WLAN IEEE 802.11n,802.11ac RF PHY layer transmitter testing

This page covers RF and PHY conformance tests for 11n device testing and 11ac device testing. These compliance tests are used for transmitter and receiver measurements of IEEE 802.11n/802.11ac compliant device. These tests are useful for test and measurements related to 802.11n and 802.11ac products.

802.11ac standard based products support RF frequency upto 6GHz. It also supports MIMO. For 802.11ac features refer WLAN 802.11ac tutorial.

Transmitter tests include transmit Spectrum Mask, Spectral Flatness, Center Frequency Tolerance, Packet Alignment, Symbol Clock Frequency Tolerance, Modulation Accuracy (Center frequency leakage and Constellation EVM). Following table-1 mentions the limit for these 11ac transmitter conformance tests.

Transmit Spectrum Mask

• Refer 11ac spectral mask for limits defined for 20 MHz, 40 MHz, 80 MHz and 160 MHz channel bandwidths

• 11ac transmitter device radiation should be as per the mask defined. measurements should be carried out with 100 kHz RBW, 30 kHz VBW

• 80 + 80 MHz Non-contiguous Spectrum Mask measurement is also need to be done

Spectral Flatness

• Allowed spectral flatness limit is 2dB from max./min. values

• It is measurement of power of each subcarrier respect to average power over a set of subcarriers as per specified range This is similar to 11n.

Transmitter Relative Constellation Error (RCE) OR Error Vector Magnitude(EVM)

The method is same as 11n
• Channel estimation is done using preamble sequence only
• Pilot subcarriers are used for phase tracking(or phase rotation)
• Minimum 16 data symbols are used in a frame, RMS average over at least 20 frames is taken.
Following table mentions the EVM limits for different MCS(modulation and code rates).

Modulation-code rate 802.11n EVM(dB) 802.11ac EVM(dB)
BPSK 1/2 -5 -5
QPSK 1/2 -10 -10
QPSK 3/4 -13 -13
16QAM 1/2 -16 -16
16QAM 3/4 -19 -19
64QAM 2/3 -22 -22
64QAM 3/4 -25 -25
64QAM 5/6 -28 -27
256QAM 3/4 Not applicable as this mod-code rate is not supported -30
256QAM 5/6 Not applicable as this mod-code rate is not supported -32

11ac receiver tests

The receiver tests include Minimum input level sensitivity, Adjacent channel rejection, Non-adjacent channel rejection and Receiver maximum input level. Following table-2 mentions the limit for these 11ac receiver conformance tests.

Min. Input level sensitivity

Following table-2 mentions min. sensitivity levels at various modulation-code rates for different bandwidths as supported by 11ac device.

At the input levels mentioned in the table, PER(Packet Error Rate) should be less than 10% with PSDU length of 4096 octets. This is for non-STBC modes with 800ns Guard Interval and BCC coding.

Technical specifications are same as 802.11n with additions of MCS and Bandwidths specific to 802.11ac.

Modulation-code rate Minimum Sensitivity level (dBm)
20MHz 40 MHz 80 MHz 160 OR 80+80 MHz
BPSK 1/2 -82 -79 -76 -73
QPSK 1/2 -79 -76 -73 -70
QPSK 3/4 -77 -74 -71 -68
16QAM 1/2 -74 -71 -68 -65
16QAM 3/4 -70 -67 -64 -61
64QAM 2/3 -66 -63 -60 -57
64QAM 3/4 -65 -62 -59 -56
64QAM 5/6 -64 -61 -58 -55
256QAM 3/4 -59 -56 -53 -50
256QAM 5/6 -57 -54 -51 -48

Adjacent and non-adjacent channel rejection

Following table mentions the limit for adjacent channel rejection and non-adjacent channel rejection for different bandwidths.

Modulation-code rate Adjacent channel rejection(dB) Non-adjacent channel rejection(dB)
20/40/80/160 MHz 80+80 MHz 20/40/80/160 MHz 80+80 MHz
BPSK 1/2 16 13 32 29
QPSK 1/2 13 10 29 26
QPSK 3/4 11 8 27 24
16QAM 1/2 8 5 24 21
16QAM 3/4 4 1 20 17
64QAM 2/3 0 -3 16 13
64QAM 3/4 -1 -4 15 12
64QAM 5/6 -2 -5 14 11
256QAM 3/4 -7 -10 9 6
256QAM 5/6 -9 -12 7 4

Following test procedure is followed to determine adjacent channel rejection and nonadjacent channel rejection.
Step-1: Set the desired signal to 3dB higher than min. sensitivity level.
Step-2: Apply interfering signal of same bandwidth as desired signal in adjacent or nonadjacent frequency. Interfering signal should be OFDM compliant with 50% min. duty cycle.
Step-3: Now increase the power of interfering signal until PER of value 10% is achieved. Set the length of PSDU equal to 4096 octets.
Step-4: Power difference at the output between interfering signal and desired signal is the rejection as needed.

11n,11ac RF PHY layer conformance testing solutions

Following test and measurement instruments are ideal for conformance testing of 802.11n and 802.11ac products. These are useful for 11n/11ac device testing and measurements. These RF and baseband instruments are ideal for 11n/11ac RF and PHY conformance testing or compliance testing.

The solutions are packaged into 802.11ac signal generation and signal analysis hardware as well as software.

Company Instrument with model number
National Instruments supports 11ac compliant RF and baseband hardware and provide signal generation and signal analysis software as per IEEE 802.11ac standard
Agilent technologies(Keysight technologies) Single channel measurements:
N9020A PXA signal analyzer(upto 160MHz BW),
N9020A MXA signal analyzer(up to 40MHz BW),
N9392A PXI microwave VSA(upto 250 MHz BW)

Hardware for MIMO measurements:
N7109 PXIe PXIe multi-channel signal analysis,
N9392A PXI Microwave VSA,
PXI based MIMO system for 11ac testing include N9362A-D01 Quad microwave down converter, M9202A digitizer, M9368C attenuator, M9352A IF amplifier/attenuator, M9302A LO
Rohde & Schwarz R&S®SMBV100A

802.11ac Related resources

WLAN 802.11ac features
11ac frame format
11ac physical layer
11ac MAC layer
11ac data rates
11ac spectral mask
11ac beamforming
11ac radio planning

802.11ad Related resources

WLAN 802.11ad technology features
802.11ad basic tutorial
802.11ad Physical Layer
802.11ad device RF PHY conformance testing

Test and Measurement Related Links

Test and Measurement Signal Generator Companies
Test and Measurement Signal Analyzer Companies
Physical layer measurements
Production tests on RF and SoC devices
RF measurements tutorial
Testing and certification facility providers
EMI and EMC solution providers
Comparison between R&S CMU200 versus Agilent 8960 wireless test equipments

RF and Wireless Terminologies