HOW CTP WORKS?

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The Collection Tree Protocol is a routing protocol used by wireless sensor networks.It is used for transferring data from sensors to the root node.The protocol tree creates a collection tree shown below:









The bottom node is called the root,or sink node,which means that all the data is sent downwards in the tree to the root. The nodes N1 to N7 can simply forward packets or can creates their own data. The most important part is that all the information is sent towards the root,no matter which node sends it.
Each node has a name and an expected transmission coefficient(ETX) to the sink. Each node will give the link quality value to its neighbour nodes.ETX is established by estimating the quality of links between the nodes and assigning a value to it.Adding the values of links between the sink and node gives the ETX of the node. Since each node calculates its own ETX a node only needs to know the link quality to the parent and the ETX of the parent in order to calculate ETX of its own.

ETXnode=ETXparent+ETXlinktoparent

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