Bushfires across remote areas can easily spread regionally due to extreme weather conditions. Unmanned aerial vehicles (UAVs) can play a significant role in postdisaster assessment as they have low-cost and flexible deployment characteristics. Detecting bushfires in their initial phase is important to save the inhabitants, infrastructure, and ecosystem. In the context of smart cities, we have applied state-of-the-art deep learning (DL) algorithms to detect and differentiate between fire and no-fire regions. However, certain factors like reachability to forest fires and timely detection of the region of interest (ROI) are quite challenging. Therefore, we incorporate UAVs for capturing the real-time images and process these images into our proposed YOLOv5-s (you only look once-small) model that helps achieve fast and accurate detection of the affected region. We have proposed a lightweight single-stage network with an improved bottleneck cross-stage partial (CSP) module and pyramid attention network (PAN) layers to enhance precise feature extraction and reduce computation time in fire detection. Notably, the HardSwish activation function outperformed ReLU in a specific fire detection scenario. Based on the provided dataset, simulation results demonstrate that the optimized model can effectively detect and differentiate between fire and nonfire regions, which may be challenging to discern with the naked eye. The results indicate that the proposed model surpasses existing models, achieving an accuracy of 97.4%, a low false-positive rate of 1.258%, and nonmaximum suppression (NMS) of 3 ms. Our model can provide real-time applications for fire and rescue relief teams.

The rapid expansion of Internet of Vehicles (IoV) networks has facilitated high throughput and reliable vehicular communications. Mobile vehicular networks face the challenges: diversification of network equipment, user mobility, and the broadcast nature of wireless channels, so physical layer security modeling of IoV communication systems has become important. The complexity of wireless communication channels makes real-time prediction of secrecy performance challenging. This paper presents an analysis of secrecy performance for mobile vehicular networks. To ensure data secure transmission, we have employed the decode-and-forward (DF) relaying scheme. The signal-to-noise ratio (SNR) of the effective end-to-end link is employed to obtain the mathematical expression results, which can evaluate the secrecy performance. The theoretical secrecy performance is confirmed via simulation. Then, we design a dense-inception convolution neural network (DI-CNN) model, and propose a DI-CNN-based intelligent prediction algorithm.Transformer, ShuffleNetV2, RegNet and YOLOv5 methods are employed to analyze the performance of DI-CNN algorithm. It is shown that the DI-CNN approach has a prediction accuracy that is 48.8% better than Transformer.

Cell-free wireless communications is a new paradigm within the future 6G networks towards implementation of the Internet of intelligence with connected people and things. In a cell-free network, a large number of distributed access points are connected to a central processing unit and serve a smaller number of users over the same time-frequency resources. The system has shown great potential in improving network performance in some perspectives compared to the co-located and conventional small-cell systems. The next-generation Internet-of-Things systems could be dispersed over large areas under a cell-free network setting. This has given rise to security concerns stemming from the exposure of wireless channels and the exponential growth of connected devices. In this talk, a novel covert downlink transmission scheme is presented that jointly optimizes beamforming and artificial noise vectors to obscure critical transmissions at an eavesdropper in CF IoT Networks.

A corrugated horn antenna is proposed for the unmanned aerial vehicle energy transmitter (UAV-ET) application. Firstly, the proposed antenna can be manufactured using polylactic acid (PLA) 3-dimensional (3-D) printing with copper conductive paint coating, which is lightweight and cost-effective compared to metal 3-D printing. Secondly, the results confirm that the sidelobe level of the antenna is below -30 dB, and radiation efficiency is above 99 % throughout the operating frequency band. Also, the proposed antenna increases the UAV-ET wireless power transfer (WPT) time by 47.5 % and 4.5 % compared to UAV-ETs equipped with a dipole array and a slotted waveguide array respectively. Furthermore, the mass production of the antenna is easy because of its design simplicity which is highly desirable for the large swarm of UAV-ETs to increase the wireless power transfer coverage for charging ground sensors.

Understanding human behaviours is critical to improving operation efficiency, individual and organisational productivity, public health management, and quality of life in cities. The proliferation of sensors and Internet of Things leads to new opportunities and challenges for human behaviour modelling and forecasting behavioural patterns at scale. Annotating behaviours of interest is expensive and often infeasible. This demands new ways for modelling behaviours at scale, moving away from fully-supervised learning approaches. Recent Generative AI approaches and Large Language Models has become a compelling choice for modelling mobility behaviours, especially in cases when training data is limited. I will present our self-supervised learning (SSL) approaches for multimodal sensor data, with different applications as examples, including human behaviour recognition and traffic flow forecasting. I will also talk about how we handle data heterogeneity and fusion of heterogenous time-series towards robust representation. I will also present a new versatile paradigm, leveraging Large Language Models (LLMs) for time-series forecasting, including for mobility and energy domain, using natural language prompts.

A ground base station (GBS) antenna array system (AAS) geometry and feed technique are proposed for 360° azimuth beam scan, elevation beam scan, azimuth beam-width control, elevation beam-width control, and in existing AASs these four capabilities do not coexist. First, the results confirm that the number of active radio-frequency (RF) switches in the proposed AAS feed network is reduced by more than 99%, and the AAS achieves a power consumption reduction of up to 50% without fully connected (FC) architecture and 35% with FC architecture compared to the existing AAS. Also, an independent GBS AAS azimuth and elevation plane beam-width control can be achieved from 65° to 0.01° which makes it suitable for GBS-assisted wireless back-hauling plus wireless charging of unmanned aerial vehicle base stations (UAV-BSs), dynamic GBS sectorisation order control, and millimeter wave beam tracking. Also, a parallel concurrent UAV-BS battery charging configuration with power source swap capability is proposed to charge UAV-BS using the GBS back-haul and onboard power amplifier (PA) system as the power sources. The results show that the proposed charging configuration improves hovering time by 180.7% compared to the existing onboard PA system configuration for battery charging. Furthermore, the proposed charging configuration can recharge the battery of the inactive state UAV-BS to increase the state of charge of two 16-Ah batteries to 80% in 180.13 min, and UAV-BS’s inactive state charging was not proposed in the existing onboard PA system configuration for UAV-BS’s battery charging.

This paper offers unified modelling for opportunistic-relay outdatedness using the joint distribution of bivariate exponential-correlated generalised-Rician fading. Line-of-sight power and larger-than-two degrees of freedom under independently-and-identically-distributed Rayleigh fading environments employing maximal ratio combining (MRC) are considered. Unavoidable infinite summations are employed, which are shown to fast-converge for a finite number of terms. Ergodic channel capacity is employed for performance assessment. Thorough comparisons between performance of selection combining and MRC are also given. Monte Carlo simulation is employed to validate this work.

The initiation of fifth-generation (5G) wireless networks has been one of the latest innovations that the world has seen in recent years, which has also formed the foundation for the upcoming sixth-generation (6G) and beyond networks. The demand for high reliability with minimal delay of Internet of Things (IoT) applications has led to transmissions of short packets, which give rise to the proposal of ultra reliable and low-latency communications (URLLC). At a glance, the simultaneous demand for both reliability and minimal latency appears to be contradicting. However, by considering the impact of finite blocklength (FBL) regimes, the formulation of URLLC can be theoretically established under a wide range of practical scenarios such as severe fading, imperfect channel state information (iCSI), line-of-sight (LoS) fading and channel correlation. It has been noted that LoS, channel correlation and iCSI conditions have received interests among the community and their formulation illustrates practicality of theoretical signal processing research. Diversity has been deployed to combat fading, strengthen reliability and simultaneously reduce latency. Under specific environment, significant research has been developed and formulated to further the application of URLLC. The deployment of short packets however challenges Shannon's classical theory and opens a new research direction, which has attracted wide attention and research efforts around the world. Further, URLLC fundamentals can also be applied to intelligent reflective surface techniques, which clearly shows their applicability and usefulness. Myriads of work have been published and much more are coming to showcase the practicality of URLLC techniques and to explore its immense potential. This Special Issue (SI) has been formed to reflect on the latest developments on URLLC amid the fast-paced initiations and ideas. Through rigorous peer review processes, the selected papers have been chosen based on their high standard and diverse topics related to URLLC. The first paper by Q. Huang et al. examines the impact of cyclic redundancy check and rateless characteristic of cascading analogue fountain code under URLLC platform. The advanced inclusion of URLLC to 5G and 6G is also addressed and outlined, which makes this work timely. Cross verification and comparisons have been performed to show the effectiveness of their proposed method. Aiming to minimise end-to-end latency, the next paper of the SI treats the application of unmanned aerial vehicles (UAVs) under an URLLC platform using a Digital Twin (DT) approach. Edge computing is deployed to ensure that latency can be reduced to its minimum, and then optimisation is extra performed so that satisfactory results can be obtained. This work brings direct benefit to industry automation by exploiting K-mean algorithms for optimisation. Task offloading has been specifically considered to test the efficiency of the propped DT framework under URLLC platform. The third paper is dedicated to vehicular communications and the effectiveness of energy harvesting roadside units. This paper begins by proposing an attention-based spatial-temporal graph convolutional network to estimate vehicular communication load. A simulated data set was created to validate the proposed work, which potentially has commercialisation by lowering the cost of EHU-RSs. The fourth paper addresses one of the most fundamental problems of URLLC, which is joint power and blocklength optimisation for reflective intelligent surfaces (RIS) under FBL regimes using time division multiple access techniques. The effectiveness of the RIS under the FBL regimes has been clearly shown. Summary: This Special Issue has given a glimpse of URLLC capability from theoretical point of view to its wide applications, which involve UAVs and other smart devices. The prospect of URLLC is evolving into its advanced version in future wireless networks. The functionality of URLLC and other techniques is to ultimately serve the end user to strengthen convenience, practicality and technology advancement. From this point of view, the current URLLC framework has sufficiently ticked certain boxes. The Special Issue Editors would like to thank the Editor in Chief Professor James Hopgood, the Managing Editor Emily Summerbell and the editorial office for their constant support without which this Special Issue would not be possible. Research data are not shared. Khoa N. Le received his Ph.D. in October 2002 from Monash University, Melbourne, Australia. From April 2003 to June 2009, he was a Lecturer at Griffith University, Gold Coast campus, Griffith School of Engineering. From January to July 2008, he was a visiting professor at Intelligence Signal Processing Laboratory, Korea University, Seoul, Korea. From January 2009 to February 2009, he was a visiting professor at the Wireless Communication Centre, University Technology Malaysia, Johor Bahru, Malaysia. He is currently Associate Professor and Director of Academic Programme, Undergraduate, Electrical Engineering, School of Engineering, Design and Built Environment, Kingswood, Western Sydney University. His research interests are in wireless communications theory with applications to physical layer security and URLLC. Dr. Le has been Editor for IEEE Transactions on Vehicular Technology, IEEE Wireless Communication Magazine, and he is currently Deputy Editor In Chief of IET Signal Processing. He was listed in World's Top 2% scientists for 2021 and Bayu Chair Professor, Chongqing University of Science and Technology, Chongqing, China, 2020–2022. Derrick Wing Kwan Ng (S′06-M′12-SM′17-F′21) received a bachelor's degree with first-class honours and a Master of Philosophy (M.Phil.) degree in electronic engineering from the Hong Kong University of Science and Technology (HKUST) in 2006 and 2008, respectively. He received his Ph.D. degree from the University of British Columbia (UBC) in Nov. 2012. He was a senior postdoctoral fellow at the Institute for Digital Communications, Friedrich-Alexander-University Erlangen-N\"urnberg (FAU), Germany. He is now working as a Scientia Associate Professor at the University of New South Wales, Sydney, Australia. His research interests include global optimization, physical layer security, IRS-assisted communication, UAV-assisted communication, wireless information and power transfer, and green (energy-efficient) wireless communications. Ng has been listed as a Highly Cited Researcher by Clarivate Analytics (Web of Science) since 2018. He received the Australian Research Council (ARC) Discovery Early Career Researcher Award 2017, the IEEE Communications Society Stephen O. Rice Prize 2022, the Best Paper Awards at the WCSP 2020, 2021, IEEE TCGCC Best Journal Paper Award 2018, INISCOM 2018, IEEE International Conference on Communications (ICC) 2018, 2021, IEEE International Conference on Computing, Networking and Communications (ICNC) 2016, IEEE Wireless Communications and Networking Conference (WCNC) 2012, the IEEE Global Telecommunication Conference (Globecom) 2011, 2021 and the IEEE Third International Conference on Communications and Networking in China 2008. He served as an editorial assistant to the Editor-in-Chief of the IEEE Transactions on Communications from Jan. 2012 to Dec. 2019. He is now serving as an editor for the IEEE Transactions on Communications, the IEEE Transactions on Wireless Communications, and an Associate Editor-in-Chief for the IEEE Open Journal of the Communications Society. Zhiguo Ding (S′03-M′05-F′20) received his B.Eng in Electrical Engineering from the Beijing University of Posts and Telecommunications in 2000, and the Ph.D degree in Electrical Engineering from Imperial College London in 2005. From Jul. 2005 to Apr. 2018, he was working in Queen's University Belfast, Imperial College, Newcastle University and Lancaster University. Since Apr. 2018, he has been with the University of Manchester as a Professor in Communications. From Oct. 2012 to Sept. 2022, he has also been an academic visitor in Princeton University. Ding’ research interests are B5G networks, machine learning, cooperative and energy harvesting networks and statistical signal processing. He is serving as an Area Editor for the IEEE Open Journal of the Communications Society, an Editor for IEEE Transactions on Vehicular Technology, and IEEE Communications Surveys & Tutorials, and was an Editor for IEEE Wireless Communication Letters, IEEE Transactions on Communications, IEEE Communication Letters from 2013 to 2016. He recently received the EU Marie Curie Fellowship 2012–2014, the Top IEEE TVT Editor 2017, IEEE Heinrich Hertz Award 2018, IEEE Jack Neubauer Memorial Award 2018, IEEE Best Signal Processing Letter Award 2018, Friedrich Wilhelm Bessel Research Award 2020, and Best Paper Award at IEEE ICCC-2021. He is a Fellow of the IEEE, a Distinguished Lecturer of IEEE ComSoc, and a Web of Science Highly Cited Researcher in two categories 2020.

In this article, different state-of-the-art metaheuristic algorithms are analyzed to incorporate the collision-free path-planning approach for UAVs in a disaster situation. The efficient path planning is used to identify the main cause of disaster like bushfires that are badly affecting the forest ecosystem throughout the globe. This novel approach is a first step toward a predisaster assessment and possibilities to save the survivors in minimal time. Different metaheuristic algorithms, such as PSO, GWO, WOA, BMO, and DGBCO, are compared for UAV path optimization capability. In order to test the robustness of our proposed model, four different scenarios are presented which include general environment, condense environment, maze environment, and dynamic environment. In each scenario, the obstacles are placed in such a way to increase the overall path complexity for a UAV to reach the destination. The exploration and exploitation groups working simultaneously in a dynamic environment make it effective for UAV path planning using the DGBCO algorithm. Based on the parameters selected, the DGBCO algorithm outperforms other algorithms and achieves 24.5% less transportation cost and 13.3% less computational time. Hence, DGBCO can be efficiently applied for UAV path-planning optimization in any of the aforementioned environments.

This letter studies physical layer security of an outdated channel-state-information (oCSI) decode-and-forward (DaF) opportunistic-relay (OR) network under equal-correlated (equ.c.) Rayleigh fading with maximal ratio combining (MRC) deployment. By assuming that relays operate under equ.c. Rayleigh fading and wiretapper-Destination operate under exponential-correlated (exp.c.) Rayleigh fading, this work (i) derives an MRC output (MRCO) distribution of multivariate equ.c. Rayleigh fading, (ii) derives an MRCO distribution of bivariate exp.c. Rayleigh fading under oCSI conditions, and (iii) expresses the secrecy outage probability (SOP) in closed form. By considering oCSI severity, channel correlation among cooperative DaF ORs, Destination, wiretapper, and MRC deployment, this work's practicality can be significantly improved. Detailed discussions are given, in which the impact of several important parameters on the SOP is discussed. Monte Carlo simulation is shown to match theoretical predictions.

A probability density function (pdf) of bivariate exponential-correlated (exp.c.) Rayleigh fading-the simplest under correlated fading-has chronically been employed to model decode-and-forward relay networks under outdated channel state information (CSI) conditions. !n addition to CSI outdatedness, CSI imperfection exists, however, their compound co-modelling-defined as acute imperfect CSI-outdated CSI- has not yet been performed in the existing literature. Using a joint pdf of trivariate exp.c. Nakagami-m fading-which is more advanced than the pdf of bivariate exp.c. Rayleigh fading-this article models acute imperfect CSI-outdated CSI, and examines its impact on relay networks. Selection combining (SC) is also employed to improve the practicality of this work. Using a pdf of bivariate exp.c. Nakagami-m fading, conditional pdfs of relay SNRs under acute-CSI severity are derived. Using the newlyderived conditional functions, pdfs of Rayleigh fading for SC deployment under acute imperfect CSI-outdated CSI severity are then obtained. Ergodic channel capacity, diversity gains, averageSNR gains, and outage probability are then computed to (a) obtain insight into the proposed findings, and (b) examine the impact of acute-CSI conditions on network performance. Existing results are employed for clarification purposes, and to show the advantage of the proposed work. Monte Carlo simulation is given, which matches theoretical predictions.

Using a well-known wiretap model, secrecy outage probability is computed under dual correlated Rician fading employing opportunistic relays. A signal-to-noise ratio distribution of dual correlated Rician fading is first obtained as a function of four nested infinite summations, which (i) converges for a finite number of terms, and (ii) is employed to compute secrecy outage probability for a passive wiretapper. Relationships among important parameters are elaborated and explained. Proof for infinite summation convergence is also given, which realises the practicality of this work. Simulation results are shown to match theoretical predictions.

Distributions of independent and identically distributed (i.i.d.) generalised-Rician fading including line- of-sight fading for colluded decode-and-forward (DF) opportunistic relays (ORs) employing maximal ratio combining under outdated channel state information (CSI) are reported in this paper. The new findings (i) generalise existing findings under i.i.d. Rayleigh fading employing selection combining, and (ii) advance theoretical developments for wireless DF-OR networks. Mathematical expressions for the ergodic channel capacity inner bounds are given to assess the effectiveness of system coherence, a transmit signal-to-noise ratio, the number of DF ORs, degrees of freedom, and line-of-sight power. Monte Carlo simulation results are also given under symbols, which match the proposed theoretical predictions.

Using an opportunistic transmission protocol in which users contend for transmission to a base station under equally-correlated generalised- Rician fading, new single-integral selection combiner output cumulative distribution functions of multivariate equally-correlated generalised- Rician fading for multiuser multiple-input- multiple-output systems, and even degrees of freedom with multiple transmit and receive antennas per user are obtained in this paper. Cross-verification is mathematically performed to validate the proposed findings. The new findings provide a useful mathematical framework to assess performance of wireless networks under equally- correlated generalised-Rician fading environments. The effectiveness of the new findings is exemplified by computing average bit error rates for the Binary Phase-Shift Keying scheme under equally-correlated generalised-Rician fading, and plotted against several important parameters. Simulation results are shown to exactly match numerical simulation. Detailed discussions are given.

Using an opportunistic transmission protocol in which users contend for transmission to a base station under equal‐correlated generalised‐Rician fading, new single‐integral selection combiner output cumulative distribution functions (cdfs) of multivariate equal‐correlated generalised‐Rician fading for multiuser multiple‐input multiple‐output systems, and even degrees of freedom with multiple transmit and receive antennas per user are obtained in this study. Corresponding infinite‐summation cdfs of multivariate equal‐correlated generalised‐Rician fading are obtained. Cross‐verification is mathematically performed to validate the proposed findings. The new findings provide a useful mathematical framework to assess performance of wireless networks under equal‐correlated generalised‐Rician fading environments. The effectiveness of the new findings is exemplified by computing average bit error rates for the binary phase‐shift keying scheme under equal‐correlated generalised‐Rician fading, and plotted against (i) a common average branch normalised signal‐to‐noise ratio, (ii) line‐of‐sight power, (iii) an even number of independently and identically distributed underlying Gaussian random variables, (iv) a total number of transmit antennas, and (v) a total number of receive antennas. Simulation results are shown to exactly match numerical simulation. Detailed discussions are given.

Distributions of colluding decode-and-forward (DF) opportunistic relays (ORs) employing maximal ratio combining under outdated channel state information (CSI) and independent and identically distributed (i.i.d.) generalized-Rician fading, including line-of-sight (LoS) fading, are fundamentally reported in this paper for the first time. DF-OR collusion can be initiated by employing a broadcast protocol at the destination. The new findings: 1) generalize existing findings under i.i.d. Rayleigh fading employing selection combining and 2) advance theoretical developments for wireless DF-OR networks. Mathematical expressions for: 1) average bit-error-rate of common modulation schemes and 2) ergodic channel capacity inner bounds are given in the compact infinite-summation form, which can be employed to assess the effectiveness of system coherence, a transmit signal-to-noise ratio, the number of DF ORs, degrees of freedom, and LoS power. Because of the LoS component under generalized-Rician fading, infinite summations must be mathematically employed, which are shown to fast converge for a finite number of terms, effectively realizing their practicality. Monte Carlo simulation results are also given under symbols, which match the proposed theoretical predictions.

This paper gives a novel perspective on physical layer security (PLS) and end-to-end (e2e) analysis under dual correlated Nakagami-m fading, and outdated channel state information, by employing 1) decode-and-forward opportunistic relays, and 2) an adaptive encoder with ON/OFF transmission. Assuming an infinite relay buffer size, two new sets of independent results for 1) non-integer fading parameter m, mathematically employing infinite summations, and 2) integer m, mathematically employing finite summations, are obtained. The adaptive encoder deployment improves transmission quality, and simultaneously enhances secrecy performance. The proposed e2e analysis coherently links secrecy, and e2e system performance for the first time under dual correlated Nakagami-m fading. Findings for wireless secrecy, and e2e system analysis with the non-integer fading parameter m offer an extra dimension to existing PLS literature, which has chronically been valid for only integer m. Convergence for infinite summations is achieved for a finite number of terms, realising the practicality of the proposed findings. Monte Carlo simulation successfully validates the new findings for non-integer m, and an asymptotic analysis under several specific scenarios is also presented.

Under dual correlated Rician fading and unknown wiretapper's channel state information, secrecy outage probability (SOP) is theoretically studied for the first time in this paper. The signal-to-noise ratio probability density function of bivariate correlated Rician fading is derived. Using an infinite-summation form for the modified Bessel functions of the first kind, compact expressions for the SOP are obtained. The new findings generalise the current findings under dual correlated Rayleigh fading, and advance theoretical developments for wireless secrecy under correlated fading. Simulation results are given, which are shown to match theoretical prediction. Detailed discussions are also given.

In this study, the authors consider a two‐way amplify‐and‐forward communication system over Nakagami‐ m fading environments, where an intermediate relay node harvests energy from its surrounding radio frequency environment using an energy harvesting technique. They propose a novel derivation approach to obtain exact expressions for user outage probability, system outage probability, and upper bound on system ergodic capacity per unit bandwidth over Nakagami‐ m fading channels. Monte–Carlo simulation results under Matlab software packages match the proposed analytical analyses confirming the correctness of the proposed derivation approach and the advantage of the system under consideration.

Wireless secrecy under dual correlated Rician fading environments is theoretically studied for correlated source-destination and source-wiretapper channels. Without considering wiretapper active jamming capability, expressions for: 1) the ergodic secrecy capacity when the wiretapper is active and 2) secrecy outage probability when the wiretapper is passive are obtained. To further improve system security, new secrecy analyses employing an adaptive encoder with ON/OFF transmission are also given. The new findings exactly reduce to existing findings under dual correlated Rayleigh fading and advance theoretical developments for wireless secrecy under dual correlated Rician fading. Monte Carlo simulation results are given, which match theoretical predictions. Under wireless secrecy context, the disadvantage of line-of-sight (LoS) power and channel correlation is evidently shown, revealing the non-usefulness of LoS power and establishing a tradeoff between the transmission security and the transmission success. Benefits of a high-average transmit signal-to-noise ratio are discussed.

Single-integral expressions for cumulative distribution functions of multivariate correlated Rayleigh and Rician fading are studied. Mathematical mistakes in the literature are identified and corrected. Corrections are cross-verified against well-known findings in the literature, which can be employed to advance further theoretical developments for correlated fading.

The well-known paper by Chen and Tellambura [1] has received great attention over the years and has formed important foundation for continuing research on multivariate cdfs in c.i.d. fading environments such as Rayleigh, Rician and Nakagami-m employing SC. However, it appears that the infinite-summation form cdfs in c.i.d. Rayleigh, Rician and Nakagami-m employing SC given in [1, (26)], [1, (28)] and [1, (29)] respectively are incorrect.

Gaussian and hyperbolic angle-of-arrival probability density functions are used to derive channel capacity of orthogonal frequency division multiplexing transmission employing diversity techniques and adaptive policies in cellular wireless fading environments. The intercarrier interference ICI power is quantified and given as a function of Doppler shift fd, symbol duration Ts, frequency correction i¾? and propagation ratio i¾?. Two scattering distributions, which have been shown to closely fit experimental empirical data, are examined in this paper: i Gaussian and ii hyperbolic. A new signal-to-interference-and-noise ratio probability density function is derived as a function of the ICI power using diversity techniques and adaptive policies. From that, effects of fdTs, i¾? and i¾? on channel capacity can be discussed. The main contribution of this work is to model ICI as a function of fd and symbol duration Ts. Two diversity techniques are considered: i maximal ratio combining and ii selective combining. Three adaptive policies are studied: i optimal rate adaptation, ii optimal rate and power adaptation and iii channel inversion with fixed rate. Closed-form expressions and bounds on various channel capacity with orthogonal frequency division multiplexing transmission under different scenarios are derived. Copyright © 2012 John Wiley & Sons, Ltd.

The downlink throughput of opportunistic‐feedback multiuser wireless systems with capture effects employing maximal ratio transmission (MRT) in a Rayleigh fading environment is studied. To the best of the authors’ knowledge, MRT has not been employed to improve multiuser system throughput with capture effects. Employing MRT means that the channel fading gains between the base station (BS) and users are a chi‐square distribution with 2 L degrees of freedom, where L is the diversity order, as opposed to Rayleigh distribution which has been examined in detail in the literature. Thus, the main challenge is to obtain a new and compact channel capacity expression for the system in which the roles of BS and users are reversed to make it practically sound. The new downlink throughput expression is derived as a function of L , fading‐gain threshold η , capture ratio z and other parameters. For large η , the capture effects are not as effective as when η is small. Effects of the capture ratio z on system throughput are also obtained. The new findings are validated using available results in the open literature.

ABSTRACT This paper derives the capacity of a fading channel with orthogonal frequency division multiplexing transmission employing diversity techniques and adaptive policies in Rayleigh fading environments. The effects of Doppler shift fd on channel capacity are analysed. The main contribution of this work is to model intercarrier interference as a function of fd and symbol duration Ts. Two diversity techniques are considered (i) maximal ratio combining (MRC) and (ii) selective combining (SC). Three adaptive policies are combined with MRC and SC to estimate the following channel capacity: (i) optimal rate adaptive; (ii) optimal power and rate adaptive; and (iii) channel inversion with fixed rate adaptive. Closed‐form expressions and bounds on channel capacity employing different diversity techniques are derived. Simulation results are given. Copyright © 2011 John Wiley & Sons, Ltd.

ABSTRACT This paper derives capacity of a fading channel with orthogonal frequency division multiplexing (OFDM) transmission employing diversity techniques and adaptive policies involving (i) power and rate, (ii) optimal rate and (iii) channel inversion with fixed rate. Two major diversity techniques are considered (i) maximal ratio combining (MRC) and (ii) selective combining (SC). Closed‐form expressions and/or bounds on various channel capacity with OFDM transmission under different scenarios are derived. Simulation results are given. Copyright © 2011 John Wiley & Sons, Ltd.

This paper derives the theoretical average bit error rate (BER) expressions of Orthogonal Frequency Division Multiplexing (OFDM) systems employing binary phase shift keying (BPSK), differential BPSK (DBPSK) and M-ary phase shift keying (MPSK) in a multi-path fading channel using the angle-of-arrival probability density function (pdf) at the mobile where a directional antenna is mounted. The channel introduces Doppler shift with the maximum Doppler spread fd. Two special cases are considered (i) fd is Gaussian distributed and (ii) fd is Rayleigh distributed. Two major diversity techniques are considered: (i) selective combining (SC), and (ii) maximal ratio combining. Detailed discussions and comparisons on performance of OFDM systems employing SC, MRC with directional antennas are given.

Abstract This paper derives the analytical bit error rate (BER) of orthogonal frequency division multiplexing (OFDM) systems employing selective diversity in Rayleigh fading environments. First, the probability density function (pdf) of inter‐carrier interference (ICI) power in Rayleigh fading environments is derived. Second, the pdf of the signal‐to‐interference ratio (SIR) is then derived. The cumulative distribution function (cdf) and hence pdf of the SIR with selective diversity are then given in the third and fourth steps. Using the BER expressions of binary phase shift keying (BPSK) and differential BPSK (DBPSK) modulation in an added white Gaussian noise (AWGN), the corresponding BER expressions of OFDM systems can then be derived. Detailed discussions are given. Possible future work is also outlined. Copyright © 2009 John Wiley & Sons, Ltd.