802.11ax EVM Measurement | IEEE 802.11 EVM specification
This page describes IEEE 802.11ax EVM Measurement as defined in IEEE 802.11 ax standard. The 802.11ax EVM test and measurement solutions are also described along with 802.11 EVM specifications.
What is EVM (Error Vector Magnitude)?
Introduction:
• EVM or Error vector magnitude provides insight into quality of the modulated signal/symbol.
• This modulated signal originates when bits are mapped to symbols in a complex modulation systems
such as QPSK, 16-QAM, 64-QAM etc.
• It is also referred as RCE (Relative Constellation Error).
• It can be expressed in units of "dB" or "rms".
• Refer Error Vector Magnitude basics >> and
EVM unit converter >> for more information.
The figure-1 depicts concept of EVM measurement. The basic EVM equation is also mentioned.
IEEE 802.11ax EVM specifications
In order to support higher data rates and capacity, 802.11ax uses 1024-QAM modulation in addition to 16-QAM, 64-QAM and 256-QAM. Following table mentions EVM specifications of 802.11ax compliant DUT (Device Under Test).
| Modulation Scheme | EVM Specifications |
|---|---|
| 16-QAM | -19 dB |
| 64-QAM | -27 dB |
| 256-QAM | -32 dB |
| 1024-QAM | -35 dB |
Source: Keysight Technologies & 11ax Standard
IEEE 802.11ax EVM Test and Measurement Solutions
To test or measure EVM of 802.11x DUT, test equipments should have tighter EVM noise floor.
Following are the companies offering test and measurement solutions for 802.11ax compliant devices.
➤National Instruments (NI) offers RF vector signal transceiver (VST) with the NI WLAN Measurement Suite.
➤Lite Point offers zSeries-PA/FEM test solution for EVM test and measurement.
The Litepoint offers following instruments among the other which are used for the test.
• z8653 6 GHz Vector Signal Analyzer (VSA), 1 GHz analysis bandwidth
• z8751 6 GHz Vector Signal Generator (VSG), 500 MHz modulation bandwidth
➤Keysight Technologies offers 802.11ax EVM Test requirement which requires following specifications.
Keysight offers 802.11ax solutions which include N7617B WLAN Signal Studio, N5182B MXG Signal Generator (SISO test),
M9421A PXI VXT Vector Transceiver (SISO test), N5182B MXG signal generator (MIMO Test),
M9421A PXI VXT (MIMO Test), 89600 VSA Software for 802.11ax signal analysis and so on.
• Better than -50dB EVM performance for chipset & PA characterization
• Better than -48dB EVM performance for 8x8 device validation
802.11 EVM specification
Following table mentions different RMS EVM limits for each modulation scheme as per 802.11 specification. It covers 802.11 a/g, 802.11n and 802.11ac EVM limits.
References:
• IEEE 802.11ax draft standard and 802.11 EVM specification section
RF and Baseband Measurement Links
WiFi 6 Resources as per IEEE 802.11ax
Advantages and disadvantages of 802.11ac (WiFi 5) Advantages and disadvantages of 802.11ax (WiFi 6) BSS coloring in 11ax RU in 802.11ax MU-OFDMA in 802.11ax MU-MIMO in 802.11ax Difference between 802.11ac Wave1 and Wave2 Difference between 802.11n,11ac,11ad WLAN 802.11ac tutorial WLAN 802.11ax tutorial WLAN 802.11ac frame structure WLAN 802.11ac Physical Layer 802.11ac MAC Layer 802.11ax basics WLAN 11a,11b,11n,11ac frame structures
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WLAN SIFS, PIFS, DIFS, EIFS, AIFS What is DCF and PCF in WLAN What is RTS and CTS in WLAN What is wlan? WLAN standards-11a,11b,11g,11n,11ac 11a WLAN Physical layer 11b WLAN Physical layer 11n WLAN Physical layer WLAN basic tutorial 802.11ac tutorial 802.11ad tutorial Difference between 11a,11b,11g,11n Difference between 11-n,11-ac and 11-ad WLAN router providers WLAN providers
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