New advancements in 5G standardization and research define the radio access processes for the next generation of the wireless systems to mitigate the inter- channel interference, delay and related impairments. The strategies to achieve such specifications, some suitable channel models have been extensively explored to incorporate the required improvement in the wireless network design parameters applicable to a variety of frequency bands and heterogeneous network standards. Obviously, the physical channel impacts the transmitted signals significantly and the effect becomes more critical in case the propagation medium encounters high variance in time, frequency and space. The user-centric approach chosen by the Third Generation Partnership Project (3GPP) model involving the Spatial Channel Model (SCM) and its derivatives along with some preferred approach based on the Directional Channel Model (DCM) have been usually applied to predict the channel behavior. Thus the understanding of physical channel behavior appears as a critical area to explore, to develop suitable hardware and software circuits for wireless networks.

This issue presents five papers, and among them, the first two are focused on the wireless channel characterization and modeling, followed by the third one discussing the dielectric resonator antenna used in boosting the signal. The fourth and fifth papers are based on the performance analysis of the link and network, respectively.

Signal propagation models and wireless channel understanding are essential for accurate interference estimation and optimum power utilization. The first paper, ?Adaptation of Path Loss Models for Terrestrial Broadcast in VHF Band in Minna City, Niger State, Nigeria?, by Moses Abiodun Stephen, Oyedum Onyedi David and Ajewole Moses Oludare, aims at adapting a propagation model that is best suited for Minna city in Niger State, Nigeria. The paper modifies the existing empirical propagation models to suit Minna city using VHF television signals of Nigeria Television Authority (NTA), Minna. The paper proposes a generalized Ericsson model for urban environment and appears as a more accurate prediction model for path loss estimation in Minna city.

The second paper, ?A Study of Rain-Induced Attenuation on Terrestrial Paths at Ku, K and Ka Bands Over Akungba-Akoko, Nigeria?, by J E Olubusade, O D Oyedum, M O Ajewole, O M Afolabi, A S Moses and J O Eichie, presents rain attenuation model to predict signal impairment, especially at higher frequencies such as Ku, K and Ka frequency bands. The model confirms that the rain-induced attenuation increases with increasing rain rate and transmitting frequency. The analysis has considered the ITU-R rain attenuation model as the standard and Lavergnat-Gole rain rate as a conversion model for the tropical region study.

, the wireless link performance can be enhanced by employing high gain antenna system using several low gain elements in the array employing various configurations. The third paper, ?Linear Chebyshev Array of Cylindrical Dielectric Resonator Antenna?, by Nipun K Mishra, considers linear array comprising four cylindrical dielectric resonator elements with uniform excitation. The paper further uses Dolph-Chebyshev distribution-based excitation for the set of optimum beam width and side lobe level designs.

In the wireless link performance analysis, the Direction Of Arrival (DOA) of the beam plays a crucial role to estimate the correction factor to improve upon the convention model results. The fourth paper, ?Performance Analysis of Direction of Arrival Estimation Algorithms for the Sound Sources?, by Ritu and Sanjeev Kumar Dhull analyzes the performance of DOA estimation algorithms and estimates its influence over the beam pattern. The information needed to calculate the DOA is obtained by analyzing the wave impinging on the linear array using MATLAB. The simulation has been done to observe the impact of various factors affecting the beam pattern. This study helps to improve the DOA estimation algorithm and selects the suitable one as per the requirement of the situation.

The last paper, ?The Impact of Ingress Packet Size on the Performance of TCP and UDP in Survivable Networks?, by Himanshi Saini and Amit Kumar Garg, evaluates the network performance to ingress packet size vitiations under optical packet switching employing Transmission Control Protocol and User Datagram Protocol. The study observes that end-to-end delay offered by TCP is higher as compared to UDP and becomes significant with the increase in the size of network. In this paper, survivable mesh networks based on state routing have been considered for their performance analysis.