Answer 5.8

The theoretical maximum channel capacity for a bandpass PSK is identical to that for an ASK channel and is given by:

Cbandpass = B log2M,

For a non brick-wall filter, this expression must be modified to allow for the extra bandwidth of a practical filter shape as follows:

Cbandpass = (B log2M) / (1 + a)

Now M = 2 for binary signalling, thus:

C = (8000 x 1) / (1 + 1) = 4000 bps.