White Space Networking with Wi-Fi like Connectivity
Networking over UHF white spaces is fundamentally different from conventional Wi-Fi along three axes: spatial variation, temporal variation, and fragmentation of the UHF spectrum. Each of these differences gives rise to new challenges for implementing a wireless network in this band. We present the design and implementation of WhiteFi, the firstWi-Fi like system constructed on top of UHF white spaces. WhiteFi incorporates a new adaptive spectrum assignment algorithm to handle spectrum variation and fragmentation, and proposes a low overhead protocol to handle temporal variation. WhiteFi builds on a simple technique, called SIFT, that reduces the time to detect transmissions in variable channel width systems by analyzing raw signals in the time domain. We provide an extensive system evaluation in terms of a prototype implementation and detailed experimental and simulation results.
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Comments
This paper studies the problem of cognitive networking over UHF white spaces (WhiteFi).
Namely, the authors present a framework for establishing Wi-Fi like systems
over unused TV spectrum bands and they focus on the simplified yet illuminating
case of a single AP with many clients.
The interesting points of this work can be summarized as follows:
1. The authors identify and analyze the differences among WiFi (ISM) and WhiteFi (TV-bands)
systems and bands by performing real-world spectrum measurements.
2. The proposed algorithms, unlike similar solutions, enable the variable bandwidth
communication which remedy the problem of spectrum fragmentation.
3. The signal detection technique is tailored to the specific requirements of
cognitive operation. That is, the introduced time-domain analysis method (SIFT)
provides the capability of detecting signals over different channel widths.
4. All the proposed algorithms are incorporated into one architecture which
has been evaluated both through simulations and experimentation over a prototype
developed system.
As the authors already stated, it would be even more interesting to study the
operation of WhiteFi systems that consist of multiple APs. In this setting, one should
also devise methods/mechanisms for addressing the issues of coordination and competition among
the various network entities (APs, clients, etc) which naturally arise in this case. Even for the
presented paradigm of one AP and many clients, it would be interesting to study the impact of
selfish or even malicious nodes which waste the common resources (spectrum in this case) and attempt
to disrupt the network operation