Receiver Characterization

The IEEE 802.11 Standard specifies a minimum receiver sensitivity that all 802.11 devices must achieve. For DSSS waveforms, this sensitivty is specified as a receive power (in dBm) in which a device must achieve no worse than a 8% packet-error-rate (PER) for an MPDU lenght of 1024 octets. For OFDM waveforms (NONHT and HTMF), minimum receiver sensitivity is specified with the criteria of no more than 10% PER with a length of 1000 octets. The receiver minimum input sensitivity requirements can be found in the following locations of the 802.11-2016 standard:

• DSSS waveforms in 15.4.6.2
• NONHT waveforms in Section 17.3.10.2
• HTMF waveforms in Section 19.3.19.1

Methodology

DSSS Experiments

A DSSS transmitter was created using the WARPLab Framework. This design transmits 1Mbps or 2Mbps DSSS waveforms at regular intervals. Independently, an 802.11 Reference Design receiver was used to measure the number of received DSSS frames at various receive powers. This node was controlled using the wlan_exp Experiments Framework and the number of receptions were calculated using the event log. The receive power independent variable was controlled with a programmable attenuator and was verified with a ​Tektronix RSA306B Spectrum Analyzer.

OFDM Experiments

The 802.11 Reference Design is able to transmit NONHT and HTMF OFDM waveforms natively. The only difference in methodology between the DSSS and OFDM Rx sensitivity experiments is that the OFDM experiments are able to use the 802.11 Reference Design on the transmit node with the Local Traffic Generator.

Results Summary

DSSS Waveform

Rate	Modulation	Minimum Sensitivity (dBm)	Achieved Sensitivity (dBm)	Improvement over Minimum (dB)
1 Mbps	DBPSK	n/a	-92	n/a
2 Mbps	DQPSK	-80	-87	7

NONHT Waveform

Rate	Modulation / Coding	Minimum Sensitivity (dBm)	Achieved Sensitivity (dBm)	Improvement over Minimum (dB)
6 Mbps	BPSK 1/2	-82	-88	6
9 Mbps	BPSK 3/4	-81	-88	7
12 Mbps	QPSK 1/2	-79	-87	8
18 Mbps	QPSK 3/4	-77	-84	7
24 Mbps	16-QAM 1/2	-74	-83	9
36 Mbps	16-QAM 3/4	-70	-77	7
48 Mbps	64-QAM 1/2	-66	-74	8
54 Mbps	64-QAM 2/3	-65	-72	7

HTMF Waveform

Rate	Modulation / Coding	Minimum Sensitivity (dBm)	Achieved Sensitivity (dBm)	Improvement over Minimum (dB)
6.5 Mbps	BPSK 1/2	-82	-87	5
13 Mbps	QPSK 1/2	-79	-85	6
19.5 Mbps	QPSK 3/4	-77	-83	6
26 Mbps	16-QAM 1/2	-74	-81	6
39 Mbps	16-QAM 3/4	-70	-76	6
52 Mbps	64-QAM 2/3	-66	-72	6
58.5 Mbps	64-QAM 3/4	-65	-71	6
65 Mbps	64-QAM 5/6	-64	-67	3

Detailed Results

DSSS Waveform

DSSS Rx Sensitivity

NONHT Waveform

NONHT Rx Sensitivity

HTMF Waveform

HTMF Rx Sensitivity

Rx Power Accuracy

To determine the accuracy of the RSSI to Rx power mapping in the 802.11 Reference Design, we use the ​Keysight N4010A Wireless Connectivity Test Set. The N4010A lets us accurately specify a power level at which a transmission is delivered to the antenna port of WARP v3 and we can use this to compare against the receive power calculated by the 802.11 Reference Design.

The above plot shows measured receive power vs. actual receive power controlled by the N4010A. Each line represents a different WARP v3 kit and frequency band (2.4GHz or 5GHz).