Time-series prediction of attenuation caused by trees for fixed wireless access systems operating in millimeter waveband

Fixed wireless access systems have become a very popular and cost effective alternative to the traditional wired solution for the customer "last-mile" connection to the backbone network. To meet the constantly increasing capacity demands, the operating frequency is moving towards higher frequency bands (e.g. millimetre waveband). As overall signal attenuation is a result of signal interaction with different types of obstacles, more than one model is needed to predict attenuation with high accuracy. Moreover, because some obstacles are not static in a real environment, dynamic effects (especially in the millimetre waveband) have to be considered. The paper investigates the modelling of dynamic vegetation effects on the received signal level for broadband radio access networks. A new 3D lattice model is introduced. Based on measurements, it is confirmed that it has enough flexibility to model accurately the temporal as well as spatial-temporal dynamic effects of a tree blocking a receiver. More laboratory experiments and field tests with different types of trees need to be performed in order to optimize the model and to evaluate the necessary power margins with respect to quality of service requirements.