5.1 Tree Structure Establishment

Following the discussion in Section 4.2, the top-down method is selected to build the tree structure network. When the grandpa node and a father node establish a connection, the notifications are disabled per default. Notifications must be enabled by the grandpa node when the connection is established. After the connection is established, the grandpa node and father node will update their own GAP connection information list according to the connected order. For the grandpa node, the father node's indexes are 0, 1, 2, and so on. For all father nodes, the grandpa node’s index is 0 in their GAP connection info list as shown in Figure 7. After connection, the grandpa node can send each father node’s index to them to establish the routing table.

Figure 7. Different Index in Grandpa Node and Father Node

After the grandpa node connects to all of the father nodes, the father node connects the children nodes in order. The father nodes and children nodes will update their GAP connection information list. For the father node, index 0 is always grandpa's node, and the children's node indexes are 1, 2, 3, and so on. For the children node, the index of the father node is always 0, as shown in Figure 8. The father node can send its index and children's node index to the children nodes. Now the whole tree structure routing table is established.

Figure 8. Different Index in Father Node and Children Node

However, it is important to note that some commands are sent directly from the grandpa node to the father node without the need for the father node to forward them to the children nodes. Because of this, there us a distinct index for each node. This document presents a simple method that uses 2 bytes to represent the index. For more details, see Figure 9.

Figure 9. Index in Tree Structure Networks

Now the tree structure network and routing table are established.