While addressing cellular network performance issues, resolving problems with coverage and capacity is critical. The coexistence of cellular networks and smaller femtocells working within the macrocell area is among the alternative solutions. The simultaneous functioning of macrocells and femtocells, however, introduces new technical challenges that pose serious concerns about the efficiency of cellular networks. Therefore, this work proposes a hybrid approach based on variant advanced antenna technologies including MIMO methods and antenna systems for the deployment of femtocells and macrocells. To accomplish this, three distinct LTE-A network models with and without femtocells are set up with different architectures for high-density areas. The models further cover tri-sector and omnidirectional antenna systems to analyze the relevant effects on the performance of the LTE-A macrocells as well as femtocells. Also, to extend the analysis, integration of different MIMO methods for the models is provided. The networks are implemented and the link performance evaluation is carried out with regard to spectral and energy efficiency, cell and user throughputs, fairness, and SINR. The results contribute to determining the performance gains and energy saving of the LTE-A femtocells as well as macrocells by employing different advanced antenna technologies.

Since internet connections are provided through a variety of disparate networks, connecting these networks and supporting heterogeneous interworking is a major issue particularly in cellular networks. The interworking issue becomes even more challenging when it comes to providing QoS for real time services. To improve QoS requirements of the real time data and to increase inter cellular mobility, we propose a cost-effective framework structure consists of four separate cellular models. The framework includes a heterogeneous interwork model that integrates cellular WiMAX and UMTS. Moreover, a pure WiMAX network model along with two pure UMTS network models is set up by the framework. The performance of the heterogeneous model is evaluated via simulation and analyzed against the measured metrics of the pure models to quantify the level of improvements from QoS of the real time packets point of view. Based on the results, the recommendations are made on the most appropriate model in regard to better QoS for VoIP in cellular networks.

Amplification attacks take advantage of insecurity of different OSI layers. By targeting broadcast address of the victim networks and sending a few packets by the attackers, they force the legitimate user in the victim networks to response to these packets and attack their own trusted networks unknowingly. Despite importance of amplification attacks, there is not any work to implement these attacks to identify their procedure and quantify and compare their impacts on the networks. In this work, we use NS2 to achieve these goals. A variety range of scenarios are designed to implement DDoS amplification attacks and collect the results in terms of different network performance measures. The quantitative results prove devastating impact of the attacks which are easily capable of rendering the target wireless networks disable for their legitimate users. 

Wireless sensor networks (WSN) are widely developed to monitor different phenomena in a variety of areas including nature, medical centers, home automation, industrial and military applications. Such development in many different fields, raises important security issues related to the reliability of the WSNs. Due to the resource constrained nature of the WSNs, these networks are the target of many different types of attacks and prone to failure. In this paper, we consider the collision attack. An attempt has been made to measure the impact of the collision attack on the performance of WSNs under variety scenarios performed by the attackers. The main contribution of this paper is to present that although the attack does not consume much energy of the attacker, it can highly disrupt the normal operation of the target sensor networks. The implementation of the proposed attack model has been done by using NS2 network simulator.