09-10-2012, 04:31 PM
Cognitive Radio Platforms:Wireless Open-Access Research Platform for Networks
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Abstract
Cognitive radio has received considerable interest as a communication
paradigm to provide dynamic spectrum allocation. However, there are still no realtime,
at-scale validations of the key concepts in cognitive wireless. In this chapter
we present theWireless Open-Access Research Platform for Networks (WARPnet),
a platform aimed at making cognitive radio a practical reality. The platform is designed
from ground-up to be deployable and provides all the functionality needed to
control and observe large-scale networks while enabling iteration on low-level algorithms.
In addition, several design flows have been developed for isolated as well
as integrated experiments. The platform supports both traditional research and cognitive
protocol research, and thus provides uniform hardware and software frameworks
to compare traditional approaches to the new clean-slate designs. During the
course of the chapter, we will identify the difference between cognitive radio and
traditional wireless networks to motivate the various features of the platform itself.
We will also explore platform architecture to enable quick prototyping of next generation
algorithms. Finally, we shall showcaseWARPnet with an example cognitive
protocol which exercises every part of the platform.
From Concepts to Platforms
One of the challenges in building a platform for experiments is in defining its specifications,
which must not only accommodate all current ideas but also ideas which
have not yet been conceived. The platform can guarantee longevity by adopting a
modular architecture, with high performance components in each module. To lay out
the specifications for such a platform, we start by noting that central to all cognitive
wireless protocol innovations there are three functional components.
1. Sense: At the heart of cognitive wireless is the ability of nodes to sense the environment
for ongoing traffic. Nodes can use the sensed spectral usage at multiple
time-scales to adjust their behavior accordingly.
WARPnet Hardware Architecture
In this section, we discuss three major components of the WARPnet hardware platform.
First is the base FPGA Board, which houses a large FPGA, multiple Radio
Boards and the Backdoor Board. Next we describe the two Radio Boards, which
are MIMO-capable and operate in several frequency ranges. Finally, we detail the
Backdoor Board which provides multiple highly-reliable communication interfaces
which can operate both over wireline infrastructure or orthogonal wireless bands. In
addition, the Backdoor Board is capable of local processing and storage.
Daughtercard Slots
To support multiple standards and especially in the evolving portions of spectrum,
RF interfaces are built as modules. A very general daughtercard interface is provided,
which has an open specification to encourage the community to design custom
boards to suit their needs. Currently, several Rice-designed daughtercards are
available, like the Radio Boards and the Analog Board (digital-to-analog converter
board). We describe two Radio Boards in the next section; details of others boards
can be found at WARP website [12].