Supporting Demanding Wireless Applications with Frequency-agile Radios
Lei Yang
Wei Hou
Lili Cao
Ben Y. Zhao
Haitao Zheng
Proceedings of 7th USENIX Symposium on Networked Systems Design and Implementation (NSDI 2010)
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Paper Abstract
With the advent of new FCC policies on spectrum allocation for next generation wireless devices, we have a rare opportunity to redesign spectrum access protocols to support demanding, latency-sensitive applications such as high-def media streaming in home networks. Given their low tolerance for traffic delays and disruptions, these applications are ill-suited for traditional, contention-based CSMA protocols.
In this paper, we explore an alternative approach to spectrum access
that relies on frequency-agile radios to perform interference-free
transmission across orthogonal frequencies. We describe Jello, a
MAC overlay where devices sense and occupy unused spectrum without
central coordination or dedicated radio for control. We show that over
time, spectrum fragmentation can significantly reduce usable
spectrum in the system. Jello addresses this using two complementary
techniques: online spectrum defragmentation, where active devices
periodically migrate spectrum usage, and non-contiguous access,
which allows a single flow to utilize multiple spectrum fragments. Our
prototype on an 8-node GNU radio testbed shows that Jello significantly
reduces spectrum fragmentation and provides high utilization while
adapting to client flows' changing traffic demands.