Bernhard Haindl

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.

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.

B-VHF - Selected Simulation Results and Assessment

B-VHF is a proposal for a future aeronautical communication system in the VHF band based on an overlay concept, i.e. during the transition phase the B-VHF system shares the same frequency band with legacy VHF systems without interfering with them. In this paper, the overlay concept is evaluated by simulations of the physical and higher layers. Simulation results show that the B-VHF overlay system works in presence of interference from legacy VHF systems. The protocol is designed to allow using the available resources very efficiently and to provide voice and data services with the required quality of service

Physical layer design for a broadband overlay system in the VHF band

In this paper, the physical layer design of the B-VHF system is described and discussed. B-VHF is a broadband communications system for air-traffic control based on multi-carrier technology which is intended to be applied as an overlay system to the existing aeronautical communications systems in the VHF band. Special focus in this paper is put on the physical layer design challenges which have to be solved in order to guarantee the co-existence between B-VHF and the legacy VHF systems. Especially, the interference avoidance techniques at the B-VHF transmitter as well as the required interference suppression techniques at the B-VHF receiver are discussed in detail.

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.

An independent technology assessmentfor a future aeronautical communication system based on potential systems like B-VHF

Air traffic management (ATM) system heavily relies upon air-ground communications. The frequency band currently used for air-ground communications (117.975 -137.000 MHz) is becoming congested. In some parts of Europe, it is extremely difficult to find a frequency to allow a new assignment to be made. This paper summarizes the communications services of current ATM systems as well as their basic operational concepts. Moreover, a comparison of different spectrum ranges and communication mechanisms used in physical and data link layers of aeronautical technologies was performed. Finally, the paper provides a comparison of several most promising technologies (LDL, B-VHF and P34) for a future aeronautical system.

Service orientation principles in integrated communication environments

Today, every modern organization aspires to improve its performance through better use of information technology. As communication technology improves, organizations can operate over wider distances and can even assemble operational components on an ad-hoc basis to meet requirements of a specific objective. Future air traffic communication studies are already discussing whether to operate IP networks that are combining voice and data transport. The problem is that although voice and data are using a common infrastructure, they remain separate at the application level. Probably, some service providers have already enjoyed reduced network infrastructure and operational costs by merging voice and data transport, but the majority may have failed to realize the significant cost, productivity, and service differentiation capabilities that converged, collaborative applications could bring. This elaborates mechanisms needed for a robust and globally interconnected network environment (including infrastructure, systems, processes, and people) in which data is shared timely and seamlessly among users, applications, and platforms. Such an environment enables substantially improved situational awareness and shortened decision-making cycles. Stepping ahead, our contribution discusses standards making application or service convergence a reality.

LISP: A novel approach towards a future communication infrastructure multilink service

Future Communication Infrastructure (FCI) air ground data link services can use various technologies (radio links) to achieve the end to end data exchange objectives. Such functionality has been developed and standardized by ICAO under the Aeronautical Telecommunication Network (ATN) activities and is also available in the Internet Protocol Suite (IPS) world, but is currently not yet operationally deployed for ATM purposes. Work comprised in SESAR P15.2.4 project provides an initial perspective of the “Multi Link Operational Concept”, i.e. the notion of using multiple data links to support the communication exchanges in the context of the future SESAR concept of operations. In the context of this task the perimeter of the FCI is limited to just the three future technologies (LDACS, AeroMACS, and SATCOM) and the ATN/IPS-based network layer. This contribution introduces LISP (Locator/Identifier Separation Protocol) as novel approach in order to enhance the ATN/IPS-based network layer. LISP is an open IETF RFC [5] describing a solution for the scalability problem of the Internet routing caused mainly by provider independent addresses and multi-homing of customer networks to different Internet service providers. The concept is based on the separation of the device identity from the physical device location in an IP network. The current approach in the IP world is overloading of IP semantics. Who and where are both represented by the same IP address. Change of location leads to a different IP address and hence changes identity causing existing sessions to be interrupted. LISP is a network-based solution supporting seamless communication while allowing roaming between different locations. LISP is an incrementally deployable architectural upgrade to anexisting infrastructure. An interesting application is the seamless migration from IPv4 to IPv6 due to its address family agnostic behavior. Early adopters will be able to use their existing infrastructure and applications and immediately benefit from LISP. This paper focuses on usage of LISP technology in aeronautical networks in order to achieve mobility, high availability and security for safety critical communication between aircraft and ground infrastructures. Fast convergence, make-before break in multilink environments, easy deployment and operation, manageable security, avoidance of scalability limits and independence of service provider infrastructure are the main topics of interest. Typical use cases demonstrate the network power of LISP support both, future aeronautical data, and voice applications. This makes LISP an interesting candidate technology to handle the mobility of the aircraft while maintaining communications when moving between different ground stations. We show how the LISP mobility system can be enhanced to include application type or QoS specific information into the data link selection. This allows path preference selection for individual data transactions transparent to the application and implementation of outgoing traffic engineering whilst utilizing the basic LISP mechanisms. Finally we discuss make-before break handover in order to improve required communication performance (RCP) figures such as availability of use or continuity.

Ground based lisp for multilink operation in ATN/IPS communication infrastructure

This paper provides an IPv6 mobility and multi-link solution proposed in SESAR project P15.02.04. It is based on the Locator/Identifier Separation Protocol with the goal to minimize the complexity in the aircraft and the overhead in the A/G datalinks. This solution is a ground based network solution, where all the routing and mobility functionalities are necessary only in network equipment on ground, fully transparent for all end systems. The scope of the ground based LISP solution is the global mobility management, i.e. it covers the vertical handover between different A/G data links and handovers between different mobility service providers.