A Survey on 
the Specification of the Physical Environment 
of Wireless Sensor Networks 
Ivano Malavolta 
Henry Muccini
Roadmap 
Background 
Contribution 
Design of the study 
Results 
Takeaways 
Conclusions
Wireless sensor networks (WSNs) 
WSNs consist of spatially distributed sensors that cooperate to 
accomplish some tasks. 
...
WSN applications 
Sensors can be distributed on roads, vehicles, hospitals, buildings, 
people and enable different applic...
WSN physical environment (1) 
What really sets WSNs apart from all the other kinds of distributed 
systems is: 
• limited ...
WSN physical environment (2) 
Information from the physical environment, like: 
• exact position of the nodes 
• informati...
Examples 
VeriSensor [1] 
GLONEMO [2] 
[3]
Roadmap 
Background 
Contribution 
Design of the study 
Results 
Takeaways 
Conclusions
Contribution 
To investigate on how practitioners specify the physical 
environment of a WSN 
Survey by interviewing WSN p...
Roadmap 
Background 
Contributions 
Design of the study 
Results 
Takeaways 
Conclusions
Research objective 
Our main research question is 
How WSN engineers currently define the physical 
environment, and how t...
Research sub-questions 
Do engineers explicitly specify the physical environment 
where the WSN is going to be deployed? 
...
Population selection (1) 
Participant profile: 
Engineer who has been concretely involved in the 
development of at least ...
Population selection (2) 
2. snowball sampling [4] - we asked selected participants to nominate 
additional experts in the...
Design of the questionnaire* 
a.Introduction 
b.Personal 
information 
Yes 
Is the WSN 
environment 
specified? 
c. Questi...
Roadmap 
Background 
Contribution 
Design of the study 
Results 
Takeaways 
Conclusions
Population 
21 practitioners: 
14 with experience ≥ 5 years 
7 with experience < 5 years 
1 
1 
14 
2 
3 
1 
1 
15 
3 
1 
...
WSN environment specification (1) 
Encouraging for our study since 
we can investigate on both types 
of development proce...
WSN environment specification (2) 
Clear trend in favor of digital 
representation 
Most used file formats: 
text-based an...
2D vs 3D 
80% 
10% 
10% 
2D 
3D 
2d and 3D 
Due to the complexity of producing 
3D models? 
Due to the fact that 2D models...
Obstacles definition 
33, 33% 
13, 13% 
33, 33% 
6, 6% 
15, 
15% 
Free space (no obstacles) 
Walls, floor, and roof 
Walls...
Hardware and nodes positioning 
94% 
10% 
Definetely useful 
Not useful 
Indeed, WSN engineers must have 
at least some kn...
Why not specifying the WSN environment? 
Why not? 
54% 
46% 
No perceived 
usefulness 
Lack of satisfactory 
tools, algori...
Potential tool (1) 
Proposal: potential tool that allows engineers to virtually deploy a WSN 
in the environment. 
Such a ...
Potential tool (2) 
24% 
33% 
43% 
Tool interaction 
By importing a file produced by means of an external 
tool (for examp...
Potential tool (3) 
About the importance of physical effects for the WSN: 
weighted sum 
Physical effect 
-2 
-1 
0 
+1 
+...
Roadmap 
Background 
Contribution 
Design of the study 
Results 
Takeaways 
Conclusions
Do engineers explicitly specify the physical environment 
where the WSN is going to be deployed? 
RQ1 
Good number of prac...
Do engineers specify the sensor nodes and their exact 
position within the physical environment of a WSN? 
RQ2 
WSN practi...
What are the most relevant features a potential tool for 
specifying the physical environment of a WSN shall expose? 
RQ3 ...
Roadmap 
Background 
Contribution 
Design of the study 
Results 
Takeaways 
Conclusions
Conclusions 
“I think that a study on modelling and analysis of the WSN 
environment is interesting and can give you some ...
References 
[1] Y. Ben Maissa, F. Kordon, S. Mouline, and Y. Thierry-Mieg, “Modeling and analyzing 
wireless sensor networ...
Ivano Malavolta | 
Gran Sasso Science Institute 
+ 39 380 70 21 600 
iivanoo 
ivano.malavolta@gssi.infn.it 
www.ivanomalav...
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A Survey on the Specification of the Physical Environment of Wireless Sensor Networks

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28th August 2014. My presentation at SEAA 2014 (http://esd.scienze.univr.it/dsd-seaa-2014) about our survey on
the specification of the physical environment of Wireless Sensor Networks (WSNs).

Accompanying paper: TO APPEAR

Abstract:
A wireless Sensor Network (WSN) consists of spatially distributed sensor nodes that cooperate in order to accomplish a specific task. What really sets WSNs apart from all the other kinds of distributed systems is the limited processing capabilities of the nodes, contingent energy restrictions, and their strict dependence to physical phenomena like attenuation, reflection, etc. Under this perspective, the physical environment in which WSN nodes are deployed strongly affects the overall quality of the system. Under this perspective, how WSN engineers currently specify the physical environment and how they would like to do it? This paper presents a survey we run by interviewing WSN engineers with a special focus on their practical needs and activities.
By analyzing the collected data, we can conclude that: a) a good number of practitioners describing the physical environment do it by GIS software or informally, b) practitioners not specifying the physical environment do not see a clear return on investment on doing it, c) practitioners rate as (definitely) useful a potential tool for deploying WSN nodes on a virtually specified physical environment.

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A Survey on the Specification of the Physical Environment of Wireless Sensor Networks

  1. 1. A Survey on the Specification of the Physical Environment of Wireless Sensor Networks Ivano Malavolta Henry Muccini
  2. 2. Roadmap Background Contribution Design of the study Results Takeaways Conclusions
  3. 3. Wireless sensor networks (WSNs) WSNs consist of spatially distributed sensors that cooperate to accomplish some tasks. Sensors are: – small – battery-powered – with limited processing power – with limited memory They can be easily deployed to monitor different environmental parameters such as temperature, movement, sound and pollution.
  4. 4. WSN applications Sensors can be distributed on roads, vehicles, hospitals, buildings, people and enable different applications such as: • environmental monitoring • medical services • battlefield operations • crisis response • disaster relief
  5. 5. WSN physical environment (1) What really sets WSNs apart from all the other kinds of distributed systems is: • limited processing capabilities of the nodes • contingent energy restrictions • strict dependence to physical phenomena like refraction, reflection, and attenuation… à The physical environment in which WSN nodes are deployed strongly affects the overall quality of the system
  6. 6. WSN physical environment (2) Information from the physical environment, like: • exact position of the nodes • information about the surrounding obstacles and their material – e.g., walls, furniture, windows, or small objects in general surely helps making an accurate estimate of the physical phenomena affecting the WSN Such data could allow a more precise measurement of the network in terms of: bit error rate, packets loss, energy consumption, etc. à enables the prediction of how the WSN will globally behave when nodes are deployed in different ways
  7. 7. Examples VeriSensor [1] GLONEMO [2] [3]
  8. 8. Roadmap Background Contribution Design of the study Results Takeaways Conclusions
  9. 9. Contribution To investigate on how practitioners specify the physical environment of a WSN Survey by interviewing WSN practitioners with a special focus on their practical needs and activities • Many practitioners describe the physical environment via GIS software or informally • practitioners not specifying the physical environment do not see a clear return on investment on doing it or perceive existing algorithms and tools as too complex • practitioners rate as definitely useful a potential tool for deploying WSN nodes on a virtual environment GOAL HOW MAIN FINDINGS
  10. 10. Roadmap Background Contributions Design of the study Results Takeaways Conclusions
  11. 11. Research objective Our main research question is How WSN engineers currently define the physical environment, and how they would like to do it? Why they should define it? To better reason on: • the network topology • how much power is consumed by the application running on the nodes with respect to the used batteries or harvested energy sources • how well an area is covered or tracked by sensors • …
  12. 12. Research sub-questions Do engineers explicitly specify the physical environment where the WSN is going to be deployed? RQ1 If so, how do they accomplish this task (e.g., formally, informally, etc.)? Do engineers specify the sensor nodes and their exact position within the physical environment of a WSN? RQ2 If so, how do they do it (do they consider obstacles, hardware configuration, etc.)? What are the most relevant features a potential tool for specifying the physical environment of a WSN shall expose? RQ3 Need to consider the exact shape of obstacles, or only an approximation? How would WSN engineers prefer to interact with such a potential tool?
  13. 13. Population selection (1) Participant profile: Engineer who has been concretely involved in the development of at least one WSN in the last 10 years Two sampling methods: 1. Convenience sampling - we directly selected WSN engineers from: – our personal contacts – reference websites, newsgroups, and other web resources about WSN OSs, node vendors, and WSN technologies in general
  14. 14. Population selection (2) 2. snowball sampling [4] - we asked selected participants to nominate additional experts in their network Resulting population 21 WSN engineers from 18 different organizations in 9 countries Main affiliation types: – university – center of excellence – company – research institution image from: http://www.hsrmethods.org/Glossary/Terms/S/Snowball%20Sampling.aspx
  15. 15. Design of the questionnaire* a.Introduction b.Personal information Yes Is the WSN environment specified? c. Questions about the WSN environment specification No c. Questions about why and how the WSN environment is not specified Is the WSN environment specified digitally? Yes c. Questions about digital WSN environment No e. Questions about the potential tool for WSN environment d. Questions about WSN Design f. Concluding questions Yes Involved in the WSN design phase? No 21 7 close-ended questions open-ended questions a) purpose of the study + terminology b) demographical info of participants c) how environment is specified d) focus on nodes and positioning e) potential tool for WSN environment f) additional comments + snowballing A transcript of the questionnare is available here: http://www.di.univaq.it/malavolta/wsn/WSNenv.pdf
  16. 16. Roadmap Background Contribution Design of the study Results Takeaways Conclusions
  17. 17. Population 21 practitioners: 14 with experience ≥ 5 years 7 with experience < 5 years 1 1 14 2 3 1 1 15 3 1 0 2 4 6 8 10 12 14 16 1000 and above 100-999 50-99 10-49 1-9 Average number of WSN nodes Number of nodes in the largest WSN project 53% 23% 19% 5% #projects < 3 3 ≥ #projects ≤ 6 #projects > 6 No info 43% 28% 5% 24% Equally indoor and outdoor Mostly indoor Mostly outdoor Indoor only
  18. 18. WSN environment specification (1) Encouraging for our study since we can investigate on both types of development processes Major trend in specifying the environment in a precise way, rather than relying on draft specifications. 48% 52% The WSN environment is explicitly specified The WSN environment is not specified 20% 30%30% 10% 10% Always by a draft Mostly by a precise specification Equally Not specififed Always by a precise specification
  19. 19. WSN environment specification (2) Clear trend in favor of digital representation Most used file formats: text-based and images Basically, those results uncover the great variance about the software used to represent the WSN environment 90% 10% Digital representation Paper-based representation 40% 30% 20% 10% Maps and GIS software Office software Dedicated software Don't know
  20. 20. 2D vs 3D 80% 10% 10% 2D 3D 2d and 3D Due to the complexity of producing 3D models? Due to the fact that 2D models are perceived to be sufficient for representing the environment of a WSN? In this case, 2D+3D representation is the main trend In their last project Best options in general? 20% 30% 50% 2D 3D 2d and 3D
  21. 21. Obstacles definition 33, 33% 13, 13% 33, 33% 6, 6% 15, 15% Free space (no obstacles) Walls, floor, and roof Walls, floor, roof, windows, and large-sized objects Walls, floor, roof, windows, large and small-sized objects No choice Clear winners: • free-space environment • only very large obstacles (e.g., walls, roofs, etc.)
  22. 22. Hardware and nodes positioning 94% 10% Definetely useful Not useful Indeed, WSN engineers must have at least some knowledge about the hardware features of the nodes used in the WSN. Examples: – transmission power of the antenna – available sensing devices – batteries voltage Do analytical models and simulation tools fit well with practitioners’ needs? Usefulness of having a hardware specification Instrument for evaluating the optimal nodes positioning 84% 0% 16% By deploying them on site (real-world testbed) Analytically By simulating the network Other “Simulation is performed only if simple, feasible and meaningful, otherwise deployment”
  23. 23. Why not specifying the WSN environment? Why not? 54% 46% No perceived usefulness Lack of satisfactory tools, algorithms or models “Because up to now it has been sufficient just to know the main features of the environment” “We mainly worked on networking protocols, able to adapt to the changes of the environment” “Unclear whether the modeling effort is going to pay off” How do they proceed to the deployment of the WSN? 37% 27% 27% 9% Not needed (adaptable WSN) Measure the WSN on the field, after deployment Preliminary measures of the area and network simulation Based on their experience “It is simpler not to model the environment and compensate for time dynamic failure with robust algorithms”
  24. 24. Potential tool (1) Proposal: potential tool that allows engineers to virtually deploy a WSN in the environment. Such a potential tool could simulate an environment where to virtually deploy a set of defined sensor nodes into a digital version of its physical environment. 48% 14% 38% 0% Definetely useful Useful Neutral Not very useful Definitely not useful
  25. 25. Potential tool (2) 24% 33% 43% Tool interaction By importing a file produced by means of an external tool (for example Autocad) By directly drawing the environment within the tool By firstly importing an image file to be used as a guide to the drawing phase within the tool When asked about their interest in defining the exact shape of the obstacles, no clear trend has been identified
  26. 26. Potential tool (3) About the importance of physical effects for the WSN: weighted sum Physical effect -2 -1 0 +1 +2 ws Attenuation 0 0 0 7 14 7 Reflection 0 0 2 11 8 5.4 Scattering 0 1 6 7 7 4 Diffraction 0 2 6 11 2 2.6 Refraction 0 4 5 9 3 2.2 Polarization 0 4 8 7 2 1.4
  27. 27. Roadmap Background Contribution Design of the study Results Takeaways Conclusions
  28. 28. Do engineers explicitly specify the physical environment where the WSN is going to be deployed? RQ1 Good number of practitioners explicitly define the WSN environment Almost equal number of practitioners do not – mainly they do not see a clear ROI – no satisfactory tool or method à Researchers should • provide a more concrete evidence about the advantages of explicitly representing the WSN environment • work further on methods, algorithms, and tools Majority of participants would prefer to – define the physical environment via mapping or GIS software – use a combination of text and images – use a combination of 2D and 3D representations
  29. 29. Do engineers specify the sensor nodes and their exact position within the physical environment of a WSN? RQ2 WSN practitioners typically: – consider free-space environment – consider only very large obstacles (e.g., walls, roofs, etc.) – rely on physically measured testbeds à do current simulation and analysis techniques demand too much effort to WSN practitioners? “Usually the available simulation tools do not provide a functionality to define and describe the environment. However, I feel that it is equally important to describe the environment and its behaviour in addition to the models that define how the networking part will function. I believe this is due to the difficulties in defining accurate models for the environment.”
  30. 30. What are the most relevant features a potential tool for specifying the physical environment of a WSN shall expose? RQ3 WSN practitioners strongly need a tool for: 1. defining the physical environment of a WSN 2. virtually deploying WSN nodes into it The tool may allow engineers to specify the environment in different ways. For example, by importing an image that will serve as the basis for a subsequent drawing phase. We believe that this option provides a good trade-off in terms of level of usability and preciseness Mininal set of physical effects to be considered: attenuation and reflection
  31. 31. Roadmap Background Contribution Design of the study Results Takeaways Conclusions
  32. 32. Conclusions “I think that a study on modelling and analysis of the WSN environment is interesting and can give you some new ideas because nowadays in most cases a WSN is intended as a set of hardware nodes, without taking into account the place where the nodes will be deployed”
  33. 33. References [1] Y. Ben Maissa, F. Kordon, S. Mouline, and Y. Thierry-Mieg, “Modeling and analyzing wireless sensor networks with verisensor: An integrated workflow,” in Transactions on Petri Nets and Other Models of Concurrency VIII, ser. Lecture Notes in Computer Science, M. Koutny, W. Aalst, and A. Yakovlev, Eds. Springer Berlin Heidelberg, 2013, vol. 8100, pp. 24–47. [Online]. Available: http://dx.doi.org/10.1007/978-3-642-40465-8 2 [2] L. Samper, F. Maraninchi, L. Mounier, and L. Mandel, “Glonemo: Global and accurate formal models for the analysis of ad-hoc sensor networks,” in Proceedings of the First International Conference on Integrated Internet Ad Hoc and Sensor Networks, ser. InterSense ’06. New York, NY, USA: ACM, 2006. [Online]. Available: http://doi.acm.org/ 10.1145/1142680.1142684 [3] http://www.remcom.com/wireless-insite [4] B. Kitchenham and S. L. Pfleeger, “Principles of survey research: part 5: populations and samples,” SIGSOFT Softw. Eng. Notes, vol. 27, pp. 17–20, September 2002.
  34. 34. Ivano Malavolta | Gran Sasso Science Institute + 39 380 70 21 600 iivanoo ivano.malavolta@gssi.infn.it www.ivanomalavolta.com Contact
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