Why MDS stands for minimum discernible signal, sometimes called minimum detectable signal. It is essentially the receiver's noise floor: the weakest signal that produces a detectable output above the receiver's own internally generated noise, conventionally the level that raises the output about 3 dB above the noise. It is calculated from the thermal noise floor of -174 dBm/Hz plus the receiver's noise figure plus 10 log of the bandwidth in hertz, so narrower bandwidth and lower noise figure both improve (lower) the MDS.