Rapid evolution of wireless systems caused an enormous growth of data streams transmitted through the networks and, as a consequence, an accompanying demand concerning spectrum resources (SR). An avoidance of advisable disturbances is one of the main demands in military communications. To solve the interference problems, dynamic spectrum management (DSM) techniques can be used. Two main techniques are possible: centralized Coordinated Dynamic Spectrum Access (CDSA) and distributed Opportunistic Spectrum Access (OSA). CDSA enables the wireless networks planning automation, and systems dynamic reaction to random changes of Radio Environment (RE). For OSA, cognitive radio (CR) is the most promising technology that enables avoidance of interference with the other spectrum users due to CR’s transmission parameters adaptation to the current radio situation, according to predefined Radio Policies rules. If DSM techniques are used, the inherent changes in EW systems are also needed. On one hand, new techniques of jamming should be elaborated, on the other hand, the rules and protocols of cooperation between communication network and EW systems should be developed.
The rapid development of systems which use wireless technologies causes the escalation of the spectrum shortage problem. That is why the concept of coordinated dynamic spectrum management has appeared. It improves efficiency of the spectrum use and makes radio communication systems more resistant to interferences. The main element of the proposed solution is a frequency broker which provides frequency assignment plans for radio networks. Direct communication between the frequency broker and radio networks enables fast change of radio data. This paper presents an anti-interference method based on dynamic spectrum management, which is an implementation and extension of IST- 104/RTG-050 research task group “Cognitive Radio in NATO II” recommendations. The solution presented by the authors was tested in emulated and real environment. The designed algorithm of frequency assignment can effectively prevent interferences (including jamming) thanks to the implementation of monitoring mechanisms capable of obtaining information about the current state of radio channels from radio networks. Directions for further development of frequency planning algorithm based on belief distorted Nash equilibria for deterministic or stochastic beliefs were proposed.
Although recent years bring massive astronomical surveys which have been extensivly searched, there are still
many mysteries burried in the data. We attempt to extract objects with untypical emission lines. Especialy those
with with weak and absent emission but without significant absorption. For that purpose we created database
which contains quasars spectra for a quick access and peaks detection code in R environment what we describe
in this article.
Drift Scanner Method is very effective procedure used to reduce the phase drift effect in the radio links. The effect "out
of tuned" signal in the basic frequency band is a result of small, long term stability codec's clocks both at the transmitter
and receiver's side as well as small stability of HF or VHF carrier frequency in the standard modulators and
demodulators in the radio transceiver configuration. The paper presents experimental results carried out in the radio links
with applied procedure of reducing total output phase drift (ppm value) by using Phase Drift Scanner method. Described
method is also useful in watermarking applications.
Proc. SPIE. 6159, Photonics Applications in Astronomy, Communications, Industry, and High-Energy Physics Experiments IV
KEYWORDS: Transmitters, Modulation, Receivers, Digital watermarking, Telecommunications, Signal processing, Orthogonal frequency division multiplexing, Digital electronics, Signal detection, Binary data
In this paper we proposed OFDM-based technology system for correspondent verification in telecommunication digital channels. The watermarking technology can be used for hiding secret digital signature in original signal. We proposed system based on psychoacoustic correction and OFDM technology using secret signature for sender detection.