Our largest depot had a wireless survey in 2021, when the building was new to us and the racking was installed but empty. The report was thorough: forty four access points, coverage maps in pleasant colours, every aisle green. The handheld scanners worked well for about eight months.
Then the first peak season arrived. From October the pick faces fill to the top beams, the bulk locations take pallets of bottled drinks and tinned goods, and aisles that were open steel frames become walls of water and metal. Scanners at the back of aisles thirty to forty began dropping their connection, reconnecting, and losing their session in the warehouse system, which sent the picker back to the start of the task. Supervisors logged it as scanner faults. We replaced batteries, then handsets, then reset access points that were perfectly healthy.
It took us two seasons to connect the tickets to the calendar. Once somebody plotted them, the pattern was plain. Complaints rose with stock levels and fell away every January.
The radio physics was not complicated. The organisational part took longer to see. The survey had been specified by the project that fitted out the building, paid from capital, and closed at handover. There was never a budget line to repeat it, because as far as anybody could tell nothing about the network had changed. Only the contents of the building had, and nobody thought of stock as part of the infrastructure.
Each large depot is now resurveyed at its fullest, in November, and again after any change to the racking layout or to what is stored in a zone. Operations tell us about re-slotting in the same way they tell facilities, because moving bulk drinks into a new zone is now a network change. The scanners report signal strength and roaming events, so we see the back of aisle thirty five going amber in October instead of hearing about it in December. And we added nine access points, mounted lower than the originals, for about fourteen thousand pounds, which is less than the overtime we paid during that first peak.
In an office the building changes when somebody moves a wall. In a warehouse it changes with every delivery. We had designed our network as if it sat inside the building, when for most of the year it sits inside the stock.
– Serguey Shinder
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