Global Navigation Satellite Systems (GNSS) are becoming the primary means of navigation for civil aviation. Nevertheless, concerns about GNSS outages remain, driving the need for Alternative Positioning, Navigation and Timing (APNT) systems to provide availability and continuity for performancebased navigation services. Although the existing Distance Measuring Equipment (DME) infrastructure is able to provide Required Navigation Performance (RNP) 1.0 accuracy, it is not robust for individual station outages. Additionally, we show that in the European airspace DME is reaching the capacity limit. To address these two problems, we propose a methodology based on modular APNT. In the presented approach, the complementary ranging sources are optimally placed to obtain robustness. It is assumed that the L-Band Digital Aeronautical Communications System (LDACS) can provide this capability. As shown in the results, the modular APNT system is able to provide robust RNP 1.0 coverage for Germany using 17 new LDACS ground stations to complement the network of 73 existing DME installations in Germany.

In this paper we discuss the first results from a set of flight experiments. The objective was to show that terrestrial ranging can support aviation services with sufficient accuracy for non-precision approach. The experimental setup is based on using LDACS signals to provide pseudorange measurements. The data analysis reveals that the position solutions are compliant with RNP 1 standards. We also propose the feasibility of RNP 0.3 using LDACS as terrestrial ranging.

Regions with dense air traffic has lower separation between aircrafts to maintain the throughput. Terminal area generally requires high throughput and some of the airports need to maintain 3− nmi separation between two aircrafts. To provide 3− nmi separation RNP 0.3 is required. In this paper we propose two possible ways to fulfill RNP 0.3 NSE requirement using LDACS as an alternate system. The first way is to use LDACS in standalone configuration and the other way is to use a hybrid configuration, where position solution is obtained using LDACS combined with DME.The results show that both the proposed methods, standalone and hybrid configuration fulfill RNP 0.3 NSE requirement. Where standalone configuration is more accurate than hybrid, due to the low ranging error of LDACS system. For our analysis the surveillance data for terminal area of Munich and Frankfurt airports were used. In standalone configuration 5 LDACS stations for Frankfurt and 6 LDACS stations for Munich are sufficient to fulfill RNP 0.3 NSE requirement. In hybrid mode both Frankfurt and Munich only need 3 LDACS stations.

Today's voice-based air-ground communication system for aircraft guidance is suffering from increasing saturation of the VHF band in high density areas. Therefore the European Union strives for a transition from analog voice communication to more spectrum efficient digital communication. This transition shall be realized, among others, through the development and implementation of the L-band Digital Aeronautical Communications System (LDACS). In order to verify the suitability of LDACS for both communications and navigation, a flight trial campaign will be performed within the nationally funded German project MICONAV. The objective of this paper is to present the planned LDACS measurement campaign. LDACS will be validated under realistic conditions: Four ground stations transmit signals; one airborne station onboard an aircraft will receive the communication messages and additionally utilize the signals from the ground stations for navigation.

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ICAO Annex 10 -Attachment H provides a guidance for a rationalization of conventional radio navigation aids to support Performance-Based navigation. An optimization of terrestrial navigation infrastructure, which includes a rationalization effort and coordinated evolution, is necessary to maintain a sufficient level of safety and operations in case of GNSS outage. This is an opportunity to introduce new signals with better ranging performance. The hybridization of new systems with legacy DME enabling a fully backup navigation system. The hybrid sytems make possible to decommission older radio navigation solutions. In this paper we present our assessment tool: marginal benefit. It is the ratio between potential DME to be decommissioned and the number of new signals deployed.

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