Transmitting Sensor Data Through Ad Hoc Networks: A Fast and

1
Transmitting Sensor Data Through Ad Hoc
Networks: A Fast and Reliable Approach
Eng. Luis Marrone
Universidad Nacional de La Plata
Email: lmarrone@linti.unlp.edu.ar
Lic. Fabio Bruschetti
Universidad Nacional de San Martín
Email: fbrusche@gmail.com
Eng. Daniel Alberto Priano
Universidad Nacional de San Martín
Email: daniel.priano@gmail.com
Mg. María Claudia Abeledo
Universidad Nacional de San Martín
Email: cabeledo@linti.unlp.edu.ar
Abstract-- In the present document we considered the unexpected
problem of transferring sensible and critical information like
health data from sites where there is no adequate physical
communications infrastructure. We propose an efficient,
affordable, easy and reliable alternative to allow experts and
professionals to get patient data in about a few seconds through
Internet for decision taking. We combine current smart devices to
collect and process analog to digital data, have built-in storage
and communications capabilities with ad hoc networks to
transport collected data. The addition of simple custom software
components to control data flow, free software tools and add-ins
all running on personal computers with minimum hardware
requirements and public Internet access to networked computing
systems, will allow expert supervision and control to be physically
virtualized at low costs, high impact and fast response.
Index Terms-- Ad hoc networks, Communication equipment,
Data acquisition, Prognostics and health management, Rural
areas, Sensors, Wireless networks.
I
I. INTRODUCTION
n many scenarios such as emergency sites, operation’s
disaster and rescues, and isolated remote areas where there
is no possibility of developing physical connectivity
infrastructure, wireless communication services would bring
enormous benefits to them [1]. Communication with and
between communities of low density and low economic level
is one of the most difficult issue to solve by any government,
specially in underdeveloped countries where most government
resources attend social, political, economic problems [2, 3].
On the other hand, private companies do not always see
This work was supported in part by San Martín National University
(UNSAM) and 508RT0355, TRIComFor-CyTED project-UNLP.

business opportunities in these kind of environments.
Through time, government administrations tried to find
mechanisms to integrate those remote communities to the
society with communications infrastructure, at least, to provide
access to knowledge, exchange products and get some
services. This is the case of certain healthcare services.
Then, healthcare services will be essential in the extreme
situations mentioned above, lack of infrastructure seems to be
a common barrier. A cost-benefit analysis might reduce the
chance for these communities and, in most cases, makes
prohibitive any acceptable access media [4].
II. RELATED WORK
A. Ad Hoc Networks: Origin And Description
The use of ad hoc voice communication was used in many
ancient societies to send messages [6]. The history of wireless
networks started in the 1970’s and the interest has been
growing ever since. During the last decade, and especially at
the end, the interest has almost exploded probably because of
the fast growing Internet. Today we see two kinds of wireless
networks but the difference between them is not as obvious as
it may seem. The first kind and most used today is a wireless
network built on-top of a wired network and thus creates a
reliable infrastructure wireless network [7].
The critical nature of ad hoc wireless networking is in part
due to a confluence of events and technologies. The events
take the form of challenges, while the technologies create
opportunities for meeting these challenges in truly novel and
impressive ways.
The first of the challenges is relatively long-term. The
advent of the Internet and subsequent broadening of the
2
Internet access and e-commerce markets have created a
significant demand for mobile services. Hundreds of millions
of users around the world want to access the Internet, and they
want to do it at any time and from virtually any place. Initial
demand for Internet access, at least in the United States, was
mainly met by wired networks [8]: telephone modems, DSL
and cable connections, or wired local area networks, with a
few wireless options available as well (Ricochet, CDPD, and
WLANs). An “irrational exuberance” met the first wave of
Internet users, sparking enormous investment in networking
technologies as well as applications (the "dotcoms"). Failed
expectations faced the demise of a large number of these
companies. This demise has masked, in the minds of some, a
broad-based increase in the use of the Internet for email and
relatively simple data services. Email, messaging, stock
quotations, and similar services are becoming fully integrated
into our professional and domestic culture, creating a sustained
demand for medium-rate services for mobile users that can be
best met by ad hoc wireless networking technology. Given the
further potential for home networking of appliances and
remote metering of utilities, the long-term demand for ad hoc
wireless networking technology seems secure |9].
The other challenge, ad hoc wireless networks, are expected
to work in the absence of any fixed infrastructure (see Figure
1). In ad hoc wireless networks, the routing and resource
management are done in a distributed manner in which all
nodes coordinate to enable communication among themselves
[6].
Wireless ad-hoc connections
Wireless adhoc
communication
Wireless
ad-hoc
nodes
Fig. 1. Ad hoc wireless network [5]
B. Risks In Wireless Ad Hoc Connections
Wireless ad hoc connections are generally considered a
security risk for the following reasons [10]:
• No physical access needed: outside nodes can gain
connection to the network by the simple fact of being
located in the radio range of any other trusted network
node
• There is no centralized management: failures such as
packet dropping and transmission impairments cannot be
easily traced avoiding to understand whether this failures
are normal or caused by an malicious attack [11]
• Compromise of links or nodes: Attackers may attempt to
take control of a trusted node to perform malicious actions
that can be very difficult to detect because of ad hoc
nodes may perform diverse behaviors [12].
• Restricted power supply: nodes that may not have
continuous external appropriate DC or AC voltage cannot
suddenly cooperate or support wireless network functions
[13].
These vulnerabilities can be mitigated with several security
schemes to protect ad hoc networks to malicious behaviors
[14].
C. Applications Of Ad Hoc Wireless Networks
Ad hoc wireless networks, due to their quick and
economically less demanding deployment, find applications in
several areas:
• Collaborative and distributed computing: Considering a
group of researchers who want to share their findings
sending data in a file format to several nodes in the
network.
• Emergency operations: In environments where
conventional infrastructure based communications
facilities doesn’t exist, immediate deployment of ad hoc
wireless networks would be an alternate solution for
coordinating activities like disaster situations, remote
medical healthcare, etc [6].
D. Wireless Networks For Medical Healthcare Applications
Due to advances in the wireless networks field, new and
innovative applications are being thought of in medical as well
as healthcare field [15]. In the medical field applications
ranging from equipment management to patient management
are being developed. Efficiency among hospital staff is
increased by using some of these newly available applications
and tools. In the healthcare field, issues such as long-term
patient care, support for elderly people and smart homes are
being discussed in the realm of wireless networks. There is
also research being done on creating teletrauma systems using
wireless channels. This will potentially allow trauma specialist
to be virtually on patients bed sides while they are being
moved to the trauma center.
In the near future homes can be designed that take care of
patients or people with disabilities without the presence of a
healthcare provider. A patient who is located remotely can be
cared for remotely by communicating his/her status in realtime to caregivers. Another issue that concerns the healthcare
field is the very large number of expensive medical devices
that are incompatible with each other. Tedious routines are
involved in translating results from one machine to another.
With wireless technology this compatibility issues can be
reduced
Another issue in the wireless networks field is data
collector devices. These devices can be implanted on normal
day to day wearable. Wireless sensors can be implanted inside
or just attached to patient's body to have significant benefits.
Patients can wear sensors that monitor and report vital signs to
3
their doctor in a real-time fashion. This helps towards the issue
of access because now the patient doesn't need to be around
the hospital all the time. This improves access and quality of
healthcare for patients and saves money for care providers.
E. Scope Of This Work
This work exposes a simple and cost effective solution that
can be implemented using ad hoc networks to transport
sensored health data from medical device connected to a
patient (an electrocardiograph device), to a doctor being in
front of a hospital’s computer. This approach also provides a
reliable data transfer from patients in the ad hoc network to
specialists connected to the Internet.
According to bioethics and human rights [16], collected
data from a human patient was replaced with simulated data
generated with a personal computer using a Microsoft Excel
spreadsheet.
F. Scenery
This work was based on an ad hoc wireless network
configured in a rural zone with a standard PC patients and one
of them also connected to public Internet through. Another
standard PC connected to Internet was located at the hospital
accessed by doctors.
This rural zone has several patients with different diseases
that must be supervised in a regular basis like diverse
cardiopathys and diabetes. The zone has insufficient medical
personnel to accomplish with all supervisions. In fact, this kind
of visits would be preferable to be held by a doctor in person
to give immediate response for patients, but these exams are
usually done by specialized technicians like nurses, blood
extractors, etc. but they are not entitled to change any medical
treatment. Only in critical cases doctors take these exams on
patient’s site.
In our case, the patient has a moderated aortic insufficiency
that requires an ECG (electrocardiogram) with prescheduled
frequency. And additional limitation was that ECG data
needed to be printed on millimeter thermal ECG paper to be
submitted to the doctor. The doctor used to provide feedback
after two or more hours, being optimistic.
G. The Solution Proposed In This Work
As shown in figures 2a and 2b, the solution includes the
following hardware and software components:
• Hardware:
- A digital ECG collector device (Dev01) with standard
USB cable
- 3 PCs (Node02 to Noder04) with wireless capability
and fixed IP addresses from 192.168.1.2 to 192.168.1.4
- Dev01 connected to Node04 through USB.
- 1 PC (Node01) with a fixed IP address is 192.168.1.1.
connected to:
a) the wireless ad hoc network with Node2 to Node4
and
b) an Internet Service Provider through ADSL (Upload
speed of 250 Kbps and download speed of 637
Kbps [17]).
•
- Node02 to Node04 has no access to Internet as Node01
gateway function is disabled
- 1 PC (Node05) located at a hospital far away from the
rural zone and connected to Internet through ADSL
(Upload speed of 2.657 Kbps and download speed of
2.361 Kbps [17]).
Software:
- Microsoft Windows XP Service Pack 3 operating
system in all nodes
- Proprietary device software in Node01 (PropSw) to
generate data files with collected data from the ECG
device
- Custom C++ software in nodes (CswNodeNN, where
NN is the node’s number) using Windows APIs and
Gnuplot [18]
- Node01 running FTP Server Service (FileZilla Server
[19])
- Node05 running FTP Client Service (FileZilla Client
[19])
Fig. 2a. Hardware and connectivity components: rural zone
Hospital
ADSL
Modem
Node05
ISP
Specialist
Fig. 2b. Hardware and connectivity components: urban zone
H. Set-up and Operation
The complete cycle consist of four phases: a) device
measure and data file creation, b) file transfer, c) data
processing and d) acceptance and completion (see figure 4).
Changes in patient’s medical treatment maybe required after
phase d but they are out of the cycle we are considering.
4
Data is backed up
and deleted from
networks
Phase a
Device
measure
and data file
creation
Phase d
Acceptance
and
completion
Data is showed
for human
acceptance
Data is copied
between ad hoc
nodes
Phase b
File transfer
Phase c
Data
processing
Data is transferred
between Internet
nodes
Fig. 3. Operation’s cycle
Once the patients’ add-hoc network is running with all
nodes connected to Node01, a shared folder is created in
Node01 (Node01.ShDir) and virtual folders are created in
remaining add-hoc network nodes (NodeNN.ShDir being NN
the node number). Then Node01 is connected to Internet and
the FTP Service (Server) is started. Dev01 is connected to
Node04.
All custom software applications are launched and running.
They were designed to run in background and can be accessed
through the Windows Systray [20].
CSwNode01 application connects Node01.ShDir using the
FTP service (Client); so any FTP client can gain access to this
folder.
PropSw generates a new ECG data file according to
scheduled frequency and saves it in a local directory of
Node04 named Node04.Dir (Phase a). CSwNode04 detects an
existing file in Node04.Dir and copies it in Node01.ShDir
directory. The application records generated files in an internal
list. When the new file disappears form Node01.ShDir it pops
up a message notifying that the new file was processed as
shown in figure 4 (Phase d).
•
•
•
•
•
•
•
•
•
•
•
•
•
X Column values inclusion
User Id
Date
Time in HH:MM:SS,d...d format (being d...d nineteen
decimals digits for seconds)
“***End of Header***” string separator
Number of input channels (1 in our case)
Quantity of Samples taken
X Dimension variable type (time in our case)
X0 value (Initial value is zero in our case)
DeltaX or X sample interval
“***End of Header***” string separator
“Y Values” and “Comments” string titles
List of y values (captured data), one value per row
As Node05 in the Hospital is connected to Internet and FTP
Service (Client) is started and CSwNode05 application shares
Node01.ShDir across Internet using the FTP service (Client).
CSwNode05 application configuration screen is shown in
figure 5.
Fig. 5. Software configuration dialog
“Configure” action button allows change of parameters and
“History” action button shows a list of processed files.
CSwNode05 checks every 5 seconds (TChecking) if any file
appears in Node01.ShDir. If so, it copies the file from
Node01.ShDir to a local directory on Node05 called
Node05.Dir through Internet using the FTP service mentioned
before (Phase b). Then pops up a message and plays an
audible alarm on Node05 to indicate that new data has been
detected and needs to be processed as shown in figure 6.
Fig. 4. Data processing confirmation
Files generated with ECG data are ASCII plain text format,
each row ends with hex values 0Dh 0Ah (Carriage Return and
Line Feed). File name extension is “.DAT”. The content and
parameters of these files are as follows:
• Software name
• Reader and Writer versions
• Field Separator type
• Decimal Separator type
• Single or Multiple Headings
• Time Preferences
Fig. 6. Pending process confirmation dialog
Once confirmed, the application opens the file and
processes the data generating a Gnuplot graphic with ECG
data as shown in figure 7a and 7b (Phase c). For each graphic
plot , the application takes each value from the list and
automatically calculates
value using , and Quantity of
Samples using the following formula:
X n = X 0 + ( n * DeltaX )
5
being n = sample number (from zero to (Quantity of
Samples – 1).
Internet file transfer latency may vary depending on both sides
ADSL real connection speeds.
In the Hospital, when the doctor closes the ECG graphic in
Node05, CSwNode05 application erases the file both in
Node05.Dir and Node01.ShDir.
J. Conclusions
The proposed solution enables the transport of critical
sensored data from small and far away communities lacking in
infrastructure and resources to any desired destination.
Comparing this method with traditional approaches, we
identify the following benefits.
The solution:
• Is built around a very simple ad hoc network
implementation at low costs (with almost any home
computers with wireless capability), there is no need of
fixed external wireless communication infrastructure, it is
fast to be deployed, it has an easy configuration and
reliable transmission with low latency. This solution can
be applied to unexpected situations where urgent results
are the key success factor.
• Only needs one public Internet physical access for the
entire wireless ad hoc network so many people can take
advantage of it immediately by simply adding a node to
the network.
• Provides more efficient results in terms of quality, costs
and time savings because feedback come in seconds,
professionals does not need to travel, many professionals
can collaborate virtually, the interchange of information is
paperless, among others.
• Could be considerably more efficient by adding better
wireless antennas with more RF gain to the ad hoc
wireless network adapters.
• Could be geographically extended by adding network
routing capabilities to ad hoc network nodes.
• Can co-operate with future fixed wireless infrastructure
when available.
Fig. 7a. ECG Graphic – Normal scale
III. REFERENCES
Fig. 7b. ECG Graphic – Enlarged scale
I. Results obtained
All ad hoc and Internet transfer response times were
captured and measured using the network protocol analyzer
Wireshark [21]. Results are as follows:
• Average file transfer time between Node04 and Node01
through the ad hoc network is TAvgad-hoc = 1.5371 sec.
• Average file transfer time between Node01 and Node05
through public Internet is TAvgInternet = 10.2023 sec.
To calculate the average total time (TAvgTotal) , we should
add the five seconds delay time (TChecking) that CSwNode05 may
incur between upcoming files checks, resulting:
TAvg Total = TAvg ad − hoc + TAvg Internet + TChecking = 16.7394 sec .
[1] Statement by Mr. Sha Zukang, Under-Secretary-General for
Economic and Social Affairs UNDESA-GAID Global Forum
on Access and Connectivity in Asia-Pacific and on
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Parliament of Australia, 4 June 2008
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6
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Ad Hoc Networking - David Lundberg - Department of
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IV. BIOGRAPHIES
Luis Marrone
(1953): Electronic Engineer with honors from UBA.
Current lecturer and researcher on Computer Networks at UNLP, graduate
and postgraduate courses. Co-Director of Master Data Networks at UNLP.
Advisor of the Scientific Research Committee of Buenos Aires (CIC) .Board
Member of the Faculty of Information Technology UNLP, and Faculty of
Engineering UBA.
Fabio Bruschetti
(1964): IT Information Systems graduate with honors
from CAECE University. Current researcher on Computer Networks at
UNSAM and lecturer on Data Processing Systems at UNSAM, Computer
Architectures at CAECE University, Networking Essentials at CAECE
University and Information Technology at UBA postgraduate department.
Daniel Alberto Priano
(1959): Electromechanical Engineer graduate
with honors from UTN. Current researcher and lecturer on Computer
Networks at UNSAM and lecturer on Thermodynamics at UTN
María Claudia Abeledo (1962): IT Information Systems graduate with
honors from CAECE University. Magister computer networking graduate
with honors from La Plata University. Current researcher and lecturer on
Computer Networks at UNSAM and current lecturer on Computer Networks
and Networking Essentials at CAECE University.