In the field of maritime surveillance, the global navigation satellite system (GNSS)-based passive radar has proven its potential for moving target detection (MTD), localization, and velocity estimation. The next stage is to investigate the possibility of obtaining the radar image of the moving ship for target recognition. However, the limited signal power budget of GNSS prevents the conventional inverse synthetic aperture radar technique that is based on target rotational motion and short observation time for GNSS-based passive radar imaging moving target. In this article, a two-stage imaging processing method relying on the target translational motion over a long observation time is proposed. The first stage confirms the presence of the target by a long-time MTD processing technique. In the second stage, based on the analysis of the Doppler history of the target signal in the slow-time domain, short-time Fourier transform and modified random sample consensus are combined to robustly estimate target velocity with reduced computation complexity. To obtain the focused bistatic image, azimuth compression is conducted by using the estimated target velocity. Finally, an image fusion operation is implemented to combine the bistatic images achievable from multiple satellites so that a multistatic image with high quality can be created. The effectiveness of the proposed method is confirmed by the real experimental results of three cargo ships illuminated by several satellites.

Abstract In this article, a relaying network with simultaneous wireless information and power transfer (SWIPT) is considered, where the relaying nodes are energy‐constrained. The relaying nodes rely on energy harvesting (EH) technique for energy supply and they use different directive transmitters for information transmission and energy transfer, respectively, to enhance the SWIPT relaying performance. A novel discrete‐time‐switch and power‐split (DTS‐PS) based energy harvesting mixture transmission (EH‐MT) protocol for each EH decode and forwarding (DF) relaying node is proposed. The expressions for the average information rate and the energy transfer power are derived analytically and verified by simulations. An optimization function is formulated, and the optimal parameters are obtained analytically and verified by simulation.

Abstract The development of satellite communication (SATCOM) puts forward demanding requirements for the modulation methods' spectral efficiency (SE) which is mainly subject to the pulse shaping and the utilisation of signal space. To date, there has rare consideration on the modification of high order phase shift keying (HOPSK) to gain higher SE in this literature. In this work, shaped offset 8PSK (SO8PSK) is developed which splits 8PSK bit transmission into three offset paths and then loads the shaping pulse onto them. The obtained modulation with continuous constrained phase and constant envelope is shown to increase the SE compared to 8PSK by about 43% and is applicable for the nonlinear and band‐limited SATCOM environment. To address the HOPSK inherent complexity, a simplified receiver is provided to reduce about two‐third matched filters. Additionally, the iterative encoding of SO8PSK is presented and it is used as the inner code of serial concatenated coding (SCC) . This modification method can be seen as a starting point to the better use of HOPSK for SATCOM.

In this study, the performance of downlink simultaneous wireless information and power transfer (SWIPT) networks over Nakagami‐ m fading is analysed. The SWIPT network is modelled as a two‐tier heterogeneous network, where one tier is the information transmission network and the other is the power transmission network. The seamless integration enables both data and energy to be transferred from access points to the users. Using the stochastic geometry theory, the expressions for outage probability at the information receiver are derived in decoupled and integrated SWIPT networks. Also, the average harvested energy at the power receiver is derived assuming a non‐linear energy harvesting model. Simulation results validate the analytical expressions and the impacts of various system parameters on the SWITP performance are investigated.

Joint radar-communication designs are exploited in applications where radar and communications systems share the same frequency band or when both radar sensing and information communication functions are required in the same system. Finding a waveform that is suitable for both radar and communication is challenging due to the difference between radar and communication operations. In this paper, we propose a new method of designing dual-functional waveforms for both radar and communication using signals from multiplexed communications users. Specifically, signals from different communications users multiplexed in the time, code or frequency domains across different data bits are linearly combined to generate an overall radar waveform. Three typical radar waveforms are considered. The coefficients of the linear combination are optimized to minimize the mean squared error with or without a constraint on the signal-to-noise ratio (SNR) for the communications signals. Numerical results show that the optimization without SNR constraint can almost perfectly approximate the radar waveform in all the cases considered, giving good dual-functional waveforms for both radar and communication. Also, among different multiplexing techniques, time division multiple access is the best option to approximate the radar waveform, followed by code division multiple access and orthogonal frequency division multiple access.

Idle nodes are used in cooperative communications to achieve diversity gain or coverage extension. Energy harvesting (EH) allows cooperative communications to be less dependent on batteries. In this study, the performance of EH decode‐and‐forward relaying is analysed in terms of achievable rate for non‐ideal relaying nodes whose circuit power cannot be neglected. Two time switching protocols, continuous time switching and discrete time switching, are studied. The analytical expressions for the achievable rate are derived and optimised. Numerical results show the validity of the analytical expressions and determine the influence of the circuit power consumption.

Wireless powered communications allow sustainable operations of low‐power applications by supplying wireless power remotely. In this study, the performance of wireless powered communications is evaluated in terms of achievable rate and bit error rate (BER), for applications where the downlink and the uplink are correlated, in contrast to previous works that assume independent uplink and downlink. Semi‐closed expressions for the achievable rate and series expressions for the BER are derived in Nakagami m fading channels, based on which the effect of link correlation is examined. Numerical results show that the link correlation has a significant impact on the achievable rate. Consequently, the optimum system parameter for correlated links is very different from that for independent links, showing the usefulness of the authors' results. Also, the link correlation has a noticeable effect on the BER, depending on the system parameters considered.

Idle nodes are used in cooperative communication to achieve performance gains. Energy harvesting (EH) technology makes cooperative communication less dependent on batteries. In this study, the performance of EH amplify‐and‐forward relaying is analysed by considering the throughput for Rician fading channels and non‐ideal relaying nodes, compared with previous works that focused on Rayleigh fading channels with ideal relaying nodes. The authors consider discrete time EH protocol and continuous time EH protocol. In addition, they derive the analytical expressions for the average throughput. Numerical results are presented to show the good performance of the system in Rician fading channels and the satisfactory performance while using the non‐ideal relaying node by examining various system parameters using the analytical expressions.

The effect of spectrum sensing errors on the performance of bit loading algorithms in cognitive radio systems based on orthogonal frequency division multiplexing is studied in terms of throughput and average bit error rate. Different spectrum sensing parameters and data transmission parameters are examined to evaluate the performance degradation. Numerical results show that the sensing errors cause significant performance degradation and that, when the signal‐to‐noise ratio is high, the inter‐carrier interferences caused by carrier frequency offset are dominant in the performance degradation.

A novel analytical framework for evaluating the statistics of the products of independent random variables is proposed. Compared with other methods which use either an infinite series or a special function, the new method provides simple and efficient closed-form approximations in terms of elementary functions, such as powers and exponentials, and therefore, is very easy to implement. The accuracy of the new approximation is examined. Numerical results show that it is quite accurate in most regions of interest. As an application, these new approximations are used in wireless communications theory to derive novel closed-form expressions for the outage probability of cascaded fading channels. Numerical examples show that the newly derived closed-form expressions provide insights on the behavior of important performance metrics as the outage probability, the bit error rate and the channel capacity.