Performance Analysis of Signal Pattern Reducing Techniques for Low Probability of Detection

Ad-hoc flexibly deployable networks destined for tactical military or civilian applications often suffer from poor synchronization which may lead to unreliable communication. Quasi-Synchronous (QS) CDMA employing Loosely Synchronous (LS) codes allows weak synchronization due to the Zero-Correlation Zone of the code's correlation functions. Apart from reliability, an essential characteristic of military networks is having low probability of detection (LPD) in the presence of adversaries employing sophisticated detection techniques. Such techniques are based on the fact that manmade signals are cyclostationary, meaning that they have some periodic structure (e.g. spreading sequence repetition) that can be exploited for improved detection. Disturbing those recurring patterns can reduce the probability of detection measured in terms of the Degree of Cyclostationarity (DCS). We aim to achieve that by employing some techniques that will perturb the signal structure by randomly selecting spreading sequences, random time dithering or a combination of the two. We study the trade-off between the communication performance and DCS reduction of such a system under these different techniques and compare the results.