Volume, 19, Issue 2, April 2013

Design of STBC-WIMAX System by Using DWT with Four Transmit Antennas in Fading Channel [Full Text]

Laith Ali Abdul-Rahaim and Rusul Noori Saeed

Abstract - This paper provides details about the two main applications of World Interoperability for Microwave Access (WiMAX) which are fixed WiMAX and Mobile WiMAX. Fixed WiMAX 802.16 delivers point to multipoint broadband wireless access to our homes and offices. Whereas Mobile WiMAX gives full mobility of cellular networks at higher broadband speeds than other broadband networks like Wi-Fi. Both applications of WiMAX are designed in a proper network planning which is helpful to offer better throughput broadband wireless connectivity at a much lower cost. The design of the STBC-WiMax systems is based on DWT, simulations results, and evaluation tests of these proposed systems. The Bit Error Rate (BERs) and the operating range of these systems are obtained using frequency domain baseband simulations as well as more realistic full-system simulations, and are compared to other systems types designed using FFT and Discrete Wavelets transform DWT. The results of both systems in the three types of channels will be examined and compared. The effects of several parameters of wireless channels on the systems will be investigated. In the STBC-WiMax system the two types of the transform FFT and WT (Wavelet Transform) are considered. The new proposed structures for the STBC-WiMax system based on wavelet transform (DWT) will be studied. Different new techniques of realization of modulation mapping in the communication systems will be used throughout the preceding sections as a data mapper to obtain a constellated data symbols prior to the sub-carrier modulation. These WiMax systems were modeled using MATLAB V7.10 to allow various parameters of the system to be varied and tested. The aim of doing that simulation is to measure the performance of WiMax under different channel conditions. 

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Design and Implementation of 2 bits BCH Error Correcting Codes using FPGA
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Samir Jasam Mohammed and Hayder Fadhil Abdulsada

Abstract - Our paper considers the prototyping of a BCH (Bose, Chaudhuri, and Hocquenghem) encoder and decoder using a Field Programmable Gate Array (FPGA) reconfigurable chip. Designing on FPGA leads to a high calculation rate using parallelization (implementation is very fast), and it is easy to modify. BCH encoder and decoder have been designed and simulated using MATLAB, Xilinx-ISE 10.1 Web PACK and implemented in a xc3s700a-4fg484 FPGA. In this implementation we used 15 bit-size code word, any 2 bits error in any position of 15 bits has been corrected. The results show that the system works quite well. Our next projects is to build (15,5), 3 error correcting BCH code. 

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Performance Analysis of Coherent Optical OFDM (CO-OFDM) System with Dispersion Compensation [Full Text]

Laith Ali Abdul-Rahaim, Ibraheem Abdullah and Mayasah Razzaq

Abstract - This paper addresses theoretically some issues related to Coherent Optical OFDM (CO-OFDM) system and identifies some parameters that affect its performance. The performance of a long-haul CO-OFDM system at 40 Gb/s is simulated taking into account the effect of fiber chromatic dispersion. The results show that the dispersion compensation helps to extend the link length for about 60 times of that of the non-compensated system. 

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On solving the local minima problem of blind adaptive MIMO equalisation [Full Text]

Y. Ben Jemaa and M. Jaidane

Abstract— We consider in this paper the problem of blind MIMO-FIR channel equalization in a real context of digital transmission where the input data belongs to a finite alphabet set. A non linear equalizer with a Volterra structure is considered. A rigorous analysis using the classical approaches is difficult due to the non-linearity of the equation that governs the equalizer. Through a novel finite alphabet approach that we propose, we demonstrate that the problem of local minima is avoided when using, for adaptation, a particular family of algorithms including classical ones such as LMS. This was proven rigorously without using any assumptions in a digital transmission context when the input remains to a finite alphabet set. 

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A Novel U-Shaped Tri-Band Antenna on High Permittivity Multilayer Substrate for Wireless Communications [Full Text]

O. Aghzout, A. Naghar, F. Medina, M. Alaydrus and M. Essaaidi

Abstract—In this paper, a detailed study of a new proposed rectangular dielectric u-shaped tri-band antenna is presented. A meticulous study considering the high permittivity material effect is introduced and discussed.All the design procedures are performed by using CSTMS software. Moreover, by introducing a slot on the rectangular radiated patch, the modified shaped patch antennaoffers improved bandwidth and allows an important miniaturization in size. Note that the proposed antenna can be used for several wireless technologies, especially for the GSM, Bluetooth, Wi-Fi, WLAN, WiMAX, all bands GPS frequencies, ISM band and ultra wide band applications. Detailed design steps, parametric studies and the simulation results for the proposed antenna are investigated under specific scenarios. Finally some concluding remarks will be drawn.