Data transmission performance in the presence of carrier phase jitter and Gaussian noise

In the operation of data transmission systems over voice-grade telephone channels, phase jitter1 is a commonly observed transmission impairment. It appears in the form of low-index angle modulation of the received data signals. It is believed that phase jitter is a very important parameter in determining system performance. Therefore, many complicated methods2,3 have been developed to recover the jittered carrier. However, recent field measurements1 show that the phase jitter in Bell System carrier systems has improved significantly over the past few years. As a result of this improvement, the following question naturally arises: How much phase jitter recovery is required for two-level and four-level systems?