 71 and an update interval delayer 72. Using the adder 71 and the update interval delayer 72, the frequency offset integrator 7 calculates an angle Δθ corresponding to the frequency offset that reflects the update to the frequency offset correction of the angle Δθ' corresponding to the frequency offset applied to the rotator, by using Equation 11, as the angle Δθ' corresponding to the frequency offset of the previous iteration. τ-1 The angle Δθ′ corresponding to the new frequency offset to be applied to the rotator is added to τ The Δθ′ input is calculated and output to the rotator 5. τ-1 is set to 0.

[0077]

number

[0078] According to the third embodiment described above, the frequency offset detection process is repeated and the division number S is reduced with each repetition, so that even if the frequency offset is large, the reception performance can be improved compared to the first embodiment and the implementation scale can be reduced compared to the second embodiment. However, since it is a repetitive process, pipeline processing is not possible and it is necessary to hold or delay the received signal until all repetitions are completed, which requires implementation and generates a delay time.

[0079] Since the present invention is characterized by the reception processing unit of the wireless communication device, the embodiment has been described, particularly the AFC processing unit and the synchronization acquisition unit of the reception processing unit. In addition to the detailed description in the embodiment, the wireless communication device has a frequency converter, a power amplifier, a transmission / reception antenna, a low-noise amplifier, a modulation / demodulation unit, etc., but since these are general functions that are not related to the essence of the present invention, their description is omitted. The reception processing unit of the wireless communication device is connected in the order of, for example, a reception antenna, a low-noise amplifier, a frequency converter, an A / D converter, a digital down converter, the AFC and synchronization acquisition processing unit of the present invention, a demodulation unit, and a decoding unit, and is mainly arranged in the front stage of the demodulation unit, and demodulates a signal whose frequency offset has been corrected by the present invention at the synchronization timing detected by the present invention. Furthermore, the present invention can be applied not only to a wireless communication device having a receiving function, but also to a wireless communication device having a transmitting function and a receiving function, and a wireless communication system composed of a wireless transmitting device and a wireless receiving device.

[0080] As described above, according to the embodiments of the present invention, by selecting a phase change vector with the minimum number of divisions of a preamble signal that can detect the frequency offset of a received signal, it is possible to simultaneously provide frequency offset detection means, frequency offset correction means, and synchronization acquisition means with the maximum detection accuracy that satisfies the frequency offset detection range of the received signal from a single phase change vector, thereby improving reception quality and reducing the implementation scale.

[0081] Furthermore, by using multi-stage connection or iterative processing, even if the correlation width is shortened in the first stage or initial processing to widen the detection range, the correlation width can be lengthened each time the number of stages or the number of iterations is increased, thereby widening the detection range and improving the detection accuracy, and the correct frequency offset can be detected.

[0082] The present invention is not limited to the above-described embodiments, and includes various modified examples and equivalent configurations within the spirit of the appended claims. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the configurations described. Furthermore, a part of the configuration of one embodiment may be replaced with the configuration of another embodiment. Furthermore, the configuration of another embodiment may be added to the configuration of one embodiment. Furthermore, a part of the configuration of each embodiment may be added, deleted, or replaced with another configuration.

[0083] In addition, each of the above-mentioned configurations, functions, processing units, processing means, etc. may be realized in hardware, for example by designing some or all of them as an integrated circuit, or may be realized in software by a processor interpreting and executing a program that realizes each function.

[0084] Information such as programs, tables, and files that realize each function can be stored in a storage device such as a memory, a hard disk, or an SSD (Solid State Drive), or in a recording medium such as an IC card, an SD card, or a DVD.

[0085] In addition, the control lines and information lines shown are those considered necessary for the explanation, and do not necessarily show all the control lines and information lines necessary for implementation. In reality, it can be considered that almost all components are connected to each other. [Explanation of symbols]

[0086] 1...Cross-correlation calculation section 2...Differential detection calculation section 3...Phase change vector selection section 4...Frequency offset calculation section 5...Rotator section 11...Complex multiplier 12...Sum calculation section 21...Complex conjugator 22...Complex multiplier 23...Sum calculation section 31...Power calculator 32...Maximum value detector 33...Selector 41...Power calculator 42...Maximum value position detector 43...Angle calculator 44...Offset calculator 51...Adder 52...1-sample delay section 53...Exponential function converter 54...Complex multiplier 6...Rotator section 61...Adder 7...Frequency offset integration section 71...Adder 72...Update interval delay section

Claims

1. 1. A wireless communication system, comprising: A radio transmitting device and a radio receiving device are provided, the wireless transmitting device adds a preamble signal known between the wireless transmitting device and the wireless receiving device to the beginning of the transmission frame and transmits the transmission frame; The wireless receiving device a cross-correlation calculation unit that calculates a cross-correlation between a preamble signal obtained by dividing a signal of a preamble section of the received transmission frame into a plurality of sections and a predetermined reference signal, and outputs the cross-correlation result; a differential detection calculation unit that performs differential detection on each of the cross-correlation results of the divided sections and calculates a phase change vector; and a phase change vector selection unit that selects a phase change vector to be used for synchronization acquisition using the maximum detected power of each of the phase change vectors calculated by summing the results of the differential detection for each section.

2. 2. The wireless communication system according to claim 1, the radio receiving device includes a plurality of the cross-correlation calculation units and a plurality of the differential detection calculation units; each of the cross-correlation calculation units calculates a cross-correlation between the preamble signal divided into different numbers and the reference signal; A wireless communication system, characterized in that each of the differential detection calculation units performs differential detection on cross-correlation results corresponding to different division numbers, and calculates a phase change vector corresponding to each division number.

3. 2. The wireless communication system according to claim 1, The phase change vector selection unit selects the phase change vector with the largest maximum value among the maximum value detected powers of the phase change vectors with a plurality of division numbers, or compares the maximum value detected powers of the phase change vectors with a predetermined threshold value and selects the phase change vector with the smallest division number and whose maximum detected power exceeds the predetermined threshold value.

4. 2. The wireless communication system according to claim 1, The wireless communication system is characterized in that the wireless receiving device includes a frequency offset calculation unit that outputs a frequency offset using a change angle of a maximum power position of the selected phase change vector.

5. 5. The wireless communication system according to claim 4, The wireless communication system is characterized in that the wireless receiving device has a rotator section that corrects the received signal in accordance with the frequency offset.

6. 5. The wireless communication system according to claim 4, the radio receiving device includes a plurality of the cross-correlation calculation units, a plurality of the differential detection calculation units, and a plurality of the frequency offset calculation units; a processing block configured by one of the cross-correlation calculation units, one of the differential detection calculation units, and one of the frequency offset calculation units is connected in multiple stages; A wireless communication system, characterized in that the processing blocks perform calculations by dividing the interval into smaller numbers as they go to later stages.

7. 7. The wireless communication system according to claim 6, the processing block includes a rotator unit at a subsequent stage of the frequency offset calculation unit, the rotator unit calculating a cumulative frequency offset up to that stage; The radio communication system according to claim 1, wherein the rotator section outputs a received signal corrected by a frequency offset.

8. 6. The wireless communication system according to claim 5, the wireless receiving device includes a frequency offset integrator that adds the frequency offset at a predetermined timing; the rotator unit corrects the received signal using the frequency offset added by the frequency offset integrator unit; The cross-correlation calculation unit calculating a cross-correlation between a preamble signal obtained by dividing the preamble section of the received signal corrected by the rotator unit into a plurality of sections and a predetermined reference signal, and outputting a plurality of cross-correlation results; A wireless communication system characterized in that calculation processing is performed by reducing the number of divisions according to the number of times of repeated processing.

9. 5. The wireless communication system according to claim 4, The wireless communication system is characterized in that the frequency offset calculation unit outputs the tail of the power peak value obtained by the cross-correlation calculation as a synchronization acquisition position.

10. A wireless receiving device, a cross-correlation calculation unit that calculates a cross-correlation between a preamble signal obtained by dividing a signal of a preamble section of the received transmission frame into a plurality of sections and a predetermined reference signal, and outputs the cross-correlation result; a differential detection calculation unit that performs differential detection on each of the cross-correlation results of the divided sections and calculates a phase change vector; a phase change vector selection unit that selects a phase change vector to be used for synchronization acquisition using the maximum detected power of each of the phase change vectors calculated by summing the results of the differential detection for each section.

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