Cognitive Jammers Assisted Covert Communication in Cognitive Radio Networks

In this work,we investigate the covert communication in cognitive radio(CR)networks with the existence of multiple cognitive jammers(CJs).Specifically,the secondary transmitter(ST)helps the primary transmitter(PT)to relay information to primary receiver(PR),as a reward,the ST can use PT's spectrum to transmit private information against the eavesdropper(Eve)under the help of one selected cognitive jammer(CJ).Meanwhile,we propose three jammer-selection schemes,namely,link-oriented jammer selection(LJS),min-max jammer selection(MMJS)and random jammer selection(RJS).For each scheme,we analyze the average covert throughput(ACT)and covert outage probability(COP).Our simulation results show that CJ is helpful to ST's covert communication,the expected minimum detection error probability and ACT can be significantly improved with the increase of false alarm of CJ.Moreover,the LJS scheme achieves best performance in ACT and COP,followed by RJS scheme,and MMJS scheme shows the worst performance.

Performance Analysis of Three Spectrum Sensing Detection Techniques with Ambient Backscatter Communication in Cognitive Radio Networks

In wireless communications, the Ambient Backscatter Communication (AmBC) technique is a promisingapproach, detecting user presence accurately at low power levels. At low power or a low Signal-to-Noise Ratio(SNR), there is no dedicated power for the users. Instead, they can transmit information by reflecting the ambientRadio Frequency (RF) signals in the spectrum. Therefore, it is essential to detect user presence in the spectrum forthe transmission of data without loss or without collision at a specific time. In this paper, the authors proposed anovel Spectrum Sensing (SS) detection technique in the Cognitive Radio (CR) spectrum, by developing the AmBC.Novel Matched Filter Detection with Inverse covariance (MFDI), Cyclostationary Feature Detection with Inversecovariance (CFDI) and Hybrid Filter Detection with Inverse covariance (HFDI) approaches are used with AmBCto detect the presence of users at low power levels. The performance of the three detection techniques is measuredusing the parameters of Probability of Detection (PD), Probability of False Alarms (Pfa), Probability of MissedDetection (Pmd), sensing time and throughput at low power or low SNR. The results show that there is a significantimprovement via the HFDI technique for all the parameters.

Radio Propagation and Wireless Coverage of LSAA-Based 5G Millimeter-Wave Mobile Communication Systems

Millimeter-wave(mm Wave) communications will be used in fifth-generation(5G) mobile communication systems, but they experience severe path loss and have high sensitivity to physical objects, leading to smaller cell radii and complicated network architectures. A coverage extension scheme using large-scale antenna arrays(LSAAs) has been suggested and theoretically proven to be cost-efficient in combination with ultradense small cell networks. To analyze and optimize the LSAA-based network deployments, a comprehensive survey of recent advances in statistical mmWave channel modeling is first presented in terms of channel parameter estimation, large-scale path loss models, and small-scale cluster models. Next, the measurement and modeling results at two 5G candidate mmWave bands(e.g., 28 GHz and 39 GHz) are reviewed and compared in several outdoor scenarios of interest, where the propagation characteristics make crucial contributions to wireless network designs. Finally, the coverage behaviors of systems employing a large number of antenna arrays are discussed, as well as some implications on future mmWave cellular network designs.

Impact of atmospheric ionization by delayed radiation from highaltitude nuclear explosions on radio communication

In this study,we investigated the motion,shape,and delayed radiation intensity of a radioactive cloud by establishing a volume-source model of delayed radiation after high-altitude nuclear explosions.Then,the spatial distribution of electron number density at different moments on the north side of the explosion point generated by delayed γ-rays and delayed β-rays from the radioactive cloud under the influence of the geomagnetic field was calculated by solving chemical reaction kinetics equations.The impact of radio communication in the different frequency bands on the process of atmospheric ionization was also studied.The numerical results of the high-altitude nuclear explosion (120 km high and with a 1 megaton equivalent at 40°N latitude) indicated that the peak of electron number density ionized delayed γ-rays is located at a height of approximately 100 km and that of electron number density ionized delayed β-rays is about 90 km high.After 1 min of explosion,the radio communication in the medium frequency (MF) and high-frequency (HF)bands was completely interrupted,and the energy attenuation of the radio wave in the very high-frequency (VHF)band was extremely high.Five minutes later,the VHF radio communication was basically restored,but the energy attenuation in the HF band was still high.After 30 min,theVHF radio communication returned to normal,but its influence on the HF and MF radio communication continued.

Simulation of Radio Path Strength for Multipath Propagation in Land Mobile Communications

Based on the characteristics of the radio propagation in land mobile communications environment, a theoretical model for the reflecting(scattering) number of each radio path is derived firstly. This model can be used to predict the variation of radio path strength, which is important for practical mobile communications engineering. Using this model, a method for simulating radio path strength is developed, with numerical results presented.

Low Altitude Satellite Constellation for Futuristic Aerial-Ground Communications

This paper discusses the significance and prospects of low altitude small satellite aerial vehicles to ensure smooth aerial-ground communications for next-generation broadband networks.To achieve the generic goals of fifthgeneration and beyondwireless networks,the existing aerial network architecture needs to be revisited.The detailed architecture of low altitude aerial networks and the challenges in resource management have been illustrated in this paper.Moreover,we have studied the coordination between promising communication technologies and low altitude aerial networks to provide robust network coverage.We talk about the techniques that can ensure userfriendly control and monitoring of the low altitude aerial networks to bring forth wireless broadband connectivity to a new dimension.In the end,we highlight the future research directions of aerial-ground communications in terms of access technologies,machine learning,compressed sensing,and quantum communications.

Cooperative Communication and Cognitive Radio(3)

Cooperative communication and cognitive radio have become hot topics in recent research of communication networks, attracting a widespread attention. Cooperative communication technique can enhance the transmission capacity of a communication system, while cognitive radio technique can improve the spectrum utilization ratio. As a result, the combination of the two techniques will have a significant impact on the future wireless mobile communication system. This lecture comes in four parts. This part introduces the key technologies for cooperative communications, and the basic concept and key technologies of Cognitive Radio (CR).

Power Allocation for Cooperative Communications in Non-Orthogonal Cognitive Radio Vehicular Ad-Hoc Networks

To achieve the better system performance for cooperative communication in non-orthogonal cognitive radio vehicular adhoc networks(CR-VANETs),this paper investigates the power allocation considering the interference to the main system in a controllable range.We propose a three-slot one-way vehicle system model where the mobile vehicle nodes complete information interaction with the assistance of other independent nodes by borrowing the unused radio spectrum with the primary networks.The end-to-end SNR relationship in overlay and underlay cognitive communication system mode are analyzed by using two forwarding protocol,namely,decode-and-forward(DF)protocol and amplify-and-forward(AF)protocol,respectively.The system outage probability is derived and the optimal power allocation factor is obtained via seeking the minimum value of the approximation of system outage probability.The analytical results have been confirmed by means of Monte Carlo simulations.Simulation results show that the proposed system performance in terms of outage under the optimal power allocation is superior to that under the average power allocation,and is also better than that under other power allocation systems.

Power Versus Bandwidth Efficiency in Wireless Communications:from Economic Sustainability to Green Radio

We carry out a comprehensive analysis of a range of wireless network efficiency considerations. Firstly, we explore the properties and the implications of the power-versus bandwidth-efficiency criteria. Secondly, we perform a detailed top-down analysis of a typical commercial wireless network, which emphasizes the inherent differences between the aforementioned two efficiency metrics, while demonstrating that the appropriate choice of the network optimization criterion can have a profound effect on the overall network performance. Finally, we address the issue of resource management and its impact on the definition of the overall system efficiency. Our results suggest that no substantial area spectral efficiency gains beyond those exhibited by the 2G cellular technol- ogy may be economically achieved, and hence, no significant economic gains may be realized by simply increasing the bps/Hz bandwidth efficiency. In contrast, manifold utility and throughput gains as well as substantial Quality of Service enhancements may be attained by the appropriate combination of improved power efficiency, bandwidth expansion as well as the appropriate evolution of the networking paradigm.

Cooperative Communication and Cognitive Radio (1)

Cooperative communication and cognitive radio have become hot topics in recent researches of communication networks,attracting a widespread attention.Cooperative communication technique can enhance the transmission capacity of a communication system,while cognitive radio technique can improve the spectrum utilization ratio.As a result,the combination of the two techniques will have significant impact on the future wireless mobile communication system.This lecture comes in four parts.This part introduces the history of cooperative communication as well as several cooperation schemes.

Cooperative Communication and Cognitive Radio (2)

Cooperative communication and cognitive radio have become hot topics in recent research of communication networks, attracting a widespread attention. Cooperative communication technique can enhance the transmission capacity of a communication system, while cognitive radio technique can improve the spectrum utilization ratio. As a result, the combination of the two techniques will have a significant impact on the future wireless mobile communication system. This lecture comes in four parts. This part analyzes the impacts of cooperative communication technology on modern wireless communication systems.

Cooperative Communication and Cognitive Radio (4)

Cooperative communication and cognitive radio have become hot topics in recent research of communication networks, attracting a widespread attention. Cooperative communication technique can enhance the transmission capacity of a communication system, while cognitive radio technique can improve the spectrum utilization ratio. As a result, the combination of the two techniques will have a significant impact on the future wireless mobile communication system. This lecture comes in four parts. This part analyzes the impacts of cooperative communication technology on modern wireless communication systems.

Radio resource management in energy harvesting cooperative cognitive UAV assisted IoT networks:A multi-objective approach

Cooperative communication through energy harvested relays in Cognitive Internet of Things(CIoT)has been envisioned as a promising solution to support massive connectivity of Cognitive Radio(CR)based IoT devices and to achieve maximal energy and spectral efficiency in upcoming wireless systems.In this work,a cooperative CIoT system is contemplated,in which a source acts as a satellite,communicating with multiple CIoT devices over numerous relays.Unmanned Aerial Vehicles(UAVs)are used as relays,which are equipped with onboard Energy Harvesting(EH)facility.We adopted a Power Splitting(PS)method for EH at relays,which are harvested from the Radio frequency(RF)signals.In conjunction with this,the Decode and Forward(DF)relaying strategy is used at UAV relays to transmit the messages from the satellite source to the CIoT devices.We developed a Multi-Objective Optimization(MOO)framework for joint optimization of source power allocation,CIoT device selection,UAV relay assignment,and PS ratio determination.We formulated three objectives:maximizing the sum rate and the number of admitted CIoT in the network and minimizing the carbon dioxide emission.The MOO formulation is a Mixed-Integer Non-Linear Programming(MINLP)problem,which is challenging to solve.To address the joint optimization problem for an epsilon optimal solution,an Outer Approximation Algorithm(OAA)is proposed with reduced complexity.The simulation results show that the proposed OAA is superior in terms of CIoT device selection and network utility maximization when compared to those obtained using the Nonlinear Optimization with Mesh Adaptive Direct-search(NOMAD)algorithm.

Transmission Restriction and Suppression of Radio over Fiber Communication System

This article puts forward long-reach and high-performance Radio over Fiber (RoF) Communication Systems.Two schemes are proposed for solving the transmission restriction factors of the RoF system and verifies the system through experiments.One scheme is 40GHz RoF system based on external modulation with odd-order sideband-suppressed.The other one is 40GHz Optical Frequency Division Multiplexing (OFDM) system based on Optical Carrier-Suppression (OCS),external modulation.Both theory and experiment prove that the two systems allow not only low chromatic dispersion,but also long-distance transmission.

Improving the Reliability of Unmanned Aircraft System Wireless Communications through Cognitive Radio Technology

Unmanned Aircraft System networks are a special type of networks where high speeds of the nodes, long distances and radio spectrum scarcity pose a number of challenges. In these networks, the strength of the transmitted/received signals varies due to jamming, multipath propagation, and the changing distance among nodes. High speeds cause another problem, Doppler Effect, which produces a shifting of the central frequency of the signal at the receiver. In this paper we discuss a modular system based on cognitive to enhance the reliability of UAS networks.

Confessional Radio Stations and Social Communication for Political Change in Africa

The role of religious groups in the political field has arised in Africa in 1990s and despite being less visible it is still active. In fact, this is the climax of a very old process in Africa. Religion always participates in politics and vice versa. It is therefore not surprising that religious groups take into account political preoccupations in their communication processes. Sometimes they get involved in political debates, particularly when the questions reveal very important choices for the Nation, as it was the case in 1960s and 1990s. But mostly, they get involved in the social field which is, for them, the key to have one foot in political field. However, beyond these considerations, this paper intends to show how the use of media by religious institutions is closely related to their understanding of the relationship between the religion as an institution, and the society.

HF Communications: Past, Present, and Future

High frequency(HF) communication, commonly covering frequency range between 3 and 30 MHz, is an important wireless communication paradigm to offer over-thehorizon or even global communications with ranges up to thousands of kilometers via skywave propagation with ionospheric refraction. It has widespread applications in fields such as emergency communications in disaster areas, remote communications with aircrafts or ships and non-light-of-the-sight military operations. This tutorial article overviews the history of HF communication, demystifies the recent advances, and provides a preview of the next few years, which the authors believe will see fruitful outputs towards wideband, intelligent and integrated HF communications. Specifically, we first present brief preliminaries on the unique features of HF communications to facilitate general readers in the communication community. Then, we provide a historical review to show the technical evolution on the three generations of HF communication systems. Further, we highlight the key challenges and research directions. We hope that this article will stimulate more interests in addressing the technical challenges on the research and development of future HF radio communication systems.

An Overview of Wireless Communication Technology Using Deep Learning

with the development of 5G,the future wireless communication network tends to be more and more intelligent.In the face of new service de-mands of communication in the future such as super-heterogeneous network,multiple communication sce-narios,large number of antenna elements and large bandwidth,new theories and technologies of intelli-gent communication have been widely studied,among which Deep Learning(DL)is a powerful technology in artificial intelligence(AI).It can be trained to con-tinuously learn to update the optimal parameters.This paper reviews the latest research progress of DL in in-telligent communication,and emphatically introduces five scenarios including Cognitive Radio(CR),Edge Computing(EC),Channel Measurement(CM),End to end Encoder/Decoder(EED)and Visible Light Com-munication(VLC).The prospect and challenges of further research and development in the future are also discussed.

New Optimal Power Allocation for Bidirectional Communications in Cognitive Relay Network Using Analog Network Coding

Cognitive radio and cooperative communication can greatly improve the spectrum efficiency in wireless communications.We study a cognitive radio network where two secondary source terminals exchange their information with the assistance of a relay node under interference power constraints.In order to enhance the transmit rate and maintain fairness between two source terminals,a practical 2-phase analog network coding protocol is adopted and its optimal power allocation algorithm is proposed.Numerical results verify the superiority of the proposed algorithm over the conventional direct transmission protocol and 4-phase amplify-and-forward relay protocol.

Relay-Assisted Cooperative Communication Networks

To facilitate the demand for a higher spectrum and power efficiency arising from the next generation mobile communication system, the introduction of relay-aided cooperative communication into the existing cellular infrastructure is considered as the most practical improvement under high rate and coverage. In comparison with the legacy cellular network, relay-aided cooperative communication network enjoys relative advantages over coverage efficiency, operation cost and transmission capacity. Transmission in relay-aided cooperative system falls into three types: the three-terminal transmission model, two-hop multi-relay parallel transmission model, and multi-hop multi-relay transmission model. For the extensive perspective of relay-aided cooperative communication in application, a profound research has been carried out in communication standards such as Worldwide Interoperability for Microwave Access (WiMAX) and Wireless World Initiative New Radio (WINNER).