Answer 6.8
- Both four-level bipolar and polar baseband
signalling occupy the same bandwidth, and have a bandwidth efficiency of 2 bits/second/Hz.
Thus for a 256 kbps data signal the bandwidth required (minimum) is 128 kHz.
- See a above.
- BPSK is a binary bandpass modulation format with a
bandwidth efficiency of only 1 bit/second/Hz maximum. Hence 256 kHz
of bandwidth is required to support 256 kbps.
- QPSK is a bandpass modulation format with four
symbol states. This has a bandwidth efficiency of 2 bits/second/Hz requiring
128 kHz of bandwidth.
- 64-QAM conveys 6 bits per symbol [log2(64) = 6]
compared with 2 bits per symbol for QPSK. The bandwidth required is thus reduced by a
factor of three compared with QPSK to 42.667 kHz.