WO2014091879A1 - Qam変調通信システムの多値差動復号装置および方法 - Google Patents
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0045—Arrangements at the receiver end
- H04L1/0047—Decoding adapted to other signal detection operation
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- 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
- H04L27/3845—Demodulator circuits; Receiver circuits using non - coherent demodulation, i.e. not using a phase synchronous carrier
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0045—Arrangements at the receiver end
- H04L1/0054—Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/06—Dc level restoring means; Bias distortion correction ; Decision circuits providing symbol by symbol detection
- H04L25/067—Dc level restoring means; Bias distortion correction ; Decision circuits providing symbol by symbol detection providing soft decisions, i.e. decisions together with an estimate of reliability
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/32—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
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0045—Arrangements at the receiver end
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L2025/0335—Arrangements for removing intersymbol interference characterised by the type of transmission
- H04L2025/03356—Baseband transmission
- H04L2025/03363—Multilevel
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- the present invention relates to a multilevel differential decoding apparatus and method for a QAM modulation communication system using QAM modulation, and more particularly to a novel for realizing decoding processing of differentially encoded multilevel modulated optical signals with a small circuit scale. Technology.
- Non-Patent Document 2 a technique for inserting a pilot signal has been proposed in order to cope with a phase slip caused by phase noise caused by multi-level modulation transmission and to guarantee transmission performance.
- a pilot signal when a pilot signal is inserted, the redundancy increases depending on the frequency of pilot insertion, which causes a problem that it becomes difficult to cope with a high transmission rate as the operation speed of the electric circuit increases.
- differential encoding As another technique for dealing with phase slip.
- This technique provides resistance to changes in absolute phase by giving information to transitions of consecutive signal points in the phase space of two I / Q signals orthogonal to each other. In this case, since no additional signal insertion is required, there is an advantage that the signal operation speed is not increased and the present invention is excellent in application to high-speed signal transmission.
- Patent Document 2 Also known is a technique for receiving a differentially encoded modulated signal and generating likelihood for the received signal (see, for example, Patent Document 2, Patent Document 3, and Patent Document 4).
- a technique for performing likelihood generation processing on each of the upper and lower bits of a received QAM (Quadrature Amplitude Modulation) signal vector is also known (for example, Patent Document 5, Patent Document 6, (See Patent Document 7).
- differential decoding is performed on the MSB 2 bits.
- a technique for performing decoding processing combining symbol rotation on the LSB side bit is also known (see, for example, Patent Document 8).
- a digital coherent transmission technique using digital signal processing has attracted attention.
- amplitude information using ADC Analog-to-Digital Converter
- ADC Analog-to-Digital Converter
- a conventional multi-level differential decoding apparatus and method of a QAM modulation communication system are designed to realize multi-level modulation technology using digital coherent technology, error correction technology, QAM modulation for the purpose of realizing optical communication with increased multi-level.
- each of the likelihood generation techniques has been presented, there has been a problem that the reduction in the phase noise tolerance due to multi-level modulation cannot be effectively saved by error correction.
- differential encoding and decoding techniques are applied to QAM modulation in order not to increase the circuit operation speed while avoiding the effect of phase slip.
- the present invention has been made to solve the above-described problem, and a multi-level differential decoding apparatus of a QAM modulation communication system capable of realizing a differential decoding process applied to multi-level modulation with a small circuit scale, and The purpose is to obtain a method.
- a multi-level differential decoding apparatus of a QAM modulation communication system includes a synchronous detection unit that receives a signal in which the upper 2 bits of N bits (N ⁇ 4) are subjected to differential encoding, An MSB coordinate rotation unit that performs coordinate rotation based on the information of the upper 2 bits of the received symbol of the received signal via the detection unit, and two sets of bit strings after coordinate rotation based on the upper 2 bits at different times An MSB symbol likelihood generator for generating likelihood for the upper 2 bits after differential decoding, and an LSB symbol likelihood for generating likelihood for lower bits consisting of lower N-2 bits of the received symbols of the received signal The error generation unit performs error correction decoding using the upper 2 bits and the lower bits of the likelihood generated from the MSB symbol likelihood generation unit and the LSB symbol likelihood generation unit.
- a soft-decision error correction decoding unit for generating a signal, in which with a.
- the differential decoding circuit is simply configured after the coordinate rotation process based on the information of the upper 2 bits representing the quadrant information, so that the differential decoding circuit can be simply configured regardless of the increase of the multi-value degree. be able to.
- FIG. 1 is a functional block diagram showing a multilevel differential decoding apparatus of a QAM modulation communication system according to Embodiment 1 of the present invention, and shows a configuration of a receiver.
- a multilevel differential decoding apparatus of a QAM modulation communication system includes a likelihood generation unit 10, a synchronous detection unit 11 that inputs a reception signal from a transmitter to the likelihood generation unit 10, and a bit LLR (Logarithm of Likelihood Ratio) generation unit 26 and soft decision error correction decoding unit 27.
- LLR Logarithm of Likelihood Ratio
- the likelihood generation unit 10 includes a quadrant information extraction unit 12, a delay unit 13, MSB coordinate rotation units 14a and 14b, an MSB symbol likelihood generation unit 15, an LSB coordinate rotation unit 24, and an LSB symbol likelihood generation unit. 25.
- two broken line frames indicate application ranges of the signal at time t-1 (one symbol before) and the signal at time t (current symbol), respectively.
- a broken line arrow from the quadrant information extraction unit 12 indicates coordinate rotation information corresponding to the quadrant of the signal at time t.
- the quadrant information extraction unit 12 uses the MSB side bits (2 bits) from the reception signal at time t to extract quadrant information in which the reception signal exists, and the MSB coordinate rotation units 14a and 14b and the LSB coordinate rotation unit 24.
- the MSB coordinate rotation unit 14 a inputs a received signal subjected to coordinate rotation according to quadrant information to the MSB symbol likelihood generation unit 15.
- the delay unit 13 delays the received signal and inputs the received signal at time t-1 (one symbol before) to the MSB coordinate rotation unit 14b.
- the MSB coordinate rotation unit 14 b performs coordinate rotation according to the quadrant information on the signal one symbol before and inputs the signal to the MSB symbol likelihood generation unit 15.
- the MSB symbol likelihood generation unit 15 generates an MSB symbol likelihood by performing MSB differential decoding using two input signals, and inputs the MSB symbol likelihood to the bit LLR generation unit 26.
- the LSB coordinate rotation unit 24 uses the quadrant information and the modulation method signal as input information to perform coordinate rotation on the LSB side bits (the N-2 bits on the lower side) of the received signal to generate LSB symbol likelihood.
- the symbol likelihood generation unit 25 generates an LSB symbol likelihood from the input signal from the LSB coordinate rotation unit 24 and inputs the LSB symbol likelihood to the bit LLR generation unit 26.
- the bit LLR generation unit 26 generates a bit LLR using the input signals from the MSB symbol likelihood generation unit 15 and the LSB symbol likelihood generation unit 25, and the soft decision error correction decoding unit 27 decodes using the bit LLR The decoded signal is generated.
- FIG. 3 is an explanatory diagram showing an example of likelihood generation of MSB side bits (MSB symbols) according to Embodiment 1 of the present invention
- FIG. 4 shows LSB side bits (LSB symbols) according to Embodiment 1 of the present invention. It is explanatory drawing which shows the example of likelihood generation of. 2 to 4, the MSB side 2 bits “00, 10, 11, 01” (refer to the inside of the broken line frame) of each signal point indicate information corresponding to each quadrant.
- each received symbol is demodulated by the synchronous detection unit 11 as a complex signal having a certain signal bit width.
- reception optical field regeneration processing and distortion equalization processing in the synchronous detection unit 11 can be realized by using normal digital coherent optical reception processing, and compensation of waveform distortion and polarization It is assumed that the separation of multiplexed signals is also realized by digital signal processing.
- the quadrant information extraction unit 12 extracts quadrant information in which a received signal exists from the received signal at a certain time t using 2 bits on the MSB side.
- the MSB coordinate rotation unit 14a performs coordinate rotation according to the quadrant information, and rearranges the received signals in a single quadrant.
- the MSB coordinate rotation unit 14b performs the same coordinate rotation corresponding to the quadrant information of the reception signal at time t for the reception signal at time t-1 (one symbol before).
- the signal point P3 in the third quadrant “11” at time t is rotated 180 degrees, rearranged at the signal point P1 in the first quadrant “00”, and at time t ⁇ 1.
- a case where the signal point P4 in the fourth quadrant “01” is rotated by 180 degrees and rearranged at the signal point P2 in the second quadrant “10” is shown.
- the rotation operation is a process for placing the reference point for likelihood generation only in the single quadrant (first quadrant).
- the signal point of the received signal at time t is located in the second quadrant. In that case, it is rotated 90 degrees and rearranged in the first quadrant. In this case, the signal point of the received signal at time t ⁇ 1 is also rotated by 90 degrees.
- the MSB symbol likelihood generation unit 15 generates a likelihood for DEQPSK (Differential Encoded Phase Shift Keying) based on only a single quadrant (first quadrant).
- DEQPSK Different Encoded Phase Shift Keying
- the MSB symbol likelihood generating unit 15 performs the Euclidean distance L1 from the virtual maximum likelihood points Q1 and Q2 (see the hatching circle) for the signal points P1 and P2 at two times t and t ⁇ 1, respectively.
- the likelihood based on L2 is obtained, and the likelihood generation after differential decoding is performed from the likelihood and transition state of the two points P1 and P2, and the likelihood for the MSB side upper 2 bits is generated.
- Likelihood generation processing after differential decoding using 2 bits can be realized by using a known DEQPSK demodulation technique.
- the feature of signal point arrangement subjected to gray coding rotated 90 degrees for each quadrant is utilized. That is, as shown in FIG. 4, the LSB coordinate rotation unit 24 performs coordinate rotation based on the quadrant information “11” extracted for the signal point P3 at time t, and the first quadrant “00” (single Rearrange to signal point P1 in quadrant). Next, the LSB symbol likelihood generation unit 25 directly determines the LSB side likelihood (without performing the differential decoding process) from the Euclidean distance L1 from the virtual maximum likelihood point Q1.
- bit LLR generation unit 26 calculates the code of the error correction code from each likelihood information (MSB symbol likelihood and LSB symbol likelihood) generated from the MSB symbol likelihood generation unit 15 and the LSB symbol likelihood generation unit 25.
- a bit likelihood (bit LLR) corresponding to the word is generated and input to the soft decision error correction decoding unit 27.
- the soft decision error correction decoding unit 27 generates a decoded signal after error correction decoding processing using the bit LLR.
- the soft decision error correction decoding unit 27 In order for the soft decision error correction decoding unit 27 to perform decoding processing more correctly, it is desirable that the unit of the code word of the error correction code is known. In this case, since information on the frame positions constituting the error correction code is required, it is necessary to change the peripheral configuration of the soft decision error correction decoding unit 27A as shown in FIG. 5 (described later).
- FIG. 5 is a functional block diagram showing another configuration example of the multilevel differential decoding apparatus of the QAM modulation communication system according to Embodiment 1 of the present invention.
- the same components as those described above (see FIG. 1) are described above.
- the same reference numerals are attached, or “A” is attached after the reference numerals, and the detailed description is omitted.
- a synchronization signal detection unit 28 is inserted.
- the MSB symbol likelihood generator 15A generates a frame head bit after differential decoding based on the frame head bit string included in the received signal, and inputs the frame head bit to the frame synchronization signal detector 28.
- a frame synchronization signal detecting unit 28 is provided, and a frame position (for example, a pulse representing the head of the frame) constituting the error correction code is softly determined.
- a frame position for example, a pulse representing the head of the frame
- the frame synchronization signal detection unit 28 is inserted between the likelihood generation unit 10A and the soft decision error correction decoding unit 27A.
- the differential decoding process and the frame synchronization signal detection process for frame position detection are performed as follows. Needless to say, this is not necessarily performed immediately before the soft decision error correction decoding unit 27A, and may be a function block (separate circuit) different from the likelihood generation unit 10A, and there is no particular problem in operation.
- the MSB symbol likelihood generator 15A for generating the MSB side likelihood applies a special change as differential decoding means for QPSK in which only one signal is arranged in each quadrant as shown in FIG. It can be used as it is.
- the LSB coordinate rotation unit 24 captures an external modulation scheme signal as input information related to the modulation scheme, and switches between using / not using the function on the LSB side, thereby enabling a differential decoding function for the QPSK signal. Therefore, it is possible to switch the operation with the differential decoding function for 16QAM signals, so that a plurality of modulation schemes can be supported.
- the multilevel differential decoding apparatus of the QAM modulation communication system according to Embodiment 1 (FIGS. 1 to 4) of the present invention is different from the upper 2 bits of the transmission symbol of N bits (N ⁇ 4).
- a synchronous detection unit 11 that receives a signal that has been subjected to dynamic coding, and an MSB coordinate rotation unit 14a that performs coordinate rotation based on the information of the upper 2 bits of the received symbols of the received signal via the synchronous detection unit 11, 14b, MSB symbol likelihood generator 15 for generating likelihoods for the upper 2 bits after differential decoding using two sets of bit strings after coordinate rotation based on the upper 2 bits at different times, and the upper 2 bits
- the LSB symbol likelihood generating unit 25 that generates likelihood for the lower bits composed of the lower N-2 bits of the received symbols of the received signal
- a soft-decision error correction decoding unit 27 that generates a decoded signal by performing error correction decoding process using the likelihood of
- the LSB symbol likelihood generation unit 25 switches the operation of the lower-order bit likelihood generation function between used and unused, using the modulation method signal for switching the modulation method as input information.
- the MSB coordinate rotation unit generates an MSB coordinate rotation unit 14a (first MSB coordinate rotation unit) that performs coordinate rotation on a received signal at a certain time t in order to generate two sets of bit strings, and a first MSB.
- an MSB coordinate rotation unit 14b (second MSB coordinate rotation unit) that performs coordinate rotation on the received signal one symbol before (time t-1) from a certain time t is included. .
- the multilevel differential decoding method of the QAM modulation communication system includes a reception step of receiving a signal in which the upper 2 bits of a transmission symbol are differentially encoded,
- the MSB coordinate rotation step for rotating the coordinates based on the information of the upper 2 bits of the received symbol and the higher bit after differential decoding using two sets of bit strings after the coordinate rotation based on the upper 2 bits at different times MSB symbol likelihood generating step for generating likelihood for 2 bits, LSB symbol likelihood generating step for generating likelihood for lower bits consisting of lower N-2 bits of received symbols of the received signal, and upper 2 bits
- a soft decision error correction decoding step of generating a decoded signal by performing error correction decoding processing using each likelihood of lower bits.
- the operation of the lower-bit likelihood generation function is switched to used / unused with the modulation scheme signal for modulation scheme switching as input information.
- the conventional apparatus needs to realize differential decoding considering a maximum of 16 combinations (4 values ⁇ 4 quadrants).
- the differential decoding process using coordinate rotation, it becomes a likelihood generation process based on only a single quadrant (first quadrant), Since only four combinations (4 values ⁇ 1 quadrant) need to be considered, the circuit scale can be greatly reduced.
- the differential decoding circuit can be easily configured regardless of the increase of the multi-value degree.
- MSB side likelihood generation based on quadrant identification in the MSB symbol likelihood generation unit 15 and LSB side bit likelihood generation in the LSB symbol likelihood generation unit 25 are independently performed to perform a plurality of modulations.
- Likelihood generation corresponding to the method can be realized by substantially the same circuit.
- the multilevel differential decoding apparatus of the QAM modulation communication system according to Embodiment 1 (FIG. 5) of the present invention includes a frame synchronization signal detection unit 28 connected to the soft decision error correction decoding unit 27A.
- a frame head bit string indicating the head of the error correction frame is assigned to the upper 2 bits subjected to differential encoding.
- the MSB symbol likelihood generation unit 15A generates a frame head bit after differential decoding based on the frame head bit string and inputs the frame head bit to the frame synchronization signal detection unit 28.
- the frame synchronization signal detection unit 28 The frame start position for error correction decoding is detected from the decoded frame start bit and input to the soft decision error correction decoding unit 27A.
- the frame synchronization signal detection unit 28 is configured independently of the likelihood generation unit 10A, generates a frame head bit after differential decoding based on the frame head bit string, and generates an error from the frame head bit after differential decoding.
- the frame start position for correction decoding is detected and input to the soft decision error correction decoding unit 27A.
- the multilevel differential decoding method of the QAM modulation communication system includes a frame synchronization signal detection step that is executed before the soft decision error correction decoding step, and is received at the reception step.
- the signal has a frame head bit string indicating the head of the error correction frame assigned to the upper 2 bits subjected to differential encoding, and the frame synchronization signal detection step performs a frame after differential decoding based on the frame head bit string.
- a head bit is generated, a frame head position for error correction decoding is detected from the frame head bit after differential decoding, and the soft decision error correction decoding step generates a decoded signal using the frame head position.
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Abstract
Description
しかし、パイロット信号を挿入すると、パイロット挿入頻度によって冗長度が増加するので、電気回路の動作速度上昇をともない、高速の伝送速度への対応が難しくなるという問題が生じる。
また、受信したQAM(Quadrature Amplitude Modulation:直交振幅変調)信号ベクトルの上位ビットと下位ビットとのそれぞれについて、尤度生成処理を行う技術も知られている(たとえば、特許文献5、特許文献6、特許文献7参照)。
この技術においては、ADC(Analog-to-Digital Converter)を用いた振幅情報を受信信号処理に適用可能なので、軟判定を用いた誤り訂正技術の併用が容易であり、受信性能を向上させることができる。
以下、図面を参照しながら、この発明の実施の形態1について説明する。
図1は、この発明の実施の形態1に係るQAM変調通信システムの多値差動復号装置を示す機能ブロック図であり、受信機の構成を示している。
また、象限情報抽出部12からの破線矢印は、時刻tの信号の象限に応じた座標回転情報を示している。
MSB座標回転部14aは、象限情報に応じて座標回転を施した受信信号をMSBシンボル尤度生成部15に入力する。
MSBシンボル尤度生成部15は、2つの入力信号を用いてMSB差動復号を行うことにより、MSBシンボル尤度を生成し、ビットLLR生成部26に入力する。
図2はこの発明の実施の形態1に用いられる多値信号点の配置例を示す説明図であり、各信号点が4ビット(N=4)の場合を示している。
図2~図4において、各信号点のうちのMSB側2ビット「00、10、11、01」(破線枠内参照)は、各象限に対応した情報を示している。
たとえば、図2のマッピングがなされた信号を想定すると、受信した各シンボルは、同期検波部11により、或る信号ビット幅を有する複素信号として復調される。
MSB座標回転部14aは、復号に際し、象限情報に応じた座標回転を行い、受信信号を単一象限に再配置する。同様に、MSB座標回転部14bは、時刻tの受信信号の象限情報に対応した同一の座標回転を、時刻t-1(1シンボル前)の受信信号に対しても行う。
2ビットを用いた差動復号後の尤度生成処理は、公知のDEQPSK復調技術を使用することにより実現可能である。
すなわち、図4に示すように、LSB座標回転部24は、時刻tでの信号点P3に対して抽出された象限情報「11」に基づき座標回転を行い、第1象限「00」(単一象限)内の信号点P1に再配置する。
次に、LSBシンボル尤度生成部25は、仮想最尤点Q1からのユークリッド距離L1から、LSB側尤度を直接(差動復号処理を行わずに)決定する。
最後に、軟判定誤り訂正復号部27は、ビットLLRを用いて誤り訂正復号処理した後の復号信号を生成する。
この場合、MSBシンボル尤度生成部15Aは、受信信号に含まれるフレーム先頭ビット列に基づき差動復号後のフレーム先頭ビットを生成して、フレーム同期信号検出部28に入力する。
MSB座標回転部は、2組のビット列を生成するために、或る時刻tの受信信号に対して座標回転を行うMSB座標回転部14a(第1のMSB座標回転部)と、第1のMSB座標回転部とは独立に、或る時刻tから1シンボル前(時刻t-1)の受信信号に対して座標回転を行うMSB座標回転部14b(第2のMSB座標回転部)と、を含む。
また、LSBシンボル尤度生成ステップは、変調方式切り替え用の変調方式信号を入力情報として、下位ビットの尤度生成機能の動作を使用/未使用に切り替える。
Claims (8)
- QAM変調を用いたQAM変調通信システムの多値差動復号装置であって、
Nビット(N≧4)の送信シンボルの上位2ビットに差動符号化が施された信号を受信する同期検波部と、
前記同期検波部を介した受信信号の受信シンボルのうちの上位2ビットの情報に基づいて座標回転を行うMSB座標回転部と、
互いに異なる時間での前記上位2ビットに基づく座標回転後の2組のビット列を用いて差動復号後の前記上位2ビットに対する尤度を生成するMSBシンボル尤度生成部と、
前記受信信号の受信シンボルのうちの下位N-2ビットからなる下位ビットについて尤度を生成するLSBシンボル尤度生成部と、
前記MSBシンボル尤度生成部および前記LSBシンボル尤度生成部から生成された前記上位2ビットおよび前記下位ビットの各尤度を用いて誤り訂正復号処理を施して復号信号を生成する軟判定誤り訂正復号部と、
を備えたQAM変調通信システムの多値差動復号装置。 - 前記LSBシンボル尤度生成部は、変調方式切り替え用の変調方式信号を入力情報として、下位ビットの尤度生成機能の動作を使用/未使用に切り替える請求項1に記載のQAM変調通信システムの多値差動復号装置。
- 前記MSB座標回転部は、前記2組のビット列を生成するために、
或る時刻の受信信号に対して座標回転を行う第1のMSB座標回転部と、
前記或る時刻から1シンボル前の受信信号に対して座標回転を行う第2のMSB座標回転部と、
を含む請求項1または請求項2に記載のQAM変調通信システムの多値差動復号装置。 - 前記軟判定誤り訂正復号部に接続されたフレーム同期信号検出部を備え、
前記同期検波部で受信される信号には、前記差動符号化が施された上位2ビットに誤り訂正フレームの先頭を示すフレーム先頭ビット列が割り当てられており、
前記MSBシンボル尤度生成部は、前記フレーム先頭ビット列に基づき差動復号後のフレーム先頭ビットを生成して、前記フレーム同期信号検出部に入力し、
前記フレーム同期信号検出部は、前記差動復号後のフレーム先頭ビットから誤り訂正復号用のフレーム先頭位置を検出して、前記軟判定誤り訂正復号部に入力する請求項1から請求項3までのいずれか1項に記載のQAM変調通信システムの多値差動復号装置。 - 前記軟判定誤り訂正復号部に接続されたフレーム同期信号検出部を備え、
前記同期検波部で受信される信号には、前記差動符号化が施された上位2ビットに誤り訂正フレームの先頭を示すフレーム先頭ビット列が割り当てられており、
前記フレーム同期信号検出部は、前記フレーム先頭ビット列に基づき差動復号後のフレーム先頭ビットを生成するとともに、前記差動復号後のフレーム先頭ビットから誤り訂正復号用のフレーム先頭位置を検出して、前記軟判定誤り訂正復号部に入力する請求項1から請求項3までのいずれか1項に記載のQAM変調通信システムの多値差動復号装置。 - QAM変調を用いたQAM変調通信システムの多値差動復号方法であって、
Nビット(N≧4)の送信シンボルの上位2ビットに差動符号化が施された信号を受信する受信ステップと、
受信信号の受信シンボルのうちの上位2ビットの情報に基づいて座標回転を行うMSB座標回転ステップと、
互いに異なる時間での前記上位2ビットに基づく座標回転後の2組のビット列を用いて差動復号後の前記上位2ビットに対する尤度を生成するMSBシンボル尤度生成ステップと、
前記受信信号の受信シンボルのうちの下位N-2ビットからなる下位ビットについて尤度を生成するLSBシンボル尤度生成ステップと、
前記上位2ビットおよび前記下位ビットの各尤度を用いて誤り訂正復号処理を施して復号信号を生成する軟判定誤り訂正復号ステップと、
を備えたQAM変調通信システムの多値差動復号方法。 - 前記LSBシンボル尤度生成ステップは、変調方式切り替え用の変調方式信号を入力情報として、下位ビットの尤度生成機能の動作を使用/未使用に切り替える請求項6に記載のQAM変調通信システムの多値差動復号方法。
- 前記軟判定誤り訂正復号ステップの前に実行されるフレーム同期信号検出ステップを備え、
前記受信ステップで受信される信号には、前記差動符号化が施された上位2ビットに誤り訂正フレームの先頭を示すフレーム先頭ビット列が割り当てられており、
前記フレーム同期信号検出ステップは、前記フレーム先頭ビット列に基づき差動復号後のフレーム先頭ビットを生成するとともに、前記差動復号後のフレーム先頭ビットから誤り訂正復号用のフレーム先頭位置を検出し、
前記軟判定誤り訂正復号ステップは、前記フレーム先頭位置を用いて前記復号信号を生成する請求項6または請求項7に記載のQAM変調通信システムの多値差動復号方法。
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