README notes on frame repeater test

README.md

@@ -47,7 +47,20 @@ $ ./build_csdr.sh
 $ ./build_rtlsdr.sh
 ```
 
-# Testing
+# Frame Repeater Automated Testing
+
+A Frame Repeater system has been developed to test the physical layer over the air.  Terminal 1 sends a burst over the air to Terminal 2, which echoes the same frames back to Terminal 1.  Terminal 1 then logs the received packets, including SNR.  The system is automated, so that it can run for hours unattended.  By analysing the log files the Packet Error Rate (PER) and SNR of both legs of the link can be analysed.  Knowing the gain of the RTLSDR receiver, we can use signal power S, and noise power N to estimate the link budget and local noise density (EMI) at the receiver.
+
+Terminal 1 is a laptop with a HackRF Tx and RTLSDR Rx.  Terminal 2 is a Pi running rpitx and a RTLSDR.
+
+Service scripts have been written to wrap up the complex command lines.
+
+`scripts/ping` is the tx service that sends the Tx bursts, and logs data on the receive bursts; `scripts/frame_repeater` is the frame repeater service that run s on the Pi.  Both service scripts include debug/test commands and command line help.  The `start_loopback` command is a good way to test the local Tx/Rx is working OK.  A nearby SSB rado tuned to the same frequency is useful to monitor transmissions.
+
+   ![Frame Repeater](doc/frame_repeater_test.png)
+   ![Frame Repeater Bench Test](doc/repeater_otc.jpg)
+
+# Command Line Testing
 
 1. Transmit two tone test signal for Pi:
    ```
@@ -260,8 +273,6 @@ $ ./build_rtlsdr.sh
    This uses a source addressing scheme to filter out locally transmitted frames. In the example above, the laptop has
    address 0x1, and the Pi addess 0x2.  We tell the rtl_fsk Rx 0x1 to ignore any packets sent from 0x1.  This neatly prevents the frame repeater from hearing it's own packets and going into a loop.
 
-   ![Frame Repeater Bench Test](doc/repeater_otc.jpg)
-
 # Reading Further
 
 1. Open IP over VHF/UHF [Part 1](http://www.rowetel.com/?p=7207) [Part 2](http://www.rowetel.com/?p=7334) [Part 3](http://www.rowetel.com/?p=7567)