JP4698714B2 - Modulation method and demodulation method - Google Patents

Description

  The present invention relates to a modulation method and a demodulation method, and more particularly to a modulation / demodulation method for a system that requires an improvement in frequency use efficiency in a field using electromagnetic waves such as wireless communication and optical communication.

  The communication method that can obtain the highest frequency utilization efficiency at present is the orthogonal frequency division multiplexing (OFDM). OFDM is composed of subdivided modulated waves, but when the number of modulated waves decreases, the frequency utilization efficiency decreases significantly. Also, in general digital quadrature modulation systems, the frequency utilization efficiency can be improved by making the roll-off rate that controls the frequency characteristics of the baseband signal steep, but in the OFDM system, the frequency utilization efficiency can be improved even if the roll-off rate is steep. There is almost no effect in improving.

  Further, as a technique for improving the frequency utilization efficiency, a transmission signal narrowing technique can be cited. A typical example is the SSB (Single Side Band) system. Multiplexing attempts using the SSB method have been made since the past. The transmission signal in the Syed Aon Mujtaba method (patent document 1 or non-patent document 1) studied earliest has a positive USB (Upper Side Band) on a positive frequency carrier. An SSB component having a positive LSB (Lower Side Band) in a negative frequency region carrier, a positive LSB in a positive frequency carrier, and a negative frequency region carrier in a negative frequency region This is a transmission signal composed of an SSB component having a negative polarity USB. However, in the Syed Aon Mujtaba system, the overall frequency bandwidth is not different from the frequency bandwidth of a single carrier modulation system such as QPSK, which does not improve the frequency utilization efficiency.

In the method of Mr. Ikuta announced next (Non-Patent Document 2 and Non-Patent Document 3), the transmission side generates a transmission signal having four types of SSB components. In addition, there is a modulation method in which an SSB component is arranged orthogonally on one side of a carrier wave, and frequency utilization efficiency is doubled that of a QPSK single carrier method by orthogonally modulating USB or LSB (Patent Document 2).
US Pat. No. 6,091,781 JP 2006-203835 A Syed Aon Mujtaba, “A Novel Scheme for Transmitting QPSK as a Single-Sideband Signal”, IEEE Globalcomm 98, vol.1, pp.592-597, 1998 Daisuke Ikuta, Fumio Takahata, “Examination of SSB transmission of BPSK signals”, 2001 IEICE General Conference Proceedings, B-5-177, March 2001 (Daisuke Ikuta, Fumio Takahata, “On SSB Transmission of BPSK Signal ", Proceedings of the IEICE General Conference, B-5-177, Mar 2001) Daisuke Ikuta, Fumio Takahata, “Study on SSB transmission of QPSK signal”, 2001 IEICE General Conference Proceedings, B-5-176, March 2001 (Daisuke Ikuta, Fumio Takahata, “On SSB Transmission of QPSK Signal ", Proceedings of the IEICE General Conference, B-5-176, Mar 2001) Oichiro Genichiro et al., “Examination of New Modulation Scheme for Frequency Utilization Efficiency”, IEICE Technical Report RCS2003-184, pp.189-194, November 20, 2003 (Gen-ichiro Ohta, Mitsuru (Uesugi, TakuroSato, Hideyoshi Tominaga, "Considerations on new Modulation Methods for Spectram Efficiency", Technical report of IEICE RCS, RCS2003-184, pp.189-194, Nov 2003)

  In order to realize a modulation scheme comparable to or exceeding the frequency utilization efficiency of OFDM using SSB technology, it is necessary to arrange USB and LSB holding independent information on one carrier frequency, and further, USB and LSB One solution is to quadrature modulate each of the. Thereby, the modulation signal is composed of four types of SSB elements having the same carrier frequency. The four types of SSB elements are orthogonal to each other in the frequency domain, but interfere with each other in the time domain. However, the above-described conventional literature does not disclose either a method for separating these four types of SSB elements on the receiving side or a method for extracting only information to be transmitted.

  For example, Non-Patent Document 3 discloses a technique for transmitting four types of SSB elements, but the four types of SSB elements do not have the same carrier frequency. Further, in Non-Patent Document 3, even when the four types of SSB elements have the same carrier frequency, the reception circuit shown in Non-Patent Document 3 retains mutual interference of the four types of SSB components, and cancels out the interference components. Since the operation and the extraction operation of the desired signal cannot be sufficiently performed, the four types of SSB elements cannot be completely demodulated. In Non-Patent Document 3, in order to completely demodulate four types of SSB elements having the same carrier frequency, it is necessary to add a guard band corresponding to the frequency band between the carrier frequency and the SSB component. When a guard band is added, the frequency bandwidth is doubled, which does not lead to an improvement in frequency utilization efficiency.

  Further, in Patent Document 2, interference components are removed only in the decoding stage among the demodulation stage and decoding stage of the receiver. The receiver disclosed in Patent Document 2 configures a quadrature detection unit, a matched filter, and a combiner as components at the demodulation stage, but interference components between signals cannot be removed by any component. That is, in Patent Document 2, interference component removal and signal separation between signals are performed in a decoding stage subsequent to the demodulation stage. In the receiver disclosed in Patent Document 2, interference components between signals are removed by a turbo decoding method. The turbo decoding method is a method for performing error removal cyclically by using a replica of an interference signal component, and is not a method utilizing the characteristics of the SSB method. Also, the turbo decoding method requires a large amount of computation, and a large processing delay is caused by the computation.

  The present invention has been made in view of the above points. In order to improve the frequency utilization efficiency of radio communication by narrowing the transmission signal by converting the digital signal into SSB, each frequency domain at the time of demodulation is provided. An object of the present invention is to provide a modulation method and a demodulation method capable of suppressing mutual interference between signals.

  The modulation method of the present invention is a modulation method for generating a modulation signal composed of two types of single sideband elements having a common carrier frequency, and the two types of single sideband elements are positive in the positive frequency region. A first single sideband element having an upper single sideband and having a positive lower singlesideband in the negative frequency region; and a positive upper singlesideband in the positive frequency region and in the negative frequency region Or a second single sideband element having a negative lower single sideband, or having a positive lower single sideband in the positive frequency region and a positive upper single in the negative frequency region. A third single-sideband element having a sideband and a fourth single-sideband having a positive lower single-sideband in the positive frequency domain and a negative upper single-sideband in the negative frequency domain It was made up of elements.

  The demodulation method of the present invention includes a first single sideband element having a positive upper single sideband in the positive frequency region and a positive lower single sideband in the negative frequency region, and a positive frequency region. Two types of single sidebands having a positive upper single sideband and a second single sideband element having a negative lower single sideband in the negative frequency region, or a positive frequency A third single sideband element having a positive lower single sideband in the region and a positive upper single sideband in the negative frequency region, and a positive lower single sideband in the positive frequency region. And a modulation signal composed of two types of single sidebands composed of a fourth single sideband element having a negative upper sideband in the negative frequency region, and is a ternary binary number A modulated signal is received, and the symbol of the modulated signal is based on '0' and '1'. And to perform binary processing for converting binary numbers to to.

  According to the present invention, four types of single sideband elements consisting of single sidebands, which are the basic elements of modulation, are arranged orthogonally around a common carrier frequency axis, so that they are almost equivalent to the OFDM system or QPSK Thus, the frequency utilization efficiency about twice that of the single carrier modulation system such as the above can be realized. Furthermore, by making the roll-off rate of the symbol signal steep, it is possible to realize frequency use efficiency that is about twice that of the OFDM system.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  First, cases (case 1 and case 2) until the inventor comes up with the idea of the present invention will be described.

(Case 1)
FIG. 1 shows a modulation signal intended by this case, that is, a modulation signal composed of four SSB elements having a common carrier frequency. As shown in FIG. 1, the four SSB elements are composed of an even symmetric positive polarity rotation SSB, an even symmetric negative polarity rotation SSB, an odd symmetric positive polarity rotation SSB, and an odd symmetric negative polarity rotation SSB. Each single sideband element has an even symmetric frequency component or an odd symmetric frequency component in each of the positive and negative frequency regions.

  Specifically, the even symmetric positive rotation SSB has a positive upper single sideband in the positive frequency region and a positive lower single sideband in the negative frequency region. The SSB has a positive upper single sideband in the positive frequency region and a negative lower single sideband in the negative frequency region, and the even symmetric negative rotation SSB has a positive polarity in the positive frequency region. The lower single sideband has a positive upper singlesideband in the negative frequency region, and the odd-symmetric negative rotation SSB has a positive lower singlesideband in the positive frequency region and a negative frequency The region has a negative upper single sideband.

ここで、フェイサとは、一方向の位相回転する基本要素であり、ｅｘｐ（ｊω_１ｔ）は角周波数ω_１の位置で正方向に位相回転し、ｅｘｐ（−ｊω_１ｔ）は角周波数−ω_１の位置で正方向に位相回転する。 Therefore, considering positive and negative components in the frequency domain, the number of SSB elements of the modulation signal is 8. Note that the eight SSB elements are conceptual, and the eight SSB elements do not physically exist alone. For example, the angular frequency omega ₁ of the signal is cos .omega ₁ t or sin .omega ₁ t. However, in order to explain the concept of the SSB element, it is necessary to convert the SSB element into an analytic signal. Therefore, when described as an example cos .omega ₁ t, an angular frequency omega ₁ of the signal, using the Euler's theorem using an analysis component of cos .omega ₁ t Feisa exp (jω ₁ t) and exp (-jω ₁ t) Can be expressed as follows.

Here, the facer is a basic element that rotates in one direction, exp (jω ₁ t) rotates in the positive direction at the position of the angular frequency ω ₁ , and exp (−jω ₁ t) has the angular frequency −. phase rotates in the forward direction at the position of the omega _1.

  On the other hand, the phase of a signal having a bandwidth for transmitting information increases in the positive direction or increases in the negative direction due to the transition of the information signal. At this time, in the frequency domain shown in FIG. 1, a signal having a bandwidth for transmitting information is a USB signal when the phase is rotated in the positive direction, and an LSB signal when the phase is rotated in the negative direction. . For example, in the even symmetric positive polarity rotation SSB shown in FIG. 1, when the phase increases in the positive direction due to the transition of the information signal, a USB component in the positive frequency region is formed, and the phase shifts in the negative direction due to the transition of the information signal. When increasing, an LSB component in the negative frequency domain is formed. That is, even symmetric positive polarity rotation SSB, even symmetric negative polarity rotation SSB, odd symmetric positive polarity rotation SSB and odd symmetric negative polarity rotation SSB shown in FIG. 1 each have a USB component and an LSB component, but in the time domain, Only one of the component and the LSB component is present.

  The four SSB elements in FIG. 1 are expressed as follows: However, information carried by USB SSB-QPSK is u (t) and v (t), and information carried by LSB SSB-QPSK is p (t) and r (t). Further, u (t) and p (t) are in-phase components, and v (t) and r (t) are quadratured-phase components. Further, the signals on the carrier waves u (t), v (t), p (t), and r (t) are U (t), V (t), P (t), and R (t), respectively.

ただし、Ｈ［ｕ（ｔ）］はｕ（ｔ）のヒルベルト変換処理を示す。 <1. Even Symmetric Positive Rotation SSB>
When the signal u (t) is converted into an analysis signal, it is expressed by the following equation.

However, H [u (t)] represents the Hilbert transform process of u (t).

Here, if the carrier angular frequency is ω ₁ , the signal u (t) is carried as SSB shown in the following equation.

<2. Odd Symmetric Positive Rotation SSB>
Using v ₊ and v ₋ in which v (t) is converted into an analytic signal in the same manner as in equation (2), signal v (t) is carried as SSB shown in the following equation.

<3. Even Symmetric Negative Rotation SSB>
Using p ₊ and p ₋ in which p (t) is converted into an analytic signal in the same manner as in equation (2), signal p (t) is carried as SSB shown in the following equation.

<4. Odd Symmetric Negative Rotation SSB>
Using r ₊ and r ₋ in which r (t) is converted into an analytic signal in the same manner as in equation (2), signal r (t) is carried as SSB shown in the following equation.

The four SSB elements have been described above. Here, a modulated signal obtained by synthesizing all four SSB elements can be expressed as S _SSB-QPSK (t) by the following equation.

  FIG. 2 shows the configuration of the modulation device according to this case.

  In the modulation device 100 shown in FIG. 2, the transmission data s (t) is input to the serial / parallel conversion unit (S / P conversion unit) 101. The S / P conversion unit 101 performs serial / parallel conversion on the transmission data s (t) to generate four parallel signals. Then, the S / P converter 101 outputs the four parallel signals subjected to serial / parallel conversion to the Nyquist filters 102, 103, 104, and 105, respectively.

  The Nyquist filters 102, 103, 104, and 105 perform a filtering process on the signals input from the S / P converter 101, respectively, to obtain signals u (t), v (t), p (t), r (t) is output.

  The adder 106 adds the output u (t) of the Nyquist filter 102 and the output p (t) of the Nyquist filter 104 to obtain u (t) + p (t). The adder 107 subtracts the output v (t) of the Nyquist filter 103 from the output r (t) of the Nyquist filter 105 to obtain r (t) −v (t).

  The Hilbert transformer 108 performs a Hilbert transform on the output (r (t) −v (t)) of the adder 107, and a signal H [r (t) −v (t)] after the Hilbert transform is sent to the adder 109. Output.

The adder 109 adds the output (u (t) + p (t)) of the adder 106 and the output H [r (t) −v (t)] of the Hilbert transformer 108 to obtain a signal I (t). Generate. The signal I (t) generated by the adder 109 is shown in the following equation.

  The adder 110 subtracts the output u (t) of the Nyquist filter 102 from the output p (t) of the Nyquist filter 104 to obtain p (t) −u (t). The adder 111 adds the output v (t) of the Nyquist filter 103 and the output r (t) of the Nyquist filter 105 in the negative direction to obtain − {r (t) + v (t)}.

  The Hilbert transformer 112 performs a Hilbert transform on the output (p (t) −u (t)) of the adder 110 and the signal H [p (t) −u (t)] after the Hilbert transform is sent to the adder 113. Output.

The adder 113 adds the output (− {r (t) + v (t)}) of the adder 111 and the output H [p (t) −u (t)] of the Hilbert transformer 112 to add the signal Q ( t). The signal Q (t) generated by the adder 113 is shown in the following equation.

The multiplier 114 receives the carrier frequency signal (cos ω ₁ t) generated by the carrier frequency signal generator 116, and the phase of the multiplier 115 is shifted by 90 ° (π / 2) by the phase shifter 117. A carrier frequency signal (sin ω ₁ t) is input. Thereby, the multiplier 114 multiplies the signal I (t) by the carrier frequency signal, and the multiplier 115 multiplies the signal Q (t) by the carrier frequency signal that is 90 ° out of phase.

Adder 118 adds the output of multiplier 114 and the output of multiplier 115. As a result, two types of USB signals (u (t), v (t)) and two types of LSB signals (p (t), r (t)) are orthogonally multiplexed into an SSB modulated wave S _SSB-QPSK (t). Is obtained. The SSB modulated wave S _SSB-QPSK (t) generated by the adder 118 is represented by the following equation.

  Here, Formula (7) and Formula (10) are equivalent. Therefore, with the configuration shown in FIG. 2, it is possible to obtain a modulation signal intended by this case, that is, a modulation signal composed of four types of SSB elements.

Next, FIG. 3 shows a configuration of a demodulation / decoding apparatus that receives, demodulates and decodes the SSB modulated wave S _SSB-QPSK (t) transmitted from the modulation apparatus 100.

In the demodulation and decoding apparatus 200 illustrated in FIG. 3, the SSB modulated wave S _SSB-QPSK (t) is input to the quadrature detection unit 201. Quadrature detection unit 201, SSB modulated _{wave S SSB-QPSK} (t) to cos .omega ₁ t or sin .omega ₁ respectively in-phase and quadrature components of multiplying the t received signal _{S SSB-QPSK} (t) to the Nyquist filter 202, 203 Output.

Each of the Nyquist filters 202 and 203 removes the in-phase component and the high-frequency component of the quadrature component of the S _SSB-QPSK (t) input from the quadrature detection unit 201 by the low-pass filter action that each of the Nyquist filters 202 and 203 Q (t) is obtained.

  The Hilbert transformers 204 and 205 perform Hilbert transform on the signals I (t) and Q (t) to obtain signals H [I (t)] and H [Q (t)].

  The adder 206 adds I (t) and H [Q (t)], the adder 207 subtracts H [Q (t)] from I (t), and the adder 208 adds Q ( t) and H [I (t)] are added, and the adder 209 subtracts H [I (t)] from Q (t).

  The decoder 210 separates two USB signals that are orthogonal to each other in frequency and outputs the separated u (t) and v (t) to the parallel-serial conversion unit (P / S conversion unit) 212. The decoder 211 separates two LSB signals that are orthogonal to each other in frequency, and outputs the separated p (t) and r (t) to the P / S converter 212.

  The P / S converter 212 obtains one system data signal s (t) by performing parallel-serial conversion on the four systems input.

  Next, the operation of the demodulation / decoding apparatus 200 in this case will be described.

First, the in-phase component of the received signal S _SSB-QPSK (t) obtained by multiplying the received signal S _SSB-QPSK (t) by cos ω ₁ t is passed through a low-pass filter included in the Nyquist filter 202, thereby causing a high-frequency component. Is removed, a signal I (t) of the following formula is obtained.

Further, the high-frequency component is obtained by passing the orthogonal component of the received signal S _SSB-QPSK (t) obtained by multiplying the received signal S _SSB-QPSK (t) by sin ω ₁ t through the low-pass filter of the Nyquist filter 203. Is removed, a signal Q (t) of the following formula is obtained.

  Here, since the signals shown in Expression (11) and Expression (12) include four types of signals, the interference component further increases compared to the case of SSB-QPSK for two signals. If this is the case, the quaternary simultaneous equations must be solved by two formulas (11) and (12). However, it is theoretically impossible to solve the quaternary simultaneous equations with two equations.

Here, it is important to pay attention to the characteristic of the SSB as an analysis signal. That is, the rotation direction in the phase space of the SSB signal is determined in one positive and negative direction. That is, among the SSB signals, the phase rotation direction is different between USB and LSB, and therefore the phase rotation direction does not change even when the Hilbert transform is performed. Therefore, the Hilbert transformer 204 and the Hilbert transformer 205 use this property to perform a Hilbert transform on the signal I (t) of the equation (11) and the signal Q (t) of the equation (12) to obtain a signal of the following equation: Get.

  Comparing equation (11) and equation (14), u (t) and H [v (t)] have the same sign, but p (t) and H [r (t)] have different signs. . Similarly, when Equation (12) and Equation (13) are compared, H [u (t)] and v (t) have different signs, but H [p (t)] and r (t) are identical. It is a sign.

Thus, the adders 206 and 207 obtain the following signals by adding and subtracting the equations (11) and (14).

Similarly, the adders 208 and 209 obtain the following signals by adding and subtracting the equations (12) and (13).

  Thus, Equation (15) and Equation (18) become a binary simultaneous equation of u (t) and v (t), and Equation (16) and Equation (17) are expressed as p (t) and r (t) This is a binary simultaneous equation. As a result, it is only necessary to solve the binary simultaneous equations using the two equations, so that each SSB signal can be separated.

However, these binary simultaneous equations actually include a Hilbert transform element and cause very strong symbol interference. FIG. 4 shows symbol interference caused by the Hilbert transform element. FIG. 4 shows a case where the symbol signal u (t) is used as the Nyquist roll-off signal in the equation (15), that is, u (t) is represented by the equation (19), and its Hilbert transform is represented by the equation (20). It is a figure which shows the interference between symbols in the time domain in the case of being performed.

Here, ω ₀ is the periodic frequency of the symbol signal, and is represented by the following equation by the symbol period T.

  In Expression (15), in addition to the desired wave u (t) on the I axis, the Hilbert transform component H [v (t)] of the signal v (t), which is an orthogonal component, coexists. For example, in FIG. 4, three consecutive symbols u (t), u (t−T), u (t−2T), and symbols v (t), v (t−T), and v (t−) that are orthogonal components. 2H) represents the Hilbert transform components H [v (t)], H [v (t−T)], and H [v (t−2T)]. In FIG. 4, the state of all symbols is set to “1”, that is, +1 for the sake of simplicity.

  In FIG. 4, for example, H [v (t)] having a signal point at the same time as u (t) having a signal point at time t = 0 does not interfere with u (t) at time t = 0. On the other hand, for symbols of t = −T and t = T adjacent to symbols having signal points at time t = 0, H [v (t)] is u (t + T) and u having signal points at the respective times. It is clear that it interferes with (t−T). This is clear even considering the odd symmetry of equation (20).

  Since this complicated interference state occurs at all signal points, it is not easy for the demodulation and decoding apparatus 200 to extract a desired information signal from the received signal. As a method for extracting a desired information signal in such an interference state, there is a method using a turbo decoder. However, since this method generates a replica of the interference component and cyclically removes the interference component, the processing time becomes long. There is also a method using a code spreading technique. However, with this method, for example, the range that can be used in a spreading code such as a Gold code is limited, so that the spreading efficiency decreases. A fundamental solution for the removal of the Hilbert transform component requires the use of the features of the interference component, but no such work has been done so far.

  Therefore, in this case, paying attention to the fact that the Hilbert transform component interferes with adjacent symbols, the interference wave is regarded as a desired wave, not as an interference wave, and the demodulation / decoding device communicates the desired wave component including the Q axis. A desired wave is extracted using points generated at three locations in the frame.

FIG. 5 shows a method for extracting a desired wave in this case. FIG. 5 shows a frame of a symbol string transmitted by the S / P converter 101 of the modulation apparatus 100 shown in FIG. In this case, a null symbol is placed at the beginning of this frame or at the end of the frame. Specifically, as shown in FIG. 5, a null symbol is arranged at T ₀ which is the head of the frame, and a null symbol is arranged at T ₁₁ which is the end of the frame. Further, as shown in FIG. 5, signals u (t) and v (t) are respectively arranged on the I axis and the Q axis for symbols other than the head and the tail of the frame.

FIG. 6 shows the effect when null symbols are arranged at the beginning and end of the frame as shown in FIG. FIG. 6 shows six signal components on the I axis and the Q axis at times t = T _{0 to} T ₅ among the symbols at times t = T _{0 to} T ₁₁ shown in FIG. As shown in FIG. 6, u (t) having a signal point on the I axis at time t = 0 is Hilbert transform component H of u (t) at time t = −T on the Q axis orthogonal to the I axis. It can be seen that only [u (t)] appears alone. Similarly, v (t) having a signal point on the Q axis at time t = 0 is equal to the Hilbert transform component H [v (t) of v (t) at time t = −T on the I axis orthogonal to the Q axis. )] Alone appears. Here, when the amplitudes of the signals u (t) and v (t) are normalized, the amount of interference with the adjacent symbol of the Hilbert transform component is about 0.63662.

  As a result, the demodulation and decoding apparatus 200 extracts u (t) and v (t) as Hilbert transform components independently at time t = −T, and then performs u (t) and v (t) at time t = 0. ) And the interference from the next symbol. That is, on the I axis, the signal component at time t = 0 is u (t) −H [v (t−T)], but u (t) that has become known at time t = −T is substituted. The value of -H [v (t-T)] is calculated. Similarly, on the Q axis, the signal component at time t = 0 is v (t) + H [u (t−T)], but v (t) that has become known at time t = −T is substituted. To calculate the value of H [u (t−T)]. Thereby, the values of u (t), u (t−T), v (t) and v (t−T) are obtained by time t = 0.

  The signal component at time t = T can be separated by using a value that has become known by time t = 0 even at time t = T. Specifically, at time t = T, the signal component on the I axis is u (t−T) −H [v (t)] − H [v (t−2T)], and v becomes known. By substituting (t) and u (t−T), the value of −H [v (t−2T)] is calculated. Similarly, on the Q axis, the signal component at time t = T is v (t−T) + H [u (t)] + H [u (t−2T)], and becomes u (t), v that has become known. By substituting (t−T), the value of H [u (t−2T)] is calculated. Thereafter, it is apparent that all symbol signals on the frame can be extracted in the same manner by using the known symbol values.

  In this way, the demodulation and decoding apparatus 200 uses the Hilbert transform components that are independently extracted at the beginning and the end of the frame in which the null symbols are arranged, and sequentially converts the Hilbert transform components that cause intersymbol interference from the beginning of the frame. By removing, the USB signals (u (t) and v (t)) are separated into signals for each SSB element. That is, in the demodulation and decoding apparatus 200, the start or end of the frame in which the null symbol is arranged is set as the start position of the separation process that separates the USB signal into two SSB elements.

  As described above, according to this case, the demodulation / decoding apparatus separates the four types of SSB signals into the USB signal (two types) and the LSB signal (two types) by performing the Hilbert transform process. Furthermore, the modulation apparatus arranges a null symbol at the beginning of the frame or at the end of the frame, so that a non-interfering portion can be secured in the time domain during demodulation. Therefore, the demodulation / decoding apparatus can separate two orthogonal components after the head of the frame or before the tail of the frame by using the Hilbert transform component that is independently extracted at the head of the frame or the tail of the frame. Therefore, since the demodulation / decoding apparatus can remove the interference component, when the digital signal is converted to the SSB, the transmission signal is narrowed to improve the frequency utilization efficiency of wireless communication. Can be suppressed.

  Also, according to this case, it has been clarified that a modulation method having a frequency utilization efficiency of 2 bits / sec / Hz can be provided by using four types of SSB signals having the same carrier frequency. In addition, as shown in FIG. 7, when the roll-off rate (Nyquist roll-off rate) is sufficiently reduced to narrow the occupied bandwidth (FIG. 7B), when the bandwidth is 1 and the roll-off rate is 1 ( Since it approaches ½ of the bandwidth of FIG. 7A), it is possible to provide a modulation method with a frequency utilization efficiency of 4 bits / sec / Hz.

(Case 2)
FIG. 8 shows a procedure of symbol signal extraction in the frame configuration shown in FIG. As shown in FIG. 8, for example, on the I axis at time t = 0, the signal (H [u (t)]) extracted on the Q axis at time t = −T is used. For the Q axis at time t = 0, the signal (−H [v (t)]) extracted from the I axis at time t = −T is used. As described above, in the symbol signal extraction procedure shown in FIG. 8, in order to extract the symbol signal, the signal extracted in the past alternates between the I axis and the Q axis (dotted arrow shown in FIG. 8). Complicated processing will occur.

  Further, in the symbol signal extraction method in Case 1, u (t) and v (t) extracted sequentially from the beginning of the frame are used in order to extract subsequent symbols, so that u (t) and v (t) There is a problem that the numerical error of is inherited genetically. For this reason, it is essential to use an error correction code such as a Reed-Solomon code. However, as shown in FIG. 8, it is applied in a state in which the signal alternates between the I axis and the Q axis. Increases complexity.

Hereinafter, this case will be specifically described. FIG. 9 shows the symbol arrangement in this case. As shown in FIG. 9, in this case, the symbol arrangement of u (t) and v (t) is alternately switched for each symbol on the I axis and the Q axis. That is, modulation apparatus 100 (FIG. 2) arranges u (t) and v (t) alternately on the I axis and the Q axis for each symbol. However, in FIG. 9, one frame is configured at time t = T _{−1 to} T ₁₀ . Further, the symbols arranged at the head and the tail of the frame are null symbols as in the case 1. Specifically, as shown in FIG. 9, at time t = T ₀ , u ₁ is arranged on the I axis and v ₁ is arranged on the Q axis. At time t = _{T 1, v 2} are arranged in the I-axis, _{u 2} are arranged in the Q axis. Similarly, at time t = T ₂ , u ₃ is arranged on the I axis and v ₃ is arranged on the Q axis. The same applies to time t = time t = T _{3 to} T ₉ .

  FIG. 10 shows the effect obtained by performing the symbol arrangement shown in FIG. As shown in FIG. 10, for example, on the I axis, the interference received by u (t) at time t = 0 is only −H [u (t−T)], and at time t = 2T, u (t) The only interference received by t-2T) is -H [u (t-T)] and -H [u (t-3T)]. That is, on the I axis, the interference received by u (t) is only the Hilbert transform component of u (t) having signal points at different times. In other words, v (t) is not included in the interference component for u (t). Similarly, as shown in FIG. 10, on the Q axis, the interference received by v (t) at time t = 0 is only from H [v (t−T)], and at time t = 2T, v The interference received by (t-2T) is only from H [v (t-T)] and H [v (t-3T)]. That is, on the Q axis, u (t) is not included in the interference component for v (t).

  As a result, the symbol arrangement shown in FIG. 9 handles only the inter-adjacent symbol interference due to the desired wave symbol (u (t) for the I axis and v (t) for the Q axis) on each of the I axis and Q axis. Compared with 1, the interference relationship can be further simplified. This makes it easier to apply an existing error correction code to this case.

Further, in the case of a sinc function, the amount of interference is processed using the value a shown in the following equation as the first step.

As a result, simultaneous equations for the entire frame can be described as:

  Naturally, in the disturbance state of the radio wave propagation environment, the amplitude fluctuates from moment to moment, so the value of a becomes effective after being stabilized by equalization processing or the like. Expression (23) is a matrix equation regarding the symbol u (t−kT) (k = 0, 1, 2,..., 9) on the I axis, and Expression (24) is the symbol v (t on the Q axis. −kT) (k = 0, 1, 2,..., 9). In addition, the value of k in Expression (23) and Expression (24) is a case where the symbol arrangement shown in FIG. 9 is given as an example, and the value of k can be arbitrarily determined.

  As described above, according to the present case, by alternately switching the symbols arranged on the I axis and the Q axis, the interference components on the I axis and the Q axis can be further simplified as compared with the case 1.

(One embodiment of the present invention)
Hereinafter, an embodiment of the present invention will be described.

  As described in the above-described case, as a modulation method for generating a modulation signal composed of four types of single sideband elements having a common carrier frequency, the above four types of single sideband elements are arranged around a common carrier frequency axis. By arranging them orthogonally to each other, it is possible to realize a frequency use efficiency that is almost the same as that of the OFDM system or about twice that of a single carrier modulation system such as QPSK.

  However, between two types of upper single sideband elements having a common carrier frequency and orthogonal in the phase domain, or between the lower four types of single sideband elements, the Hilbert transform components of each other are adjacent symbols at the time of demodulation. Interference occurs.

  For example, as described in the above-described case, in FIG. 6, in the null symbol section at the beginning of the frame arranged at time t = −T, symbols u (t) and v ( It shows that the values of the symbols u (t) and v (t) are extracted using the fact that the Hilbert transform component of t) appears as an interference component on the orthogonal counterpart. Equations (23) and (24) are obtained by simultaneous equations using the values of extracted symbols u (t) and v (t), and all symbols u (t−nT), v (T−nT) (where n = 1, 2,..., K) is extracted.

  However, in Expression (23) and Expression (24), the error included in the values of the symbols u (t) and v (t) extracted at time t = −T is inherited. Therefore, detection errors of sampling values of I and Q including symbols u (t−nT) and v (t−nT), and symbols u (t−nT) and v (t−nT) solved by simultaneous equations The calculation error included in the value increases as the symbols u (t−nT) and v (t−nT) arranged at the end of the frame. That is, there is an adverse effect of inheriting a genetic error for the symbols u (t) and v (t) extracted using the equations (23) and (24).

  Therefore, in the present invention, symbol arrangement on the Q-axis is alternated for each symbol in the multiplexed single sideband wave between two types of upper single sideband elements or between the lower four types of single sideband elements. Furthermore, the symbol series is converted into a binary value. Further, the receiving side decoding unit provides a means for converting the ternary binary digitized symbol back into binary data (that is, binary number based on '0' and '1') and returning the data, Complete with functions as a communication system.

  Specifically, without changing the numerical value of the binary bit string, the bit that becomes ‘1’ is continuous, that is, the continuity of ‘1’ in the bit string is removed. Here, two elements of “0” and “1” are used in a general binary number, whereas three elements of “−1”, “0”, and “1” are used in a ternary binary number. The expression of numerical values is diversified by having three elements. In the modulation processing of digital communication, although the information signal to be transmitted is input in a state expressed in general binary numbers ('0' and '1'), '-1' and '1' in the modulation unit Conversion to represent is generally performed. In one embodiment of the present invention, the continuity of modulation symbol signals represented by −1 and ‘1’ is removed by using such a situation.

  Hereinafter, the principle of one embodiment of the present invention will be described.

Here, as shown in Expression (25), a binary number in which N “1” s are continuous is used. Also, the bits at both ends of the N bit strings shown in Expression (25) are set to “0”. At this time, if “1” is further added to the least significant bit (“1”) of the N-digit bit string, the bit in the (N + 1) -th digit becomes “1”, and all N “1” s become “0”. .

  On the other hand, in contrast to the equation (25), when the N + 1 digit bit is' 1 'using a binary number in which N' 0's are consecutive, the least significant bit ('0') of the N digit bit string When “1” is subtracted from “)”, both ends of the N bit strings become “0”, and all the N “0” s become “1”.

Therefore, the present invention eliminates intersymbol interference by determining the occurrence of intersymbol interference components of the in-phase component of the modulation signal and the quadrature component of the modulation signal based on the relationship between the polarities of the symbols before and after the modulation signal. To do. This will be specifically described with reference to FIGS. 11A and 11B. For example, in the 9-digit binary number (binary code) shown in FIG. 11A, the portions where “1” continues are 2 ⁰ , 2 ¹ , 2 ² , 2 ³ and 2 ⁶ , 2 ⁷ . Therefore, as shown in FIG. 11A, 2 ⁰ , 2 ¹ , 2 ² , and 2 ³ in which “1” continues are expressed as shown in Expression (26) by being converted into a ternary binary number, and “1” 2 ⁶ and 2 ⁷ that are consecutive are represented by Expression (27) by being converted into a ternary binary number. As shown in Expression (26), 2 ⁰ , 2 ¹ , 2 ² , and 2 ³ in which “1” continues are the same as the value obtained by subtracting “1” from 2 ⁴ = 1 to 2 ⁰ . Similarly, as shown in Expression (27), 2 ⁶ and 2 ^{7 in which} “1” continues are the same as the value obtained by subtracting “1” from 2 ⁸ = 1 to 2 ⁶ .

Further, for example, in the 8-digit binary number shown in FIG. 11B, the portions where '1' continues are 2 ⁰ , 2 ¹ , 2 ² , 2 ³ and 2 ⁵ , 2 ⁶ . Therefore, as shown in FIG. 11B, 2 ⁰ , 2 ¹ , 2 ² , and 2 ³ in which “1” continues are expressed as Equation (28) by being converted into a ternary binary number, and “1” 2 ⁵ , 2 ⁶ , which are consecutive, are expressed as shown in Expression (29) by being converted into a ternary binary number.

Here, as shown in FIG. 11B, ^{2 4} is '1' next to the code after ternary binarized (3-valued binary code), ^{2 5} becomes "-1". That is, in FIG. 11B, a portion where “1” and “−1” continue is newly generated even in the code after ternarization and binary conversion. Therefore, as shown in FIG. 11B, the 2 bits of 2 ⁵ and 2 ⁶ in which “1” and “−1” are continuous are further converted into a ternary binary number to obtain a formula (30). It is represented by 1 bit.

As a result, the 8-digit binary number shown in FIG. 11B can be expressed without a portion where “1” and “−1” continue as a whole, as shown in Expression (31).

  In the signal processing, it is desirable that the ternarization / binarization operation is performed by a single operation. FIG. 12 shows that the conversion of the ternary binarization shown in FIG. 11A is possible by continuously performing a single operation.

Specifically, the processing unit that performs ternary binarization of the modulation apparatus on the transmission side changes the digit that is “1” to “−1” when “1” is present in the binary code illustrated in FIG. 12. And “1” is uniquely added to the sign of the digit one digit above. In FIG. 12, since 2 ⁰ , 2 ¹ , 2 ² , 2 ³ and 2 ⁶ , 2 ⁷ are “1” and are continuous, the processing unit that performs ternary binary conversion performs the above operation six times. Do. Then, as shown in FIG. 12, the processing unit that performs ternary binary digitization can obtain the same ternary binary code as in FIG. 11A by simply adding the results of six operations. Yes, that is, continuity of '1' can be removed.

  Further, FIG. 13 shows that the conversion of the ternary binarization shown in FIG. 11B is possible in the same manner as FIG. In the operation result of removing the continuity of “1”, even when a portion where “1” (or “−1”) continues is newly generated, as shown in FIG. It is sufficient to repeat the operation of setting “−1” and adding “1” to the sign of the digit one digit above. Thereby, the continuity of '1' can be removed as in FIG.

  Next, the process of the ternary binarization process in the modulation apparatus on the transmission side will be described. FIG. 14 is an example of a flowchart showing a signal processing process for performing binarization and binarization in the present invention. Here, k shown in FIG. 14 represents the digit position of the bit string, the digit position of the least significant bit is k = 1, and the digit position of the most significant bit is k = N. Further, m represents the number of processings in which the ternary binary conversion processing is performed in one cycle from the least significant bit to the most significant bit.

  In step (hereinafter referred to as ST) 101, k and m are initialized, and k = 0 and m = 0.

  In ST102, 1 is added to the digit position k, so that k = k + 1. That is, the first time is k = 1, and the digit position is set to the least significant bit.

  In ST103, it is determined whether Bit (k), which is a bit at digit position k, is '1'. When Bit (k) is “1” (in the case of ST103: Yes), in ST104, Bit (k) is set to “−1”, and the bit is one digit higher than the digit position k (digit position k + 1). 1 is added to Bit (k + 1). In ST105, 1 is added to the processing count m.

  In ST106, it is determined whether or not the digit position of the bit subjected to the ternary binary conversion processing is the most significant (that is, whether or not k = N). If the digit position of the bit subjected to the ternary binary conversion processing has not reached the most significant (k = N) (ST106: No), the process returns to ST102. In addition, when the digit position of the bit subjected to the ternary binary conversion processing is the most significant (k = N) (ST106: Yes), it is confirmed that “1” is not included in all the bits. In order to do this, the process returns to ST101 and starts from the beginning.

  On the other hand, when Bit (k) is not “1” in ST103 (ST103: No), in ST107, whether or not the digit position k is the most significant (k = N), and ternary 2 It is determined whether the digitization process has never been performed (whether m = 0). When the digit position k is not the most significant bit, or when the ternary binary conversion process has been performed once or more (ST107: No), the process returns to ST102. Further, when the digit position k is the most significant bit and the ternary binary conversion process has never been performed (ST107: Yes), the process ends. In the present invention, as shown in FIG. 11A, ‘1’ may occur in the (N + 1) th digit that is one bit higher than the most significant bit.

  As shown in FIG. 14, by repeating a simple process, a binary ternarization and binary conversion can be performed by a simple process.

  Next, a process (binarization process) in which the decoding / demodulation apparatus on the receiving side returns a ternary binary code to a binary code will be described.

Specifically, the processing unit that performs binarization of the decoding / demodulation apparatus sets a digit having “−1” to “1” when “−1” is present in the ternary binary code, The operation of adding “−1” to the sign of the digit one digit above is uniquely performed. For example, FIG. 15 shows a process of the decoding / demodulating apparatus corresponding to the ternary binary conversion process shown in FIG. 11A. In FIG. 15, 2 ⁰ and 2 ⁶ are “−1”, and 2 ⁴ and 2 ⁸ are “1”. Thus, - as a process of the operation for ending the '1' at the beginning '1', four operations from 2 ⁰ to 2 ^4, and, there are two operations from 2 ⁶ to 2 ^8. The six operation code does not contain the '-1' in all digits from 2 ⁰ to 2 ^8, i.e., it is possible to obtain a general binary code, binarized is completed.

Similarly to FIG. 15, FIG. 16 shows the processing of the decoding / demodulating apparatus corresponding to the ternary binary processing shown in FIG. 11B. In FIG. 16, 2 ⁰ and 2 ⁴ are “−1”, and 2 ⁷ is “1”. Thus, - as a process of the operation for ending the '1' at the beginning '1', four operations from 2 ⁰ to 2 ^4, and, there are three operation from 2 ⁴ to 2 ^7. The seven operations in all digits from 2 ⁰ to 2 ⁷ can obtain a general binary code, binarized is completed.

  Next, the process of the binarization process in the decoding / demodulation apparatus on the receiving side will be described. FIG. 17 is an example of a flowchart showing a signal processing process for binarizing a ternary binary code according to the present invention. Here, k shown in FIG. 17 represents the digit position of the bit string, the digit position of the least significant bit is k = 1, and the digit position of the most significant bit is k = N. In addition, m represents the number of times that the binarization processing of the ternary binary code is performed in one round from the least significant bit to the most significant bit.

  In ST201, k and m are initialized, and k = 0 and m = 0.

  In ST202, 1 is added to the digit position k, so that k = k + 1. That is, the first time is k = 1, and the digit position is set to the least significant bit.

  In ST203, it is determined whether or not Bit (k), which is a bit at digit position k, is “−1”. When Bit (k) is “−1” (in the case of ST203: Yes), in ST204, Bit (k) is set to “1”, and the bit is one digit higher than the digit position k (digit position k + 1). −1 is added to Bit (k + 1). In ST205, 1 is added to the processing count m.

  In ST206, it is determined whether or not the digit position of the bit subjected to the binarization processing of the ternary binary code is the most significant (that is, whether or not k = N). When the digit position of the bit subjected to the binarization processing of the ternary binary code has not reached the most significant (k = N) (ST206: No), the process returns to ST202. When the digit position of the bit subjected to the binarization processing of the ternary binary code is the most significant (k = N) (ST206: Yes), all bits include “−1”. In order to confirm that there is no error, the process returns to ST201 and processing is performed from the beginning.

  On the other hand, when Bit (k) is not “−1” in ST203 (ST203: No), in ST207, whether or not the digit position k is the most significant (k = N), and ternarization is performed. It is determined whether the binary code binarization process has never been performed (whether m = 0). When the digit position k is not the most significant bit, or when the binarization process of the ternary binary code has been performed one or more times (ST207: No), the process returns to ST202. Further, when the digit position k is the most significant bit and the ternary binarization process has not been performed (ST207: Yes), the process ends.

  As shown in FIG. 17, similarly to FIG. 14, the binary conversion of the ternary binary code can be performed by a simple process by repeating simple processing.

  As described above, according to the present invention, two types of upper single sideband elements having a common carrier frequency and orthogonal in the phase region, or the lower four types of single sideband elements are demodulated. By removing the inter-symbol interference caused by the Hilbert transform component of each symbol, it is possible to extract a desired symbol with high reliability. Furthermore, it is composed of two types of upper single sideband elements and lower four types of single sideband elements, and by using four types of single sideband elements sharing the carrier frequency, it is almost equivalent to the OFDM system. Alternatively, it is possible to reliably realize about twice the frequency utilization efficiency of a single carrier modulation method such as QPSK. Further, by making the roll-off rate of the symbol signal steep, it is possible to realize frequency use efficiency that is about twice that of the OFDM system.

  INDUSTRIAL APPLICABILITY The present invention narrows a transmission signal by converting a digital signal into an SSB and improves the frequency utilization efficiency of wireless communication, can suppress mutual interference between signals and can be widely applied to various wireless devices. .

The figure which shows four types of SSB elements of Case 1 The block diagram which shows the structure of the modulation apparatus of case 1 The block diagram which shows the structure of the demodulation decoding apparatus of case 1 The figure which shows the symbol interference in the SSB signal of case 1 The figure which shows the frame structure of the SSB signal of case 1 The figure which shows the interference condition of the I-axis and the Q-axis in each symbol of case 1 The figure which shows that frequency utilization efficiency improves when the roll-off rate of case 1 is made small. The figure which shows the procedure of signal extraction of case 1 Diagram showing the symbol arrangement for case 2 The figure which shows the interference condition of I-axis and Q-axis in each symbol of case 2 The figure which shows the principle of the ternary binary number which concerns on one embodiment of this invention The figure which shows the principle of the ternary binary number which concerns on one embodiment of this invention The figure which shows the ternary binarization process based on one embodiment of this invention The figure which shows the ternary binarization process based on one embodiment of this invention The flowchart which shows the process of the ternary binarization based on one embodiment of this invention The figure which shows the binarization process of the ternary binary code which concerns on one embodiment of this invention The figure which shows the binarization process of the ternary binary code which concerns on one embodiment of this invention The flowchart which shows the process of binarization of the ternary binary code which concerns on one embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Modulator 101 S / P converter 102,103,104,105,202,203 Nyquist filter 106,107,109,110,111,113,118,206,207,208,209 Adder 108,112,204 , 205 Hilbert transformer 114, 115 multiplier 116 carrier frequency signal generator 117 phase shifter 200 demodulation decoding device 201 quadrature detection unit 210, 211 decoder 212 P / S conversion unit

Claims (4)

A modulation method for generating a modulation signal composed of two types of single sideband elements having a common carrier frequency,
The two types of single sideband elements are:
A first single sideband element having a positive upper single sideband in the positive frequency region and a positive lower single sideband in the negative frequency region; and a positive upper single sideband in the positive frequency region And a second single sideband element having a negative single-sideband in the negative frequency region and a negative single-sideband in the positive frequency region and negative A third single sideband element having a positive upper single sideband in the frequency domain, a positive lower single sideband in the positive frequency domain and a negative upper singleband in the negative frequency domain. A fourth single sideband element having
Modulation method. In the communication frame in which the symbols of the modulation signal are arranged, the in-phase component of the modulation signal and the quadrature component of the modulation signal are ternarized and binary to remove the continuity of the symbols, and for each symbol Are alternately arranged on the I axis and the Q axis,
The modulation method according to claim 1. A first single sideband element having a positive upper single sideband in the positive frequency region and a positive lower single sideband in the negative frequency region; and a positive upper single sideband in the positive frequency region Two types of single sidebands comprising a second single sideband element having a wave and a negative single sideband in the negative frequency region, or a positive lower side in the positive frequency region A third single sideband element having a single sideband wave and having a positive upper single sideband wave in the negative frequency region; and a negative single sideband wave having a positive lower sideband wave in the positive frequency region and a negative electrode in the negative frequency region A modulated signal composed of two types of single sidebands composed of a fourth single sideband element having an upper single sideband having a characteristic, and receiving the modulated signal converted into a binary value,
A binary conversion process is performed for converting the symbol of the modulation signal into a binary number based on '0' and '1';
Demodulation method. Determining the occurrence of inter-adjacent symbol interference components of the in-phase component of the modulation signal and the quadrature component of the modulation signal based on the relationship with the polarity of the preceding and following symbols, thereby removing the inter-adjacent symbol interference component;
The demodulation method according to claim 3.

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