Bluetooth and Wi-Fi fight over 2.4GHz

Mon, 22 Jun 2026 00:00:00 GMT

I have a phone running a Snapcast client: it pulls synced audio over Wi-Fi and plays it out to a pair of Bluetooth headphones. It buffered constantly: a few seconds of audio, then a stall, then a reconnect.

The Wi-Fi signal was excellent (RSSI -44), the server was idle, and the same stream played fine elsewhere, so naturally I blamed everything except the obvious thing. Eventually I just pinged the server with Bluetooth on, then turned Bluetooth off and pinged again. Same Wi-Fi network, same location, seconds apart:

# Bluetooth ON (streaming to the headphones)
10 packets transmitted, 8 received, 20% packet loss
rtt min/avg/max/mdev = 8.6/238.6/742.4/254.4 ms

# Bluetooth OFF
10 packets transmitted, 10 received, 0% packet loss
rtt min/avg/max/mdev = 7.4/9.1/10.8/0.9 ms

The only variable was Bluetooth, and it took the link from a flawless 9ms to 238ms average with 20% loss.

The cause is 2.4GHz coexistence. Bluetooth lives in the 2.4GHz band,¹ and so did my Wi-Fi. On a phone the two typically share a single radio and antenna,² so pushing audio out over Bluetooth while pulling audio in over 2.4GHz Wi-Fi means they have to take turns and they trample each other. Snapcast streams real-time PCM with a ~1s buffer;³ with packets arriving 250ms+ late and one in five dropped, the buffer starves and the client gives up and reconnects.

The fix was to get Wi-Fi off the band Bluetooth is squatting on: move the phone to 5GHz. Bluetooth stays on 2.4GHz, Wi-Fi moves up, and they stop fighting.

There was one more gotcha. The 5GHz SSID didn’t even show up in the phone’s Wi-Fi scans as the router had auto-selected channel 104, which phones won’t see. I pinned the router’s 5GHz radio to channel 36 and the problem disappeared entirely:

# 5GHz channel 36, Bluetooth still ON
12 packets transmitted, 12 received, 0% packet loss
rtt min/avg/max/mdev = 8.9/10.3/13.7/1.3 ms

10ms average, 1.3ms jitter, zero loss with Bluetooth doing exactly what it was doing before. The audio has been rock solid since.

Bluetooth operates in the 2.4 GHz ISM band (2.400–2.4835 GHz), the same unlicensed band used by 2.4 GHz Wi-Fi. “Improved Spectrum Coexistence in 2.4 GHz ISM Band Using Optimized Chaotic Frequency Hopping for Wi-Fi and Bluetooth Signals”, Sensors (NCBI/PMC). ↩
Phones commonly use a combined Wi-Fi/Bluetooth chip that shares a single antenna between the two radios, requiring time-division coexistence so they transmit in alternating time slots rather than simultaneously. “Systems and methods for coexistence between plurality of wireless communications modules sharing single antenna”, US Patent 9,130,605. ↩
Snapcast reads PCM chunks from its source and tags them with server time for synchronized playback; its default read/buffer size is 1000 ms. Note that, while it supports an uncompressed pcm codec, its default wire codec is FLAC rather than raw PCM. Snapcast README — codecs and buffering. ↩

]]>

RSS Feed for bluetooth - James Stone's Blog

Bluetooth and Wi-Fi fight over 2.4GHz

Footnotes