Introduction

This document discusses a recommended setup for production testing of the Mesh Rider radios in an end-product (e.g. a UAV and a GCS). Every interface (Ethernet, USB, Wireless etc) of all Mesh Rider radios are fully tested prior to the radios being shipped. However, it is still often a good idea to perform a final test of the radio's link inside the end-product before shipping out your product to your end customer. This should be a quick and easy go/no-go test to determine if there were any problems during the final integration such as electrical damage, or loose/damaged wiring.

For details on how to access the radio's command prompt or over it's other APIs, please see our Remote Management Guide.

Test Setup

Fig. 1 shows how you can set up your production test.

Fig. 1 Production test setup

Performance Expectations

In order to decide on a suitable go/no-go threshold for the performance, we recommend performing your tests with known good units, and then allowing for a few dB of performance spread.

Path Loss Estimate

The antennas are setup to achieve nearly ideal link conditions. Therefore, you can estimate the received signal strength using the Friis Free-Space Pathloss formula.

Pr = Pt + Ggolden + Gdut - 32.44 - 20*log(distance) - 20*log(frequency) - atten

For example, if the operating frequency is 2.4-GHz, and 0 dBi antennas are used, and the transit power is 27 dBm, then the received power in this case is -53 dBm. We suggest adding sufficient pathloss so that the radio is around 5 - 10 dB higher than the failure point. For example, if you typically see the network getting overloaded at -80 dBm, you could make sure the received power is around -75 dBm.

Notes on transmitted power

The output power of the transmitter is not constant. It is controlled by four factors:

Each of these settings applies a limit to the final output power. It is possible to fix the modulation rate to MCS0 (highest power) using the commands

PHY=$(/usr/share/simpleconfig/get_fes_phy.sh)
iw wlan${PHY} set bitrates ht-mcs-2.4 0

This will not survive a reboot, and can be reset using iw wlan${PHY} set bitrates.

Test Procedure

The RF side of the radios includes both a transmitter and a receiver. You can test the receiver by looking at the RSSI reported by the DUT, and you can test the transmitter by looking at the RSSI reported by the golden unit. The RSSI can be checked by running

iw wlan${PHY} station dump | grep "signal: "

The output looks like this

signal: -51 [-58, -52] dBm

The first number is the combined signal strength, the second is the signal strength on antenna 0, and the last is the signal strength on antenna 1. In order to be able to differentiate the transmitted power on each antenna, it is necessary to only mount one antenna at a time on the DUT. You can also get the combined signal strength in json format using

ubus call iwinfo assoclist '{"device":"wlan'${PHY}'"}'

Additional Tests

The purpose of the test above was for a quick go/no-go check to make sure that there was nothing wrong with the RF side of the radio. Ideally, you would test every interface that you are using to make sure there were no issues during shipping/integration. Below are some suggested tests that you can consider adding to your production setup.