Efficient Spectrum Sharing in Heterogeneous Wireless Environments

Today, spectrum is scarce because of the growing number of wireless devices and the steadily increasing demand for high data rates. Streaming and online gaming are a new kind of challenge for wireless networks in terms of delay and throughput. Systems like LTE enable high data-rates (100 MBit/s and above) combined with a low latency. Despite of all these new transmission technologies a major bottleneck is caused by the available spectrum. Furthermore this problem gets exacerbated by a static frequency assignment. To overcome this bottleneck new concepts for adaptive spectrum assignment with respect to load situation need to be developed. In this article we describe and evaluate an architecture which is able to handle different kinds of spectrum sharing techniques. Furthermore, our approach is able to deal with short time sharing (up to one minute). Therefore, we developed a Spectrum Management System (SMS) which is based on a hierarchical organized distributed hash table (DHT) architecture. Additionally, our system deploys databases for additional information like spectrum usage rules, incumbents or network coverage information (described by polygons). To enable the handling of time-critical spectrum data, we introduce a time synchronisation protocol named Lightweight Time Synchronisation (LT-Sync) which considers the system architecture and estimates transmission delays.