Optical wireless communication (OWC) is an innovative technology that is gaining more attention as the demand for capacity continues to increase. It is one of the most promising alternative technologies for indoor and outdoor applications. In this paper, the effect of the inner wall coating material, color and roughness on the performance of OWC system implementing single-diffuse topology is studied. A new procedure is proposed to generate a rough surface model with predetermined statistical properties to simulate the matte painting material on the internal walls of a room. Additionally, a new technique that applies the geometrical theory of diffraction (GTD) in conjunction with a ray tracing (RT) scenario is developed to evaluate the scattered optical beam due to a primary ray incident on a Lambertian surface. The performance of the single-diffuse OWC strategy is assessed by investigating some important performance measurements such as signal strength and the bit error rate (BER) due to unavoidable ambient light which is modeled as an additive white Gaussian noise. It is shown that the surface roughness of the matte painting on the Lambertian diffuse surface has a major effect on the indoor OWC system performance.

This paper presents the design of a fractal unit cell absorber for electromagnetic energy absorption in the 2.45 GHz band. The configuration is based on a second-order Minkowski-inspired fractal geometry, through which a compact structure is realized. The proposed design is achieved using full-wave electromagnetic simulations and the study of an equivalent circuit model. At 2.45 GHz, the synthesized structure achieves a near-perfect absorptivity of 99%, with a modest footprint of 0.11λ. The realized structure can serve as a constituent element for the design of absorber arrays to mitigate multipath effects and prevent eavesdropping attacks in indoor wireless environments.

The objective of the work is to design a compact MIMO antenna at 3.5 GHz suitable for 5G applications. MIMO antenna is suitable choice for increasing the signal to noise ratio of mobile communication systems. The channel capacity can be increased by improving signal to noise ratio. At the same time, high isolation between the elements should be maintained.  Planar inverted F antenna (PIFA) is used as a unit element for MIMO antenna in this work. The unit element dimensions are 9.5 x 7 mm2. Two shorting pins are used for getting better impedance matching. Four elements are arranged in the FR4 substrate with dielectric constant 4.4 and thickness of 1.6 mm. The performance of 4 element Multiple Input Multiple Output (MIMO) antenna is optimized using HFSS software. The results show that the   better impedance matching at desired frequency band and a gain of 4.2 dB in the bore-sight axis is obtained for the four elements. The gain of four element antenna is improved from - 0.52 dB to 4.2 dB than two element antenna. The isolation between the elements is obtained below -15 dB . The overall volume of the antenna is 25.3 x 26.8 x 1.6 mm3, which ensures compactness suitable for mobiles.

Due to increased number of IoT devices, the marketplace is showing significant growth of sensor deployments around the world. The context involved in any IoT environment needs proper storage, processing and interpretation to get deeper insights from it. Previous research has not focussed much on context-ware security in IoT environment and has primarily relied on context-ware computing methods. In this research paper we implement logical decisions among IoT nodes in healthcare system using ontological approach. With the help of ontological method collected data is transferred between various healthcare devices to the knowledge base thereby achieving security of context like patient data by providing deeper insights, so as to generate intelligent suggested solutions. Incorporation of context-aware rules based on common experience for specific healthcare scenario is done to get implicit insight among IoT nodes.  This work designs security ontology using Security Toolbox: Attacks & Countermeasures (STAC) framework that is implemented in Protégé 5. Moreover, Pellet (Incremental) reasoned is used to evaluate the ontology. Emergency ontology that can prove helpful at emergency times has also been designed.  Different parameters addressed in this work are authentication, access-control, authorization and privacy using context-awareness methodology that can enable naive users make informed security decision. 

This paper presents an improved hybrid Equal Gain Combiner-Maximal Ratio Combiner (EGC-MRC) diversity scheme in 5G millimeter wave (mm-wave) frequency. The term 5G mm-wave refers to the radio frequency spectrum between 24 GHz and 100 GHz. The signal interference is a challenging task in 5G mm-wave frequency, and radio network suffer from co-channel and adjacent channel interference. 5G network deployment depends on large number of antennas, which resulted in signal interference. The conventional receiver’s diversity techniques have high hardware complexity and are characterized by low performance. A new hybrid EGC-MRC diversity scheme was proposed as an improvement on the performance of existing MRC scheme. In achieving this, Probability Density Function (PDF) of the hybrid model was derived using the instantaneous Signal-to- Noise Ratio (SNR) obtained from the output of MRC and EGC diversity schemes. The performance of the developed model was evaluated using Outage Probability 〖(P〗_out) and Processing time (P_t)  at different SNR with L number of paths. Simulation of the MRC, EGC and hybrid EGC-MRC models were carried out using MATLAB 2018a and the results compared. The output results showed that hybrid EGC-MRC performed better than EGC and MRC by having a lower P_out   and〖 P〗_t. This new model has the potential to mitigate network interference, multipath propagation, and hardware complexity in 5G mm-wave frequency. Therefore, the developed model can be deployed by network operators to solve signal interference in 5G network.