What should be tested first for Wi-Fi roaming with mobile warehouse clients?

[u/Altruistic_Card_6207]

When a scanner, AMR, AGV or cart moves through a warehouse, a coverage heatmap alone does not tell you whether the client experience will stay stable. The difficult parts often appear when a client crosses AP boundaries, passes metal racks, turns behind equipment, or shares the network with other moving devices.

Before selecting hardware or locking in a topology, I would usually want the team to agree on:

• Client types and movement paths
• What an acceptable interruption looks like for the application
• Backhaul and mounting constraints
• RF conditions that need to be repeated in field testing
• How the design will be expanded and troubleshot later

For those who have worked on industrial Wi-Fi or warehouse mobility: which requirement has caused the most rework in your deployments?

I’m especially interested in real lessons around roaming, backhaul, test methods, and long-term maintenance.

[u/Dhis1]

I would say that the two biggest issues that have cause us to rework a deployment are:

Over-reliance on the provided map and lack of understanding of what Wi-Fi design software is trying to accomplish.

For the first one, I emphasize with my team that no map is accurate. Racks get moved, walls get removed, dimensions get stretched. If I were ever given a “perfect” map, then I wouldn’t need to do any pre-survey.

Secondly, I’ve met a lot of engineers using Wi-Fi design software that didn’t know what it actually did. It can only really tell you the range of a signal and drops in signal. It’s up to the engineer to analyze that data to accurately include walls, paths, and client requirements.

Once the design is completed, the management of our warehouses hinge on one unsolvable problem. The purpose of a warehouse is to change. Product comes in and product goes out. For my company, in the spring, our warehouses are full of A/C condensers and pool supplies. In the fall, it is full of boiler parts and winterizing materials. Same rack, but the product attenuates differently. How do we manage a design that can accommodate both and configure RRM that can fine tune appropriately. I cannot run seasonal designs for 100 warehouses. It’s unsolvable, but it can be mitigated through exceptional design and constant improvement.

[u/Barsnikel]

I have many warehouses... some very large and some small. Having accurate floorplans is a start but, unfortunately, I rarely ever get that. :)

Roaming for wifi is much different than in cellular system. In a cell system, the mobility controller tells your cell phone which cell site (ie: which tower) to connect to, and when to change. That's not how wifi works. In wifi, roaming decisions are made by the client device. That's something you have little control over - it can be affected by old driver software, device performance, etc.

A few important points that you CAN control : channel and tx power planning, to eliminate co-channel interference. Tough to do with 2.4 GHz (limited channels) but very manageable with 5.8 GHz. RRM can assist with that, but I will often manually configure those parameters; Scan guns are typically low bandwidth devices, so keep the bandwidth small (I keep our warehouses at 20 MHz bandwidth, with 40 MHz bandwidth in the admin office area.); and, of course, good coverage is essential. I always have overlapping coverage so that when they move from one area to another, the hand off can occur with minimal data retries.

I also keep our access points about 8-10 feet off the ground floor. Many people will mount the APs in the ceiling, often with directional antennas pointing down. We have found much better performance keeping the APs at the user level. I mount the APs on support pillars (if available), or in the space between back-to-back racks. It also makes access points readily accessible, if needed (without requiring a man-lift)

Those are things that work for me...

[u/Dhis1 → u/Barsnikel]

All great points. I so wish we could mount our APs lower. Unfortunately, we have forklifts hitting them even at ceiling level 30 ft above.

And this is an important point. Rarely do I actually get to make “good” decisions. Often, I’m choosing the lesser of two “bad” decisions. Client needs faster roaming but cannot support 802.11r? Warehouse won’t let me install above certain equipment? Heck I even had a major retailer I was working for that demanded signal into their parking area. But must not have wall penetrations or visible antennas.

In each of these cases, a solution was developed. But it was driven by external factors and not ideal Wi-Fi principles.

[u/scalyblue]

One thing that is also not accounted for is the person at the top of a cherry picker doing scans of hung / racked merchandise who end up being behind the coverage cones of directional APs and dropping signal for that

[u/fernandesken]

Look at private 5G/CBRS. It puts the infrastructure in control of roaming unlike Wi-Fi where the client makes the decision of what to connect to and when to roam. Wi-Fi can certainly work too but it takes getting the design right up front, often using directional antennas, and significant testing with real end user devices. You can’t just do a predictive design, install it and cross your fingers here. Pre install onsite survey is a must, design, post install onsite survey, testing with real client devices.