Bit Error Rate (BER) is the number of erroneous bits received, normalized by the total number of bits received. Communications links typically require a BER < 1e-6. Eb/No is the energy per bit divided by the noise. It is the digital equivalent of the signal-to-noise ratio. The larger the Eb/No, the better the signal performance and the lower the BER.
Starting with STK 10, STK determines BER in one of two ways. For standard-type modulation, STK uses a formula based on Eb/No as computed in the link budget. For nonstandard modulation, STK determines the BER by using a lookup table in the demodulation file (.dmd).
The demodulation file accounts for modulation type as well as coding. An example demodulation file is as follows:
| ModulationName | BPSK-BCH-63-30 |
| BERPoints | |
| 4.4 | 1.0e-2 |
| 5.0 | 3.0e-3 |
| 5.5 | 1.0e-3 |
| 5.95 | 3.0e-4 |
| 6.3 | 1.0e-4 |
| 6.65 | 3.0e-5 |
| 6.9 | 1.0e-5 |
| 7.25 | 3.0e-6 |
| 7.5 | 1.0e-6 |
| 7.75 | 3.0e-7 |
| 7.95 | 1.0e-7 |
To learn more about modulation in STK, please see
Modulators in the STK Help.
In much older versions (STK 9 and earlier), STK determined BER in one of two ways. For standard-type modulation, STK used a formula based on Eb/No as computed in the link budget. For nonstandard modulation, STK determined the BER by using a lookup table in the modulation file (.mod). The modulation file accounted for modulation type as well as coding. The header of an example modulation file was structured as follows:
| BandwidthRatio | 2.0 |
| ModulationType | BPSK |
| NumberOfPoints | 11 |
