ON THE LOCATION-AWARE COOPERATIVE SPECTRUM SENSING IN URBAN ENVIRONMENT

Spectrum sensing is a key enabling technology for cognitive radio networks (CRNs). The main objective of spectrum sensing is to provide more spectrum access opportunities to cognitive radio users without interfering with the operations of the licensed network. Spectrum sensing decisions can lead to erroneous sensing with low performance due to fading, shadowing and other interferences caused by either terrain inconsistency or dense urban structure. In order to improve spectrum sensing decisions, in this paper a cooperative spectrum sensing scheme is proposed. The propagation conditions such as the variance and intensity of terrain and urban structure between two points with respect to signal propagation are taken into consideration. We have also derived the optimum fusion rule which accounts for location reliability of secondary users (SUs). The analytical results show that the proposed scheme slightly outperforms the conventional cooperative spectrum sensing approaches

Crowd sourced self beacon mapping with isolated signal aware bluetooth low energy positioning

In the past few decades, there has been an increase in the demand for positioning and navigation systems in various fields. Location-based service (LBS) usage covers a range of different variations from advertising and navigation to social media. Positioning based on a global navigation satellite system (GNSS) is the commonly used technology for positioning nowadays. However, the GNSS has a limitation of needing the satellites to be in line-of-sight (LOS) to provide an accurate position. Given this limitation, several different approaches are employed for indoor positioning needs. Bluetooth low energy (BLE) is one of the wireless technologies used for indoor positioning. However, BLE is well-known for having unstable signals, which will affect an estimated distance. Moreover, unlike Wi-Fi, BLE is not commonly and widely used, and BLE beacons must thus be placed to enable a venue with BLE positioning. The need to deploy the beacons results in a lengthy process to place and record the position of each placed beacon. This thesis proposes several solutions to solve these problems. A filter based on a Fourier transform is proposed to stabilise a BLE signal to obtain a more reliable reading. This allows the BLE signals to be less affected by internal variation than unfiltered signal. An obstruction-aware algorithm is also proposed using a statistical approach, which allows for the detection of non-line-of-sight (NLOS). These proposed solutions allow for a more stable BLE signal, which will result in a more reliable estimation of distance using the signal. The proposed solutions will enable accurate distance estimation, which will translate into improved positioning accuracy. An improvement in 88% of the test points is demonstrated by implementing the proposed solutions. Furthermore, to reduce the calibration needed when deploying the BLE beacons, a beacon-mapping algorithm is proposed that can be used to determine the position of BLE beacons. The proposed algorithm is based on trilateration with added information about direction. It uses the received signal strength (RSS) and the estimated distance to determine the error range, and a direction line is drawn based on the estimated error range. Finally, to further reduce the calibration needed, a crowdsource approach is proposed. This approach is proposed alongside a complete system to map the location of unknown beacons. The proposed system uses three phases to determine the user location, determine the beacons’ position, and recalculate BLE scans that have insufficient number of known BLE beacons. Each beacon and user’s position determined is assigned a weight to represent the reliability of that position. This is important to ensure that the position generated from a more reliable source will be emphasised. The proposed system demonstrates that the beacon-mapping system can map beacons with a root mean squared error (RMSE) of 4.64 m and a mean of absolute error (MAE) of 4.28 m

成層圏飛翔体通信における無線通信路及びその性能に関する研究

制度:新 ; 文部省報告番号:甲2383号 ; 学位の種類:博士(国際情報通信学) ; 授与年月日:2007/3/15 ; 早大学位記番号:新447