From f0a6279960036fb3402d6483bf407f4972d1c389 Mon Sep 17 00:00:00 2001 From: billz Date: Mon, 11 Mar 2024 12:39:56 +0100 Subject: [PATCH] Add 802.11ac throughput faq --- docs/faq.md | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/docs/faq.md b/docs/faq.md index b2d571e2..c6ab0d83 100644 --- a/docs/faq.md +++ b/docs/faq.md @@ -67,6 +67,7 @@ If you would like to see a new FAQ that you feel would assist other users, [star * [Why can't I access wireless mode 'N' (802.11n)?](#wireless-mode) * [How do I exclude NAT rules from IP traffic on localhost?](#iptables) * [Why is the channel dropdown disabled on the Hotspot page?](#channels) +* [802.11ac is supposed to operate at 433 Mbps. Why is my AP's throughput so much less?](#433ac) * [Why is the maximum throughput of my 802.11n AP reduced by half?](#wirelessn) * [Can I connect the WiFi client to a WEP network?](#wep) * [Can I turn the hotspot on/off over SSH?](#hotspotssh) @@ -760,6 +761,11 @@ RaspAP is capable of detecting the frequencies (channels) supported by each of y In this case, selecting a compatible 2.4 GHz wireless mode will populate the list of available channels for that interface. Alternatively, select another interface or connect a 5 GHz capable external wireless adapter. RaspAP will automatically detect the adapter and add it to the list of available interfaces. +## 802.11ac is supposed to operate at 433 Mbps. Why is my AP's throughput so much less? +The 802.11ac wireless standard uses 433 Mbps per spatial stream in the 5GHz band. Therefore, the theoretical maximum speed for a single-stream device is 433 Mbps when using an 80 MHz wide channel. However, real-world speeds are often significantly less due to a number of factors. + +In the Raspberry Pi's case, its onboard wireless chipset is connected to the primary System on a Chip (SoC) with a 4-bit SDIO link that runs at 41.7 MHz. 4 bits x 41.7 suggests about 160 Mbps should be possible with 802.11ac on this device. In practice, iPerf tests won't get close to this figure because SDIO is a simplex link (that is, half-duplex) with overhead in each of the protocol and transport layers. Given these restrictions, real-world iPerf tests in the range of 90-100 Mbps are actually quite good for this hardware. + ## Why is the maximum throughput of my 802.11n AP reduced by half? In order to achieve optimal throughput with 802.11n, the wireless stream must operate at a 40 MHz wide channel on the 2.4 GHz band. A 20 MHz channel will restrict you to 72 Mbps. Your `hostapd.conf` might have the required settings, but this is no guarantee of a 40 MHz channel.