Deterministic Formulization of SNR for Wireless Multiuser DS-CDMA Networks

Wireless Multiuser receivers suffer from their relatively higher computational complexity that prevents widespread use of this technique. In addition, one of the main characteristics of multi-channel communications that can severely degrade the performance is the inconsistent and low values of SNR that result in high BER and poor channel capacity. It has been shown that the computational complexity of a multiuser receiver can be reduced by using the transformation matrix (TM) algorithm [4]. In this paper, we provide quantification of SNR based on the computational complexity of TM algorithm. We show that the reduction of complexity results high and consistent values of SNR that can consequently be used to achieve a desirable BER performance. In addition, our simulation results suggest that the high and consistent values of SNR can be achieved for a desirable BER performance. The performance measure adopted in this paper is the consistent values of SNR.Comment: 9 pages IEEE format, International Journal of Computer Science and Information Security, IJCSIS July 2009, ISSN 1947 5500, Impact Factor 0.42

An Efficient Routing Algorithm for Mesh-Hypercube (M-H) Networks

Proceedings of the International Conference on Parallel and Distributed Processing Techniques and Applications (PDPTA'08, ISBN Set # 1-60132-084-1), Editors: Hamid R. Arabnia and Youngsong Mun, 2008.This paper presents an efficient routing algorithm for the Mesh-Hypercube (M-H) network. The M-H network is one of the new interconnection networking techniques use to build high performance parallel computers. The combination of M-H networks offers high connectivity among multiple nodes, fault-tolerance, and load scalability. However, the performance of M-H networks may degrade significantly in the presence of frequent link or node failures. When a link or node failure occurs, neither the hardware schemes nor point to point and multistage routing algorithms can be used without adding extra links. This paper presents an efficient single bit store and forward (SBSF) routing algorithm for MH network that based on the round robin scheduling algorithm. Simulation and numerical results suggest that the proposed routing algorithm improves the overall performance of M-H network by both reducing the transmission delay and increasing the total data throughput even in the presence of faulty nodes.http://www.world-academy-of-science.org

A New Mathematical Model for Optimizing the Performance of Parallel and Discrete Event Simulation Systems

Null message algorithm is an important conservative time management protocol in parallel discrete event simulation systems for providing synchronization between the distributed computers with the capability of both avoiding and resolving the deadlock. However, the excessive generation of null messages prevents the widespread use of this algorithm. The excessive generation of null messages results due to an improper use of some of the critical parameters such as frequency of transmission and Lookahead values. However, if we could minimize the generation of null messages, most of the parallel discrete event simulation systems would be likely to take advantage of this algorithm in order to gain increased system throughput and minimum transmission delays. In this paper, a new mathematical model for optimizing the performance of parallel and distributed simulation systems is proposed. The proposed mathematical model utilizes various optimization techniques such as variance of null message elimination to improve the performance of parallel and distributed simulation systems. For the sake of simulation results, we consider both uniform and non-uniform distribution of Lookahead values across multiple output lines of an LP. Our experimental verifications demonstrate that an optimal NMA offers better scalability in parallel discrete event simulation systems if it is used with the proper selection of critical parameters

A Mathematical Model for Evaluating the Performance of Multicast Systems

© 2008 IEEE. Reprinted, with permission, from Syed S. Rizvi, Aasia Riasat, and Khaled M. Elleith, "A Mathematical Model for Evaluating the Performance of Multicast Systems," The 1st IEEE International Workshop on IP Multimedia Communications (IPMC 2008) August 4 - 7, 2008, St. Thomas U.S. Virgin IslandsThe Internet is experiencing the demand of high-speed real-time applications, such as live streaming multimedia, videoconferencing, and multiparty games. IP multicast is an efficient transmission technique to support these applications. However, there are several architectural issues in this technique that hinder the development and the deployment of IP multicast such as a lack of an efficient multicast address allocation scheme. On the other hand, End System Multicasting (ESM) is a very promising application-layer scheme where all the multicast functionality is shifted to the end-users. Supporting high-speed real-time applications always demand a sound understanding of these schemes and the factors that might affect the end-user requirements. In this paper we attempt to propose both analytical and the mathematical models for characterizing the performance of IP multicast and ESM. Our proposed mathematical model can be used to design and implement a more efficient and robust ESM model for the future networks

The Impact of Reduced Computational Complexity Of Multiuser Detectors on the Processing Gain in a Wireless DS-CDMA Multiuser System

In this paper, a new scheme for reducing the computational complexity of multiuser receivers is presented. It utilizes the transformation matrix (TM) algorithm to improve the performance of multiuser receivers by effectively reducing the bit error rate (BER). In addition, a deterministic formalization of the processing gain (PG) for a multiuser DS-CDMA system is presented. The proposed formalization of the PG demonstrates that how the reduced BER could be used to achieve reasonable values of PG by which unwanted signals or interference can be suppressed relative to the desired signal at the receiving end. The proposed algorithms not only are shown to substantially improve the performance of the multiuser detectors by means of reduced BER but also have a much lower multi-access interference. The performance measure adopted in this paper is the achievable bit rate for a fixed probability of error (10-7) and consistent values of the PG

Minimizing the Null Message Exchange in Conservative Distributed Simulation

The final publication is available at http://link.springer.com/chapter/10.1007%2F978-1-4020-6266-7_80.The performance of a conservative time management algorithm in a distributed simulation system degrade s significantly if a large number of null messages are exchanged across the logical processes in order to avoid deadlock. This situation gets more severe when the exchange of null messages is increased due to the poor selection of key parameters such as lookahead values. However, with a mathematical model that can approximate the optimal values of parameters that are directly involved in the performance of a time management algorithm, we can limit the exchange of null messages. The reduction in the exchange of null messages greatly improves the performance of the time management algorithm by both minimizing the transmission overhead and maintaining a consistent parallelization. This paper presents a generic mathematical model that can be effectively used to evaluate the performance of a conservative distributed simulation system that uses null messages to avoid deadlock. Since the proposed mathematical model is generic, the performance of any conservative synchronization algorithm can be approximated. In addition, we develop a performance model that demonstrates that how a conservative distributed simulation system performs with the null message algorithm (NMA). The simulation results show that the performance of a conservative distributed system degrades if the NMA generates an excessive number of null messages due to the improper selection of parameters. In addition, the proposed mathematical model presents the critical role of lookahead which may increase or decrease the amount of null messages across the logical processes. Furthermore, the proposed mathematical model is not limited to NMA. It can also be used with any conservative synchronization algorithm to approximate the optimal values of parameters.http://link.springer.com/chapter/10.1007%2F978-1-4020-6266-7_8

Deterministic Formulization of End-to-End Delay for Multicast Systems

End-System multicasting (ESM) is a promising application-layer scheme that has been recently proposed for implementing multicast routing in the application layer as a practical alternative to the IP multicasting. Moreover, ESM is an efficient application layer solution where all the multicast functionality is shifted to the end users. However, the limitation in bandwidth and the fact that the message needs to be forwarded from host-to-host using unicast connection, and consequently incrementing the end-to-end delay of the transmission process, contribute to the price to pay for this new approach. Therefore, supporting high-speed real-time applications such as live streaming multimedia, videoconferencing, distributed simulations, and multiparty games require a sound understanding of these multicasting schemes such as IP multicast and ESM and the factors that might affect the end-user requirements. In this paper, we present both the analytical and the mathematical models for formalizing the end-to-end delay efficiency of both IP and ESM multicast systems. For the sake of the experimental verifications of the proposed models, simulation results are presented in this paper. Finally, the proposed formulization can be used to design and implement a more robust and efficient multicast systems for the future networks

Combining Private and Public Key Encryption Techniques for Providing Extreme Secure Environment for an Academic Institution Application

This paper presents the implementation of a secure application for an academic institution that offers numerous services to both students and the faculty. The primary focus of this paper is to provide a technical implementation of a new architecture for encrypting the database. The scope of this paper mainly includes but is not limited to symmetric and public-key cryptography, authentication, key management, and digital signatures. The final results of this paper demonstrate that what security features one should implement in order to achieve a highly secured application. This paper presents the implementation of a stand alone system that can be implemented on any legacy systems, and still operates effectively. In other words, it is self sufficient in terms of the data that it stores

Performance Model for a Conservative Distributed Simulation Environment Using Null Messages to Avoid Deadlock

A conservative distributed simulation requires all logical processes (LPs) to follow the causality constraint requirement. This implies that all event-messages are processed in strictly timestamp order. Apart from the timestamp of each event generated by LPs, synchronization between all LPs is the second most important requirements. Finally, there must not be a deadlock in the distributed environment. A deadlock may occur when there is no events present in the queue of LP. In such case, to avoid deadlock, Chandy-Misra-Bryant presented an algorithm called Null Message Algorithm (NMA) [3]. These null messages are passed as an event-message to other LPs and it stored in one of queues of LPs. This null message indicates that till the time stamp of that null message, all other events in the queue which have lesser time stamp than null message’s time stamp are safe to process. It means that there won’t be any arrival of any events from that logical process until current simulation time is equal to the time stamp of the null message. With the time stamp of the null message, a Lookahead value is added to the time stamp of that null message. This Lookahead value can be measure on certain kind of parameters such as delay to transmit a message, propagation delay, etc. therefore, calculating value of Lookahead is the most important part as Lookahead value affects the performance of the conservative distributed event simulation. Proper value of Lookahead can reduce the number of null messages which decreases the traffic of the network. In this paper, we demonstrate some calculation on the Lookahead which shows the performance of the distributed event simulation

A Quantitative Analysis Of Handover Time At MAC Layer For Wireless Mobile Networks

Extensive studies have been carried out for reducing the handover time of wireless mobile network at medium access control (MAC) layer. However, none of them show the impact of reduced handover time on the overall performance of wireless mobile networks. This paper presents a quantitative analysis to show the impact of reduced handover time on the performance of wireless mobile networks. The proposed quantitative model incorporates many critical performance parameters involve in reducing the handover time for wireless mobile networks. In addition, we analyze the use of active scanning technique with comparatively shorter beacon interval time in a handoff process. Our experiments verify that the active scanning can reduce the overall handover time at MAC layer if comparatively shorter beacon intervals are utilized for packet transmission. The performance measures adopted in this paper for experimental verifications are network throughput under different network loads.http://airccse.org/journal/jwmn/1109s2.pd