4.3.1 Meaning of the Result Graphs in G3-PLC

The meaning of each result graph in the spreadsheets is described in the table below. The name of each one refers to the DUT operation, position and kind of data.

Attention: The “Y axis” of the graphs represents a value measured (dB or dBμV or %) in each test and the “X axis” represents the attenuation value (dB) or RSSI (dBμV) in each test.
Table 4-1. Graph Names Description
Graph NameDescription
RSSI (dBµV)The Received Signal Strength Indication in dBμV
Noised SymbolsNumber of corrupted symbols in payload due to impulsive noise
Corrupted CarriersNumber of corrupted carriers in payload due to narrow/broad band noise
SNR BE (dB)SNR of corrupted carriers in payload due to narrow/broad-band noise in quarters of dB
SNR Impulsive (dB)SNR of corrupted symbols in payload due to impulsive noise in quarters of dB
SNR Background (dB)Signal-to-Noise Ratio of the carriers that have not narrow band noise and from the symbols without impulsive noise
SNR Worst Carrier (dB)Signal-to-Noise Ratio of the most noised carried in quarters of dB
SNR Worst Symbol (dB)Signal-to-Noise Ratio of the most noised symbol in quarters of dB
SNR Header (dB)The SNR Header is the SNR of the header in quarters of dB
SNR Payload (dB)The SNR Payload is the SNR of the payload in quarters of dB
LQI (dB)

The LQI parameter indicates the mean SNR per carrier.

The LQI is an integer ranging from 0x00 to 0xFF and LQI values in-between are uniformly distributed between these two limits. The LQI value is derived from the average SNR (where averaging is done over all active tones and pilot tones, if present, in the bandplan and overall OFDM symbols in the received packet) where the SNR-to-LQI mapping is:

  • SNR ≤ -10 dB maps to LQI 0x00
  • SNR ≥ 53.75 dB maps to LQI 0xFF
  • -10 < SNR < 53.75 dB is linearly interpolated between 0x00 and 0xFF (the nominal step size is 0.25 dB)

The value analyzed in the spreadsheet is the average of all LQI received.

FER (%)Frame Error Rate, percentage of lost frames against sent frames.
The different value results obtained from the PLC Tester Tool are related to the attenuation programmed on the setup for each test, so it is very important to calibrate the setup to obtain comparable results, mainly the FER.
Figure 4-9. Typical Frame Error Rate Versus Attenuation for G3-PLC on CEN-A with Microchip Reference EKs
Additionally, Python Scripts provide results related to the RSSI calculated on the reception, the simplest way to compare the results between different devices.
Figure 4-10. Typical Frame Error Rate Versus RSSI for G3-PLC on CEN-A with Microchip Reference EKs
From a theoretical point of view, the FER vs RSSI shows:
  • A gain of 3 dB between the modulations BPSK, QPSK, 8PSK.
  • Additional gain is obtained using ROBO modulation that adds more energy to each symbol.
  • Sensitivity is improved with coherent modulations in exchange for greater complexity in the reception and lower baudrate.