Ramzi Saifan

Efficient Spectrum Searching and Monitoring in Cognitive Radio Network

Two objectives of sensing in cognitive radio (CR) are to detect the primary user (PU) accurately and quickly, which are contradicting objectives. Therefore, many papers try to optimize this tradeoff and find the minimum sensing time which protects the PU. The trends are classified in enhancing false alarm probability (Pf) and detection probability (Pd), optimizing inter-sensing time, in-band sensing (monitoring) time optimization, and out-of-band sensing (search) time optimization. The PU model used in most of these work was a simple two states model (busy/idle renewal process). In this work, we developed a model for the PU in its idle state. The model enables the CR node to benefit from its previous measurements. It assumes that there are multi-idle states, each with specific length and known probability of staying in it. We used this model to find the best sensing time, energy detection threshold, and false alarm probability of the channel being sensed in monitoring. Also, we developed an out-of-band optimization formulation. The formulation finds the best number of channels to sense, the threshold of each channel, the sensing time of each channel, and Pf of each channel such that the PU is protected, the sensing time is minimized, and the CR will find an available channel with very high probability.

Spectrum decision for efficient routing in cognitive radio network

The cognitive radio (CR) nodes in a cognitive radio network (CRN) do not have license to use specific spectrum band. Instead, they use the spectrum bands of the licensed primary users (PU) without interfering with the PU. When the PU becomes active, interfering CRs should leave to another available spectrum band within the PUs tolerable interference delay (TID). Therefore, CRN operates over wide spectrum bands which span many channels. Since each channel is typically licensed to one PU, this requires that channels be sensed separately. This adds monitoring overhead, where the CR should monitor (sense) the channel every TID, which reduces the throughput. For this reason, the node cannot monitor the whole set of channels. Deciding which set of channels to monitor affect other functions in the CRN like routing. Work done on routing in literature assumes that each node maintains a set of available channels which is obtained by sensing. Route setup decision will be made based on the available sets at all nodes. However, there may be some other available channels that the node is not aware of their availability which may enhance the routing quality metric. Also, taking into consideration only the sets of channels available at the CR nodes may preclude finding an end-to-end path. In this paper, we propose a spectrum decision framework that is complementary to the existing routing protocols. This framework is based on two objectives: 1) enhancing the route quality by sensing a few more channels at some nodes. These channels can enhance the quality by: reducing the switching time, requiring shorter sensing time, or expected to be available for longer time; 2) increasing the probability of finding a path by sensing more channels at some nodes in case the routing protocol did not find a path. Simulation results show that the proposed framework can result in enhancement that can be as high as 100% over the routing protocols that build their decisions based on the available channels at each node only.

An efficient reversible data hiding algorithm using two steganographic images

Reversible data hiding (RDH) algorithms are concerned with concealing data within images such that the original image can be fully recovered upon the extraction of hidden data. A substantial interest has grown recently in RDH algorithms that are based on using dual images in order to increase the embedding capacity. In this paper, we propose a RDH algorithm that is based on this concept. Effectively, embedding and extraction of data in the proposed algorithm is performed in three successive phases. In the first phase, four simple rules are used to embed about one bit in each pixel in the two images. On the other hand, the other two phases employ the concept of prediction for embedding secret data bits but without using any complex predictors. Specifically, these phases use one image as the prediction of the other image. Performance evaluation of the proposed algorithm showed its ability to embed around 1.23 bits per pixel with stego image quality above 48dB. Moreover, the proposed algorithm is of low computational complexity and requires no communication of overhead information. A novel dual-image reversible data hiding algorithm is proposed.Three consecutive stages that exploit the similarity between the two images to embed data are used.Significant increase in the embedding capacity with excellent stego image quality is achieved.

A Novel Algorithm for Defending Path-Based Denial of Service Attacks in Sensor Networks

Existing end-to-end security mechanisms are vulnerable to path-based denial of service attacks (PDoS). If checking integrity and authenticity of a message is done only at the final destination, the intermediate nodes are going to forward bogus packets injected by an adversary many hops before they are detected. Therefore, the adversary can easily overwhelm intermediate nodes by bogus or replayed packets. This attack exhausts the nodes along the path. In addition, other downstream nodes that depend on the exhausted nodes as intermediate nodes will be isolated, and they have to find alternative paths. Regarding broadcast traffic that originated from the base station, if packets were injected by an adversary, the whole networks nodes will be exhausted. Therefore, there is a need to enable intermediate nodes to filter out bogus packets. We adopted a link layer security scheme to enable en route intermediate nodes to filter out any bogus or replayed packet as soon as it is injected into the network. Our scheme can handle different types of traffic. Simulation results show that our algorithm outperforms the one-way hash chain (OHC) algorithm and that it is more scalable.

MT-CHR: A modified threshold-based cluster head replacement protocol for wireless sensor networks

Abstract The Threshold-based Low-energy Adaptive Clustering Hierarchy (T-LEACH) protocol declares that cluster heads do not have to turn over every round but rather every batch of rounds. In other words, nodes keep serving as cluster heads as long as their energy is higher than a threshold energy. This article imposes upon major drawbacks of T-LEACH protocol and presents a Modified Threshold-based Cluster Head Replacement (MT-CHR) protocol. In the MT-CHR protocol, a new probability of being a cluster head, for any node in any round, has been proposed which agrees fairly with the assumptions introduced in LEACH protocol. Moreover, a new expression for threshold energy is proposed in which delaying the first node death and avoiding any data loss are taken into consideration. The performance of MT-CHR is evaluated using alive nodes, network lifetime, as well as network utilization performance metrics. The results are further compared with those obtained importantly from LEACH and T-LEACH protocols and the contributions of MT-CHR protocol are extremely impressive. As far as the real sensor network is concerned, the MT-CHR protocol is highly applicable and very effective as long-lasting networks are ascertained.

Mobility and Direction Aware Ad-hoc on Demand Distance Vector Routing Protocol☆

Abstract Mobile Ad hoc Network (MANET) is a rapidly growing wireless technology with wide range of applications. MANET routing faces challenges due to their Ad hoc nature, and many routing algorithms have been proposed. Reactive routing protocols are preferred due to less control overhead and scalability, but they suffer from frequent link breakages due to the high-mobility of the nodes. To reduce the link breakages and get a stable route, a new reactive routing protocol is proposed that is tree-based mobility-aware. The proposed Mobility and Direction Aware Ad-hoc On Demand Distance Vector routing protocol (MDA-AODV) aims to handle the mobility and direction factors in ad-hoc networks. MDA-AODV guides the route discovery and route reply depending on the speed of the participating nodes and their directions. Qualnet simulator version 7.1, using two offered load simulations (packet-rate and CBR connections), was used to investigate the effect and the advantages of MDA-AODV over AODV protocol. The simulation results show that the proposed scheme decreases control overhead by (4.6 ÷ 5.2%). It also accomplishes (37 ÷ 41%) lower route losses compared to AODV. The delivery ratio is increased by (29 ÷ 47%). The consumed energy and end-to-end delay of the proposed protocol is also compared to that of AODV.

SARDH: A novel sharpening-aware reversible data hiding algorithm☆

Abstract Reversible data hiding (RDH) algorithms allow data protection and exact recovery of the original cover image upon data extraction. Most of RDH algorithms attempt to embed data while maintaining high peak signal-to-noise ratio. However, it has been deemed recently that some applications may demand improving the image contrast while embedding data. Additionally, stego images with better contrast could be less attractive to attacker, given the fact they have no idea about the original cover image. In this paper, we propose a sharpening-aware RDH (SARDH) algorithm that is capable of embedding significant amount of data in addition to sharpening the image. Experimental results proved the ability of SARDH algorithm in embedding large payloads and providing sharper stego images.

A Framework for Cooperative In-Band Sensing in Cognitive Radio Network

Many existing in-band sensing algorithms for CRNs adopted a periodic sensing/transmission architecture, where all the CR users do periodic sensing. Each periodic detection cycle is divided into two parts: sensing and transmission times. Sensing times are affected by many factors. In some worse scenarios (e.g., low SNRs), it may take more than half of the channel idle time for sensing. In this paper, we propose a new cooperative in-band sensing framework to increase sensing efficiency and robustness. In our framework, each CR operates in one of the two modes: Transmission and Sensing. The CRs that have data to send switch to Transmission Mode, provided that there is enough number of CR nodes in sensing mode. Therefore, CRs in transmission mode do not have to do any sensing during transmission, which imply that they can send for longer times. CRs in sensing mode send warning messages in case they detected the presence of PU. This cooperation (among CRs) is done on the same channel of transmission without the need for a CCC. Simulation and analytical results show that our sensing framework outperforms traditional sensing framework/approaches that require periodic sensing. At the end, we identify a set of important open problems to be addressed under this sensing framework.

An efficient speech recognition system for arm‐disabled students based on isolated words

Over the previous decades, a need has emerged to empower human‐machine communication systems, which are essential to not only perform actions, but also obtain information especially in education applications. Moreover, any communication system has to introduce an efficient and easy way for interaction with a minimum possible error rate. The keyboard, mouse, trackball, touch‐screen, and joystick are all examples of tools which were built to provide mechanical human‐to‐machine interaction. However, a system with the ability to use oral speech, which is the natural form of communication between humans instead of mechanical communication systems, can be more practical for normal students and even a necessity for arm‐disabled students who cannot use their arms to handle traditional education tools like pens and notebooks. In this paper, we present a speech recognition system that allows arm‐disabled students to control computers by voice as a helping tool in the educational process. When a student speaks through a microphone, the speech is divided into isolated words which are compared with a predefined database of huge number of spoken words to find a match. After that, each recognized word is translated into its related tasks which will be performed by the computer like opening a teaching application or renaming a file. The speech recognition process discussed in this paper involves two separate approaches; the first approach is based on double thresholds voice activity detection and improved Mel‐frequency cepstral coefficients (MFCC), while the second approach is based on discrete wavelet transform along with modified MFCC algorithm. Utilizing the best values for all parameters in just mentioned techniques, our proposed system achieved a recognition rate of 98.7% using the first approach, and 98.86% using the second approach of which is better in ratio than the first one but slower in processing which is a critical point for a real time system. Both proposed approaches were compared with other relevant approaches and their recognition rates were noticeably higher.

Factors affecting keystroke dynamics for verification data collecting and analysis

Nowadays, mobile devices are used to serve various functions; accessing the internet, accessing emails and storing information. Some of the stored and accessed data contain sensitive information such as passwords, bank credentials, and other important data. Consequently, authenticating users has become an important issue, especially with mobile systems. The development of the mobile systems has changed to touch screen system for user-friendly and quick access mechanism. This research studies the factors that affect the Keystroke Dynamics as authentication and verification technique. The study includes a questioner and data collection using HTML-Javascript-self-constructed webpage. The study involves 78 users in several situations. Five features, (Key Code, Up-Down latency, Down-Down latency, Key Hold and Overall latency) are analyzed while capturing samples from users and stored in a table format. Different machines, platforms and situations are used.