Tradeoff Bet. SNR and Bandwidth.

[Peon666]

I read in my analog communication book:

"A relatively small increase in bandwidth buys a large advantage in terms of reduced transmission power. But a large increase in transmitted power buys a meager advantage in bandwidth reduction. Hence, in practice, the exchange between B and SNR is usually in the sense of increasing B to reduce transmitted power and rarely the other way round."

So, if we increase a little bandwidth single power is reduced to a large extent. That's right. But is that an advantage?

 

[Averagesupernova]

Not 100% sure what you are asking. Typically in order to reduce the power required at the transmitter and still be able to receive an intellible signal, the bandwidth in the receiver is reduced which improves the S/N ratio. Of course, a reduced bandwidth means less data can be transmitted in a given period of time.
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The question seems to be geared toward FM or FSK systems. Increasing the frequency swing reduces the power in a given chunk of spectrum within the bandwidth of the transmission but the overall power will remain unchanged.