High accuracy SFOL DME/N pulse and its recommended implementation in South Korea for alternative aircraft navigation

The SFOL pulse is a high accuracy DME/N pulse developed from using Genetic Algorithms. This pulse complies with the current DME/N specifications and is significantly less susceptible to multipaths than previous DME pulses. Recent analysis of the SFOL showed that the multipath-induced ranging error of the SFOL pulse was five times and two and half times less than the conventional Gaussian and Smoothed Concave Polygon pulses. To implement DMEs transmitting the SFOL, first, it would be desirable if modern DMEs currently deployed in the field can be modified to transmit the SFOL pulse without significant changes. It is expected that the biggest modification is required in the pulse shaping process. Currently, we are investigating a pre-distortion of the SFOL pulse for the typical power amplifier of a DME designed to transmit Gaussian pulses. A successful development of the pre-distortion may enable Gaussian pulse-based DMEs to transmit the SFOL pulse with relatively little changes. Second, the terrain in South Korea consists of numerous high mountains that would make it difficult to plan effective DME/DME networks due to the limited line of sights between DMEs and aircraft. Considering the airspace and major airport locations in South Korea, we are developing search algorithms that will result in cost effective DME/DME network layouts in the difficult terrain conditions. The paper will introduce a promising pre-distortion of the SFOL pulse and a strategy in planning of optimal DME/DME networks in South Korea with a recommended network layout.