Performance analysis of CDMA-based wireless communication systems using the simplified improved Gaussian approximation method

The limitations initially prevalent in CDMA-based systems have been gradually solved thereby making CDMA a very promising access mode for future communication systems. Following the move towards higher data transmission rates, however, a number of other problems have emerged that need to be tackled. As a result, current world-wide research on CDMA-based systems is geared towards high speed, highly mobile multimedia communication applications. In this paper, the performance of a multi-user DS-CDMA communication system operating in a Rayleigh fading environment is investigated. Performance expressions are derived and the variation of the performance with various system parameters is presented. Tanzania Journal of Science Vol. 30 (2) 2004: pp. 41-5

Throughput analysis of extended ARQ schemes

Various Automatic Repeat Request (ARQ) schemes have been used to combat errors that befall information transmitted in digital communication systems. Such schemes include simple ARQ, mixed mode ARQ and Hybrid ARQ (HARQ). In this study we introduce extended ARQ schemes and derive expressions for their throughput performance. We then compare their performance with mixed mode ARQ schemes where it is shown that extended ARQ schemes outperform the mixed mode ARQ schemes. We also show how the parameters for the schemes can be chosen to maximize performance.Keywords: ARQ, extended ARQ, HARQ, mixed mode ARQ, throughpu

The Z-Transform Applied to a birth-death Process Having Varying birth and death rates

The analysis of a birth-death process using the z-transform was recently reported for processes hav-ing fixed transition probabilities between states. The current report extends that analysis to proc-esses having transition probabilities that can differ from state to state. It is then shown that the model can be used to study practical queuing and birth-death systems where the arrival, birth, ser-vice and death rates may differ from state to state.Keywords: Markov processes, birth-death models, frame synchronization, queuing systems, z-transfor

The Z-Transform Applied to Birth-Death Markov Processes

Birth-death Markov models have been widely used in the study of natural and physical processes. The analysis of such processes, however, is mostly performed using time series analysis. In this report, a finite state birth‑death Markov process is analyzed using the z‑transform approach. The performance metrics of the system and their variation with the system parameters are then derived and presented. Keywords: Markov processes, birth-death models, frame synchronization, queuing systems, z-transform. Journal of Science and Technology Vol. 28 (2) 2008: pp. 75-8

Challenges in the Management of Road Safety in Tanzania: The Need for an Integration Framework

Tanzania is hardest hit by daily accident deaths and casualties on the roads. Although various measures have been taken by the government, enforcement agencies and NGOs, accidents and fatalities keep growing at a rate above that of killer diseases like malaria, tuberculosis and HIV. The main causes observed were that road safety has multiple key autonomous stakeholders having different fragmented information systems which are not inter-operable because of being proprietary in nature, thus inhibiting the timely and coordinated sharing of information among them. This paper presents the lessons learned from different stakeholders following a series of workshops and meetings with these key stakeholders to understand the problem from their institutional contexts. Hence, anintegration framework is developed and implemented to facilitate enforcement of road traffic regulations and to enable the different stakeholders cooperate and share information efficiently and with transparency in sustained road safety regulations enforcement. It is envisaged that if the integrated platform is successfully adopted, it can reduce the heavy duplication of efforts and investment in incoherent data systems by individual stakeholders in terms of hardware, consumables and personnel resources. The integrated platform for the road safety management system is in place, however, it needs a policy direction from the government to galvanise the major stakeholders

Comparison of direct return and birth-death return receivers.

The performance of frame synchronized communication systems is governed largely by the design chosen for the receiver. Some systems employ a structure in which the receiver returns directly to the sync phase when a valid marker is encountered while in the loss verify state. These have been greatly studied. In some systems, the return path in the loss verify phase is implemented as a birth-death process. These systems have not received much attention. In this report, a receiver which employs a birth-death like structure in the loss path is investigated. Expressions for the performance parameters are derived and compared with those obtained for direct return systems. It is found that both types of receivers have the same performance at lower error rates and low loss verify number, M. At high error rates and high values of M, however, the birth-death receiver outperforms the direct-return receiver. To the knowledge of the author, this is the first time that performance expressions have been reported in this form. Tanzania Journal of Science Volume 27 (2001), pp. 59-7

The analysis of an optical fibre communication system using laser rate equations.

Fibre dispersion has been the main limitation to high-speed data transmissions employing optical fibres. Various techniques and methods for combating this limitation have therefore been proposed. Such techniques include electrical and optical dispersion compensation, optical and electrical pulse shaping, and modifications of the fibre dispersion profiles. Some of these techniques and methods have resulted into very effective but expensive systems, and it has been difficult to adopt them. Others have resulted into inexpensive systems with moderate performance, and some of these have been adopted. In the present paper, the effect of electrical pulse shaping on dispersion-induced pulse distortion is investigated by computer simulation techniques. The results show that the detrimental effects of the dispersion can be greatly reduced without incurring very high costs. Moreover, this method is applicable to systems employing standard optical fibres, the major component in the already installed systems. Tanzania Journal of Science Volume 27 (2001), pp. 73-8