Multicarrier code-division multiple-access is one of the effective techniques to gain its multiple access capability, robustness against fading, and to mitigate the ISI.In this paper, we propose an improved mulcarrier CDMA system with adaptive subchannel allocation. We analyzed the performance of our proposed system in frequency selective fading environment with narrowband interference existing...

In this paper, a code-division multiple access (CDMA) cellular overlay system is investigated, employing the idea of multicarrier CDMA, which has recently received significant attention as an alternative to traditional single-carrier CDMA [1]. Overlay is pursued here as a means of long-term transition from narrowband cellular to CDMA cellular. A major result of this paper is the demonstration t...

In this article we identify some of the key problems that may be encountered when designing a broadband multiple access system with bandwidth on the order of tens or even hundreds of megahertz. We commence with a comparative discussion in terms of the characteristics of three typical code-division multiple access schemes: single-carrier directsequence CDMA (SC DS-CDMA), multicarrier CDMA (MC-CD...

In this contribution, we have studied the performance of a Turbo-Coded (TC) Code Division Multiple Access (CDMA) based two-way relaying scheme. More explicitly, we employ a seven-user CDMA model, where two of the CDMA users are communicating with each other with the aid of an additional relay node, while the other five CDMA users are interferers. More explicitly, two CDMA users exchange their i...

Parallel simulation has not been widely accepted by the simulation practitioners due to the lack of language support and tools necessary for developing eecient parallel simulators. This paper describes the design of SPaDES (Structured Parallel Discrete-Event Simulation), a struc-tured parallel simulation workbench for developing portable simulation models, and a platform for designing experimen...

This paper describes a CSIM-based simulation tool, called MultiSim, which allows eecient simulation of large-scale mul-tiprocessors. Methods are described for simulating several variations of wormhole routing, including multicast communication , the use of variable-sized buuers at routers within the network, and the use of virtual channels. The key to eecient simulation of such networks is that...

Code Division Multiple Access (or CDMA) is a multiple access technique based on spectral spreading that has been tremendously successful in the wireless domain. The effectiveness of CDMA in applications like cellular networks, satellite systems and Wireless Local Loop systems has strongly contributed to maintaining the application of CDMA to the optical domain, also known as Optical CDMA, an ac...

A new-design methodology for the design of optimal spread-spectrum sequences for asynchronous code-division multiple acces (A-CDMA) and chip-synchronous CDMA (CS-CDMA) systems is proposed. We derive general results on the partial auto-correlation function of the optimal spreading sequences for CS-CDMA and A-CDMA systems with respect to the minimization of the average bit error rate under the st...

One of the main disadvantage of multi-carrier CDMA (MC-CDMA) signals is the high peak power of the transmitted signals which limits their applications. To account for this issue, we provide a simple signal processing for reducing the high crest factor (CF) of MC-CDMA signals. Using this modified MC-CDMA signal, the high CF due to Walsh spreading sequences can be mitigated without explicit side ...

The 3 generation mobile communication system will base on Code Division Multiple Access (CDMA) system, because CDMA system can provide more capacity than TDMA and FDMA systems. But signal will suffer from the interference called Multiple Access Interference (MAI).This problem can be reduced by using multi-user detection technique. This paper examines the Performance of Parallel Interference Can...