Citation
Abstract
Non-Return-to-Zero Mark (NRZ-M) modulation is often used to resolve data sense in suppressed carrier telemetry systems. This is because such systems are subject to half cycle slips that result in complementing the encoded data stream, The performance of coded telemetry systems with NRZ-M is sensitive to the order in which the various operations are done. This means that a system that demodulates the NRZ-M waveform and then decodes will perform differently from a system that does the decoding first, In this report, the performance of the NASA standard (7, 1/2) convolutional codes is determined for several systems using NRZ-M. In addition, several different demodulation schemes for NRZ-M are considered. It is shown that, even for the best soft-decision method examined, there is a 2.7 dB loss at a decoded bit error rate of 5 X 10-3 if the NRZ-M demodulation occurs before rather than after Viterbi decoding.
Details
- Volume
- 42-77
- Published
- May 15, 1984
- Pages
- 33–40
- File Size
- 451.9 KB