Waqas Khalid

Sixth-generation (6G) networks pose substantial security risks because confidential information is transmitted over wireless channels with a broadcast nature, and various attack vectors emerge. Physical layer security (PLS) exploits the dynamic characteristics of wireless environments to provide secure communications, while reconfigurable intelligent surfaces (RISs) can facilitate PLS by controlling wireless transmissions. With RIS-aided PLS, a lightweight security solution can be designed for l

This paper investigates the physical layer security and data transmission for the underlay device-to-device (D2D) networks, and considers a combination of the reconfigurable intelligent surface (RIS) and full-duplex (FD) jamming receiver for the robustness and security enhancements of the system. In the demonstrated spectrum sharing setup, the total power of the D2D networks is conceived to the transmitter and receiver to transmit a private message and emit the artificial noise (AN) signals. To

A light-addressable gold electrode modified with CdS and FePt or with CdS@FePt nanoparticles via an interfacial dithiol linker layer is presented. XPS measurements reveal that trans-stilbenedithiol provides high-quality self-assembled monolayers compared to benzenedithiol and biphenyldithiol, in case they are formed at elevated temperatures. The CdS nanoparticles in good electrical contact with the electrode allow for current generation under illumination and appropriate polarization. FePt nanop

Reconfigurable intelligent surfaces (RISs) have been considered as a promising technology for the sixth-generation (6G) wireless networks that can control wireless channels in a desirable way and significantly enhance the network performance. Simultaneous transmitting and reflecting-RISs (STAR-RISs) can overcome limitation of reflecting-only RISs by leveraging the higher design flexibility and full-space coverage. Despite the benefits, the modeling and analysis of STAR-RISs are complicated becau

This paper investigates the reconfigurable intelligent surface (RIS)-empowered dynamic power splitting designs for simultaneous wireless information and power transfer (SWIPT) systems while adopting various practical hardware issues. Specifically, we adopt the physical size of the RIS and the placement of the RIS plane to phase-align the reflected signals towards the desired direction. The analytical phase shift model for the reflecting elements is presented to characterize an intertwined relati

An electrochemical sensor for p-aminophenyl phosphate (pAPP) is reported. It is based on the electrochemical conversion of 4-aminophenol (4AP) at a quantum dot (QD) modified electrode under illumination. Without illumination no electron transfer and thus no oxidation of 4AP can occur. pAPP as substrate is converted by the enzyme alkaline phosphatase (ALP) to generate 4AP as a product. The QDs are coupled via 1,4-benzenedithiol (BDT) linkage to the surface of a gold electrode and thus allow poten

Fifth-generation (5G) networks will not satisfy the requirements of the latency, bandwidth, and traffic density in 2030 and beyond, and next-generation wireless communication networks with revolutionary enabling technologies will be required. Beyond 5G (B5G)/sixth-generation (6G) networks will achieve superior performance by providing advanced functions such as ultralow latency, ultrahigh reliability, global coverage, massive connectivity, and better intelligence and security levels. Important a

Non-orthogonal multiple access (NOMA) has gained attention as a promising multiple access scheme for the Internet of Things (IoT). A typical setting of user ordering in NOMA networks with user priority difference allows a service priority for solely low-rate high-priority users. In contrast, the diverse quality of service (QoS) requirements and service priorities are prerequisite features of users in the IoT. In this paper, we consider a downlink transmission scenario for NOMA-IoT networks in wh

The continuous growth of interconnected devices in the Internet of Things (IoT) presents a challenge in terms of network resources. Cognitive radio (CR) is a promising technology thatcan address the IoT spectral demands by enabling an opportunistic spectrum access (OSA) scheme. The application of full duplex (FD) radios in spectrum sensing enables secondary users (SUs) to perform sensing and transmission simultaneously, and improves the utilization of the spectrum. However, random and dense dist

Spectrum sensing has gained new aspects with the advent of cognitive radio and opportunistic spectrum access techniques. Spectrum sensing plays a vital role in cognitive radio networks, and its reliability determines the success of transmission. It also enables the spectrum access for unlicensed users, enhancing the spectral utilization. The successful integration of primary users and secondary users requires the secondary users to be capable of efficient sensing and keeping precise track of the

Fifth-generation (5G) heterogeneous network deployment poses new challenges for 5G-based cognitive radio networks (5G-CRNs) as the primary user (PU) is required to be more active because of the small cells, random user arrival, and spectrum handoff. Interweave CRNs (I-CRNs) improve spectrum utilization by allowing opportunistic spectrum access (OSA) for secondary users (SUs). The sum utilization of spectrum, i.e., joint utilization of spectrum by the SU and PU, depends on the spatial and tempora

The integration of unmanned aerial vehicles (UAVs) with a cognitive radio (CR) technology can improve the spectrum utilization. However, UAV network services demand reliable and secure communications, along with energy efficiency to prolong battery life. We consider an energy harvesting UAV (e.g., surveillance drone) flying periodically in a circular track around a ground-mounted primary transmitter. The UAV, with limited-energy budget, harvests radio frequency energy and uses the primary spectr

Abstract Among all the construction materials used in construction industry concrete is the most used one. With its main cementing ingredient being OPC But production of OPC comes at a cost both financial and environment that is why if OPC can be replaced to some extend by another material that is cheaper to produce than financial and environmental cost of concrete can be reduced significantly. Some industrial waste materials have cementing and pozzolanic properties thus they can used to replace