JP4836559B2 - Receiving method and receiving apparatus - Google Patents

Description

  The present invention relates to a receiving method and a receiving apparatus that enable high speed and high capacity by separating and receiving multiple signals only by independent component analysis, for example, in mobile communication.

Receiving radio signals transmitted from a plurality of transmitters arranged at different locations using an independent component analysis (ICA) method by a single receiver and obtaining respective demodulated signals A possible technique is described in Patent Document 1 below.

JP 2005-51344 A

  In the case of receiving a plurality of radio waves radiated from antennas of a plurality of transmission devices arranged at different places, a plurality of radio waves are received by a carrier having the same frequency. Separating each signal component even when modulated with different modulation schemes or when transmitting multiple modulation signals of two or more waves of different data that are statistically independent with modulation schemes having the same frequency Is possible. However, the technique described in Patent Document 1 has not received multiple signals only by independent component analysis, and has not achieved high-speed communication and high capacity.

  Accordingly, an object of the present invention is to provide a receiver and a receiving method capable of increasing the speed and capacity of communication.

In order to solve the above-described problem, the present invention includes a received signal input step in which a plurality of mixed signals obtained by mixing a plurality of independent chaotic original signals obtained from a predetermined information signal are input;
A signal separation step of separating a plurality of mixed signals into a plurality of separated signals corresponding to a plurality of chaotic original signals by independent component analysis;
A signal identification step that associates a plurality of separated signals with a plurality of chaotic original signals with reference to the chaotic original signal generation mechanism, and
The plurality of chaotic original signals is a receiving method that is a chaotic signal sequence generated by mapping so as to correspond to a code signal obtained by serial-to-parallel conversion of an information signal.

The present invention includes a reception signal input unit to which a plurality of mixed signals obtained by mixing a plurality of independent chaotic original signals obtained from a predetermined information signal are input,
A signal separation unit that separates a plurality of mixed signals into a plurality of separated signals corresponding to a plurality of chaotic original signals by independent component analysis;
A signal identification unit that associates a plurality of separated signals and a plurality of chaotic original signals with reference to a chaotic original signal generation mechanism;
The plurality of chaotic original signals are a receiving device that is a chaotic signal sequence generated by mapping so as to correspond to a code signal obtained by serial-to-parallel conversion of an information signal.

  A receiving method and a receiving apparatus according to the present invention separate and receive multiple signals only by independent component analysis by transmitting in parallel a plurality of mutually independent chaotic original signals obtained from information signals to be transmitted. High speed communication and high capacity can be achieved. Further, according to the present invention, it is not necessary to generate a spread code synchronized with the transmission side and perform spread demodulation on the reception side as in the spread modulation method, and the reception method and the receiving apparatus can be simplified. The present invention can be used as a technique for increasing the transmission speed in the next generation, that is, the fourth generation mobile communication to about 1 Gbit / second.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a communication system according to one embodiment. As an example, three chaos original signals s ₁ , s ₂ , and s ₃ are input to the transmitter 1. Each of the chaotic original signals s ₁ , s ₂ , and s ₃ is a chaotic signal sequence generated by mapping so as to correspond to a code signal obtained by serial-to-parallel conversion of transmission data. The transmitter 1 includes three multipliers ML1, ML2, and ML3. For multiplier ML1～ML3, the carrier signal of the same frequency from the carrier signal source 2 is supplied, the original signal s ₁ ~s ₃ is frequency-converted into RF band. Then, the frequency-converted signals are supplied to the transmission antennas AT1, AT2, AT3 through power amplifiers (not shown) and emitted as radio waves. The transmission signal is transmitted using a frequency band of one channel.

  The transmitted radio wave is received by the receiving antennas AT11, AT12, AT13 via the spatial transmission path 10. In the spatial transmission path 10, a plurality of different propagation paths (so-called multipaths) are formed by reflectors or the like, and radio waves emitted from the transmission antennas are mixed and received by the reception antennas AT11 to AT13. . Usually, the number of antennas used for transmission and reception is assumed to be equal. High speed communication and high capacity are achieved by transmitting predetermined data in parallel in space.

  Reception signals obtained from the reception antennas AT11 to AT13 are respectively supplied to multipliers ML11, ML12, and ML13 constituting the receiver 11 via a power amplifier (not shown). The multipliers ML11 to ML13 are supplied with a carrier signal from the carrier signal source 12, and frequency conversion from the RF band to the baseband is performed. The carrier signal on the transmission side and the carrier signal on the reception side are controlled so as to have the same frequency and phase.

A plurality of mixed signals x ₁ , x ₂ , and x ₃ obtained by mixing a plurality of chaotic original signals are obtained from each of the multipliers ML 11 to ML 13. The plurality of mixed signals x ₁ , x ₂ , x ₃ are converted into digital signals and supplied to the signal separation unit 13. The signal separation unit 13 estimates and separates a plurality of chaotic original signals from the mixed signals x ₁ , x ₂ , and x ₃ from the multipliers ML 11 to ML 13 by independent component analysis (ICA). Signal separation by independent component analysis is generally a process represented by the following equation.

X (t) on the left side of Equation (1) is a vector indicating the time series of the received mixed signal series x ₁ (t), x ₂ (t),..., X _N (t), A is a mixed matrix with a as an element, and S (t) on the right side
Is a vector indicating the time series of the chaotic original signal series s ₁ (t), s ₂ (t),..., S _N (t) to be separated.

  That is, in the example of (N = 3), the mixed signal received at a certain time t is as shown below.

x ₁ (t) = a ₁₁ * s ₁ (t) + a ₁₂ * s ₂ (t) + a ₁₃ * s ₂ (t)
x ₂ (t) = a ₂₁ * s ₁ (t) + a ₂₂ * s ₂ (t) + a ₂₃ * s ₂ (t)
x ₃ (t) = a ₃₁ * s ₁ (t) + a ₃₂ * s ₂ (t) + a ₃₃ * s ₂ (t)

On the receiving side, the mixing matrix A (weighting factor) is unknown. Actually, the weighting coefficient changes depending on the direction of the receiving antenna. Assuming statistical properties of the original signal S (t), that is, a non-Gaussian distribution of the signal, the mixed signal X (t) is separated into independent components corresponding to the chaotic original signal S (t).

The signal separation unit 13 separates three independent components corresponding to the three chaotic original signals and supplies them to the signal identification unit 14. The signal identification unit 14 performs processing for identifying the correspondence between the independent component separated with reference to the chaos original signal generation mechanism and the chaos original signal, and the separated signals s ₁ ′ and s ₂ ′ from the signal identification unit 14. , S ₃ 'is output. Although not shown, the separation signals s ₁ ′, s ₂ ′, and s ₃ ′ are converted into serial data by a parallel → serial conversion circuit.

  The signal identification unit 14 performs identification processing based on the properties of the original signal. For example, for the identification process, the receiving side teaches in advance the generation mechanism of the independent component. The signal separation unit 13 and the signal identification unit 14 are not limited to a hardware configuration, and may be a software processing configuration. When a chaotic signal generated by mapping is used as an original signal, mappings generated by the chaotic signal are prepared in advance for the number of possible patterns, and it is possible to identify which mapping generates the separated signal.

As described above, the receiver 11 according to the embodiment of the present invention is provided with the MIMO (Multiple
Input Multiple Output), and the communication capacity can be increased.

2, 3 and 4 show experimental results, in which the horizontal axis indicates time change and the vertical axis indicates normalized amplitude. As an example, an example is shown in which two chaotic original signals s ₁ (t) (FIG. 2A) and s ₂ (t) (FIG. 2B) shown in FIG. ₂ are transmitted. 3A and 3B show the mixed signals x ₁ (t) and x ₂ (t) represented by the following equations.

x ₁ (t) = a ₁₁ * s ₁ (t) + a ₁₂ * s ₂ (t)
x ₂ (t) = a ₂₁ * s ₁ (t) + a ₂₂ * s ₂ (t)

As an experimental circuit, the same waveform operation (operation of phase, amplitude, etc.) as interference generated when transmitted in a multipath environment is applied to two chaotic original signals s ₁ (t) and s ₂ (t). performed, configuration is used for adding multiplied by the gain a ₁₁ ~a ₂₂ respectively two signals of the result.

The mixed signals x ₁ (t) and x ₂ (t) are subjected to signal separation processing by independent component analysis. In the experiment, no signal identification was performed. As a result of the signal separation processing, separated signals s ₁ (t) ′ (FIG. 4A) and s ₂ (t) ′ (FIG. 4B) are obtained. When the chaotic original signals s ₁ (t) (FIG. 2A) and s ₂ (t) (FIG. 2B) shown in FIG. ₂ are compared with the separated signals s ₁ (t) ′ and s ₂ (t) ′ shown in FIG. It can be seen that both signals are almost the same signal and the original signal can be separated.

  Next, a specific example of one embodiment of the present invention will be described with reference to FIGS. In this example, the present invention is applied to CDMA (Code Division Multiple Access). As an example, the transmitting side corresponds to one mobile station, and the receiving side corresponds to a base station. The reverse relationship may be used. Usually, a large number of mobile stations exist, but for simplicity, only one mobile station exists and uses a band of one channel.

FIG. 5 shows the configuration of the transmission side. The original signals s _{1 to} s ₃ input to the transmitter 1a are modulated information signals obtained by performing serial-to-parallel conversion of information to be transmitted and information-modulating each information signal after parallel conversion. Modulation information signals s _{1 to} s ₃ are supplied to multipliers ML4, ML5, and ML6, respectively. The spreading codes from the code generator 4 are input to the multipliers ML4 to ML6. The spreading codes supplied to the multipliers ML4 to ML6 are different time-series code signals.

The signals spread-modulated by the multipliers ML4 to ML6 are supplied to the multipliers ML1, ML2, and ML3. For multiplier ML1～ML3, the carrier signal of the same frequency from the carrier signal source 2 is supplied, the modulation information signal s ₁ ~s ₃ is frequency-converted into RF band. Then, the frequency-converted signals are supplied to the transmission antennas AT1, AT2, AT3 via a power amplifier (not shown), and are emitted as radio waves.

  The transmitted radio wave is received by the receiving antennas AT11, AT12, AT13 on the receiving side shown in FIG. 6 via the spatial transmission path. A CDMA receiver 11a is connected to the receiving antennas AT11 to AT13.

  Received signals obtained from the reception antennas AT11, AT12, and AT13 are supplied to multipliers ML11, ML12, and ML13, respectively, via a power amplifier (not shown). The multipliers ML11 to ML13 are supplied with a carrier signal from the carrier signal source 12, and frequency conversion from the RF band to the baseband is performed. The carrier signal on the transmission side and the carrier signal on the reception side are controlled so as to have the same frequency and phase.

The mixed signals x ₁ , x ₂ , and x ₃ from the multipliers ML 11 to ML 13 are converted into signal separation units 13.
To be supplied. The signal separation unit 13 estimates and separates the modulation information signal as the chaotic original signal from the mixed signals x ₁ , x ₂ , and x ₃ from each of the multipliers ML 11 to ML 13 by independent component analysis (ICA). .

  In the configuration of the conventional CDMA receiver, a spreading demodulation unit (also referred to as a despreading unit) corresponding to the spreading modulation unit (multipliers ML4 to ML6) on the transmission side is provided. A modulated information signal is obtained by supplying a synchronized spreading code. In the example described above, such a spread demodulation unit is not provided, and the modulation information signal is directly separated by the signal separation unit 13 based on independent component analysis.

The signal separation unit 13 separates three independent components corresponding to the three chaotic original signals (that is, modulation information signals), and supplies them to the signal identification unit 14. The signal identification unit 14 performs processing for identifying the correspondence between the separated independent components and the chaotic original signal, and the modulated identification information signals s ₁ ′, s ₂ ′, and s ₃ ′ are output from the signal identification unit 14. The The signal identification unit 14 performs identification processing based on the properties of the chaotic original signal.

Further, the separated modulation information signals s ₁ ′, s ₂ ′, and s ₃ ′ from the signal identification unit 14 are converted into the signal verification unit 1.
5 is supplied. The signal verification unit 15 receives the spread code from the code generation unit 16. The signal verification unit 15 performs a process for verifying that the identification result by the signal identification unit 14 is correct. When a chaotic signal is used as a signal source, the type of signal can be verified using a mechanism that generates a chaotic signal (for example, a map such as a logistic map). The final separated modulation information signals s ₁ ″, s ₂ ″, s ₃ ″ can be obtained from the signal verification unit 15. Although it is not essential to provide the signal verification unit 15, the signal verification unit 15 improves the error rate. Note that the signal separation unit 13, the signal identification unit 14, and the signal verification unit 15 are not limited to a hardware configuration, and may have a software processing configuration.

  As the spreading code, a chaos spreading code is used. For example, a complex chaotic spreading code with a constant power is used. The complex chaotic spreading code is a spread code for spread spectrum that has a two-component real type spreading code of I and Q. From the orthogonality of the chaotic spreading code, signal separation can be performed by independent component analysis.

  A chaotic spreading code is a sequence generated repeatedly using a Chebyshev polynomial, which is an orthogonal polynomial, as a mapping. For example, second-order, third-order, and fourth-order Chebyshev polynomials are shown below.

T (2, x) = 2x ² -1
T (3, x) = 4x ³ -3x
T (4, x) = 8x ⁴ -8x ² +1

  The mapping by these Chebyshev polynomials is as shown in FIG. In FIG. 7, the horizontal axis is x, the vertical axis is y, and an advantageous mapping that maps a closed section (−1 ≦ x ≦ 1) to a closed section (−1 ≦ y ≦ 1). T2 indicates the characteristic of mapping by the second-order Chebyshev polynomial, T3 indicates the characteristic of mapping by the third-order Chebyshev polynomial, and T4 indicates the characteristic of mapping by the third-order Chebyshev polynomial. The chaotic spreading code can generate different sequences depending on the setting of the initial value in addition to the order. A configuration for generating a chaos spreading code is described in Japanese Patent Application Laid-Open No. 2003-140885 according to the proposal of the present inventor. By using chaotic spreading codes, the number of types of codes can be increased, and since the configuration of spreading codes is not simple, communication security can be improved. Further, a chaotic signal generated by this Chebyshev polynomial can be uniquely mapped to a certain binary sequence from the theory of symbolic dynamics. In this case, it is possible to read where the information starts from, for example, “1111111111111111111 ... 11111111” as a pilot signal meaning “flow information from here” in the symbol string to be sent.

8, FIG. 9 and FIG. 10 show experimental results, in which the horizontal axis indicates time change and the vertical axis indicates normalized amplitude. As an example, an example of transmitting two chaotic original signals s ₁ (t) (FIG. 8A) and original signals s ₂ (t) (FIG. 8B) is shown. One original signal s ₂ (t) is a pulse signal of 1.6 kHz. 9A and 9B show the mixed signals x ₁ (t) and x ₂ (t) represented by the following equations.

x ₁ (t) = a ₁₁ * s ₁ (t) + a ₁₂ * s ₂ (t)
x ₂ (t) = a ₂₁ * s ₁ (t) + a ₂₂ * s ₂ (t)

As an experimental circuit, a waveform operation (operation of phase, amplitude, etc.) similar to interference generated when transmitted in a multipath environment is performed on _one chaotic original signal s ₁ (t), and the resulting signal And the pulse signal are multiplied by gains a _{11 to} a ₂₂ and added.

The mixed signals x ₁ (t) and x ₂ (t) are subjected to signal separation processing by independent component analysis. In the experiment, signal identification and signal verification were not performed. As a result of the signal separation processing, separated signals s ₁ (t) ′ (FIG. 10A) and s ₂ (t) ′ (FIG. 10B) are obtained. Comparing the original signals s ₁ (t) (FIG. 8A) and s ₂ (t) (FIG. 8B) with the separated signals s ₁ (t) ′ and s ₂ (t) ′ shown in FIG. It turns out that it became the same signal and the original signal was able to be isolate | separated.

  FIG. 11 shows an example of a chaotic CDMA waveform. In FIG. 11, eight antennas are used. On the left side, an information signal (bit signal), a chaotic spreading code, a carrier signal for frequency conversion, and a transmission signal that is frequency-converted and transmitted from one antenna are shown. A total of eight transmission signals are generated using different information signals and chaotic spreading codes.

  The mixed signal received by the receiving antenna is demodulated and can be separated into eight signals shown on the right side of FIG. 11 by the signal separation unit. For example, the separated signal at the top corresponds to the left bit signal that has been spread-modulated with a chaotic spreading code.

  Next, another embodiment of the present invention will be described. Another embodiment is a combination of CDMA and OFDM (Orthogonal Frequency Division Multiplex) modulation schemes.

  FIG. 12 shows the configuration of the transmission side. Information signals to be transmitted are input from the input terminals 20a, 20b, 20c, and 20d, respectively. The information signal is supplied to the spreading sections 21a, 21b, 21c, and 21d, and is spread by a chaotic spreading code from the input terminals 22a, 22b, 22c, and 22d, for example, a complex spreading code with constant power.

Output signals from the spreading sections 21a to 21d are respectively supplied to S / P converters 23a, 23b, 23c, and 23d, and converted from serial data to parallel data. The data series is divided into a plurality of data series by the S / P converters 23a to 23d. Data series from the S / P converters 23a to 23d are supplied to the mappers 24a, 24b, 24c, and 24d, respectively. Each of the mappers 24a to 24d performs modulation of digital modulation (QAM (Quadrature Amplitude Modulation), PSK (Phase Shift Keying), etc.).

The outputs of the mappers 24a to 24d are supplied to Inverse Fast Fourier Transform (IFFT) units 25a, 25b, 25c, and 25d, and time domain waveforms are generated. Outputs of the IFFT units 25a to 25d are supplied to guard interval (GI) adding units 26a, 26b, 26c, and 26d, and the guard intervals are added in symbol time units. The outputs of the guard intervals 26a to 26d are respectively supplied to the transmission antennas AT1, AT2, AT3, and AT4 via a power amplifier (not shown) and transmitted as radio waves.

  Each of the S / P converters 23a to 23d divides data into channels corresponding to the number of subcarriers in the OFDM modulation scheme. When the number of OFDM subcarriers is n, for example, the S / P converter 23a forms n-channel parallel data. The data series of each channel is supplied to the mapper and is converted into an OFDM signal by the IFFT unit, and a guard interval is added for each OFDM symbol in the guard interval adding unit. That is, although collectively shown in FIG. 12, each of the mapper 24a, IFFT unit 25a, and guard interval adding unit 26a has a number of portions in parallel equal to the number of subcarriers n. The other transmission antennas AT2, AT3, AT4 have the same configuration.

  FIG. 13 shows the configuration of a receiver according to another embodiment of the present invention. For example, received signals from four receiving antennas AT11, AT12, AT13, and AT14 are supplied to the guard interval removing units 31a, 31b, 31c, and 31d, respectively. The guard interval removal units 31a to 31d remove the guard interval according to the timing of the received OFDM symbol.

  Output signals of the guard interval removing units 31a to 31d are supplied to FFT (Fast Fourier Transform) units 32a, 13b, 32c, and 32d, respectively. The time domain signals are converted into frequency domain signals by the FFT units 32a to 32d. The processing from the guard interval removing units 31a to 31d to the P (parallel) / S (serial) converters 36a to 36d is performed on a parallel data sequence of n subcarriers in OFDM.

  The data symbols being output from the FFT units 32 a to 32 d are supplied to the signal separation unit 33, and the output of the signal separation unit 33 is supplied to the signal identification unit 34. As in the above-described embodiment, the signal separation unit 33 separates independent components corresponding to a plurality of modulation information signals and supplies them to the signal identification unit 34. The signal identification unit 34 performs identification processing based on the properties of the original signal. For example, for the identification process, the receiving side teaches in advance the generation mechanism of the independent component.

  An output signal of the signal identification unit 34 is supplied to the signal verification unit 35. Although not shown, the chaotic spreading code from the code generation unit is input to the signal verification unit 35. The signal verification unit 35 performs a process for verifying that the identification result by the signal identification unit 34 is correct.

  The separated signal series from the signal verifying unit 35 performs processing reverse to that of the mapper on the transmission side and is supplied to demappers 36a, 36b, 36c, and 36d that perform digital demodulation processing, respectively. Outputs of the demappers 36a to 36d are supplied to P / S converters 37a, 37b, 37c, and 37d, respectively. The number of channels equal to the number of subcarriers of OFDM are combined into one channel by the P / S converters 37a to 37d. Outputs of the P / S converters 37a to 37d are taken out to output terminals 38a, 38b, 38c, and 38d.

  Although the embodiment of the present invention has been specifically described above, the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible. For example, a pulse whose pulse interval or pulse amplitude is randomly controlled by a chaotic sequence may be generated.

It is a block diagram which shows the structure of the transmission side and receiving side of one Embodiment of this invention. It is a wave form diagram which shows the waveform of the original signal used for description of one embodiment of this invention. It is a wave form diagram which shows the waveform of the mixed signal used for description of one embodiment of this invention. It is a wave form diagram which shows the waveform of the isolation | separation signal used for description of one embodiment of this invention. It is a block diagram which shows the more concrete structure of the transmission side in one embodiment of this invention. It is a block diagram which shows the more concrete structure of the receiving side in one embodiment of this invention. It is a graph used for description of a chaos spreading code. It is a wave form diagram which shows the waveform of the original signal used for description of one embodiment of this invention. It is a wave form diagram which shows the waveform of the mixed signal used for description of one embodiment of this invention. It is a wave form diagram which shows the waveform of the isolation | separation signal used for description of one embodiment of this invention. It is a wave form diagram used for description when performing chaotic CDMA in one embodiment of this invention. It is a block diagram which shows the structure of the transmission side in other embodiment of this invention. It is a block diagram which shows the structure of the receiving side in other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a ... Transmitter 2 ... Carrier signal source 4 ... Code generation part 10 ... Spatial transmission path 11, 11a ... Receiver 12 ... Carrier signal source 13, 33 ... Signal separation unit 14, 34 ... Signal identification unit 15, 35 ... Signal verification unit ML ... Multiplier AT1-AT4 ... Transmission antenna AT11-AT14 ... Reception antenna

Claims (4)

A received signal input step in which a plurality of mixed signals obtained by mixing a plurality of independent chaotic original signals obtained from a predetermined information signal are input;
A signal separation step of separating the plurality of mixed signals into a plurality of separated signals corresponding to the plurality of chaotic original signals by independent component analysis;
A signal identification step in which the plurality of separated signals and the plurality of chaotic original signals are associated with each other by referring to the chaotic original signal generation mechanism,
The receiving method, wherein the plurality of chaotic original signals are chaotic signal sequences generated by mapping so as to correspond to a code signal obtained by serial-to-parallel conversion of the information signal. The reception method according to claim 1,
The plurality of mixed signals are a mixture of transmission signals emitted from a plurality of transmission antennas, and the reception signal input step is reception that is reception by the reception antenna and frequency conversion processing by a carrier signal of the same frequency. Method. A reception signal input unit to which a plurality of mixed signals obtained by mixing a plurality of independent chaotic original signals obtained from a predetermined information signal are input;
A signal separation unit that separates the plurality of mixed signals into a plurality of separated signals corresponding to the plurality of chaotic original signals by independent component analysis;
A signal identifying unit that associates the plurality of separated signals and the plurality of chaotic original signals with reference to a chaotic original signal generation mechanism;
The receiving device, wherein the plurality of chaotic original signals are chaotic signal sequences generated by mapping so as to correspond to a code signal obtained by serial-to-parallel conversion of the information signal. Modulated information signals obtained by modulating a plurality of signals obtained by serial-to-parallel conversion of information signals are spread and transmitted by a plurality of chaotic spreading codes ,
A plurality of mixed signals obtained by mixing signals spread by the plurality of chaotic spreading codes are input.
Separating the plurality of mixed signals into a plurality of separated signals corresponding to the plurality of modulation information signals by independent component analysis;
A reception method for associating the plurality of separated signals with the plurality of modulation information signals,
A receiving method, wherein the chaotic spreading code is a complex chaotic spreading code with constant power.

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