2008/3

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    Performance of Advanced Hybrid Link Adaptation Algorithms in Mobile Radio Channel
    (Společnost pro radioelektronické inženýrství, 2008-09) Wieser, Vladimir; Psenak, Vladimir
    The fast power adaptation is essential for WCDMA based mobile radio networks, as 3G UMTS. Although the first version of UMTS has been released in 1999 (Release 99) evolution was not finished yet. Quality of Service (QoS) and user data rate (e.g. HSDPA and HSUPA) are continuously increasing from release to release. Even though link adaptation frequency (1500 times per second) seems to be enough to span accidental fadings of mobile radio channel, used link adaptation algorithm is based on non-actual information about mobile radio channel state, which causes transmitter reaction delay to the actual channel state. Usage of appropriate prediction method to estimate near future channel state seems to be a valuable step to improve hybrid link adaptation algorithm. In this article we have described and simulated the new SIR-slot based advanced link adaptation algorithms. Algorithms were designed to increase efficiency of data transmission among a user equipment and base stations (uplink) for different simulation environments (pedestrian channel with mobile subscriber speed 5 km/h, 15 km/h and vehicular channel with speed 45 km/h).
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    Estimating PSNR in High Definition H.264/AVC Video Sequences Using Artificial Neural Networks
    (Společnost pro radioelektronické inženýrství, 2008-09) Slanina, Martin; Ricny, Vaclav
    The paper presents a video quality metric designed for the H.264/AVC codec. The metric operates directly on the encoded H.264/AVC bit stream, parses the encoding parameters and processes them using an artificial neural network. The network is designed to estimate peak signal-to-noise ratios of the video sequence frames, thus enabling computation of full reference objective quality metric values without having the undistorted video material prior to encoding for comparison. We present the metric framework and test its performance for LDTV (low definition television) as well as HDTV (high definition television) video material.
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    Preamble Design Problematic with 802.11a IEEE Standard (Minn’s Training Sequence Approach)
    (Společnost pro radioelektronické inženýrství, 2008-09) Oni, Romeo R. A.
    Generally OFDM systems use a predefined signal pattern, called preamble [2] [3], which helps the receiver to achieve a better signal detection (coarse, fine time synchronization) with the frequency offset and channel estimation. In most of the time having all these conditions fulfilled the receiver achieves relatively a good performance while keeping as low as possible the total consuming power and the BER (Bite Error Rate). This paper presents the results obtained while combining a part of the preamble [2] [3] and the Minn\'s training sequence. We have got interesting performance results comparable to those results obtained for the relatively new standard 802.16a.
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    Dispersion and Pulse Interferences Investigation for UWB Signal Propagation
    (Společnost pro radioelektronické inženýrství, 2008-09) Urban, Robert; Zvanovec, Stanislav
    The Ultra WideBand (UWB) technology utilizing nanosecond pulses has been one of the main phenomena in communications and radar applications for several years. This paper discusses the basic measurement techniques of impulse systems, particularly focusing on the dispersion and pulse interferences of the UWB propagation channel. Propagation aspects of two-ray approach are investigated in depth, using both measurements and simulations.
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    Bistatic and Multistatic Radar Systems
    (Společnost pro radioelektronické inženýrství, 2008-09) Bezousek, Pavel; Schejbal, Vladimir
    Radar systems, based on bistatic radar concept attracted a substantial attention in the recent years. Passive coherent location systems using \"transmitters of opportunity\" like radio or TV broadcasters, GSM base stations, satellite communication and GNSS signals proved their potential in detection and tracking moving targets over a significant area. In this paper the multistatic location system with non-cooperative transmitters is described and various aspects of signal processing and signal parameters are discussed.