Question

Derive an expression for power penalty with impairment

Answer 1

Physical layer design should take into consideration the effect of number of system impairments.  

Normally impairment gives a power penalty to the System.  

In presence of impairment a higher signal strength will be needed at the receivers end to maintain a desired bit rate of error.  

One way to explain power penalty is the increase in signal strength required  (dB) to maintain the same bit error rate in the presence of impairments.  

Another process to elaborate the power penalty is the reduction in signal-to-noise ratio as quantified by value of γ (the argument to the Q(.)) due to specific impairment.

Answer 2

Due to impairments, a system may face power penalty.

Therefore, more signal power may be needed at the transmitter end to keep up with the bit error rate.

Hence, an expression for power penalty with impairments can be defined as the increase in signal power that is needed to maintain a similar bit error rate.