Transmitting device, receiving device, communication system, transmitting method, receiving method, control circuit, and storage medium

Abstract

A transmission device (1) comprises: a plurality of transmission antennas (13a, 13b); a modulation unit (10) that generates a modulation signal; a coding rule selection unit (11) that selects a time-space block coding rule in correspondence to the value of the modulation signal (11); and a STBC coding unit (12), which is a coding unit that performs space-time block coding on the modulation signal using the selected time-space coding rule, thereby generating transmission signals respectively transmitted from the plurality of transmission antennas (13a, 13b).

Description

Technical Field

[0001] The present disclosure relates to a transmission device, a reception device, a communication system, a transmission method, a reception method, a control circuit, and a storage medium that perform transmission diversity.

Background Art

[0002] As modulation methods with a small envelope fluctuation amount and capable of realizing excellent power efficiency, the FSK (Frequency Shift Keying) method, the PSK (Phase Shift Keying) method, etc. are known.

[0003] Also, as a method for improving transmission quality, hitherto, transmission diversity methods in wireless communication systems having a plurality of transmission antennas, such as a MISO (Multi Input and Single Output) system and a MIMO (Multiple Input and Multiple Output) system, have been proposed.

[0004] As one of the transmission diversity methods, Non-Patent Document 1 discloses an STBC (Space-Time Block Code) technique that is a space-time block code. In the STBC technique, a plurality of orthogonal sequences are generated by performing complex conjugation and code inversion on a plurality of temporally consecutive symbols, and each of the orthogonal sequences is transmitted from a different transmission antenna. In the STBC technique, the transmission sequence is orthogonally coded in two dimensions of time and space. The coding in the STBC technique, that is, STBC coding, is generally called Alamouti coding. A reception device that receives an STBC-coded transmission signal can easily estimate the transmission bit sequence by performing decoding using channel information on the received two symbols. Thereby, in the STBC technique, a diversity gain corresponding to the number of transmission antennas, that is, a full transmission diversity gain can be obtained.

Prior Art Documents

Non-Patent Documents

[0005] [Non-Patent Document 1] S.M. Alamouti, “A Simple Transmit Diversity Technique for Wireless Communications,” IEEE Journal on Select Areas in Communications, Vol. 16, No. 8, pp. 1451-1458, October 1998. [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] However, in the STBC technique, there is a sign inversion process between two temporally consecutive symbols in the signal transmitted from one transmit antenna. For this reason, when STBC coding is applied to a signal modulated by an FSK modulation method or the like in which one symbol is composed of a plurality of samples, there is a problem that the amount of variation of the envelope increases because the amplitude value periodically drops to 0 at the symbol boundary.

[0007] The present disclosure has been made in view of the above, and an object thereof is to obtain a transmission device capable of suppressing the amount of variation of the envelope even when STBC coding is applied. [Means for Solving the Problems]

[0008] In order to solve the above-described problems and achieve the object, a transmission device according to the present disclosure includes a plurality of transmit antennas, By frequency offset modulation a modulation unit that generates a modulation signal, In the frequency carrier of the modulation signal modulated by frequency offset modulation, so that different spatio-temporal block coding rules are applied to adjacent frequency carriers in the frequency domain a code rule selection unit that selects a space-time block code rule according to the value of the modulation signal, and an encoding unit that generates transmission signals to be transmitted from each of the plurality of transmit antennas by performing space-time block coding on the modulation signal using the selected space-time block code rule, and is characterized by including the above. [Effects of the Invention]

[0009] The transmission device according to the present disclosure has an effect of being able to suppress the amount of variation in the envelope even when STBC coding is applied.

Brief Description of the Drawings

[0010]

Figure 1

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Modes for Carrying Out the Invention

[0011] Hereinafter, a transmission device, a reception device, a communication system, a transmission method, a reception method, a control circuit, and a storage medium according to embodiments of the present disclosure will be described in detail with reference to the drawings.

[0012] Embodiment 1. Fig. 1 is a diagram showing a configuration example of a communication system 3 according to Embodiment 1. The communication system 3 includes a transmission device 1 and a reception device 2.

[0013] The transmission device 1 includes a modulation unit 10, a coding rule selection unit 11, a STBC encoding unit 12, and a plurality of transmission antennas 13a and 13b. Hereinafter, when it is not necessary to distinguish each of the transmission antennas 13a and 13b, it may be simply referred to as the transmission antenna 13.

[0014] The modulation unit 10 generates a modulation signal by frequency offset modulation. Specifically, the modulation unit 10 performs primary modulation on the input transmission bit sequence by the FSK method. That is, the modulation unit 10 maps the transmission bit sequence to an FSK modulation symbol sequence. The transmission bit sequence may be a bit sequence subjected to preprocessing such as interleaving and error correction coding. Hereinafter, the modulation signal primarily modulated by the FSK method is also referred to as an FSK signal.

[0015] The coding rule selection unit 11 selects the STBC coding rule to be used in the STBC encoding unit 12 according to the value of the signal primarily modulated by the modulation unit 10. Although the detailed method for the coding rule selection unit 11 to select the STBC coding rule will be described later, the coding rule selection unit 11 selects one of two STBC coding rules with different positions of negative codes according to the carrier frequency of the FSK signal.

[0016] The STBC encoding unit 12 performs space-time block coding on the signal primarily modulated by the modulation unit 10 using the STBC coding rule selected by the coding rule selection unit 11, thereby generating transmission signals to be transmitted from each of the plurality of transmission antennas 13a and 13b, and is an example of an encoding unit that outputs each of the generated plurality of transmission signals to the corresponding transmission antennas 13a and 13b.

[0017] The transmission antennas 13a and 13b radiate the transmission signals output from the STBC encoding unit 12 as radio waves.

[0018] Further, the transmission device 1 may add a CP (Cyclic Prefix) to the STBC encoding result or perform post-processing such as spreading. When adding a CP, for example, between the STBC encoding unit 12 and each of the transmission antennas 13a and 13b, a CP addition unit for the number of transmission antennas 13 is provided, and the STBC encoding unit 12 outputs the processed signal to the corresponding CP addition unit. The CP addition unit adds a CP to the signal output from the STBC encoding unit 12 and outputs the signal after CP addition to the corresponding transmission antenna 13. Also, when performing spreading, for example, between the STBC encoding unit 12 and each of the transmission antennas 13a and 13b, a spreading processing unit for the number of transmission antennas 13 is provided. The STBC encoding unit 12 outputs the processed signal to the corresponding spreading processing unit. The spreading processing unit multiplies the signal output from the STBC encoding unit 12 by a spreading sequence and outputs the signal after spreading processing to the corresponding transmission antenna 13.

[0019] Here, an example in which the transmission device 1 includes two transmission antennas 13 is described, but the transmission device 1 may include three or more transmission antennas 13. That is, the transmission device 1 only needs to include two or more transmission antennas 13. When there are three or more transmission antennas 13, the STBC encoding unit 12 generates transmission signals for the number of transmission antennas 13 and outputs each of the generated transmission signals to the corresponding transmission antenna 13.

[0020] Note that in FIG. 1, among the components of the transmission device 1, the components related to baseband signal processing are illustrated, but the transmission device 1 may include components not illustrated in FIG. 1. For example, in addition to the components shown in FIG. 1, the transmission device 1 may include a filter, an analog unit that performs analog signal processing, and the like.

[0021] In this embodiment, it is assumed that Alamouti coding is used as the transmission diversity method, that is, STBC coding. Also, in this embodiment, the STBC coding unit is called a "block", and the unit of frequency shift modulation, that is, the data unit of FSK modulation, is called a "symbol". The signal modulated by FSK is a signal with a frequency corresponding to the bit value, and becomes a signal sampled at a certain time interval. A "symbol", which is a signal modulated by FSK, is a signal with a frequency corresponding to the bit value, and the time signal constituting the "symbol" is called a "sample".

[0022] In this embodiment, the description is made on the premise that FSK modulation is performed as the primary modulation. However, the method of primary modulation is not limited to FSK modulation, and modulation methods that transmit information based on the phase rotation amount between signal points, such as MSK (Minimum Shift Keying) modulation and GMSK (Gaussian MSK) modulation, may also be used. The method of primary modulation is preferably a modulation method having constant envelope property.

[0023] The receiving device 2 includes a receiving antenna 20, a coding rule selection unit 21, an STBC decoding unit 22, and a demodulation unit 23.

[0024] The receiving antenna 20 receives the signal transmitted from the transmitting device 1 as a received signal, and outputs the received signal to each of the coding rule selection unit 21 and the STBC decoding unit 22.

[0025] The coding rule selection unit 21 selects the same coding rule as the STBC coding rule used in the transmitting device 1, and outputs the selected STBC coding rule to the STBC decoding unit 22. Note that the transmitting device 1 may notify the receiving device 2 of the STBC coding rule used on the transmission side by using a pilot signal or the like included in the transmission signal, or the receiving device 2 may estimate the STBC coding rule used on the transmission side based on the received signal. The method by which the coding rule selection unit 21 selects the STBC coding rule used in the transmitting device 1 is not limited.

[0026] The STBC decoder 22 performs STBC decoding on the received signal using the STBC coding rule selected by the coding rule selection unit 21, and outputs the decoded signal to the demodulation unit 23.

[0027] The demodulation unit 23 performs demodulation corresponding to the FSK method, which is primary modulation, i.e., frequency offset demodulation, on the decoded signal that is the result of decoding by the STBC decoder 22, thereby obtaining an estimated bit sequence that is the estimation result of the transmission bit sequence.

[0028] When preprocessing such as error correction coding is performed on the transmission bit sequence in the transmission device 1, the receiving device 2 performs decoding processing corresponding to the preprocessing such as deinterleaving and error correction decoding on the demodulation result by the demodulation unit 23. When soft decision error correction decoding is performed on the demodulation result by the demodulation unit 23, the demodulation unit 23 may obtain a soft decision value. Also, when CP addition is performed in the transmission device 1, the receiving device 2 includes a CP removal unit that removes the CP after the receiving antenna 20, and the received signal after the CP is removed by the CP removal unit is output to each of the coding rule selection unit 21 and the STBC decoder 22.

[0029] In addition, in FIG. 1, an example in which there is one receiving antenna 20 is shown, but there may be a plurality of receiving antennas 20. When there are a plurality of receiving antennas 20, a receiving diversity decoder (not shown) provided in front of the coding rule selection unit 21 or the coding rule selection unit 21 synthesizes a plurality of received signals received by the plurality of receiving antennas 20, and the STBC decoder 22 performs STBC decoding on the synthesized received signal.

[0030] Note that in FIG. 1, among the components of the receiving apparatus 2, the components related to baseband signal processing are illustrated, but the receiving apparatus 2 may include components not illustrated in FIG. 1. For example, in the receiving apparatus 2, time synchronization processing, frequency synchronization processing, channel estimation, etc. are also performed. However, since general processing can be applied to these processes, illustration and description of the functional units that perform these processes are omitted. In the following description of the operation of the receiving apparatus 2, it is assumed that time synchronization processing, frequency synchronization processing, channel estimation processing, etc. are ideally performed. When time synchronization processing, frequency synchronization processing, channel estimation processing, etc. are not ideally performed, errors may occur, etc. However, since the method for dealing with errors is the same as that of a receiving apparatus that performs general STBC decoding, the description is omitted here.

[0031] Subsequently, the operation of the communication system 3 according to Embodiment 1 will be described. First, the overall operation of the transmitting apparatus 1 will be described. FIG. 2 is a flowchart for explaining an example of the processing procedure of the transmitting apparatus 1 according to Embodiment 1.

[0032] The modulation unit 10 of the transmitting apparatus 1 generates an FSK signal by performing FSK modulation on the input transmission bit sequence (step S101). The modulation unit 10 outputs the generated FSK signal to the code rule selection unit 11 and the STBC encoding unit 12.

[0033] The code rule selection unit 11 selects an STBC code rule based on the FSK signal output by the modulation unit 10 (step S102). The code rule selection unit 11 outputs the selected STBC code rule to the STBC encoding unit 12.

[0034] The STBC symbolization unit 12 generates an STBC-coded signal by performing STBC coding on the samples within the symbol of the FSK signal output by the modulation unit 10 using the STBC coding rule selected by the coding rule selection unit 11. The STBC symbolization unit 12 generates a transmission signal by dividing the STBC-coded signal into signals corresponding to each of the transmission antennas 13a and 13b (step S103). The STBC symbolization unit 12 outputs each of the generated plurality of transmission signals to the corresponding transmission antennas 13a and 13b.

[0035] The FSK signal has the advantage of little envelope fluctuation. However, when STBC coding is performed between symbols, the amplitude value periodically drops to 0 at the symbol boundary due to the code inversion process being performed on temporally consecutive symbols. As a result, the envelope of the transmission signal fluctuates. In the present embodiment, in order to suppress the envelope fluctuation, while maintaining the spatio-temporal orthogonality in STBC coding, STBC coding is performed within the symbol of the FSK signal based on the carrier frequency of the FSK signal so as to reduce the influence of the code inversion process of temporally consecutive symbols. The details of the method for selecting the STBC coding rule and the STBC coding process within the symbol will be described later.

[0036] The transmission antennas 13a and 13b transmit the transmission signal output from the STBC symbolization unit 12 as radio waves toward the receiving device 2 (step S104).

[0037] Next, the functions of the coding rule selection unit 11 and the STBC symbolization unit 12 of the transmission device 1 will be described. The coding rule selection unit 11 selects one of a plurality of STBC coding rules with different positions of negative codes based on the frequency carrier of the FSK signal output from the modulation unit 10. FIG. 3 is a diagram showing the FSK signal in the frequency domain. FIG. 3 shows the FSK signal in the frequency domain having M frequency carriers output from the modulation unit 10. In the coding rule selection unit 11, as shown in FIG. 3, based on the value of the input FSK signal, the STBC coding rule is selected such that different STBC coding rules are applied to adjacent FSK carriers in the frequency domain among the M FSK carriers.

[0038] FIG. 4 is a diagram showing a 4 - valued FSK signal in the frequency domain. The FSK signal shown in FIG. 4 has M = 4, and when the transmission bit sequence is "00", the frequency carrier is f1, when the transmission bit sequence is "01", the frequency carrier is f2, when the transmission bit sequence is "10", the frequency carrier is - f2, and when the transmission bit sequence is "11", the frequency carrier is - f1. The modulation unit 10 selects a frequency corresponding to the transmission bit sequence to generate an FSK signal. The coding rule selection unit 11 selects coding rule #1 when the frequency of the FSK signal is f1 or - f2, and selects coding rule #2 when the frequency of the FSK signal is f2 or - f1, so that different STBC coding rules are selected between adjacent FSK carriers.

[0039] Here, coding rule #1 is represented by the following mathematical formula (1). In mathematical formula (1), x (k) t represents the transmission signal transmitted at the t - th position in the STBC block from the k - th transmission antenna 13. Also, in mathematical formula (1), z t represents the t - th FSK signal in the FSK signal to be STBC - encoded. k and t are natural numbers. The maximum value of t is determined according to the size of the STBC code, and in this embodiment, t = 2. In the configuration example shown in FIG. 1, the transmission antenna 13a is the first transmission antenna 13, and the transmission antenna 13b is the second transmission antenna 13. * indicates complex conjugate.

[0040]

Number

[0041] Also, coding rule #2 is represented by the following mathematical formula (2). Coding rule #2 has a different position of the negative sign from coding rule #1.

[0042]

Number

[0043] FIG. 5 is an explanatory diagram of the encoding procedure of the STBC encoder 12. The STBC encoder 12 performs STBC encoding within the FSK symbols of the FSK signal output from the modulator 10 using the STBC code rule selected by the code rule selection unit 11. Among the FSK signals of one symbol composed of M samples, the STBC encoder 12 uses the FSK samples from the 0th to (M / 2 - 1)th as z0 in Expressions (1) and (2), and the FSK samples from the M / 2th to the (M - 1)th as z1 in Expressions (1) and (2), and uses combinations of FSK samples separated by (M / 2 - 1) samples within the same FSK symbol to perform STBC encoding using the STBC code rule selected by the code rule selection unit 11. Here, the combination of FSK samples separated by (M / 2 - 1) samples refers to a combination in which (M / 2 - 1) FSK samples are sandwiched between two FSK samples.

[0044] FIG. 6 is an explanatory diagram of a specific example of the encoding procedure of the STBC encoder 12 for a 4 - value FSK signal. In FIG. 6, as an FSK symbol composed of 4 samples generated by the modulator 10, for the 0th symbol, the frequency of the FSK signal is f1, that is, the information bit sequence is "00", and for the 1st symbol, the frequency of the FSK signal is f2, that is, the information bit sequence is "01". At this time, the code rule selection unit 11 selects the code rule #1 for the 0th symbol and the code rule #2 for the 1st symbol. The STBC encoder 12 first uses the FSK signal of the 0th sample of the 0th symbol as z0 and the FSK signal of the 2nd sample as z1, and generates an STBC - encoded signal using the code rule #1 shown in Expression (1), and sets the 0th sample of the 0th symbol of the STBC - encoded signal as x (k) 0, and the 2nd sample as x (k) 1. Similarly, using the FSK signal of the 1st sample of the 0th symbol as z0 and the FSK signal of the 3rd sample as z1, an STBC - encoded signal is generated using the code rule #1 shown in Expression (1), and the 1st sample of the 0th symbol of the STBC - encoded signal is set as x (k) 0, and the 3rd sample as x (k) 1. Also, for the 1st symbol of the STBC - encoded signal, it is generated in the same manner as the 0th symbol using the code rule #2.

[0045] Figure 6 shows the transmitted signals TX1 and TX2 after STBC encoding. The transmitted signal TX1 is the signal transmitted from the transmission antenna 13a with k = 1, and the transmitted signal TX2 is the signal transmitted from the transmission antenna 13b with k = 2. Also, Figure 6 shows the signal point transitions in the transmitted signal TX2. The numbers within [] in the figure represent the order of samples within each FSK symbol. For example, [0] refers to the 0th sample. As shown in Figure 6, the signal point transitions at the transmission antenna 13b are continuous within and between FSK symbols, and it can be confirmed that the increase in the envelope fluctuation amount due to STBC encoding can be suppressed.

[0046] In the present embodiment, in the code rule selection unit 11, the STBC code rule is selected according to the frequency of the FSK signal output from the modulation unit 10 so as to select an STBC code rule in which the positions of negative codes are different between adjacent FSK carriers, thereby suppressing the increase in the envelope fluctuation amount between FSK symbols. Further, the STBC encoding unit 12 uses the selected STBC code rule to perform STBC encoding using a combination of the FSK signals from the 0th to (M / 2 - 1)th samples and from the M / 2th to the M - 1th samples of the FSK symbol, whereby the increase in the envelope fluctuation amount within the FSK symbol can be suppressed.

[0047] In the example shown in FIG. 4, when the frequency of the FSK signal output from the modulation unit 10 is f1, that is, when the transmission bit sequence is "00", and when the frequency of the FSK signal is -f2, that is, when the transmission bit sequence is "10", the coding rule #1 represented by the formula (1) is selected. When the frequency of the FSK signal is f2, that is, when the transmission bit sequence is "01", and when the frequency of the FSK signal is -f1, that is, when the transmission bit sequence is "11", the coding rule #2 represented by the formula (2) is selected. However, the assignment of the coding rules may be reversed. That is, the coding rule selection unit 11 may select the coding rule #2 represented by the formula (2) when the frequency of the FSK signal output from the modulation unit 10 is f1, that is, when the transmission bit sequence is "00", and when the frequency of the FSK signal is -f2, that is, when the transmission bit sequence is "10". When the frequency of the FSK signal is f2, that is, when the transmission bit sequence is "01", and when the frequency of the FSK signal is -f1, that is, when the transmission bit sequence is "11", the coding rule #1 represented by the formula (1) may be selected. Also, the STBC coding rule selected by the coding rule selection unit 11 may be other than the STBC coding rules represented by the formula (1) and the formula (2), and a combination of STBC coding rules may be selected such that the STBC coded signals in each transmission antenna 13 are phase continuous within and between symbols.

[0048] Also, when the modulation unit 10 oversamples the FSK signal L times by phase interpolation, a similar effect can be obtained by performing STBC coding using the FSK signals from the 0th to (ML / 2 - 1)th samples and from the ML / 2th to the ML - 1th samples in the STBC coding unit 12.

[0049] As described above, the transmission device 1 according to Embodiment 1 includes a plurality of transmission antennas 13a and 13b, a modulation unit 10 that generates a modulation signal, a code rule selection unit 11 that selects a space-time block code rule according to the value of the modulation signal, and a space-time block encoder that performs space-time block coding on the modulation signal using the selected space-time block code rule to generate transmission signals to be transmitted from each of the plurality of transmission antennas 13a and 13b. The STBC encoder 12. The modulation unit 10 can generate an FSK signal as a modulation signal by performing modulation by the FSK method. Further, the code rule selection unit 11 can select an STBC code rule based on the value of the frequency carrier of the modulation signal modulated by the FSK method. More specifically, the code rule selection unit 11 selects an STBC code rule based on the value of the modulation signal such that different STBC code rules are applied to adjacent frequency carriers in the frequency domain at the frequency carrier of the modulation signal modulated by the FSK method in the first stage. At this time, the code rule selection unit 11 selects an STBC code rule such that STBC code rules with different negative code positions are applied to adjacent frequency carriers in the frequency domain. Further, the STBC encoder 12 performs STBC coding within the FSK symbol using the selected STBC code rule, so that even when STBC coding is applied to a signal modulated by the FSK method in the first stage, compared with conventional STBC coding, An increase in the envelope fluctuation amount of the transmission signal can be suppressed. For example, with the above configuration, an envelope fluctuation amount equivalent to that of the FSK signal at the time of 1 branch before STBC coding can be realized. Therefore, in the present embodiment, it is possible to prevent a decrease in power efficiency in any of the transmission antennas 13 compared with conventional STBC coding. Furthermore, since the space-time orthogonality between the transmission antennas 13 is maintained in the processing in the STBC encoder 12 in the same manner as in conventional STBC coding, it is possible to prevent a decrease in the transmission diversity gain.

[0050] In addition, in the first embodiment, the description was made on the premise that Alamouti coding is used as the STBC coding. However, the STBC coding unit 12 may use STBC coding other than Alamouti coding. The coding method used by the STBC coding unit 12 may be any method that performs coding by complex conjugation and code inversion of signals.

[0051] Next, the hardware configuration for realizing the communication system 3 will be described. The functions of the modulation unit 10, the coding rule selection unit 11, the STBC coding unit 12, the coding rule selection unit 21, the STBC decoding unit 22, and the demodulation unit 23 are realized by a processing circuit which is an electronic circuit.

[0052] This processing circuit may be dedicated hardware, or may be a control circuit including a CPU (Central Processing Unit) that executes a program stored in a memory and the memory.

[0053] When the above processing circuit is realized by dedicated hardware, the processing circuit is a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof.

[0054] When the above processing circuit is a control circuit including a CPU that executes a program stored in a memory and the memory, the control circuit is, for example, the control circuit 300 shown in FIG. 7. FIG. 7 is a diagram showing a configuration example of a control circuit 300 for realizing the functions of the communication system 3 according to the first embodiment. The control circuit 300 has a processor 300a and a memory 300b.

[0055] The processor 300a can realize the functions of the communication system 3 by reading and executing the programs corresponding to the respective processes stored in the memory 300b. The processor 300a is a CPU and is also called an arithmetic unit, a microprocessor, a microcomputer, a DSP (Digital Signal Processor), etc.

[0056] The memory 300b is, for example, a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable ROM), an EEPROM (registered trademark) (Electrically EPROM), a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a DVD (Digital Versatile Disk), etc. Further, the memory 300b is also used as a temporary memory in each process executed by the processor 300a.

[0057] Note that the functions of the modulation unit 10, the coding rule selection unit 11, and the STBC encoding unit 12 of the transmission device 1 may be realized by different processing circuits, or the functions of the modulation unit 10, the coding rule selection unit 11, and the STBC encoding unit 12 may be realized by a single processing circuit. The same applies to the coding rule selection unit 21, the STBC decoding unit 22, and the demodulation unit 23 in the receiving device 2. Further, the functions of the transmission device 1 and the receiving device 2 may be realized by combining dedicated hardware and a CPU. Also, the way of dividing the functional units of the transmission device 1 and the receiving device 2 is an example, and the components described as one functional unit may be realized using a plurality of processing circuits.

[0058] Embodiment 2. FIG. 8 is a diagram showing a configuration example of the modulation unit 10a according to Embodiment 2. Note that the transmission device 1a (not shown) according to Embodiment 2 is the same as the transmission device 1 according to Embodiment 1, except that it has a modulation unit 10a instead of the modulation unit 10. Hereinafter, mainly the parts different from Embodiment 1 will be described, and the description of the parts the same as those in Embodiment 1 will be omitted.

[0059] In Embodiment 1, the modulation unit 10 shown in FIG. 1 used a modulation method that transmits information based on the phase rotation amount between samples, such as FSK modulation, as the primary modulation for the transmission bit sequence. In Embodiment 2, the modulation unit 10a performs spreading on the transmission bit sequence, and by modulating the spread bit sequence using the shift QAM (Quadrature Amplitude Modulation) method of the π / 4 shift QAM method, the same effect as in Embodiment 1 can be obtained. That is, in Embodiment 2, by performing spreading on the modulation method that transmits information based on the phase of each sample point, the envelope fluctuation amount can be kept constant, and the same effect as in Embodiment 1 can be achieved.

[0060] The modulation unit 10a includes a spreading bit generation unit 100 and a shift QAM unit 101.

[0061] The spreading bit generation unit 100 generates a spreading bit sequence from the input transmission bit sequence. Specifically, the spreading bit generation unit 100 generates a spreading bit sequence composed of N samples based on the specified spreading rate N and the modulation method used by the shift QAM unit 101. The spreading bit generation unit 100 outputs the generated spreading bit sequence to the shift QAM unit 101.

[0062] The shift QAM unit 101 performs primary modulation on the spreading bit sequence of N samples output by the spreading bit generation unit 100 using the shift QAM method corresponding to the spreading rate N, and generates a modulation signal including a modulated symbol sequence obtained by mapping. The shift QAM unit 101 outputs the generated modulation signal to each of the code rule selection unit 11 and the STBC encoding unit 12.

[0063] Here, an example will be described in which the spreading rate N of the spreading bit generation unit 100 is 4 and the modulation method used by the shift QAM unit 101 is the π / 4 shift QPSK method. However, the modulation unit 10a is not limited to such an example, and the spreading rate N may be other than 4, or the modulation method used by the shift QAM unit 101 may be a modulation method other than the π / 4 shift QPSK method. For example, the modulation unit 10a may set the spreading rate N of the spreading bit generation unit 100 to 4 and the modulation method used by the shift QAM unit 101 to the π / 4 shift DQPSK (Differential QPSK) method. Further, the modulation unit 10a may set the spreading rate N of the spreading bit generation unit 100 to 2 and the modulation method used by the shift QAM unit 101 to the π / 2 shift BPSK (Binary Phase Shift Keying) method.

[0064] FIG. 9 is an explanatory diagram of the operation of the spreading bit generation unit 100 of the modulation unit 10a shown in FIG. 8. FIG. 9 shows an example in which the spreading rate N of the spreading bit generation unit 100 is 4 and the modulation method used by the shift QAM unit 101 is the π / 4 shift QPSK method. For even symbols, the spreading bit generation unit 100 generates a spreading bit sequence for 4 samples of "00", "00", "01", "01" when the transmission bit sequence is "00", and outputs it to the shift QAM unit 101. Similarly, the spreading bit generation unit 100 generates a spreading bit sequence for 4 samples of "00", "01", "10", "00" when the transmission bit sequence is "01", generates a spreading bit sequence for 4 samples of "00", "11", "01", "10" when the transmission bit sequence is "10", and generates a spreading bit sequence for 4 samples of "00", "10", "10", "11" when the transmission bit sequence is "11". Also, for odd symbols, the spreading bit generation unit 100 generates a spreading bit sequence for 4 samples of "11", "11", "10", "10" when the transmission bit sequence is "00", and outputs it to the shift QAM unit 101. Similarly, the spreading bit generation unit 100 generates a spreading bit sequence for 4 samples of "11", "10", "01", "11" when the transmission bit sequence is "01", generates a spreading bit sequence for 4 samples of "11", "00", "10", "01" when the transmission bit sequence is "10", and generates a spreading bit sequence for 4 samples of "11", "01", "01", "00" when the transmission bit sequence is "11".

[0065] FIG. 10 is an explanatory diagram of the operation of the shift QAM section 101 of the modulation section 10a shown in FIG. 8. The shift QAM section 101 maps the 4-sample spread bit sequence output by the spread bit generation section 100 by the π / 4 shift QPSK method in which the mapping points shift by π / 4 for each sample, and generates a modulation signal. Here, for the even samples, the shift QAM section 101 maps to a phase of "0" when the value of the spread bit sequence is "00" for each sample, to a phase of "π / 2" when the value of the spread bit sequence is "01", to a phase of "-π / 2" when the value of the spread bit sequence is "10", and to a phase of "π" when the value of the spread bit sequence is "11". Also, here, for the odd samples, the shift QAM section 101 maps to a phase of "π / 4" when the value of the spread bit sequence is "00" for each sample, to a phase of "3π / 4" when the value of the spread bit sequence is "01", to a phase of "-π / 4" when the value of the spread bit sequence is "10", and to a phase of "-3π / 4" when the value of the spread bit sequence is "11".

[0066] The code rule selection section 11 of the transmission device 1a selects a code rule based on the value of the N / 2-th sample among the N samples from the 0-th to the (N - 1)-th samples of the modulation signal output from the modulation section 10a. For example, in the case of N = 4 shown in FIGS. 9 and 10, the code rule selection section 11 selects a code rule based on the value of the 2-nd sample among the 4 samples from the 0-th to the 3-rd samples. Specifically, the code rule selection section 11 selects the code rule #1 represented by the above formula (1) when the N / 2-th sample of the modulation signal corresponds to a signal point with a phase of π / 2, and selects the code rule #2 represented by the above formula (2) when the N / 2-th sample of the modulation signal corresponds to a signal point with a phase of -π / 2.

[0067] In the example shown in FIG. 10, in the case of even samples, the shift QAM unit 101 maps signal points on the I / Q axes. However, in the case of odd samples, the signal points may be mapped on the I / Q axes. In this case, for example, when the N / 2-th sample of the modulation signal corresponds to a signal point with a phase of 3π / 4, the code rule selection unit 11 selects the code rule #1 represented by the above formula (1). When the N / 2-th sample of the modulation signal corresponds to a signal point with a phase of -3π / 4, the code rule #2 represented by the above formula (2) may be selected. Also, the correspondence between the code rule and the value of the modulation signal may be reversed. That is, in the above, when the N / 2-th sample of the modulation signal corresponds to a signal point with a phase of π / 2, the code rule #1 is used, and when the N / 2-th sample of the modulation signal corresponds to a signal point with a phase of -π / 2, the code rule #2 is used. However, when the N / 2-th sample of the modulation signal corresponds to a signal point with a phase of -π / 2, the code rule #1 may be selected, and when the N / 2-th sample of the modulation signal corresponds to a signal point with a phase of π / 2, the code rule #2 may be selected.

[0068] The STBC encoding unit 12 of the transmission device 1a performs STBC encoding on the modulation signal output from the modulation unit 10a using the STBC code rule selected by the code rule selection unit 11. The operation of STBC encoding in the STBC encoding unit 12 is the same as that in the first embodiment, and STBC encoding is performed using the combination of the samples from the 0-th to (N / 2 - 1)-th samples and the samples from the N / 2-th to (N - 1)-th samples among the modulation symbols composed of N samples.

[0069] As described above, the transmission device 1a according to the second embodiment can produce the same effects as those of the first embodiment by generating a spread bit sequence, performing shift QAM modulation on the generated spread bit sequence, and further selecting an STBC code rule according to the value of the symbol after shift QAM modulation. Since the configuration and operation on the receiving side in the second embodiment are the same as those of the receiving device 2 according to the first embodiment, the description thereof is omitted.

[0070] As described above, the modulation unit 10a of the transmission device 1a according to the second embodiment includes a spreading bit generation unit 100 that generates a spreading bit sequence from the input transmission bit sequence, and a shift QAM unit 101 that generates a modulation signal from the spreading bit sequence by the shift QAM modulation method. In the case of the spreading rate N, the modulation signal is composed of n samples from the 0th to the (N - 1)th. At this time, the code rule selection unit 11 selects the STBC code rule based on the value of the (N / 2)th sample of the modulation signal. The spreading bit generation unit 100 generates a spreading bit sequence from the transmission bit sequence based on the modulation method used by the shift QAM unit 101 and the predetermined spreading rate N. Even in the transmission device 1a having such a modulation unit 10a, similar to the transmission device 1 according to the first embodiment, an increase in the envelope fluctuation amount of the transmission signal can be suppressed.

[0071] Note that since the hardware configuration of the transmission device 1a is the same as that of the transmission device 1 according to the first embodiment, the description thereof is omitted here.

[0072] The configurations shown in the above embodiments are merely examples, and it is possible to combine them with other known technologies, combine the embodiments with each other, and omit or change a part of the configuration without departing from the gist.

[0073] For example, the code rules #1 and #2 shown by the above formulas (1) and (2) are also examples. For example, if the positions of the negative signs are different between the code rule #1 and the code rule #2, they are not limited to those represented by the formulas (1) and (2).

Explanation of Signs

[0074] 1, 1a Transmission device, 2 Receiver, 3 Communication system, 10, 10a Modulation unit, 11, 21 Code rule selection unit, 12 STBC encoding unit, 13, 13a, 13b Transmission antenna, 20 Receiver antenna, 22 STBC decoding unit, 23 Demodulation unit, 100 Spreading bit generation unit, 101 Shift QAM unit, 300 Control circuit, 300a Processor, 300b Memory.

Claims

1. A plurality of transmission antennas, A modulation unit that generates a modulation signal by frequency offset modulation, A code rule selection unit that selects a space-time block code rule according to the value of the modulation signal so that different space-time block code rules are applied to adjacent frequency carriers in the frequency domain for the frequency carrier of the modulation signal modulated by the frequency offset modulation, An encoding unit that generates a transmission signal to be transmitted from each of the plurality of transmission antennas by performing space-time block encoding on the modulation signal using the selected space-time block code rule, A transmission device characterized by comprising the above.

2. A plurality of transmission antennas, A modulation unit that generates a modulation signal, A code rule selection unit that selects a space-time block code rule according to the value of the modulation signal, An encoding unit that generates a transmission signal to be transmitted from each of the plurality of transmission antennas by performing space-time block encoding on the modulation signal using the selected space-time block code rule, comprising, The modulation unit, A spreading bit generation unit that generates a spreading bit sequence from the input transmission bit sequence, A shift quadrature amplitude modulation unit that generates the modulation signal from the spreading bit sequence by a shift quadrature amplitude modulation method, having, The modulation signal is composed of n samples from the 0th to the (n - 1)th, The code rule selection unit is characterized in that it selects the space-time block code rule based on the value of the n / 2th sample of the modulation signal. A transmission device.

3. The code rule selection unit is characterized in that it selects the space-time block code rule so that different space-time block code rules with different negative code positions are applied to adjacent frequency carriers in the frequency domain. The transmission device according to Claim 1.

4. The diffusion bit generation unit generates the diffusion bit sequence from the transmission bit sequence based on the modulation method used by the shift quadrature amplitude modulation unit and a predetermined diffusion rate. The transmission device according to claim 2.

5. The modulation signal is composed of n samples from the 0th to the (n - 1)th, The encoding unit performs the space-time block encoding using a combination of samples arranged with n / 2 - 1 samples sandwiched therebetween within the same symbol of the modulation signal. The transmission device according to claim 1 or 2.

6. A receiving device that receives a transmission signal transmitted by the transmission device according to claim 1 or 2 as a received signal, A code rule selection unit that selects the space-time block code rule used in the transmission device for the received signal, A decoding unit that performs space-time block decoding on the received signal using the selected space-time block code rule, A demodulation unit that demodulates the decoding result by the decoding unit, A receiving device characterized by comprising.

7. The transmission device according to claim 1 or 2, A receiving device that receives a transmission signal transmitted by the transmission device as a received signal, Comprising, The receiving device is A code rule selection unit that selects the space-time block code rule used in the transmission device for the received signal, A decoding unit that performs space-time block decoding on the received signal using the selected space-time block code rule, A demodulation unit that demodulates the decoding result by the decoding unit, A communication system characterized by comprising.

8. A transmission device including a plurality of transmission antennas, A modulation step of generating a modulation signal by frequency offset modulation, A code rule selection step of selecting a space-time block code rule according to the value of the modulation signal so that different space-time block code rules are applied to adjacent frequency carriers in the frequency domain in the frequency carrier of the modulation signal modulated by the frequency offset modulation, An encoding step of generating a transmission signal to be transmitted from each of the plurality of transmission antennas by performing space-time block coding on the modulation signal using the selected space-time block code rule, A transmission method characterized by including the above.

9. A transmission device including a plurality of transmission antennas, A modulation step of generating a modulation signal, A code rule selection step of selecting a space-time block code rule according to the value of the modulation signal, An encoding step of generating a transmission signal to be transmitted from each of the plurality of transmission antennas by performing space-time block coding on the modulation signal using the selected space-time block code rule, Including, The modulation step is, A spreading step of generating a spread bit sequence from the input transmission bit sequence, A shift quadrature amplitude modulation step of generating the modulation signal from the spread bit sequence by a shift quadrature amplitude modulation method, Including, The modulation signal is composed of n samples from the 0th to the (n - 1)th, In the code rule selection step, The transmission device is characterized in that the space-time block code rule is selected based on the value of the n / 2th sample of the modulation signal.

10. In the code rule selection step, The transmission device according to claim 8, characterized in that the space-time block coding rule is selected such that the space-time block coding rule in which the positions of negative codes are different for the frequency carriers adjacent in the frequency domain is applied.

11. In the spreading step, The transmission device according to claim 9, characterized in that the spreading bit sequence is generated from the transmission bit sequence based on the modulation method used in the shift quadrature amplitude modulation step and a predetermined spreading rate.

12. The modulation signal is composed of n samples from the 0th to the (n-1)th, In the encoding step, the transmission device performs the space-time block encoding using a combination of samples arranged with n / 2-1 samples sandwiched between them within the same symbol of the modulation signal, according to the transmission method described in claim 8 or 9.

13. A receiving device that receives a transmission signal transmitted by the transmission method according to claim 8 or 9 as a received signal, A coding rule selection step of selecting the space-time block coding rule used in the transmission method for the received signal, A decoding step of performing space-time block decoding on the received signal using the selected space-time block coding rule, A demodulation step of demodulating the decoding result of the decoding step, A receiving method characterized by including the above.

14. A control circuit for controlling a transmission device having a plurality of transmission antennas, A modulation step of generating a modulation signal by frequency offset modulation, A coding rule selection step of selecting the space-time block coding rule according to the value of the modulation signal so that different space-time block coding rules are applied to the frequency carriers adjacent in the frequency domain in the frequency carrier of the modulation signal modulated by the frequency offset modulation, An encoding step of generating a transmission signal to be transmitted from each of the plurality of transmission antennas by performing space-time block encoding on the modulation signal using the selected space-time block code rule. A control circuit characterized by causing the transmission device to execute . **Claim 15**: A control circuit for controlling a transmission device having a plurality of transmission antennas, A modulation step of generating a modulation signal, A code rule selection step of selecting a space-time block code rule according to the value of the modulation signal, An encoding step of generating a transmission signal to be transmitted from each of the plurality of transmission antennas by performing space-time block encoding on the modulation signal using the selected space-time block code rule, Causing the transmission device to execute, The modulation step includes, A spreading step of generating a spread bit sequence from the input transmission bit sequence, A shift quadrature amplitude modulation step of generating the modulation signal from the spread bit sequence by a shift quadrature amplitude modulation method, And includes, The modulation signal is composed of n samples from the 0th to the (n - 1)th, In the code rule selection step, The space-time block code rule is selected based on the value of the n / 2th sample of the modulation signal. A control circuit characterized by this. **Claim 16** In a storage medium storing a program for controlling a transmission device having a plurality of transmission antennas, the program A modulation step of generating a modulation signal by frequency offset modulation, A code rule selection step of selecting the space-time block code rule according to the value of the modulation signal so that different space-time block code rules are applied to adjacent frequency carriers in the frequency domain in the frequency carrier of the modulation signal modulated by the frequency offset modulation. An encoding step of generating transmission signals to be transmitted from respective ones of the plurality of transmission antennas by performing space-time block encoding on the modulation signal using the selected space-time block code rule; A storage medium, characterized in that the transmission device is caused to execute the above. **Claim 17**: In a storage medium storing a program for controlling a transmission device having a plurality of transmission antennas, the program includes: A modulation step of generating a modulation signal; A code rule selection step of selecting a space-time block code rule according to the value of the modulation signal; An encoding step of generating transmission signals to be transmitted from respective ones of the plurality of transmission antennas by performing space-time block encoding on the modulation signal using the selected space-time block code rule; Causing the transmission device to execute the above, The modulation step includes: A spreading step of generating a spread bit sequence from the input transmission bit sequence; A shift quadrature amplitude modulation step of generating the modulation signal from the spread bit sequence by a shift quadrature amplitude modulation method; Including the above, The modulation signal is composed of n samples from the 0th to the (n - 1)th, In the code rule selection step, A storage medium, characterized in that the space-time block code rule is selected based on the value of the n / 2th sample of the modulation signal.

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