Spread spectrum communication device, spread spectrum communication system, control circuit, storage medium, and communication method

Abstract

The modulation unit modulates a transmission bit sequence and converts it into a data symbol sequence. The spreading unit uses a spreading code to perform direct spectrum spreading processing on the modulated data symbol sequence to generate a spread signal. The waveform shaping unit upsamples the spread signal and band-limits the transmission spectrum. The frequency conversion unit converts the band-limited spread signal into a plurality of arbitrary carrier frequencies to generate spread signals of the plurality of carrier frequencies. The weighting unit has a plurality of weighting coefficients that have different amplitudes for each spread signal of the plurality of carrier frequencies and whose amplitudes change for each sample of the spread signal of the plurality of carrier frequencies, and multiplies all samples of the spread signal of the plurality of carrier frequencies by the corresponding weighting coefficients, respectively, to generate weighted signals of the spread signals of the plurality of carrier frequencies. The channel synthesis unit adds the weighted signals of the spread signals of the plurality of carrier frequencies to generate a synthesized signal of the spread signals of the plurality of carrier frequencies.

Description

[Technical field]

[0001] The present disclosure relates to a spread spectrum communication device, a spread spectrum communication system, a control circuit, a storage medium, and a communication method for performing spread spectrum communication. [Background technology]

[0002] In wireless communication, harmful radio interference that causes communication failures, whether accidental or intentional, has a serious adverse effect on the operation of wireless communication services. In addition, wireless communication that uses public radio waves is easier to intercept than wired communication due to its characteristics, so information security measures are important. One of the measures against these threats is spread spectrum, which has excellent noise resistance and confidentiality. Spread spectrum is a technology that spreads wireless communication signals over a wide frequency band for communication. Well-known spread spectrum technologies include Frequency Hopping (FH) adopted in the Bluetooth (registered trademark) standard and Direct Sequence Spread Spectrum (DS-SS) adopted in the wireless LAN (Local Area Network) standard (IEEE (Institute of Electrical and Electronics Engineers) 802.11b). In the DS-SS method, a data string is spread over a wide band using a PN (Pseudo Random Noise) code or the like and transmitted, and the original digital data is restored using the same PN code on the receiving side. By spreading the spectrum over a wide band and not concentrating it in a specific band, it is possible to make it less susceptible to interference, and by increasing the spreading rate, it is possible to improve the spreading gain, so it is also used for long-distance wireless communication. However, frequency resources are limited, and it is necessary to secure a wide and continuous frequency band in order to perform spectrum spreading. Therefore, there is a method of collecting multiple available discrete frequencies to secure a spreading band and perform spread spectrum communication. However, there is a problem that the peak factor, which is the ratio of the average power to the peak power of the transmission signal, becomes high when multiple frequency carriers are multiplexed and transmitted, and the transmission spectrum is distorted due to clipping due to amplifier saturation.

[0003] To solve such a problem, the amplifier must be operated in a back-off region where the transmission power is equal to or greater than the peak factor. If the transmission power is kept low, the wireless transmission distance becomes short, and if the transmission power is high, an expensive amplifier with a linear relationship between the input and output of the amplifier is required. As an example, Patent Document 1 discloses a communication system that suppresses the level of a signal by weighting surrounding signals including a peak signal according to the ratio of the instantaneous peak power of a multi-channel multiplexed signal to a predetermined threshold. Patent Document 2 discloses a communication system that reduces the peak factor of a transmission signal by multiplexing the m data by giving different timing offsets to each of the m data in a transmission device that transmits data using m channels, where m is a natural number equal to or greater than 2. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3927521 [Patent Document 2] Patent No. 5478731 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the technology described in Patent Document 1 performs nonlinear processing to suppress the peak factor, which affects the linear system, resulting in a trade-off between communication quality and reduction of the peak factor.The technology described in Patent Document 2 uses linear processing and does not cause a decrease in communication quality, but reduces the peak factor by adjusting the overlap of peak occurrence points using amplitude fluctuations during oversampling of a single carrier signal, which results in no effect when a constant envelope modulation signal with a small peak factor is used.

[0006] The present disclosure has been made in consideration of the above, and aims to provide a spread spectrum communication device that can distribute a spectrum across any number of discrete frequencies to enable spread spectrum communication, while reducing the peak factor during multi-carrier transmission and transmitting with high power efficiency. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, the spread spectrum communication device of the present disclosure includes a modulation unit, a spreading unit, a waveform shaping unit, a frequency conversion unit, a weighting unit, and a channel synthesis unit. The modulation unit modulates a transmission bit sequence using one or more of the phase, frequency, and amplitude of a carrier wave to convert the sequence into a data symbol sequence. The spreading unit performs a direct spectrum spreading process on the modulated data symbol sequence using a spreading code to generate a spread signal. The waveform shaping unit upsamples the spread signal and limits the band of the transmission spectrum. The frequency conversion unit converts the band-limited spread signal into a plurality of arbitrary carrier frequencies to generate spread signals of the plurality of carrier frequencies. The weighting unit has a plurality of weighting coefficients whose amplitudes are different for each of the spread signals of the plurality of carrier frequencies and whose amplitudes change for each sample of the spread signal of the plurality of carrier frequencies, and multiplies all samples of the spread signal of the plurality of carrier frequencies by corresponding weighting coefficients among the plurality of weighting coefficients, respectively, to generate weighted signals of the spread signals of the plurality of carrier frequencies. The channel combiner adds weighted signals of spread signals of a plurality of carrier frequencies to generate a combined signal of the spread signals of a plurality of carrier frequencies. Effect of the Invention

[0008] The spread spectrum communication device according to the present disclosure has the advantage of being able to distribute a spectrum across any number of discrete frequencies to enable spread spectrum communication, while reducing the peak factor during multi-carrier transmission and enabling transmission with high power efficiency. [Brief description of the drawings]

[0009] [Figure 1]FIG. 1 is a schematic diagram illustrating an example of a configuration of a transmission device in a spread spectrum communication system according to a first embodiment; [Diagram 2] FIG. 1 shows an example of weighting coefficients for two frequency channels. [Diagram 3] FIG. 1 shows an example of changing the period of the time window of the weighting coefficients for two frequency channels. [Figure 4] FIG. 3 is a diagram showing an example of a case where the amplitude of the weighting coefficients in FIG. 2 is made different between frequency channels; [Diagram 5] FIG. 3 shows an example of a case where the amplitude of some of the weighting coefficients of frequency channel A is fixed to 1 and the amplitude of some of the weighting coefficients of frequency channel B is fixed to 0 for the weighting coefficients of FIG. [Figure 6] A diagram showing an example of the frequency spectrum of two frequency channel signals after frequency conversion. [Figure 7] FIG. 13 is a diagram showing an example of a frequency spectrum of a frequency channel signal after multiplication by a weighting coefficient. [Figure 8] FIG. 13 is a diagram showing an example of a frequency spectrum of a frequency channel signal after multiplication by a weighting coefficient. [Figure 9] 1 is a flowchart showing an example of a procedure of a communication method according to a first embodiment. [Figure 10] FIG. 1 is a block diagram showing an example of a control circuit for implementing a transmission device according to a first embodiment; [Figure 11] FIG. 13 is a schematic diagram illustrating an example of a configuration of a transmission device in a spread spectrum communication system according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A spread spectrum communication device, a spread spectrum communication system, a control circuit, a storage medium, and a communication method according to embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0011] Embodiment 1 The first embodiment relates to a spread spectrum transmitting device in a spread spectrum communication system, and a modulation process of the spread spectrum transmitting device will be described with reference to Fig. 1 to Fig. 7. In the following, the spread spectrum transmitting device will be referred to as a transmitting device. Also, the spread spectrum communication device includes a transmitting device. The spread spectrum communication system includes a transmitting device and a receiving device, and performs wireless communication between the transmitting device and the receiving device by a spread spectrum communication method.

[0012] Fig. 1 is a diagram illustrating an example of a configuration of a transmission device of a spread spectrum communication system according to a first embodiment. As illustrated in Fig. 1, the transmission device 10 according to the first embodiment includes a modulation unit 103, a spreading unit 104, a waveform shaping unit 105, a frequency conversion unit 106, a weighting unit 107, a channel synthesis unit 108, a digital-to-analog conversion unit 109, a transmission radio frequency unit 110, and a transmission antenna 111. A transmission bit sequence 100, a spreading code 101, and a weighting coefficient 102 are input to the transmission device 10. First, information input to the transmission device 10 will be described, and then each processing unit of the transmission device 10 will be described.

[0013] A transmission bit sequence 100 is transmission information bits or a bit sequence obtained by encoding the transmission information bits, and is input to a modulation section 103 .

[0014] The spreading code 101 is a sequence with a chip period for spreading the modulated signal, which is a signal modulated by the modulation unit 103, and is input to the spreading unit 104. The spreading code 101 may be a PN code, a GOLD code, or a phase rotation sequence in which the frequency changes over time and the amplitude is constant. Here, the length of the spreading code 101 is K chips. In one example, the spreading code 101 is C μ,kWhen it is set in this way, a phase rotation sequence represented by the following formula (1) can be used as the spreading code 101. Here, μ is a coefficient for adjusting the phase rotation amount of the phase rotation sequence represented by the formula (1), and values that are relatively prime to each other are set for the phase rotation sequence length K. Also, k indicates the number corresponding to the k-th position of the phase rotation sequence, and is represented by an integer value of 0 ≦ k < K. Note that the spreading code 101 applied in Embodiment 1 is not limited to these.

[0015]

Number

[0016] The weighting coefficient 102 is a weighting coefficient W for controlling the amplitude of each frequency channel signal before synthesis in order to suppress the peak factor after synthesizing the frequency channel signals after frequency conversion. m Here, a case of spectrum spreading transmission using two frequency channels A and B will be described as an example.

[0017] The weighting coefficient 102 can be a series of samples equal to the number of samples of the spread signal generated by repeating the time window for the length of the spread signal using a time window of multiple sample periods of the spread signal of multiple carrier frequencies. FIG. 2 is a diagram showing an example of each weighting coefficient for two frequency channels. Graph 200 shows the weighting coefficient 1021a of frequency channel A, and graph 201 shows the weighting coefficient 1021b of frequency channel B. In these diagrams, the horizontal axis shows time and the vertical axis shows amplitude. If the number of oversamples for the chip rate is V, the weighting coefficients 1021a and 1021b of frequency channel A and frequency channel B are real number series of length K×V. It is necessary to suppress the spread of the spectrum as much as possible when adjusting the amplitude of the frequency channel signal, and it is desirable to use a time window for the weighting coefficient 1021a of frequency channel A and the weighting coefficient 1021b of frequency channel B. A commonly known Hann window or the like can be used for the time window. However, the time window applied in the first embodiment is not limited to this. If the period of the time window used for the weighting coefficients 1021a and 1021b of frequency channel A and frequency channel B is N, then the weighting coefficients 1021a and 1021b are a sequence in which the time window is repeated {(K×V) / N} times. In addition, the shorter the time window period N, the wider the spectrum of the frequency channel signal after application of the weighting coefficients 1021a and 1021b, and the longer the time window period N, the more the spectrum is suppressed from spreading. For this reason, it is necessary to set the time window period N within a range that can be tolerated by the system.

[0018] In addition, a weighting factor 102 cyclically shifted by a different sample offset is used for each spread signal of a plurality of carrier frequencies. In the case of FIG. 2, in order to suppress a peak factor after synthesis of a frequency channel signal different from the weighting factor 1021a and the weighting factor 1021b, a time window applied between the weighting factor 1021a and the weighting factor 1021b is offset by L samples in the time direction. In one example, if a time window is relatively offset in the time direction between the weighting factor 1021a and the weighting factor 1021b and assigned with an N / 2 sample offset, the amplitude average in the time direction when the weighting factor 1021a and the weighting factor 1021b are added can be made constant, so that it is possible to suppress a peak factor after synthesis of the frequency channels after frequency conversion. The sample offset is also called a time offset.

[0019] The period N of the time window may be changed within the length K×V of the weighting factor 102. The weighting factor 102 may be a first weighting factor, which is a sequence obtained by repeatedly using the M time windows and combining them in a random order, and a second weighting factor, which is a number of spread signals of a plurality of carrier frequencies, is generated by cyclically shifting the M time windows by different sample offsets before combining the first weighting factor. FIG. 3 is a diagram showing an example in which the period of the time window of each weighting factor for two frequency channels is changed. Graph 300 shows a weighting factor 1022a for frequency channel A, and graph 301 shows a weighting factor 1022b for frequency channel B. In these diagrams, the horizontal axis indicates time, and the vertical axis indicates amplitude. The weighting factor 1022a for frequency channel A and the weighting factor 1022b for frequency channel B in FIG. 3 are examples in which two types of time windows, period N1 and period N2, are used. The timing for switching between the period N1 and the period N2 is the same for the weighting coefficient 1022a and the weighting coefficient 1022b. In addition, a time offset L1 and a time offset L2 are applied between the weighting coefficient 1022a and the weighting coefficient 1022b for each period of the time window. In this example, two types of periods N1 and N2 are used, but the weighting coefficients may be generated using three or more periods. In this way, by randomly changing the periods of the weighting coefficients 1022a and 1022b, the frequency channel signal with the spectrum dispersed is converted into a signal with more complex time amplitude fluctuation, making it difficult for the receiving side to restore the signal, and improving confidentiality.

[0020] Also, the weighting coefficient 102 assigned to each frequency channel may have a different average amplitude. That is, the weighting coefficient 102 may have a different average amplitude for each spread signal of a plurality of carrier frequencies. FIG. 4 is a diagram showing an example of a case where the amplitude of the weighting coefficient is made different between frequency channels for the weighting coefficients in FIG. 2. Graph 400 shows the weighting coefficient 1023a of frequency channel A, and graph 401 shows the weighting coefficient 1023b of frequency channel B. In these diagrams, the horizontal axis shows time, and the vertical axis shows amplitude. FIG. 4 shows an example of a case where the maximum amplitude of the weighting coefficient 1023a of frequency channel A is set to 1, and a case where the maximum amplitude of the weighting coefficient 1023b of frequency channel B is set to 1 / √2. In this way, by making the amplitudes of the weighting coefficients 1023a and 1023b different between frequency channels, a power difference can be given between frequency channels after spectrum dispersion, and power control can be performed according to the line quality of each frequency channel.

[0021] Also, the amplitude of a part of the weighting coefficient 102 may be set to 0, and a time to stop transmission may be generated for each spread signal of the carrier frequency, i.e., for each frequency channel. The amplitude of a part of the weighting coefficient 102 may be fixed to a fixed value, for example, 1, and a time to continuously transmit the frequency channel signal input without amplitude control may be generated for each spread signal of the carrier frequency, i.e., for each frequency channel. By setting the amplitude to a fixed value, the transmission power can be made constant. FIG. 5 is a diagram showing an example in which the amplitude of a part of the weighting coefficient of frequency channel A is fixed to 1 and the amplitude of a part of the weighting coefficient of frequency channel B is fixed to 0, with respect to the weighting coefficients of FIG. 2. Graph 500 shows the weighting coefficient 1024a of frequency channel A, and graph 501 shows the weighting coefficient 1024b of frequency channel B. In these diagrams, the horizontal axis shows time, and the vertical axis shows amplitude.

[0022] Returning to Fig. 1, each processing unit of the transmission device 10 will be described. The modulation unit 103 performs primary modulation on the transmission bit sequence 100 using one or more of the phase, frequency, and amplitude of the carrier wave, and converts it into a data symbol sequence. Examples of the modulation method in the primary modulation are PSK (Phase Shift Keying) and FSK (Frequency Shift Keying). However, the modulation method applied in the first embodiment is not limited to these. The data symbol sequence output by the modulation unit 103 is input to the spreading unit 104.

[0023] The spreading unit 104 has the input spreading code 101, and performs direct spectrum spreading processing on the data symbol sequence modulated by the modulation unit 103 using the spreading code 101 to generate a baseband spread signal. The baseband spread signal is also called a spread signal. In the direct spectrum spreading processing, for example, the spreading code 101 is multiplied by the data symbol sequence output from the modulation unit 103 to generate a K-chip spread signal.

[0024] The waveform shaping section 105 upsamples the spread signal output from the spreading section 104 and also limits the band of the transmission spectrum, thereby shaping the waveform of the spread signal.

[0025] The frequency conversion unit 106 converts the band-limited spread signal into a plurality of arbitrary carrier frequencies, and generates spread signals of the plurality of carrier frequencies. In one example, the frequency conversion unit 106 generates an IF (Intermediate Frequency) frequency channel signal by converting one baseband spread signal after waveform shaping into the carrier frequency of one or more arbitrary frequency channels. However, when there is one frequency channel signal input, the input signal is output as is. FIG. 6 is a diagram showing an example of the frequency spectrum of two frequency channel signals after frequency conversion. Frequency channels 602, 603, and 604 represent frequencies in use. Frequency channel A and frequency channel B respectively represent vacant frequencies f A ,f BThe frequency conversion unit 106 has a function of converting the IF frequency channel signals into a plurality of arbitrary discrete IF frequency channel signals in this manner. In the first embodiment, the IF frequency channel signals are generated by frequency conversion, but they may be directly converted into RF (Radio Frequency) signals. The IF frequency channel signals and the RF signals correspond to spread signals of a plurality of carrier frequencies.

[0026] 1, the weighting unit 107 has multiple weighting coefficients 102, the amplitude of which is different for each spread signal of the multiple carrier frequencies and the amplitude of which changes for each sample of the spread signal of the multiple carrier frequencies, and multiplies all samples of the spread signal of the multiple carrier frequencies by corresponding weighting coefficients 102 out of the multiple weighting coefficients 102, respectively, to generate weighted signals of the spread signals of the multiple carrier frequencies. In one example, the weighting unit 107 multiplies one or more frequency channel signals by weighting coefficients 102 assigned to each frequency channel.

[0027] As shown in Fig. 2, the weighting unit 107 may use a time window of multiple sample periods of the spread signal of multiple carrier frequencies, and repeat the time window for the length of the spread signal to generate a sequence of the same number of samples as the spread signal, and cyclically shift the sequence by a sample offset that differs for each spread signal of multiple carrier frequencies to generate multiple weighting coefficients 1021a and 1021b, and multiply each of the spread signals of multiple carrier frequencies by the corresponding weighting coefficients 1021a and 1021b to generate weighted signals of the spread signals of multiple carrier frequencies. Fig. 7 is a diagram showing an example of the frequency spectrum of the frequency channel signal after multiplication by the weighting coefficient. Fig. 7 shows a frequency spectrum 700 after frequency channel A is multiplied by the weighting coefficient 1021a shown in Fig. 2, and a frequency spectrum 701 after frequency channel B is multiplied by the weighting coefficient 1021b shown in Fig. 2. As shown in Fig. 7, when the frequency channel signal is multiplied by the weighting coefficients 1021a and 1021b, the frequency channel A and the frequency channel B are transmitted with equal power.

[0028] As shown in Fig. 3, the weighting unit 107 may generate weighted signals of the spread signals of the multiple carrier frequencies by multiplying each of the spread signals of the multiple carrier frequencies by corresponding weighting coefficients 1022a, 1022b among the multiple weighting coefficients 1022a, 1022b having time windows of multiple different periods generated for each of the spread signals of the multiple carrier frequencies. In this case, the multiple weighting coefficients 1022a, 1022b are generated by using M time windows with different sample periods, where M is an integer of 2 or more, as described above, and combining the M time windows repeatedly in a random order as a first weighting coefficient, and by generating second weighting coefficients by cyclically shifting each of the M time windows before combining the first weighting coefficient by a different sample offset for each of the spread signals of the multiple carrier frequencies, the number of which is equal to the number of the spread signals of the multiple carrier frequencies.

[0029] As shown in Fig. 4, the weighting coefficients 1023a and 1023b may make the average amplitude different for each spread signal of the multiple carrier frequencies, and the weighting unit 107 may multiply the spread signals of the multiple carrier frequencies by the weighting coefficients 1023a and 1023b corresponding to each spread signal of the multiple carrier frequencies using the weighting coefficients 1023a and 1023b having different average amplitudes for each spread signal of the multiple carrier frequencies, thereby generating weighted signals of the spread signals of the multiple carrier frequencies. Fig. 8 is a diagram showing an example of the frequency spectrum of the frequency channel signal after multiplication by the weighting coefficient. Fig. 8 shows a frequency spectrum 801 after frequency channel A is multiplied by the weighting coefficient 1023a shown in Fig. 4, and a frequency spectrum 802 after frequency channel B is multiplied by the weighting coefficient 1023b shown in Fig. 4. As shown in Fig. 8, when the weighting coefficients 1023a and 1023b are multiplied to the frequency channel signal, the frequency channel B is transmitted with half the power compared to the frequency channel A. By changing the amplitude ratio of weighting coefficients 1023a, 1023b and multiplying the frequency channel signals in this manner, it is possible to distribute the spectrum to discrete frequency channels and transmit it with a power ratio that corresponds to the amplitude ratio of weighting coefficients 1023a, 1023b for each frequency channel.

[0030] As shown in FIG. 5, the weighting unit 107 may set a part of the weighting coefficient 1024b to an amplitude of 0 and generate a time for stopping transmission for each spread signal of the carrier frequency, or may set the amplitude of the weighting coefficient 1024a to a fixed value and generate a time for making the transmission power constant for each spread signal of the carrier frequency.

[0031] Returning to Fig. 1, the channel synthesis unit 108 adds weighted signals of spread signals of multiple carrier frequencies to generate a synthesized signal of spread signals of multiple carrier frequencies. Specifically, the channel synthesis unit 108 adds multiple frequency channel signals after application of the weighting coefficient 102 to output one synthesized channel signal. However, when there is one weighted frequency channel signal input, the input signal is output as is.

[0032] The digital-to-analog converter 109 converts the digital composite signal obtained after frequency channel synthesis from the channel synthesizer 108 into an analog composite signal. The digital composite signal is also called a transmission digital signal, and the analog composite signal is also called a transmission analog signal.

[0033] The transmission high frequency section 110 performs frequency conversion on the transmission analog signal output from the digital-to-analog conversion section 109, and generates a radio frequency signal that is a transmission signal in a radio frequency band.

[0034] The transmitting antenna 111 emits the radio frequency signal generated by the transmitting high frequency unit 110 as a radio wave.

[0035] Next, a communication method in the transmitting device 10 shown in Fig. 1 will be described. Fig. 9 is a flowchart showing an example of the procedure of the communication method according to the first embodiment. First, the modulator 103 executes a modulation step of modulating the transmission bit sequence 100 using one or more of the phase, frequency, and amplitude of the carrier wave to convert it into a data symbol sequence (step S11). Next, the spreader 104 executes a spreading step of directly performing spectrum spreading processing on the modulated data symbol sequence using the spreading code 101 to generate a spread signal (step S12). After that, the waveform shaping unit 105 executes a waveform shaping step of upsampling the spread signal and limiting the band of the transmission spectrum (step S13).

[0036] Next, the frequency conversion unit 106 executes a frequency conversion step of converting the band-limited spread signal into a plurality of arbitrary carrier frequencies to generate spread signals of the plurality of carrier frequencies (step S14). After that, the weighting unit 107 executes a weighting step of multiplying all samples of the spread signal of the plurality of carrier frequencies by the weighting coefficients 102 to generate weighted signals of the spread signals of the plurality of carrier frequencies (step S15). Here, the weighting coefficients 102 have different amplitudes for the spread signals of the plurality of carrier frequencies and the amplitudes change for each sample of the spread signals of the plurality of carrier frequencies, and the plurality of carrier frequencies are provided for each spread signal of the plurality of frequencies.

[0037] Next, the channel synthesis unit 108 executes a channel synthesis step of adding weighted signals of spread signals of multiple carrier frequencies to generate a composite signal of spread signals of multiple carrier frequencies (step S16). After that, the digital-to-analog conversion unit 109 executes a digital-to-analog conversion step of converting the composite signal of spread signals of multiple carrier frequencies into an analog composite signal (step S17). Next, the transmission high frequency unit 110 executes a radio frequency signal generation step of performing frequency conversion on the analog composite signal to generate a radio frequency signal that is a transmission signal in a radio frequency band (step S18). Then, the transmission antenna 111 executes a radio wave emission step of emitting the radio frequency signal as a radio wave (step S19). This ends the communication method.

[0038] Next, the hardware configuration of the transmitting device 10 according to the first embodiment will be described. The modulating unit 103, the spreading unit 104, the waveform shaping unit 105, the frequency converting unit 106, the weighting unit 107, the channel synthesizing unit 108, the digital-to-analog converting unit 109, and the transmitting high frequency unit 110 of the transmitting device 10 are realized by processing circuits. The processing circuit may be a dedicated hardware, or a control circuit having a memory and a CPU (Central Processing Unit) that executes a program, which is a computer program stored in the memory. Here, the memory corresponds to a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, a magnetic disk, an optical disk, and the like. When the processing circuit is a control circuit having a CPU, the control circuit is, for example, a control circuit 900 having a configuration shown in FIG. 10.

[0039] 10 is a block diagram showing an example of a control circuit that realizes the transmission device according to the first embodiment. As shown in FIG. When the modulation unit 103, spreading unit 104, waveform shaping unit 105, frequency conversion unit 106, weighting unit 107, channel synthesis unit 108, digital-to-analog conversion unit 109 and transmission radio frequency unit 110 of the transmitting device 10 are realized by the control circuit 900 shown in FIG. 10, programs for operating as each of the modulation unit 103, spreading unit 104, waveform shaping unit 105, frequency conversion unit 106, weighting unit 107, channel synthesis unit 108, digital-to-analog conversion unit 109 and transmission radio frequency unit 110 of the transmitting device 10 are stored in the memory 902, and the processor 901 reads out and executes the above programs stored in the memory 902, thereby realizing the modulation unit 103, spreading unit 104, waveform shaping unit 105, frequency conversion unit 106, weighting unit 107, channel synthesis unit 108, digital-to-analog conversion unit 109 and transmission radio frequency unit 110. The memory 902 is also used as a temporary memory for each process performed by the processor 901. Note that some of the modulation unit 103, spreading unit 104, waveform shaping unit 105, frequency conversion unit 106, weighting unit 107, channel synthesis unit 108, digital-to-analog conversion unit 109, and transmission radio frequency unit 110 may be realized by dedicated hardware, and the rest may be realized by the control circuit 900. The dedicated hardware here refers to a single circuit, a composite circuit, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a circuit that combines these.

[0040] As described above, the transmission device 10 of the spread spectrum communication system according to the first embodiment has a function of generating a plurality of frequency channel signals for a direct spread spectrum signal, applying the weighting factor 102 to which different amplitude fluctuations are given by using a time window offset in time for each frequency channel signal, distributing the spectrum to a plurality of arbitrary discrete frequencies, enabling spread communication, while reducing the peak factor during multi-carrier transmission and transmitting with high power efficiency. As a result, since the peak factor can be reduced, it becomes possible to use a highly power-efficient and inexpensive amplifier such as a class C amplifier compared to conventional multi-carrier transmission without weighting, and the wireless transmission distance can also be extended. In addition, by randomly changing the period of the time window applied to the weighting factor 102, the frequency channel signal with the spectrum distributed can be converted into a signal with more complex time amplitude fluctuation, making it difficult to restore the signal on the receiving side, thereby improving confidentiality. Furthermore, by applying the weighting factors 1023a and 1023b with different average amplitudes to each frequency channel, the spectrum can be distributed to discrete frequency channels at a power ratio according to the amplitude ratio of the weighting factors 1023a and 1023b and transmitted.

[0041] Embodiment 2 In the first embodiment, a spread signal is generated in the spreading section 104 and the waveform shaping section 105 using one type of spreading code 101, and multiple frequency channel signals are generated from the single spread signal generated in the frequency conversion section 106. In contrast, in the second embodiment, a case will be described in which multiple spread signals are generated using multiple spreading codes, and multiple frequency channel signals are generated from the multiple spread signals in the frequency conversion section.

[0042] Fig. 11 is a diagram showing a schematic example of a configuration of a transmission device of a spread spectrum communication system according to a second embodiment. The same components as those in the first embodiment are given the same reference numerals, and the description thereof will be omitted. As shown in Fig. 11, in the second embodiment, a spreading code 101A input to a transmission device 10A is different from the spreading code 101 in the first embodiment, and in the transmission device 10A according to the second embodiment, a spreading section 104A, a waveform shaping section 105A, and a frequency conversion section 106A are different from those in the first embodiment, and therefore these will be described below.

[0043] The spreading code 101A includes a plurality of sequences with different chip periods for spreading a modulated signal, and is input to the spreading unit 104A. The plurality of spreading codes 101A may be a PN code, a GOLD code, a phase rotation sequence in which the frequency changes over time and the amplitude is constant, or the like. Here, the length of the spreading code 101A is K chips. In one example, the coefficient μ of the phase rotation sequence expressed by the formula (1) may be changed and used as the plurality of spreading codes 101A. In addition, sequences obtained by cyclically shifting the phase rotation sequence generated by the formula (1) with different shift amounts may be used as the plurality of spreading codes 101A. However, the spreading code 101A applied in the second embodiment is not limited to these.

[0044] The number of spreading units 104A is the same as the maximum number of frequency channels used for transmission. Each of the multiple spreading units 104A multiplies the multiple spreading codes 101A by the data symbol sequence output from the modulation unit 103 to generate multiple spread signals of K chips. However, a configuration may be adopted in which only one spreading unit 104A is used to generate multiple spread signals of K chips by time division processing. In this way, the spreading unit 104A has multiple different spreading codes 101A, and performs spectrum spreading processing directly on the modulated data symbol sequence to generate multiple spread signals.

[0045] The number of waveform shaping units 105A is the same as the maximum number of frequency channels used for transmission. Each of the waveform shaping units 105A upsamples the spread signals output from the spreading units 104A and limits the band of the transmission spectrum. However, a configuration may be adopted in which only one spreading unit 104A is used to upsample the spread signals by time division processing and limits the band of the transmission spectrum. The waveform shaping units 105A shape the spread signals.

[0046] The frequency conversion unit 106A converts the multiple band-limited baseband spread signals to an arbitrary carrier frequency, and generates spread signals of the same number of carrier frequencies as the band-limited baseband spread signals. In one example, the frequency conversion unit 106A converts the multiple baseband spread signals after waveform shaping by the multiple waveform shaping units 105A to a carrier frequency of an arbitrary frequency channel, and generates an IF frequency channel signal.

[0047] Using the frequency channel signal generated by frequency conversion unit 106A, the subsequent weighting unit 107, channel synthesis unit 108, digital-to-analog conversion unit 109 and transmission high-frequency unit 110 perform transmission processing similar to that of embodiment 1, and the radio frequency signal generated by transmission high-frequency unit 110 is radiated from transmission antenna 111 as radio waves.

[0048] In this way, in the second embodiment, a plurality of spread signals are generated using a plurality of spreading codes 101A, and a plurality of frequency channel signals are generated from the plurality of spread signals in the frequency conversion unit 106A. This results in dispersing the spread signals by different spreading codes 101A for each frequency channel, and thus has the effect of further complicating signal restoration on the receiving side and realizing further improved confidentiality in addition to the effect of the first embodiment.

[0049] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or the embodiments may be combined with each other. Also, parts of the configurations may be omitted or modified without departing from the spirit of the invention. [Explanation of symbols]

[0050] 10,10A transmitter, 100 transmission bit sequence, 101,101A spreading code, 102,1021a,1021b,1022a,1022b,1023a,1023b,1024a,1024b weighting coefficients, 103 modulation section, 104,104A spreading section, 105,105A waveform shaping section, 106,106A frequency conversion section, 107 weighting section, 108 channel synthesis section, 109 digital-to-analog conversion section, 110 transmission high frequency section, 111 transmission antenna.

Claims

1. a modulation unit that modulates a transmission bit sequence using one or more of a phase, a frequency, and an amplitude of a carrier wave to convert the bit sequence into a data symbol sequence; a spreading unit that performs a direct spectrum spreading process on the modulated data symbol sequence using a spreading code to generate a spread signal; a waveform shaping unit that upsamples the spread signal and limits the band of a transmission spectrum; a frequency conversion unit that converts the band-limited spread signal into a plurality of arbitrary carrier frequencies to generate spread signals of the plurality of carrier frequencies; a weighting unit having a plurality of weighting coefficients, the amplitudes of which are different for each of the spread signals of the plurality of carrier frequencies and the amplitudes of which change for each sample of the spread signals of the plurality of carrier frequencies, multiplying all samples of the spread signals of the plurality of carrier frequencies by corresponding weighting coefficients among the plurality of weighting coefficients, to generate weighted signals of the spread signals of the plurality of carrier frequencies; a channel synthesis unit that adds weighted signals of the spread signals of the plurality of carrier frequencies to generate a synthesized signal of the spread signals of the plurality of carrier frequencies; A spread spectrum communication device comprising:

2. the spreading unit has a plurality of different spreading codes and performs a direct spectrum spreading process on the modulated data symbol sequence to generate a plurality of spread signals; The waveform shaping unit upsamples the plurality of spread signals and performs band limiting of a transmission spectrum, 2. The spread spectrum communication device according to claim 1, wherein the frequency conversion unit converts the band-limited spread signals into an arbitrary carrier frequency and generates spread signals of the same number of carrier frequencies as the band-limited spread signals.

3. 2. The spread spectrum communication device according to claim 1, wherein the weighting section uses a time window of a plurality of sample periods of the spread signals of the plurality of carrier frequencies to generate a sequence of the same number of samples as the spread signals by repeating the time window for a length of the spread signals, and cyclically shifts the sequence by a sample offset that differs for each of the spread signals of the plurality of carrier frequencies to obtain the plurality of weighting coefficients, and multiplies each of the spread signals of the plurality of carrier frequencies by a corresponding weighting coefficient to generate weighted signals of the spread signals of the plurality of carrier frequencies.

4. 4. The spread spectrum communication device according to claim 3, wherein said weighting section includes time windows of M different sample periods, where M is an integer of 2 or more, and generates a first weighting coefficient as a sequence obtained by repeatedly using said M time windows and combining said signals in a random order, and generates second weighting coefficients for each of said spread signals of a plurality of carrier frequencies by cyclically shifting each of said M time windows before combining said first weighting coefficients by a different sample offset, the second weighting coefficients being generated for each of said spread signals of a plurality of carrier frequencies, the second weighting coefficients being generated for each of said spread signals of a plurality of carrier frequencies, and the weighting coefficients are generated by multiplying each of said spread signals of a plurality of carrier frequencies by a corresponding weighting coefficient,

5. The weighting coefficients are set so that average amplitudes of the spread signals of the carrier frequencies are different from each other, 2. The spread spectrum communication device according to claim 1, wherein the weighting section multiplies each of the spread signals of the plurality of carrier frequencies by a corresponding weighting factor to generate weighted signals of the spread signals of the plurality of carrier frequencies.

6. 2. The spread spectrum communication device according to claim 1, wherein the weighting unit generates a time for stopping transmission for each spread signal of the carrier frequency by setting an amplitude of a part of the weighting coefficients to 0, or generates a time for making a transmission power constant for each spread signal of the carrier frequency by setting the amplitude to a fixed value.

7. A spread spectrum communication system comprising the spread spectrum communication device according to any one of claims 1 to 6.

8. A control circuit for controlling a communication device that performs spectrum spreading in a spread spectrum communication system, comprising: a modulation step of modulating the transmission bit sequence using one or more of a phase, a frequency, and an amplitude of a carrier wave to convert the bit sequence into a data symbol sequence; a spreading step of performing a direct spectrum spreading process on the modulated data symbol sequence using a spreading code to generate a spread signal; a waveform shaping step of upsampling the spread signal and limiting the band of a transmission spectrum; a frequency conversion step of converting the band-limited spread signal into a plurality of arbitrary carrier frequencies to generate spread signals of the plurality of carrier frequencies; a weighting step of multiplying all samples of the spread signal of the plurality of carrier frequencies by corresponding weighting coefficients among a plurality of weighting coefficients, the weighting coefficients having different amplitudes for the spread signals of the plurality of carrier frequencies and varying in amplitude for each sample of the spread signal of the plurality of carrier frequencies, to generate weighted signals of the spread signal of the plurality of carrier frequencies; a channel synthesis step of adding weighted signals of the spread signals of the plurality of carrier frequencies to generate a synthesized signal of the spread signals of the plurality of carrier frequencies; A control circuit that causes the communication device to execute the above.

9. In the spreading step, a direct spectrum spread process is performed on the modulated data symbol sequence using a plurality of different spreading codes to generate a plurality of spread signals; In the waveform shaping step, the plurality of spread signals are upsampled and a band of a transmission spectrum is limited; 9. The control circuit according to claim 8, wherein in said frequency conversion step, the plurality of band-limited spread signals are converted to an arbitrary carrier frequency, and spread signals of the carrier frequency, the number of which is the same as that of the band-limited spread signals, are generated.

10. 9. The control circuit according to claim 8, wherein in the weighting step, a time window of a plurality of sample periods of the spread signals of the plurality of carrier frequencies is used to repeat the time window for a length of the spread signals to generate a sequence of the same number of samples as the spread signals, and the sequence is cyclically shifted by a sample offset that differs for each of the spread signals of the plurality of carrier frequencies to obtain the plurality of weighting coefficients, and the weighting coefficients are multiplied for each of the spread signals of the plurality of carrier frequencies to generate weighted signals of the spread signals of the plurality of carrier frequencies.

11. 11. The control circuit according to claim 10, wherein M is an integer equal to or greater than two, the control circuit includes M time windows with different sample periods, the M time windows are repeatedly used to combine signals in a random order to obtain a first weighting coefficient, and second weighting coefficients are generated for each of the spread signals of the plurality of carrier frequencies by cyclically shifting the M time windows before combining the first weighting coefficients by different sample offsets, the second weighting coefficients being generated for each of the spread signals of the plurality of carrier frequencies, the second weighting coefficients being generated for each of the spread signals of the plurality of carrier frequencies, the second weighting coefficients being generated for each of the spread signals of the plurality of carrier frequencies by multiplying the spread signals of the plurality of carrier frequencies by the weighting coefficients corresponding thereto, to generate weighted signals for the spread signals of the plurality of carrier frequencies.

12. The weighting coefficients are set so that average amplitudes of the spread signals of the carrier frequencies are different from each other, 9. The control circuit according to claim 8, wherein in the weighting step, the spread signals of the plurality of carrier frequencies are multiplied by the corresponding weighting coefficients to generate weighted signals of the spread signals of the plurality of carrier frequencies.

13. 9. The control circuit according to claim 8, wherein in the weighting step, an amplitude of a part of the weighting coefficients is set to 0 to generate a time for stopping transmission for each spread signal of the carrier frequency, or the amplitude is set to a fixed value to generate a time for making a transmission power constant for each spread signal of the carrier frequency.

14. A storage medium for storing a program for controlling a communication device that performs spectrum spreading in a spread spectrum communication system, comprising: The program is a modulation step of modulating the transmission bit sequence using one or more of a phase, a frequency, and an amplitude of a carrier wave to convert the bit sequence into a data symbol sequence; a spreading step of performing a direct spectrum spreading process on the modulated data symbol sequence using a spreading code to generate a spread signal; a waveform shaping step of upsampling the spread signal and limiting the band of a transmission spectrum; a frequency conversion step of converting the band-limited spread signal into a plurality of arbitrary carrier frequencies to generate spread signals of the plurality of carrier frequencies; a weighting step of multiplying all samples of the spread signal of the plurality of carrier frequencies by corresponding weighting coefficients among a plurality of weighting coefficients, the weighting coefficients having different amplitudes for the spread signals of the plurality of carrier frequencies and varying in amplitude for each sample of the spread signal of the plurality of carrier frequencies, to generate weighted signals of the spread signal of the plurality of carrier frequencies; a channel synthesis step of adding weighted signals of the spread signals of the plurality of carrier frequencies to generate a synthesized signal of the spread signals of the plurality of carrier frequencies; A storage medium for causing the communication device to execute the above.

15. In the spreading step, a direct spectrum spread process is performed on the modulated data symbol sequence using a plurality of different spreading codes to generate a plurality of spread signals; In the waveform shaping step, the plurality of spread signals are upsampled and a band of a transmission spectrum is limited; 15. The storage medium according to claim 14, wherein in the frequency conversion step, the plurality of band-limited spread signals are converted to an arbitrary carrier frequency, and spread signals of the carrier frequency, the number of which is the same as that of the band-limited spread signals, are generated.

16. A communication method in a communication device that performs spectrum spreading in a spread spectrum communication system, comprising: a modulation step in which the communication device modulates a transmission bit sequence using one or more of a phase, a frequency, and an amplitude of a carrier wave to convert the transmission bit sequence into a data symbol sequence; a spreading step in which the communication device performs a direct spectrum spreading process on the modulated data symbol sequence using a spreading code to generate a spread signal; a waveform shaping step in which the communication device upsamples the spread signal and limits the band of a transmission spectrum; a frequency conversion step in which the communication device converts the band-limited spread signal into a plurality of arbitrary carrier frequencies to generate spread signals of the plurality of carrier frequencies; a weighting step in which the communication device multiplies all samples of the spread signals of the plurality of carrier frequencies by corresponding weighting coefficients among a plurality of weighting coefficients, the weighting coefficients having different amplitudes for the spread signals of the plurality of carrier frequencies and varying in amplitude for each sample of the spread signals of the plurality of carrier frequencies, to generate weighted signals of the spread signals of the plurality of carrier frequencies; a channel synthesis step of the communication device adding weighted signals of the spread signals of the plurality of carrier frequencies to generate a synthesized signal of the spread signals of the plurality of carrier frequencies; A communication method comprising:

17. In the spreading step, the communication device performs a direct spectrum spread process on the modulated data symbol sequence using a plurality of different spreading codes to generate a plurality of spread signals; In the waveform shaping step, the communication device upsamples the plurality of spread signals and performs band limiting of a transmission spectrum; 17. The communication method according to claim 16, wherein in the frequency conversion step, the communication device converts the band-limited spread signals into arbitrary carrier frequencies, and generates spread signals of the carrier frequencies as many as the band-limited spread signals.

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