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As a curious bystander, why is wifi typically so short range? Today the frequencies of wifi and mobile networks seem to get increasingly similar, somewhere in s

by klabb3 4y ago

As a curious bystander, why is wifi typically so short range? Today the frequencies of wifi and mobile networks seem to get increasingly similar, somewhere in single digit GHz. Yet my wifi router struggles with some drywall 3m away, despite several bulky antennas.

giantrobot 4y ago
There's a few reasons: 1. WiFi is largely unmanaged so all the clients basically act like they're on an Ethernet hub. If they detect a signal they wait a random period before trying to send again. 2. Besides interference from nodes on the same network, you're getting interference from other networks on the same channel. Your WAP and WiFi card ignore those networks logically but they still need to yell at each other over the noise. This makes for dropped frames that need to be retransmitted. 3. WiFi is using unlicensed bands and has very low radiated power limits. The 2.4GHz and 5GHz bands in particular don't propagate well. This keeps a neighborhood of networks from making the spectrum totally unusable. Even still areas dense with WiFi networks make for really shitty interference. Cellular on the other hand is aggressively managed. For one handsets and towers transmit on different channels. Your upstream won't affect my downstream. Besides every channel being multiplexed a tower can tell a handset to change channels or even entire bands in order to managed congestion.
- klabb3 4y ago
  Thank you! This was exactly the level of explanation I was looking for.
zinekeller 4y ago
Different applications. Wi-Fi is designed to send bulk data but sacrifice coverage, while wireless telecommunications are designed to be reliable in thousands and have guaranteed coverage but sacrifices raw throughput.
bragr 4y ago
I believe consumer unregulated devices like wifi APs are limited to a broadcast power of 1W for one thing. Second, if you are indoors, it is more likely your phone is using a frequency band bellow 1Ghz

by klabb3 4y ago

giantrobot 4y ago

There's a few reasons: 1. WiFi is largely unmanaged so all the clients basically act like they're on an Ethernet hub. If they detect a signal they wait a random period before trying to send again. 2. Besides interference from nodes on the same network, you're getting interference from other networks on the same channel. Your WAP and WiFi card ignore those networks logically but they still need to yell at each other over the noise. This makes for dropped frames that need to be retransmitted. 3. WiFi is using unlicensed bands and has very low radiated power limits. The 2.4GHz and 5GHz bands in particular don't propagate well. This keeps a neighborhood of networks from making the spectrum totally unusable. Even still areas dense with WiFi networks make for really shitty interference. Cellular on the other hand is aggressively managed. For one handsets and towers transmit on different channels. Your upstream won't affect my downstream. Besides every channel being multiplexed a tower can tell a handset to change channels or even entire bands in order to managed congestion.

klabb3 4y ago
Thank you! This was exactly the level of explanation I was looking for.

zinekeller 4y ago

Different applications. Wi-Fi is designed to send bulk data but sacrifice coverage, while wireless telecommunications are designed to be reliable in thousands and have guaranteed coverage but sacrifices raw throughput.

bragr 4y ago

I believe consumer unregulated devices like wifi APs are limited to a broadcast power of 1W for one thing. Second, if you are indoors, it is more likely your phone is using a frequency band bellow 1Ghz