Miodrag Sajatovic

B-VHF - an overlay system concept for future ATC communications in the VHF band

In this paper, the European research project B-VHF is introduced which is funded by the European Commission and has started in January 2004. The main goal of the B-VHF project is to prove that it is feasible to establish a multi-carrier based overlay system for future air traffic control (ATC) communications in the very high frequency (VHF) band without causing interference to the legacy VHF systems. Note this overlay system concept enables in-band transition from the current to a future ATC communications system and, thus, allows future ATC communications to stay in the advantageous and protected VHF band. The focus in this paper is on the technical approach for realizing the overlay concept. Thus, the technology behind B-VHF are described in detail and how it is applied for realizing an overlay system in the VHF band.

Physical layer specification of the L-band Digital Aeronautical Communications System (L-DACS1)

L-DACS1 is the broadband candidate technology for the future L-band Digital Aeronautical Communications System (L-DACS). The flexible design of L-DACS1 allows the deployment as an inlay system in the spectral gaps between two adjacent channels used by the Distance Measuring Equipment (DME) as well as the non-inlay deployment in unused parts of the L-band. In this paper, the specification of the L-DACS1 physical layer enabling the deployment as an inlay and as a non-inlay or as a mixed inlay and non-inlay system is presented. Apart from the transmitter design, the design of the L-DACS1 receiver is addressed including methods for mitigating interference from other L-band systems. Special emphasis is put on channel estimation which has to be robust towards interference. The different proposed algorithms for channel estimation are evaluated in simulations of the overall L-DACS1 physical layer performance. The results show that L-DACS1 is capable of operating even under severe interference conditions, hence confirming the feasibility of the inlay concept.

B-AMC a system for future broadband aeronautical multi- carrier communications in the L-BAND

The Broadband Aeronautical Multi-carrier Communications (B-AMC) system is a candidate for a future aeronautical communications system to be operated in the L-Band (960-1164 MHz). It is based on the Broadband-VHF (B-VHF) system recently developed for aeronautical communications in the VHF band. As conditions in the L-Band significantly differ from those in the VHF band, basic physical layer parameters had to be adapted, which in turn required a re-design of the higher layers as well. B-AMC offers air/ground (A/G) as well as direct air/air (A/A) communication capabilities without ground relay. The physical layer has been designed to coexist with other systems located in the aeronautical L-Band. The B-AMC data link layer is optimized for low latency and low duty cycle data communication. The B-AMC study is funded by EUROCONTROL.

B-AMC — broadband aeronautical multi-carrier communications

The broadband aeronautical multi-carrier communications (B-AMC) system is a promising candidate for the future L-band radio system called L-band digital aeronautical communications system (L-DACS). In this paper, the design of the physical (PHY) as well as of the data link layer (DLL) is addressed. As B-AMC is intended to be operated in the L-band between two adjacent distance measuring equipment (DME) channels, the avoidance of mutual interference between existing L-band systems and B-AMC has been in the focus of the PHY layer design. In order to demonstrate the feasibility of the coexistence with DME, a draft frequency planning has been performed for Europe, resulting in successful frequency assignments in wide parts of Europe. The B-AMC DLL supports data link communication with low latency and high throughput. It is designed to be highly configurable and to support different service requirement sets and traffic profiles. In this paper, the current DLL configuration featuring a low RL duty-cycle and graceful degradation is discussed in detail.

Interference mitigation for broadband L-DACS

One deployment option for the future broadband L-band digital aeronautical communications system (L-DACS) is operating as an inlay system between two adjacent channels of the distance measuring equipment (DME) system. Investigations for the broadband aeronautical multi-carrier communications (B-AMC) [1] system, one candidate for the broadband L-DACS, have shown that interference originating from DME systems operating in adjacent channels has a strong impact on the B-AMC system. To enable the utilization of spectral gaps between two adjacent DME channels, two efficient methods for mitigating the impact of interference are proposed and investigated for the B-AMC system, namely pulse blanking and erasure based decoding. Simulations show that the impact of DME interference onto the L-DACS can be reduced considerably by choosing an appropriate coding scheme to make the transmit signal robust against interference. The impact of interference is mitigated by means of the proposed methods, resulting in a performance close to the performance in the interference-free case.

Improvement of L-DACS1 design by combining B-AMC with P34 and WiMAX technologies

All currently pursued Air Traffic Management (ATM) concepts and associated roadmaps, i.e. Single European Sky ATM Research (SESAR) in Europe and Next Generation Air Transportation System (NextGen) in the USA, heavily rely upon trajectory exchange between airborne and ground automated systems. Facilitating such exchanges requires high performance Air-Ground (A/G) data link communications. The decision about what technology the future data link shall be based upon has not yet been taken, but it is obvious, that the selected data link technology must be globally accepted and standardized.

Aircraft Identification Tag Study Equipment And Implementation Scenarios

The EUROCONTROL Experimental Centre (EEC) developed an innovative concept called aircraft identification tag (AIT), which aims at: (i) Reducing voice communication errors by allowing the controller to visually identify the aircraft that is currently using the voice channel. (ii) Improving the security of controller-pilot voice communications by allowing authentication of received voice communications. In July 2006, EUROCONTROL launched an initial feasibility study on the AIT concept to provide EUROCONTROL with enough information to decide and give orientations for a full feasibility analysis of the AIT concept, in view of a possible operational implementation. This paper summarizes the findings of the second deliverable of this initial feasibility study - AIT equipment and implementation scenarios.

LDACS1 conformance and compatibility assessment

In this paper the results of conformance and compatibility measurements of an L-band Digital Aeronautical Communication System Type 1 (LDACS1) transmitter are presented. The measurements were performed at the Institute of Electrodynamics, Microwave and Circuit Engineering (EMCE) of TU Vienna as well as in the labs of the German air navigation service provider Deutsche Flugsicherung GmbH (DFS) in connection with the SESAR project P15.2.4. Prior to the deployment of any new aviation communication system, the compatibility towards legacy systems has to be confirmed. For this purpose, an LDACS1 transmitter prototype was developed by Frequentis AG/TU Vienna to validate the LDACS1 system specification and prove the spectral compatibility of LDACS1 with the legacy L-band systems (e.g. DME, SSR, and UAT). Previous analysis has indicated that the DME/TACAN-LDACS coexistence is one of the most critical scenarios due to its wide and extensive use in the civil aviation.

Operational concept for multi-carrier broadband VHF communications

Operational air traffic management needs have led to the concept of the broadband VHF (B-VHF) aeronautical communications system. This explains the functional principles, architecture, and internal mechanisms of the B-YHF system, showing how it can be used to provide the existing aeronautical voice and data link communications services and a multitude of new data link services expected for the next decade or two.