Showing papers on "Keying published in 2017"

Frequency Shift Chirp Modulation: The LoRa Modulation

Abstract: Low power wide area networks (LPWAN) are emerging as a new paradigm, especially in the field of Internet of Things (IoT) connectivity. LoRa is one of the LPWAN and it is gaining quite a lot of commercial traction. The modulation underlying LoRa is patented and has never been described theoretically. The aim of this letter is to give the first rigorous mathematical signal processing description of the modulation and demodulation processes. We provide as well a theoretical derivation of the optimum receiver entailing a low-complexity demodulation process, resorting to the Fast Fourier Transform. We compare then the performance of the LoRa modulation and the frequency-shift keying modulation both in an additive white gaussian noise channel and a frequency selective channel, showing the superiority of the LoRa modulation in the frequency selective channel. The results of this letter will enable a further assessment of the LoRa based networks, much more rigorous than what has been done until now.

Joint OSNR monitoring and modulation format identification in digital coherent receivers using deep neural networks

Abstract: We experimentally demonstrate the use of deep neural networks (DNNs) in combination with signals’ amplitude histograms (AHs) for simultaneous optical signal-to-noise ratio (OSNR) monitoring and modulation format identification (MFI) in digital coherent receivers. The proposed technique automatically extracts OSNR and modulation format dependent features of AHs, obtained after constant modulus algorithm (CMA) equalization, and exploits them for the joint estimation of these parameters. Experimental results for 112 Gbps polarization-multiplexed (PM) quadrature phase-shift keying (QPSK), 112 Gbps PM 16 quadrature amplitude modulation (16-QAM), and 240 Gbps PM 64-QAM signals demonstrate OSNR monitoring with mean estimation errors of 1.2 dB, 0.4 dB, and 1 dB, respectively. Similarly, the results for MFI show 100% identification accuracy for all three modulation formats. The proposed technique applies deep machine learning algorithms inside standard digital coherent receiver and does not require any additional hardware. Therefore, it is attractive for cost-effective multi-parameter estimation in next-generation elastic optical networks (EONs).

Digital Signal Processing for Coherent Transceivers Employing Multilevel Formats

Abstract: Digital coherent transceivers have revolutionized optical fiber communications due to their superior performance offered compared to intensity modulation and direct detection based alternatives. As systems employing digital coherent transceivers seek to approach their information theoretic capacity, the use of multilevel modulation formats combined with appropriate forward error correction becomes essential. Given this context, in this tutorial paper, we, therefore, explore the digital signal processing (DSP) utilized in a coherent transceiver with a focus on multilevel modulation formats. By way of an introduction, we open by discussing the photonic technology required to realize a coherent transceiver. After discussing this interface between the analog optical channel and the digital domain, the rest of the paper is focused on DSP. We begin by discussing algorithms that correct for imperfections in the optical to digital conversion, including IQ imbalance and timing skew. Next, we discuss channel equalization including means for their realization for both quasi-static and dynamic channel impairments. Synchronization algorithms that correct for the difference between the transmitter and receiver oscillators both optical and electrical are then discussed and issues associated with symbol decoding highlighted. For most of the cases, we start with polarization division multiplexed quadrature phase-shift keying format as a basis and then discuss the extension to allow for high-order multilevel formats. Finally, we conclude by discussing some of the open research challenges in the field.

Speech encryption using chaotic shift keying for secured speech communication

Abstract: This paper throws light on chaotic shift keying-based speech encryption and decryption method. In this method, the input speech signals are sampled and its values are segmented into four levels, namely L 0, L 1, L 2, and L 3. Each level of sampled values is permuted using four chaotic generators such as logistic map, tent map, quadratic map, and Bernoulli’s map. A chaotic shift keying mechanism assigns logistic map for L 0, tent map for L 1, quadratic map for L 2, and Bernoulli’s map for L 3 for shuffling the speech samples at every level. Further, the sampled values are permuted using Chen map which uncovers the chaotic behavior. Various testing methods are applied to analyze the efficiency of the system. The results prove that the proposed system is highly secured against the attackers and possesses a powerful diffusion and confusion mechanism for better speech communication in the field of telecommunication.

A dual-function MIMO radar-communications system using frequency-hopping waveforms

Abstract: The dual use of radio signals for simultaneous operation of radar and communications has recently attracted significant interest. In this paper, we develop a method for information embedding into the emission of multiple-input multiple-output (MIMO) radar using frequency-hopping (FH) waveforms. The set of orthogonal waveforms used to implement the primary MIMO radar operation is generated using FH codes. The secondary communication function is implemented by embedding one phase-shift keying (PSK) communication symbol in each frequency hop, i.e., the number of embedded communication symbols during each radar pulse equals the number of transmit antennas times the length of the FH code. We show that the communication operation is transparent to the MIMO radar function of the dual-function system. Standard ratio testing is used to detect the embedded PSK symbols at the communication receiver. The achievable data rate is proportional to the pulse repetition frequency, the number of transmit elements, the length of the FH code, and the size of the PSK constellation. The performance of the proposed technique is investigated in terms of the symbol error rate.

All-Electronic 100-GHz Bandwidth Digital-to-Analog Converter Generating PAM Signals up to 190 GBaud

Abstract: We demonstrate an all-electronic digital-to-analog converter (DAC) with 100-GHz electrical bandwidth, sampling at 240 GSa/s, based on digital band interleaving (DBI). We discuss digital predistortion techniques for compensating the nonideal performance of the high-speed and radio-frequency components in our DBI architecture. We then test the DAC by generating up to 190-GBaud Nyquist-shaped pulse amplitude modulation. We analyze the performance of the digital band interleaved DAC and demonstrate coherent detection of single-polarization optical binary phase-shift keying at 140 GBaud.

Region-of-Interest Signaling Vehicular System Using Optical Camera Communications

Abstract: This technical paper introduces an optical camera communication system for vehicles. The purpose of the communication system incorporated into car (using existing light-emitting diode (LED) lights and ordinary cameras) is to add region-of-interest signaling functionality for cars via either their headlights or taillights. A low-data-rate but reliable link via the optical channel is the objective. In particular, the communication system, contributes a spatial modulation approach called spatial-2-phase-shift keying (S2-PSK) that uses a pair of optical light sources on a car (either a pair of rear-LEDs or a pair of front-LEDs) as a transmitter. A typical camera (i.e., less than 30 frames/s), either a global shutter or a rolling shutter, can be used to receive light-modulated data. As a remarkable physical layer (PHY) operating mode among image sensor communication PHY modes recently contributed to IEEE 802.15.7r1 (TG7r1), the communication system, along with technical details on the S2-PSK communication protocol, is described in this paper. In addition, in order to deal with the noisy optical channel and the low-performance challenge of a camera receiver, we have suggested a rate-1/2 line coding and an intelligent decoding approach in our intended vehicular communication scenario. Finally, numerical analyses on the performance of our system and experiment results are addressed.

Hierarchical Hypothesis and Feature-Based Blind Modulation Classification for Linearly Modulated Signals

Abstract: This paper presents a hierarchical hypothesis test and a feature-based blind modulation classification (BMC) algorithm for linearly modulated signals. The proposed BMC method is based on the combination of elementary cumulant (EC) and cyclic cumulants. The EC is used to decide whether the constellations are from real, circular, or rectangular class, which is referred to as macro classifier. The cyclic cumulant is used to classify modulation within a subclass, which is referred to as micro classifier. For the micro classification, we use positions of nonzero cyclic frequencies (symbol rate frequency or carrier frequency) of the received signals. A hierarchical hypothesis-based theoretical framework has been developed to find the probability of error for the proposed classification. The method works over a flat fading channel without any knowledge of the signal parameters. The proposed method is more robust than the one based on EC and at the same time it requires lower complexity than the maximum likelihood approach. To validate the proposed scheme, measurement is carried out in realistic scenarios. The performance of the new algorithm is compared with the existing methods. In this paper, we have considered a six-class problem including binary phase-shift keying, quadrature phase-shift keying (QPSK), offset-QPSK, $\pi$ /4-QPSK, minimum shift keying, and 16-quadrature amplitude modulation.

Subcarrier PSK Performance in Terrestrial FSO Links Impaired by Gamma-Gamma Fading, Pointing Errors, and Phase Noise

Abstract: For terrestrial free-space optical (FSO) communication systems, subcarrier intensity modulation represents an attractive alternative to on-off keying or pulse-position modulation, which is mainly because of the larger spectral efficiency. However, some degradation of the error performance must be taken into account due to nonperfect synchronization of carrier frequency and phase. In a recently published paper, the average bit error probability has been analyzed for $M$ -ary phase-shift keying in the presence of phase noise for a terrestrial FSO link impaired by lognormal fading. In the this paper, we are extending this study to a gamma-gamma model, which is usually applied in case of moderate-to-strong scintillation effects. On top of that, pointing errors, caused by a misalignment between transmitter and receiver of the FSO link, are considered as well. Since a closed-form solution is not available under general conditions and because numerical methods are time-consuming, suffering in part also from serious convergence and stability problems, we provide approximate closed-form expressions, which are accurate enough over a wide signal-to-noise ratio range.

An Integrated Passive Phase-Shift Keying Modulator for Biomedical Implants With Power Telemetry Over a Single Inductive Link.

Abstract: This paper presents a passive phase-shift keying (PPSK) modulator for uplink data transmission for biomedical implants with simultaneous power and data transmission over a single 13.56 MHz inductive link. The PPSK modulator provides a data rate up to 1.35 Mbps with a modulation index between 3% and 38% for a variation of the coupling coefficient between 0.05 and 0.26. This modulation scheme is particularly suited for biomedical implants that have high power demand and low coupling coefficients. The PPSK modulator operates in conjunction with on-off-keying downlink communication. The same inductive link is used to provide up to 100 mW of power to a multi-channel stimulator. The majority of the system on the implant side was implemented as an application specific integrated circuit (ASIC), fabricated in 0.6-[Formula: see text] high voltage CMOS technology. The theory of PPSK modulation, simulated and measured performance evaluation, and comparison with other state-of-the-art impedance modulation techniques is presented. The measured bit error rate around critical coupling at 1.35 Mbps is below 6 ×10(-8).

Underwater Wireless Optical Communications Using Silicon Photo-Multipliers

Abstract: We study the use of Silicon photo-multipliers (SiPMs) for underwater wireless optical communications (UWOC) and discuss their main interests and drawbacks, compared with photo-multiplier tubes. This comparison is mainly based on practical considerations regarding system implementation and the attainable link span. Presenting an appropriate model for signal attenuation in water and considering the simple On-Off keying modulation, we bring clearance on the real interest of using an SiPM in the UWOC context. We also elucidate the main drawbacks of these components in practice, in particular, regarding the limitation on the transmission data rate, as well as the nonlinear distortion caused on the received signal in relatively short ranges, where the signal intensity is too large.

Differential Chaos Shift Keying: A Robust Modulation Scheme for Power-Line Communications

Abstract: The past few years have witnessed a tremendous development in power-line communications (PLCs) for the realization of smart grids. Since power lines were not originally intended for conveying high-frequency signals, any communication over these lines would be exposed to severe adversarial factors, such as interference, impulsive, and phase noise. This elucidates the importance of employing robust modulation techniques and motivates research in this direction. Indeed, the aim of this brief is to propose a differential chaos shift keying (DCSK) modulation scheme as a potential candidate for smart grid communication networks. This DCSK class of noncoherent modulation is very robust against linear and nonlinear channel distortions. More importantly, the demodulation process can be carried out without any channel estimator at the receiver side. In this work, we analyze the bit error rate performance of DCSK over multipath PLC channels in which phase, background, and impulsive noise are present. A simulator is developed to verify the performance of the proposed DCSK against direct sequence code division multiple access and direct sequence differential phase shift keying. The results presented in this work prove the advantages of this low-cost noncoherent modulation technique for PLC systems over its rivals.

Multilevel modulation scheme using the overlapping of two light sources for visible light communication with mobile phone camera.

Abstract: Visible light communication (VLC) with light emitting diodes (LEDs) is an emerging technology for 5G wireless communications. Recently, using complementary metal-oxide-semiconductor (CMOS) image sensor as VLC receiver is developed owing to its flexibility and low-cost. However, two illumination levels such as on-off keying (OOK) signal are used. To improve the system throughput and reduce complexity of the hardware design, in this paper, we propose and experimentally demonstrate a multilevel modulation scheme for VLC system utilizing the overlapping of two light sources for the first time, and the two light sources are modulated by an OOK and a Manchester signal respectively. At the receiver, a CMOS camera can demodulate the Manchester and the OOK signal simultaneously. Meanwhile, a low-pass filter (LPF) is used to enhance the system performance. The experimental results demonstrate that the proposed multilevel modulation scheme can achieve a net data rate of 4.32 kbit/s.

Nonlinear silicon photonic signal processing devices for future optical networks

Abstract: In this paper, we present a review on silicon-based nonlinear devices for all optical nonlinear processing of complex telecommunication signals. We discuss some recent developments achieved by our research group, through extensive collaborations with academic partners across Europe, on optical signal processing using silicon-germanium and amorphous silicon based waveguides as well as novel materials such as silicon rich silicon nitride and tantalum pentoxide. We review the performance of four wave mixing wavelength conversion applied on complex signals such as Differential Phase Shift Keying (DPSK), Quadrature Phase Shift Keying (QPSK), 16-Quadrature Amplitude Modulation (QAM) and 64-QAM that dramatically enhance the telecom signal spectral efficiency, paving the way to next generation terabit all-optical networks.

Generalized Solution for the Demodulation of Reaction Shift Keying Signals in Molecular Communication Networks

Abstract: This paper considers a diffusion-based molecular communication system, where the transmitter uses reaction shift keying (RSK) as the modulation scheme We focus on the demodulation of RSK signal at the receiver The receiver consists of a front-end molecular circuit and a back-end demodulator The front-end molecular circuit is a set of chemical reactions consisting of multiple chemical species The optimal demodulator computes the posteriori probability of the transmitted symbols given the history of the observation The derivation of the optimal demodulator requires the solution to a specific Bayesian filtering problem The solution to this Bayesian filtering problem had been derived for a few specific molecular circuits and specific choice(s) of observed chemical species The derivation of such solution is also lengthy The key contribution of this paper is to present a general solution to this Bayesian filtering problem, which can be applied to any molecular circuit and any choice of observed species

Generalized Blind Detection of OOK Modulation for Free-Space Optical Communication

Abstract: For optimal detection of ON – OFF keying symbols in free-space optical (FSO) communication, the receiver requires the instantaneous channel fading coefficient. In this letter, to increase the bandwidth efficiency of the FSO channel, we propose a blind data detection method, i.e., without requiring transmission of any training symbols. The proposed blind detection is a two-step method that performs block-by-block detection. Simulation results show that the proposed receiver can achieve a significantly lower bit-error-rate performance compared with the existing blind methods in the context of FSO communications. In addition, the proposed blind method has a simple structure, which makes it particularly suitable for fast FSO communications.

Design of a backscatter-based Tag-to-Tag system

Abstract: Practical technologies for the Internet of Things (IoT) must provide connectivity to all objects under a common framework irrespective of their size or value. Power requirement, cost of wireless devices and scalability have proved critical bottlenecks for the universal deployment of the IoT. One approach to address these issues is the use of a communication paradigm where the devices communicate via backscattering and exploit harvested power from an external RF source. In a Backscattering Tag-to-Tag Network (BTTN), the tags themselves are able to read and interpret the backscattered communications from other neighboring tags. In the tag-to-tag link, the BTTN tag has to demodulate a receiving signal with a low modulation index. In order to improve the link range, we propose a power-efficient demodulator design that enables the receiving tag to quantify the amplitude-shift keying (ASK) modulated signal with a modulation index as low as 0.6%. The demodulator consumes 1.21 µW at 1.1 V supply voltage at a data rate of 10 kbps.

Transmitter-Precoding-Aided Spatial Modulation Achieving Both Transmit and Receive Diversity

Abstract: We propose and investigate a precoding-aided spatial modulation (PSM) scheme, which can simultaneously achieve transmit and receive diversity and, hence, is referred to as the TRD-PSM scheme. In TRD-PSM systems, information is transmitted jointly using an amplitude-phase modulation and a receive-antenna-based space-shift keying modulation. We consider two types of linear precoders, namely transmitter zero forcing (TZF) and transmitter minimum mean square error (TMMSE), so as to facilitate low-complexity signal detection. In order to satisfy the different requirement for complexity and reliability, we introduce/propose a range of detection algorithms, which include a joint maximum likelihood detector (JMLD), a simplified JMLD, a successive maximum likelihood detector (SMLD), a simplified SMLD, and a ratio-threshold-test-assisted maximum likelihood detector. We address the principles, characteristics, complexity, and performance of these detection algorithms. Furthermore, we analyze the average bit error probability of the TZF- and TMMSE-assisted TRD-PSM systems employing, respectively, the JMLD and the simplified JMLD and at both small and large scales. Finally, numerical and simulation results are provided to demonstrate and compare the achievable performance of TRD-PSM systems employing various precoding and detection algorithms, as well as to validate the formulas derived.

Millimeter-Wave Transmission for Small-Cell Backhaul in Dense Urban Environment: a Solution Based on MIMO-OFDM and Space-Time Shift Keying (STSK)

Abstract: Next generation wireless standards will exploit the wide bandwidth available at the millimeter-wave (mm-Wave) frequencies, in particular the $E$ -band (71–76 and 81–86 GHz). This large available bandwidth may be converted into multi-gigabit capacity, when efficient and computationally affordable transceivers are designed to cope with the constrained power budget, the clustered fading, and the high level of phase noise, which actually characterize mm-wave connections. In this paper, we propose a viable multiple-input multiple-output (MIMO) solution for high bit-rate transmission in the $E$ -band with application to small-cell backhaul based on space-time shift keying (STSK) and orthogonal frequency division multiplexing. STSK provides an efficient tradeoff between diversity and multiplexing without inter-channel interference and without the need for large antenna arrays. These features make STSK theoretically preferable over other throughput-oriented space-time coding techniques, namely, spatial multiplexing and spatial modulation, which were recently considered in the literature for mm-wave MIMO applications. In this paper, we consider the most significant channel impairments related to small-cell backhaul in dense urban environment, namely, the correlated fading with and without the presence the line-of-sight, the phase noise, the rain attenuation, and shadowing. In addition, we consider small-size MIMO systems ( $2 \times 2$ and $4 \times 4$ ), and low-cost base station equipments in the perspective of easily deployable small-cell network components. Comparative results, obtained by intensive simulations targeted at assessing link performance and coverage, have clearly shown the superior performance of STSK against counterpart techniques, although obtained at the cost of a somewhat reduced spectral efficiency.

Joint automotive radar-communications waveform design

Abstract: The paper studies the problem of waveform design for a joint Radar-Communications (RadComms) system in an automotive setting characterized by a multitarget environment The envisaged joint waveform allows exploitation of existing infrastructure to support additional functionalities In this contribution, an automotive radar employing Phase Modulated Continuous Waveform (PMCW) is considered wherein, the transmission of communications bits is additionally facilitated Particularly, the RadComms system is enabled by the transmission of Differential Phase Shift Keying (DPSK) communications symbols, each symbol modulated by the PMCW sequence Further, the receiver processing includes demodulation of the communication symbols in addition to the extraction of the radar parameters — range, Angles of Arrival (AoA) and Doppler returns of the targets In particular, FFT and subspace-based methods are proposed for estimating the radar parameters which are subsequently used in the demodulation of the communication symbols using diversity combining techniques The performed study demonstrates the impact of the joint set-up on the two systems It also highlights the effect of system parameters on the performance of receiver algorithms and the trade-off between the FFT and sub-spaced based processing

Elliptical Core Few Mode Fibers for Multiple-Input Multiple Output-Free Space Division Multiplexing Transmission

Abstract: We experimentally demonstrate space division multiplexed data transmission using the LP01, LP11a and LP11b modes over a 1 km length of elliptical-core few mode fiber at 1550 nm using 10 Gb/s ON–OFF keying data per spatial channel. Space division multiplexed transmission without the use of any multiple input multiple output digital signal processing showed no power penalty relative to the single-mode or the back to back cases.

Coherent UDWDM-PON With Dual-Polarization Transceivers in Real-Time

Abstract: We report a real-time experimental demonstration of a long-reach coherent ultra-dense wavelength-division multiplexing (WDM)-passive optical network (PON) system with quadratic-amplitude modulation (QAM)-based dual-polarization optical transceivers. Using field-programmable gate array-based digital signal processing, the transmission of 20-WDM channels in 2.5-GHz grid, employing both 2.5-Gb/s dual-polarization quadrature phase-shift keying (DP-QPSK) and 3.75-Gb/s DP-8PSK signals, is successfully demonstrated with bit-error rate in real-time. The performance is evaluated over 100-km standard single mode fiber in terms of receiver sensitivity and ODN power budget for both modulation formats, showing the feasibility of coherent PON scenarios using flexible dual-polarization strategies supported by software-defined transceivers.

Multi-Set Space-Time Shift Keying and Space- Frequency Space-Time Shift Keying for Millimeter-Wave Communications

Abstract: In this paper, we introduce a novel OFDM-aided multifunctional multiple-input multiple-output scheme based on multi-set space-time shift keying (MS-STSK), where the information transmitted over each subcarrier is divided into two parts: STSK codeword and the implicit antenna combination (AC) index. In MS-STSK, a unique combination of antennas can be activated at each subcarrier to convey extra information over the AC index while additionally transmitting the STSK codeword. Furthermore, inspired by the MS-STSK concept, this scheme is extended also to the frequency domain in the novel context of our multi-space-frequency STSK (MSF-STSK), where the total number of subcarriers is partitioned into blocks to implicitly carry the block’s frequency index. The proposed MSF-STSK scheme benefits from the huge bandwidths available at mmWaves for partitioning the total number of OFDM subcarriers into blocks to convey more information over the frequency domain. Both proposed systems use STSK codewords as the basic transmission block, and they can achieve higher data throughput and better BER performance than STSK. Moreover, given that the system is meant to operate at mmWaves, antenna arrays relying on several antenna elements are employed at both the transmitter and receiver for analogue beamforming with the aid of phase shifters and power amplifiers to overcome the effect of high path loss.

Chaotic Image Encryption with Hash Keying as Key Generator

Abstract: This paper proposes an image encryption algorithm using Hash key as key generator for permutation and diffusion. SHA-1 algorithm is used to generate symmetric secret key for encryption/decryption p...

Chip Averaging Chaotic ON–OFF Keying: A New Non-Coherent Modulation for Ultra Wide Band Direct Chaotic Communication

Abstract: This letter proposes a new adaptive threshold modulation scheme, called chip averaging chaotic ON–OFF keying (CA-COOK). This new scheme is applied to non-coherent modulations in ultra-wideband direct chaotic communication. Mainly, the proposed method deals with the “estimation problem” caused by the bit energy variation of the chaotic carrier signal. This is completed by adopting the Cell Averaging Constant False Alarm Rate paradigm used in radar, and each bit period is divided into several chips, where one of those chips is bearing the information. Bit-error-rate performance in additive-white-Gaussian-noise, two-path Rayleigh, and IEEE802.15.4a office NLOS channel models, is analyzed and compared with well-known and challenging chaos-based communication systems. Simulation results show the effectiveness of the proposed CA-COOK.

Unity-Rate Codes Maximize the Normalized Throughput of ON–OFF Keying Visible Light Communication

Abstract: In this letter, we aim for maximizing the throughput of a visible light communication (VLC) system. Explicitly, we conceive a soft-in soft-out decoder providing soft feedback for the classic run length limited (RLL) codes, hence facilitating iterative decoding for exchanging valuable extrinsic information between the RLL and the error correction modules of a VLC system. Furthermore, we propose a unity rate code for our VLC system, which, hence, becomes capable of matching the ON–OFF keying capacity, while maintaining a flicker-free dimming value of 50%.

A Shock Tube Experimental System for Communication Performance Evaluation Under the Time-Varying Plasma Flow Channel

Abstract: Plasma sheath can severely affect the electromagnetic waves and lead to the radio blackout problem. Existing simulation works on the influence of plasma on communications, either failed to illustrate the high dynamics of the plasma or suffered from high computational complexity. In this paper, we propose an experimental system based on a shock tube to evaluate the communication performance over the plasma channel. In order to compare the performance of different modulation modes simultaneously, we initiatively mixed frequency-shift keying (FSK), pulse-position modulation, and quadrature phase-shift keying (QPSK) together in the transmission signal. Since the duration of the plasma generated by the shock tube is short in each experiment instance, we employ the achievable rate to evaluate the communication performance. Specifically, according to our experimental results, the communication performance of FSK is the best and most stable, while the QPSK is the worst and most unstable, indicating that the plasma channel has the greatest impact on the phase domain compared with the frequency domain and the time domain. Finally, the nonstationary and high dynamic characteristics of the plasma channel are verified in our designed experiment.

Modulation classification of satellite communication signals using cumulants and neural networks

Abstract: National Aeronautics and Space Administration (NASA) is investigating cognitive technologies for their future communication architecture. These technologies are expected to reduce the operational complexity of the network, increase science data return, and reduce interference to self and others. In order to increase situational awareness, signal classification algorithms could be applied to identify users and distinguish sources of interference. As a preliminary step, we seek to develop a system with the ability to discern signals typically encountered in satellite communication. Proposed is an automatic modulation classifier which utilizes higher order statistics (cumulants) and an estimate of the signal-to-noise ratio. These features are extracted from baseband symbols and then processed by a neural network for classification. The modulation types considered are phase-shift keying (PSK), amplitude and phase-shift keying (APSK), and quadrature amplitude modulation (QAM). Physical layer properties specific to the Digital Video Broadcasting - Satellite - Second Generation (DVB-S2) standard, such as pilots and variable ring ratios, are also considered. This paper will provide simulation results of a candidate modulation classifier, and performance will be evaluated over a range of signal-to-noise ratios, frequency offsets, and nonlinear amplifier distortions.

34.5 m Underwater optical wireless communication with 2.70 Gbps data rate based on a green laser with NRZ-OOK modulation

Abstract: This study proposed and experimentally demonstrated a high-speed long-distance underwater optical wireless communication (UOWC) system using a 520 nm green laser diode (LD) with non-return-to-zero on-off keying (NRZ-OOK) modulation scheme. The UOWC link offers maximum data rates up to 4.60 Gbps, 3.93 Gbps, 3.48 Gbps and 2.70 Gbps over the underwater distances of 2.3 m, 11.5 m, 20.7 m and 34.5 m with the bit-error rates below the forward error correction (FEC) criterion of 3.8 χ 10−3. To the best of our knowledge, UOWC data rate of 2.70 Gbps at 34.5 m is the highest at present.

GLRT-Based Sequence Detection of OOK Modulation Over FSO Turbulence Channels

Abstract: For the optimal detection of ON-OFF keying symbols in free-space optical (FSO) communication, the receiver requires the instantaneous channel fading coefficient. In this letter, to increase the bandwidth efficiency of the FSO channel, we propose a generalized likelihood ratio test-based sequence detection (SD) method, which significantly reduces the complexity of maximum likelihood SD.