Telecommunications Demystified

Chapter 9

Channel Filtering and Equalizers

In Chapter 5, we talked about using modulators to map bits m to a signal s(t) that could be sent over the channel. We saw that the channel added a noise n(t) to the sent signal, giving the receiver the noisy r(t) = s(t) + n(t). We took this a step further when we talked about demodulators, which, given r(t) = s(t) + n(t), did their best to regenerate the original bit sequence m.

Now we take this even further. This time we’ll consider something called pulse shaping at the modulator. Modulators still take bits m and turn them to a signal s(t)– we just consider a more general way to do this. We can now talk of channels that do two things–add a noise and do a filtering c(t), giving the receiver r(t) = ...