ncrease signal power-Decrease signal noise

Increase signal power
This is same as speaking louder in a noisy room. We intuitively know that as the signal to noise ratio is
increased, the errors decrease. Assuming that we can do nothing about the environment, the most obvious thing
to do is to increase the transmitter power. But this is not always possible. Most communication devices have no
ability to increase power. Examples of power-limited devices are telephone handsets and satellites. Both of
these have a fixed amount of power and can not increase their transmitting power beyond a certain point. In
fact most are designed to operate at their maximum power and have no spare power available.
There are actually some disadvantages to using this scheme. When amplifier characteristics are not linear,
increasing the power means both signal and noise are amplified making the situation worse. You can see this
mechanism at work in a radio. When you increase the volume, the noisiness of the signal goes from bad to
intolerable
Decrease signal noise
We are at a party and the room is too noisy for conversation, we may move to a quieter corner where
there is less noise. If you turn on the air conditioner in the room and the TV reception goes bad, you turn off the
offending item to improve the reception. These are some means of noise reduction. In a communication device,
the only noise that is under the designer’s control is thermal and inter-modulation noise of the system. Assuming
that the system is designed to minimize these, we do not have any way of reducing the noise. We are at the
mercy of the environment and have to accept this as a given.