Adnan Rashdi

Grouping technique for cooperative spectrum sensing in cognitive radios

Cognitive networks can potentially solve the problems of spectrum scarcity by accommodating unlicensed (secondary) users in under-utilized segments of the spectrum. Spectrum sensing serves as the primary stimulus for a cognitive radio and is vitally important for ensuring that the unlicensed users do not offer intolerable levels of interference to licensed (primary) users. Cooperative spectrum sensing provides the capability to cognitive networks to overcome problems related to “hidden” primary users. In this paper, we present a novel technique that takes advantage of cooperative diversity to establish clustering among cooperating secondary users. This technique is then extended to group-based spectrum sensing to establish a tasking mechanism. The technique ensures enhanced agility that will result in a reduction of interference to primary users through their early detection.

Remote energy monitoring, profiling and control through GSM network

This paper presents design and development of a GSM based energy monitoring, profiling and control system. Our system integrates digital energy meters installed at consumer unit with an electric supply companys energy monitoring system. Single phase or three phase digital electric meter can be used with indigenously developed add on transmission module, which takes the meter reading and utilizes the GSM network to transmit the energy usage reading using Short Message Service (SMS) back to the energy supplier. At the supplier end, an energy monitoring system is used to manage all received meter readings, compute the billing cost, update the database and maintain an energy consumption profile for each user. Various alerts and control can also be generated by the supplier. A simple, cost effective and reliable working prototype of complete system has been developed using digital energy meter manufactured by MicroTech Limited, Pakistan to demonstrate an efficient and transparent means of automatic meter reading, billing and notification through the use of GSM network.

Spectrum Management for Digital Subscriber Lines

The performance of the digital subscriber lines (DSL) systems is severely constrained by the crosstalk due to the electromagnetic coupling among the multiple lines in a binder. Static spectrum management (SSM), the traditional way of ensuring spectral management, employs spectral masks which can be overly conservative and lead to poor performance. Dynamic spectrum management (DSM), a new paradigm overcomes this problem by designing an adaptive spectra of each modem to match specific topology of the network. In this paper we present a centralized spectrum management (CSM) algorithm which shows significant performance gains over DSM iterative waterfilling algorithm when applied to the very high bit rate digital subscriber lines (VDSL) upstream transmission.

Secure end-to-end communication over GSM and PSTN networks

GSM (Global System for Mobiles) is the most widely spread mobile communication system in the world. An important objective in mobile communication systems is secure speech communication. GSM suffers from various security weaknesses. The GSM voice traffic is secure outside the core network but it has no security over the core network. This system can be made thoroughly secure by encrypting the speech which is to be transmitted on the GSM voice channel. In this paper we have demonstrated a real-time prototype of an end-to-end secure communication system developed in MATLAB Simulink. Our technique comprises of encryption of the speech before entering the GSM handset which adds security and confidentiality to our communication. The encryption algorithm is private to the communicating GSM subscribers and even the service providing company will not judge what was said. This is amazing because now the GSM channel will become exclusively concealed and confidential to the two subscribers so that even the company people cannot listen to them.

A cluster based cooperative technique for Spectrum Sensing using Rely Factor

Recently, a low cost and reliable remote sensing infrastructure has emerged as one of the fundamental requirements for communication in sensor nodes of Cognitive Radio (CR) applications. To achieve this, an Energy Efficient Wireless Sensor Network (EEWSN) has significant importance for monitoring the entire CR Network (CRN). The foremost important aspect in CRN is the spectrum sensing for which different techniques have been proposed. In this paper, a Rely Factor (R-F) based scheme is proposed with Cluster based Cooperative Spectrum Sensing (CCSS) to reduce the bandwidth limitations in CRN using energy detection, which is the least complex spectrum sensing technique. The R-F based scheme is worked out on Signal to Noise Ratio (SNR), local sensing difference and threshold of energy detector of each sensor node. All these factors are combined using Fuzzy Logic to enhance the detection performance of sensor nodes. The results are shown in the form of Receiver Operating Curves (ROC) by simulations.

On the Security of LBlock against the Cube Attack and Side Channel Cube Attack

In this research, a recently proposed lightweight block cipher LBlock, not tested against the cube attack has been analyzed. 7, 8 and 9 round LBlock have been successfully attacked with complexities of O(210.76), O(211.11) and O(247.00) respectively. For the case of side channel cube attack, full version of LBlock has been attacked using a single bit leakage model with the complexity of O(255.00) cipher evaluations. For this purpose, a generic practical platform has been developed to test various stream and block ciphers against the latest cube attack.

Combining algebraic and side channel attacks on stream ciphers

A cryptanalysis technique can be termed successful if its complexity is better than brute force attack, even though it may not be practically feasible due to high complexity. However, it is a proven fact that combining different type of attack techniques in past has paid dividends with regards to overall complexity. We, in this paper propose novel idea of combining algebraic and side channel attacks on stream ciphers. Algebraic cryptanalysis has a high cost when pitched against stream ciphers with nonlinear update and for side channel attacks, adversary needs to have a continued access to ciphers implementation. On the other hand combining both these attacks can overcome their individual shortcomings to a great extent, thereby making it practically feasible. Algebraic and side channel attacks have been earlier combined on block ciphers, but no work on applying such attacks against stream ciphers has been published so far.

Echocardiography image enhancement using adaptive fractional order derivatives

Medical ultrasound images are low contrast in nature. Information regarding tissues and other important structure is required by a physician to assess patients health. Therefore image enhancement is a critical pre-processing task. In this paper a methodology based on emerging topic of fractional calculus is proposed. Proposed method is simple yet effective. In the proposed algorithm, input image is first divided into smooth, texture and edge regions using gradient magnitude of each pixel. Then appropriate order of fractional differential mask is selected to enhance each pixel. Proposed method is compared with state-of-the-art histogram equalization method and fixed-order fractional differential methods. Results are verified quantitatively and qualitatively. For quantitative analysis average gradient and entropy are used. Simulation results verify the effectiveness of proposed method.

Collusion-resistant Sybil attack detection scheme in mobile ad hoc networks

MANET is a collection of number of nodes that formulates; either, a temporary or permanent, self-organized wireless network that dont rely on any pivotal central architecture or control. They are designed to use in situations where infrastructure network is either non-existent or its extremely costly to deploy. MANETs require a distinctive, unique and insistent identity for each node for its security protocols to be effective; Sybil attacks present a grave threat to such networks. We can create large number of logical identities in a Sybil attack on a single physical device by a selfish malicious node which gives a false impression to the network that they are different benign nodes and uses them to launch a harmonized attack against the network or a node. Node cooperation is very important for detection of Sybil attack, but unfortunately nodes may not always behave cooperatively and may collude in hostile environments for disrupting the detection accuracy of such systems. Sybil nodes cannot be accurately detected in the presence of malicious collusion which results in serious impact on detection accuracy of Sybil attacks. This paper proposed a novel scheme in order to detect a Sybil attack resistant to collusion by incorporating a trust based mechanism that would mitigate the benefit (the payoff gained) from collusion. Experimental results show that our proposed scheme detects Sybil or whitewashers new identities accurately and reduces the benefits of collusion in the presence of mobility.

Design of a high gain pencil beam dipole antenna using parasitic elements in X-band

Using parasitic elements in different configurations, many parameters of an antenna can be modified. Most of these approaches were found to alter the fundamental characteristics such as input impedance, gain, polarization and radiation pattern of an antenna. Array antennas with high gain comprise of complex feed distribution which is a major hurdle design at higher microwave frequencies. Using parasitic elements show promise in addressing the complexity of amplitude and phase distribution in a very large array. Simulated results during research using parasitic elements with a dipole has shown promise in achieving desired radiation pattern characteristics without employing a complex feed network. The gain and beamwidth are both optimized to obtain the desired solution for a narrow beam high gain antenna providing high isolation when used in a bistatic configuration. The effect of parasitic elements on a dipole in relation to gain is also discussed; based on which an analytical model is proposed for the design in X-Band.