Need of wireless communication is increasing to work from distance. That is why new applications are made everyday which increases demand of spectrum but due to limitation of spectrum and inefficient utilization of spectrum. A new paradigm is constituted which is called Cognitive Radio Network (CRN). It get more attention in recent times due to most promising solution for the efficient utilization of spectrum. Spectrum sensing in CRN makes it prone to many attacks on each layer. One of these attacks is PUE attack where a malicious user pretends to be a primary user and not let others to use primary user's channel in its absence. It may cause Denial of Service attack in the network. There are many techniques available in the literature for detection and prevention of PUE attack but still there are some limitations in these approaches. Current research provides detection results based on the energy level of all users in the network. In this paper we provide a novel approach to prevent PUE attacker based on signal activity patterns. Simulation is done in MATLAB-2013 and results show that proposed method gives excellent performance.

Cognitive Radio has been considered a key technology in the future wireless communication. These radio networks with their spectrum sensing capability have become one of the most reliable wireless communication networks. Basically, these networks employ two types of users PU’s (Primary Users) having licensed frequency band for their usage and SU’s (Secondary Users) that can intelligently detect which communication channels are available and move into vacant ones while avoiding occupied ones. To have communication among these users, a routing protocol is used whose basic purpose is to provide a reliable route from source to destination. An important parameter while designing a routing strategy is the consideration of overall throughput of path. In this paper we consider the same to find the most optimal throughput path using fuzzy logic theory. MATLAB-7.01 is used for implementation and results show that our proposed scheme outperforms shortest spectrum aware routing scheme.

Mobile Ad hoc Network (MANET) consists of wireless mobile nodes that can be set up any time at any place without the requirement of pre-requisite infrastructure. The nodes in these networks have several constraints such as battery power, processing capability and bandwidth. Moreover each node in MANET has to act as a relay node for others for the successful network operations. In an ideal environment in spite of above mentioned limitations, the node performs this community task faithfully but as in real world there exists nodes with selfish attitude also. Therefore, this paper is an effort to evaluate the efficacy of network with nodes having such behavior prevailing in realistic environment. Various researchers have evaluated the network performance in idealistic conditions but none has made an effort to evaluate it in practical condition such as in presence of obstacles. To make the scenario realistic different number, type and shape of obstacles were taken. The work was accomplished by designing a simulator in MATLAB-11.

Mobile Ad hoc Network (MANET) is a self-organized wireless network, consisting of nodes (mobile devices) responsible for its creation, operation and maintenance. The communication in the MANET is of multihop in nature due to absence of any fixed infrastructure. An attacker may intrude easily into MANET by posing as legitimate intermediate node and present various types of security attacks on data exchanges taking place between source and destination. In this paper we study the impact of presence of black hole node on MANET performance on the basis of reachability, hop count, neighbor node density and path optimality. We observe that as the percentage of black hole nodes increases, the MANET performance degrades significantly.

In order to facilitate communication in Mobile Ad hoc Network (MANET), routing protocols are developed. The performance of these protocols depends upon various factors such as: transmission range, number of nodes deployed and mobility of the nodes. Another factor which affects the performance of MANET routing protocols is the environment in which ad hoc network is deployed. The MANET environment may contain obstacles such as mountains lakes, buildings and river. These obstacles restrict nodes movement but may or may not obstruct the effective transmission range of nodes deployed. This paper is an effort to evaluate the performance of MANET routing protocols in presence of obstacles by designing a simulator in MATLAB-10. To make the situation more realistic obstacle of different shapes, size, number and type were introduced in the simulation region. We found significant impact of the same on the performance of routing protocols.