Amer M. Magableh

The increased usage of renewable energy sources (RESs) and the intermittent nature of the power they provide lead to several issues related to stability, reliability, and power quality. In such instances, energy storage systems (ESSs) offer a promising solution to such related RES issues. Hence, several ESS techniques were proposed in the literature to solve these issues; however, a single ESS does not fulfill all the requirements for certain operations and has different tradeoffs for overall system performance. This is mainly due to the limited capability of a single ESS and the potency concerning cost, lifespan, power and energy density, and dynamic response. In order to overcome the tradeoff issue resulting from using a single ESS system, a hybrid energy storage system (HESS) consisting of two or more ESSs appears as an effective solution. Many studies have been considered lately to develop and propose different HESSs for different applications showing the great advantages of using multiple ESSs in one combined system. Although these individual methods have been well documented, a comprehensive review of HESS-integrated RE has not been fully investigated in the literature before. Thus, as a novel contribution to the literature, this study aims to review and analyze the importance and impact of HESSs in the presence of renewable energy towards sustainable development that will facilitate this newly emerging topic to researchers in this field. In this regard, the present scenario and recent trend of HESSs in RESs at the global level, including a comparison with main ESS features, are discussed and analyzed along with the concept, design, classifications, and a detailed comparison of HESSs. The emerging role of HESSs in terms of their benefits and applications has been analyzed. Recent control and optimization methods of HESSs associated with RESs and their advantages and disadvantages have been reviewed. Finally, open issues and new challenges toward more efficient, sustainable, and green energy have also been highlighted herein. All the highlighted insights of this review will hopefully lead to increased efforts toward the development of an advanced HESS for future renewable energy optimal operation.

Space modulation techniques (SMTs) are a group of multiple‐input–multiple‐output wireless systems in which the spatial indexes of transmit antennas are utilized to convey additional information bits. The SMTs promise significant enhancements in terms of spectral and energy efficiencies and attract significant research interest in literature. Several SMTs have been proposed including spatial modulation (SM) and quadrature SM. In this study, the performance of dual‐hop decode‐and‐forward relaying SM and quadrature SM in the presence of wireless power transfer is analyzed and thoroughly discussed. Specifically, we derive exact closed‐form expressions for the pairwise error probability (PEP). In addition, we derive simple and accurate asymptotic expressions for the PEP at high signal‐to‐noise ratio, which provides insight into the influence of different system parameters. The obtained PEP expressions are then employed to evaluate the overall average bit error rate (BER). It is worth highlighting that the derived expressions are unified in the sense that they are valid for the aforementioned SMTs and for two well‐known practical energy harvesting protocols, namely, power‐splitting receiver and time‐switching receiver. In addition, we derive a unified closed‐form expressions for the outage probability and achievable throughput at the destination node. The impact of diverse system parameters, such as the power‐splitting factor, the energy‐harvesting time factor, and the distance between the source and the relay nodes, on the overall system performance is studied. The accuracy of the analytical derivations is validated through Monte Carlo simulations results.

In this article, we propose an opportunistic transmission protocol for cooperative communication systems with L relay nodes under the influence of fading channels. Unlike the protocols previously known in the literature, and given the fact that direct single-link communication outperforms multilink cooperative communication in terms of throughput for same channel conditions, we adopt the channel conditions of the direct link as a main criterion to use whether the direct link in the transmission or the indirect cooperative link. Different performance metrics are derived to demonstrate the performance of the proposed protocol along with a switching combining with a preferable link scheme. These metrics include the bit error rate (BER), outage probability, signal to interference noise ratio (SNR) gain, average throughput and the sum SNR–throughput product (SSTP). The latter performance metric is introduced to compare the maximum achievable throughput as well as the SNR range at a given quality of service (QoS). Our results show that the proposed opportunistic protocol improves the throughput as compared to the conventional cooperative communication systems for the whole range of average SNR. On the other hand, it improves the coverage range as compared to the direct link communication.

Femtocells can be employed in cellular systems to enhance the indoor coverage, especially in the areas with high capacity growing demands and high traffic rates. In this paper, we propose an efficient resource utilization protocol, named as shared access protocol (SAP), to enable the unauthorized macrocell user equipment to communicate with partially closed‐access femtocell base station to improve and enhance the system performance.The system model considers a femtocell that is equipped with a total ofNseparated antennas or channels to multiplex independent traffic. Then, a set ofN₁channels is used for closed access only by the authorized users, and the remaining set of channel resources can be used for open access by either authorized or unauthorized users upon their demands and spatial locations. For this system model, we obtain the signal‐to‐interference ratio characteristics, such as the distribution and the moment generating function, in closed forms for two fading models of indoor and outdoor environments. The signal‐to‐interference ratio statistics are then used to derive some important performance measures of the proposed SAP in closed form, such as the average bit error rate, outage probability, and average channel capacity for the two fading models under consideration. Numerical results for the obtained expressions are provided and supported by Monte Carlo simulations to validate the analytical development and study the effectiveness of the proposed SAP under different conditions. Copyright © 2013 John Wiley & Sons, Ltd.

The ergodic capacity of single input multiple output (SIMO) wireless communication systems over Nakagami-m fading channels is available in the literature for the case of identically independent distributed (i.i.d.) subchannels. However, the non- identically independent Nakagami-m case is more practical and has not been considered in the literature. In this paper, we derive an analytical expression for the ergodic capacity of SIMO wireless communication systems over non-identically independent Nakagami-m subchannels. We also derive an expression for the capacity of i.i.d. Nakagami-m case which requires much less computational time as compared to expressions reported in literature. Numerical results are presented and verified via Monte-Carlo simulation.