## BER performance for QAM |
Question 6.7 Question 6.8 Question 6.9 |

#### Comparing the BER curves for PSK and QAM, the intuitive advantage of QAM over PSK drawn from the constellation diagram is borne out, with an approximately 3.5 dB gain in noise immunity for 16-QAM compared with 16-PSK. This improvement comes at the expense of a somewhat more complicated modem design, needing to handle both amplitude and phase information, and to combat both amplitude and phase errors on the channel. In practice, the performance benefits usually outweigh the complexity such that QAM is frequently used in preference to PSK modulation. If the channel amplitude distortion is particularly severe, such as to dominate errors due to noise, then PSK could prove superior under these conditions. |