Citation
Abstract
This article investigates the concept of node synchronization using state metrics. In this study, the branch metrics are integrated over a fixed time interval and the results are compared to the detection threshold. If the threshold is exceeded, the out-of-sync hypothesis is accepted, otherwise, the in-sync hypothesis is accepted. It is shown that the detection threshold can be chosen independent of any particular convolutional code with fixed code rate and constraint length if the code has reasonably good bit error rate performance. Three node synchronization schemes are compared in this article: (1) a scheme using the syndrome (Scheme 1); (2) a scheme using the frame-sync patterns (Scheme 2); and (3) a scheme using the state metrics (Scheme 3). At very low SNRs, Scheme 2 can be faster than Scheme 1. For Voyager’s rate 1/2 and constraint length 7 convolutional code, this happens for SNRs of less than 0.75 dB. This result is obtained by assuming that the coded frame-sync pattern has good aperiodic autocorrelation properties. For a fixed false alarm probability, the sequential detection scheme based on the syndrome is faster than Scheme 3 with fixed integration time. A sequential detection technique is needed to improve the speed of Scheme 3.
Details
- Volume
- 42-94
- Published
- August 15, 1988
- Pages
- 201–209
- File Size
- 359.6 KB