Method for applying spread-spectrum techniques to optical communication is presented. The interference suppression capability of spread-spectrum systems is shown to be enhanced by optical transform domain processing.Effects of jammer in DSSS communication system are demonstrated in thispaper.Several possible implementations of this system are suggested, and applications to fiber optics, laser r...

As discussed in Chapter 0, a spread spectrum modulation produces a transmitted spectrum much wider than the minimum bandwidth required. There are many ways to generate spread spectrum signals. We are going to introduce some of the most common spread spectrum techniques such as direct sequence (DS), frequency hop (FH), time hop (TH), and multicarrier (MC). Of course, one can also mix these sprea...

Independent Component Analysis (ICA) technique separates mixed signals blindly without any information of mixing system. The present work studies and analyses the issues involved in interference rejection in direct sequence spread spectrum communication systems based on Independent Component Analysis technique. The ICA technique tries to separate the unwanted interfering signal from the desired...

A major challenge in wide deployment of smart wireless devices, using different technologies and sharing the same 2.4 GHz spectrum, is to achieve coexistence across multiple technologies. The IEEE 802.11 (WLAN) and the IEEE 802.15.4e TSCH (WSN) where designed with different goals in mind and both play important roles for respective applications. However, they cause mutual interference and degra...

AbstmctThis paper proposes new multiuser detectors for frequency-hopped spread spectrum multiple-access (FHSSMA) based on binary frequency shift keying (BFSK) modulation and channelized frequency hopping. With knowledge of hopping sequences and envelopes of active users, the proposed scheme is a sub-optimal detector under maximum likelihood test. Diversity combining is employed as an anti-multi...

Mobile telephone systems divide the coverage area among low transmitting power sectors. This allows the so-called frequency reuse between sectors: geographically “distant” sectors might employ the same electromagnetic frequencies, since the probability of interference between them is small. The electromagnetic frequencies available for mobile communications are very limited and their use is reg...

In HF radio communications, the performance is often limited by the large amount of mostly narrowband interfering signals from other HF users. Therefore, when evaluating HF spread-spectrum systems, a statistical model of the interference is necessary. In this work, we perform a comparison between a frequency-hopping (FH) and a direct-sequence (DS) spread-spectrum system, for an interference mod...

As the number of wireless devices sharing the unlicensed 2.4 GHz ISM band increases, interference is becoming a problem of paramount importance. We experimentally investigate the effects of controlled 802.11b interference as well as realistic urban RF interference on packet delivery performance in IEEE 802.15.4 body area networks. Our multi-channel measurements, conducted with Tmote Sky sensor ...

The number of radio systems operating in the 2.4 GHz band is rising as a result of increased usage of wireless technologies. Since such devices interfere with one another, satisfactory co-existence becomes important. Several techniques serve to reduce the interference. Included among these are frequency hopping (FH) and power control. From the simulation results it can be seen that frequency ho...

The pressure dependence of the Mott, spin-density-wave and superconducting instabilities of the metallic state of the Bechgaard and Fabre salts is analyzed using weak coupling scaling theory. We show how the mechanism of quantum interference between pairings in the density-wave and superconducting channels, when combined to the influence of intrachain Umklapp scattering and inter-chain hopping ...