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WiMAX (world interoperability for microwave access) continues its development to achieve high capacity services with large cell coverage. Although, users at the cell border achieves only poor signal to interference plus noise ratio (SINR) conditions due to the high amount of interference from neighboring cells. In Egypt the 3.5 GHz band is expected to be used for the IEEE 802.16e mobile WiMAX networks...
OFDM Wireless systems are currently in the focus of research and development. High hardware cost of such systems is an initiative to redesign the critical functional blocks in order to satisfy timing and power constrains as well as to minimize overall circuit complexity and cost. One such critical functional block is the CoOrdinate Rotation DIgital Computer (CORDIC) that can be used in various applications...
In this paper, we present a modified ultra-wideband (UWB) antenna for ultra-wideband applications such as Wireless Communication and WiMax systems. It consists of a two circular-disc patch fed by a 50 Omega coaxial feed line. The obtained bandwidth (SWR les 2) is about 10 GHz (from 0.650 to 10 GHz with a bandwidth ratio (1:15.4)). The radiation characteristics are as expected for dipole antennas.
WiMAX (Worldwide Interoperability for Microwave Access) has the potential to impact all forms of telecommunications. In a fixed wireless communication, WiMAX can replace the telephone company's copper wire networks, the cable TV's coaxial cable infrastructure while offering Internet Service Provider services. In its mobile variant, WiMAX has the potential to replace cellular networks. However, it...
WiMAX systems are based on the IEEE 802.16-2004 and IEEE 802.16e-2005 standards which define a physical (PHY) layer and the medium access control (MAC) layer for broadband wireless access systems operating at frequencies below 11 GHz. Multiple-antenna techniques can be used to increase diversity and improve the bit error rate (BER) performance of wireless systems, increase the cell range, increase...
WiMAX top level SIMULINK model with all system details has been implemented for simulation purpose. This paper has focused on channel estimation with different interpolation approaches for fixed/mobile OFDM system with parameters from WiMAX standards. The Doppler shift had a greater impact on the relative performancebetween the different channel estimators and interpolation approaches. One of the...
Compression of medical images should be lossless to preserve details and to avoid wrong diagnosis. However, to achieve high compression ratios while maintaining image quality, only regions of interest (ROI). i.e., abnormal regions need to be losslessly compressed. The rest of the image if lossy compressed can lead to a reasonable overall compression ratios. In this paper, two techniques for determining...
In this paper, we introduce the rate adaptation problem in adaptive wireless multiuser OFDM systems and illustrate its optimal solution. Due to the high complexity of this solution, we illustrate a previously proposed two-step algorithm that was suggested to simplify the adaptation process. This algorithm is based on equal distribution of power on OFDM subcarriers. We then propose a new modification...
The increasing importance of portable computing/telecommunications applications has motivated the studies on broadband wireless network technologies such as wireless ATM (asynchronous transfer mode) or WATM. Orthogonal frequency division multiplexing (OFDM) is especially suitable for high-speed communication due to its resistance to inter symbol interference ISI. This paper describes an ATM network...
ATM operates on reliable wire-line backbones providing high-quality transport services in terms of delay, data corruption and data loss. When moving to the mobile radio channel, specific actions are undertaken to cope with a much tougher communication environment where noise, interference, and terminal mobility drastically cut down the network reliability and performance. This paper identifies alternative...
Telecom Egypt has decided to serve villages and urban areas by using fixed wireless access method; cdma2000 system is used where the deployment of wire lines network is difficult or not economical. The main disadvantage of the spreading and modulation of cdma2000 system is the occurrence of inter-symbol interference (ISI) due to multipath fading channel and difficulties of synchronization. MC-CDMA...
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