Khalid A. Darabkh

Performance evaluation of selective and adaptive heads clustering algorithms over wireless sensor networks

Target tracking in wireless sensor networks can be considered as a milestone of a wide range of applications to permanently report, through network sensors, the positions of a mobile target to the base station during its move across a certain path. While tracking a mobile target, a lot of open challenges arise and need to be investigated and maintained which mainly include energy efficiency and tracking accuracy. In this paper, we propose three algorithms for tracking a mobile target in wireless sensor network utilizing cluster-based architecture, namely adaptive head, static head, and selective static head. Our goal is to achieve a promising tracking accuracy and energy efficiency by choosing the candidate sensor nodes nearby the target to participate in the tracking process while preserving the others in sleep state. Through Matlab simulation, we investigate the performance of the proposed algorithms in terms of energy consumption, tracking error, sensor density, as well as target speed. The results show that the adaptive head is the most efficient algorithm in terms of energy consumption while static and selective static heads algorithms are preferred as far as the tracking error is concerned especially when the target moves rapidly. Furthermore, the effectiveness of our proposed algorithms is verified through comparing their results with those obtained from previous algorithms.

Efficient Improvements on the BDND Filtering Algorithm for the Removal of High-Density Impulse Noise

Switching median filters are known to outperform standard median filters in the removal of impulse noise due to their capability of filtering candidate noisy pixels and leaving other pixels intact. The boundary discriminative noise detection (BDND) is one powerful example in this class of filters. However, there are some issues related to the filtering step in the BDND algorithm that may degrade its performance. In this paper, we propose two modifications to the filtering step of the BDND algorithm to address these issues. Experimental evaluation shows the effectiveness of the proposed modifications in producing sharper images than the BDND algorithm.

Performance evaluation of multiuser diversity in multiuser two-hop cooperative multi-relay wireless networks using maximal ratio combining over Rayleigh fading channels

Multiuser diversity MUD cooperative wireless networks combine the features of the MIMO systems without confronting the physical layer constraints by providing multiple copies of the transmitted signal from the source to the destination with the help of the relay node. Cooperative wireless networks have attracted the full attention in the last few years and are implemented widely in many wireless communication systems to adapt for the fading impairments, provide higher data rates, and improve the performance of the wireless communication systems. In this paper, we present an informative study for the reason of evaluating the performance of the MUD in the multiuser two-hop cooperative multi-relay networks using maximal ratio combining. Furthermore, we derive tight closed-form expressions of outage probability and symbol error probability for the amplify-and-forward and fixed decode-and-forward protocols with the MUD. Additionally, we conduct a simulation study to show to what extent our analytical and simulation results agree with each other. It is worthy to mention that our analytical and simulation results agree fairly with each other under high average signal-to-noise ratio, whereas they show that our proposed system with multiple relays provides significant improvements over those previously proposed systems having only one relay. Copyright

Queuing Analysis and Simulation of Wireless Access and End Point Systems using Fano Decoding

Wireless networks are a growing technology due to its ability to receive data in areas where it is very hard to plug-in using wires. TCP Reno assumes in his congestion algorithms that the packet loss is the major cause of network congestion. In wireless networks, this is not correct because having a high bit error rate leads also to a packet loss. Link layer approach is one of the most efficient proposed solutions to maintain TCP over wireless networks. For example, having hybrid ARQ type 1 with Fano decoding, which is an error correction technique, is very appropriate and is of concern in wireless networks due to its capability of offering decoding steps, which are dependent to the channel state. In this paper, we propose a novel queuing model to see the effect of employing Fano decoding on the buffer of wireless access or end points since it is a very effective network parameter and cannot be neglected. Our queuing model is concerned not only about those departed packets after being decoded using Fano algorithm, but also the way packets arrive to the wireless access or end point systems. An analytical study has been conducted to derive a general form expression for the average number of packets residing in the system’s buffer. On the other hand, a simulation study using programming language has been performed to validate our analytical results.

Incorporating automatic repeat request and thresholds with variable complexity decoding algorithms over wireless networks: queuing analysis

Wireless networks are spreading very fast compared to wired-based networks because of its ease in installation, lower cost, reduced dependence on infrastructure and support for emerging mobile and sensing applications. Unfortunately, wireless channels are less efficient in carrying much of data. Moreover, they are characterised by having lower signal-to-noise ratio, resulting in more corrupted packets. Consequently, the performance of such networks may be severely affected due to invoking transmission control protocol (TCP) congestion algorithms whenever a packet is lost. The authors propose a novel queuing model that utilises Fano decoding and automatic repeat request (ARQ) to reduce the drawbacks of TCP in wireless networks. The proposed model describes how received packets are corrected based on Fano decoding mechanism and how the retransmission of corrupted packets is performed. The major aim of proposing this queuing model, when ARQ is totally incorporated, is to find a generic form expression for the average system capacity. The proposed model is validated through simulation in which the results show perfect agreement with those of the analytical model. The authors do not stop to this extent, but rather verify the correctness of the results through comparing them with those obtained in the previous work, where the mechanism of ARQ was completely neglected.

Improving UDP performance using intermediate QoD-aware hop system for wired/wireless multimedia communication systems

Multimedia communication in wireless networks is challenging due to the inherent complexity and constraints of multimedia data. To reduce the high bandwidth requirement of video streaming, videos are compressed by exploiting spatial and temporal redundancy, thus yielding dependencies among frames as well as within a frame. Unnecessary transmission and maintenance of useless packets in the buffers cause further loss and degrade the quality of delivery (QoD) significantly. In this paper, we propose a QoD-aware hop system that can decide when and which packets could be dropped without degrading QoD. Moreover, the transmission of useless packets causes network congestion and vain payment by the wireless system subscriber. In this paper, we focus on two types of frame discarding policies to maintain QoD: partial frame discarding policy (PFD) and early frame discarding policy (EFD). PFD policy discards the succeeding packets of a frame if a packet of the frame cannot be served. On the other hand, in EFD policy, when it is likely to fail to serve packets of a frame (based on a threshold) the subsequent packets of the frame are discarded. We first provide an analytical study of average buffer occupancy based on these discarding policies and show the closed-form expressions for average buffer occupancy. We then perform our simulations by implementing a Markovian model and measure the frameput (the ratio of number of frames served) rather than the number of packets served. Copyright

Evaluation of channel adaptive access point systemwith Fano decoding

The popularity of wireless networks is increasing due to their mobility, flexibility, and scalability. High error rate over wireless channels leads current transmission control protocol congestion algorithms to be maintained. Finding approaches at lower layers to overcome this is very efficient and powerful. However, Fano decoding is an efficient error correction mechanism, especially in wireless networks, due to its capability of being adaptive to the channel. In this paper, Stop-and-wait with hybrid automatic repeat request using Fano decoding is adopted at the link layer. Consequently, we propose novel analytical and numerical studies for the distribution of packets in the system of wireless access point or base station. Moreover, the capacity of a sufficient access point system is evaluated numerically.

Efficient PFD-Based Networking and Buffering Models for Improving Video Quality over Congested Links

Video traffic over the Internet becomes increasingly popular and is expected to comprise the largest proportion of the traffic carried by wired and wireless networks. On the other hand, videos are usually compressed by exploiting spatial and temporal redundancy for the reason of increasing the number of video streams that can be simultaneously carried over links. Unfortunately, receiving high-quality video streaming over the Internet remains a challenge due to the packet loss encountered in the congested wired and wireless links. In addition, the problem is more apparent in wireless links due to not only employing limited system capacity, but also some of the major drawbacks of wireless networks, out of which the bandwidth limitations and link asymmetry which refers to the situation where the forward and reverse paths of a transmission have different channel capacities. Therefore, the wireless hops may be congested which result in dropping many video frames. Additionally, as a result of compressing videos, dependencies among frames and within a frame arise. Consequently, the overall video quality tends to be degraded dramatically. The main challenge is to support the growth of video traffic while keeping the perceived quality of the delivered videos high. In this paper, we extend our previous work concerning improving video traffic over wireless networks through professionally studying the dependencies between video frames and their implications on the overall network performance. In other words, we propose very efficient network and buffer models proportionately to novel algorithms that aim to minimize the cost of aforementioned possible losses by selectively discarding frames based on their contribution to picture quality, namely, partial and selective partial frame discarding policies considering the dependencies between video frames. The performance metrics that are employed to evaluate the performance of the proposed algorithms include the rate of non-decodable frames, peak signal-to-noise ratio, frameput, average buffer occupancy, average packet delay, as well as jitter. Our results are so promising and show significant improvements in the perceived video quality over what is relevant in the current literature. We do not end up to this extent, but rather the effect of producing different bit-stream rates by the FFMPEG codecs on aforementioned performance metrics has been extensively studied.

LEACH enhancements for wireless sensor networks based on energy model

The low-energy adaptive clustering hierarchy (LEACH) protocol is one of the most adaptive protocols used in the wireless sensor networks (WSNs). LEACH is a hierarchical model that provides a powerful strategy for energy balancing, using head rotations. However, the original LEACH protocol suffers from many drawbacks and many researchers proposed new methods to mitigate them. In this paper, we propose two approaches based on an energy model to enhance cluster heads (CHs) selection method through not only minimizing the power consumption of network nodes, but also minimizing the number of CHs. The first proposed approach effectively selects a cluster head that has the lowest power consumption when communicating with other nodes. In addition to what is proposed in the first approach, the idea of incorporating the shortest distance has been considered in the second proposed approach. This significantly decreases the energy consumption and increases the lifetime of associated nodes.

An improved image least significant bit replacement method

With the development of internet technologies and communication services, message transmissions over the internet still have to face all kinds of security problems. Hence, how to protect secret messages during transmission becomes a challenging issue for most of the researchers. It is worth mentioning that many applications in computer science and other related fields rely on steganography and watermarking techniques to ensure information safety during communication. In this paper, we propose a new steganographic method to embed the secret data inside a cover image based on least-significant-bit (LSB) replacement method. The embedding process predominantly concentrates on distributing the secret message inside one share of a color image to appear like a 3D geometric shape. The dimensions of the geometric shape are variable pursuant to the size of secret message. Data distribution process makes our method to be of a great interest as of being so difficult for the hackers or intruders to reconstruct the shape from stego-images, thereby the security is improved. Furthermore, we compare the performance of our approach with two other relevant approaches in terms of peak signal-to-noise ratio (PSNR). The contribution of our approach was immensely impressive.