How can NH and BH parameters can be calculated for a large network (>50 nodes)

XBee & XBee Gateway XBee - DigiMesh
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1

fine tune network configuration parameters to improve overall network performance.

2

Which XBee product are you working with?

3

Xbee Series 2
model xb24-z7wit-004

4

I would suggest using the Network Map function in XCTUNG to determine where each module is. Then adjust the modules parameters accordingly.

5

Thanks mvut.

i´ve been measuring and monitoring network performance. i want to share my results.

  1. network set up.

network size aprox 100 nodes (all routers).

Coordinator
Agregate routing active every 20 seconds.
NH= 30
BH=0
No sleep

Routers
jv enabled =1
NW 5 minutes (watchdog)
NH = 1E
BH= 0
DH = LH= 0 (coordinator is data concentrator)
No sleep.

Monitoring results:

  • ND finds all nodes on network

  • Link quality is ok : > 220 on almost every node.

  • Radio to radio distance is 10 -20 meters (indoor)

  • Broadcast messages arrive to all nodes on network.

  • Unicast transmitions from coordinator to router uses 64 bit address.

  • When unicast transmition is succesful roundtrip is 200 ms
    (OK for me)

  • When unicast tx fail (from coordinator to router), for some nodes
    a second or third retry finally goes successful with 200 ms round
    trip.

  • My guess : Aparently network address resolution apears to be the
    problem, for nodes wich always fail unicast. Since i can´t see any
    response over the air, and aparently unicast timeout happens.

¿do you think NH /BH setting my help?

6

A large increase in the AR time or simply just issuing the AR once would be a big help. Issuing AR more than once is something you should only do in network that are moving. Otherwise once per day or only issuing it once and then again when you have issues is more than enough.

Adjusting the BH and NH really would not do anything as you are getting through. Adjusting these values would only help if you were not able to communicate with distant modules.

7

Thanks again mvut.

I will make some tests.

¿ Do you know how to calculate (or estimate) the time a broadcast storm would take for a given network? (for AR and address resolution for example)

I will also perform this experiments :

  • Implement some periodic io monitoring on unicast
    “Failing” nodes to keep their route on tables.

  • Since nodes are close to each other, i also will try
    to reduce RF power,

Any other advise is welcome, i will post back results
and conclusions back to the forum.

8

Sorry I don’t have any information on when a broadcast storm would occur. But AR really should not be used very often.

9

IF you really want to learn what happens on a network, I would strongly recommend getting a Good Zigbee sniffer.

10

Thank you.

for a big network (100 nodes): is Network watchdog (NW) apropiate ?

there is not much traffic must of the time; thats why i use AR every 20 secs.

anyway i will take your advise: will increase both NW and AR periods

11

Yes, the network watchdog timer is very relevant. Just make sure that the value you provide it is more than 3 times the polling rate of the modem. That is make sure that your value is more than 3 times the time in between poll cycles from the coordinator to that radio.

Just because you are not sending much data does not mean that there is not a lot of traffic over the RF for network management. That is why it is very important that you purchase and use a sniffer. Especially on larger networks. It helps you to understand the Real traffic that occurs and what settings you should be adjusting.