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Propagation Channel (propagation + channel)
Selected AbstractsArray antenna assisted doppler spread compensator for OFDMEUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 5 2002Minoru Okada This paper proposes a novel array-antenna-assisted Doppler spread compensator for orthogonal frequency division multiplexing (OFDM), which is sensitive to fast time-variation of the radio propagation channel. In the proposed compensator, a linear array antenna is installed on top of the vehicle. The compensator estimates the received signal at a certain point on the linear array antenna by using space domain interpolation. Because the relative position of the estimated receiving point with respect to the ground does not change during the effective symbol duration of an OFDM signal, the time variation due to the movement of the vehicle can be compensated for. Computer simulation shows that the compensator can compensate for the bit error rate performance degradation due to time-variation of the channel when the velocity of the vehicle is up to 180km/h and a two-element array antenna is used at the carrier frequency of 600 MHz. The bit error rate performance can be further improved by using a four-element array antenna. [source] Active measurements of antenna diversity performances using a specific test-bed, in several environmentsINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 3 2010Moctar Mouhamadou Abstract The diversity performances of the wireless devices operating in a multipath propagation environment are usually presented in terms of correlation coefficient, diversity gain and effective diversity gain. These parameters can be measured in reverberation chamber. This paper presents some active measurements of antenna diversity performances on a small wireless terminal in several realistic environments. The measurements were performed in the WiMax band, i.e. at 3.5 GHz, in a reverberation chamber where the channel is statistically uniform, in a real indoor propagation channel, and in an outdoor-to-indoor environment. The diversity performances are evaluated by using a specific test-bed constituted by an arbitrary signal generator and two radio-frequency digitizers. The effectiveness of diversity is presented in terms of effective diversity gain, signal to noise ratio, bit error rate and frame error rate. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010. [source] Alternative approach to low-noise amplifier design for ultra-wideband applicationsINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 2 2007Qiang Li Abstract Conventional ultra-wideband low-noise amplifiers require a flat gain over the entire 3.1,10.6 GHz bandwidth, which severely restraints the trade-off spaces in low noise amplifier design. This article proposes a relaxed gain-flatness requirement based on system level investigations. Considering the wireless transceiver front-end with antenna and propagation channel, the unflat-gain low-noise amplifier with an incremental gain characteristic does not degrade the performance of overall system. As an alternative to its flat-gain counterpart, the proposed unflat gain requirement tolerates gain ripple as large as 10 dB, which greatly eases the design challenges to low-noise amplifier for ultra-wideband wireless receivers. Two low-noise amplifier examples are given to demonstrate the feasibility and design flexibility under the proposed gain-flatness requirement. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007. [source] Review of generative models for the narrowband land mobile satellite propagation channelINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 4 2008F. P. Fontan Abstract The land mobile satellite (LMS) propagation channel is frequently described using statistical models. These models usually make different assumptions regarding the behavior of the direct signal, the diffuse multipath component and the shadowing effects. This paper analyzes the theoretical formulation and implementation of time-series synthesizers based on three typical statistical models: Loo, Corazza,Vatalaro and Suzuki, describing their similarities and differences. The discussion is not limited to the amplitude of the complex envelope but also to the phase variations and Doppler spectra. Finally, guidelines are also provided for comparing model parameters supplied by different authors. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||