AbstractThe Advanced Communication Technology Satellite (ACTS) is an experimental communications satellite system launched in September 1993. ACTS introduces many new technologies, including operation in the Ka frequency band. ACTS uses multiple hopping narrow beams and very small aperture terminal (VSAT) technology to establish a system availability of 99.5% for a bit-error-rates of 5x10 or be...

In this paper, we propose a sub-band basis spectrum model which is a new spectrum representation model based on a linear combination of sub-band basis vectors. We apply sparse coding to the pitch-synchronously analyzed log-spectra. Based on the approximation of the resulting basis, we obtain subband basis vectors with 1-cycle sinusoidal shapes that have mel-scale for lower frequencies and equal...

This paper presents results from spectrum occupancy measurements in the 2.3-2.4 GHz band at Turku, Finland. The band is currently under study in European regulation and standardization for mobile communication systems. We review the recently introduced Licensed Shared Access (LSA) concept as a potential means for making the 2.3-2.4 GHz band available for mobile communications on a shared basis ...

An active, photonic band gap-based microcavity emitter in the near infrared is demonstrated. We present direct measurement of the spontaneous emission power and spectrum from a microcavity formed using a two-dimensional photonic band gap structure in a half wavelength thick slab waveguide. The appearance of cavity resonance peaks in the spectrum correspond to the photonic band gap energy. For d...

The UHF band between 470-790 MHz, currently occupied by digital terrestrial TV (DTT) distribution in Europe, is widely regarded as a premium spectrum band for providing mobile coverage. With the exponential increase in wireless data traffic in recent years, there has been growing interests in gaining access to this spectrum band for wireless broadband services. The secondary access in TV White ...

The natural outcome of theoretical calculations of microwave background anisotropy is the angular power spectrum Cl as a function of multipole number l. Experimental Cl’s are needed for direct comparison. Estimation procedures using statistics linear in the pixel amplitudes as well as the conventional but less useful quadratic combinations are described. For most current experiments, a single b...

In 1939 Keilin and Hartree (2) advanced the concept that there are two cytochrome components reacting between cytochrome c and oxygen; namely, cytochrome a and cytochrome a3. They based their hypothesis principally on the action of carbon monoxide which caused the a-band of reduced cytochrome a to spread toward 590 rnp and the r-band at 448 rnp to shift to 430 rnp and to be replaced by a very p...

In this paper a model to investigate the spectrum opportunities for cognitive radio networks in three radar frequency bands L, S and C at a specific location is introduced. We consider underlay unaware spectrum sharing model. The Secondary System we assume is an OFDM based system. The followed strategy is built upon defining a specific co or adjacent channel as a spectrum opportunity if -and on...

Spectrum access protocols permit secondary users to transmit on frequency bands that are not being utilized by the primary owners. A cognitive radio that wishes to transmit in a band must first decide if the band is available (i.e., not being used by the owner) and then it must periodically re-evaluate the band’s availability once it begins transmitting in the band to ensure that a signal from ...