CPM Signals Research Articles

A Novel Acquisition Algorithm Based on a Composite Waveform for Weak CPM Signals

A Novel Acquisition Algorithm Based on a Composite Waveform for Weak CPM Signals

Enhanced Emitters Localization Based on Partial Knowledge of CPM Signals

Enhanced Emitters Localization Based on Partial Knowledge of CPM Signals

A carrier frequency estimation algorithm for Multi-h CPM signals

Considering the problem that Multi-h CPM signal transmission performance is excellent but carrier frequency synchronization is complex, the article proposed a multi-h CPM non-data assisted carrier frequency estimation algorithm based on maximum likelihood. Firstly, the importance of carrier frequency synchronization is explained by simulating the influence of carrier frequency offset on transmission error performance. Then, the carrier phase deviation, frequency deviation, propagation delay, modulation index error and symbol error joint likelihood function in signal transmission are given. The likelihood function is derived and the maximum likelihood carrier frequency estimation is derived in detail. Then the flow chart of the carrier frequency synchronization algorithm based on maximum likelihood is designed. Finally, the ARTM Tier2 signal is simulated by Matlab simulation. The results show that the proposed algorithm is suitable for Multi-h CPM signals and has good carrier frequency estimation performance, and is insensitive to symbol timing deviation and modulation index synchronization error.

CPM Signal of the Iterative Timing Synchronization Research

CPM as a typical constant envelope modulation, timing synchronization method of research is becoming increasingly important. Articles research associate of constant envelope modulated signal timing synchronization methods, respectively, measured from the errors of timing synchronization, synchronize the system's structure, partial adjustment aspects are discussed. Theoretical analysis on the basis of performance in different conditions, and verify its performance. Meanwhile, encode with sync cascade simulation testing, discusses the overall robustness of the algorithm.

Symbol Timing Estimation with Multi-h CPM Signals

A new symbol timing estimation algorithm for Multi-h CPM signals is proposed. It is an extension to an existing non-data aided symbol timing estimator that is only for Single-h CPM signals. A reduced-complexity scheme of proposed algorithm is introduced with negligible performance losses. Performance in AWGN channel is assessed by computer simulation, and the simulation results show that the proposed algorithm is suitable for full response and partial response formats. Meanwhile, it has a good performance and is not sensitive to the carrier frequency

Feedforward Joint Clock and Phase Estimation Schemes for SOQPSK-Type Signals

Feedforward algorithms are investigated for estimating carrier phase and symbol timing in SOQPSK modulations. We begin showing that an SOQPSK signal with correlated data symbols is equivalent to a conventional CPM signal with independent data. Then, based on maximum likelihood criteria, we derive joint phase and timing synchronization schemes that are suitable for full digital implementation. The performance of the proposed algorithms is investigated by simulation and the results are compared with Cramer-Rao bounds. It turns out that the timing estimation accuracy is very close to the theoretical limits. Also, the proposed estimators largely outperform other synchronizers already known in literature with a comparable complexity.

Research on the Method of CPM Signal Phase Smoothing Based on Atomic Function

Continuous Phase Modulation Signal has the advantages of continuous phase, faster decay speed of power spectrum, constant envelope and so on, which is widely used in Communication Systems. The phase smoothing degree is one of main factors that affect the decay speed of CPM signal power spectrum. One method of smoothing CPM signal phase based on Atomic function is proposed. The expressions of frequency modulation function and phase modulation function are given as well as the method of CPM signal modulating by orthogonal method. This paper analyses the time-frequency characteristics and realizes the Process of CPM signal orthogonal modulation by MATLAB. The spectrum characteristics of the signal generated has great improvement compared with MSK signal.

A Low-Complexity Iterative Phase Noise Tracker for Bit-Interleaved Coded CPM Signals in AWGN

This paper considers iterative detection of bit-interleaved coded continuous phase modulation in the presence of both phase noise (PN) and additive white Gaussian noise (AWGN). The proposed receiver iterates between a detection module and an estimation module. The detection module operates according to the sum-product algorithm and the factor graph framework in order to perform coherent maximum a posteriori bit detection in AWGN, using a PN estimate provided by the estimation module. The latter module, which results from the expectation-maximization algorithm for maximum likelihood estimation of the unknown PN samples, is implemented as a smoothing phase-locked loop that uses soft decisions provided by the detector. The separation between the detection and the estimation modules allows the use of an off-the-shelf (coherent) bit detector. The technique is further characterized by a very low computational complexity, a small error performance degradation and a small number of overhead symbols.

A Constellation Space Dimensionality Reduced Sub-Optimal Receiver for Orthogonal STBC CPM Modulation in a MIMO Channel

We consider burst orthogonal space-time block coded (OSTBC) CPM modulation in a MIMO flat slow Rayleigh fading channel. The optimal receiver must process a multidimensional non-linear CPM signal on each antenna. This task imposes a high load on the receiver computational performance and increases its complexity. We analytically derive a suboptimal receiver with a reduced number of front end matched filters (MFs) corresponding to the CPM dimension. Our derivation is made fully in the constellation signal space, and the reduction is based on the linear orthogonal projection to the optimal subspace. Criterion optimality is a standard space-time rank and determinant criterion. The optimal arbitrary-dimensional subspace search leads to the eigenvector solution. We present the condition on a sufficient subspace dimension and interpret the meaning of the corresponding eigenvalues. It is shown that the determinant and rank criterion for OSTBC CPM is equivalent to the uncoded CPM Euclidean distance criterion. Hence the proposed receiver may be practical for uncoded CPM and foremost in a serially concatenated (SC) CPM system. All the derivations are supported by suitable error simulations for binary 2REC h= 1/2, but the procedure is generally valid for any CPM variant. We consider OSTBC CPM in a Rayleigh fading AWGN channel and SC CPM in an AWGN channel.

Non-coherent detectors for quadrature-multiplexed continuous phase modulation signals

Here, non-coherent detectors for quadrature-multiplexed continuous phase modulation (QM-CPM) signals are developed (Fonseka et al. , 2008). QM-CPM signals are more spectrally efficient than CPM signals, and multiamplitude QM-CPM signals can be constructed that outperform QAM. The non-coherent detectors view a QM-CPM signal as having composite states that represent the information modulated both onto the in-phase and quadrature-phase carriers. Viterbi decoding is used to jointly detect the quadrature-multiplexed signal components. Optimal sequence-based quadrature-matched filter (QMF) detectors are presented for use with QM-CPM detection and a QM-MSK detector is developed in detail. Differential phase and envelope (DPE) detectors are also presented which require less computation and are able to outperform the QMF-type detectors when the unknown carrier phase varies (phase jitter, phase hits etc.) within the sequence length used in the sequence-based QMF detectors. In the absence of these phase fluctuation effects, as the sequence length used in the QMF detectors increases, the performance of the QMF detectors approaches the performance of optimal non-coherent detection. The DPE-type detectors perform within about 2.5 dB of optimal coherent detection.

Quadrature multiplexed CPM

This paper introduces a family of bandwidth efficient modulation schemes called quadrature multiplexed continuous phase modulation (QM-CPM). QM-CPM can be thought of as an alternative to smooth pulse-shaped quadrature amplitude modulation (QAM). Like pulse-shaped QAM, QM-CPM modulates smooth continuous signals onto the in-phase (I) and the quadrature-phase (Q) channels, but these signals are derived from CPM signals instead of being filtered to attain their desired smoothness and spectral properties. QM-MSK (QMminimum shift keying) is developed and is shown to double the bits/Hz over MSK while maintaining MSK's normalized minimum distance of d <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> = 2.0. Classes of M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> -ary QMCPFSK (QM-continuous phase frequency shift keying) signals are derived from constant envelope M-ary CPFSK signals to construct bandwidth efficient modulation schemes which are comparable to and offer advantages over pulse-shaped QAM.

Fasting and postprandial small intestinal slow waves non‐invasively measured in subjects with total gastrectomy

Slow wave is essential to initiate gastrointestinal tract motility. Subjects with total gastrectomy (TG) provide an opportunity to study small intestinal slow wave in the absence of stomach interference. The aims of this study were to determine the origin of 3 cycles per min (cpm) slow wave recorded via electrogastrogram (EGG) and the characteristics of putative small intestinal slow waves in TG subjects. Thirty-three subjects with TG (25 male, age: 44-83 years) were consecutively enrolled. In each subject, the myoelectricity-like signals of the gastrointestinal tract were recorded using 3-channel EGG. Fourier transform-based spectral analysis was performed to derive the EGG parameters including dominant frequency/power, % normal rhythm (2-4 cpm), and power ratio. Neither visual nor spectral analysis of the EGG revealed any waves at a frequency of about 3 cpm. The most frequently observed peaks in the power spectra of all subjects were those at approximately 1, approximately 6 and approximately 11 cpm with occurrences of 97%, 6.1% and 90.9%, respectively. Based on visual analysis of all recorded signals, the approximately 11 cpm signal was exactly rhythmically recorded rather than the approximately 1 cpm. The recorded approximately 11 cpm wave had a frequency of 10.9 +/- 1.0 cpm in the fasting state and 10.9 +/- 1.3 cpm in the fed state (NS), and a power of 31.5 +/- 3.2 dB in the fasting state and 35.2 +/- 3.8 dB in the fed state (P < 0.0001). None of other factors, including sex, age, and body mass index, had any impact on this approximately 11 cpm wave. Small intestinal slow wave can be recorded non-invasively using EGG via cutaneous electrodes in TG subjects. Sex, age and body mass index have no effect on the intestinal slow waves. The power rather than frequency of intestinal slow wave is increased after a solid meal.

Innovations-based MAP estimation with application to phase synchronization for serially concatenated CPM

A novel adaptive soft-input soft-output (A-SISO) module is developed for maximum a posteriori (MAP) symbol detection with parameter uncertainty. In contrast to the existing A-SISO algorithms that use linear prediction, the parameter estimation in the proposed structure is operated in a more general least-squares sense. Based on this scheme, a family of fixed-interval A-SISO (FI-A-SISO) algorithms is utilized to implement blind iterative phase synchronization for serially concatenated continuous phase modulation (SCCPM). For SCCPM systems, the forward-only FI-A-SISO algorithms are shown to be much more robust than the forward-backward FI-A-SISO algorithms in acquiring and tracking a time-varying carrier phase. The reason has to do with rotational invariance of CPM signals. This result can be extended to any rotationally invariant convolutional coded system with an unknown carrier phase.

Performance of optimum and suboptimum OFDM-CPM receivers over multipath fading channels

Summary A class of orthogonal frequency division multiplexing-continuous phase modulation (OFDM-CPM) signals is introduced in which binary data sequence is mapped to complex symbols using the concept of correlated phase states of a CPM signal. Canonical optimum and suboptimum multiple-symbol-observation OFDM-CPM receivers are derived. Multipath channel with AWGN is assumed. The receivers are analyzed for bit error rate (BER) performance in terms of high- and low-SNR bounds. These bounds are illustrated as a function of parameter h, time delay and attenuation level. It is shown that OFDM-CPM systems, with h ¼ 0:5; 0:25 and an observation interval length of two symbols, can outperform conventional OFDM-PSK system for a two-ray multipath model. Copyright # 2005 John Wiley & Sons, Ltd.

Electrogastrographic biofeedback: a technique for enhancing normal gastric activity

Biofeedback has been used effectively for approximately 40 years as a technique to help individuals learn to control muscle activity, brain waves, certain autonomic nervous system responses such as heart rate and blood pressure, and, more recently, constipation and fecal and urinary incontinence. In the present study, biofeedback of electrogastrographic (EGG) activity was used to determine the extent to which healthy subjects could increase normal 3 cpm gastric myoelectric activity. Thirteen experimental participants were provided with biofeedback of their EGG activity on a computer screen, and instructed to try to make their own EGG signal match a simulated 3 cpm signal that was also present on the screen. Subjects were told to relax using various forms of imagery, and to heighten their awareness of their stomach activity. Thirteen control participants did not receive any biofeedback but were otherwise given the same instructions. Both groups showed an increase in 3 cpm activity while relaxing. However, over four trials separated by 2-7 days, experimental participants showed an increased percentage of 3 cpm activity during biofeedback sessions, while control participants showed a decrease in 3 cpm activity during the corresponding sessions. In conclusion, we have demonstrated that healthy subjects can increase their normal gastric 3 cpm activity with the use of EGG biofeedback.

On Walsh Filtering Method for Decoding of CPM Signals

Walsh filtering has been used as a method to reduce receiver complexity in several coding and modulation systems, especially in continuous phase modulation systems. In this paper, we show that its lowpass filtering ability is poor and alias components arising from an adjacent channel can significantly degrade the maximum-likelihood decoding. Instead, a lowpass filtering method is more robust against adjacent channel interference and thus gives less decoding errors than the Walsh filtering method.

Glycosylation affects the protein stability and cell surface expression of Kv1.4 but Not Kv1.1 potassium channels. A pore region determinant dictates the effect of glycosylation on trafficking.

Kv1.1 and Kv1.4 potassium channels are plasma membrane glycoproteins involved in action potential repolarization. We have shown previously that glycosylation affects the gating function of Kv1.1 and that a pore region determinant of Kv1.1 and Kv1.4 affects their cell surface trafficking negatively or positively, respectively. Here we investigated the role of N-glycosylation of Kv1.1 and Kv1.4 on their protein stability, cellular localization pattern, and trafficking to the cell surface. We found that preventing N-glycosylation of Kv1.4 decreased its protein stability, induced its high partial intracellular retention, and decreased its cell surface protein levels, whereas it had little or no effect on these parameters for Kv1.1. Exchanging a trafficking pore region determinant between Kv1.1 and Kv1.4 reversed these effects of glycosylation on these chimeric channels. Thus it appeared that the Kv1.4 pore region determinant and the sugar tree attached to the S1-S2 linker showed some type of dependence in promoting proper trafficking of the protein to the cell surface, and this dependence can be transferred to chimeric Kv1.1 proteins that contain the Kv1.4 pore. Understanding the different trafficking programs of Kv1 channels, and whether they are altered by glycosylation, will highlight the different posttranslational mechanisms available to cells to modify their cell surface ion channel levels and possibly their signaling characteristics.

A BEM-based detector for CPM signals transmitted over frequency-flat fading channels

In this paper, the expectation-maximization (EM) algorithm for maximum a posteriori (MAP) estimation of a random vector is applied to the problem of symbol detection for continuous phase modulation signals transmitted over time-selective Rayleigh-fading channels. This results in a soft-in-soft-out detection algorithm suitable for iterative detection/decoding schemes. Simulation results show that the error performance provided by the proposed solution is very close to that of a MAP detector endowed with an ideal knowledge of the channel state both in uncoded and coded transmissions.

OFDM-CPM signals for wireless communications

A class of orthogonal frequency division multiplexingcontinuous phase modulation (OFDM-CPM) signals is introduced in which the binary data sequence is mapped to complex symbols using the concept of correlated phase states of a CPM signal. A multiple-symbol-observation receiver is used to decode the received sequence, and an investigation of bit error rate over typical wireless multipath channels with additive white Gaussian noise is presented. The performance of a variety of OFDM-CPM signals is presented and analyzed. Performance is a function of parameter and the observation interval, both of which are at the disposal of the system designer. It is shown that OFDM-CPM is a promising signalling scheme in multipath fading channels. Results for multi- and asymmetric OFDM-CPM signals are also presented. The peak-to-average power ratio (PAPR) performance of these signals is also presented, and an algorithm to reduce PAPR is proposed that is based on a multi-amplitude CPM constellation. It is shown through numerical simulations that the proposed algorithmreduces the PAPR of a 128-carrier OFDM-CPM signal by more than 4 dB.

OFDM-CPM signals

A class of orthogonal frequency division multiplexing–continuous phase modulation (OFDM-CPM) signals is introduced in which binary data sequence is mapped to complex symbols using the concept of correlated phase states of a CPM signal. Various types of signals are defined as a function of parameter h and pulse duration. An investigation of bit error rate and peak-to-average-power ratio performance of these signals is also presented.