I am building my first wireless systems and have beeen reading up on the benefits, limitations, abilities, and applications of the Zigbee mesh protocol and the point-to-point / star network 802.15.4 protocol. I recently purchased my first set of radios, two Zigbee mesh ones (XB24-Z7CIT-004https://www.sparkfun.com/products/11217). I did this because I wanted to keep my abilities open for when I want to expand my capabilities into a more complicated network. I have not yet had a chance to get hands-on with my radios.
Everything I've been reading describes the technical differences, but as a beginner I feel that I will understand so much better with real-world examples and want someone in my position to come across this post in their searches. Below is my current understanding and some examples that I think are applicable. Please tell me if they are wrong, what incorrect assumptions are being made, and a better approach.
802.15.4 is best for two devices communicating with each other. For example, a robot and its hand-held controller. Star networking is good if you have a single computer reading and recording values from several, say temperature, sensors in a warehouse.
Zigbee (mesh) I am not understanding well. So far, I understand that the mesh network allows a communication path to exist between an arbitrary number of paths (radios). Mesh networks allow decentralized communication between the radios. The are robust to single and multipoint radio failures, interference, and signal blockage. I need some examples of optimal uses. What are you guys using your mesh networks for?
Also, will I be able to use my Zigbee mesh radios for simple point-to-point communication? I have heard that speed and data throughput rates are slower with Zigbee mesh, although datasheet specs seem to be the same (or I'm looking at simply kbps values and there's more to it). Am I correct in saying that Zigbee mesh has an "API mode" where communication becomes simple for basic stuff?
My main question is what are the real world examples of each protocol, what kinds of tasks do not translate well between the two, and was buying two (2) Zigbee mesh radios somewhat pointless (cost was similar)? Let's try to turn this into an example-based reference while still including all necessary technical details. Also include common and not-so-common pitfalls!
This not pretty, A is my Arduino (Main Controller) B-P are nodes , sensors, outputs or sensors&outputs. A mesh network simply uses a neighbouring node to repeat the signal either receiving or transmitting to an unbusy neighbour, these are called hops until it reaches its destination.
Meshes are aware of which node is available to receive & transmit data, reducing the amount of hops to its destination.
I do not use the zigbees as they are too expensive, but i have read the datasheets & looked at the library.
The Zigbee library contains all the advanced features that you wish to understand, the majority of the workload is done withing the Zigbee units, hence the cost. And the majority of users are plug'n'players, so there has not been a full compendium of data to follow.
Most of the advanced features have been wrapped up in the libray, this allows easier coding and simplifying tasks.
So, in a star network lets say that 4 of the 10 nodes had data to report back the the "host" (in this case, the Arduino). Are nodes aware of traffic? How would one ensure that the "center of the star" (host or Arduino) receives all data from all nodes?
Is it correct to say that a mesh network handles this kind of traffic elegantly?
brian15co:
Is it correct to say that a mesh network handles this kind of traffic elegantly?
Depends what you mean by 'elegantly', but it ought to take care of the routing for you. How elegantly it does this is another matter - my cobbled-together nRF24L01+ mesh network was anything but elegant, but it sorted the routing out and got the data where it needed to be.
Imagine the nodes are 16 (telepathic) people, 4 people have there arms full, 11 dont & 1 in reciving is waiting.
Receiving knows which package is coming first & last, the people have already organised between themselves who there passing their packets to.
The system is as elegant by how the Master Prioritizes which data is more important and which is not.
Imagine the nodes are 16 (telepathic) people, 4 people have there arms full, 11 dont & 1 in reciving is waiting.
Receiving knows which package is coming first & last, the people have already organised between themselves who there passing their packets to.
Ok, if I understand correctly, this behavior is with a Zigbee mesh network. Let's say I had the xBee series 1 (802.15.4) set up as a star network with 1 master radio listening for 15 slave radios. If 4 radios had data to provide at one single moment, would some get lost? Is Zigbee Mesh the only way to handle this kind of scenario?
Let's say I had some 802.15.4 radios set up as a star network with 1 master radio listening for 15 slave radios. If 4 radios had data to provide at one single moment, would some get lost (using 802.15.4)?
Is a Zigbee mesh the only (best) way to handle this kind of scenario?
That promo video states "The Aria has 6,000 networks & 70,000 nodes", i'm very sure this is a proven system, as a hotel as large as the Aria would want the highest quality possible & the most reliable.
I do not use these, generally depending on how many pipes are available &/ what data is of the most priority, or to the lesser which data is received first.
Depending on the features of the radio, CRC is a checksum feature, that compares the checksum of the packet, to see if the data has been corrupted/altered, a packet may contain a footer&header and seperate checksum of the encapsulated data. The checksums can be used to rebuild the data.
I do not know the failure rate, i believe it would be insubstantial.
Is a Zigbee mesh the only (best) way to handle this kind of scenario?
That is dependent on the features & failure rate of each radio, which could be 1,000's of different products & a myriad of views to what is best.
JB_AU, I am not sure I understand your responses, apologies
That promo video states "The Aria has 6,000 networks & 70,000 nodes", i'm very sure this is a proven system, as a hotel as large as the Aria would want the highest quality possible & the most reliable.
What promo video are you talking about?
I do not use these, generally depending on how many pipes are available &/ what data is of the most priority, or to the lesser which data is received first.
What are you referring to by "these"? Zigbee or 802.15.4? You mentioned before you don't use ZigBee, but I'm not clear as to what you are referring to.
By pipes, do you mean different paths that data could follow to reach the receiving radio?
Are both protocols capable of specifying data priority, or is it more of a first-in-first-out (FIFO) thing or similar?
