Power consumption is one of the most important factors

in wireless sensor network research, but most simulators do

not provide support for visualizing the power consumption

of an entire sensor network. This makes it hard to develop,

debug, and understand mechanisms and protocols based on

power-saving mechanisms. We present Cooja TimeLine, an

extension to Contiki’s Cooja network simulator, that visualizes

radio traffic and radio usage of sensor networks. Cooja

TimeLine makes is possible to visually see the behavior of

low-power protocols and mechanisms thereby increasing the

understanding of the behavior of sensor networks. We see

this as an important tool for the field moving forward

Dunkels, Adam

Eriksson, Joakim

Österlind, Fredrik

English

Swedish Institute of Computer Science Publications Database

Demo Abstract: Cooja TimeLine:
A Power Visualizer for Sensor Network Simulation
Fredrik ¨Osterlind, Joakim Eriksson, Adam Dunkels
fros@sics.se, joakime@sics.se, adam@sics.se
Swedish Institute of Computer Science
Abstract
Power consumption is one of the most important factors
in wireless sensor network research, but most simulators do
not provide support for visualizing the power consumption
of an entire sensor network. This makes it hard to develop,
debug, and understand mechanisms and protocols based on
power-saving mechanisms. We present Cooja TimeLine, an
extension to Contiki’s Cooja network simulator, that visual-
izes radio traffic and radio usage of sensor networks. Cooja
TimeLine makes is possible to visually see the behavior of
low-power protocols and mechanisms thereby increasing the
understanding of the behavior of sensor networks. We see
this as an important tool for the field moving forward.
1 Introduction
Power consumption is one of the most important factors
in wireless sensor network research, but power consumption
is not tangible and therefor difficult to understand. Simu-
lators are a widely used tool to study, develop, and debug
sensor networks. Yet sensor network simulators do not pro-
vide support for visualizing the power consumption of the
networks that are simulated.
We present Cooja TimeLine, a module for the Contiki
Cooja network simulator that visualizes both the power con-
sumption and the network traffic of sensor networks. We
have used Cooja TimeLine in the development of many of
the power-saving mechanisms and protocols in the Contiki
operating system.
In sensor networks, duty cycling MAC protocols are used
to maintain a low power consumption of nodes. Even if
the underlying principles behind power-saving MAC proto-
cols are becoming widely understood [4], the implications of
these protocols are not. For example, when a modern duty
cycling protocol is used, nodes cannot overhear the transmis-
sions of other nodes. Yet, many recent protocols are designed
under the assumption that nodes can overhear each other. We
argue that visualization tools like Cooja TimeLine greatly
simplifies understanding and debugging of duty-cycled sen-
sor network applications.
Copyright is held by the author/owner(s).
SenSys’10, November 3–5, 2010, Zurich, Switzerland.
ACM 978-1-4503-0344-6
Figure 1. The Cooja TimeLine module in Cooja.
2 Cooja TimeLine
Cooja TimeLine shows a time line for each node in the
simulation. On the time line, the power state of the radio
transceiver of each node is shown in a color code: white if
the transceiver is off, gray if it is on. Radio transmissions
and receptions are shown in the same time line: transmis-
sions are blue and receptions are green. Two simultaneous
transmissions to a node, which results in radio interference,
is shown in red. Transmissions and receptions are shown
with bit granularity. See Figure 1 for a Cooja screenshot
with a TimeLine module.
Cooja TimeLine observes the state of the emulation of
the radio transceiver of all nodes in a simulation. As the
simulation progresses, the contents of the window is scrolled
to the left as simulated time passes.
The TimeLine module does not care about the specific
type of radio that is emulated in each node. The architecture
is general enough to support any type of emulated radio. We
currently have implementations of one CC2420 radio emula-
tor as well as an abstract radio that is not tied to any particular
hardware platform.
3 Usage
We have been using the Cooja TimeLine module for sev-
eral tasks in and around the Contiki operating system. We
have found TimeLine to be useful for development and de-
bugging of both low-level mechanisms [1, 2] and higher level
protocols [3, 5]. We have identified three activities where
TimeLine has been particularly useful to us: synchronization
debugging, power debugging, and congestion debugging.
3.1 Visualizing Synchronization
Depending on the protocol under study, synchronization
is either wanted or unwanted. Protocols that use synchro-
nization will want their nodes to be synchronized. Other
protocols run into unwanted or pathological synchronization
conditions.
With the Cooja TimeLine module, synchronization is
easy to visually identify. When nodes synchronize their
transmissions or reception windows, the color markings will
appear directly above and beneath each other in the Time-
Line, making it easy to see. If synchronization is unwanted,
it is normally easy to backtrack the simulation logs to see
what caused the synchronization to occur. Likewise, if syn-
chronization is wanted, but does not occur, it is possible to
use the simulation logs or the debugger to investigate the
causes. An explicitly synchronized network is shown in Fig-
ure 2.
Figure 2. An explicitly synchronized multi-hop network.
3.2 Visualizing Power
Power is typically the main metric in sensor network re-
search and power consumption is often dominated by the
power consumption of the radio transceiver. As Cooja Time-
Line tracks the state of each radio transceiver, it is possible
to visually approximate the power consumption of an entire
sensor network. This is shown in Figure 3, which shows
a broadcast transmission with the low-power listening Con-
tikiMAC radio duty cycling protocol.
If there is a problem with the power consumption in a net-
work, e.g. because of a misbehaving protocol or application,
it is possible to immediately visually identify the problem.
We have used Cooja TimeLine to debug and develop the
duty cycling protocols in the Contiki operating system, such
as ContikiMAC, Contiki X-MAC, and Contiki LPP. The
original versions of Contiki X-MAC and Contiki LPP were
developed without the support of Cooja TimeLine. When we
first ran Cooja TimeLine on them, we witnessed several cor-
ner cases where the code failed to correctly turn off the radio.
Cooja TimeLine significantly improved the implementations
of these protocols.
3.3 Visualizing Congestion
Network congestion occurs when many transmitters want
to send, despite there not being enough bandwidth available.
In a low-power duty cycled network, congestion is made
Figure 3. The radio duty cycle is visualized.
worse by the fact that a single transmission can occupy a
significant amount of bandwidth. Specifically, a single-hop
broadcast with an asynchronous duty cycling protocol results
in a large number of link-layer transmissions. When many si-
multaneous transmitters send broadcasts, congestion occurs.
Congestion is next to impossible to debug in a testbed or
a real deployed network, because radio transmissions cannot
be seen. With Cooja TimeLine, however, congestion condi-
tions are easily seen. By using the zoom functionality of the
TimeLine module, it is possible to visually inspect the traffic
intensity over both short and long timescales. Congestion is
thus easily identified, as shown in Figure 4.
Figure 4. A congested network.
4 Conclusions
We present Cooja TimeLine, a graphical module for the
Contiki Cooja network simulator. Cooja TimeLine draws a
moving graph of the state of on-board peripherals of each
node as well as the radio traffic being sent between nodes.
This makes it easy to visually inspect network traffic, power
consumption, and synchronization in a simulated sensor net-
work. We have been using Cooja TimeLine for both low-
level and high-level mechanisms and protocols in the Contiki
operating system. We have found CoojaTimeLine to be par-
ticularly useful for debugging synchronization, power con-
sumption, and congestion, but there are many other uses as
well. We see Cooja TimeLine as an important tool for devel-
oping an understanding of the behavior of low-power duty
cycled sensor networks, which is not possible using tradi-
tional debuggers or simulators.
5 References
[1] F. ¨Osterlind and A. Dunkels. Approaching the maximum 802.15.4
multi-hop throughput. In Proceedings of the Workshop on Hot Topics
in Embedded Networked Sensor Systems (HotEmnets), June 2008.
[2] F. ¨Osterlind, N. Wirstro¨m, N. Tsiftes, N. Finne, T. Voigt, and
A. Dunkels. StrawMAN: Making Sudden Traffic Surges Graceful in
Low-Power Wireless Networks. In Proceedings of the 2010 ACM
HotEMNETS Workshop on Hot Topics in Embedded Networked Sen-
sosr, Killarney, Ireland, June 2010.
[3] N. Tsiftes, J. Eriksson, and A. Dunkels. Low-Power Wireless IPv6
Routing with ContikiRPL. In Proceedings of the International Con-
ference on Information Processing in Sensor Networks (ACM/IEEE
IPSN), Stockholm, Sweden, April 2010.
[4] M. Welsh. The next decade of sensor networking. Keynote at the 2010
European Workshop on Sensor Networks (EWSN).
[5] D. Yazar and A. Dunkels. Efficient Application Integration in IP-Based
Sensor Networks. In Proceedings of the ACM BuildSys 2009 workshop,
in conjuction with ACM SenSys 2009, November 2009.


Approaching the maximum 802.15.4 multi-hop throughput.

Efficient Application Integration in IP-Based Sensor Networks.

Low-Power Wireless IPv6 Routing with ContikiRPL.

StrawMAN: Making Sudden Traffic Surges Graceful in Low-Power Wireless Networks.

The next decade of sensor networking. Keynote at the

Cooja TimeLine: A Power Visualizer for Sensor Network Simulation

Power consumption is one of the most important factors in wireless sensor network research, but most simulators do not provide support for visualizing the power consumption of an entire sensor network. This makes it hard to develop, debug, and understand mechanisms and protocols based on power-saving mechanisms. We present Cooja TimeLine, an extension to Contiki’s Cooja network simulator, that visualizes radio traffic and radio usage of sensor networks. Cooja TimeLine makes is possible to visually see the behavior of low-power protocols and mechanisms thereby increasing the understanding of the behavior of sensor networks. We see this as an important tool for the field moving forward.ContikiReSensePromo

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http://soda.swedishict.se/4002/1/osterlind10timeline.pdf

Cooja TimeLine: A Power Visualizer for Sensor Network Simulation

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RISE – Research Institutes of Sweden