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The number of elements reduction in different antenna array configurations such as linear, circular, rectangular, planar, and non-planar is of main concern for several research groups. This minimizes the complexity of the feeding network in static antenna arrays, whereas, in adaptive antenna arrays, it reduces the number of active components. The main issue in the array synthesis is to preserve the radiation pattern with minimum distortion compared to the original pattern. These issues are addressed by many researchers in linear, planar, and concentric circular arrays, but no attempt is made in the synthesis of uniform circular antenna arrays (UCAAs) that have elements distributed on a single circle. This is because the synthesis is almost performed in one plane where the radiation patterns in other planes are not predicted. In this paper, most of the aforementioned challenges are treated; the number of elements is reduced, the radiation pattern has minimum distortion, and the radiation pattern is symmetric in all array orthogonal planes. This is performed by dividing the original UCAA's 3D radiation pattern into a suitable number of 2D plane patterns, each of which is separately synthesized using the specified number of elements. The 2D pattern synthesis process for a particular plane is confined to estimating a new set of non-uniform excitation coefficients while keeping the original UCAA's array radius. To construct the final set of synthesized excitation coefficients for the 3D array pattern synthesis, we aggregate all of the estimated sets of excitation coefficients and take the average. To verify the efficacy of the proposed technique, the original and synthesized arrays are realized using the CST Microwave Studio using 2 ⁄ dipole elements. The results indicated that substantially matched patterns were obtained. Furthermore, the coupling between the synthesized array elements is decreased, which enhances the radiation efficiency and realized array gain.

A Mobile Ad-Hoc Networks (MANET) is widely used in many industrial and people's life applications, such as earth monitoring, natural disaster prevention, agriculture biomedical related applications, and many other areas. Security threat is one of the major aspects of MANET, as it is one of the basic requirements of wireless sensor network, yet this problem has not been sufficiently explored. The main purpose of this paper is to study different MANETs routing protocols with three scenarios of Denial of Service (DoS) attacks on network layer using proactive routing protocol i.e. Optimized Link State Routing (OLSR) and Reactive routing protocols like Ad hoc On-Demand Distance Vector (AODV), Hybrid routing protocols like Geographic Routing Protocol (GRP). Moreover, a comparative analysis of DoS attacks for throughput, Data loss, delay and network load is taken into account. The performance of MANET under the attack is studied to find out which protocol is more vulnerable to the attack and how much is the impact of the attack on both protocols. The simulation is done using OPNET 17.

The synthesis of pencil beam and arbitrarily shaped beam patterns of linear antenna arrays (LAA) using reduced number of antenna elements attracts the attention of researchers in recent years. In this paper, a hybrid beamforming technique based on the combination of the genetic algorithm (GA) optimization technique and the 1 minimization method denoted as (GA/ 1) is introduced for LAAs synthesis. The proposed GA/ 1 beamforming technique optimizes both the elements excitations and interelement spacing to synthesize the desired LAA pattern with a minimum number of antenna elements. The GA/ 1 technique provides an excellent approximation to the desired radiation pattern with high accuracy and low complexity (less number of iterations and computational time) compared to the other synthesis approaches introduced in the literature. In addition, as an application of this work, the proposed GA/ 1 technique is used to build up a proposed hybrid precoding and beamforming (HP-BF) structure for Massive Multi-input Multi-output (M-MIMO) systems. In this structure, the transmit antenna array is synthesized for maximum gain realization using the existing number of antenna elements. In the HP-BF structure, the proposed GA/ 1 technique is used to make full use of the existing transmit array elements to synthesize the radiation pattern of much larger size and higher gain arrays without the need for additional elements. Thereby, significant savings in the number of antenna elements and their corresponding radio frequency (RF) chains are achieved, which reduces the system complexity. In addition, the array gain maximization will maximize the received signal to noise ratio (SNR) giving rise to higher system performance in terms of spectral efficiency (SE) and power utilization. INDEX TERMS Array synthesis, analog phase shifters, hybrid precoding and beamforming structure, Massive Multi-input Multi-output, millimeter waves, spectral efficiency, uniform linear array.

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