Virtual testbeds model them by seamlessly
integrating physical, simulated, and emulated
sensor nodes and radios in real time.
By Geoff CouLson, BaRRy PoRteR, ioannis ChatziGiannaKis,
ChRistos Koninis, stefan fisCheR, Dennis PfisteReR,
DanieL BiMsChas, toRsten BRaun, PhiLiPP huRni,
MaRKus anwanDeR, GeRaLD waGenKneCht, sánDoR P. feKete,
aLexanDeR KRöLLeR, anD toBias BauMGaRtneR
wIReLess sensoR ne TwoRKs (WSNs) play a key
role in the emerging “real-world Internet,” with
several large-scale WSNs being deployed; see, for
example, Bernat2 and Dudek et al. 9 However, WSN
development is inherently complex, involving
hardware design, embedded and distributed
programming, heterogeneity, scale, and unpredictable
environmental changes. Addressing this complexity,
testbed-based experimentation (recommended by
Weiser32) is increasingly the norm for developing
and optimizing WSN systems in a controllable
environment prior to deployment.
The WSN research community has historically
relied on three main approaches to testbed-based
experimentation: physical, simulation, and emulation.
However, researchers appreciate that each involves
significant drawbacks when used in
isolation (see the sidebar “Physical
Testbeds vs. Simulation vs. Emulation”). Therefore, they seek to combine all three to enable a more complete evaluation of the system being
developed. Unfortunately, each approach requires different coding styles
and tools, forcing researchers to expend significant effort reimplementing their systems for different tools/
platforms/approaches. As a remedy,
techniques have been developed to
reduce the transitioning effort among
the three approaches, but further work
is needed to address the emerging
requirement for more flexible experimental facilities.
Our work abstracts the concept of
testbeds to yield virtual testbeds (VTBs)
programmed similarly regardless of
whether their underlying realization is
physical, simulated, or emulated. VTBs
are private, custom-designed, per-ex-periment, virtualized testbed instances that enable developers to seamlessly
combine and/or interchange physical
elements, including sensor nodes and
radios, with simulations and emulations of these elements.
We are developing a reference implementation of the VTB abstraction
on top of a large-scale federated physical testbed infrastructure (see Figure
1), augmenting the inherent flexibility
of the VTB abstraction in terms of scal-
;;; Physical, emulated, and simulated
elements of wireless sensor net works
can be seamlessly mixed to gain
massive-scale “virtual testbeds” with
desired trade-offs involving fidelity,
repeatability, and network size.
;;; the relative speed difference between
internet links and low-power wireless
radios allows sensor nodes at physically
distant testbed sites to interconnect
(virtually) over the internet.
;;; the wiseBeD approach of recursively
and hierarchically applying a common
web services aPi to physical, simulated,
and federated or hybrid testbeds
facilitates transparent composition of
virtual testbeds that can be accessed
and controlled by common tools.