Phase Constellation Research Articles

Mode division multiplexing chaotic encryption scheme based on key intertwining and accompanying transmission.

A mode division multiplexing (MDM) chaotic encryption scheme based on key intertwining and accompanying transmission is proposed in this paper. Based on the weakly coupled few-mode fiber (FMF), data and time-varying keys can be accompanied by transmission in two modes, LP01 and LP11, respectively. In order to generate a new key, the current key is XORed with all of the keys from all the preceding moments, one by one. To implement chaotic masking in the digital domain, the three chaotic sequences corresponding to the new key are adopted to encrypt the data at the constellation phase, data symbol block, and subcarrier levels. An 8.89 Gb/s encrypted 16QAM-OFDM signal transmission over 1 km weakly-coupled FMF is experimentally demonstrated. The receiver with the correct key can recover the data normally, while the BER of the illegal receiver remains around 0.5. In the case of the key transmission bit rate of 1 Gb/s, the cracking efficiency threshold of the time-varying key encryption scheme is 5.21 × 106 times that of the time-invariant key encryption scheme, which suggests that the proposed work is a promising candidate for future physical layer security.

Analysis of Initial Deployment Strategy for Low-Orbit Large-Scale Constellations

With the development of commercial space technology, low-orbit large-scale satellite constellation has shown great development potential in communication services and military applications due to its advantages of low delay, strong signal, high coverage rate, fast communication rate, and low cost of mass production. It has become an urgent problem in the field of satellite constellations to study the perturbation evolution law of low-orbit large-scale constellation initialization and orbit maintenance, and how to maintain and control the deployment and initialization of low-orbit satellite constellations efficiently, economically, and stably. In this paper, the satellite motion law, constellation configuration evolution characteristics, and constellation initialization control strategy are analyzed considering the perturbation of earth’s nonspherical gravity and atmospheric drag under the orbit deviation of satellite orbit elements. Firstly, MonteCarlo simulation was used to simulate the deviation of satellite initial orbit elements, and the evolution law of ascending ascension point and phase angle of different constellations was analyzed and, secondly, establish the initialization phase constellation deployment and the ascending node right ascension deployment of mathematical equations, using Starlink constellation (V1.0-L3, 8) satellite TLE data; initialization of Leo constellation orbit plane is analyzed, by considering the orbit bias satellite simulation data; the same orbital plane satellite initialization phase deployment method is analyzed; finally, this paper provides some suggestions for the future deployment and maintenance control strategy of low-orbit constellation.

Performance analysis of dual‐function multiple‐input multiple‐output radar‐communications using frequency hopping waveforms and phase shift keying signalling

A signal embedding scheme into the emission of multiple-input multiple-output (MIMO) frequency hopping (FH) radar is analysed. In this scheme, the phase shift keying (PSK) communication symbols are multiplied with the frequency hops in fast-time, resulting in dual-function radar-communication (DFRC) waveforms. The authors examine the impact of PSK symbol embedding on the ambiguity function (AF) and power spectral density (PSD) and show that modulation of the radar pulse can benefit the radar functionality. The effect of PSK symbol embedding on the radar target detection performance of the DFRC system is delineated. The authors’ analyses show that the use of the DFRC waveforms enhances target detection performance. The authors also provide the symbol error rates (SERs) corresponding to different phase constellations at the communication receiver and address the practical data transfer rates that can be achieved with the underlying embedding scheme.

An intellectual power network for rural areas design

Internet and digital data transmission technologies are now widely used in industrial and agrarian complex. Meanwhile, the laying of dedicated lines for monitoring and management of remote objects in rural areas is not always economically and technically feasible. In this case, it is proposed to use existing power supply lines as a data transmission channel. In the article the modeling of data transmission with the help of Simulink module of Matlab package in conditions of the noise polluted channel is carried out. A generalized scheme of receiving/transmitting information, including a random sequence generator, QPSK modulator and demodulator, forming filters for transmitter and receiver, the counter of bit error probability is developed. To improve the performance of the channel at high noise it is proposed to use modulation by varying the length of the carrier frequency. An Omron microcontroller was used as the software and hardware for the transceiver. With the help of simulation, the characteristics of the communication channel operation were determined. Phase constellation diagrams, signal spectrum analysis and bandwidth at signal/noise parameters: 15 and 50 dB were investigated. The results of simulation modeling showed satisfying results in receiving/transmitting modulated signal.

Maximum Likelihood Detection in a Four-Dimensional Stokes-Space Receiver

The maximum likelihood detection rule for a four-dimensional direct-detection optical front-end is derived. The four dimensions are two intensities and two differential phases. Three different signal processing algorithms, composed of symbol-by-symbol, sequence and successive detection, are discussed. To remedy dealing with special functions in the detection rules, an approximation for high signal-to-noise ratios (SNRs) is provided. Simulation results show that, despite the simpler structure of the successive algorithm, the resulting performance loss, in comparison with the other two algorithms, is negligible. For example, for an 8-ring/8-ary phase constellation, the complexity of detection reduces by a factor of 8, while the performance, in terms of the symbol error rate, degrades by 0.5 dB. It is shown that the high-SNR approximation is very accurate, even at low SNRs. The achievable rates for different constellations are computed and compared by the Monte Carlo method. For example, for a 4-ring/8-ary phase constellation, the achievable rate is 10 bits per channel use at an SNR of 25 dB, while by using an 8-ring/8-ary phase constellation and an error correcting code of rate 5/6, this rate is achieved at an SNR of 20 dB.

Signal integrity analysis on a microstrip ultra-wideband coupled-line coupler

ABSTRACTIn this paper, a compact, single-section, Ultra-wideband (UWB) coupled-line coupler designed using concentric loop in the signal plane and defect in the ground plane is presented. Bandwidth enhancement is achieved with low coupling at the X-band satellite downlink range to improve the signal strength for defence applications. Return loss greater than 15 dB and isolation greater than 20 dB is achieved over the entire UWB band. The prototype is fabricated and tested to validate the simulation results. Further to detect the quality of the output signal, signal integrity analysis is performed and metrics such as error vector magnitude (EVM), magnitude and phase error, eye pattern, constellation plots and signal to noise ratio are presented for the proposed UWB coupled-line coupler.

A Novel Constellation Phase Rotation Method to Reduce Transmitter Noise in Metro Links

We present a novel constellation phase rotation method to mitigate the digital-to-analog converters (DACs) quantization penalty resulting from pre-compensation of chromatic dispersion (CD) in optical metro links, where low-resolution DACs may be used to be cost- and power-efficient. The CD-induced constellation rotation increases the peak-to-average power ratio of the emitted signals, hence increasing the DAC quantization penalty. To cancel this rotation, we propose a two-step method that first determines the suitable rotation angle with an oriented bounding box algorithm and second applies the rotation just before the DAC input. We experimentally demonstrate a +1 dB of system signal-to-noise ratio improvement for 16-QAM signals with a 4-bit DAC.

Constellation Phasing with Differential Drag on Planet Labs Satellites

A methodology is presented for the differential drag control of a large fleet of propulsionless satellites deployed in the same orbit. The controller places satellites into a constellation with specified angular offsets and zero relative speed. Time-optimal phasing is achieved by first determining an appropriate relative placement because the satellites are interchangeable. A second optimization problem is then solved as a large coupled system to find the drag command profile required for each satellite. The control authority is the available ratio of low-drag to high-drag ballistic coefficients of the satellites given realistic operational constraints. The controller is able to successfully phase constellations with up to 100 satellites in simulations. On-orbit performance of the controller is demonstrated by phasing Planet Labs’s Flock 2p constellation of 12 CubeSats, launched in June 2016, into a 510 km sun-synchronous orbit.

The method of «blind» carrier frequency estimation of radio signals with linear digital modulation

Carrier frequency estimation in the conditions of a priori uncertainty of signal modulation and parameters is prerequisite for realization of frequency synchronization circuits in software-defined radio. To implement this operation the method of «blind» carrier frequency estimation of radio signals with amplitude, phase and quadrature-amplitude shift keying, which does not require prior information about modulation type, signal and communication channel parameters, is proposed in the article. The basis of method is calculation of constellation symbols cross-correlation and clock synchronization by Gardner method. As opposed to known approaches proposed method does not require two-dimensional objective function calculation which can reduce the number of computing operations. This is achieved by implementation of previous clock synchronization and reducing the two-dimensional objective function in one-dimensional. Verification of developed method is carried out by statistical modeling using more than 20 types of phase constellations. The practical significance of received results consists in reduction of carrier frequency estimation time and simplification of practical implementation at the expense of employment of approved clock synchronization circuits.

A New Hierarchical $M$ -ary DCSK Communication System: Design and Analysis

Multiresolution $M$ -ary differential chaos shift keying (MR- $M$ -DCSK) modulation using non-uniformly spaced phase constellation is a promising technique that can satisfy different bit-error-rate (BER) requirements within one symbol over multipath fading channels. However, the BER performance always deteriorates as the modulation order $M$ becomes larger. To overcome this shortcoming, a new hierarchical square-constellation-based $M$ -DCSK communication system using non-uniformly spaced distance constellation is proposed, which can be easily extended to other-constellation scenarios, e.g., rectangular, star, and asymmetrical square constellations. Furthermore, an adaptive transmission scheme is designed by modifying the distance between the two constellation points in the last hierarchical level. In addition, theoretical BER expressions of the proposed systems are derived over multipath Rayleigh fading channels, which are consistent with the simulated results. Analytical and simulated results show that the proposed system not only can provide lower energy consumption as compared with the conventional MR- $M$ -DCSK system but also can efficiently adjust BER performance based on the signal-to-noise ratio information. Therefore, the proposed system can serve as a desirable alternative for energy-efficient short-range wireless-communication applications.

Design of an Adaptive Multiresolution $M$ -Ary DCSK System

Multiresolution M-ary differential chaos shift keying (MR-M-DCSK) system enables unequal-priority transmission via exploiting non-uniformly spaced phase constellations. In this letter, an adaptive MR-M-DCSK system is proposed by using a new constellation parameter design. Aiming at maximizing the spectral efficiency, the constellation parameter is carefully selected based on signal-to-noise ratio, and then is further optimized by a new search algorithm. Both the analytical and simulation results show that the proposed adaptive MR-M-DCSK system not only can enhance the spectral efficiency as compared with the adaptive M-DCSK system, but can satisfy different bit-error-rate requirements for different bits within a symbol as well.

Phase‐modulation based dual‐function radar‐communications

The authors develop a novel phase-modulation based dual-function system with joint radar and communication platforms. A bank of transmit beamforming weight vectors is designed such that they form the same transmit power radiation patterns, whereas the phase associated with each transmit beam towards the intended communication directions belongs to a certain phase constellation. During each radar pulse, a binary sequence is mapped into one point of the constellation which, in turn, is embedded into the radar emission by selecting the transmit weight vectors associated with that constellation point. The communication receiver detects the phase of the received signal and uses it to decode the embedded binary sequence. The proposed technique allows information delivery to the intended communication receiver regardless of whether it is located in the sidelobe region or within the main radar beam. Three signalling strategies are proposed which can be used to achieve coherent communications, non-coherent communications, and non-coherent broadcasting, respectively. It is verified that the proposed method provides improved bit error performance as compared to previously reported sidelobe modulation based dual-functionality techniques.

Methods for the automatic recognition of digital modulation of signals in cognitive radio systems

This paper considers one of the problematic issues of creating radio systems based on cognitive radio technology, viz., automatic recognition of the digital-modulation formats of radio signals. In accordance with the recommendations of the E2R and the European Telecommunications Standards Institute (ETSI) consortium, cognitive radio systems have the ability to modulate/demodulate signals in all frequency bands and in all modes of modulation. This process should be performed automatically, according to the current technical capabilities of the available communication system, the requirements for the quality of communication, and different external conditions. This article provides an analysis of the promising methods of automatic recognition of digitally modulated radio signal formats, viz., using the shape of the phase constellation, using the distribution difference of instantaneous phases, and using high-order cumulants. According to the results of the analysis, we propose methods of recognition that are based on cumulant analysis for cognitive radio systems. It is proposed that the decision-making device be an artificial neural network.

PAPR Reduction Using Low Complexity PTS to Construct of OFDM Signals Without Side Information

Partial transmit sequence (PTS) is one of the most well-known peak-to-average power ratio (PAPR) reduction techniques proposed for orthogonal frequency-division multiplexing (OFDM) systems. The main drawbacks of the conventional PTS (C-PTS) are high computational complexity and transmission of several side information bits. A new PTS with simple detector is proposed in this paper to deal with these drawbacks of C-PTS. The candidates can be generated through cyclically shifting each sub-block sequence in time domain and combining them in a recursive manner. At the receiver, by utilizing the natural diversity of phase constellation for different candidates, the detector can successfully recover the original signal without side information. Numerical simulation shows that the proposed scheme performs very well in terms of PAPR. The probability of detection failure of the side information demonstrates that the detector could work without any side information with high reliability. The proposed scheme achieves almost the same bit error rate (BER) performance as the C-PTS with perfect side information, under both additive white Gaussian noise (AWGN) channel and Rayleigh fading channel.

Gain-Control-Free Blind Carrier Frequency Offset Acquisition for QAM Constellations

This paper introduces a novel blind frequency offset estimator for quadrature amplitude modulated (QAM) signals. Specifically, after a preliminary frequency compensation, the estimator is based on the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">¿/2</i> -folded phase histogram of the received data. Then, the frequency offset estimate is taken as the frequency compensation value that minimizes the mean square error between the phase histogram measured on the received samples and the reference phase probability density function analytically calculated in the case of zero frequency offset. The ¿/2 -folded phase histogram of the received data is here called Constellation Phase Signature, since it definitively characterizes the phase distribution of signal samples belonging to a particular QAM constellation, and it has already been employed to develop a gain-control-free phase estimator that well performs both for square and cross constellations. Also the here described frequency offset estimator has the remarkable property to be gain-control-free and, thus, it can be fruitfully employed in frequency acquisition stages. The asymptotic performance of the estimator has been analytically evaluated and assessed by numerical simulations. Theoretical analysis and numerical results show that the novel frequency offset estimator outperforms state-of-the art estimators in a wide range of signal-to-noise ratio (SNR) values.

Full constellation phase detector for carrier recovery in high-order QAM systems

A full constellation phase detector that improves carrier acquisition performance in high-order quadrature amplitude modulation (QAM) is proposed. The weighting function of the phase detector is mathematically derived, and simulated phase detector characteristics are presented for 256QAM. The results of an experimental evaluation are also reported, which show that the carrier recovery loop based on the proposed phase detector has a large frequency acquisition range and low phase tracking error in high-order QAM.

Error Probability Performance of Equi-Energy Combined Transmission of Differential Phase, Amplitude, and Polarization

A unified framework was recently developed for optimizing the bit error rate (BER) incurred in the simultaneous differential modulation of the optical resources of polarization, phase, and/or amplitude, extending the conventional Stokes' parameters of polarization optics to a set of D2 generalized Stokes' parameters (GSPs). Novel optimal receiver structures were identified for multienergy polarization shift keying (POLSK), the optimality of differential phase amplitude shift keying (DPASK) and multichip differential phase shift keying (MC-DPSK) modulation formats was assessed, and optimal receivers for combinations of POLSK and DPSK were formulated. In this paper, the probability of error performance was evaluated for the newly introduced family of advanced modulation formats combining differential phase, polarization, and/or amplitude modulation, generically described as multichip differential state of POLSK. The symbol error rate and the BER for such systems are derived here in terms of the geometry of Stokes' signal space (the space of GSPs). The resulting formalism is applied to assess the performance of recently introduced MC-DPSK and MUB-coded systems (differential phase constellations based on maximally unbiased bases), as well as DPASK formats, establishing improved tradeoffs between sensitivity and spectral efficiency relative to conventional optical DPSK systems

A full-rate, full-diversity four-antenna quasi-orthogonal space-time block code

We present a complex, full-rate quasi-orthogonal space-time block code for four transmit antennas. Using carefully tailored constellation phase rotations, we show that this code achieves full diversity for specialized PSK-based constellations. The optimal receiver for the new code decouples the symbol detection problem into pairs of symbols, thus greatly reducing complexity. Finally, we present and compare performance of the new code with several other codes in the literature. The new code is shown to perform as well as the best known code of its class.

Auto calibration with training sequences for wireless local loop at 26 GHz

Quadrature signal processing is widely used in current communication receivers. However, all inphase/quadrature (I/Q) processing receiver structures face a common problem of matching the amplitudes and phases of the inphase and the quadrature branches. This article proposes an auto calibration method, for I/Q imbalance compensation using base band digital processing on training sequences transmitted with data bursts of a test platform for a wireless local loop at 26 GHz. After a description of the test platform, a calibration method is proposed and its influence on the improvement of the transmission's performance, in term of phase constellation diagram and bit-error rate, presented.

Maximum likelihood sequence detection using a pilot tone

This paper derives, analyzes, and simulates a maximum likelihood (ML) sequence detector (MLSD) for a linearly modulated signal transmitted with a pilot tone (PT-MLSD). The transmitted signal is distorted by a time-varying frequency-selective Rayleigh fading channel and corrupted by additive Gaussian noise. The received signal is unsynchronized in that there are residual carrier frequency, carrier phase, and symbol timing offsets. The PT-MLSD treats the channel as a stochastic process, and so symbol sequences are distinguished by their autocovariances. Coherent communication is possible even in overspread channels. As the sequences' autocovariances explicitly account for the channel's time variation, the PT-MLSD's bit error rate (BER) floor is normally lower than the BER floor suffered by receivers that estimate the channel impulse response conventionally. Both the data-bearing signal and pilot tone are used together for synchronization, equalization, and detection. The pilot tone is only needed to remove the constellation's phase ambiguity and provide a stable amplitude reference for QAM constellations. It is not needed for estimating the channel impulse response. The pilot tone does not require a spectral null for its insertion, and it does not significantly degrade the peak-to-average or maximum-to-minimum power ratios. Thus, many of the disadvantages of other pilot tone systems are avoided, as there is no bandwidth expansion, and linear amplification is not made appreciably more difficult.