JP6387538B2 - Wireless communication system, wireless communication apparatus, and wireless communication method - Google Patents

Description

  The present invention relates to a wireless communication apparatus, a wireless communication system, and a wireless communication method that communicate with signals of a plurality of polarizations.

  For modulation schemes for digital transmission, phase modulation (PSK modulation) in which information is transmitted by changing the phase of the carrier wave, quadrature amplitude modulation (QAM) in which the transmission speed (frequency utilization efficiency) is increased by changing the amplitude and phase are often used. Used.

  These modulation schemes can increase the transmission rate by increasing the number of bits per symbol, but achieve the same bit error rate (BER) because the inter-symbol linear distance (Euclidean distance) decreases. This requires high signal power. Under the condition of constant transmission power, it is important to increase the minimum inter-symbol distance (minimum Euclidean distance) to improve the bit error rate. Arrangement) is known (see, for example, Non-Patent Document 1).

  In addition, in an additive white Gaussian noise (AWGN) environment, symbol errors occur between adjacent symbols on the phase plane, so graying is performed so that the adjacent symbols have a 1-bit difference (Hamming distance is 1). It is known that the bit error rate of each modulation method can be minimized by using the signal point arrangement. Furthermore, a trellis coded modulation method (TCM) is known as a coded modulation method that increases an Euclidean distance equivalently by combining an error correction code and digital modulation (for example, see Non-Patent Document 2).

  On the other hand, power amplifiers used in wireless communication systems suffer from performance degradation due to non-linearity, so it is important to reduce the peak-to-average power ratio (PAPR) of transmitted signals, especially during multicarrier transmission and high power transmission. . PAPR depends on a modulation method, filter characteristics, and the like, and PAPR countermeasures by coding modulation and peak value suppression are known.

  In recent years, with the widespread use of wireless communication systems, a shortage of frequency resources has become apparent, especially in the microwave band, and transmission techniques for achieving high frequency utilization efficiency are required. The orthogonal polarization multiplexing technique pays attention to the wavefront direction of a radio wave radiated from an antenna, and transmits independent signals having wavefronts orthogonal to each other at the same frequency.

  When this orthogonal multiplexing polarization technology is applied, in the case of linear polarization used in fixed wireless communication or the like, V and H polarization multiplexing using vertical (V) polarization and horizontal (H) polarization can be realized. In this case, the frequency utilization efficiency is doubled compared to the case where the orthogonal polarization multiplexing technique is not applied (see, for example, Patent Document 1). The V and H polarization multiplexed signals can be transmitted and received by, for example, arranging two linear radiating elements orthogonally in a cross shape.

  Furthermore, in satellite communication, a polarization multiplexing system is known that multiplexes signals into a plurality of polarizations to improve frequency use efficiency (see, for example, Non-Patent Document 3). In this method, a bit is assigned to each polarization, and a signal point is obtained by multiplexing (synthesizing) values obtained by mapping each polarization component before synthesis onto the horizontal (H) / vertical (V) polarization IQ plane. Form. At this time, the signal point arrangement is optimized so that the minimum Euclidean distance between symbols on each polarization of H / V is maximized.

JP 2007-189306 A

Gerard J. Foschini, Richard D. Gitlin, Stephen B. Weinstein, “Optimization of Two-Dimensional Signal Constellation in the Presence of Gaussian Noise”, IEEE Trans. Commun., Vol. COM-22, No. 1, pp. 28 -38, Jan. 1974. G. Ungerboeck "Trellis-coded modulation with redundant signal sets part1 and part2", IEEE Comm. Mag., Vol. 25, No. 2, pp.5-21, 1987. M. Yofune, J. Webber, K. Yano, H. Ban, and K. Kobayashi, “Optimization of Signal Design for Poly-Polarization Multiplexing in Satellite Communications,” IEEE Communications Letters, Vol. 17, No. 11, pp. 2017-2020, Nov. 2013.

  However, in Non-Patent Document 3, normalization is performed with the average power of the total H / V for each symbol H (n) and V (n) on the H / V polarization as in the following formula (E0). As a result, since optimization is performed under the condition of constant transmission power (H / V total power = 1), there is a possibility that the maximum power (peak power) of the optimal arrangement becomes large.

However, H (n) and V (n) are IQ components (complex numbers) of the nth symbol (1 ≦ n ≦ 2 ^N ) for H / V polarized waves, and H _opt (n) and V _opt (n) are , IQ component (complex number) of optimal arrangement normalized by the average power of H / V total, N is the number of bits per symbol on H / V polarization, and | ... | means an absolute value.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to optimize the signal point by suppressing PAPR with respect to a multidimensional transmission system such as a polarization multiplexing system. To provide a wireless communication system, a wireless communication apparatus, and a wireless communication method using an arrangement.

According to one aspect of the present invention, there is provided a wireless communication system that performs transmission and reception by multidimensional transmission in which signal points are assigned to a space constituted by first and second carrier signals, and includes a transmitter and a receiver, The machine includes a transmission antenna, an error correction coding processing unit for performing error correction coding processing on a transmission symbol, and a first storage unit, and the first storage unit is configured to transmit a signal for each transmission symbol. The signal point arrangement calculated so as to minimize the influence on the bit error rate of the code assigned to each symbol at the time of normalization and error correction for the peak power with respect to the point arrangement is stored, and the first storage unit Based on the stored information, in multi-dimensional transmission, a map that allocates the output of the error correction coding processing unit in the in-phase component and quadrature phase component planes of the first and second carrier signals. And a transmission unit that performs orthogonal modulation on the first and second carrier signals based on the processing result of the mapping processing unit and sends out from the transmission antenna, and the receiver includes a reception antenna, For a signal received by the receiving antenna, a receiving unit that performs quadrature detection on each of the first and second carrier signals, and a second that stores information corresponding to the signal point arrangement stored in the first storage unit A maximum likelihood determination processing unit for performing maximum likelihood determination on the first and second carrier signals in multidimensional transmission based on information stored in the storage unit and the second storage unit, and maximum likelihood determination And an error correction decoding processing unit for executing error correction decoding processing based on the determination result of the processing unit.

  Preferably, the normalization for peak power relative to the signal point constellation is a normalization for the total peak power of the first and second carrier signals.

  Preferably, the normalization for the peak power with respect to the signal point arrangement is a normalization for the peak power of each of the first and second carrier signals.

  Preferably, the signal constellation is normalized for the peak power with respect to the signal constellation, and for each transmission symbol, a monotonically increasing function with a value obtained by dividing the Hamming distance by the Euclidean distance is minimized for the set of transmission symbols. It is calculated as follows.

  Preferably, the function is a sum of transmission symbols obtained by dividing the Hamming distance by the Euclidean distance for each transmission symbol.

  Preferably, the first and second carrier signals are two polarized carrier signals orthogonal to each other.

  Preferably, the first and second carrier signals are carrier signals having different frequencies.

According to another aspect of the present invention, there is provided a radio communication apparatus that performs transmission by multidimensional transmission in which signal points are allocated to a space constituted by first and second carrier signals, and includes error correction for a transmission antenna and a transmission symbol. An error correction encoding processing unit for executing encoding processing and a storage unit are provided, and the storage unit assigns each transmission symbol to each symbol at the time of normalization and error correction for peak power with respect to signal point arrangement The signal constellation calculated so as to minimize the influence of the generated code on the bit error rate is stored, and based on the information stored in the storage unit, the output of the error correction coding processing unit is output in multi-dimensional transmission. , Mapping processing units to be allocated in the in-phase component and quadrature phase component planes of the first and second carrier signals, and the first and second based on the processing result of the mapping processing unit Run the quadrature modulation on the carrier signal, further comprising a transmitting unit for transmitting from the transmitting antenna.

According to still another aspect of the present invention, there is provided a wireless communication apparatus that performs reception by multidimensional transmission in which signal points are assigned to a space constituted by first and second carrier signals, and is received by a reception antenna and a reception antenna. A reception unit that performs quadrature detection for each of the first and second carrier signals, and a storage unit, wherein the storage unit normalizes peak power with respect to the constellation for each transmission symbol and The signal point arrangement calculated so as to minimize the influence on the bit error rate of the code assigned to each symbol at the time of error correction is stored, and in multidimensional transmission based on the information stored in the storage unit, A maximum likelihood determination processing unit for performing maximum likelihood determination on the first and second carrier signals, and an error correction decoding process based on a determination result of the maximum likelihood determination processing unit Further comprising an error correction decoding processing unit for executing.

  Preferably, the normalization for peak power relative to the signal point constellation is a normalization for the total peak power of the first and second carrier signals.

  Preferably, the normalization for the peak power with respect to the signal point arrangement is a normalization for the peak power of each of the first and second carrier signals.

  Preferably, the signal constellation is normalized for the peak power with respect to the signal constellation, and for each transmission symbol, a monotonically increasing function with a value obtained by dividing the Hamming distance by the Euclidean distance is minimized for the set of transmission symbols. It is calculated as follows.

  Preferably, the function is a sum of transmission symbols obtained by dividing the Hamming distance by the Euclidean distance for each transmission symbol.

  Preferably, the first and second carrier signals are two polarized carrier signals orthogonal to each other.

  Preferably, the first and second carrier signals are carrier signals having different frequencies.

According to still another aspect of the present invention, there is provided a wireless communication method for performing transmission / reception by multidimensional transmission in which signal points are allocated to a space constituted by first and second carrier signals, wherein the transmitter has an error in a transmission symbol. The step of executing the correction coding process, and the transmitter minimizes the influence on the bit error rate of the code assigned to each symbol at the time of normalization and error correction for the peak power with respect to the constellation for each transmission symbol. Based on the signal point arrangement calculated so as to be converted, a mapping process for assigning the result of the error correction coding process in the in-phase component and quadrature phase component planes of the first and second carrier signals in multidimensional transmission is performed. And a transmitter performs quadrature modulation on the first and second carrier signals based on the result of the mapping process, Transmitting from the transmitter, the receiver performing quadrature detection on the received signal and the first and second carrier signals, respectively, and the receiver based on the signal point arrangement in the transmitter In transmission, the method includes a step of executing maximum likelihood determination for the first and second carrier signals, and a step of executing an error correction decoding process by the receiver based on the determination result of the maximum likelihood determination.

  According to the present invention, it is possible to perform transmission or reception with a signal point arrangement having an excellent bit error rate with respect to a multi-dimensional transmission system such as a polarization multiplexing system while suppressing PAPR.

It is a functional block diagram for demonstrating the structure of the transmitter 1000 of this Embodiment. It is a functional block diagram for demonstrating the structure of the receiver 2000 of this Embodiment. It is a conceptual diagram which shows the outline | summary of a non-orthogonal polarization multiplexing system. It is a conceptual diagram which shows the outline | summary of a multi-polarization spatial modulation system. It is a figure which shows the result of having searched the optimization arrangement | positioning which makes the minimum Euclidean distance the maximum. FIG. 6 is a diagram illustrating signal point arrangement on the IQ plane in each of the H / V polarized waves of arrangement A in FIG. 5. FIG. 6 is a diagram showing signal point arrangement on the IQ plane in each of the H / V polarized waves of arrangement B in FIG. 5. FIG. 6 is a diagram illustrating signal point arrangement on an IQ plane in each of H / V polarized waves of arrangement C in FIG. 5. It is a figure which shows the evaluation value of each optimal arrangement | positioning searched shown in FIG. It is a figure which shows the transceiver structure which simulated the BER characteristic. It is a figure which shows the result of the BER simulation about each optimal signal point arrangement | positioning. 6 is a flowchart for explaining processing in a transmitter 1000 and a receiver 2000.

  Hereinafter, a radio communication system according to an embodiment of the present invention will be described with reference to the drawings. In the following embodiments, components and processing steps given the same reference numerals are the same or equivalent, and the description thereof will not be repeated unless necessary.

  The radio communication system of the present embodiment is generally a radio communication system that performs transmission and reception by “multidimensional transmission” in which signal points are assigned to a space constituted by first and second carrier signals.

  More specifically, preferably, in such “multidimensional transmission”, the information corresponding to the signal points of the space constituted by the first carrier signal is degenerated and constituted by the second carrier signal. On the contrary, the information corresponding to the signal point in the space constituted by the second carrier signal is degenerated and the space constituted by the first carrier signal. The present invention can be applied to a wireless communication system in which the degeneracy is solved by the signal points.

  However, in the following description, as an example, the radio communication system according to the present embodiment will be described as adopting a polarization multiplexing communication system.

  Preferably, in the present embodiment, a communication system in a system that transmits information using two polarizations of horizontal polarization and vertical polarization, and a system system that does not stand out between transmission and reception as in satellite communication The state used in is more preferable. Note that a communication device having only the transmission function can be configured to include only the transmission function of the present embodiment, and a communication device having only the reception function can be configured to include only the reception function of the present embodiment. The transceiver can also be configured to have a transmission / reception function.

  In addition, the wireless communication system of the present embodiment is a wireless communication device that simultaneously uses two orthogonal polarizations (which are orthogonal at a realistic level and the cross polarization component need not be 0) for information transmission. It is a target. However, in the transmitter, receiver, and transmitter / receiver of this embodiment, it is possible to temporarily stop the polarization multiplexing communication function as described below and switch to communication using the conventional communication method. It is also possible to configure the system.

(Configuration of transmitter and receiver)
FIG. 1 is a functional block diagram for explaining the configuration of transmitter 1000 according to the present embodiment.

  Referring to FIG. 1, transmitter 1000 receives an error correction coding processing unit 100 that receives a digital data signal (information bit) to be transmitted, performs error correction coding processing on the information bit, and converts the information bit into a transmission symbol. Is provided. In addition to the error correction coding process, an “interleave process” or the like may be executed.

  Transmitter 1000 further includes an S / P converter 102 for serial / parallel conversion (S / P conversion) of symbols to be transmitted, and a transmission symbol converted to a parallel signal in I / Q mapping data storage unit 106. V / H mapping processing for mapping each polarization component of horizontal polarization (H polarization) and vertical polarization (V polarization) to signal points in a signal space diagram (constellation) based on the retained information Unit 104.

  Here, the I component means an in-phase component in quadrature modulation, the Q component means a quadrature phase component in quadrature modulation, and I / Q mapping means I component and Q component. This means that signal points are arranged on a plane stretched by.

  The transmitter 1000 further includes a quadrature modulation unit 108a that quadrature modulates the I / Q component for V polarization from the V / H mapping processing unit 104 with a corresponding modulation scheme (for example, QPSK modulation scheme), and V / H A quadrature modulation unit 108b that quadrature modulates the I / Q component for the H polarization from the H mapping processing unit 104 with a corresponding modulation method (for example, QPSK modulation method), and a digital / analog conversion of the output of the quadrature modulation unit 108a A D / A conversion unit 110a for converting the output of the quadrature modulation unit 108b, and a D / A conversion unit 110b for digital / analog conversion of the output of the orthogonal modulation unit 108b.

  The output of the D / A conversion unit 110a is amplified by a power amplifier (not shown), subjected to filter processing for suppressing unnecessary frequency components by the transmission filter processing unit 112a, and then transmitted from the vertically polarized antenna 114a. The output of the D / A conversion unit 110b is amplified by a power amplifier (not shown), filtered by the transmission filter processing unit 112b, and then transmitted from the horizontal polarization antenna 114b.

  In FIG. 1, it is assumed that the process for horizontal polarization and the process for vertical polarization are executed in synchronization with each other.

  FIG. 2 is a functional block diagram for explaining the configuration of the receiver 2000 of the present embodiment.

  Referring to FIG. 2, receiver 2000 performs a reception filter for filtering a signal amplified by a low-noise amplifier (not shown) of a reception signal from vertical polarization antenna 200a, horizontal polarization antenna 200b, and vertical polarization antenna 200a. A processing unit 202a, a reception filter processing unit 202b for filtering a signal amplified by a low noise amplifier (not shown) from a reception signal from the horizontally polarized antenna 200b, and an analog-to-digital conversion for a signal from the reception filter processing unit 202a An analog-digital conversion unit (A / D conversion unit) 204a and an A / D conversion unit 204b for analog-digital conversion of a signal from the reception filter processing unit 202b are provided.

  Receiver 2000 further includes quadrature detection units 206a and 206 that receive signals from A / D conversion units 204a and 204b, respectively, and separate I / Q components on the constellation.

  Based on the mapping information from the I / Q mapping data storage unit 210, the maximum likelihood determination processing unit 208 calculates the likelihood for a predetermined signal point on the signal space diagram for the signals from the quadrature detection units 206a and 206b. The maximum likelihood decoding is performed by the MLD (Maximum Likelihood Detection) method. In the MLD method, a metric is calculated using all combinations of transmission signals that can be transmitted from a transmission antenna with respect to a reception signal. Then, a combination of transmission signals that gives the minimum distance is selected.

  The “signal point” refers to a reference position defined on the constellation by the modulation method, and the “symbol” is a unit of information that is modulated on the transmission side and transmitted by the reference clock. Means “sign”.

  The bit information of the transmission signal calculated by the maximum likelihood determination processing unit 208 is subjected to error correction by the error correction decoding processing unit 214 via the P / S conversion unit 212 that performs parallel / serial conversion (P / S conversion). Are output as received symbols.

Note that convolutional decoding and deinterleaving processing may be performed in the error correction decoding processing unit 214 according to the configuration on the transmitter side.
(Signal system for improving frequency utilization efficiency in orthogonal polarization multiplexing modulation)
As described in Non-Patent Document 3 mentioned above, “non-orthogonal polarization multiplexing method” and “multi-polarization spatial modulation method” are methods for improving frequency utilization efficiency in orthogonal polarization multiplexing. Proposed.

  The following is a summary of the contents.

(Non-orthogonal polarization multiplexing)
FIG. 3 is a conceptual diagram showing an outline of the non-orthogonal polarization multiplexing system.

  Referring to FIG. 3 (a), in this non-orthogonal polarization multiplexing system, a non-orthogonal polarization (represented as S in FIG. 3 (a)) is additionally combined with the orthogonal H / V polarization. By increasing the amount of transmission information, it is possible to perform more efficient transmission than the conventional method using only H / V polarized waves independently.

  At this time, a plurality of signal points are simultaneously arranged in the H / V space as shown in FIG. Signal points in this method are formed by combining values mapped to the respective polarization components H / V polarization before combination.

  In FIG. 3A, the non-orthogonal polarization component is only S polarization, but more generally, a plurality of non-orthogonal polarization components can be assumed.

Here, _assuming that the complex signal point of the modulation scheme assigned to the _nth polarization S _n is r _{n, a} , the signal point arrangement points Ha, Va on the H / V polarization after polarization synthesis are given by the following equations. Given.

However, a is the symbol number ^{(1 ≦ a ≦ 2 b)} , b is the number of bits of the or one symbol, N is the polarized wave number (the number of multiplexing), m _sn the polarization S _n amplitude, [psi _Sn is polarized Let S _{n be} the polarization angle (relative to H polarization).

  FIG. 3 (b) shows the H when the S-polarized wave that is non-orthogonal to the H / V-polarized wave is additionally combined, assuming QPSK modulation for each of the H-polarized wave, V-polarized wave, and S-polarized wave. The signal point arrangement of polarization and V polarization is shown.

That is, when the number of polarization multiplexing in the non-orthogonal polarization multiplexing system is 3, and the number of modulation bits allocated to each polarization is 2 bits (QPSK), the information bit i is represented by rn _{, a} as shown in the following equation. (N) and q (n) are assigned, and mapping is performed on the signal points Ha and Va expressed by Equations (1) and (2).

However, i (n) = (0, 1), q (n) = (0, 1).

Under this setting condition, the amplitude m _s1 (= 1) and the polarization angle ψ _S1 (= 0 °) of the reference polarization S ₁ (H polarization) are fixed, and the amplitude m _s2 of S ₂ / S ₃ , It is assumed that the polarization angles ψ _S2 and ψ _S3 with respect to m _s3 and the polarization S ₁ are changed. As an example, when m _s2 = 1 and ψ _S2 = 90 °, the combination of parameters that maximizes the minimum Euclidean distance when m _s3 and ψ _S3 are changed is (m _s1 , m _s2 , m _s3 ) = (1: 1: 0.707), (ψ _S1 , ψ _S2 , ψ _S3 ) = (0 °: 90 °: 45 °). This is the arrangement shown in FIG.

  In this case, in the H-polarization space or the V-polarization space, one signal point (symbol) corresponds to 6-bit information, and is degenerate fourfold. However, by combining information of signal points of H polarization and V polarization, information bits to be expressed can be specified by solving the degeneracy.

(Multi-polarization spatial modulation system)
In the multi-polarization spatial modulation method, the combined vector expressed by the I / Q component of the carrier wave and the polarization angle φ _l is regarded as one arrangement point in the H / V space, and the modulation multi-value number is increased. Enables more efficient transmission than conventional methods.

  FIG. 4 is a conceptual diagram showing an outline of such a multi-polarization spatial modulation system.

  As shown in FIG. 4A, one signal point is simultaneously arranged on the H / V space. That is, in the conventional method, the signal points are arranged such that the H space and the V space are independent from each other. In the multi-polarization spatial modulation system, signal points are arranged in a space spanned by H and V by controlling the polarization angle.

Here, when a reference (assigned to I / Q components of the carrier wave) the complex signal points of the modulation scheme and r _c, constellation points H _a on H / V polarized wave in this manner, V _a, the following It is given by the formula.

Where c is the symbol number of the reference modulation method (1 ≦ c ≦ 2 ^d ), d is the number of bits of the reference modulation method, angle φ _l is the polarization angle (1 ≦ l ≦ 2 ^e ), and e is The number of bits assigned to the polarization angle.

In the multi-polarization spatial modulation method, when the modulation method used as a reference is QPSK (2 bits) and 1 bit is assigned to the polarization angle, information bits i, q, and k are assigned to r _c and φ as shown in the following equation. , Mapping is performed on the signal points Ha and Va expressed by the equations (4) and (5).

However, i = (0, 1), q = (0, 1), k = (0, 1), and 0 ° ≦ ψ ≦ 180 °.

  Under this setting condition, when the polarization angle at which the minimum Euclidean distance is maximized when the polarization angle ψ is changed from 0 ° to 180 ° is obtained, it is 45 ° or 135 °.

  This is the arrangement shown in FIG.

  For example, in FIG. 4B, if ψ = 45 °, each signal point (symbol) corresponds to 3-bit information and is degenerate in a double manner. However, by combining information of signal points of H polarization and V polarization, information bits to be expressed can be specified by solving the degeneracy.

  As explained above, the “non-orthogonal polarization multiplexing method” and the “multi-polarization spatial modulation method” use the following properties in order to improve the frequency utilization efficiency over the conventional polarization multiplexing method. In common.

  That is, the conventional orthogonal polarization multiplexing modulation using V polarization and H polarization defines signal points using multi-level modulation in V polarization and H polarization which are physically independent from each other. . As a result, the efficiency is doubled as compared with the case where only the V polarization or only the H polarization is used.

  On the other hand, the “non-orthogonal polarization multiplexing method” or “multi-polarization spatial modulation method” is not limited to V polarization and H polarization, but also to a space constituted by V polarization and H polarization. Also, by assigning signal points, frequency utilization efficiency higher than that of the conventional method is achieved.

  Therefore, in the following, when such a method for assigning signal points to a space composed of V polarization and H polarization is generically referred to as a “multi-polarization spatial multiplexing transmission method”.

  As described above, FIGS. 3 and 4 show a case where the arrangement of signal points is determined so that the minimum Euclidean distance between the signal points is maximized.

  However, in an additive white Gaussian noise (AWGN) environment, a symbol error occurs between adjacent symbols. Therefore, it is possible to increase the Euclidean distance between adjacent symbols and reduce the Hamming distance. Contributes to improvement.

  On the other hand, the cause of the increase in PAPR described above is the peak power of signal point arrangement.

  Therefore, in the present embodiment, as shown in the following formulas (E1) and (E2), each symbol is normalized by the peak power of the total H / V (or each polarization of H / V), and then the signal point arrangement is performed. Optimize.

  Therefore, in the following, when the normalization by the formula (E1) or the formula (E2) is generically referred to, it is referred to as “normalization of peak power with respect to signal point arrangement”.

  At this time, in order to meet the condition of constant transmission power (H / V total power = 1), the processing of Expression (E3) is further performed.

Therefore, the processing such as Expression (E3) is referred to as “normalization of transmission power with respect to signal point arrangement”.

  For optimization of signal point arrangement, evaluation criteria such as an evaluation criterion for maximizing the minimum Euclidean distance and a criterion for minimizing an evaluation equation (for example, equation (E4)) combining the Hamming distance Hdist and the Euclidean distance Edist are used. Standards tailored to the subject can be used. By combining the evaluation formula (E4) with the normalization methods of the formulas (E1) and (E2), the influence of the code assigned to each symbol in error correction, which is a main factor of BER characteristic degradation, is minimized. Such a low PAPR signal point arrangement can be easily derived.

2 ^N represents the total number of symbols on the H / V polarization plane, and N represents the number of bits per symbol on the H / V polarization.

  Here, by using a monotonically increasing function as the function of the evaluation formula (E4), an arrangement that improves the BER characteristics from among the signal point arrangements that can be generated (the average Euclidean distance between symbols is large, and the BER characteristics are deteriorated). It is possible to easily derive symbols (arrangements with few Hdist: large and Edist: small).

  In this function, for all symbols on the H / V polarization plane, a value obtained by dividing the Hamming distance by the Euclidean distance for each symbol is included as an argument of the function, and the contribution from each symbol to the function F is equal. It is trying to become.

n is the symbol index (1 ≦ n ≦ 2 ^N ) on the H / V polarization plane, and as described above, the function F is a value specified by n (Hdist (n) / Edist (n)) Thus, a monotonically increasing function with respect to the increase of each element is shown, and the signal point arrangement is determined so that the value of this function F is minimized.

  Here, conversely, when the function F is a monotonously decreasing function for each element increase with respect to a set of (Hdist (n) / Edist (n)), which is a value specified by n, this function The signal point arrangement may be determined so that the value of F is maximized. In the present specification, since both are substantially equivalent, “the function F is a value designated by n (Hdist (n) / Edist (n)). In the case of “denotes a monotonically increasing function with respect to increase and determines the signal point arrangement so that the value of the function F is minimized”, the latter case also has significance. These two cases are collectively referred to as “for each transmission symbol (on the H / V polarization plane), a monotonically increasing function whose argument is a value obtained by dividing the Hamming distance by the Euclidean distance is minimized for a set of transmission symbols. The signal point arrangement is determined so as to be

More specifically, the function F of the equation (E4) can be, for example, the sum of (Hdist (n) / Edist (n)) as illustrated below the equation (E4).
(Signal arrangement)
Hereinafter, a specific example in which the signal arrangement is calculated according to the above criteria will be described.

  Here, a signal in which IQ (2 bits) is assigned to three virtual polarizations is synthesized as shown in Equation (E5), and mapped to the IQ plane on the H / V polarization (represented by 6 bits per symbol). As a result, signal point arrangement data (I / Q mapping data) on H / V polarization is formed.

Where H is an IQ component (complex number) of horizontal polarization, V is an IQ component (complex number) of vertical polarization, and α _k and β _k are mapping coefficients (k / th polarization) to H / V polarization. This is a complex parameter that controls the amplitude, phase, and polarization angle of each polarization. The real part imaginary part takes a value in the range of ± 1. x _k (n) is a complex signal point of the modulation scheme assigned to the k-th polarization. Further, as an optimization condition, it is assumed that the H / V polarization is completely synchronized and no interference occurs.

  Further, when the power balance of H / V polarization is not guaranteed, a power amplifier for high power is required on the transmission side (when the magnitude relationship of H / V polarization power is indefinite, it is adjusted to a large power. Therefore, when the power of each polarization of H / V in the optimal arrangement is different, the signal point arrangement of H / V equal power is multiplied by the polarization rotation matrix (Equation (E6)) of an appropriate angle θ. Make adjustments. Note that there is no difference in BER characteristics between the arrangements before and after power equalization.

(Specific example of signal arrangement)
FIG. 5 is a diagram illustrating a result of searching for an optimized arrangement that maximizes the minimum Euclidean distance.

  FIG. 6 is a diagram showing signal point arrangement on the IQ plane in each of the H / V polarizations of arrangement A in FIG.

  FIG. 7 is a diagram showing signal point arrangement on the IQ plane in each of the H / V polarizations of arrangement B in FIG.

  FIG. 8 is a diagram showing signal point arrangement on the IQ plane in each of the H / V polarizations of arrangement C in FIG.

In FIG. 5, for each of the real part / imaginary part of the mapping coefficient of the formula (E5),
± 1 (0.00001 step)
2 ^{6 [bit / symbol] for} constellation of signal points that can be generated when changing in the range
The result of searching for an optimized arrangement that maximizes the minimum Euclidean distance for all (= 64) symbols is shown together with a normalization criterion.

  As shown in FIG. 6, the arrangement A is a conventional optimum arrangement normalized by the formula (E0) (average power of H / V total).

  As shown in FIG. 7, the arrangement B is an optimum arrangement when normalized by the formula (E1) (H / V total peak power).

  As shown in FIG. 8, the arrangement C is an optimum arrangement when normalized by the formula (E2) (peak power of each polarization of H / V).

  For the arrangements B and C, the processing of Expression (E3) is performed on the arrangement generated with the mapping coefficient shown in FIG. 5, and the transmission power is constant (H / V total power = 1).

  FIG. 9 is a diagram showing the evaluation value of each optimum arrangement searched for in FIG.

  As shown in FIG. 9, compared with the conventional optimum arrangement A, the PAPR of the arrangements B and C normalized by the formula (E1) or (E2) is reduced.

  FIG. 10 is a diagram illustrating a transceiver configuration that simulates the BER characteristics.

  With the configuration of the polarization multiplexing type transceiver shown in FIG. 10, the BER characteristics when the nonlinear distortion of the power amplifier is affected in each arrangement of FIGS. 6 to 8 were confirmed by computer simulation.

  FIG. 11 is a diagram showing the result of BER simulation for each optimum signal point arrangement.

  In the simulation, the error correction method is LDPC (Low-Density Parity-Check) coding / BP (Belief Propagation) decoding (coding rate R = 1/2 and 5/6, BP decoding). Necessary noise power estimation is ideal), the influence of nonlinear distortion of the power amplifier is given by the Rapp model, and the coefficient p representing the nonlinearity strength is 1.5.

  Such simulation methods are disclosed in the following documents, for example.

Literature: SC Thompson, JG Proakis, and JR Zeidler, “The Effectiveness of Signal Clipping for PAPR and Total Degradation Reduction in OFDM Systems,” IEEE GLOBECOM 2005
As shown in FIG. 11, the error rate of the arrangement B optimized by the method of the equation (E1) is BER = 10 ⁻² , and the required Eb / N0 is improved by about 0.4 dB, and is improved by about 1.0 dB at a coding rate of 5/6. On the other hand, the error rate of the arrangement C optimized by the method of the formula (E2) is improved by about 0.2 dB at a coding rate of 5/6 while improving the PAPR as shown in FIG. .

  As described above, according to the present embodiment, it is possible to easily derive an optimal signal point arrangement having an excellent bit error rate with respect to the polarization multiplexing scheme while suppressing PAPR.

  The relationship between each symbol and the signal point arrangement on the I / Q plane of the H / V polarization calculated as shown in FIGS. 7 and 8 is the I / Q mapping data storage unit 106 or I / Q described above. It is assumed that it is stored in the mapping data storage unit 210.

  FIG. 12 is a flowchart for explaining processing in transmitter 1000 and receiver 2000.

  Referring to FIG. 12, first, transmitter 1000 performs error correction coding processing of a transmission signal (S100).

  Subsequently, the transmitter 1000 performs optimization as described above, and sends signals to the V polarization space and the H polarization space based on the I / Q mapping data stored in the I / Q mapping data storage unit 106. Mapping is performed (S102).

  The transmitter 1000 further modulates (orthogonally modulates) the signal in the V polarization space and the H polarization space (S104), performs D / A conversion, and then transmits the V polarization and the H polarization from the antenna. A signal is transmitted (S106).

  On the other hand, the receiver 2000 receives V polarization and H polarization by the antenna (S110), and after A / D conversion, performs quadrature detection for each of the V polarization component and the H polarization component (S112). .

  Furthermore, the receiver 2000 is optimized as described above, and performs maximum likelihood estimation in the V polarization space and the H polarization space based on the I / Q mapping data stored in the I / Q mapping data storage unit 210. (S114), and error correction decoding processing is performed to obtain received symbols (S116).

  As described above, according to the signal point arrangement of the present embodiment, it is possible to easily derive a signal point arrangement having an excellent bit error rate with respect to a multidimensional transmission method such as a polarization multiplexing method while suppressing PAPR. .

  It is possible to perform transmission or reception with a signal point arrangement having an excellent bit error rate with respect to a multi-dimensional transmission system such as a polarization multiplexing system while suppressing PAPR.

  Embodiment disclosed this time is an illustration of the structure for implementing this invention concretely, Comprising: The technical scope of this invention is not restrict | limited. The technical scope of the present invention is shown not by the description of the embodiment but by the scope of the claims, and includes modifications within the wording and equivalent meanings of the scope of the claims. Is intended.

  100 error correction coding processing unit, 102 S / P conversion unit, 104 V / H mapping processing unit, 106, 210 I / Q mapping data storage unit, 108a, 108b orthogonal modulation unit, 110a, 110b D / A conversion unit, 112a, 112b Transmission filter processing unit, 114a, 200a Vertical polarization antenna, 114b, 200b Horizontal polarization antenna, 202a, 202b Reception filter processing unit, 204a, 204b A / D conversion unit, 206a, 206b Quadrature detection unit, 208 Likelihood determination processing unit, 212 P / S conversion unit, 214 error correction decoding processing unit, 1000 transmitter, 2000 receiver.

Claims (16)

A wireless communication system that performs transmission and reception by multidimensional transmission in which signal points are assigned to a space constituted by first and second carrier signals,
With a transmitter and receiver,
The transmitter is
A transmitting antenna;
An error correction coding processing unit for performing error correction coding processing on a transmission symbol;
A first storage unit,
The first storage unit is calculated for each transmission symbol so as to minimize the influence on the bit error rate of the code assigned to each symbol at the time of normalization and error correction with respect to the peak power with respect to the signal point arrangement. Store the signal point arrangement
Based on the information stored in the first storage unit, the output of the error correction coding processing unit is allocated in the in-phase component and quadrature phase component planes of the first and second carrier signals in the multi-dimensional transmission. A mapping processing unit;
A transmission unit that performs orthogonal modulation on the first and second carrier signals based on the processing result of the mapping processing unit and transmits the first carrier signal from the transmission antenna;
The receiver
A receiving antenna;
A receiver that performs quadrature detection on the first and second carrier signals for the signals received by the receiving antenna;
A second storage unit that stores information corresponding to the signal point arrangement stored in the first storage unit;
A maximum likelihood determination processing unit for performing maximum likelihood determination on the first and second carrier signals in the multi-dimensional transmission based on the information stored in the second storage unit;
A wireless communication system including an error correction decoding processing unit for executing an error correction decoding process based on a determination result of the maximum likelihood determination processing unit.   The wireless communication system according to claim 1, wherein the normalization with respect to the peak power with respect to the signal point arrangement is a normalization with respect to a total peak power of the first and second carrier signals.   The wireless communication system according to claim 1, wherein the normalization with respect to the peak power with respect to the signal point arrangement is a normalization with respect to the peak power of each of the first and second carrier signals.   The signal constellation is normalized with respect to the peak power with respect to the signal constellation, and for each transmission symbol, a monotonically increasing function using a value obtained by dividing the Hamming distance by the Euclidean distance as an argument is minimized for the set of transmission symbols. The wireless communication system according to claim 2, wherein the wireless communication system is calculated as follows.   The wireless communication system according to claim 4, wherein the function is a sum of transmission symbols obtained by dividing the Hamming distance by the Euclidean distance for each transmission symbol.   The wireless communication system according to any one of claims 1 to 5, wherein the first and second carrier signals are two polarized carrier signals orthogonal to each other.   The wireless communication system according to claim 1, wherein the first and second carrier signals are carrier signals having different frequencies. A wireless communication apparatus that performs transmission by multidimensional transmission that assigns signal points to a space constituted by first and second carrier signals,
A transmitting antenna;
An error correction coding processing unit for performing error correction coding processing on a transmission symbol;
A storage unit,
For each transmission symbol, the signal point calculated to minimize the influence on the bit error rate of the code assigned to each symbol at the time of normalization and error correction for peak power with respect to the signal point arrangement Remember the arrangement,
Based on the information stored in the storage unit, a mapping processing unit that allocates the output of the error correction coding processing unit in the in-phase component and quadrature phase component planes of the first and second carrier signals in the multi-dimensional transmission When,
A wireless communication apparatus, further comprising: a transmission unit that performs orthogonal modulation on the first and second carrier signals based on a processing result of the mapping processing unit and transmits the first carrier signal from the transmission antenna. A wireless communication apparatus that performs reception by multidimensional transmission that assigns signal points to a space constituted by first and second carrier signals,
A receiving antenna;
A receiver that performs quadrature detection on the first and second carrier signals for the signals received by the receiving antenna;
A storage unit,
For each transmission symbol, the signal point calculated to minimize the influence on the bit error rate of the code assigned to each symbol at the time of normalization and error correction for peak power with respect to the signal point arrangement Remember the arrangement,
Based on the information stored in the storage unit, in the multi-dimensional transmission, a maximum likelihood determination processing unit for performing maximum likelihood determination on the first and second carrier signals,
A wireless communication device further comprising: an error correction decoding processing unit for executing an error correction decoding process based on a determination result of the maximum likelihood determination processing unit.   The wireless communication apparatus according to claim 8 or 9, wherein the normalization with respect to the peak power with respect to the signal point arrangement is a normalization with respect to a total peak power of the first and second carrier signals.   The wireless communication apparatus according to claim 8 or 9, wherein the normalization with respect to the peak power with respect to the signal point arrangement is a normalization with respect to the peak power of each of the first and second carrier signals.   The signal constellation is normalized with respect to the peak power with respect to the signal constellation, and for each transmission symbol, a monotonically increasing function using a value obtained by dividing the Hamming distance by the Euclidean distance as an argument is minimized for the set of transmission symbols. The wireless communication device according to claim 10 or 11, which is calculated by the following.   The wireless communication apparatus according to claim 12, wherein the function is a sum of transmission symbols obtained by dividing a Hamming distance by a Euclidean distance for each transmission symbol.   The wireless communication apparatus according to any one of claims 8 to 12, wherein the first and second carrier signals are two polarized carrier signals orthogonal to each other.   The wireless communication apparatus according to any one of claims 8 to 12, wherein the first and second carrier signals are carrier signals having different frequencies. A wireless communication method for performing transmission and reception by multidimensional transmission that assigns signal points to a space constituted by first and second carrier signals,
A transmitter performing error correction coding processing on the transmitted symbols;
Signal point constellation calculated so that the transmitter minimizes the impact on the bit error rate of the code assigned to each symbol at the time of normalization and error correction for peak power with respect to the signal point constellation for each transmission symbol Performing a mapping process for assigning the error correction coding process result in the in-phase component and quadrature phase component planes of the first and second carrier signals in the multi-dimensional transmission,
A transmitter performing orthogonal modulation on the first and second carrier signals based on the result of the mapping process, and transmitting from the transmission antenna;
A receiver performing quadrature detection on the received signal for the first and second carrier signals, respectively;
A receiver performing a maximum likelihood determination on the first and second carrier signals in the multi-dimensional transmission based on the signal point arrangement in the transmitter; and
And a receiver that executes error correction decoding processing based on the determination result of the maximum likelihood determination.