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Showing papers on "Keying published in 2021"


Journal ArticleDOI
TL;DR: In this paper, the performance of hybrid continuous-phase frequency shift keying (CPFSK)/optical quadrature-phase shift-keying (OQPSK) modulation transmission techniques with return-to-zero (RZ) line coding scheme-based fiber systems in passive optical networks is studied.
Abstract: This study shows hybrid continuous-phase frequency shift keying (CPFSK)/optical quadrature-phase shift keying (OQPSK) modulation transmission techniques’ performance efficiency with return-to-zero (RZ) line coding scheme–based fiber systems in passive optical networks. Max. Q factor/min. bit error rate variations versus modulation frequency and fiber length are studied in detail for various bits/symbol, based on hybrid proposed modulation transmission techniques. Also, optical power and received electrical power variations are simulated with fiber-length variations at a specified modulation frequency of 300 GHz. Max. Q Factor, min. BER, max. signal power, and min. noise power variations are based on hybrid modulation techniques for CPFSK/OQPSK of 32 bits/symbol and a modulation frequency of 500 GHz through a fiber length of 30 km.

72 citations


Journal ArticleDOI
TL;DR: In this paper, the authors simulated the bidirectional Er-Yb codoped fiber amplifiers (CDFs)-based DPSK modulation scheme for high speed fiber system capacity.
Abstract: This paper simulates the bidirectional Er-Yb codoped fiber amplifiers (CDFs)-based DPSK modulation scheme for high speed fiber system capacity. The combination of Erbium-Ytterbium codoped fibers into a single fiber has been developed for the extension of the absorption bands for doped fibers. The signal gain variations versus pump wavelength variations have been demonstrated for various doped amplifiers with the proposed Er-Yb CDFs at amplifier length of 5 m. Also the signal gain variations versus pump wavelength variations have been illustrated for the proposed Er-Yb CDFs at 5 m amplifier length in different pumping configurations. The total optical power, max. Q factor, total electrical power, output optical signal/noise ratio, and signal gain variations versus fiber length variations have between simulated and clarified in the presence of bidirectional various lengths of Er-Yb CDFs.

52 citations


Journal ArticleDOI
TL;DR: In this article, the authors presented high modulated soliton power transmission interaction with optical fiber and optical wireless communication channels at flow rate of 40 Gbps and 20 km link range at the optical receiver.
Abstract: This paper has presented high modulated soliton power transmission interaction with optical fiber and optical wireless communication channels at flow rate of 40 Gbps and 20 km link range. The proposed modulation schemes are continuous phase frequency shift keying (CPFSK), Quadrature amplitude modulation (QAM), differential phase shift keying (DPSK), frequency shift keying (FSK), pulse amplitude modulation (PAM), minimum shift keying (MSK), and optical quadrature phase shift keying (OQPSK). CPFSK has presented better performance than other proposed modulation schemes for both optical fiber and optical wireless communication channels. The enhancement of optical signal/noise ratio at fiber/wireless channel, received electrical power and signal/noise ratio at optical receiver with increase of bits per symbol for different proposed modulation schemes except for CPFSK scheme. Therefore it is evident that CPFSK modulation scheme is more efficient and better performance than other modulation schemes for different communication channels. The obtained results are simulated with optisystem program version 13.

48 citations


Journal ArticleDOI
TL;DR: In this article, a simple approach based on photonic reservoir computing (P-RC) was proposed for modulation format identification in optical fiber communications. But the proposed technique utilizes very simple devices and thus offers a resource efficient alternative approach to MFI.
Abstract: We present a simple approach based on photonic reservoir computing (P-RC) for modulation format identification (MFI) in optical fiber communications. Here an optically injected semiconductor laser with self-delay feedback is trained with the representative features from the asynchronous amplitude histograms of modulation signals. Numerical simulations are conducted for three widely used modulation formats (on–off keying, differential phase-shift keying, and quadrature amplitude modulation) for various transmission situations where the optical signal-to-noise ratio varies from 12 to 26 dB, the chromatic dispersion varies from −500 to 500 ps/nm, and the differential group delay varies from 0 to 20 ps. Under these situations, final simulation results demonstrate that this technique can efficiently identify all those modulation formats with an accuracy of >95% after optimizing the control parameters of the P-RC layer such as the injection strength, feedback strength, bias current, and frequency detuning. The proposed technique utilizes very simple devices and thus offers a resource-efficient alternative approach to MFI.

39 citations


Journal ArticleDOI
TL;DR: This paper derives exact BER expressions under additive white Gaussian noise and Rayleigh fading channels for an arbitrary number of NOMA users and finds the optimal power assignment that minimizes the system's average BER for N=2 and 3 users cases.
Abstract: Non-orthogonal multiple access (NOMA) is a promising candidate for future mobile networks as it enables improved spectral-efficiency, massive connectivity and low latency. This paper derives exact and asymptotic bit error rate (BER) expressions under Rayleigh fading channels for NOMA systems with arbitrary number of users and arbitrary number of receiving antennas and modulation orders, including binary phase-shift keying and rectangular/square quadrature amplitude modulation. Furthermore, the power coefficients’ bounds, which ensure users’ fairness, and solve the constellation ambiguity problem, are derived for $N=2$ and 3 users cases with any modulation orders. In addition, this paper determines the optimal power assignment that minimizes the system’s average BER. These results provide valuable insight into the system’s BER performance and power assignment granularity. For instance, it is shown that the feasible power coefficients range becomes significantly small as the modulation order, or $N$ , increases, where the BER performance degrades due to the increased inter-user interference. Hence, the derived expressions can be crucial for the system scheduler in allowing it to make accurate decisions of selecting appropriate $N$ , modulation orders, and power coefficients to satisfy the users’ requirements. The presented expressions are corroborated via Monte Carlo simulations.

38 citations


Journal ArticleDOI
TL;DR: In this paper, a high-speed optical coherent receiver for optical communications based on Graphene-on-plasmonic slot waveguide photodetectors is presented.
Abstract: Graphene-based photodetectors have attracted significant attention for high-speed optical communication due to their large bandwidth, compact footprint, and compatibility with silicon-based photonics platform. Large-bandwidth silicon-based optical coherent receivers are crucial elements for large-capacity optical communication networks with advanced modulation formats. Here, we propose and experimentally demonstrate an integrated optical coherent receiver based on a 90-degree optical hybrid and graphene-on-plasmonic slot waveguide photodetectors, featuring a compact footprint and a large bandwidth far exceeding 67 GHz. Combined with the balanced detection, 90 Gbit/s binary phase-shift keying signal is received with a promoted signal-to-noise ratio. Moreover, receptions of 200 Gbit/s quadrature phase-shift keying and 240 Gbit/s 16 quadrature amplitude modulation signals on a single-polarization carrier are realized with a low additional power consumption below 14 fJ/bit. This graphene-based optical coherent receiver will promise potential applications in 400-Gigabit Ethernet and 800-Gigabit Ethernet technology, paving another route for future high-speed coherent optical communication networks. Graphene-based photodetectors have many advantages for applications. Here, the authors demonstrate a high-speed optical coherent receiver for optical communications based on graphene-on-plasmonic slot waveguide photodetectors.

27 citations


Journal ArticleDOI
TL;DR: In this article, an all-optical aggregation and de-aggregation scheme between one 8-ary quadrature amplitude modulation (8QAM) signal and three binary phase shift keying (BPSK) signals is proposed and theory simulated based on nonlinear effects in high nonlinear fiber (HNLF).
Abstract: An all-optical aggregation and de-aggregation scheme between one 8-ary quadrature amplitude modulation (8QAM) signal and three binary phase shift keying (BPSK) signals is proposed and theory simulated based on nonlinear effects in high nonlinear fiber (HNLF). In this scheme, the input 8QAM signal is de-aggregated into three BPSK signals by deploying self-phase modulation (SPM), cross-phase modulation (XPM), four wave mixing (FWM) and parameter amplification (PA) effect. Firstly, an improved amplitude compression loop (ACL) is designed based on SPM effect to convert 8QAM signal into quadrature phase shift keying (QPSK) signal. A degenerate phase sensitive amplifier (PSA) based on FWM effect is used to decompose QPSK signal into the first two BPSK signals (BPSK-1 and BPSK-2). The third BPSK signal (BPSK-3) can be extracted from the probe light modulated in its phase by the input 8QAM signal thanks to XPM and PA effect. Secondly, BPSK-3 is converted into an atypical on-off keying (OOK) signal through a 1-bit delay interference (DI). BPSK-1 and BPSK-2 are recombined into one QPSK signal through a coupler. Finally, the recombined QPSK signal and the atypical OOK signal are aggregated into one 8QAM signal by using XPM and PA effect. The error vector magnitude (EVM) and bit error ratio (BER) of the 8QAM and BPSK signal before and after de-aggregation and aggregation are calculated to analyse the performance of the scheme. The scheme can be applied in the network node to connect different networks which explore to use 8QAM and BPSK signal respectively.

21 citations


Journal ArticleDOI
TL;DR: In this article, a fully integrated binary phase shift keying (BPSK) tag is presented to work in conjunction with narrowband FSK radar for concurrent multitarget range tracking and vital signs sensing.
Abstract: In this article, fully integrated binary phase shift keying (BPSK) tags are presented to work in conjunction with narrowband frequency-shift keying (FSK) radar for concurrent multitarget range tracking and vital signs sensing. Without the employment of any radio frequency (RF) mixer, the developed BPSK tag introduces a frequency offset by generating periodic phase shifts to the radar carrier frequencies with optimized power level. The theory of BPSK tag-based range tracking and vital signs sensing in conjunction with FSK radar signal is developed. An impedance-modulated 24-GHz tag architecture without any active RF components is proposed and its implementation and characterization are presented. The system performance is evaluated in the following residential indoor scenarios: single tag ranging, concurrent multiple tags and an untagged human target detection, and multiple tagged human targets tracking. Promising ranging performance demonstrates the potential for the proposed system to be adopted in various indoor tracking applications.

21 citations


Journal ArticleDOI
01 Mar 2021
TL;DR: A physical layer based on high-bandwidth on-off keying modulation allows for highly efficient transmitter frontend designs that avoid operation of amplifier stages in a resistive mode, which has the potential of reducing their energy usage by an order of magnitude.
Abstract: Energy consumption is one of the critical issues in optical wireless communications transmitter design and a limiting factor to miniaturization and deployment in mobile devices. In order to reduce energy requirements, we assess a physical layer based on high-bandwidth on-off keying modulation. The use of on-off keying allows for highly efficient transmitter frontend designs that avoid operation of amplifier stages in a resistive mode, which has the potential of reducing their energy usage by an order of magnitude. Link-level simulations show that this physical layer can deal with typical frontend limitations and can operate in challenging non-line-of-sight channels. For these reasons, we believe that the solution evaluated here can deliver a significant contribution to optical wireless communications technology in a wide range of use cases.

16 citations


Journal ArticleDOI
01 Jan 2021
TL;DR: In this paper, the power spectral densities of variable on-off keying (VOOK) and variable pulse position modulation (VPPM) modulation schemes were derived and their bandwidth requirements and spectral efficiencies were derived.
Abstract: Visible light communication (VLC) is being envisioned as an enabling technology to provide the much-needed spectral relief for the ever-increasing demand for Internet connectivity and data consumption. Since VLC uses illumination sources for lighting as well as communication, it is required to provide dimming control for proper lighting and enhanced error performance for reliable data communication. In this paper, we address both these issues holistically. We formulate and study the power spectral densities of dimming-based modulation schemes, namely variable on-off keying (VOOK) and variable pulse position modulation (VPPM), and hence, derive their bandwidth requirements and spectral efficiencies. Moreover, the capacity of VLC systems is severely limited by the inter-symbol interference (ISI) occurring as a result of the multipath propagation of light signals in VLC. We propose to ameliorate the error performance of VLC systems by using channel equalization for ISI mitigation, thereby enhancing the system capacity. We develop the analytical model of a dimmable VLC system employing channel equalization and use this model to study the effect of dimming and data rate on the error performance of VOOK and VPPM schemes. We present simulation and analytical results to show that the performance of dimming-based modulation schemes is significantly improved using channel equalization.

15 citations


Journal ArticleDOI
TL;DR: An air-based macroscopic molecular communication testbed exploiting fluorescence properties of water-based solutions of Uranine and Rhodamine 6G is presented and a platform is set for implementing a multiuser scenario, where the same channel is made accessible to multiple users by simultaneous use of different dyes for data transmission with small co-channel interference.
Abstract: An air-based macroscopic molecular communication testbed exploiting fluorescence properties of water-based solutions of Uranine and Rhodamine 6G is presented in this work. The testbed comprises of an industrial sprayer as its transmitter, a 2 m long tube as transmission channel, and a high-speed camera-based detector. The transmission distances considered cover a range over several tens of centimeters to meters. Concerning modulation schemes, molecular shift keying and molecular concentration shift keying are implemented and compared with on-off keying serving as a benchmark. It is shown that the former two can be used to decrease the bit error rate and/or to increase the bit rate. Furthermore, a platform is set for implementing a multiuser scenario, where the same channel is made accessible to multiple users by simultaneous use of different dyes for data transmission with small co-channel interference.

Journal ArticleDOI
TL;DR: The convolutional neural network (CNN) is utilized to recognize both the azimuthal and radial index of superposed LG modes with non-zero radial index based on the artificial-intelligence-enhanced optoelectronic systems.
Abstract: Beyond orbital angular momentum of Laguerre-Gaussian (LG) modes, the radial index can also be exploited as information channel in free-space optical (FSO) communication to extend the communication capacity, resulting in the LG- shift keying (LG-SK) FSO communications. However, the recognition of radial index is critical and tough when the superposed high-order LG modes are disturbed by the atmospheric turbulences (ATs). In this paper, the convolutional neural network (CNN) is utilized to recognize both the azimuthal and radial index of superposed LG modes. We experimentally demonstrate the application of CNN model in a 10-meter 768-ary LG-SK FSO communication system at the AT of Cn2 = 1e-14 m−2/3. Based on the high recognition accuracy of the CNN model (>95%) in the scheme, a colorful image can be transmitted and the peak signal-to-noise ratio of the received image can exceed 35 dB. We anticipate that our results can stimulate further researches on the utilization of the potential applications of LG modes with non-zero radial index based on the artificial-intelligence-enhanced optoelectronic systems.

Posted Content
TL;DR: In this article, the authors considered a multiple-input multiple-output (MIMO) dual-function radar-communication (DFRC) system that employs an orthogonal frequency division multiplexing (OFDM) and a differential phase shift keying (DPSK) modulation, and studied the design of the radiated waveforms and of the receive filters employed by the radar and the users.
Abstract: In this work we consider a multiple-input multiple-output (MIMO) dual-function radar-communication (DFRC) system that employs an orthogonal frequency division multiplexing (OFDM) and a differential phase shift keying (DPSK) modulation, and study the design of the radiated waveforms and of the receive filters employed by the radar and the users. The approach is communication-centric, in the sense that a radar-oriented objective is optimized under constraints on the average transmit power, the power leakage towards specific directions, and the error rate of each user, thus safeguarding the communication quality of service (QoS). We adopt a unified design approach allowing a broad family of radar objectives, including both estimation- and detection-oriented merit functions. We devise a suboptimal solution based on alternating optimization of the involved variables, a convex restriction of the feasible search set, and minorization-maximization, offering a single algorithm for all of the radar merit functions in the considered family. Finally, the performance is inspected through numerical examples.

Journal ArticleDOI
TL;DR: A soft-start scheme is proposed to address the current overshoot problem of inductive wireless power transfer systems and can be essentially applied to WPT systems with different compensation topologies.
Abstract: The energy efficiency of an inductive wireless power transfer (WPT) system will deviate from the possible peak value if the magnetic coupling of the transmitter and receiver coils or the load resistance changes. To achieve maximum-efficiency tracking regardless of coupling or load changes, on – off keying (OOK) modulation is used. However it has the issue of large surge current in the circuits during OOK modulation. The current overshoots of a series–series (SS) compensated WPT system at the startup stage might be much higher than the rated current. The current overshoots not only increase the stress on the power switch devices but also cause high voltage spikes across the windings and the resonant capacitors which is a challenge for insulation design. A soft-start scheme is proposed to address the current overshoot problem. The principle of the soft-start scheme can be essentially applied to WPT systems with different compensation topologies. The experimental results of a 3.3-kW prototype verify that the proposed soft-start scheme effectively suppress the current overshoots.

Journal ArticleDOI
TL;DR: An efficient inexact gradient descent method is proposed to obtain the channel capacity-achieving input distribution of visible light communication (VLC), and it is proved that the gaps between the original functions and the approximations can be arbitrarily small.
Abstract: In this article, we propose an efficient inexact gradient descent method to obtain the channel capacity-achieving input distribution of visible light communication (VLC). Under both a peak and an average optical power constraints, finding the channel capacity of VLC is formulated as a mixed continuous-discrete optimization problem without an analytical expression of the objective function. To solve this challenging problem, we first adopt the numerical integration method to approximate the objective function and its gradient. Here, we prove that the gaps between the original functions and the approximations can be arbitrarily small. Then, based on the approximated functions, we describe the method, and theoretically show that the obtained solution sequence converges to the channel capacity-achieving discrete distribution of VLC. We also provide simulation results to verify the effectiveness and optimality of the proposed method. More importantly, the simulations numerically reveal that on-off keying (OOK) modulation achieves the capacity of VLC channel at low signal-to-noise ratio (SNR), while pulse amplitude modulation (PAM) achieves the capacity at high SNR.

Journal ArticleDOI
TL;DR: This work aims to study the performance of the MC system in terms of reliable information exchange for the channel with finite-state memory, which introduces intersymbol interference (ISI), and the derivation of analytical expressions for the upper and the lower bound of the constrained channel capacity.
Abstract: This letter focuses on the analysis of a diffusion-based molecular communication (MC) system where the received signal is approximated as a Poisson random variable. Concentration shift keying (CSK) is used as the modulation technique for encoding information in the system. In particular, this work aims to study the performance of the MC system in terms of reliable information exchange for the channel with finite-state memory, which introduces intersymbol interference (ISI). The main objective is the derivation of analytical expressions for the upper and the lower bound of the constrained channel capacity for a range of values of the modulated symbols, i.e., for a number of different sets of amplitude levels of CSK modulation, and for various levels of ISI. In addition, the numerical evaluation of the derived expressions is presented. Results allow discussing the relationship between ISI level and achievable channel capacity. Moreover, numerical outcomes highlight how the estimation of the bounds is not affected by the presence of ISI in the case of binary CSK modulation, as the bounds remain quite tight.

Journal ArticleDOI
TL;DR: A time asynchronous scheme for successive interference cancellation receivers that maximally suppresses the inter-user interference compared to any other time asynchronous schemes is proposed.
Abstract: Two-user non-orthogonal multiple access systems with quadrature phase-shift keying modulation are studied. A time asynchronous scheme for successive interference cancellation receivers that maximally suppresses the inter-user interference compared to any other time asynchronous schemes is proposed. Exact bit error rate (BER) solutions for the two users operating in the additive white Gaussian noise channel using the proposed scheme are derived. A simpler closed-form BER approximation for the weaker user is also presented. Compared to the symbol-synchronous scheme, numerical results show the proposed asynchronous scheme reduces the BER for the stronger signal by a factor of one-half.

Proceedings ArticleDOI
13 Apr 2021
TL;DR: In this article, the MIMO C-OOK modulation, which is upgraded from camera on-off keying (one of scheme is applied in IEEE 802.15.7-2018 standard), with the matched filter technique in receiver side, the proposed scheme can improve the data rate and communication distance comparing with the conventional scheme.
Abstract: Currently, the wireless communication technologies are deployed commonly in many aspects such as Internet of Thing systems, eHealth systems, satellite communication system. Besides that, Radio frequency systems are emerged as the indispensable ingredients for almost the communication system. However, the effect of Radio Frequency with the human health are found by the researchers around the world. Example, the higher frequency will impact with human health is higher if the energy of signal exceeds the threshold. The Visible Light Waveform is researched to instead of Radio frequency band with three candidates: Visible Light Communication (VLC), Optical Camera Communication (OCC), and Light Fidelity (LiFi). In this paper, we overview the MIMO C-OOK modulation, that is upgraded from Camera On-Off Keying (one of scheme is applied in IEEE 802.15.7-2018 standard). with the matched filter technique in receiver side, the proposed scheme can improve the data rate and communication distance comparing with the conventional scheme.

Journal ArticleDOI
TL;DR: In this paper, a method of phase modulation and phase-shift keying for spin-torque nano-oscillators (STNOs) is presented, and demonstrated transmission of a voice signal (telephony) with their STNO-based gear.
Abstract: Researchers present a method of phase modulation and phase-shift keying for spin-torque nano-oscillators (STNOs), and demonstrate transmission of a voice signal (telephony) with their STNO-based gear. The key elements of the proposed method are the ability of an STNO to be synchronized by an external signal, and to shift its phase relative to the source's phase according to an additional control signal. These properties allow not only control of the phase, but also reduction of phase noise, which is a main issue for all oscillators with nanoscale dimensions. The results comprise a significant advance for wireless data and signal communication with nano-oscillators.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a scheme for automatic dual determination of modulation types and signal to noise ratios (SNR) for next generations of wireless communication systems, fifth generation (5G) and beyond.
Abstract: In order to pursue rapid development of the new generation of wireless communication systems and elevate their security and efficiency, this paper proposes a novel scheme for automatic dual determination of modulation types and signal to noise ratios (SNR) for next generations of wireless communication systems, fifth-generation (5G) and beyond. The proposed scheme adopts unique signatures depicted in two-dimensional asynchronously sampled in-phase-quadrature amplitudes’ histograms (2D-ASIQHs)-based images and applies the support vector machines (SVMs) tool. Along with the estimation of the instantaneous SNR values over 0–35 dB range, the determination of nine modulation types that belong to different modulation categories i.e., phase-shift keying (Binary-PSK, Quadrature-PSK, and 8-PSK), amplitude-shift keying (2-ASK and 4-ASK) and quadrature-amplitude modulation (4-QAM, 16-QAM, 32-QAM, and 64-QAM) could be achieved by this scheme. The application of this scheme has been simulated using a channel model that is impaired by additive white Gaussian noise (AWGN) and Rayleigh fading, covering a broad range of SNRs of 0–35 dB. The performance of this dual-determination scheme shows high modulation recognition accuracy and low mean SNR estimation error. Therefore, it can be a better alternative for designers of next generation wireless communication systems.

Journal ArticleDOI
TL;DR: An embedded UAC system with the STM32H743 processor as the core and the peripheral sending/receiving circuit as the signal conditioning circuit module is proposed and a fast and robust frame synchronization algorithm based on the segmented fast Fourier transform is applied.
Abstract: Underwater acoustic communication (UAC) modem is an important infrastructure of underwater network construction. In recent years, with the performance improvement of the STM32 processor, the realization of reliable UAC through high-performance STM32 processor is conducive to reduce the system power consumption, cheapen the hardware cost, and ease the development difficulty. In this letter, we propose an embedded UAC system with the STM32H743 processor as the core and the peripheral sending/receiving circuit as the signal conditioning circuit module. The system can support a variety of modulation and demodulation methods, including single/multi-carrier frequency-shift keying and orthogonal frequency division multiplexing. Furthermore, in order to reduce the computational cost of the system, a fast and robust frame synchronization algorithm based on the segmented fast Fourier transform is applied. The sea trials show that the system can realize the reliable UAC transmission of 100 b/s–1 kb/s in the distance of 5–8 km in the shallow water area.

Journal ArticleDOI
TL;DR: A novel method of steganographic transmission which is based on phase drift in phase-shift keying or quadrature amplitude modulation (QAM) and is included in the so-called dirty constellation techniques.
Abstract: Modern telecommunications systems require the use of various transmission techniques, which are either open or hidden. The open transmission system uses various security techniques against its unauthorized reception, and cryptographic solutions ensure the highest security. In the case of hidden transmissions, steganographic techniques are used, which are based on the so-called covert channels. In this case, the transparency and stealth of the transmission ensure its security against being picked up by an unauthorized user. These covert channels can be implemented in multimedia content, network protocols, or physical layer transmissions. This paper focuses on wireless covert channels. We present a novel method of steganographic transmission which is based on phase drift in phase-shift keying or quadrature amplitude modulation (QAM) and is included in the so-called dirty constellation techniques. The proposed approach is based on the drift correction modulation method, which was previously used in the watermarking of audio-signals. The developed solution is characterized by a variable bit rate, which can be adapted to the used modulation type and transmission conditions occurring in radio channels. In the paper, we present the method of generating and receiving hidden information, simulation research, and practical implementation of the proposed solution using the software-defined radio platform for selected QAM.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the features of an OCC system when the periods of reception and transmission are slightly different from each other, and proposed a demodulation procedure using a maximum-likelihood sequence detection method, which can be implemented by the Viterbi algorithm.
Abstract: We consider optical camera communication (OCC) between a camera receiver with optical lenses and distributed transmitters. This article investigates the features of an OCC system when the periods of reception and transmission are slightly different from each other. We describe a received light signal model for the OCC system with on-off keying and regard the received signals generated from a probability distribution of a Gaussian mixture model. We obtain the parameters of the probability distributions by applying a variational Bayesian inference method and utilize them for channel estimation. In addition, we define cost functions and minimize them to demodulate the transmitted bit sequences. The demodulation procedure uses a maximum-likelihood sequence detection method, which can be implemented by the Viterbi algorithm and estimates a synchronization parameter by minimizing the cost functions. Our new demodulation method requires neither synchronization devices nor training sequences for estimating the parameters. Moreover, the receiver does not need the precise transmission period, which is difficult to know in advance in practical situations because of the frequency tolerance of the clock generator in the transmitter. To validate our developed method, we conducted numerical simulations and compared the results with those from an oracle estimator that knows the parameters other than the bit sequence in advance. We also experimented in a real setup situation, and the results show the efficiency of our developed method.

Journal ArticleDOI
TL;DR: In this article, a chaotic-based frequency modulated (CBFM) waveform for joint monostatic and bistatic radar-communication systems is proposed, where information is embedded in the pulses using chaos shift keying (CSK).
Abstract: In this article, we propose the utilization of chaos-based frequency modulated (CBFM) waveforms for joint monostatic and bistatic radar-communication systems. Short-duration pulses generated via chaotic oscillators are used for wideband radar imaging, while information is embedded in the pulses using chaos shift keying (CSK). A self-synchronization technique for chaotic systems decodes the information at the communication receiver and reconstructs the transmitted waveform at the bistatic radar receiver. Using a nonlinear detection scheme, we show that the CBFM waveforms closely follow the theoretical bit-error rate (BER) associated with bipolar phase-shift keying (BPSK). We utilize the same nonlinear detection scheme to optimize the target detection at the bistatic radar receiver. The ambiguity function for both the monostatic and bistatic cases resembles a thumbtack ambiguity function with a pseudo-random sidelobe distribution. Furthermore, we characterize the high-resolution imaging capability of the CBFM waveforms in the presence of noise and considering a complex target.

Journal ArticleDOI
TL;DR: Two molecular type permutation shift keying in the space domain and time-interleaved MTPSK-SD are proposed for MIMO MCvD systems to improve the BER performance by reducing ILI.
Abstract: Molecular communication (MC) is a bio-inspired communication paradigm, which lays the foundation for the Internet of Bio-NanoThings (IoBNT) in the medical field As a high energy-efficient information transfer method, MC via diffusion (MCvD) is envisioned as a promising candidate for IoBNT but suffers from low date rates due to the long tail of the channel impulse response (CIR) To this end, the multiple-input–multiple-output (MIMO) technique has been introduced to MCvD However, the intersymbol interference (ISI) and interlink interference (ILI) deteriorate the bit error rate (BER) performance of MIMO MCvD systems In this article, molecular type permutation shift keying in the space domain (MTPSK-SD) and time-interleaved MTPSK-SD are proposed for MIMO MCvD systems to improve the BER performance by reducing ILI The principle of MTPSK-SD is further generalized to the spatiotemporal domain, yielding three spatiotemporal modulation schemes, which can provide desirable BER performance without requiring any CIR information in the communication scenarios affected by different levels of ISI and ILI Two low-complexity detectors are proposed to obtain different tradeoffs between anti-ILI and anti-ISI performance Furthermore, a complementary coding scheme, which can effectively reduce the ILI under the considered symmetrical system topology, is designed and applied to all the proposed modulation schemes Additionally, the BER upper bound is analyzed Numerical simulations on BER corroborate the analysis and show that the proposed schemes are promising multimolecule modulation alternatives, which outperform the existing MIMO MCvD modulation schemes

Journal ArticleDOI
TL;DR: A regression model is built to extract EVM information from complex signal constellation diagrams using a small number of received symbols to be used as a low-complexity alternative to conventional bit-error-rate estimation, enabling solutions for intelligent optical performance monitoring.
Abstract: We propose a fast and accurate signal quality monitoring scheme that uses convolutional neural networks for error vector magnitude (EVM) estimation in coherent optical communications. We build a regression model to extract EVM information from complex signal constellation diagrams using a small number of received symbols. For the additive-white-Gaussian-noise-impaired channel, the proposed EVM estimation scheme shows a normalized mean absolute estimation error of 3.7% for quadrature phase-shift keying, 2.2% for 16-ary quadrature amplitude modulation (16QAM), and 1.1% for 64QAM signals, requiring only 100 symbols per constellation cluster in each observation period. Therefore, it can be used as a low-complexity alternative to conventional bit-error-rate estimation, enabling solutions for intelligent optical performance monitoring.

Journal ArticleDOI
TL;DR: In this paper, a VLC system using phase-shift keying (PSK), non-return-to-zero on-off keying, and orthogonal frequency division multiplexing (OFDM) was proposed.
Abstract: The visible light communication (VLC) technique using a rolling-shutter sensor-based commercial camera has an advantage in that the LED and camera mounted on an underwater device ( e.g. , drone, sensor) can be effectively used as a transmitter (Tx) and a receiver (Rx), respectively, under water. On the other hand, a suitable modulation technique has not been well considered to realize a VLC system using a rolling-shutter sensor in an underwater channel that includes high ambient light conditions. In this paper, we design VLC systems using phase-shift keying (PSK), non-return-to-zero on- off keying (NRZ-OOK), and orthogonal frequency division multiplexing (OFDM), and evaluate them through simulations and experiments. The results suggested that the VLC system using PSK or OFDM is more resilient than that using NRZ-OOK in an underwater channel with low-frequency ambient light, and that a VLC system using PSK or NRZ-OOK is more tolerant than that using OFDM in environments with high ambient light, resulting in pixel saturation. In conclusion, the present study has demonstrated that PSK is the most suitable modulation technique for a VLC system using a rolling-shutter sensor in an underwater channel that includes high ambient light conditions.

Journal ArticleDOI
TL;DR: The current work presents a study of the implementation of a quadrature chaos phase-shift keying communication system (QCPSK) based on the employment of different chaos oscillators using the bit error ratio as the estimation method for the QCPSK system’s baseband model performance in the AWGN propagation channel.
Abstract: The current work presents a study of the implementation of a quadrature chaos phase-shift keying communication system (QCPSK) based on the employment of different chaos oscillators. The research takes two directions, with one being the study of the chaos synchronization’s noise immunity for several chaos oscillators that are the potential core blocks of the QCPSK system. The correlation coefficient over time is used to estimate the synchronization noise immunity. The second direction is the estimation of the QCPSK system’s baseband model performance in the AWGN propagation channel using the bit error ratio (BER) as the estimation method for several chaos oscillators employed as the core of the QCPSK system’s model.

Journal ArticleDOI
TL;DR: In this article, the effects of atmospheric turbulence on the performance of a hybrid dense wavelength division modulation (DWDM) of free space optical (FSO) communication using advanced modulations are presented.
Abstract: In this paper, the effects of atmospheric turbulence on the performance of a hybrid dense wavelength division modulation (DWDM) of free space optical (FSO) communication using advanced modulations are presented. Enhancement in the capacity of transmission and bit rates of the optical networks is obtained by DWDM technology based on FSO communication systems. Proposed modulations are included Return-to-Zero Differential Phase Shift Keying (RZ-DPSK) and Non-Return-to-Zero Differential Phase Shift Keying (NRZ-DPSK) that each of them increases spectrum efficiency. Furthermore, the optical power budget of the proposed system is analytically calculated. Variation of Bit Error Rate and Max quality factor of the designed system with different path distance and input power are obtained considering outdoor atmosphere channel model. As a result, the RZ-DPSK modulation has better performance in comparison to NRZ-DPSK modulation when the atmospheric condition is considered.

Journal ArticleDOI
TL;DR: A maximum-likelihood (ML) coherent detector for PSK-LoRa and a novel noncoherent detector for IQCSS are proposed and shown that the proposed IQCIM produces a significant increase of spectral efficiency compared to LoRa with similar complexity, at an energy cost of approximately 0.9 dB.