With the start of the series I gave a general overview on which benefits wireless communication is offering and which challenges are present in different Industries. Now let’s start to dig deeper with a short look on how we can happily and especially reliable automate together even with many wireless devices at one Access Point. The highlights of looking into wireless physics I am saving up for my fourth part of the series.
One, two, three, more AGVs
If you start to automate anything you will start most of the times with a single action or a single node. The first one works? Fine – now scale up! After all: The fun begins as soon as you start to have more than one node – this is what I refer to as ‘Automating together’.
As seen above: One autonomous guided vehicle (AGV) is OK – you can travel along with some load and it’s a good start. You are really getting the capability of modularity, flexibility and increased speed with having a high number of those in your plant.
Now we are slowly getting to the point: All of those mobile devices, in that case AGVs, have the need to communicate. And this needs to happen in a way where you are not putting your production on stake just because you went for some flexibility and modularity!
Challenge – low and reliable latency
I am going to keep that very specific: Let’s assume we have 4 AGVs with data in need for low and reliable latency (the automation protocol, let’s call it PROFINET) and some further data streams (let’s call it video stream). And now you need a Quality of Service which makes sure that your controller can make the right automation decisions.
So how is Quality of Service (QoS) done in todays Wireless LAN networks? The traffic at a client and at the AP gets aligned to certain queues according to the traffics priority within the telegram. The queues with the highest priority is of course the one which gets preferably send out.
That’s a nice method as long as you have just one client. As soon as you got more devices with high priority data you will base your communication on luck. Having more mobile devices which shall automate and therefore having high priority (read automation) traffic is making things complicated. Bad luck may lead to an interruption or even stop of your production, logistic processes, … whatever got automated. See the picture above. I guess you can see the dollars flushing at the word ‘stopped production’.
To be fair: With a low data rate consumption, with a low number of clients, with certain measures on wireless network planning you are increasing your chances (but ‘just’ increasing changes!) to be successful for sending in time.
Solution – turn things the other way round
Here is how Industrial Wireless LAN with iPCF overcomes that design shortcoming of classical WLAN implementations: getting the intelligence for communication from the client to the Access Point (AP).
As you can see below: The AP makes sure that the data exchange happens in a certain sequence with the clients which enables the automation protocol to do his task (see picture below).
This cyclical polling makes Industrial Wireless LAN unique and makes a full support of automation protocols, even including safety mechanisms.
For the final touch there are Siemens-like recommendations available (if you do it exactly in that way, then it will work. We tested it. Thoroughly.).
Following up on Industrial Wireless LAN
Is the statement that automating multiple IIoT devices is a piece of cake? That would be exaggerated not only because I want to have further pieces of my blog series:
- WLAN – Automating together (iPCF); you just read through it.
- IWLAN – Enabling mobile applications (iPCF)
- IWLAN – Related to interference (WLAN)
- IWLAN – Building block for IIoT (WLAN)
- IWLAN – Raising the standards (WLAN and iPCF)
In my next post I am speaking about real mobility. The ones who kept attention might have recognized that we were just speaking about one AP. Depending on the environment that are just some square meters where my AGVs could move with a valid connection; that’s obviously not a whole factory.
So stay tuned for the next part of how roaming (that’s the word to jump with a client from one AP to the next) can be done in a time critical way.
Summary – Automating together
Being alone is often half the fun. Being at dozens may also ruin your communication experiencing. Here we step in with mechanisms to ensure a low and reliable latency to get your important points across to the receiver!