LitePoint

📡 How EVM Shapes Wi-Fi Performance — And Why LitePoint’s IQsniffer Is the Ultimate Truth Detector Ever wondered why a client sitting just 3 ft from your AP still can’t hold MCS 11? You open Wireshark and see most frames at MCS 10 or MCS 9. It’s tempting to blame the client or the environment — but sometimes, the real issue lies in the AP’s own transmitter quality. Let’s talk about EVM (Error Vector Magnitude) — the measure of how accurately a radio transmits its modulation symbols. Instead of thinking of it as a “signal integrity score,” imagine it as a precision meter for how cleanly your AP can express its constellation points. Even with strong RSSI, if EVM drifts beyond the IEEE threshold, the receiver’s constellation starts to blur — and the adaptive rate control immediately steps down to a lower MCS. For 1024-QAM (MCS 11), the IEEE requires EVM ≤ –38 dB — a tight target. Here’s where the Telecom Infra Project OpenWiFi AP EAP101 made by Edgecore Wi-Fi really stands out. During our test, it maintained a –42 dB EVM per chain at 10 dBm transmit power, comfortably exceeding the spec by 5dB and providing a stable foundation for maintaining MCS11. ⚙️ Test Setup We used the LitePoint IQsniffer to capture and analyze a 500 ms Wi-Fi 6 downlink session in a fully conductive test environment: AP: Edgecore EAP101 (2×2) Clients: Two Intel BE200 STAs (2×2 each) Traffic: 2 × 100 Mbps UDP downlink traffic (one per STA) Traffic Generator: Candela Technologies, Inc. LANforge Channel: 1 (2.4 GHz / 20 MHz BW) RSSI at STAs: ≈ –42 dBm Each AP chain was split: one leg tapped by the IQsniffer and the other passed through a variable attenuator to the clients. 📊 What the Data Shows From that 500 ms capture, the IQsniffer recorded Layer 1 IQ data, a .pcap, and a detailed .csv dataset — allowing true per-packet and per-MCS analysis. Key insights: * The vast majority of packets were HE-SU, with only a small handful of HE-MU frames detected. * MPDU aggregation reached up to 44 MPDUs per AMPDU, showing efficient frame packing and airtime use. * Airtime and throughput were evenly balanced between both clients — clear evidence of fair scheduling. * Average EVM remained steady around –42 dB, aligning with the AP’s transmit quality. 🧠 Why It Matters Even with perfect RSSI, a small EVM degradation on the transmit side can make or break your top-end rates. What your users perceives as “bad Wi-Fi” could actually be transmitter-induced noise pushing the constellation below threshold. And remember — the noise at the receiver is the sum of TX noise + channel noise + RX noise. That’s why tools like the LitePoint IQsniffer are game-changers. They don’t just decode packets — they expose the physical-layer truth. 👏 A huge round of applause to our at LitePoint for creating such a powerful diagnostic tool, and to Edgecore Networks for consistently delivering open-source based, high-performance APs that hold their own under the microscope.