Multiple Differential Detection Research Articles

Multi-Carrier Differential Trellis-Coded Modulation/Demodulation Employing Multiple Differential Detection with Channel Prediction and Its Application

Multi-Carrier Differential Trellis-Coded Modulation/Demodulation Employing Multiple Differential Detection with Channel Prediction and Its Application

Planar Eddy Current Sensor Array With Null-Offset

Aiming at the problem of low resolution of traditional eddy current sensor for buried defects detection in metal materials, a null-offset planar eddy current sensor array is designed, realized, and tested. The arrayed sensor is composed of a spatially periodic excitation coil and multiple differential detection coils, which are skillfully designed and can effectively suppress the common mode component in the induced voltage and improve the signal-noise-ratio of the sensor. The null-offset eddy current sensor is fabricated and utilized to detect the buried defects 0.5-mm depth beneath the surface of aluminum alloy test pieces. The simulation and experimental results show that the null-offset eddy current detection unit improves the detection resolution of buried defects by more than 1000 times.

An Off-Line Underwater Acoustic Software Modem for Multiple Differential Detection Employing Per-Survivor Processing with Channel Prediction

An Off-Line Underwater Acoustic Software Modem for Multiple Differential Detection Employing Per-Survivor Processing with Channel Prediction

航空复合材料内部缺陷差动式激光红外热成像检测

The existence of internal defects of aviation composites is a serious threat to air safety. In this paper, a novel infrared thermal imaging technique with laser as a heat source was applied to detect the internal defects in the carbon fiber reinforced plastics(CFRP) used in aviation field. With the advantages of remote feature and high-power density of laser, the positioning detection for the internal delamination defects of CFRP could be realized precisely. Multiple differential detection was carried out for the defect specimen as same as the reference specimen by using laser infrared thermal imaging technology. At the same time, according to the spatial position relationship between the specimen and the thermal imager, the max temperature difference in thermographs would be selected to calculate the diameter of the internal delaminate defect. The result shows that the laser infrared thermal imaging technology can effectively detect the internal delamination defects of CFRP. Especially, the differential laser infrared thermal imaging technology used for the first time can effectively eliminate the influence of the uneven laser energy distribution and make the defect image much clearer.

Double decision-feedback multiple differential detection for double differential encoding

Double decision-feedback multiple differential detection for double differential encoding

Generalization of channel estimation weights for multiple differential detection based on per-survivor processing

Generalization of channel estimation weights for multiple differential detection based on per-survivor processing

簡易な1次伝送路予測による判定帰還多重遅延検波とその音響通信への応用

簡易な1次伝送路予測による判定帰還多重遅延検波とその音響通信への応用

Performance Improvement of DPSK Signal Reception Using Reconfigurable Multiple Bit Differential Detection in the Presence of Carrier Frequency Offset

In this paper we propose a reconfigurable multiple bit differential detection (MBDD) algorithm with diversity reception in the form of postdetection equal-gain combining (EGC) that can be used for the differential phase shift keying (DPSK) signal reception in the presence of significant frequency offsets. The proposed algorithm is based on the MBDD algorithm with the introduction of a mechanism for the estimation of the frequency offset. The algorithm is checking N c frequency offsets around zero offset and chooses the one that is the most likely. The analysis shows that the receiver with the proposed algorithm provides signal reception with almost equal quality in a wide range of carrier frequency offsets around zero frequency offset.

SISO FB-MAP Detection for Turbo-Coded Differential PSK Systems

For turbo-coded differential phase-shift-keying (DPSK) systems under correlated flat-fading channels, a serial iterative structure of soft-input-soft-output (SISO) forward/backward MAP (FB-MAP) detection and SISO decoder is proposed to reduce the computational complexity of MAP detection without performance degradation. The simulation results show that the FB-MAP detection scheme offers the same or better bit error rate (BER) performance with lower computational complexity when compared with the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a posteriori</i> probability (APP) demodulator, the SISO MAP detection, and the SISO multiple-symbol differential sphere decoder (MSDSD) scheme. Although the computational complexity is higher than the iterative filtered multiple differential detection (IF-MDD) scheme, the proposed detection scheme can have better BER performance.

Low-complexity joint channel estimation and decoding for pilot symbol-assisted modulation and multiple differential detection systems with correlated Rayleigh fading

Joint channel estimation and decoding in a time-varying Rayleigh fading channel is considered. Knowing that the optimal solution or even the truncated near-optimal solution using iterative processing has an exponential complexity which hinders the practicability, a reduced complexity approach is proposed. This approach keeps the existing channel estimation and decoding schemes almost intact, while applying iterative processing to effectively exchange information between them. Thus, the complexity is rendered linear, and estimator adaptability can be easily established. We apply this approach to pilot symbol-assisted modulation (PSAM) and differentially modulated systems. It turns out that the performance is improved and the robustness to fading parameters is enhanced. Through simulations, we also show that the proposed method performs almost as well as the near-optimal design.

Metric weighted diversity combining based on multiple differential phase detection and its performance in mobile communication environments

Metric weighted diversity combining based on multiple differential phase detection and its performance in mobile communication environments

Iterative decoding of GMSK modulated convolutional code with multiple differential detection

A novel receiver architecture for the serial concatenation system of a convolutional code and a Gaussian minimum shift keying (GMSK) modulator is proposed. A maximum a posteriori probability algorithm for the multiple differential detection (MDD) of GMSK signals, which accepts a priori information and provides a soft-output for the subsequent convolutional decoder, is derived. The soft-output of the decoder is fed back to the MDD receiver for further improvement, thus resulting in an iterative decoding structure.

Comparison on maximum-likelihood sequence estimation schemes incorporating carrier phase estimation

This paper compares the following two maximum likelihood sequence estimation schemes incorporating carrier phase estimation for coded MPSK: (1) the respective-state channel estimation and (2) the multiple differential detection. This paper confirms by analysis and computer simulation that both schemes have similar performance in the absence of intersymbol interference.

Multiple differential detection of parallel concatenated convolutional (turbo) codes in correlated fast Rayleigh fading

A new technique for iterative decoding of parallel concatenated convolutional (turbo) codes (PCCCs) for the correlated fast Rayleigh fading channel is proposed and evaluated. This technique is based upon the use of a multiple differential detector (MDD) receiver structure which exploits the statistical characteristics of the fading process to overcome the effects of the rapid phase and amplitude variations. Since traditional MDD receivers cannot be used with PCCCs because they do not produce soft output and are not compatible with channel interleaving, a novel MDD receiver structure is derived which overcomes these shortfalls. In addition, with careful use of extrinsic information related to the a posteriori probability distribution function of the transmitted symbols, the receiver is designed in such a fashion as to allow channel estimation to improve with each iteration. Evaluation of the proposed receiver by means of computer simulation has shown dramatic performance improvements in fast Rayleigh fading channels as compared to long constraint-length conventional convolutional codes using both single and traditional MDD receiver structures.

Multiple-symbol differential detection of GMSK for mobile communications

A new multiple differential detection (MDD) sequence estimator is described which uses a decision feedback for the demodulation of a GMSK signal. This technique is based upon a maximum-likelihood sequence estimation of the transmitted phases rather than on a symbol-by-symbol detection. An upper and a lower bound on the bit error probability of the described detector in the case of an AWGN channel and a two-ray Rayleigh fading channel are derived. The performance of the detection algorithm in a mobile radio communication system is obtained through computer simulation. Comparisons with the coherent detection algorithm show that the proposed detection algorithm is quite attractive both in an AWGN and in a multipath channel.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Multiple differential detection with adaptive sequence estimation (MDD-ASE)–-mobile radio transmission performance in frequency selective fading environment

This paper aims at the improvement of the transmission performance of the differential detection system in the mobile radio transmission channel in a frequency selective environment. The multiple differential detection with adaptive sequence estimation (MDD-ASE) is proposed, and the performance is analyzed by a computer simulation. In MDD-ASE, not only the differential detection by one-symbol delay but also the differential detection by two- or more-symbol delays are applied. The soft decision is applied to the output of the multiple differential detection, and the symbol sequence is estimated by Viterbi algorithm (VA). The bit error rate (BER) performance is improved by the extended observation time by the multiple differential detection and the sequence estimation. The number of states in VA and the processing complexity of the adaptive algorithm increases exponentially with the extension of the observation time. Consequently, the following method is proposed: (i) the number of parameters to be estimated is reduced; and (ii) the sequence candidates stored in each path of VA are fed back. In this paper, the configuration and operation of MDD-ASE are described first and then the transmission performance of the 40 kbit/s QPSK modulation system is presented. As a result of analysis for the static and the dynamic performances of ADD-MSE using one- and two-symbol differential detection, it is shown that the improvement effect is almost the same as in coherent detection DFE.

Optimal decoding of coded PSK and QAM signals in correlated fast fading channels and AWGN: a combined envelope, multiple differential and coherent detection approach

The maximum likelihood sequence estimator for the reception of coded digital phase modulated signals with single or multiamplitude constellations, transmitted over a multiplicative, frequency-nonselective (i.e., flat) correlated fast fading Rayleigh or Rician channel and corrupted by additive white Gaussian noise (AWGN), is derived. Due to this correlation, the errors caused by fading tend to occur in bursts. In the analysis, no assumption simplifying the problem is made. For fast fading the authors consider the most general case where both phase and amplitude distortion resulting from the fading process could change significantly and thus cannot be assumed to be constant over a number of transmitted symbols. It is shown that the estimator's hardware structure consists of a combination of envelope, multiple differential and coherent detectors. With multiple differential detectors they define a receiver structure consisting of a combination of more than one distinct differential detectors each of them employing a progressively increasing (by the symbol duration) time-delay element. The outputs of these detectors are jointly processed by means of an algorithm which is presented in a recursive form. The derivation of this new receiver is general enough to accommodate trellis coded phase shift keying (PSK) and quadrature amplitude modulated (QAM) systems. Differentially encoded signals, such as the /spl pi//4-shift differential quadrature phase shift keying (DQPSK) scheme can also be incorporated. In order to reduce the overall receiver implementation complexity, several reduced complexity, near-optimal versions of the algorithm are presented. These reduced complexity receivers are based on the use of only a few multiple differential detectors. Performance evaluation results for reduced complexity trellis coded /spl pi//4-shift DQPSK, /spl pi//4-shift 8-DQAM (differential quadrature amplitude modulation) and 8-DPSK (differential phase shift keying) systems have demonstrated that the proposed receivers significantly reduce the error floors caused by fading.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Multiple differential detection of continuous phase modulation signals

A sequence estimation algorithm for the differential detection of the continuous phase modulation (CPM) signals, yielding significant gains in BER performance and with considerable resistivity to fading, is introduced. These advantages, along with the reduced hardware complexity, low cost, and fast synchronization which characterize the differential detector, make the proposed receiver useful for land mobile radio and mobile-satellite communications. The new receiver is based on multiple differential detection. The multiple differential detection strategy provides the decoder with more information regarding the transmitted data and applies a noise decorrelation process on the received signal, useful to the sequence estimation. The algorithm is derived in a general form, and can be applied on any CPM scheme, with any degree of complexity. The authors have evaluated the receiver for two of the most popular CPM schemes, the tamed frequency modulation (TFM) and Gaussian minimum-shift keying (GMSK) (with B/sub 1/T=0.25), in the presence of additive white Gaussian noise (AWGN) and Rician fading. The BER performance evaluation results indicated significant gains and considerable reduction of error floors. In AWGN improvements close to 9 dB have been verified.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Bit error rate of binary and quaternary DPSK signals with multiple differential feedback detection

A differentially coherent detection scheme with improved bit error rate (BER) performance is presented for differentially encoded binary and quaternary phase shift keying (PSK) modulation. The improvement is based on using L symbol detectors with delays of 1, 2, . . ., L symbol periods and on feeding back detected PSK symbols. Exact formulas for the bit error probability are derived for the case that correct symbols are fed back. The effect of symbol errors in the feedback path on the BER is determined by computer simulations. >