Noncoherent pulse combining for improved multiple access LPI network performance

The authors examine the advantages of using noncoherent pulse combining to improve the overall covertness of a tactical low probability of intercept (LPI) radio network. To illustrate the advantages of this technique, a candidate network is selected which can serve a large number of simultaneous customers through the use of frequency and time division multiple access. A transmitted pulse structure is also selected which is amenable to varying data rates. Using fixed network parameters, a baseline LPI performance standard is established, and pulse combining is then employed at the communications receiver to reduce the required received signal-to-noise ratio for a given communications performance level. When network users employ noncoherent combining on a symbol pulse by pulse basis, the authors demonstrate that a significant increase in LPI performance is attained, which can be traded for a longer operating range or improved covertness by allowing the transmitter to reduce power. However, the use of pulse combining does result in reduced throughput. The authors discuss these advantages and disadvantages through the use of LPI system quality factors, which allow a quantitative assessment of the vulnerability of a communications system to interception by an intercept receiver