Information-bearing Signal Research Articles

Nature's Electric Potential: A Systematic Review of the Role of Bioelectricity in Wound Healing and Regenerative Processes in Animals, Humans, and Plants.

Natural endogenous voltage gradients not only predict and correlate with growth and development but also drive wound healing and regeneration processes. This review summarizes the existing literature for the nature, sources, and transmission of information-bearing bioelectric signals involved in controlling wound healing and regeneration in animals, humans, and plants. It emerges that some bioelectric characteristics occur ubiquitously in a range of animal and plant species. However, the limits of similarities are probed to give a realistic assessment of future areas to be explored. Major gaps remain in our knowledge of the mechanistic basis for these processes, on which regenerative therapies ultimately depend. In relation to this, it is concluded that the mapping of voltage patterns and the processes generating them is a promising future research focus, to probe three aspects: the role of wound/regeneration currents in relation to morphology; the role of endogenous flux changes in driving wound healing and regeneration; and the mapping of patterns in organisms of extreme longevity, in contrast with the aberrant voltage patterns underlying impaired healing, to inform interventions aimed at restoring them.

Dirty-Paper Coding Based Secure Transmission for Multiuser Downlink in Cellular Communication Systems

This paper studies the secure transmission in a multiuser broadcast channel where only the statistical channel state information of the eavesdropper is available. We propose to apply secret dirty-paper coding (S-DPC) in this scenario to support the secure transmission of one user and the normal (unclassified) transmission of the other users. By adopting the S-DPC and encoding the secret message in the first place, all the information-bearing signals of the normal transmission are treated as noise by potential eavesdroppers and thus provide secrecy for the secure transmission. In this way, the proposed approach exploits the intrinsic secrecy of multiuser broadcasting and can serve as an energy-efficient alternative to the traditional artificial noise (AN) scheme. To evaluate the secrecy performance of this approach and compare it with the AN scheme, we propose two S-DPC-based secure transmission schemes for maximizing the secrecy rate under constraints on the secrecy outage probability (SOP) and the normal transmission rates. The first scheme directly optimizes the covariance matrices of the transmit signals, and a novel approximation of the intractable SOP constraint is derived to facilitate the optimization. The second scheme combines zero-forcing dirty-paper coding and AN, and the optimization involves only power allocation. We establish efficient numerical algorithms to solve the optimization problems for both schemes. Theoretical and simulation results confirm that, in addition to supporting the normal transmission, the achievable secrecy rates of the proposed schemes can be close to that of the traditional AN scheme, which supports only the secure transmission of one user.

Non‐linear transceiver design for secure communications with artificial noise‐assisted MIMO relay

This study investigates the problem of physical layer security for amplify-and-forward (AF) multiple-input multiple-output (MIMO) relay systems operating in the presence of a passive eavesdropper. Specifically, the authors consider the robust design of an artificial noise (AN)-assisted non-linear transceiver employing Tomlinson–Harashima precoding (THP), with imperfect knowledge of the legitimate channel states. The design problem can be reformulated as a two-level optimisation, where the outer problem aims to optimise the source precoder as a function of the relay precoder, while the inner problem at the relay aims to jointly optimise the relay precoder as well as the power allocation between the AN and the information-bearing signals. To solve the inner problem, the authors adopt a bisection method which attempts to maximise the AN power level, to confuse the eavesdropper, while satisfying the mean-squared-error requirement for the intended user. Some relaxation for the objective function is applied to transform the problem into a standard convex optimisation one. Regarding the outer problem, closed-form solutions for the precoders can be derived by an iterative method based on the Karush–Kuhn–Tucker conditions. Simulation results illustrate the superior secrecy performance provided by the proposed non-linear transceiver design with AN and THP.

A Novel Multiple-Access Correlation-Delay-Shift-Keying

In Correlation-Delay-Shift-Keying (CDSK), the reference signal and the information-bearing signal are added together during a certain time delay. Because the reference signal is not strictly orthogonal to the information-bearing signal, the cross-correlation between the adjacent chaotic signal (Intra-signal Interference, ISI) will be introduced into the demodulation at the receiver. Therefore, the Bit-Error Ratio (BER) of CDSK is higher than that of Differential-Chaos-Shift-Keying (DCSK). To avoid the ISI component and enhance the BER performance of CDSK in multiuser scenario, Multiple-Access CDSK with No Intra-signal Interference (MA-CDSK-NII) is proposed. By constructing the repeated chaotic generator and applying the Walsh code sequence to modulate the reference signal, in MA-CDSK-NII, the ISI component will be eliminated during the demodulation. Gaussian approximation method is adopted here to obtain the exact performance analysis of MA-CDSK-NII over additive white Gaussian noise (AWGN) channel and Rayleigh multipath fading channels. Results show that, due to no ISI component and lower transmitting power, the BER performance of MA-CDSK-NII can be better than that of multiple-access CDSK and Code-Shifted Differential-Chaos-Shift-Keying (CS-DCSK).

Secure transmission in the random cognitive radio networks with secrecy guard zone and artificial noise

The authors study the secure transmission design in random cognitive radio networks where the primary users, the secondary users and the eavesdroppers are randomly distributed according to Poisson point processes. Centring on this scenario, the authors propose a simple and decentralised secure transmission scheme by jointly incorporating the secrecy guard zone and artificial noise. In particular, this transmission scheme helps to enhance secrecy performance via differentiating between secondary transmitters in accordance with the eavesdropping environment. They then analyse the connection outage and secrecy outage performance of the secondary network, based on which they obtain the closed-form expression of the secrecy throughput. They further determine the optimal transmission power of the secondary transmitters and the optimal power allocation between the information-bearing signal and artificial noise to maximise the secrecy throughput of the secondary network under primary and secondary outage constraints. The authors’ analysis highlights that introducing secrecy guard zone provides better security performance, and artificial noise performs as additional interference to insert a control between the reliability and security. Numerical results show how the system parameters affect the achievable maximum secrecy throughput, the optimal transmission power and the optimal power allocation between the information-bearing signal and the artificial noise.

High Security Differential Chaos-Based Modulation With Channel Scrambling for WDM-Aided VLC System

Visible light communication (VLC) systems have relatively higher security compared with traditional radio-frequency (RF) channel thanks to line-of-sight (LOS) propagation. However, due to the broadcasting property of optical channels, VLC systems may also suffer from malicious attacks or eavesdropping. In this paper, we present a differential chaos-based modulation with channel scrambling (DCM-CS) for wavelength-division multiplexing (WDM) aided VLC system to enhance the transmission security over red, green, and blue (RGB) channels. The proposed scheme exploits the diversity property of light emitting diodes (LED) and the natural high-security property of chaotic sequences being sensitive to the initial value and nonperiodic. At the transmitter, the binary phase shift keying (BPSK) symbols are modulated by the chaotic sequences differentially, then the modulated information-bearing chaotic signals and the corresponding reference chaotic sequences are converted to nonnegative signals and transmitted over RGB channels. It is noticeable that the RGB channels change dynamically and are equivalently scrambled, where the secrecy information is shared in an uncoordinate way between the transmitters and legitimate receivers; hence, the security is further enhanced. Theoretical bit error rate (BER) and secrecy capacity expressions are derived, and simulation results are provided and compared to prove the benefits achieved by the proposed scheme.

Energy efficiency analysis and enhancement for secure transmission in SWIPT systems exploiting full duplex techniques

This paper investigates the secure transmission in simultaneous wireless information and power transfer (SWIPT) system, where a source node communicates with a wireless-powered full duplex destination node in the presence of a passive eavesdropping node. To take advantage of the benefits from SWIPT and full duplex techniques, we propose a two-phase time-sharing protocol: the destination node harvests energy form the source node in the first phase, while the information-bearing signal is transmitted under the protection of artificial noise sent from the destination node in the second phase. The transmit power of the artificial noise is converted from the harvested energy and self-interference exists at the destination. We derive the closed-form expressions for the connection outage probability (COP), the secrecy outage probability (SOP) and the transmission outage probability (TOP), based on which the secrecy energy efficiency (SEE) is formulated. Furthermore, we determine the optimal time allocation factor and transmission power that maximize the SEE while satisfying the COP and SOP constraints. Finally, numerical results verify our analytical results and show that there are tradeoffs among security, reliability and energy efficiency. When the residual loopback interference is mitigated under some certain level, our proposed optimization scheme can significantly boost the SEE.

Accumulate and Jam: Towards Secure Communication via A Wireless-Powered Full-Duplex Jammer

This paper develops a new cooperative jamming protocol, termed accumulate-and-jam (AnJ), to improve physical layer security in wireless communications. Specifically, a full-duplex (FD) friendly jammer is deployed to secure the direct communication between source and destination in the presence of a passive eavesdropper. We consider the friendly jammer as an energy-constrained node without embedded power supply but with an energy harvesting unit and rechargeable energy storage; it can thus harvest energy from the radio frequency (RF) signals transmitted by the source, accumulate the energy in its battery, and then use this energy to perform cooperative jamming. In the proposed AnJ protocol, based on the energy status of the jammer and the channel state of source-destination link, the system operates in either dedicated energy harvesting (DEH) or opportunistic energy harvesting (OEH) mode. Thanks to the FD capability, the jammer also harvests energy from the information-bearing signal that it overhears from the source. We study the complex energy accumulation and consumption procedure at the jammer by considering a practical finite-capacity energy storage, of which the long-term stationary distribution is characterized through applying a discrete-state Markov Chain. An alternative energy storage with infinite capacity is also studied to serve as an upper bound. We further derive closed-form expressions for two secrecy metrics, i.e., secrecy outage probability and probability of positive secrecy capacity. In addition, the impact of imperfect channel state information on the performance of our proposed protocol is also investigated. Numerical results validate all theoretical analyses and reveal the merits of the proposed AnJ protocol over its half-duplex counterpart.

Multilevel code‐shifted differential‐chaos‐shift‐keying system

The M-ary differential-chaos-shift-keying (M-ary DCSK) system offers a good noise performance over an additive white Gaussian noise (AWGN) channel in the category of non-coherent detection chaotic systems. However, the way that the M-ary DCSK system utilises the available Walsh codes results in a relatively low bandwidth efficiency (BE). Moreover, the number of delay elements required at the transmitter and receiver increases exponentially with the number of bits per symbol. To overcome the aforementioned problems, the authors propose a multilevel code-shifted DCSK (MCS-DCSK) system in this study. In the proposed MCS-DCSK system, the reference chaotic signal and the information-bearing chaotic signals are orthogonal and are transmitted in the same time slot. They show that the MCS-DCSK system significantly outperforms the M-ary DCSK system in terms of BE and complexity. They also derive analytical bit-error-rate expressions for the MCS-DCSK system over additive white Gaussian noise and multipath fading channels, and verify them with simulation results.

Detecting weak signals in high dimensions

Fast emerging high-throughput technology advances scientific applications into a new era by enabling detection of information-bearing signals with unprecedented sizes. Despite its potential, the analysis of ultrahigh-dimensional data involves fundamental challenges, wherein the deluge of a large amount of irrelevant data can easily obscure the true signals. Classical statistical methods for low to moderate-dimensional data focus on identifying strong true signals using false positive control criteria. These methods, however, have limited power for identifying weak true signals embedded in an extremely large amount of noise. This paper seeks to facilitate the detection of weak signals by introducing a new approach based on false negative instead of false positive control. As a result, a high proportion of weak signals can be retained for follow-up study. The new procedure is completely data-driven and fast in computation. We show in theory its efficiency and adaptivity to the unknown features of the data including signal intensity and sparsity. Simulation studies further evaluate the method under various model settings. We apply the new method in a real-data analysis on detecting genomic variants with varying signal intensities.

Fountain-Coding Aided Strategy for Secure Cooperative Transmission in Industrial Wireless Sensor Networks

Cooperative relaying communications is an efficient paradigm for end-to-end data delivery in industrial wireless sensor networks. However, due to the broadcast nature of radio propagation, it is challenging to guarantee the secrecy of cooperative transmissions under eavesdropping attacks. To deal with this issue, a fountain-coding aided relaying scheme is proposed in this paper, for which all the source packets are first encoded with fountain codes (FCs) and then transmitted over the channels. Based on the basic characteristic of FC transmissions, a sufficient number of coded packets have to be successfully received to recover the original data. Therefore, transmission secrecy is guaranteed if the legitimate receiver can accumulate the required number of FC packets before the eavesdropper does. To satisfy this condition, a cooperative jamming method is utilized to worsen the received signal quality at the eavesdropper. By applying the constellation rotation approach, the information-bearing signal and the jamming signal are designed carefully to reduce the negative effect of the jamming procedure on the legitimate receiver. To evaluate how the scheme behaves in wireless fading channels, the authors propose a novel performance metric, i.e., the quality-of-service violating probability (QVP), and derive its closed-form expression. Compared to the commonly used metrics in physical-layer security such as secrecy outage probability, QVP can give a more comprehensive performance evaluation for the system, including the delay, the reliability, and the security level as well. Finally, the theoretical analysis is validated by simulation results.

Robust Masked Beamforming for MISO Cognitive Radio Networks With Unknown Eavesdroppers

This paper studies a cognitive radio network (CRN), in which a multiple-input single-output (MISO) secondary transmitter (SU-Tx) aims to send confidential messages to its receiver (SU-Rx) in the presence of unknown eavesdroppers, while having to control its generated interference to the primary users (PUs) under a given threshold. Because the eavesdroppers are unknown, this paper considers the artificial noise (AN) approach or masked beamforming to provide the information secrecy. The objective of this paper is to maximize the power of AN in order to degrade the eavesdroppers, subject to the signal-to-interference-plus-noise ratio (SINR) constraint at the SU-Rx, as well as the interference temperature limits (ITLs) for the PUs. In the case of perfect channel state information (CSI), we reveal that the optimal strategy for the information-bearing signal is beamforming. Imperfect CSI cases of bounded and stochastic uncertainties are investigated. In the case of ellipsoid-bounded errors, we derive the equivalent forms for the SINR and ITL constraints and then transform the optimization problem into a form of semidefinite programming (SDP). For the case of probabilistic CSI uncertainties, we propose an outage-constrained robust formulation where the CSI errors are Gaussian distributed. With the aid of two kinds of Bernstein-type inequalities, we reexpress the probabilistic constraints into deterministic forms, which results in a safe approximate solution.

Secure Communication With a Wireless-Powered Friendly Jammer

In this paper, we propose to use a wireless-powered friendly jammer to enable secure communication between a source node and destination node, in the presence of an eavesdropper. We consider a two-phase communication protocol with fixed-rate transmission. In the first phase, wireless power transfer is conducted from the source to the jammer. In the second phase, the source transmits the information-bearing signal under the protection of a jamming signal sent by the jammer using the harvested energy in the first phase. We analytically characterize the long-time behavior of the proposed protocol and derive a closed-form expression for the throughput. We further optimize the rate parameters for maximizing the throughput subject to a secrecy outage probability constraint. Our analytical results show that the throughput performance differs significantly between the single-antenna jammer case and the multi-antenna jammer case. For instance, as the source transmit power increases, the throughput quickly reaches an upper bound with single-antenna jammer, while the throughput grows unbounded with multi-antenna jammer. Our numerical results also validate the derived analytical results.

Entanglement distribution over quantum code-division multiple-access networks

We present a method for quantum entanglement distribution over a so-called code-division-multiple-access network, in which two pairs of users share the same quantum channel to transmit information. The main idea of this method is to use different broad-band chaotic phase shifts, generated by electro-optic modulators (EOMs) and chaotic Colpitts circuits, to encode the information-bearing quantum signals coming from different users, and then recover the masked quantum signals at the receiver side by imposing opposite chaotic phase shifts. The chaotic phase shifts given to different pairs of users are almost uncorrelated due to the randomness of chaos and thus the quantum signals from different pair of users can be distinguished even when they are sent via the same quantum channel. It is shown that two maximally-entangled states can be generated between two pairs of users by our method mediated by bright coherent lights, which can be more easily implemented in experiments compared with single-photon lights. Our method is robust under the channel noises if only the decay rates of the information-bearing fields induced by the channel noises are not quite high. Our study opens up new perspectives for addressing and transmitting quantum information in future quantum networks.

고밀집 환경에서 대용량 MIMO WLAN의 네트워크 용량 최대화를 위한 결합 공간 분할 및 재사용 기법

In this paper, joint spatial division and reuse (JSDR) scheme is proposed for maximizing network throughput in densely-deployed wireless local area networks equipped with massive antenna array. The proposed JSDR scheme divides the massive spatial space into two subspaces: one is for suppressing the interference from the neighboring access points and another is for sensing the carrier sensing and transmitting the information-bearing signals to intended stations. By using computer simulation, the proposed JSDR can provide 133% higher network throughput, compared to the carrier sensing technique defined in the IEEE 802.11 standard so that the proposed JSDR is suitable for the next generation WLAN systems. ※ This work was supported by ICT RD Revised March 25, 2015; Accepted March 25, 2015 The Journal of Korean Institute of Communications and Information Sciences '15-03 Vol.40 No.03

Secrecy Rate Maximization With Artificial-Noise-Aided Beamforming for MISO Wiretap Channels Under Secrecy Outage Constraint

The secrecy rate maximization with the artificial noise (AN) aided beamforming for the multipel-input-single-output (MISO) wiretap channel is addressed in this paper under the constraint of secrecy outage probability. The channel state information (CSI) of the main channel is assumed to be perfectly known while the CSI of the eavesdropper is modeled as a complex Gaussian random vector. The generalized AN scheme where the AN is not constrained to be orthogonal to the information-bearing signal is considered. The complete solution to the maximum achievable secrecy rate and the corresponding optimal power allocation between the information-bearing signal and the AN is obtained without making any approximation of the secrecy outage probability constraint. The result shows that the optimal AN is always orthogonal to the information-bearing signal.

Multicarrier chaotic communications in multipath fading channels without channel estimation

A multi-carrier chaotic shift keying(MC-CSK) communication scheme with low probability of interception(LPI) is proposed in this article. We apply chaotic spreading sequences in the frequency domain, mapping a different chip of a chaotic sequence to an individual orthogonal frequency division multiplexing(OFDM) subcarrier. In each block size of $M$ OFDM symbols, we use one pilot OFDM symbol inserted time-spaced in all-frequency to transmit the reference chaotic signal and use the other M-1 OFDM symbols to transmit the information-bearing signals each spreaded by the reference chaotic signal. At the receiver, we construct a differential detector after DFT and recover the information bits from the correlations between the pilot OFDM symbol and the other M-1 OFDM symbols in each block size of M. Performance analysis and computer simulations show that the MC-CSK outperforms differential chaos shift keying(DCSK) in AWGN channels with high bandwidth efficiency for the block size of M=2 and that the MC-CSK exploits effectively the frequent diversity of the multipath channel.

Basic Concepts in Telecommunications Systems

Wikipedia defines a telecommunication system in the following terms: “Telecommunication occurs when the exchange of information between two entities (communication) includes the use of technology [1]. Communication technology uses channels to transmit information (as electrical signals), either over a physical medium (such as signal cables), or in the form of electromagnetic waves”. Poor’s definition of a telecommunication system brings out very clearly its intimate relationship to statistics: “Signal detection and estimation is the area of study that deals with the processing of information-bearing signals for the purpose of extracting information from there. Applications of the theory of signal detection and estimation are found in many areas, such as communications and automatic control”. Signal detection is commonly called hypothesis testing in statistics and, it, hand-inhand with estimation, forms the central core of statistics. Thus the importance of statistics for telecommunication systems is inherent in the very definition of these systems [2].

Reference-Adaptive CDSK: An Enhanced Version of Correlation Delay Shift Keying

In this brief, a new chaotic communication scheme, named reference-adaptive correlation delay shift keying (RA-CDSK) is proposed as an enhanced version of CDSK. According to the relationship between adjacent information symbols, our scheme employs the information-bearing signal or the sequence generated by the discrete-time chaotic circuit as the reference signal for the next bit period. As a result, compared with CDSK and its improved schemes, the uncertainty caused by intrasignal interference and noise interference is made lower when the received signal correlates with its delayed version at the receiver. The bit-error-rate (BER) performance of our scheme is also studied analytically based on Gaussian approximation for discrete-time implementations. Simulations in additive white Gaussian noise channel are performed and compared with CDSK, generalized CDSK (GCDSK), and single-input–multiple-output CDSK (SIMO-CDSK). Results show that the BER performance of RA-CDSK is always much better than CDSK and GCDSK, and can even outperform SIMO-CDSK with a small spreading factor and at a high $E_{b}/N_{0}$ level. Moreover, for different $E_{b}/N_{0}$ levels, the best BER performance of RA-CDSK can be gained with a reasonable spreading factor.

Phase-Separated DCSK: A Simple Delay-Component-Free Solution for Chaotic Communications

In this brief, a phase-separated differential chaos shift keying (PS-DCSK) modulation scheme is proposed as a simple delay-component-free version of DCSK modulation. Separated by orthogonal sinusoidal carriers rather than time delay, the reference and information-bearing signals in DCSK are transmitted simultaneously and parallel in the proposed system. As a result, PS-DCSK not only can avoid the difficult-to-implement radio-frequency delay line problem but also can achieve a doubled attainable data rate, enhanced communication security, and equivalent bit-error-rate (BER) performance with respect to DCSK. Finally, analytical expressions for the BER performance of the proposed system are derived and verified by computer simulation results over additive Gaussian white noise and Rayleigh fading channels.