The Spaces Between Us: Setting and Maintaining Boundaries in Wireless Spectrum Access
Lei Yang
Ben Y. Zhao
Haitao Zheng
Proceedings of The 16th Annual International Conference on Mobile Computing and Networking (MobiCom 2010)
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Paper Abstract
Guardbands are designed to insulate transmissions on adjacent frequencies from mutual interference. As more devices in a given area are packed into orthogonal wireless channels, choosing the right guardband size to minimize cross-channel interference becomes critical to network performance. Using both WiFi and GNU radio experiments, we show that the traditional "one-size-fits-all" approach to guardband assignment is ineffective, and can produce throughput degradation up to 80%. We find that ideal guardband values vary across different network configurations, and across different links in the same network. We argue that guardband values should be set based on network conditions and adapt to changes over time.
We propose Ganache, an intelligent guardband configuration system that
dynamically sets and adapts guardbands based on local topology and
propagation conditions. Ganache includes three key mechanisms: an
empirical model of guardband sizes based on power heterogeneity of
adjacent links, network-wide frequency and guardband assignment, and
local guardband adaptation triggered by real-time detection of
cross-band interference. We deploy a Ganache prototype on a local 8-node
GNU radio testbed. Detailed experiments on different topologies show
that to minimize interference, traditional fixed-size configurations
allocate more than 40% of available spectrum to guardbands, while
Ganache does the same using only 10% of the spectrum, leading to a 150%
gain in throughput.