VoIP over WLAN: What about the Presence of Radio Interference?

In this chapter, the performance of VoIP over WLAN is analyzed under the effect of physical layer interference, in the presence and absence of cross-traffic. The goal is twofold: first to underline the importance of radio interference in the behavior of a WLAN when supporting VoIP applications; second to outline solutions to avoid interference and thus optimizing a VoIP call over aWLAN. To this aim, an experimental approach based on cross-layermeasurements is adopted, describing and commenting meaningful results obtained from a number of experiments conducted by the authors on a testbed operating in a semi-anechoic chamber and emulating two typical real life scenarios

Cross-Layer measurement on an IEEE 802.11g wireless network supporting MPEG-2 video streaming applications in the presence of interference

The performance of wireless local area networks supporting video streaming applications, based on MPEG-2 video codec, in the presence of interference is here dealt with. IEEE 802.11g standard wireless networks, that do not support QoS in according with IEEE 802.11e standard, are, in particular, accounted for and Bluetooth signals, additive white Gaussian noise, and competitive data traffic are considered as sources of interference. The goal is twofold: from one side, experimentally assessing and correlating the values that some performance metrics assume at the same time at different layers of an IEEE 802.11g WLAN delivering video streaming in the presence of in-channel interference; from the other side, deducing helpful and practical hints for designers and technicians, in order to efficiently assess and enhance the performance of an IEEE 802.11g WLAN supporting video streaming in some suitable setup conditions and in the presence of interference. To this purpose, an experimental analysis is planned following a cross-layer measurement approach, and a proper testbed within a semianechoic chamber is used. Valuable results are obtained in terms of signal-to-interference ratio, packet loss ratio, jitter, video quality, and interference data rate; helpful hints for designers and technicians are finally gained

PSD estimation in Cognitive Radio systems: a performance analysis

Peer Reviewe

Reliable and Repeatable Power Measurements in DVB-T Systems

Non

On Employing a Savitzky-Golay Filtering Stage to Improve Performance of Spectrum Sensing in CR Applications Concerning VDSA Approach

Abstract In this paper, a filtering stage based on employing a Savitzky-Golay (SG) filter is proposed to be used in the spectrum sensing phase of a Cognitive Radio (CR) communication paradigm for Vehicular Dynamic Spectrum Access (VDSA). It is used to smooth the acquired spectra, which constitute the input for a spectrum sensing algorithm. The sensing phase is necessary, since VDSA is based on an opportunistic approach to the spectral resource, and the opportunities are represented by the user-free spectrum zones, to be detected through the sensing phase. Each filter typology presents peculiarities in terms of its computational cost, de-noising ability and signal shape reconstruction. The SG filtering properties are compared with those of the linear Moving Average (MA) filter, widely used in the CR framework. Important improvements are proposed