Cognitive Radio (CR) significantly improve spectrum utilization through dynamic spectrum access (DSA). Efficient utilization of the unused or partially used spectrum for providing opportunistic access to secondary users (SU) is the main function of CR. CR has to sense continuously radio environment and keep on adjusting its transmission parameters for opportunistic transmission without causing ...

In this paper, a combination of Space-Time BlockCoding (STBC) and Discrete Fourier Transform (DFT) frequency coding for OFDMA systems is proposed which provides low computational complexity, low envelope fluctuations of the transmit signals at each transmit antenna and significant performance gains for transmission over mobile radio channels due to exploitation of spatial diversity. The resulti...

This demonstration shows how VESNA wireless sensor nodes can be used for cognitive radio experiments involving wireless sensor networks. SNE-ISMTV is a radio frontend that has been developed for this purpose. Spectrum sensing capability in the TV white-spaces and 2.4 GHz ISM band is demonstrated by running receivers in a swept-tuned spectrum analyzer configuration and displaying measured spectr...

The demand for wireless connectivity to the Internet is increasing. As the network grows and assimilates an increasing range of both wireless and wire line link technologies, it is becoming increasingly heterogeneous. Compared to wire line transmission technologies, practical radio data transmission technologies are far more limited in capacity and reliability. This has lead to the development ...

Abstract This paper presents wavelet based analysis for transmission line fault location. Faults in power transmission lines cause transients that travel at a speed close to the speed of light and propagate along the line as traveling waves (TWs). Traveling wave theory is utilized in capturing the travel time of the transients along the monitored lines between the fault point and the protective...

The increasingly growing number of mobile devices and volume of mobile data traffic necessitate establishing an effective self-organizing wireless ad hoc network to efficiently utilize radio spectrum and energy. The transmissions time and bandwidth should be dynamically coordinated based on instantaneous traffic load of the links in the network. Energy consumption in a mobile device can be redu...

We demonstrate directlymodulated VCSELs supporting 2x2 MIMO-OFDM 5.6-GHz radio over fiber signaling over 20-km WDM-PON. Error-free signal demodulation of 64-subcarrier 4-QAM signals modulated at 198.5-Mb/s is achieved after fiber and 2-m indoor wireless transmission. OCIS codes: (060.0060) Fiber optics and optical communications; Radio frequency photonics (060.5625)

This paper attempts to provide some insight into the nature of radio propagation in that part of the spectrum (upper VHF to microwave) used by experimenters for high-speed digital transmission. It begins with the basics of free space path loss calculations, and then considers the effects of refraction, diffraction and reflections on the path loss of Line of Sight (LOS) links. The nature of non-...

[1] Here we present electron temperature variations observed with incoherent scatter radar during a European Incoherent Scatter Scientific Association Heating experiment with high‐frequency (HF) radio wave transmission at frequencies above the peak ionospheric critical frequency. The electron temperature increased from 2000 K up to 2800 K during the HF transmission periods. During the experimen...

In the fourth-generation (4G) mobile communication system, all communications including realtime communications is expected to be carried by packets multiplexed on a shared radio channel to improve the radio resource efficiency. Because the delay characteristics and the throughput of a packet radio channel vary greatly with changes in both traffic volume and radio channel quality, NTT DoCoMo pr...