Fastest module and mode to communicate with Xbee's

Question

I am struggling for years to use Xbee's in a home automation system where every room has a touch pannel and one gateway with Xbee and TCPIP is the center of the system.

Can someone advice to below questions please?

1/ What is the fastest way to communicate? API or AT mode?

2/ It looks like enabling ACK causes many delays and slows down the average speed. Is it really needed the ACK? Will the network still heal itselves whith out using ACK?

3/ Should there be a difference in speed between Zigbee mesh and Digi mesh? During my recent tests I can not notice any difference. I send strings of 46 bytes simultaniously between 2 nodes at 50 times / sec. Both get all messages ( so 100 messages of 46 bytes) But more is a problem although it is only 50 % of the > 100kbps in the specs.

4/ Between 2 nodes the speed is ok for fast dimming and color changes. The problem starts when I want to send the same data to multiple nodes.

Broadcast seems the worst choice with huge delays.
Unicast to multiple nodes works but now my question is how to get the maximum speed out of it.

For example I use S3B modules to avoid to many hops..

Is there a way of asking/forcing the network to use as LESS hops as possible to increase the speed? But still keep the requirement that the message need to arrive!

Since I read S3B 900 should go 610 m indoors, even when the modules are in the wall they should be able to reach the coordinator in a normal to huge house right?

5/ Point to multipoint with S3B , how to configure it? My central unit I call master, the nodes in every room I call slaves.

6/ Should point to multipoint be faster then digi mesh?

7/ Can point to multipoint handle simultaniously data from master to slaves and some slaves to master?

8/ Imagine a huge house, Can I have 1 and only 1 repeater in the middle to avoid to many hops? IF so how to do that please?

Thanks in advance and kind regards,

Wim

Answer 1

I think there is a great deal of misunderstanding.

First off, the throughput is NOT 100kbps but more like 30kbps for 1 hop and 15kbps for 2 hops.

IF you are sending data to a large amount of nodes, it really depends on the amount of nodes and what it is you want to do on which one is faster.

In reality, sending a Broadcast packet to all nodes in some situations may actually be faster than sending a Unicast packet to all nodes (API).

Any mesh network will always use the fewest amount of hops possible to get the data from the Base to the remote.

What you may not be taking into account is the Rout Discovery process. That is if you have more nodes that you are sending data to then entries in a routing table, a Rout discovery will be required. Each time a new rout discovery is required, the new rout is added to the table and the oldest entire is removed. This is where using either Broadcast packets instead of unicast comes in or simply switching to Source routing.

All distance figures are up to distances and you may not achieve that distance in your location.

If it is a 1 hop network, then point to multi-point with a Repeater would be faster. That is done by setting the TO command.

Answer 2

"Any mesh network will always use the fewest amount of hops possible to get the data from the Base to the remote."

Can y please confirm that? That is very surprising to hear, I thought it would chosse the way with best signal, even if it means more hops!
But you can confirm this, even when the signal between 2 nodes not high, it will chose that path if it means less hops?

I asked 8 questions, you did not answr them all, why not?

All of them are important for us to understand it better and find the best solution,

Thanks in advance

Wim

Comments

Think about what you just said. What you just said is that if there were 100 nodes within a network and I wanted to send the data that only required one router to get it to the destination, that I would have to use ALL 100 nodes first.  Does that make sense? No it doesn't.  What does make sense is to use the fewest hops possible to get the data from point A to point C which for the exception of the Zigbee products is what the mesh protocols used by the XBee due.