Relationship between the Transmission distance and the Modulation scheme

[wangarikimani]

Hi,

I understand that a QPSK modulated signal will be transmitted further than a 16QAM or 16PSK signal in a LOS transmission. What is the relationship between the transmitting power, the transmission distance, the Bandwidth and the type of digital modulation scheme for Microwave or LOS transmission?

Thanks,
Grace.

[ash]

The gist of it is, the lower the bandwidth or power requirements to achieve a certain level of BER for a modulation scheme, the less power you need to transmit. If you keep power the same, then the transmission distance increases.

In the case of the modulation schemes you mention, for the same BER, QPSK requires less power. This is due to the constellations (the closer they are, the higher chance of error), energy per bit, power spectral density, etc.