Faraz Ahsan

Adaptive image denoising using cuckoo algorithm

This paper presents a novel denoising approach based on smoothing linear and nonlinear filters combined with an optimization algorithm. The optimization algorithm used was cuckoo search algorithm and is employed to determine the optimal sequence of filters for each kind of noise. Noises that would be eliminated form images using the proposed approach including Gaussian, speckle, and salt and pepper noise. The denoising behaviour of nonlinear filters and wavelet shrinkage threshold methods have also been analysed and compared with the proposed approach. Results show the robustness of the proposed filter when compared with the state-of-the-art methods in terms of peak signal-to-noise ratio and image quality index. Furthermore, a comparative analysis is provided between the said optimization algorithm and the genetic algorithm.

Highlighting the effects of joint MAC layer misbehavior and virtual link attack in wireless ad hoc networks

In wireless ad hoc networks, employing the IEEE 802.11 technology, access to the wireless medium is scheduled according to the CSMA/CA protocol. This protocol was designed with the assumption that nodes would follow properly its operation and never deviate from it. However, it is common to have selfish nodes that may choose to disobey this protocol in order to either gain more bandwidth or degrade the network performance. In this paper we analyze and quantify the impact of each misbehaving technique on the network performance using extensive simulations. We emphasize on the propagation of MAC layer misbehavior effects to the higher layers, particularly to the routing layer, in a pure ad hoc environment.

Analysis of file system space utilization patterns in UNIX based volumes

File system is an abstraction of the physical storage medium. One of its objectives is to facilitate cataloguing of data in the form of files and directories on the physical storage media for easy and efficient retrieval. Over the years, even though storage capacities have increased drastically but no major architectural enhancement in the area of file systems have appeared. In this paper, we present our findings and an analysis of a study of the usage patterns of storage volumes in UNIX environment. This study is based only on those parameters that are directly related to the efficiency of a file system, i.e., file size, number of files in a directory, number of subdirectories in a directory, file name lengths and path lengths. The distribution of these parameters has been studied under different conditions of utilization. The results obtained are significantly important and provide considerable information for he design of a new file system.

Engaging the jammer on the jammed channel in MANET

Jamming attack, in the form of either continuous or periodic, can easily be deployed in wireless network due to openness of the underlying medium. Traditional strategies do not work against jammer, therefore either nodes passively doze out till the jamming phase is over or they actively move out of the jammed region. For small devices having lesser or no mobility, channel hop is an alternate where nodes move to another channel and try to re-establish the network. If the jammer is well informed about the network, it can follow legitimate nodes on the newer channel. In this paper, we propose the idea that when the nodes resume on the newer channel, they engage the jammer on the jammed channel by alternatively visiting and sending legal packets on the network in a coordinated manner. This way, even if the jammer is intelligent, a legal packet will result in a jam-burst, i.e. pretending to be channel in use. Later, simulation results in favor of the idea are presented.

Neighbor based channel hopping coordination: Practical against jammer?

As compared to its wired counterpart, wireless network is relatively new and is exposed to some additional threats specific to the underlying medium. Among these threats the jamming attack which can take place easily due to the open nature of wireless medium. A device or person can continuously emit radio signals to disturb a valid conversation. If it lasts for sometime continuously, it can result in total collapse of a network using single channel. In order to evade a jammer in an ad hoc network, we propose a proactive channel hopping scheme based neighbor correspondence. Rather than detect and react we rely on prevention is better than cure. Each node communicates with its neighbors on different channels, coordinated between them dynamically. Furthermore, the control and data channels of each node are separated. This way redundancy at the node-level is provided so that even if nodes on the jammed channel can not be approached but they still are able to contact others by visiting their control channels; avoiding the node on the jammed channel from starvation. Hence, even if the network is exposed to the jammer, a complete failure is prevented. The simulation results show that our scheme is efficient and is able to reduce the jammers impact significantly, as compared to the scheme presented.

Optimization of probabilistic & decentralized load balancer on SSI cluster

The work done in this research attempts to improve the load balancer of OpenMosix. Interestingly trivial changes made to any load balancing algorithm can produce dramatic results. The parameters that effect the load balancing algorithm are first evaluated with the default configurations and then modifications have been made to the /proc file-system dynamically to optimize it in OM. A stronger system in the SSI is assigned most of the workload for a given process whereas relatively slower systems are not as much active; hence reducing the overall efficiency. Making the faster systems pretend to be slower, results are more optimized among the whole SSI nodes. The results show that tuning the speed and decay interval parameters from the /proc interface improves the performance of the overall SSI for the given task.