In RPL protocol (Routing Protocol for Low Power and Lossy Networks) we can use Expected Transmission Count (ETX) as the default metric for rank computation, which is frequently used in lossy networks and shows the number of retransmission. The ETX of a link will be measured and updated continuously, once the link starts to carry data traffic.
What factors cause increase or decrease in ETX after data transmission?
ETX is calculated based on the packet delivery ratio of forward (denoted df) and reverse direction (denoted dr) of a link, i.e. ETX = 1/(df x dr), ETX >=1. df, dr are determined by counting dedicated probe packets successfully received. Therefore, ETX value can be influenced by interference among nodes, link quality changes due to mobility, asymmetric links (read this: https://pdos.csail.mit.edu/papers/grid:mobicom03/paper.pdf).
ETX is calculated based on the packet delivery ratio of forward (denoted df) and reverse direction (denoted dr) of a link, i.e. ETX = 1/(df x dr), ETX >=1. df, dr are determined by counting dedicated probe packets successfully received. Therefore, ETX value can be influenced by interference among nodes, link quality changes due to mobility, asymmetric links (read this: https://pdos.csail.mit.edu/papers/grid:mobicom03/paper.pdf).
By the way, what is the simulator you are using to explore the RPL protocol?
In multi-hop wireless networks, ETX (Expected Transmission count)metric finds high-throughput paths . ETX reduce the expected total number of packet transmissions required to successfully deliver a packet to the final destination.
The ETX metric assimilate the effects of link loss ratios, asymmetry
in the loss ratios between the two directions of each link, and interference
among the successive links of a path (link quality changes due to mobility).
Thanks all for your valuable information about ETX.
Actually I implement RPL in Matlab simulator.
Deae Zahra,,
if you have time compare the result from the Mathlab tool with Cooja simulator,,
Regards
Muneer
how to calculate ETX in matlab and how to use df &dr to calculate ETX ?
Dear Zahra Aslani,
the answer to her question is shown in my figure.
https://www.researchgate.net/post/What_factors_cause_changes_in_ETX_value
Best regards
Anatol Badach
- Badges
- Science topic