Analysis of TV White Space using a Spectrum Observatory
The concept of Dynamic Spectrum Access (DSA) allows the under-utilised spectrum to be made available for Secondary Users (SUs) on condition that such SUs do not cause harmful interference for the Primary User (PU). The first step in assigning the Radio Frequency (RF) spectrum to SUs, is to determine the PU spectrum usage, which can be done via spectrum sensing or by using a geolocation database. A geolocation database is currently the approach preferred by regulators across the world to deploy DSA in the TV bands. The aim of this study is to implement a Spectrum Observatory that also includes the building blocks for a geolocation database. The Spectrum Observatory is a research tool that contains a geolocation database, and that is used for DSA research. Central to both the geolocation database and the Spectrum Observatory is the computation node, which is responsible for performing propagation prediction over a large area. Field strengths are computed for all PU transmitters to determine the geographic location of channels that might be available to SUs. Propagation prediction is computationally intensive and time-consuming, however, and thus it effectively becomes the limiting factor in extending the geolocation-based approach for DSA to other parts of the spectrum. A High Performance Cluster Computer (HPCC) implementation for the computation node is thus presented in this dissertation. Four propagation models are implemented and adapted for parallelisation. The performance analysis indicates computational speed-up for all propagation models on the HPCC, and factors affecting linear scalability are identified. The success of implementing a Spectrum Observatory for DSA is directly dependent on the choice of propagation model used in the Spectrum Observatory for the propagation prediction. The above-mentioned HPCC was used to do analysis on the TV White Space (TVWS) availability, while using different propagation models. The Free-space Loss model, the Hata-Davidson model and the Irregular Terrain Model (ITM) model in both Area mode and Point-to-Point (P2P) mode were investigated. The investigation involved comparing the amount of TVWS predicted for the country of South Africa, by using the different propagation models. The different propagation models were also verified against selected industry radio propagation software. The TVWS research results showed that a considerable number of TVWS channels are indeed available for most of the propagation models. The terrain-aware ITM P2P model showed slightly more TVWS available for provinces with mountainous areas, thus showing its advantage over empirical models. The mean number of TVWS channels available for South Africa, according to the different propagation models, is 0.0 for the Free-space loss model, 30.4 for the Hata-Davidson model, 41.2 for the ITM Area model and 42.1 channels according to the ITM P2P model. The favourable results from the TVWS analysis, especially when using a terrain-aware propagation model, and the speed-up obtained when using an HPCC as the computation node for the Spectrum Observatory strengthens the argument for geolocationbased DSA in the TV bands. By further improving the computation node and refining the propagation models, the concept of geolocation-based DSA in other parts of the RF spectrum can also be promoted.
- Engineering