Wi-Fi IEEE 802.11 physical layer testing

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1. Wi-Fi IEEE 802.11 Physical layer testing

Physical layer testing includes tests that are defined in IEEE 802.11 and other impairment testing as mentioned below:

IEEE 802.11 TX: TX output power, IEEE spectral mask, spectral flatness, and Error Vector Magnitude (EVM).
IEEE 802.11 RX: PER, sensitivity, and interference immunity tests.
RF impairment tests: Crest factor, CFO, symbol clk error (ppm), IQ offset, DC power, gain imbalance, and quadrature error.

1.1. Lab measurements

The figure below shows the lab bench used to realize physical layer testing on ST67W611M1.

The bench measures the DUT ST67W611M1 in conducted mode. It is hosted by a Nucleo U575ZI-Q that connects to PC via its ST-link using USB connector. Both DUT and host are placed in a Faraday’s cage. The bench uses Tera Term to establish a serial connection with the DUT. The bench needs no special FW such as a production or a manufacturing FW, the regular FW (mission profile) is the used one. Customers will received signed binaries to use (no building, just flashing) and then they can build/flash their host’s FW using their tools/procedures. The tester is R&S CMW270. It is connected to the PC via an ethernet cable. This allows piloting it by the PC and running automatic test scripts using the CMWRun program. At the end of a testing campaign, test reports are automatically generated by the CMWRun tool.

Test procedure: here below we give an example of the test procedure that we follow to realize PER testing.

DUT using the regular FW in station mode.
CMW270 tester is set in Access Point mode.
Using a serial connection terminal, PC sends the CLI command
```
wifi_scan
```
to the DUT in order to make a WI-FI scan for nearby access points. At the Terminal we can see that the DUT is able to see the AP of the tester. Please use the following link for the full list of CLI commands: ST67W611M Wi-Fi® – CLI Project.
PC then sends the CLI command
```
wifi_sta_connect
```
to connect the DUT to the AP of the tester.
Once the station-to-AP connection is established, the tester takes over and automatically continues the next steps without any intervention to send more commands to the DUT. Commands the DUT is realized over the air by the tester. This is known as “Signaling testing”.
The CMW270 starts transmitting TX MAC data packets in WLAN data frames.

On the other side, the DUT receives the data frames. The MAC layer of the DUT acknowledges the received WLAN data frames with WLAN Ack frames.
The DUT pass the MAC frame data to its next layer. No IP frame inside, data discarded.
PER is calculated as PER = unacknowledged/transmitted packets.
Testing ends by an automatic report generation that we present in the coming section.

1.2. Measurement results and reporting

This Section shows physical test results examples using the above explained bench.

1.2.1. TX testing

The three figures of this section show examples of TX testing measurements where:

IEEE 802.11 Physical layer TX tests: TX output power, IEEE spectral mask, spectral flatness, and Error Vector Magnitude (EVM).

Transmitter RF impairment tests: Crest factor, CFO, symbol clk error (ppm), IQ offset, DC power, gain imbalance, and quadrature error.

1.2.2. RX testing

The figures of this section show RX PER measurements versus the number of received packets, and RX PER versus received signal power for sensitivity testing.