Ahmed Musa

An evolving recommender-based framework for virtual learning communities

This article presents a recommender framework to provide personalised suggestions for learners taking introductory undergraduate courses. The framework utilises memory-based collaborative filtering algorithm combined with an imbedded web crawler to update learning material. The process of providing recommendation is divided into four steps: learner model extraction, neighbourhood formation, top-N recommendation presentation, and material update. The framework was implemented and has been successfully tested on real learners taking an introductory mathematics course. The learners of the course were divided into two groups. One of the groups, control group, was taught the material of the course using the traditional face-to-face approach. However, the students in the other group, experimental group, had the advantage to use the framework. The performance of the learners in both groups was tested and the results showed that the learners in the experimental group outperformed their counterparts in the control group.

Developing a virtual laboratory for a communication and computer networking course

Educational institutions face financial challenges in maintaining and upgrading traditional physical laboratories. Moreover, university students have challenges in understanding the theoretical issues involved in communication and networking courses. This paper presents a new computer-aided laboratory to help the students to enhance the practical view of communication and networking systems using computer modelling and simulation and to replace a physical laboratory. The new laboratory was build using a component-based approach that integrates modelling and simulation tools, namely MATLAB, SIMULINK, VPI and OPNET. These components were integrated through the development of graphical user interface. Through this interface, the student navigates through experiments of the laboratory. The new laboratory curricula and interface were tested on students and their feedback showed that the students were satisfied. The students gave comments and suggestions for future improvements.

An efficient compression technique using Lempel-Ziv algorithm based on dynamic source encoding scheme

This paper proposes an efficient text compression technique based on dynamic source encoding scheme using Lempel-Ziv algorithms. A statistical analysis is performed to count the occurrence of each character in the original source. Accordingly, each character is replaced by a weighted fixed-length code in lieu of arbitrary codes such as ASCII. This replacement generates an equivalent binary source with two symbols zero and one. Thereafter, the bitwise Lempel-Ziv algorithms can be applied to the nth-order extension binary source that contains 2 n symbols. As a result, the proposed technique achieves a high compression ratio in comparison with those techniques that use static and arbitrary source encoding schemes. In the decompression process, a header file includes all characters sorted in descending order based on their frequency of occurrences along with the extension order (n) is received. Thus, each character can be restored back based on the code shared between the compression and decompression processes.

Architecture of a Dual-Stage Optical Label Switch Using Out-of-Band Wavelength and Code Optical Properties

A method of generating circuits in an optical network is optical multiple-protocol lambda switching (OMPlambdaS). For OMPlambdaS, the wavelength of the optical carrier is used as an out- of-band label to route data through the network without requiring periodic conversion to the electrical state. A method of adding a second dimension of optical encoding as an out-of-band label used for routing data through a label-switched network is presented. Combining wavelength and code multiplexing techniques generates an O3 circuit-switched network with a data capacity of up to 5.7 Tb/s on each point-to-point link in the network. The proposed architecture uses two stages to process and map labels for each bit transmitted through the network. The architecture and simulation results for the dual-stage optical label switch (DSOLS) are presented.

Limitations of all optical circuit-switched high data rate networks

This paper presents a method of adding a second dimension of optical encoding, as an out-of-band label, to be used for routing data through a label-switched network. Combining wavelength and code multiplexing techniques generates an optical circuit-switched network that can handle a data capacity of up to several Tb/s on each point-to-point link in the network. The proposed architecture uses two stages to process and map labels for each bit transmitted through the network. The architecture for the Dual Stage Optical Label Switch (DSOLS) is presented along with simulation results of its expected performance. A simulation package is used to analyze system performance. Using data generated from simulations a performance metric, based on Bit Error Rate (BER) to be used by an upper level routing algorithm is presented. Finally, a method of measuring the metric for a 2×2 (two codes and two wavelengths) DSOLS is described.

Analysis of Phase noise of RF signals in Analog Fiber Optic Systems

Stability of phase is a critical issue in several applications, especially those that require the transmission of reference signals. A fiber optic system is considered the best medium for the transmission of reference signals due to its high bandwidth, superior stability and immunity to external interference. Even in fiber optic links, phase stability becomes an issue as the microwave frequency of operation is increased. We quantify phase noise in an analog fiber optic system and also study the effect of optical amplification on the noise. The amplifier is placed at three different positions in the link, to check for significant variations in phase noise when no other link parameters are changed. The study also examines how phase noise is affected by changing transmitter power and wavelength. Experimental results indicate fluctuations in phase noise greater than 10dB for different transmitter power outputs while wavelength changes produce very little effect on the noise. Optical amplification increases the average phase noise by 3 to 6dB depending on the location of the amplifier in the link. In addition to experimental studies, computer simulations using virtual photonics (VPI) software are performed to confirm experimental results.

An Efficient Bit-Level Lossless Grayscale Image Compression Based on Adaptive Source Mapping

Image compression is an essential technique for saving time and storage space for the gigantic amount of data generated by images. This paper introduces an adaptive source-mapping scheme that greatly improves bit-level lossless grayscale image compression. In the proposed mapping scheme, the frequency of occurrence of each symbol in the original image is computed. According to their corresponding frequencies, these symbols are sorted in descending order. Based on this order, each symbol is replaced by an 8-bit weighted fixed-length code. This replacement will generate an equivalent binary source with an increased length of successive identical symbols (0s or 1s). Different experiments using Lempel-Ziv lossless image compression algorithms have been conducted on the generated binary source. Results show that the newly proposed mapping scheme achieves some dramatic improvements in regards to compression ratios.

Efficient Routing for Hybrid Optical-CDMA and WDM All-Optical Networks

This article presents a routing algorithm for all-optical networks that utilizes near future WDM and optical-CDM technologies. The assumption that parallel channels traversing the same path have the same metric (cost) is no longer valid. The algorithm adopts a flooding mechanism to compute metrics corresponding to every possible path between the source and destination nodes based on the link impairments and switch characteristics. From amongst computed costs, a selection is taken minimizing the cost by using Viterbi algorithm. This way, codes and wavelengths are assigned based on the characteristics of each link for each possible route, thus optimizing the networks performance

Dual Stage Optical Label Switch using out-of-band wavelength and code optical properties

A method of generating circuits in an optical network is Optical Multiple Protocol Lamda Switching (OMP?S). For OMPλS, the wavelength of the optical carrier is used as an out-of-band label to route data through the network without requiring periodic conversion to the electrical state. Presented is a method of adding a second dimension of optical encoding, as an out-of-band label, to be used for routing data through a label-switched network. Combining wavelength and code multiplexing techniques generates an O3 circuit-switched network with a data capacity of up to 5.7 Tb/s on each point-to-point link in the network. The proposed architecture uses two stages to process and map labels for each bit transmitted through the network. The architecture for the Dual Stage Optical Label Switch (DSOLS) is presented.