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The automatic identification system is used by the ships, and the VHF data link (VDL) mode 4 system is used by the avionics industry. Based on ground infrastructure, the traditional surveillance applications for ships are built with radar support. The major drawback of radar is the inability to see behind large obstacles. This obstacle affects the attenuation signal at receiving ship. Therefore, we present an obstacle-based radio propagation model that considers the effect caused by the presence of obstructing ships in line of sight. This model is evaluated in terms of throughput, collision, and packet transmission under distributed slotted MAC.

Several studies have shown insufficient security in air traffic communication. Controller-Pilot Datalink Communications (CPDLC) is used to communicate in text over the VHF data link, and Automatic Dependent Surveillance – Broadcast (ADS-B) determines the position of an aircraft. The vulnerability of air data communication was confirmed by successful experiments using Software-Defined Radio, where both CPDLC and ADS-B messages were transmitted in a safe environment. Neither ADS-B messages nor CPDLC messages are encrypted during transmission. The encoding of FANS-1/A messages was demonstrated, and the experiments showed that it is possible to send such messages with relatively inexpensive technology.

In recent year, the VDES (VHF Data Exchange System) has drawn extensive attention and admiration in the international maritime field and Internet of Vessels. It has been identified as a core data exchange platform for e-Navigation strategy in the future. However, the traditional Self-Organizing Time Division Multiple Access (SOTDMA) protocol of the Automatic Identification System (AIS) has not met the demands of the huge increases in VHF Data Link (VDL) loading. This paper proposes an improved SOTDMA (iSOTDMA) protocol for VDES to reduce the slot reservation collision rate, thereby improving the system performance. Finally, we present experimental results which show that the proposed iSOTDMA protocol can achieve better performance than the original SOTDMA in terms of slot reservation conflict rate.

Due to the rapidly increasing number of flights and high usage of VHF channels, the VHF spectrum is becoming much more crowded, and use of analog waveforms will likely not maintain the required performance. Therefore, digital communications have been considered due to larger spectral efficiency. Notably, VHF data link modes 2 and 3 (VDL2 and 3) using D8PSK modulation has been proposed. VDL2 and 3 received attention due to its simplicity and more constant amplitude waveform, yielding lower PAPR. Recently, advanced VHF digital link (A-VDL) was proposed for VHF. This scheme enables use of essentially the same platform as VDL except for the physical layer processing, including modulation. The proposed A-VDL, following DVB-S2 standard, uses APSK modulation with higher modulation order than VDL, hence providing higher spectral efficiency than VDL. Compared to the widely used QAM, APSK is more resistant to amplifier amplitude and phase distortions. Thus, APSK has become of interest for satellite communications, as well as VHF communications in A-VDL. In this paper, we investigate other advanced technologies such as channel encoding technique low-density parity-check (LDPC), more efficient standardized voice encoders, as well as better pulse shaping filters than the classical square-root raised-cosine filter used in VDL and A-VDL. Via simulations and analysis, we compare the proposed scheme's link margin, PAPR, and spectral efficiency compared to VDL and A-VDL, which both use Reed Solomon (RS) encoding. In addition, as another way of generating the same VDL waveforms (or possibly other single-carrier aeronautical band waveforms), we investigate the single-carrier type waveform used in cellular LTE and 5G uplink communication links, the discrete Fourier transform-spread OFDM (DFT-s-OFDM), and discuss how we can take advantage of using the same LTE and 5G hardware resources., Comment: This article has been accepted for publication in IEEE DASC Conference 2020

Improved communications performance and higher data rates are necessary to support future airspace operations. Application of new technologies to update the existing aeronautical Very High Frequency (VHF) communications can provide a viable solution with higher data rates that satisfy future airspace requirements while addressing areas of concern with the current VHF Digital Link (VDL) Mode 2 performance.

Novel air traffic management (ATM) strategies are proposed through the Next Generation Air Transportation and Single European Sky for ATM Research projects to improve the capacity of the airspace and to meet the demands of the future air traffic. The implementation of the proposed solutions leads to increasing use of wireless data for aeronautical communications. Another emerging trend is the unmanned aerial vehicles. The unmanned aerial systems (UASs) need reliable wireless data link and dedicated spectrum allocation for its operation. On-board broadband connectivity also needs dedicated spectrum to satisfy the quality of service requirements of the users. With the growing demand, the aeronautical spectrum is expected to be congested. However, the studies revealed that the aeronautical spectrum is underutilized due to the static spectrum allocation strategy. The aeronautical communication systems, such as air-air and air-ground communication systems, inflight infotainment systems, wireless avionics intra-communications, and UAS, can benefit significantly from the introduction of cognitive radio-based transmission schemes. This paper summarizes the current trends in aeronautical spectrum management followed by the major applications and contributions of cognitive radio in solving the spectrum scarcity crisis in the aeronautical domain. Also, to cope with the evolving technological advancement, researchers have prioritized the issues in the case of cognitive radio that needs to be addressed depending on the domain of operation. The proposed cognitive aeronautical communication systems should also be compliant with the Aeronautical Radio Incorporated and Aerospace Recommended Practice standards. An overview of these standards and the challenges that need immediate attention to make the solution feasible for a large-scale operation, along with the future avenues of research is also furnished. Published version

The VHF Data Exchange System (VDES) is a new communications system the development of which is being coordinated by the International Association of Marine Aids-to-navigation and Lighthouse Authorities (IALA) in consultation with the International Telecommunication Union (ITU). It is seen as a key supporting element of the International Maritime Organisation (IMO) e-Navigation initiative. The General Lighthouse Authorities of the United Kingdom and Ireland (GLA) recognise the potential of VDES to serve as an important component of e-Navigation communications and support its development through a range of research projects. After giving an overview of the VDES concept, this paper reports on progress to date, including the results of a VDES channel sounding campaign conducted by the GLA. The campaign examined radio propagation conditions for all channels intended for use in ship-to-shore and shore-to-ship VDES communications. A comprehensive series of sea trials were conducted over five days, near Harwich in the United Kingdom. Five operational scenarios were examined, spanning four of the six IMO Maritime Service Portfolio (MSP) area categories. System components and deployment were consistent with real world maritime use. Key findings from the sounding campaign have been published by the ITU (Rep. ITU-R M.2317). The current paper expands on earlier work by presenting the results of a detailed statistical analysis of the sounding data. The channels are characterised both in terms of their frequency-selectivity and time-variant behaviour. A set of tapped-delay line channel models are derived which can serve as a basis for waveform-level computer simulations and evaluation of VDES physical layer performance. The integration of realistic channel models in such simulations makes it possible to assess the communication performance in different operational scenarios and under a range of propagation, weather and sea state conditions, replacing the need for repeated and costly sea trials during the initial system design phase. Finally, the paper gives an update on the work of the IALA e-Navigation Committee to develop a comprehensive VDES channel model, including the ship-air and ship-satellite channels.

ITU-R M.1842-1, which is one of the renowned specification for VHF data exchange system (VDES) devoted to maritime mobile applications, has been standardized wireless transmission protocols according to the peculiar characteristics of a maritime communications scenario. Generally, in the Annex-4 of ITU-R M.1842-1, the VHF data link protocols for maritime mobile services are described along with a TDMA frame structure. Physical layer parameters of ship-adhoc network (SANET) are contrived to meet the requirements of the specification. In order to increase the link throughput of real-time services, in this paper, we investigate the performance of the SANET with the multiple antennas, where transmit diversity and multiplexing techniques are employed. Based on the analysis of the packet error rate and throughput under the maritime channel model in a coastline area, we select the efficient multiple antenna schemes for SANET to improve the link reliability.

The paper deals with a conception and implementation of selected parts of laboratory experimental receiver for processing Aeronautical VDL2 data link (VHF Data Link mode 2) messages. For acquiring of digitized signal a software defined RTL-SDR receiver is used. Program MATLAB is used for further signal processing. Implementation of message detection, signal filtration, demodulation, symbol and bit synchronization blocks are described in this paper.

Some of the recent systems, such as VHF data link (VDL), are based on the line‐of‐sight links between aircraft and ground stations, thus limiting their deployment to the continental domain. In oceanic areas, satellite‐based systems are proposed as the main solution for future aeronautical data link communications known as aeronautical mobile satellite service (AMSS). Both systems are intended to support very different types of services with mobile nodes. In this context, traffic characterization, communication architecture and protocols have to be explored and validated. These are the fields in which a simulator becomes handy, allowing the validation of techniques and algorithms. This chapter describes the simulations that consider those technologies that are dedicated to en‐route airspace for safety of life communications, mainly supporting the communications taking place between a controller and a pilot. VDL mode 2 is the subject of the first presented simulation model.

With the incoming of the new era of 5G mobile communications and Internet of Things (IoT), the aeronautical communications for aircraft, Air-to-Ground (A/G) communications and Air-to-Air (A/A) communications, confronts with new challenges of high safety, large transmission capacity, low latency, high elasticity, and synthetic service providing etc. In this paper, the new requirement and challenges of future aeronautical communications are reviewed. Moreover, the future aeronautical communications architecture is envisioned and the typical wareforms recommended for 5G are deeply analyzed. Finally, the transition from the current aeronautical datalinks is prospectively discussed.

Activities have been initiated in ICAO and AEEC to further develop the Aeronautical Telecommunications Network/Internet Protocol Suite (ATN/IPS) rather than the ATN/Open System Interconnection (ATN/OSI) protocols for use by safety and regularity of flight applications. Aside from the basic approach to mobility within a given Air/Ground Access Network an approach to multi-link operation over multiple Air/Ground Access Networks is needed. A description of local mobility management using PMIPv6 for the VHF Digital Link Mode 2 (VDL-2) terrestrial access network was provided in [1]. This paper proposes the use of MIPv6 as the global mobility management protocol which provides the desired multi-link capability.

VDL(VHF Data Link) Mode E uses TDMA(Time Division Multiple Access) based aeronautical communication technologies for airborne environments. In the VDL Mode E, aircraft uses RR(Reservation Requests) slot to request data slot. However, RR needs a long guard time, since aircraft communication spans a considerable distance. The more number of aircrafts causes a larger amount of guard times which can make a throughput decreased. In this paper, we propose an enhanced MAC to reduce the guard time by using the distance information of aircraft. The ground station sends management data including time stamp. And then all aircraft can measure their distance from the ground station.

Commercial communication systems design software is usually shipped with libraries and toolboxes covering standards like GSM or UMTS. For designing aeronautical communication systems such ready-to-use libraries are rare. Low-level elements and functional blocks have to be adopted and used instead. In this paper a toolbox consisting of system elements for the use with electronic design automation software was developed. It enables radiofrequency design engineers to perform system level simulations using specialised components dedicated to aeronautical communication. For this, functional blocks within the physical layer of VHF Data Link were defined and made available. They cover basic radio frequency (RF) baseband operations as well as modulation, demodulation and power-ramp functionality. The library was tested and verified with a VHF Data Link Mode 4 signal generation application as well as with a VHF Data Link Mode 2 system simulation set-up. While the toolbox presented in this paper is intended to speed up development cycles by providing ready-to-use VHF Data Link functional blocks to radiofrequency system engineers, it is also a useful tool in signal generation and receiver testing.

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.

VDL Mode E is a digital communications system proposed as a worldwide standard for replacement of the existing analog AM voice system used for VHF aeronautical communications. It provides a needed increase in voice channel capacity as well as offering a digital data link for CPDLC with the high integrity and low latency needed for time-critical ATC messages. This report summarizes results of measurements of proposed minimum requirements for an aeronautical receiver for VDL Mode E. A software defined radio (SDR) currently used in Commercial Air Transport communications was used for the tests.

Reasonable possibility of modem building in the class of non-coherent systems, which is suitable for use in the equipment of standard infrastructure of aviation radiotelephony communication, is described. It comes to standard narrowband analog VHF (Very High Frequency) aeronautical radio channels in the 118–137 MHz band. The flow chart of data communication via the voice path of aeronautical radiostation with a high level of information protection in the air channel, which can be used in the unmanned aerial vehicle control systems, is shown. The parameters of incoherent modem, which provides the technical ability to create a secure air channel, are worked out. Devices of phase synchronization in the voice path of aeronautical station are not required in the proposed modem. It is able to operate stably at the speeds higher than 6.2 kbit/s under the ratio “signal/noise” not less than 25 dB. The use of this modem creates the conditions for ensuring the necessary level of information security in the aeronautical air channel (a possibility of “strong” cryptography application).

VHF data link (VDL) mode 3 is a digital TDMA communications system developed by the FAA and industry partners as a replacement for the existing 25 kHz analog AM systems currently used for VHF aeronautical communications. VDL mode 3 provides increased channel capacity and security for both voice and data link communications. This paper provides a report on the first Supplemental Type Certification recently issued for production-ready and FAA Technical Standard Order (TSO) approved VDL Mode 3 avionics

The standards for CSTDMA Class B AIS will shortly be published by the International Electrotechnical Commission and equipment will become available during 2006. The perceived benefits that Class B brings to leisure craft users and its relatively low cost will make it attractive in the market place. A rapid take-up of Class B use can therefore be expected. This paper considers the impact that increased use of Class B will have on users of Class A AIS that are compulsorily fitted to larger vessels to meet the requirements of the International Maritime Organization Safety of Life at Sea convention. The CSTDMA Class B system has been designed to prevent overloading of the AIS VHF data link. This is briefly reviewed but there are a number of other aspects that need to be considered. These include: the increased garbling of Class B messages compared to those of Class A; the problems accruing from the low update rate of Class B information; the increase in display information that will need to be managed; and the possible increase in inappropriate manoeuvres of leisure craft caused by misplaced reliance on AIS. As a result of the investigation the paper highlights the fact that Class B users must not assume that their own presence, in the form of Class B transmissions, will be particularly visible on the bridge of many SOLAS vessels. This will continue to be the case for many years into the future, until such vessels are mandated to carry radar with AIS target overlay capability.

Metrics of voice communications between pilots and air traffic control provide important indices of NAS system performance. They help to characterize current operations, define requirements for fut...

The purpose of this study was to analyze digital data link communications technologies in a line-of-sight environment. Because there is a global debate over selecting the next generation VHF data link (VDL) technology, this paper evaluates each of them for the terminal and enroute airspace only. First, this study provides a historical review of the purpose of data link applications; second, how the current system is failing to meet today's requirements, leading to problems within the US National Air Space (NAS); third, a technical and economic analysis of VDL technologies; and last, a recommendation for selecting a VDL technology.

The Marine Corps has frequent requirements for beyond-line-of-sight communications for voice and narrowband data in challenging terrains that normally limit or truncate links. The Naval Research Laboratory has developed a two-channel narrowband VHF relay that supports narrowband communications using standard Marine Corps radios. This relay is lightweight and designed to be borne aloft at altitudes above 65, 000 ft., providing connectivity to nodes as far as 150 nmi from the relay payload. This paper documents the design and the operation of the balloon-borne VHF relay, dubbed "Surrogate TACSAT", and details results from testing conducted out of Yuma Proving Ground in March of 2014.

The Automatic Identification System (AIS) is used worldwide as a maritime system for identifying and locating vessels by exchanging data in Very High Frequency (VHF) band with other nearby ships, AIS base stations and satellites. It is an important system for safety of navigation to assist collision avoidance and enables marine traffic supervision and management. However, the expanding use of AIS band by other emerging applications and services has caused significant increase on the maritime VHF Data Link (VDL) load, hampering smooth exchange of critical AIS information. Instead of assigning new frequency resources for new marine VDL services, in this paper we present a solution to overcome this spectrum scarcity issue by utilizing Cognitive Radio (CR) technology in maritime AIS VHF network. A preliminary analysis of the performance of such an approach is carried out taking into account the different properties and challenges of marine communication channels due to sea surface movement. The outcome of our study shows how the application of CR techniques to maritime VDL indeed represents an appealing alternative to static spectrum allocation schemes to deal with overloading issues in AIS networks.

VHF radio system has been used for Air Traffic Control (ATC) communication, Aircraft Operational Communication (AOC) etc. on the continental area. The data communication system of the VHF radio system uses communication protocols specified in the international standards called SARPs (Standards and Recommended Practices) of the ICAO (International Civil Aviation Organization). The VHF data communication system is commonly called the VHF datalink system. The VHF datalink system has been implemented into AOC, however it has not yet been implemented into ATC communication in Japan. By using the VHF datalink system, an air traffic controller can exchange requests or instructions with a pilot on a flying aircraft, and it significantly contributes to the safety of flight.

Self-organising radio systems have been proposed for aeronautical and maritime communication, navigation and surveillance applications. In aviation, the introduction of the VHF Data Link (VDL) Mode 4 is currently being discussed, while the implementation of Automatic Identification Systems (AIS) is planned in the maritime domain. Operating in an autonomous mode, a self-organising radio system employing Time Division Multiple Access (TDMA) does not require a terrestrial infrastructure, such as base stations. The concept of self-organisation is based on the cooperative behaviour of a large number of users sharing a common VHF radio channel. Analyses have shown that uncoordinated stations, so-called hidden users, can cause interference in self-organising radio systems. This paper presents two different approaches to autonomous self-organisation together with the results of investigations of intra-system interference. Such analyses may help to introduce potential improvements to the system performance, which reduce the effect of hidden users in this very promising GNSS-based technology.

This paper presents the modeling and simulation of a Very High Frequency Data Link Mode 2 (VDL2) sub network to support Controller Pilot Data Link Communication (CPDLC), at El Dorado International Airport in Bogota City. The modeling and simulation were made in order to determine performance characteristics and determine if VDL2 could meet future traffic load increase. The simulation was performed using Network Simulator 2 (NS2). An overview of the technologies currently used for air-ground communication in Colombia is presented. Also this paper shows a glimpse of the features of the VDL Mode 2 protocol and CPDLC service. The VDL Mode 2 subnet model and the subsequent simulation were derived from the characteristics of Colombian airspace and air traffic conditions in the Bogota Terminal Area (TMA). Finally, the simulation results are presented.

SESAR and NextGen are defining the future airspace system in Europe and the USA. A key element of both initiatives is to develop the next generation cockpit data communication systems, which will after a transition phase be data-centric and based on IPv6 as being specified by ICAO in the ATN/IPS SARPS [1]. Against this background, a central goal of the European research project SANDRA (Seamless Aeronautical Networking through integration of Data-links, Radios, and Antennas) [2], started in Oct. 2010 with 3 years duration, is to define and validate a reference aeronautical communication architecture, including new concepts and technologies that are assumed to be essential for the implementation of the future data communication system. Focusing on the air-to-ground communication and on the development of the aircraft SANDRA terminal, the project further designed and implemented an integrated aeronautical communication system for validation in a testbed and, further, in flight trials scheduled for June 2013 on DLR's Advanced Technology Research Aircraft (ATRA), an Airbus A320. The testbed represents a proof-of-concept prototype aircraft communication system, integrating prototypes developed and implemented in SANDRA, comprising an Integrated Modular Radio (IMR) that integrates VDL Mode 2 (VDL2), AeroMACS, Inmarsat SwiftBroadband (SBB) service on BGAN, and DVB-S2 link technologies, an Integrated Router (IR), and a transport mechanism for ATN/OSI-over-IP for mobile nodes. The focus of this paper is on the IPv6 networking and related aspects. The IR together with the respective ground network entities implements the core networking functions in compliance with ICAO ATN/IPS SARPS. Instead of relying on physical segregation, SANDRA takes a first step towards segregation of operational and non-operational domains relying on IPsec [3]. Improvement of bandwidth efficiency is also addressed through implementation of RoHC and resource sharing between operational and non-operational data traffic while ensuring segregation through IPsec and QoS requirements of data with high priority.

The International Civil Aviation Organization is currently developing Draft Standards and Recommended Practices for the VHF air/ground (A/G) digital communications system using time division multiple access (TDMA). This system provides up to four time slots that can be configured in a number of ways to meet differing voice and data communications requirements. This paper reports on a simulation of the data communications delay performance with a two-voice, two-data (2V2D) configuration. The simulation includes a model of the media access control layer with priority queuing for air traffic service data communications between ground and airborne stations. Simulation results show that the performance of the digital channel is improved by combining polling with prioritized message queuing. Furthermore, downlink message delays are reduced significantly by balancing the utilization factors of random access slots and interlayer priority queue management.

Civil aviation business is currently experiencing the beginning of an operational change from voice based toward data based control mechanisms. This change shall be accompanied through a technological improvement that is in particular a change from an ISO/OSI toward a TCP/IP based network infrastructure. This paper presents outcomes of two independent investigations of utilizing the initial specification for the Aeronautical Telecommunication Network (ATN) using Internet Protocol Suite (IPS) standards and protocols via aeronautical data links. Thereby, both studies had one common objective, namely the validation of the ATN/IPS via aeronautical data links. One study was conducted by University of Salzburg through the evaluation of simulations, while the other study was conducted by the Swedish air navigation service provider LFV through flight trials based on real protocol implementations. Despite the difference of the evaluation scenarios the conclusions that can be drawn from both studies are similar.

Aircraft traffic management on the airport surface will require the effective utilization of communications, navigation and surveillance (CNS). This paper describes an experiment which provides a glimpse of future automation. The experiment combines precision surface radar, high-accuracy differential GPS (DGPS) position determination, automatic dependent surveillance (ADS), and ground and airborne automation systems able to inter-communicate via a VHF data link. In particular, this paper describes the air/ground communications provided by the VHF Data Link. Two classes of messages are processed: continual and ad hoc. The former include DGPS corrections, ADS messages and target data. The latter include graphical taxi clearances and hold bar set-reset information. The work described in this paper is the result of a cooperative venture among NASA, Westinghouse-Norden Systems and ARINC. >

In this paper, we focus on self-organizing time division multiple access (STDMA) protocol, which can provide slot selection algorithm in VHF data link communication. Almost all the previous researches about STDMA protocol are the theoretical analysis of the protocol. They hardly intuitively evaluate the whole performance of the protocol. Therefore, it is necessary to implement the STDMA protocol with simulation tool. Firstly we discuss the overview of the STDMA protocol and then introduce how to implement the protocol in GloMoSim. In the end of the paper, the performance of the STDMA protocol is analyzed through simulations. The simulation results show that STDMA protocol has the self-organizing characteristic in the slot selection.

As the standard equipment of the commercial aircrafts, air-ground data link system is widely used in modern aviation transport. However, its validity was unsatisfactory in our testing, especially in error of transmission. In this paper, some influencing factors during air-ground data transmitting were analyzed from the signal transmission. Considering ACARS was based on ARINC-618 protocol, a fundamental study in this article on transmission signal and demodulating signal of the ground air data link system was done on the basis of ACARS signal generated by the transient aircrafts. Keywords-ACARS, Very High Frequency (VHF), Signal Analysis

In order to verify the performance of aviation VHF Data Link Mode 2(VDL2) system that will be used in the next generation civil aviation in China, the physical layer and link layer models of VDL2 system based on OPNET are built first used for parameter simulation. Then, the effect of aircraft number on the average retransmission delay is simulated. The effects of offered load on the average subnet delay, the probability of successfully sending data packet, and the system throughput are further testified. The simulation results demonstrate that if the offered load is no more than 0.65, VDL2 system subnet delay can meet the requirement, throughput is raised significantly with the offered load increasing and the probability of successfully sending packet can reach to 80 percent. The results can be taken as an important reference to future practical application of VDL2 system.

The legacy DSB-AM (Double Sideband Amplitude Modulation) system used for today’s voice communication in the VHF-band is far away of meeting the demands of increasing air traffic and associated communication load. The introduction of VDL (VHF Digital Link) Mode 2 in Europe has already unfolded the paradigm shift from voice to data communication. Legacy systems, such as DSB-AM and VDL Mode 2 are expected to continue to be used in the future. However, they have to be supplemented in the near future by a new data link technology mainly for two reasons. First, only additional communication capacity can solve the frequency congestion and accommodate the traffic growth expected within the next 10-20 years in all parts of European airspace (ICAO-WGC, 2006). Second, the modernization of the Air Traffic Management (ATM) system as performed according to the SESAR (http://www.sesarju.eu/) and NextGen (http://www.faa.gov/nextgen/) programs in Europe and the US, respectively, heavily relies on powerful data link communications which VDL Mode 2 is unable to support. Based on the conclusions of the future communications study (Budinger, 2011), the ICAO Working Group of the Whole (ICAO-WGW, 2008) has foreseen a new technology operating in the L-band as the main terrestrial component of the Future Communication Infrastructure (FCI) (Fistas, 2011) for all phases of flight. Hence, such L-band technology shall meet the future ATM needs in the en-route and the Terminal Manoeuvring Area (TMA) flight domains as well as within airports. The latter application area will be supplemented by the AeroMACS technology at many large airports (Budinger, 2011). A final choice of technology for the L-band has not been made yet. Within the future communications study, various candidate technologies were considered and evaluated. However, it was found that none of the considered technologies could be fully recommended before the spectrum compatibility between the proposed systems and the legacy systems has been proven. This will require the development of prototypes for testing in a real environment against operational legacy equipment. The future communications study has identified two technology options for the L-band Digital Aeronautical Communication System (LDACS) as the most promising candidates for meeting the requirements on a future aeronautical data link. The first option, named LDACS1, is a Frequency-Division Duplex (FDD) configuration utilizing Orthogonal Frequency-Division Multiplexing (OFDM), a highly efficient multi-carrier modulation technique which enables the use of higher-order modulation schemes and Adaptive Coding and Modulation (ACM). OFDM has been adopted for current and future mobile radio communications technologies

The power spectral analysis of very high frequency (VHF) communication radios is important to understanding how they affect each other and how they affect VHF surveillance radios. In this paper, we propose an analytical method for lower-bound radio frequency (RF) power spectrum estimation with the consideration of both power amplifier nonlinearity and broadband noise. We then demonstrate how to apply the proposed spectral estimation method to compute the lower-bound power spectra of VHF digital link mode 2 (VDL-2), plain old ACARS (POA) and double-sideband-amplitude-modulated (DSB-AM) voice signals. Finally we present the estimated lower-bound power spectra and shed light on where the discrete spectral line component comes from and how the nonlinearity of a power amplifier leads to the spectral regrowth.

• The Aeronautical Mobile Airport Communications System (AeroMACS) is a new communications system intended for safety communications on the airport surface currently in the initial development phase — Targeting ground/aircraft applications requiring a high data throughput (> 3 Mbps) over short connection time (20 to 30 minutes) ♦ Not possible with current safety datalinks such as VHF data link (VDL) ♦ NextGenATM and System Wide Information Management (SWIM) services such as navigation database loads, weather data, air[port taxi guidance with moving map data are candidate applications

Media Independent Aircraft Messaging (MIAM) is a new protocol that provides a standardized interface for the exchange of data between aircraft and ground systems. Although it is envisioned to accommodate broadband IP and other communication networks in the future, the initial version of this protocol only supports existing ACARS networks. One of the immediate intents of MIAM is to support the transfer of messages much larger than possible in the ACARS subnetworks through message segmentation and reassembly features. In an attempt to reduce the impact of MIAM transfers on the ACARS networks, the protocol includes data compression, segment temporization, and flow regulation controls. This paper begins with a discussion of the MIAM protocol. The protocol is analyzed and tested through detailed simulations of the ACARS VDL Mode 2 subnetwork with various traffic profiles and protocol parameters. As the inclusion of large messages may add significant load, the study investigates the flow regulation features of MIAM and its effects on the underlying ACARS network, looking for adverse impacts on other ACARS traffic. The findings of this study are presented and discussed in conclusion.

The Single European Sky Air Traffic Management (ATM) research programme SESAR has identified continued growth in demand for aircraft communications as air traffic increases and communications become more network centric. Alongside existing systems such as VHF Data Link Mode 2, new systems such as the L-band Digital Aeronautical Communication System (LDACS) and the Aeronautical Mobile Airport Communications System (AeroMACS) are being proposed. This growth is likely to increase the size, weight and cost of avionics radio communication equipment, so there is a need to examine new radio architectures which will help limit these increases. SANDRA is a European Commission programme which aims to design and demonstrate an integrated communications system using software defined radio techniques. The concepts behind the integrated communications system are described, including improved modularity using high-speed digital links, security, redundancy and certification. The specific requirements of the SANDRA programme and details of the proof-of-concept demonstrator are outlined.

Dimensioning the mobile link for aeronautical communications between aircraft and the satellite is a critical issue due to the limited power available, in particular if an omnidirectional antenna is used on board the aircraft. Also there are large channel variations due to the different effects occurring on the L-band mobile link and over-dimensioning of the user terminal or satellite should be avoided. In this context, this paper analyses the interest of using Adaptive Coding and Modulation (ACM) for the mobile link of future aeronautical satellite systems in L band for a European coverage. It analyses in particular the different effects to be compensated, their impact on the link budget and the link dimensioning and performance improvement when using ACM. Finally complementary analyses that would be necessary to further investigate this topic are identified and presented at the end of the paper.

The problematic addressed in this paper aims at designing a security architecture for the whole set of digital aeronautical communications. This security architecture, focused on aeronautical data link communications, would have to consider the di erent parts of aeronautical communications related to aircraft segment, satellite air-ground segment and ground segment. Consequently, this security architecture would be able to interconnect in a secure way the \aircraft" world and the \outside" world (Internet for instance). Thus, the architecture we introduce is dynamic and exible with regards to several factors such as tra c density or service priorities thanks to an available network resources based adaptive security management.

The FAA planned Data Communications Network Service (DCNS) will enable digital air/ground (A/G) communication between Air Traffic Control (ATC) facilities and VHF Digital Link (VDL) Mode 2 (VDL-2) equipped aircraft. In successive program segments, ATC services will evolve to include both ‘essential’ and ‘safety critical’ applications. Appropriate requirements will be imposed on the DCNS to transport these applications. These requirements will place challenging demands on the performance of the VDL-2 A/G links.

In order to efficiently make use of all the spectrum resource in VHF band for aeronautic communications, Non-Continuous OFDM (NC-OFDM) scheme in VHF, named as Non-Continuous Broadband VHF (NC-B-VHF) system, is designed and evaluated in this paper. Specifically, the structure of NC-B-VHF system is presented. The critical modules to implement the applicable system are discussed and exemplified. Meanwhile, the Peak to Average Power Ratio (PAPR) reduction is testified. Furthermore, the capacity of the NC-B-VHF system is compared with the VDL mode 2 and mode 3. About 2.7 times gain can be achieved by NC-B-VHF. The paper also predicts a drastically increasing of the capacity of NC-B-VHF if involves the structure of the cognitive radio, which makes the subcarriers dynamically adapt to the spectrum holes and the interference from the out-of-bands. Simulation results show that more than twice gain can be obtained in the capacity compared with the traditional B-VHF system.

VHF Aircraft Communications Addressing and Reporting System (ACARS) is the most popular VHF aeronautical datalink. It is used for such applications as airline operation and air traffic control. VHF ACARS has only a 2400 bit/s (bps) transmission rate air-ground link. The VHF Digital Link mode 2 (VDL2) system, which has a thirteen times higher transmission rate air-ground link than VHF ACARS, is very similar to VHF ACARS. Both systems can deal with messages in ACARS format. Even though the systems are well used for various operations, their effective link capacities are not so clear. Finding out effective communication performance, including real link capacity and acceptable maximum delay, is useful for the design layout of ground facilities and rebuild datalink operation guidance in the near future. We built both VHF ACARS and VDL2 protocol models on an OPNET protocol simulator to evaluate their effective communication performance. This paper gives an outline of the protocol models and comparison results of these performances by simulation. Statistics such as transmission delay and throughput have been obtained under various load conditions for up to 200 aircraft. Before starting the simulation, we analyzed message data length and the message generation interval of VHF ACARS from real communication logs in Japan. The message data length was mostly distributed randomly, below 660 bytes, and messages exceeding 660 bytes rarely appeared. The message generation interval mostly followed Pareto distribution. We assumed that the message data length and data generation interval followed uniform distribution and Pareto distribution respectively. We found the following by analyzing simulation results. i) When data traffic load generated from an aircraft equaled the load directed to the aircraft, the VDL2 system was able to process 4.6 times more congested load than the VHF ACARS. ii) When data traffic load generated from an aircraft was five times higher than the load directed to the aircraft, the VDL2 system was able to process 8.8 times more congested load than the VHF ACARS. The load condition approximated real VHF ACARS data generation ratio between forward link and reverse link.