What is the exact meaning of NH in xbee s2c?

Question

1) If there is a network topology like E1-R1-C-R2-E2, it is 3 hops between E1 and E2. Then what is NH (maximum unicast hops)?
I think NH is 3. But your manual says NH like this. I can't understand what you said.
NH (Maximum Unicast Hops)
Sets or reads the maximum number of hops across the network. This limit sets the maximum
broadcast hops value (BH) and determines the unicast timeout.
The timeout is computed as (50 * NH) + 100 ms. The default unicast timeout of 1.6 seconds (NH=0x1E)
is enough time for data and the acknowledgment to traverse approximately 8 hops. For 8 hops , NH is not 8 but 30(0x1E).
2) For 8 hops, you recommend NH=0x1E(30). I am not sure..
What is the formula between NH and hop number?

Answer 1

In what you have described, if each router is only in range of its end device child and the Coordinator, then you would have 4 hops to go from E1 to E2.

Hops means that amount of re-transmissions needed to get the data from Point 1 to point 5.

The added time in the NH value for the additional hops is to make sure that if there is any retransmission's for data collisions Etc you have the time.

Comments

Your manual says that for 8 hops, it recommended NH=0x1E(30).
Please show me the recommend NH for hop=1, 2, 3, 4, 5, 6, 7 if you can do that.

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What manual are you working with? Can you provide a link to it?  Can you also provide a page number that you are seeing this on?

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In your xbee s2c manual (2016's July version).
command table list..

NH (Maximum Unicast Hops)
Sets or reads the maximum number of hops across the network. This limit sets the maximum
broadcast hops value (BH) and determines the unicast timeout.
The timeout is computed as (50 * NH) + 100 ms. The default unicast timeout of 1.6 seconds (NH=0x1E)
is enough time for data and the acknowledgment to traverse approximately 8 hops.

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This is member helping member. Not Digi Technical Support answering these.  You are going to need to do some reading in the current manual located at http://www.digi.com/resources/documentation/DigiDocs/90002002/default.htm#concepts/c_xbee_pro_zigbee_transmission_timeouts.htm%3FTocPath%3DTransmission%252C%2520addressing%252C%2520and%2520routing%7CTransmission%2520timeouts%7C_____0.  

There is an entire section on Timeouts and how to calculate them.