WiFi hotspot range limited by device transmitter range

Question

I am attempting to set up a network for a large, warehouse-type space (~5000 sqm) with dozens of various devices. Not wanting to run miles of cable everywhere, we bought WiFi access points that boasted ranges of over 50 metres. As an total beginner in computer networking, I neglected to consider the transmitter ranges of the devices - I have no idea what the relationship is between AP range, device range, and signal quality.

See hastily-drawn image below, where the dotted line corresponds to the maximum signal range of the respectively-coloured device.

• Device A can see AP and vice versa. All good, right?
• Device B cannot see AP and vice versa. No connectivity, right?
• Device C can see AP but the AP is out of the device's transmitter range. So what happens when the AP's signal can reach the device but not vice versa? Is any data transfer possible at this point? What's the typical range of a smartphone or laptop WiFi transmitter, anyway? If neither the AP nor the device can be moved, what's the solution here?

Answer 1

Let me start out by saying that warehouses can often be a very difficult environment to deploy wireless and it is often best to get a wireless expert to design the wireless for them. Any solution given here would just be a general idea and may not work in your environment without visiting the specific location, knowing the network needs of the devices, understanding what is being stored/moved in the warehouse (and how), etc.

Speaking to this type of problem generally, this is often addressed in an enterprise environment by providing a full deployment of access points that provide adequate coverage everywhere. However this doesn't often lend itself to wide open spaces such as warehouses (or stadiums, convention centers, etc).

In a space like you describe with devices using low powered radios, typically you would want to turn down the transmit power on the AP and use passive and/or active gain to increase the transmit and receive capabilities of the AP. Most often, this takes the form of high gain and/or directional antennas. While that is the most common, there are signal amplifiers and I have also seen locations that used leaky coax quite successfully.

On the flip side, this type of deployment can also run afoul of a number of other problems, such as the hidden node problem, which may need to get addressed. End result is that I am back to the beginning and would recommend you hire a wireless expert if you want good and reliable coverage in a warehouse type setting.