Agreed with Jose, external antennas, and in addition, directional antennas.
This question reminded me of an Aerohive Case Study about a facility using Directional Antennas between shelving pathways, and thought it would be insightful,
"Distribution centre: a dynamic environment full of challenges
Providing a distribution centre of this size with Wi-Fi is a challenge, especially in this sector – for example because of the shelf life of products and the rapid changes to the shelves and their contents. Lantech provided predictive advice on the installation of the Wi-Fi network, based on an empty distribution centre. A logistics centre is a dynamic environment; the shelf layout changes constantly.
The height and size of the distribution centre demands that access points (APs) be set up correctly. It’s crucial to measure exactly where the APs should be placed for the best range. So Lantech used directional antennas to ensure a working network in the paths between all the shelving systems. Network users move through all paths and between shelves, so that the APs have to take over the connection from each other seamlessly. The set-up also needs to prevent interference.
Among other things the Wi-Fi network is used for order picking; products have to be scanned when they enter the truck, for example, and these scanners are linked to the stock management via the internet. The AP245X was used in the distribution centre. The network has a total of 81 APs. " - https://www.aerohive.com/wp-content/uploads/Aerohive_Manufacturing_Case-Study_Nabuurs.pdf
