wireless sensor network

1. Security protocols &
platform
FOR WSN BASED MEDICAL APPLICATIONS
-AVIJIT MATHUR
SUPERVISOR: DR. THOMAS NEWE

2. Overview
WSN: Nodes collected and organized in some fashion in order to make a cooperative
network.
Usage: Monitoring of patients wirelessly. (Routine/emergency/mass causality) thereby
providing healthcare services.
As the population increases there is a need for continuous medical monitoring.
Patients monitored wirelessly has several advantages.
Traditional wired methods do not allow mobility with the added difficulty of time constraints.
Provide a secure, reliable and energy-efficient Wireless Sensor Network for medical devices.

3. In Home/hospital architecture
Base StationRepeater
Access point 1
Access point 2
Access point 3
GSM/3g/
4g
WiFi
WiMAX
ZIGBEE
BLE

4. Topologies
Star
Mesh:
Hierarchical tree
Clustered Hierarchical
Star Topology
Partial Mesh
Topology
Hierarchical Tree
Clustered HierarchicalCluster Head Central Hub/Switch
Gateway Nodes Sensor Nodes
Source: A Performance Comparison of Different Topologies for
Wireless Sensor Networks by Akhilesh Shrestha and Liudong Xing

5. ZIGBEE Bluetooth Low energy Wi-Fi 4G
Range 10-100 m >60m
(10m for Classic BT)
Depends on specification In Kilometers
Power Low Very Low
(High for classic BT and
medium for others)
High
(variable for WiFi Direct)
High
Entries 254
(>64000 per network)
 2 Billion
 (Classic: 7)
Depends on no. of IP
addresses
-
Latency Low 3 ms (compared to 100ms
in classic BT)
Variable -
Self healing Yes - Yes Yes
Topologies Mesh, Star and Cluster-
tree
Star Star, Point-to-Point Ring
Data transmission rate Up to 250Kbps 1Mbps (BT v4.0: 25Mbps) 11Mbps & 54Mbps
(250 Mbps: WiFi Direct)
100Mbps & 1Gbps(fixed
access)
Bandwidth 2.4GHz, 915MHz & 868
MHz
2.4 GHz only
(BT + HS: 6-9 GHz)
2.4, 3.6 & 5 GHz Similar to WiFi
Transmission technique DSSS DS/FA? Adaptive FHSS
(Classic BT: FHSS)
DSSS, CCK & OFDM OFDMA

6. IEEE 802.15.6
New standard specified for Wireless Body Area Networks (WBANs)
Extremely low power, good data rate and safety compliant.
Flexible frequencies => selecting the right physical layer very important
MICS and WMTS do not support high data rate while ISM band supports high data rate at the
cost of interference.
PHY layers
Security levels
Source :An Overview of IEEE 802.15.6 Standard (Invited Paper)
Kyung Sup Kwak, Sana Ullah, and Niamat Ullah; UWB-ITRC Center, Inha University;
253 Yonghyun-dong, Nam-gu, Incheon (402-751), South Korea
Table Source:Body Area Networks
Arif Onder ISIKMAN, Loris Cazalony, Feiquan Chenz, Peng Lix
Chalmers University of Technology, SE-412 96, Gothenburg, Sweden
IEEE 802.15.4 / ZigBee IEEE 802.15.6
Range 10-100m 2-5m
Data rate 20,40 & 250 Kbps Few Kbps – 10 Mbps
Power 25-35mW 0.01 mW (stand by),
40mW (active)
Entries 65535 devices 256 devices per network

7. Security & Reliability
Security services: Authentication, access control, data confidentiality,
integrity and Non-repudiation.
Reliability depends on two main factors: network connectivity and
sensing coverage.
Security is very important as the technology may be
vulnerable to attacks
Traditional security mechanisms
(PKI) cannot be used.
Semantic security
Secure routing & storage are most important
Source: Integrated Modeling for Wireless Sensor Networks by
Liudong Xing, Ph. D., University of Massachusetts, Dartmouth & Howard E. Michel, Ph.D., University of Massachusetts, Dartmouth

8. Security protocols
TinySec
MiniSec
SPINS: SNEP & uTesla
LiSP
MAC
SIA

9. Security Mechanism
Steganography: Channel is hidden under the Physical layer to provide covert data transmission
Cryptography: Encryption & authentication mechanisms
Key management: Global, pair-wise node, pair-wise group & individual
Localization: Geographically detect a malicious node
Trust management: Select route based on trustworthy nodes
Data Partitioning
6 6
6
6
7
7
7
6
Periodic key generation
Data: D
D1
D2
D3
D1
D1
D2
D3 D3
Source: Wireless Sensor Network Attacks and Security Mechanisms : A Short Survey David Martins and Hervé Guyennet
Computer Science Department, University of Franche-Comté, France

10. Energy management
Energy consuming layers
Use VCO based radio architecture since it is:
Robust to interference
Allows communication at different carrier frequencies
Better sleep synchronization
Uses Flash over SRAM memory
Efficient programming techniques
Collision avoidance
Idle listening periods must be reduced
Routing: with the usage of real-time protocols, reduce the size of routing tables
Clustering: Hierarchical clustering
Data gathering

11. Issues & Challenges
Privacy & security
Trust
Coverage
Communication delay
Need for reliable, fault tolerant, self-healing and organising cluster-scheme for key distribution
Choosing the right blend of encryption and authentication schemes
Movement of patient is challenging with regards to architecture, coverage and routing.
Decentralized security mechanism.

12. Findings
Research into network topologies and clustering algorithms.
Securing both the nodes and the communication network.
Group key distribution techniques.
WSNs require node scalability and mobile agent.
Sensors may capture confidential data.
Motes must authenticate the stored public key of Base station.
In the future it may be possible for patients to interpret their results on a PDA/desktop.

13. Findings
Key management schemes to be further researched.
Nodes should automatically decide on a routing strategy.
Medical environment may call for high reporting times from the nodes (emergency).
Reporting of failed nodes and healing of the network is important.
Connectivity: USB, Ethernet, RS232 + WiFi, ZigBee,
Bluetooth & cellular.
Machine learning algorithm can act as a mediator.
Image source: Medical Applications based on Wireless Sensor Networks by Stanković, Stanislava

15. Motes
Tmote Sky
Tmote sky: http://insense.cs.st-andrews.ac.uk/examples/
Micaz: http://www.cse.chalmers.se/~larandr/master.html
Shimmer: http://www.eecs.Harvard.edu/~mdw/proj/codeblue
Shimmer
Micaz

16. The End
THANK YOU