A video call that stutters and drops despite showing four bars of WiFi. A VoIP call where the other end sounds like they are speaking through a wall, even though a browser-based speed test shows 200 Mbps. These are the symptoms of a WiFi problem that raw signal strength measurement does not capture, because the issue is usually not signal — it is latency, jitter, and packet loss at the levels that voice and video codecs cannot tolerate.