Wi-Fi at some businesses is quite far ranging. You can usually hook up to a McDonald’s Wi-Fi signal from hundreds of feet away. I have seen a device on the back of my local McDonald’s that I think is an outdoor antenna.
But others only work in the building or very close. The Racino near me is a good example. It is a huge facility, a couple of acres indoors. The signal is everywhere inside. They must have antennas all over the place. But no signal in the parking lot at all. I experimented the other day and the Wi-Fi signal stops as soon as you exit the door. But the doors, and indeed the entire front of the building, is just glass with widely spaced metal frames. How does the signal not get out?
I bet you can tune a WiFi signal transmitter to limit it’s transmitting range. They have it tuned so it stops before it reaches the parking lot. Why someone would intentionally do this is a good question, or maybe it just worked out that way.
Yeah, the metal frame might block the signal. Some commercial windows might also have “low emission” metallic coatings embedded in them that affect wifi (as a side effect of their glare blocking).
Good wifi design should limit transmit power to avoid interference as well as keeping unwanted guests off your network. Transmit power can be adjusted radio and device to optimize the footprint.
Many people just set transmit power to maximum on the “more is better” concept.
There are such things as directional antennas, which direct the signal in certain directions, and not (or very weakly) in other directions.
Setting up a wi-fi system using such antennas would no doubt be more complicated (and more expensive) than using standard wi-fi antennas, but could certainly be done if a business strongly wanted to confine their wi-fi use to inside their premises.
McD’s wants you to use the drive thru so their wifi would work in the parking lot so you can use their app; other places may want you in the building so they don’t care if it works outside the building.
I agree some commrical window coatings are metallic, which may block WIFI signals. However, unless it’s a recent building, deliberately designed for wiifi restrictions, this would more likely be a convenient coincidence. It is also possible to estimate someone’s position from relative signal strength to each Access Point. If A and B are on the wall, but C is inside, detecting a sigal strong in A and B but below a certain threshhold on C means you have left the building.
Some advanced WifFi systems have strong management features (My favourite was the “stomp” feature, where one Access Point was dedicated to sending a signal to interfere with other WiFI if it detected an unauthorized access point, to prevent you from plugging your personal WiFI hotspot into the corporate network.) I would not be surprised if geographic limitations were an available feature nowadays.
Window frames alone will do approximately nothing to block WiFi signals. Radio waves can pass through an aperture if its dimension is at least half the wavelength of the signal. WiFi uses 2.4Ghz and 5GHz, with wavelengths of 12.5cm and 6cm. Business windows are usually on the order of a meter on a side.
I suspect this is the crux of it. Most businesses do the minimum possible to supply wifi outside their premises, and the OP is comparing this to McD’s who are making a positive effort to supply wifi in their parking lot, to encourage people to use it (and hopefully buy something).
WiFi in larger business premises - and likely in many smaller ones - can be a very interesting beast. They generally don’t use the common domestic types of systems, but rather much more sophisticated and nefarious systems.
A couple of things they will do. They track you. Places like large box stores, hardware stores and shopping malls cover their premises with small base stations. These will identify your phone - even if it doesn’t connect to the WiFi system - and track your movements. Where you pause, maybe to look in a window, or look at a product is tracked. Come back another day - they will correlate the visits. They may never identify you, but they will build a profile of you that may inform what they do. Even if it is just a matter of moving store displays around to better effect.
If you actually connect to the WiFi system, they will pull all sorts of tricks. Want to price compare to a rival? Funny the rival’s web site can’t be found. Any business of any size will want to mine the WiFi stream for any data of value. Visits to their own web sites correlated with where you are standing, attempts to visit rivals, anything else that might be of value.
The upshot can be that the footprint of a sizeable business’s WiFi is much more carefully managed than one might assume. Even a large chain fast food outlet or coffee shop might be expected to be doing this. Your local friendly corner café - probably not. They likely just have a cheap domestic base station with only the most basic controls enabled.
Minimally, just never connect to unknown WiFi systems. Where unknown means a WiFi you don’t personally know is safe. Turn the option to auto join or join after asking off.
Your phone isn’t silent. If WiFi is enabled, by default it may be pinging for a connection, or engaging in even just a partial negotiation when it sees a possible connection. The ping, or any transmission, includes the phone’s unique MAC address. That is enough to track you. No actual connection needed.
The WiFi connection protocol is not great, and devices tend to be noisy in ways that you would not expect. I would not be surprised if there are not corner cases in the protocols that can be used to cajole your phone into transmitting, even just one packet is enough. Like many protocols, they were designed in a kinder, simpler, time.
One of the worst situations is when you disable SSID on your home router. This stops your home WiFi from sending out packets identifying itself. So what happens when you get home? No packets with SSID, so how does you phone reconnect? Well your phone just sends out packets asking for your home WiFi by name. But your phone doesn’t know when you are home, so it is pinging your home WiFi all the time. Even at the shopping mall. (There is a nasty exploit sitting here if you work through the implications.)
Enabled personal hot spot? Your phone will be bleating its WiFi presence everywhere.
It doesn’t surprise me that my phone’s Wifi isn’t silent, but it does surprise and scare me that it broadcasts the MAC address without even connecting. So now I clearly understand how they can track and identify me, but how to track my position? By extrapolating from my Wifi’s signal strength?
I didn’t know this, but I’ve never disabled SSID anyway because at least I knew that it’s at best security by obscurity and no real obstacle to find the network anyway. That it’s even harmful is new to me.
Ok, that was the only risk in this context that was obvious to me.
Yeah, Bluetooth is now the big one. It is so ubiquitous in devices that you may as well paint your social security number across your back along with a target. I would expect any modern customer tracking system to be using Bluetooth now in addition to how they use their WiFi.
Those helpful traffic signs that say: travel time to XXX? They are just reading Bluetooth addresses from cars that travel under the signs and correlating them with addresses read from cars that are arriving at XXX. You can connect the dots from here.
Can’t avoid needing a MAC address. If you want a reply, you need to say where to send it. No point sending anything out unless there might be a reply. So every header has the sender’s MAC address. Just part of the layer 2 protocol. You could have a protocol which was based on bi-directional broadcasts, but it would be both wasteful, noisy, and somewhat pointless.
Among other possibilities. Depends on sophistication of the system. One reason for many small controlled coverage base stations. Which is where we came in.