SWRA648 May   2019 CC1352P , CC1352R , CC2642R , CC2642R-Q1 , CC2652P , CC2652R , CC2652R7 , CC2652RB , CC2652RSIP

 

  1.   Bluetooth Low Energy Tree Structure Network
    1.     Trademarks
    2. 1 Introduction
    3. 2 Bluetooth Low Energy Basic Knowledge
    4. 3 Three Kinds of Bluetooth Low Energy Network Structure
      1. 3.1 Star Network
      2. 3.2 Mesh
      3. 3.3 Tree Structure Network
    5. 4 Bluetooth Low Energy Tree Structure Network Analysis
      1. 4.1 Role Analysis in Bluetooth Low Energy Tree Structure
      2. 4.2 Tree Structure Network Establishment Analysis
    6. 5 Bluetooth Low Energy Tree Structure Network Realization
      1. 5.1 Tree Structure Establishment
      2. 5.2 Role Differentiation in Tree Structure Network
      3. 5.3 Data Transmission in Tree Structure Network
    7. 6 Bluetooth Low Energy tree Structure Network Test
    8. 7 References

4.2 Tree Structure Network Establishment Analysis

In theory, there are two ways to establish the tree structure network:

  • Top-down: first the grandpa node connects to all of the father nodes. Then, each father node connects to its own child nodes.
  • Bottom-up: first each father node connects to its own child nodes. Then, the grandpa node connects to each father node.

In the bottom-up method, after the first father node connects with its own children nodes, the father node is advertising. When the second father node starts to connect with its own child nodes, the first father node can incorrectly be connected to by the second father node.

wrong-connection.pngFigure 5. With Bottom-Up Network Establishment, There is a Risk of a Wrong Connection Between Father Devices

In order to avoid this, a feature that keeps track of what devices connect to what devices such as directed advertising or a white list is needed. However, this complicated the code since it means that the network must be formed with the same device in the same position each time.

For the top-down method, when the father node is connected it stops advertising, so different father nodes will never connect to each other. This network establishment method can simplify the software effort compared to implementing directed advertising or a white list.

top-down-establishment.pngFigure 6. Top-Down Establishment