The most challenging problem in Cognitive radio is the detection of unused frequency bands and exploit them opportunistically for spectrum access. Cognitive radios must be able to efficiently detect the primary users even in low signal-to-noise ratio (SNR) condition and in fading environments. These difficulties can be overcome by exploiting the cyclostationary signatures exhibited by communications signal. Cyclostationary signatures are embedded in the physical properties of communications signal and they can be used to distinguish between the primary user and secondary user.In this paper, we investigate the problem of detecting vacant spectral bands using cyclostationary feature extraction method. Approaches for the detection of cyclostationary signatures are outlined and the simulation results are presented.

The dynamic growth of Information and Communication Technology (ICT) have considerably increased the energy requirements and also contribute a growing fraction to CO 2 emissions, thereby creating a need for wireless communications to be more energy-efficient. In this paper, Cell Zooming concept is implemented for reducing the overall power consumption of the network for a five cell microcellular network adopting SON technique. When the traffic load is low in central base station, it could be switched off while its users are given coverage by cell zooming the neighboring cells. Simulation results indicate that by using the Cell Zooming concept, nearly 20% of the overall power consumption of the network can be reduced. This would herald the emergence of the Green Base Station in Wireless Cellular Network.

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The explosive growth of mobile communications coupled with the recent findings regarding the health and environmental hazards gives rise to a compelling case to reduce the electromagnetic pollution (EMP). While the harmful effects of EMP have been widely reported, there appears to be no objective measure to quantify EMP from the mobile communications perspective. Such an objective measure is a prerequisite to model, measure, monitor and manage EMP. In this paper, an attempt is made to define EMP in mobile communications and propose electromagnetic pollution index (EPI) as the product of normalized polluted area and polluting energy in a cell. Assuming free space propagation and isotropic antennas, a model for EPI is developed and relationships are derived to understand the fundamental factors contributing to EPI. To illustrate the use of EPI, an example is presented along with insights into managing EMP. Suggestions are made regarding the scope for further work in extending the model and multi-disciplinary research in EMP. As managing EMP is emerging as an important aspect of preserving our biosphere, this paper serves the need for a first step towards 'True' Green Mobile Communications.

Ultra-Wideband (UWB) communication system provides high accurate localization due to the high multipath resolution capacity. For Ultra-Wideband (UWB) Localization systems, time-based schemes namely Time of Arrival (TOA) and Time Difference of Arrival (TDOA) provide very good accuracy due to the high time resolution (large bandwidth) of UWB signals. Due to the inherent suitability aad accuracy of time-based approaches for UWB systems, particularly the TDOA technique, it is proposed as the appropriate UWB localization technique for the precision automobUe parking system. UWB pulse of 0.5 ns pulse width is simulated. Tests measurements are conducted using Impulse Radio UWB transceiver test setup. The TDOA values are measured for different positions of tag and reference nodes. Time-delay estimation is obtained by generalized cross correlation method and position esti....tion is obtained by direct method (DM) using hyperboHc navigation. The precision of the obtained position estimation is improved by an iterative Davidon-Fletcher-Powell (DFP) algorithm. The performance of the technique is analysed by determining the mean square error for various reference nodes densities. The proposed system is composed of UWB nodes, UWB tags and an UWB location server. With UWB tags, equipped only with transmitters, on targets and UWB nodes with both transmitters and receivers, installed on infrastructure, the system calculates the position of the tags precisely.