WO2024171448A1 - Wireless communication system, reception device, wireless communication method, and reception program - Google Patents

Wireless communication system, reception device, wireless communication method, and reception program Download PDF

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Publication number
WO2024171448A1
WO2024171448A1 PCT/JP2023/005786 JP2023005786W WO2024171448A1 WO 2024171448 A1 WO2024171448 A1 WO 2024171448A1 JP 2023005786 W JP2023005786 W JP 2023005786W WO 2024171448 A1 WO2024171448 A1 WO 2024171448A1
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constellation
unit
received
signal
reference constellation
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PCT/JP2023/005786
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French (fr)
Japanese (ja)
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圭太 栗山
健太郎 田中
仁 長谷川
利文 宮城
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日本電信電話株式会社
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Priority to PCT/JP2023/005786 priority Critical patent/WO2024171448A1/en
Publication of WO2024171448A1 publication Critical patent/WO2024171448A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/01—Equalisers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
    • H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
    • H04L27/38—Demodulator circuits; Receiver circuits

Definitions

  • the present invention relates to a wireless communication system, a receiving device, a wireless communication method, and a receiving program.
  • constellation information is shared between the transmitting device and the receiving device before data communication begins.
  • a transmitting device transmits a digital signal using the nonlinear region of an amplifier
  • a receiving device performs demodulation using a reference constellation that takes into account the input/output characteristics of the amplifier.
  • a technique is known that improves demodulation performance by calculating an appropriate log-likelihood ratio (LLR) for a nonlinear distortion constellation in high-frequency band single-carrier transmission (see, for example, Non-Patent Document 1).
  • LLR log-likelihood ratio
  • the control signal can sometimes reduce transmission capacity.
  • the present invention has been made in consideration of the above-mentioned problems, and aims to provide a wireless communication system, a receiving device, a wireless communication method, and a receiving program that can improve demodulation performance without reducing transmission capacity.
  • a wireless communication system is a wireless communication system in which a receiving device demodulates a received signal based on a pilot signal transmitted by a transmitting device, the receiving device comprising an equalization unit that performs equalization processing on the pilot signal received from the transmitting device to output a received constellation, an indexing unit that assigns a predetermined index for each signal point of a predetermined constellation to each convergence point of the received constellation based on each signal point of the predetermined constellation, and a center of gravity of each cluster of the convergence points to which the indexing unit assigns the same index, for demodulating the received signal.
  • the demodulation unit includes a reference constellation calculation unit that calculates a reference constellation to be referenced for demodulation, a storage unit that stores the reference constellation calculated by the reference constellation calculation unit, a determination unit that compares the reference constellation calculated by the reference constellation calculation unit with the reference constellation stored in the storage unit based on a pilot signal received after the equalization unit outputs the received constellation, and determines which reference constellation will improve demodulation accuracy, and a demodulation unit that demodulates the received signal using the reference constellation that the determination unit determines will improve demodulation accuracy.
  • the receiving device is characterized by having an equalization unit that performs equalization processing on a pilot signal received from a transmitting device and outputs a received constellation; an indexing unit that assigns a predetermined index to each of the convergence points of the received constellation based on each of the signal points of the specified constellation; a reference constellation calculation unit that calculates the center of gravity of each of the clusters of the convergence points to which the indexing unit assigns the same index as a reference constellation to be referenced for demodulating the received signal; a storage unit that stores the reference constellation calculated by the reference constellation calculation unit; a determination unit that compares the reference constellation calculated by the reference constellation calculation unit with the reference constellation stored in the storage unit based on a pilot signal received after the equalization unit outputs the received constellation, and determines which reference constellation increases demodulation accuracy; and a demodulation unit that demodulates the received signal using the reference constellation that the determination unit determines increases demodulation accuracy.
  • a wireless communication method is a wireless communication method in which a receiving device demodulates a received signal based on a pilot signal transmitted by a transmitting device, the method comprising: an equalization step of performing an equalization process on the pilot signal received from the transmitting device to output a received constellation; an indexing step of assigning a predetermined index for each signal point of a predetermined constellation to each convergence point of the received constellation based on each signal point of the predetermined constellation; and an indexing step of assigning the center of gravity of each cluster of the convergence points assigned the same index by the indexing step to a cluster of the convergence points for demodulating the received signal.
  • a reference constellation calculation process for calculating a reference constellation to be referred to, a storage process for storing the calculated reference constellation in a storage unit, a determination process for comparing the reference constellation calculated in the reference constellation calculation process with the reference constellation stored in the storage unit based on a pilot signal received after the received constellation is output by the equalization process, and determining which reference constellation improves demodulation accuracy, and a demodulation process for demodulating the received signal using the reference constellation determined in the determination process to improve demodulation accuracy.
  • the present invention makes it possible to improve demodulation performance without reducing transmission capacity.
  • FIG. 1 is a diagram illustrating an example of a configuration of a wireless communication system according to an embodiment.
  • 2 is a functional block diagram illustrating functions of a transmission device.
  • FIG. 1A is a graph illustrating an example of the input/output characteristics of an amplifier unit
  • FIG. 1B is a diagram illustrating a constellation of a transmission signal before the amplifier unit amplifies the transmission signal
  • FIG. 1C is a diagram illustrating a constellation of a transmission signal after the amplifier unit amplifies the transmission signal using a nonlinear region.
  • FIG. 2 is a functional block diagram illustrating functions of a receiving device according to an embodiment.
  • FIG. 2 is a conceptual diagram illustrating an overview of an operation of a receiving device according to an embodiment.
  • FIG. 11 is a diagram showing a specific example of the operation of a receiving device according to an embodiment.
  • FIG. 1 is a diagram showing an example of the configuration of a wireless communication system 1 according to one embodiment.
  • the wireless communication system 1 is configured such that, for example, a transmitting device 2 transmits a modulated digital signal that has been amplified using a nonlinear region, and a receiving device 4 receives and demodulates the digital signal.
  • the transmitting device 2 also transmits a pilot signal to the receiving device 4 for calculating, for example, communication path information (e.g., CSI: Channel State Information).
  • the receiving device 4 calculates communication path information using the received pilot signal and transmits the calculated communication path information to the transmitting device 2.
  • the receiving device 4 also demodulates the received signal based on the pilot signal transmitted by the transmitting device 2.
  • the pilot signal may be transmitted until the equalization process described below is performed, or may be transmitted periodically each time the equalization process is performed.
  • FIG. 2 is a functional block diagram illustrating the functions of the transmitting device 2. As shown in FIG. 2, the transmitting device 2 has an information bit generating unit 21, a pilot signal generating unit 22, a modulating unit 23, a D/A converting unit 24, a transmission power control unit 25, an amplifying unit 26, and an antenna 200.
  • the transmitting device 2 has an information bit generating unit 21, a pilot signal generating unit 22, a modulating unit 23, a D/A converting unit 24, a transmission power control unit 25, an amplifying unit 26, and an antenna 200.
  • the information bit generator 21 generates information bits to be transmitted to the receiver 4 and outputs them to the modulator 23.
  • the information bit generator 21 may also have an error correction coding function and an interleaving function.
  • the pilot signal generating unit 22 generates a pilot signal to be transmitted to the receiving device 4 and outputs it to the modulating unit 23.
  • the pilot signal is, for example, an M sequence used for estimating the communication channel response and calculating the equalization weights used in the equalization process, and is modulated by BPSK or QPSK.
  • the modulation unit 23 modulates the information bits generated by the information bit generation unit 21 into a data signal, for example, by a single carrier multi-level modulation method, and outputs the data signal to the D/A conversion unit 24.
  • single carrier multi-level modulation methods used by the modulation unit 23 include BPSK, QPSK, and quadrature amplitude modulation such as 64QAM and 256QAM.
  • the D/A conversion unit 24 converts the data signal digitally modulated by the modulation unit 23 into an analog signal and outputs it to the transmission power control unit 25.
  • the transmission power control unit 25 controls the transmission power so that the data signal converted into an analog signal by the D/A conversion unit 24 has the desired communication quality.
  • the amplifier 26 amplifies the analog signal converted by the D/A converter 24 in accordance with the control of the transmission power by the transmission power control unit 25, and radiates it via the antenna 200.
  • FIG. 3 is a diagram illustrating the amplification characteristics of the amplifier 26.
  • FIG. 3(a) is a graph illustrating the input/output characteristics (amplification characteristics) of the amplifier 26.
  • FIG. 3(b) is a diagram illustrating the constellation of the transmission signal before it is amplified by the amplifier 26.
  • FIG. 3(c) is a diagram illustrating the constellation of the transmission signal after it has been amplified by the amplifier 26 using the nonlinear region as well.
  • the amplifier 26 has a linear region that amplifies and outputs the input in proportion to the input, and a nonlinear region that amplifies excessive input nonlinearly.
  • FIG. 3(b) illustrates an ideal constellation without distortion.
  • FIG. 4 is a functional block diagram illustrating the functions of the receiving device 4 according to one embodiment.
  • the receiving device 4 according to one embodiment has an antenna 400, an amplifier 40, an A/D converter 41, an estimator 42, an equalization weight calculator 43, an equalizer 44, an indexer 45, a reference constellation calculator 46, a likelihood calculator 47, a demodulator 48, an information bit detector 49, a memory 50, and a determiner 51.
  • the amplifier 40 amplifies the analog signal received by the receiver 4 via the antenna 400 and outputs it to the A/D converter 41.
  • the A/D conversion unit 41 converts the analog signal amplified by the amplifier unit 40 into a digital signal and outputs it to the estimation unit 42 and the equalization unit 44.
  • the A/D conversion unit 41 converts the pilot signal transmitted by the transmitter 2 into a digital signal and outputs it to the estimation unit 42.
  • the A/D conversion unit 41 also converts the data signal corresponding to the information bits to be transmitted by the receiver 4 from the transmitter 2 into a digital signal and outputs it to the equalization unit 44.
  • the pilot signal converted into a digital signal by the A/D converter 41 is transmitted when the transmitter 2 and receiver 4 start communication.
  • the estimation unit 42 estimates the communication channel response based on the pilot signal input from the A/D conversion unit 41.
  • the equalization weight calculation unit 43 calculates the equalization weights used by the equalization unit 44 based on the communication channel response estimated by the estimation unit 42.
  • the equalization unit 44 performs equalization processing on the pilot signal received from the transmitting device 2, for example, using the inverse response of the communication channel response, and outputs a received constellation. Specifically, the equalization unit 44 calculates an estimate of the transmitted signal by inversely calculating the amplitude and phase information of the communication channel response. The equalization unit 44 then outputs the result of the equalization processing to the indexing unit 45 and the likelihood calculation unit 47.
  • the indexing unit 45 performs processing to assign a predetermined index for each signal point of the specified constellation to each convergence point of the received constellation output by the equalization unit 44 based on each signal point of the specified constellation.
  • the indexing unit 45 determines, as the specified constellation, an initial distortion constellation obtained by adding the initial value of the nonlinear distortion of the constellation associated with wireless communication between the transmitting device 2 and the receiving device 4 to an ideal constellation without distortion.
  • the reference constellation calculation unit 46 calculates the center of gravity of each cluster of convergence points to which the indexing unit 45 assigns the same index as a reference constellation to be referenced for demodulating the received signal.
  • the likelihood calculation unit 47 calculates the likelihood of the reference constellation calculated by the reference constellation calculation unit 46, and outputs the calculation result to the demodulation unit 48, the storage unit 50, and the determination unit 51.
  • the likelihood calculation unit 47 may perform hard or soft decisions when calculating the likelihood.
  • the demodulation unit 48 demodulates the received signal using the reference constellation for which the likelihood calculation unit 47 has calculated the likelihood, and outputs the demodulated signal to the information bit detection unit 49.
  • the demodulation unit 48 also has a function of demodulating the received signal using a reference constellation that a determination unit 51 (described later) has determined will improve demodulation accuracy.
  • the information bit detection unit 49 detects information bits from the signal demodulated by the demodulation unit 48.
  • the information bit detection unit 49 may also have an error correction decoding function and a deinterleaving function.
  • the storage unit 50 stores the reference constellation calculated by the reference constellation calculation unit 46.
  • the determination unit 51 compares the reference constellation newly calculated by the reference constellation calculation unit 46 with the reference constellation stored in the storage unit 50 based on the pilot signal received after the equalization unit 44 outputs the received constellation, and determines which reference constellation improves demodulation accuracy.
  • Figure 5 is a conceptual diagram showing an overview of the operation of the receiving device 4 ( Figure 4) according to one embodiment.
  • the equalization unit 44 performs equalization processing on the received signal (S100). At this time, the equalization unit 44 outputs the received constellation shown in (a) (equalized output).
  • the indexing unit 45 performs a process (indexing) of assigning a predetermined index for each signal point of the specified constellation to each convergence point of the received constellation output by the equalization unit 44 based on each signal point of the specified constellation (S102).
  • the reference constellation calculation unit 46 performs clustering using a clustering algorithm such as the k-means method, for example, to classify convergence points that have the same index.
  • the reference constellation calculation unit 46 calculates the center of gravity of each cluster of convergence points to which the indexing unit 45 has assigned the same index as the reference constellation shown in (b) (S104).
  • the reference constellation calculated by the reference constellation calculation unit 46 is a constellation that reflects distortion in wireless communication with respect to an ideal constellation.
  • the reference constellation calculation unit 46 may use an ideal constellation that does not take distortion into account as the initial center of gravity, or may use a constellation obtained by multiplying the ideal constellation by a nonlinear distortion according to, for example, the input/output characteristics of an amplifier as the initial center of gravity.
  • the demodulation unit 48 demodulates the received signal using the reference constellation calculated by the reference constellation calculation unit 46 (S106).
  • FIG. 6 is a diagram showing a specific example of the operation of the receiving device 4 according to one embodiment. As shown in FIG. 6, for example, for the initial frame of a received pilot signal, the receiving device 4 uses the constellation symbol information for the output of the equalization unit 44 (S200) and performs clustering of the convergence points of the received constellation (S202).
  • the receiving device 4 uses an MCS index or the like as symbol information to detect the number k of symbol mapping candidates and the ideal reference point position.
  • the receiving device 4 may estimate the number k of symbol mapping candidates by performing blind estimation.
  • the receiving device 4 When performing clustering of convergence points of the received constellation, the receiving device 4 performs the k-means method until convergence, for example, using the ideal reference point position as the initial center of gravity.
  • the initial center of gravity may be determined by randomly selecting k points from the received signal points, or may be determined by multiplying the ideal constellation by known device specifications or a general distortion model (for example, an amplification distortion model such as the Rapp model).
  • the receiving device 4 calculates the center of gravity of each cluster (S204) and demodulates the received signal using each center of gravity as a reference constellation (S206).
  • the storage unit 50 stores, for example, the reference point position of the initial frame (hereinafter referred to as the previous frame).
  • the receiving device 4 uses the constellation symbol information for the output of the equalization unit 44 (S210) and performs clustering of the convergence points of the received constellation (S212).
  • the receiving device 4 uses an MCS index or the like as symbol information to detect the number k of symbol mapping candidates and the ideal reference point position.
  • the receiving device 4 may estimate the number k of symbol mapping candidates by performing blind estimation.
  • the receiving device 4 does not need to perform the process of S210 due to the process of S200.
  • the receiving device 4 When performing clustering of convergence points of the received constellation, the receiving device 4 performs the k-means method until convergence, for example, using the ideal reference point position as the initial center of gravity.
  • the initial center of gravity may be determined by randomly selecting k points from the received signal points, or may be determined by multiplying the ideal constellation by known device specifications or a general distortion model (for example, an amplification distortion model such as the Rapp model).
  • the receiving device 4 calculates the center of gravity of each cluster (S214) and calculates the minimum distance between the centers of gravity of the reference constellation (S216).
  • the receiving device 4 may use the maximum or average value of the Euclidean distance between the ideal reference point position and the center of gravity point.
  • the receiving device 4 determines whether the minimum distance between the centers of gravity is equal to or less than a predetermined threshold (S218), and if the minimum distance between the centers of gravity is equal to or less than the predetermined threshold (S218: Yes), proceeds to processing of S220, and otherwise (S218: No), proceeds to processing of S222.
  • the receiving device 4 demodulates the received signal using the center of gravity calculated in the process of S214 as the reference constellation.
  • the receiving device 4 demodulates the received signal using the reference point position of the previous frame as the reference constellation.
  • the receiving device 4 demodulates the received signal using the reference constellation that the determination unit 51 determines will improve demodulation accuracy.
  • the receiving device 4 determines that the signal point positions of the reference constellation have been changed with a certain degree of accuracy by the previous frame of the pilot signal, and an outlier subsequently occurs in the reference constellation, it will discard the calculation result of the reference constellation where the outlier occurred and use the reference constellation of the previous frame.
  • the receiving device 4 rejects the reference constellation calculated for all frames of the pilot signal, the original predetermined constellation, such as the ideal constellation, continues to be used as the reference constellation.
  • the frequency with which the receiving device 4 updates the reference constellation through the operation shown in FIG. 6 may be variable or may be fixed.
  • the receiving device 4 uses the received constellation to calculate a reference constellation to be used for demodulating the received signal, thereby improving demodulation performance without reducing transmission capacity.
  • the wireless communication system 1 can improve the demodulation performance of the receiving device 4 even when, for example, the amplifier unit 26 of the transmitting device 2 has nonlinear distortion. Furthermore, the wireless communication system 1 does not require a control signal to notify the receiving device 4 of the nonlinear distortion characteristics of the amplifier unit 26, and can prevent a decrease in transmission capacity.
  • each component of the transmitting device 2 and the receiving device 4 in the above-described embodiment may be configured in part or in whole by hardware, or may be configured by having a processor execute a program.
  • the components constituting the transmitting device 2 and the receiving device 4 are configured in part or in whole by having a processor execute a program, the program may be recorded on a recording medium and supplied, or may be supplied via a network.
  • the wireless communication system 1 can improve demodulation performance without reducing transmission capacity for distortions in general (e.g., IQ imbalance, etc.) that cause contraction/rotation of a constellation without random fluctuation within a wireless frame.
  • the form of the wireless communication system 1 is not limited to an antenna configuration such as SISO/MIMO, a system configuration, etc.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)

Abstract

According to one embodiment, a wireless communication system has a reception device that comprises an equalization unit that performs equalization processing on a pilot signal received from a transmission device and thereby outputs a reception constellation, an indexing unit that assigns a predetermined index to each convergence point of the reception constellation for every signal point of a prescribed constellation, a reference constellation calculation unit that calculates the respective weights of each cluster of convergence points that have been assigned the same index by the indexing unit as a reference constellation, and a storage unit that stores the calculated reference constellation. The reception device compares the stored reference constellation and a reference constellation based on a pilot signal received after the equalization unit has outputted the reception constellation and uses the reference constellation determined to increase demodulation precision to demodulate a received signal.

Description

無線通信システム、受信装置、無線通信方法、及び受信プログラムWireless communication system, receiving device, wireless communication method, and receiving program
　本発明は、無線通信システム、受信装置、無線通信方法、及び受信プログラムに関する。 The present invention relates to a wireless communication system, a receiving device, a wireless communication method, and a receiving program.
　無線通信システムにおいて、デジタル信号を変調して送信する場合、データ通信を開始する前に、送信装置と受信装置との間でコンスタレーションの情報を共有することが行われている。 In wireless communication systems, when modulating and transmitting digital signals, constellation information is shared between the transmitting device and the receiving device before data communication begins.
　例えば、送信装置が増幅器の非線形領域を用いてデジタル信号を送信する場合、受信装置は、増幅器の入出力特性を考慮した参照コンスタレーションを用いて復調を行う。また、高周波数帯シングルキャリア伝送における非線形歪みコンスタレーションに対する適正な対数尤度比（ＬＬＲ）を算出することにより、復調性能を改善する技術が知られている（例えば、非特許文献１参照）。 For example, when a transmitting device transmits a digital signal using the nonlinear region of an amplifier, a receiving device performs demodulation using a reference constellation that takes into account the input/output characteristics of the amplifier. In addition, a technique is known that improves demodulation performance by calculating an appropriate log-likelihood ratio (LLR) for a nonlinear distortion constellation in high-frequency band single-carrier transmission (see, for example, Non-Patent Document 1).
　しかしながら、従来は、例えば送信装置の増幅器などの部品に個体差がある場合や、送信装置の性能に増幅器などの部品の温度特性などが影響を与える場合などには、受信装置が受信信号を復調する性能が劣化することがあった。 However, in the past, for example, when there were individual differences in components such as the amplifiers of the transmitting device, or when the temperature characteristics of components such as the amplifiers affected the performance of the transmitting device, the receiving device's ability to demodulate the received signal could deteriorate.
　また、送信装置と受信装置との間でコンスタレーションの情報を共有するために、送信装置がコンスタレーションの歪み特性を通知するための制御信号を受信装置へ送信する場合、制御信号によって伝送容量が低下することがあった。 In addition, when a transmitting device transmits a control signal to a receiving device to notify the receiving device of the distortion characteristics of the constellation in order to share constellation information between the transmitting device and the receiving device, the control signal can sometimes reduce transmission capacity.
　本発明は、上述した課題を鑑みてなされたものであり、伝送容量を低下させることなく復調性能を向上させることができる無線通信システム、受信装置、無線通信方法、及び受信プログラムを提供することを目的とする。 The present invention has been made in consideration of the above-mentioned problems, and aims to provide a wireless communication system, a receiving device, a wireless communication method, and a receiving program that can improve demodulation performance without reducing transmission capacity.
　本発明の一態様にかかる無線通信システムは、送信装置が送信するパイロット信号に基づいて受信装置が受信信号を復調する無線通信システムにおいて、前記受信装置が、前記送信装置から受信したパイロット信号に等化処理を行って受信コンスタレーションを出力する等化部と、所定コンスタレーションの信号点それぞれに基づいて、前記受信コンスタレーションの収束点それぞれに対し、前記所定コンスタレーションの信号点ごとに予め定められたインデックスを付すインデックス化部と、前記インデックス化部が同一のインデックスを付した前記収束点のクラスタそれぞれの重心それぞれを、受信信号を復調するために参照する参照コンスタレーションとして算出する参照コンスタレーション算出部と、前記参照コンスタレーション算出部が算出した参照コンスタレーションを記憶する記憶部と、前記等化部が受信コンスタレーションを出力した後に受信したパイロット信号に基づいて、前記参照コンスタレーション算出部が算出した参照コンスタレーションと、前記記憶部が記憶した参照コンスタレーションとを比較し、復調精度が高まる参照コンスタレーションがいずれであるかを判定する判定部と、復調精度が高まると前記判定部が判定した参照コンスタレーションを用いて受信信号を復調する復調部とを有することを特徴とする。 In one aspect of the present invention, a wireless communication system is a wireless communication system in which a receiving device demodulates a received signal based on a pilot signal transmitted by a transmitting device, the receiving device comprising an equalization unit that performs equalization processing on the pilot signal received from the transmitting device to output a received constellation, an indexing unit that assigns a predetermined index for each signal point of a predetermined constellation to each convergence point of the received constellation based on each signal point of the predetermined constellation, and a center of gravity of each cluster of the convergence points to which the indexing unit assigns the same index, for demodulating the received signal. The demodulation unit includes a reference constellation calculation unit that calculates a reference constellation to be referenced for demodulation, a storage unit that stores the reference constellation calculated by the reference constellation calculation unit, a determination unit that compares the reference constellation calculated by the reference constellation calculation unit with the reference constellation stored in the storage unit based on a pilot signal received after the equalization unit outputs the received constellation, and determines which reference constellation will improve demodulation accuracy, and a demodulation unit that demodulates the received signal using the reference constellation that the determination unit determines will improve demodulation accuracy.
　また、本発明の一態様にかかる受信装置は、送信装置から受信したパイロット信号に等化処理を行って受信コンスタレーションを出力する等化部と、所定コンスタレーションの信号点それぞれに基づいて、前記受信コンスタレーションの収束点それぞれに対し、前記所定コンスタレーションの信号点ごとに予め定められたインデックスを付すインデックス化部と、前記インデックス化部が同一のインデックスを付した前記収束点のクラスタそれぞれの重心それぞれを、受信信号を復調するために参照する参照コンスタレーションとして算出する参照コンスタレーション算出部と、前記参照コンスタレーション算出部が算出した参照コンスタレーションを記憶する記憶部と、前記等化部が受信コンスタレーションを出力した後に受信したパイロット信号に基づいて、前記参照コンスタレーション算出部が算出した参照コンスタレーションと、前記記憶部が記憶した参照コンスタレーションとを比較し、復調精度が高まる参照コンスタレーションがいずれであるかを判定する判定部と、復調精度が高まると前記判定部が判定した参照コンスタレーションを用いて受信信号を復調する復調部とを有することを特徴とする。 The receiving device according to one aspect of the present invention is characterized by having an equalization unit that performs equalization processing on a pilot signal received from a transmitting device and outputs a received constellation; an indexing unit that assigns a predetermined index to each of the convergence points of the received constellation based on each of the signal points of the specified constellation; a reference constellation calculation unit that calculates the center of gravity of each of the clusters of the convergence points to which the indexing unit assigns the same index as a reference constellation to be referenced for demodulating the received signal; a storage unit that stores the reference constellation calculated by the reference constellation calculation unit; a determination unit that compares the reference constellation calculated by the reference constellation calculation unit with the reference constellation stored in the storage unit based on a pilot signal received after the equalization unit outputs the received constellation, and determines which reference constellation increases demodulation accuracy; and a demodulation unit that demodulates the received signal using the reference constellation that the determination unit determines increases demodulation accuracy.
　また、本発明の一態様にかかる無線通信方法は、送信装置が送信するパイロット信号に基づいて受信装置が受信信号を復調する無線通信方法において、前記送信装置から受信したパイロット信号に等化処理を行って受信コンスタレーションを出力する等化工程と、所定コンスタレーションの信号点それぞれに基づいて、前記受信コンスタレーションの収束点それぞれに対し、前記所定コンスタレーションの信号点ごとに予め定められたインデックスを付すインデックス化工程と、前記インデックス化工程により同一のインデックスを付した前記収束点のクラスタそれぞれの重心それぞれを、受信信号を復調するために参照する参照コンスタレーションとして算出する参照コンスタレーション算出工程と、算出した参照コンスタレーションを記憶部が記憶する記憶工程と、前記等化工程により受信コンスタレーションを出力した後に受信したパイロット信号に基づいて、前記参照コンスタレーション算出工程により算出した参照コンスタレーションと、前記記憶部が記憶した参照コンスタレーションとを比較し、復調精度が高まる参照コンスタレーションがいずれであるかを判定する判定工程と、前記判定工程により復調精度が高まると判定した参照コンスタレーションを用いて受信信号を復調する復調工程とを含むことを特徴とする。 Furthermore, a wireless communication method according to one aspect of the present invention is a wireless communication method in which a receiving device demodulates a received signal based on a pilot signal transmitted by a transmitting device, the method comprising: an equalization step of performing an equalization process on the pilot signal received from the transmitting device to output a received constellation; an indexing step of assigning a predetermined index for each signal point of a predetermined constellation to each convergence point of the received constellation based on each signal point of the predetermined constellation; and an indexing step of assigning the center of gravity of each cluster of the convergence points assigned the same index by the indexing step to a cluster of the convergence points for demodulating the received signal. It is characterized by including a reference constellation calculation process for calculating a reference constellation to be referred to, a storage process for storing the calculated reference constellation in a storage unit, a determination process for comparing the reference constellation calculated in the reference constellation calculation process with the reference constellation stored in the storage unit based on a pilot signal received after the received constellation is output by the equalization process, and determining which reference constellation improves demodulation accuracy, and a demodulation process for demodulating the received signal using the reference constellation determined in the determination process to improve demodulation accuracy.
　本発明によれば、伝送容量を低下させることなく復調性能を向上させることができる。 The present invention makes it possible to improve demodulation performance without reducing transmission capacity.
一実施形態にかかる無線通信システムの構成例を示す図である。FIG. 1 is a diagram illustrating an example of a configuration of a wireless communication system according to an embodiment. 送信装置が有する機能を例示する機能ブロック図である。2 is a functional block diagram illustrating functions of a transmission device. FIG. （ａ）は、増幅部の入出力特性を例示するグラフである。（ｂ）は、増幅部が増幅させる前の送信信号のコンスタレーションを例示する図である。（ｃ）は、増幅部が非線形領域も用いて増幅させた後の送信信号のコンスタレーションを例示する図である。1A is a graph illustrating an example of the input/output characteristics of an amplifier unit, FIG. 1B is a diagram illustrating a constellation of a transmission signal before the amplifier unit amplifies the transmission signal, and FIG. 1C is a diagram illustrating a constellation of a transmission signal after the amplifier unit amplifies the transmission signal using a nonlinear region. 一実施形態にかかる受信装置が有する機能を例示する機能ブロック図である。FIG. 2 is a functional block diagram illustrating functions of a receiving device according to an embodiment. 一実施形態にかかる受信装置の動作の概要を示す概念図である。FIG. 2 is a conceptual diagram illustrating an overview of an operation of a receiving device according to an embodiment. 一実施形態にかかる受信装置の動作の具体例を示す図である。FIG. 11 is a diagram showing a specific example of the operation of a receiving device according to an embodiment.
　以下に、図面を用いて無線通信システムの一実施形態を説明する。図１は、一実施形態にかかる無線通信システム１の構成例を示す図である。無線通信システム１は、例えば送信装置２が非線形領域を用いて増幅させた変調後のデジタル信号を送信し、当該デジタル信号を受信装置４が受信して復調するように構成されている。 Below, an embodiment of a wireless communication system will be described with reference to the drawings. FIG. 1 is a diagram showing an example of the configuration of a wireless communication system 1 according to one embodiment. The wireless communication system 1 is configured such that, for example, a transmitting device 2 transmits a modulated digital signal that has been amplified using a nonlinear region, and a receiving device 4 receives and demodulates the digital signal.
　また、送信装置２は、例えば通信路情報（例えばＣＳＩ：Channel State Information）を算出するためのパイロット信号を受信装置４に対して送信する。受信装置４は、受信したパイロット信号を用いて通信路情報を算出し、算出した通信路情報を送信装置２に対して送信する。また、受信装置４は、送信装置２が送信したパイロット信号に基づいて受信信号を復調する。 The transmitting device 2 also transmits a pilot signal to the receiving device 4 for calculating, for example, communication path information (e.g., CSI: Channel State Information). The receiving device 4 calculates communication path information using the received pilot signal and transmits the calculated communication path information to the transmitting device 2. The receiving device 4 also demodulates the received signal based on the pilot signal transmitted by the transmitting device 2.
　なお、パイロット信号は、後述する等化処理を行うときまで送信されるものであってもよいし、定期的に等化処理が行われるごとに送信されるものであってもよい。 The pilot signal may be transmitted until the equalization process described below is performed, or may be transmitted periodically each time the equalization process is performed.
　図２は、送信装置２が有する機能を例示する機能ブロック図である。図２に示すように、送信装置２は、情報ビット生成部２１、パイロット信号生成部２２、変調部２３、Ｄ／Ａ変換部２４、送信電力制御部２５、増幅部２６、及びアンテナ２００を有する。 FIG. 2 is a functional block diagram illustrating the functions of the transmitting device 2. As shown in FIG. 2, the transmitting device 2 has an information bit generating unit 21, a pilot signal generating unit 22, a modulating unit 23, a D/A converting unit 24, a transmission power control unit 25, an amplifying unit 26, and an antenna 200.
　情報ビット生成部２１は、受信装置４に伝送すべき情報ビットを生成し、変調部２３に対して出力する。また、情報ビット生成部２１は、誤り訂正符号化機能、及びインターリーブ機能を備えていてもよい。 The information bit generator 21 generates information bits to be transmitted to the receiver 4 and outputs them to the modulator 23. The information bit generator 21 may also have an error correction coding function and an interleaving function.
　パイロット信号生成部２２は、受信装置４に対して送信すべきパイロット信号を生成し、変調部２３に対して出力する。パイロット信号は、通信路応答の推定や、等化処理に用いる等化ウエイトの算出などに用いられる例えばＭ系列などであり、ＢＰＳＫやＱＰＳＫにより変調される。 The pilot signal generating unit 22 generates a pilot signal to be transmitted to the receiving device 4 and outputs it to the modulating unit 23. The pilot signal is, for example, an M sequence used for estimating the communication channel response and calculating the equalization weights used in the equalization process, and is modulated by BPSK or QPSK.
　変調部２３は、情報ビット生成部２１が生成した情報ビットを例えばシングルキャリア多値変調方式によってデータ信号に変調し、Ｄ／Ａ変換部２４に対して出力する。変調部２３が行うシングルキャリア多値変調方式には、例えばＢＰＳＫ、ＱＰＳＫ、直交振幅変調である６４ＱＡＭ、２５６ＱＡＭなどがある。 The modulation unit 23 modulates the information bits generated by the information bit generation unit 21 into a data signal, for example, by a single carrier multi-level modulation method, and outputs the data signal to the D/A conversion unit 24. Examples of single carrier multi-level modulation methods used by the modulation unit 23 include BPSK, QPSK, and quadrature amplitude modulation such as 64QAM and 256QAM.
　Ｄ／Ａ変換部２４は、変調部２３がデジタル変調したデータ信号をアナログ信号に変換し、送信電力制御部２５に対して出力する。 The D/A conversion unit 24 converts the data signal digitally modulated by the modulation unit 23 into an analog signal and outputs it to the transmission power control unit 25.
　送信電力制御部２５は、Ｄ／Ａ変換部２４がアナログ信号に変換したデータ信号を所望の通信品質とするように送信電力を制御する。 The transmission power control unit 25 controls the transmission power so that the data signal converted into an analog signal by the D/A conversion unit 24 has the desired communication quality.
　増幅部２６は、送信電力制御部２５による送信電力の制御に応じて、Ｄ／Ａ変換部２４が変換したアナログ信号を増幅させ、アンテナ２００を介して放射する。 The amplifier 26 amplifies the analog signal converted by the D/A converter 24 in accordance with the control of the transmission power by the transmission power control unit 25, and radiates it via the antenna 200.
　図３は、増幅部２６の増幅特性を例示する図である。図３（ａ）は、増幅部２６の入出力特性（増幅特性）を例示するグラフである。図３（ｂ）は、増幅部２６が増幅させる前の送信信号のコンスタレーションを例示する図である。図３（ｃ）は、増幅部２６が非線形領域も用いて増幅させた後の送信信号のコンスタレーションを例示する図である。 FIG. 3 is a diagram illustrating the amplification characteristics of the amplifier 26. FIG. 3(a) is a graph illustrating the input/output characteristics (amplification characteristics) of the amplifier 26. FIG. 3(b) is a diagram illustrating the constellation of the transmission signal before it is amplified by the amplifier 26. FIG. 3(c) is a diagram illustrating the constellation of the transmission signal after it has been amplified by the amplifier 26 using the nonlinear region as well.
　図３（ａ）に示すように、増幅部２６は、入力に比例するように増幅させて出力する線形領域と、過大な入力に対して非線形に増幅させる非線形領域とを有する。 As shown in FIG. 3(a), the amplifier 26 has a linear region that amplifies and outputs the input in proportion to the input, and a nonlinear region that amplifies excessive input nonlinearly.
　図３（ｂ）に示すように、増幅部２６が増幅させる前の送信信号のコンスタレーションには歪みが生じていない。また、増幅部２６が線形領域のみを用いて送信信号を増幅させた場合にも同様に、送信信号のコンスタレーションには歪みが生じない。つまり、図３（ｂ）は、歪のない理想コンスタレーションを例示している。 As shown in FIG. 3(b), no distortion occurs in the constellation of the transmission signal before it is amplified by the amplifier 26. Similarly, no distortion occurs in the constellation of the transmission signal when the amplifier 26 amplifies the transmission signal using only the linear region. In other words, FIG. 3(b) illustrates an ideal constellation without distortion.
　一方、図３（ｃ）に示すように、増幅部２６が非線形領域も用いて送信信号を増幅させた場合、コンスタレーションに歪み（振幅減少）が生じる。 On the other hand, as shown in FIG. 3(c), if the amplifier 26 also uses the nonlinear region to amplify the transmission signal, distortion (reduction in amplitude) occurs in the constellation.
　図４は、一実施形態にかかる受信装置４が有する機能を例示する機能ブロック図である。図４に示したように、一実施形態にかかる受信装置４は、アンテナ４００、増幅部４０、Ａ／Ｄ変換部４１、推定部４２、等化ウエイト算出部４３、等化部４４、インデックス化部４５、参照コンスタレーション算出部４６、尤度算出部４７、復調部４８、情報ビット検出部４９、記憶部５０、及び判定部５１を有する。 FIG. 4 is a functional block diagram illustrating the functions of the receiving device 4 according to one embodiment. As shown in FIG. 4, the receiving device 4 according to one embodiment has an antenna 400, an amplifier 40, an A/D converter 41, an estimator 42, an equalization weight calculator 43, an equalizer 44, an indexer 45, a reference constellation calculator 46, a likelihood calculator 47, a demodulator 48, an information bit detector 49, a memory 50, and a determiner 51.
　増幅部４０は、受信装置４がアンテナ４００を介して受信したアナログ信号を増幅させ、Ａ／Ｄ変換部４１に対して出力する。 The amplifier 40 amplifies the analog signal received by the receiver 4 via the antenna 400 and outputs it to the A/D converter 41.
　Ａ／Ｄ変換部４１は、増幅部４０が増幅させたアナログ信号をデジタル信号に変換し、推定部４２及び等化部４４に対して出力する。例えば、Ａ／Ｄ変換部４１は、送信装置２が送信するパイロット信号をデジタル信号に変換し、推定部４２に対して出力する。また、Ａ／Ｄ変換部４１は、受信装置４が送信装置２から伝送されるべき情報ビットに相当するデータ信号をデジタル信号に変換し、等化部４４に対して出力する。 The A/D conversion unit 41 converts the analog signal amplified by the amplifier unit 40 into a digital signal and outputs it to the estimation unit 42 and the equalization unit 44. For example, the A/D conversion unit 41 converts the pilot signal transmitted by the transmitter 2 into a digital signal and outputs it to the estimation unit 42. The A/D conversion unit 41 also converts the data signal corresponding to the information bits to be transmitted by the receiver 4 from the transmitter 2 into a digital signal and outputs it to the equalization unit 44.
　なお、Ａ／Ｄ変換部４１がデジタル信号に変換したパイロット信号は、送信装置２と受信装置４とが通信を開始するときに送信される。 The pilot signal converted into a digital signal by the A/D converter 41 is transmitted when the transmitter 2 and receiver 4 start communication.
　推定部４２は、Ａ／Ｄ変換部４１から入力されたパイロット信号に基づいて、通信路応答を推定する。 The estimation unit 42 estimates the communication channel response based on the pilot signal input from the A/D conversion unit 41.
　等化ウエイト算出部４３は、推定部４２が推定した通信路応答に基づいて、等化部４４が用いる等化ウエイトを算出する。 The equalization weight calculation unit 43 calculates the equalization weights used by the equalization unit 44 based on the communication channel response estimated by the estimation unit 42.
　等化部４４は、送信装置２から受信したパイロット信号に対し、例えば通信路応答の逆応答などを用いた等化処理を行って受信コンスタレーションを出力する。具体的には、等化部４４は、通信路応答の振幅、位相情報を逆算して送信信号の推定値を算出する。そして、等化部４４は、等化処理を行った結果をインデックス化部４５及び尤度算出部４７に対して出力する。 The equalization unit 44 performs equalization processing on the pilot signal received from the transmitting device 2, for example, using the inverse response of the communication channel response, and outputs a received constellation. Specifically, the equalization unit 44 calculates an estimate of the transmitted signal by inversely calculating the amplitude and phase information of the communication channel response. The equalization unit 44 then outputs the result of the equalization processing to the indexing unit 45 and the likelihood calculation unit 47.
　インデックス化部４５は、所定コンスタレーションの信号点それぞれに基づいて、等化部４４が出力した受信コンスタレーションの収束点それぞれに対し、所定コンスタレーションの信号点ごとに予め定められたインデックスを付す処理を行う。 The indexing unit 45 performs processing to assign a predetermined index for each signal point of the specified constellation to each convergence point of the received constellation output by the equalization unit 44 based on each signal point of the specified constellation.
　例えば、インデックス化部４５は、送信装置２と受信装置４との無線通信にともなうコンスタレーションの非線形歪みの初期値を歪のない理想コンスタレーションに対して付与した初期歪みコンスタレーションを所定コンスタレーションとする。 For example, the indexing unit 45 determines, as the specified constellation, an initial distortion constellation obtained by adding the initial value of the nonlinear distortion of the constellation associated with wireless communication between the transmitting device 2 and the receiving device 4 to an ideal constellation without distortion.
　参照コンスタレーション算出部４６は、インデックス化部４５が同一のインデックスを付した収束点のクラスタそれぞれの重心それぞれを、受信信号を復調するために参照する参照コンスタレーションとして算出する。 The reference constellation calculation unit 46 calculates the center of gravity of each cluster of convergence points to which the indexing unit 45 assigns the same index as a reference constellation to be referenced for demodulating the received signal.
　尤度算出部４７は、参照コンスタレーション算出部４６が算出した参照コンスタレーションの尤度を算出し、算出結果を復調部４８、記憶部５０、及び判定部５１に対して出力する。尤度算出部４７は、尤度を算出するときに硬判定を行ってもよいし、軟判定を行ってもよい。 The likelihood calculation unit 47 calculates the likelihood of the reference constellation calculated by the reference constellation calculation unit 46, and outputs the calculation result to the demodulation unit 48, the storage unit 50, and the determination unit 51. The likelihood calculation unit 47 may perform hard or soft decisions when calculating the likelihood.
　復調部４８は、尤度算出部４７が尤度を算出した参照コンスタレーションを用いて受信信号を復調し、情報ビット検出部４９に対して出力する。また、復調部４８は、復調精度が高まると判定部５１（後述）が判定した参照コンスタレーションを用いて受信信号を復調する機能を備える。 The demodulation unit 48 demodulates the received signal using the reference constellation for which the likelihood calculation unit 47 has calculated the likelihood, and outputs the demodulated signal to the information bit detection unit 49. The demodulation unit 48 also has a function of demodulating the received signal using a reference constellation that a determination unit 51 (described later) has determined will improve demodulation accuracy.
　情報ビット検出部４９は、復調部４８が復調した信号から情報ビットを検出する。また、情報ビット検出部４９は、誤り訂正復号機能、及びデインターリーブ機能を備えていてもよい。 The information bit detection unit 49 detects information bits from the signal demodulated by the demodulation unit 48. The information bit detection unit 49 may also have an error correction decoding function and a deinterleaving function.
　記憶部５０は、参照コンスタレーション算出部４６が算出した参照コンスタレーションを記憶する。 The storage unit 50 stores the reference constellation calculated by the reference constellation calculation unit 46.
　判定部５１は、等化部４４が受信コンスタレーションを出力した後に受信したパイロット信号に基づいて、参照コンスタレーション算出部４６が新たに算出した参照コンスタレーションと、記憶部５０が記憶した参照コンスタレーションとを比較し、復調精度が高まる参照コンスタレーションがいずれであるかを判定する。 The determination unit 51 compares the reference constellation newly calculated by the reference constellation calculation unit 46 with the reference constellation stored in the storage unit 50 based on the pilot signal received after the equalization unit 44 outputs the received constellation, and determines which reference constellation improves demodulation accuracy.
　次に、受信装置４の動作例について説明する。図５は、一実施形態にかかる受信装置４（図４）の動作の概要を示す概念図である。 Next, an example of the operation of the receiving device 4 will be described. Figure 5 is a conceptual diagram showing an overview of the operation of the receiving device 4 (Figure 4) according to one embodiment.
　受信装置４は、受信信号に対して等化部４４が等化処理を実行する（Ｓ１００）。このとき、等化部４４は、（ａ）に示した受信コンスタレーションを出力する（等化出力）。 In the receiving device 4, the equalization unit 44 performs equalization processing on the received signal (S100). At this time, the equalization unit 44 outputs the received constellation shown in (a) (equalized output).
　次に、インデックス化部４５は、所定コンスタレーションの信号点それぞれに基づいて、等化部４４が出力した受信コンスタレーションの収束点それぞれに対し、所定コンスタレーションの信号点ごとに予め定められたインデックスを付す処理（インデックス化）を行う（Ｓ１０２）。 Next, the indexing unit 45 performs a process (indexing) of assigning a predetermined index for each signal point of the specified constellation to each convergence point of the received constellation output by the equalization unit 44 based on each signal point of the specified constellation (S102).
　参照コンスタレーション算出部４６は、例えば同一のインデックスを付された収束点ごとに分類するように、例えばｋ平均法などのクラスタリングアルゴリズムを用いてクラスタリングを行う。 The reference constellation calculation unit 46 performs clustering using a clustering algorithm such as the k-means method, for example, to classify convergence points that have the same index.
　そして、参照コンスタレーション算出部４６は、インデックス化部４５が同一のインデックスを付した収束点のクラスタそれぞれの重心それぞれを、（ｂ）に示した参照コンスタレーションとする算出を行う（Ｓ１０４）。つまり、参照コンスタレーション算出部４６が算出した参照コンスタレーションは、理想コンスタレーションに対して無線通信における歪を反映させたコンスタレーションとなっている。 Then, the reference constellation calculation unit 46 calculates the center of gravity of each cluster of convergence points to which the indexing unit 45 has assigned the same index as the reference constellation shown in (b) (S104). In other words, the reference constellation calculated by the reference constellation calculation unit 46 is a constellation that reflects distortion in wireless communication with respect to an ideal constellation.
　なお、参照コンスタレーション算出部４６は、歪を考慮していない理想コンスタレーションを初期重心としてもよいし、理想コンスタレーションに対して例えば増幅器の入出力特性に応じた非線形歪みを乗じたコンスタレーションを初期重心としてもよい。 The reference constellation calculation unit 46 may use an ideal constellation that does not take distortion into account as the initial center of gravity, or may use a constellation obtained by multiplying the ideal constellation by a nonlinear distortion according to, for example, the input/output characteristics of an amplifier as the initial center of gravity.
　その後、復調部４８は、参照コンスタレーション算出部４６が算出した参照コンスタレーションを用いて受信信号を復調する（Ｓ１０６）。 Then, the demodulation unit 48 demodulates the received signal using the reference constellation calculated by the reference constellation calculation unit 46 (S106).
　図６は、一実施形態にかかる受信装置４の動作の具体例を示す図である。図６に示すように、受信装置４は、例えば受信したパイロット信号の初期フレームなどについては、等化部４４の出力に対して、コンスタレーションのシンボル情報を利用し（Ｓ２００）、受信コンスタレーションの収束点のクラスタリングを行う（Ｓ２０２）。 FIG. 6 is a diagram showing a specific example of the operation of the receiving device 4 according to one embodiment. As shown in FIG. 6, for example, for the initial frame of a received pilot signal, the receiving device 4 uses the constellation symbol information for the output of the equalization unit 44 (S200) and performs clustering of the convergence points of the received constellation (S202).
　例えば、受信装置４は、シンボル情報としてＭＣＳインデックスなどを利用し、シンボルマッピングの候補数ｋと、理想参照点位置を検出する。受信装置４は、ブラインド推定を行ってシンボルマッピングの候補数ｋを推定してもよい。 For example, the receiving device 4 uses an MCS index or the like as symbol information to detect the number k of symbol mapping candidates and the ideal reference point position. The receiving device 4 may estimate the number k of symbol mapping candidates by performing blind estimation.
　また、受信装置４は、受信コンスタレーションの収束点のクラスタリングを行うときに、例えば理想参照点位置を初期重心として、ｋ平均法を収束するまで実施する。初期重心は、受信信号点からランダムなｋ個を選定することによって決められてもよいし、既知の装置仕様や、一般的な歪みモデル（例えばＲａｐｐモデルなどの増幅歪みモデル）を理想コンスタレーションに乗じて決められてもよい。 When performing clustering of convergence points of the received constellation, the receiving device 4 performs the k-means method until convergence, for example, using the ideal reference point position as the initial center of gravity. The initial center of gravity may be determined by randomly selecting k points from the received signal points, or may be determined by multiplying the ideal constellation by known device specifications or a general distortion model (for example, an amplification distortion model such as the Rapp model).
　そして、受信装置４は、各クラスタの重心を算出し（Ｓ２０４）、各重心を参照コンスタレーションとして受信信号の復調を行う（Ｓ２０６）。 Then, the receiving device 4 calculates the center of gravity of each cluster (S204) and demodulates the received signal using each center of gravity as a reference constellation (S206).
　また、受信装置４は、各クラスタの重心を算出すると（Ｓ２０４）、記憶部５０が例えば初期フレーム（以下前フレームと記す）の参照点位置を記憶する。 In addition, when the receiving device 4 calculates the center of gravity of each cluster (S204), the storage unit 50 stores, for example, the reference point position of the initial frame (hereinafter referred to as the previous frame).
　また、受信装置４は、例えば受信したパイロット信号の第２フレーム以降の受信データについては、等化部４４の出力に対して、コンスタレーションのシンボル情報を利用し（Ｓ２１０）、受信コンスタレーションの収束点のクラスタリングを行う（Ｓ２１２）。 Furthermore, for example, for received data from the second frame onwards of the received pilot signal, the receiving device 4 uses the constellation symbol information for the output of the equalization unit 44 (S210) and performs clustering of the convergence points of the received constellation (S212).
　例えば、受信装置４は、シンボル情報としてＭＣＳインデックスなどを利用し、シンボルマッピングの候補数ｋと、理想参照点位置を検出する。受信装置４は、ブラインド推定を行ってシンボルマッピングの候補数ｋを推定してもよい。 For example, the receiving device 4 uses an MCS index or the like as symbol information to detect the number k of symbol mapping candidates and the ideal reference point position. The receiving device 4 may estimate the number k of symbol mapping candidates by performing blind estimation.
　なお、受信装置４は、Ｓ２００の処理により、Ｓ２１０の処理を行わなくてもよい。 Note that the receiving device 4 does not need to perform the process of S210 due to the process of S200.
　また、受信装置４は、受信コンスタレーションの収束点のクラスタリングを行うときに、例えば理想参照点位置を初期重心として、ｋ平均法を収束するまで実施する。初期重心は、受信信号点からランダムなｋ個を選定することによって決められてもよいし、既知の装置仕様や、一般的な歪みモデル（例えばＲａｐｐモデルなどの増幅歪みモデル）を理想コンスタレーションに乗じて決められてもよい。 When performing clustering of convergence points of the received constellation, the receiving device 4 performs the k-means method until convergence, for example, using the ideal reference point position as the initial center of gravity. The initial center of gravity may be determined by randomly selecting k points from the received signal points, or may be determined by multiplying the ideal constellation by known device specifications or a general distortion model (for example, an amplification distortion model such as the Rapp model).
　そして、受信装置４は、各クラスタの重心を算出し（Ｓ２１４）、参照コンスタレーションとした重心間の最小距離を算出する（Ｓ２１６）。 Then, the receiving device 4 calculates the center of gravity of each cluster (S214) and calculates the minimum distance between the centers of gravity of the reference constellation (S216).
　なお、受信装置４は、閾値判定を行うときに、理想参照点位置と重心点のユークリッド距離の最大値や平均値などを用いてもよい。 When performing threshold determination, the receiving device 4 may use the maximum or average value of the Euclidean distance between the ideal reference point position and the center of gravity point.
　次に、受信装置４は、重心間の最小距離が所定の閾値以下であるか否かを判定し（Ｓ２１８）、重心間の最小距離が所定の閾値以下である場合（Ｓ２１８：Ｙｅｓ）にはＳ２２０の処理へ進み、その他の場合（Ｓ２１８：Ｎｏ）にはＳ２２２の処理へ進む。 Next, the receiving device 4 determines whether the minimum distance between the centers of gravity is equal to or less than a predetermined threshold (S218), and if the minimum distance between the centers of gravity is equal to or less than the predetermined threshold (S218: Yes), proceeds to processing of S220, and otherwise (S218: No), proceeds to processing of S222.
　Ｓ２２０の処理において、受信装置４は、Ｓ２１４の処理により算出した重心点を参照コンスタレーションとして受信信号を復調する。 In the process of S220, the receiving device 4 demodulates the received signal using the center of gravity calculated in the process of S214 as the reference constellation.
　また、Ｓ２２２の処理において、受信装置４は、前フレームの参照点位置を参照コンスタレーションとして受信信号を復調する。 In addition, in the process of S222, the receiving device 4 demodulates the received signal using the reference point position of the previous frame as the reference constellation.
　つまり、受信装置４は、復調精度が高まると判定部５１が判定した参照コンスタレーションを用いて受信信号を復調する。 In other words, the receiving device 4 demodulates the received signal using the reference constellation that the determination unit 51 determines will improve demodulation accuracy.
　このように、受信装置４は、例えばパイロット信号の前フレームによって参照コンスタレーションの信号点位置の変更が所定の精度でできていると判定した場合、その後に参照コンスタレーションに外れ値が生じると、外れ値が生じた参照コンスタレーションの算出結果を棄却して、前フレームの参照コンスタレーションを使用する。 In this way, if the receiving device 4 determines that the signal point positions of the reference constellation have been changed with a certain degree of accuracy by the previous frame of the pilot signal, and an outlier subsequently occurs in the reference constellation, it will discard the calculation result of the reference constellation where the outlier occurred and use the reference constellation of the previous frame.
　したがって、受信装置４は、パイロット信号の全フレームに対して算出した参照コンスタレーションを棄却した場合、理想コンスタレーションなどの当初の所定コンスタレーションが参照コンスタレーションとして使用され続ける。 Therefore, when the receiving device 4 rejects the reference constellation calculated for all frames of the pilot signal, the original predetermined constellation, such as the ideal constellation, continues to be used as the reference constellation.
　なお、受信装置４が図６に示した動作により参照コンスタレーションを更新する頻度は可変であってもよいし、固定されていてもよい。 Note that the frequency with which the receiving device 4 updates the reference constellation through the operation shown in FIG. 6 may be variable or may be fixed.
　以上説明したように、一実施形態にかかる受信装置４は、受信コンスタレーションを用いて、受信信号を復調するために参照する参照コンスタレーションとして算出するので、伝送容量を低下させることなく復調性能を向上させることができる。 As described above, the receiving device 4 in one embodiment uses the received constellation to calculate a reference constellation to be used for demodulating the received signal, thereby improving demodulation performance without reducing transmission capacity.
　すなわち、無線通信システム１は、例えば送信装置２の増幅部２６に非線形歪みがある場合でも、受信装置４の復調性能を改善することができる。また、無線通信システム１は、増幅部２６の非線形歪み特性を受信装置４へ通知するための制御信号が不要になり、伝送容量が低下することを防止することができる。 In other words, the wireless communication system 1 can improve the demodulation performance of the receiving device 4 even when, for example, the amplifier unit 26 of the transmitting device 2 has nonlinear distortion. Furthermore, the wireless communication system 1 does not require a control signal to notify the receiving device 4 of the nonlinear distortion characteristics of the amplifier unit 26, and can prevent a decrease in transmission capacity.
　また、上述した実施形態における送信装置２及び受信装置４を構成する各部は、一部又は全部が、ハードウェアによって構成されてもよいし、プログラムをプロセッサに実行させることによって構成されてもよい。 Furthermore, each component of the transmitting device 2 and the receiving device 4 in the above-described embodiment may be configured in part or in whole by hardware, or may be configured by having a processor execute a program.
　また、送信装置２及び受信装置４を構成する各部は、一部又は全部がプログラムをプロセッサに実行させることによって構成されている場合、当該プログラムが記録媒体に記録されて供給されてもよいし、ネットワークを介して供給されてもよい。 In addition, if the components constituting the transmitting device 2 and the receiving device 4 are configured in part or in whole by having a processor execute a program, the program may be recorded on a recording medium and supplied, or may be supplied via a network.
　なお、上述した実施形態においては、増幅部２６に非線形歪みがある場合を例に説明したが、無線通信システム１は、無線フレーム内でのランダム変動がないコンスタレーションの収縮／回転を生じる歪み（例えば、ＩＱインバランスなど）全般に対し、伝送容量を低下させることなく復調性能を向上させることができる。また、無線通信システム１の形態は、ＳＩＳＯ／ＭＩＭＯなどのアンテナ構成や、システム構成などを限定されない。 In the above embodiment, the case where the amplifier unit 26 has nonlinear distortion has been described as an example, but the wireless communication system 1 can improve demodulation performance without reducing transmission capacity for distortions in general (e.g., IQ imbalance, etc.) that cause contraction/rotation of a constellation without random fluctuation within a wireless frame. In addition, the form of the wireless communication system 1 is not limited to an antenna configuration such as SISO/MIMO, a system configuration, etc.
　１・・・無線通信システム、２・・・送信装置、４・・・受信装置、２１・・・情報ビット生成部、２２・・・パイロット信号生成部、２３・・・変調部、２４・・・Ｄ／Ａ変換部、２５・・・送信電力制御部、２６・・・増幅部、４０・・・増幅部、４１・・・Ａ／Ｄ変換部、４２・・・推定部、４３・・・等化ウエイト算出部、４４・・・等化部、４５・・・インデックス化部、４６・・・参照コンスタレーション算出部、４７・・・尤度算出部、４８・・・復調部、４９・・・情報ビット検出部、５０・・・記憶部、５１・・・判定部、２００，４００・・・アンテナ 1: Wireless communication system, 2: Transmitter, 4: Receiver, 21: Information bit generator, 22: Pilot signal generator, 23: Modulator, 24: D/A converter, 25: Transmission power controller, 26: Amplifier, 40: Amplifier, 41: A/D converter, 42: Estimator, 43: Equalizer weight calculator, 44: Equalizer, 45: Indexer, 46: Reference constellation calculator, 47: Likelihood calculator, 48: Demodulator, 49: Information bit detector, 50: Memory, 51: Determinator, 200, 400: Antenna

Claims (7)

  1. 　送信装置が送信するパイロット信号に基づいて受信装置が受信信号を復調する無線通信システムにおいて、
    　前記受信装置は、
    　前記送信装置から受信したパイロット信号に等化処理を行って受信コンスタレーションを出力する等化部と、
    　所定コンスタレーションの信号点それぞれに基づいて、前記受信コンスタレーションの収束点それぞれに対し、前記所定コンスタレーションの信号点ごとに予め定められたインデックスを付すインデックス化部と、
    　前記インデックス化部が同一のインデックスを付した前記収束点のクラスタそれぞれの重心それぞれを、受信信号を復調するために参照する参照コンスタレーションとして算出する参照コンスタレーション算出部と、
    　前記参照コンスタレーション算出部が算出した参照コンスタレーションを記憶する記憶部と、
    　前記等化部が受信コンスタレーションを出力した後に受信したパイロット信号に基づいて、前記参照コンスタレーション算出部が算出した参照コンスタレーションと、前記記憶部が記憶した参照コンスタレーションとを比較し、復調精度が高まる参照コンスタレーションがいずれであるかを判定する判定部と、
    　復調精度が高まると前記判定部が判定した参照コンスタレーションを用いて受信信号を復調する復調部と
    　を有することを特徴とする無線通信システム。     In a wireless communication system in which a receiving device demodulates a received signal based on a pilot signal transmitted by a transmitting device,
    The receiving device includes:
    an equalization unit that performs equalization processing on the pilot signal received from the transmitting device and outputs a received constellation;
    an indexing unit that assigns a predetermined index for each signal point of the predetermined constellation to each convergence point of the reception constellation based on each signal point of the predetermined constellation;
    a reference constellation calculation unit that calculates the centers of gravity of the clusters of the convergence points to which the indexing unit assigns the same index as each other as a reference constellation to be referenced in order to demodulate a received signal;
    a storage unit that stores the reference constellation calculated by the reference constellation calculation unit;
    a determination unit that compares the reference constellation calculated by the reference constellation calculation unit with the reference constellation stored in the storage unit based on a pilot signal received after the equalization unit outputs the received constellation, and determines which reference constellation improves demodulation accuracy;
    a demodulation unit that demodulates a received signal using the reference constellation determined by the determination unit when demodulation accuracy is improved.
  2. 　前記インデックス化部は、
    　前記送信装置と前記受信装置との無線通信にともなうコンスタレーションの非線形歪みの初期値を歪のない理想コンスタレーションに対して付与した初期歪みコンスタレーションを前記所定コンスタレーションとすること
    　を特徴とする請求項１に記載の無線通信システム。     The indexing unit is
    2. The wireless communication system according to claim 1, wherein the predetermined constellation is an initial distortion constellation obtained by adding an initial value of a nonlinear distortion of a constellation accompanying wireless communication between the transmitting device and the receiving device to an ideal constellation without distortion.
  3. 　送信装置から受信したパイロット信号に等化処理を行って受信コンスタレーションを出力する等化部と、
    　所定コンスタレーションの信号点それぞれに基づいて、前記受信コンスタレーションの収束点それぞれに対し、前記所定コンスタレーションの信号点ごとに予め定められたインデックスを付すインデックス化部と、
    　前記インデックス化部が同一のインデックスを付した前記収束点のクラスタそれぞれの重心それぞれを、受信信号を復調するために参照する参照コンスタレーションとして算出する参照コンスタレーション算出部と、
    　前記参照コンスタレーション算出部が算出した参照コンスタレーションを記憶する記憶部と、
    　前記等化部が受信コンスタレーションを出力した後に受信したパイロット信号に基づいて、前記参照コンスタレーション算出部が算出した参照コンスタレーションと、前記記憶部が記憶した参照コンスタレーションとを比較し、復調精度が高まる参照コンスタレーションがいずれであるかを判定する判定部と、
    　復調精度が高まると前記判定部が判定した参照コンスタレーションを用いて受信信号を復調する復調部と
    　を有することを特徴とする受信装置。     an equalization unit that performs equalization processing on a pilot signal received from a transmitting device and outputs a received constellation;
    an indexing unit that assigns a predetermined index for each signal point of the predetermined constellation to each convergence point of the reception constellation based on each signal point of the predetermined constellation;
    a reference constellation calculation unit that calculates the centers of gravity of the clusters of the convergence points to which the indexing unit assigns the same index as each other as a reference constellation to be referenced in order to demodulate a received signal;
    a storage unit that stores the reference constellation calculated by the reference constellation calculation unit;
    a determination unit that compares the reference constellation calculated by the reference constellation calculation unit with the reference constellation stored in the storage unit based on a pilot signal received after the equalization unit outputs the received constellation, and determines which reference constellation improves demodulation accuracy;
    A receiving device comprising: a demodulation unit that demodulates a received signal using the reference constellation determined by the determination unit when demodulation accuracy is improved.
  4. 　前記インデックス化部は、
    　前記送信装置との無線通信にともなうコンスタレーションの非線形歪みの初期値を歪のない理想コンスタレーションに対して付与した初期歪みコンスタレーションを前記所定コンスタレーションとすること
    　を特徴とする請求項３に記載の受信装置。     The indexing unit is
    4. The receiving device according to claim 3, wherein the predetermined constellation is an initial distortion constellation obtained by adding an initial value of nonlinear distortion of a constellation accompanying wireless communication with the transmitting device to an ideal constellation without distortion.
  5. 　送信装置が送信するパイロット信号に基づいて受信装置が受信信号を復調する無線通信方法において、
    　前記送信装置から受信したパイロット信号に等化処理を行って受信コンスタレーションを出力する等化工程と、
    　所定コンスタレーションの信号点それぞれに基づいて、前記受信コンスタレーションの収束点それぞれに対し、前記所定コンスタレーションの信号点ごとに予め定められたインデックスを付すインデックス化工程と、
    　前記インデックス化工程により同一のインデックスを付した前記収束点のクラスタそれぞれの重心それぞれを、受信信号を復調するために参照する参照コンスタレーションとして算出する参照コンスタレーション算出工程と、
    　算出した参照コンスタレーションを記憶部が記憶する記憶工程と、
    　前記等化工程により受信コンスタレーションを出力した後に受信したパイロット信号に基づいて、前記参照コンスタレーション算出工程により算出した参照コンスタレーションと、前記記憶部が記憶した参照コンスタレーションとを比較し、復調精度が高まる参照コンスタレーションがいずれであるかを判定する判定工程と、
    　前記判定工程により復調精度が高まると判定した参照コンスタレーションを用いて受信信号を復調する復調工程と
    　を含むことを特徴とする無線通信方法。     A wireless communication method in which a receiving device demodulates a received signal based on a pilot signal transmitted by a transmitting device, comprising:
    an equalization step of performing an equalization process on the pilot signal received from the transmitting device and outputting a received constellation;
    an indexing step of assigning a predetermined index for each signal point of the predetermined constellation to each convergence point of the received constellation based on each signal point of the predetermined constellation;
    a reference constellation calculation step of calculating the centers of gravity of the clusters of the convergence points to which the same index is assigned in the indexing step as reference constellations to be referenced for demodulating a received signal;
    a storage step of storing the calculated reference constellation in a storage unit;
    a determination step of comparing the reference constellation calculated in the reference constellation calculation step with the reference constellation stored in the storage unit based on a pilot signal received after the received constellation is output in the equalization step, and determining which reference constellation improves demodulation accuracy;
    and a demodulation step of demodulating a received signal using a reference constellation determined in the determination step to improve demodulation accuracy.
  6. 　前記インデックス化工程では、
    　前記送信装置と前記受信装置との無線通信にともなうコンスタレーションの非線形歪みの初期値を歪のない理想コンスタレーションに対して付与した初期歪みコンスタレーションを前記所定コンスタレーションとすること
    　を特徴とする請求項５に記載の無線通信方法。     In the indexing step,
    The wireless communication method according to claim 5, wherein the predetermined constellation is an initial distortion constellation obtained by adding an initial value of a nonlinear distortion of a constellation accompanying wireless communication between the transmitting device and the receiving device to an ideal constellation without distortion.
  7. 　請求項３又は４に記載の受信装置の各部としてコンピュータを機能させるための受信プログラム。 A receiving program for causing a computer to function as each part of the receiving device according to claim 3 or 4.
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WO2016012382A1 (en) * 2014-07-22 2016-01-28 Deutsches Zentrum Fuer Luft- Und Raumfahrt E.V. Method for receiving a digital signal in a digital communication system
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WO2016012382A1 (en) * 2014-07-22 2016-01-28 Deutsches Zentrum Fuer Luft- Und Raumfahrt E.V. Method for receiving a digital signal in a digital communication system
JP2017059889A (en) * 2015-09-14 2017-03-23 日本放送協会 Single carrier type transmitter and receiver
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