Usean gigabitin langaton tiedonsiirto 60 GHz:lla: keilanmuodostus ja mittauksia

Usage of wireless communication systems has been growing steadily during the past decades as more and more services and users are starting to utilize various cloud based systems. Need for higher data rates and the exponential increase of users are becoming significant difficulties for the current wireless communication systems. To tackle this problem, frequency bands of several gigahertz have been suggested for the next generation of local and personal communication systems (WLAN/WPAN). The extremely large unlicensed band at 60 GHz is an attractive option to provide multi-gigabit data rates over short distances. However, even at short distances systems have to compensate the poor link budget which is due to increased frequency and bandwidth. To mitigate these losses, highly directional communication with antenna arrays and beamforming is proposed. IEEE 802.11ad standard is one of the most promising millimeter wave standards to offer multi-gigabit data rates for WLAN/WPAN use. In comparison to the legacy IEEE 802.11 standards, the IEEE 802.11ad introduces completely new medium access control (MAC) and physical (PHY) layers due to highly directional communication. This thesis studies the IEEE 802.11ad standard, focusing on the renewed MAC and PHY layers, beamforming mechanisms, and overall performance in a home environment. While previous academic work has included measurements at 60 GHz, these measurements have been limited to laboratory and office areas which do not realistically model an actual end-user environment. Additionally, the measurement equipment in these research papers has not explicitly implemented the IEEE 802.11ad standard. Hence, measurements in this thesis are conducted with a prototype implementing the mandatory parts of the standard resulting in a more thorough realization of the performance. The results indicate that the prototype performs well in a home environment. Overall, theoretical PHY data rates of above 2 Gbps are to be expected in most cases if operated in similar environment

Spatial Interpolation of Cyclostationary Test Statistics in Cognitive Radio Networks

The focus of this paper is on evaluating different spatial interpolation methods for the construction of radio environment map (REM) using field measurements obtained by cyclostationary based mobile sensors. Mobile sensing devices employing cyclostationary detectors provide lot of advantages compared to widely used energy detectors such as robustness to noise uncertainty and ability to distinguish among different primary user signals. However, mobile sensing results are not available at locations between the sensors making it difficult for a secondary user (possibly without a spectrum sensor) to decide whether or not to use primary user resources at that location. To overcome this, spatial interpolation of test statistics measured at limited number of locations can be carried out to create a channel occupancy map at unmeasured locations between the sensors. For this purpose, different spatial interpolation techniques for the cyclostationary test statistic have been employed in this paper such as inverse distance weighting (IDW), ordinary Kriging (OK), and universal Kriging (UK). The effectiveness of these methods is demonstrated by applying them on extensive real-world field measurement data obtained by mobile-phone-compliant spectrum sensors. The field measurements were carried out using four mobile spectrum sensors measuring eight DVB-T channels at more than hundred locations encompassing roughly one-third of the area of the city of Espoo in Finland. The accuracy of the spatial interpolation results based on the field measurements is determined using the cross validation approach with the widely used root mean square error (RMSE) as the metric. Field measurement results indicate that reliable results with spatial coverage can be achieved using Kriging for cyclostationary based test statistics. Comparison of spatial interpolation results of cyclostationary test statistics is also carried out with those of energy values obtained during the measurement campaign in the form of received signal strength indicator (RSSI). Comparison results clearly show the performance improvement and robustness obtained by the use of cyclostationary based detectors instead of energy detectors.Peer reviewe