0. Speaker： CHUN-Ting Lin Advisor： Dr. Ho-Ting Wu​ Date: 2015/12/31
Tree network based on Bluetooth 4.0 for wireless sensor network applications
Speaker： CHUN-Ting Lin
Advisor： Dr. Ho-Ting Wu​
Date: 2015/12/31

1. Outline Introduction Bluetooth Low Energy (BLE)
Network Size and Data Routing
Hardware Design and Implementation
Software Design
Measurements and Results
Conclusion
Reference

2. Introduction
WSNs are deployed to collect information about physical parameters of interest using the respective sensors (eg. temperature, acceleration, light, etc.) in its nodes. 
The important parameters of the wireless technologies used in WSNs are power consumption, throughput, latency, range, and network topology.

3. Introduction(Cont.)
Comparison of wireless technologies in WSNs

4. Introduction(Cont.) Star topology is the default BLE topology.
This topology is its lack of ability to extend the network’s range.
Tree networks are implemented to address this limitation.

5. Bluetooth Low Energy (BLE)
Bluetooth 4.0 (including BLE) is the latest specification update in this trend which was introduced in the year 2010.
Advantage：
ultra-low power consumption
wireless products working on standard coin-cell batteries for years
low cost of the components
multi-vendor operability
enhanced range

6. Bluetooth Low Energy (BLE) (Cont.)

7. Implementation of Tree Network
BLE, which only supports star topology, is used.
Mesh networking is the preferred topology for WSNs but it is complex to implement.
In comparison, tree topology is simpler and can still be used to extend the range of the network

8. Implementation of Tree Network(Cont.)
Root node:
This is the main node in the tree network. This node can be viewed as a gateway sensor or a data collecting center in analogy to WSNs.
Intermediary node:
A node which connects two or more nodes located at higher and lower positions in the hierarchy of a tree network.
Leaf node:
A node which connects to just one node higher up in the hierarchy of the tree network

9. Network Size and Data Routing
Network size is an important parameter which determines if a network can cover the area where the WSN is to be deployed.
Using the hardware and software developed, the maximum possible size of a network is limited by the fact that each node is given a unique identity number.

10. Network Size and Data Routing(Cont.)

11. Network Size and Data Routing(Cont.)

12. Hardware Design and Implementation
Three possible devices which can act as root nodes in this project are:
USB dongle from TI CC2540 mini DK in conjunction with Btool (included in BLE-stack provided by Texas Instrument).
SMARTRF05 evaluation board (EB) mounted on the CC2540DK central evaluation module (EM).
a smartphone with BLE technology supported by third party applications.

13. Hardware Design and Implementation(Cont.)
For the other two types of nodes, a single piece of hardware is designed and adjusted as necessary to enable specific sensors on the different boards (peripheral BLE).

14. Hardware Design and Implementation(Cont.)
Hardware implementation

15. Software Design
The software used in this project is organized under five different sections:
Operating System Abstraction Layer (OSAL)
Hardware Abstraction Layer (HAL)
Protocol stack
Profiles
Applications

16. Software Design(Cont.)
Peripheral BLE devices need the GATT (GENERIC ATTRIBUTE PROFILE) profile so that central devices can discover the services available and request to read and write data.
The GATT profile allows for the data exchange between central and peripheral devices.

17. Software Design(Cont.)
This custom profile defines five characteristics (SIMPLEPROFILE_CHAR1 to SIMPLEPROFILE_CHAR5).
SIMPLEPROFILE_CHAR1

18. Software Design(Cont.)
Characteristic number 4 includes configuration settings defined in the profile so that notification can be enabled .
SIMPLEPROFILE_CHAR4

19. Measurements and Results
There are some parameters which are important from the WSN perspective.
The parameters include :
the power consumption of the network
latency
data transmission
Speed
node recognition
Routing
failure detection

20. Measurements and Results(Cont.)
Node life based on power consumption

21. Measurements and Results(Cont.)

22. Conclusion
With appropriate software modification, the size of the network can be enlarged as demanded by a WSN application.
The tree topology can be used with Bluetooth low energy for the purposes of range extension, extending the number of network nodes or data processing by the central node.

23. Reference
B.K. Maharjan, U. Witkowski and R. Zandian,“Tree network based on Bluetooth 4.0 for wireless sensor network applications,”in: Proc. 6th European Embedded Design Education Research Conf., 2014, pp
E. Mackensen, M. Lai, T.M. Wendt,“Bluetooth low energy (BLE) based wireless sensors,”Proceedings of IEEE Sensors , 2012, pp. 1–4

24. Thanks for listening ! Happy New Year !