Radio propagation studies and spectrum sensing

The paper presents an overview of the need address the spectrum crunch to deliver higher data rates for future wireless networks. Two techniques which are currently being investigated are the use of dynamic spectrum access and new frequency bands in the mm wave. Both techniques require thorough propagation studies. In the case of dynamic spectrum access it is necessary to ensure that the technique used to identify the primary user is sufficiently robust to reduce the possibility of interference. Two possible approaches are sensing the spectrum to identify unused frequency bands and the second approach involves the setting up of a large data base identifying the availability of frequency bands in space i.e. geographic location and time. To evaluate the feasibility of sensing, it is necessary to identify a minimum detection threshold level to detect the primary user. To evaluate the sensing approach a number of sensing devices have been evaluated under the EU funded project, CREW at Durham University with respect to a number of transmissions ranging from simple CW transmissions to more demanding WiFi transmissions, frequency hopping and frequency sweeps. Low cost and high cost sensing engines were evaluated including commercial off the shelf equipment and custom designed devices such as the receiver of the frequency swept channel sounder at Durham University. The test which was performed in the large anechoic chamber at Durham University with devices tested simultaneously to ensure uniformity identified high end devices as the only ones that are capable of detecting the primary user for the different types of modulation. This is an important result since for the sensing approach to be successful it would need the capability to detect the primary user with a high level of confidence at a low cost. The second approach whi