RX performance

RX performance is usually characterized by quoting sensitivity, which is determined through a Packet Error Rate (PER) measurement.

The IEEE 802.11 specification defines the parameters for sensitivity measurements for the different PHY modes. A sensitivity measurement involves a Vector Signal Generator (VSG) transmitting a fixed number of packets (typically 10,000) of a specific modulation type and length at a known signal strength. The Device Under Test (DUT) records the number of packets successfully received (that is, Cyclic Redundancy Check (CRC) check passes). The ratio of failed packets to total transmitted packets is the PER. The sensitivity is defined as the receive signal strength (in dBm) where a 10% or lower PER is achieved.

To find this limit, a sweep of signal strength at the VSG must be performed (that is, the PER measurement repeated multiple times at different signal strengths). Various approaches to sweeping the transmit power can be adopted in order to minimize test time, or a linear sweep of the entire receive signal strength range can be performed in order to produce a bathtub curve of receive signal strength (x-axis) vs PER (y-axis), from which the sensitivity can be identified.

Use the Wi-FiĀ® Radio test sample to enable RX mode and record the packet statistics on the DUT. For example, the following sequence sets the device into receive mode on channel 7 in the 2.4 GHz band.

wifi_radio_test init 7
wifi_radio_test rx 1

Once RX mode is enabled, the VSG should be enabled to transmit 10,000 packets at the required modulation, code rate, and transmit power. Once complete, request the DUT to record the number of successfully received packets with the wifi_radio_test get_stats command. The PER can be calculated from the number of successfully received packets.

Then disable the DUT to make it ready for another measurement at an alternate receive signal strength (controlled through the transmit power at the VSG) with the command wifi_radio_test rx 0.