RFmx WLAN SEM measurement uses the configurations and masks conforming to IEEE Standard 802.11-2016, IEEE Standard P802.11ax/D8.0, IEEE Standard P802.11be/D7.0, and IEEE Standard P802.11bn/D0.3 specifications. This topic explains the configurations and masks that the RFmx WLAN SEM measurement uses.

Refer to the SEM topic for more information on single and multicarrier SEM measurements.

Offset Segments

The frequency ranges adjacent to the carrier channels on which some spectral emission mask limit is imposed are collectively known as SEM offset segments. The offset segments are specified by their start and stop frequencies relative to the center frequency of the carrier channel. When you set the SEM Mask Type property to Standard, the offset segments' start and stop frequencies and mask levels are automatically configured according to the Standard property and the Channel Bandwidth property, conforming to IEEE Standard specifications. Additionally, if you set the Standard property to 802.11n, then the OFDM Freq Band property is also considered for automatically configuring compliant offset segments. When you set the SEM Mask Type property to Custom, you can manually configure the following properties for each offset segment:

  • SEM Offset Start Freq (Hz)
  • SEM Offset Stop Freq (Hz)
  • SEM Offset Sideband
  • SEM Offset Rel Limit Start (dB)
  • SEM Offset Rel Limit Stop (dB)

The signs of the offset segment relative start and stop frequencies, specified by the SEM Offset Start Freq (Hz) and SEM Offset Stop Freq (Hz) properties respectively, are interpreted as shown in the following examples.

Configured by you Measurement interpretation of the configuration
SEM Offset Start Freq (Hz) ← +9 MHz SEM Offset Stop Freq (Hz) ← +11 MHz SEM Offset Start Freq (Hz) ← 9 MHz SEM Offset Stop Freq (Hz) ← 11 MHz
SEM Offset Start Freq (Hz) ← –11 MHz SEM Offset Stop Freq (Hz) ← –9 MHz SEM Offset Start Freq (Hz) ← 9 MHz SEM Offset Stop Freq (Hz) ← 11 MHz
SEM Offset Start Freq (Hz) ← –9 MHz SEM Offset Stop Freq (Hz) ← +11 MHz SEM Offset Start Freq (Hz) ← –9 MHz SEM Offset Stop Freq (Hz) ← +11 MHz

The SEM Offset Rel Limit Start (dB) and SEM Offset Rel Limit Stop (dB) properties determine the SEM mask level for each of the offset segments. The SEM Offset Rel Limit Start (dB) and SEM Offset Rel Limit Stop (dB) properties are mask levels for the corresponding SEM Offset Start Freq (Hz) and SEM Offset Stop Freq (Hz) of the specific offset segment. These mask levels are relative to the measured peak power level in the carrier channel.

The resolution bandwidth and video bandwidth for performing the SEM measurement conforms to the IEEE Standard 802.11-2016, IEEE Standard P802.11ax/D8.0, IEEE Standard P802.11be/D7.0, and IEEE Standard P802.11bn/D0.3 specifications.

Preamble Puncturing

In accordance with the specifications in IEEE Standard P802.11ax/D8.0, IEEE Standard P802.11be/D7.0 and IEEE Standard P802.11bn/D0.3, you can configure additional offset segments for the following,

  • 80 MHz and 160 MHz MU PPDUs in 802.11ax.
  • 80 MHz, 160 MHz, and 320 MHz MU PPDUs in 802.11be.
  • 80 MHz, 160 MHz, and 320 MHz MU PPDUs in 802.11bn.

In the previous cases, the preamble is punctured (absent) from certain unoccupied 20 Mhz subchannels. To enable automatic configuration of such additional offset segments, configure the following properties.

Property Description
Standard 802.11ax, 802.11be or 802.11bn
Channel Bandwidth (Hz)
  • 80.000E+6, 160.000E+6 if you set the Standard property to 802.11ax.
  • 80.000E+6, 160.000E+6, 320.000E+6 if you set the Standard property to 802.11be.
  • 80.000E+6, 160.000E+6, 320.000E+6, if you set the Standard property to 802.11bn.
OFDM Preamble Puncturing Enabled True
OFDM Preamble Puncturing Bitmap An integer between 0x1 and 0xF for 80 MHz PPDU, an integer between 0x1 and 0xFF for 160 MHz PPDU, and an integer between 0x1 and 0xFFFF for 320 MHz PPDU
0s and 1s in the binary representation of the integer OFDM Preamble Puncturing Bitmap indicate the presence of a punctured 20 MHz subchannel and an active 20 MHz subchannel, respectively. The Least Significant Bit corresponds to the lower frequency 20 MHz subchannel. OFDM Preamble Puncturing Bitmap is interpreted by the SEM measurement as illustrated by the following examples for the 80 MHz PPDU.
OFDM Preamble Puncturing Bitmap Active 20 MHz Subchannels
0x1 0b0000 0001 –40 MHz to –20 MHz
0x2 0b0000 0010 –20 MHz to 0 MHz
0xE 0b0000 1110 –20 MHz to 0 MHz, 0 MHz to 20 MHz, 20 MHz to 40 MHz

Similarly, for a 160 MHz PPDU, the bitmap interpretation is shown in the following example.

OFDM Preamble Puncturing Bitmap Active 20 MHz Subchannels
0x1 0b0000 0001 –80 MHz to –60 MHz
0x2 0b0000 0010 –60 MHz to –40 MHz
0x48 0b0100 1000 –20 MHz to 0 MHz, 40 MHz to 60 MHz

Similarly, for a 320 MHz PPDU, the bitmap interpretation is shown in the following example.

OFDM Preamble Puncturing Bitmap Active 20 MHz Subchannels
0x1 0b0000 0000 0000 0001 –160 MHz to –140 MHz
0x2 0b0000 0000 0000 0010 –140 MHz to –120 MHz
0x148 0b0000 0001 0100 1000 –100 MHz to –80 MHz, –40 MHz to –20 MHz, 0 MHz to 20 MHz